For decades, essential hypertension has been primarily viewed from a hemodynamic, neural, and renal perspective. However, based on mounting evidence from clinical, epidemiological, and experimental studies, it has become increasingly recognized that disturbances in carbohydrate and lipid metabolism often accompany high blood pressure, and that essential hypertension may also represent a disorder of cardiovascular endocrinology and metabolism (1, 2). In patients with essential hypertension, clustering of metabolic cardiovascular risk factors -including glucose intolerance, hyperinsulinemia, and hypertriglyceridemiamay promote susceptibility to target organ damage and partly explain why conventional antihypertensive agents have failed to reduce the risk for coronary heart disease to the extent predicted from epidemiological studies (2).Recently, a provocative hypothesis has emerged in which inherited disorders of carbohydrate or lipid metabolism are held to be at the core of the hypertension syndrome and to contribute to the primary pathogenesis of increased blood pressure. Studies in nonobese subjects with a family history of hypertension and in a variety of experimental animal models have suggested that alterations in carbohydrate and/or lipid metabolism can influence the regulation of blood pressure and might precede the development of hypertension (3-5). The lack of insulin resistance in patients with secondary forms of hypertension, together with observations of disordered carbohydrate and lipid metabolism in cultured adipocytes from hypertensive animals, indicates that at least some endocrine-metabolic disturbances are not simply a consequence of increased blood pressure (4,(6)(7)(8). Hence, there is intense interest in identifying genetic mechanisms that may underlie the association between increased blood pressure and other cardiovascular risk factors in essential hypertension.The spontaneously hypertensive rat (SHR) is the most 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 hypert...

The hypodactylous (hd) locus impairs limb development and spermatogenesis, leading to male infertility in rats. We show that the hd mutation is caused by an insertion of an endogenous retrovirus into intron 10 of the Cntrob gene. The retroviral insertion in hd mutant rats disrupts the normal splicing of Cntrob transcripts and results in the expression of a truncated protein. During the final phase of spermiogenesis, centrobin localizes to the manchette, centrosome, and the marginal ring of the spermatid acroplaxome, where it interacts with keratin 5-containing intermediate filaments. Mutant spermatids show a defective acroplaxome marginal ring and separation of the centrosome from its normal attachment site of the nucleus. This separation correlates with a disruption of head-tail coupling apparatus, leading to spermatid decapitation during the final step of spermiogenesis and the absence of sperm in the epididymis. Cntrob may represent a novel candidate gene for presently unexplained hereditary forms of teratozoospermia and the "easily decapitated sperm syndrome" in humans.

Abnormalities in carbohydrate and lipid metabolism are common in patients with essential hypertension and in the spontaneously hypertensive rat (SHR). To identify chromosome regions contributing to this clustering of cardiovascular risk factors in the SHR, we searched for quantitative trait loci (QTL) associated with insulin resistance, glucose intolerance, and dyslipidemia by using the HXB/BXH recombinant inbred (RI) strains. Analysis of variance in RI strains suggested significant effects of genetic factors. A genome screening of the RI strains with more than 700 markers revealed QTL significantly associated with insulin resistance on Chromosomes (Chrs) 3 and 19. The Chr 19 QTL was confirmed by testing a previously derived SHR-19 congenic strain: transfer of a Chr 19 segment delineated by markers D19Rat57 and D19Mit7 from the Brown Norway (BN/Cr) strain onto the genetic background of the SHR/Ola was associated with decreased insulin and glucose concentrations and ameliorated insulin resistance at the tissue level. These findings suggest that closely linked genes on Chr 19, or perhaps even a single gene with pleiotropic effects, influence the clustering of metabolic disturbances in the SHR-BN model.

The frequent coincidence of hypertension and dyslipidemia suggests that related genetic factors might underlie these common risk factors for cardiovascular disease. To investigate whether quantitative trait loci (QTLs) regulating lipid levels map to chromosomes known to contain genes regulating blood pressure, we used a genome scanning approach to map QTLs influencing cholesterol and phospholipid phenotypes in a large set of recombinant inbred strains and in congenic strains derived from the spontaneously hypertensive rat and normotensive Brown-Norway (BN.Lx) rat fed normal and high cholesterol diets. QTLs regulating lipid phenotypes were mapped by scanning the genome with 534 genetic markers. A significant relationship ( P Ͻ 0.00006) was found between basal HDL2 cholesterol levels and the

The spontaneously hypertensive rat (SHR) is the most widely studied animal model of essential hypertension. Despite Ͼ 30 yr of research, the primary genetic lesions responsible for hypertension in the SHR remain undefined. In this report, we describe the construction and hemodynamic characterization of a congenic strain of SHR (

Recent linkage studies in the spontaneously hypertensive rat (SHR) suggest that a blood pressure regulatory gene or genes may be located on rat chromosome 1q. To investigate this possibility, we replaced a region of chromosome 1 in the SHR (defined by the markers D1Mit3 and Igf2) with the corresponding chromosome segment from the normotensive Brown-Norway (BN) strain. In male SHR congenic rats carrying the transferred BN chromosome segment, 24-hour average systolic and diastolic blood pressures were significantly lower than in male progenitor SHR. Polymerase chain reaction genotyping using 60 polymorphic microsatellite markers dispersed throughout the genome confirmed the congenic status of the new strain designated SHR.BN-D1Mit3/Igf2. These findings provide direct evidence that a blood pressure regulatory gene exists on the differential segment of chromosome 1 that is sufficient to decrease blood pressure in the SHR. The SHR.BN-D1Mit3/Igf2 congenic strain represents an important new model for fine mapping and characterization of genes on chromosome 1 involved in the pathogenesis of spontaneous hypertension.

Alemayehu, Adamu, Laura Breen, Drahomira Krenova, and Morton P. Printz. Reciprocal rat chromosome 2 congenic strains reveal contrasting blood pressure and heart rate QTL. Physiol Genomics 10: 199-210, 2002. First published July 23, 2002 10.1152/physiolgenomics.00065.2002.-Evidence exists implying multiple blood pressure quantitative trait loci (QTL) on rat chromosome 2. To examine this possibility, four congenic strains and nine substrains were developed with varying size chromosome segments introgressed from the spontaneously hypertensive rat (SHR/lj) and normotensive Wistar-Kyoto rat (WKY/lj) onto the reciprocal genetic background. Cardiovascular phenotyping was conducted with telemetry over extended periods during standard salt (0.7%) and high-salt (8%) diets. Our results are consistent with at least three independent pressor QTL: transfer of SHR/lj alleles to WKY/lj reveals pressor QTL within D2Rat21-D2Rat27 and D2Mgh10-D2Rat62, whereas transfer of WKY/lj D2Rat161-D2Mit8 to SHR/lj reveals a depressor locus. Our results also suggest a depressor QTL in SHR/lj located within D2Rat161-D2Mgh10. Introgressed WKY/lj segments also reveal a heart rate QTL within D2Rat40-D2Rat50 which abolished salt-induced bradycardia, dependent upon adjoining SHR/lj alleles. This study confirms the presence of multiple blood pressure QTL on chromosome 2. Taken together with our other studies, we conclude that rat chromosome 2 is rich in alleles for cardiovascular and behavioral traits and for coordinated coupling between behavior and cardiovascular responses. hypertension; genetic; salt; SHR; telemetry PUTATIVE ARTERIAL PRESSURE loci have been identified on over half of the chromosomes of the spontaneously hypertensive rat (SHR) and on numerous chromosomes of the Dahl salt-sensitive (Dahl-S) hypertensive rat (5,16,17,21). However, when individual loci are separated out and expressed on a uniform homozygous genetic background, as in congenics or consomics, their individual contributions to elevated arterial pressure sums to greater than 100% of the total observed hypertension in the original genetic model. This finding likely implies 1) a modifying influence of the heterozygous genetic background, 2)

The polydactylous rat strain (PD/Cub) is a highly inbred (F Ͼ 90) genetic model of metabolic syndrome. The aim of this study was to analyze the genetic architecture of the metabolic derangements found in the PD/Cub strain and to assess its dynamics in time and in response to diet and medication. We derived a PD/Cub ϫ BN/Cub (Brown Norway) F2 intercross population of 149 male rats and performed metabolic profiling and genotyping and multiple levels of genetic linkage and statistical analyses at five different stages of ontogenesis and after high-sucrose diet feeding and dexamethasone administration challenges. The interval mapping analysis of 83 metabolic and morphometric traits revealed over 50 regions genomewide with significant or suggestive linkage to one or more of the traits in the segregating PD/Cub ϫ BN/Cub population. The multiple interval mapping showed that, in addition to "single" quantitative train loci, there are more than 30 pairs of loci across the whole genome significantly influencing the variation of particular traits in an epistatic fashion. This study represents the first whole genome analysis of metabolic syndrome in the PD/Cub model and reveals several new loci previously not connected to the genetics of insulin resistance and dyslipidemia. In addition, it attempts to present the concept of "dynamic genetic architecture" of metabolic syndrome attributes, evidenced by shifts in the genetic determination of syndrome features during ontogenesis and during adaptation to the dietary and pharmacological influences.quantitative trait loci; pharmacogenetics; nutrigenetics; triglyceride; insulin resistance; obesity METABOLIC SYNDROME is a complex condition arising from an intricate network of interacting genetic and environmental factors. The dynamics of the increase in its worldwide prevalence qualify the syndrome as a major healthcare issue for years to come. The syndrome comprises several clinical features, each representing a complex trait of its kind, i.e., hypertriglyceridemia, hyperinsulinemia, insulin resistance, obesity, and hypertension (11,36). It is therefore self evident that detailed analysis of the genetic determinants underlying such metabolic clustering is rather complicated in the general human population and only somewhat more feasible in particular circumstances, e.g., in population isolates (32). Although some progress has been made and several studies succeeded in identification of genes potentially involved in the pathogenesis of metabolic syndrome (13,17,35,51), its genetic determination is far from being fully understood.As in other complex diseases, defined animal models of metabolic syndrome are proving to be important tools for deciphering the causative genes and gene-gene and geneenvironment interactions (8). There are numerous rodent strains expressing all or a subset of metabolic syndrome attributes found in humans [e.g., Otsuka Long-Evans Tokushima Fatty rat (16), Goto-Kakizaki rat (10), hereditary hypertriglyceridemic rat (53, 54), and spontaneously hypertensive rat ...