Associations between gut microbiota and sarcopenia or its defining parameters in older adults: A systematic review

Altered gut microbiota (GM) potentially contribute to development or worsening of sarcopenia through a gut-muscle axis. This systematic review aims to compare GM between persons with sarcopenia or low sarcopenia-defining parameters (muscle mass, strength, and physical performance) to those with preserved muscle status, as well as to clarify possible associations between sarcopenia (-defining parameters) and relative abundance (RA) of GM-taxa or GM-(α- or β) diversity indices, in order to clarify whether there is robust evidence of the existence of a GM signature for sarcopenia. This systematic review was conducted according to the PRISMA-reporting guideline and pre-registered on PROSPERO (CRD42021259597). PubMed, Web of Science, Embase, ClinicalTrials.gov, and Cochrane library were searched until 20 July 2023. Included studies reported on GM and sarcopenia or its defining parameters. Observational studies were included with populations of mean age ≥50 years. Thirty-two studies totalling 10 781 persons (58.56% ♀) were included. Thirteen studies defined sarcopenia as a construct. Nineteen studies reported at least one sarcopenia-defining parameter (muscle mass, strength or physical performance). Studies found different GM-taxa at multiple levels to be significantly associated with sarcopenia (n = 4/6), muscle mass (n = 13/14), strength (n = 7/9), and physical performance (n = 3/3); however, directions of associations were heterogeneous and also conflicting for specific GM-taxa. Regarding β-diversity, studies found GM of persons with sarcopenia, low muscle mass, or low strength to cluster differently compared with persons with preserved muscle status. α-diversity was low in persons with sarcopenia or low muscle mass as compared with those with preserved muscle status, indicating low richness and diversity. In line with this, α-diversity was significantly and positively associated with muscle mass (n = 3/4) and muscle strength (n = 2/3). All reported results were significant (P < 0.05). Persons with sarcopenia and low muscle parameters have less rich and diverse GM and can be separated from persons with preserved muscle mass and function based on GM-composition. Sarcopenia and low muscle parameters are also associated with different GM-taxa at multiple levels, but results were heterogeneous and no causal conclusions could be made due to the cross-sectional design of the studies. This emphasizes the need for uniformly designed cross-sectional and longitudinal trials with appropriate GM confounder control in large samples of persons with sarcopenia and clearly defined core outcome sets in order to further explore changes in GM-taxa and to determine a sarcopenia-specific GM-signature.

Pancreatic cancer and sarcopenia: a narrative review of the current status

Pancreatic cancer is still a difficult disease to treat, despite recent advances in surgical techniques and chemotherapeutic drugs. Its incidence continues to rise, as does the number of older patients. Sarcopenia is defined as a progressive and generalized loss of skeletal muscle mass and strength. Sarcopenia is present in approximately 40% in patients with pancreatic cancer. Sarcopenia is primarily diagnosed through imaging, and progress is being made in the development of automated methods and artificial intelligence, as well as biomarker research. Sarcopenia has been linked to a poor prognosis in pancreatic cancer patients. However, some studies suggest that sarcopenia is not always associated with a poor prognosis, depending on the resectability of pancreatic cancer and the nature of treatment, such as surgery or chemotherapy. Recent meta-analyses have found that sarcopenia is not linked to postoperative complications. It is still debated whether there is a link between sarcopenia and drug toxicity during chemotherapy. The relationship between sarcopenia and immunity has been investigated, but the mechanism is still unknown.

Trial in Elderly with Musculoskeletal Problems due to Underlying Sarcopenia-Faeces to Unravel the Gut and Inflammation Translationally (TEMPUS-FUGIT): protocol of a cross-sequential study to explore the gut-muscle axis in the development and treatment of sarcopenia in community-dwelling older adults

BACKGROUND

Gut microbiota (GM) might play a role in muscle metabolism and physiological processes through a hypothesized gut-muscle axis, influencing muscle mass and function and thus, sarcopenia. The Trial in Elderly with Musculoskeletal Problems due to Underlying Sarcopenia-Faeces to Unravel the Gut and Inflammation Translationally (TEMPUS-FUGIT) aims to explore the gut-muscle axis in sarcopenia.

METHODS

First, in a cross-sectional case-control phase, 100 community-dwelling adults without sarcopenia will be compared to 100 community-dwelling adults (≥ 65 years) with sarcopenia of similar age-, gender and BMI-ratio, participating in the ongoing 'Exercise and Nutrition for Healthy AgeiNg' (ENHANce; NCT03649698) study. Sarcopenia is diagnosed according to the European Working Group on Sarcopenia in Older People 2 (EWGSOP2) criteria. GM composition and intestinal inflammatory markers (fecal calprotectin, lactoferrin and S100A12) will be determined in fecal samples. Systemic inflammatory markers (hs-CRP, IL-4, IL-6, TNF-α, IL-13, IL-1β and creatine kinase) will be determined in fasted blood samples. Both groups will be compared using appropriate statistical testing, whereas linear regression will be used for cross-sectional associations between gut, inflammatory and sarcopenia parameters. Second, in the longitudinal phase, sarcopenic older adults will be requested to deliver five fecal samples during the 12-week intervention to assess the effects of protein, omega-3 and a physical exercise program on the GM.

DISCUSSION

TEMPUS-FUGIT aims to explore the gut-muscle axis by comparing GM composition between sarcopenic and non-sarcopenic older adults and to determine the association of GM with intestinal and systemic inflammatory markers and sarcopenia-defining parameters (muscle mass, muscle strength and physical performance). Furthermore, effects of single or combined, optimized and individualized anabolic interventions (exercise, protein and omega-3 supplementation), on GM will be explored in persons with sarcopenia. TEMPUS-FUGIT aims to impact clinical practice by clarifying the relationship between the gut-muscle axis and sarcopenia. TEMPUS-FUGIT is expected to contribute to the discovery of clinical and microbial biomarkers for sarcopenia and insights in its pathophysiology, opening possible future perspectives for novel sarcopenia treatment strategies targeting GM.

TRIAL REGISTRATION

ClinicalTrails.gov NCT05008770, registered on August 17, 2021; first participant enrolled on September 21 2021.

Chronological changes in the gut microbiota and intestinal environment in recipients and donors of living donor liver transplantation

BACKGROUND/PURPOSE

This prospective study aimed to investigate the dynamic changes in the gut microbiota (GM) and associated intestinal environment, which were assessed by measuring fecal organic acid (OA) concentrations, during the early period after liver transplantation (LT). To understand the fundamental characteristics of the human GM, data obtained from living donors were also analyzed.

METHODS

Fixed-point observation was performed in 23 recipients and 21 donors for up to 2 weeks after LT. The GM and OA concentrations were investigated using ribosomal RNA-targeted reverse-transcription quantitative polymerase chain reaction and high-performance liquid chromatography, respectively.

RESULTS

Before LT, the recipients exhibited remarkable dysbiosis and OA depletion, which were proportional to the model for end-stage liver disease score. Correlations between the abundances of some specific strains and OA concentrations were observed. After LT, while donor lobectomy caused only slight, transient and reversible changes in the GM and OA concentrations, recipients exhibited delayed recovery in these factors. However, no clear evidence of causality was observed between the GM or OA concentrations and LT outcomes.

CONCLUSIONS

The GM and intestinal environment in LT recipients exhibited characteristics that were clearly different from those in donors. LT did not normalize but rather disrupted the GM during the early post-LT period, but its negative clinical impact could be minimized with perioperative management.

ILC3s restrict the dissemination of intestinal bacteria to safeguard liver regeneration after surgery

It is generally believed that environmental or cutaneous bacteria are the main origin of surgical infections. Therefore, measures to prevent postoperative infections focus on optimizing hygiene and improving asepsis and antisepsis. In a large cohort of patients with infections following major surgery, we identified that the causative bacteria are mainly of intestinal origin. Postoperative infections of intestinal origin were also found in mice undergoing partial hepatectomy. CCR6⁺ group 3 innate lymphoid cells (ILC3s) limited systemic bacterial spread. Such bulwark function against host invasion required the production of interleukin-22 (IL-22), which controlled the expression of antimicrobial peptides in hepatocytes, thereby limiting bacterial spread. Using genetic loss-of-function experiments and punctual depletion of ILCs, we demonstrate that the failure to restrict intestinal commensals by ILC3s results in impaired liver regeneration. Our data emphasize the importance of endogenous intestinal bacteria as a source for postoperative infection and indicate ILC3s as potential new targets.

The psoas muscle depletion index is related to the degree of cirrhosis and skeletal muscle loss in patients with end-stage liver disease

Objective: To establish a new psoas muscle depletion index (PDI) from healthy young donors and to explore the correlation between the PDI and the severity of cirrhosis in patients with endstage liver disease (ESLD). Methods: Clinical data of 461 healthy donors were collected during the period 2014-2019, and clinical data of 331 patients with ESLD were collected during the period 2014-2018. The patients were divided into four groups by PDI severity: PDI ≥ 0.90, PDI = 0.75-0.90, PDI = 0.50-0.75 and PDI ≤ 0.50 (Gsev). Differences in international normalised ratio (INR), total bilirubin and serum creatinine levels, and Child-Pugh (CP) and model for end-stage liver disease (MELD) scores were compared. The sarcopenia incidence according to the PDI and the psoas muscle index (PMI) in different weight groups were also compared. Results: Gsev had the highest CP (10.2 ± 2.1) and MELD (20.1 ± 7.4) scores and total bilirubin (166.3 ± 192.0 umol/L) and blood creatinine (92.9 ± 90.2 umol/L) levels and the lowest haemoglobin (93.8 ± 21.7 g/L) and blood albumin (30.9 ± 5.8 g/L) levels. Gsev showed significant changes in INR (1.74 ± 0.65) and blood sodium (135.3 ± 5.65 mmol/L). If PDI <0.75 was used as the diagnostic criterion for sarcopenia, the incidence was 53.3% in patients weighing >90 kg and 53.6% in those weighing <60 kg. This differed from the PMI, with an incidence of 3.3% in patients weighing >90 kg. Conclusions: The PDI had no significant correlation with body height, body weight or body mass index (BMI) in healthy individuals and patients with ESLD. The PDI was significantly correlated with the severity of cirrhosis and loss of skeletal muscle.

Bacterial translocation in patients undergoing major gastrointestinal surgery and its role in postoperative sepsis

Bacteria of the human intestinal microflora have a dual role. They promote digestion and are part of a defense mechanism against pathogens. These bacteria could become potential pathogens under certain circumstances. The term “bacterial translocation” describes the passage of bacteria of the gastrointestinal tract through the intestinal mucosa barrier to mesenteric lymph nodes and other organs. In some cases, the passage of bacteria and endotoxins could result in blood stream infections and in multiple organ failure. Open elective abdominal surgery more frequently results in malfunction of the intestinal barrier and subsequent bacterial translocation and blood stream infections than laparoscopic surgery. Postoperative sepsis is a common finding in patients who have undergone non-elective abdominal surgeries, including trauma patients treated with laparotomy. Postoperative sepsis is an emerging issue, as it changes the treatment plan in surgical patients and prolongs hospital stay. The association between bacterial translocation and postoperative sepsis could provide novel treatment options.

Importance of "muscle" and "intestine" training before major HPB surgery: A review

Major hepato-pancreato-biliary (HPB) surgery is one of the most invasive abdominal surgeries. Through the experiences of several clinical trials, including those involving patients undergoing major HPB surgery, we have recognized the importance of "muscle" and "intestine" training before surgery. This review article summarizes the results of our clinical trials, specifically focusing on the importance of "muscle" and "intestine". The patients with low skeletal muscle mass or those with low functional exercise capacity showed a significantly worse postoperative course and poor long-term survival after surgery for HPB malignancy. The introduction of prehabilitation (preoperative physical and nutritional support) improved nutritional status and functional exercise capacity, even in patients with malignancy. Daily physical activity was correlated with nutritional status before surgery. These results indicated the usefulness of prehabilitation. The intestinal microenvironment, which is extrapolated from the fecal concentrations of short-chain fatty acids (SCFAs), showed a significant association with the incidence of surgery-induced bacterial translocation and postoperative infectious complications (POICs). The use of perioperative synbiotics not only increased the fecal levels of SCFAs but also prevented the incidence of POICs. A recent study also indicated that there are correlations between muscle mass and the intestinal microenvironment. Further investigation is required to determine the best "muscle" and "intestine" training protocol to improve the outcomes of major HPB surgeries.

Clinical importance of "occult-bacterial translocation" in patients undergoing highly invasive gastrointestinal surgery: A review

In the clinical setting, mild bacteremia cannot be detected by conventional culture methods, only by a highly sensitive bacterial detection system. One of the major causes of mild bacteremia is bacterial translocation (BT) induced by a dysregulated intestinal microenvironment and increased intestinal epithelial permeability. This condition is called "occult-bacterial translocation (O-BT)"; however, the concept of O-BT is not yet fully recognized. In our previous studies, done using a highly sensitive bacterial detection system such as bacterium-specific ribosomal RNA-targeted reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), O-BT was commonly observed in patients who underwent highly invasive surgery. We collected blood and mesenteric lymph node (MLN) samples from patients undergoing esophagectomy for esophageal cancer, before and after they were subjected to surgical stress. The detection rate of bacteria in these samples increased from approximately 20% before surgical stress to more than 50% after surgical stress. Moreover, positivity for bacteria in the blood or MLN samples was associated with the incidence of postoperative infectious complications (POICs). Using the RT-qPCR system, it is possible to detect the specific bacteria that cause O-BT immediately after surgery. This may allow us to select the exact antibiotic that targets possible pathogenic bacteria of POICs.