Abstract
Background: Zonulin is the endogenous protein known to control the permeability of intestinal tight junction reversibly. Zonulin is actively engaged in intestinal innate immunity and is over-expressed in autoimmune diseases where tight junction of intestine plays a pivotal role, such as celiac disease, malabsorption disorder, and type 1 diabetes. Waist-Height ratio was well known as one of indices of obesity and also Waist-Hip ratio was known of abdominal obesity. We investigated that the associations among Waist-Height, Waist-Height ratio, and the level of Zonulin by assessing obesity-related biomarkers, such as liver enzymes, lipid profiles, and insulin resistance, in a population of adolescents.
Methods: The study included 198 adolescents aged 12-18 years; 92 were overweight/obese and 106 were of normal-weight. We assessed anthropometric and laboratory measures, including body mass index (BMI), BMI z-score, Waist-Height, Waist-Hip ratio, blood pressure, liver enzyme levels, lipid profiles, and insulin sensitivity. Serum Zonulin levels were measured using an enzyme-linked immunosorbent assay.
Results: The mean age of the participants was 15.2±2.5 years. Circulating serum Zonulin levels were significantly increased in overweight/obese participants compared with those in normal-weight participants (P=0.042). Zonulin levels were significantly and positively associated with BMI, BMI z-score, alanine aminotransferase levels, triglyceride, fasting insulin, and insulin resistance as indicated by the homeostasis model assessment of insulin resistance (HOMA-IR) (all P<0.05). In multivariate linear regression analysis, alanine aminotransferase (P<0.0001), triglyceride (P<0.0001), and HOMA-IR (P=0.001) contributed independently to circulating Zonulin levels after controlling for the effect of BMI z-score. Zonulin levels were more strongly associated with Waist-Hip ratio rather than Waist-Height ratio.
Conclusions: Zonulin was associated with indices of obesity. Waist-Hip ratio was more strongly associated with levels of Zonulin. The positive correlation between these parameters suggests putative pathophysiological mechanism linking Zonulin to metabolic dysfunction in adolescents.
Discriminatory value of alanine aminotransferase for diabetes prediction: the Insulin Resistance Atherosclerosis Study
