Genetically determined exercise capacity affects systemic glucose response to insulin in rats

Area of Science:

• Exercise physiology
• Metabolic health
• Genetics

Background:

• Aerobic exercise capacity influences morbidity, mortality, and insulin resistance.
• Conflicting results from exercise interventions may stem from intrinsic (genetic) and extrinsic (environmental) factors.
• The distinct contributions of these factors to insulin sensitivity remain unclear.

Purpose of the Study:

• To investigate the roles of genetically determined aerobic exercise capacity and exercise training in modulating insulin sensitivity.
• To compare insulin sensitivity in sedentary and exercised high-capacity runners (HCR) and low-capacity runners (LCR).

Main Methods:

• Comparison of sedentary and aerobically interval-trained HCR and LCR models.
• Assessment of untrained exercise capacity, body weight, random glucose levels, and glucose infusion rates via hyperinsulinemic euglycemic clamping.
• Echocardiography for morphological and functional cardiac parameters.
• Measurement of 2-deoxyglucose uptake and citrate synthase activity in muscle and adipose tissue.

Main Results:

• Sedentary LCR exhibited a diabetic phenotype (higher glucose, lower glucose infusion rate) compared to HCR.
• Four weeks of aerobic interval training improved aerobic exercise capacity, particularly in LCR.
• Exercise enhanced glucose uptake and citrate synthase activity in HCR but not LCR, indicating that genetic predisposition for low exercise capacity impairs exercise-induced metabolic improvements.

Conclusions:

• Genetic predisposition for low aerobic exercise capacity is associated with impaired insulin sensitivity.
• This genetic factor impedes exercise-induced improvements in insulin response.
• Exercise interventions may not fully overcome the negative metabolic consequences of a low genetic predisposition for aerobic exercise capacity.