Akebia saponin D from Dipsacus asper wall. Ex C.B. Clarke ameliorates skeletal muscle insulin resistance through activation of IGF1R/AMPK signaling pathway

Abstract

Ethnopharmacological relevance: Dipsacus asper Wall. Ex C.B. Clarke (DA), a perennial herb, is one of the most commonly used herbs in Traditional Chinese Medicine for strengthening muscles and bones and regulating blood vessels. Akebia saponin D (ASD/AVI) is a triterpenoid saponin extracted from the root of DA, which has favorable pharmacological properties such as anti-osteoporosis, anti-apoptosis, liver protection and hypolipidemic.

Aim of the study: To explore the underlying mechanisms and regulatory role of Akebia saponin D (ASD/AVI) on high-fat diet-induced insulin resistance in skeletal muscle.

Materials and methods: C2C12 cells were used to explore the best concentration in the skeletal muscle insulin resistance model in an in vitro experiment. The protective effect of AVI on insulin resistance and the corresponding signaling pathway were detected by glucose content measurement, quantitative PCR, and Western blot. A high-fat diet STZ-induced insulin resistance mice model was used to evaluate the protective function of AVI in vivo. After four weeks of treatment, ITT, OGTT, and treadmill tests were applied to examine insulin sensitivity and their serum and skeletal muscle tissues were collected for further analysis.

Results: AVI effectively reduced body weight, blood glucose levels and calorie intake in insulin-resistant mice, and reduced lipid accumulation and in their muscle tissue. AVI also improved glucose uptake and insulin sensitivity in both in vivo and in vitro experiments. Following AVI administration, there was an increase in the expression of the AMPK signaling pathway. Our experiments further confirmed that AVI specifically targets the IGF1R, thereby more effectively regulating the insulin signaling pathway.

Conclusion: AVI improves type 2 diabetes-induced insulin resistance in skeletal muscle by activating the IGF1R-AMPK signaling pathway, promoting glucose uptake and energy metabolism in IR.

Keywords: AMPK; Akebia saponin D(ASD/AVI); Dipsacus asper wall; IGF1R; Insulin resistance; Type 2 diabetes.