Onset and development of hypertriglyceridemia in the Zucker rat (fa/fa).

Triglyceridemia was studied in genetically obese Zucker rats (fa/fa) and their lean littermates aged 1-8 wk. Hypertriglyceridemia was manifest in the obese from 2 wk onwards. Hepatic triacylglycerol secretion rate (TGSR) measured after administration of Triton WR-1339, was similar in obese and lean pups aged 2 wk. At 4 wk TGSR was twice as high in the obese as in the lean. Lipoprotein lipase (LPL) activity was abnormal in the tissues of obese animals, being either increased in white adipose tissue from 1 wk onwards or decreased in brown adipose tissue and cardiac and skeletal muscle from 2 wk onwards. The simultaneous appearance in the 2-wk-old obese of a decrease in LPL activity of the latter tissues, and hypertriglyceridemia strongly suggests a cause-effect relationship particularly since TGRS is normal. After weaning, LPL capacity of white adipose tissue in the obese, although considerably increased, was apparently not high enough to compensate for both an increased TGSR and a decreased LPL activity in other tissues.