Surgical removal of omental fat does not improve insulin sensitivity and cardiovascular risk factors in obese adults

Abstract

Background & aims: Visceral adipose tissue (VAT) is an important risk factor for the metabolic complications associated with obesity. Therefore, a reduction in VAT is considered an important target of obesity therapy. We evaluated whether reducing VAT mass by surgical removal of the omentum improves insulin sensitivity and metabolic function in obese patients.

Methods: We conducted a 12-month randomized controlled trial to determine whether reducing VAT by omentectomy in 22 obese subjects increased their improvement following Roux-en-Y gastric bypass (RYGB) surgery in hepatic and skeletal muscle sensitivity to insulin study 1. Improvement was assessed by using the hyperinsulinemic-euglycemic clamp technique. We also performed a 3-month, longitudinal, single-arm study to determine whether laparoscopic omentectomy alone, in 7 obese subjects with type 2 diabetes mellitus (T2DM), improved insulin sensitivity study 2. Improvement was assessed by using the Frequently Sampled Intravenous Glucose Tolerance Test.

Results: The greater omentum, which weighed 0.82 kg (95% confidence interval: 0.67-0.97), was removed from subjects who had omentectomy in both studies. In study 1, there was an approximate 2-fold increase in muscle insulin sensitivity (relative increase in glucose disposal during insulin infusion) and a 4-fold increase in hepatic insulin sensitivity 12 months after RYGB alone and RYGB plus omentectomy, compared with baseline values (P<.001). There were no significant differences between groups (P>.87) or group x time interactions (P>.36). In study 2, surgery had no effect on insulin sensitivity (P=.844) or use of diabetes medications.

Conclusions: These results demonstrate that decreasing VAT through omentectomy, alone or in combination with RYGB surgery, does not improve metabolic function in obese patients.

Trial registration: ClinicalTrials.gov NCT00212160 NCT00270439.

Figure 1. Effects of bariatric surgery with or without omentectomy on skeletal muscle and hepatic insulin sensitivity

The relative increase (above basal) in glucose disposal during insulin infusion and the hepatic insulin sensitivity index were determined at baseline (before surgery), and at 6 and 12 months after Roux-en-Y gastric bypass (RYGB) surgery alone (n=11) or RYGB surgery plus omentectomy (n=11) in obese subjects with and without type 2 diabetes, by using the hyperinsulinemic glucose clamp procedure with radioactive tracer infusion. Data for hepatic insulin sensitivity were log-transformed for analysis. Values are shown as means with 95% confidence intervals. There were significant main effects of time on skeletal muscle and hepatic insulin sensitivity (both P<0.001) but no significant differences between groups (P=0.897 and P=0.874, respectively) or group×time interactions (P=0.959 and P=0.361, respectively); *P<0.00002 vs. value before surgery.

Figure 2. Effects of omentectomy alone on insulin sensitivity and glucose effectiveness

Insulin sensitivity (Si) and glucose effectiveness (Sg) were determined by using the frequently sampled intravenous glucose tolerance test and minimal model in obese subjects with type 2 diabetes (n=7) before and 3 months after laparoscopic omentectomy. Data for glucose effectiveness were log-transformed for analysis. Values are shown as means with 95% confidence intervals. There were no significant differences in Si (P=0.844) or Sg (P=0.663).