Study participants

The study participants were community-dwelling older women who attended voluntary lunch events held in seven community centers in Nishinomiya City, Hyogo Japan. The inclusion criteria for this study were receipt of an annual health examination in community centers before lunch events between September 2015 and October 2015. Individuals who were<65years old, those with diabetes, cardiovascular diseases, or rheumatism, and those with an estimated glomerular filtration rate (eGFR) of<30ml/min/1.73m2 were excluded. Owing to the number of men being too small (n=16), these participants were excluded from the analysis. A further seven patients were excluded because of missing anthropometric or blood data. Of 232 older adults who participated in health examinations, 144 were included in our analysis. Of these, 85 underwent our health examination in 2017 and were included in the analysis examining the association between plasma ADMA levels and reductions in muscle mass and muscle strength over 2-years. The grip strength of one participant was not measured in the health examination conducted in 2017.

This study was conducted in accordance with the 2013 revision of the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of Mukogawa Womens University (approval number 15-04). All participants provided written informed consent for participation in this study and publication of the article. The sample size was determined based on the number of participants who underwent the health examination.

Blood samples were collected in the morning (from 10:00 to 11:00AM). The blood samples of 118 participants were collected following overnight fasting, whereas 26 participants self-reported eating something beforehand. Serum albumin, creatinine, and tumor necrosis factor (TNF)- levels were measured by a clinical laboratory (LSI Medience Corp., Tokyo, Japan) using the improved bromcresol method, enzymatic method, and chemiluminescent enzyme immunoassay, respectively. eGFR levels were calculated based on age and serum creatinine levels.

Anthropometric measurements were then performed and included height, weight, skeletal muscle mass, and grip strength. Weight and limb skeletal muscle mass were measured by bioimpedance analysis using the InBody 430 body composition analyzer (BioSpace Inc., Cerritos, CA, USA). Body mass index (BMI) was calculated as weight (kg) divided by height (m) squared. Skeletal muscle mass index (SMI) was calculated as limb skeletal muscle mass (kg) divided by height (m) squared. The grip strength of the dominant hand was measured with the patient being in a standing position using a grip strength dynamometer (GRIP-D, Takei Scientific Instrument Co. Ltd., Japan). The higher value (kg) measure from two trials was used for the analysis. These anthropometric data were collected by well-trained staff .

Plasma samples were obtained by centrifugation of the participants blood samples using heparin and stored at30C. Plasma ADMA levels were measured in our laboratory using a competitive enzyme-linked immunosorbent assay, according to previously described methods28. Briefly, blood samples were pretreated with N-succinimidyl 3-maleimidobenzoate (SMB) and mixed with monoclonal anti-SMB-ADMA antibody. The mixtures were added to plates coated with ADMA-SMB-bovine serum albumin conjugates and incubated overnight at 4C. After labeling with horseradish peroxidase-bound secondary antibodies, ADMA levels were detected by chemiluminescence using o-phenylenediamine. The cross-reactivity of this ELISA system with L-arginine was<0.01%.

Sarcopenia is indicated by low muscle strength, low physical performance, and low height-adjusted muscle mass. We measured grip strength and skeletal muscle mass by bioimpedance analysis during the health examinations. In this study, sarcopenia was defined as a grip strength of<18kg and SMI of<5.7kg/m2 based on the definition of the Asian Working Group for Sarcopenia 2019 Consensus3.

Other demographic data including age, current medication status (antihypertension and antidislipiemia), smoking status (current smoker, previous smoker, or nonsmoker), and drinking habits (every day, sometimes, or never) were obtained.

Quantitative variables are expressed as the meanstandard deviation (SD) (median). Categorical variables are expressed as numbers (percentages). We categorized the participants into those with and thosewithout sarcopenia. The two groups were compared using unpaired t-tests for quantitative variables with normal distributions, MannWhitney U tests for quantitative variables with non-normal distributions, and chi-square tests for categorical variables. Because there is no established cutoff value for plasma ADMA levels indicative of sarcopenia, the cutoff was estimated using a receiver-operating characteristic (ROC) curve and the Youden Index. The odds ratio (OR) and 95% confidence interval (CI) for sarcopenia were determined by logistic regression analysis. The covariates of multivariate-adjusted logistic regression analysis were age (categorized by an increment of 5years), lower BMI (<18.5kg/m2), smoking (current and previous), habitual alcohol consumption (every day and sometimes), current medication for hypertension or dyslipidemia, and high serum TNF- levels (1.56pg/ml of the median value). Low serum albumin level was also a covariate; however, none of the participants had low serum albumin levels (<4.0g/dl)29. Therefore, the median was used as the reference value (<4.4g/dl). To examine the associations between plasma ADMA levels and reduced muscle mass and muscle strength, the within-subject differences in SMI and grip strength between 2015 and 2017 were compared between those with lower plasma ADMA levels and those with higher plasma ADMA levels using MannWhitney U tests. All statistical data were analyzed using SPSS v. 26.0 (IBM Corp., Armonk, NY, USA) software. Two-tailed p values of<0.05 were considered statistically significant.

Informed consent was obtained from all individual participants included in the study. Informed consent was obtained from legal guardians. Written informed consent was obtained from all participants.

Link:
Association between asymmetric dimethylarginine and sarcopenia ... - Nature.com