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M Pravenec

Publications and source records attributed to M Pravenec.

At least 19 recordsLinked to original sources
PubMed2006

Fat-specific transgenic expression of resistin in the spontaneously hypertensive rat impairs fatty acid re-esterification.

OBJECTIVE: To investigate the mechanism by which fat-specific transgenic expression of resistin affects fatty acid metabolism in the spontaneously hypertensive rat (SHR). DESIGN: Basal- and adrenaline-stimulated lipolysis, basal- and insulin-stimulated lipogenesis as well as the site (glycerol versus acyl moiety) of glucose incorporated into triglycerides were determined in adipose tissue isolated from SHR-Resistin transgenic and SHR control rats. RESULTS: A moderate expression of transgenic resistin in adipose tissue was associated with significant increase in the FFA/glycerol ratio during adrenaline-stimulated lipolysis in the SHR-Resistin transgenic rats (3.27+/-0.26) compared to SHR controls (2.11+/-0.10, P=0.0005). Transgenic SHR also exhibited a significant decrease in FFA re-esterification in adipose tissue (approximately by 23%). CONCLUSION: These findings raise the possibility that the prodiabetic effects of transgenic resistin may be partly mediated by increased FFA release from adipose tissue due to impaired FFA re-esterification in adipocytes.

Adipocytes↗
PubMed2004

Genetic analysis of "metabolic syndrome" in the spontaneously hypertensive rat.

In the current review, we summarize results of genetic analyses of "metabolic syndrome" in the spontaneously hypertensive rat (SHR). These results include (1) linkage analyses in the HXB/BXH recombinant inbred (RI) strains derived from SHR and Brown Norway (BN-Lx) strains which revealed quantitative trait loci (QTL) for hemodynamic and metabolic traits on several chromosomes, (2) genetic isolation of these putative QTL within differential chromosome segments of SHR.BN congenic strains, (3) detailed mapping of these QTL within limited chromosome segments of SHR.BN congenic sublines, (4) sequencing of selected positional candidate genes which revealed important mutations in the Cd36 and Srebp1 SHR genes, (5) functional tests of these candidate genes in SHR transgenic lines, and (6) integrated gene expression profiling and linkage mapping in RI strains which will be used to identify co-regulated genes and to determine co-segregation of transcriptional profiles with physiological and pathophysiological phenotypes.

Animals↗
PubMed2003

Genetic isolation of quantitative trait loci for blood pressure development and renal mass on chromosome 5 in the spontaneously hypertensive rat.

Total genome scans of genetically segregating populations derived from spontaneously hypertensive rats (SHR) and other rat models of essential hypertension suggested a presence of quantitative trait loci (QTL) regulating blood pressure on multiple chromosomes, including chromosome 5. The objective of the current study was to test directly a hypothesis that chromosome 5 of the SHR carries a blood pressure regulatory QTL. A new congenic strain was derived by replacing a segment of chromosome 5 in the SHR/Ola between the D5Wox20 and D5Rat63 markers with the corresponding chromosome segment from the normotensive Brown Norway (BN/Crl) rat. Arterial pressures were directly monitored in conscious, unrestrained rats by radiotelemetry. The transfer of a segment of chromosome 5 from the BN strain onto the SHR genetic background was associated with a significant decrease of systolic blood pressure, that was accompanied by amelioration of renal hypertrophy. The heart rates were not significantly different in the SHR compared to SHR chromosome 5 congenic strain. The findings of the current study demonstrate that gene(s) with major effects on blood pressure and renal mass exist in the differential segment of chromosome 5 trapped within the new SHR.BN congenic strain.

Analysis of Variance↗
PubMed2003

Transgenic expression of CD36 in the spontaneously hypertensive rat is associated with amelioration of metabolic disturbances but has no effect on hypertension.

Spontaneously hypertensive rats (SHR/NIH strain) harbor a deletion variant in the Cd36 fatty acid transporter and display defective fatty acid metabolism, insulin resistance and hypertension. Transgenic rescue of Cd36 in SHR ameliorates insulin resistance and improves dyslipidemia. However, the role of Cd36 in blood pressure regulation remains controversial due to inconsistent blood pressure effects that were observed with transgenic expression of Cd36 on the SHR background. In the current studies, we developed two new SHR transgenic lines, which express wild type Cd36 under the control of the universal Ef-1 alpha promoter, and examined the effects of transgenic expression of wild type Cd36 on selected metabolic and cardiovascular phenotypes. Transgenic expression of Cd36 in the new lines was associated with significantly decreased serum fatty acids, amelioration of insulin resistance and glucose intolerance but failed to induce any consistent changes in blood pressure as measured by radiotelemetry. The current findings confirm the genetic association of defective Cd36 with disordered insulin action and fatty acid metabolism in the SHR/NIH strain and suggest that Cd36 is linked to other gene(s) on rat chromosome 4 that regulate blood pressure.

Adipose Tissue↗
PubMed2002

Chromosomal mapping of HCaRG, a novel hypertension-related, calcium-regulated gene.

We recently identified a novel gene that is negatively regulated by extracellular calcium concentration with higher levels of transcripts in hypertensive animals (SHR). We named this gene HCaRG (Hypertension-related, Calcium-Regulated Gene). In this work we report the chromosomal localization of the HCaRG gene among different species. We identified a BglII RFLP between BN.lx and SHR rats. We then analysed the strain distribution pattern of this RFLP in 31 RIS, originating from BN.lx and SHR rats, and compared it to the segregation of 475 markers localized in the rat genetic map. Hcarg localizes to the rat chromosome 7 between the markers Mit3 and Mit4. This region is homologous to human chromosome 8q21-24. We identified three clones in Genbank that contain the sequence of HCaRG. It was therefore possible to narrow down the localization of human HCaRG to chromosome 8q24.3. Furthermore, a suggestive localization of mouse Hcarg based on conservation of linkage between human and mouse is on chromosome 15. We previously identified a putative calcium-binding motif (EF-Hand) and a nuclear receptor-binding domain (LxxLL) in the rat sequence of the HCaRG protein. Sequence comparison between five different species showed that these domains are highly conserved. Furthermore, a search of ESTs in Genbank for homologous sequences showed that HCaRG is expressed only in eukaryotes, particularly in mammals.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Chromosome assignment of Cd36 transgenes in two rat SHR lines by FISH and linkage mapping of transgenic insert in the SHR-TG19 line.

The chromosome position of the Cd36 insert was determined by FISH in two rat transgenic lines (SHR/Ola-TgN(EF1aCd36)10Ipcv (SHR-TG10) and SHR/Ola-TgN(EF1aCd36)19Ipcv (SHR-TG19). The Cd36 transgene construct labelled with digoxigenin-11-dNTP was used as a probe in the FISH analysis. In accord with the previous finding that the SHR-TG10 harbours 6-8 copies of the transgene, the signals from both metaphase and interphase nuclei of SHR-TG10 preparations were rather strong and the probe hybridized to both copies of chromosome 1 at band q55. The probe hybridization to SHR-TG19 metaphase preparations also showed homozygosity of the transgene with localization of both copies to chromosome 11 at band q11. The signals were distinct but much weaker compared to the SHR-TG10, which again is in accord with the fact that the SHR-TG19 line harbours only a single copy of the transgene. In order to look for a possible impact of the insertion site neighbourhood upon the transgene phenotypic effect, we performed linkage mapping of the transgene in the SHR-TG19 line. By linkage mapping, the placement of the transgene to the proximal part of RNO11 was confirmed, the critical interval being 4 cM between D11Rat20 and D11Rat21, in good agreement with the RH map. Within the close neighbourhood of the inserted Cd36 transgene, there are several genes known to be expressed in kidney, and so the influence of some regulatory sequences enhancing kidney expression of the Cd36 transgene can be envisaged.

Animals↗
PubMed2001

Genetic and correlation analysis of hepatic copper content in the rat.

Thirty recombinant inbred (RI) strains derived from the spontaneous hypertensive rat (SHR/OlaIpcv) and the Brown Norway (BN-Lx/Cub) progenitors were used to search for quantitative trait loci (QTLs) that are responsible for differences in liver copper between these two strains. The heritability of liver copper concentration (expressed as microg/g liver wet wt and microg/g liver dry wt) and liver copper store (microg/whole liver) was estimated to be 57, 57, and 46%, respectively. In a total genome scan of the RI strains, involving over 600 genetic markers, suggestive association was found between liver copper store (microg/whole liver) and the D16Wox9 marker on chromosome 16 (lod score = 2.8), and between liver copper concentration (microg/g dry wt) and the D10Cebrp1016s2 marker on chromosome 10 (lod score = 3.0). These putative QTLs are responsible for nearly 34 and 40% of the additive genetic variability for liver copper store and concentration, respectively.

Animals↗
PubMed2001

Defective fatty acid uptake in the spontaneously hypertensive rat is a primary determinant of altered glucose metabolism, hyperinsulinemia, and myocardial hypertrophy.

Genetic linkage studies implicated deficiency of CD36, a membrane fatty acid (FA) transporter, in the hypertriglyceridemia and hyperinsulinemia of the spontaneously hypertensive rat (SHR). In this study we determined whether loss of CD36 function in FA uptake is a primary determinant of the SHR phenotype. In vivo, tissue distribution of iodinated, poorly oxidized beta-methyliodophenyl pentadecanoic acid (BMIPP) was examined 2 h after its intravenous injection. Fatty acid transport was also measured in vitro over 20 to 120 s in isolated adipocytes and cardiomyocytes obtained from SHR and from a congenic line (SHRchr4) that incorporates a piece of chromosome 4 containing wild-type CD36. SHR heart and adipose tissue exhibited defects in FA uptake and in conversion of diglycerides to triglycerides that are similar to those observed in the CD36 null mouse. However, a key difference in SHR tissues is that fatty acid oxidation is much more severely impaired than fatty acid esterification, which may underlie the 4-5-fold accumulation of free BMIPP measured in SHR muscle. Studies with isolated adipocytes and cardiomyocytes directly confirmed both the defect in FA transport and the fact that it is underestimated by BMIPP. Heart, oxidative muscle, and adipose tissue in the SHR exhibited a large increase in glucose uptake measured in vivo using [(18)F]fluorodeoxyglucose. Supplementation of the diet with short-chain fatty acids, which do not require CD36-facilitated transport, eliminated the increase in glucose uptake, the hyperinsulinemia, and the heart hypertrophy in the SHR. This indicated that lack of metabolic energy consequent to deficient FA uptake is the primary defect responsible for these abnormalities. Hypertension was not alleviated by the supplemented diet suggesting it is unrelated to fuel supply and any contribution of CD36 deficiency to this trait may be more complex to determine. It may be worth exploring whether short-chain FA supplementation can reverse some of the deleterious effects of CD36 deficiency in humans, which may include hypertrophic cardiomyopathy.

Adipose Tissue↗
PubMed2001

Identification of a mutation in ADD1/SREBP-1 in the spontaneously hypertensive rat.

It has recently been proposed that primary mutations in genes involved in fatty acid and lipid metabolism may contribute to the pathogenesis of insulin resistance and dyslipidemia often observed in spontaneous forms of hypertension. In the current study in the spontaneously hypertensive rat (SHR), we mapped and sequenced the gene encoding a key transcription factor known as ADD1 (adipocyte determination and differentiation factor 1) or SREBP-1c (sterol regulatory element binding protein- c) that has recently been identified as a master regulator of genes involved in the hepatic control of lipid and carbohydrate metabolism. We found that (1) the gene for ADD1/SREBP-1c maps to a region of rat Chromosome 10 previously reported to contain a quantitative trait locus involved in the regulation of hepatic cholesterol levels and (2) the SHR harbors a valine-to-methionine substitution in the COOH terminal portion of the ADD1/SREBP-1 protein that is not present in 44 other strains of laboratory rats. These findings, together with previous studies showing that transgenic expression of SREBP-1 isoforms has major effects on hepatic fatty acid and cholesterol biosynthesis, suggest that naturally occurring variation in the gene encoding the SREBP-1 isoforms might contribute to inherited variation in lipid metabolism in the SHR versus other strains of rats. These results should serve to motivate future transfection studies of the effect of the SHR mutant on SREBP-1 expression and activation in vitro, as well as the development of congenic and transgenic strains of SHR to investigate the effects of different variants of SREBP-1 on carbohydrate and lipid metabolism in vivo.

Amino Acid Sequence↗
PubMed2001

Transgenic rescue of defective Cd36 ameliorates insulin resistance in spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) display several features of the human insulin-resistance syndromes. Cd36 deficiency is genetically linked to insulin resistance in SHR. We show that transgenic expression of Cd36 in SHR ameliorates insulin resistance and lowers serum fatty acids. Our results provide direct evidence that Cd36 deficiency can promote defective insulin action and disordered fatty-acid metabolism in spontaneous hypertension.

Animals↗
PubMed2001

Genetic isolation of a blood pressure quantitative trait locus on chromosome 2 in the spontaneously hypertensive rat.

OBJECTIVES: Total genome scans of genetically segregating populations derived from the spontaneously hypertensive rat (SHR) and other rat models of hypertension have suggested the presence of quantitative trait loci (QTL) regulating blood pressure and cardiac mass on multiple chromosomes, including chromosome 2. The objective of the current study was to directly test for the presence of a blood pressure QTL on rat chromosome 2. DESIGN: A new congenic strain was derived by replacing a segment of chromosome 2 in the SHR between D2Rat171 and D2Arb24 with the corresponding chromosome segment from the normotensive Brown Norway rat. Arterial pressures were directly monitored in conscious rats by radiotelemetry. RESULTS: We found that the SHR congenic strain (SHR-2) carrying a segment of chromosome 2 from the Brown Norway rat had significantly lower systolic and diastolic blood pressures than the SHR progenitor strain. The attenuation of hypertension in the SHR-2 congenic strain versus the SHR progenitor strain was accompanied by significant amelioration of cardiac hypertrophy. CONCLUSIONS: These findings demonstrate that gene(s) with major effects on blood pressure exist in the differential segment of chromosome 2 trapped within the new SHR.BN congenic strain.

Animals↗
PubMed2001

Workshop: excess growth and apoptosis: is hypertension a case of accelerated aging of cardiovascular cells?

Several groups including ours have demonstrated cardiac hyperplasia in neonates from genetically hypertensive rat strains. We have shown that similar problems exist in the kidney as well. More recently, we found that excessive heart and kidney weight is neonatally related to inhibition of apoptosis. Using recombinant inbred strains derived from a reciprocal cross between Brown Norway and spontaneously hypertensive rat progenitor strains, we mapped the inhibition of neonatal apoptosis to 2 distinct loci on chromosomes 1 (Myl 2) and 18 (Abrb 2). Positional candidate genes at these loci are being explored. These studies have also demonstrated that the loci determining kidney and heart weights in neonates are distinct from those determining increased organ weight in adults. The impact of blood pressure per se is also divergent because adult kidney weight is negatively correlated whereas heart weight is positively correlated with it. Analyses by extremes of low and high percentiles from fetal life to adulthood identified a single locus determining heart weight at Acaa on chromosome 8 in newborn (P=0.0003) and adult (P=0.016) rats. The Acaa region contains a DNA mismatch repair gene (hMLH1). The kinetics of neonatal growth through adulthood by prelabeling DNA with [(3)H]thymidine in pregnant mares showed that although the growth process is complex and nonlinear in the kidney of hypertensive rats, there is an increased turnover of cells, that is, reduced half-life of DNA. This observation is supported by the presence of shorter telomere fragments in kidneys of spontaneously hypertensive rats. These studies suggest that cardiovascular cells from hypertensive animals are subject to accelerated turnover, potentially leading to their accelerated aging.

Animals↗
PubMed2001

Y-chromosome transfer induces changes in blood pressure and blood lipids in SHR.

Previous studies with chromosome-Y consomic strains of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats suggest that a quantitative trait locus for blood pressure regulation exists on chromosome Y. To test this hypothesis in the SHR-Brown Norway (BN) model and to study the effects of chromosome Y on lipid and carbohydrate metabolism, we produced a new consomic strain of SHR carrying the Y chromosome transferred from the BN rat. We found that replacing the SHR Y chromosome with the BN Y chromosome resulted in significant decreases in systolic and diastolic blood pressures in the SHR.BN-Y consomic strain (P<0.05). To elicit possible dietary-induced variation in lipid and glucose metabolism between the SHR progenitor and chromosome-Y consomic strains, we fed rats a high-fructose diet for 15 days in addition to the normal diet. On the high-fructose diet, the SHR.BN-Y consomic rats exhibited significantly increased levels of serum triglycerides and decreased levels of serum HDL cholesterol versus the SHR progenitor rats. Glucose tolerance and insulin/glucose ratios, however, were similar in both strains on both normal and high-fructose diets. These findings provide direct evidence that a gene or genes on chromosome Y contribute to the pathogenesis of spontaneous hypertension in the SHR-BN model. These results also indicate that transfer of the Y chromosome from the BN rat onto the SHR background exacerbates dietary-induced dyslipidemia in SHR. Thus, genetic variation in genes on the Y chromosome may contribute to variation in blood pressure and lipid levels and may influence the risk for cardiovascular disease.

Animals↗
PubMed2000

Mapping of quantitative trait loci (QTL) of differential stress gene expression in rat recombinant inbred strains.

OBJECTIVE: Stress has been shown to be a major environmental contributor to cardiovascular diseases through its effects on blood pressure variability and cardiac function. The cellular stress response is characterized by the expression of specific heat stress genes (hsps), under the transcriptional control of heat shock transcription factors (HSTFs). The levels of hsp mRNA depend on the severity of the stress, with hstf1 acting as a stress sensor. The aim of this work was to evaluate the genetic contribution of the variability in hsp expression, and to identify its putative quantitative trait loci (QTL). METHODS: Twenty recombinant inbred rat strains (RIS) were studied. The animals underwent a standardized, identical 1 h immobilization stress in restraint cages, followed by 1 h of rest before sacrifice. Total RNA was extracted from the heart kidneys and adrenals, and the mRNA levels of hsp27, hsp70, hsp84, hsp86 and hsp105 were measured. The strain distribution pattern (SDP) of hsp expression was correlated with that of 475 polymorphic markers distributed throughout the RIS genome. A polymorphism of rat hstf1 in RIS was used for its mapping in RIS. RESULTS: Despite an identical stress being applied to all strains, hsp expression showed up to a 1 2-fold gradient with little intra-strain variability, indicative of a strong genetic contribution to the trait Heritability ranged from 50 to 77% for most hsp genes in the three target organs. The continuous SDP of stress gene expression indicated the polygenic nature of the trait A common locus on chromosome 7 (at D7Cebrp187s3 marker) was consistently associated with all hsp expression in most of the organs [with a likelihood of odds (LOD) score of 3.0 for hsp27 expression]. We have mapped rat hstf1 on chromosome 7 at the same locus. Finally, the D4Mit19 marker was significantly associated with hsp84 expression in the heart (LOD score of 3.1). CONCLUSION: Two loci were linked with the differential expression of HSPs in response to immobilization stress in target organs of RIS. The chromosome 7 locus unveiled for all HSPs could explain up to 42% of the observed inter-strain variability of hsp levels in response to stress. We propose hstf1 as a positional candidate at this locus.

Adrenal Glands↗
PubMed2000

Genetic analysis of rat chromosome 1 and the Sa gene in spontaneous hypertension.

Linkage studies in segregating populations derived from the spontaneously hypertensive rat (SHR) indicate that a blood pressure quantitative trait locus exists on rat chromosome 1 in the vicinity of the Sa gene. On the basis of these findings and the observation of increased renal expression of the Sa gene in SHR versus normotensive rats, the Sa gene has been proposed as a candidate gene for spontaneous hypertension. In SHR congenic strains, we and others have found that replacement of a segment of SHR chromosome 1 that contains the Sa gene with the corresponding chromosome segment from a normotensive Brown Norway (BN) rat or Wistar-Kyoto rat can reduce blood pressure. To test whether the Sa gene is necessary for the effect of this region of chromosome 1 on blood pressure, we studied a new SHR congenic subline that harbors a smaller segment of BN chromosome 1 that does not include the Sa gene. Transfer of this subregion of chromosome 1 from the BN rat onto the SHR background was associated with significant reductions in blood pressure comparable to those previously observed on transfer of a larger region of chromosome 1 that included the Sa gene. Thus, in the SHR-BN model of hypertension, the results of these mapping studies (1) demonstrate that molecular variation in the Sa gene is not required for the effect of this region of chromosome 1 on blood pressure and (2) should direct attention toward other candidate genes within the differential chromosome segment of the new congenic subline.

Alleles↗
PubMed2000

Contribution of autosomal loci and the Y chromosome to the stress response in rats.

Stress is a critical contributor to cardiovascular diseases through its impact on blood pressure variability and cardiac function. Familial clustering of reactivity to stress has been demonstrated in human subjects, and some rodent models of hypertension are hyperresponsive to stress. Therefore, the present study was designed to uncover the genetic determinants of the stress response. We performed a total genome linkage search to identify the loci of the body temperature response to immobilization stress in a set of recombinant inbred strains (RIS) originating from reciprocal crosses of spontaneously hypertensive rats (SHR) with a normotensive Brown Norway Lx strain. Two quantitative trait loci (QTLs) were revealed on chromosomes (Chrs) 10 and 12 (logarithm of odds scores, 2.2 and 1. 3, respectively). The effects of these QTLs were enhanced by a high sodium diet (logarithm of odds scores, 4.0 and 3.3 for Chrs 10 and 12, respectively), which is suggestive of a salt-sensitive component for the phenotype. Congenics for Chr 10 confirmed both the QTL and the salt effect in RIS. Negatively associated loci were also identified on Chrs 8 and 11. Interaction between the loci of Chrs 10 and 12 was demonstrated, with the rat strains bearing SHR alleles at both loci having the highest thermal response to stress. Furthermore, the Y Chr of SHR origin enhanced the response to immobilization stress, as demonstrated in 2 independent models, RIS and Y Chr consomics. However, its full effect requires autosomes of the SHR strain. These findings provide the first evidence for the genetic determination of reactivity to stress with interactions between autosomal loci and between the Y and autosomal Chrs that contribute to the explanation of the 46% of variance in the stress response.

Animals↗
PubMed2000

SHR.BN-congenic strains for genetic analysis of multifactorially determined traits.

The laboratory rat is an important laboratory animal with multiple well-defined inbred strains, including some of the most widely used animal models of human diseases. Recent advances in the development of rat genetic resources will enable the exploitation of the full potential of rat models of human diseases and, in addition, the rat can provide useful information for comparative genomics of humans and mice. In the current review, we describe the development of congenics strains by introgression of differential chromosome segments from the Brown Norway (BN) rat to the genetic background of the spontaneously hypertensive rat (SHR). These SHR.BN-congenic strains and recombinant sublines derived from them were developed as a model system for genetic analysis of multifactorially determined pathophysiological and morphological conditions.

Animals↗