Increased myocardial susceptibility to repetitive ischemia with high-fat diet-induced obesity.

Obesity and diabetes are frequently associated with cardiovascular disease. When a normal heart is subjected to brief/sublethal repetitive ischemia and reperfusion (I/R), adaptive responses are activated to preserve cardiac structure and function. These responses include but are not limited to alterations in cardiac metabolism, reduced calcium responsiveness, and induction of antioxidant enzymes. In a model of ischemic cardiomyopathy inducible by brief repetitive I/R, we hypothesized that dysregulation of these adaptive responses in diet-induced obese (DIO) mice would contribute to enhanced myocardial injury. DIO C57BL/6J mice were subjected to 15 min of daily repetitive I/R while under short-acting anesthesia, a protocol that results in the development of fibrotic cardiomyopathy. Cardiac lipids and candidate gene expression were analyzed at 3 days, and histology at 5 days of repetitive I/R. Total free fatty acids (FFAs) in the cardiac extracts of DIO mice were significantly elevated, reflecting primarily the dietary fatty acid (FA) composition. Compared with lean controls, cardiac FA oxidation (FAO) capacity of DIO mice was significantly higher, concurrent with increased expression of FA metabolism gene transcripts. Following 15 min of daily repetitive I/R for 3 or 5 days, DIO mice exhibited increased susceptibility to I/R and, in contrast to lean mice, developed microinfarction, which was associated with an exaggerated inflammatory response. Repetitive I/R in DIO mice was associated with more profound significant downregulation of FA metabolism gene transcripts and elevated FFAs and triglycerides. Maladaptive metabolic changes of FA metabolism contribute to enhanced myocardial injury in diet-induced obesity.

Effects of diet-induced obesity on inflammation and remodeling after myocardial infarction.

Epidemiological studies indicate that obesity, insulin resistance, and diabetes are important comorbidities of patients with ischemic heart disease and increase mortality and development of congestive heart failure after myocardial infarction. Although ob/ob and db/db mice are commonly used to study obesity with insulin resistance or diabetes, mutations in the leptin gene or its receptor are rarely the cause of obesity in humans, which is, instead, primarily a consequence of dietary and lifestyle factors. Therefore, we used a murine model of diet-induced obesity to examine the physiological effects of obesity and the inflammatory and healing response of diet-induced obese (DIO) mice after myocardial ischemia-reperfusion injury. DIO mice developed hyperinsulinemia and insulin resistance and hepatic steatosis, with significant ectopic lipid deposition in the heart and cardiac hypertrophy in the absence of significant changes in blood pressure. The mRNA levels of chemokines at 24 h and cytokines at 24 and 72 h of reperfusion were higher in DIO than in lean mice. In granulation tissue at 72 h of reperfusion, macrophage density was significantly increased, whereas neutrophil density was reduced, in DIO mice compared with lean mice. At 7 days of reperfusion, collagen deposition in the scar was significantly reduced and left ventricular (LV) dilation and cardiac hypertrophy were increased, indicative of adverse LV remodeling, in infarcted DIO mice. Characterization of a murine diet-induced model of obesity and insulin resistance that satisfies many aspects commonly observed in human obesity allows detailed examination of the adverse cardiovascular effects of diet-induced obesity at the molecular level.

Analysis of VEGF-responsive genes involved in the activation of endothelial cells.

BACKGROUND: Identification of the genes and pathways associated with the activation of endothelial cells (ECs) could help uncover the role of ECs in wound healing, vascular permeability, blood brain barrier function, angiogenesis, diabetic retinopathy, atherosclerosis, psoriasis, and growth of solid tumors. DESIGN: Herein, we embedded ECs in 3D type I collagen gel, left unstimulated or stimulated with VEGF165, and subjected to suppression subtractive hybridization followed by differential display (SSHDD). Gene fragments obtained from SSHDD were subjected to DNA sequence analysis. Database search with nucleotide sequence were performed using the BLAST algorithm and expression of candidate genes determined by northern blot analysis. RESULTS: A total of approximately 32 cDNA fragments, including known regulators of angiogenesis, and a set of genes that were not reported to be associated with activation of ECs and angiogenesis previously were identified. We confirmed the mRNA expression of KDR, alpha2 integrin, Stanniocalcin, including a set of 11 candidate genes. Western immunoblotting results indicated that KDR, alpha2 integrin, MMP-1, MMP-2, and VE-cadherin genes were indeed active genes. CONCLUSION: We have identified a set of 11 VEGF-responsive endothelial cell candidate genes. Their expression in endothelial cell is confirmed by northern blot analyses. This preliminary report forms as a foundation for functional studies to be performed to reveal their roles in EC activation and pathophysiological events associated with the vasculature including tumor growth.

Regulation of cell-cell interactions by phosphatidic acid phosphatase 2b/VCIP.

We identified vascular endothelial growth factor and type I collagen inducible protein (VCIP), also known as phosphatidic acid phosphatase 2b (PAP2b), in a functional assay of angiogenesis. VCIP/PAP2b exhibits an Arg-Gly-Asp (RGD) cell adhesion sequence. Immunoprecipitation and fluorescence-activated cell sorting analyses demonstrated that VCIP-RGD is exposed to the outside of the cell surface. Retroviral transduction of VCIP induced cell aggregation/cell- cell interactions, modestly increased p120 catenin expression and promoted activation of the Fak, Akt and GSK3beta protein kinases. Furthermore, expression of recombinant VCIP promoted adhesion, spreading and tyrosine phosphorylation of Fak, Shc, Cas and paxillin in endothelial cells. GST-VCIP-RGD, but not GST-VCIP-RGE, specifically interacted with a subset of integrins, and these interactions were effectively blocked by anti-alpha(v)beta(3) and anti-alpha(5)beta(1) integrin antibodies, and by PAP2b/VCIP-derived peptides. Interestingly, PAP2b/VCIP is expressed in close proximity to vascular endothelial growth factor, von Willebrand factor and alpha(v)beta(3) integrin in tumor vasculatures. These findings demonstrate an unexpected function of PAP2b/VCIP, and represent an important step towards understanding the molecular mechanisms by which PAP2b/VCIP-induced cell-cell interactions regulate specific intracellular signaling pathways.