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BACKGROUND The spontaneously hypertensive rat (SHR) is the most widely used model of essential hypertension and is susceptible to left ventricular hypertrophy (LVH) and myocardial fibrosis. Recently, a quantitative trait locus (QTL) that influences heart interstitial fibrosis was mapped to chromosome 8. Our aim was to dissect the genetic basis of this QTL(s) predisposing SHR to hypertension, LVH, and interstitial fibrosis. METHODS Hemodynamic and histomorphometric analyses were performed in genetically defined SHR.PD-chr.8 minimal congenic strain (PD5 subline) rats. RESULTS The differential segment, genetically isolated within the PD5 subline, spans 788kb and contains 7 genes, including the promyelocytic leukemia zinc finger (Plzf) gene that has been implicated in hypertrophy and cardiac fibrosis. Mutant Plzf allele contains a 2,964-bp deletion in intron 2. The PD5 congenic strain, when compared with the SHR, showed significantly reduced systolic blood pressure by approximately 15mm Hg (P = 0.002), amelioration of LVH (0.23±0.02 vs. 0.39±0.02g/100g body weight; P < 0.00001), and reduced interstitial fibrosis (17,478±1,035 vs. 41,530±3,499 μm(2); P < 0.0001). The extent of amelioration of LVH and interstitial fibrosis was disproportionate to blood pressure decrease in congenic rats, suggesting an important role for genetic factors. Cardiac expression of Plzf was significantly reduced in prehypertensive (8 and 21 days) congenic animals compared with controls. CONCLUSIONS These results provide compelling evidence of a significant role for genetic factors in regulating blood pressure, LVH, and cardiac fibrosis and identify mutant Plzf as a prominent candidate gene.

BackgroundThe role of folate deficiency and associated hyperhomocysteinemia in the pathogenesis of metabolic syndrome is not fully established. In the current study, we analyzed the role of folate deficiency in pathogenesis of the metabolic syndrome in the spontaneously hypertensive rat (SHR).MethodsMetabolic and hemodynamic traits were assessed in SHR/Ola rats fed either folate-deficient or control diet for 4 weeks starting at the age of 3 months.ResultsCompared to SHRs fed a folate-replete diet, SHRs fed a folate-deficient diet showed significantly reduced serum folate (104 ± 5 vs. 11 ± 1 nmol/L, P < 0.0005) and urinary folate excretion (4.3 ± 0.6 vs. 1.2 ± 0.1 nmol/16 h, P < 0.0005) together with a near 3-fold increase in plasma total homocysteine concentration (4.5 ± 0.1 vs 13.1 ± 0.7 μmol/L, P < 0.0005), ectopic fat accumulation in liver, and impaired glucose tolerance. Folate deficiency also increased systolic blood pressure by approximately 15 mm Hg (P < 0.01). In addition, the low-folate diet was accompanied by significantly reduced activity of antioxidant enzymes and increased concentrations of lipoperoxidation products in liver, renal cortex, and heart.ConclusionsThese findings demonstrate that the SHR model is susceptible to the adverse metabolic and hemodynamic effects of low dietary intake of folate. The results are consistent with the hypothesis that folate deficiency can promote oxidative stress and multiple features of the metabolic syndrome that are associated with increased risk for diabetes and cardiovascular disease.

Background The angiotensin receptor blocker telmisartan has unique chemical properties that enable it to partially activate the peroxisome proliferator activated receptor gamma (PPARG) as well as block angiotensin II type 1 receptors. Methods To directly test whether some of the metabolic effects of telmisartan require the presence of PPARG, we studied mice in which the gene (Pparg) for PPARG had been deleted in fat or in muscle. Results We found that knockout of Pparg in fat tissue greatly impaired the ability of telmisartan to increase adiponectin levels and to enhance sensitivity to insulin-stimulated glucose incorporation into adipose tissue lipids. In contrast, muscle-specific Pparg knockout had relatively little or no impact on the ability of telmisartan to increase adiponectin levels or affect glucose metabolism either in fat or muscle. These findings provide compelling evidence that the ability of telmisartan to increase adiponectin levels and stimulate glucose use in adipose tissue may depend on the presence of PPARG in fat. Conclusions We conclude that PPARG in adipose tissue is required for at least several of the metabolic actions of telmisartan.