The study participants comprised 1107 students including 621(56.1%) girls and 486 (43.9%) boys with a mean (SD) age of 12.57 (3.3) years. Of them, 331(29.9%) were in the 6-9.9-year age group, 426(38.5%) and 350(31.6%) were in the 10-13.9-year and the 14-18-year -age groups, respectively. Overall 438(39.5%) had normal weight, 377(34%) were overweight and 295(26.6%) were obese. Of the total population studied, 931 participants including 413 (44.4%) boys and 518(55.6%) underwent sonography.
The mean value of the variables studied was not significantly different in terms of gender; the only significant difference was documented for liver enzymes: the mean ALT, AST and ALP were significantly higher in girls than in boys (19.50 ± 10.4 vs. 17.98 ± 9.74, 24.04 ± 10.5 vs. 22.60 ± 10.15 and 525.43 ± 248.7 vs. 477.49 ± 269.56 U/L, respectively, p < 0.05).
As presented in Table , from lower to higher BMI category, anthropometric measures, ALT, total cholesterol, LDL-C, TG and SBP increased, and HDL-C decreased significantly. AST was not significantly different between normal weight and overweight group, but was significantly higher in obese group than in others; DBP was not significantly different between overweight and obese groups, but was lower in the normal weight group than in others. FPG and ALP were not significantly different between groups. Correlations of waist circumference and cardio-metabolic risk factors with liver enzymes are presented in Table , and shows significant correlations in different BMI categories. Elevated ALT, AST and ALP levels were documented in respectively 4.1%, 6.6% and 9.8% of normal weight group. The corresponding figure was 9.5%, 9.8% and 9.1% in overweight group, and 16.9%, 14.9% and 10.8% in obese group, respectively.
Characteristics* of the study population according to the body mass index category
Correlation between waist circumference and cardio-metabolic risk factors with liver enzymes according to sex and body mass index
Figure shows the mean values of ALT, AST and ALP by the number of components of the metabolic syndrome in normal-weight, overweight and obese groups. In all three BMI categories, ALT increased significantly by increasing the number of the components of the metabolic syndrome. The corresponding figure for AST was significant only in the overweight group, whereas mean ALP decreased significantly in the normal weight group.
Mean (95%CI) of liver enzymes according to the number of components of the metabolic syndrome.
Table shows that in general, odds ratio for elevated liver enzymes and sonographic fatty liver increased significantly with higher number of the components of the metabolic syndrome and higher BMI categories before and after adjustment for age. Among total study population, ORs for elevated ALT or elevated AST in children/adolescents with high FBS, high TG and high total cholesterol were significantly higher than ORs in subjects with none of these metabolic abnormalities. Whereas, associations of low HDL-C and high LDL-C with elevated ALT and AST were not significant.
Odds ratio for elevated liver enzymes and sonographic fatty liver according to the number of the metabolic syndrome components and categories of body mass index before and after adjustment for age
While in overweight group, ORs for elevated AST or elevated ALT in children/adolescents with high TG were significantly higher than ORs in those with normal TG, the associations between other metabolic variables and elevated ALT, AST and ALP were not significant. In obese group, ORs for elevated ALT or elevated AST in subjects with high TG and high total cholesterol were significantly higher than ORs in those without these metabolic abnormalities Relationship between elevated ALT and the number of the metabolic syndrome components showed that the prevalence of metabolic syndrome components in children/adolescents who had ultrasonographic examinations with 0, 1, 2, and ≥ 3 risk factors were 19.7%, 40.5%, 33.4%, and 6.4%, respectively. The unadjusted ORs for elevated ALT levels in children/adolescents with 1, 2, and ≥ 3 risk factors were 1.06 (95% CI, 0.05-2.19), 1.61 (95% CI, 0.79-3.27), and 3.69 (95% CI, 1.61-8.45), respectively, that was significant for subjects with ≥ 3 risk factors. The unadjusted ORs for elevated AST were significant in children/adolescents with 2 risk factors [3.18 (95% CI, 1.52-6.67)], and for subjects with ≥ 3 risk factors [2.71, 95% CI, 1.05-7.0). Both adjusted and unadjusted ORs for fatty liver were significant in children/adolescents with 1, 2, and ≥ 3 risk factors. While for elevated ALT, the adjusted OR was significant only in subjects with ≥ 3 risk factors [3.69 (95% CI, 1.61-8.45)], for elevated AST it was significant in children/adolescents with either 2 risk factors [3.22 (95% CI, 1.53-6.78)], or ≥ 3 risk factors [2.86 (95% CI, 1.08-7.6)]. The adjusted OR for elevated ALP was significant only in subjects with 2 risk factors [2.14 (95% CI, 1.12-4.07)].