Short‐term calorie restriction reverses vascular endothelial dysfunction in old mice by increasing nitric oxide and reducing oxidative stress

Abstract

SummaryTo determine if short-term calorie restriction reverses vascular endothelial dysfunction in old mice, old (O, n = 30) and young (Y, n = 10) male B6D2F1 mice were fed ad libitum (AL) or calorie restricted (CR, approximately 30%) for 8 weeks. Ex vivo carotid artery endothelium-dependent dilation (EDD) was impaired in old ad libitum (OAL) vs. young ad libitum (YAL) (74 ± 5 vs. 95 ± 2% of maximum dilation, P < 0.05), whereas old calorie-restricted (OCR) and YCR did not differ (96 ± 1 vs. 94 ± 3%). Impaired EDD in OAL was mediated by reduced nitric oxide (NO) bioavailability associated with decreased endothelial NO synthase expression (aorta) (P < 0.05), both of which were restored in OCR. Nitrotyrosine, a cellular marker of oxidant modification, was markedly elevated in OAL (P < 0.05), whereas OCR was similar to Y. Aortic superoxide production was 150% greater in OAL vs. YAL (P < 0.05), but normalized in OCR, and TEMPOL, a superoxide dismutase (SOD) mimetic that restored EDD in OAL (to 97 ± 2%), had no effect in Y or OCR. OAL had increased expression and activity of the oxidant enzyme, NADPH oxidase, and its inhibition (apocynin) improved EDD, whereas NADPH oxidase in OCR was similar to Y. Manganese SOD activity and sirtuin1 expression were reduced in OAL (P < 0.05), but restored to Y in OCR. Inflammatory cytokines were greater in OAL vs. YAL (P < 0.05), but unaffected by CR. Carotid artery endothelium-independent dilation did not differ among groups. Short-term CR initiated in old age reverses age-associated vascular endothelial dysfunction by restoring NO bioavailability, reducing oxidative stress (via reduced NADPH oxidase-mediated superoxide production and stimulation of anti-oxidant enzyme activity), and upregulation of sirtuin-1.

Nicotinamide mononucleotide supplementation reverses vascular dysfunction and oxidative stress with aging in mice

“…We have previously demonstrated that arterial SIRT1 activity is reduced with aging and contributes to the age‐related impairment in endothelial function (Donato et al ., 2011; Gano et al ., 2014). We and others also have shown that lifelong CR prevents (Csiszar et al ., 2009; Donato et al ., 2013) and short‐term CR reverses (Rippe et al ., 2010) the age‐associated decline in endothelial function and that these effects are associated with enhanced arterial SIRT1 activity. Consistent with these observations, we recently found that 4 weeks of treatment with the SIRT1 activator SRT1720 restores endothelial function (i.e., EDD) in old mice (Gano et al ., 2014).…”

“…As established in our previous work (Rippe et al ., 2010; Sindler et al ., 2011; Fleenor et al ., 2013; LaRocca et al ., 2013), aging in the control animals was associated with an impairment in ex vivo carotid artery EDD in response to acetylcholine due to reduced NO‐mediated dilation (Fig. 1A,B).…”

“…Consistent with our previous work (Rippe et al ., 2010; Sindler et al ., 2011; Fleenor et al ., 2013; Gano et al ., 2014), pharmacofunctional experiments revealed that arteries from old untreated mice showed a complete restoration of maximal EDD in the presence of the superoxide dismutase mimetic, TEMPOL, indicating that excessive superoxide‐related oxidative stress was the cause of the age‐associated impairment of EDD (Fig. 2A).…”

“…We have previously shown that lifelong caloric restriction (CR), as well as short‐term CR in old animals, prevents or reverses endothelial dysfunction and large elastic artery stiffening by reducing superoxide production, increasing NO bioavailability, and modifying structural proteins (Rippe et al ., 2010; Donato et al ., 2013). However, because adherence to CR is not practical for most humans, there is growing interest in pharmacological therapies that may induce the benefits of CR.…”

“…In this context, the mammalian SIRT1, one of seven members in the sirtuin family of protein deacetylases/deacylases, is a nicotinamide adenine dinucleotide (NAD + )‐dependent deacetylase that acts as a metabolic energy sensor implicated in several of the beneficial effects of CR, including reduced oxidative stress (Boily et al ., 2008; Merksamer et al ., 2013). Our previous work shows that reduced SIRT1 expression and activity is a key mechanism mediating impaired EDD in aging arteries (Rippe et al ., 2010; Donato et al ., 2011; Gano et al ., 2014), and our recent findings indicate that pharmacological activation of SIRT1 with the compound SRT1720 improves EDD in old mice in part by reducing oxidative stress (Gano et al ., 2014). …”