An exploratory investigation of β-aminoisobutyric acid as a biomarker: possible relationships between urinary BAIBA and lifestyle habits

Background β-Aminoisobutyric acid (BAIBA) is a metabolite of valine and thymine and has been identified as a myokine released from skeletal muscle in response to exercise. Experimental studies have suggested that BAIBA exerts multiple metabolic effects, including promotion of adipose tissue browning and improvement of glucose metabolism. However, evidence regarding BAIBA in humans, particularly its relationships with lifestyle habits, remains unknown, and even the normal plasma range has not been established. We aimed to evaluate plasma and urinary BAIBA excretion in healthy adults and to investigate their associations with lifestyle factors, including physical activity and dietary habits. Methods Fifteen healthy young adults were enrolled in this cross-sectional observational study. Total BAIBA was measured in plasma and one-fiftieth aliquots of 24-h urine samples. Body composition, dietary intake, physical activity, and lifestyle habits were assessed. Results Plasma total BAIBA was detectable in only 33% of participants, whereas urinary 24-h total BAIBA calculated by one-fiftieth urine storage of a 24-h urine collection was measurable in all individuals. Participants with detectable plasma BAIBA showed approximately five-fold higher urinary BAIBA excretion than those with undetectable plasma levels [median 1001 vs. 172 μmol/day, p = 0.002]. A higher 24-h urinary BAIBA level was associated with habitually skipping breakfast. Conclusions In this small exploratory study, total 24-h urinary BAIBA excretion may reflect systemic BAIBA status more consistently than plasma BAIBA concentration in healthy young adults and appeared to differ according to breakfast-skipping habits. This hypothesis-generating observation should be confirmed in larger studies with adjustment for potential confounders.