Membrane Proteomics of Impaired Energetics and Cytoskeletal Disorganization in Elderly Diet-Induced Diabetic Mice

Diabetic
cardiomyopathy is a well-recognized complication of diabetes,
but its pathophysiology is unclear. We aimed to investigate the mechanisms
underlying cardiac dysfunction in an elderly type 2 diabetic (T2DM)
mouse model, using membrane proteomic analyses. Elderly mice were
fed a high fat diet for 12 weeks to induce T2DM, and myocardial structure
and function were assessed by echocardiography. Cardiomyocytes were
isolated by Langendorff perfusion and subjected to iTRAQ-based quantitative
membrane proteomic profiling, immunoblotting, and real-time quantitative
reverse-transcriptase polymerase chain reaction. Compared to controls,
elderly T2DM mice showed worse systolic function, more myocardial
fibrosis and up-regulation of several heart failure markers (all p < 0.05). Cardiomyocyte membrane proteomic profiling
revealed that 417 proteins had differential expressions related to
perturbations in several biological processes in T2DM mice compared
with the control. The most up-regulated proteins were involved in
oxidative phosphorylation, whereas many down-regulated proteins were
involved in cytoskeletal regulation. Differential protein expression
correlated with myocardial systolic velocity by tissue Doppler. In
addition, cardiomyocyte immunofluorescence staining showed greater
disorganization of thick/parallel F-actin stress fibers and marked
reduction in F-to-G-actin ratio in T2DM vs control (p < 0.05), which paralleled worsened myocardial systolic velocity.
We concluded that cardiac contractile dysfunction in elderly T2DM
mice was associated with impaired energetics and cytoskeletal disorganization.