Proteomic Analysis of Akita Mice Reveals 9 Proteins Altered during Early Stages of Diabetic Cardiomyopathy

Abstract

Cardiovascular disease is the leading cause of diabetic morbidity and over 10% of patients with type 1 diabetes (T1DM) die before they are 40 years old. This study utilized Akita mice, a murine model with T1DM progression analogous to that of humans. Diabetic cardiomyopathy in Akita mice presents as diastolic impairment as early as 3 months of age and significant cardiac atrophy by 5 weeks. Hearts from recently diabetic mice (5 weeks) were analyzed with label free proteomics to identify proteins which may play a critical role in the pathophysiology of diabetic cardiomyopathy (n=3). At this early stage, 9 proteins were differentially expressed in diabetic mice: GANC, PLEKHN1, COLIA1, GSTK1, ATP1A3, RAP1A, ACADS, EEF1A1, HRC, EPHX2, and PKP2 (gene names). A recent study demonstrated that deletion of EPHX2, encoding soluble epoxide hydrolase (sEH), attenuated the development of hyperglycemia in response to the pancreatic toxin, streptozotocin. Immunoblots of five week old Akita heart homogenates showed a 30% increase in expression of sEH (P<0.01). By twelve weeks, cardiac sEH increased 145% +/- 20% compared to control littermates (P<0.001) but no differences were found in hearts from 3 or 4 week old mice. qPCR results suggest that these changes are driven largely by transcriptional regulation with no differences in EPHX2 gene expression at 3 and 4 weeks and a 50% and 100% increase at 5 and 12 weeks respectively. In addition, immunoblots indicate an approximate 100% increase in sEH in gastrocnemius tissue of 12 week old Akita mice (P<0.01). Our results suggest that an increase in sEH is a key factor in the development of diabetic cardiomyopathy. Furthermore, the increased presence of this protein in multiple tissues suggests that it may be useful as a diagnostic target.