Effects of aging and type 2 diabetes on cardiac structure and function: Underlying mechanisms

We characterized long-term changes in cardiac structure and function in a high-fat diet/streptozotocin mouse model of aging and type 2 diabetes mellitus (T2D) and examined how the intersection of both conditions alters plasma metabolomics. We also evaluated the possible roles played by oxidative stress, arginase activity and pro-inflammatory cytokines. C57BL/6 male mice (13-month-old) were used. Control animals (n = 13) were fed regular chow for 10 months (aged group). T2D animals (n = 25) were provided a single injection of streptozotocin and fed a high fat diet for 10 months. In select endpoints, young animals were used for comparison. To monitor changes in left ventricular (LV) structure and function, echocardiography was used. At the terminal study (23 months), blood was collected and hearts processed for biochemical or histological analysis. Echo yielded diminished diastolic function with aging and T2D. LV fractional shortening and ejection fraction decreased with T2D by 16 months peaking at 23 months. Western blots noted increases in fibronectin and type I collagen with aging/T2D and greater levels with T2D in α-smooth muscle actin. Increases in plasma and/or myocardial protein carbonyls, arginase activity and pro-inflammatory cytokines occurred with aging and T2D. Untargeted metabolomics and cheminformatics revealed differences in the plasma metabolome of T2D vs. aged mice while select classes of lipid metabolites linked to insulin resistance, were dysregulated. We thus, document changes in LV structure and function with aging that in select endpoints, are accentuated with T2D and link them to increases in OS, arginase activity and pro-inflammatory cytokines.