Leucine-enriched amino acid supplementation and exercise to prevent sarcopenia in patients on hemodialysis: a single-arm pilot study.

Background: Sarcopenia, which is strongly associated with mortality and quality of life, occurs in up to 40% of hemodialysis patients. Here, we investigated the preventive effects of leucine-enriched amino acid supplementation and resistance exercise in non-sarcopenic hemodialysis patients, and characterized the biochemical and immunophenotypic profiles of those who benefited from the intervention. Methods: Twenty-two patients on maintenance hemodialysis at our hospital were enrolled in this single center, prospective, single-arm pilot trial. For the first 12 weeks, the subjects were administered a total of 6 g of leucine per day. Three grams were supplied via capsules, and the remaining three grams were provided via beverages containing macro- and micro- nutrients, such as 10 µg of vitamin D and 290 mg of calcium. The supplements were not provided for the next 12 weeks. Muscle mass, grip strength, and physical performance were measured using the bioimpedance analyzer (BIA), handgrip strength (HGS), and short physical performance battery (SPPB) protocols, respectively, at baseline, 12 weeks, and 24 weeks. In addition, serum biochemistry, immunophenotype of peripheral blood mononuclear cells, and nutritional status was assessed at the three time points. Those who showed 5% or more improvement in parameters were defined as responders, otherwise, as non-responders (ClinicalTrials.gov identification number: NCT04927208). Results: Twenty-one out of twenty-two patients (95.4%) showed improvement in at least one or more parameters among muscle mass, grip strength, and physical performance. After 12 weeks of intervention, skeletal muscle index was increased in 14 patients (63.6%), and grip strength was improved in 7 patients (31.8%). Baseline grip strength lower than 35.0 kg was the strongest predictor of improvement in grip strength (AUC 0.933 from ROC curve). Grip strength showed a significant increase in females than males (7.6 ± 8.2 vs. -1.6 ± 7.2%, p = 0.03), in age over 60 than under 60 (5.3 ± 6.2 vs. -1.4 ± 9.1%, p = 0.04), and in higher (≥95%) than lower (<95%) exercise compliance (6.8 ± 7.7 vs. -3.2 ± 6.4%, p = 0.004). In SPPB study, gait speed and sit-to-stand time was improved in 13 patients (59.1%) and 14 patients (63.6%), respectively. Baseline hemoglobin lower than 10.5 g/dl and hematocrit lower than 30.8% were predictor of improvement in the sit-to-stand time (AUC 0.862 and 0.848, respectively). Serum biochemistry results showed that, compared to non-responders, responders in muscle mass had lower baseline monocyte fraction (8.4 ± 1.9 vs. 6.9 ± 1.1%, p = 0.03), and responders in grip strength had lower baseline total protein (6.7 ± 0.4 vs. 6.4 ± 0.3 g/dL, p = 0.04). Immunophenotypic analysis found that the intervention tended to increase the naïve/memory CD8+ T cell ratio (from 1.2 ± 0.8 to 1.4 ± 1.1, p = 0.07). Conclusion: Leucine-enriched amino acid supplementation and resistance exercise induced significant improvement in muscle mass, strength, and physical function in subpopulation of the non-sarcopenic hemodialysis patients. Those who benefited from the intervention were old-age females with lower baseline grip strength or lower hemoglobin or hematocrit, and who have good exercise compliance. Therefore, we propose that the intervention will help to prevent sarcopenia in selected patients on maintenance hemodialysis.

Does whey protein supplementation during resistance exercise have additional benefits for decreasing hepatic fat content?

BACKGROUND: Exercise and diet have positive effects on hepatic fat reduction, and protein supplementation is known to lower hepatic fat accumulation. However, the effect of a combination of exercise and whey protein supplementation (WPS) on hepatic fat content (HFC) is unknown. METHODS: We investigated the effect of WPS on HFC during resistance exercise and diet control intervention for four weeks. A total of 34 sedentary males participated and were randomly assigned to two groups: a protein supplement group (PSG, n = 18) and a control group (CG, n = 16). The PSG took 60 g of WPS per day, and the CG took 60 g of an isocaloric placebo per day. All participants were fed a calorie-controlled diet throughout the study period, with their daily caloric intake determined by their resting metabolic rate and physical activity level. Both groups performed resistance exercises supervised by experts at 60-70% of their maximum efforts for 60 min/day, 6 days/week for 4 weeks. HFC was assessed using the controlled attenuation parameter (CAP) after an 8 h fast, at pre-, mid-, and post-intervention. Liver enzymes and lipid profile were also analyzed after an 8 h fast and pre- and post-intervention. RESULTS: The CAP was significantly reduced after 4 weeks of intervention in both groups (PSG, p < .001; CG, p = .002). However, there was no significant interaction between the group and changes in CAP. Interestingly, when comparing the pre- and mid-tests, both groups also had significantly reduced CAP (PSG, p = .027; CG, p = .028), but there was a significant difference in the amount of change in CAP between the two groups (PSG, -47.2 ± 25.4 dB/m; CG, -19.5 ± 15.1 dB/m; p = .042). For liver enzymes, there was a significant interaction between the two groups and a change in aspartate transaminase (AST) (p = .038). However, alanine aminotransferase (ALT) levels were significantly decreased only in the PSG group (p = .002). In lipids, both groups showed significantly decreased total cholesterol (p < .001) and low-density lipoprotein cholesterol (p < .001) after the intervention. CONCLUSION: Our data showed that WPS may not enhance the overall effects of resistance exercise on HFC and lipid profiles. However, in part, WPS may have a beneficial effect on liver enzymatic changes and rapid response to resistance exercise-induced HFC reduction.

Effects of Whey Protein Supplement on 4-Week Resistance Exercise-Induced Improvements in Muscle Mass and Isokinetic Muscular Function under Dietary Control.

(1) The purpose of this study was to investigate the effect of whey protein supplementation under dietary control on improvements in muscle mass and function following resistance exercise training. (2) Thirty-two men were randomly assigned to a whey protein supplementation group taking whey protein isolate (PSG, n = 17) and a placebo group (CON, n = 15). Participants were provided with three meals per day corresponding to the estimated individual daily energy intake. The supervised resistance exercise program was conducted 60 min per day, six days per week, for four weeks. (3) Post-intervention, there was a significant interaction between groups in terms of muscle mass increase (p = 0.033, η2 = 0.14), with a greater increase in the PSG. There were also significant interactions between the groups and increases in peak torque of the dominant knee flexors (p = 0.048, η2 = 0.12), dominant shoulder extensors, and non-dominant shoulder extensors (p = 0.028, η2 = 0.15; p = 0.015, η2 = 0.18), and the total work of the dominant knee and shoulder extensors (p = 0.012, η2 = 0.19; p = 0.013, η2 = 0.19), with greater increases in the PSG. (4) These results suggest that whey protein supplementation enhances resistance exercise-induced increase in muscle mass and overall muscular strength and endurance, independent of dietary influence.

Higher Intake of Total Dietary Essential Amino Acids Is Associated with a Lower Prevalence of Metabolic Syndrome among Korean Adults.

We hypothesized that a well-balanced intake of total essential amino acids (EAAs) may be associated with lower prevalence of metabolic syndrome among Korean adults. This population-based cross-sectional study included 25,787 participants aged ≥30 years from the 2008-2019 Korea National Health and Nutrition Examination Survey. Dietary information was obtained from 24 h recall data. Demographic and lifestyle factors were assessed using self-administered questionnaires, and metabolic biomarkers were obtained from a health examination. Total essential amino acid score (EAAS) was calculated to determine whether essential amino acid (EAA) intake meets the recommended nutrient intake (RNI). Multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models. After adjusting for multiple confounding factors, participants with higher EAAS had a significantly lower prevalence of high blood pressure (OR: 0.86, 95% CI: 0.75-0.98), hypertriglyceridemia (OR: 0.86, 95% CI: 0.76-0.98), and Metabolic syndrome (MetS) (OR: 0.86, 95% CI: 0.74-0.996). Spline regression analysis confirmed linearity of the association between total EAAS and MetS. EAA intake and MetS are associated with an inverse dose-response relationship in which metabolic disease may be prevented when the overall EAA intake meets the RNI.

Dietary Essential Amino Acid Intake Is Associated with High Muscle Strength in Korean Older Adults.

The relationship between daily dietary intake of an individual or all essential amino acids (EAAs) and muscle strength in older adults is still inadequately characterized. This population-based cross-sectional study included 5971 participants aged ≥65 years from the 2014-2019 Korea National Health and Nutrition Examination Survey. Dietary information was derived from the 24 h recall data. Total essential amino acid score (EAAS) was calculated with an intake that satisfied the recommended nutrient intake (RNI) in each essential amino acid (EAA). The mean handgrip strength was estimated from triplicate measurements obtained using the dominant hand, and high muscle strength was defined as handgrip strength ≥28 kg for men and ≥18 kg for women. Multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models. After multivariable adjustment, we found that a high total EAAS was associated with high muscle strength in Korean older adults (OR: 1.38, 95% CI: 1.07-1.79). High muscle strength was significantly enhanced with increased total EAA intake from animal sources (OR: 1.27, 95% CI: 1.02-1.58), but there was no significant association with total EAA intake from non-animal sources. EAA intake and high muscle strength are associated based on a positive dose-response relationship in which high muscle strength is further increased when the overall EAA intake meets the RNI. Thus, Korean older adults should ensure an adequate intake of all EAAs from various food sources (especially animal sources) to meet the RNI as a prerequisite for achieving high muscle strength.

Improvement of chewing and swallowing risks in community-dwelling older adults using texture-modified food.

BACKGROUND/OBJECTIVES: Understanding the mechanism of chewing and swallowing food is important when creating a proper diet for older adults. This study investigated whether texture-modified model foods can reduce the difference in chewing and swallowing parameters between healthy community-living young and older adults. SUBJECTS/METHODS: In total, 35 older and 20 young adults (mean age: 75 and 25 years, respectively), matched for sex and number of teeth, were recruited and their unstimulated salivation and tongue pressure were measured. Simultaneous assessment of chewing and swallowing characteristics was conducted using surface electromyography and a videofluoroscopic swallowing study while the participants ingested 8 g of model food with one to four levels of hardness. RESULTS: The average tongue pressure and salivation among older adults were 61% and 49.7%, respectively, of the corresponding values observed in young adults. The older adult group used significantly (P < 0.05) increased muscle force with more chewing cycles (P < 0.05) than the young adult group, which was maintained even when consuming foods with the lowest hardness, although without chewing. However, the age effect on oral processing time existed only for the hardest foods. Swallowing difficulties among older adults were demonstrated by the significant increase in vallecula aggregation time. The total food intake duration was significantly (P < 0.05) longer in older adults than in young adults, regardless of food hardness. CONCLUSIONS: There were measurable differences in the process of chewing and swallowing food between young and older adults, which can be improved with food hardness control. Adjusting food hardness may help food intake in healthy older adults.

Higher Branched-Chain Amino Acid Intake Is Associated with Handgrip Strength among Korean Older Adults.

Sarcopenia is a disease of old age characterized by decreased muscle mass and strength. Branched-chain amino acids (BCAAs) promote muscle mass synthesis and increase muscle strength. We aimed to develop a dietary amino acid database and to examine the association between BCAA intake and handgrip strength in Korean older adults. Data from the Korea National Health and Nutrition Examination Survey 2014-2018 were used. Overall, 4852 participants aged ≥65 years were included in the study. Demographic, lifestyle, and health data were obtained through interviews and questionnaires. The 24-h recall method was used to assess dietary intake. An amino acid database was established using the 9th revision of the Korean Standard Food Composition Table. The mean handgrip strength was estimated from triplicate measurements obtained using the dominant hand. Multivariable linear regression analysis was performed to assess the association between BCAA intake and handgrip strength. Grains greatly contributed to amino acid intake; however, a significant negative association was observed between handgrip strength and increased BCAA intake through grains. In the fully adjusted model, leucine intake and handgrip strength showed a positive association. Thus, consuming BCAAs (especially leucine) via a variety of food sources can help maintain muscle health in older people.

Estimation of Dietary Amino Acid Intake and Independent Correlates of Skeletal Muscle Mass Index among Korean Adults.

The aim of this study was to develop a database to identify dietary amino acid intake levels, and to determine whether any amino acid groups were independently correlated with skeletal muscle mass index (SMI). We used data from the Korea National Health and Nutrition Examination Survey 2008-2011, and a total of 3292 participants aged 50-64 years were included in the analysis. Dietary data were obtained using the 24 h recall method. Data regarding dietary amino acid intake was assessed using the computer-aided nutritional analysis program 4.0 published by the Korean Nutrition Society. Multivariate linear regression analysis was used to identify independent correlates of SMI. The major food group that contributed the highest essential amino acid intake was grain and grain products (histidine 25.5%, isoleucine 43.9%, leucine 44.2%, methionine 31.0%, phenylalanine 44.8%, tryptophan 26.4%, and valine 50.8%). Higher SMI was independently associated with sex (men), lower age and body mass index, higher levels of physical activity, and a higher intake of energy and branched-chain amino acids. These results are expected to be used as a basis for developing dietary amino acid intake guidelines for Koreans.

Protein Intake Recommendation for Korean Older Adults to Prevent Sarcopenia: Expert Consensus by the Korean Geriatric Society and the Korean Nutrition Society.

Sarcopenia, a common clinical syndrome in older adults, is defined as decreased muscle mass, strength, and physical performance. Since sarcopenia is associated with the incidence of functional decline, falls, and even mortality in older adults, researchers and health care providers have been keen to accumulate clinical evidence to advocate the screening and prevention of sarcopenia progression in older adults. The factors that may accelerate the loss of muscle mass and function include chronic diseases, inactivity, and deficiency in appropriate nutritional support. Among these, nutritional support is considered an initial step to delay the progression of muscle wasting and improve physical performance in community-dwelling older adults. However, a nationwide study suggested that most Korean older adults do not consume sufficient dietary protein to maintain their muscle mass. Furthermore, considering age-associated anabolic resistance to dietary protein, higher protein intake should be emphasized in older adults than in younger people. To develop a dietary protein recommendation for older adults in Korea, we reviewed the relevant literature, including interventional studies from Korea. From these, we recommend that older adults consume at least 1.2 g of protein per kg of body weight per day (g/kg/day) to delay the progression of muscle wasting. The amount we recommend (1.2 g/kg/day) is 31.4% higher than the previously suggested recommended daily allowance (i.e., 0.91 g/kg/day) for the general population of Korea. Also, evidence to date suggests that the combination of exercise and nutritional support may enhance the beneficial effects of protein intake in older adults in Korea. We found that the current studies are insufficient to build population-based guidelines for older adults, and we call for further researches in Korea.

Experimental Modeling of Horizontal and Vertical Wave Forces on an Elevated Coastal Structure.

A large-scale physical model was created in Oregon State University's Large Wave Flume to collect an extensive dataset measuring wave-induced horizontal and vertical forces on an idealized coastal structure. Water depth was held constant while wave conditions included regular, irregular, and transient (tsunami-like) waves with different significant wave heights and peak periods for each test. The elevation of the base of the test specimen with respect to the stillwater depth (air gap) was also varied from at-grade to 0.28 m above the stillwater level to better understand the effects of raising or lowering a nearshore structure on increasing or decreasing the horizontal and vertical wave forces. Results indicate that while both horizontal and vertical forces tend to increase with increasing significant wave height, the maximum and top 0.4% of forces increased disproportionally to other characteristic values such as the mean or top 10%. As expected, the horizontal force increased as the test specimen was more deeply submerged and decreased as the structure was elevated to larger air gaps above the stillwater level. However, this trend was not true for the vertical force, which was maximized when the elevation of the base of the structure was equal to the elevation of the stillwater depth. Small wave heights were characterized by low horizontal to vertical force ratios, highlighting the importance of considering vertical wave forces in addition to horizontal wave forces in the design of coastal structures. The findings and data presented here may be used by city planners, engineers, and numerical modelers, for future analyses, informed coastal design, and numerical benchmarking to work toward enabling more resilient nearcoast structures.