Physical inactivity affects skeletal muscle insulin signaling in a birth weight-dependent manner

Area of Science:

• Endocrinology
• Metabolic Research
• Exercise Physiology

Background:

• Low birth weight (LBW) is a risk factor for metabolic disorders.
• The impact of physical inactivity on insulin and AMPK signaling in LBW individuals remains unclear.

Purpose of the Study:

• To investigate if physical inactivity unmasks defects in insulin and AMPK signaling pathways in low birth weight (LBW) subjects.
• To compare the effects of bed rest on insulin sensitivity and signaling between LBW and normal birth weight (NBW) individuals.

Main Methods:

• Twenty LBW and 20 NBW subjects underwent a 9-day bed rest protocol.
• Euglycemic-hyperinsulinemic clamp and skeletal muscle biopsies were performed pre and post bed rest.
• Western blotting analyzed Akt, AS160, GLUT4, and AMPK signaling pathways.

Main Results:

• Both LBW and NBW groups exhibited similar reductions in peripheral insulin action post bed rest.
• Insulin and AMPK signaling remained unaffected by bed rest in NBW subjects.
• LBW subjects displayed decreased insulin-stimulated Akt phosphorylation and altered AMPK expression post bed rest, with lower insulin response in AS160 phosphorylation.

Conclusions:

• Bed rest-induced insulin resistance is not solely explained by impaired muscle insulin or AMPK signaling in either group.
• Reduced muscle insulin signaling in LBW subjects post bed rest, despite similar insulin resistance, suggests a potential heightened risk for type 2 diabetes with physical inactivity.