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. Therefore, we evaluated whether reducing VAT mass by surgical removal of the omentum, improves insulin sensitivity and metabolic function in obese patients. Methods We conducted: 1) a 12-month randomized controlled trial to determine whether reduction in VAT by omentectomy in 22 obese subjects enhances Roux-en-Y gastric bypass (RYGB) surgery-induced improvement in hepatic and skeletal muscle insulin sensitivity, assessed by using the hyperinsulinemic-euglycemic clamp technique, and 2) a 3-month longitudinal single-arm study to determine whether laparoscopic omentectomy alone in 7 obese subjects with type 2 diabetes mellitus (T2DM) improves insulin sensitivity, assessed by using the Frequently Sampled Intravenous Glucose Tolerance Test. Results The greater omentum, weighing 0.82 kg (95% CI: 0.67–0.97) was removed from subjects who had omentectomy in both studies. In study 1, muscle insulin sensitivity (relative increase in glucose disposal during insulin infusion) approximately doubled and hepatic insulin sensitivity increased by ~4-fold at 12 months after RYGB alone and RYGB plus omentectomy compared with baseline (P<0.001). There were no significant differences between groups (P>0.87) or group×time interactions (P>0.36). In study 2, surgery had no effect on insulin sensitivity (P=0.844) and use of diabetes medications. Conclusions These results demonstrate that decreasing VAT through omentectomy, whether performed alone or in combination with RYGB surgery, does not improve metabolic function in obese patients.

Changes in Subcutaneous Fat Cell Volume and Insulin Sensitivity After Weight Loss

“…Furthermore, a study of weight loss induced by diet/lifestyle intervention showed that a reduction in visceral but not subcutaneous fat mass correlated with metabolic improvement (6). On the other hand, several studies have shown that removal of a subset of visceral adipose tissue (the greater omentum) in connection with bariatric surgery does not cause additional improvements in the metabolic profile (7)(8)(9).…”

Adipose tissue in control of metabolism

“…In support of this, transplantation of subcutaneous but not visceral adipose tissue improves glucose tolerance and insulin sensitivity in rodents , Foster et al 2013. Although there is still a controversy about metabolic function of subcutaneous and visceral fat in humans (Thorne et al 2002, Fabbrini et al 2010, the fat distribution, rather than total fat mass, most likely plays an important role in the development of obesity and its associated diseases. More studies are urgently needed to elucidate whether transplantation of subcutaneous fat in humans is as efficient as that in rodents.…”

Independent tissue contributors to obesity-associated insulin resistance

“…This observation is in line with studies using interventions such as omentectomy (0.3 to 1.0 kg VAT loss; refs. 18,19) or liposuction (0.4 to 1.7 kg SAT loss; ref. 20), which have limited effects on insulin resistance.…”