Hyperglycemia-induced production of acute phase reactants in adipose tissue

Chronic elevation of systemic levels of acute phase reactants and inflammatory cytokines found in patients with diabetes and the often-associated metabolic syndrome X (hypertriglyceridemia, low serum high density lipoprotein cholesterol, hypertension, and accelerated atherosclerosis) may be responsible for the increased incidence of cardiovascular problems in this population. Here we examine the contribution of adipose tissue to the systemic elevation of acute phase reactants associated with chronic hyperglycemia. We demonstrate that adipose tissue expresses a number of acute phase reactants at high levels, including serum amyloid A3 (SAA3), alpha1-acid glycoprotein, the lipocalin 24p3 as well as plasminogen activator inhibitor-1 (PAI-1). Additionally, we show SAA3 is expressed at low levels under normal conditions but in the diabetic state is dramatically up-regulated in adipose tissue while down-regulated in liver. Furthermore, pro-inflammatory stimuli and high glucose can lead to the induction of SAA3 in adipose tissue in vivo as well as in the 3T3-L1 adipocyte cell line. Adipose tissue may therefore play a major role in the pathogenic sequelae of Type II diabetes, in particular the cardiovascular problems associated with prolonged hyperglycemia.