Hypothalamic MSG-obese rats show hyperinsulinemia and tissue insulin resistance, and they display intense parasympathetic activity. Current analysis investigates whether early subdiaphragmatic vagotomy prevents tissue insulin sensitivity impairment in adult obese MSG-rats. Hypothalamic obesity was induced by MSG (4 mg/g BW), daily, from birth up to 5 days. Control animals receiving saline solution. On the 30th day rats underwent bilateral subdiaphragmatic vagotomy or sham surgery. An intravenous glucose tolerance test (i.v.GTT) was performed when rats turned 90 days old. Total white fat tissue (WAT) from rat carcass was extracted and isolated; the interscapular brown fat tissue (IBAT) was weighed. Rather than blocking obesity, vagotomy reduced WAT and IBAT in MSG-obese rats when the latter were compared to sham MSG-rats. High blood fasting insulin and normal glucose levels were also observed in MSG-obese rats. Although glucose intolerance, high insulin secretion, and significant insulin resistance were recorded, vagotomy improved fasting insulinemia, glucose tolerance and insulin tissue sensitivity in MSG-obese rats. Results suggest that increased fat accumulation is caused, at least in part, by high blood insulin concentration, and enhanced parasympathetic activity on MSG-obese rats.

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The aim of the present study was to evaluate the preventive effects of taurine (TAU) supplementation upon monosodium glutamate (MSG)-induced obesity. Rats treated during the first 5 days of life with MSG or saline were distributed into the following groups: control (CTL), CTL-treated with TAU (CTAU), MSG and MSG-supplemented with TAU (MTAU). CTAU and MTAU received 2.5% of TAU in their drinking water from 21 to 90 days of life. At the end of treatment, MSG and MTAU rats were hyperinsulinemic, glucose intolerant and insulin resistant, as judged by the HOMA index. MSG and MTAU rat islets secreted more insulin at 16.7 mM glucose compared to CTL. MSG rats also showed higher triglycerides (TG) and non-esterified fatty acids (NEFA) plasma levels, Lee Index, retroperitoneal and periepidydimal fat pads, compared with CTL, whereas plasma lipid concentrations and fat depots were lower in MTAU, compared with MSG rats. In addition, MSG rats had a higher liver TG content compared with CTL. TAU decreased liver TG content in both supplemented groups, but fat content only in MTAU rats. TAU supplementation did not change glucose homeostasis, insulin secretion and action, but reduced plasma and liver lipid levels in MSG rats.

One of the most consumed pesticides in the world is glyphosate, the active ingredient in the herbicide ROUNDUP®. Studies demonstrate that glyphosate can act as an endocrine disruptor and that exposure to this substance at critical periods in the developmental period may program the fetus to induce reproductive damage in adulthood. Our hypothesis is that maternal exposure to glyphosate during pregnancy and lactation in mice will affect the development of male reproductive organs, impairing male fertility during adult life. Female mice consumed 0.5% glyphosate-ROUNDUP® in their drinking water [glyphosate-based herbicide (GBH) group] or filtered water [control (CTRL) group] from the fourth day of pregnancy until the end of the lactation period. Male F1 offspring were designated, according to their mother’s treatment, as CTRL-F1 and GBH-F1. Female mice that drank glyphosate displayed reduced body weight (BW) gain during gestation, but no alterations in litter size. Although GBH male F1 offspring did not exhibit modifications in BW, they demonstrated delayed testicular descent. Furthermore, at PND150, GBH-F1 mice presented a lower number of spermatozoa in the cauda epididymis and reduced epithelial height of the seminiferous epithelium. Notably, intratesticular testosterone concentrations were enhanced in GBH-F1 mice; we show that it is an effect associated with increased plasma and pituitary concentrations of luteinizing hormone. Therefore, data indicate that maternal exposure to glyphosate-ROUNDUP® during pregnancy and lactation may lead to decreased spermatogenesis and disruptions in hypothalamus–pituitary–testicular axis regulation in F1 offspring.

Swimming exercises by weaning pups inhibited hypothalamic obesity onset and recovered sympathoadrenal axis activity, but this was not observed when exercise training was applied to young adult mice. However, the mechanisms producing this improved metabolism are still not fully understood. Low-intensity swimming training started at an early age and was undertaken to observe glycemic control in hypothalamic-obese mice produced by neonatal treatment with monosodium L-glutamate (MSG). Whereas MSG and control mice swam for 15 min/day, 3 days a week, from the weaning stage up to 90 days old, sedentary MSG and normal mice did not exercise at all. After 14 h of fasting, animals were killed at 90 days of age. Perigonadal fat accumulation was measured to estimate obesity. Fasting blood glucose and insulin concentrations were also measured. Fresh isolated pancreatic islets were used to test glucose-induced insulin release and total catecholamine from the adrenal glands was measured. Mice were also submitted to intraperitoneal glucose tolerance test. MSG-obese mice showed fasting hyperglycemia, hyperinsulinemia, and glucose intolerance. Severe reduction of adrenal catecholamines content has also been reported. Besides, the inhibition of fat tissue accretion, exercise caused normalization of insulin blood levels and glycemic control. The pancreatic islets of obese mice, with impaired glucose-induced insulin secretion, were recovered after swimming exercises. Adrenal catecholamine content was increased by swimming. Results show that attenuation of MSG-hypothalamic obesity onset is caused, at least in part, by modulation of sympathoadrenal axis activity imposed by early exercise, which may be associated with subsequent glucose metabolism improvement.

The parasympathetic nervous system is important for β-cell secretion and mass regulation. Here, we characterized involvement of the vagus nerve in pancreatic β-cell morphofunctional regulation and body nutrient homeostasis in 90-day-old monosodium glutamate (MSG)-obese rats. Male newborn Wistar rats received MSG (4 g/kg body weight) or saline [control (CTL) group] during the first 5 days of life. At 30 days of age, both groups of rats were submitted to sham-surgery (CTL and MSG groups) or subdiaphragmatic vagotomy (Cvag and Mvag groups). The 90-day-old MSG rats presented obesity, hyperinsulinemia, insulin resistance, and hypertriglyceridemia. Their pancreatic islets hypersecreted insulin in response to glucose but did not increase insulin release upon carbachol (Cch) stimulus, despite a higher intracellular Ca2+ mobilization. Furthermore, while the pancreas weight was 34% lower in MSG rats, no alteration in islet and β-cell mass was observed. However, in the MSG pancreas, increases of 51% and 55% were observed in the total islet and β-cell area/pancreas section, respectively. Also, the β-cell number per β-cell area was 19% higher in MSG rat pancreas than in CTL pancreas. Vagotomy prevented obesity, reducing 25% of body fat stores and ameliorated glucose homeostasis in Mvag rats. Mvag islets demonstrated partially reduced insulin secretion in response to 11.1 mM glucose and presented normalization of Cch-induced Ca2+ mobilization and insulin release. All morphometric parameters were similar among Mvag and CTL rat pancreases. Therefore, the higher insulin release in MSG rats was associated with greater β-cell/islet numbers and not due to hypertrophy. Vagotomy improved whole body nutrient homeostasis and endocrine pancreatic morphofunction in Mvag rats.

Ala supplementation led to more pronounced metabolic improvements compared to Arg, possibly due to suppression of lipogenesis through activation of the AMPK/ACC pathway.

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.