Abstract
The insulin-like growth factor (IGF) system, acting in concert with other hormone axes, is important in normal metabolism. In obesity, the hyperinsulinaemia that accompanies peripheral insulin resistance leads to reduced growth hormone (GH) secretion, while total IGF-I levels are relatively unchanged due to increased hepatic GH sensitivity. IGF-binding protein (IGFBP)-1 levels are suppressed in relation to the increase in insulin levels in obesity and low levels predict the development of type 2 diabetes several years later. Visceral adiposity and hepatic steatosis, along with a chronic inflammation, contribute to the IGF system phenotype in individuals with metabolic syndrome and type 2 diabetes mellitus, including changes in the normal inverse relationship between IGFBP-1 and insulin, with IGFBP-1 concentrations that are inappropriately normal or elevated. The IGF system is implicated in the vascular and other complications of these disorders and is therefore a potential therapeutic target.
Highlights
Throughout evolution the insulin-like growth factors (IGFs), their IGF-binding proteins (IGFBPs) and receptors have had central roles in growth, metabolism and reproduction [1]
Articles included were retrieved through PubMed using the MeSH terms “insulin-like growth factor” or “IGFBP” and identified by a manual search for English-language, full-text papers that related to obesity, insulin resistance and diabetes mellitus for the period 2009 to April 2014
It appears likely that sensitivity to insulin in obesity is preserved in some tissues where it plays a central role in the growth hormone (GH)-IGF axis response, by inhibiting pituitary GH, increasing hepatic GH responsiveness and suppressing hepatic IGFBP-1 secretion [30,39]
Summary
Throughout evolution the insulin-like growth factors (IGFs), their IGF-binding proteins (IGFBPs) and receptors have had central roles in growth, metabolism and reproduction [1]. Articles included were retrieved through PubMed using the MeSH terms “insulin-like growth factor” or “IGFBP” and identified by a manual search for English-language, full-text papers that related to obesity, insulin resistance and diabetes mellitus for the period 2009 to April 2014. An understanding of the role of the IGF system in obesity, insulin resistance and diabetes requires an in depth knowledge of its role in normal metabolism. This will be described first, after which the recent IGF literature in relation to obesity, insulin resistance and type 2 diabetes will be reviewed in the context of previous work
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