Serum Leptin Levels In Type-1 Diabetic Children and Adolescents versus Healthy Controls: Relationship to Age, Gender, Body Mass Index, Gonadal Hormones and Pubertal Stages

Background: leptin, the product of the obese (ob) gene is produced mainly by
adipose tissues. Thus, it is thought to play a k ey role in the regulation of body fat
mass. It appears to be an integral component of various hypothalamo-pituitary
endocrine feedback loops. Impaired growth and pubertal delay had been observed in
children with type -1 diabetes mellitus. Also they are more prone to develop obesity.
Objectives: Since childhood and puberty are periods of major metabolic and
endocrine changes, the present study was conducted to: (1) Evaluate developmental
changes of serum leptin levels in children and adolescents with type -1 diabetes
mellitus in comparison with matched healthy controls in respect with chronological
age and pubertal stages (2) Evaluate if leptin concentration would be related to
obesity observed in children and adolescents with type-1 diabetes during puberty.
The study included 60 children (32 girls and 28 boys) with age range between 6-16 years with a mean age of 11.7 ± 4.3 diagnosed as type -1 diabetes mellitus by the
criteria of American Diabetes Association (ADA) as well as 48 healthy children (24
girls and 24 boys) with matched age and sex with diabetic patients. The patient and
control children were grouped according to their chronological age into 4 groups (6-7yr , 8-10yr, 11-13yr and 14-16yr) and according to stages of puberty into 3 groups:
prepuberty P1,early puberty P2 and overt puberty P3. Serum leptin levels and BMI
were measured to all patients and controls. Also, serum testosterone in boys and
serum estradiol in girls were measured by ELISA method.
The results of the study showed that Serum leptin levels significantly increased
parallel with age and with pubertal stages both in control and diabetic girls. The
maximum levels were observed at 14-16yr age group and at overt stage of puberty.
Serum leptin levels were significantly higher in diabetic girls than controls at all
studied groups. In control boys, leptin levels were significantly higher at 8-10yr and
during P1 stage then a significant decline occurred thereafter. In contrast, the
diabetic boys showed no such decline either with age or with pubertal staging.
Diabetic boys had significantly higher leptin levels than control boys at all studied
groups. Serum leptin levels in girls were significantly higher than boys either in
control or diabetic children. Diabetic children (girls and boys) were significantly
older than controls during P2 and P3 stage. BMI was significantly increased in
diabetic children (girls and boys) than controls during P1,P2 and P3 stage whereas serum estradiol in diabetic girls and testosterone in diabetic boys were significantly lower than controls during P2 and P3 stages. Significant positive correlations were observed between serum leptin levels versus age, BMI and estradiol hormone in control girls (r=0.75, P<0.001,r= 0.64,P<0.001 and r=0.77,P<0.001 respectively). Also significant positive correlations were found in diabetic girls between serum leptin levels and each of age, BMI and estradiol hormone (r = 0.64, P<0.001, r = 0.72,P<0.001 and r = 0.66, P<0.001 respectively). In control boys significant negative correlations were observed between serum leptin level and each of age (r=-0.4, P<0.05) and testosterone hormone (r = - 0.62, P<0.001) whereas non significant with BMI. Significant positive correlations were found in diabetic boys between serum leptin levels and each of age (r = 0.67, P<0.001) BMI (r = 0.57, P<0.01), while the correlation with testosterone was non significant. In conclusion leptin appears to participate in various endocrinological and physiological process in human body. Among the more notable are obesity and pubertal delay-associated diabetes. Thus, it may be involved in regulation of body weight and signaling the onset of puberty and maintenance of reproductive function thereafter.