Understanding the gut microbiota and sarcopenia: a systematic review.

BACKGROUND: Gut microbiota dysbiosis and sarcopenia commonly occur in the elderly. Although the concept of the gut-muscle axis has been raised, the casual relationship is still unclear. This systematic review analyses the current evidence of gut microbiota effects on muscle/sarcopenia. METHODS: A systematic review was performed in PubMed, Embase, Web of Science, and The Cochrane Library databases using the keywords (microbiota* OR microbiome*) AND (sarcopen* OR muscle). Studies reporting the alterations of gut microbiota and muscle/physical performance were analysed. RESULTS: A total of 26 pre-clinical and 10 clinical studies were included. For animal studies, three revealed age-related changes and relationships between gut microbiota and muscle. Three studies focused on muscle characteristics of germ-free mice. Seventy-five per cent of eight faecal microbiota transplantation studies showed that the recipient mice successfully replicated the muscle phenotype of donors. There were positive effects on muscle from seven probiotics, two prebiotics, and short-chain fatty acids (SCFAs). Ten studies investigated on other dietary supplements, antibiotics, exercise, and food withdrawal that affected both muscle and gut microbiota. Twelve studies explored the potential mechanisms of the gut-muscle axis. For clinical studies, 6 studies recruited 676 elderly people (72.8 ± 5.6 years, 57.8% female), while 4 studies focused on 244 young adults (29.7 ± 7.8 years, 55.4% female). The associations of gut microbiota and muscle had been shown in four observational studies. Probiotics, prebiotics, synbiotics, fermented milk, caloric restriction, and exercise in six studies displayed inconsistent effects on muscle mass, function, and gut microbiota. CONCLUSIONS: Altering the gut microbiota through bacteria depletion, faecal transplantation, and various supplements was shown to directly affect muscle phenotypes. Probiotics, prebiotics, SCFAs, and bacterial products are potential novel therapies to enhance muscle mass and physical performance. Lactobacillus and Bifidobacterium strains restored age-related muscle loss. Potential mechanisms of microbiome modulating muscle mainly include protein, energy, lipid, and glucose metabolism, inflammation level, neuromuscular junction, and mitochondrial function. The role of the gut microbiota in the development of muscle loss during aging is a crucial area that requires further studies for translation to patients.

The role of gut microbiota in bone homeostasis.

AIMS: The effect of the gut microbiota (GM) and its metabolite on bone health is termed the gut-bone axis. Multiple studies have elucidated the mechanisms but findings vary greatly. A systematic review was performed to analyze current animal models and explore the effect of GM on bone. METHODS: Literature search was performed on PubMed and Embase databases. Information on the types and strains of animals, induction of osteoporosis, intervention strategies, determination of GM, assessment on bone mineral density (BMD) and bone quality, and key findings were extracted. RESULTS: A total of 30 studies were included, of which six studies used rats and 24 studies used mice. Osteoporosis or bone loss was induced in 14 studies. Interventions included ten with probiotics, three with prebiotics, nine with antibiotics, two with short-chain fatty acid (SCFA), six with vitamins and proteins, two with traditional Chinese medicine (TCM), and one with neuropeptide Y1R antagonist. In general, probiotics, prebiotics, nutritional interventions, and TCM were found to reverse the GM dysbiosis and rescue bone loss. CONCLUSION: Despite the positive therapeutic effect of probiotics, prebiotics, and nutritional or pharmaceutical interventions on osteoporosis, there is still a critical knowledge gap regarding the role of GM in rescuing bone loss and its related pathways. Cite this article: Bone Joint Res 2021;10(1):51-59.

High-dose omeprazole infusion compared with scheduled second-look endoscopy for prevention of peptic ulcer rebleeding: a randomized controlled trial.

BACKGROUND AND STUDY AIM: Previous studies have shown that both scheduled second-look endoscopy and high-dose continuous omeprazole infusion are effective in preventing peptic ulcer rebleeding. The aim of this noninferiority trial was to compare the efficacy of these two strategies for the prevention of rebleeding following primary endoscopic hemostasis. PATIENTS AND METHODS: Consecutive patients who received endoscopic treatment for bleeding peptic ulcers (actively bleeding, with nonbleeding visible vessels) were randomized to two treatment groups following hemostasis. One group (second-look endoscopy group) received the proton pump inhibitor (PPI) omeprazole as an intravenous bolus every 12 hours for 72 hours and a second endoscopy within 16 - 24 hours with retreatment for persistent stigmata of bleeding. The other group (PPI infusion group) received continuous high-dose omeprazole infusion for 72 hours. Patients who developed rebleeding underwent surgery if repeat endoscopic therapy failed. The primary outcome was the rebleeding rate within 30 days after initial hemostasis. The margin for noninferiority was set at 5 %. RESULTS: A total of 153 patients were randomized to the PPI infusion group and 152 to the second-look endoscopy group. Rebleeding occurred within 30 days in 10 patients (6.5 %) in the PPI infusion group and in 12 patients (7.9 %) in the second-look endoscopy group (P = 0.646). Surgery was required for rebleeding in six patients from the PPI infusion group and three patients in the second-look endoscopy group (P = 0.32). Intensive care unit stay, transfusion requirements, and mortality were not different between the groups. Patients in the second-look endoscopy group were discharged 1 day earlier than those in the PPI infusion group (P < 0.001). CONCLUSIONS: After endoscopic hemostasis, high-dose PPI infusion was not inferior to second-look endoscopy with bolus PPI in preventing peptic ulcer rebleeding. TRIAL REGISTRATION: ClinicalTrials.gov (NCT: 00164931).

Magnolol inhibits colonic motility through down-regulation of voltage-sensitive L-type Ca2+ channels of colonic smooth muscle cells in rats.

This study aimed to investigate the effect of magnolol (5,5'-diallyl-2,2'-biphenyldiol) on contraction in distal colonic segments of rats and the underlying mechanisms. Colonic segments were mounted in organ baths for isometric force measurement. Whole-cell voltage-sensitive L-type Ca(2+) currents were recorded on isolated single colonic smooth muscle cells using patch-clamp technique. The spontaneous contractions and acetylcholine (ACh)- and Bay K 8644-induced contractions were inhibited by magnolol (3-100 µM). In the presence of Bay K8644 (100 nM), magnolol (10-100 µM) inhibited the contraction induced by 10 µM ACh. By contrast, tetrodotoxin (100 nM) and Nώ-nitro-L-arginine methyl ester (L-NAME 100 µM) did not change the inhibitory effect of magnolol (10 µM). In addition, magnolol (3-100 µM) inhibited the L-type Ca(2+) currents. The present results suggest that magnolol inhibits colonic smooth muscle contraction through downregulating L-type Ca(2+) channel activity.