Comparison of the serum creatinine- and cystatin-C-based indices as screening biomarkers for sarcopenia in community-dwelling older adults

From a Solitary Blood-Derived Biomarker to Combined Biomarkers of Sarcopenia: Experiences From the Korean Frailty and Aging Cohort Study

Sarcopenia is recognized as a complex and multifactorial disorder that includes nutritional deficiency, inactivity, proinflammatory status, hormonal changes, neurological degeneration, and metabolic disturbances. It's pathogenesis is not fully understood. Therefore, identifying specific biomarkers of sarcopenia will help us understand its pathophysiology. The most frequently reported blood-derived biomarkers of sarcopenia are growth factors, neuromuscular junctions, endocrine systems, mitochondrial dysfunction, inflammation-mediated and redox processes, muscle protein turnover, blood metabolomics, and behavior-mediated biomarkers. Here, we address the implications of sarcopenia biomarkers based on our research experience with Korean Frailty and Aging Cohort Study cohort data. It includes free testosterone, myostatin, fibroblast growth factor 21 (FGF-21), growth differentiation factor 15 (GDF-15), procollagen type III N-terminal peptide (P3NP), creatinine-based biomarkers, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), brain-derived neurotrophic factor (BDNF), metabolites (proline, alanine, tryptophan), and multi-biomarker risk score. We attempted to explain the paradoxical findings of myostatin and FGF-21 levels in relation to sarcopenia. GDF-15 levels were associated with sarcopenia prevalence but not its incidence. Plasma P3NP and BDNF levels may be biomarkers of muscle quality rather than quantity. Lower erythrocyte eicosapentaenoic acid (EPA) and docosahexaenoic acid levels were associated with slow gait speed, and erythrocyte EPA levels were associated with low handgrip strength. We developed a multi-biomarker risk score for sarcopenia and found that its accuracy in diagnosing sarcopenia was higher than that of any single biomarker.

Association between sarcopenia index and the risk of second hip fracture in older adults

BACKGROUND

The sarcopenia index (SI), calculated as the ratio of serum creatinine to cystatin C level, represents skeletal muscle mass and strength. This study aimed to investigate the association between SI and the risk of second hip fractures, considering various demographic and clinical factors to improve second hip fracture risk prediction.

METHODS

This prospective cohort study included older adults with low-energy hip fractures who were monitored for at least two years to track the incidence of subsequent hip fractures. Baseline demographic, clinical, and biochemical data were collected. The SI was calculated as serum creatinine [mg/dL]/cystatin C [mg/L]) × 100. Logistic regression models were used to evaluate the relationship between the SI and the risk of a second hip fracture. Subgroup analyses were conducted to assess the effects of potential modifiers, including gender, body mass index, hypertension, diabetes, and estimated glomerular filtration rate. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the predictive performance of SI.

RESULTS

A total of 637 patients were included, 59 of whom experienced a second hip fracture during the follow-up period. The patients with second hip fracture exhibited significantly lower SI levels than those without (48.93 ± 8.54 versus 62.95 ± 14.39, P < 0.001). Logistic regression analysis revealed a significant association between a lower muscle-reduction index and an increased risk of a second hip fracture in the fully adjusted model (odds ratio: 0.91; 95% confidence interval: 0.87-0.94; P < 0.001). The area under the ROC curve for predicting a second hip fracture based on the SI was 0.822, indicating good predictive accuracy. Furthermore, subgroup analyses revealed that SI was inversely associated with second hip fracture.

CONCLUSIONS

The SI serves as a significant predictor of second hip fractures in older adults, even after considering age, gender, and clinical factors.

Association between skeletal muscle mass and the prognosis of patients undergoing percutaneous coronary intervention: a retrospective study

BACKGROUND

The predicted skeletal muscle mass index (pSMI) is a proven and reliable index that reflects muscle mass; however, its ability to predict major adverse cardiovascular events (MACES) in patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI) remains uncertain.

METHODS

A total of 1340 enrolled patients were ultimately included in the study and stratified according to the pSMI tertiles. The primary endpoint was a complex set of MACEs, including all-cause mortality, nonfatal myocardial infarction, and unplanned revascularization. The Kaplan‒Meier method was used to generate a cumulative incidence curve of MACEs and secondary endpoint events of all-cause mortality. Due to the competing risk relationship between all-cause mortality and cardiovascular mortality, non-fatal myocardial infarction, and unplanned revascularization events, a competing risk model was employed to analyze the cumulative event incidence curves of competing risk events.The restricted cubic spline analysis was conducted to examine the linear association between pSMI and the incidence of MACE. A univariate and multivariate Cox regression model was utilized to identify predictors of MACEs. The predictive value of the pSMI was evaluated by determining the area under the ROC curve.

RESULTS

During a median follow-up of 31.38 months, 217 patients developed MACEs. The Kaplan-Meier survival curve showed the lowest risk of MACEs and all-cause mortality in the high pSMI group(log-rank test, P < 0.05). After adjusting for competing risk factors for all-cause death, the cumulative events of cardiac death in the T3 group were lower than other two groups (Gray's test, P < 0.001), with no significant difference in the cumulative incidence of non-fatal myocardial infarction and unplanned revascularization between the pSMI groups (Gray's test, P > 0.05). The adjusted hazard ratio (HR) for the incidence of MACEs in the highest pSMI tertile was 0.335(95% CI 0.182-0.615; P < 0.001), as shown by multivariable Cox regression analysis. Subgroup analysis revealed that the pSMI was negatively correlated with the incidence of MACEs in a population of nonelderly individuals, and those without heart failure (all P < 0.05). Both the univariate and fully adjusted restriction cubic spline (RCS) curves showed a linear relationship between the pSMI and MACEs. In addition, the inclusion of the pSMI in the basic risk prediction model improved prognostic prediction (the area under the ROC curve increased from 0.647 to 0.682, P = 0.033).

CONCLUSION

In patients with CAD undergoing PCI, the pSMI is a protective factor and potentially simple method for assessing the risk of MACEs independently.

CLINICAL TRIAL NUMBER

Not applicable.

Serum creatinine- and cystatin C-based indices are associated with the risk of subsequent sarcopenia: evidence from the China Health and Retirement Longitudinal Study

Background

Serum creatinine (Cr)- and cystatin C (CysC)-based indices have been suggested as alternative markers for sarcopenia, but their predictive value for sarcopenia risk is uncertain, which was investigated in the present study in the Chinese population with the middle and older ages.

Methods

Data from the China Health and Retirement Longitudinal Study (CHARLS) were collected in the 2011 and 2015 waves. All participants were free of sarcopenia at the baseline. Sarcopenia was diagnosed when low muscle mass and grip strength or low physical performance were present. Four indices were computed: predictive skeletal muscle mass index (pSMI), total-body muscle mass (TBMM), creatinine-to-cystatin C ratio (CCR), and sarcopenia index (SI). Restricted cubic splines and logistic regression models were used to assess the effects of these indices on sarcopenia risk.

Results

Among 4,527 participants without sarcopenia at the baseline (2011), the median age was 58 year-old (IQR: 52-65), with 52.7% women. Followed up in year 2015, the incidence of sarcopenia was 20.8 per 1,000 person-years (376/4,527). Neither CCR nor SI showed linear or non-linear associations with the risk of subsequent sarcopenia. However, a decrease in pSMI and TBMM was significantly associated with an increased risk of sarcopenia [adjusted per-SD decrease OR, 2.93; 95% CI, 2.09-4.13, p < 0.001; adjusted per-SD decrease OR: 2.38, 95% CI: 1.80-3.16, p < 0.001, respectively].

Conclusion

In the middle and older age of Chinese population, decreased pSMI and TBMM were associated with an increased risk of subsequent sarcopenia, whereas CCR and SI showed no such correlation. Thus, pSMI and TBMM may serve as potential biological indicators for predicting the risk of sarcopenia, and decreased pSMI and TBMM may be the early biomarkers for diagnosis and intervention of sarcopenia.

Unlocking diagnosis of sarcopenia: The role of circulating biomarkers - A clinical systematic review

Sarcopenia, the gradual loss of muscle mass, strength, and function with age, poses a significant risk to older adults, making early diagnosis crucial for preventing disability and enhancing quality of life. Biomarkers are vital for the early detection, monitoring progression, and assessing the efficacy of treatments for sarcopenia, offering a detailed evaluation of muscle health. This systematic review examined the clinical potential of circulating biomarkers in sarcopenia by analyzing studies up to May 2024 from PubMed, Scopus, Web of Science. A total of 45 studies involving 641,730 patients were reviewed, revealing notable biomarker differences between sarcopenic and non-sarcopenic individuals. Sarcopenic patients exhibited lower levels of certain microRNAs, hemoglobin, albumin, and anti-inflammatory factors, alongside higher levels of red and white blood cells, pro-inflammatory factors, growth factors, matrix proteins, free thyroxine, cortisol, and adiponectin. Additionally, they had lower levels of irisin, free triiodothyronine, and insulin, with reduced phosphatidylcholines and elevated spermidine. The studies were generally of fair to good quality, but due to heterogeneity, a meta-analysis was not feasible. The review underscores the need for standardized biomarkers and diagnostic criteria and suggests that improving outcomes for sarcopenic patients may involve addressing inflammation, metabolic, and hormonal issues through nutrition, medication, and exercise.

Serum creatinine and serum cystatin C as an index of muscle mass in adults

PURPOSE OF REVIEW

Serum creatinine reflects both muscle mass and kidney function. Serum cystatin C has recently been recommended as an additional marker for estimating kidney function, and use of both markers together may provide an index of muscle mass. This review aims to describe the biological basis for and recent research examining the relationship of these markers to muscle mass in a range of adult populations and settings.

RECENT FINDINGS

This review identified 67 studies, 50 of which had direct measures of muscle mass, and almost all found relationships between serum creatinine and cystatin C and muscle mass and related outcomes. Most studies have been performed in older adults, but similar associations were found in general populations as well as in subgroups with cancer, chronic kidney disease (CKD), and other morbid conditions. Creatinine to cystatin C ratio was the measure examined the most often, but other measures showed similar associations across studies.

SUMMARY

Measures of serum creatinine and cystatin C together can be an index of muscle mass. They are simple and reliable measures that can be used in clinical practice and research. Further study is needed to determine actionable threshold values for each measure and clinical utility of testing and intervention.

Association between macro- and microvascular damage and sarcopenia index in individuals with type 2 diabetes mellitus

Sarcopenia was recently reported to be relevant to an increased macro-and microvascular disease risk. Sarcopenia index (SI) has been identified as a surrogate marker for sarcopenia. The aim of the present study was to investigate the association between macro- and microvascular disease and SI in patients with type 2 diabetes mellitus (T2DM). A total of 783 patients with T2DM were enrolled in this cross-sectional study. The SI was calculated by (serum creatinine [mg/dL]/cystatin C [mg/L]) × 100. The subjects were divided into three groups according to SI tertiles: T1 (41.27-81.37), T2 (81.38- 99.55), and T3 (99.56-192.31). Parameters of macro- and microvascular complications, including diabetic retinopathy (DR), micro- and macroalbuminuria (MAU), diabetic peripheral neuropathy (DPN), and lower extremity peripheral artery disease (LEAD) were evaluated. Multivariate logistic regression analysis revealed that when taking the top tertile of SI as a reference, an increasing trend of the prevalence of DR, MAU, DPN, and LEAD were presented (all P for trend  < 0.05), where the OR (95% CI) for DR prevalence was 1.967 (1.252-3.090) in T2, 2.195 (1.278-3.769) in T1, for MAU was 1.805 (1.149-2.837) in T2, 2.537 (1.490-4.320) in T1, for DPN was 2.244 (1.485-3.391) in T2, 3.172 (1.884-5.341) in T1, and for LEAD was 2.017 (1.002-4.057) in T2, 2.405 (1.107-5.225) in T1 (all P < 0.05). Patients with lower SI were more inclined to have an increased risk of macro- and microvascular damage in T2DM population, which may be related to sarcopenia.