Objectives: The purpose of this study was to investigate the possibility of impaired lipolysis of triglyceride-rich lipoproteins in patients with abdominal visceral fat accumulation by assessing two major lipolytic enzymes in the plasma, lipoprotein lipase (LPL) and hepatic lipase (HL).
Design and patients: A total of 31 patients [20 men, 11 women, age 50 +/- 7 years old, body mass index (BMI) 26 +/- 2 kg/m2 (mean +/- sd)] were analyzed. Visceral fat and subcutaneous fat areas were evaluated using a computerized tomographic (CT) method at the level of the umbilicus. Total lipolytic activity in the postheparin plasma (PHP) was measured using Triton X-100-emulsified triolein and LPL activity was calculated as the activity in whole plasma inhibited by the 5D2 monoclonal antibody for LPL. LPL enzyme mass was determined by a sandwich enzyme immunoassay.
Results: The visceral fat area was found to be negatively correlated with LPL mass (V vs LPL mass, r = -0.37, P = 0.04) in PHP and had a tendency toward negative correlation with the LPL activity in the PHP (V vs LPL activity, r = -0.29, P = 0.12). Subcutaneous fat area, on the other hand, did not show any correlation with LPL activity (r = 0.13, P = 0.49) or mass (r = 0.22, P = 0.25) in the PHP. The visceral fat area was found to be positively correlated with fasting serum insulin levels (r = 0.67, P < 0.01). Body mass index (BMI) was not correlated with LPL mass or activity in the PHP. Multi-regressional analysis showed that abdominal visceral fat could be correlated with LPL mass in the PHP, independently of fasting serum insulin. The HL activity from PHP of the patients did not show significant correlation with visceral fat area, subcutaneous fat area or body mass index.
Conclusions: Fat distribution affects LPL mass and activity, either directly or via another metabolic abnormality such as insulin resistance, leading to impaired hydrolysis of triglycerides in chylomicrons and very low density lipoproteins (VLDL) in these subjects.