Role of Dietary Supplements and Probiotics in Modulating Microbiota and Bone Health: The Gut-Bone Axis

Abstract

Osteoporosis is characterized by an alteration of bone microstructure with a decreased bone mineral density, leading to the incidence of fragility fractures. Around 200 million people are affected by osteoporosis, representing a major health burden worldwide. Several factors are involved in the pathogenesis of osteoporosis. Today, altered intestinal homeostasis is being investigated as a potential additional risk factor for reduced bone health and, therefore, as a novel potential therapeutic target. The intestinal microflora influences osteoclasts' activity by regulating the serum levels of IGF-1, while also acting on the intestinal absorption of calcium. It is therefore not surprising that gut dysbiosis impacts bone health. Microbiota alterations affect the OPG/RANKL pathway in osteoclasts, and are correlated with reduced bone strength and quality. In this context, it has been hypothesized that dietary supplements, prebiotics, and probiotics contribute to the intestinal microecological balance that is important for bone health. The aim of the present comprehensive review is to describe the state of the art on the role of dietary supplements and probiotics as therapeutic agents for bone health regulation and osteoporosis, through gut microbiota modulation.

Keywords: bone health; dietary supplements; gut microbiota; microbiota; osteoporosis; probiotics.

Figure 1

The gut-bone axis: pathways and factors starting from gut dysbiosis that determine bone metabolism alterations favoring osteoclasts. Abbreviations—SCFAs: short-chain fatty acids; PAMPs: pathogen-associated molecular patterns; D Cell: somatostatin-producing cells; T Cell: type of leukocyte that is an essential part of the immune system; OB: osteoblast; OC: osteoclast; RNK-L: receptor activator of nuclear factor-κB ligand; OPG: osteoprotegerin; VDR: vitamin D receptor; IGF-1: insulin-like growth factor one.

Figure 2

Lifestyle intervention and supplementation that might reduce bone loss; these modulators might exert their therapeutic effects through different known biological pathways, such as OPG, RANK, and TRAF. Abbreviations—OPG: osteoprotegerin; RANK-L: receptor activator of nuclear factor-κB ligand; RANK: receptor activator of nuclear factor κB; TRAF: tumor necrosis factor receptor-associated factor.