Improving the comprehension of sarcopenic state determinants: An multivariate approach involving hormonal, nutritional, lifestyle and genetic variables

Sarcopenia as a Risk Factor for Alzheimer's Disease: Genetic and Epigenetic Perspectives

Sarcopenia, defined as the age-associated loss of muscle mass and increased fragility with age, is increasing worldwide. The condition often precedes the development of Alzheimer's disease, thereby decreasing the levels of mobility and physical activity in those affected. Indeed, the loss of muscle mass has, in some studies, been associated with an increased risk of Alzheimer's disease and other dementias. However, a detailed understanding of the interplay between both conditions is not available and needs to be thoroughly addressed. In the following review, we focus on several genes, specifically APOE, BDNF, ACE, FTO, and FNDC5, that have been associated with both conditions. We also discuss the epigenetic regulation of each of these genes along with non-coding RNAs (ncRNAs) that may have a role in the development of both the sarcopenic and Alzheimer's disease phenotypes. Finally, we assert that the application of systems biology will unravel the relationship between sarcopenia and Alzheimer's disease and believe that the prevention of muscle loss in older age will reduce the incidence of debilitating cognitive decline.

The association between sedentary behaviour and sarcopenia in older adults: a systematic review and meta-analysis

BACKGROUND

Sedentary behaviour is considered to contribute to sarcopenia when combined with physical inactivity. Whether sedentary behaviour is independently associated with sarcopenia remains controversial. The aim of this study is to explore the association between sedentary behaviour and sarcopenia in older adults in community and long-term care facility settings.

METHODS

Eight electronic databases including MEDLINE, PsycINFO, Wanfang were searched from inception until August 2023. The review included cross-sectional and longitudinal studies concerning the association between sedentary behaviour and sarcopenia among participants over 60 years old. Evidence was pooled by both random-effects meta-analysis and narrative synthesis. Subgroup analyses explored variation according to adjustment of physical activity, settings, and measurements of sedentary behaviour and sarcopenia. Quality assessment for individual studies was performed with the Joanna Briggs Institute (JBI) Critical Appraisal Checklist.

RESULTS

Seventeen articles (16 cross-sectional studies and 1 longitudinal study) of 25,788 participants from community or long-term care facility settings were included. The overall quality of the included studies was rated high. Meta-analysis of 14 cross-sectional studies showed that sedentary behaviour was independently positively associated with sarcopenia: pooled odd ratio 1.36 (95% confidence interval, 1.18-1.58). The independent positive association remained in subgroup analyses by adjustment of physical activity, settings, and measurements of sedentary behaviour and sarcopenia. The narrative analysis corroborated the findings of the meta-analysis and provided additional evidence suggesting that interruptions in sedentary periods were linked to a decreased likelihood of developing sarcopenia.

CONCLUSIONS

The findings support the hypothesis that sedentary behaviour is independently positively associated with sarcopenia in older adults, providing vital indications for the development of strategies to prevent sarcopenia.

SYSTEMATIC REVIEW REGISTRATION

The systematic review protocol has been registered with the PROSPERO database (CRD42022311399).

Prevalence of vitamin D deficiency in South America: a systematic review and meta-analysis

CONTEXT

Vitamin D deficiency is considered a global public health issue, even in low-latitude countries where there is abundant sunlight radiation. Nevertheless, the prevalence of vitamin D insufficiency and deficiency in the South American continent has not been well characterized.

OBJECTIVE

The aim of this review was to estimate the prevalence of vitamin D deficiency (25-hydroxy-calciferol < 20 ng/mL) in South American populations.

DATA SOURCES

Seven electronic databases (MEDLINE, Web of Science, Embase, Biblioteca Virtual de Saúde, SciELO, Scopus, and Google Scholar) were searched systematically for observational studies published before July 1, 2021, and reporting vitamin D status of healthy adults in South America.

DATA EXTRACTION

Data were extracted using a standardized form. Risk of bias was assessed by the Joanna Briggs Institute Critical Appraisal Instrument for Studies Reporting Prevalence. All steps were conducted independently by two authors. Data were pooled using a random-effects model. Stratified meta-analysis and meta-regression were conducted (R software).

DATA ANALYSIS

Of 9460 articles identified, 96 studies with a total of 227 758 participants were included. The overall prevalence of vitamin D deficiency was 34.76% (79 studies; 95%CI, 29.68-40.21; I2 = 99%). There were significant differences in prevalence rates related to age, sex, country, latitude, season, and year of publication.

CONCLUSION

The prevalence of vitamin D deficiency is unexpectedly elevated in South American populations. Public health strategies should include efforts to prevent, detect, and treat vitamin D deficiency.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020169439.

Genetic Associations with Aging Muscle: A Systematic Review

The age-related decline in skeletal muscle mass, strength and function known as 'sarcopenia' is associated with multiple adverse health outcomes, including cardiovascular disease, stroke, functional disability and mortality. While skeletal muscle properties are known to be highly heritable, evidence regarding the specific genes underpinning this heritability is currently inconclusive. This review aimed to identify genetic variants known to be associated with muscle phenotypes relevant to sarcopenia. PubMed, Embase and Web of Science were systematically searched (from January 2004 to March 2019) using pre-defined search terms such as "aging", "sarcopenia", "skeletal muscle", "muscle strength" and "genetic association". Candidate gene association studies and genome wide association studies that examined the genetic association with muscle phenotypes in non-institutionalised adults aged ≥50 years were included. Fifty-four studies were included in the final analysis. Twenty-six genes and 88 DNA polymorphisms were analysed across the 54 studies. The ACTN3, ACE and VDR genes were the most frequently studied, although the IGF1/IGFBP3, TNFα, APOE, CNTF/R and UCP2/3 genes were also shown to be significantly associated with muscle phenotypes in two or more studies. Ten DNA polymorphisms (rs154410, rs2228570, rs1800169, rs3093059, rs1800629, rs1815739, rs1799752, rs7412, rs429358 and 192 bp allele) were significantly associated with muscle phenotypes in two or more studies. Through the identification of key gene variants, this review furthers the elucidation of genetic associations with muscle phenotypes associated with sarcopenia.