2022-11-08Bone unhealthy is a silent condition that can develop in both adults and the elderly, inducing bone structural change and osteoporosis, with a decreased bone mineral density (BMD), leading to fragility fractures. Around 200 million people worldwide are affected by osteoporosis. According to recent statistics from the International Osteoporosis Foundation, it is estimated that one in three women and one in five men over the age of 50 will develop osteoporotic fractures in their lifetime.
Recent studies have shown that osteoporotic patients manifest gut microbial instability, characterized by elevated diversity that is correlated with decreased bone mass. Gut physiology and the gut microbial population are both involved in the regulation of bone metabolism at different levels. One study involving 181 postmenopausal women, divided into 3 groups— normal BMD group, osteopenia group, and osteoporosis group—fecal microbiota sample analysis revealed that Actinomyces and Clostridium species were more prevalent in subjects with osteoporosis, whereas Bacteroidetes and Firmicutes were more prevalent in healthy individuals. Interestingly, Actinomyces might be involved in the development of osteonecrosis of the jaw, whereas Firmicutes contribute to an estrogen analogue conversion, with anabolic effects on bone. Bone is impacted by gut microbial dysbiosis that both impairs the intestinal absorption of calcium and dysregulates osteoclasts’ activity via the serum levels of insulin-like growth factor 1 (IGF-1). Moreover, microbiota alterations also reduce bone strength and quality, and affect the balance OPG/RANKL pathway in osteoclasts.
The beneficial effects of the administration of probiotics on bone tissue are widely recognized, such that they have been named by some researchers “the new calcium and vitamin D” for bone health. Several studies have demonstrated that probiotics (i.e., L. reuteri, L. paracasei, and L. helveticus) prevent bone loss in the ovariectomy-induced postmenopausal mouse model. Furthermore, in a double-blind placebo-controlled study, 12-month daily administration of Lactobacillus reuteri decreased the loss of tibia BMD in elderly women. Slevin et al report that supplementation with fructooligosaccharides 24 months to alter the gastrointestinal flora , slowed the rate of total-body and spinal bone loss in postmenopausal women with osteopenia.
Therefore, probiotics might play a key role in bone tissue, through modulation of the gut microbiota, providing a health benefit in frail subjects. Although, these clinical trials have generated promising results, further studies on the characterization of the mechanism(s) of action of probiotics should be performed, to harvest novel knowledge and design targeted regimes.
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