A role for nutritional intervention in addressing the aging neuromuscular junction

Resveratrol and Vitamin D: Eclectic Molecules Promoting Mitochondrial Health in Sarcopenia

Sarcopenia refers to the progressive loss and atrophy of skeletal muscle function, often associated with aging or secondary to conditions involving systemic inflammation, oxidative stress, and mitochondrial dysfunction. Recent evidence indicates that skeletal muscle function is not only influenced by physical, environmental, and genetic factors but is also significantly impacted by nutritional deficiencies. Natural compounds with antioxidant properties, such as resveratrol and vitamin D, have shown promise in preventing mitochondrial dysfunction in skeletal muscle cells. These antioxidants can slow down muscle atrophy by regulating mitochondrial functions and neuromuscular junctions. This review provides an overview of the molecular mechanisms leading to skeletal muscle atrophy and summarizes recent advances in using resveratrol and vitamin D supplementation for its prevention and treatment. Understanding these molecular mechanisms and implementing combined interventions can optimize treatment outcomes, ensure muscle function recovery, and improve the quality of life for patients.

The impact of malnutrition on the effectiveness of intradialytic exercise in hemodialysis patients: amulticenter cohort study

PURPOSE

Low physical function can be effectively improved via intradialytic exercise. However, the association between the effects of intradialytic exercise on physical function and malnutrition severity has not been studied extensively. This study aimed to investigate the impact of nutritional status severity on physical function in patients undergoing hemodialysis with low physical function to whom intradialytic exercise was prescribed.

METHODS

The participants were patients with decreased mobility [walking speed < 1.0 m/s and/or Short Physical Performance Battery (SPPB) < 12] who had been undergoing hemodialysis thrice a week for 6 months and performing intradialytic exercise program. Patients were divided into groups based on the Geriatric Nutritional Risk Index (GNRI) [Non-malnutrition group (GNRI > 98), Gentle/slim malnutrition group (GNRI ≤ 98, GNRI ≥ 92), Mild malnutrition group (GNRI < 92, GNRI ≥ 82), Severe malnutrition group (GNRI < 82)]. The primary outcomes were Grip strength, isometric knee extension strength (IKES), SPPB, and 10-m walking speed measured at baseline and at 6 months. Statistical analyses were performed using a linear mixed-effects model with the intention-to-treat analysis, including within-group analysis and between-group comparison.

RESULTS

A total of 805 participants were included in the study. Within-group comparisons showed significantly improved IKES, 10-m walking speed, and SPPB improved, except in the Severe malnutrition group. Grip strength significantly improved in the Gentle/slim and mild malnutrition groups. Between-group comparison with controls showed that the improvement in Grip strength was significantly bigger in the Gentle/slim malnutrition group [0.98 (0.15 to 1.82) kg] than in the non-malnutrition group. However, IKES in the Severe malnutrition group [- 5.14 (- 9.18 to - 1.10) %] less significantly improve than that in the non-malnutrition group. No significant differences were found in the other indices.

CONCLUSION

In patients with severe malnutrition, the changes in IKES scores resulting from Intradialytic exercise were significantly smaller than those observed in non-malnourished patients. Therefore, it is necessary to initiate suitable nutritional and exercise therapy based on the severity of malnutrition.

Bidirectional associations of high-level cognitive domains with hand motor function and gait speed in high-functioning older adults: A 7-year study

BACKGROUND

Whether age-related decline in the musculoskeletal system may contribute to a decline in cognitive performance or vice versa is unclear. Understanding the direction of their associations and the extent to which upper and lower extremities similarly predict subtle changes in high-level cognitive performance will help elucidate their mechanisms, especially that of the hand dexterity.

METHODS

We evaluated the bidirectional associations of motor performance and high-level cognitive domains in 165 highly cognitively and physically healthy older adults. Motor performance tests consisted of handgrip strength, hand dexterity, assessed with the Purdue Pegboard Test (PPT), and usual and maximum gait speeds. High-level cognitive measures included executive function and information processing speed. The Trail Making Test (TMT)B and the letter and category fluency tests (LFT and CFT) evaluated executive function, while the TMTA and Digit Symbol assessed processing speed. Measurements were taken at baseline and at 2-, 5- and 7-year follow-up.

RESULTS

Generalized linear mixed-effect models showed that baseline hand dexterity and its trajectory predicted changes in TMTB, CFT, TMTA, and Digit Symbol over time, and vice versa. Baseline maximum gait speed was associated with LFT over time and vice versa. No associations were found for handgrip and usual gait speed.

CONCLUSION

The positive bidirectional association observed both in hand dexterity and maximum gait speed with executive function performance and that of hand dexterity with processing speed over time highlights a reciprocal relationship where each factor affects the other and both factors are dependent on each other, suggesting commonality in their neural basis.

The effects of 12 weeks resistance training and vitamin D administration on neuromuscular joint, muscle strength and power in postmenopausal women

BACKGROUND

This study aimed to examine the effects of 12 weeks of resistance training (RT) and vitamin D (VitD) supplementation on muscle strength and C-terminal agrin fragment (CAF) and Neurotrophin-3 (NT-3) concentrations as potential biomarkers in postmenopausal women.

METHODS

This was a randomized double-blind placebo-controlled study. Forty-four healthy postmenopausal women (55.84 ± 4.70 years and 29.61 ± 4.26 kg/m2) were randomly assigned into four groups: (1) Resistance training + placebo (RT + PLA), (2) Vitamin D supplementation (VitD), (3) Resistance training + vitamin D (RT + VitD), and (4) Placebo (PLA). VitD was supplemented as an oral capsule containing 50000 IU of cholecalciferol every two weeks. RT involved leg press, chest press, leg extension, leg curl, and shoulder press exercises, performed with 3-4 sets at 70-85 % of 1RM, three times a week.

RESULTS

Circulating levels of CAF and NT-3 did not significantly change following the intervention period in the study groups (p > 0.05). There were significant increases in upper and lower body muscle strength and power for RT + VitD and RT + PLA ( < 0.05), but not for VitD or PLA (p > 0.05). The muscle function gains for RT + VitD and RT + PLA were higher than those for VitD and PLA but did not differ between them.

CONCLUSION

12-week of RT interventions resulted in significant increases in muscle strength and power in postmenopausal women. However, VitD supplementation did not result in any additional benefits. The positive changes in muscle function promoted by RT do not seem to be associated with changes in the neuromuscular joint via the CAF or NT-3 as potential biomarkers.

Cancer Cachexia: Underlying Mechanisms and Potential Therapeutic Interventions

Cancer cachexia, a multifactorial metabolic syndrome developed during malignant tumor growth, is characterized by an accelerated loss of body weight accompanied by the depletion of skeletal muscle mass. This debilitating condition is associated with muscle degradation, impaired immune function, reduced functional capacity, compromised quality of life, and diminished survival in cancer patients. Despite the lack of the known capability of fully reversing or ameliorating this condition, ongoing research is shedding light on promising preclinical approaches that target the disrupted mechanisms in the pathophysiology of cancer cachexia. This comprehensive review delves into critical aspects of cancer cachexia, including its underlying pathophysiological mechanisms, preclinical models for studying the progression of cancer cachexia, methods for clinical assessment, relevant biomarkers, and potential therapeutic strategies. These discussions collectively aim to contribute to the evolving foundation for effective, multifaceted counteractive strategies against this challenging condition.

Trend and prediction of citations on the topic of neuromuscular junctions in 100 top-cited articles since 2001 using a temporal bar graph: A bibliometric analysis

BACKGROUND

A neuromuscular junction (NMJ) (or myoneural junction) is a chemical synapse between a motor neuron (MN) and a muscle fiber. Although numerous articles have been published, no such analyses on trend or prediction of citations in NMJ were characterized using the temporal bar graph (TBG). This study is to identify the most dominant entities in the 100 top-cited articles in NMJ (T100MNJ for short) since 2001; to verify the improved TBG that is viable for trend analysis; and to investigate whether medical subject headings (MeSH terms) can be used to predict article citations.

METHODS

We downloaded T100MNJ from the PubMed database by searching the string ("NMJ" [MeSH Major Topic] AND ("2001" [Date - Modification]: "2021" [Date - Modification])) and matching citations to each article. Cluster analysis of citations was performed to select the most cited entities (e.g., authors, research institutes, affiliated countries, journals, and MeSH terms) in T100MNJ using social network analysis. The trend analysis was displayed using TBG with two major features of burst spot and trend development. Next, we examined the MeSH prediction effect on article citations using its correlation coefficients (CC) when the mean citations in MeSH terms were collected in 100 top-cited articles related to NMJ (T100NMJs).

RESULTS

The most dominant entities (i.e., country, journal, MesH term, and article in T100NMJ) in citations were the US (with impact factor [IF] = 142.2 = 10237/72), neuron (with IF = 151.3 = 3630/24), metabolism (with IF = 133.02), and article authored by Wagh et al from Germany in 2006 (with 342 citing articles). The improved TBG was demonstrated to highlight the citation evolution using burst spots, trend development, and line-chart plots. MeSH terms were evident in the prediction power on the number of article citations (CC = 0.40, t = 4.34).

CONCLUSION

Two major breakthroughs were made by developing the improved TBG applied to bibliographical studies and the prediction of article citations using the impact factor of MeSH terms in T100NMJ. These visualizations of improved TBG and scatter plots in trend, and prediction analyses are recommended for future academic pursuits and applications in other disciplines.

Beneficial effects of dietary supplementation with green tea catechins and cocoa flavanols on aging-related regressive changes in the mouse neuromuscular system

Besides skeletal muscle wasting, sarcopenia entails morphological and molecular changes in distinct components of the neuromuscular system, including spinal cord motoneurons (MNs) and neuromuscular junctions (NMJs); moreover, noticeable microgliosis has also been observed around aged MNs. Here we examined the impact of two flavonoid-enriched diets containing either green tea extract (GTE) catechins or cocoa flavanols on age-associated regressive changes in the neuromuscular system of C57BL/6J mice. Compared to control mice, GTE- and cocoa-supplementation significantly improved the survival rate of mice, reduced the proportion of fibers with lipofuscin aggregates and central nuclei, and increased the density of satellite cells in skeletal muscles. Additionally, both supplements significantly augmented the number of innervated NMJs and their degree of maturity compared to controls. GTE, but not cocoa, prominently increased the density of VAChT and VGluT2 afferent synapses on MNs, which were lost in control aged spinal cords; conversely, cocoa, but not GTE, significantly augmented the proportion of VGluT1 afferent synapses on aged MNs. Moreover, GTE, but not cocoa, reduced aging-associated microgliosis and increased the proportion of neuroprotective microglial phenotypes. Our data indicate that certain plant flavonoids may be beneficial in the nutritional management of age-related deterioration of the neuromuscular system.

The Impact of Milk Fat Globule Membrane with Exercise on Age-Related Degeneration of Neuromuscular Junctions

Morphological changes in neuromuscular junctions (NMJs), which are synapses formed between α-motor neurons and skeletal muscle fibers, are considered to be important in age-related motor dysfunction. We have previously shown that the intake of dietary milk fat globule membrane (MFGM) combined with exercise attenuates age-related NMJ alterations in the early phase of aging. However, it is unclear whether the effect of MFGM with exercise on age-related NMJ alterations persists into old age, and whether intervention from old age is still effective when age-related changes in NMJs have already occurred. In this study, 6- or 18-month-old mice were treated with a 1% MFGM diet and daily running wheel exercise until 23 or 24 months of age, respectively. MFGM treatment with exercise was effective in suppressing the progression of age-related NMJ alterations in old age, and even after age-related changes in NMJs had already occurred. Moreover, the effect of MFGM intake with exercise was not restricted to NMJs but extended to the structure and function of peripheral nerves. This study demonstrates that MFGM intake with exercise may be a novel approach for improving motor function in the elderly by suppressing age-related NMJ alterations.

Impairment Mechanisms and Intervention Approaches for Aged Human Neuromuscular Junctions

The neuromuscular junction (NMJ) is a chemical synapse formed between a presynaptic motor neuron and a postsynaptic muscle cell. NMJs in most vertebrate species share many essential features; however, some differences distinguish human NMJs from others. This review will describe the pre- and postsynaptic structures of human NMJs and compare them to NMJs of laboratory animals. We will focus on age-dependent declines in function and changes in the structure of human NMJs. Furthermore, we will describe insights into the aging process revealed from mouse models of accelerated aging. In addition, we will compare aging phenotypes to other human pathologies that cause impairments of pre- and postsynaptic structures at NMJs. Finally, we will discuss potential intervention approaches for attenuating age-related NMJ dysfunction and sarcopenia in humans.

Health Benefits of β-Hydroxy-β-Methylbutyrate (HMB) Supplementation in Addition to Physical Exercise in Older Adults: A Systematic Review with Meta-Analysis

Both regular exercise training and beta-hydroxy-beta-methylbutyrate (HMB) supplementation are shown as effective treatments to delay or reverse frailty and reduce cognitive impairment in older people. However, there is very little evidence on the true benefits of combining both strategies. The aim of this meta-analysis was to quantify the effects of exercise in addition to HMB supplementation, on physical and cognitive health in older adults. Data from 10 randomized controlled trials (RCTs) investigating the effect of HMB supplementation and physical function in adults aged 50 years or older were analyzed, involving 384 participants. Results showed that HMB supplementation in addition to physical exercise has no or fairly low impact in improving body composition, muscle strength, or physical performance in adults aged 50 to 80 years, compared to exercise alone. There is a gap of knowledge on the beneficial effects of HMB combined with exercise to preserve cognitive functions in aging and age-related neurodegenerative diseases. Future RCTs are needed to refine treatment choices combining HMB and exercises for older people in particular populations, ages, and health status. Specifically, interventions in older adults aged 80 years or older, with cognitive impairment, frailty, or limited mobility are required.