Influence of leptin administration to pregnant mice on fetal gene expression and adaptation to sweet and fatty food in adult offspring of different sexes.

Elevated leptin in pregnant mice improves metabolism in offspring fed high-calorie diet and its influence may be sex-specific. Molecular mechanisms mediating leptin programming action are unknown. We aimed to investigate programming actions of maternal leptin on the signaling function of the placenta and fetal liver and on adaptation to high-calorie diet in male and female offspring. Female C57BL/6J mice received leptin injections in mid-pregnancy. Gene expression was assessed in placentas and in the fetal brain and liver at the end of pregnancy. Metabolic parameters and gene expression in the liver, brown fat and hypothalamus were assessed in adult male and female offspring that had consumed sweet and fatty diet (SFD: chow, lard, sweet biscuits) for 2 weeks. Females had lower blood levels of leptin, glucose, triglycerides and cholesterol than males. Consuming SFD, females had increased Ucp1 expression in brown fat, while males had accumulated fat, decreased blood triglycerides and liver Fasn expression. Leptin administration to mothers increased Igf1 and Dnmt3b expression in fetal liver, decreased post-weaning growth rate, and increased hypothalamic Crh expression in response to SFD in both sexes. Only in male offspring this administration decreased expression of Fasn and Gck in the mature liver, increased fat mass, blood levels of glucose, triglycerides and cholesterol and Dmnt3a expression in the fetal liver. The results suggest that the influence of maternal leptin on the expression of genes encoding growth factors and DNA methyltransferases in the fetal liver may mediate its programming effect on offspring metabolic phenotypes.

Studying sex differences in responses to fibroblast growth factor 21 administration in obese mice consuming a sweet-fat diet.

In animals, obesity caused by consumption of a sweet-fat diet (SFD) is the most adequate mouse model of human diet-induced obesity. Fibroblast growth factor 21 (FGF21) reduces body weight, beneficially affects taste preferences, and corrects glucose metabolism in obese mice. Sex is known to influence FGF21 effects in different models of diet-induced and hereditary obesity. In mice with SFD-induced obesity, the effects of FGF21 have been studied only in males. The aim of this study was to compare the effects of FGF21 on body weight, food preferences and glucose and lipid metabolism in C57Bl/6J male and female mice with SFD-induced obesity. Mice were fed with a diet consisting of standard chow, lard and cookies for 10 weeks, then they were injected with FGF21 (1 mg per 1 kg) or vehicle for 7 days. Body weight, weights of different types of food, blood parameters, glucose tolerance, gene and protein expression in the liver, gene expression in the white, brown adipose tissues, and the hypothalamus were assessed. FGF21 administration reduced body weight, did not alter total energy consumption, and activated orexigenic pathways of hypothalamus in mice of both sexes. However, sex dimorphism was found in the realization of the orexigenic FGF21 action at the transcriptional level in the hypothalamus. Metabolic effects of FGF21 were also sex-specific. Only in males, FGF21 exerted beneficial antidiabetic action: it reduced fatty acid and leptin plasma levels, improved glucose-tolerance, and upregulated hepatic expression of Ppargc1, Fasn, Accα, involved in lipid turnover, gene Insr and protein glucokinase, involved in insulin action. Only in obese females, FGF21 induced preference of standard diet to sweet food. Thus, in mouse model of obesity induced by consumption of a sweet-fat diet, the catabolic effect of FGF21 was not sex-specific and hormonal, transcriptional and behavioral effects of FGF21 were sex-specific. These data suggest elaboration of different approaches to use FGF21 analogs for correction of metabolic consequences of obesity in different sexes.

Estradiol-dependent and independent effects of FGF21 in obese female mice.

The f ibroblast growth factor 21 (FGF21) synthesized in the liver, acting as a hormone, increases insulin sensitivity and energy expenditure. FGF21 administration has potent benef icial effects on obesity and diabetes in humans, cynomolgus monkey, and rodents. The therapeutic effects of FGF21 have been studied mainly in males. They are not always manifested in females, and they are accompanied by sex-specif ic activation of gene expression in tissues. We have suggested that one of the causes of sexual dimorphism in response to FGF21 is the effect of estradiol (E2). Currently, it is not known how estradiol modif ies the pharmacological effects of FGF21. The objec tive of this study was to study the inf luence of FGF21 on metabolic characteristics, food intake, and the expression of carbohydrate and fat metabolism genes in the liver, adipose tissue, and hypothalamus in female mice with alimentary obesity and low (ovariectomy) or high (ovariectomy + E2) blood estradiol level. In ovariectomized (OVX) females, the development of obesity was induced by the consumption of a high sweet-fat diet (standard chow, lard, and cookies) for 8 weeks. We investigated the effects of FGF21 on body weight, blood levels, food preferences and gene expression in tissues when FGF21 was administered separately or in combination with E2 for 13 days. In OVX obese females, FGF21, regardless of E2-treatment, did not affect body weight, and adipose tissue weight, or glucose tolerance but increased the consumption of standard chow, reduced blood glucose levels, and suppressed its own expression in the liver (Fgf21), as well as the expression of the G6pc and Acacα genes. This study is the f irst to show the modif ication of FGF21 effects by estradiol: inhibition of FGF21-inf luence on the expression of Irs2 and Pklr in the liver and potentiation of the FGF21-stimulated expression of Lepr and Klb in the hypothalamus. In addition, when administered together with estradiol, FGF21 exerted an inhibitory effect on the expression of Cpt1α in subcutaneous white adipose tissue (scWAT), whereas no stimulating FGF21 effects on the expression of Insr and Acacß in scWAT or inhibitory FGF21 effect on the plasma insulin level were observed. The results suggest that the absence of FGF21 effects on body and adipose tissue weights in OVX obese females and its benef icial effect on food intake and blood glucose levels are not associated with the action of estradiol. However, estradiol affects the transcriptional effects of FGF21 in the liver, white adipose tissue, and hypothalamus, which may underlie sex differences in the FGF21 effect on the expression of metabolic genes and, possibly, in pharmacological FGF21 effects.

Influence of leptin administration to pregnant female mice on obesity development, taste preferences, and gene expression in the liver and muscles of their male and female offspring.

. The consumption of food rich in sugar and fat provokes obesity. Prenatal conditions have an impact on taste preferences and metabolism in the adult offspring, and this impact may manifest differently in different sexes. An increase in blood leptin level in pregnant females reduces the risk of obesity and insulin resistance in the offspring, although the mechanisms mediating this effect are unknown. Neither is it known whether maternal leptin affects taste preferences. In this study, we investigated the effect of leptin administration to pregnant mice on the development of diet-induced obesity, food choice, and gene expression in the liver and muscles of the offspring with regard to sex. Leptin was administered to female mice on days 11, 12, and 13 of pregnancy. In male and female offspring, growth rate and intake of standard chow after weaning, obesity development, gene expression in the liver and muscles, and food choice when kept on a high-calorie diet (standard chow, lard, sweet cookies) were recorded. Leptin administration to pregnant females reduced body weight in the female offspring fed on the standard diet. When the offspring were given a high-calorie diet, leptin administration inhibited obesity development and reduced the consumption of cookies only in males. It also increased the consumption of standard chow and the mRNA levels of genes for the insulin receptor and glucose transporter type 4 in the muscles of both male and female offspring. The results demonstrate that an increase in blood leptin levels in pregnant females has a sex-specif ic effect on the metabolism of the offspring increasing resistance to obesity only in male offspring. The mechanism underlying this effect includes a shift in food preference in favor of a balanced diet and maintenance of insulin sensitivity in muscle tissues.

Pharmacological effects of fibroblast growth factor 21 are sex-specific in mice with the lethal yellow (Ay) mutation.

Hypothalamic melanocortin 4 receptors (MC4R) regulate energy balance. Mutations in the MC4R gene are the most common cause of monogenic obesity in humans. Fibroblast growth factor 21 (FGF21) is a promising antiobesity agent, but its effects on melanocortin obesity are unknown. Sex is an important biological variable that must be considered when conducting preclinical studies; however, in laboratory animal models, the pharmacological effects of FGF21 are well documented only for male mice. We aimed at investigating whether FGF21 affects metabolism in male and female mice with the lethal yellow (Ay) mutation, which results in MC4R blockage and obesity development. Obese C57Bl-Ay male and female mice were administered subcutaneously for 10 days with vehicle or FGF21 (1 mg per 1 kg). Food intake (FI), body weight (BW), blood parameters, and gene expression in the liver, muscles, brown adipose tissue, subcutaneous and visceral white adipose tissues, and hypothalamus were measured. FGF21 action strongly depended on the sex of the animals. In the males, FGF21 decreased BW and insulin blood levels without affecting FI. In the females, FGF21 increased FI and liver weight, but did not affect BW. In control Ay-mice, expression of genes involved in lipid and glucose metabolism (Ppargc1a, Cpt1, Pck1, G6p, Slc2a2) in the liver and genes involved in lipogenesis (Pparg, Lpl, Slc2a4) in visceral adipose tissue was higher in females than in males, and FGF21 administration inhibited the expression of these genes in females. FGF21 administration decreased hypothalamic POMC mRNA only in males. Thus, the pharmacological effect of FGF21 were significantly different in male and female Ay-mice; unlike males, females were resistant to catabolic effects of FGF21.

Effect of gonadectomy and estradiol on the expression of insulin signaling cascade genes in female and male mice.

A positive effect of estradiol on insulin sensitivity has been shown for females and males. Insulin sensitivity is higher in females than in males, and males show a greater tendency to develop metabolic disorders. It is believed that these sex differences are due to a protective effect of estradiol in females, but not in males. Estradiol is a steroid hormone, and its effect is due to the modulation of target gene expression, but the effect of estradiol on the expression of genes encoding insulin signal transduction and glucose transport has not been sufficiently studied. The aim of the study was to compare the molecular mechanisms of the estradiol influence on insulin sensitivity in mice of both sexes. The effect of gonadectomy and estradiol (1 µg/animal, three days) on the expression of insulin signaling cascade genes in muscle, adipose tissue, and liver, as well as on the expression of Fgf21, estradiol receptors (Esr1/2), and transcription factor Stat3 in the liver in female and male mice was investigated. Estradiol levels were lower and glucose blood levels and insulin resistance were higher in Sham operated (Sham) males compared to Sham females. Irs2, Pik3cd, and Esr1/2 mRNA levels were lower in the liver of Sham males than in Sham females. In females, gonadectomy reduced the level of estradiol in the blood, increased insulin resistance and blood glucose levels compared to Sham females. Administration of estradiol to gonadectomized females decreased blood insulin levels and insulin resistance. In males, gonadectomy, on the contrary, increased the blood estradiol level, decreased blood insulin level and insulin resistance. Estradiol did not affect the parameters studied in males. The development of insulin resistance in gonadectomized females was associated with a decreased expression of the Irs2 gene in the liver. Increased insulin sensitivity in gonadectomized males was associated with increased levels of Irs2 and Pik3cd mRNA in the liver. It can be assumed that increasing the level of estradiol in the blood activates the expression of the Irs2 gene in the liver regardless of animal sex. Also, estradiol seems to regulate the transport of glucose in adipose tissue regardless of animal sex: in females and males, an increase in the blood estradiol level was associated with a decrease in the expression of the Slc2a4 gene in adipose tissue. Thus, the effects of estradiol on the expression of insulin cascade genes do not seem to depend on animal sex, but have tissue specificity. Since the molecular mechanism of estradiol influence on the expression of insulin cascade genes in females and males is the same, the cause of sexual differences in insulin sensitivity and the rate of development of metabolic disorders may be a decrease in the level of estradiol in the blood, as well as a decrease in the expression of estradiol receptors in the liver in males compared to females.

Impact of sex on the adaptation of adult mice to long consumption of sweet-fat diet.

In rodents, the most adequate model of human diet-induced obesity is obesity caused by the consumption of a sweet-fat diet (SFD), which causes more pronounced adiposity in females than in males. The aim of this work was to determine the sex-associated effect of SFD on the expression of genes related to carbohydrate-lipid metabolism in adult mice. For 10 weeks, male and female С57Bl mice were fed a standard laboratory chow (Control group) or a diet, which consisted of laboratory chow supplemented with sweet cookies, sunflower seeds and lard (SFD group). Weights of body, liver and fat depots, blood concentrations of hormones and metabolites, liver fat, and mRNA levels of genes involved in regulation of energy metabolism in the liver, perigonadal and subcutaneous white adipose tissue (pgWAT, scWAT) and brown adipose tissue (BAT) were measured. SFD increased body weight and insulin resistance in mice of both sexes. Female mice that consumed SFD (SFD females) had a greater increase in adiposity than SFD males. SFD females showed a decreased expression of genes related to lipogenesis (Lpl) and glucose metabolism (G6pc, Pklr) in liver, as well as lipogenesis (Lpl, Slca4) and lipolysis (Lipe) in pgWAT, suggesting reduced energy expenditure. In contrast, SFD males showed increased lean mass gain, plasma insulin and FGF21 levels, expressions of Cpt1α gene in pgWAT and scWAT and Pklr gene in liver, suggesting enhanced lipid and glucose oxidation in these organs. Thus, in mice, there are sex-dependent differences in adaptation to SFD at the transcriptional level, which can help to explain higher adiposity in females under SFD consumtion.

[STUDYING THE ROLE OF BRAIN MELANOCORTIN RECEPTORS IN THE SUPPRESSING OF FOOD INTAKE UNDER ETHER STRESS IN MICE].

Melanocortin (MC) system regulates food intake under the rest conditions. Stress inhibits food intake. It is not clear whether brain MC system is involved in stress-induced anorexia in mice. The aim of the work was to investigate the effect of pharmacological blockade and activation of brain MC receptors on food intake under stress. C57B1/6J male mice were subjected to ether stress (0.5 minute ether anesthesia) before the administration of saline solution or synthetic non-selective blocker (SHU9119) or agonist (Melanotan II) of MC receptors into the lateral brain ventricle. Food intake was pre-stimulated with 17 hours of fasting in all mice. Ether stress decreased food intake, increased the plasma corticosterone level and hypothalamic mRNA AgRP (natural MC receptor antagonist) level at 1 hour after the stress. Pharmacological blockade of the MC receptors weakened stress-induced anorexia and decreased mRNA AgRP level in the hypothalamus. Pharmacological stimulation of the MC receptors enhanced ether stress-induced anorexia and hypercortisolism. Thus, our data demonstrated that the central MC system was involved in the development of stress-induced anorexia in mice.

[The influence of hyperleptinemia during pregnancy on fetal weight and obesity development in progeny mice with agouti yellow mutation].

Maternal obesity increases the risk of obesity in the offspring, and obesity is accompanied by an increase in blood leptin levels. Leptin can influence the progeny metabolism via its influence on fetal growth and, possibly, via its action on AgRP expression in placenta. The "yellow" mutation at the mouse agouti locus (A(y)) evokes obesity and increases blood leptin levels in pregnant mice. The aim was to examine the influence of A(y) mutation in pregnant mice on fetal weight, placental expression of AgRP gene and food intake and obesity development in progeny. A(y) pregnant females as compared to control ones had increased circulating leptin levels on days 13 and 18 of pregnancy. Both fetal weight and placental expression of AgRP gene were increased on day 13 of pregnancy and decreased on day 18 of pregnancy in A(y) females as compared to control ones. Both control (a/a) and obesity prone (A(y)/a) male young born to A(y) mothers had lowered body weight and enhanced food intake between 5 and 11 weeks of age as compared to male progeny of control mothers. The enhanced leptin levels during pregnancy in mice are associated with retardation of obesity development in obesity prone male offspring and with changes in fetal weight and AgRP gene expression in placenta.

[Effect of ovariectomy on GLUT4 mRNA levels in adipose and muscle tissues in females of mice C57BL/6J-Agouti Yellow].

Mutation Yellow at the agouti locus in mice (AY/a-mice) causes the increase of food intake and development of obesity and type 2 diabetes. In AY/a-females the disturbances of glucose and fat metabolisms occur after puberty. Previously we demonstrated that in AY/a-females regulation of blood glucose levels by estradiol was impaired. To investigate the mechanisms of estradiol regulatory action disturbance we determined the effects of ovariectomy and estradiol treatment on mRNA GLUT4 levels in adipose tissue and muscles in AY/a-females. C57BL/6J females, not carrying the Yellow mutation at the agouti locus (a/a-mice), were used as a control. The data suggest that one of the reasons for violations of estradiol regulation of glucose metabolism in AY/a-females is decreasing GLUT4 gene transcription activity in muscle tissue.

Exaggerated anorexigenic response to restraint stress in A(y) mice is associated with elevated CRFR2 mRNA expression in the hypothalamus.

The "lethal yellow" mutation at the mouse agouti locus (A(y)) results in hyperphagia, obesity, and type 2 diabetes at rest, but helps to reduce food intake under stress. The aim of this work was to investigate mechanisms of exaggerated anorectic response to stress in A(y) mice. All parameters were measured in C57BL/6J male mice of a/a (control) and A(y)/a genotypes before, 0, 1, and 3h after a 1-h restraint. Baseline food intake and plasma insulin concentrations were higher in A(y)/a mice compared to a/a mice. Restraint reduced food intake and plasma insulin concentrations only in A(y)/a mice. Stress-induced anorexia in A(y)/a mice was independent of pathways involving hypothalamic-pituitary-adrenal axis activity and hypothalamic orexigenic neuropeptide (agouti-related peptide and neuropeptide Y) gene expressions and corticotrophin-releasing factor type 1 receptor (CRFR1). Gene expression of CRFR2 was elevated in A(y)/a mice with genotype differences particularly manifested immediately after the restraint. Hypothalamic CRFR2 is known to mediate anorectic signals from CRF-related peptides. Thus, our data suggest that stress-induced anorexia in A(y)/a mice may be associated with increased anorectic signals mediated by CRFR2 in the hypothalamus.

[Effect of estradiol on food intake, glucose and fat metabolism in mice C57BL/6J with mutation yellow at the agouti locus].

Mutation yellow at the agouti locus in mice (A(y)/a-mice) causes the increase of food intake and development of obesity and type 2 diabetes. In A(y)/a-females the disturbances of glucose and fat metabolisms occur after puberty. We have assumed that the mutation yellow violates the regulatory effect of estradiol on glucose and fat metabolism in mice. We investigated the effects of ovariectomy and estradiol treatment on body weight, food intake, glucose tolerance, plasma levels of glucose, insulin and etherified fatty acids in A(y)/a-females. C57Bl/6J females, not carrying yellow mutation at the agouti locus (a/a-mice), were used as a control. The data suggest that the yellow mutation did not affect estradiol regulation of food intake and glucose blood levels after a night of fasting, but, apparently, prevented estradiol participation in the regulation of glucose and fat metabolisms in the muscle and fat tissues.

Regulation of food consumption during pregnancy and lactation in mice.

The aim of the present work was to assess the expression of agouti-like protein and neuropeptide Y in pregnant and lactating mice and to compare this with the leptin level and food consumption. Food consumption, blood leptin levels, and agouti-like protein and neuropeptide Y mRNA levels in the hypothalamus of C57Bl/6J mice were assessed on days 7, 13, and 18 of pregnancy and on days 10 and 21 of lactation, and in virgin females of the same ages. During pregnancy, food consumption and leptin levels decreased on day 7 and increased in day 18 of pregnancy, while neuropeptide Y mRNA levels increased on day 13 and then remained unaltered, and the agouti-like protein level increased on day 18. After parturition, food consumption continued to increase, while leptin levels and neuropeptide Y mRNA levels decreased to normal. Thus, hyperphagia in pregnancy was due to sequential activation of the expression of neuropeptide Y and agouti-like protein, while in lactation hyperphagia resulted from mechanisms not associated with changes in the expression of these neuropeptides.

Pregnancy and lactation have anti-obesity and anti-diabetic effects in A(y)/a mice.

AIM: Dominant 'yellow' mutation at the mouse agouti locus (A(y)) results in obesity. Pregnancy and lactation are characterized by large energy demand. The aim of this study was to investigate whether obesity would develop in pregnant and suckling A(y) mice. METHODS: Body weight and food intake in pregnancy, lactation, and after weaning, plasma leptin, insulin, corticosterone and blood glucose concentrations on days 7, 13 and 18 of pregnancy, days 1, 10, 21 and 80 postpartum, glucose and insulin tolerance on pregnancy days 7 and 18 were measured in C57Bl/6J mice of a/a (normal metabolism) and A(y)/a genotypes. The same parameters were also measured in age-matched virgin females. RESULTS: Virgin A(y)/a females exhibited hyperphagia, enhanced body weight, glucose intolerance and normal blood parameters at the mating age. With age, they developed obesity, hyperleptinaemia, hyperinsulinaemia and hyperglycaemia. Obesity did not develop in mated A(y)/a mice; during suckling, they had equal food intake and body weight as a/a mice. During pregnancy, glucose tolerance was enhanced in A(y)/a mice and became equal in both genotypes. In both genotypes, concentrations of hormones increased, and glucose decreased from pregnancy day 7 to day 18 and returned to normal values after parturition. A(y)/a mice did not differ from a/a in corticosterone, insulin and glucose levels during pregnancy and lactation, in leptin levels during suckling; however, A(y)/a mice had two times higher leptin levels than a/a during pregnancy. After weaning, A(y)/a mice began to eat and weigh more than a/a exhibiting normal metabolic parameters for 50 days. CONCLUSION: Pregnancy and lactation retard obesity and diabetes development in A(y) mice.

[Food intake regulation in pregnant and lactating mice].

OBJECTIVE: Hormone leptin inhibits appetite. It decreases hypothalamic expression of orexigenic neuropeptides, agouti-related peptide (AgRP), and neuropeptide Y (NPY). Pregnancy and lactation are characterized by hyperphagia. Food intake regulation during pregnancy and lactation is poorly understood. The aim of the work was to estimate hypothalamic expression of NPY and AgRP in pregnant and suckling mice and correlate it with food intake and blood leptin level. MEASUREMENTS: Daily food intake, and levels of leptin in blood and mRNA of AgRP and NPY in hypothalamus on day 7, 13, 18 of pregnancy, 10, 21 of lactation in C57B1/6J female mice and in age-matched virgin females. RESULTS: In the course of pregnancy, food intake increased, leptin level decreased on day 7 and increased on day 18, NPY expression was increasing until day 13 and then remained unchanged, AgRP expression increased on day 18 of pregnancy. In suckling females, food intake continued to grow, but levels ofleptin and NPY and AgRP expression decresed and became equal with that in virgin females. CONCLUSION: In pregnant mice, hyperphagia results from NPY followed by AgRP expression activation, in suckling mice--from other mechanisms which are not connected with changes in expression of these neuropeptides.

[The effect of the "yellow" mutation at the mouse agouti locus on the hormonal profile of pregnancy and lactation].

The "yellow" mutation at the mouse agouti locus (A(y)/a-mice) results in obesity and type 2 diabetes. Maternal obesity in A(y)-mice impaired glucose tolerance in adult Agouti-negative offspring. Changes of hormone pattern during pregnancy and lactation are known to disregulate glucose metabolism in the adult progeny. The aim of the study was to assay blood levels of glucose, insulin, corticosterone and leptin during pregnancy (days 7, 13, 18) and lactation (days 1, 10, 21) in C57B1/6J mice of a/a (normal metabolism) and A(y)/a genotypes. A(y)/a-mice did not differ from a/a-mice in insulin and glucose levels during pregnancy and lactation, in corticosterone levels during pregnancy, but had higher leptin levels in pregnancy and lactation and increased corticosterone levels during lactation. A(y)/a-mice may be considered as a genetic model for studying impact of maternal leptin and corticosterone in developmental programming.

[Dynamics of food intake and blood level of hormones regulating appetite in pregnant and lactating mice].

Leptin, insulin, corticosterone regulate food intake. Hyperphagia and hormonal rearrangement are typical for pregnancy and lactation. The aim of the study is to correlate food intake with blood levels of these hormones in pregnant and lactating mice. Food intake, body weight, blood glucose, insulin, leptin and corticosterone levels were measured in virgin C57B1/6J micc and on the day 7, 13,17 of pregnancy, and day 1, 7, 14, 30 postpartum. Insulin sensitivity was measured at the day 7, 17 of pregnancy. Food intake and body weight increased towards the second postpartum week and then decreased. Insulin sensitivity decreased towards the end of the pregnancy. Mothers differed from virgin females in hormones and glucose levels only during pregnancy. Leptin level was decreased at the day 7 of gestation, insulin level - during whole gestation. Glucose fell, and leptin and corticosterone increased from the day 7 to 17. Probably, these hormones affect food intake only in pregnant females and do not influence appetite during lactation.

[Postnatal development of corticosteroid function of the adrenals in C57BL/6J-Ay mice].

We studied postnatal development of corticosteroid function of the adrenals in mice during the period of elevated activity of the hypothalamic-pituitary-adrenal system and the influence of mutant gene Ay on this process. Normally, a corticosterone peak in blood and increased basal and stimulated steroidogenesis in vitro are observed in 3-week old mice. In 3-week old Ay/a mice (hyperexpression of protein agouti) a corticosterone peak in blood is lowered and genotypic differences in steroidogenesis in vitro are absent, as compared to a/A mice (absence of agouti), while at the ages of 10 and 15 weeks, there were no genotypic differences in the blood level of corticosterone and steroidogenesis in vitro was elevated. Thus, a high level of corticosterone during the period of elevated activity of the hypothalamic-pituitary-adrenal system in 3-week old mice is determined by enhanced steroidogenic function of the adrenals. Mutant gene Ay in male mice affected the postnatal development of the adrenal function: the peak of corticosterone in blood was lowered during the period of elevated activity of the system.

[Repeating of emotional stress prevents development of melanocortin obesity and type 2 diabetes in the mice with the Agouti yellow mutation].

Brain melanocortin system (MC-system) participates in regulation of energy homeostasis. Dominant mutation yellow of the Agouti gene leads to the hyperphagia, obesity and type 2 diabetes. Stress is known to inhibit food intake and body weight. The aim of the work was to study effects of repeating emotional stress on food intake and lipid-carbohydrate metabolism in Ay-mice. Male mice of C57B1/6J strain predisposed to the obesity (Ay/a-genotype) and normal (a/a-genotype) were used. In control group food intake, body weight and blood levels of insulin and leptin were increased in Ay/a-mice as compared to a/a-mice. Repeating emotional stress (30 min restraint 3 times a week for 5 weeks) did not alter food intake and indices of lipid-carbohydrate metabolism in a/a-mice and decreased food intake, body weight and blood levels of insulin and leptin in Ay/a-mice. Insulin and leptin blood levels were the same in Ay/a- and a/a-mice on 5 week of treatment. The stress increased basal and stress-induced concentrations of corticosterone to an equal degree in Ay/a- and a/a-mice. Thus, light repeating emotional stress hampered development of obesity and 2 type diabetes in the mice with the Agouti yellow mutation.

[Steroidogenesis in adrenal glands of young and adult female mice with hyperexpression of the Aguoti gene].

Dominant mutation Agouti yellow (AY) leads to ectopic overexpression of the Agouti gene and yellow coat color in mice. Furthermore, the mutation Ay increased adrenal response to emotional stress. The study assessed whether pleiotropic effect of the mutation Ay on adrenals function was dependent on sex and age. 3- and 15-week old female C57B1/6J mice of two agouti-genotypes: Ay/a (ectopic Agouti-gene overexpression) and a/a (absence of Agouti-protein), were investigated. Cyclic AMP level (adenylate cyclase activity) and corticosterone production in adrenal isolated cells stimulated by ACTH and dibutyrul cAMP (db-cAMP) were measured. ACTH increased cAMP accumulation to the same extent in Ay/a- and a/a-mouse adrenal cells of both ages. The dibutyrul cAMP-induced corticosterone production was higher in Ay/a than in a/a-mouse adrenal cells of both ages. The ACTH-induced corticosterone production in 3-week- old Ay/a-m/CQ was lower and in 15-week old Ay/a-mice was higher than in a/a-mice of the respective ages. The ACTH- and db-cAMP-induced steroidogenesis was not changed in Ay/a-mice and decreased in a/a-mice with age. Thus, in females as well as in males, the mutation Agouti yellow did not affect adenylate cyclase activity, increased db-cAMP-induced corticosterone production and disturbed development of adrenal cortex.