Medical Physiology and Metabolism Laboratory, Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, Shiga, Japan.
Medical Chemistry Laboratory, Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, Shiga, Japan.
Br J Nutr. 2022 Feb 14;127(3):377-383. doi: 10.1017/S0007114521001082. Epub 2021 Mar 25.
Bitter melon (Momordica charantia L.) has been shown to have various health-promoting activities, including antidiabetic and hypoglycaemic effects. Improvement in insulin sensitivity and increase in glucose utilisation in peripheral tissues have been reported, but the effect on insulin secretion from pancreatic β-cells remains unclear. In this study, we investigated the effect of bitter melon fruit on insulin secretion from β-cells and the underlying mechanism. The green fruit of bitter melon was freeze-dried and extracted with methanol. The bitter melon fruit extract (BMFE) was fractionated using ethyl acetate (fraction A), n-butanol (fraction B) and water (fraction C). Insulin secretory capacity from INS-1 rat insulinoma cell line and rat pancreatic islets, as well as glucose tolerance in rats by oral glucose tolerance test (OGTT), was measured using BMFE and fractions. ATP production in β-cells was also examined. BMFE augmented insulin secretion from INS-1 cells in a dose-dependent manner. The significant augmentation of insulin secretion was independent of the glucose dose. Fraction A (i.e. hydrophobic fraction), but not fractions B and C, augmented insulin secretion significantly at the same level as that by BMFE. This finding was also observed in pancreatic islets. In OGTT, BMFE and fraction A decreased blood glucose levels and increased serum insulin levels after glucose loading. The decrease in blood glucose levels was also observed in streptozotocin-induced diabetic rats. In addition, BMFE and fraction A increased the ATP content in β-cells. We concluded that hydrophobic components of BMFE increase ATP production and augment insulin secretion from β-cells, consequently decreasing blood glucose levels.
苦瓜（Momordica charantia L.）已被证明具有多种促进健康的作用，包括抗糖尿病和降血糖作用。据报道，苦瓜能改善胰岛素敏感性并增加外周组织对葡萄糖的利用，但对胰岛β细胞胰岛素分泌的影响尚不清楚。在这项研究中，我们研究了苦瓜果实对β细胞胰岛素分泌的影响及其潜在机制。苦瓜的绿果经冷冻干燥并用甲醇提取。苦瓜果提取物（BMFE）用乙酸乙酯（A 部分）、正丁醇（B 部分）和水（C 部分）进行分级。通过口服葡萄糖耐量试验（OGTT）测量 BMFE 和各分级物对 INS-1 大鼠胰岛素瘤细胞系和大鼠胰岛胰岛素分泌能力以及大鼠葡萄糖耐量的影响。还检查了β细胞中的 ATP 产生。BMFE 以剂量依赖性方式增强 INS-1 细胞的胰岛素分泌。胰岛素分泌的显著增强与葡萄糖剂量无关。A 部分（即疏水性部分）而非 B 和 C 部分在相同水平上显著增强胰岛素分泌，这一发现也在胰岛中观察到。在 OGTT 中，BMFE 和 A 部分在葡萄糖负荷后降低血糖水平并增加血清胰岛素水平。在链脲佐菌素诱导的糖尿病大鼠中也观察到血糖水平降低。此外，BMFE 和 A 部分增加了β细胞中的 ATP 含量。我们得出结论，BMFE 的疏水性成分增加了 ATP 的产生，并增强了β细胞的胰岛素分泌，从而降低了血糖水平。
