Relationship between sympathetic reactivity and body weight loss in morbidly obese subjects

Abstract

OBJECTIVE:To investigate the possible role of peripheral sympathetic activity in gastric bypass-induced body weight loss. SUBJECTS AND METHODS:In 42 morbidly obese patients (sex: 36 f/6 m; BMI: 46.070.7 kg/m 2 ) undergoing a gastric bypass, the skin vasoconstrictor reflex in answer to a deep inspiration was measured by laser Doppler fluximetry. The extent of vasoconstriction, measured at the second finger of the left hand, was expressed as percent reduction of the basal blood flux (% vasoconstriction). Insulin sensitivity was assessed before surgery in a subset of patients (n ¼ 11), by the method of euglycemic, hyperinsulinemic clamp. Body weight and composition were evaluated before, and 3, 6 and 12 months after surgery. At the same time points, energy intake (kJ/day) was evaluated by means of both food record diary and alimentary anamnesis. RESULTS: The % vasoconstriction, which was significantly (P ¼ 0.01) greater in normoglycemic subjects than in diabetic ones, was also significantly (P ¼ 0.03) related to the extent of insulin sensitivity measured during the euglycemic clamp. The % vasoconstriction showed a significant (P40.0001), positive correlation with weight reduction obtained between the 6th and 12th months following surgery; as a consequence, % vasoconstriction was significantly (P ¼ 0.0004) related to the overall body weight loss achieved during the year following the operation. These correlations remained significant in multiple regression analysis with adjustment for age, initial body weight, plasma glucose and insulin (P ¼ 0.0007 and 0.006, respectively). The % vasoconstriction was also significantly (P ¼ 0.0006), negatively related to energy intake measured 12 months after surgery. CONCLUSIONS: In conditions of stable body weight, the sympathetic nervous system (SNS) reactivity is influenced by the degree of insulin resistance. A high capacity to activate the SNS, measured before surgery, is associated with both a larger gastric bypass-induced weight loss and a lower energy intake, at the phase of weight stabilization.

The effect of insulin on cardiac autonomic balance predicts weight reduction after gastric bypass

“…In keeping with our previous results [13], the present study further underlines the involvement of the autonomic nervous system in the outcome of surgically induced weight loss.…”

“…The presence of a rapid and a slow phase of weight reduction following gastric bypass has been well documented [26]: this profile is due mainly to the pattern of energy intake, which is extremely low in the early postoperative period and, then, progressively increases up to 1 year after surgery [13,26,27]. Our results clearly indicate that, besides energy intake, other factors can influence weight loss at different phases of the process.…”

“…Although our previous [13] and current results clearly establish that autonomic nervous system responsiveness is predictive of weight loss, the underlying mechanisms remain unknown.…”

“…In a previous study [13], we investigated the sympathetically mediated vasoconstrictive response to a deep inspiration, at the capillary level, in a group of obese subjects undergoing a gastric bypass. We were able to demonstrate that an elevated sympathetic reactivity was associated significantly with a larger % EWL, 12 months after the operation.…”

Impact of Different Bariatric Surgical Procedures on Insulin Action and β-Cell Function in Type 2 Diabetes

“…1)-in other words, when weight-stabilized subjects had gained insulin sensitivity in exact proportion to the weight change. Strikingly similar results are obtained when plotting data from two other clamp studies, using caloric restriction (38) or RYGB (70). In contrast, in 107 patients, 35 of whom with type 2 diabetes, undergoing BPD and restudied 2 years later, the increase in insulin sensitivity definitely exceeded the prediction; i.e., insulin resistance was normal or supernormal at BMI values still in the obese range (67).…”