The importance of sonographic evaluation of muscle depth and thickness prior to the 'tiny percutaneous needle biopsy'

Microbiopsy Sampling for Examining Age-Related Differences in Skeletal Muscle Fiber Morphology and Composition

Introduction: The increasingly popular microbiopsy is an appealing alternative to the more invasive Bergström biopsy given the challenges associated with harvesting skeletal muscle in older populations. Parameters of muscle fiber morphology and composition derived from the microbiopsy have not been compared between young and older adults.

Purpose: The purpose of this study was to examine muscle fiber morphology and composition in young (YM) and older (OM) males using the microbiopsy sampling technique. A secondary aim was to determine if specific strength is associated with serum levels of C-terminal agrin fragment [CAF; an indicator of neuromuscular junction (NMJ) degradation].

Methods: Thirty healthy, YM (n = 15, age = 20.7 ± 2.2 years) and OM (n = 15, age = 71.6 ± 3.9 years) underwent ultrasound imaging to determine whole-muscle cross-sectional area (CSA) of the vastus lateralis and rectus femoris as well as isometric and isokinetic (60°⋅s^–1 and 180°⋅s^–1) peak torque testing of the knee extensors. Microbiopsy samples of the vastus lateralis were collected from 13 YM and 11 OM, and immunofluorescence was used to calculate CSA and proportion of type I and type II fibers.

Results: Peak torque was lower in OM at all velocities (p ≤ 0.001; d = 1.39–1.86) but only lower at 180°⋅s^–1 (p = 0.003; d = 1.23) when normalized to whole-muscle CSA. Whole-muscle CSA was smaller in OM (p = 0.001; d = 1.34), but atrophy was not present at the single fiber level (p > 0.05). Per individual, ∼900 fibers were analyzed, and type I fiber CSA was larger (p = 0.05; d = 0.94) in OM which resulted in a smaller type II/I fiber CSA ratio (p = 0.015; d = 0.95). CAF levels were not sensitive to age (p = 0.159; d = 0.53) nor associated with specific strength or whole-muscle CSA in OM.

Conclusion: The microbiopsy appears to be a viable alternative to the Bergström biopsy for histological analyses of skeletal muscle in older adults. NMJ integrity was not influential for age-related differences in specific strength in our healthy, non-sarcopenic older sample.

The relationship between extracellular water-to-body water ratio and sarcopenia according to the newly revised Asian Working Group for Sarcopenia: 2019 Consensus Update

OBJECTIVE

The purpose of this study was to evaluate the association between sarcopenia and extracellular water-to-total body water ratio (ECW/TBW), one of the results of bioimpedance that can be easily measured in communities, following the recent revision of the Asian Working Group for Sarcopenia.

METHODS

This study data were extracted from the baseline data of Namgaram-2. Among the surveyed subjects, 885 persons aged 60 years or older were selected as study subjects. All surveys were conducted on a one-on-one interview basis; blood tests, physical function evaluations (hand grip strength, short physical performance battery; SPPB), and dual-energy X-ray absorptiometry (DEXA) and bioimpedance were also conducted. The Asian Working Group's revised definition of sarcopenia was applied. ECW/TBW was one of the results of bioimpedance this study.

RESULTS

A high ECW/TBW was 1.63 times higher in the low grip strength group than in the robust group (P = 0.017) and was 2.13 times higher in the low SPPB group compared to the robust group (P < 0.001). ECW/TBW higher than 0.391 was 2.17 times more likely to occur in sarcopenic patients compared to the robust group (P < 0.001). In addition, ECW/TBW lower than 0.391 was 3.65 times more likely to occur in severely sarcopenic patients compared to the robust group (P = 0.002).

CONCLUSION

The ECW/TBW may be one of the valid research tools to evaluate the strength and physical performance of the elderly. In addition, it is expected to be one of the effective indicators for tracking physical function under newly revised sarcopenia criteria.

Healthy Aging Within an Image: Using Muscle Radiodensitometry and Lifestyle Factors to Predict Diabetes and Hypertension

The strong age dependency of many deleterious health outcomes likely reflects the cumulative effects from a variety of risk and protective factors that occur over one's life course. This notion has become increasingly explored in the etiology of chronic disease and associated comorbidities in aging. Our recent work has shown the robust classification of individuals at risk for cardiovascular pathophysiology using CT-based soft tissue radiodensity parameters obtained from nonlinear trimodal regression analysis (NTRA). Past and present lifestyle influences the incidence of comorbidities like hypertension (HTN), diabetes (DM) and cardiac diseases. 2,943 elderly subjects from the AGES-Reykjavik study were sorted into a three-level binary-tree structure defined by: 1) lifestyle factors (smoking and self-reported physical activity level), 2) comorbid HTN or DM, and 3) cardiac pathophysiology. NTRA parameters were extracted from mid-thigh CT cross-sections to quantify radiodensitometric changes in three tissue types: lean muscle, fat, and loose-connective tissue. Between-group differences were assessed at each binary-tree level, which were then used in tree-based machine learning (ML) models to classify subjects with DM or HTN. Classification scores for detecting HTN or DM based on lifestyle factors were excellent (AUCROC: 0.978 and 0.990, respectively). Finally, tissue importance analysis underlined the comparatively-high significance of connective tissue parameters in ML classification, while predictive models of DM onset from five-year longitudinal data gave a classification accuracy of 94.9%. Altogether, this work serves as an important milestone toward the construction of predictive tools for assessing the impact of lifestyle factors and healthy aging based on a single image.