Prior exercise increases net hepatic glucose uptake during a glucose load

Area of Science:

• Physiology
• Metabolic Science
• Exercise Science

Background:

• Understanding glucose metabolism is crucial for managing metabolic health.
• Exercise is known to influence glucose homeostasis, but the specific mechanisms in the liver require further elucidation.

Purpose of the Study:

• To investigate whether prior exercise potentiates net hepatic glucose uptake (NHGU) during a controlled glucose infusion.
• To differentiate the contributions of hepatic and peripheral tissues to enhanced glucose disposal after exercise.

Main Methods:

• Surgical implantation of catheters and Doppler probes in dogs for precise physiological measurements.
• Controlled studies involving exercise or rest followed by a hyperinsulinemic-euglycemic clamp with glucose infusion.
• Measurement of arterial-portal venous glucose gradients, hormonal levels, and glucose uptake in hepatic and hindlimb tissues.

Main Results:

• Prior exercise significantly increased NHGU during the glucose clamp compared to sedentary controls (Delta7.3 +/- 0.7 vs. Delta3.7 +/- 0.5).
• Hindlimb glucose uptake was also markedly higher in exercised dogs (32 +/- 4 mg/min) versus sedentary dogs (13 +/- 2 mg/min).
• Increased NHGU accounted for approximately 30% of the additional glucose infusion required in the exercised state.

Conclusions:

• Prior exercise enhances NHGU independently of systemic hormonal and glycemic changes, suggesting an intrinsic hepatic effect.
• Post-exercise glucose disposal is improved due to augmented glucose uptake by both the liver and skeletal muscle.
• These findings highlight exercise as a key modulator of hepatic and peripheral glucose utilization.