Mountain caviar is a fruit of Kochia scoparia that contains momordin Ic as a major saponin constituent. Its extract (MCE) has been shown to suppress blood glucose elevations in the human oral glucose tolerance test (OGTT) as well as increases in blood glucose in OGTT, gastric emptying (GE), and glucose incorporation in the small intestine in rats. However, the effects of MCE and momordin Ic on glucose absorption in mice and these action mechanisms have not been examined for more than 2 decades. Therefore, we herein investigated the effects of MCE, its saponin fraction, and momordin Ic on blood glucose elevations in mice. Mouse blood glucose elevation tests were performed on carbohydrate-loaded mice. The mountain caviar saponin fraction significantly delayed blood glucose elevations in glucose-, sucrose-, and soluble starch-loaded mice. In glucose-loaded mice, the saponin fraction, MCE, and momordin Ic significantly suppressed rapid glucose elevations after glucose loading, but not sucrose loading. A mouse GE study was performed by loading with glucose and phenolphthalein solution. Momordin Ic and MCE strongly suppressed mouse GE. Intestinal glucose absorption was evaluated by the incorporation of 2-deoxyglucose (2-DG) into Caco-2 cell layers and mouse duodenum wall vesicles. The results obtained showed that momordin Ic inhibited the incorporation of 2-DG into Caco-2 cells and mouse duodenum vesicles. Collectively, these results suggest that MCE, particularly the principal saponin, momordin Ic, preferably suppressed glucose-induced blood glucose elevations and delayed carbohydrate-induced glucose elevations in mice. The underlying mechanism was found to involve the suppression of GE and intestinal glucose absorption.

Graphical Abstract

中文翻译：

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山鱼子酱提取物的降血糖作用和皂苷（包括苦瓜苷 Ic）对葡萄糖吸收的抑制机制

山鱼子酱是地肤子的果实，含有苦瓜苷 Ic 作为主要皂苷成分。其提取物 (MCE) 已被证明可以抑制人类口服葡萄糖耐量试验 (OGTT) 中的血糖升高，以及大鼠 OGTT 中血糖、胃排空 (GE) 和小肠葡萄糖掺入的增加。然而，MCE 和苦瓜苷 Ic 对小鼠葡萄糖吸收的影响以及这些作用机制在 20 多年来一直没有得到研究。因此，我们在此研究了 MCE、其皂苷组分和苦瓜苷 Ic 对小鼠血糖升高的影响。对碳水化合物负荷小鼠进行小鼠血糖升高测试。山鱼子酱皂苷成分显着延缓了葡萄糖、蔗糖和可溶性淀粉负载小鼠的血糖升高。在葡萄糖负荷小鼠中，皂苷组分、MCE 和苦瓜素 Ic 显着抑制葡萄糖负荷后血糖的快速升高，但不能抑制蔗糖负荷。通过加载葡萄糖和酚酞溶液进行小鼠 GE 研究。苦瓜苷 Ic 和 MCE 强烈抑制小鼠 GE。通过将 2-脱氧葡萄糖 (2-DG) 掺入 Caco-2 细胞层和小鼠十二指肠壁囊泡来评估肠道葡萄糖吸收。获得的结果显示苦瓜苷Ic抑制2-DG掺入Caco-2细胞和小鼠十二指肠囊泡中。总的来说，这些结果表明，MCE，特别是主要的皂苷，苦瓜苷 Ic，可以更好地抑制小鼠中葡萄糖诱导的血糖升高并延迟碳水化合物诱导的血糖升高。研究发现其潜在机制涉及抑制 GE 和肠道葡萄糖吸收。

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