Dietary intake of medium- and long-chain triacylglycerols ameliorates insulin resistance in rats fed a high-fat diet.

OBJECTIVE

Excessive accumulation of visceral fat is strongly associated with insulin resistance. The present investigation examined the effects of dietary intake of medium- and long-chain triacylglycerols (MLCTs), which have been shown to induce significantly lower visceral fat accumulation in rats and humans, on high-fat diet-induced obesity and insulin resistance in rats. These effects were then compared with those observed in long-chain triacylglycerol (LCT)-fed rats.

METHODS

After an 8-wk feeding of a high-fat diet, which induced severe whole-body insulin resistance, male Sprague-Dawley rats were fed a standard diet containing LCTs or MLCTs for 6 wk. After the dietary treatment, an oral glucose tolerance test was performed.

RESULTS

Although body weight and total intra-abdominal fat mass did not differ between the two groups, mesenteric fat weight in the MLCT-fed group was significantly lower than that in the LCT group (P < 0.05). The increase in plasma insulin concentrations, but not in glucose, after glucose administration (area under the curve) was significantly smaller in the MLCT group than in the LCT group (P < 0.01) and was significantly associated with mesenteric fat weight (P < 0.05). MLCT-fed rats had significantly higher plasma adiponectin concentrations compared with LCT rats (P < 0.05). Adiponectin concentrations were negatively correlated with the area under the curve for plasma insulin (P < 0.05) and tended to be inversely related to mesenteric fat weight (P = 0.08).

CONCLUSIONS

These results suggest that dietary intake of MLCTs may improve insulin resistance in rats fed a high-fat diet, at least in part through increased adiponectin concentrations caused by a lower mesenteric fat mass.