Obese mice exhibited fasting hyperglycemia, hyperinsulinemia, and impaired glucose tolerance, as well as decreased serum levels of adiponectin and increased levels of leptin, resistin, and insulin-like growth factor 1.
In men with abdominal obesity, subcutaneous abdominal adipocyte size is positively associated with measures of impaired glucose tolerance and administration of GH at doses that raise IGF-1 levels within the normal range, decreases abdominal subcutaneous adipocyte size, suggesting that GH administration improves the health of adipose tissue.Clinical trials number: NCT00131378.
Thus, overexpression of human IGFBP-3 or its mutant devoid of IGF binding ability leads to glucose intolerance with, however, different effects on insulin secretion, insulin sensitivity, and lipid homeostasis in aging mice.
A prolonged hyperactivity of the IGF-1/insulin axis in the face of insulinotropic nutrition, on the other hand, can lead to collapse of the pancreatic islets and glucose intolerance.
These results support the growth-promoting role of the IGF system in placental/fetal development and suggest that the IGF1R and IGFBP3 DNA methylation profiles are dysregulated in IGT, potentially affecting the fetal metabolic programming.
Strikingly, mice lacking GHR developed metabolic features that were not observed in the IGF-1R mutants, including marked peripheral adiposity, insulin resistance, and glucose intolerance.
We studied, prospectively, the relationship between an IGF-I gene polymorphism, retinal vessel diameters, and incident diabetic retinopathy in subjects with impaired glucose tolerance (IGT) or type 2 diabetes.
Whether the administration of low-dose GH, recombinant IGF-I or combined IGF-I/IGF-binding protein 3 therapy prevents future development of IGT or type 2 diabetes in high-risk normoglycaemic and GH-deficient individuals merits further long-term studies.
These findings demonstrate the importance of the normal inverse relationship between serum insulin and IGFBP-1 levels in glucoregulation and that sustained dysregulation of the insulin/IGF-I/IGFBP-1 axis is associated with impaired glucose tolerance and abnormalities of insulin action.