Diabetic cardiomyopathy characterized by left ventricular hypertrophy predisposes diabetic and obese individuals to development of cardiac dysfunction and subsequently to heart failure. Whether hyperinsulinemia has an underlying role in development and or progression of diabetic heart disease is not well understood. We therefore studied the effects of acute hyperinsulinemia on cardiac function in euglycemic states. Acute hyperinsulinemia neither affected baseline nor inotropic response to β-adrenergic stimulation. Previous studies from our laboratory have indicated a potential role for GRK2, a serine threonine kinase in development of cardiac dysfunction in diabetic states in humans as well as in mice. To assess whether GRK2 mediates the detrimental effects of chronic hyperinsulinemia on cardiac dysfunction in mouse model of diet induced obesity, we utilized cardiomyocyte knockout of GRK2. Our results suggested lack of cardiac functional impairments in high fat fed wildtype mice, which hindered our attempts to ascertain the role of GRK2 in diabetic cardiomyopathy. Mouse models of diet induced obesity have been routinely used to study the effects of obesity and diabetes on cardiac dysfunction but recent evidence from multiple research groups has emphasized the need for evaluation of the utility and relevance of the murine diet induced obesity model for studying cardiovascular abnormalities associated with hyperinsulinemic states, including T2DM and obesity. We therefore studied the effect of chronic fat feeding (>20 weeks) alone or in combination with concomitant hypertension on cardiac function in C57BL/6J mice. Different diets were formulated with either lard (32% saturated fat, 68% unsaturated fat) or hydrogenated coconut oil (95% saturated fat) as the source of fat and fatty acids, which contributed 60% of total calories. Insulin resistance and glucose intolerance were readily observed in mice fed a high fat diet in each of the studies. HFD resulted in the development of cardiac hypertrophy; however cardiac function as measured by B-mode echocardiography and LV catheterization was unaffected in high fat diet groups compared to their respective control diet groups. Further, dietary fat feeding regardless of the source of fat modestly altered the gene expression of a few pathological hypertrophic markers or of fibrosis related genes. However, there was an increase in expression of PPARa target genes such as Pdk4 and fatty acid metabolism genes including CD36, AcadL and Cpt1b. Cardiac mitochondrial function as assessed by oxygen consumption rates, ATP synthesis rates and reactive oxygen species production rates were unaltered in high fat diet fed mice. These results suggest that while chronic fat feeding in mice causes cardiac hypertrophy and potentially cardiometabolic remodeling, it might not be sufficient to activate pathological hypertrophic mechanisms that impair cardiac function and cause cardiac fibrosis.
| Identifer | oai:union.ndltd.org:uiowa.edu/oai:ir.uiowa.edu:etd-8535 |
| Date | 01 August 2019 |
| Creators | Tadinada, Satya Murthy |
| Contributors | Abel, Evan Dale |
| Publisher | University of Iowa |
| Source Sets | University of Iowa |
| Language | English |
| Detected Language | English |
| Type | dissertation |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | Copyright © 2019 Satya Murthy Tadinada |
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