The L-enantiomer of β- aminobutyric acid (L-BAIBA) as a potential marker of bone mineral density, body mass index, while D-BAIBA of physical performance and age.

Background: As both L- and D-BAIBA are increased with exercise, we sought to determine if circulating levels would be associated with physical performance.

Method: Serum levels of L- and D-BAIBA were quantified in 120 individuals (50% female) aged 20-85 years and categorized as either a "low" (LP), "average"(AP) or "high" performer (HP).Association analysis was performed using Spearman (S) and Pearson (P) rank correlation.

Results: Using the Spearman (S) rank correlation, L-BAIBA positively associated with BMI (0.23) and total fat mass (0.19) in the 120 participants, with total fat mass in the 60 males (0.26) but with both BMI (0.26) and BMD (0.28) in the 60 females. In the HP females, L-BAIBA positively associated with BMD (0.50) and lean mass (0.47).Using the Pearson (P) rank correlation D-BAIBA was positively associated with age (0.20) in the 120 participants and in the LP females (0.49). D-BAIBA associated with gait speed (S 0.20) in the 120 participants. In HP males, this enantiomer had a negative association with appendicular lean/height (S -0.52) and in the AP males with BMD (S -0.47). No associations were observed in HP or AP females, whereas, in LP females, in addition to a positive association with age, a positive association was observed with grip strength (S 0.45), but a negative with BMD (P -0.52, S -0.63) and chair stands (P -0.47, S -0.51).

Conclusions: L-BAIBA may play a role in BMI and BMD in females, not males, whereas D-BAIBA may be a marker for aging.