Department of Diabetes, Endocrinology, and Nutrition, Graduate School of Medicine, Kyoto University , Kyoto , Japan.
Am J Physiol Endocrinol Metab. 2019 Jul 1;317(1):E53-E64. doi: 10.1152/ajpendo.00200.2018. Epub 2019 Apr 16.
Gastric inhibitory polypeptide (GIP) is an incretin secreted from enteroendocrine K cells and potentiates insulin secretion from pancreatic β-cells. GIP also enhances long-chain triglyceride (LCT) diet-induced obesity and insulin resistance. Long-term intake of medium-chain triglyceride (MCT) diet is known to induce less body weight and fat mass gain than that of LCT diet. However, the effect of MCT diet feeding on GIP secretion and the effect of GIP on body weight and fat mass under MCT diet-feeding condition are unknown. In this study, we evaluated the effect of single MCT oil administration on GIP secretion and compared the effect of long-term MCT and LCT diet on body weight and fat mass gain in wild-type (WT) and GIP-knockout (GIP KO) mice. Single administration of LCT oil induced GIP secretion but that of MCT oil did not in WT mice. Long-term intake of LCT diet induced GIP hypersecretion and significant body weight and fat mass gain compared with that of control fat (CF) diet in WT mice. In contrast, MCT diet did not induce GIP hypersecretion, and MCT diet-fed mice showed smaller increase in body weight and fat mass gain compared with CF diet-fed mice. In GIP KO mice, body weight and fat mass were markedly attenuated in LCT diet-fed mice but not in MCT diet-fed mice. Our results suggest that long-term intake of MCT diet stimulates less GIP secretion and suppresses body weight and fat mass gain compared with that of LCT diet.
胃抑制多肽（GIP）是一种从肠内分泌 K 细胞分泌的肠促胰岛素，可增强胰岛β细胞的胰岛素分泌。GIP 还会促进长链甘油三酯（LCT）饮食诱导的肥胖和胰岛素抵抗。已知长期摄入中链甘油三酯（MCT）饮食会导致体重和脂肪量增加少于 LCT 饮食。然而，MCT 饮食喂养对 GIP 分泌的影响以及 GIP 在 MCT 饮食喂养条件下对体重和脂肪量的影响尚不清楚。在这项研究中，我们评估了单次 MCT 油给药对 GIP 分泌的影响，并比较了长期 MCT 和 LCT 饮食对野生型（WT）和 GIP 敲除（GIP KO）小鼠体重和脂肪量增加的影响。LCT 油的单次给药会诱导 GIP 分泌，但 WT 小鼠的 MCT 油则不会。与对照脂肪（CF）饮食相比，长期摄入 LCT 饮食会导致 GIP 过度分泌，并导致 WT 小鼠体重和脂肪量显著增加。相比之下，MCT 饮食不会引起 GIP 过度分泌，而且 MCT 饮食喂养的小鼠体重和脂肪量增加幅度小于 CF 饮食喂养的小鼠。在 GIP KO 小鼠中，LCT 饮食喂养的小鼠体重和脂肪量明显减少，但 MCT 饮食喂养的小鼠则没有。我们的结果表明，与 LCT 饮食相比，长期摄入 MCT 饮食会刺激较少的 GIP 分泌，并抑制体重和脂肪量增加。
