J Korean Soc Pediatr Endocrinol.  2005 Dec;10(2):195-203.

The Effect of Obesity on Serum Growth Factors, and Insulin-like Growth Factor Binding Protein-3 Proteolysis in Children with Simple Obesity

• Lee SW
• Rhie YJ
• Hwang IT
• Han DK
• Kim DH
• Kim HS

Abstract

PURPOSE
In children with simple obesity, spontaneous and stimulated growth hormone (GH) secretion are diminished, but their heights usually are normal or even taller for their age and sex. The exact mechanism to explain the discrepancy between impaired GH secretion and normal height velocity has not been elucidated. In this study, we aimed to determine the level of serum growth factors, and the degree of insulin-like growth factor binding protein (IGFBP)-3 proteolysis, and to assess the alteration of the IGF system associated with accelerated or normal growth in simple obesity.
METHODS
We evaluated serum growth factors, and IGFBP-3 proteolysis in 27 obese, 25 obesity risk group, and 28 age-matched control group. We measured serum levels of insulin-like growth factor (IGF)-I, IGFBP-1, -3, and free IGF-I by immuno-radiometric assay and IGFBP-3 fragment by Western immunoblotting.
RESULTS
The height was taller in obese children than in lean control group. The results showed no significant difference in the level of serum total IGF-1 and IGFBP-3 between obese and normal control group. Although there was no significant difference in other components, serum free IGF-I levels were significantly increased (P<0.05) and showed positive correlation with their height in obese children (r=0.25, P<0.05). The degree of IGFBP-3 proteolysis was increased in obesity and obesity risk group compared to control group. The densities of the IGFBP-3 proteolytic fragment approximate 18 kDa also showed positive correlation with levels of free IGF-I (r=0.23, P<0.05) and height (r=0.19, P<0.05).
CONCLUSION
These findings may suggest that elevated levels of serum IGFBP-3 proteolytic fragments showing decreased affinity to IGF-I result in the increase of biologically active free IGF-I, thereby maintain normal growth in the obese children.

Keyword

Simple obesity; IGF-I; IGFBP-3; Proteolysis; Free IGF-I; Normal growth

MeSH Terms

Blotting, Western
Carrier Proteins
Child*
Growth Hormone
Humans
Insulin-Like Growth Factor Binding Protein 1
Insulin-Like Growth Factor Binding Protein 3
Insulin-Like Growth Factor I
Intercellular Signaling Peptides and Proteins*
Obesity*
Proteolysis*
Carrier Proteins
Growth Hormone
Insulin-Like Growth Factor Binding Protein 1
Insulin-Like Growth Factor Binding Protein 3
Insulin-Like Growth Factor I
Intercellular Signaling Peptides and Proteins