Apolipoprotein C3 Deficiency Results in Diet-Induced Obesity and Aggravated Insulin Resistance in Mice

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Abstract
Our aim was to study whether the absence of apolipoprotein (apo) C3, a strong inhibitor of lipoprotein lipase (LPL), accelerates the development of obesity and consequently insulin resistance. Apoc3−/− mice and wild-type littermates were fed a high-fat (46 energy %) diet for 20 weeks. After 20 weeks of high-fat feeding, apoc3−/− mice showed decreased plasma triglyceride levels (0.11 ± 0.02 vs. 0.29 ± 0.04 mmol, P < 0.05) and were more obese (42.8 ± 3.2 vs. 35.2 ± 3.3 g; P < 0.05) compared with wild-type littermates. This increase in body weight was entirely explained by increased body lipid mass (16.2 ± 5.9 vs. 10.0 ± 1.8 g; P < 0.05). LPL-dependent uptake of triglyceride-derived fatty acids by adipose tissue was significantly higher in apoc3−/− mice. LPL-independent uptake of albumin-bound fatty acids did not differ. It is interesting that whole-body insulin sensitivity using hyperinsulinemic-euglycemic clamps was decreased by 43% and that suppression of endogenous glucose production was decreased by 25% in apoc3−/− mice compared with control mice. Absence of apoC3, the natural LPL inhibitor, enhances fatty acid uptake from plasma triglycerides in adipose tissue, which leads to higher susceptibility to diet-induced obesity followed by more severe development of insulin resistance. Therefore, apoC3 is a potential target for treatment of obesity and insulin resistance.