Caloric restriction reverses high-fat diet-induced endothelial dysfunction and vascular superoxide production in C57Bl/6 mice

Abstract

Obesity is frequently associated with endothelial dysfunction. We hypothesized that high-fat feeding dysregulates the balance between endothelial derived nitric oxide and superoxide formation. Furthermore, we examined whether caloric restriction could reverse the detrimental vascular effects related to obesity. Male C57Bl/6 mice were fed with normal-fat diet (fat 17%) or high-fat diet (fat 60%) for 150 days. After establishment of obesity at day 100, a subgroup of obese mice were put on caloric restriction (CR) (70% of ad libitum energy intake) for an additional 50 days. At day 100, aortic rings from obese mice receiving high-fat diet showed impaired endothelium-dependent vasodilation in response to acetylcholine (ACh). Caloric restriction reversed high-fat diet-induced endothelial dysfunction. At day 150, impaired vasodilatory responses to ACh in obese mice without caloric restriction were markedly improved by preincubation with the tetrahydrobiopterin (BH(4)) precursor sepiapterin and L-arginine, a substrate for endothelial nitric oxide synthase (eNOS). Additionally, inhibition of vascular arginase by L-norvaline partially, and superoxide scavenging by Tiron completely, restored endothelial cell function. Obese mice showed increased vascular superoxide production, which was diminished by endothelial denudation, pretreated of the vascular rings with apocynin (an inhibitor of reduced nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), oxypurinol (an inhibitor of xanthine oxidase), N(G)-nitro-L-arginine methyl ester (LNAME; an inhibitor of eNOS), or by adding the BH(4) precursor sepiapterin. Caloric restriction markedly attenuated vascular superoxide production. In obese mice on CR, endothelial denudation increased superoxide formation whereas vascular superoxide production was unaffected by L-NAME. Western blot analysis revealed decreased phosphorylated eNOS (Ser1177)-to-total eNOS expression ratio in obese mice as compared to lean controls, whereas the phospho-eNOS/NOS ratio in obese mice on CR did not differ from the lean controls. In conclusion, the present study suggests that caloric restriction reverses obesity induced endothelial dysfunction and vascular oxidative stress, and underscores the importance of uncoupled eNOS in the pathogenesis.

p38 mitogen-activated protein kinase is involved in arginase-II-mediated eNOS-Uncoupling in Obesity

“…Although multiple mechanisms underlying endothelial dysfunction in obesity and diabetes are demonstrated [29], functional defect of eNOS such as eNOS-uncoupling rather than decreased eNOS gene expression seems to be the major contributor to endothelial dysfunction in obesity and diabetes [13]. In line with this study, our present study demonstrates that despite augmented eNOS expression in the aortas of the obese WT mice (Figure 1), the endotheliumdependent relaxation (not the endothelium-independent relaxation) is decreased as compared to the lean mice fed NC (Figure 2), suggesting dysfunctional eNOS or uncoupling of eNOS in obesity.…”

“…Moreover, genetic ablation of Arg-II slows down endothelial senescence and protects mice from age-associated endothelial inflammatory responses through inhibition of eNOS-uncoupling [10], implying a causative role of Arg-II in eNOS-uncoupling and endothelial dysfunction in aging. Although eNOSuncoupling has been described in obesity [13], it is however not known whether Arg-II plays a role in this context in obesity.…”

Healthy human aging: intrinsic and environmental factors

“…Two primary epigenetic codes, DNA methylation and histone modification, are believed to dynamically influence chromatin structure, resulting in expression changes of relevant genes (LI et al, 2011). In most studies on calorie restriction the limitation of total calories derived from carbohydrates, fats, and proteins was to a level 25%-60% below that of control group fed ad libitum, however containing all essential nutrients, extension in life span can approach 50% in rodents (KOUBOVA;GUARENTE, 2003;WEINDRUCH et al, 1986;KETONEN et al, 2010;WU et al, 2008;SUN et al, 2004).…”

Caloric restriction and redox state: Does this diet increase or decrease oxidant production?

“…[51][52][53] Another large body of work demonstrates that ROS release from mitochondria or tissues from CR animals is decreased. 37,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] Other publications found no changes in ROS production with CR 46,[68][69][70][71] and many propose that CR-induced decreases in ROS release depend on tissues examined, time on the diet, animal age when the diet was initiated, and gender. No experimental publication was located demonstrating that CR in rodents enhances ROS generation in non-inflammatory tissues.…”