SHROB Rats Research Articles

Sex-specific differences in hepatic steatosis in obese spontaneously hypertensive (SHROB) rats

BackgroundPatients with metabolic syndrome, who are characterized by co-existence of insulin resistance, hypertension, hyperlipidemia, and obesity, are also prone to develop non-alcoholic fatty liver disease (NAFLD). Although the prevalence and severity of NAFLD is significantly greater in men than women, the mechanisms by which gender modulates the pathogenesis of hepatic steatosis are poorly defined. The obese spontaneously hypertensive (SHROB) rats represent an attractive model of metabolic syndrome without overt type 2 diabetes. Although pathological manifestation caused by the absence of a functional leptin receptor has been extensively studied in SHROB rats, it is unknown whether these animals elicited sex-specific differences in the development of hepatic steatosis.MethodsWe compared hepatic pathology in male and female SHROB rats. Additionally, we examined key biochemical and molecular parameters of signaling pathways linked with hyperinsulinemia and hyperlipidemia. Finally, using methods of quantitative polymerase chain reaction (qPCR) and western blot analysis, we quantified expression of 45 genes related to lipid biosynthesis and metabolism in the livers of male and female SHROB rats.ResultsWe show that all SHROB rats developed hepatic steatosis that was accompanied by enhanced expression of SREBP1, SREBP2, ACC1, and FASN proteins. The livers of male rats also elicited higher induction of Pparg, Ppara, Slc2a4, Atox1, Skp1, Angptl3, and Pnpla3 mRNAs. In contrast, the livers of female SHROB rats elicited constitutively higher levels of phosphorylated JNK and AMPK and enhanced expression of Cd36.ConclusionBased on these data, we conclude that the severity of hepatic steatosis in male and female SHROB rats was mainly driven by increased de novo lipogenesis. Moreover, male and female SHROB rats also elicited differential severity of hepatic steatosis that was coupled with sex-specific differences in fatty acid transport and esterification.

A novel dual PPAR-γ agonist/sEH inhibitor treats diabetic complications in a rat model of type 2 diabetes.

The metabolic syndrome is a cluster of risk correlates that can progress to type 2 diabetes. The present study aims to evaluate a novel molecule with a dual action against the metabolic syndrome and type 2 diabetes. We developed and tested a novel dual modulator, RB394, which acts as a soluble epoxide hydrolase (sEH) inhibitor and a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist in rat models of the metabolic syndrome-the obese spontaneously hypertensive (SHROB) rat and the obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid (ZSF1) rat. In SHROB rats we studied the ability of RB394 to prevent metabolic syndrome phenotypes, while in ZSF1 obese diabetic rats we compared RB394 with the ACE inhibitor enalapril in the treatment of type 2 diabetes and associated comorbid conditions. RB394 (10mg/kg daily) and enalapril (10mg/kg daily) were administered orally for 8weeks. RB394 blunted the development of hypertension, insulin resistance, hyperlipidaemia and kidney injury in SHROB rats and reduced fasting blood glucose and HbA1c, improved glucose tolerance, reduced blood pressure and improved lipid profiles in obese ZSF1 rats. A reduction in liver fibrosis and hepatosteatosis was evident in RB394-treated obese ZSF1 rats. Unlike RB394, enalapril did not demonstrate any positive effects in relation to diabetes, hyperlipidaemia or liver dysfunction in obese ZSF1 rats. RB394 ameliorated diabetic nephropathy by reducing renal interstitial fibrosis and renal tubular and glomerular injury in obese diabetic ZSF1 rats. Intriguingly, enalapril demonstrated a weaker action against diabetic nephropathy in obese ZSF1 rats. These findings demonstrate that a novel sHE inhibitor/PPAR-γ agonist molecule targets multiple risk factors of the metabolic syndrome and is a glucose-lowering agent with a strong ability to treat diabetic complications.

Activation of Dorsomedial Hypothalamic Neurons Promotes Physical Activity and Decreases Food Intake and Body Weight in Zucker Fatty Rats.

Previous reports have shown that running wheel activity or voluntary exercise prevents hyperphagia and obesity in various animal models of obesity, but such effects seem only minimal in obese animals lacking leptin or leptin receptors. The mechanisms underlying this ineffectiveness remain unclear. Here, we identified the action of neuronal activation in the dorsomedial hypothalamus (DMH) in modulating physical activity, food intake and body weight using leptin receptor mutant obese Zucker (Lepr(fa), ZF) and Koletsky (Lepr(fak), SHROB) rats. Ad lib-fed SHROB rats with locked running wheels became hyperphagic and gained body weight rapidly. These alterations were not ameliorated in ad lib-fed SHROB rats with voluntary access to running wheels, but the body weight of SHROB rats with running wheel access was significantly decreased when they were pair-fed to the amounts consumed by lean controls. Determinations of hypothalamic gene expression revealed that sedentary ad lib-fed SHROB rats had increased expression of neuropeptide Y (Npy) and decreased expression of pro-opiomelanocortin (Pomc) in the arcuate nucleus (ARC). Both ARC Npy and Pomc expression were further altered under running and pair-fed conditions, indicating that both genes are appropriately regulated in response to increased energy demands or alterations caused by running activity and food restriction. Strikingly, c-Fos immunohistochemistry revealed that while voluntary running activity elevated the number of c-Fos positive cells in the DMH (particularly in the ventral and caudal subregions) of intact rats, such activation was not observed in ZF rats. Using adeno-associated virus (AAV)-mediated expression of the designer receptors hM3D(Gq) in the ventral and caudal DMH of ZF rats, we found that chemogenetic stimulation of neurons in these DMH subregions via injection of the designer drug clozapine N-oxide (CNO) significantly increased their running activity and reduced their food intake and body weight. Together, these results demonstrate that activation of ventral and caudal DMH neurons promotes physical activity and decreases food intake and body weight and suggest that intact DMH neural signaling is likely crucial for exercise-induced reductions of food intake and body weight in obese rats lacking leptin receptors.

Lipidized prolactin-releasing peptide improved glucose tolerance in metabolic syndrome: Koletsky and spontaneously hypertensive rat study

Background/ObjectivesProlactin-releasing peptide (PrRP) has a potential to decrease food intake and ameliorate obesity, but is ineffective after peripheral administration. We have previously shown that our novel lipidized analogs PrRP enhances its stability in the circulation and enables its central effect after peripheral application. The purpose of this study was to explore if sub-chronic administration of novel PrRP analog palmitoylated in position 11 (palm11-PrRP31) to Koletsky-spontaneously hypertensive obese rats (SHROB) could lower body weight and glucose intolerance as well as other metabolic parameters.Subjects/MethodsThe SHROB rats (n = 16) were used for this study and age-matched hypertensive lean SHR littermates (n = 16) served as controls. Palm11-PrRP31 was administered intraperitoneally to SHR and SHROB (n = 8) at a dose of 5 mg/kg once-daily for 3 weeks. During the dosing period food intake and body weight were monitored. At the end of the experiment the oral glucose tolerance test was performed; plasma and tissue samples were collected. Thereafter, arterial blood pressure was measured.ResultsAt the end of the experiment, vehicle-treated SHROB rats showed typical metabolic syndrome parameters, including obesity, glucose intolerance, dyslipidemia, and hypertension. Peripheral treatment with palm11-PrRP31 progressively decreased the body weight of SHR rats but not SHROB rats, though glucose tolerance was markedly improved in both strains. Moreover, in SHROB palm11-PrRP31 ameliorated the HOMA index, insulin/glucagon ratio, and increased insulin receptor substrate 1 and 2 expression in fat and insulin signaling in the hypothalamus, while it had no effect on blood pressure.ConclusionsWe demonstrated that our new lipidized PrRP analog is capable of improving glucose tolerance in obese SHROB rats after peripheral application, suggesting that its effect on glucose metabolism is independent of leptin signaling and body weight lowering. These data suggest that this analog has the potential to be a compound with both anti-obesity and glucose-lowering properties.

Lipidomics to analyze the influence of diets with different EPA:DHA ratios in the progression of Metabolic Syndrome using SHROB rats as a model

The role of specific proportions of ω-3 EPA and DHA, in the modulation of inflammation and oxidative stress markers associated to the progression of Metabolic Syndrome was investigated. Potential inflammatory eicosanoids and docosanoids were discussed together to biomarkers of CVD, obesity, inflammation and oxidative stress in an animal model of metabolic disorders. Results evidenced a noteworthy health effect of 1:1 and 2:1 EPA:DHA proportions over 1:2 EPA:DHA based diets through a down-regulation in the production of strong pro-inflammatory ω-6 eicosanoids, a decrement of biomarkers of oxidative stress, and a modulation of fatty acid desaturase activities and plasma and membrane PUFAs towards greater anti-inflammatory profiles. Outcomes contribute to the general knowledge on the health benefits of marine lipids and their role on the progress of MetS, inflammation and oxidative stress. Results shed light on controversial protective mechanisms of EPA and DHA to better design dietary interventions aimed at reducing MetS.

Cardiovascular disease-related parameters and oxidative stress in SHROB rats, a model for metabolic syndrome.

SHROB rats have been suggested as a model for metabolic syndrome (MetS) as a situation prior to the onset of CVD or type-2 diabetes, but information on descriptive biochemical parameters for this model is limited. Here, we extensively evaluate parameters related to CVD and oxidative stress (OS) in SHROB rats. SHROB rats were monitored for 15 weeks and compared to a control group of Wistar rats. Body weight was recorded weekly. At the end of the study, parameters related to CVD and OS were evaluated in plasma, urine and different organs. SHROB rats presented statistically significant differences from Wistar rats in CVD risk factors: total cholesterol, LDL-cholesterol, triglycerides, apoA1, apoB100, abdominal fat, insulin, blood pressure, C-reactive protein, ICAM-1 and PAI-1. In adipose tissue, liver and brain, the endogenous antioxidant systems were activated, yet there was no significant oxidative damage to lipids (MDA) or proteins (carbonylation). We conclude that SHROB rats present significant alterations in parameters related to inflammation, endothelial dysfunction, thrombotic activity, insulin resistance and OS measured in plasma as well as enhanced redox defence systems in vital organs that will be useful as markers of MetS and CVD for nutrition interventions.

Targets of protein carbonylation in spontaneously hypertensive obese Koletsky rats and healthy Wistar counterparts: a potential role on metabolic disorders.

Oxidative stress is a concomitant factor in the pathogenesis of MetS that induces oxidative PTM as carbonylation. Through the use of a redox proteomics approach, we have thoroughly mapped the occurrence of protein targets of carbonylation in the genetically-induced MetS model SHROB rat. The present research brings a new insight of MetS pathogenesis and it may provide valuable information to understand the biological impact of oxidative stress in patients with MetS.

Excess oxidative stress in genetically obese rats is independent of elevated inflammatory markers (693.11)

Oxidative stress is elevated in obese humans and rodents and may contribute to obesity‐associated conditions. These conditions include elevated blood pressure, lipids, glucose, and insulin resistance, all of which are components of the metabolic syndrome and are present in the spontaneously hypertensive obese (SHROB/Kol) rat model of prediabetes. In the present study, SHROB (N=27) were compared to lean SHR/Kol (N=11) littermates obtained from Charles River Labs (Wilmington,MA). Oxidative stress was measured by assay of peroxides by the ferric orange xylenol method (Sigma, St. Louis, MO) and nitrotyrosine by immunoassay. Plasma and organ lipid peroxides were increased up to 3‐fold in SHROB rats relative to lean SHR. Nitrotyrosine immunoreactivity in solublized kidney extracts was increased by genetic obesity (SHROB: 290±52 vs SHR: 4.1±1.3 pmol/g wet weight). Similar results were obtained for liver. The activity in the liver cytosol of the protective enzyme superoxide dismutase was not different (SHROB: 63±5 vs SHR: 53±7 U/mg protein). Another protective enzyme, catalase, was also unchanged in the liver cytosol (SHROB: 95±6 vs SHR: 93±13 U/mg protein). Thus, the enzymes responsible for breaking down reactive oxygen species fail to up‐regulate in response to increased oxidative stress in SHROB. We tested whether increased oxidative stress may reflect inflammation in SHROB rats. The inflammatory markers tumor necrosis factor alpha (TNF‐a) and interleukin‐6 in plasma did not differ between SHROB and SHR (P>0.3 for each). The anti‐inflammatory mediator adiponectin was actually increased in plasma from SHROB (N = 15) relative to SHR (N = 11; 12.2 ± 0.3 versus 9.27 ± 0.6 ug/ml). Thus the increased oxidative stress in genetically obese and hypertensive SHROB rats is not a consequence of a global inflammatory state.Grant Funding Source: Supported by Ophthalmology Education Worldwide

Eicosapentaenoic acid/docosahexaenoic acid 1:1 ratio improves histological alterations in obese rats with metabolic syndrome

BackgroundMarine polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with improvement in the Metabolic Syndrome (MS). The aim of this study is to evaluate how three fish-oil diets with different eicosapentaenoic acid/docosahexaenoic acid ratios (EPA/DHA ratio) affect the histology of liver, kidney, adipose tissue and aorta in a preliminary morphological study. This work uses an animal model of metabolic syndrome in comparison with healthy animals in order to provide information about the best EPA:DHA ratio to prevent or to improve metabolic syndrome symptoms.Methods35 Wistar rats, as a control, and 35 spontaneously hypertensive obese rats (SHROB) were fed for 13 weeks with 3 different suplemmentation of fish oil containing EPA and DHA ratios (1:1, 2:1 and 1:2, respectively). All samples were stained with haematoxylin/eosin stain, except aorta samples, which were stained also with Verhoeff and van Gieson’s stain. A histological study was carried out to evaluate changes. These changes were statistically analyzed using SPSS IBM 19 software. The quantitative data were expressed by mean ± SD and were compared among groups and treatments using ANOVA with post-hoc tests for parametric data and the U-Mann–Whitney for non-parametric data. Qualitative data were expressed in frequencies, and compared with contingency tables using χ2 statistics.ResultsEPA:DHA 1:1 treatment tended to improve the density and the wrinkling of elastic layers in SHROB rats. Only Wistar rats fed with EPA:DHA 1:1 treatment did not show mast cells in adipose tissue and has less kidney atrophy. In both strains EPA:DHA 1:1 treatment improved inflammation related parameters in liver and kidney.ConclusionsEPA:DHA 1:1 treatment was the most beneficial treatment since improved many histological parameters in both groups of rats.

Urinary Biomarkers Track the Progression of Nephropathy in Hypertensive and Obese Rats

To determine whether urinary biomarkers of acute kidney injury can be used to monitor the progression of chronic kidney injury in a rat model of hypertension and obesity. A suite of novel urinary biomarkers were used to track the progression of kidney damage in SHROB and SHR-lean rats. Urinary albumin, NAG, clusterin, osteopontin, RPA-1 and fibrinogen levels were significantly elevated over time and were closely associated with the severity of histopathologically determined nephropathy in both SHROB and SHR-lean rats. Urinary biomarkers, such as albumin, fibrinogen, NAG, clusterin, RPA-1 and osteopontin, may serve as useful tools to track the progression of chronic kidney disease associated with hypertension and obesity.

Vasoactive effects of prostaglandins from the perivascular fat of mesenteric resistance arteries in WKY and SHROB rats

AimsWe have studied the vasoactive role of prostaglandins derived from perivascular adipose tissue (PVAT) and their effects on endothelial function in healthy rats and rats with metabolic syndrome (SHROB). Main methodsMesenteric resistance arteries (MRA) from SHROB and control rats (WKY) were mounted on wire myographs: a) together with a sphere of naturally occurring perivascular adipose tissue (with-PVAT group), or b) dissecting all the adventitial tissue (without-PVAT group). Key findingsEndothelial function, tested by acetylcholine reactivity of SHROB arteries with PVAT, was significantly lower than that of WKY. With-PVAT arteries, especially the SHROB, showed lower responses than those without PVAT. NO synthase inhibition diminished the acetylcholine responses in every group except the with-PVAT SHROB group. Blockade of cyclooxygenase-2, PGI2-IP, TXA2-TP, or TXA2 synthase increased to different extents the arterial responses in the SHROB with-PVAT group. PVAT from both rat strains revealed cyclooxygenase-2 activity and immunoassay confirmed the release of PGE2, PGI2 and TXA2. SignificanceOur major finding is that PVAT is a source of vasoactive prostaglandins in WKY and SHROB. We also report that the presence of visceral PVAT causes endothelial dysfunction of resistance arteries in the SHROB. The vascular responses to prostaglandins partly underlie the endothelial dysfunction of SHROB arteries.

Renal denervation attenuates impairment of renal function and kidney injury in obese spontaneously hypertensive rats

Background: Hypertension and obesity are associated with increased systemic sympathetic drive possibly contributing to the development of renal dysfunction. Renal sympathetic denervation (RDN) is a new strategy to decrease sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive. Methods: Blood pressure was measured by telemetrie. Kidney function was determined and renal perfusion was measured by Magnetic Resonance Imaging (MRI). Glomerulosclerosis was scored by semiquantitative morphometric evaluation and desmin staining was performed to quantify glomerular podocyte damage. Obese spontaneously hypertensive rats with RDN at the age of 34 weeks (SHR-ob RDN, n=15) were compared to sham operated SHR-ob (SHR-ob) and their normotensive lean controls (Ctr.). Animals were sacrificed at the age of 48 weeks. Results: In SHR-ob, RDN significantly reduced blood pressure for 100 days (220±8 vs. 156±7 mmHg, p < 0.001). Heart rate was not modulated. Renal catcholamine levels, tyrosin hydroxylase staining and tyrosin hydroxylase proteine levels were significantly reduced after RDN suggesting effective renal denervation. Development of renal dysfunction as characterized by increased urinary albumin/creatinine ratio and reduced glomerulary filtration rate were attenuated by RDN in SHR-ob. Attenuation of renal injury by RDN was confirmed by renal desmin staining, a marker for glomerular podocyte damage. RDN prevented glomerulosclerosis, as scored by semiquantitative morphometric evaluation. Percentage of apoptotic TUNEL-positive cells and renal gene expression of p53 and BAX were significantly increased in SHR-ob but not modified by RDN. In SHR-ob, renal perfusion was significantly reduced compared to Ctr. and normalized by RDN. Conclusion: In SHR-ob rats, RDN resulted in a stable and sustained blood pressure lowering effect for 100 days and attenuated impairment of renal function and glomerular damage. RDN may therefore provide protection in obese and hypertensive patients with renal dysfunction.

Hydrochlorothiazide exacerbates metabolic syndrome in the SHROB rat model

Metabolic syndrome consists of hypertension, insulin resistance, dyslipidemia and fatty liver. Thiazides are the leading treatment for hypertension, but some clinical studies have suggested adverse metabolic effects. We sought for the first time to characterize the metabolic effects of thiazides in an animal model of metabolic syndrome. SHROB rats are obese, hypertensive and express every component of human metabolic syndrome. Adult female SHROB rats (N=6 per group) were fed a purified diet (AIN 93) replete with electrolytes and treated in their drinking water for 5 weeks with either vehicle (250 ppm saccharine and 100 ppm sodium benzoate) or hydrochlorothiazide (achieved dose of 44±2 mg/kg/d). Systolic blood pressure fell progressively from 184±5 to 142±2 mmHg with thiazide treatment while remaining unchanged in controls. Heart rate was not affected. Body weight, food intake, and water intake did not differ between groups, nor did fasting glucose or insulin. Oral glucose tolerance testing (6 g/kg by gavage after an 18h fast) showed increased plasma glucose levels in the thiazide group (at 60 min post load, 394±48 vs 214±51 mg/dL in controls, P&lt;0.05 by t‐test). Insulin levels at the same time were half again higher in SHROB treated with thiazide (90±20 vs 61±14 ng/mL in controls, NS, but two‐way ANOVA shows a difference, P&lt;0.05 by F‐test). Relative liver mass was increased in the thiazide group relative to controls (43±3 vs 35±3 g/kg body weight, P&lt;0.05 by t‐test). Thus, thiazide was an effective antihypertensive therapy in the SHROB model of metabolic syndrome but worsened glucose tolerance and insulin resistance and enlarged the already fatty liver. The secretory response of the pancreas to glucose was apparently not impaired or even increased, suggesting that insulin signaling may be affected by thiazides.Research support for this study was given by Ophthalmology Education Worldwide

Rodent Models of Diabetes and Diabetes Complications

The rats listed here have been extensively studied as animal models of diabetic complications and their pathogenesis. The results of studies with the SHROB, JCR:LAcp and OLETF rats are instructive in understanding macro vascular diseases. The Cohen, GK, SHROB and OLETF rats are model of diabetic kidney disease. The SHROB rat might also be useful for diabetic retinopathy study. The importance of mitochondrial inactivity in diabetes was demonstrated with the ZDF rat. The heterogeneous complication models may be useful to understand pathogenesis, prevention and treatment of complications of diabetes mellitus.

Sitagliptin lowers glucagon and improves glucose tolerance in prediabetic obese SHROB rats

The SHROB (spontaneously hypertensive rat - obese strain) is a model of prediabetes and metabolic syndrome with insulin resistance, glucose intolerance and hypertension. Inhibitors of dipeptidyl dipeptidase IV (DPP-IV) are effective hypoglycemic agents in type 2 diabetes through potentiation of incretin hormones that act in the pancreas to increase insulin and decrease glucagon release. We sought to determine whether the DPP-IV inhibitor sitagliptin might be effective in prediabetes relative to standard therapy with the sulfonylurea glyburide, by using the SHROB model. SHROB show normal fasting glucose but are insulin resistant and hyperglucagonemic. SHROB were treated for six weeks with vehicle, sitagliptin (30 mg/kg/d) or glyburide (1 mg/kg/d) and compared with untreated lean spontaneously hypertensive rats. Body weight, food intake and fasting glucose were all unchanged in all three SHROB groups, but glucagon was reduced by 33% by sitagliptin while remaining unchanged following glyburide or vehicle. In oral glucose (6 g/kg) tolerance testing, both sitagliptin and glyburide lowered plasma glucose. Both sitagliptin and glyburide shifted peak insulin secretion earlier (30 min for glyburide and 60 min for sitagliptin but 240 min for vehicle). Only sitagliptin significantly enhanced insulin secretion. Sitagliptin is effective in normalizing excess glucagon levels and delaying exaggerated insulin secretion in response to a glucose challenge in a prediabetic model.

Oxidative stress in genetically obese SHROB rats

Oxidative stress is elevated in human obesity and several animal models. Oxidative stress, through the damaging effects of oxygen radicals, may contribute to obesity‐associated conditions. These include elevated blood pressure, lipids, glucose, and insulin resistance, all of which are present in the spontaneously hypertensive obese (SHROB/Kol) rat model of prediabetes. In the present study, SHROB (N=27) were compared to lean SHR/Kol (N=11) littermates. Oxidative stress was measured by assay of peroxides in plasma and the lipid fraction of kidney and liver tissue. Plasma and organ lipid peroxides were increased up to 3‐fold in untreated SHROB rats relative to lean SHR littermates. The activity in the liver cytosol of the protective enzyme superoxide dismutase was not different (SHROB: 63±5 vs SHR: 53±7 U/mg protein). Another protective enzyme, catalase, was also unchanged in the liver cytosol (SHROB: 95±6 vs SHR: 93±13 U/mg protein). Thus, the enzymes responsible for breaking down superoxide and hydrogen peroxide fail to up‐regulate in response to increased oxidative stress in SHROB. Subsequent oxidative damage may contribute to insulin resistance in the liver and renal and hepatic dysfunction.

Metabolic dysregulation in the SHROB rat reflects abnormal expression of transcription factors and enzymes that regulate carbohydrate metabolism

The Koletsky (SHROB) strain of rats is spontaneously hypertensive and displays insulin resistance, hyperglucagonemia and hypertriglyceridemia but is normoglycemic under fasting conditions. The aim of this study was to unravel the pattern of expression of genes encoding key regulatory enzymes involved in carbohydrate metabolism in the liver and kidney that may be impacted in this strain. We found that SHROB animals have decreased β-adrenergic receptor density and, consequently, blunted increases in cAMP levels in response to β-adrenergic agonists. They also have lower levels of hepatic as well as renal phospho enolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) mRNA and protein than their lean littermates. Expression of the genes for glycogen phosphorylase and glycogen synthase was also decreased. Hepatocytes from the SHROB animals exhibited glycogen depletion of only 50% compared to 86% by hepatocytes from lean littermates when challenged with either glucagon or forskolin to stimulate adenylyl cyclase. The expression of C/EBPα and C/EBPβ, two key transcription factors that are essential for the coordinated expression of genes involved in glucose homeostasis, was depressed in livers of the SHROB rats, as were levels of HNF-4α, PPARα and PGC-1α. We conclude that overproduction of glucose is prevented in the SHROB rats by decreased expression of the genes for glycogen phosphorylase and the gluconeogenic enzymes PEPCK and G6Pase, which may prevent progression to diabetes in this model.

Therapeutic Actions of Allylmercaptocaptopril and Captopril in a Rat Model of Metabolic Syndrome

Hypertension often coexists with hyperlipidemia, insulin resistance, and glucose intolerance in metabolic syndrome. Allylmercaptocaptopril is a conjugate of the angiotensin-converting enzyme inhibitor captopril with allicin, an active principle in garlic with multiple beneficial actions on metabolic-syndrome abnormalities. We sought to test the hypothesis that the conjugation of allicin to captopril may confer additional therapeutic actions in metabolic disease. We compared allylmercaptocaptopril (53.5 mg/kg/day orally for 60 days) to an equimolar dose of captopril (40 mg/kg/day) in the spontaneously hypertensive, obese rat (SHROB) model. Allylmercaptocaptopril prevented progressive weight gain, without a detectable effect on food intake. Both captopril and allylmercaptocaptopril lowered blood pressure, but allylmercaptocaptopril was more effective. Allylmercaptocaptopril, but not captopril, improved cardiac hypertrophy, as indicated by heart weight and ventricular-wall thickness. Allylmercaptocaptopril improved, whereas captopril impaired, oral glucose tolerance after a fast. Triglycerides were decreased by both captopril and allylmercaptocaptopril. Total cholesterol and non-HDL cholesterol were reduced by captopril but not by allylmercaptocaptopril. The SHROB rats developed severe glomerulosclerosis and renal failure. Allylmercaptocaptopril showed significant nephro-protection, as indicated by reductions in urinary protein loss, urinary protein-to-creatinine ratio, and plasma creatinine. Captopril showed the same trends and also prevented the decline of creatinine clearance. Finally, both allylmercaptocaptopril and captopril reduced the basal level of lipolysis in isolated abdominal adipocytes, and restored the response to catecholamine stimulation. Both captopril and allylmercaptocaptopril are effective in attenuating multiple abnormalities of metabolic syndrome. Allylmercaptocaptopril may have additional effectiveness on improving glucose tolerance, further lowering blood pressure, reducing cardiac hypertrophy, preventing weight gain, and protecting against renal disease.

Voluntary running activity is not sufficient for preventing the obesity of Koletsky (fak/fak) rats.

Recent data have demonstrated variability in the degree to which voluntary exercise prevents the hyperphagia and obesity in rodent obesity models. OLETF rats lacking CCK1 receptors and melanocortin-4 receptor knockout mice normalize food intake and body weight when given access to a running wheel, whereas exercise seems to have only minimal effects on the obesity of Zucker fatty (fa/fa) or Koletsky (fak/fak, SHROB) rats both congenitally lacking leptin receptors. To further characterize responses to voluntary exercise in the absence of leptin signaling, we determined food intake, body weight and hypothalamic gene expression in SHROB rats in response to running wheel access. We found that sedentary SHROB rats had increased food intake and body weight as compared to lean rats. SHROB rats did use the running wheel but to a less degree than that demonstrated in other models and this degree of activity did not significantly affect food intake or body weight. When we pair fed SHROB rats to the amounts consumed by lean controls, running activity was increased and overall resulted in body weight loss. This combination also resulted in a decrease in blood glucose levels, but did not significantly alter fat mass. Real-time RT PCR determination revealed that the combination of pair feeding and voluntary exercise resulted in further increased NPY and decreased POMC gene expression in the arcuate nucleus compared to sedentary SHROB rats. Together, these data demonstrated that voluntary exercise is not sufficient for preventing the obesity of SHROB rats. (Supported by DK074269).

High sucrose diet promotes longevity in obese hypertensive SHROB rats

The SHROB rat is a model of metabolic syndrome showing severe obesity, hypertension and end stage renal disease. SHROB live a little more than half as long as their SHR siblings (Figure). Median life expectancy (MLE) does not differ by sex in either SHROB or SHR. The shortened lifespan of SHROB is primarily a result of renal failure. We hypothesized that a high sucrose diet would accelerate renal disease and reduce longevity. We added sucrose to regular chow in a 1:1 ratio, replacing vitamins and minerals (AIN93). Median life expectancy was extended by nearly one-hundred days by the high sucrose diet, a highly significant effect (P < 0.005, Chi-square). The beneficial effect of replacing dietary protein with sucrose greatly exceeded any possible adverse effect of simple carbohydrate excess.