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Objective: Treating sarcopenia remains a challenge, and nutritional interventions present promising approaches. We summarize the effects of leucine supplementation in treating older individuals with sarcopenia associated with aging or to specific disorders, and we focus on the effect of leucine supplementation on various sarcopenia criteria, e.g., muscular strength, lean mass, and physical performance. Methods: A literature search for articles related to this topic was performed on the relevant databases, e.g., the PubMed/Medline, Embase, EBSCO, Cochrane, Lilacs, and Dialnet. The identified articles were reviewed according to Preferred Reporting Items for Systematic reviews and meta-analyses (PRISMA) guidelines. Results: Of the 163 articles we consulted, 23 met our inclusion criteria, analysing the effect of leucine or leucine-enriched protein in the treatment of sarcopenia, and 13 of these studies were based on randomized and placebo-controlled trials (RCTs). In overall terms, the published results show that administration of leucine or leucine-enriched proteins (range 1.2–6 g leucine/day) is well-tolerated and significantly improves sarcopenia in elderly individuals, mainly by improving lean muscle-mass content and in this case most protocols also include vitamin D co-administration. The effect of muscular strength showed mix results, and the effect on physical performance has seldom been studied. For sarcopenia-associated with specific disorders, the most promising effects of leucine supplementation are reported for the rehabilitation of post-stroke patients and in those with liver cirrhosis. Further placebo-controlled trials will be necessary to determine the effects of leucine and to evaluate sarcopenia with the criteria recommended by official Working Groups, thereby limiting the variability of methodological issues for sarcopenia measurement across studies.

Treating sarcopenia in older individuals remains a challenge, and nutritional interventions present promising approaches in individuals that perform limited physical exercise. We assessed the efficacy of leucine administration to evaluate whether the regular intake of this essential amino acid can improve muscle mass, muscle strength and functional performance and respiratory muscle function in institutionalized older individuals. The study was a placebo-controlled, randomized, double-blind design in fifty participants aged 65 and over (ClinicalTrials.gov identifier NCT03831399). The participants were randomized to a parallel group intervention of 13 weeks’ duration with a daily intake of leucine (6 g/day) or placebo (lactose, 6 g/day). The primary outcome was to study the effect on sarcopenia and respiratory muscle function. The secondary outcomes were changes in the geriatric evaluation scales, such as cognitive function, functional impairment and nutritional assessments. We also evaluated whether leucine administration alters blood analytical parameters and inflammatory markers. Administration of leucine was well-tolerated and significantly improves some criteria of sarcopenia in elderly individuals such as functional performance measured by walking time (p = 0.011), and improved lean mass index. For respiratory muscle function, the leucine-treated group improved significantly (p = 0.026) in maximum static expiratory force compared to the placebo. No significant effects on functional impairment, cognitive function or nutritional assessment, inflammatory cytokines IL-6, TNF-alpha were observed after leucine administration compared to the placebo. The use of l-leucine supplementation can have some beneficial effects on sarcopenia and could be considered for the treatment of sarcopenia in older individuals.

Background Health-related quality of life (HRQoL) may be impaired in the presence of sarcopenia. Since a specific quality of life questionnaire became available for sarcopenia (SarQol), cutoffs to screen for this condition have been proposed, prompting the need to assess them in different populations. Due to the lack of consensus on diagnostic criteria, the tool has not yet been analyzed in screening for sarcopenic obesity. Aim Our aim is to measure the SarQoL’s metric properties and establish a cutoff in QoL assessments that could be used along the diagnostic pathway for sarcopenia and sarcopenic obesity in community-dwelling older women. Methods This cross-sectional study assessed women aged ≥ 70 years using the SarQol, sarcopenia criteria (EWGSOP2) and sarcopenic obesity criteria (ESPEN/EASO). Cutoffs for the SarQol were defined with a receiver-operating characteristics (ROC) curve, and sensitivity and specificity were analyzed. Results Of the 95 included women (mean age 76.0 years, standard deviation [SD] 5.7), 7.3% ( n =  7) were classified as having sarcopenic obesity, 22.1% ( n =  21) as having sarcopenia, and 70.5% ( n =  67) as not having sarcopenia. The total SarQol score was higher in women without sarcopenia (66.5 SD 16.2) versus those with sarcopenia (56.6 SD 15.6) and sarcopenic obesity (45.1 SD 7.9). A cutoff of ≤ 60 points is proposed for sarcopenia screening (area under the ROC curve [AUC] 0.67; 95% confidence interval [CI] 0.53–0.80; sensitivity 61.9%; specificity 62%), and ≤ 50 points for sarcopenic obesity (AUC 0.85; 95% CI 0.74–0.95; sensitivity 71.4%; specificity 76.9%). Conclusions Quality of life is compromised in women with sarcopenia and especially in those with sarcopenic obesity. The SarQol could be useful in screening for these conditions, providing insight into health-related quality of life in older people with sarcopenia.

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.

Sarcopenia and frailty are important conditions that become increasingly prevalent with age. There is partial overlap between the two conditions, especially in terms of the physical aspects of the frailty phenotype: low grip strength, gait speed, and muscle mass. This study examined whether administration of the essential branched-chain amino acid leucine, besides improving sarcopenia, may reduce frailty assessed by frailty index (FI) in older institutionalized people living in nursing homes. We conducted a secondary analysis of a placebo-controlled, randomized, double-blind design study (ClinicalTrials.gov NCT03831399). The study included fifty males and females aged 65 and over who were living in nursing homes and did not have dementia. The participants were randomized to a parallel group intervention of 13 weeks’ duration, with a daily intake of leucine (6 g/day) or placebo (lactose, 6 g/day). The outcome of this study was to evaluate whether there was a change in the level of a 95 item FI compared to the baseline and to compare the effect of the leucine group versus the placebo group. A significant inverse correlation was found between FI and performance of the activities of daily life, cognitive function, gait and balance, muscle function parameters, and nutritional status (p < 0.001 in all cases). There were no statistically significant differences in FI levels at baseline (placebo group FI 0.27 ± 0.08 and leucine group FI 0.27 ± 0.10) and at the 13 week follow-up (placebo group FI 0.28 ± 0.10 and leucine group FI 0.28 ± 0.09). There were also no significant differences between the leucine and placebo groups in the mean FI difference between baseline and follow-up (p = 0.316, Cohen’s d: 0.04). This pilot study showed that a nutritional supplementation with leucine did not significantly modify the frailty index in older nursing home residents.

Background Muscle strength is one of the most reliable measures used for the identification of sarcopenia. The European Working Group on Sarcopenia in Older People update (EWGSOP2) proposed the use of grip strength and chair stand tests, while clarifying that isometric torque methods can be used when performing the grip strength test is impossible. This study aims to evaluate the diagnostic accuracy of isometric knee extension strength in screening for sarcopenia. Methods This cross-sectional study included community-dwelling women aged 70 years and over. IKE and sarcopenia criteria (EWGSOP2) were assessed. Skeletal muscle mass was assessed by bioelectrical impedance analysis; muscle mass strength by handgrip; and physical performance by the 5 times sit-to-stand test, the Short Physical Performance Battery, and gait speed. The diagnostic accuracy for each sarcopenia criterion was calculated using sensitivity, specificity, positive and negative predictive value, and the area under the curve (AUC). Cutoff points for sarcopenia from IKE were defined with the ROC curve. Results The sample comprised 94 women with a mean age of 75.9 years (standard deviation 5.6, range 70–92), of whom 25.5% ( n  = 24) met criteria for sarcopenia—mainly severe sarcopenia (73.8%, n  = 17). Correlations were observed between IKE and each individually analyzed sarcopenia criterion except skeletal muscle mass, with AUC values exceeding 0.70 in all cases. The IKE cutoff showing the highest accuracy for the diagnosis of sarcopenia was 12.5 kg or less (AUC 0.76, 95% confidence interval [CI] 0.64–0.88; sensitivity: 65.2%, 95% CI 45.7–84.7; specificity 77.4%, 95% CI 60.3–94.5; positive predictive value 62.5%, 95 CI% 42.7–82.3; negative predictive value 88.8%, 95% CI 75.9–100). Conclusions IKE could be a suitable tool for measuring muscular strength in sarcopenia when other strength parameters cannot be assessed or in people with walking difficulties.