Postabsorptive VLDL-TG Fatty Acid Storage in Adipose Tissue in Lean and Obese Women

Adipose tissue lipoprotein lipase (LPL) is a necessary enzyme for storage of very-low-density lipoprotein-triglyceride (VLDL-TG), but whether it is a rate-determining step is unknown. To test this hypothesis we included 10 upper-body obese (UBO), 11 lower-body obese (LBO), and 8 lean women. We infused ex vivo-labeled VLDL-C-14-TG and then performed adipose tissue biopsies to understand the relationship between VLDL-TG storage and LPL activity in femoral and upper-body subcutaneous fat. Both fractional tracer storage and rate of storage of the VLDL-TG tracer were evaluated. VLDL-TG storage was also examined as a function of regional adipose tissue blood flow (ATBF), insulin, VLDL-TG turnover, regional fat mass, fat-free mass (FFM), and fat cell size. LPL activity per adipocyte was significantly greater in obese than lean women but not significantly different per gram lipid. Both VLDL-TG fractional tracer storage per kg lipid and VLDL-TG storage rate per kg lipid were similar in abdominal and femoral fat in all three groups and were not significantly different between groups. Multiple regression analysis identified FFM and femoral fat mass as significant independent predictors of VLDL-TG fractional tracer storage and insulin as a significant predictor of VLDL-TG fatty acid storage rate. LPL activity, ATBF, and VLDL-TG turnover did not predict VLDL-TG storage. We conclude that lower FFM and greater plasma insulin are associated with greater VLDL-TG deposition in abdominal subcutaneous and femoral fat. Greater femoral fat mass signals greater femoral VLDL-TG storage. We suggest that the differences in VLDL-TG storage in abdominal and femoral fat that occur with progressive obesity are regulated through mechanisms other than LPL activity.