431 Impact of a bariatric surgery-induced weight loss on ectopic fat mobilization in skeletal muscle; relationship with insulin resistance

Abstract

Severe obesity is frequently associated with abnormal ectopic fat deposition in like skeletal muscle. This may be linked to insulin resistance. After bariatric surgery-induced weight loss, the modulation of adiposity and skeletal muscle in the context of insulin resistance is not known. The purpose of the study was to measure the impact of weight loss and changes in insulin resistance following a biliopancreatic diversion with duodenal switch (BPD-DS) procedure on thigh's adiposity and skeletal muscle. Anthropometric measures, mid-thigh computed tomography (CT) and blood parameters (fasting plasma triglycerides, glucose and insulin) were measured at baseline and at 12 months in severely obese subjects who underwent BPD-DS (n = 40) and in a severely obese control group (n = 20). At baseline, the two groups were similar for age, sex and blood sample parameters but not for weight (126.7 ± 22.2 vs. 115.0 ± 18.9 kg; P = 0.049, BPD-DS vs. control group respectively) and body mass index (BMI) (47.0 ± 5.4 vs. 42.8 ± 4.6 kg/m2; P = 0.004). At 12 months, in the BDP-DS group, there were significant decrement in weight (37.7 ± 9.5%), BMI (36.7 ± 7.4%) as well as in mid-thigh CT composition: total adipose tissue (49.3 ± 15.1%), deep adipose tissue (51.9 ± 18.9%), subcutaneous adipose tissue (49.2 ± 15.0%), total skeletal muscle (19,6 ± 7,6%), low-density muscle (fat infiltrated) (34,4 ± 14,7%) and normal density muscle (11.0 ± 10.2%); all P ≤ 0.001. Regarding blood parameters, BPD-DS was associated with a decrease in triglycerides levels (1.8 ± 1.2 to 1.2 ± 0.6 mmol/L; P = 0.027), insulin resistance (HOMA) (8.4 ± 6.1 to 1.4 ± 1.0; P < 0.001), plasma insulin (184.4 ± 113.9 to 44.0 ± 35.1 ìU/ml; P < 0.001) and fasting glucose (7.0 ± 2.6 to 5.0 ± 0.5 mmol/L; P = 0.006). There were no changes in mid-thigh CT composition and blood samples parameters in the control group. At 12 months, thigh deep adipose tissue was associated with triglycerides levels (r = 0.474; P = 0.002), plasma insulin (r = 0.658; P < 0.001) and HOMA (r = 0.674; P < 0.001). Furthermore, low-density muscle (fat infiltrated) correlated with HOMA (r = 0.576; P < 0.001). BPD-DS surgery-induced weight loss is associated with major impacts on both lean and fat thigh mass. Subcutaneous and deep thigh fat decreased in the same proportion. Furthermore, the surgery has more beneficial impact on fat infiltrated muscle than on the normal density muscle. Mobilization of ectopic fat on thigh, that is thigh deep adipose tissue and low-density muscle, may be one mechanism promoting the reduction of insulin resistance after BPD-DS.