A comparison of abdominal subcutaneous adipose tissue pattern in obese and lean HIV-infected women

Cells from the superficial and deep subcompartments of the abdominal subcutaneous adipose tissue (SAT) compartment have distinct metabolic activities in vitro. The effect of differing energy balance on the relative in vivo sizes of these subcompartments has not been reported. We retrospectively investigated the effects of obesity and leanness on the relative amounts of superficial and deep SAT in the bulky posterior abdominal adipose tissue in HIV(+) women. We studied the baseline results of MRI scans in 32 obese and 28 lean HIV-infected women. We also compared the change in response to specific interventions. Abdominal MRI slices were obtained at the L4-L5 and L2-L3 intervertebral spaces and were divided into anterior and posterior halves. The posterior portions were further subdivided into deep (PDSAT) and superficial layers (PSSAT) based on tissue planes visible on the MRI. Fat areas in adjacent landmark levels at the trochanter and anterior superior iliac spine were also obtained. PDSAT was larger at L4-L5 than at L2-L3 in both the lean and obese groups. PDSAT was larger than PSSAT at L4-L5 in obese women, and there was preferential loss of PDSAT in obese women who completed a 12-wk energy-deficit diet and exercise program. The contents of PDSAT and PSSAT did not differ in the lean group, and proportional increases in both SAT subcompartments were noted in response to weight gain. In summary, obesity is associated with a preferential increase in PDSAT and greater loss in PDSAT after weight loss. This study defines distinct metabolism responses in fat subcompartments.