Abstract 13920: Impact of Diabetes on Acute Kidney Injury After Myocardial Infarction: Possible Involvement of Toll-like Receptor in the Kidney

Abstract

Background: Comorbid acute kidney injury (AKI) predicts poor prognosis in patients with acute myocardial infarction (MI). Although type 2 diabetes (T2D) is a well-known risk factor of AKI after MI, the mechanism of the increased risk remains unclear. Here we hypothesized that T2D increases AKI after MI via toll-like receptor (TLR)-mediated inflammation. Methods and Results: OLETF, a rat model of obese T2D, and LETO, non-diabetic controls, at 25-30 weeks of age were randomized into sham and permanent coronary ligation (MI) groups. At baseline, body weight (617±23 vs. 537±13 g), fasting plasma glucose (267±32 vs. 153±15 mg/dl) and urinary protein level (6.4 vs. 0.6 g/gCr), but not serum creatinine, were significantly higher in OLETF than in LETO. Histologically, glomerular size was increased by 17% without mesangial proliferation in OLETF compared to that in LETO, indicating that OLETF developed early-stage nephropathy by this age. At 12 h after MI, mRNA levels of TLR2, TLR4, IL-6 and TNF-α in the kidney were increased by 1.6-, 1.2-, 2.6-, 1.5-fold, respectively, in OLETF but not in LETO. Furthermore, immunoblot analyses showed that phosphorylation levels of p38 MAPK and JNK, downstream mediators of the TLR signal, were significantly elevated by MI in OLETF. Histological abnormalities in the kidney or increase in serum creatinine were not detected in either LETO or OLETF 12 h after MI. However, in immunohistochemical analyses, areas positive for neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were significantly increased by 4.0- and 5.3-fold, respectively, and NGAL mRNA level was increased by 1.8-fold after MI in OLETF but not in LETO. In sham-operated LETO and OLETF, areas positive for NGAL and KIM-1 were barely detected. Infarct sizes were similar and cardiac BNP mRNA levels in the non-infarcted left ventricle were equally elevated at 12 h after MI in LETO and OLETF, suggesting that MI-induced cardiac loads were comparable in the two groups. However, mortality at 48 h after MI was significantly higher in OLETF than in LETO (68% vs. 18%, P<0.05). Conclusion: The results suggest that AKI after MI is enhanced in T2D via TLR-mediated inflammation. The cardio-renal interaction may underlie increased post-MI mortality in T2D.