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M Pravenec

Publications and source records attributed to M Pravenec.

At least 37 records · Page 2Linked to original sources
PubMed2000

Genetic analysis of cardiovascular risk factor clustering in spontaneous hypertension.

The SHR is the most widely studied animal model of hypertension. In this strain, as in many humans with essential hypertension, increased blood pressure has been reported to cluster with other risk factors for cardiovascular disease, including insulin resistance and dyslipidemia. However, the genetic mechanisms that mediate this clustering of risk factors for cardiovascular disease or the hypertension "metabolic syndrome" remain poorly understood. In the current studies, we have demonstrated (1) that a gene or genes responsible for a whole spectrum of cardiovascular risk factors mapped to a limited segment of the centromeric region of rat chromosome 4, (2) that a spontaneous deletion in the gene for Cd36 that encodes a fatty acid transporter and is located directly at the peak of QTL linkages on chromosome 4 has been indirectly linked to the transmission of insulin resistance, defective fatty acid metabolism, and increased blood pressure, and (3) based on complementation analysis in two transgenic lines expressing wild-type Cd36 on the genetic background of the SHR strain harboring the deletion variant of Cd36, we have established that defective Cd36 can be a determinant of disordered fatty acid metabolism, glucose intolerance, and insulin resistance in spontaneous hypertension.

Animals↗
PubMed1999

Identification of Cd36 (Fat) as an insulin-resistance gene causing defective fatty acid and glucose metabolism in hypertensive rats.

The human insulin-resistance syndromes, type 2 diabetes, obesity, combined hyperlipidaemia and essential hypertension, are complex disorders whose genetic basis is unknown. The spontaneously hypertensive rat (SHR) is insulin resistant and a model of these human syndromes. Quantitative trait loci (QTLs) for SHR defects in glucose and fatty acid metabolism, hypertriglyceridaemia and hypertension map to a single locus on rat chromosome 4. Here we combine use of cDNA microarrays, congenic mapping and radiation hybrid (RH) mapping to identify a defective SHR gene, Cd36 (also known as Fat, as it encodes fatty acid translocase), at the peak of linkage to these QTLs. SHR Cd36 cDNA contains multiple sequence variants, caused by unequal genomic recombination of a duplicated ancestral gene. The encoded protein product is undetectable in SHR adipocyte plasma membrane. Transgenic mice overexpressing Cd36 have reduced blood lipids. We conclude that Cd36 deficiency underlies insulin resistance, defective fatty acid metabolism and hypertriglyceridaemia in SHR and may be important in the pathogenesis of human insulin-resistance syndromes.

Animals↗
PubMed1999

Effect of chromosome 19 transfer on blood pressure in the spontaneously hypertensive rat.

Linkage studies in the spontaneously hypertensive rat (SHR) have suggested that a gene or genes regulating blood pressure may exist on rat chromosome 19 in the vicinity of the angiotensinogen gene. To test this hypothesis, we measured blood pressure in SHR progenitor and congenic strains that are genetically identical except for a segment of chromosome 19 containing the angiotensinogen gene transferred from the normotensive Brown Norway (BN) strain. Transfer of this segment of chromosome 19 from the BN strain onto the genetic background of the SHR induced significant decreases in systolic and diastolic blood pressures in the recipient SHR chromosome 19 congenic strain. To test for differences in angiotensinogen gene expression between the congenic and progenitor strains, we measured angiotensinogen mRNA levels in a variety of tissues, including aorta, brain, kidney, and liver. We found no differences between the progenitor and congenic strains in the angiotensinogen coding sequence or in angiotensinogen expression that would account for the blood pressure differences between the strains. In addition, no significant differences in plasma levels of angiotensinogen or plasma renin activity were detected between the 2 strains. Thus, transfer of a segment of chromosome 19 containing angiotensinogen from the BN rat into the SHR induces a decrease in blood pressure without inducing any major changes in plasma angiotensinogen levels or plasma renin activity. These results indicate that the differential chromosome segment trapped in the SHR chromosome 19 congenic strain contains a quantitative trait locus that influences blood pressure in the SHR but that this blood pressure effect is not explained by differences in plasma angiotensinogen levels or angiotensinogen expression.

Angiotensinogen↗
PubMed1999

Genetic isolation of a chromosome 1 region affecting susceptibility to hypertension-induced renal damage in the spontaneously hypertensive rat.

Linkage studies in the fawn-hooded hypertensive rat have suggested that genes influencing susceptibility to hypertension-associated renal failure may exist on rat chromosome 1q. To investigate this possibility in a widely used model of hypertension, the spontaneously hypertensive rat (SHR), we compared susceptibility to hypertension-induced renal damage between an SHR progenitor strain and an SHR congenic strain that is genetically identical except for a defined region of chromosome 1q. Backcross breeding with selection for the markers D1Mit3 and Igf2 on chromosome 1 was used to create the congenic strain (designated SHR.BN-D1Mit3/Igf2) that carries a 22 cM segment of chromosome 1 transferred from the normotensive Brown Norway rat onto the SHR background. Systolic blood pressure (by radiotelemetry) and urine protein excretion were measured in the SHR progenitor and congenic strains before and after the induction of accelerated hypertension by administration of DOCA-salt. At the same level of DOCA-salt hypertension, the SHR.BN-D1Mit3/Igf2 congenic strain showed significantly greater proteinuria and histologically assessed renal vascular and glomerular injury than the SHR progenitor strain. These findings demonstrate that a gene or genes that influence susceptibility to hypertension-induced renal damage have been trapped in the differential chromosome segment of the SHR.BN-D1Mit3/Igf2 congenic strain. This congenic strain represents an important new model for the fine mapping of gene(s) on chromosome 1 that affect susceptibility to hypertension-induced renal injury in the rat.

Animals↗
PubMed1999

Genetics of Cd36 and the clustering of multiple cardiovascular risk factors in spontaneous hypertension.

Disorders of carbohydrate and lipid metabolism have been reported to cluster in patients with essential hypertension and in spontaneously hypertensive rats (SHRs). A deletion in the Cd36 gene on chromosome 4 has recently been implicated in defective carbohydrate and lipid metabolism in isolated adipocytes from SHRs. However, the role of Cd36 and chromosome 4 in the control of blood pressure and systemic cardiovascular risk factors in SHRs is unknown. In the SHR. BN-Il6/Npy congenic strain, we have found that transfer of a segment of chromosome 4 (including Cd36) from the Brown Norway (BN) rat onto the SHR background induces reductions in blood pressure and ameliorates dietary-induced glucose intolerance, hyperinsulinemia, and hypertriglyceridemia. These results demonstrate that a single chromosome region can influence a broad spectrum of cardiovascular risk factors involved in the hypertension metabolic syndrome. However, analysis of Cd36 genotypes in the SHR and stroke-prone SHR strains indicates that the deletion variant of Cd36 was not critical to the initial selection for hypertension in the SHR model. Thus, the ability of chromosome 4 to influence multiple cardiovascular risk factors, including hypertension, may depend on linkage of Cd36 to other genes trapped within the differential segment of the SHR. BN-Il6/Npy strain.

Animals↗
PubMed1999

Mapping of quantitative trait loci for seminal vesicle mass and litter size to rat chromosome 8.

The spontaneously hypertensive rat (SHR) and the Brown Norway (BN) rat differ significantly in litter size (7.6 versus 4.5 pups). In the HXB and BXH sets of recombinant inbred (RI) strains derived from SHR and BN rats, heritability of litter size and of selected male reproductive parameters such as sperm production, sperm count, sperm morphology and motility, and the mass of the testis, epididymides, and seminal vesicles were estimated and a search was undertaken for quantitative trait loci (QTL) associated with these phenotypes. The mass of seminal vesicles was significantly associated with a QTL near the D8Cebr204S21 marker on chromosome 8 (LOD score = 4.1, P = 0.00001); this QTL was responsible for 46% of the genetic variability of the trait. The same gene marker on chromosome 8 also showed a suggestive association with the litter size. Litter size was significantly correlated with the mass of seminal vesicles (r = 0.58, P = 0.003). These findings indicate that the variability in litter size among RI strains may be due in part to differences in the mass of seminal vesicles and it is possible that both mass of seminal vesicles and litter size are determined by a pleiotropic effect of the same QTL on rat chromosome 8.

Animals↗
PubMed1999

HXB/Ipcv and BXH/Cub recombinant inbred strains of the rat: strain distribution patterns of 632 alleles.

The HXB/Ipcv and BXH/Cub sets of recombinant inbred (RI) strains were derived from the spontaneously hypertensive rats (SHR/OlaIpcv) and normotensive Brown Norway (BN-Lx/Cub) rats. The RI strains were produced as a model system for genetic and correlation analysis of spontaneous hypertension and other risk factors of cardiovascular disease such as insulin resistance and dyslipidemia. The RI strains were phenotyped in multiple hemodynamic and metabolic traits. In the current study, we describe strain distribution patterns of 632 genetic markers.

Alleles↗
PubMed1999

Genetic analysis of the rat hypodactylous mutation.

Autosomal recessive rat hypodactylous mutation Hd leads in homozygous condition to reductive changes of the digital arch of all feet. There is a variable preaxial reduction of the number of fingers in both sexes. Moreover, homozygous males are sterile. Testes of homozygous Hd/Hd and +/Hd adult rats were examined in the light and electron microscopes. Spatial organization of stages of the spermatogenetic cycle was not confirmed in Hd/Hd testes comparing with +/Hd males. Significant decrease in the number of germ cells in seminiferous tubules of Hd/Hd testes was accompanied with loosening and vacuolization of the seminiferous epithelium. The assignment of the Hd locus to RNO10 excluded the suspected homology between rat and mouse Hd mutations. More precise mapping using microsatellite markers revealed close linkage of the Hd locus with the D1OMit8 marker defining Syb2 gene coding for synaptobrevin 2. A chromosomal segment of RNO10 carrying Hd and Syb genes is being incrossed onto BN and SHR inbred strains in order to examine the modifying influences of different genetic backgrounds.

Abnormalities, Multiple↗
PubMed1999

Endotoxin response in spontaneously hypertensive rats: a role of the TNFalpha-gene region.

We have shown previously that administration of endotoxin induces a smaller decrease of body temperature in spontaneously hypertensive rats (SHR) than in normotensive Brown Norway (BN) rats. Several studies have suggested that tumor necrosis factor alpha (TNFalpha) is one of the mediators of the body-temperature response to endotoxin. To test whether the TNFalpha gene could be involved in determination of the observed difference in the body-temperature response to endotoxin, we studied SHR (n = 6) and a congenic strain, SHR.1N (n = 5), which differs from SHR by a segment of chromosome 20 originating from BN and containing the TNFalpha gene. Body temperature was recorded continuously by means of radiotelemetry. We showed that, in both strains, an intraperitoneal injection of endotoxin (500 microg/kg of body weight) induces a rapid hyperthermic phase (20-40 minutes post-injection), which is followed, first, by a hypothermic phase (100-120 minutes post-injection) and, then, by a late hyperthermic phase (seven hours). Although both strains demonstrated a similar trend in the response, a significant difference was observed between the two response curves (P = 0.0001). Further analysis at each time point revealed that the two strains differed significantly at a peak of the hypothermic phase (P = 0.035) and the late hyperthermic phase (P = 0.035). In conclusion, these data indicate that the differential chromosomal segment of SHR.1N contains a gene(s) causally related to the body-temperature response to endotoxin. In the light of previously published data, the TNFalpha gene appears to be the most likely candidate gene within the segment.

Animals↗
PubMed1999

Hematocrit and hemoglobin values are negatively correlated with insulin resistance in spontaneous hypertension.

It has been recently reported that increased hematocrit and hemoglobin values often accompany insulin resistance and compensatory hyperinsulinemia in humans. In the current study, we analyzed the relationship between hematocrit/hemoglobin on the one hand and insulin resistance, dyslipidemia, and hypertension on the other hand in HXB/BXH recombinant inbred (RI) strains derived from the spontaneously hypertensive rat (SHR) and the Brown Norway (BN) rat. The SHR progenitor strain had a significantly increased hematocrit values and it was also hypertensive and insulin-resistant when compared with the BN progenitor. The distribution of hematocrit and hemoglobin values among RI strains was continuous, suggesting a polygenic mode of inheritance. Analysis of RI strains revealed that hemoglobin was negatively correlated with insulin and insulin/glucose ratio, and that hematocrit was negatively correlated with insulin-stimulated glucose uptake in isolated adipocytes. There was no relationship between hematological parameters and blood pressure or lipid phenotypes in RI strains. The findings of the current study suggest that hematocrit and hemoglobin values might be added to the clustering variables related to the insulin resistance syndrome in the SHR strain.

Animals↗
PubMed1998

Quantitative trait loci for compensatory renal hypertrophy in the mouse.

Reduction in numbers of nephrons or decrease in kidney function due to a variety of diseases results in compensatory renal hypertrophy (CRH). Recently, it has been proposed that CRH may be a prerequisite for progression of renal injury; genetic dissection of CRH may be therefore helpful in understanding the process whereby people with partial renal insufficiency progress to end-stage renal disease. Since genetic analysis of CRH in humans is quite limited, we searched for genetic determinants of CRH after unilateral nephrectomy using a total genome scan of the mouse BXD recombinant inbred strains. We demonstrated that CRH is a highly heritable trait and we identified a quantitative trait locus on mouse chromosome 11 near the D11Mit14 marker that exerts a major effect on CRH (lod score = 3.4) and is responsible for approximately 52% of genetic variation in CRH. This marker maps near Ace, Gh, and Ngfr positional candidate genes.

Animals↗
PubMed1998

A genetic and correlation analysis of liver cholesterol concentration in rat recombinant inbred strains fed a high cholesterol diet.

Liver cholesterol concentration in rats fed a high cholesterol diet, is under genetic control which is supported by significant differences observed among inbred strains. For instance, the Brown Norway (BN-Lx/Cub) rat developed a twofold higher liver cholesterol concentration than the spontaneously hypertensive rat (SHR/Ola). In the current study, we used 30 recombinant inbred (RI) strains, derived from BN-Lx and SHR progenitors, to locate quantitative trait loci (QTL) that are responsible for differences in liver cholesterol concentrations between the BN-Lx and SHR strains. The heritability of liver cholesterol was estimated to be 0.55 and a significant association was detected between concentration of liver cholesterol and the D10Cebrp1016s2 marker on chromosome 10 (lod score = 3.3); this putative QTL was responsible for nearly 64% of additive genetic variability and thus represents a major genetic determinant of liver cholesterol concentration. Liver cholesterol concentrations significantly correlated with intermediate density lipoprotein (IDL) cholesterol levels.

Animals↗
PubMed1998

Genetic dissection of testicular weight in the mouse with the BXD recombinant inbred strains.

Testicular weights were studied in the mouse BXD recombinant inbred (RI) strains. These strains were derived from DBA/2J and C57BL/6J progenitors that differ significantly in their testicular weights (0.224 g +/- 0.015 vs. 0.161 g +/- 0.03, P < 0.0001). The heritability of testicular weights was calculated to be 0.53, and the minimum number of responsible effective factors was estimated to be 5.7. The total genome scanning of the BXD RI strains with over 1000 markers revealed a quantitative trait locus (QTL) on mouse Chromosome (Chr) 13 near the D13Mit3 marker (LOD score 6.9). This QTL region was designated Twq1 and associated with over 75% of genetic variability.

Animals↗