In nondiabetic C57BL/6J mice, canagliflozin affects the skeleton in a sex- and age-dependent manner

Canagliflozin (CANA) is a sodium glucose cotransporter-2 inhibitor that reduces blood glucose levels. Sodium glucose cotransporter-2 is primarily expressed in the kidney, but not in any bone cells, therefore effects on the skeleton are likely to be non-cell autonomous. Originally developed to treat type II diabetes, CANA use has expanded to treat cardiovascular and renovascular disease. Clinical trials examining CANA in diabetic patients have produced contradictory reports on fracture risk, but there are limited data of CANA in nondiabetic conditions. In nondiabetic preclinical models, short-term treatment with CANA negatively affected trabecular bone whereas long-term treatment reduced cortical bone mineralization in male but not female mice. To investigate the skeletal effects of an intermediate period of CANA treatment, we treated male and female C57BL/6 J mice with CANA (180 ppm) for 6 months. Age at treatment initiation was also evaluated, with cohorts starting CANA prior to skeletal maturity (3-months-old) or in adulthood (6-months-old). Longitudinal assessments of bone mineral density revealed early benefits of CANA treatment in female mice. At euthanasia, both trabecular and cortical bone morphology were improved by CANA treatment in males and females. Bone formation was reduced at the endosteal surface. CANA decreased osteoblast number in male mice and bone marrow adiposity in females. Overall, more skeletal benefits were recorded in CANA-treated females than males. Urinary calcium output increased with CANA treatment, but parathyroid hormone was not changed. Despite reduced fasting blood glucose, body composition and whole-body metabolism were minimally changed by CANA treatment. For all outcome measures, limited differences were recorded based on age at treatment initiation. This study demonstrated that in nondiabetic C57BL/6 J mice, an intermediate period of CANA treatment improved bone morphology, but reduced osteoblast and bone marrow adipocyte number as well as serum procollagen type 1 N-terminal pro-peptide in a sex-specific manner.