Study on the inhibitory effect of uremic plasma on lipoprotein lipase

An investigation was undertaken to determine which plasma factors from normal controls and patients with chronic renal failure (CRF) exert have inhibitory effects on the activity of lipoprotein lipase (LPL) purified from heparinized human plasma by using an accurate LPL assay system. Inhibitors of LPL were found to be present in the plasma. The inhibition of the LPL activity was significantly greater in CRF patients than in normal controls. Following hemodialysis (HD), the same concentration of uremic plasma led to less inhibition. The inhibitors existed only in lipoprotein deficient plasma (LPDS), which demonstrated an LPL-inhibitory activity at extremely high concentrations with a significant difference between the patients and normal controls. There was no difference between the two groups at low concentrations. A specific inhibitory effect on LPL in LPDS was noted in the 7S and 4S fractions separated by gel filtration employing Sephacryl S-200 column chromatography. The inhibitory effect of the 7S fraction was found to be dependent on the concentration, and the difference between the two groups was similar to that for LPDS. The results obtained in the present study suggest that the plasma from CRF patients exhibited a strong inhibitory action on the LPL activity as compared to the plasma from normal controls, and the inhibitory action was due primarily due to poor excretion of dialyzable inhibitors.