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Acute Exercise Stimulates Carnitine Biosynthesis and OCTN2 Expression in Mouse Kidney

Background/Aims: Carnitine is essential for the transport of long-chain FAs (FA) into the mitochondria for energy production. During acute exercise, the increased demand for FAs results in a state of free carnitine deficiency in plasma. The role of kidney in carnitine homeostasis after exercise is not known. Methods: Swiss Webster mice were sacrificed immediately after a 1-hour moderate intensity treadmill run, and at 4-hours and 8-hours into recovery. Non-exercising mice served as controls. Plasma was analyzed for carnitine using acetyltransferase and [14C] acetyl-CoA. Kidney was removed for gene and protein expression of butyrobetaine hydroxylase (γ-BBH), organic cation transporter (OCTN2), and peroxisome proliferator-activated receptor (PPARα), a regulator of fatty acid oxidation activated by FAs. Results: Acute exercise caused a decrease in plasma free carnitine levels. Rapid return of free carnitine to control levels during recovery was associated with increased γ-BBH expression. Both mRNA and protein levels of OCTN2 were detected in kidney after exercise and during recovery, suggesting renal transport mechanisms were stimulated. These changes were accompanied with a reciprocal increase in PPARα protein expression. Conclusions: Our results show that the decrease in free carnitine after exercise rapidly activates carnitine biosynthesis and renal transport mechanism in kidney to establish carnitine homeostasis.