Skeletal muscle pericyte response to acute and chronic electrical stimulation

Pericytes are mural cells that are located on the outer surface of blood capillaries where they attach to endothelial cells and regulate vascular function, including dilation and angiogenesis. Recent studies suggest that pericytes in skeletal muscle may contribute to myofiber repair in response to injury. However, the pericyte response to exercise remains largely unexplored. PURPOSE: The purpose of this study was to evaluate pericyte quantity and gene expression in skeletal muscle following electrical stimulation, a method that can be used to simulate resistance exercise in mice. METHODS: Adult wild-type mice were subjected to an electrical stimulation protocol that results in 20 eccentric and 20 concentric contractions during a single session or (n=5; n=4 sham). A separate cohort of mixed-sex mice were subjected to electrical stimulation twice weekly for 4 weeks (n=4; n=4 sham) and 9 weeks (n=3; n=3 sham). At the end of each study, gastrocnemius-soleus complexes were dissected 24h following the final bout of stimulation. Pericyte quantity was assessed by multiplex flow cytometry in all samples. NG2+CD45-CD31- and CD146+CD45-CD31- pericytes were isolated following the acute study and gene expression was evaluated using high throughput qPCR. RESULTS: Acute electrical stimulation resulted in a non-significant trend for an increase in total pericyte content in skeletal muscle and a significant increase in the percentage of NG2+CD45-CD31- pericytes expressing the mesenchymal stem/stromal cell (MSC) marker CD140A. Isolation of pericytes based on CD146 revealed a population of cells highly engaged in the synthesis of factors necessary for myogenesis, satellite cell activation, and extracellular matrix remodeling post-acute stimulation. Finally, a pericyte to MSC transition was also observed with 4 weeks of stimulation, but no changes in overall pericyte quantity were noted at 4 or 9 weeks. CONCLUSION: This study provides evidence that resistance exercise promotes a pericyte to MSC transition, an event that may be necessary for pericytes to engage in skeletal muscle repair and adaptation

Exploring the Association between Vascular Dysfunction and Skeletal Muscle Mass, Strength and Function in Healthy Adults: A Systematic Review

Background: The prevalence of vascular dysfunction increases with advancing age, as does the loss of muscle mass, strength and function. This systematic review explores the association between vascular dysfunction and skeletal muscle health in healthy adults. Methods: EMBASE and MEDLINE were searched for cross-sectional and randomized controlled studies between January 2009 and April 2019, with 33 out of 1246 studies included based on predefined criteria. Assessments of muscular health included muscle mass, strength and function. Macrovascular function assessment included arterial stiffness (pulse wave velocity or augmentation index), carotid intima-media thickness, and flow-mediated dilation. Microvascular health assessment included capillary density or microvascular flow (contrast enhanced ultrasound). Results: All 33 studies demonstrated a significant association between vascular function and skeletal muscle health. Significant negative associations were reported between vascular dysfunction and -muscle strength (10 studies); -mass (9 studies); and -function (5 studies). Nine studies reported positive correlations between muscle mass and microvascular health. Conclusions: Multiple studies have revealed an association between vascular status and skeletal muscle health in healthy adults. This review points to the importance of screening for muscle health in adults with vascular dysfunction with a view to initiating early nutrition and exercise interventions to ameliorate functional decline over tim

Is It Time to Reconsider the U.S. Recommendations for Dietary Protein and Amino Acid Intake?

Since the U.S. Institute of Medicine’s recommendations on protein and amino acid intake in 2005, new information supports the need to re-evaluate these recommendations. New lines of evidence include: (1) re-analysis/re-interpretation of nitrogen balance data; (2) results from indicator amino acid oxidation studies; (3) studies of positive functional outcomes associated with protein intakes higher than recommended; (4) dietary guidance and protein recommendations from some professional nutrition societies; and (5) recognition that the synthesis of certain dispensable amino acids may be insufficient to meet physiological requirements more often than previously understood. The empirical estimates, theoretical calculations and clinical functional outcomes converge on a similar theme, that recommendations for intake of protein and some amino acids may be too low in several populations, including for older adults (≥65 years), pregnant and lactating women, and healthy children older than 3 years. Additional influential factors that should be considered are protein quality that meets operational sufficiency (adequate intake to support healthy functional outcomes), interactions between protein and energy intake, and functional roles of amino acids which could impact the pool of available amino acids for use in protein synthesis. Going forward, the definition of “adequacy” as it pertains to protein and amino acid intake recommendations must take into consideration these critical factors

Growth and Gastrointestinal Tolerance in Healthy Term Infants Fed Milk-Based Infant Formula Supplemented with Five Human Milk Oligosaccharides (HMOs): A Randomized Multicenter Trial

Background: Five of the most abundant human milk oligosaccharides (HMOs) in human milk are 2′-fucosyllactose (2′-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), 3′-sialyllactose (3′-SL) and 6′-sialyllactose (6′-SL). Methods: A randomized, double-blind, controlled parallel feeding trial evaluated growth in healthy term infants fed a control milk-based formula (CF; n = 129), experimental milk-based formula (EF; n = 130) containing five HMOs (5.75 g/L; 2′-FL, 3-FL, LNT, 3′-SL and 6′-SL) or human milk (HM; n = 104). Results: No significant differences (all p ≥ 0.337, protocol evaluable cohort) were observed among the three groups for weight gain per day from 14 to 119 days (D) of age, irrespective of COVID-19 or combined non-COVID-19 and COVID-19 periods. There were no differences (p ≥ 0.05) among the three groups for gains in weight and length from D14 to D119. Compared to the CF group, the EF group had more stools that were soft, frequent and yellow and were similar to the HM group. Serious and non-serious adverse events were not different among groups, but more CF-fed infants were seen by health care professionals for illness from study entry to D56 (p = 0.044) and D84 (p = 0.028) compared to EF-fed infants. Conclusions: The study demonstrated that the EF containing five HMOs supported normal growth, gastrointestinal (GI) tolerance and safe use in healthy term infants