Vagotomy ameliorates islet morphofunction and body metabolic homeostasis in MSG-obese rats

The parasympathetic nervous system is important for β-cell secretion and massregulation. Here, we characterized involvement of the vagus nerve in pancreaticβ-cell morphofunctional regulation and body nutrient homeostasis in 90-day-oldmonosodium glutamate (MSG)-obese rats. Male newborn Wistar rats received MSG (4 g/kgbody weight) or saline [control (CTL) group] during the first 5 days of life. At 30days 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 ratspresented obesity, hyperinsulinemia, insulin resistance, and hypertriglyceridemia.Their pancreatic islets hypersecreted insulin in response to glucose but did notincrease insulin release upon carbachol (Cch) stimulus, despite a higherintracellular Ca²⁺ mobilization. Furthermore, while the pancreas weightwas 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 totalislet and β-cell area/pancreas section, respectively. Also, the β-cell number perβ-cell area was 19% higher in MSG rat pancreas than in CTL pancreas. Vagotomyprevented obesity, reducing 25% of body fat stores and ameliorated glucosehomeostasis in Mvag rats. Mvag islets demonstrated partially reduced insulinsecretion in response to 11.1 mM glucose and presented normalization of Cch-inducedCa²⁺ mobilization and insulin release. All morphometric parameters weresimilar among Mvag and CTL rat pancreases. Therefore, the higher insulin release inMSG rats was associated with greater β-cell/islet numbers and not due to hypertrophy.Vagotomy improved whole body nutrient homeostasis and endocrine pancreaticmorphofunction in Mvag rats.