The age-related increase in renal clusterin mRNA is accelerated in obese Zucker rats

Clusterin is a multifunctional glycoprotein associated with development and tissue injury. Because renal function decreases with advancing age in the obese Zucker rat, clusterin mRNA expression was examined in the kidney of young adult Zucker rats and compared with age-related changes in renal clusterin mRNA expression in Fischer 344 (F344) rats. Renal clusterin mRNA levels in the obese Zucker rat were 2.5-fold higher by 3 mo of age and fourfold higher at 5 mo of age compared with the lean strain. In comparison, renal clusterin mRNA in 12-mo-old F344 rats was twofold higher than in 3-mo-old animals and was tenfold higher at 24 mo of age. Clusterin mRNA was positively correlated with urinary protein excretion and negatively correlated with creatinine clearance in Zucker rats. Clusterin was increased in select nephrons of the obese Zucker rat kidney and in 24-mo-old F344 rat kidney as assessed by in situ hybridization. Increased expression of clusterin mRNA occurred mostly in the tubular epithelium of dilated, convoluted proximal tubules. These data indicate that renal clusterin mRNA levels increase as a function of age and that age-related increases in renal clusterin and the associated tubular abnormalities are accelerated in obese Zucker rats.