Studies in postmenopausal women and ovariectomized mice show that the probiotic mix Lacticaseibacillus paracasei DSM13434, Lactiplantibacillus plantarum DSM 15312 and DSM 15313 (L. Mix) can protect from bone loss caused by sex steroid deficiency. Whether probiotic bacteria can protect bone also in sex steroid-deficient males is less studied. We used the orchiectomized mouse as a model for age-dependent bone loss caused by decreasing sex hormone levels in males. We treated 10-week-old male mice with either vehicle (veh) or L. Mix for 6 weeks, starting 2 weeks before orchiectomy (orx) or sham surgery. Importantly, mice treated with L. Mix had a general increase in total body bone mineral density (BMD) and lean mass (P ≤ 0.05) compared with veh-treated mice. Detailed computer tomography analysis of dissected bones showed increased trabecular BMD of the distal metaphyseal region of the femur in L. Mix compared to veh-treated orx mice (+8.0%, P ≤ 0.05). In the vertebra, L. Mix treatment increased trabecular bone volume fraction BV/TV (+11.5%, P ≤ 0.05) compared to veh in orx mice. Also, L. Mix increased the levels of short-chain fatty acids (SCFAs) such as propionate and acetate and important intermediates in SCFA synthesis such as succinate and lactate in the cecal content of male mice. In conclusion, L. Mix treatment resulted in a general increase in BMD in adult male mice and prevented trabecular bone loss in femur and vertebra of orx mice. These bone protective effects of L. Mix were associated with increased levels of SCFAs in the cecal content of male mice
