Antifatigue Effects of 5-Aminolevulinic Acid Chronic Treatment on Mice.

5-aminolevulinic acid (5-ALA) is a heme precursor involved in mitochondrial activation. A clinical study suggested that 5-ALA supplementation alleviates fatigue in healthy individuals who experience chronic physical tiredness. However, the detailed mechanisms are unknown. Therefore, we investigated the mechanism underlying the antifatigue effect of 5-ALA using fatigue mouse models. C57BL/6N mice were orally administered 5-ALA hydrochloride or distilled water for 8 weeks. Fatigue mouse models were developed by housing the mice in a cage filled with water for 4 days. Fatigue was evaluated through running distance via a treadmill test. The decrease in the running distance in female mice significantly recovered after 5-ALA administration. 5-ALA administration ameliorated the decreased blood glucose levels in fatigue mouse models. These results suggest that 5-ALA improves fatigue-induced hypoglycemia by promoting the use of fatty acids. PpIX's concentration in the FCX of the fatigue mouse models significantly increased after 5-ALA treatment. Decreased levels of 3-methoxy-4-hydroxyphenylglycol and noradrenaline (NA) turnover ratio in the FCX recovered to non-fatigue levels after 5-ALA treatment. Therefore, the antifatigue effect of 5-ALA in mice could be related to the activation of the NA neuronal systems in the FCX and the increase in energy production via glycogenesis activation from peripheral adipose tissue.