Association of insulin-like growth factor-1 [IGF-1], dietary intake and cognitive functions in normal school age children

ABSTRACT

Insulin-like growth factor I [IGF-I] is a hormone that mediates the effects of growth hormone and plays a critical role in somatic growth regulation and organ development. It is hypothesized that it also plays a key role in human brain development. The dietary determinants of circulating levels of components of the IGF system are of interest, as these may mediate some of the effects of diet on later health. However, few studies have examined the relationship between diet and IGF-1 levels in children, as well as the relationship between IGF-1 and mental development. To investigate the role of diet on levels of IGF-I and their relationships with measures of IQ in a group of healthy children. The study included 222 apparently healthy children [113 boys and 109 girls], their height for age and weight for age were between 10[th]-90[th] percentiles according to World Health Organization [WHO] growth standards, their age ranged 8-11 years and all were prepubescent. They were chosen randomly from primary schools located in urban Giza Governorate. Nutritional status was assessed by 24-hours dietary intake history and anthropometric measurements [weight, height]. Plasma IGF-1 was evaluated by radioimmu-noassay technique, growth hormone [GH] was determined by immuno-enzymatic assay. Intelligence quotient [IQ] was measured with the Arabic version of the revised-Wechsler Intelligence Scale for Children. Familial background was investigated through structured questionnaire. IGF-1 levels [mean +/- SD] were 142.6 +/- 43.3 ng/mL for girls and 139.4 +/- 39.6ng/mL for boys. GH level was within normal range. IQ scores [mean +/- SD] were 101.03 +/- 17.4 and 103.11 +/- 19.8 for boys and girls, respectively. IGF-1 levels were associated positively with IQ [r=0.81, p boys and r=0.79, p girls]. IGF-1 was positively associated with intakes of protein, zinc, calcium, and phosphorus, and was negatively associated with fat intake. Multiple regression analysis shows that plasma levels of IGF-1 were associated with BMI, dietary intakes of animal protein, zinc and animal fat [R[2]=0.33, p<0.01] independent of age and sex. This study provides a preliminary evidence that IGF-1 is associated with brain development in childhood. Additional longitudinal research is required to clarify the role of IGF-1 in neurodevelopment, because IGF-1 levels are modifiable through diet and other environmental exposures