STAT4 and diabetic kidney disease: In the renal tubular interstitial region, microarray analysis identified several JAK/STAT family members with downregulated expression in patients with early diabetic nephropathy, whereas most JAK/STAT family members such as JAK1, JAK2, JAK3, STAT1, STAT3, STAT4, and STAT5B were upregulated in patients with progressive diabetic nephropathy compared with controls.