Independent association between serum C-peptide levels and fat mass-to-lean mass ratio in the aging process

Association between early-pregnancy serum C-peptide and risk of gestational diabetes mellitus: a nested case-control study among Chinese women

OBJECTIVE

To examine the association of early-pregnancy serum C-peptide with incident gestational diabetes mellitus (GDM) and the predictive ability of maternal C-peptide for GDM.

METHODS

A nested case-control study of 332 GDM cases and 664 controls was established based on the Tongji-Shuangliu Birth Cohort. The GDM cases and controls were matched at 1:2 on maternal age (± 3 years) and gestational age (± 4 weeks). Multivariable conditional logistic regression was applied to assess the association of C-peptide with risk of GDM. Partial Spearman's correlation coefficients were estimated for the correlations between C-peptide and multiple metabolic biomarkers. C-statistics were calculated to assess the predictive ability of early-pregnancy C-peptide for GDM.

RESULTS

Of 996 pregnant women, median maternal age was 28.0 years old and median gestational age was 11.0 weeks. After adjustment for potential confounders, the odds ratio of GDM comparing the extreme quartiles of C-peptide was 2.28 (95% confidence interval, 1.43, 3.62; P for trend < 0.001). Partial correlation coefficients ranged between 0.07 and 0.77 for the correlations of C-peptide with fasting insulin, homeostatic model of insulin resistance, leptin, fasting blood glucose, triglycerides, glycosylated hemoglobin, waist-hip ratio, systolic blood pressure, and low-density lipoprotein cholesterol (P ≤ 0.025), and were - 0.11 and - 0.17 for high-density lipoprotein cholesterol and adiponectin (P < 0.001). Serum C-peptide slightly improved the predictive performance of the model with conventional predictive factors (0.66 vs. 0.63; P = 0.008).

CONCLUSION

While the predictive value for subsequent GDM should be validated, early-pregnancy serum C-peptide may be positively associated with risk of GDM.

Serum C-peptide as a key contributor to lipid-related residual cardiovascular risk in the elderly

OBJECTIVES

The serum levels of C-peptide, an important risk factor for cardiovascular disease (CVD), increase with age. This study aimed to investigate the association between serum C-peptide and increased risk for CVD with altered lipid metabolism in the elderly.

METHODS

This was a population-based cross-sectional study that included 3091 elderly participants aged ≥65 years. Serum C-peptide and lipid levels were measured according to standard protocols. Sampling weights were used to estimate the characteristics of study participants. Stratified analysis of covariance was used to evaluate the changes in the serum lipid levels according to quartiles of serum C-peptide levels, and the linear trend was assessed using a linear model. The logistic regression model was carried out to determine the association between the serum C-peptide levels and serum lipid levels.

RESULTS

The results of the analysis of covariance stratified by sex and serum insulin level showed that the serum triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) levels were significantly associated with changes in the serum C-peptide levels, independent of the serum insulin level. The logistic regression analyses indicated that the serum C-peptide levels were positively associated with the serum TG levels, and negatively associated with the serum HDL-C levels. A significant dose-response association was obtained in both men and women.

CONCLUSIONS

Serum C-peptide levels were strongly associated with increased serum TG and reduced HDL-C levels in the elderly. Our results suggest that serum C-peptide increases the risk of CVD via a pathway that increases TG or decreases HDL-C levels.