Insulin signaling pathway in the masseter muscle of dexamethasone-treated rats

Area of Science:

• Biochemistry
• Molecular Biology
• Physiology

Background:

• Glucocorticoids, like dexamethasone, can alter intracellular signaling pathways, including those downstream of the insulin receptor/insulin-like growth factor receptor (IR/IGF1R).
• The impact of glucocorticoids on the insulin signaling pathway within the masseter muscle, a key masticatory muscle, is not well understood.

Purpose of the Study:

• To investigate the effects of dexamethasone treatment on the IR/IGF1R signaling pathway in the masseter muscle of Wistar rats.
• To analyze changes in protein expression and phosphorylation levels in response to insulin stimulation after dexamethasone administration.

Main Methods:

• Male Wistar rats were administered dexamethasone (1 mg/kg) or saline intraperitoneally for 10 consecutive days.
• Masseter muscle samples were collected and analyzed for IR/IGF1R pathway components and their phosphorylation states, both basally and after insulin infusion.

Main Results:

• Dexamethasone treatment led to body weight loss but did not affect masseter muscle weight.
• Expression of total insulin receptor (IR) and phosphatidylinositol 3-kinase (PI3K) proteins was reduced by dexamethasone.
• While total IRS1, Akt, and ERK1 levels were unchanged, insulin-induced IRS1 phosphorylation was impaired, and Akt phosphorylation was attenuated in dexamethasone-treated rats.

Conclusions:

• Dexamethasone treatment significantly impacts the insulin signaling pathway in the masseter muscle.
• The observed alterations in protein expression and phosphorylation suggest a functional impairment of insulin signaling in this muscle following glucocorticoid exposure.
• The masseter muscle exhibits distinct responses in its insulin signaling pathway phosphorylation compared to other muscle tissues.