乳清蛋白的胰岛素原效应部分是通过氨基酸和 GIP 对β细胞的直接作用介导的。

BACKGROUND

Whey protein increases postprandial serum insulin levels. This has been associated with increased serum levels of leucine, isoleucine, valine, lysine, threonine and the incretin hormone glucose-dependent insulinotropic polypeptide (GIP). We have examined the effects of these putative mediators of whey's action on insulin secretion from isolated mouse Langerhans islets.

METHODS

Mouse pancreatic islets were incubated with serum drawn from healthy individuals after ingestion of carbohydrate equivalent meals of whey protein (whey serum), or white wheat bread (control serum). In addition the effect of individual amino acid combinations on insulin secretion was also tested. Furthermore, the stimulatory effects of whey serum on insulin secretion was tested in vitro in the absence and presence of a GIP receptor antagonist ((Pro(3))GIP[mPEG]).

RESULTS

Postprandial amino acids, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) responses were higher after whey compared to white wheat bread. A stimulatory effect on insulin release from isolated islets was observed with serum after whey obtained at 15 min (+87%, P < 0.05) and 30 min (+139%, P < 0.05) postprandially, compared with control serum. The combination of isoleucine, leucine, valine, lysine and threonine exerted strong stimulatory effect on insulin secretion (+270%, P < 0.05), which was further augmented by GIP (+558% compared to that produced by glucose, P < 0.05). The stimulatory action of whey on insulin secretion was reduced by the GIP-receptor antagonist (Pro(3))GIP[mPEG]) at both 15 and 30 min (-56% and -59%, P < 0.05).

CONCLUSIONS

Compared with white wheat bread meal, whey causes an increase of postprandial insulin, plasma amino acids, GIP and GLP-1 responses. The in vitro data suggest that whey protein exerts its insulinogenic effect by preferential elevation of the plasma concentrations of certain amino acids, GIP and GLP-1.

背景

乳清蛋白会增加餐后血清胰岛素水平。这与血清亮氨酸、异亮氨酸、缬氨酸、赖氨酸、苏氨酸和肠促胰岛素激素葡萄糖依赖性胰岛素释放肽（GIP）水平升高有关。我们研究了这些假定的乳清作用介导物对分离的小鼠胰岛胰岛素分泌的影响。

方法

用健康人摄入乳清蛋白（乳清血清）或白小麦面包（对照血清）等效碳水化合物餐后的血清孵育小鼠胰腺胰岛。此外，还测试了单个氨基酸组合对胰岛素分泌的影响。此外，还在不存在和存在 GIP 受体拮抗剂 ((Pro(3))GIP[mPEG]) 的情况下，在体外测试了乳清血清对胰岛素分泌的刺激作用。

结果

与白小麦面包相比，摄入乳清后，餐后氨基酸、葡萄糖依赖性胰岛素释放肽（GIP）和胰高血糖素样肽 1（GLP-1）反应更高。与对照血清相比，在 15 分钟（+87%，P<0.05）和 30 分钟（+139%，P<0.05）时，从分离的胰岛中观察到血清对胰岛素释放有刺激作用。亮氨酸、异亮氨酸、缬氨酸、赖氨酸和苏氨酸的组合对胰岛素分泌有强烈的刺激作用（+270%，P<0.05），GIP 进一步增强了这种作用（与葡萄糖相比增加了 558%，P<0.05）。GIP 受体拮抗剂 (Pro(3))GIP[mPEG]) 在 15 分钟和 30 分钟时均降低了乳清对胰岛素分泌的刺激作用（-56%和-59%，P<0.05）。