[Major gene mutations associated with obesity and diabetes mellitus].

Obesity and diabetes mellitus are associated with low or elevated serum leptin and insulin levels (U-like relation). Mutations in LEP and INS are linked to leptin and insulin decrease while mutations in LEPR and INSR to their increase. Homozygous LEP mutations are associated with the early onset of severe obesity and diverse impairment of physiological functions. Recessive LEPR mutations are associated with similar pathology in homozygous state. Missense mutations of INS are dominant. They induce synthesis of chimeric pro-insulin that may interfere folding and processing of active insulin molecules. In the heterozygous state they cause insulin deficiency and PND. Recessive INS mutations do not induce synthesis of anomalous pro-insulin, and they are associated with PND only in homozygous state. Mutations of INSR induce insulin resistance, lipodystrophy, other pathology, and suggest an important role of insulin in glucose level regulation and in stimulation of fat accumulation as well.

[Molecular mechanisms of the alternative lipogenic function of insulin].

The proposed hypothesis suggests that major function of insulin is stimulation of triglyceride accumulation in adipose tissue and glycogen synthesis in liver and muscles. The impairment of insulin functioning diminishes triglyceride storage in adipose tissue, elevates the level of its metabolite in periphery and suppresses glucose intake by cells. Leptin disturbs direct insulin action on adipocytes, and prevents fat accumulation. Leptin deficiency or impairment of its functioning facilitate lipogenic effect of insulin, and induce obesity. Lipodystrophy decreases leptin secretion and enhances triglyceride production activated by insulin. Triglycerides are not accumulated in adipose tissue because of its deficiency, and overwhelm peripheral tissues. Lipid metabolites decrease glucose consumption and induce lipoatrophic diabetes. The hypothesis on the lipogenic insulin functioning is confirmed by specific knockout of Insr gene in only tissue: muscles, adipose tissue and other, and by the restoration of its expression in transgenic mice.

[Genetic variations in energy balance regulation].

Single nucleotide polymorphism (SNP) near certain genes revealed association of FAT(fat mass and obesity-associated gene), MC4R (melanocortin 4 receptor gene), and other genes with obesity. Participation of the FAT expression products in the regulation of energy balance remains to be clarified. The function of MC4R encoding melanocortin 4 receptor (MC4R) is somewhat better understood. alpha-, beta-, and gamma-MSH encoded by the POMC gene bind to MC4R, reduce food intake, and slow down fat accumulation. Expression of POMC that codes MSH is enhanced by leptin binding to the receptor (LepRb) in hypothalamic neurons. Mutations in human and animal MC4R, POMC, and LEP genes are known to be associated with obesity. More than 60 mutations in MC4R, more than 20 mutations in POMC and fewer LEP mutations have been reported. Nonsense mutations and reading frame shifts block gene expression and thereby disrupt protein synthesis. Missense mutations frequently affect protein folding in endoplasmic reticulum; unfolded or misfolded proteins remain in the cytoplasm and undergo degradation. Certain missence mutations do not interfere with gene expression and folding of proteins but impair their functioning at the periphery. P.S127L mutation in MC4R, p.E206X and p.F144L mutations in POMC as well as other mutations in homozygous and heterozygous forms account for disturbed energy balance in man. The LEP gene has been reported to contain G133fsX15, p.R105X, p.R1O5W, and p.S141C mutations. As a rule, they are associated with obesity and other pathological conditions only in homozygous forms.

[A new mutation c.422C>G (p.S141C) in homo- and heterozygous forms of the human leptin gene].

Mutation g.15409C>G, c.422C>G (p.S141C) in homo- and heterozygous forms of the human LEP gene was identified among some patients of the high mountain village of Karaul, Ashkhabad oblast, Turkmenistan, some of which suffer from adiposity. It causes the substitution S120C in the secreted leptin. The mature leptin molecule (146 aa) has only two Cys residues (C96 and C146) forming an S-S bridge, which is important for the hormone function. A third mutation, C120, in the molecule might disturb the correct formation of the S-S bond and could alter the leptin activity.

[The interconnections of molecular mechanisms of hormone actions and their role in pathogenesis of obesity, insulin resistance, and diabetes mellitus].

The various hormones, proteins and other compounds related to developing obesity, insulin resistance and type 2 diabetes are analyzed in the paper. 1) Leptin, ciliary neurutrophic factor, adiponectin, glucagon-like peptide 1, peptide YY, neuromedin S, as well as the protein receptors of these hormones decrease the food consumption, increase the energy turnover, and prevent obesity, insulin resistance, and type 2 diabetes development. The mediators of these hormone and receptor actions are melanocyte stimulating hormone (MSH), corticotropin-releasing hormone (CRH), and the others. 2) Ghrelin, endogenose cannabinoides, galanin-like peptide and the mediators of their actions: neuropeptide Y (NPY) and Agouti gene related protein (AGRP) increase the appetite and food consumption. Peroxisome proliferation-activated receptor (PPAR) performs the similar action on food intake. The activation of the first group compound functioning decreases the obesity, increases the energy turnover, facilitates the insulin action and prevents the insulin resistance and type 2 diabetes. Increasing the activities of the second group, as well as, decreasing the actions of the first one of substances induce the opposite effects and facilitate obesity, insulin resistance, and type 2 diabetes developments. The interconnections of the molecular mechanisms of so many hormone actions make the very complicated tusk to study the various endocrine disorders including diabetes mellitus as well.

[Adiponectin, a new hormone: its role in the pathogenesis of diabetes mellitus].

Adiponectin is a hormone of adipose tissue, activating lipid metabolism and other physiological functions. Adiponectin deficiency induces obesity and decreases insulin-regulated carbohydrate metabolism, thus leading to insulin resistance. Blood level of adiponectin falls in type 2 diabetes. Adiponectin receptors--AdipoR1 and AdipoR2--are proteins with 7 transmembrane domains, which are synthesized mostly in muscles and the liver and function in a close connection with G proteins. Obesity and diabetes lower the tissue concentration of the receptors, thus impeding adiponectin regulation of lipid exchange and lowering the effectiveness of the insulin control of carbohydrate exchange. Adiponectin also influences cardiovascular functions and prevents atherosclerosis and some of the other kinds of vascular pathology.

[Molecular and genetic study of the role of hormones, receptors, and enzymes in regulation of reproduction, lipid metabolism, and other human physiological functions].

Prevalence of uterine progesterone receptors over estrogen ones, high uterine cAMP level, and low uterine prostaglandin level are necessary conditions of normal pregnancy. In cases of spontaneous and antiprogestin RU486-induced abortions, estrogen receptors prevail over progesterone ones, cAMP level decreases, and prostaglandin concentration in decidual tissue increases. Porcine and bovine beta-lipotropines were the first proteins, whose correct amino acid sequence was first determined in Russia. Several research centers carried out collaborative studies of the nucleotide sequences of human and animal proopiomelanocortin (lipotropin precursor) and prolactin cDNA. Researchers constructed genetic engineering producers of human pre-proinsulin and somatostatin, identified structural genes expressed in pancreatic beta-cells, studied antigenic properties of glutamic acid decarboxylase (GAD), which determine insulin-dependent diabetes, and identified the cholesterase determinant. They revealed mutations in the genes of proopiomelanocortin and melanocortin receptors (MC4-P), which inhibit leptin regulation of appetite and are associated with human obesity.

[Achievements in molecular genetics studies of diabetes mellitus].

Tissue specific insulin receptor knockout mice have been employed to study the features of non-insulin-dependent diabetes mellitus (NIDDM) at Research Division, Joslin Diabetes Center, Boston, Massachusetts. The muscle insulin receptor knockout (MIRKO) mice display muscle insulin resistance but do not develop hyperinsulinemia or diabetes. White adipose tissue of MIRKO mice have increased the sensitivity to insulin and its glucose uptake is dramatically elevated that activates fat accumulation and induces obesity which results from an increase in adipocyte number (hyperplasia) of the same size as well as individual cells in the control mice. MIRKO mouse adipose tissue increased secretion of adiponectin that increases the insulin sensitivity and do not alter the leptin production. The liver insulin receptor knockout (LIRKO) mice develop a syndrome like NIDDM with hyperinsulinemia and hyperglycemia, decreased liver size and its function since insulin is an important liver growth factor but they do not suffer with fat accumulation The fat tissue insulin receptor knockout (FIRKO) mice become lean with the 50-60% reduction of fat masses. FIRKO mouse remains resistant to obesity with age and as a result it has high insulin sensitivity and normal glucose tolerance. They eat normal amount of food, increase the longevity of life and decrease the mortality. The beta-cell insulin receptor knockout in combination with the insulin receptor substrates 1 or 2 or both knockouts mice develop beta-cell insensitivity to insulin and the insensitivity to the stimulation of insulin secretion by glucose. The animals show the alterations of beta-cell growth and 20% of experimental mice develop II type diabetes. The brain insulin receptor knockout (BIRKO) mice are obese and insulin resistant. They have increased appetite, hyperinsulinemia, hypertrigliceridemia, and decreased responses of neurons to epinephrine. The endothelial cell insulin receptor knockout mice have the normal levels of insulin and glucose in the circulation, and the normal or decreased blood pressure. They look healthy but have decreased level of the vascular endothelial growth factor in blood which may prevent the development of retinopathy as NIDDM complication.

[The role of leptin and its peptide mediators in neurophysiology]. / Rol' leptina i ego belkovykh mediatorov v neirofiziologii.

The adipocyte hormone leptin binds to its receptors in hypothalamic neurons and decreases appetite and food consumption. Its effect on appetite is mediated by melanocortines (MC) that are derivative of proopiomelanocortin (POMK) and their receptor (MC4-R). The knock-out of POMC gene or MC4-R gene causes obesity in animals. However, the growth of the animals intensifies and their reproductive function does not cease. The paper covers consequences of mutations in genes responsible for leptin regulation of various functions.

[Protein hormones, receptors, and other proteins in mechanisms of hormonal regulation]. / Belkovye gormony, retseptory i drugie belki v mekhanizmakh gormonal'noi reguliatsii.

The amino acid sequence of porcine beta-lipotropin was the first protein primary structure studied in Russia. This peptide as well as ACTH is liberated after proteolysis of proopiomelanocortin (POMC). alpha-MSH and beta-MSH (melanocortins), which are the fragments of ACTH and beta-lipotropin respectively, are the mediators of leptin action on appetite and lipid metabolism. The structure and molecular aspects of hormone signaling of the membrane receptors of leptin and melanocortins were analysed in the connection to the regulation of food consumption, growth, and puberty. Some aspects of insulin receptor and IGF-I receptor as well as intracellular receptors of lipid hormones (steroid and thyroid hormones) were also discussed. The postulate: "All organs, tissues, and cells of humans and animals are endocrine" is formulated on the basis of the accumulated data.

[Leptin--a new hormone in endocrinology]. / Leptin--novyi gormon v éndokrinologii.

Research of recent years has fundamentally revised modern endocrinology. Many organs and tissue that have never before been treated as endocrinal or involved in production of various hormones, became such. In particular, adipose tissue secreting to blood an important hormone--leptin--became the study object of particular interest.

[Screening of mutations in genes of pro-opiomelanocortin in patients with constitutional exogenous obesity]. / Skrining mutatsii v gene proopiomelanokortina u bol'nykh konstutsional'no-ékzogennym ozhireniem.

Proopiomelanocortin (POMC) is a precursor of ACTH, beta- and gamma-liportopins, alpha-, beta- and gamma-MSH, beta-endorphin. alpha-, beta- and gamma-MSH are synthesized by hypothalamus neurons, and leptin stimulates their synthesis. These hormones regulate food consumption and energy metabolism by via melanocortin receptors (MC3-R and MC4-R) in hypothalamus. Screening mutations in the coding region of human POMC has been carried out with PCR, SSCP and DNA sequencing and the association study of these mutations and human obesity has been performed. Group of patients with the exogenous obesity (BMI 37.8 +/- 6.8 kg/m2) consisted of 228 persons (173 women and 55 men). 145 blood donors (67 women and 78 men) without obesity (BMI J25 kg/m2, 23.1 +/- 2.2 kg/m2) and 170 women without apparent obesity at the beginning of the study were included in the control group. 8 polymorph sites: insertions; missense and silent mutations have been identified in the coding region of POMC. Among them 1) two heterozygous mutations: the insertion of 6 b.p. (GGGCCC) in codon 176 inducing the insertion of two amino acid residues (Arg-Ala) in POMC and nonsense mutation (G-7316-T) in codon 180 of gamma-LTH coding region of the same DNA chain were identified in 4 women (5.8%) out of 69 patients with morbid obesity (BMI 40-53 kg/m2). These mutations were not found in control (n = 315). 2) The new heterozygous mutation T-7130-C (Phe118Leu) in active site of alpha-MSH has been identified in POMC gene of a woman suffering with obesity since the early childhood. 3) Mutation A-7341-G (Glu188Gly) seemed to have a protective effect because it was revealed more frequently in control (3.9%) than in obese patients (0.66%). The results of genetic study of two pedigrees suggested the dominant influence of the first two mutations (1 and 2) on woman obesity.

[Study of the association between constitutional exogenous obesity and polymorphism of the apolipoprotein B gene]. / Issledovanie sviazi konstitutsional'no-ékzogennogo ozhireniia s polimorfizmom v lokuse gena apolipoproteina B.

An attempt was made to associate the insertion-deletion (Ins/Del) polymorphism of the apolipoprotein B gene (apoB) with obesity and to identify alleles and genotypes predisposing to this disorder. The apoB Ins/Del allele frequencies observed in the Russian population were similar to those in West European populations and significantly differed from frequencies reported for Asian populations. Patients with obesity did not differ from healthy individuals in allele and genotype frequencies regardless of whether total or sex-stratified samples were compared. Estimation of relative risk for individuals with genotype Ins/Ins did not reveal a significant association between obesity and this genotype. Thus, constitutional exogenous obesity did not prove to be associated with the Ins/Del polymorphism of the apoB gene in the Russian population.

[All human and animal organs, tissues and cells are endocrine]. / Vse organy, tkani i kletki zhivotnykh i cheloveka iavliutsia éndokrinnymi.

All known hormones are shown to be synthesized and secreted by different structures of the brain and nervous system, including neurons and glial cells and many of them are neurotransmitters. It should be recognized that all the organs, tissues, and cells of animals and man are endocrine and secrete different hormones into the intercellular space and blood.

[First advances in molecular endocrinology obtained using the Cre/LoxP system]. / Pervye dostizheniia v molekuliarnoi éndokrinologii, poluchennye s ispol'zovaniem sistemy Cre/LoxP.

The insulin-like growth factor I (IGF-I) is produced in the liver and is considered mediating the effect of the growth hormone (GH). However, a knock-out only in liver IGF-I slightly disturbs the growth and development of mice. Such mice develop insulin resistance of various organs, including muscles. A knock-out in the liver insulin gene also results in insulin resistance. Selective inactivation of the gene for glucokinase (a target of insulin) in pancreatic islets or in the liver suppresses insulin secretion in the pancreas.

[Genetic engineering approaches to the study of insulin-dependent diabetes mellitus markers]. / Genno-inzhenernye podkhody k izucheniiu markerov insulinzavisimogo sakharnogo diabeta.

In the present study, gene-engineering producers for proinsulin and peptide fragments of glutamic acid decarboxylase (GAD), the main autoantigens of islet cells responsible for development of insulin-dependent diabetes mellitus (IDDM), were prepared. Basing on the obtained antigens. ELISA was developed to determine the autoantibodies in sera of patients. Sera from the following two groups of IDDM patients were studied: 1) adult patients with recently developed IDDM before insulinotherapy, and 2) adult patients with long-lasting IDDM with associated complications. Insulin/proinsulin antibodies were detected in 20% patients of group 1 and 41.7% patients of group 2. In sera from IDDM patients, antibodies to two GAD fragments containing amino acid sequences 1-80 and 151-585 were also detected. 16% of sera from patients with recently developed IDDM and 37.5% of sera from patients with long-lasting IDDM reacted with N-terminal GAD fragment. 12% of sera from group 1 and 45.8% of sera from group 2 reacted with central-C-terminal GAD fragment. The rate of sera of IDDM patients with detected antibodies in this study was some lower than that described in the literature.