Increased ADRP expression in human atherosclerotic lesions correlates with plaque instability

Adipose differentiation-related protein (ADRP) is intrinsically associated with the surface of lipid droplets implicated in the development of atherosclerosis. We analyzed expression of ADRP in human popliteal artery plaques. Atherosclerotic plaque tissue from the popliteal artery was obtained from 18 patients undergoing lower extremity amputation for arteriosclerosis obliterans, and with either stable (n = 6) or unstable (n = 12) atherosclerotic plaques. Plaques were histologically classified as either unstable (>= 40% lipid core plaque area) or stable (< 40% lipid core plaque area). Control tissues consisted of sections of mesenteric arteries obtained from 10 patients without a history of atherosclerosis, but undergoing a subtotal gastrectomy. Plaque tissues were analyzed for expression of ADRP and protein kinase C (PKC) protein by immunohistochemical methods, and ADRP mRNA expression was measured using the reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemical analyses showed that ADRP expression was higher in samples of unstable plaque when compared with expression in stable plaque (gray intensities 103.56 +/- 1.187 vs 106.95 +/- 1.389, respectively, P < 0.05) and that ADRP expression was associated with increased PKC expression (gray intensities 102.32 +/- 1.730 vs 104.70 +/- 0.959, respectively, P < 0.01). Consistent with ADRP protein expression, expression of ADRP mRNA was also higher in unstable plaque compared to expression in stable plaque (relative expression 1.17 +/- 0.15 vs 0.81 +/- 0.03, respectively, P < 0.05). In conclusion: this study demonstrated that increased expression of ADRP in human atherosclerosis was associated with plaque instability.