Clinical Markers of the Metabolic Syndrome and Insulin Resistance in Youth from Northern Mexico

Full text: Background. Obesity in children and adolescents is a growing problem worldwide. In Mexico, almost 4 of every 10 adolescents are overweight or obese. The metabolic syndrome (MS) is highly associated to obesity, and includes abdominal obesity, altered glucose metabolism, dyslipidemia and hypertension. This cluster of cardiometabolic risk factors is generally diagnosed in adults, but the presence of its components is increasing in the pediatric population. One of the initial stages of metabolic alteration could be insulin resistance (IR), but it is not easy to diagnose without specialized blood analyses. Some studies show that clinically useful markers of IR, such as Acanthosis nigricans (AN) might detect early glucose metabolism alterations, but its association with IR has been inconsistent. Our objective was to find the best predictors of insulin sensitivity in youth (9-17 y) from Northern Mexico, including possible new markers such as leptin and adiponectin. Methods. We evaluated anthropometric, body composition, biochemical and clinical parameters (including AN) in 131 participants with a wide range of body size. Leptin and adiponectin were evaluated by radioimmunoassay, abdominal fat content was measured by dual X-ray absorptiometry (DXA) and whole-body composition by deuterium oxide dilution. The MS was diagnosed in participants >10 y using the pediatric International Diabetes Federation (IDF) definition. A multiple linear equation was generated using insulin sensitivity index (ISI0,120) as the dependent variable, and several markers as independent variables: Z-body mass index (Z-BMI), waist circumference, blood lipids, leptin, adiponectin and AN, among others. Several models, including a different number of potential predictor variables were tested. Subjects provided information on pubertal development by a self-applied auto-questionnaire, to adjust the association by the probable influence of puberty on insulin sensitivity. Results. The MS was present in 15% of the participants (17% boys, 14% girls, respectively, p>0.05). Twelve subjects had glucose intolerance, and two had type-2 diabetes. Subjects with altered values of the MS variables had lower insulin sensitivity, higher levels of leptin and lower levels of adiponectin. Participants with at least one component of the MS had higher values of leptin compared to subjects with no components present (p<0.05), and the mean leptin content increased with the number of MS factors. The best predictors of insulin sensitivity were body size (Z-BMI), abdominal fat, leptin, and adiponectin, since they were selected in all the models explored (range of R2=0.68-0.73). AN was not a significant contributor in any of the multiple regression models; nonetheless, participants with AN had a lower insulin sensitivity than participants without AN (p<0.05), as well as altered values of the MS components. Conclusion. In addition to body size and central adiposity, adipokine levels appear to be good markers of insulin sensitivity and could be used to diagnose and monitor earlier metabolic disturbances in youths. AN could be used to explore individuals at risk, but more studies are needed to ascertain its utility as an insulin sensitivity marker in this type of population. (author)