Effects of Leucine Administration in Sarcopenia: A Randomized and Placebo-controlled Clinical Trial

Where to Find Leucine in Food and How to Feed Elderly With Sarcopenia in Order to Counteract Loss of Muscle Mass: Practical Advice

The term sarcopenia refers to the loss of skeletal muscle mass and strength that generally occurs during aging. The interventions that have proved most effective in reducing the severity and preventing the worsening of sarcopenia include physical exercise, especially resistance, and the administration of dietary supplements in association with a targeted diet; nutritional intervention is the main therapeutic approach for elderly people, since they are very often sedentary (also due to possible disabilities). Among the various nutrients, high biological value proteins and leucine are of particular interest for their demonstrated effects on the health of skeletal muscle. The intake of food containing proteins and leucine during meals stimulates muscle protein synthesis. Lower blood levels of leucine were associated with lower values of the skeletal muscle index, grip strength and performance. The international guidelines recommended that a leucine intake of 3 g at three main meals together with 25-30 g of protein is the goal to be achieved to counteract loss of lean mass in elderly. Food composition databases rarely show the amounts of leucine contained in foods and therefore it becomes difficult to build a diet that follows these guidelines. A table was therefore created for the first time in the literature to collect all the foods richest in leucine, thanks to the union of the most important Italian food databases. Moreover, in order to implement a diet that follows the right recommendations, another tables shows nutritional composition of breakfast, lunch and dinner (that each provide 3 grams of leucine and 25 grams of protein) for seven days.

5q35 duplication presents with psychiatric and undergrowth phenotypes mediated by NSD1 overexpression and mTOR signaling downregulation

PURPOSE

Nuclear receptor binding SET domain protein 1, NSD1, encodes a histone methyltransferase H3K36. NSD1 is responsible for the phenotype of the reciprocal 5q35.2q35.3 microdeletion-microduplication syndromes. We expand the phenotype and demonstrate the functional role of NSD1 in microduplication 5q35 syndrome.

METHODS

Through an international collaboration, we report nine new patients, contributing to the emerging phenotype, highlighting psychiatric phenotypes in older affected individuals. Focusing specifically on the undergrowth phenotype, we have modeled the effects of Mes-4/NSD overexpression in Drosophila melanogaster.

RESULTS

The individuals (including a family) from diverse backgrounds with duplications ranging in size from 0.6 to 4.5 Mb, have a consistent undergrowth phenotype. Mes-4 overexpression in the developing wing causes undergrowth, increased H3K36 methylation, and increased apoptosis. We demonstrate that altering the levels of insulin receptor (IR) rescues the apoptosis and the wing undergrowth phenotype, suggesting changes in mTOR pathway signaling. Leucine supplementation rescued Mes-4/NSD induced cell death, demonstrating decreased mTOR signaling caused by NSD1.

CONCLUSION

Given that we show mTOR inhibition as a likely mechanism and amelioration of the phenotype by leucine supplementation in a fly model, we suggest further studies should evaluate the therapeutic potential of leucine or branched chain amino acids as an adjunct possible treatment to ameliorate human growth and psychiatric phenotypes and propose inclusion of 5q35-microduplication as part of the differential diagnosis for children and adults with delayed bone age, short stature, microcephaly, developmental delay, and psychiatric phenotypes.

Respiratory Sarcopenia and Sarcopenic Respiratory Disability: Concepts, Diagnosis, and Treatment

The condition of muscle fiber atrophy and weakness that occurs in respiratory muscles along with systemic skeletal muscle with age is known as respiratory sarcopenia. The Japanese Working Group of Respiratory Sarcopenia of the Japanese Association of Rehabilitation Nutrition narratively reviews these areas, and proposes the concept and diagnostic criteria. We have defined respiratory sarcopenia as "whole-body sarcopenia and low respiratory muscle mass followed by low respiratory muscle strength and/or low respiratory function." Respiratory sarcopenia can be caused by various factors such as aging, decreased activity, undernutrition, disease, cachexia, and iatrogenic causes. We have also created an algorithm for diagnosing respiratory sarcopenia. Respiratory function decreases with age in healthy older people, along with low respiratory muscle mass and strength. We have created a new term, "Presbypnea," meaning a decline in respiratory function with aging. Minor functional respiratory disability due to aging, such as that indicated by a modified Medical Research Council level 1 (troubled by shortness of breath when hurrying or walking straight up hill), is an indicator of presbypnea. We also define sarcopenic respiratory disability as "a disability with deteriorated respiratory function that results from respiratory sarcopenia." Sarcopenic respiratory disability is diagnosed if respiratory sarcopenia is present with functional disability. Cases of respiratory sarcopenia without functional disability are diagnosed as "at risk of sarcopenic respiratory disability." Functional disability is defined as a modified Medical Research Council grade of 2 or more. Rehabilitation nutrition, treatment that combines rehabilitation and nutritional management, may be adequate to prevent and treat respiratory sarcopenia and sarcopenic respiratory disability.

Sarcopenia: Molecular Pathways and Potential Targets for Intervention

Aging is associated with sarcopenia. The loss of strength results in decreased muscle mass and motor function. This process accelerates the progressive muscle deterioration observed in older adults, favoring the presence of debilitating pathologies. In addition, sarcopenia leads to a decrease in quality of life, significantly affecting self-sufficiency. Altogether, these results in an increase in economic resources from the National Health Systems devoted to mitigating this problem in the elderly, particularly in developed countries. Different etiological determinants are involved in the progression of the disease, including: neurological factors, endocrine alterations, as well as nutritional and lifestyle changes related to the adoption of more sedentary habits. Molecular and cellular mechanisms have not been clearly characterized, resulting in the absence of an effective treatment for sarcopenia. Nevertheless, physical activity seems to be the sole strategy to delay sarcopenia and its symptoms. The present review intends to bring together the data explaining how physical activity modulates at a molecular and cellular level all factors that predispose or favor the progression of this deteriorating pathology.

Respiratory Muscle Strengths and Their Association with Lean Mass and Handgrip Strengths in Older Institutionalized Individuals

The study of reduced respiratory muscle strengths in relation to the loss of muscular function associated with ageing is of great interest in the study of sarcopenia in older institutionalized individuals. The present study assesses the association between respiratory muscle parameters and skeletal mass content and strength, and analyzes associations with blood cell counts and biochemical parameters related to protein, lipid, glucose and ion profiles. A multicenter cross-sectional study was performed among patients institutionalized in nursing homes. The respiratory muscle function was evaluated by peak expiratory flow, maximal respiratory pressures and spirometry parameters, and skeletal mass function and lean mass content with handgrip strength, walking speed and bioimpedance, respectively. The prevalence of reduced respiratory muscle strength in the sample ranged from 37.9% to 80.7%. Peak expiratory flow significantly (p < 0.05) correlated to handgrip strength and gait speed, as well as maximal inspiratory pressure (p < 0.01). Maximal expiratory pressure significantly (p < 0.01) correlated to handgrip strength. No correlation was obtained with muscle mass in any of parameters related to reduced respiratory muscle strength. The most significant associations within the blood biochemical parameters were observed for some protein and lipid biomarkers e.g., glutamate-oxaloacetate transaminase (GOT), urea, triglycerides and cholesterol. Respiratory function muscle parameters, peak expiratory flow and maximal respiratory pressures were correlated with reduced strength and functional impairment but not with lean mass content. We identified for the first time a relationship between peak expiratory flow (PEF) values and GOT and urea concentrations in blood which deserves future investigations in order to manage these parameters as a possible biomarkers of reduced respiratory muscle strength.

Leucine-Enriched Protein Supplementation Increases Lean Body Mass in Healthy Korean Adults Aged 50 Years and Older: A Randomized, Double-Blind, Placebo-Controlled Trial

Early prevention of sarcopenia could be an important strategy for muscle retention, but most studies have focused on subjects aged 65 or older. Therefore, in this study we investigated the effects of leucine-enriched protein supplementation on muscle condition in a sample including late middle-aged adults. A 12-week intervention was performed for 120 healthy community-dwelling adults by providing either leucine-enriched protein supplement [leucine 3 g, protein mixture (casein 50% + whey 40% + soy 10%) 17 g, vitamin D 800IU (20 µg), calcium 300 mg, fat 1.1 g, carbohydrate 2.5 g] or isocaloric carbohydrate supplement twice per day. Appendicular skeletal muscle mass index (ASMI) and lean body mass (LBM) were measured by dual-energy X-ray absorptiometry. A total of 111 participants completed the study, with a dropout rate of 9.2%. LBM normalized by height and body weight (LBM/Wt) was significantly increased (p < 0.001) in the intervention group (0 wk: 633.9 ± 8.5 vs. 12 wk 636.9 ± 8.4 in the intervention group; 0 wk: 638.6 ± 8.3 vs. 12 wk: 632.9 ± 8.1 in the control group). In subgroup analyses, significant differences remained only in subjects between 50 and 64 years of age. We concluded that leucine-enriched protein supplementation can have beneficial effects by preventing muscle loss, mainly for late middle-aged adults.