# Role of Branched‐Chain Amino Acids in Mitigating Osteosarcopenia: An Experimental Study Using Ovariectomised Mice Models

## TL;DR

This study shows that BCAA supplementation helps reduce muscle loss and partially preserve bone health in a mouse model of postmenopausal osteosarcopenia.

## Contribution

The study identifies BCAAs as a potential therapy for osteosarcopenia by modulating the bone-to-muscle signaling pathway involving sclerostin and Wnt signaling.

## Key findings

- BCAA supplementation increased lean mass and improved muscle weight in ovariectomized mice.
- BCAA preserved bone microarchitecture by increasing cortical thickness and modulating bone turnover markers.
- BCAA reduced muscle atrophy markers and enhanced muscle hypertrophy through MHC upregulation.

## Abstract

Osteosarcopenia, characterised by concurrent bone loss and muscle atrophy, presents a significant challenge in aging populations, particularly in postmenopausal women. The current therapeutic options potentially treat bone and muscle loss independently, highlighting the importance of an integrated approach. This study aimed to investigate the effects of branched‐chain amino acid (BCAA) supplementation on muscle and bone health using ovariectomised (OVX) mice, a model for postmenopausal osteoporosis and sarcopenia.

Female C57BL/6 mice were divided into sham‐operated and OVX groups, with OVX mice further subdivided to receive 0.25 mg/kg (Low) or 1 mg/kg (High) of BCAA supplementation for 16 weeks. Muscle mass, function and mitochondrial health were assessed alongside bone mineral density (BMD), bone turnover markers and histological evaluations. Additionally, the study explored mechanistic insights into sclerostin modulation and its influence on Wnt signalling through plasma and tissue analyses.

The hind limb fat mass was increased in the OVX group but reduced with BCAA supplementation, while hindlimb lean mass (p < 0.01) and total lean mass (p < 0.001) were significantly higher in the OVX + High‐BCAA group compared with the OVX group. Gastrocnemius muscle weight was lower in the OVX group but improved (p < 0.05) with both Low‐ and High‐BCAA supplementation. BCAA preserved bone microarchitecture by improving cortical thickness (p < 0.01) and modulating bone turnover markers, including osteocalcin (p < 0.01) levels. Plasma sclerostin levels were regulated, suggesting a role in bone remodelling. In muscle, BCAA enhanced hypertrophy by upregulating MHC expression (p < 0.05) and downregulating atrophy markers such as Atrogin‐1 (Low‐BCAA, p < 0.001; High BCAA, p < 0.001) and MuRF‐1 (Low‐BCAA, p < 0.01; High BCAA, p < 0.001). Additionally, BCAA mitigated the cytotoxic effects of H2O2 in osteocytic MLO‐Y4 cells, reducing sclerostin levels (p < 0.05) and improving cellular viability (p < 0.05). In C2C12 cells, BCAA reversed sclerostin‐induced muscle atrophy (p < 0.01), increasing MHC expression (p < 0.01) and myotube diameter (p < 0.01) while reducing Atrogin‐1 (p < 0.01) and MuRF‐1 (p < 0.001) expression.

BCAA supplementation alleviates muscle atrophy and partially preserves bone microarchitecture in OVX mice. Importantly, our data highlight bone‐derived sclerostin as a molecular link that transmits bone signals to muscle; BCAA mitigates osteosarcopenia by modulating this bone‐to‐muscle endocrine axis via Wnt signalling. Although improvements in bone structure were modest, the findings position BCAAs as a promising adjunct therapy targeting the integrated bone–muscle unit.