Alteration of the counterregulatory responses to insulin-induced hypoglycemia and of cognitive function after massive weight reduction in severely obese subjects

The autonomic nervous system (ANS) and hypothalamic-pituitary-adrenal (HPA) axis are reported as activated in excess in the morbidly obese state and, therefore, changes after weight loss can be anticipated. The aim of this study was to investigate the impact of a massive (similar to30%) weight reduction on the activation of the HPA axis and the ANS following bariatric surgery. Eight (7 women, 1 man) severely obese (125 +/- 12 kg; body mass index [BMI], 45 +/- 4 kg/m(2)) nondiabetic subjects, underwent a 3-hour hyperinsulinemic (1,034 pmol/kg/h) glucose clamp study at hypoglycemia of arterial B-glucose concentration of 3.4 mmol/L. Cognitive function was evaluated by a visuospatial computerized problem-solving test, the Perceptual Maze Test (PMT). The mean weight loss was 40 +/- 9 kg approximately 12 months postsurgery when their weight was stabilized (85 6 kg; BMI, 31 +/- 3 kg/m(2)), and insulin sensitivity improved to an average increase of 376% +/- 250% (P < .01) of initial value. Before weight reduction, all patients demonstrated brisk peak responses in glucagon, epinephrine, pancreatic polypeptide (PP), norepinephrine, and cortisol, indicative of preserved or exaggerated activation of ANS and HPA axis. In the reduced-obese state, all these responses were attenuated and most markedly so for glucagon, which was totally abolished. In contrast, the growth hormone (GH) response was increased after weight reduction. The cognitive function was clearly modified by weight reduction both during normoglycemia and hypoglycemia and was changed preferentially to a speed-preferring strategy in the reduced-obese state compared with a more accuracy preferred problem-solving process of PMT test presurgery. These results demonstrate a reduction of the glucose counterregulatory hormonal responses, increased insulin sensitivity, and perturbed cognitive function after massive weight reduction. It may be speculated on if the increased insulin sensitivity and reduced counterregulation to hypoglycemia could predispose to low plasma glucose concentrations.