Hepatoprotective and cardioprotective effects of empagliflozin in spontaneously hypertensive rats fed a high-fat diet

A combination of liver and heart dysfunction worsens the prognosis of human survival. The aim of this study was to investigate whether empagliflozin (a sodium-glucose transporter-2 inhibitor) has beneficial effects not only on cardiac and renal function but also on hepatic function. Adult (6-month-old) male spontaneously hypertensive rats (SHR) were fed a high-fat diet (60% fat) for four months to induce hepatic steatosis and mild heart failure. For the last two months, the rats were treated with empagliflozin (empa, 10 mg.kg-1.day-1 in the drinking water). Renal function and oral glucose tolerance test were analyzed in control (n=8), high-fat diet (SHR+HF, n=10), and empagliflozin-treated (SHR+HF+empa, n=9) SHR throughout the study. Metabolic parameters and echocardiography were evaluated at the end of the experiment. High-fat diet feeding increased body weight and visceral adiposity, liver triglyceride and cholesterol concentrations, and worsened glucose tolerance. Although the high-fat diet did not affect renal function, it significantly worsened cardiac function in a subset of SHR rats. Empagliflozin reduced body weight gain but not visceral fat deposition. It also improved glucose sensitivity and several metabolic parameters (plasma insulin, uric acid, and HDL cholesterol). In the liver, empagliflozin reduced ectopic lipid accumulation, lipoperoxidation, inflammation and pro-inflammatory HETEs, while increasing anti-inflammatory EETs. In addition, empagliflozin improved cardiac function (systolic, diastolic and pumping) independent of blood pressure. The results of our study suggest that hepatoprotection plays a decisive role in the beneficial effects of empagliflozin in preventing the progression of cardiac dysfunction induced by high-fat diet feeding.

Corrigendum for: Sex Differences in Blood Pressure, Free Radicals and Plasma Cholesterol Fractions in Ren-2 Transgenic Rats of Various Ages

List of changes: On the basis of author's request the publisher of Physiological Research decided to change the license of the article to CC BY license.

Sex differences in blood pressure, free radicals and plasma cholesterol fractions in Ren-2 transgenic rats of various ages

Sex-related cardiovascular differences were observed in humans as well as in experimental animals. Our previous study demonstrated a marked sexual dimorphism in blood pressure (BP) of 9-month-old heterozygous transgenic Ren 2 rats (TGR), in which mouse Ren-2 renin gene was inserted into the genome of normotensive Hannover Sprague-Dawley rats (HanSD). We found significantly elevated BP only in male TGR, whereas BP of TGR females was similar to that of HanSD females. The aim of our present study was to compare BP of 3- and 6-month-old heterozygous TGR with age- and sex-matched HanSD under the same conditions as we measured in 9-month-old rats. We also monitored the amount of oxidative stress marker, thiobarbituric acid-reactive substances (TBARS), and a main intracellular antioxidant, reduced glutathione in the heart, kidneys and liver. We also measured plasma triglycerides and cholesterol levels. We found an increased mean arterial pressure in both female and male 3-month-old TGR (172±17 vs. 187±4 mm Hg, respectively) compared to HanSD (115±5 vs. 133±3 mm Hg, respectively) but there was a marked sexual dimorphism of 6 month-old TGR where only males were hypertensive (145±5 mm Hg) while females became normotensive (123±7 mm Hg). We did not find any relationship between BP values and concentrations of TBARS or glutathione or plasma lipid levels. Our results demonstrated that 6-month-old TGR exhibited a marked sexual BP dimorphism, which was not dependent on the abnormalities in oxidative stress or cholesterol metabolism.

Sex differences in blood pressure, free radicals and plasma cholesterol fractions in Ren-2 transgenic rats of various ages

Sex-related cardiovascular differences were observed in humans as well as in experimental animals. Our previous study demonstrated a marked sexual dimorphism in blood pressure (BP) of 9-month-old heterozygous transgenic Ren 2 rats (TGR), in which mouse Ren-2 renin gene was inserted into the genome of normotensive Hannover Sprague-Dawley rats (HanSD). We found significantly elevated BP only in male TGR, whereas BP of TGR females was similar to that of HanSD females. The aim of our present study was to compare BP of 3- and 6-month-old heterozygous TGR with age- and sex-matched HanSD under the same conditions as we measured in 9-month-old rats. We also monitored the amount of oxidative stress marker, thiobarbituric acid-reactive substances (TBARS), and a main intracellular antioxidant, reduced glutathione in the heart, kidneys and liver. We also measured plasma triglycerides and cholesterol levels. We found an increased mean arterial pressure in both female and male 3-month-old TGR (172±17 vs. 187±4 mm Hg, respectively) compared to HanSD (115±5 vs. 133±3 mm Hg, respectively) but there was a marked sexual dimorphism of 6 month-old TGR where only males were hypertensive (145±5 mm Hg) while females became normotensive (123±7 mm Hg). We did not find any relationship between BP values and concentrations of TBARS or glutathione or plasma lipid levels. Our results demonstrated that 6-month-old TGR exhibited a marked sexual BP dimorphism, which was not dependent on the abnormalities in oxidative stress or cholesterol metabolism.

Antihypertensive and metabolic effects of empagliflozin in Ren-2 transgenic rats, an experimental non-diabetic model of hypertension

The new antidiabetic drugs, gliflozins, inhibit sodium-glucose transporter-2 in renal proximal tubules promoting glucose and sodium excretion. This leads not only to a significant improvement of glucose control but also to the reduction of blood pressure and body weight in both diabetic patients and experimental models. We examined whether these beneficial effects can also be achieved in a non-diabetic hypertensive model, namely in Ren-2 transgenic rats (TGR). Adult 6-month-old hypertensive TGR and their normotensive controls (Hannover Sprague-Dawley rats), were either untreated or treated with empagliflozin (10 mg/kg/day) for two months. Telemetric blood pressure monitoring, renal parameters as well as cardiac function via echocardiography were analyzed during the experiment. At the end of the study, the contribution of major vasoactive systems to blood pressure maintenance was studied. Metabolic parameters and markers of oxidative stress and inflammation were also analyzed. Empagliflozin had no effect on plasma glucose level but partially reduced blood pressure in TGR. Although food consumption was substantially higher in empagliflozin-treated TGR compared to the untreated animals, their body weight and the amount of epididymal and perirenal fat was decreased. Empagliflozin had no effect on proteinuria, but it decreased plasma urea, attenuated renal oxidative stress and temporarily increased urinary urea excretion. Several metabolic (hepatic triglycerides, non-esterified fatty acids, insulin) and inflammatory (TNF-α, leptin) parameters were also improved by empagliflozin treatment. By contrast, echocardiography did not reveal any effect of empagliflozin on cardiac function. In conclusion, empagliflozin exerted beneficial antihypertensive, anti-inflammatory and metabolic effects also in a non-diabetic hypertensive model.

GPR10 gene deletion in mice increases basal neuronal activity, disturbs insulin sensitivity and alters lipid homeostasis

G-protein-coupled receptor GPR10 is expressed in brain areas regulating energy metabolism. In this study, the effects of GPR10 gene deficiency on energy homeostasis in mice of both sexes fed either standard chow or a high-fat diet (HFD) were studied, with a focus on neuronal activation of PrRP neurons, and adipose tissue and liver metabolism. GPR10 deficiency in males upregulated the phasic and tonic activity of PrRP neurons in the nucleus of the solitary tract. GPR10 knockout (KO) males on a standard diet displayed a higher body weight than their wild-type (WT) littermates due to an increase in adipose tissue mass; however, HFD feeding did not cause weight differences between genotypes. Expression of lipogenesis genes was suppressed in the subcutaneous adipose tissue of GPR10 KO males. In contrast, GPR10 KO females did not differ in body weight from their WT controls, but showed elevated expression of lipid metabolism genes in the liver and subcutaneous adipose tissue compared to WT controls. An attenuated non-esterified fatty acids change after glucose load compared to WT controls suggested a defect in insulin-mediated suppression of lipolysis in GPR10 KO females. Indirect calorimetry did not reveal any differences in energy expenditure among groups. In conclusion, deletion of GPR10 gene resulted in changes in lipid metabolism in mice of both sexes, however in different extent. An increase in adipose tissue mass observed in only GPR10 KO males may have been prevented in GPR10 KO females owing to a compensatory increase in the expression of metabolic genes.

Sex differences in blood pressure of aged Ren-2 transgenic rats

Sex-related differences were observed not only in human but also in experimental hypertension. The aim of our study was to compare blood pressure (BP) of aged male and female heterozygous transgenic rats (TGR) harboring Ren-2 mouse gene, with their normotensive Hannover Sprague-Dawley (HanSD) controls. At the age of 9 months, systolic (SBP) and diastolic blood pressure (DBP) were measured by a direct puncture of carotid artery in rats awaking from isoflurane anesthesia. Thiobarbituric acid-reactive species (TBARS) formation was monitored as indicator of lipid peroxidation damage in heart, kidney and liver, whereas intracellular content of reduced glutathione was determined in the same organs as the main intracellular antioxidant. Furthermore, plasma triglycerides and total cholesterol as well as high-density lipoprotein (HDL) and low-density lipoprotein (LDL) fractions of cholesterol were measured. As compared to HanSD rats, we found significantly elevated BP only in male TGR (MAP: 123±1 vs. 171±5, SBP: 150±2 vs. 208±7, and DBP: 99±3 vs. 140±4 mm Hg), but not between TGR and HanSD females, which were both normotensive. We also did not find any significant differences in TBARS and reduced glutathione in the three above mentioned organs as well as in plasma cholesterol or its HDL and LDL fractions between transgene-negative HanSD and TGR animals of either sex. However, we found significant sex differences in TBARS, glutathione and plasma lipids in both rat strains. Our results confirmed that aged TGR exhibit a marked sexual BP dimorphism, which does not seem to be dependent on oxidative stress or abnormal cholesterol metabolism.

Renoprotection Provided by Additional Diuretic Treatment in Partially Nephrectomized Ren-2 Transgenic Rats Subjected to the Combined RAS and ETA Blockade

Objective

Our previous study in heterozygous Ren-2 transgenic rats (TGR) demonstrated that long-term treatment with endothelin receptor A (ET_A) blocker atrasentan added to the renin-angiotensin system (RAS) blockade had renoprotective effects in a model of chronic kidney disease (CKD) induced by partial nephrectomy. Since ET_A blockade is known to cause edema, we were interested whether diuretic treatment added to this therapy would be beneficial.

Design and Methods

Partial nephrectomy (NX) was performed at the age of 3 months in TGR rats which were subjected to: (i) RAS blockade alone (angiotensin receptor blocker losartan and angiotensin converting enzyme inhibitor trandolapril), (ii) combined RAS (losartan and trandolapril) and ET_A receptor blockade (atrasentan), or (iii) diuretic (hydrochlorothiazide) added to the combined RAS + ET_A blockade for 50 weeks following NX.

Results

At the end of the study systolic blood pressure and cardiac hypertrophy were similarly decreased in all treated groups. Survival was significantly improved by ET_A receptor blockade added to RAS blockade with no further effects of diuretic treatment. However, additional diuretic treatment combined with RAS + ET_A blockade decreased body weight and had beneficial renoprotective effects - reductions of both kidney weight and kidney damage markers. Proteinuria gradually increased in rats treated with RAS blockade alone, while it was substantially lowered by additional ET_A blockade. In rats treated with additional diuretic, proteinuria was progressively reduced throughout the experiment.

Conclusion

A diuretic added to the combined RAS and ET_A blockade has late renoprotective effects in CKD induced by partial nephrectomy in Ren-2 transgenic rats. The diuretic improved: renal function (evaluated as proteinuria and creatinine clearance), renal morphology (kidney mass, glomerular volume), and histological markers of kidney damage (glomerulosclerosis index, tubulointerstitial injury).

Distinct effects of bosentan on NO-dependent vasodilation and calcium influx in heterozygous Ren-2 transgenic rats on high-salt diet

Our studies in hypertensive Ren-2 transgenic rats (TGR) demonstrated that chronic administration of atrasentan (ETA receptor antagonist) decreased blood pressure by reduced Ca2+ influx through L-type voltage-dependent calcium channels (L-VDCC) and attenuated angiotensin II-dependent vasoconstriction. We were interested whether bosentan (nonselective ET(A)/ET(B) receptor antagonist) would have similar effects. Young 4-week-old (preventive study) and adult 8-week-old (therapeutic study) heterozygous TGR and their normotensive Hannover Sprague-Dawley (HanSD) controls were fed normal-salt (NS, 0.6 % NaCl) or high-salt (HS, 2 % NaCl) diet for 8 weeks. An additional group of TGR fed HS was treated with bosentan (100 mg/kg/day). Bosentan had no effect on BP of TGR fed high-salt diet in both the preventive and therapeutic studies. There was no difference in the contribution of angiotensin II-dependent and sympathetic vasoconstriction in bosentan-treated TGR compared to untreated TGR under the condition of high-salt intake. However, bosentan significantly reduced NO-dependent vasodilation and nifedipine-sensitive BP component in TGR on HS diet. A highly important correlation of nifedipine-induced BP change and the BP after L-NAME administration was demonstrated. Although bosentan did not result in any blood pressure lowering effects, it substantially influenced NO-dependent vasodilation and calcium influx through L-VDCC in the heterozygous TGR fed HS diet. A significant correlation of nifedipine-induced BP change and the BP after L-NAME administration suggests an important role of nitric oxide in the closure of L-type voltage dependent calcium channels.

Role of angiotensin II in chronic blood pressure control of heterozygous Ren-2 transgenic rats: Peripheral vasoconstriction versus central sympathoexcitation

Our previous studies demonstrated that chronic systemic blockade of renin-angiotensin system (RAS) lowered blood pressure (BP) of Ren-2 transgenic rats (TGR) by the attenuation of both angiotensin II-dependent and sympathetic vasoconstriction. Since systemic RAS blockade also inhibits brain RAS, we were interested which effects on these two types of vasoconstriction will have the central RAS blockade in hypertensive TGR rats. Adult male heterozygous TGR rats and their Hannover Sprague Dawley (HanSD) controls were subjected to chronic systemic or intracerebroventricular administration of either angiotensin type 1 receptor blocker losartan or direct renin inhibitor aliskiren for 4 weeks. Additional groups of TGR and HanSD rats were used for the evaluation of acute peripheral and brain effects of angiotensin II. Both chronic systemic and intracerebroventricular administrations of losartan or aliskiren normalized BP of TGR animals. BP effect of brain RAS blockade was based solely on the reduced sympathetic vasoconstriction, while systemic RAS blockade attenuated both angiotensin II-dependent and sympathetic vasoconstriction. Surprisingly, neither peripheral nor central pressor effects of acute angiotensin II administration were enhanced in TGR compared to HanSD rats. In conclusion, sympathoinhibition represents the main mechanism of BP reduction in heterozygous TGR rats subjected to chronic brain or systemic RAS blockade, while peripheral attenuation of angiotensin II-dependent vasoconstriction during systemic RAS blockade is less important. Our data suggest that the participation of angiotensin II in BP control of adult heterozygous TGR rats is shifted from peripheral vasoconstriction to central sympathoexcitation. Similar mechanisms cannot be excluded in human essential hypertension.

Renoprotective effects of ET(A) receptor antagonists therapy in experimental non-diabetic chronic kidney disease: Is there still hope for the future?

Chronic kidney disease (CKD) is a life-threatening disease arising as a frequent complication of diabetes, obesity and hypertension. Since it is typically undetected for long periods, it often progresses to end-stage renal disease. CKD is characterized by the development of progressive glomerulosclerosis, interstitial fibrosis and tubular atrophy along with a decreased glomerular filtration rate. This is associated with podocyte injury and a progressive rise in proteinuria. As endothelin-1 (ET-1) through the activation of endothelin receptor type A (ET(A)) promotes renal cell injury, inflammation, and fibrosis which finally lead to proteinuria, it is not surprising that ET(A) receptors antagonists have been proven to have beneficial renoprotective effects in both experimental and clinical studies in diabetic and non-diabetic CKD. Unfortunately, fluid retention encountered in large clinical trials in diabetic CKD led to the termination of these studies. Therefore, several advances, including the synthesis of new antagonists with enhanced pharmacological activity, the use of lower doses of ET antagonists, the addition of diuretics, plus simply searching for distinct pathological states to be treated, are promising targets for future experimental studies. In support of these approaches, our group demonstrated in adult subtotally nephrectomized Ren-2 transgenic rats that the addition of a diuretic on top of renin-angiotensin and ET(A) blockade led to a further decrease of proteinuria. This effect was independent of blood pressure which was normalized in all treated groups. Recent data in non-diabetic CKD, therefore, indicate a new potential for ET(A) antagonists, at least under certain pathological conditions.

Critical developmental periods in the pathogenesis of hypertension

Hypertension is one of the major risk factor of cardiovascular diseases, but after a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. One reason is that blood pressure is a quantitative trait with multifactorial determination. Numerous genes, environmental factors as well as epigenetic factors should be considered. There is no doubt that although the full manifestation of hypertension and other cardiovascular diseases usually occurs predominantly in adulthood and/or senescence, the roots can be traced back to early ontogeny. The detailed knowledge of the ontogenetic changes occurring in the cardiovascular system of experimental animals during particular critical periods (developmental windows) could help to solve this problem in humans and might facilitate the age-specific prevention of human hypertension. We thus believe that this approach might contribute to the reduction of cardiovascular morbidity among susceptible individuals in the future.

Age-dependent salt hypertension in Dahl rats: fifty years of research

Fifty years ago, Lewis K. Dahl has presented a new model of salt hypertension - salt-sensitive and salt-resistant Dahl rats. Twenty years later, John P. Rapp has published the first and so far the only comprehensive review on this rat model covering numerous aspects of pathophysiology and genetics of salt hypertension. When we summarized 25 years of our own research on Dahl/Rapp rats, we have realized the need to outline principal abnormalities of this model, to show their interactions at different levels of the organism and to highlight the ontogenetic aspects of salt hypertension development. Our attention was focused on some cellular aspects (cell membrane function, ion transport, cell calcium handling), intra- and extrarenal factors affecting renal function and/or renal injury, local and systemic effects of renin-angiotensin-aldosterone system, endothelial and smooth muscle changes responsible for abnormal vascular contraction or relaxation, altered balance between various vasoconstrictor and vasodilator systems in blood pressure maintenance as well as on the central nervous and peripheral mechanisms involved in the regulation of circulatory homeostasis. We also searched for the age-dependent impact of environmental and pharmacological interventions, which modify the development of high blood pressure and/or organ damage, if they influence the salt-sensitive organism in particular critical periods of development (developmental windows). Thus, severe self-sustaining salt hypertension in young Dahl rats is characterized by pronounced dysbalance between augmented sympathetic hyperactivity and relative nitric oxide deficiency, attenuated baroreflex as well as by a major increase of residual blood pressure indicating profound remodeling of resistance vessels. Salt hypertension development in young but not in adult Dahl rats can be attenuated by preventive increase of potassium or calcium intake. On the contrary, moderate salt hypertension in adult Dahl rats is attenuated by superoxide scavenging or endothelin-A receptor blockade which do not affect salt hypertension development in young animals.

Apolipoprotein A5 in health and disease

High plasma levels of triglycerides (TG) are an independent risk factor in the development of cardiovascular disease, with about 50 % of the final levels being determined genetically. Apolipoprotein A5 (APOA5) is the last discovered member of the apolipoprotein APOA1/C3/A4 gene cluster, found by comparative sequencing analysis. The importance of APOA5 gene for determination of plasma triglyceride levels has been suggested after development of transgenic and knock-out mice (transgenic mice displayed significantly reduced TG, whereas knock-out mice had high TG). In Czech population, alleles C-1131 and Trp19 are associated with elevated levels of plasma TG and higher risk of myocardial infarction development. These alleles also play some role in nutrigenetics and actigenetics of lifestyle interventions leading to the plasma cholesterol changes as well as in the pharmacogenetics of statin treatment. On the contrary, APOA5 mutations detected in Czech population did not show strict effect on plasma TG levels. Val153 → Met variant exhibit the sexspecific effect of HDL-cholesterol levels. The suggested roles of APOA5 variants in determination of the plasma remnant particles, plasma concentrations of C-reactive protein or some anthropometrical parameters were excluded.

Abnormal Igf2 gene in Prague hereditary hypertriglyceridemic rats: its relation to blood pressure and plasma lipids

Prague hypertriglyceridemic (HTG) rats represent a suitable model of metabolic syndrome. We have established the set of F(2) hybrids derived from HTG and Lewis progenitors to investigate the relationship between respective polymorphism(s) of Igf2 gene and blood pressure (BP) or other cardiovascular phenotypes. HTG rats had elevated systolic BP and plasma triglycerides but lower plasma cholesterol compared to Lewis rats of both genders. In males, there was higher mean arterial pressure, diastolic BP and relative heart weight in HTG than in Lewis rats. The results obtained in the total population of F(2) hybrids indicated strong segregation of Igf2 genotype with plasma triglycerides. There was no segregation of Igf2 genotype with any BP component except BP changes occurring after the blockade of either renin-angiotensin system (RAS) or NO synthase. When F(2) population was analyzed according to gender, male F(2) progeny homozygous for HTG Igf2 allele had significantly higher plasma triglycerides and greater BP changes after NO synthase blockade than those homozygous for Lewis allele. On the contrary, male F(2) progeny homozygous for HTG Igf2 allele had significantly lower plasma cholesterol and smaller BP changes after RAS blockade. PCR analysis of Igf2 gene by using of microsatelite D1Mgh22 has shown polymorphism between HTG and Lewis rats. Sequence analysis of cDNA revealed insertion of 14 nucleotides in HTG gene. In conclusion, polymorphism in Igf2 gene may be responsible for differences in lipid metabolism between HTG and Lewis rats. It remains to determine how these abnormalities could be involved in BP regulation by particular vasoactive systems.

The participation of brain NO synthase in blood pressure control of adult spontaneously hypertensive rats

Increased blood pressure (BP) in genetic hypertension is usually caused by high activity of sympathetic nervous system (SNS) which is enhanced by central angiotensin II but lowered by central nitric oxide (NO). We have therefore evaluated NO synthase (NOS) activity as well as neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS) protein expression in brainstem and midbrain of adult spontaneously hypertensive rats (SHR) characterized by enhanced sympathetic vasoconstriction. We also studied possible participation of brain NO in antihypertensive effects of chronic captopril treatment of adult SHR. NOS activity was increased in midbrain of SHR compared to Wistar-Kyoto (WKY) rats. This could be ascribed to enhanced iNOS expression, whereas nNOS expression was unchanged and eNOS expression was reduced in this brain region. In contrast, no significant changes of NOS activity were found in brainstem of SHR in which nNOS and iNOS expression was unchanged, but eNOS expression was increased. Chronic captopril administration lowered BP of adult SHR mainly by attenuation of sympathetic tone, whereas the reduction of angiotensin II-dependent vasoconstriction and the decrease of residual BP (amelioration of structural remodeling of resistance vessels) were less important. This treatment did not affect significantly either NOS activity or expression of any NOS isoform in the two brain regions. Our data do not support the hypothesis that altered brain NO formation contributes to sympathetic hyperactivity and high BP of adult SHR with established hypertension.

Apolipoprotein A5 and hypertriglyceridemia in Prague hypertriglyceridemic rats

High plasma triglyceride (TG) level is a major independent risk factor of coronary heart disease. A newly identified Apolipoprotein A5 (Apoa5) gene has been shown to play an important role in determining plasma TG concentrations in humans and mice. Prague hereditary hypertriglyceridemic (HTG) rats are a useful model of human hypertriglyceridemia and other symptoms of metabolic syndrome. Thus, the variation of Apoa5 gene and its expression were studied in this strain under normal conditions and after chronic fructose loading. Lewis and Wistar rats served as normotriglyceridemic controls. Plasma TG were significantly higher in HTG rats in comparison with both control strains. Screening of the coding regions and intron-exon boundaries of Apoa5 gene did not reveal any mutation of this gene in HTG rats in comparison with Lewis and Wistar ones. However, rat Apoa5 gene contains only one intron in contrast with two introns of mouse Apoa5 gene. Under the basal conditions the expression of Apoa5 was lower in all age groups of HTG rats compared to Wistar animals. Furthermore, during chronic fructose loading there were no significant changes of Apoa5 expression in HTG rats, although plasma TG levels rose 3-4 times within first two days of fructose loading and were increased during the whole period of fructose treatment. In conclusion, Apoa5 does not seem to be a genetic determinant of hypertriglyceridemia in HTG rats. The absence of significant changes in Apoa5 gene expression during chronic fructose-induced TG elevation excludes its major role in mechanisms compensating severe hypertriglyceridemia.

Polymorphism in Nos2 gene is absent in Prague colony of Dahl/Rapp salt-sensitive and salt-resistant rats

We have searched for polymorphism of inducible nitric oxide synthase gene (Nos2 gene) in the Prague colony of salt-sensitive and salt-resistant Dahl/Rapp rats. Specific primers were used to confirm previously described Nos2 gene polymorphism because this gene was suggested to be a potential candidate gene for genetic hypertension. Phenotyping (blood pressure, organ weight, plasma lipids) have confirmed the data known from other colonies of Dahl/Rapp rats. However, in our colony we were not able to find any Nos2 gene polymorphism between salt-sensitive and salt-resistant rats, which was previously described in animals from Harlan colony. Moreover, the genetic homogeneity of our salt-sensitive and salt-resistant rats in terms of Nos2 gene was the same as in the original Brookhaven colony of Dahl rats. This is surprising because our colony has been established from breeding pairs kindly provided by Prof. J.P. Rapp more than 15 years ago. It seems that the polymorphism found in Harlan colony could be the result of previous contamination or genetic drift during the breeding conditions specific for this colony.

Polymorphism in Nos2 gene is absent in Prague colony of Dahl/Rapp salt-sensitive and salt-resistant rats

We have searched for polymorphism of inducible nitric oxide synthase gene (Nos2 gene) in the Prague colony of salt-sensitive and salt-resistant Dahl/Rapp rats. Specific primers were used to confirm previously described Nos2 gene polymorphism because this gene was suggested to be a potential candidate gene for genetic hypertension. Phenotyping (blood pressure, organ weight, plasma lipids) have confirmed the data known from other colonies of Dahl/Rapp rats. However, in our colony we were not able to find any Nos2 gene polymorphism between salt-sensitive and salt-resistant rats, which was previously described in animals from Harlan colony. Moreover, the genetic homogeneity of our salt-sensitive and salt-resistant rats in terms of Nos2 gene was the same as in the original Brookhaven colony of Dahl rats. This is surprising because our colony has been established from breeding pairs kindly provided by Prof. J.P. Rapp more than 15 years ago. It seems that the polymorphism found in Harlan colony could be the result of previous contamination or genetic drift during the breeding conditions specific for this colony.

Altered balance of vasoactive systems in experimental hypertension: the role of relative NO deficiency

This review summarizes our findings concerning the altered balance of vasoactive systems (namely sympathetic nervous system and nitric oxide) in various forms of experimental hypertension--genetic hypertension (SHR, HTG rats), salt hypertension (Dahl rats) and NO-deficient hypertension (L-NAME-treated rats). An attempt is made to define relative NO deficiency (compared to the existing level of sympathetic vasoconstriction), to describe its possible causes and to evaluate particular indicators of its extent. A special attention is paid to reactive oxygen species, their interaction with NO metabolism, cell Ca2+ handling and blood pressure regulation. Our current effort is focused on the investigation of abnormal regulation of cytosolic Ca2+ levels in smooth muscle and endothelium of hypertensive animals. Such a research should clarify the mechanisms by which genetic and/or environmental factors could chronically modify blood pressure level.

Does Cd36 gene play a key role in disturbed glucose and fatty acid metabolism in Prague hypertensive hypertriglyceridemic rats?

Close links between hypertension, hypertriglyceridemia, insulin resistance and other symptoms of metabolic syndrome was demonstrated in humans and experimental animals. Quantitative trait loci for defects in glucose and fatty acid metabolism, hypertriglyceridemia and hypertension were mapped in spontaneously hypertensive rats (SHR) on chromosome 4 and defective Cd36 gene was identified in this region. Here we investigated the polymorphism of Cd36 gene in Prague hereditary hypertriglyceridemic (HTG) rats, which represent another model of genetic hypertension and metabolic syndrome. These animals were compared with NIH-derived SHR and two different normotensive control strains (WKY, LEW). In spite of the fact that HTG and SHR rats had similar metabolic disturbances, genotype analysis of PCR products has shown that Cd36 mutation was not present in HTG rats. In conclusion, we have revealed that defective Cd36 is probably a candidate gene for disorded fatty-acid metabolism, glucose intolerance and insulin resistance in NIH-derived SHR, but other genes might play a role in pathogenesis of metabolic syndrome in Prague hereditary hypertriglyceridemic rats. This is in accordance with the absence of defective Cd36 gene in original SHR from Japan.

Does Cd36 gene play a key role in disturbed glucose and fatty acid metabolism in Prague hypertensive hypertriglyceridemic rats?

Close links between hypertension, hypertriglyceridemia, insulin resistance and other symptoms of metabolic syndrome was demonstrated in humans and experimental animals. Quantitative trait loci for defects in glucose and fatty acid metabolism, hypertriglyceridemia and hypertension were mapped in spontaneously hypertensive rats (SHR) on chromosome 4 and defective Cd36 gene was identified in this region. Here we investigated the polymorphism of Cd36 gene in Prague hereditary hypertriglyceridemic (HTG) rats, which represent another model of genetic hypertension and metabolic syndrome. These animals were compared with NIH-derived SHR and two different normotensive control strains (WKY, LEW). In spite of the fact that HTG and SHR rats had similar metabolic disturbances, genotype analysis of PCR products has shown that Cd36 mutation was not present in HTG rats. In conclusion, we have revealed that defective Cd36 is probably a candidate gene for disorded fatty-acid metabolism, glucose intolerance and insulin resistance in NIH-derived SHR, but other genes might play a role in pathogenesis of metabolic syndrome in Prague hereditary hypertriglyceridemic rats. This is in accordance with the absence of defective Cd36 gene in original SHR from Japan.