Metabolic syndrome and its association with components of sarcopenia in older community-dwelling Chinese

Relationship between atherosclerotic burden and sarcopenia in U.S. adults: A cross-sectional study based on the NHANES database

Sarcopenia, characterized by the progressive loss of skeletal muscle mass and strength, significantly impacts the people, leading to increased frailty and mortality. The atherogenic index of plasma (AIP), a biomarker for lipid imbalance, may be linked to sarcopenia due to shared pathways of inflammation and metabolic dysregulation. Data from the National Health and Nutrition Examination Survey (NHANES) 2011-2018 cycles were analyzed. The AIP was calculated as the logarithm of the ratio of triglycerides to High density lipoprotein cholesterol. Sarcopenia was defined using the appendicular skeletal muscle mass index (ASMBMI) adjusted for body mass index (BMI). Multivariable linear regression and logistic regression models were employed to assess the association between AIP and ASMBMI, as well as sarcopenia. Restrictive cubic spline curves were utilized to analyze potential nonlinear associations between AIP and outcome indicators. Additionally, subgroup analyses and intergroup interaction tests were performed. Elevated AIP levels were associated with decreased ASMBMI and an increased risk of sarcopenia. After adjusting for confounding factors, the association between AIP and ASMBMI remained significant (Beta [95% CI] = -0.02 [-0.03, -0.01], P < 0.001). AIP was significantly associated with sarcopenia (OR [95% CI] = 2.6 [1.78, 3.81], P = < 0.001). AIP is significantly associated with reduced muscle mass and potentially with sarcopenia, suggesting that lipid metabolism plays a critical role in muscle health. Identifying AIP as a modifiable risk factor could have important public health implications for managing sarcopenia.

Association between non-insulin-based insulin resistance indicators and frailty progression: a national cohort study and mendelian randomization analysis

BACKGROUND

Insulin resistance (IR) is linked to an increased risk of frailty, yet it remains unclear whether the non-insulin-based IR indicators are associated with frailty trajectories and physical function decline. It aimed to examine the associations of triglyceride-glucose (TyG) index, metabolic score for insulin resistance (METS-IR), estimated glucose disposal rate (eGDR) and with long-term deficit-accumulation frailty trajectories and physical function decline.

METHODS

Data from 6722 participants in the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Baseline TyG index, METS-IR, eGDR, along with the frailty index (FI) over nine years, were calculated. FI trajectories were assessed using group-based trajectory model (GBTM). Logistic regression models were used to analyze the associations between IR indicators with FI trajectory and frailty risk. Restricted cubic splines (RCS) models were utilized to detect potential dose-response associations. Linear mixed-effects model was used to evaluate associations with FI development speed. Age, gender, educational level, marital status, smoking status, drinking status, life satisfaction, social activity and sleep duration were adjusted. Additionally, a two-sample Mendelian randomization (MR) was performed to assess the causality of observed associations.

RESULTS

Three FI trajectories including low-stable frailty, moderate-increasing frailty, and accelerated rising frailty were identified. Regarding the frail risk, each SD increment in TyG index was associated with a 16.1% increase in the risk of frailty (OR = 1.161; 95%CI: 1.092, 1.235). An inverse association was observed for eGDR with the OR (95%CI) being 0.741 (0.696, 0.788). A linear relationship was observed between baseline TyG index and frailty risk (P nonlinear = 0.696), but nonlinear association patterns for eGDR (P nonlinearity < 0.010) and METS-IR (P nonlinearity < 0.010). Each SD increment of TyG index was associated with greater FI increase (β = 0.005 SD/y; 95%CI = 0.002, 0.008 SD/y; P < 0.001). A similar association pattern was observed for METS-IR, and participants in the highest quartile of METS-IR showed significantly greater FI progression, with β value of 0.013 (95% CI = 0.004, 0.022). Each SD increment of eGDR was associated with a slower increase in FI (β=-0.006 SD/y, 95% CI=-0.009, -0.003 SD/y; P < 0.001). Participants in the highest quartile of eGDR presented a lower annual change in FI compared with participants in quartile 1 group during follow-up (β=-0.013 SD/y, 95% CI=-0.022, -0.005 SD/y; P for trend = 0.001). Similar findings were observed for physical function decline. Findings from MR analysis showed a causal relationship between higher TyG index and increased risk of frailty (β = 0.214, 95% CI = 0.079, 0.349; P = 0.002).

CONCLUSIONS

The non-insulin-based IR indicators, including TyG index, METS-IR and eGDR, were independently associated with the frailty progression and physical function decline. Monitoring and managing abnormal glucose metabolism should be recommended as a part of comprehensive strategies to prevent or delay the progression of frailty.

Associations of metabolic syndrome and its components with sarcopenia, and the mediating role of insulin resistance: Findings from NHANES database

BACKGROUND

To investigate the association between metabolic syndrome (MetS) and its components with sarcopenia, and to explore the extent to which insulin resistance (IR) mediates this association, using data from the National Health and Nutrition Examination Survey (NHANES).

METHODS

We analyzed cross-sectional data from 15,779 adults in the NHANES from 1999 to 2006 and 2011-2018. Multivariable logistic regression models were used to determine the odds ratios (ORs) between MetS, its components, the number of MetS components, and sarcopenia. Mediation analysis was performed to explore the role of the homeostatic model assessment of insulin resistance (HOMA-IR) in MetS and its components-induced sarcopenia.

RESULT

In the fully adjusted model, MetS increased the prevalence of sarcopenia by 1.96-fold (95% CI: 1.73-2.22). Among the individual components, central obesity, hypertension, and hyperglycemia were associated with an increased prevalence of sarcopenia. Sarcopenia prevalence also increased linearly with the number of MetS components, with the highest prevalence observed in the presence of all five components (OR: 3.80, 95% CI: 2.79-5.16). Sex-stratified analysis showed that the prevalence of MetS for sarcopenia was higher in males than females. The mediating effects of HOMA-IR on the association between MetS and its components (central obesity, hypertension, and hyperglycemia) with sarcopenia were significant, with mediation effects of 51.7%, 30.7%, 33.2%, and 79.1%, respectively. There was no significant direct association between hyperglycemia and sarcopenia beyond the HOMA-IR pathway.

CONCLUSION

MetS and its individual components, excluding hypertriglyceridemia and low high density lipoprotein cholesterol, were associated with a higher prevalence of sarcopenia, especially in males. This association was partially or fully mediated by IR.

Correlation between low handgrip strength and metabolic syndrome in older adults: a systematic review

Muscle weakness has been associated to insulin resistance and metabolic syndrome in the general population. However, it is still unclear whether this association is maintained in older adults. This study investigated correlations between low handgrip strength (HGS) and metabolic syndrome, or some of its components, in older adults through a systematic review of the literature. Searches were conducted in the Virtual Health Library Regional Portal, Scopus, Cochrane, Embase, MEDLINE/ PubMed, SciELO, and Web of Science databases for relevant studiesinvestigating muscle weakness (measured by hand dynamometer) and metabolic syndrome or its components in older adult populations, published up to September 2023. From the 2050 references initially identified, 20 studies, comprising a total of 31,264 older adults of both genders, completely met the inclusion/exclusion criteria. Eighteen studies showed that lower HGS was associated with metabolic syndrome or some of its risk factors, such as abdominal obesity, hyperglycemia, insulin resistance, dyslipidemia, or high blood pressure. Two studies found that older men with high blood pressure had increased HGS. Most studies included in this systematic review revealed a significant correlation between reduced HGS and metabolic syndrome or some of its components, especially abdominal obesity and insulin resistance. We conclude that below-average HGS can be associated with metabolic syndrome in older adults.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Muscle Quality Index in Morbidly Obesity Patients Related to Metabolic Syndrome Markers and Cardiorespiratory Fitness

BACKGROUND

Muscle quality index (MQI) is an emerging health indicator obtained by dividing handgrip strength by body mass index (BMI) that needs to be studied in morbidly obese patients (defined by BMI ≥ 35 kg/m²).

OBJECTIVE

To determine the association between MQI, metabolic syndrome (MetS) markers, and cardiorespiratory fitness (CRF), and as a second objective to determine the potential mediation role of MQI in the relationship between abdominal obesity and systolic blood pressure (SBP) in this sample.

METHODS

This cross-sectional study included 86 severely/morbidly obese patients (age = 41.1 ± 11.9 y, nine men). MQI, metabolic syndrome markers, CRF, and anthropometric parameters were measured. Two groups were developed according to MQI; High-MQI (n = 41) and Low-MQI (n = 45).

RESULTS

The Low-MQI group reported higher abdominal obesity (High-MQI: 0.7 ± 0.1 vs. Low-MQI: 0.8 ± 0.1 WC/height; p = 0.011), SBP (High-MQI: 133.0 ± 17.5 vs. Low-MQI: 140.1 ± 15.1 mmHg; p = 0.048), and lower CRF (High-MQI; 26.3 ± 5.9 vs. Low-MQI; 22.4 ± 6.1 mL/kg/min, p = 0.003) than the High-MQI group. Waist-to-height ratio (β: -0.07, p = 0.011), SBP (β: -18.47, p = 0.001), and CRF (β: 5.21, p = 0.011) were linked to MQI. In a mediation model, the indirect effect confirms that MQI is a partial mediator of the association between abdominal obesity with SBP.

CONCLUSIONS

MQI in morbidly obesity patients reported an inverse association with MetS markers and a positive association with CRF (VO2_max). It mediates the relationship between abdominal obesity and SBP.

Home-based gait speed and the association with sociodemographic and anthropometric variables: A national study (ELSI-Brazil)

OBJECTIVES

To investigate home-based gait speed performance for men and women stratified by age group and its associations with sociodemographic and anthropometric variables.

METHODS

Data from the 2^nd wave of the Brazilian Longitudinal Study of Aging (ELSI-Brazil, 2019-2021) were used. Gait speed was tested twice at home over 3.0 meters at usual pace. Associations of sociodemographic and anthropometric variables with gait speed were evaluated using gamma regression.

RESULTS

Median gait speed value reduced with increasing age in both sexes [men: 0.70 m/s (50-59 years) to 0.53 m/s (≥80 years); women: 0.68 m/s (50-59 years) to 0.48 m/s (≥80 years)] and was significantly lower in women than men in the age groups of 60-69 and 70-79 years. Age group and education among men and age group, education, and waist circumference among women were significantly associated with gait speed.

CONCLUSIONS

Our findings may be helpful as reference values to identify mobility limitation among older Brazilians.

The Roles of Androgens in Humans: Biology, Metabolic Regulation and Health

Androgens are an important and diverse group of steroid hormone molecular species. They play varied functional roles, such as the control of metabolic energy fate and partition, the maintenance of skeletal and body protein and integrity and the development of brain capabilities and behavioral setup (including those factors defining maleness). In addition, androgens are the precursors of estrogens, with which they share an extensive control of the reproductive mechanisms (in both sexes). In this review, the types of androgens, their functions and signaling are tabulated and described, including some less-known functions. The close interrelationship between corticosteroids and androgens is also analyzed, centered in the adrenal cortex, together with the main feedback control systems of the hypothalamic-hypophysis-gonads axis, and its modulation by the metabolic environment, sex, age and health. Testosterone (T) is singled out because of its high synthesis rate and turnover, but also because age-related hypogonadism is a key signal for the biologically planned early obsolescence of men, and the delayed onset of a faster rate of functional losses in women after menopause. The close collaboration of T with estradiol (E2) active in the maintenance of body metabolic systems is also presented Their parallel insufficiency has been directly related to the ravages of senescence and the metabolic syndrome constellation of disorders. The clinical use of T to correct hypoandrogenism helps maintain the functionality of core metabolism, limiting excess fat deposition, sarcopenia and cognoscitive frailty (part of these effects are due to the E2 generated from T). The effectiveness of using lipophilic T esters for T replacement treatments is analyzed in depth, and the main problems derived from their application are discussed.