Expression and Roles of Lynx1, a Modulator of Cholinergic Transmission, in Skeletal Muscles and Neuromuscular Junctions in Mice.

Lynx1 is a glycosylphosphatidylinositol (GPI)-linked protein shown to affect synaptic plasticity through modulation of nicotinic acetylcholine receptor (nAChR) subtypes in the brain. Because of this function and structural similarity to α-bungarotoxin, which binds muscle-specific nAChRs with high affinity, Lynx1 is a promising candidate for modulating nAChRs in skeletal muscles. However, little is known about the expression and roles of Lynx1 in skeletal muscles and neuromuscular junctions (NMJs).

A Novel Egr-1-Agrin Pathway and Potential Implications for Regulation of Synaptic Physiology and Homeostasis at the Neuromuscular Junction.

Synaptic transmission requires intricate coordination of the components involved in processing of incoming signals, formation and stabilization of synaptic machinery, neurotransmission and in all related signaling pathways. Changes to any of these components cause synaptic imbalance and disruption of neuronal circuitry. Extensive studies at the neuromuscular junction (NMJ) have greatly aided in the current understanding of synapses and served to elucidate the underlying physiology as well as associated adaptive and homeostatic processes.

Muscle strength and force development in high- and low-functioning elderly men: Influence of muscular and neural factors.

Background: Aging leads to a loss of muscle strength and functional capacity likely resulting from a combination of neural and muscle alterations. The aim of this study was to identify possible disparities in muscle strength and force development profiles in high- and low-functioning elderly men and to investigate muscular and neurophysiological factors that could explain the differences.

Methods: Sixty community-dwelling men in good general health were divided in two groups based on a functional capacity (FC) z-score derived from 6 tests of the Short Physical Performance Battery and Senior Fitness Test (Normal and fast 4m-walk tests, normal and fast Timed-up and go, chair and stair tests).

Mitochondrial energy deficiency leads to hyperproliferation of skeletal muscle mitochondria and enhanced insulin sensitivity.

Diabetes is associated with impaired glucose metabolism in the presence of excess insulin. Glucose and fatty acids provide reducing equivalents to mitochondria to generate energy, and studies have reported mitochondrial dysfunction in type II diabetes patients. If mitochondrial dysfunction can cause diabetes, then we hypothesized that increased mitochondrial metabolism should render animals resistant to diabetes.

The impact of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, mitochondrial content, and intramyocellular lipids in men.

Background: The exact impact of ageing on skeletal muscle phenotype and mitochondrial and lipid content remains controversial, probably because physical activity, which greatly influences muscle physiology, is rarely accounted for. The present study was therefore designed to investigate the effects of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, and mitochondrial and intramyocellular lipid content in men.

Methods: Recreationally active young adult (20-30 yo; YA); active (ACT) and sedentary (SED) middle-age (50-65 yo; MA-ACT and MA-SED); and older (65 + yo; 65 + ACT and 65 + SED) and pre-frail older (65 + PF) men were recruited.

Muscle Strength and Body Weight Mediate the Relationship Between Physical Activity and Usual Gait Speed.

Background: Usual gait speed (UGS) is recognized as a good indicator of a variety of health conditions as well as a predictor of future disability and mortality. There is evidence that UGS increases with physical activity. Muscle function and body composition changes may mediate these changes.

Is handgrip strength normalized to body weight a useful tool to identify dynapenia and functional incapacity in post-menopausal women?

Objective: To investigate whether handgrip strength normalized to body weight could be a useful clinical tool to identify dynapenia and assess functional capacity in post-menopausal women.

Method: A total of 136 postmenopausal women were recruited. Body composition (Dual Energy X-ray Absorptiometry [DEXA], Bio-electrical Impedence Analysis [BIA]), grip strength (dynamometer) and functional capacity (senior fitness tests) were evaluated.

Caloric restriction and aerobic exercise in sarcopenic and non-sarcopenic obese women: an observational and retrospective study.

Background: Sarcopenic obese (SO) individuals are a unique subset of subjects that combines obesity and sarcopenia. Traditional weight loss programmes including aerobic exercises may worsen their condition by further reducing their lean mass. The objective of this observational and retrospective study was to verify the effect of a mixed weight loss programme combining caloric restriction and exercise on body composition, and lipid-lipoprotein profile of obese women according to their sarcopenic status.

Physical activity in advanced Parkinson's disease: impact of subthalamic deep brain stimulation.

Background: Maintaining a physically active lifestyle promotes general health. Recent studies have demonstrated that patients with Parkinson's disease (PD) fail to meet the suggested levels of physical activity and that targeted interventions do not always improve this behavior. One validated treatment for motor symptoms in PD is subthalamic stimulation (STN DBS).

The relationship between muscle fiber type-specific PGC-1α content and mitochondrial content varies between rodent models and humans.

PGC-1α regulates critical processes in muscle physiology, including mitochondrial biogenesis, lipid metabolism and angiogenesis. Furthermore, PGC-1α was suggested as an important regulator of fiber type determination. However, whether a muscle fiber type-specific PGC-1α content exists, whether PGC-1α content relates to basal levels of mitochondrial content, and whether such relationships are preserved between humans and classically used rodent models are all questions that have been either poorly addressed or never investigated.

Subthalamic stimulation improves motor function but not home and neighborhood mobility.

Objective: Subthalamic (STN) deep brain stimulation (DBS) is a recognized therapy for alleviating motor symptoms of Parkinson's disease (PD). However, little is known about its impact on mobility, an important component of quality of life (QoL). To address this issue, we assessed the impact of STN DBS on life-space mobility and QoL.

Identifying recreational physical activities associated with muscle quality in men and women aged 50 years and over.

Background: Several studies conducted in a laboratory-related environment have shown that exercise is associated with increased muscle quality in older adults. The aim of the present study was to investigate whether recreational exercise may also be associated with muscle quality in men and women aged 50 years and over.

Methods: Data are from 312 individuals (215 women) aged 50 years and older.

Exploring the role of muscle mass, obesity, and age in the relationship between muscle quality and physical function.

Background: Divergent conclusions emerge from the literature regarding the relationship between muscle quality (defined as muscle strength per unit of muscle mass) and physical function. These contrasted results may be due to the influence of factors such as age, obesity, and muscle mass itself. Consequently, the aim of the present study was to explore the role of these factors in the relationship between muscle quality (MQ) and physical function.

Increased sensitivity to mitochondrial permeability transition and myonuclear translocation of endonuclease G in atrophied muscle of physically active older humans.

Mitochondrial dysfunction is implicated in skeletal muscle atrophy and dysfunction with aging, with strong support for an increased mitochondrial-mediated apoptosis in sedentary rodent models. Whether this applies to aged human muscle is unknown, nor is it clear whether these changes are caused by sedentary behavior. Thus, we examined mitochondrial function [respiration, reactive oxygen species (ROS) emission, and calcium retention capacity (CRC)] in permeabilized myofibers obtained from vastus lateralis muscle biopsies of healthy physically active young (23.

Muscle quantity is not synonymous with muscle quality.

Background: Greater muscle mass can generally produce greater muscle strength. However, whether higher muscle mass is associated with higher muscle quality (muscle strength relative to muscle mass) remains unknown. Furthermore, the nature of this relationship, and how their interaction determines the presence of functional impairments are unknown.

Toward a sex-specific relationship between muscle strength and appendicular lean body mass index?

Background: In spite of some dissociation between muscle mass and strength, muscle strength is often used as a proxy to identify individuals with low muscle mass (sarcopenia). Thus, the aim of the present study was to investigate the relationship between muscle strength and the appendicular lean body mass index (app LBMI).

Methods: One hundred and five individuals were recruited.

Clinical relevance of different muscle strength indexes and functional impairment in women aged 75 years and older.

Background: Muscle mass index has long been used as a useful index to evaluate the risks of developing functional impairments. However, there is evidence that other indexes (particularly muscle strength-based indexes) may be more relevant. Thus, the purpose of this study was to compare the association between different indexes of muscle mass or strength with self-reported and measured functional performance to determine which index would be clinically relevant to detect individuals at risk of functional impairments.

Relationship between long sleep duration and functional capacities in postmenopausal women.

Study Objective: The purpose of the present study was to examine the relationship between long sleep duration and functional capacities.

Methods: We conducted a cross-sectional study at the Department of Kinanthropology at the University of Quebec at Montreal. Forty eight non-frail postmenopausal women aged between 49 to 75 years were recruited using advertisements in local papers.

Muscle quality as a potential explanation of the metabolically healthy but obese and sarcopenic obese paradoxes.

Background: Obesity has been associated with metabolic complications. However, two subgroups of obese individuals (namely "sarcopenic obese" and "metabolically healthy but obese" individuals) with low muscle mass appear to have a better metabolic profile. Despite having a lower muscle mass, these individuals appear to have higher muscle strength, suggesting higher muscle quality.

Is functional capacity related to the daily amount of steps in postmenopausal women?

Objective: The aim of this study was to investigate the relationship between functional capacity, muscle function, and daily step count in postmenopausal women.

Methods: Fifty-seven postmenopausal women aged 50 to 70 years were recruited. Body composition (body weight, body mass index, fat mass, and skeletal muscle mass), energetic metabolism (maximal oxygen consumption, total energy expenditure, daily step count), and functional capacity (muscle strength, muscle quality, chair stand, balance and alternate step tests) were measured.

Effects of tai chi training in dynapenic and nondynapenic postmenopausal women.

Objective: The purpose of the present study was to investigate the effects of a 12-week tai chi program in type I dynapenic and nondynapenic postmenopausal women.

Methods: Sixty-two postmenopausal women were recruited. Body composition, handgrip strength, functional capacities, cardiorespiratory functions (forced expiratory volume in 1 s and oxygen consumption per unit time peak), and quality of life (36-item Short-Form Health Survey) were measured before and after the intervention.

Menopause and sarcopenia: A potential role for sex hormones.

Menopause is associated with a decline in estrogen levels, which could lead to an increase in visceral adiposity as well as a decrease in bone density, muscle mass and muscle strength. This decline in muscle mass, known as sarcopenia, is frequently observed in postmenopausal women. Potential causes of sarcopenia include age-related changes in the hormonal status, low levels of physical activity, reduced protein intake and increased oxidative stress.