Low sensitivity to the antilipolytic effects of insulin in adipose tissue has been linked with impaired insulin-mediated glucose uptake in skeletal muscle. The aims of this study were: 1) to compare adipose tissue morphology in obese adults with high- (HIGH) vs. low-sensitivity (LOW) to the antilipolytic effects of insulin, and 2) compare the effects of exercise training on adipose tissue from HIGH vs. LOW subjects. Using isotopic dilution methods before and during a hyperinsulinemic-euglycemic clamp, we measured the antilipolytic response to insulin in a total of 36 obese adults - and we identified sub-cohorts of 13 LOW (64±7% lipolytic suppression by insulin; BMI: 34±4kg/m2) and 13 HIGH (82±3% lipolytic suppression by insulin; BMI:33±3kg/m2). Abdominal subcutaneous adipose tissue (aSAT) samples were collected before the clamp (non-insulin stimulated). Measurements were made before and after a 12-week endurance exercise training program (4 days/week). Before training, capillary density (# of capillaries/mm2) in aSAT samples for LOW was significantly lower than HIGH (p=0.004). Collagen abundance in aSAT extracellular matrix (ECM) was lower in LOW (p=0.013). In response to training, the antilipolytic response to insulin was significantly improved in LOW (72±5% lipolytic suppression by insulin; p<0.001) but not HIGH. This was accompanied by an increased capillary density (p=0.03), and collagen abundance in ECM (p = 0.02), along with a slight reduction in fat mass (1±1kg; p=0.05). Adipocyte size was reduced in both groups (p=0.02).

In summary, aSAT from obese adults with low antilipolytic sensitivity to insulin displayed lower capillarization and ECM collagen abundance compared with obese adults with high sensitivity to the antilipolytic effects of insulin. Importantly, morphological adaptations to exercise training accompanied an increased antilipolytic sensitivity to insulin in subjects with low antilipolytic sensitivity before training.


C. Ahn: None. M. W. Schleh: None. B. J. Ryan: None. A. Ludzki: None. P. Varshney: None. J. B. Gillen: None. S. Chen: None. J. F. Horowitz: None.


National Institutes of Health (R01DK077966, P30DK089503, T32DK007245, F32DK117522); Canadian Institutes of Health Research (DFS146190, 338735)

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