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1.
The relationships between sarcopenic skeletal muscle loss during ageing and macronutrient metabolism, obesity and onset of diabetes.
Welch, AA, Hayhoe, RPG, Cameron, D
The Proceedings of the Nutrition Society. 2020;(1):158-169
Abstract
Skeletal muscle is integral to the metabolism and utilisation of macronutrients; however, substantial muscle loss and morphological changes occur with ageing. These are associated with loss of muscle function and accelerate rapidly from the age of 60 years, leading to the conditions of sarcopenia and frailty. As the relationship between muscle ageing and macronutrient metabolism and utilisation has seen limited research to date, this review focuses on the interactions between skeletal muscle changes during ageing, metabolism and utilisation of fat, carbohydrates and overall energy expenditure.Skeletal muscle contributes less to resting energy expenditure during ageing, potentially contributing to onset of obesity from middle age. Age-related changes to skeletal muscle lead to glucose dysregulation, with consequent reduction in glycaemic control, increased insulin resistance and ultimately onset of type-2 diabetes. Recent studies indicate that high total fat and SFA intake are detrimental to skeletal muscle, while higher intakes of PUFA are protective. Age-associated changes in skeletal muscle may also reduce total fatty acid utilisation.In conclusion, further research is needed to understand the relationships between macronutrient metabolism and utilisation and age-related changes to skeletal muscle. No dietary recommendations exist specifically for skeletal muscle health during ageing, but we advise individuals to follow healthy eating guidelines, by consuming sufficient protein, fruit and vegetables, and limited SFA and to maintain physically active lifestyles. Clinicians responsible for managing type-2 diabetes need to be aware of growing evidence relating age-related skeletal muscle changes to diabetes onset and progression.
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2.
Assessing skeletal muscle radiodensity by computed tomography: An integrative review of the applied methodologies.
Poltronieri, TS, de Paula, NS, Chaves, GV
Clinical physiology and functional imaging. 2020;(4):207-223
Abstract
Low-radiodensity skeletal muscle has been related to the degree of muscle fat infiltration and seems to be associated with worse outcomes. The aim of this study was to summarize the methodologies used to appraise skeletal muscle radiodensity by computed tomography, to describe the terms used in the literature to define muscle radiodensity and to give recommendations for its measurement standardization. An integrative bibliographic review in four databases included studies published until August 2019 in Portuguese, English or Spanish and performed in humans, adults and/or the elderly, of both sex, which investigated skeletal muscle radiodensity through computed tomography (CT) of the region between the third and fifth lumbar vertebrae and evaluated at least two muscular groups. One hundred and seventeen studies were selected. We observed a trend towards selecting all abdominal region muscle. A significant methodological variation in terms of contrast use, selection of skeletal muscle areas, radiodensity ranges delimitation and their cut-off points, as well as the terminologies used, was also found. The methodological differences detected are probably due to the lack of more precise information about the correlation between skeletal muscle radiodensity by CT and its molecular composition, among others. Therefore, until the gaps are addressed in future studies, authors should avoid arbitrary approaches when reporting skeletal muscle radiodensity, especially when it comes to prognosis inference. Studies using both CT and direct methods of muscle composition evaluation are encouraged, to enable the definition and validation of the best approach to classify fat-infiltrated muscle tissue, which will favour the nomenclature uniformization.
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3.
Protein intake in older people : Why, how much and how?
Kiesswetter, E, Sieber, CC, Volkert, D
Zeitschrift fur Gerontologie und Geriatrie. 2020;(4):285-289
Abstract
The protein intake of older people has gained increasing scientific interest as a potential factor to delay the age-associated decline in muscle mass and consequently to counteract the development of sarcopenia. The skeletal muscle of older people seems less responsive to the anabolic stimulus of protein intake. Therefore, higher protein needs are discussed to overcome this anabolic resistance and to maintain muscle mass as far as possible. Besides the total amount of protein consumed, the distribution, quality and timing in relation to physical exercise are considered relevant; however, deriving clear recommendations for clinical practice is still difficult as positive results of protein intake on muscle metabolism found in experimental trials cannot simply be transferred to everyday conditions and randomized controlled trials often failed to show improvements in muscular outcomes related to protein supplementation. The effectiveness of protein supplementation may depend on functional resources of the older persons and the habitual protein intake. There is still a need for studies with well-defined protocols and populations to further elucidate the role of protein in the prevention and treatment of sarcopenia.
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4.
The Influence of Physical Activity on the Bioactive Lipids Metabolism in Obesity-Induced Muscle Insulin Resistance.
Imierska, M, Kurianiuk, A, Błachnio-Zabielska, A
Biomolecules. 2020;(12)
Abstract
High-fat diet consumption and lack of physical activity are important risk factors for metabolic disorders such as insulin resistance and cardiovascular diseases. Insulin resistance is a state of a weakened response of tissues such as skeletal muscle, adipose tissue, and liver to insulin, which causes an increase in blood glucose levels. This condition is the result of inhibition of the intracellular insulin signaling pathway. Skeletal muscle is an important insulin-sensitive tissue that accounts for about 80% of insulin-dependent glucose uptake. Although the exact mechanism by which insulin resistance is induced has not been thoroughly understood, it is known that insulin resistance is most commonly associated with obesity. Therefore, it is believed that lipids may play an important role in inducing insulin resistance. Among lipids, researchers' attention is mainly focused on biologically active lipids: diacylglycerols (DAG) and ceramides. These lipids are able to regulate the activity of intracellular enzymes, including those involved in insulin signaling. Available data indicate that physical activity affects lipid metabolism and has a positive effect on insulin sensitivity in skeletal muscles. In this review, we have presented the current state of knowledge about the impact of physical activity on insulin resistance and metabolism of biologically active lipids.
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5.
Metabolic adaptations after bariatric surgery: adipokines, myokines and hepatokines.
Faramia, J, Ostinelli, G, Drolet-Labelle, V, Picard, F, Tchernof, A
Current opinion in pharmacology. 2020;:67-74
Abstract
This review addresses the impact of bariatric surgery on the endocrine aspects of white adipose tissue, muscle and the liver. We describe literature supporting the notion that adipokines, myokines and hepatokines likely act in concert and drive many of the long-term metabolic improvements following surgery. Circulating adiponectin is increased while secretion of pro-inflammatory interleukins (1, 6 and 8) decreases, alongside leptin secretion. The metabolic improvements observed in the muscle might relate to reduction of myokines contributing to insulin resistance (including myostatin, brain-derived neurotrophic factor and fibroblast growth factor-21). Subject to exception, hepatokine secretion is generally increased (such as insulin-like growth factor-binding protein 2, adropin and sex hormone-binding globulin). In conclusion, bariatric surgery restores metabolic functions by enhancing the time-dependent secretion of anti-inflammatory, insulin-sensitizing and antilipemic factors. Further research is needed to understand the molecular mechanisms by which these factors may trigger the remission of obesity-related comorbidities following bariatric surgery.
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6.
Milk for Skeletal Muscle Health and Sarcopenia in Older Adults: A Narrative Review.
Granic, A, Hurst, C, Dismore, L, Aspray, T, Stevenson, E, Witham, MD, Sayer, AA, Robinson, S
Clinical interventions in aging. 2020;:695-714
Abstract
Skeletal muscle aging manifests as a decline in muscle quantity and quality that accelerates with aging, increasing the risk of sarcopenia. Sarcopenia is characterized by a loss of muscle strength and mass, and contributes to adverse health outcomes in older adults. Intervention studies have shown that sarcopenia may be treated by higher protein intake in combination with resistance exercise (RE). In comparison, less is known about the role of whole protein-containing foods in preventing or treating sarcopenia. Liquid milk contains multiple nutrients and bioactive components that may be beneficial for muscle, including proteins for muscle anabolism that, alone or with RE, may have myoprotective properties. However, there is a lack of evidence about the role of milk and its effects on muscle aging. This narrative review considers evidence from three observational and eight intervention studies that used milk or fortified milk, with or without exercise, as an intervention to promote muscle health and function in older adults (aged 50-99 years). The observational studies showed no association between higher habitual milk consumption and muscle-related outcomes. The results of intervention studies using fortified milk in relation to elements of sarcopenia were also negative, with further inconclusive results from the studies using a combination of (fortified) milk and exercise. Although milk contains nutrients that may be myoprotective, current evidence does not show beneficial effects of milk on muscle health in older adults. This could be due to high habitual protein intakes (>1.0 g/kg BW/d) in study participants, differences in the type of milk (low-fat vs whole) and timing of milk consumption, length of interventions, as well as differences in the sarcopenia status of participants in trials. Adequately powered intervention studies of individuals likely to benefit are needed to test the effectiveness of a whole food approach, including milk, for healthy muscle aging.
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7.
The Role of Nutrition in Attenuating Age-Related Skeletal Muscle Atrophy.
Abiri, B, Vafa, M
Advances in experimental medicine and biology. 2020;:297-318
Abstract
The elderly population is increasing rapidly worldwide, and we are faced with the significant challenge for maintaining or improving physical activity, independence, and quality of life. Sarcopenia, the age-related decline of skeletal muscle mass, is characterized by loss of muscle quantity and quality resulting to a gradual slowing of movement, a decrease in strength and power, elevated risk of fall-related injury, and often frailty. Supplemental, hormonal, and pharmacological approaches have been attempted to attenuate sarcopenia but these have not achieved outstanding results. In this review, we summarize the current knowledge of nutrition-based therapies for counteracting sarcopenia.
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8.
The Importance of Fatty Acids as Nutrients during Post-Exercise Recovery.
Lundsgaard, AM, Fritzen, AM, Kiens, B
Nutrients. 2020;(2)
Abstract
It is well recognized that whole-body fatty acid (FA) oxidation remains increased for several hours following aerobic endurance exercise, even despite carbohydrate intake. However, the mechanisms involved herein have hitherto not been subject to a thorough evaluation. In immediate and early recovery (0-4 h), plasma FA availability is high, which seems mainly to be a result of hormonal factors and increased adipose tissue blood flow. The increased circulating availability of adipose-derived FA, coupled with FA from lipoprotein lipase (LPL)-derived very-low density lipoprotein (VLDL)-triacylglycerol (TG) hydrolysis in skeletal muscle capillaries and hydrolysis of TG within the muscle together act as substrates for the increased mitochondrial FA oxidation post-exercise. Within the skeletal muscle cells, increased reliance on FA oxidation likely results from enhanced FA uptake into the mitochondria through the carnitine palmitoyltransferase (CPT) 1 reaction, and concomitant AMP-activated protein kinase (AMPK)-mediated pyruvate dehydrogenase (PDH) inhibition of glucose oxidation. Together this allows glucose taken up by the skeletal muscles to be directed towards the resynthesis of glycogen. Besides being oxidized, FAs also seem to be crucial signaling molecules for peroxisome proliferator-activated receptor (PPAR) signaling post-exercise, and thus for induction of the exercise-induced FA oxidative gene adaptation program in skeletal muscle following exercise. Collectively, a high FA turnover in recovery seems essential to regain whole-body substrate homeostasis.
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9.
Guidelines on clinical presentation and management of nondystrophic myotonias.
Stunnenberg, BC, LoRusso, S, Arnold, WD, Barohn, RJ, Cannon, SC, Fontaine, B, Griggs, RC, Hanna, MG, Matthews, E, Meola, G, et al
Muscle & nerve. 2020;(4):430-444
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Abstract
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.
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10.
A Narrative Review of Handgrip Strength and Cognitive Functioning: Bringing a New Characteristic to Muscle Memory.
Shaughnessy, KA, Hackney, KJ, Clark, BC, Kraemer, WJ, Terbizan, DJ, Bailey, RR, McGrath, R
Journal of Alzheimer's disease : JAD. 2020;(4):1265-1278
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Abstract
BACKGROUND Measures of handgrip strength have not only emerged as a clinically viable screening tool for determining risk for morbidity, functional disability, and early mortality, but also for helping to identify cognitive deficits. However, the phenomena that links low handgrip strength with cognitive decline remains unclear. The role of the muscular and neural systems, and their adaptations to muscle strengthening activities over the life course, may provide important information for how age-related changes to muscle mass, strength, and neural capacity influence cognition. Moreover, disentangling how handgrip strength and cognitive function are associated may help to inform healthcare providers working with aging adults and guide targeted interventions aiming to preserve muscle and cognitive functioning. OBJECTIVE To 1) highlight and summarize evidence examining the associations of handgrip strength and cognitive functioning, and 2) provide directions for future research in this area. METHODS Articles from the PubMed database were searched from November 2018-May 2019. The search term algorithm, inclusion and exclusion criteria were pre-specified by investigators. RESULTS Several cross-sectional and longitudinal studies have revealed that measures of handgrip strength were associated with cognitive declines regardless of age demographics and the presence of comorbidities. CONCLUSION Handgrip strength can be used in clinical and epidemiological settings for helping to determine the onset and progression of cognitive impairment. Future research should continue to examine how handgrip strength and cognitive function are linked.