Previous studies demonstrated that, compared with long-chain TAG (LCT), dietary medium-chain TAG (MCT) could improve
glucose tolerance in rats and humans. It has been well established that
adiponectin acts to increase
insulin sensitivity. The effects of dietary MCT on
adiponectin serum concentration and
mRNA levels in adipose tissue were studied in rats. Male Sprague-Dawley rats were fed a diet containing 20% MCT or LCT for 8 wk. After 6 wk of dietary treatment, an oral
glucose tolerance test was performed. Rats fed the MCT diet had less body fat accumulation than those fed the LCT diet (P < 0.01). The cell diameter of the perirenal adipose tissue, one of the abdominal adipose tissues, was smaller (P < 0.01) in the MCT diet group. The serum
adiponectin concentration was higher (P < 0.01) in the MCT diet group than in the LCT diet group. The
adiponectin content in the perirenal adipose tissue was higher (P < 0.01) in the MCT diet group. The MCT-fed group had a higher
adiponectin mRNA level in their perirenal adipose tissue (P < 0.05). The increase of the plasma
glucose concentration after
glucose administration (area under the curve) was smaller (P < 0.01) in the MCT diet group than in the LCT diet group. These findings suggest that dietary MCT, compared with LCT, results in a higher serum
adiponectin level with transcriptional activation of the
adiponectin gene in rats. We speculate that improved
glucose tolerance in rats fed an MCT diet may be, at least in part, ascribed to this higher serum
adiponectin level.