Classes of Antibiotics:

Beta-lactam antibiotics are the most widely used class of drugs for the treatment of bacterial infections. They include penicillin and its derivatives, such as methicillin and amoxicillin. The beta-lactam ring portion of the antibiotic targets the penicillin-binding proteins (PBP), found in the bacterial cell membrane, which function in the synthesis of the cell wall. Binding of the antibiotic to the PBPs prevents the PBPs from performing their essential role and results in the death of the bacterial cell.

Gram positive bacteria acquire resistance to beta-lactam antibiotics through the production of a protein called PBP2a, which is able to avoid the inhibitory effects of the antibiotics. This is the mechanism by which MRSA is able to persist despite treatment with multiple beta-lactam antibiotics.

The genes for beta-lactamase enzymes are probably the most international in distribution: random mutations of the genes encoding the enzymes have given rise to modified catalysts with increasingly extended spectra of resistance. The archetypical plasmid-encoded beta-lactamase, TEM, has spawned a huge tribe of related enzyme families, providing ample proof this adaptability. The beta-lactamase genes are ancient and have been found in remote and desolate environments, which implied that novel beta-lactamases with altered substrate ranges occur in the environment. (Davies, “origins and Evolution of Antibiotic Resistance” Microbiology and Molecualr Biology Reviews, 2010, p. 417-433)

–Amoxicillin: is used to treat a wide variety of bacterial infections. It is a penicillin-type antibiotic that works by stopping the growth of bacterial. Amoxicillin is a widely utilized beta-lactam antimicrobial drug approved by the U.S. Food and Drug Administration (FDA) for use in the primary care setting. Amoxicillin is an aminopenicillin created by adding an extra amino group to penicillin to battle antibiotic resistance. This drug is indicated for the treatment of infections caused by susceptible isolates of selected bacteria, specifically those that are beta-lactamase–negative, including ear, nose, and throat infections, Helicobacter pylori eradication, lower respiratory and urinary tract infections, acute bacterial sinusitis, and skin and structure infections.

Amoxicillin is effective against a wide range of gram-positive bacteria, offering additional coverage against some gram-negative organisms compared to penicillin. Amoxicillin’s spectrum of activity includes coverage against Streptococcus species, with heightened efficacy against Listeria monocytogenes and Enterococcus spp. Furthermore, amoxicillin also demonstrates effectiveness against Haemophilus influenzae, select Escherichia coli strains, Actinomyces spp., Clostridium species, Salmonella spp., Shigella spp., and Corynebacteria spp.

Fluoroquinolones:

–Ciprofloxacin: is a member of the fluorquinolone drug class that is sued to treat various Gram-engative bacteria such as Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae and E coli and Gram-positive bacteria such as Staphylococcus auereus. (Chegini, “Bacteriophages: The promising therapeutic approach for enhancing ciprofloxacin efficacy against bacterial infection” J Clin Lab Anal, 2023).

Gepotidacin: This antibiotic is in phase III (GSK). It could become the first novel oral antibotic treatment for uncomplicated urinary tract infections in over 20 years. Gepotidacin provides activity against most srains of E. coli, including isolates that are highly reistant to current antibiotics. It binds to two different enzymes, which would reuqire the bacteria to develop mutations in both enzymes to become resistant . GSK also ahs an exclusive licence with Spero Therapeutics for another antibiotic to treat complicated urinary tract infections called tebipenem pivoxil hydrobromide (tebipenem HBr). This drug belogs to a class of antibiotic agents called carbapenems, which are typically reserved for sever bacterial infections of suspecte mutlidrug-resistant bacterail infections.

Macrolide antibotics: such as erthyromycine were introduced to content with the problem of methicillin resistance and are widely used for the treatment of Gram-positive infections. The macrolides and related antibiotics act by binding at different sites in the peptide exit tunnel of the 50S ribosome subunit. Resistance can occur by modificaiton of the RNA or protein components of the tunnel.

Streptomycin: was introduced in 1944 for the treatment of tuberculosis. Mutant strains of Mycobacterium tuberculosis resistant to therapeutic concentrations of the antibiotic were found to arise during patient treatment.

Combination of antibiotics:

Antibiotic combination therapy is the application of two or more antibiotics and is widely sued in clinical settings to prevent the evolution of resistance. Compared to monotherpiees, such therapies can improve treatment efficiency, expand antibiotic coverage or reduce health damage ot humans. For example, beta-lactams are used in combination with aminoglycosides and fluoroquinolones for the treatment of gram-negative bacteria of sepsis and severe Pseudomonas infections.

Antibiotic adjuvants:

Antibiotic adjuvants can provide an alternative and complementary strategy that can target antibiotic resistance or enhcnace antibiotic action to restore or improve the antimicrobial activity of commonly used antibiotic. The adjuvants commonly used can be classified into beta-lactamase inhibitors, efflux pump inhibitors and outer membrane permeabilizers.

Antibiotic Resistance:

The gut microbioa in healthy adults is a reservoir for multiple ARGs. A major parte of the gut reistome has its origin in soil and water habitates, and some in food. As these populations had little exposure to antibiotics, their ubiquitous ARGs such as tetracylcine and several beta-lactam resistance genes are environmentally derived. Only a small fraction of ARGs pose a threat to human health. (Staley, “Long- and short-term effects of fecal microbiota transplantation on antibiotic reistance genes: results form a randomized placebo-controlled trial” (2024)

Type I cytokine receptors are transmembrane receptors expressed on the surface of cells that recognize and respond to cytokines with four alpha-helical strands. These receptors are also known as hemopoietin receptors and share a common amino acid motif (WSXWS) int he extracellular portion. Type I cytokine receptors include interleukin receptors, colony stimulating factor receptors and other cytokine receptors.

The signal transducing chains are often shared between different receptors within the family. For example, the IL-2 receptor shares a common gamma chain (CD132) with the IL-4 reeptor. The common beta chain (CD131) is shared between the GM-CSF recetpor and the IL-3 receptor.

Leptin or obesity receptor (Ob-R) is a ember of class I cytokine receptor family, Ob-R, expressed in six isoforms, is the product of alternative RNA splicing of db gene. According to its structural differences, the receptor’s isoforms are divided into three classes: long, short, and secretory isoforms. A long, fully active isoform of Ob-Rb is expressed mainly in the hypothalamus, where it takes part in energy homeostasis and in the regulation of secretory organs’ activity. Ob-Rb is also present on all types of immune cells, invovled in innate and adaptive immunity. Short leptin isoforms that contain box 1 motif are able to bind JAK kinases as well as to activate some other signal transduction cascades. A solube isoform can regulate serum leptin concentraiton and serve as a carreir protein delivering the hormone to its membrane receptors and is able to transduct the signal into the cell. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

A long, fully active isoform of Ob-Rb is epxressed mainly in the hypothalamus, where it takes part in energy, homeostasis, and int he regulation of secretory organs’ activity. Ob-Rb is also rpesent in all types of immune cells, involved in innate and adaptive immunity. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

Lack of a full-lenght Ob-Rb recetpor is responsible for the development of the early obesity phenotype in db/db mice and in obese rats. (Wasik, “Leptin Recetpors” European Journal of Medical Research” 2010, 50-54).

Short leptin isoforms that comtain box 1 motif are able to bind JAK kisnases and to activate some signal transduction cascades. However, the effect of short isoform activation differs from that of long isoform activation. Their main function is presumably connected with leptin internalization and degradation. A short isoform, Ob-Ra is the most common Ob-R isoform that can be found in many various cells and tissues, cinlduign kidney, lugns, liver, speen, and macroppages. (Wasik, “Leptin Receptors” European Journal of Medical Research” 2010, 50-54).

A major role in leptin signal transduction through membrane receptors is mediated through JAK/STATE pathway. Among all Ob-R isoforms, only the full lenght isoform is able to fully transduce and activaiton signal into the cell. Ob-Rb is considered a fully active receptor, because it contains 3 intracellular motifs necessary to activate the JAK/STATE pathway.

Antimicrobial resistance (AMR) and persistence are associated with an elevated risk of treatment failure and relapsing infections. Alhtough AMR has been widely acknowledged as a pressing issue, the incidence of infections and spread of MDR bacteria is still rising. In addition, the increased use of implanted medical devices such as joint prostheses, artifical heart valves, vascular endoprostheses and pacemakers leads to a higher incidence of biofilm assocaited infeciton, which in turn leads to anotehr important phenomenon; antibiotic tolerance. Antibotic resistance frequenlty resutls in dealyed adequate antibiotic treatment, increasing morbidity and mortality. AMR is the inherited ability of microorganisms to grow at high antibiotic concentration. It is usually quantified by measuring the mininum inhibitory concetnraiton (MIC) of a particular antibiotic wherein resistant bacteria are able to multiply and grow at concetnrations of antibiotics, which are fatal to other strains of the same species. In general, Gram-negative bacteria are less permeable than Gram-positive and show an intrinsic resistance to many antibacterial compounds such as the cell was acive glycoppetide vancomycin. These large molecules are unable to cross the outer bacterial membrane of Gram-negative bacteria and thus cannot target the cell wall of Gram-negative bacteria. In contrast, the Gram-positive bacteria Staphylococcus aureus is naturally susceptible to almost every antibiotic that has been developed, but it is well known for quickly acquiring antibiotic resistance by emans of botaining specific genetic modifications. (Huemer, “Antibiotic resistance and persistence – Implications for human health and treatment perspectives” EMBO Reports, 21, 2020).

Essentially any of the accessory genetic elements found in bacteria are capable of acquiring r genes and promoting their transmission; the type of element involved varies with the genus of the pathogen. In the streptococcie, miningococci and related genera, the exchange of both virulence and pathogenicity genes is highly promiscuous; the principal mechanisms for DNA traffic appears to be transformation. (Davies, “origins and Evolution of Antibiotic Resistance” Microbiology and Molecualr Biology Reviews, 2010, p. 417-433).

Antibiotic presistence or heterotolerance is defined as the ability of a bacterial subpopulation to surive high bactericidal drug concentrations to which the bacteria are fully susceptible. One major chacteristic of antibiotic peristence is a biphasic killing, with a rapid killing of the susceptible populations and a slower killing of the persister subpopulation. Persistent infections are ongoing infections, which are not cleared by the host, whereas antibiotic persistence is used to describe a bacterial population that suvives antibiotic exposure wihtout being resistant. (Huemer, “Antibiotic resistance and persistence – Implications for human health and treatment perspectives” EMBO Reports, 21, 2020)

To combat damage to themselves by antibiotics, bacteria have evolved stratgies that include both intrinsic and acquired resistance. Intrinsic resistance is ahceived by invactivaiton of antibiotics by hydrolytic or chemically modified enzymes, modification of antibiotic targets, cell membrane permeability barriers and antibiotic efflux pumps. In contrast, acquired antibiotic resistance is acieved through HGT, including transformation (bacteria absorb naked DNA for the eternal environment and insert it inot the genome), transduciton (chromosomal and extrachromosomal DNA is transferred between donor and recipitn bacteria via a bacteriophage intermediate), conjugation (mobile genetic elements such as plasmids and integratie and conjugative elements (ICEs) are transferred form one bacterium to another) adn membrane fesicle transport (vesicle-mediated transfer of DNA). These stregies ahve greatly helped bacteria to acquire resistance to antibiotics adn certian extensively ARB such as carbapenemase-producing colistin-resistant Klebsiella pneumonaie are now resistant to almost all antibotics.

Horizontal Gene Transfer:

Acquisition of foreign DNA material through horizontal gene transfer (HGT) is one of the most important drivers of bacterial evolution and it is frequently responsible for the development of antimicrobial resistance. Most antimicrobial agents used in clinical practice are (or derive from) products naturally found in the environmment (mostly soil). Bacteria sharing the environment with these molecules harbor intrinsic genetic determinants of resistance and there is robust evidence suggesting that such environmental resitome is a prolific source for the acquisition of antibiotic resistance genes in clinically relevant bacteria. Classically, bacteria acquire external genetic material through three main strategies (i) transformation (incorporation of naked DNA), ii) transduction (phage mediated) and, (iii) conjugation (bacterial “sex”). (Arias, “Mechanisms of Antibiotic Resistance” Microbiol Spectr, 2016, 4(2)).

The ecological role of naturally produced antibiotics should be to inhibit competitors. Given this role, resistance genes should have evolved to counteract antimicrobial action, so taht the function of each of these determinants is to avoid the activity of one specific antibotic (or a family of antibiotics with similar structures). Work with genes acquired by horizonatal gene transfer (HGT) confirm this idea. Plasmid-encoded beta-lactamases serve to resist beta-lactam antibiotics and are not active agaisnt other kinds of drugs. The same applies for mutation-drived resistance; quinolone reistance is the consequence of mutations in topoisoerases genes, which do not alter bacterial susceptibility to other antibotics. The only impact that hte acquisition of resistance is usually supposed to have on bacterial physiology is to produce a general metabolic burden. (Rojo, “Metabolic regulation of antibiotic resistance” FEMS Microbiol Rev 35 (2011) 768-789)

Mutations/modifications of an antibiotic target molecule:

Spontaneous mutations or post translational modifications of an antibiotic target molecule can elad to conformational changes that result in ineffective target binding and attenuation of antibiotic activity.

–Mutations in ribosomal protein genes: 

Ability to pump antibiotics out of cells: The production of complex bacterial machineries capable to extruTetracycline resistance is one of thede a toxic compound out of the cell can result in antimicrobial resistance.  classic examples of efflux-mediated resistance, where the Tet efflux pumps extrdue tetracyclines using protein exhcange as the source of energy. Currenlty, more than 20 different tet genes have been described, most of which are harbored in MGEs. (Arias, “Mechanisms of Antibiotic Resistance” Microbiol Spectr, 2016, 4(2)).

Decreased permeability of the bacterial cell membrane: Intracellular concentrations of antibiotics can be kept low via decreased permeability of the bacterial cell membrane, such as by reducing or mutating proins that would allow entry of antibiotic into the cell. (Huemer, “Antibiotic resistance and persistence – Implications for human health and treatment perspectives” EMBO Reports, 21, 2020)

Modifying antibiotics: Antibiotics can be inactivated by the transfer of chemical groups to vulnerable sites thus inhibiting target binding and function or directly destroyed by hydrolysis. Inactivation of antibiotics by addition of a chemical group, such as acyl, nucleotidyl, phosphate or ribitoyl groups, resulting in steric hindrance can casue antibiotic resistance.

Bacteria can also become resistant to antibiotics by the production of enzymes that digest/metabolize the antibiotic. (Popl, “ARDB-Antibiotic Resistance Genes Database” Nucleic Acids Research 2009, 37)

The main mechanisms fo beta-lactam resistance relies on the destruction of these compound by the action of beta-lactamases. These enzmes destroy the amide bond of the beta-lactam ring, rendering the antimicrobial ineffective. Beta-lactamases were first described in the early 1940s one year before penicillin was introduced to the market; however, there is evidence of their existence for millions of years. (Arias, “Mechanisms of Antibiotic Resistance” Microbiol Spectr, 2016, 4(2)).

Phenotypic Resistance:

Phenotypic resistance refers to those transient situations in which a bacterial population, otherwise susceptible to a given antibiotic, is refractory to its action. This transient resistance does not require a genetic change and thus it is not inheritable. The growth rate is the first parameter that impacts the phenotype of susceptibility to antibiotics of bacterial populations. The relevance of growth rate on the activity of penicillin was already described in 1944, in a study that showed that the activity o this antibotic was impared when cells grew slowly. However, this effect is not restricted to just beta-lactam antibiotics. It has been shown that resting cells are fully resistant to ampicillin or to tetracylcine, whereas streptomycin or ciprofloxacin is still active agaisnt cells in the stationary phase, although their activity is lwoer than that obeserved for exponentially growing bacteria. This situation has been called “drug indifference” and can be relevant for the persistence of bacterial infections even in patients under antibiotic treatment, when bacterai are in a host location that restricts grwoth or when the microoriganisms have ocnsumed the host resources and their growth is impaired. This can be particulalry important in the case of long lasting infections, becasue it was demonstrated that the concentraiton of antibiotics required to cure an experimental infection increases with the duration of the infection. The existance of resting or slow-growing cells which are refractory to treatment, is supposed to be the reason for the need to use prolonged regimes for treating infections by organisms such as Mycobacterium tuberculosis where hypoxia triggers dormancy and TB the organisms undergoes significant metabolic reprograming, with upregulation of stress-related gens and down-regulation of many central metabolism pathways. (Rojo, “Metabolic regulation of antibiotic resistance” FEMS Microbiol Rev 35 (2011) 768-789)

Metabolic Shifts:

Two other situations that might confer phenotypic resistance are persistence and growth in biofilms. Whereas it was first propsoed that this situation might be due to the existence of a fraction of nongrowing cells into any bacterial population that is phenotypically resitant to antibiotics, more recent work indicates that there are several difference mechanisms that can lead to prersistence. Metabolic enzymes, global regulationrs and toxin-antitoxin systems are among those elements that are relevant for devleoping persiter pehnotype. Among genes coding for metabolic enzymes, it was ofund that the lnockout of ygfA, which codes for a putative t-formyl-THF cycloligase involved in folate biosynthesis or of yigB, which may clock metabolism by depleting the pool fo flavin monoculcoetide, dereases persistence. Folate deficiency impaired the biosynthesis of purines, thymidilate and methionine. Overepxression of YgfA increased tolerance to ofloxacin. These reuslts support the existence of a linkdage between some specific metabolic pathways and bacterail persistence. Detailed anlsyes of P. aeruginosa biofims showed that the response to antibiotics was highly dependent on the metabolic state of each population. For instance, aerobically growing bacteria were sensitive to ciprofloxacin, but resistant to polymyxin, whereas the opposite was found for cells grwoting in the deepest part of the biofilm, which present an anaerobic metabolism. While some metabolic shifts can make bacteria phenotypically resistant to a particular antibotic, the opposite might occur as well where some specific grwoing conditions can make bacterai more susceptible during infection than when growing in vitro. For example, Listeria monocytogenes is an intracellular pathogen that grows inside mammal cells using hexose phosphates present in the host cytosol. For frwoing into host cells, Listeria upregulates a set of virulence detemrinatns, whose expression is under control of the transcriptional regulator PrfA. One of the PrfA0regulated determiants required for intracellular growth is the sugar phosphate transporter Hpt. This transporter is highly expressed during Listeria intracellular growth, but its expression is very low when bacteria grwo in vitro in the media regulalry used for suspectiblity tests. (Rojo, “Metabolic regulation of antibiotic resistance” FEMS Microbiol Rev 35 (2011) 768-789)

Given that antibiotic susceptbility can change as a consequence of laterations in the bacterail metabolism, it is conceivable that bacterail colonization of novel habits might select antibiotic resistance even int he absence of antibiotic selective pressure. One of the best known chronic infectious diseases is cystic fibrosis, which is the most prevalent inherited disease in the Caucasion population. CF pateitns suffer chronic infections in their lungs by different bacterail species such as P. aeruginosa. (Rojo, “Metabolic regulation of antibiotic resistance” FEMS Microbiol Rev 35 (2011) 768-789)

Introduction:

Type II diabetes or non-insulin-dependnet diabets mellitus accounts for over 90% of the diagnosed cases of diabetes and affects more than 16 million people in the US and some 200 million people around the world. Type II diabetes is a metabolic disease characterized by hyperglycemia and is a worldwide major public health care problem, affecting some 194 million worldwide.

Pathology:

Decreased Insulin Receptors/Insulin Resistance: Contrasting with type I diabetes, type II diabetic individuals have normal or even greatly elevated insulin levels. Their symptoms arise from an apparent paucity of insulin receptors on normally insulin responsive cells. It has been hypothesized that the increased insulin production resulting from overeating, consequent obesity, eventually, suppresses the synthesis of insulin receptor.  In Type II diabetic people, either the body does not produce enough insulin or the cells ignore insulin. Thus, instead of being absorbed by the cells, the glucose remains in blood leading to hyperglycemia.

Studies of genetically predisposed individuals have indicated that insulin resistance in the muscle is the primary or initating defect leading to the ultimate development of T2D. Thus, skeletal muscle is a mian target to fight against development of insulin-resistance in prediabetic state or during early stage of T2D. (Magnan, “Regnerating islet-derived protein 3 alpha: a promising therapy for diabetes. Preliminary data in rodents and in humans” Heliyon 8 (2022).

Inflammation: Type 2 diabetes is associated with a high cardiovascular risk, which is even increased if renal damage is superimposed. Peripheral blood mononuclear cells (PBMCs) and pro-inflammatory cytokines are key factors linking type 2 diabetes and atherosclerosis. Navarro (Nephrol Dial Transplant (2008) 23: 919-926) discloses disclsoses isolating PBMCs from diabetic patients with normal renal function and different stages of diabetic nephropathy and showing a relationship between inflammatory activation of PBMCs by enhanced mRNA expression of TNF-alpha and IL-6.

Causes of Diabetes

Obesity is the most important nutritional disorder in the western world, with the estimates of its prevalence ranging from 30-50% within the middle aged population. It is usually defined as a body weight more than 20% in excess of the ideal body weight. Obesity is associated with an increased risk for cardiovascular diseases, diabetes, stroke, muscular dystruphy and infertility. In particular, obesity can evolve to type II diabetes in successvie phases.

Obesity is defined by the WHO as an abnormal or excessive fat accumulation that may impair health. It is defined by body mass index (BMI), weight in kilograms divided by the square of height in meters, in adults over 30 kg/m2. (Chavda, Molecules 2022, 27, 4315).

The genetic basis for obesity and diabetes has gradually progressed. Zhang cloned the mouse obesity (ob) gene and its human homologue in 1994 (Zhang, Nature, 372 (2994) 425-432). Mutation in ob leads to symptoms of obesity. Several other single gene mutations resulting in obesity in mice have been identified. For example, the yellow mutation at the agouti locus has been found to cause a pleiotropic syndrome which causes moderate adult onset obesity, a yellow coat color, and a high incidence of tumor formation (Herberg and Coleman (1977), Metabolism 26: 59) and an abnormal anatomic districution of body fat (Coleman (1973) Diabetologia 14: 141-148).

The most widely used method to gauge obesity is the body mass index BMI which is equal to weight-height2in kg-m2.  A BMI of 30 is most comonly used as a thereshold for obesity. A BMI between 25’30 should be viewed as medically significant.

Complications/Symptoms of Diabetes:

see WebMD (discusses diabetic nephropathy, diabetic neuropathy, and diabetic retinopathy).

Prevention/Treatment Strategies:

Treatment of T2D includes lifestyle changes such as diet, exercise, and mutraceuticals, as well as administration of medications such as metformin. Conventionally, two sorts of therapeutic agents have been used for the treatment of T2D. (Chavda, Molecules 2022, 27, 4315).

The obesity market is currently dominated by Novo Nordisk and Eli Lilly. Several companies including Pfizer, Roche, Viking Therapeutics and Rivus Pharmaceuticals are also developing obesity therapeutics. Some leverage the GLP-1 pathway, while others commit to different mechanisms, including amylin analogs and mitochondrial uncoupling. Other players in the space include Veru Pharmaceuticals, Regneron, Altimmune, Amgen and Amylyx.

Currenlty, various pharmacological approaches are avialbe for treating hyperglycemia and subsequently, T2DM. These may be groups into the following classes:

Insulin secretogogues: including sulphony-ureas (e.g., glipizide, glimepiride, glyburide), meglitinides (e.g., nateglidine, repaglinide), dipeptidyl peptidase IV 9DDP-IV inhibitors (e.g., sitagliptin, vildagliptin, alogliptin, dutogliptin, linagliptin, saxogliptin), and glucagon-like peptide-1 receptor (GLP-1R) agonists (e.g., liragludie, albiglutide, exenatide, lixisenatide, dulaglutide, semaglutide) which enahce secretion of insulin by acting on the pancreatic beta-cells. Suponyl-ureas adn meglitinides have limited effiacy and tolerability, cause weight gain and often induce hypoglycemia. DPP-IV inhibitors have limited efficacy. Marekted GLP-1R agonists are peptides adminsitered by subcutaneous injection. Liraglutide is additionally prroved for teh treatment of obesity.

Biguanides (e.g., metformin) are thought to act primarily by decreasing heaptic glucose production. Biguanides often casue gastrointestinal disturbances and lactin acidsosis, further limited their use.

Inhibitors of alpha-glucosiase (e.g., acarbose) decreases intestinal glucose absorption. These agents often cause gastrointestinal disturbances.

Thiazolidinediones (e.g. pioglitazone, rosiglitazone) act on a specific receptor (peroxisome proliferator-activated receptor-hamma) in the liver, musle and fat tiessues. They regualted lipid metabolism subsequently enhancing the response of these tissues to the actions of insulin. Frequent use of these drugs may lead to weight gain and may induce edmea and anemia.

Insulin is used in more severe cases, either alone or in combination with the above agents, and frequent use may also lead to weight gain and carries a risk of hyoplycemia.

Sodium-glucose linked transporter cotransporter 2 (SGLT2) inhibitors (e.g., dapagliflozin, empagliflozin, canaglifloxin, ertugliflozin) inhbit reabsorption of glucose in the kidneys adn thereby lwoer glucose levesl int he blood. This emerging class of drugs may be assocaited with ketoacidosis and urinary tract infections.

Lectins:

–Regenerating islet-derived protein 3alpha (Reg3alpha, Reg3A) (hepatocarcinoma-intestinal-pancreas/pancreatitis-associated protein (HIP/PAP)): is a 16 kDA type C lectin protein with a single carbohydrate binding domain. Reg3alpha is also secreted and carries out its biological activites in an autocrine and paracine manner. It could also act in an endocrine manner since it is also detected in the bloodstream. This protein has been shown to drive tissue repair and regeneration as well as protection against oxidative sttress and cell death in the liver, pacreas and intestine. It also promotes motor neuron axonal survival and guidance and Schwann cell proliferation. It shows anti-inflammatory activites and yeilds antibacterial activiteis in the digestive tract. The prtoein shows an intrinsic ROS cavenger actiity targeted on the extra-cellular matrix in the context of inflammation. Administration of Reg3alpha has been shown to control glucose homeostasis and could potentially be a new target of interest in the treatment of type 2 daibetes. In this respect, recombinant human Reg3alpha prtoein was adminsitered to insulin resistant mice fed a high fat diet. An increase in insulin sensitivity during an oral glucose tolerance test and decrease in teh pro-inflammtory cytokine C-X-C Motif Chemokine Ligand 5 (CXCL5) was evidenced. There was also an increase in glucose uptake in the skelatal musle. (Magnan, “Regnerating islet-derived protein 3 alpha: a promising therapy for diabetes. Preliminary data in rodents and in humans” Heliyon 8 (2022).

Biomarkers Related to Diabetes:

Lower Your A1C levels:

When you have diabetes you should check your blood sugar regularly. Also recommended is to check A1C levels, which measures the amount of sugar which attaches to the protein hemaglobin. In general, A1C levels should be below 7%. When you take steps ot lower your A1C, you can reduce complications such as nerve damage, eye problems and heart disease.

Incretins (“Incretin homones):

Incretins stimulate beta cells to release insulin and were discovered in the early 1972. These products are secreted in the intestine, affecting the functioning of beta cells. The most commonly known incretins include glucagon-like peptide-1 (GLP-1) and glucose-dependent inulinotropic polypeptide (GIP). GLP-1 and GIP are peptide hormones that are secreted with the benefit of utilizing cells from intestines called enteroendocrine cells in reaction to the consumption of nutrients, and they have an important function in posprandial metabolism. With the identification of glucose equilibrium, their most favorable condition, the incretin effect, begins to improve the glucose-stimulated release of insulin from the pancreas. GIP is considered to be the essential incretin hormone accounting for this effect.( Chavda, Molecules 2022, 27, 4315)

GLP-1 is a 30 amino acid long incretin hormone secreted by the L-cells in the intestine in response to ingestion of food. GLP-1 has been shown to simulate insulin secretyion in a physiological adn glucose-dependent manner, decrease glucagon secretion, inhibit gastric emptying, decrease appetite, and stimulate proliferation of beta-cells. In non-clinal experiments GLP-1 promotes continued beta-cell competence by stimulating transcription of genes important for glucose-dependent insuline secretion and by promoting beta-cell neogensis. In a healthy individual, GLP-1 plays an important role regualting post-prandial blood glucose leves by sitmulating glucose-dependet insulin secretion by the pancrease resutling in increased glucose absorption in the periphery. GLP-1 also suppresses glucoan secretion leading to reduced heaptic glucose output. In addition, GLP-1 delays gastric emptying and slows small bowel motility delaying food absorption. In people with T2DM, the normal post-prandial rise in GLP-1 is absent or reduced. (WO 2018/109607)

In 2019, the FDA approved Novo’s Rybelsus for the first oral GLP-1 for type 2 diabetes. Considered by many to be the next frontier in obesity treatment, oral medicines are under development by a number of companies, including Novo, whose amycretin is in phase I trials  and Lilly, which has a Phase III trial underway for orforglipron. Brazilian owned multinational company Eurofarma also has a Phase III study under way for its oral candidate sibutramine/topiramate XR. Phizer recently accouned that it would move forward with a modified release formulation of its candidate danuglipron and in December 2023, San Francisco-based Structure Therapeutics accouned postive resutls form a Phase IIa trail of its weight-loss pill GSBR-1290. (clinicaspace, “Obesity and Diabetes Markets Explode”, 2024).

Glucagon-like peptide 1 (GLP-1) Agonists:

GLP-1 receptor agonists make up a class of medications used for the treatment of type 2 diabetes and obesity. The first GLP-1 receptor agonist to reive FDA approval was exenatide in 2005 and the FDA subsequently approved several other drugs with the same mechanisms of action. More than 15 years latter, these products remain costly with monthly net prices rising to more than $600 in 2017. The mediuan annual out of pocket cost in Medicare Part D exceeded $15000 in 2019. Manufacturers earned mroe than 10 billion on GLP-1 agonists in the US alone in 2021. (JAMA, “Patents and Regulatory Exlusivities on GLP-1 Receptor Agonists”, 2023, 330(7)).

Other FDA approved GLP-1 receptor agonstis include Victoza (Liaglutide), Bydureon (Exenatide), Saenda (Liraglutide), Adlyxin (Lixisensatide), Xultophy (liraglutide), Soliqua (lixisenatide)and Ozempic, Rybelsus (Semaglutide).

Most marketed GLP-1 receptor agonists are drug-device combinations with active ingredients sold together with their subcutaneous inector pens. Device patents expiring later than other patents may force generic firms to either wait until these patents expire before market entry or undertake lenghty and costly patent challenges. (JAMA, “Patents and Regulatory Exlusivities on GLP-1 Receptor Agonists”, 2023, 330(7))

GLP-1 is a hormone that is screted by the small intestine, generally promotes the biosynthesis and secretion of insultin, inhibits the secretion of glucagon. (Song, WO 2008/082274)

Song, WO 2008/082274 discloses an insulinotropic peptide for promoting the syntehsis and expression of insulin such as GLP-1 conjugate haivng improved in vivo duration and stability which includes an insulinotropic peptide, a non-peptide polymer and an immunoglobulin Fc region which are covalently linked to each other. If the insulinotropic peptide to be coupled at a site other than the N-temrinus, a reactive thiolgroup can be introduced to the site of amino acid resiude to be modified in the native amino acid sequence to form a covalent bond using a maleimide linker at hte non-peptidyl polymer. Alternatively, a reactive amine group can be introduced to the site of amino acid resiude to form a covalent bond using an aldehyde linker at the non-eptidyl polymer.

–Exenatide (Gyetta, AstraZeneca):  is a GLP-1 receptor agonist released from the gut and acts to increase glucose-dependent insulin secretion from pancreatic beta cells, suppress glucagon secretion, delay gastric emptying, and reduce food intake. The binding of the drug to pancreatic GLP-1 receptors mediates these actions. Administration of exenatide has shown restoration in the insulin response that is usually defective in type 2 diabetic patients. Researchers also observed the prolonged release of insulin in response to elevated glucose levels was also observed in patients treated with exenatide. Treatment with exenatide leads to the decreased release of glucagon during hyperglycemic periods, which reduces hepatic glucose output as well as decreases insulin demand. Delayed gastric emptying decreases the rate at which glucose arrives in the bloodstream. Exenatide is available as an immediate-release solution and extended-release suspension for subcutaneous administration. The administration of these injections should be in the thigh, abdomen, or upper arm. Additionally, patients should receive instruction to use a different injection site for each dose to prevent infection.

Exenatide is made by Amylin Pharmaceuticals and commercialized by AstraZeneca. Exenatide was approved by the FDA in April 2005, for people whose diabetes is not well controlled on other oral medications.

–Semaglutide (Ozempic, Novo Nordisk): is a GLP-1 RA and widely used. An oral form of Simaglutide to be adminsitered once a wekk is also available. (Chavda, Molecules 2022, 27, 4315)

–Tirzepaptide (Mounjaro™): is comparable to GLP-1 agonists, as it is a dual GIP/GLP-1 agonist. The FDA has approved tirzepatide under the brand name Mounjaro, which has become a revolutionary agent for the management and treatment of T2D and achieving weight loss. The most common side effects assocaited with tirzepatide are related to gastrointestinal tract like nausea, vomiting and diarrhea. Tirzepatide is a single molecule that combines dual agonism of glucose-dependent insulain tropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. Tirzepatide binds to GIP and GLP-1 receptors with high affinity that is similar to that of native GIP and about 5 fold weaker than that of native GLP-1. Native GIP and GLP-1 are incretin hormones that stimulate insulin secretion and decrease glocagon secretion. GIP also plays a role in nutrient and energy metabolism, while GLP-1 also delays gastric emptying, suppresses appetide and improved satiety. Eli Lilly is developing irzepatide for the treatment of type 2 diabetes mellitus (T2DM), obesity, cardiovscular disorders in T2DM, hert failure, non-alcoholic steatohepatitis, obstructive sleep apnoea and for reducing mortaility/morbidity in obsity. (Syed Druges (2022) 82: 121-1220).

Tirzepatide is a synthetic linear peptide molecule containing 39 amino acids. Residues derive form GLP-1, GIP and semaglutide and few residues are unique. The strucure is based on the native GIP sequence and includes C20 fatty diacid moeity (eicosanedionic acid) linke via hydrophilic linkesconnecte to lysine reisudes at C20 position. The peptide sequence contains two non-coded amino acid resiudes at position 2 and 13 which are responsible for its long half-life and high affinity to albumin. The main critical improvements are modificaiton of residues in the peptide backbone to obtain GIP receptor activating activity. Tirzepatide is the first agent that functions as a dual agonist for the two main human GLP-1 and GIP incretins. It has impressive glycemic efficacy. Moreover, it is the first effective drug to have demonstrated notable body weight loss in a phase 3 study in patients with T2D. Trizepatide has significanlty better therapetuic efficacy than current drugs. It is also superior to semaglutide and insulin degludec. Phase 1 clinicl trails which lasted for 4 weeks, followed by 4 weeks of safety investigation, for tirzepatide showed a remarkable statistical decrease in HbA1c, and postprandial glucose levels were also found to be diminished. A 26 week long phase 2 clinical trials, which also included a dulaglutide group, showed better efficacy over dulaglutide. It also contributed to reduction of weight and decreased appetide in the subjects. In the SURPASS-1 phase 3 clinical trails, which included six countries worldwide, patietns who had ongoing treatment with SLGT2 inhibitors were included. Soytel with or without metformin, a dose-dependent impact on HbA1c and weight loss was observed, which was larger than that of the slective GLP-1RA dulaglutide. Meanwhile, in a 12-week phase 2 trial with moderate dose escalation regimens, gastrointestinal tolerability improved when starting with a lower dose and slowly increaseing to the highest effective doses. Other additional effect of tirzepatide were noted to lowering the concentrations of very low-density lipoproteins and triglycerides, in addition to a reduction in blood pressure, as well as an elevation of high density lipoprotein concentraiton. The adverse events most commonly reported were nausea, vomiting and diarrhea, which were mild to moderate and occurred mostly during the dose-escalation period.   (Chavda, Molecules 2022, 27, 4315) Besoe most common adverse events were gastrointestinal events, including nausea, vomiting and diarrhea. Most of these events were mild to moderate. n (US 2020/0023040) disclsoes administration of tirzepatide from a lower starting escalation dose to a higher maintenance dose.

Metformin: is an FDA approved drug to treat Type 2 diabetes. It is an oral medication approved for people as young as 10. While Mounjaro provides better blood glucose control and more potential weight loss than metformin, metformin is often more cost effective for many people. Metformin has been a mainstay when it comes to treating type 2 diabetes for decades. Metformin remains the go to choice for many providers when prescribing a Type 2 diabetes medication because it works and is cost effective. Metformin effectively lowers hemoglobin A1C (HbA1C or A1C). Your A1C represents your average blood glucose over 3 months.

Metformin is a biguanide. Similarly to Mounjaro, it lowers the amount of glucose the liver makes. But Metformin does not increase pancreas release of insulin. Instead, it makes the body more sensitive to the insulin one makes naturally. It also lowers the amount of glucose one absorbed from the food. Because Mounjaro and metformin work in two different ways, they can be combined for additional blood glucose improvement.

–Metformin and Herbal Formula:

Metformin and a Chinese herbal formula may ameliorate type 2 diabetes with hyperlipidemia via enriching beneficial bacteria, such as Blautia and Faecalibacterium. The herbs used were Rhizona Anemarrhenae, Momordica charantia, Coptis chinensis, Ale vera and red yeast rice (Zhao, “Structural alteration of gut microbiota during the amelioration of human type 2 diabetes with hyperlipidemia by Metformin and a traditional chinese herbal formula: a multicenter, randomized, open label clinical trial” mBio, May/June 2018, volume 9).

Naltrexone and Bupropion (Takeda, Contrave): is indicated for weight loss. BUPROPION; NALTREXONE is a combination of two drugs that helps one lose weight. The product is used with a reduced calrie diet and exericse. The product can also help in maintaining weight loss. Pateints should watch out for new or worsening depression or thoughts of suicide.

liraglutide (Novo Nordisk, Victoza): is approved in 2010 for type 2 diabetes.

Insulin: insulin or its analogs, such as insulin lispro, insulin aspart, and oral agents like glipizide, glimepride, metformin, acarbose, pioglitzone and saagliptin. In addition to these agents, a short acting insulin that can be inhaled just before nutrient intake –Exubera® –haary 2006. (Chavda, Molecules 2022, 27, 4315)s been approved by the FDA in Junuary 2006. (Chavda, Molecules 2022, 27, 4315)

–NovoLog is a modified type of medical insulin used to treat type 1 and type 2 diabetes. It is generally used by injection under the skin but may also be used by injection intoa vein. It works like human insulin by increasing the amount of glucose that itssues take in and decreasing the amount of glucose made by the liver. It is a manufactured from of human inslun where a single amino acid hs been changed (protein with aspartic acid at the B28 potion). It was approved by the FDA in 2000. In 2022, it was the 76th most commonly prescribed medication in the US. Manufacturing includes eyast, which have had the gene for insulin aspart put into their genome.

Inhbitors of sodium-glucose cotransporter 2 (SGL2):

–Empaglifloxin (Jardiance): is an antidiabetic mediciton used to improve glocuse control in people with type 2 diabetes. It is taken orally. The use of empaglifloxin has been shown to improve outcomes in epople with established CVD and it can help to slow the rate of kidney funciton decline. It is an inhibitor of the sodium glucose co-transporter-2 (SGLT02) and works by increasing sugar loss in the urine. It was developed by Boehringer Ingelheim and is co-marketed by Eli Lilly. It is on the EHO Model List of Essential Medicines

–Farxiga (Dapagliflozin): is used to treat type 2 diabetes. It is also used to treat adults with heart failure and chronic kidney disease. It reversibly inhibits sodium-glucose co-transporter 2 (SGL2-) in the renal proximal convoluted tubule to reduce glucose reabsorption and increase urinary glucose excretion. It was developed by Bristol-Myers Squibb and AstraZeneca. It is on the WHO Model List of Essential Medicines

Organ transplantes: In the late 1990s, ressearchers first showed that pancreatic islet cells recovered form deease donors could help patients with T1D live an insulin-free existence. However, only a limited number of donor pancreases are available each year and those organs are often of variable quality. (Eli Dolgen Nature Biotechnology, 40, March 2022, pp. 291-295)

Stem Cell Protocols:

Stem cel differentiation proteocls (initially for naked administraiton together with immunosuppression)geard toward producing insulin-producing beta cells has been of intense focus given the limited availability and quality of deceased donor pancreatic islet cells. In parallel, the field has endeavored to obviate the need for immunosuppression through the use of immune privileged devices or protective materials; an approach called “islet encapsulation”. ViaCyte for example is focused on adminsitering its cells inside ouches deisgned to keep out immune cells. This encapsulation device named “Encaptra” is a pouch made of polytetrafluoethylene membranes with 0.45 um pores that is inserted into a skin flap The device relies on a well-characterized human enbryonic stem cell (hESC) line known as CyT49, The cmpany then oconverts those cells into pancreatic progenitors through a stepwise differentiation protocl. Over the course of 12 days in the laboratory, the cells progress sequentially through various stages of develoment –mesendoderm, anterio definitive endoderm, primitve gut tube, posterio foregul, before forming the pancreatic endoderm cells which go into the transplantable packets. (Eli Dolgen Nature Biotechnology, 40, March 2022, pp. 291-295)

Introduction: Definitions:

During embryoic development, cells specialize in carrying out particular functios. In all animals except sponges, the process is irreversible: once a cell deifferentiates to serve a function, it and its descendants can never serve any other. A sponge cell that had specialized to serve one function (such as lining the cavity where feeding occurs) can lose the special attributes that serve that funciton and change to serve another function (such as being a gamete). Thus a sponge cell can dedifferentiate and redifferentiate. Cells of all other animals are organized into tissues, each of which is characterized by cells of particular morphology and capability. The fact that all other animals differnetiate irreversibly suggests that organisms with bodies contining cells specialized to serve particular functions may have an advantage over those with cells that potentially have multiple functions.

In the process of embryonic development, the cells of mot types of animals organize into three layers (called germ layers): an otuer extoderm, an inner endoderm and an intermediate mesoderm.

Blastula: Shortly after fertilization, an animal zygote first undergoes a series of mitotic divisions, called cleavage, which produces a ball of cells, the blastula.

Blastopore: In most naimals, the blastula fold inward at one point to form a hollow sac with an opening at one end called the blastopore.

Endothermy: Mammals are endothermic, an adaptation that has allowed them to be active at any time of the day or night. Also, more efficient blood circulation provided by the four chambered heard and more efficient respiration provided by the diaphragm make possible the higher metaboix rrate on which endothermy depedns.

Gastrula: An embryo at this stage is called a gastrula. The subsequent growth adn movement of the cells of the gastrula differ form one group of animals to another, relfecting the evolutionary history of the group.

Larva: Embryos of most kinds of animals develop into a larva, which looks unlike the adult of the species, lives in a different habitate, and eats different sorts of food. In most groups it is very small. A larva undergoes metamorphosis, a reorganization, to transform into the adult body form.

Mammals: Most mammals are herbivores,e ating mostly or only plants. Cellulose forms the builk of a plant’s body and is a major source of food for mammalian herbivores. Mammals do not have the necessary enzymes, however, for breaking the links between glucose molecuels in cellulose. Herbivorous mammals rely on a mutualistic partinership with bacteria in their digestive tracts that have the necessary cellulose splitting enzyems. Mammls such as cows have huge, four chambered fermentation vats derived form esophagus and stomach. The first chamber is the largest and holds a dense population of cellulose digesting bacteria. Rodents, horses, rabbits and elephants, by contrast, have relatively small sotmachs and instead difgest plant material in their alrge intestine, like a temrite. Even with these complex adaptations for digesting cellulose, a mouthful of plant is less nutritious than a mouthful of meat. Herbivores must consume alrge amounts of plant material to gain sufficient nutrition.

Placenta: In most mammla species, females carry their developing young internally in a uterus, nourishing them through the placenta. The placenta is a specialized organ that brings the bloodstream of the fetus into close contact with the bloodstream of the mother. Food, water and oxygen can pass across and wastes can pass over to the mother’s blood and be carried away.

Primates: are the mammalian group that gave rise to human species. In general, humans and chimpanzees exhibit a level of genetic similartiy normally found between closely related species of the same genus. In fact, there is a 99% sequence similarity between chimpanzees and humans.

Tissues: The cells of all animals except sponges are organized into structural and funcitonal units called tissues –collections of cells that are specialized to perform specific tasks.

Development of Particular Types of Animals:

Sponges:

As is true of many marine invertebrate animals, larval sponges are free swimming. After a sponge larva attaches to an appropriate surface, it metamorphoses into an adult and remains attached to that surface for teh rest of its life.

A unique feature of sponge cells is theri ability to differentiate form one type to anotehr, and to dedifferentiate from a specialized state to an unspecialized one. If a sponge is put thorugh a fine sieve or coarse cloth so that the cells are separated, they will seek each other out and reasemble the entire sponge -a phenomenon that does not occur in any other animal.

Flatworms:

Like sponges, a flatworm lacks a circulatory system for teh transport of oxygen and food molecules. The thin boyd of a flatworm allows gas to diffuse between its cells and the surrounding enviornment (oxygen diffuses in and carbon dioxide diffuses out).

The reproductive systems of flatworms are coplex. Most are hermaphroditic, each individual containing both male and female sexual strcuture. In most freshwater faltworms, fertilized eggs are laid in cocoons strung in ribbons and hatch into miniature adults. In constast, some marine species pass thorugh a larval stage, the fertized egg undergoing spiral cleavage, and the embryo giving rise to a larva that swims or drifts until metamorphosing into an adult, at which point it settles in an appropriate habitate.

Flatworms are known for their regenreative capacity: when a single individual of some species is divided into two or more parts, an entirely new flatworm can regrow what is missing from each bit.

Reptiles: Many lizards, including anoles, skinks and geckos, ahve the ability to lose their tails and then regenerate a new one. This ability allows these lizards to exape from predators.

Birds: Modern birds lack teeth and have only vestigial tials, but they still retain many reptilian characteristics. For instance, birds lay aminiotic eggs. Also, reptilian scales are present on the feet and lower legs of birds. Feathers are modified reptilian scales made of keratin, jsut like hair and scales. Feathers provide lift for flight and conserve heat. Feathers develop from tiny pits in the skin called follicals.

The revved-up metabolism need to power flight requires efficient blood circulation, so taht the oxygen captured by the lungs can be delivered to the flight muslces quickly. In the heart of most living reptiles, oxygen rich blood coming from the lungs mixes with oxygen poor blood returning from the body becasue the wall dividing the ventricle into tow chambers is not compelte. In birds, the wall dividing the ventricle is complete, and the two blood cirulations do not mixe. So flight muscles receive fully oxygenetaed flood.

Mammals: There are about 4000 living species of mammals which is less than the number of fishes, amphibians, reptiles, or birds. Most large, land swelling veterbrates are mammals. Mammals are distinguished form other classes of verterates by hair and mammary glands.

–Bats: are the only mammals capable of powered flight. Like the wings fo birds, bat wings are modified forelimbs, but bats have developed wings by modifying theirforearms in different ways.

Circulatory System:

Open circulatory system:

In an open circulatory system, the blood passes from vessels into sinuses (open areas within the body), mixes with body fluid that bathes the cells of tissues, then reenters vessels in another location.

Closed circulatory system:

In a closed circulatory system, the blood flows entirely within blood vessels, so it is physically separated for other body fluids. Blood moves thorugh a closed circulatory system faster and more efficiently than it does thorugh an open system.

Development of Plants:

Meristems: Meristems are clusters of small cells with dense cytoplams and proportinately large nuelei taht act as stem cells. One cell divides to give rise to two cells, of which one reamins meristematic, while the other udnergoes differentiation and contributes to the plant body. In this way, the population of meristem cells is continually renewed. Molecular genetic evidence supports the hypothesis that animal stem cells and plant meristem cells may share some common pathways of gene expression.

Transmissible spongiform encephalopahties (TSEs) are an unusual group of diseases characterized by the presence of numerous small cavities in the brains of affected individuals. These cavisties are casued by the loss of neurons, and can take decades to form following the initial infection by the causative agent.

TSEs include scapie in sheep, bovine spongiform encepholopathy (BSE( or “mad cow” disease, chronic wasting disease in deer, and Creutzfeld-Jakob disease (CJD) in humans.

TSEs can be transmitted experimentally by ijecting infected brain tissue into a recipient animal’s brain. TSEs can also spead via tissue transplants and apparently by consumption of tainted food. In the late 20th century, the diease kuru was discovered among member of the Fore people of Papua New Guidea. These members engaged in ritualistic consumption of their dead which lead to the spread of a commonly fatal TSE through the tribes.

Mad cod disease spread widely among cattle herds of England in the 1990s becaseu cows were fed bone meal prepared form sheep and cattle carcasses to increase the protein content of their diet. Like the Fore, teh cattle were eating the tissues of animals that had died of the disease.

TSEs are casued by prions (proteinaceous infectious particles).

Human Cell Atlas (maps every cell of the human body)

See also types of cells

See also fertilization and embryonic development

Introduction:

Cell development starts as a fertilized egg (Zygote) that must undergo cell division to produce the new individual. Thus extensive cell divisions is required. However, in many cases it does not incuded much growth as the egg cell itself is quite large.

As cells divide, precise changes in gene expression result in differences between cells that ultimately result in cell specialization. In differentiated cells, certain genes are expressed at particular times, but other genes may not be expressed at all.

Pattern formation involves cells abilities to detect positional information that guides their ultimate fate. In animal embryos, the timing and number of cell divisions are species specific, and this period of rapid cell division following fertilization is called cleavage. During cleavage, the enormous mass of the zygote is subdivided into a larger and larger number of smaller and smaller cells, called blastomeres. Cleavage is not done by an increase in the overall sie of the embryo. The G1 and G2 phases of the cell cycle, during which a cell increases its mass and size, are greatly shortened or climinated alltogether during cleavage. This is controlled by cyclins and clin-dependent kinases. For exaple, zebrafish blastomeres divide once every 15 minutes during cleavage to create an embryo with a thousand cells in just under 3 hours. As a comparison, cycling adult human intestinal epithelial cells divide on average once every 19 hr.

As development continues the form of the body, its organs and anatomical features is generated. Morphogenesis may invovle cell death, cell division, cell migration, changes in cell shape and differentiation.

Cell Differentiation:

A human contains about 300 ytes of differentiated cells. They can be distinguised based on the particular porteins they synthesize, their morphologies and their specific functions. During development, cells become different from one another because of the differential expression of subsets of genes, both at different time and in different locations of the devleoping embryo.

Before differentiation takes place, cells make a molecular decision to become a particular cell type. The standard procedure to test whether a cell or group of cells is determined is to move the donor cell(s) to a different location in a host embryo. If the cells of the transplant develop into the same type of cell that they would have if left undisturbed, they they are considered to be determined. For example, a cell in the prospective brain region of an amphibian embryo at the early gastrula stage has not yet been determined if transplanted elsewhere in the embryo. It will develop according to the site of transplant. By the late gastrula stage, however, additional cell interactions have occurred and determination has taken place. The cell will develop as neural tissue o matter where it is transplanted.

Determination usually takes places in stages, with a cell first becoming partially committed. In a chicken embryo, for example, tissue at the base of the leg bud normally gives rise to the thigh. I this tissue is transplanted to the tip of the identical looking wing bud, which would normally give rise to the wing tip, the transplanted tissue will develop into a toe rather than a thigh. The tissue has already been determened, but it is not yet committed to being a particular part of the leg. Thus, it can be influenced by the positional signaling at the time of the wing bud to form a tip but in this case, a tip of leg.

Cells initiate development by using transcription factors to change patterns of gene expression. When genes encoding these transcription factors are activated, one of their effects is to reinforces their own activation. This reinforcement makes the developmental switch deterministic, initiating a chain of events that leads down a particular developmental pathway.

Cells in which a set of regulatory genes have been activated may not actually undergo differentiation until some time later, when other factors interact with the regulatory proteins and cause it to activate still other genes. Nevertheless, once the initial “switch” is thrown, the cell is fully committed to its future developmental path.

Cells become committed to follow a particular developmental pathway by differential inheritance of cytoplasmic determinants, which are maternally produced and deposited into the egg during oogenesis or via cell-cell interaations.

Plant Development:

A major difference between animals and plants is that most animals are mobile. Plants, in contrast, are anchored in position and most therefore endure whatever environment they experience.

Instead of creating a body in which every part is specified to have a fixed size and location, a plant assembles its body throughout its life span from a few types of modules, such as leaves, roots, branch nocdes and flowers. Each module has a rigidly controlled structure and organization, but how the modules are utilized is flexible; it can be adjusted to environmental condtiions.

Plasnts develop by building their bodies outward, creating new parts from groups of stem cells that are contained in structures called meritems. As meristomatic stem cells cotinually divide, they produce cells that can differentiate into teh tissues of the plant. The plant cell cycle is regualted by the same mechanisms as animal cells and yeast by cyclins and cyclin-dependent kianses. For example, overexpression of a Cdk inhibitor can result in strong inhibition of cell division in leaft meristems, leading to significant changes in leaf size and shape.

Lipolytic enzymes are a group of enzymes that break down water-insoluble esters and produce fatty acids. They are used in many industrial processes including detergents, fuels, clothing, beverage and pulp. 

Phospholipase Enzymes

Phospholipase A2 (PLA2):

–Structure/mechanisms of action: PLA2 belongs to the lipolytic family of enzymes that hydrolyze the ester bond at the sn-2 position of the phospholipids. Upon hydrolysis of the phospholipids, PLA2s release free fatty acids and generate lysophospholipids (LPLs). Free fatty acids such as arachidonic acid (AA) and oleic acid (OA) are important sources of energy. (Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023). 

A Ca2+ ion is required for both binding of the substrate and for catalysis. However, Group VI phospholipase A2 enzymes are members of the PLA2 superfamily that are characterized as Ca2+-independent PLA2 (iPLA2) enzymes. (Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

PLA2s exist as active enzymes and as inactive PLA2-like proteins in snake venom. PLA2 enzymes catalyse the hydrolysis of the sn-2 ester bond of cell-membrane phospholipids and are classified into 14 groups, from which the groups IA and IIA are present in elapid and viperid venoms. (Fernandes, “The chemistry of snake venom and its medicinal potential” Nature. 6, 451-469 2022). pages451–469 (20pages451–469 (2022)

–Functions:

The PLA2s play important roles both physiologically and pathologically, with their expression increasing significantly in diseases such as sepsis, inflammation, different cancers, glaucoma, obesity and Alzheimer’s disease. Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

The PLA2 superfamily has been classified into 16 groups (groups I to XVI), based on the chronology of their discovery, as well as based on their location in the body, substrate specificity. Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

PLA2-IIA also plays a major role in host defense via its antimicrobial activity. It degrades bacterial membrane by hydrolyzing phosphatidylethanolamine and phosphatidylglycerol, which are abundant in the bacterial membrane. Blood plasma concentration of sPLA2-IIA can increase up to 500-fold in patients with acute diseases such as sepsis, peritonitis and bacterial infection, compared to healthy persons. (Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

Secreted PLA2s, especially groups IIA, V and X, can play an important role in atherosclerosis. A study showed that young adults (age 24 to 39 years) with cardiovascular disease had an increased level of GIIA sPLA2 in their blood plasma, which may contribute to atherogenicity. (Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

sPLA2s are widely known to be overexpressed in various tumors and cancer cells. (Khan, “The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles” Intl J. Mol Sci, 24(2), 2023).

The Copyright Office has published a report on copyright and artifical intelligen (AI) which can be found at chrome-https://www.copyright.gov/ai/Copyright-and-Artificial-Intelligence-Part-1-Digital-Replicas-Report.pdf.

The Report uses the term “digital replica” to refer to a video, image, or audio recording that has been digitally created or manipulated to realistically but fasely depict and individual. 

The Report notes many deficiencies with respect to existing laws as they apply to digital replicas. For example, digital replicas that are produced by ingesting copies of preexisting copyright works, or by altering them, such as superimposing someone’s face onto an audiovisual work or simulating their voice singing they lyrics of a musical work, may implicate copryight exclusive rights, including the rights to reproduce a work and to prepare derivative works. Copyright does not, however, protect an individual’s identiy in itself, even when incorproated into a work of authorship. 

Under the Lanham Act, claims such as false endorsement involving a digital replica are limited to unauthorized commercial uses, and most federal courts also require a showing of consumer awareness of the depicted individual in order to establish a likelihood of confusion, limiting the Lanham Act’s protection to well-known figures and commercial circumstances. It may be difficult for many individuals, including less famous artists and performers, to prove that the challnged conduct is likely to confuse consumers regarding the plaintiff’s association with, or approval of, the defendant’s commerical activiteis. And issues like AI-gnerated “revenge porn” would likely fall beyond its reach. 

The report reccomends a new federal law which covers all individuals, at least for the individual’s lifetime that targets digital replicas, whether generated by AI or otherwise, taht are so realistic taht they are difficult to distinguish from authentic depictions. Liability should arise from teh distribution or making available of an unauthorized digital replica, but not the act of creation alone. It should nott be limtied to commercial uses,a s the harms caused are often personal in nature. It should require actual knowledge both tthat hte representation was a digital replica of a particular indivdual and that it was unauthorized. The statute should include a safe harbor mechanism that incentivizes online servie providers to remove unauthorized digital replicas after receiving effective notice or otherwise obtaining knowledge that they are unauthorized. Individaul should be albe to licesne and monetize their digital replica rights, subject to gaurdrails, but not to assign them outright. Effective remedies should be provided, both injunctive releif and monetary damages as well as statutory damages and/or prevailing party attorney’s fees. 

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