HFS Rats Research Articles

Blood-brain barrier lesion - a novel determinant of autonomic imbalance in heart failure and the effects of exercise training.

Heart failure (HF) is characterized by reduced ventricular function, compensatory activation of neurohormonal mechanisms and marked autonomic imbalance. Exercise training (T) is effective to reduce neurohormonal activation but the mechanism underlying the autonomic dysfunction remains elusive. Knowing that blood-brain barrier (BBB) lesion contributes to autonomic imbalance, we sought now to investigate its involvement in HF- and exercise-induced changes of autonomic control. Wistar rats submitted to coronary artery ligation or SHAM surgery were assigned to T or sedentary (S) protocol for 8 weeks. After hemodynamic/autonomic recordings and evaluation of BBB permeability, brains were harvesting for ultrastructural analysis of BBB constituents, measurement of vesicles trafficking and tight junction's (TJ) tightness across the BBB (transmission electron microscopy) and caveolin-1 and claudin-5 immunofluorescence within autonomic brain areas. HF-S rats vs. SHAM-S exhibited reduced blood pressure, augmented vasomotor sympathetic activity, increased pressure and reduced heart rate variability, and, depressed reflex sensitivity. HF-S also presented increased caveolin-1 expression, augmented vesicle trafficking and a weak TJ (reduced TJ extension/capillary border), which determined increased BBB permeability. In contrast, exercise restored BBB permeability, reduced caveolin-1 content, normalized vesicles counting/capillary, augmented claudin-5 expression, increased TJ tightness and selectivity simultaneously with the normalization of both blood pressure and autonomic balance. Data indicate that BBB dysfunction within autonomic nuclei (increased transcytosis and weak TJ allowing entrance of plasma constituents into the brain parenchyma) underlies the autonomic imbalance in HF. Data also disclose that exercise training corrects both transcytosis and paracellular transport and improves autonomic control even in the persistence of cardiac dysfunction.

Combined caloric restriction and exercise provides greater metabolic and neurocognitive benefits than either as a monotherapy in obesity with or without estrogen deprivation

Neurodegeneration, as indicated by brain dysfunction and cognitive decline, is one of the complications associated with obesity and estrogen deprivation. Calorie restriction and exercise regimes improved brain function in neurodegenerative diseases. However, the comparative effects of a combination of calorie restriction with exercise, calorie restriction, and an exercise regime alone on brain/cognitive function in obesity with or without estrogen deprivation have not been investigated. Sixty female rats were fed a normal diet (ND) or a high-fat diet (HFD) for 27 weeks. At week 13, the ND-fed rats underwent a sham operation with sedentary lifestyle, HFD-fed rats were divided into two groups: each having either a sham operation (HFS) or ovariectomy (HFO). At week 20, HFD-fed rats in each group were divided into four subgroups undergoing either a sedentary lifestyle, calorie restriction, exercise regime or a combination of calorie restriction and exercise for 7 weeks. Insulin resistance, cognitive decline and hippocampal pathologies were found in both HFS and HFO rats. HFO rats had higher levels of insulin resistance and hippocampal reactive oxygen species levels than HFS rats. Calorie restriction decreased metabolic disturbance and hippocampal oxidative stress but failed to attenuate cognitive decline in HFS and HFO rats. Exercise attenuated metabolic/hippocampal dysfunctions, resulting in improved cognition only in HFS rats. Combined therapies restored brain function, and cognitive function in HFS and HFO rats. Therefore, a combination of calorie restriction with exercise is probably the greatest lifestyle modification to diminish the brain pathologies and cognitive decline in obesity with or without estrogen deprivation.

PCSK9 inhibitor and atorvastatin reduce cardiac impairment in ovariectomized prediabetic rats via improved mitochondrial function and Ca2+ regulation.

Post‐menopausal women have a higher risk of developing cardiometabolic dysfunction. Atorvastatin attenuates dyslipidaemia and cardiac dysfunction but it can have undesirable effects including increased risk of diabetes and myalgia. Currently, the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor efficiently reduces low‐density lipoprotein cholesterol (LDL‐C) levels more effectively than atorvastatin. We have been suggested that PCSK9 inhibitor attenuated cardiometabolic impairment more effectively than atorvastatin in ovariectomized prediabetic rats. Female Wistar rats (n = 48) were fed a normal diet (ND) or high‐fat diet (HFD) for 12 weeks. Then, HFD rats were assigned to a sham‐operated (Sham) or ovariectomized (OVX) group. Six weeks after surgery, the OVX group was subdivided into 4 treatment groups: vehicle (HFOV), atorvastatin (HFOA) (40 mg/kg/day; s.c.), PCSK9 inhibitor (HFOP) (4 mg/kg/day; s.c.) and oestrogen (HFOE2) (50 µg/kg/day; s.c.) for an additional 3 weeks. Metabolic parameters, cardiac and mitochondrial function, and [Ca2+]i transients were evaluated. All HFD rats became obese‐insulin resistant. HFS rats had significantly impaired left ventricular (LV) function, cardiac mitochondrial function and [Ca2+]i transient dysregulation. Oestrogen deprivation (HFOV) aggravated all of these impairments. Our findings indicated that the atorvastatin, PCSK9 inhibitor and oestrogen shared similar efficacy in the attenuation in cardiometabolic impairment in ovariectomized prediabetic rats.

Cardiac remodeling and higher sensitivity to ischemia–reperfusion injury in female rats submitted to high-fat high-sucrose diet: An in vivo/ex vivo longitudinal follow-up

Prediabetes is an important risk factor for Type 2 diabetes and cardiovascular complications, such as myocardial infarction. However, few studies explore female sex in this context. Here, we aim to investigate the effects of high-fat high-sucrose diet on cardiac parameters and sensitivity to ischemia–reperfusion injury of female Wistar rats. Female Wistar rats received for 5 months normal diet (CTRL group) or high-fat high-sucrose diet (HFS group). Every month, MRI was performed to follow myocardial morphology, function and perfusion; cardiac and hepatic triglyceride content; and amount of sub-cutaneous and visceral adipose tissues. Then, ex vivo experiments were performed on isolated perfused hearts to evaluate tolerance to ischemia–reperfusion, with simultaneous measurement of energy metabolism by 31P MRS and contractile function. Coronary flow was measured before and after ischemia. At the end of the experiments, hearts were freeze-clamped for biochemical assays. Five months of high-fat high-sucrose diet induced a prediabetic condition in female Wistar rats, associated with an increase in myocardial perfusion, systolic and diastolic wall thickness. HFS rats also exhibited higher sensitivity to ischemia–reperfusion injury in comparison to controls, characterized by impaired cardiac function, energy metabolism and endothelial function. Biochemical analyses in hearts highlighted eNOS uncoupling, higher malondialdehyde level and lower S-Glutathionylation of proteins in HFS rats, indicating higher oxidative stress. Prediabetes induced by energy-dense diet was associated with modification of cardiac morphology and higher myocardial sensitivity to ischemia–reperfusion injury. These results may be related to the high risk of cardiovascular complications among Type 2 diabetic women.

Estrogen deprivation aggravates intracellular calcium dyshomeostasis in the heart of obese-insulin resistant rats.

The incidence of cardiovascular disease and metabolic syndrome increases after the onset of menopause, giving evidence for the vital role of estrogen. Intracellular calcium [Ca2+ ]i regulation plays an important role in the maintenance of left ventricular (LV) contractile function. Although either estrogen deprivation or obesity has been shown to strongly affect the metabolic status and LV function, the effects of estrogen deprivation on the cardiometabolic status and cardiac [Ca 2+ ]i regulation in the obese-insulin resistant condition have never been investigated. Our hypothesis was that estrogen deprivation aggravates LV dysfunction through the increased impairment of [Ca 2+ ]i homeostasis in obese-insulin resistant rats. Female rats were fed on either a high-fat (HFD, 59.28% fat) or normal (ND, 19.77% fat) diet for 13 weeks. Then, rats were divided into sham (HFS and NDS) operated or ovariectomized (HFO and NDO) groups. Six weeks after surgery, metabolic status, LV function and incidence of [Ca 2+ ]i transients were determined. NDO, HFS, and HFO rats had evidence of obese-insulin resistance indicated by increased body weight with hyperinsulinemia and euglycemia. Although NDO, HFS, and HFO rats had markedly reduced %LV fractional shortening, E/A ratio and decreased [Ca 2+ ]i transient amplitude and decay rate, HFO rats had the most severe impairments. These findings indicate that estrogen deprivation had a strong impact on abnormal LV function through [Ca 2+ ]i regulation. In addition, evidence was found that in obese-insulin resistant rats, estrogen deprivation severely aggravates LV dysfunction via increased impairment of [Ca 2+ ]i homeostasis.

Both oophorectomy and obesity impaired solely hippocampal-dependent memory via increased hippocampal dysfunction.

Our previous study demonstrated that obesity aggravated peripheral insulin resistance and brain dysfunction in the ovariectomized condition. Conversely, the effect of obesity followed by oophorectomy on brain oxidative stress, brain apoptosis, synaptic function and cognitive function, particularly in hippocampal-dependent and hippocampal-independent memory, has not been investigated. Our hypothesis was that oophorectomy aggravated metabolic impairment, brain dysfunction and cognitive impairment in obese rats. Thirty-two female rats were fed with either a normal diet (ND, n = 16) or a high-fat diet (HFD, n = 16) for a total of 20 weeks. At week 13, rats in each group were subdivided into sham and ovariectomized subgroups (n = 8/subgroup). At week 20, all rats were tested for hippocampal-dependent and hippocampal-independent memory by using Morris water maze test (MWM) and Novel objective recognition (NOR) tests, respectively. We found that the obese-insulin resistant condition occurred in sham-HFD-fed rats (HFS), ovariectomized-ND-fed rats (NDO), and ovariectomized-HFD-fed rats (HFO). Increased hippocampal oxidative stress level, increased hippocampal apoptosis, increased hippocampal synaptic dysfunction, decreased hippocampal estrogen level and impaired hippocampal-dependent memory were observed in HFS, NDO, and HFO rats. However, the hippocampal-independent memory, cortical estrogen levels, cortical ROS production, and cortical apoptosis showed no significant difference between groups. These findings suggested that oophorectomy and obesity exclusively impaired hippocampal-dependent memory, possibly via increased hippocampal dysfunction. Nonetheless, oophorectomy did not aggravate these deleterious effects under conditions of obesity.

Testosterone Deprivation Aggravates Left-Ventricular Dysfunction in Male Obese Insulin-Resistant Rats via Impairing Cardiac Mitochondrial Function and Dynamics Proteins

Background: We have previously reported that testosterone deprivation at a very young age accelerated, but did not aggravate, left-ventricular (LV) dysfunction in obese insulin-resistant rats. However, the effects of testosterone deprivation during adulthood on LV function in obese insulin-resistant rats remains unclear. We hypothesized that testosterone deprivation aggravates LV dysfunction and cardiac autonomic imbalance via the impairment of cardiac mitochondrial function and dynamics proteins, a reduction in insulin receptor function, and an increase in apoptosis in obese insulin-resistant rats. Methods: Male rats were fed on either a normal diet (ND) or a high-fat diet (HFD) for 12 weeks. They were then subdivided into 2 groups: sham operation (NDS, HFS) and orchiectomy (NDO, HFO). Metabolic parameters, blood pressure, heart rate variability (HRV), and LV function were determined at baseline and before and after orchiectomy. Mitochondrial function and dynamics proteins, insulin signaling, and apoptosis were determined 12 weeks postoperatively. Results: HFS rats exhibited obese insulin resistance, depressed HRV, and LV dysfunction. In HFO rats, systolic blood pressure was increased with more excessive depression of HRV and increased LV dysfunction, compared with HFS rats. These adverse cardiac effects were consistent with markedly increased mitochondrial dysfunction, reduced mitochondrial complex I and III proteins, reduced mitochondrial fusion proteins, and increased apoptosis, compared with HFS rats. However, testosterone deprivation did not lead to any alteration in the insulin-resistant condition in HFO rats, compared with HFS rats. Conclusion: We concluded that testosterone deprivation during adulthood aggravated the impairment of mitochondrial function, mitochondrial respiratory complex, mitochondrial dynamics proteins, and apoptosis, leading to LV dysfunction in obese insulin-resistant rats.

Estrogen deprivation aggravates cardiometabolic dysfunction in obese-insulin resistant rats through the impairment of cardiac mitochondrial dynamics

The incidence of cardiovascular disease and metabolic syndrome increases after the onset of menopause, suggesting estrogen has a vital role in their prevention. Mitochondrial dynamics are known to play an important role in the maintenance of cardiac physiological function. However, the effects of estrogen deprivation on cardiometabolic status and cardiac mitochondrial dynamics under conditions of obese-insulin resistance have never been investigated. We hypothesized that estrogen deprivation aggravates cardiac dysfunction through increased cardiac mitochondrial fission in obese-insulin resistant rats. Female rats were fed on either a high fat (HFD, 57.60% fat) or normal (ND, 19.77% fat) diet for 13 weeks. The rats were then divided into 4 groups. Two sham groups (HFS and NDS) and 2 operated or ovariectomized (HFO and NDO) groups (n = 8/group). Six weeks after surgery, metabolic status, heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial function and dynamics, and metabolic parameters were determined. Insulin resistance developed in NDO, HFS and HFO rats as indicated by increased plasma insulin and HOMA index. Although rats in both NDO and HFS groups had markedly impaired LV function indicated by reduced %LVFS and impaired cardiac mitochondrial function, rats in the HFO group had the most severe impairments. Moreover, the estrogen deprived rats (NDO and HFO) had increased cardiac mitochondrial fission through activation of phosphorylation of Drp-1 at serine 616. Our findings indicated that estrogen deprivation caused the worsening of LV dysfunction through increased cardiac mitochondrial fission in obese-insulin resistant rats.

Vildagliptin reduces cardiac ischemic-reperfusion injury in obese orchiectomized rats.

Obesity and testosterone deprivation are associated with coronary artery disease. Testosterone and vildagliptin (dipeptidyl peptidase-4 inhibitors) exert cardioprotection during ischemic-reperfusion (I/R) injury. However, the effect of these drugs on I/R heart in a testosterone-deprived, obese, insulin-resistant model is unclear. This study investigated the effects of testosterone and vildagliptin on cardiac function, arrhythmias and the infarct size in I/R heart of testosterone-deprived rats with obese insulin resistance. Orchiectomized (O) or sham operated (S) male Wistar rats were divided into 2 groups to receive normal diet (ND) or high-fat diet (HFD) for 12 weeks. Orchiectomized rats in each diet were divided to receive testosterone (2 mg/kg), vildagliptin (3 mg/kg) or the vehicle daily for 4 weeks. Then, I/R was performed by a 30-min left anterior descending coronary artery ligation, followed by a 120-min reperfusion. LV function, arrhythmia scores, infarct size and cardiac mitochondrial function were determined. HFD groups developed insulin resistance at week 12. At week 16, cardiac function was impaired in NDO, HFO and HFS rats, but was restored in all testosterone- and vildagliptin-treated rats. During I/R injury, arrhythmia scores, infarct size and cardiac mitochondrial dysfunction were prominently increased in NDO, HFO and HFS rats, compared with those in NDS rats. Treatment with either testosterone or vildagliptin similarly attenuated these impairments during I/R injury. These finding suggest that both testosterone replacement and vildagliptin share similar efficacy for cardioprotection during I/R injury by decreasing the infarct size and attenuating cardiac mitochondrial dysfunction caused by I/R injury in testosterone-deprived rats with obese insulin resistance.

0093 : Endothelium masks increased sympathetic vasopressor activity in rats with metabolic syndrome

Despite sympathetic hyperactivation is considered as a key trigger of hypertension, in some obese or metabolic syndrome (MetS) subjects, such altered sympatho-vagal balance was not associated with changes in arterial blood pressure. Vascular endothelium is a potent modulator of adrenergic vascular tone, thus we aimed to determine, in a rat model of MetS, whether the endothelium and especially the classical vasodilatory eNOS-NO pathway could counteract the effect of increased sympathetic vasopressor action. After14 weeks of high fat high sucrose diet (HFS), HFS developed several features of MetS phenotype, such as increased body mass, abdominal fat accumulation, high LDL and triglycerides levels, higher fasting blood glucose and insulinemia, as well as impaired glucose and insulin tolerance compared with control rats (Ctrl) fed with standard diet. As assessed by catecholamine assay and heart rate variability analysis (HRV), HFS rats also presented increased sympathetic outflow but without consequences on skin microcirculation and arterial blood pressure. In HFS rats, vascular reactivity test revealed hyporeactivity to α1-adrenergic receptors (AR) stimulation with unchanged α 1DAR expression. This phenomenon was rather due to endothelial adaptation since endothelial removal or eNOS inhibition by L-NAME normalized adrenergic vasoconstriction in HFS rats. In addition, eNOS phosphorylation (activation site, ser1177) was increased by PE in HFS ones only. In line with this result, eNOS inhibition in-vivo also revealed higher blood pressure in HFS rats compared to Ctrl ones. In conclusion, tonic restrain of adrenergic vasopressor action by endothelium is increased in HFS rats which contribute to maintain their blood pressure in normal range. The author hereby declares no conflict of interest

0175 : Phenotypic remodeling of perivascular adipose tissue in a rat model of metabolic syndrome: vascular consequences and beneficial impact of exercise training

This study was designed to evaluate the impact of high fat and high sucrose diet (HFS) on perivascular adipose tissue (PVAT) and its consequence on vascular function. Whether exercise training was able to counteract this alterations has been investigated as a potential therapeutic strategy. Rats were fed with standard (Ctrl rats) or HFS diet (HFS rats) for 15 weeks. After 6 weeks, HFS rats were randomly assigned into 2 groups: sedentary and trained group (HFS-Ex). PVAT remodeling was assessed by a proteome profiler, histological and biochemical assays. The impact of PVAT secretion on vascular function was assessed on isolated aortic rings incubated or not with PVAT secretum. We reported increased PVAT mass in HFS rats associated with increase in both white to brown adipocytes proportion and uncoupling protein 1 level. Despite no major effect of HFS diet on PVAT adipokines profile was reported, adiponectin level and secretion were reduced in PVAT of HFS rats. As a potential consequence, we observed a marked endothelial dysfunction in Ctrl aortic rings incubated with PVAT secretum of HFS rats. The use of a non-specific antioxidant (N-Acetyl cysteine) in the organ bath blunted the deleterious effect of HFS secretum on endothelial function, suggesting a redox-dependent mechanism in this phenomenon. Exercise training in HFS rats normalized PVAT mass but has no effect on the browning process. However, this strategy was able to normalize adiponectin level in PVAT of HFS rats and finally abolished the detrimental effect of its secretion on endothelial function. Diet-induced metabolic syndrome leads to PVAT remodeling inducing deleterious vasoactives properties. The ability of exercise training to modulate this phenomenon could be considered as a good strategy to counteract the potential role of PVAT in the development of chronic vascular dysfunction in metabolic syndrome disease. The author hereby declares no conflict of interest

0294 : Glucuronide metabolites of hydroxytyrosol are responsible for the antioxidative properties of olive oil

Hydroxytyrosol (HT) is known to be a strong polyphenolic antioxidant of olive oil. However, its in vivo effects are controversial since intestinal absorption is low and it is highly metabolized into glucuronides (GC), suggesting that these metabolites could be responsible of HT biological activity in vivo . Our objectives were to study the direct effects of HT and its glucuronides on vascular function and the oxidative stress vascular protection on healthy and diabetic rats The vascular function was assessed on aortas from diabetic-High Fat Sucrose diet (HFS) and age-matched (22 weeks) control fed with a standard diet (SD) Wistar rats, in comparison to young (9 weeks) control Wistar rats (ySD). The endothelium-dependent and independent vasorelaxing effects of these compounds were assessed via incremental doses of HT and GC (10 -9 to 10 -4 M) and compared to Resveratrol (Res). Expression and phosphorylation of Ser 1177 eNOS were measured by Western blot. To evaluate the anti-oxidative effects of these polyphenols (100 μM, 5min), vascular function was assessed in presence/absence of t -BOOH (500μM, 30min). HT and GC did not show any endothelium-dependent and independent vasorelaxation effects in ySD and HFS rats while Res produced vasorelaxing effect at 10 -4 M in all groups of rats and no vasorelaxant effects were noticed in SD rats. The overall absence of vasorelaxing effect can be explained by the lack eNOS phosphorylation. As for the antioxidative properties, HT, GC and Res increased significantly endothelium-dependent relaxation in comparison of aorta rings treated only with t -BOOH (79.9%±9.2, 74.1%±8.6, 71.0%±8.2, 48.4%±5.3 respectively). In addition, co-incubation of HT/GC and Res/GC increased even more the vasorelaxation under pro-oxydant conditions. In diabetic HFS rats, (i) the incubation for 5min with HT and GC did not improve neither vasorelaxation nor the contraction; (ii) however, a prolonged 30 min incubation resulted in more pronounced and significant contractile (64.8%±12.4 and 95.6%±16.3, respectively) and endothelium-dependent relaxation effects (30%±7.5 and 58.1%±10.3 respectively) for GC in comparison to HT. In conclusion, GC seems to be responsible for the anti-oxidative properties of olive oil but further experimentations have to be realized concerning its possible interconversion in HT by β-glucuronidase. The author hereby declares no conflict of interest

0149 : Antioxidant molecules of tea (Camellia sinensis) decrease hepatic lipogenesis and steatosis in a high fat-sucrose diet NAFLD rat model

Recent studies suggested that oxidative stress could trigger lipid accumulation in liver and thus subsequent development of hepatic steatosis which contributes to alter blood lipid level leading to increase cardiovascular risk factors. Tea has been described to prevent liver disorders and decrease cardiovascular risk. However, whether tea decreases oxidative stress and thus prevents hepatic steatosis has never been investigated. Therefore we aimed to investigate the effects of tea on oxidative stress and lipid accumulation in a rat model of high fatsucrose diet (HFS) induced metabolic syndrome (fed during 14 weeks) and in isolated rat hepatocytes.Wistar rats were randomly divided into three groups: Ctrl, HFS and HFS+Tea rats which had free access to tea infusion drink instead of water (n=15). Lipid profile of the liver, lipogenesis gene expression and oxidative stress were measured in each group of rat. Isolated hepatocytes were treated with the ROS inducer t-BHP in the presence or not of antioxidant tempol or tea. Then, superoxide anion production and lipid accumulation were measured using specific fluorescent probes. We reported that HFS diet-induced elevated hepatic lipid content by enhancing lipogenic gene expression in HFS rats compared to Ctrl ones. HFS diet-induced hepatic steatosis was attenuated by tea which was mainly associated with decrease hepatic oxidative stress and increased plasma total antioxidant capacity. The key role of antioxidant properties of tea in such phenomenon was confirmed in primary culture of rat hepatocytes. Indeed, we reported that increased ROS production with t-BHP resulted in lipid accumulation in hepatocytes, which was normalized by both tempol and tea. To conclude, we clearly reported that the antioxidant properties of tea protect rats from HFS diet-induced hepatic steatosis via its anti-lipogenesis effects. The consequence of such nutritional strategy on cardiovascular risk factor would constitute the next step of this work. The author declares a conflict of interest : Les travaux ont été réalisés dans le cadre d’une bourse CIFRE Thés de la Pagode-Université de Toulon

Fat and Sucrose Intake Induces Obesity-Related Bone Metabolism Disturbances: Kinetic and Reversibility Studies in Growing and Adult Rats.

Metabolic and bone effects were investigated in growing (G, n = 45) and mature (M, n = 45) rats fed a high-fat/high-sucrose diet (HFS) isocaloric to the chow diet of controls (C, n = 30 per group). At week 19, a subset of 15 rats in each group (HFS or C, at both ages) was analyzed. Then one-half of the remaining 30 HFS rats in each groups continued HFS and one-half were shifted to C until week 27. Although no serum or bone marrow inflammation was seen, HFS increased visceral fat, serum leptin and insulin at week 19 and induced further alterations in lipid profile, serum adiponectin, and TGFβ1, TIMP1, MMP2, and MMP9, suggesting a prediabetic phenotype and cardiovascular dysfunction at week 27 more pronounced in M than G. These events were associated with dramatic reduction of osteoclastic and osteoid surfaces with accelerated mineralizing surfaces in both HFS age groups. Mineral metabolism and its major regulators were disturbed, leading to hyperphosphatemia and hypocalcemia. These changes were associated with bone alterations in the weight-bearing tibia, not in the non-weight-bearing vertebra. Indeed in fat rats, tibia trabecular bone accrual increased in G whereas loss of trabecular bone in M was alleviated. At diaphysis cortical porosity increased in G and even more in M at week 27. After the diet switch, metabolic and bone cellular disturbances fully reversed in G, but not in M. Trabecular benefit of the obese was preserved in both age groups and in M the age-related bone loss was even lighter after the diet switch than in prolonged HFS. At the diaphysis, cortical porosity normalized in G but not in M. Hypocalcemia in G and M was irreversible. Thus, the mild metabolic syndrome induced by isocaloric HFS is able to alter bone cellular activities and mineral metabolism, reinforce trabecular bone, and affect cortical bone porosity in an irreversible manner in older rats.

Obesity accelerates cognitive decline by aggravating mitochondrial dysfunction, insulin resistance and synaptic dysfunction under estrogen-deprived conditions

Chronic consumption of a high-fat diet (HF) causes peripheral insulin resistance, brain insulin resistance, brain mitochondrial dysfunction and cognitive impairment. Estrogen deprivation has also been found to impair cognition. However, the combined effect of both conditions on the brain is unclear. We hypothesized that estrogen deprivation causes brain insulin resistance, brain mitochondrial dysfunction, hippocampal synaptic dysfunction and cognitive impairment, and that consumption of a HF accelerates these impairments in an estrogen-deprived condition. Seventy-two female rats were divided into sham (S) and ovariectomized (O) groups. Rats in each group were further divided into two subgroups to be fed with either a normal diet (ND) or HF for 4, 8 and 12weeks. At the end of each period, the Morris water maze test was carried out, after which the blood and brain were collected for metabolic and brain function analysis. Obesity, peripheral insulin resistance, increased brain oxidative stress and hippocampal synaptic dysfunction were observed at the eighth week in the NDO, HFS and HFO rats. However, these impairments were worse in the HFO rats. Interestingly, brain insulin resistance, brain mitochondrial dysfunction and cognitive impairment developed earlier (week eight) in the HFO rats, whereas these conditions were observed later at week 12 in the NDO and HFS rats. Either estrogen deprivation or HF appears to cause peripheral insulin resistance, increased brain oxidative stress, hippocampal synaptic dysfunction, brain mitochondrial dysfunction and brain insulin resistance, which together can lead to cognitive impairment. A HF accelerates and aggravates these deleterious effects under estrogen-deprived conditions.

0205 : Exercise training prevents microvascular dysfunction in a rat model of diet-induced metabolic syndrome

Metabolic syndrome (MetS) is associated with increased risk of cardiovascular disease (CVD). One important key feature underlying the pathophysiology of CVD is microvascular dysfunction. Although, exercise training is a well recognized strategy to reduce cardiovascular and metabolic disorders, the impact on MetS induced microvascular dysfunction is poorly described and the underlying mechanisms remain unknown. Thus, the aim of this work was to evaluate the effect of physical activity on microvascular reactivity in a rat model of MetS. Rats were fed with standard (Ctrl group) or high-fat and sucrose diet (HFS group) for 14 weeks. After 6 weeks, HFS rats were randomly assigned into 2 groups: sedentary (HFS) and trained group (HFS-Ex). In vivo endothelial function was evaluated by skin Laser Doppler technique associated to transcutaneous iontophoresis at 06 and 14 weeks. Body weight, metabolic parameters and blood pressure were also measured. High-fat and sucrose diet induced a significant body weight raise accompanied by the increase of serum level of glucose, triglycerides, HDL and LDL-cholesterol. All of these parameters were restored after 4 weeks of exercise training in HFS-Ex group. In addition, skin endothelium-dependent dilation, which was decreased in HFS compared to Ctrl, was prevented by exercise training. This result could be explained by increased level of eNOS expression and phosphorylation on its activation site (ser1177). These results mainly suggest that an exercise training strategy, which is able to partially correct metabolic disorders in a model of MetS in rats, also prevents in vivo microvascular dysfunction.

0301 : Effects of low and high polyphenols content lettuces consumption on high fat diet induced metabolic syndrome and endothelial dysfunction

Consumption of vegetables has been recommended to reduce the risk of cardiovascular disease. The protection against disease is partly due to bioactive molecules including polyphenols. In order to evaluate the effects of such polyphenols, we supplemented High Fat diet rats with low and high polyphenolic content lettuces. 32 Wistar rats were divided in 4 groups, a control group (Ctrl), a high fat and sucrose diet group (HFS, 60% fat+10%sucrose) and 2 groups that after 6 weeks of HFS diet were supplemented 8 weeks with both HFS diet and either a low or high polyphenol content lettuces (HFS-LP; Blond Oak Leaf, 30g/day vs. HFS-HP; Red Oak Leaf, 30g/day). After 14 weeks of HF diet including 8 weeks of supplementation, we performed a glucose tolerance test and an evaluation of arterial blood pressure (BP) by tail cuff method. Then, aortic endothelial function and eNOS dependent vasodilatation were evaluated ex vivo on isolated rings. Firstly, we observed a higher body weight in HFS group (502±21g) compared to Ctrl group (417±14g) without any effect of both supplementations. Regarding glycemic control, HFS group presented increased fasting blood glucose (1,37g/l vs. 1,20g/l) as well as an impairment of glucose tolerance. Interestingly, both groups with lettuces intake displayed healthy fasting blood glucose values (1.14g/l and 1.15g/l) and an improvement of glucose tolerance. Moreover, both lettuces treatments managed to normalize the increase in mean BP observed in HFS group (HFS; 131mmHg; HFS-LP 120 mmHg; HFS-HP, 117mmHg). However, no effect of lettuce consumption was observed on endothelial dysfunction and impaired eNOS dependent vasodilatation observed in HFS rats. In conclusion, we observed in this study a major effect of lettuce intake on glycemic control as well as arterial BP. However, no effect regarding the difference in polyphenols content has been reported here underlying that the effects were independent of the specific polyphenols contained in the HP lettuce.

Obese-insulin resistance accelerates and aggravates cardiometabolic disorders and cardiac mitochondrial dysfunction in estrogen-deprived female rats.

Women have a lower incidence of cardiovascular diseases (CVD) than men at a similar age but have an increased incidence of CVD and metabolic syndrome after menopause, indicating the possible protective effects of estrogen on cardiometabolic function. Although obesity is known to increase CVD risks, its impact on the heart on estrogen deprivation is still inconclusive. We investigated the effects of obese-insulin resistance on cardiometabolic function in estrogen-deprived ovariectomized rats. Adult female ovariectomized (O) or sham (S)-operated rats randomly received either normal diet (ND, 19.77 % fat) or high-fat diet (HF, 57.60 % fat) (n = 6/group) for 12 weeks. The heart rate variability (HRV), left ventricular (LV) performance, cardiac autonomic balance, cardiac mitochondrial function, metabolic parameters, oxidative stress, and apoptotic markers were determined at 4, 8, and 12 weeks. Insulin resistance developed at week 8 in NDO, HFS, and HFO rats as indicated by increased plasma insulin and HOMA index. However, only HFO rats had elevated plasma cholesterol level at week 8, whereas HFS rats had showed elevation at week 12. In addition, only HFO rats had depressed HRV, impaired LV performance indicated by decreased fractional shortening (%FS) and cardiac mitochondrial dysfunction indicated by increased mitochondrial ROS level, mitochondrial depolarization and swelling, as early as week 8, whereas other groups exhibited them at week 12. Either estrogen deprivation or obesity alone may impair metabolic parameters, cardiac autonomic balance, and LV and mitochondrial function. However, an obese insulin-resistant condition further accelerated and aggravated the development of these cardiometabolic impairments in estrogen-deprived rats.

High dietary salt decreases antioxidant defenses in the liver of fructose-fed insulin-resistant rats

In this study we investigated the hypothesis that a high-salt diet to hyperinsulinemic rats might impair antioxidant defense owing to its involvement in the activation of sodium reabsorption to lead to higher oxidative stress. Rats were fed a standard (CON), a high-salt (HS), or a high-fructose (HF) diet for 10 weeks after which, 50% of the animals belonging to the HF group were switched to a regimen of high-fructose and high-salt diet (HFS) for 10 more weeks, while the other groups were fed with their respective diets. Animals were then euthanized and their blood and liver were examined. Fasting plasma glucose was found to be significantly higher (approximately 50%) in fructose-fed rats than in the control and HS rats, whereas fat liver also differed in these animals, producing steatosis. Feeding fructose-fed rats with the high-salt diet triggered hyperinsulinemia and lowered insulin sensitivity, which led to increased levels of serum sodium compared to the HS group. This resulted in membrane perturbation, which in the presence of steatosis potentially enhanced hepatic lipid peroxidation, thereby decreasing the level of antioxidant defenses, as shown by GSH/GSSG ratio (HFS rats, 7.098±2.1 versus CON rats, 13.2±6.1) and superoxide dismutase (HFS rats, 2.1±0.05 versus CON rats, 2.3±0.1%), and catalase (HFS rats, 526.6±88.6 versus CON rats, 745.8±228.7 U/mg ptn) activities. Our results indicate that consumption of a salt-rich diet by insulin-resistant rats may lead to regulation of sodium reabsorption, worsening hepatic lipid peroxidation associated with impaired antioxidant defenses.

Salt overload in fructose-fed insulin-resistant rats decreases paraoxonase-1 activity

Paraoxonase 1 (PON1) is a HDL-associated esterase/lactonase and its activity is inversely related to the risk of cardiovascular diseases. The aim of the present study was to evaluate the effect of a high-salt diet on serum PON1 activity in fructose-fed insulin-resistant rats. Adult male Fischer rats were initially divided into two groups. Control (CON), which received a normal salt diet and drinking water throughout the study; high fructose (HF), which received a normal salt diet and 20% fructose supplemented drinking water. After 10 weeks, half of the animals from HF group were randomly switched to a high-salt diet and 20% fructose supplemented drinking water (HFS) for more 10 weeks. Serum PON1 activity was determined by synthetic substrate phenyl acetate. HFS rats showed markedly decreased PON1 activity (HFS rats, 44.3 ± 14.4 g/dL versus CON rats, 64.4 ± 13.3 g/dL, P < 0.05) as compared to controls. In parallel, the level of oxidative stress, as indicated by thiobarbituric acid reactive substances (TBARS), was increased in HFS rats by 1.2-fold in the liver in relation to controls and was negatively correlated with PON activity. Differential leukocyte counts in blood showed a significant change in lymphocytes and monocytes profile. In conclusion, these results show that PON1 activity is decreased in fructose-fed insulin-resistant rats on a high-salt diet, which may be associated with increased oxidative stress, leading to inflammation.