We have previously reported that normal Wistar rats fed an isocaloric,
sucrose-rich (63%) diet (SRD) developed
glucose intolerance and elevated
triglyceride levels in plasma as well as in heart and liver tissue. This metabolic state was accompanied by
hyperinsulinism both in vivo and in vitro, suggesting that a state of
insulin resistance has developed. The aim of this study was to gather information on the various plasma post-
heparin lipolytic activities in rats fed a SRD. Hepatic
triglyceride lipase (H-TGL) was evaluated by both,
protamine sulfate inhibition (PSI) of extrahepatic
lipoprotein lipase (LPL) and
heparin-Sepharose affinity chromatography (H-SAC). Both methods rendered comparable results. Total
triglyceride lipase (T-TGL) was measured after Krauss et al. and
monoglyceride hydrolase (MGH) after Vogel et al. Our results have shown a significant decline of plasma T-TGL (5.32 +/- 0.34 means +/- SEM vs. 7.48 +/- 0.64 mumol
glycerol ml-1 h-1; p less than 0.01), H-TGL (3.71 +/- 0.28 vs. 5.05 +/- 0.69; p less than 0.05), LPL (1.61 +/- 0.26 vs. 2.42 +/- 0.41; p less than 0.05) and MGH (558 +/- 108 mumol
glycerol l-1 min-1 vs. 1,165 +/- 45; p less than 0.001) activities. Thus, feeding a
sucrose-rich diet induced a state of
hyperlipemia and
insulin resistance in which not only plasma T-TGL but also H-TGL and MGH activities were significantly decreased. This suggests that the latter two
enzymes are also under nutritional and/or hormonal control.