Revisiting pancreatic islet isolation in murine models: A practical and effective technical protocol.

The endocrine pancreas is composed of clusters of cell groups called pancreatic islets. These cells are responsible for the synthesis and secretion of hormones crucial for glycemic homeostasis, such as insulin and glucagon. Therefore, these cells were the targets of many studies. One method to study and/or understand endocrine pancreatic physiology is the isolation of these islets and stimulation of hormone production using different concentrations of glucose, agonists, and/or antagonists of specific secretagogues and mimicking the stimulation of hormonal synthesis and secretion. Many researchers studied pancreatic physiology in murine models due to their ease of maintenance and rapid development. However, the isolation of pancreatic islets involves meticulous processes that may vary between rodent species. The present study describes a simple and effective technical protocol for isolating intact islets from mice and rats for use as a practical guide for researchers. The method involves digestion of the acinar parenchyma by intraductal collagenase. Isolated islets are suitable for in vitro endocrine secretion analyses, microscopy techniques, and biochemical analyses.

Maternal exposure to tributyltin alters the breast milk, hormonal profile, and thyroid morphology of dams and induces sex-specific changes in neonate rat offspring.

Tributyltin (TBT) is the chemical substance commonly used worldwide to prevent biofouling of vessels. Due to its ability to bioaccumulate and biomagnify, even after being banned, significant concentrations of TBT can be detected in sediment, affecting marine and human life. Although studies have shown that direct exposure to TBT alters physiological parameters in mammals, the relationship between exposure to TBT during pregnancy and lactation, considered critical windows for metabolic programming, has not been fully elucidated. Our hypothesis is that offspring whose mothers were exposed to TBT during critical stages of development may exhibit dysfunctions in endocrine-metabolic parameters. We used pregnant Wistar rats that were divided into groups and received the following treatments from gestational day 7 until the end of lactation by intragastric gavage: vehicle (ethanol 0.01%; Control), low TBT dose (100 ng/kg of body weight (bw)/day; TBT100ng) and high TBT dose (1000 ng/kg bw/day; TBT1000ng). Dams and offspring at birth and weaning (21 days old) were studied. Maternal exposure to TBT promoted dose-dependent changes in dams. The findings for adiposity, milk composition and lipid profile were more pronounced in TBT100 ng dam; however, thyroid morphology was altered in TBT1000 ng dam. Female offspring were differentially affected by the dose of exposure. At birth, females in the TBT100ng group had low body weight, lower naso-anal length (NAL), and higher plasma T4, and at weaning, females in the TBT100ng group had lower insulin and leptin levels. Females in the TBT1000ng group had lower NAL at birth and lower leptinemia and weight of white adipose tissue at weaning. Male offspring from TBT groups showed high T3 at birth, without biometric alterations at birth or weaning. Despite these findings, both sexes exhibited dose-dependent morphological changes in the thyroid gland. Thus, maternal exposure to TBT constitutes an important route of contamination for both dams and offspring.

Puberty as a DOHaD programming window: high-fat diet induces long-term hepatic dysfunction in male rats.

The aim of this study was to evaluate whether high-fat (HF) diet intake during puberty can program obesity as well as generate glucose imbalance and hepatic metabolic dysfunctions in adult life. Male Wistar rats were randomly assigned into two groups: rats fed standard chow (NF) and rats fed a HF from postnatal 30-day-old (PND30) until PND60. Then, both groups were fed a standard chow from PND60 until PND120. Euthanasia and samples collections occurred at PND120. HF animals were overweight (+11%) and had increased adiposity, hyperphagia (+12%), hyperglycaemia (+13%), hyperinsulinemia (+69%), and hypertriglyceridemia (+34%). Plasma glucose levels during intravenous glucose tolerance test (ivGTT) and intraperitoneal insulin tolerance test (ipITT) were also higher in the HF group, whereas Kitt was significantly lower (-34%), suggesting reduced insulin sensitivity. In the same sense, HF animals present pancreatic islets hypertrophy and high ß-cell mass. HF animals also had a significant increase in blood glucose levels during pyruvate tolerance test, indicating increased gluconeogenesis. Hepatic morphology analyses showed an increase in lipid inclusion in the HF group. Moreover, PEPCK and FAS protein expression were higher in the livers of the HF animals (+79% and + 37%, respectively). In conclusion, HF during puberty causes obese phenotype leading to glucose dyshomeostasis and nonalcoholic fatty liver disease, which can be related to the overexpression of proteins PEPCK and FAS.

Nicotine exposure during breastfeeding alters the expression of endocannabinoid system biomarkers in female but not in male offspring at adulthood.

Early nicotine exposure compromises offspring's phenotype at long-term in both sexes. We hypothesize that offspring exposed to nicotine during breastfeeding show deregulated central and peripheral endocannabinoid system (ECS), compromising several aspects of their metabolism. Lactating rats received nicotine (NIC, 6 mg/Kg/day) or saline from postnatal day (PND) 2 to 16 through implanted osmotic minipumps. Offspring were analyzed at PND180. We evaluated protein expression of N-acylphosphatidylethanolamide-phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), diacylglycerol lipase (DAGL), monoacylglycerol lipase (MAGL) and cannabinoid receptors (CB1 and/or CB2) in lateral hypothalamus, paraventricular nucleus of the hypothalamus, liver, visceral adipose tissue (VAT), adrenal and thyroid. NIC offspring from both sexes did not show differences in hypothalamic ECS markers. Peripheral ECS markers showed no alterations in NIC males. In contrast, NIC females had lower liver DAGL and CB1, higher VAT DAGL, higher adrenal NAPE-PLD and higher thyroid FAAH. Endocannabinoids biosynthesis was affected by nicotine exposure during breastfeeding only in females; alterations in peripheral tissues suggest lower action in liver and higher action in VAT, adrenal and thyroid. Effects of nicotine exposure during lactation on ECS markers are sex- and tissue-dependent. This characterization helps understanding the phenotype of the adult offspring in this model and may contribute to the development of new pharmacological targets for the treatment of several metabolic diseases that originate during development.

Pesticides as endocrine disruptors: programming for obesity and diabetes.

PURPOSE: Exposure to pesticides has been associated with obesity and diabetes in humans and experimental models mainly due to endocrine disruptor effects. First contact with environmental pesticides occurs during critical phases of life, such as gestation and lactation, which can lead to damage in central and peripheral tissues and subsequently programming disorders early and later in life. METHODS: We reviewed epidemiological and experimental studies that associated pesticide exposure during gestation and lactation with programming obesity and diabetes in progeny. RESULTS: Maternal exposure to organochlorine, organophosphate and neonicotinoids, which represent important pesticide groups, is related to reproductive and behavioral dysfunctions in offspring; however, few studies have focused on glucose metabolism and obesity as outcomes. CONCLUSION: We provide an update regarding the use and metabolic impact of early pesticide exposure. Considering their bioaccumulation in soil, water, and food and through the food chain, pesticides should be considered a great risk factor for several diseases. Thus, it is urgent to reformulate regulatory actions to reduce the impact of pesticides on the health of future generations.

Adverse perinatal conditions and the developmental origins of thyroid dysfunction-Lessons from Animal Models.

PURPOSE: Nutritional, hormonal, and environmental status during development can predispose the individual to obesity and endocrine diseases later in life, an association known as metabolic programming. In general, weight loss or gain are seen in thyroid disorders, and thyroid function can be affected by body adiposity. In addition, hyper- and hypothyroidism can be related to metabolic programming. Our aim was to gather evidence that regardless of the type or critical window of metabolic imprinting, offspring exposed to certain adverse perinatal conditions have a higher risk of developing thyroid dysfunction. METHODS: We reviewed literature data that relate insults occurring during pregnancy and/or lactation to short- and long-term offspring thyroid dysfunction in animal models. RESULTS: Few studies have addressed the hypothalamic-pituitary-thyroid axis and thyroid dysfunction related to metabolic programming. The literature shows that under- and overnutrition, exposure to endocrine disruptors, early weaning, maternal thyroid disease and maternal high-fat diet can induce alterations in offspring thyroid function in a sex-dependent manner. CONCLUSION: Based on the few available data, mainly in rodent models, we can conclude that diet, hormones, and environmental contaminants are related to the developmental origins of later thyroid dysfunction by interrupting the normal maturation of the thyroid gland.

Maternal high-fat diet aggravates fructose-induced mitochondrial damage in skeletal muscles and causes differentiated adaptive responses on lipid metabolism in adult male offspring.

Maternal high-fat diet (HFD) is associated with metabolic disturbances in the offspring. Fructose is a highly consumed lipogenic sugar; however, it is unknown whether skeletal muscle of maternal HFD offspring respond differentially to a fructose overload. Female Wistar rats received standard diet (STD: 9% fat) or isocaloric high-fat diet (HFD: 29% fat) during 8 weeks before mating until weaning. After weaning, male offspring received STD and, from 120 to 150 days-old, they drank water or 15% fructose in water (STD-F and HFD-F). At 150th day, we collected the oxidative soleus and glycolytic extensor digitorum longus (EDL) muscles. Fructose-treated groups exhibited hypertriglyceridemia, regardless of maternal diet. Soleus of maternal HFD offspring showed increased triglycerides and monounsaturated fatty acid content, independent of fructose, with increased fatty acid transporters and lipogenesis markers. The EDL exhibited unaltered triglycerides content, with an apparent equilibrium between lipogenesis and lipid oxidation markers in HFD, and higher lipid uptake (fatty acid-binding protein 4) accompanied by enhanced monounsaturated fatty acid in fructose-treated groups. Mitochondrial complexes proteins and Tfam mRNA were increased in the soleus of HFD, while uncoupling protein 3 was decreased markedly in HFD-F. In EDL, maternal HFD increased ATP synthase, while fructose decreased Tfam predominantly in STD offspring. Maternal HFD and fructose induced mitochondria ultrastructural damage, intensified in HFD-F in both muscles. Thus, alterations in molecular markers of lipid metabolism and mitochondrial function in response to fructose are modified by an isocaloric and moderate maternal HFD and are fiber-type specific, representing adaptation/maladaptation mechanisms associated with higher skeletal muscle fructose-induced mitochondria injury in adult offspring.

Late effects of early weaning on food preference and the dopaminergic and endocannabinoid systems in male and female rats.

Early weaning (EW) is associated with obesity later in life. Here, using an EW model in rats, we investigated changes in feeding behavior and the dopaminergic and endocannabinoid systems (ECS) in the adult offspring. Lactating Wistar rats were divided into two groups: EW, dams were wrapped with a bandage to interrupt suckling during the last 3 days of breastfeeding; CONT; dams fed the pups throughout the period without hindrances. EW animals were compared with CONT animals of the same sex. At PN175, male and female offspring of both groups could freely self-select between high-fat and high-sugar diets (food challenge test). EW males preferred the high-fat diet at 30 min and more of the high-sugar diet after 12 h compared to CONT males. EW females did not show differences in their preference for the palatable diets compared to CONT females. Total intake of standard diet from PN30-PN180 was higher in both male and female EW animals, indicating hyperphagia. At PN180, EW males showed lower type 2 dopamine receptor (D2r) in the nucleus accumbens (NAc) and dorsal striatum, while EW females had lower tyrosine hydroxylase in the ventral tegmental area and NAc, D1r in the NAc, and D2r in the prefrontal cortex. In the lateral hypothalamus, EW males had lower fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, whereas EW females showed lower N-arachidonoyl-phosphatidylethanolamine phospholipase-D and increased FAAH. Early weaning altered both the dopaminergic and ECS parameters at adulthood, contributing to the eating behavior changes of the progeny in a sex-dependent manner.

Breastfeeding undernutrition changes iBAT-involved thermogenesis protein expression and leads to a lean phenotype in adult rat offspring.

Nutritional insults early in life have been associated with metabolic diseases in adulthood. We aimed to evaluate the effects of maternal food restriction during the suckling period on metabolism and interscapular brown adipose tissue (iBAT) thermogenically involved proteins in adult rat offspring. Wistar rats underwent food restriction by 50% during the first two-thirds of lactation (FR50 group). Control rats were fed ad libitum throughout lactation (CONT group). At birth, the litter size was adjusted to eight pups, and weaning was performed at 22 days old. Body weight and food and water intake were assessed every two days. High- (HCD, 4,589 cal) and normal-caloric diet (NCD, 3,860 cal) preferences, as well as food intake during the dark part of the cycle, were assessed. At 100 days old, the rats were euthanized, and blood and tissues were removed for further analyses. Adult FR50 rats, although hyperphagic and preferring to eat HCD (P<.001), were leaner (P<.001) than the CONT group. The FR50 rats, were normoglycemic (P=.962) and had hypertriglyceridemia (P<.01). In addition, the FR50 rats were dyslipidemic (P<.01), presenting with a high atherogenic risk by the Castelli indexes (P<.01), had a higher iBAT mass (P<.01), fewer ß3 adrenergic receptors (ß3-AR, P<.05) and higher iBAT expression of uncoupled protein 1 (UCP1, P<.05) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α, P<.001) than the CONT rats. In conclusion, maternal food restriction during early breastfeeding programs rat offspring to have a lean phenotype, despite hyperphagia, and increased iBAT UCP1 and PGC-1α protein expression.

Lean in one way, in obesity another: effects of moderate exercise in brown adipose tissue of early overfed male Wistar rats.

BACKGROUND: Early postnatal overfeeding (PO) induces long-term overweight and reduces brown adipose tissue (BAT) thermogenesis. Exercise has been suggested as a possible intervention to increase BAT function. In this study, we investigated chronical effects of moderate-intensity exercise in BAT function in postnatal overfed male Wistar rats METHODS: Litters' delivery was on postnatal-day 0 - PN0. At PN2, litters were adjusted to nine (normal litter - NL) or three pups (small litter - SL) per dam. Animals were weaned on PN21 and in PN30 randomly divided into sedentary (NL-Sed and SL-Sed) or exercised (NL-Exe and SL-Exe), N of 14 litters per group. Exercise protocol started (PN30) with an effort test; training sessions were performed three times weekly at 60% of the VO2max achieved in effort test, until PN80. On PN81, a temperature transponder was implanted beneath the interscapular BAT, whose temperature was assessed in periods of lights-on and -off from PN87 to PN90. Sympathetic nerve activation of BAT was registered at PN90. Animals were euthanized at PN91 and tissues collected RESULTS: PO impaired BAT thermogenesis in lights-on (pPO < 0.0001) and -off (pPO < 0.01). Exercise increased BAT temperature in lights-on (pExe < 0.0001). In NL-Exe, increased BAT activity was associated with higher sympathetic activity (pExe < 0.05), ß3-AR (pExe < 0.001), and UCP1 (pExe < 0.001) content. In SL-Exe, increasing BAT thermogenesis is driven by a combination of tissue morphology remodeling (pExe < 0.0001) with greater effect in increasing UCP1 (pExe < 0.001) and increased ß3-AR (pExe < 0.001) content. CONCLUSION: Moderate exercise chronically increased BAT thermogenesis in both, NL and SL groups. In NL-Exe by increasing Sympathetic activity, and in SL-Exe by a combination of increased ß3-AR and UCP1 content with morphologic remodeling of BAT. Chronically increasing BAT thermogenesis in obese subjects may lead to higher overall energy expenditure, favoring the reduction of obesity and related comorbidities.

Metformin Improves Autonomic Nervous System Imbalance and Metabolic Dysfunction in Monosodium L-Glutamate-Treated Rats.

Metformin is an antidiabetic drug used for the treatment of diabetes and metabolic diseases. Imbalance in the autonomic nervous system (ANS) is associated with metabolic diseases. This study aimed to test whether metformin could improve ANS function in obese rats. Obesity was induced by neonatal treatment with monosodium L-glutamate (MSG). During 21-100 days of age, MSG-rats were treated with metformin 250 mg/kg body weight/day or saline solution. Rats were euthanized to evaluate biometric and biochemical parameters. ANS electrical activity was recorded and analyzed. Metformin normalized the hypervagal response in MSG-rats. Glucose-stimulated insulin secretion in isolated pancreatic islets increased in MSG-rats, while the cholinergic response decreased. Metformin treatment normalized the cholinergic response, which involved mostly the M3 muscarinic acetylcholine receptor (M3 mAChR) in pancreatic beta-cells. Protein expression of M3 mAChRs increased in MSG-obesity rats, while metformin treatment decreased the protein expression by 25%. In conclusion, chronic metformin treatment was effective in normalizing ANS activity and alleviating obesity in MSG-rats.

Early metformin treatment improves pancreatic function and prevents metabolic dysfunction in early overfeeding male rats at adulthood.

NEW FINDINGS: What is the central question of this study? Studies reported the efficacy of metformin as a promising drug for preventing or treating of metabolic diseases. Nutrient stresses during neonatal life increase long-term risk for cardiometabolic diseases. Can early metformin treatment prevent the malprogramming effects of early overfeeding? What is the main finding and its importance? Neonatal metformin treatment prevented early overfeeding-induced metabolic dysfunction in adult rats. Inhibition of early hyperinsulinaemia and adult hyperphagia might be associated with decreased metabolic disease risk in these animals. Therefore, interventions during infant development offer a key area for future research to identify potential strategies to prevent the long-term metabolic diseases. We suggest that metformin is a potential tool for intervention. ABSTRACT: Given the need for studies investigating the possible long-term effects of metformin use at crucial stages of development, and taking into account the concept of metabolic programming, the present work aimed to evaluate whether early metformin treatment might program rats to resist the development of adult metabolic dysfunctions caused by overnutrition during the neonatal suckling phase. Wistar rats raised in small litters (SLs, three pups per dam) and normal litters (NLs, nine pups per dam) were used as models of early overfeeding and normal feeding, respectively. During the first 12 days of suckling, animals from SL and NL groups received metformin, whereas the controls received saline injections. Food intake and body weight were monitored from weaning until 90 days of age, when biometric and biochemical parameters were assessed. The metformin treatment decreased insulin concentrations in pups from SL groups, and as adults, these animals showed improvements in glucose tolerance, insulin sensitivity, body weight gain, white fat pad stores and food intake. Low-glucose insulinotrophic effects were observed in pancreatic islets from both NL and SL groups. These results indicate that early postnatal treatment with metformin inhibits early overfeeding-induced metabolic dysfunctions in adult rats.

Thyroid redox imbalance in adult Wistar rats that were exposed to nicotine during breastfeeding.

Maternal nicotine exposure causes several consequences in offspring phenotype, such as obesity and thyroid dysfunctions. Nicotine exposure can increase oxidative stress levels, which could lead to thyroid dysfunction. However, the mechanism by which nicotine exposure during breastfeeding leads to thyroid gland dysfunction remains elusive. We aimed to investigate the long-term effects of maternal nicotine exposure on redox homeostasis in thyroid gland, besides other essential steps for thyroid hormone synthesis in rats from both sexes. Lactating Wistar rats were implanted with osmotic minipumps releasing nicotine (NIC, 6 mg/kg/day) or saline (control) from postnatal day 2 to 16. Offspring were analyzed at 180-day-old. NIC males showed lower plasma TSH, T3 and T4 while NIC females had higher T3 and T4. In thyroid, NIC males had higher sodium-iodide symporter protein expression, whereas NIC females had higher thyroid-stimulating hormone receptor (TSHr) and thyroperoxidase (TPO) protein expression. TPO activity was lower in NIC males. Hydrogen peroxide generation was decreased in NIC males. Activities of superoxide dismutase, catalase and glutathione peroxidase were compromised in NIC animals from both sexes. 4-Hydroxynonenal was higher only in NIC females, while thiol was not affected in NIC animals from both sexes. NIC offspring also had altered expression of sex steroid receptors in thyroid gland. Both sexes showed similar thyroid morphology, with lower follicle and colloid size. Thyroid from female offspring exposed to nicotine during breastfeeding developed oxidative stress, while the male gland seemed to be protected from redox damage. Thyroid dysfunctions seem to be associated with redox imbalance in a sex-dependent manner.

Hepatic lipid metabolism in adult rats using early weaning models: sex-related differences.

Non-pharmacological early weaning (NPEW) induces liver damage in male progeny at adulthood; however, pharmacological early weaning (PEW) does not cause this dysfunction. To elucidate this difference in liver dysfunction between these two models and determine the phenotype of female offspring, de novo lipogenesis, ß-oxidation, very low-density lipoprotein (VLDL) export, and gluconeogenesis in both sexes were investigated in the adult Wistar rats that were weaned after a normal period of lactation (control group) or early weaned either by restriction of access to the dams' teats (NPEW group) or by reduction of dams' milk production with bromocriptine (PEW group). The offspring received standard diet from weaning to euthanasia (PN180). NPEW males had higher plasma triglycerides and TyG index, liver triglycerides, and cholesterol by de novo lipogenesis, which leads to intracellular lipids accumulation. As expected, hepatic morphology was preserved in PEW males, but they showed increased liver triglycerides. The only molecular difference between PEW and NPEW males was in acetyl-CoA carboxylase-1 (ACC-1) and stearoyl-CoA desaturase-1 (SCD-1), which were lower in PEW animals. Both early weaning (EW) females had no changes in liver cholesterol and triglyceride contents, and the hepatic cytoarchitecture was preserved. The expression of microsomal triglyceride transfer protein was increased in both the female EW groups, which could constitute a protective factor. The changes in hepatic lipid metabolism in EW offspring were less marked in females. EW impacted in the hepatic cytoarchitecture only in NPEW males, which showed higher ACC-1 and SCD-1 when compared to the PEW group. As these enzymes are lipogenic, it could explain a worsened liver function in NPEW males.

Cholinergic-pathway-weakness-associated pancreatic islet dysfunction: a low-protein-diet imprint effect on weaned rat offspring.

Currently, metabolic disorders are one of the major health problems worldwide, which have been shown to be related to perinatal nutritional insults, and the autonomic nervous system and endocrine pancreas are pivotal targets of the malprogramming of metabolic function. We aimed to assess glucose-insulin homeostasis and the involvement of cholinergic responsiveness (vagus nerve activity and insulinotropic muscarinic response) in pancreatic islet capacity to secrete insulin in weaned rat offspring whose mothers were undernourished in the first 2 weeks of the suckling phase. At delivery, dams were fed a low-protein (4% protein, LP group) or a normal-protein diet (20.5% protein, NP group) during the first 2 weeks of the suckling period. Litter size was adjusted to six pups per mother, and rats were weaned at 21 days old. Weaned LP rats presented a lean phenotype (P < 0.01); hypoglycaemia, hypoinsulinaemia and hypoleptinaemia (P < 0.05); and normal corticosteronaemia (P > 0.05). In addition, milk insulin levels in mothers of the LP rats were twofold higher than those of mothers of the NP rats (P < 0.001). Regarding glucose-insulin homeostasis, weaned LP rats were glucose-intolerant (P < 0.01) and displayed impaired pancreatic islet insulinotropic function (P < 0.05). The M3 subtype of the muscarinic acetylcholine receptor (M3mAChR) from weaned LP rats was less responsive, and the superior vagus nerve electrical activity was reduced by 30% (P < 0.01). A low-protein diet in the suckling period malprogrammes the vagus nerve to low tonus and impairs muscarinic response in the pancreatic ß-cells of weaned rats, which are imprinted to secrete inadequate insulin amounts from an early age.

Early weaning leads to specific glucocorticoid signalling in fat depots of adult rats.

PURPOSE: Early weaning (EW) is a stressful condition that programmes a child to be overweight in adult life. Fat mass depends on glucocorticoids (GC) to regulate adipogenesis and lipogenesis. We hypothesised that the increased adiposity in models of EW was due to a disturbed HPA axis and/or disrupted GC function. METHODS: We used two experimental models, pharmacological early weaning (PEW, dams were bromocriptine-treated) and non-pharmacological early weaning (NPEW, dams' teats were wrapped with a bandage), which were initiated during the last 3 days of lactation. Offspring from both genders was analysed on postnatal day 180. RESULTS: Offspring in both models were overweight with increased visceral fat mass, but plasma corticosterone was increased in both genders in the PEW group but not the NPEW group. NPEW males had increased GRα expression in visceral adipose tissue (VAT), and GRα expression decreased in PEW males in subcutaneous adipose tissue (SAT). Females in both EW groups had increased 11ßHSD1 expression in SAT. PEW males had increased C/EBPß expression in SAT. PEW females had lower PPARy and FAS expression in VAT than the NPEW females. We detected a sex dimorphism in VAT and SAT in the EW groups regarding 11ßHSD1, GRα and C/EBPß expression. CONCLUSIONS: The accumulated adiposity induced by EW exhibited distinct mechanisms depending on gender, specific fat deposition and GC metabolism and action. The higher proportion of VAT/SAT in both sets of EW males may be related to the action of GC in these tissues, and the higher conversion of GC in SAT in females may explain the differences in the fat distribution.

Early weaning induces short- and long-term effects on pancreatic islets in Wistar rats of both sexes.

KEY POINTS: The World Health Organization recommends exclusive breastfeeding until 6 months of age as an important strategy to reduce child morbidity and mortality. Studies have associated early weaning with the development of obesity and type 2 diabetes in adulthood. In our model, we demonstrated that early weaning leads to increased insulin secretion in adolescent males and reduced insulin secretion in adult offspring. Early weaned males exhibit insulin resistance in skeletal muscle. Early weaning did not change insulin signalling in the muscle of female offspring. Taking into account that insulin resistance is one of the primary factors for the development of type 2 diabetes mellitus, this work demonstrates the importance of breastfeeding in the fight against this disease. ABSTRACT: Early weaning (EW) leads to short- and long-term obesity and diabetes. This phenotype is also observed in experimental models, in which early-weaned males exhibit abnormal insulinaemia in adulthood. However, studies regarding the effect of EW on pancreatic islets are rare. We investigated the mechanisms by which glycaemic homeostasis is altered in EW models through evaluations of insulin secretion and its signalling pathway in offspring. Lactating Wistar rats and their pups were divided into the following groups: non-pharmacological EW (NPEW): mothers were wrapped with an adhesive bandage on the last 3 days of lactation; pharmacological EW (PEW): mothers received bromocriptine to inhibit prolactin (1 mg/kg body mass/day) on the last 3 days of lactation; and control (C): pups underwent standard weaning at PN21. Offspring of both sexes were euthanized at PN45 and PN180. At PN45, EW males showed higher insulin secretion (vs. C). At PN170, PEW males exhibited hyperglycaemia in an oral glucose tolerance test (vs. C and NPEW). At PN180, EW male offspring were heavier; however, both sexes showed higher visceral fat. Insulin secretion was lower in EW offspring of both sexes. Males from both EW groups had lower glucokinase in islets, but unexpectedly, PEW males showed higher GLUT2, than did C. EW males exhibited lower insulin signalling in muscle. EW females exhibited no changes in these parameters compared with C. We demonstrated distinct alterations in the insulin secretion of EW rats at different ages. Despite the sex dimorphism in insulin secretion in adolescence, both sexes showed impaired insulin secretion in adulthood due to EW.

Moderate exercise training since adolescence reduces Walker 256 tumour growth in adult rats.

KEY POINTS: Cancer growth, cell proliferation and cachexia index can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins in adolescence. Walker 256 tumour-bearing rats who started exercise training during adolescence did not revert the basal low glycaemia and insulinaemia observed before tumour cell inoculation. The moderate exercise training improved glucose tolerance and peripheral insulin sensitivity only in rats exercised early in adolescence. The chronic effects of our exercise protocol are be beneficial to prevent cancer cachexia and hold clear potential as a nonpharmacological therapy of insulin sensitization. ABSTRACT: We tested the hypothesis that moderate exercise training, performed early, starting during adolescence or later in life during adulthood, can inhibit tumour cell growth as a result of changes in biometric and metabolic markers. Male rats that were 30 and 70 days old performed a treadmill running protocol over 8 weeks for 3 days week-1 , 44 min day-1 and at 55-65% V̇O2max . After the end of training, a batch of rats was inoculated with Walker 256 carcinoma cells. At 15 days after carcinoma cell inoculation, the tumour was weighed and certain metabolic parameters were evaluated. The data demonstrated that physical performance was better in rats that started exercise training during adolescence according to the final workload and V̇O2max . Early or later moderate exercise training decreased the cachexia index, cell proliferation and tumour growth; however, the effects were more pronounced in rats that exercised during adolescence. Low glycaemia, insulinaemia and tissue insulin sensitivity was not reverted in Walker 256 tumour-bearing rats who trained during adolescence. Cancer growth can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins during adolescence. In addition, improvement in glucose-insulin homeostasis might be involved in this process.

Monosodium l-glutamate-obesity onset is associated with disruption of central control of the hypothalamic-pituitary-adrenal axis and autonomic nervous system.

The hypothalamic-pituitary-adrenal axis (HPA) exerts important catabolic peripheral effects and influences autonomic nervous system (ANS)-mediated processes. Impaired negative-feedback control or reduced HPA axis sensitivity and altered ANS activity appear to be associated with the development and maintenance of obesity. In the present study, we examined the hypothesis that the central HPA axis is dysregulated favouring ANS disbalance in monosodium l-glutamate (MSG)-induced rat obesity. Glucose homeostasis, corticosterone, leptin and ANS electrical activity were evaluated. Adult MSG-induced obese rats exhibited fasting hyperinsulinaemia, insulin resistance, glucose intolerance, hypercorticosteronaemia, hyperleptinaemia and altered ANS activity. A decrease in food intake was observed during corticotrophin-releasing hormone (CRH) treatment in both control and MSG-treated rats. By contrast, food intake was significantly elevated in control rats treated with dexamethasone (DEXA), whereas no alterations were observed following DEXA treatment in MSG-induced obese rats. After DEXA injection, an increase in fasting insulin and glucose levels, associated with insulin resistance, was seen in both groups. As expected, there was a decrease of parasympathetic activity and an increase of sympathetic nervous activity in CRH-treated control animals and the opposite effect was seen after DEXA treatment. By contrast, there was no effect on ANS activity in MSG-rats treated with CRH or DEXA. In conclusion, impairment of the HPA axis can lead to disbalance of ANS activity in MSG-treated rats, contributing to the establishment and maintenance of obesity.

Maternal high-fat diet consumption induces sex-dependent alterations of the endocannabinoid system and redox homeostasis in liver of adult rat offspring.

Maternal diet plays a critical role in health development. Perinatal overnutrition induces metabolic dysfunctions and obesity in the offspring. Obesity is associated with endocannabinoid system (ECS) over activation and oxidative stress. Liver ECS activation induces hepatic steatosis, inflammation and fibrosis while the antagonism of cannabinoid receptors ameliorates these alterations. Here, we investigated the effect of perinatal maternal high-fat diet (HF, 29% of calories as fat) on the ECS and antioxidant system in liver of male and female adult rat offspring (180 days old). Maternal HF diet increased hepatic cannabinoid receptors, ECS metabolizing enzymes and triglyceride content, with male offspring more affected. ECS changes are likely independent of estradiol serum levels but associated with increased hepatic content of estrogen receptor, which can stimulate the expression of ECS components. Differently, maternal HF diet decreased the activity of the antioxidant enzymes glutathione peroxidase, superoxide dismutase and catalase, and increased oxidative stress markers in both sexes. Alterations in the redox homeostasis were associated with mitochondria damage but not with liver fibrosis. Our data suggest that maternal HF diet induces ECS over activation in adulthood, and that male offspring are at higher risk to develop liver disease compared with female rats.