Skeletal muscle-selective knockout of LKB1 increases insulin sensitivity, improves glucose homeostasis, and decreases...

Area of Science:

• Cell Metabolism
• Endocrinology
• Molecular Biology

Background:

• Liver Kinase B1 (LKB1) is a tumor suppressor crucial for cell metabolism.
• LKB1 activates AMP-activated protein kinase (AMPK), an energy-sensing enzyme.
• The role of LKB1 in skeletal muscle and its impact on insulin sensitivity were unclear.

Purpose of the Study:

• To investigate the role of skeletal muscle LKB1 in insulin sensitivity and glucose homeostasis.
• To elucidate the molecular mechanisms linking LKB1 to insulin signaling pathways.

Main Methods:

• Generation of muscle-specific LKB1 knockout (MLKB1KO) mice.
• Assessment of glucose tolerance, insulin sensitivity, and glucose uptake via hyperinsulinemic-euglycemic clamp.
• Analysis of Akt phosphorylation and expression of TRB3 (an Akt inhibitor) in skeletal muscle.

Main Results:

• MLKB1KO mice exhibited enhanced insulin sensitivity, with decreased fasting glucose and insulin levels.
• Improved glucose tolerance and increased muscle glucose uptake were observed in MLKB1KO mice.
• MLKB1KO mice showed increased insulin-stimulated Akt phosphorylation and significantly reduced muscle TRB3 expression.
• Direct binding between Akt and TRB3 was confirmed, and TRB3 overexpression inhibited Akt phosphorylation.

Conclusions:

• Skeletal muscle LKB1 acts as a negative regulator of insulin sensitivity and glucose homeostasis.
• LKB1-mediated regulation of TRB3 provides a novel link between LKB1, Akt signaling, and metabolic control.
• These findings highlight LKB1's dual role in tumor suppression and cellular metabolism, with implications for metabolic diseases.