Cell-free culture supernatant of Lactobacillus curvatus Wikim38 inhibits RANKL-induced osteoclast differentiation and ameliorates bone loss in ovariectomized mice

Emerging Insights into the Endocrine Regulation of Bone Homeostasis by Gut Microbiome

Gut microbiota plays an important role in the regulation of bone homeostasis and bone health. Recent studies showed that these effects could be mediated through microbial metabolites released by the microbiota like short-chain fatty acids, metabolism of endogenous molecules such as bile acids, or a complex interplay between microbiota, the endocrine system, and the immune system. Importantly, some studies showed a reciprocal relationship between the endocrine system and gut microbiota. For instance, postmenopausal estrogen deficiency could lead to dysbiosis of the gut microbiota, which could in turn affect various immune response and bone remodeling. In addition, evidence showed that shift in the indigenous gut microbiota caused by antibiotics treatment may also impact normal skeletal growth and maturation. In this mini-review, we describe recent findings on the role of microbiome in bone homeostasis, with a particular focus on molecular mechanisms and their interactions with the endocrine and immune system. We will also discuss the recent findings on estrogen deficiency and microbiota dysbiosis, and the clinical implications for the development of new therapeutic strategies for osteoporosis and other bone disorders.

Heat-killed Limosilactobacillus reuteri ATCC PTA 6475 prevents bone loss in ovariectomized mice: A preliminary study

Osteoporosis is an important health problem that occurs due to an imbalance between bone formation and resorption. Hormonal deficiency post-menopause is a significant risk factor. The probiotic Limosilactobacillus reuteri has been reported to prevent ovariectomy (Ovx)-induced bone loss in mice and reduce bone loss in postmenopausal women. Despite the numerous health benefits of probiotics, as they are live bacteria, the administration is not risk-free for certain groups (e.g., neonates and immunosuppressed patients). We evaluated the effects of L. reuteri (ATCC PTA 6475) and its heat-killed (postbiotic) form on Ovx-induced bone loss. Adult female mice (BALB/c) were randomly divided into four groups: group C-control (sham); group OVX-C-Ovx; group OVX-POS-Ovx + heat-killed probiotic; group OVX-PRO-Ovx + probiotic. L. reuteri or the postbiotic was administered to the groups (1.3x109 CFU/day) by gavage. Bacterial morphology after heat treatment was accessed by scanning electron microscopy (SEM). The treatment started one week after Ovx and lasted 28 days (4 weeks). The animals were euthanized at the end of the treatment period. Bone microarchitecture and ileum Occludin and pro-inflammatory cytokines gene expression were evaluated by computed microtomography and qPCR techniques, respectively. The Ovx groups had lower percentage of bone volume (BV/TV) and number of bone trabeculae as well as greater total porosity compared to the control group. Treatment with live and heat-killed L. reuteri resulted in higher BV/TV and trabecular thickness than the Ovx group. The heat treatment caused some cell surface disruptions, but its structure resembled that of the live probiotic in SEM analysis. There were no statistical differences in Occludin, Il-6 and Tnf-α gene expression. Both viable and heat-killed L. reuteri prevented bone loss on ovariectomized mice, independently of gut Occludin and intestinal Il-6 and Tnf-α gene expression.

Protective Effects of the Postbiotic Lactobacillus plantarum MD35 on Bone Loss in an Ovariectomized Mice Model

Postmenopausal osteoporosis is caused by estrogen deficiency, which impairs bone homeostasis, resulting in increased osteoclastic resorption without a corresponding increase in osteoblastic activity. Postbiotics have several therapeutic properties, including anti-obesity, anti-diabetic, anti-inflammatory, and anti-osteoporotic effects. However, the beneficial effects of the postbiotic MD35 of Lactobacillus plantarum on bone have not been studied. In this study, we demonstrated that the postbiotic L. plantarum MD35, isolated from young radish water kimchi, influences osteoclast differentiation in mouse bone marrow-derived macrophage (BMM) culture. In addition, it was effective protecting against estrogen deficiency-induced bone loss in ovariectomized (OVX) mice, an animal model of postmenopausal osteoporosis. In BMM cells, postbiotic MD35 inhibited the receptor activator of nuclear factor-kappa B of NF-κB ligand (RANKL)-induced osteoclast differentiation by attenuating the phosphorylation of extracellular signal-related kinase, significantly suppressing the resorption activity and down-regulating the expression of RANKL-mediated osteoclast-related genes. In the animal model, the oral administration of postbiotic MD35 remarkably improved OVX-induced trabecular bone loss and alleviated the destruction of femoral plate growth. Therefore, postbiotic MD35 could be a potential therapeutic candidate for postmenopausal osteoporosis by suppressing osteoclastogenesis through the regulation of osteoclast-related molecular mechanisms.

From Cells to Environment: Exploring the Interplay between Factors Shaping Bone Health and Disease

The skeletal system is an extraordinary structure that serves multiple purposes within the body, including providing support, facilitating movement, and safeguarding vital organs. Moreover, it acts as a reservoir for essential minerals crucial for overall bodily function. The intricate interplay of bone cells plays a critical role in maintaining bone homeostasis, ensuring a delicate balance. However, various factors, both intrinsic and extrinsic, can disrupt this vital physiological process. These factors encompass genetics, aging, dietary and lifestyle choices, the gut microbiome, environmental toxins, and more. They can interfere with bone health through several mechanisms, such as hormonal imbalances, disruptions in bone turnover, direct toxicity to osteoblasts, increased osteoclast activity, immune system aging, impaired inflammatory responses, and disturbances in the gut-bone axis. As a consequence, these disturbances can give rise to a range of bone disorders. The regulation of bone's physiological functions involves an intricate network of continuous processes known as bone remodeling, which is influenced by various intrinsic and extrinsic factors within the organism. However, our understanding of the precise cellular and molecular mechanisms governing the complex interactions between environmental factors and the host elements that affect bone health is still in its nascent stages. In light of this, this comprehensive review aims to explore emerging evidence surrounding bone homeostasis, potential risk factors influencing it, and prospective therapeutic interventions for future management of bone-related disorders.

Modulation of bone remodeling by the gut microbiota: a new therapy for osteoporosis

The gut microbiota (GM) plays a crucial role in maintaining the overall health and well-being of the host. Recent studies have demonstrated that the GM may significantly influence bone metabolism and degenerative skeletal diseases, such as osteoporosis (OP). Interventions targeting GM modification, including probiotics or antibiotics, have been found to affect bone remodeling. This review provides a comprehensive summary of recent research on the role of GM in regulating bone remodeling and seeks to elucidate the regulatory mechanism from various perspectives, such as the interaction with the immune system, interplay with estrogen or parathyroid hormone (PTH), the impact of GM metabolites, and the effect of extracellular vesicles (EVs). Moreover, this review explores the potential of probiotics as a therapeutic approach for OP. The insights presented may contribute to the development of innovative GM-targeted therapies for OP.

Phenotype-genotype analysis of Latilactobacills curvatus from different niches: Carbohydrate metabolism, antibiotic resistance, bacteriocin, phage fragments and linkages with CRISPR-Cas systems

The potential probiotic function of Latilactobacills curvatus has attracted the attention of researchers. To explore the differences in the genomes of L. curvatus, nine strains were isolated from various sources, including feces and fermented vegetables and compared with 25 strains from the NCBI database. The findings indicated that the average genome size, GC content, and CDS of L. curvatus were 1.94 MB, 41.9%, and 1825, respectively. Its core genome is associated with transcription, translation, carbohydrate transport and metabolism, and defense functions. The pan-genome of L. curvatus was in a closed state. The genetic diversity of L. curatus is mainly manifested in its ability to use carbohydrates, antibiotic resistance, bacteriocin operon, and polymeric regularly interspaced short palindromic repeats (CRISPR)-Cas for bacterial immunity. The CRISPR system of 34 strains of L. curvatus was predominantly found to be of the IIA type with a few IIC and IE types. These findings will contribute to a better understanding of this species.

Dietary regulations for microbiota dysbiosis among post-menopausal women with type 2 diabetes

Type 2 diabetes (T2D) and T2D-associated comorbidities, such as obesity, are serious universally prevalent health issues among post-menopausal women. Menopause is an unavoidable condition characterized by the depletion of estrogen, a gonadotropic hormone responsible for secondary sexual characteristics in women. In addition to sexual dimorphism, estrogen also participates in glucose-lipid homeostasis, and estrogen depletion is associated with insulin resistance in the female body. Estrogen level in the gut also regulates the microbiota composition, and even conjugated estrogen is actively metabolized by the estrobolome to maintain insulin levels. Moreover, post-menopausal gut microbiota is different from the pre-menopausal gut microbiota, as it is less diverse and lacks the mucolytic Akkermansia and short-chain fatty acid (SCFA) producers such as Faecalibacterium and Roseburia. Through various metabolites (SCFAs, secondary bile acid, and serotonin), the gut microbiota plays a significant role in regulating glucose homeostasis, oxidative stress, and T2D-associated pro-inflammatory cytokines (IL-1, IL-6). While gut dysbiosis is common among post-menopausal women, dietary interventions such as probiotics, prebiotics, and synbiotics can ease post-menopausal gut dysbiosis. The objective of this review is to understand the relationship between post-menopausal gut dysbiosis and T2D-associated factors. Additionally, the study also provided dietary recommendations to avoid T2D progression among post-menopausal women.

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

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.