The effects of synbiotic and/or vitamin D supplementation on gut-muscle axis in overweight and obese women: a study protocol for a double-blind, randomized, placebo-controlled trial

Abstract

Background Sarcopenia refers to an age-related loss of skeletal muscle content, strength, and function, leading to a decrease in mobility. Obesity may exacerbate age-related complications such as sarcopenia through inflammatory pathways. In addition, intestinal dysbiosis has been proposed as an emerging contributor to sarcopenia due to the stimulation of the immune system and elevated barrier permeability of the intestine. Targeting microbiome with synbiotic and vitamin D supplementation may modulate the microbiome followed by the enhancement of sarcopenia indices. Thus, the present study aims to evaluate the effect of synbiotic supplementation with or without vitamin D on the intestinal microbiome and its relationship with strength, muscle function, and body composition in middle-aged overweight and obese women. Methods This multi-factorial, double-blind, randomized controlled trial will be conducted on 88 participants in eight weeks. The participants will be allocated into four groups receiving vitamin D placebo (weekly) and synbiotic placebo (daily), vitamin D and synbiotic placebo, vitamin D placebo and symbiotic, and vitamin D and synbiotic. Intestinal microbiome assessment will be done by DNA isolation and real-time polymerase chain reaction (PCR). In addition, anthropometric indices, body composition, muscle strength, and physical performance will be evaluated by standard methods. All measurements will be made at the beginning and end of the study. Discussion The previous studies showed that probiotics were involved in reducing inflammation, insulin sensitivity, modulation of atrophy markers such as atherogen-1, and decreasing reactive oxygen indices. In addition, vitamin D was found to improve the intestinal microbiome and facilitate muscle anabolism. The present protocol is novel as it aims to investigate the impact of the co-supplementation of synbiotic and vitamin D on the gut microbiome and sarcopenia indices. Trial registration This trial has been registered in the Iranian Registry of Clinical Trials (IRCT20090822002365N25, date of registration: March 2021).

Progress of linking gut microbiota and musculoskeletal health: casualty, mechanisms, and translational values

“…Besides directly affecting calcium absorption, vitamin D also regulates intestinal mucosal homeostasis by maintaining the integrity of the intestinal barrier, which affects immune system function and inflammatory responses. 216 , 217 Vitamin D improves homeostasis of the intestinal microbiome and facilitates muscle anabolism 218 . Vitamin D can inhibit the levels of pro-inflammatory factors and promote the anti-inflammatory factors secretion of body.…”

Dietary Polysaccharides Exert Anti-Fatigue Functions via the Gut-Muscle Axis: Advances and Prospectives

“…The induced exercise stress reduced the level of Turicibacter and increased the number of Ruminococcus gnavus , which plays a significant role in immune function [ 63 ]. In addition, various studies indicated that probiotics can support healthy digestion and resistance function, as well as aid in the regulation of muscle anabolism, the elevation of insulin sensitivity, the increase in amino acid biosynthesis or AMPK signaling, and the limiting of low-grade inflammation and oxidative stress by metabolite production [ 23 , 27 , 125 ]. The increased relative abundance of Proteobacteria is considered as a potential diagnostic criterion for the risk of metabolic disorders and fatigue diseases [ 126 ].…”

“…Over the past few decades, the functions and properties of skeletal muscle have been extensively studied, which contributes to the characterization of muscle and provides unique insights for the inter-tissue communication network of the organism [ 24 , 49 ]. Numerous factors contribute to the loss of muscle mass and function, such as senility [ 26 ], special diet [ 27 ], exercise [ 46 ], inflammation [ 32 ], mitochondrial dysfunction [ 16 ], etc. Another important factor not to be neglected is the gut physiology, as the gut microbiota can interact with skeletal muscle by regulating various processes affecting host physiology, including those involving systemic inflammation, energy provision and use, oxidative stress, and mitochondrial function, as well as endocrine and insulin resistance [ 23 , 130 ].…”

“…Previous studies advocated that the relative representation of Faecalibacterium prausnitzii , Roseburia inulinivorans , and Alistipes shahii was depleted in sarcopenic subjects, in which their metabolic capacity for producing SCFAs, carotenoids, isoflavones, and amino acids was reduced [ 26 ]. Recent publications have highlighted that vitamin D supplementation can improve the health of obese women through the gut-muscle axis, mainly improving the intestinal microbiome function and homeostasis, as well as facilitating muscle anabolism and maintaining muscle mass [ 27 ]. The effect of the gut-muscle axis is manifested by the significant reversal of muscular atrophy in mice by treatment with intestinal microorganisms and their hallmark metabolites [ 133 ].…”

“…Even though the concept of the gut-muscle axis has been proposed, its causal relationship is still unclear. Previous investigation has shown that there is a relationship between sarcopenia and gut microbiota, known as the gut-muscle axis [ 26 , 27 ]. A previous review summarized that gut microbiota can interact with the host’s muscle mass and function through regulating inflammation, immunity, and energy metabolism, directly or indirectly establishing a connection with muscle disease, thereby realizing the “gut-muscle axis” and affecting the physiological function of the body [ 28 ].…”