Reduction in visceral adipose tissue is associated with improvement in apolipoprotein B-100 metabolism in obese men

We investigated the effect of reduction in visceral obesity on the kinetics of apolipoprotein B-100 (apoB) metabolism in a controlled dietary intervention study in 26 obese men. Hepatic secretion of very low density lipoprotein (VLDL) apoB was measured using a primed, constant, infusion of 1-[C-13]leucine. In seven men receiving the reduction diet, intermediate density lipoprotein (IDL) and low density lipoprotein (LDL) apoB kinetics were also determined. ApoB isotopic enrichment was measured using gas chromatography-mass spectrometry, and SAAM-II was used to estimate the fractional turnover rates. Subcutaneous and visceral adipose tissues at the L3 vertebra were quantified by magnetic resonance imaging. With weight reduction there was a significant decrease (P < 0.05) in body mass index, waist circumference, and visceral adipose tissue. The plasma concentrations of total cholesterol, triglyceride, insulin, and lathosterol also significantly decreased (P < 0.05). Compared with weight maintenance, weight reduction significantly decreased the VLDL apoB concentration, pool size, and hepatic secretion of VLDL apoB (Delta+2.5 +/- 4.6 vs. Delta-14.7 +/- 4.0 mg/kg fat free mass day; P = 0.010), but did not significantly alter its fractional catabolism. Weight reduction was also associated with an increased fractional catabolic rate of LDL apoB (0.24 +/- 0.07 vs. 0.54 +/- 0.10 pools/day; P = 0.002) and conversion of VLDL to LDL apoB (11.7 +/- 2.58 vs. 56.3 +/- 11.4%; P = 0.008). A change in hepatic VLDL apoB secretion was significantly correlated with a change in visceral adipose tissue area (r = 0.59; P = 0.043), but not plasma concentrations of insulin, free fatty acids, or lathosterol. The data support the hypothesis that a reduction in visceral adipose tissue is associated with a decrease in the hepatic secretion of VLDL apoB, and this may be due to a decrease in portal lipid substrate supply. Weight reduction may also increase the fractional catabolism of LDL apoB, but this requires further evaluation.