Abstract
Our previous research showed that capsaicin exhibits hypoglycemic effects by activating the transient receptor potential vanilloid 1 (TRPV1) channel in diabetic rats. Interestingly, capsiate was also able to activate the TRPV1 channel, but with a non-significant hypoglycemic effect. This study aimed to investigate the effect of capsaicin on the glycometabolism of streptozotocin (STZ)-induced diabetic rats by blocking the TRPV1 channel. After a 4-week capsaicin treatment (6 mg/kg·bw), the serum insulin level of STZ-induced diabetic rats increased from 15.2 to 22.1 mIU/L, the content of hepatic glycogen and muscle glycogen increased by 81.2 and 20.2%, respectively, and the blood glucose level decreased significantly from 19.3 to 14.7 mmol/L. When the TRPV1 channel was blocked, capsaicin lost the above-mentioned effects, and the hypoglycemic effect was no longer significant. It was concluded that a combined up-regulation of both TRPV1 receptors and pancreatic duodenal homeobox-1 (PDX-1) led to the hypoglycemic effect of capsaicin, which partially explains our previous observation: capsiate activating TRPV1 without showing a significant hypoglycemic effect was due to the lack of a significant up-regulation of PDX-1. Based on the experimental results, we speculated that two signaling pathways [TRPV1-(PDX1)-(GLUT2/GK) and TRPV1-(PDX-1)-(IRS1/2)] exist in the pancreas of STZ-induced diabetic rats.
Highlights
Diabetes is a metabolic disorder caused by insufficient insulin secretion, action, or resistance [1,2,3]
The results showed that capsaicin up-regulated the expression of glucose transporter 2 (GLUT2) and GK, down-regulated the expression of phosphoenolpyruvate carboxykinase (PEPCK) and G6Pase, and improved gluconeogenesis and glycolysis in the glycometabolism of diabetic rats in order to regulate the level of blood glucose
The mediation of transient receptor potential vanilloid 1 (TRPV1) receptors in the hypoglycemic effect of capsaicin was studied from the perspective of glycometabolism
Summary
Diabetes is a metabolic disorder caused by insufficient insulin secretion, action, or resistance [1,2,3]. It is widely recognized as one of the leading causes of death and disability in the Western world. Capsaicin treatment can stimulate the secretion of insulin from rat islet cells by activating the transient receptor potential vanilloid 1 (TRPV1) ion channel, thereby achieving a hypoglycemic effect [7]. Capsicum has long been used in the treatment of diabetes in traditional Jamaican medicine, TRPV1 Receptor-Mediated Hypoglycemic Mechanism
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