Gender-specific effects of caloric restriction on the balance of vascular nitric oxide and superoxide radical

Effect of long-term inorganic nitrate administration on myocardial ischemia-reperfusion injury in ovariectomized rats

Introduction: Menopause is associated with reduced nitric oxide (NO) bioavailability and lower tolerance against myocardial ischemia-reperfusion (IR) injury. This study investigated whether long-term nitrate administration provides resistance against myocardial IR injury in ovariectomized (OVX) rats. Method: After ovariectomy, female rats were assigned to the OVX and the OVX + nitrate groups (n = 14/group); the latter group consumed nitrate (100 mg/L) for 9 months. At month 9, each group was divided into two subgroups (n = 7/subgroup), of which one subgroup was exposed to myocardial IR (IR+ hearts) and the other was not exposed (IR- hearts). The hearts of rats were isolated, and NO metabolite (NOx), oxidative stress indices, and mRNA expressions of endothelial (eNOS), inducible (iNOS), and neuronal (nNOS) NO synthases, as well as markers of apoptosis, were measured in the IR- and IR+ hearts. In the IR+ hearts, cardiac function indices (CFI) and the infarct size were also measured. Results: Nitrate increased catalase activity (97%) and eNOS expression (2.94-fold) in the IR- hearts. In the IR+ hearts, nitrate reduced left ventricular (LV) end-diastolic pressure (11.6%) and infarct size (26.2%) and increased recovery of LV developed pressure (44.0%) and peak rate of positive (28.9%) and negative (15.4%) changes in LV pressure. In addition, in the IR+ hearts, nitrate increased eNOS and B-cell lymphoma-2 (Bcl-2) as well as decreased iNOS, Bcl-2 associated X protein (Bax), caspase-3, caspase-8, caspase-9, and tumor necrosis factor-α (TNF-α) expression. Nitrate increased total antioxidant capacity (TAC) and catalase (CAT) activity and decreased malondialdehyde (MDA) levels at month nine in serum and IR+ hearts. Conclusion: The favorable effects of nitrate against IR injury were associated with higher eNOS and Bcl-2 expression, CAT activity, TAC, and lower iNOS, Bax, caspase-3, caspase-8, caspase-9 and TNF-α expression, and MDA in the heart tissue. Nitrate preconditioning alleviated IR-induced myocardial injury in OVX rats; this effect was associated with eNOS upregulation before IR and the blunting of OVX-induced eNOS downregulation, iNOS upregulation, apoptosis, and oxidative stress in heart tissue after IR.

Protective effects of long-term nitrate administration against ovariectomy-induced kidney dysfunction in rats

BACKGROUND

Menopause is associated with higher risks of chronic kidney disease. We determined the effect of nitrate on ovariectomy-induced kidney dysfunction METHODS: Control, ovariectomized (OVX), control + nitrate, and OVX + nitrate female Wistar rats (n = 10/group); sodium nitrate (100 mg/L) administered in drinking water for 9 months. Glomerular filtration rate (GFR) and albumin excretion rate (AER) were calculated from serum and urine parameters. At month 9, serum and kidney levels of nitric oxide (NO) metabolites (NOx), oxidative stress indices, and mRNA expression of endothelial NO synthase (eNOS) were measured; with histological analyses of the kidney.

RESULTS

Compared to controls, OVX rats had lower GFR (31%, p = 0.0079), higher glomerular tuft volume (30%, p = 0.0402), and Bowman's capsule space (39%, p = 0.0224). OVX rats had lower serum NOx (33%, p = 0.0061) and kidney eNOS mRNA expression (34%, p = 0.0368). Nitrate administration to: (i) control rats increased serum NOx (59%, p < 0.0001), with no effect on other parameters; (ii) OVX rats increased serum (85%, p < 0.0001) and kidney (106%, p = 0.0008) NOx values, and restored kidney eNOS expression to normal value. Nitrate administration to OVX rats increased GFR (36%, p = 0.0361) and restored glomerular tuft volume and Bowman's capsule space to normal values. In OVX rats, it also increased serum catalase (CAT) activity, serum and kidney total antioxidant capacity (TAC), and decreased serum malondialdehyde (MDA).

CONCLUSIONS

Low-dose long-term nitrate administration protects against ovariectomy-induced kidney dysfunction in rats. This effect is associated with reducing ovariectomy-induced oxidative stress and restoring eNOS-derived NO deficiency in systemic circulation and the kidney.

Time-restricted feeding (TRF) for prevention of age-related vascular cognitive impairment and dementia

Aging is the most significant risk factor for vascular cognitive impairment (VCI), and the number of individuals affected by VCI is expected to exponentially increase in the upcoming decades. Yet, there are no current preventative or therapeutic treatments available against the development and progression of VCI. Therefore, there is a pressing need to better understand the pathophysiology underlying these conditions, for the development of novel tools and interventions to improve cerebrovascular health and delay the onset of VCI. There is strong epidemiological and experimental evidence that lifestyle factors, including nutrition and dietary habits, significantly affect cerebrovascular health and thereby influence the pathogenesis of VCI. Here, recent evidence is presented discussing the effects of lifestyle interventions against age-related diseases which in turn, inspired novel research aimed at investigating the possible beneficial effects of dietary interventions for the prevention of cognitive decline in older adults.

Beneficial Effects of Low-Calorie-Carbohydrate/High-Agar Diet on Cardiometabolic Disorders Associated with Non-Alcoholic Fatty Liver Disease in Obese Rats

Energy restriction and low carbohydrate diets are recommended as nutrition therapies to prevent becoming overweight or obese. However, their beneficial effects in non-alcoholic fatty liver disease (NAFLD) are less well investigated. In addition, the effects of the type of polysaccharides incorporated into these diets and their contents have been scarcely studied. Therefore, this study aimed to elucidate whether low-calorie-carbohydrate high-agar diets could improve liver metabolic dysfunction, membrane fluidity, oxidative damage, and endothelial dysfunction in obese rats. Obesity was induced by feeding rats a high-fat diet (HFD) for 10 weeks. The obese rats were then divided into two homogenous groups: the first group was fed low-calorie-carbohydrate/high-agar diet (LCC/HA) and the second continued to consume the HFD for 4 weeks [obese control (Ob-C)]. Normo-ponderal rats were fed a normal diet during the entire study, and were used as the control (N-C). Compared with the Ob-C group, body weight, hepatic lipids, low density lipoproteins cholesterol (C), the non esterified cholesterol/phospholipids ratio, serum transaminases activities, and lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) were reduced in LCC/HA group (P<0.05). However, the serum concentration of high density lipoproteins-C was enhanced (P<0.05). In addition, we observed improved antioxidant defence and endothelial dysfunction associated with antioxidant enzymes, such as superoxide dismutase, glutathione peroxidase, and catalase (P<0.05), and nitric oxide level (P<0.05). These findings suggest that hypocaloric diets low in energy and carbohydrates and rich in agar may be beneficial against HFD-induced hepatic steatosis damage, and may be a promising therapeutic strategy to counteract NAFLD development associated with obesity.

Calorie restriction reprograms diurnal rhythms in protein translation to regulate metabolism

Calorie restriction (CR) delays aging and affects the circadian clocks by reprogramming circadian rhythms in gene expression. To expand on the circadian mechanisms in CR, we assayed rhythms in the protein translation by analyzing polysome-associated mRNAs in the liver of mice fed ad libitum (AL) and CR diets. Global comparison of the diets revealed that <1% of transcripts were differentially abundant in the polysomes. In contrast, the large differential, up to 10%, was detected when CR and AL diets were compared at individual times throughout the day. Most transcripts that were rhythmic under AL lost their rhythms, and many new transcripts gained rhythms under CR. Only a small fraction of transcripts, including the circadian clock genes, were rhythmic under both diets. Thus, CR strongly reprograms translation. CR affected translation of enzymes regulating long-chain acetyl-coenzyme A (Acyl-CoA) metabolism. The expression of the Acyl-CoA thioesterase (ACOT) family was induced upon CR, leading to the increased transcriptional activity of peroxisome proliferator-activated receptor α, the transcriptional factor regulated by the ACOT products. We propose that the differential translation induced by CR leads to a temporal partition and reprogramming of metabolic processes and provides a link between CR, lipid metabolism, and the circadian clock.-Makwana, K., Gosai, N., Poe, A., Kondratov, R. V. Calorie restriction reprograms diurnal rhythms in protein translation to regulate metabolism.

Caloric Restriction and Its Effect on Blood Pressure, Heart Rate Variability and Arterial Stiffness and Dilatation: A Review of the Evidence

Essential hypertension, fast heart rate, low heart rate variability, sympathetic nervous system dominance over parasympathetic, arterial stiffness, endothelial dysfunction and poor flow-mediated arterial dilatation are all associated with cardiovascular mortality and morbidity. This review of randomised controlled trials and other studies demonstrates that caloric restriction (CR) is capable of significantly improving all these parameters, normalising blood pressure (BP) and allowing patients to discontinue antihypertensive medication, while never becoming hypotensive. CR appears to be effective regardless of age, gender, ethnicity, weight, body mass index (BMI) or a diagnosis of metabolic syndrome or type 2 diabetes, but the greatest benefit is usually observed in the sickest subjects and BP may continue to improve during the refeeding period. Exercise enhances the effects of CR only in hypertensive subjects. There is as yet no consensus on the mechanism of effect of CR and it may be multifactorial. Several studies have suggested that improvement in BP is related to improvement in insulin sensitivity, as well as increased nitric oxide production through improved endothelial function. In addition, CR is known to induce SIRT1, a nutrient sensor, which is linked to a number of beneficial effects in the body.

Study of insulin vascular sensitivity in aortic rings and endothelial cells from aged rats subjected to caloric restriction: Role of perivascular adipose tissue

The prevalence of metabolic syndrome is dramatically increasing among elderly population. Metabolic syndrome in aged individuals is associated with hyperinsulinemia and insulin resistance both in metabolic tissues and in the cardiovascular system, with this fact being associated with the cardiometabolic alterations associated to this condition. Caloric restriction (CR) improves insulin sensitivity and is one of the dietetic strategies most commonly used to enlarge life and to prevent aging induced cardiovascular alterations. The aim of this study was to analyze the possible beneficial effects of CR in aging-induced vascular insulin resistance both in aortic rings and in primary culture of endothelial cells. In addition, the inflammatory profile of perivascular adipose tissue (PVAT) and its possible role in the impairment of vascular insulin sensitivity associated with aging was also assessed. Three experimental groups of male Wistar rats were used: 3 (3m), 24 (24m) fed ad libitum and 24months old rats subjected to 20% CR during their three last months of life (24m-CR). Aorta rings surrounded or not by PVAT were mounted in an organ bath and precontracted with phenylephrine (10^-7.5M). Changes in isometric tension were recorded in response to cumulative insulin concentrations (10^-8-10^-5.5M) in the presence or absence of L-NAME (10^-4M). Aortic rings and primary aortic endothelial cells were incubated in presence/absence of insulin (10^-7M) and the activation of the PI3K/Akt and MAPK pathways as well as nitrite and nitrates concentrations and the mRNA levels of eNOS, insulin receptor, and GLUT-4 were assessed. CR prevented the aging-induced decrease in the vasodilator response to insulin and the aging-induced increase in the vasoconstrictor response to high insulin concentrations. Changes between 24m and 24m-CR aorta rings were abolished in the presence of L-NAME. CR induced-improvement in insulin vascular sensitivity was related with activation of the PI3K/Akt both in aortic rings and in aortic endothelial cells in response to insulin. CR attenuated the overexpression of iNOS, TNF-α and IL-1β in the PVAT of aged rats although aortic rings surrounded by PVAT from 24m rats showed and increased vasorelaxation in response to insulin compared to aortic rings from 3m and 24m-CR rats. In conclusion, a moderate protocol of CR improves insulin vascular sensitivity and prevents the aging induced overexpression of pro-inflammatory cytokines in PVAT.

Caloric Restriction as a Strategy to Improve Vascular Dysfunction in Metabolic Disorders

Caloric restriction (CR) has proved to be the most effective and reproducible dietary intervention to increase healthy lifespan and aging. A reduction in cardiovascular disease (CVD) risk in obese subjects can be already achieved by a moderate and sustainable weight loss. Since pharmacological approaches for body weight reduction have, at present, a poor long-term efficacy, CR is of great interest in the prevention and/or reduction of CVD associated with obesity. Other dietary strategies changing specific macronutrients, such as altering carbohydrates, protein content or diet glycemic index have been also shown to decrease the progression of CVD in obese patients. In this review, we will focus on the positive effects and possible mechanisms of action of these strategies on vascular dysfunction.

Mild caloric restriction reduces blood pressure and activates endothelial AMPK-PI3K-Akt-eNOS pathway in obese Zucker rats

Genetic obesity models exhibit endothelial dysfunction associated to adenosine monophosphate-activated protein kinase (AMPK) dysregulation. This study aims to assess if mild short-term caloric restriction (CR) restores endothelial AMPK activity leading to an improvement in endothelial function. Twelve-week old Zucker lean and obese (fa/fa) male rats had access to standard chow either ad libitum (AL, n=8) or 80% of AL (CR, n=8) for two weeks. Systolic blood pressure was significantly higher in fa/fa AL rats versus lean AL animals, but was normalized by CR. Endothelium-dependent relaxation to acetylcholine (ACh, 10(-9) to 10(-4) M) was reduced in fa/fa AL compared to control lean AL rats (p<0.001), and restored by CR. The AMPK activator AICAR (10(-5) to 8·10(-3) M) elicited a lower relaxation in fa/fa AL rings that was normalized by CR (p<0.001). Inhibition of PI3K (wortmannin, 10(-7) M), Akt (triciribine, 10(-5) M), or eNOS (L-NAME, 10(-4) M) markedly reduced AICAR-induced relaxation in lean AL, but not in fa/fa AL rats. These inhibitions were restored by CR in Zucker fa/fa rings. These data show that mild short-term CR improves endothelial function and lowers blood pressure in obesity due to the activation of the AMPK-PI3K-Akt-eNOS pathway.

[Energy restriction reduces oxidative stress in the aorta and heart and corrects the atherogenic risk in obese rat]

AIM OF THE STUDY

The aim was to see if 40% of caloric restriction can improve in rats, the oxidative stress induced by a high fat diet on liver, heart and aorta, and have a positive impact on the lipoproteins-cholesterol contents.

METHODS

Male Wistar rats (n=12) consumed at weaning obesegenic diet. The obese rats were divided into two groups (n=6) each consumed for 4 weeks a normocaloric diet (1,60 MJ) or a calorie restricted diet (40% of energy of the standard diet [0.96 MJ]). A control group (n=6) was fed a standard diet during the experiment.

RESULTS

Caloric restriction decreased cholesterol and low-density lipoproteins-cholesterol, whereas the high-density lipoproteins-cholesterol was elevated. Levels of cholesterol in the aorta and heart were lowered in the group that consumed caloric restriction compared to normocaloric diet. The values of thiobarbituric acid reactive substances and hydroperoxides were lowered in the aorta and the heart. The caloric restriction compared to normocaloric diet increased positively the superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities in the heart and those of catalase and superoxide dismutase in aorta.

CONCLUSION

In obese rats, caloric restriction may play a role in the antioxidant defense of cardiovascular system by reducing proatherogenic cholesterol and lipid peroxidation and increasing the antioxidant activity of some enzymes, which was in favor of reduction of cardiometabolic risk associated with obesity.

[Caloric restriction suppresses endothelial cells senescence via down-regulation of NOX4 induced by HNF3γ]

The aim of current study is to investigate the molecular mechanism that caloric restriction (CR) suppresses endothelial cells senescence. Human aortic endothelial cells (HAECs) were divided into 5 groups: control group, high caloric group (about 1.5 times caloric intake of control group), low caloric group (about 0.5 times caloric intake of control group), siRNA plus low caloric group (low caloric treatment pretreated with special siRNA targeting hepatocyte nuclear factor 3γ (HNF3γ)), and siRNA plus high caloric group (high caloric treatment pretreated with special siRNA targeting HNF3γ). The gene and protein expressions of HNF3γ and NADPH oxidase 4 (NOX4) were quantified by real-time quantitative PCR (RT-qPCR) and Western blotting, respectively. Intracellular reactive oxygen species (ROS) production was measured by flow cytometry. Endothelial cells senescence was assayed by senescence associated β-galactosidase staining. After verifying the binding of HNF3γ to NOX4 promoter region by chromatin immunoprecipitation assay (ChIP), NOX4 promoter activity was assayed by dual-luciferase reporter system. Compared with the control group, the mRNA and protein expression levels of HNF3γ,and the ratio of phosphorylated HNF3γ protein increased significantly (P<0.05) in low caloric group, and decreased significantly (P<0.05) in high caloric group and siRNA plus low or high caloric group; whereas the mRNA and protein levels of NOX4 intracellular ROS and endothelial cells senescence decreased significantly (P<0.05) in low caloric group and increased significantly (P<0.05) in high caloric group and siRNA plus low or high caloric group. ChIP result showed there were four HNF3γ binding sites in NOX4 gene promoter region (-6, -76, -249 and -954 bp) and HNF3γ could bind to all 4 predicted sites. According to the results of dual-luciferase reporter system, HNF3γ binding to 1 site (-6 bp), 2 sites (-6 and -76 bp), 3 sites (-6, -76 and -249 bp) and 4 sites(-6, -76, -249 and -954 bp) could suppress NOX4 promoter activity to 80.15±4.64%, 40.02.±2.15%, 16.46±2.24% and 12.13±1.46% compared with that of baseline, respectively ( P<0.05). In a word, low caloric intake decreases the production of intracellular ROS and suppresses endothelial cells senescence through promoting HNF3γ binging to NOX4 promoter region and inhibiting NOX4 gene expression induced by up-regulated HNF3γ.

Sexual dimorphism in cardiac triacylglyceride dynamics in mice on long term caloric restriction

Human studies indicate augmented myocardial lipid metabolism in females, and that sex and obesity interact to predict myocardial fatty acid oxidation and storage. Altered lipid dynamics precede cardiomyopathies, and many studies now address high fat diets. Conversely, caloric restriction (CR), is the most studied model for longevity and stress resistance, including protection against myocardial ischemia. However, no information exists on the effects of long-term caloric restriction (CR) on triacylglyceride (TAG) content and dynamics in the heart. This study explored the effects of CR, sex and age on TAG dynamics in mouse hearts. Male and female SVJ129 mice were fed either normal (ND) or CR diet for 3 or 10 months. In 5-month-old mice, CR similarly decreased cardiac TAG in males (ND: 25.5±4.5 nmol/mg protein; CR: 12.6±2.7, P<0.05) and females (ND: 30.1±4.4; CR: 13.7±1.2) (no significant differences in TAG content were seen between sexes). CR reduced the contribution of exogenous palmitate to oxidative metabolism in males and females, by 15% and 11% respectively, versus ND, without affecting cardiac workload. CR also induced a larger reduction in TAG turnover in male (68%) than female hearts (38%). Interestingly, in 5 month old male mice, CR reproduced the lower TAG turnover rates of middle-aged males (ND 13-month-old male=423±76 nmol/mg protein/min). Thus, long term CR reduces TAG pool dynamics. Despite reduced content, hearts of female mice subjected to CR retained a more dynamic TAG pool than males, while males respond with greater metabolic remodeling of cardiac lipid dynamics.