ORIGINAL ARTICLE C-Peptide Is a Sensitive Indicator for the Diagnosis of Metabolic Syndrome in Subjects from Central Mexico M. Elba Gonzalez-Mejia, MD, PhD, 1 Leonardo M. Porchia, PhD, 2 Enrique Torres-Rasgado, PhD, 1 Guadalupe Ruiz-Vivanco, MS, 1 Patricia Pulido-Pe ´ rez, MS, 2 Blanca G. Ba ´ ez-Duarte, PhD, 1 and Ricardo Pe ´ rez-Fuentes, MD, PhD 1,2 Abstract Background: Metabolic Syndrome (MetS) is associated with elevated risk for developing diabetes and car- diovascular disease. A key component of MetS is the development of insulin resistance (IR). The homeostatic model assessment (HOMA) model can determine IR by using insulin or C-peptide concentrations; however, the efficiency of insulin and C-peptide to determine MetS has not been compared. The aim of the study was to compare the efficiency of C-peptide and insulin to determine MetS in Mexicans. Methods: Anthropometrics, glucose, insulin, C-peptide, triglycerides, and high-density lipoproteins were de- termined in 156 nonpregnant females and 114 males. Subjects were separated into normal or positive for MetS. IR was determined by the HOMA2 calculator using insulin or C-peptide. Correlations were calculated using the Spearman correlation coefficient (r). Differences between correlations were determined by calculating Steiger’s Z. The sensitivity was determined by the area under receiver operating characteristics curve (AUC) analysis. Results: Independent of the MetS definition [Adult Treatment Panel III (ATP III), International Diabetes Federation (IDF), or World Health Organization (WHO)], C-peptide and insulin were significantly higher in MetS subjects (P < 0.05). C-peptide and insulin correlated with all components of MetS; however, for waist circumference, waist-to-hip ratio, and fasting plasma glucose, C-peptide correlated better than insulin (P < 0.05). Moreover, C-peptide (AUC = 0.72–0.78) was a better marker than insulin (AUC = 0.62–0.72) for MetS (P < 0.05). Finally, HOMA2-IR calculated with C-peptide (AUC = 0.80–0.84) was more accurate than HOMA2-IR calculated with insulin (AUC = 0.68–0.75, P < 0.05) at determining MetS. Conclusion: C-peptide is a strong indicator of MetS. Since C-peptide has recently emerged as a biomolecule with significant importance for inflammatory diseases, monitoring C-peptide levels will aid clinicians in pre- venting MetS. Introduction I n Mexico, with a large obesity problem and more pop- ulation living an inactive lifestyle, Metabolic Syndrome (MetS) is rapidly becoming a major health concern. 1 A cur- rent report suggested that 54.8% of the Mexican population is positive for MetS, 2 which has increased twofold since 1993. 3 Moreover, MetS is associated with a fivefold increased risk for developing type 2 diabetes and a twofold increased risk for developing cardiovascular disease, 4 thus making the correct identification of MetS more beneficial for disease prevention. Since its first description in the 1920s, MetS has been as- sociated with hypertension and hyperglycemia, with the ad- dition of central adiposity, hypertriglyceridemia, and insulin resistance (IR) in later reports. 5,6 Lacking any specific genetic or physical markers, 7,8 many organizations have developed their own definitions, which are based around these central concepts 9 ; however, the use of any of them can inappropri- ately misidentify subjects with or without MetS. Even though the World Health Organization’s (WHO) definition, which mainly focuses on IR and impaired glucose tolerance, 7 is the preferred definition for MetS, the National Cholesterol Education Program Adult Treatment Panel III’s 1 Facultad de Medicina, Beneme ´rita Universidad Auto ´noma de Puebla, Puebla, Me ´xico. 2 Laboratorio de Fisiopatologı ´a en Enfermedades Cro ´ nicas, Centro de Investigacio ´n Biome ´dica de Oriente, Instituto Mexicano del Seguro Social, Puebla, Me ´xico. METABOLIC SYNDROME AND RELATED DISORDERS Volume 14, Number 2, 2016 Ó Mary Ann Liebert, Inc. Pp. 1–7 DOI: 10.1089/met.2015.0067 1