Adiponectin reportedly reduces
insulin-resistance. Exercise has also been shown to lessen
insulin-resistance, though it is not known whether exercise increases levels of
adiponectin and/or its receptors or whether its effects are dependent on exercise intensity and/or frequency.
Catecholamine levels have been shown to increase during exercise and to fluctuate based on exercise intensity and duration. In light of this information, we examined the effects of exercise on
catecholamine,
adiponectin, and
adiponectin receptor levels in rats. Our data showed that blood
adiponectin levels increased by 150% in animals that exercised at a rate of 30 m/min for 60 min 2 days per week, but not 5 days, per week; no such increase was observed in rats that exercised at a rate of 25 m/min for 30 min. The effects of exercise on
adiponectin receptor mRNA were variable, with
adiponectin receptor 1 (AdipoR1) levels in muscle increasing up to 4 times while
adiponectin receptor 2 (AdipoR2) levels in liver fell to below half in response to exercise at a rate of 25 m/min for 30 min 5 days per week. We also observed that urinary
epinephrine levels and plasma
lipids were elevated by exercise at a rate of 25 m/min for 30 min 2 days per week. Exercise frequency at a rate of 25 m/min for 30 min correlated with AdipoR1 and AdipoR2
mRNA expression in the muscle and liver, respectively (r=0.640, p<0.05 and r=-0.808, p<0.0005, respectively). Urinary
epinephrine levels correlated with AdipoR2
mRNA expression in liver tissues (r=-0.664, p<0.05) in rats that exercised at a rate of 25 m/min for 30 min. Thus, exercise may regulate
adiponectin receptor mRNA expression in tissues, which might cause increases in
glucose uptake and
fatty acid oxidation in the muscle. The effect of exercise on
adiponectin levels depends on the specific conditions of the exercise.