Choi YJ, et al. J Korean Med Sci. 2013 Nov;28(11):1632-1638. http://dx.doi.org/10.3346/jkms.2013.28.11.1632

Background: Irisin is an adipomyokine secreted by muscle and adipose cells, and it plays a role in glucose, fat, and bone metabolism. This study aimed to determine the correlation of serum irisin levels with anthropometric, metabolic, and bone parameters in obese children and adolescents.Methods: This single-center study included 103 Korean children and adolescents: 54 (52.4%) obese participants with a body mass index (BMI) ≥95th percentile and 49 (47.6%) healthy controls with BMI within the 15th to 85th percentile. Various parameters were measured, including fasting blood glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride and glucose (TyG) index, lipid profile, alkaline phosphatase (ALP), osteocalcin, and 25(OH)-Vitamin D levels. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA) in 33 healthy subjects.Results: Serum irisin was significantly higher in the obese group than in the control group (mean 18.1 ± 3.5 vs. 16.2 ± 2.0 ng/mL; p = 0.001). Serum irisin level was positively correlated with chronological age (r = 0.28; p = 0.004), height SDS (r = 0.24; p = 0.02), BMI SDS (r = 0.37; p < 0. 001), fasting glucose (r = 0.27; p = 0.007), fasting insulin (r = 0.23; p = 0.03), HOMA-IR (r = 0.21; p = 0.04), osteocalcin (r = 0.27; p = 0.006) and negatively correlated with HDL cholesterol (r = -0.29; p = 0.005). All these correlations were evident in obese subjects but not in healthy subjects. ALP and 25(OH)-Vitamin D were unrelated to irisin levels. Among 33 healthy subjects, total body-less head (TBLH) BMD Z-score was positively correlated with serum irisin (r = 0.39; p = 0.03), osteocalcin (r = 0.40; p = 0.02), fasting insulin (r = 0.39; p = 0.04), and HOMA-IR (r = 0.38; p = 0.047).Conclusion: This study demonstrated an association between irisin levels and glucose, lipid, and bone parameters in children and adolescents. Our findings suggest that irisin has a potential role in metabolic disorders and bone health in obese children and adolescents.

Childhood obesity frequently persists into adulthood, and is associated with insulin resistance (IR) and increased long-term morbidity and mortality. We compared IR criteria concerning 'age-specific cut-off points (ACOP)' and 'fixed cut-off points (FCOP)' for the identification of IR, and we investigated their correlation with metabolic syndrome (MS). The data were acquired from the 5th Korea National Health and Nutrition Examination Survey (2010–2011). Participants aged from 10 to17 years underwent fasting plasma glucose, insulin concentrations and lipid panel measurements. High fasting plasma insulin levels or increased homeostatic model assessment insulin resistance (HOMA-IR) were defined as IR. We analyzed MS and IR frequencies according to FCOP or ACOP. Among 719 participants, 165 (22.9%) were overweight or obese based on their body mass index. We found no prevalence of MS in underweight/normal weight participants and 12.7 % prevalence rate in overweight or obese participants. IR according to ACOP was more closely associated with MS than IR according to FCOP. No differences were found in predicting the frequency of MS using FCOP or ACOP in both fasting plasma insulin and HOMA-IR. The frequencies of MS in participants with IR defined using ACOP and FCOP were similar. However, IR using ACOP was more closely associated with MS than IR using FCOP.

We aimed to investigate serum lipid profiles and glycemic control in adolescents and young adults with type 1diabetes mellitus (T1DM). This cross-sectional study included 29 Korean young adults and adolescents with T1DM. The median age was 17 years (range, 10-25 years) and 18 (62.1%) were female. We compared the lipid profiles of patients with dyslipidemia and those without dyslipidemia. Correlations between glycosylated hemoglobin (HbA1c) and lipid profiles (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglyceride [TG]) were determined by linear regression analysis. Of the 29 patients with T1DM, 11 (37.9%) were classified as having dyslipidemia due to the following lipid abnormality: TC≥200 mg/dL in 8 patients, LDL-C≥130 mg/dL in 4 patients, TG≥150 mg/dL in 2 patients, and HDL-C≤35 mg/dL in 2 patients. Compared to patients without dyslipidemia, patients with dyslipidemia were more likely to have higher values of HbA1c (median, 10.6%; range, 7.5%-12.3% vs. median, 8.0%; range, 6.6%-10.0%; P=0.002) and a higher body mass index z score (median, 0.7; range, -0.57 to 2.6 vs. median, -0.4; range, -2.5 to 2.2; P=0.02). HbA1c levels were positively correlated with TC (P=0.03, R (2)=0.156) and TG (P=0.005, R (2)=0.261). A substantial proportion of adolescents and young adults with T1DM had dyslipidemia. We found a correlation between poor glycemic control and poor lipid profiles in those patients.