Exploratory Longitudinal Analysis of the Circulating CHIT1 Activity in Pediatric Patients with Obesity

Macrophage activation and cytokine release play a pivotal role in inflammation-mediated metabolic disturbances in obesity. The proinflammatory macrophage secretes human chitotriosidase (CHIT1). The expression of the CHIT1 in visceral adipose tissue is associated with cytokine production. Our study aimed to assess whether the CHIT1 circulating activity, as a macrophage activation indicator, reflects the change of the adiposity level and the insulin resistance (IR) in children with obesity. We longitudinally (median follow-up period of 7 months; IQR [5 to 8.5] and {2 to 13} months) evaluated the CHIT1 circulating activity, the adiposity level (waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WtHR), and body mass index (BMI)-for-age z score), and two surrogate markers of IR (Homeostatic Model Assessment for Insulin Resistance, HOMA-IR and the triglycerides-to-high density lipoprotein cholesterol ratio, TG/HDLc) in 29 pediatric patients (16 girls and 13 boys) with obesity. We found a significant reduction in CHIT1 circulating activity (Wilcoxon test, p = 0.015) and a decrease in TG/HDLc at the follow-up evaluation (Wilcoxon test, p < 0.001). Indicators of adiposity were positively correlated with HOMA-IR at baseline, among which WC was the sole indicator associated with HOMA-IR (Spearman’s rank correlation coefficients, p < 0.05) at follow-up. Human chitotriosidase has the potential to be a valuable measure of the progression of subclinical inflammation in children with obesity. Subclinical inflammation, as expressed by the circulating CHIT1 activity, progresses independently of the abdominal adiposity, as measured by the clinical indicators, and is associated with a change in insulin resistance.

Evaluation of Circulating Chitotriosidase Activity in Children with Obesity

Childhood obesity progresses to metabolic disturbances via low-grade inflammation. Identifying novel molecules that reflect the activity of the immune responses is critical in understanding its underlying pathogenesis. Our exploratory study aimed to evaluate the change of chitotriosidase (CHIT1) plasma activity according to Body Mass Index (BMI)-for-age z score in pediatric patients. The study evaluated 68 children consisting of 47.1% girls with a mean age of 12.47 ± 3.71 years and 52.9% boys with a mean age of 11.93 ± 3.18 years. The effect of the most frequent CHIT1 gene variants, the 24 base pair duplication (dup24) and G102S polymorphism, upon the association between circulating CHIT1 activity and the obesity level, was also investigated. A significantly higher logCHIT1 plasma activity was found in children with extreme obesity than in children with overweight (p = 0.048 for the uncorrected CHIT1 and 0.026 for the corrected CHIT1). The BMI-for-age z score significantly (p = 0.031) predicts increased CHIT1 activity in children with overweight, obesity, and extreme obesity after controlling for the two gene variants, age, gender, and time since weight gain. Dup24 and G102S polymorphism were significant independent predictors (p-values < 0.002) for the change of CHIT1 plasma activity. Circulating CHIT1 might be an accurate indicator of inflammation in children with obesity. Its role and the effect of the dup24 and G102S variants on the CHIT1 activity should be validated in a larger cohort.