Diabetes in chronic liver disease: from old concepts to new evidence

The liver is one of the principal organs involved in glucose metabolism together with skeletal muscle and adipose tissue. A link between diabetes and chronic liver disease (CLD) was first observed in the early half of the last century, but to date several questions remain unsolved. Altered glucose tolerance has been well described in alcoholic CLD, non-alcoholic fatty liver disease, chronic hepatitis C and portal hypertension. Moreover, insulin resistance is assuming an ever-growing importance in CLD; chronic hepatitis C has recently been proposed as a metabolic disease and insulin sensitivity as a predictive factor for liver fibrosis.CLD is also complicated by acquired growth hormone (GH) resistance, characterized by low concentrations of insulin-like growth factor-1 (IGF-1) with respect to normal or elevated GH levels. GH resistance in CLD is determined by several factors, including malnutrition, impaired liver function and reduced expression of hepatic GH receptors. We recently described the possible role of tumour necrosis factor-alpha (TNF-alpha) in blunting the hepatic response to GH in patients with chronic hepatitis C. The role of GH in impaired glucose metabolism is well known, and recent evidence suggests a receptor and/or post-receptor modulation of insulin signalling. Moreover, as in other chronic inflammatory conditions, pro-inflammatory cytokines may directly modulate the signal cascade that follows insulin binding to its receptor in the course of CLD. In this review, the proposed links between impaired glucose tolerance and CLD are analysed, special emphasis being focussed on the most recent findings concerning the interplay of chronic inflammation, GH resistance and insulin resistance.