Effects of PPARalpha, gamma and delta haplotypes on plasma levels of lipids, severity and progression of coronary atherosclerosis and response to statin therapy in the lipoprotein coronary atherosclerosis study.

Peroxisome proliferator-activated receptors (PPARs) alpha, delta and gamma are nuclear transcription factors that regulate fatty acid biosynthesis. Our objectives were to determine the effects of PPAR haplotypes on biochemical, angiographic, clinical phenotypes and their responses to treatment with fluvastatin. We genotyped 372 Lipoprotein and Coronary Atherosclerosis Study subjects for seven single nucleotide polymorphisms (SNPs) in PPARalpha (-35 089A>C, 484C>G), delta (-4401C>T, 294T>C) and gamma (34C>G, 25 506C>T, 161C>T) by restriction mapping or 5' exonuclease assay. We reconstructed and estimated haplotypes frequencies using four algorithms. Linkage disequilibrium (LD) was calculated by D' and haplotype effects by permutation and regression analyses. The PPARD and PPARG SNPs were in LD. The baseline plasma triglyceride levels and their responses to treatment with fluvastatin were associated with PPARD haplotypes (P = 0.01). Triglyceride levels were lowest and highest in homozygotes with diplotypes 3 and 4 (130.1 +/- 40.8 and 194.2 +/- 44.6 mg/dl, P < 0.001), respectively. PPARD haplotype 3 was also an independent determinant of plasma apolipoprotein (apo)B (P = 0.021) and apoC-III (P = 0.001) levels, mean number of coronary lesions (P = 0.046) and changes in triglyceride (P = 0.01) and apoC-III (P = 0.047) levels in response to fluvastatin. Plasma triglyceride levels (P = 0.044), the mean number of coronary lesions (P = 0.026) and changes in minimum lumen diameter in response to fluvastatin (P = 0.022) were also associated with PPARG haplotypes. No significant associations between PPARA haplotypes and the phenotypes or significant interactions between PPAR haplotypes and the occurrence of new clinical events were detected. PPARD and PPARG haplotypes are independent determinants of plasma levels of lipids, severity of coronary atherosclerosis and its response to therapy.

Evolution of expression of cardiac phenotypes over a 4-year period in the beta-myosin heavy chain-Q403 transgenic rabbit model of human hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM), the most common cause of sudden cardiac death in the young, is characterized by a diverse array of cardiac phenotypes evolving over several decades. We have developed transgenic rabbits that fully recapitulate the phenotype of human HCM and provide for the opportunity to delineate the sequence of evolution of cardiac phenotypes, and thus, the pathogenesis of HCM. We determined evolution of biochemical, molecular, histological, structural and functional phenotypes at 4 age-periods in 47 beta-myosin heavy chain-glutamine (MyHC-Q)-403 transgenic rabbits. Ca(+2) sensitivity of myofibrillar ATPase activity was reduced very early and in the absence of other discernible phenotypes. Myocyte disarray also occurred early, prior to, and independent of hypertrophy and fibrosis. The latter phenotypes evolved predominantly during puberty in conjunction with activation of stress-related signaling kinases. Myocardial contraction and relaxation velocities were decreased early despite normal global cardiac function and in the absence of histological phenotype. Global cardiac function declined with aging, while left atrial size was increased along with Doppler indices of left ventricular filling pressure. Thus, Ca(+2) sensitivity of myofibrillar ATPase activity is a primary phenotype expressed early and independent of the ensuing phenotypes. Pathogenesis of myocyte disarray, which exhibits age-independent penetrance, differs from those of hypertrophy and fibrosis, which show age-dependent expression. Myocardial dysfunction is an early marker that predicts subsequent development of hypertrophy. These findings in an animal model that recapitulates the phenotype of human HCM, implicate involvement of multiple independent mechanisms in the pathogenesis of cardiac phenotypes in HCM.

Aldosterone, through novel signaling proteins, is a fundamental molecular bridge between the genetic defect and the cardiac phenotype of hypertrophic cardiomyopathy.

BACKGROUND: Human hypertrophic cardiomyopathy (HCM), the most common cause of sudden cardiac death in the young, is characterized by cardiac hypertrophy, myocyte disarray, and interstitial fibrosis. The genetic basis of HCM is largely known; however, the molecular mediators of cardiac phenotypes are unknown. METHODS AND RESULTS: We show myocardial aldosterone and aldosterone synthase mRNA levels were elevated by 4- to 6-fold in humans with HCM, whereas cAMP levels were normal. Aldosterone provoked expression of hypertrophic markers (NPPA, NPPB, and ACTA1) in rat cardiac myocytes by phosphorylation of protein kinase D (PKD) and expression of collagens (COL1A1, COL1A2, and COL3A1) and transforming growth factor-beta1 in rat cardiac fibroblasts by upregulation of phosphoinositide 3-kinase (PI3K)-p100delta. Inhibition of PKD and PI3K-p110delta abrogated the hypertrophic and profibrotic effects, respectively, as did the mineralocorticoid receptor (MR) antagonist spironolactone. Spironolactone reversed interstitial fibrosis, attenuated myocyte disarray by 50%, and improved diastolic function in the cardiac troponin T (cTnT)-Q92 transgenic mouse model of human HCM. Myocyte disarray was associated with increased levels of phosphorylated beta-catenin (serine 38) and reduced beta-catenin-N-cadherin complexing in the heart of cTnT-Q92 mice. Concordantly, distribution of N-cadherin, predominantly localized to cell membrane in normal myocardium, was diffuse in disarrayed myocardium. Spironolactone restored beta-catenin-N-cadherin complexing and cellular distribution of N-cadherin and reduced myocyte disarray in 2 independent randomized studies. CONCLUSIONS: The results implicate aldosterone as a major link between sarcomeric mutations and cardiac phenotype in HCM and, if confirmed in additional models, signal the need for clinical studies to determine the potential beneficial effects of MR blockade in human HCM.