Beneficial effects of lifelong caloric restriction on endothelial function are greater in conduit arteries compared to cerebral resistance arteries

Abstract

Endothelial dysfunction occurs in conduit and cerebral resistance arteries with advancing age. Lifelong caloric restriction (CR) can prevent the onset of age-related dysfunction in many tissues, but its effects on cerebral resistance artery function, as compared with conduit artery function, have not been determined. We measured endothelium-dependent dilation (EDD) in the carotid artery and middle cerebral artery (MCA) from young (5-7 months), old ad libitum fed (AL, 29-32 months), and old lifelong CR (CR, 40 % CR, 29-32 months) B6D2F1 mice. Compared with young, EDD for old AL was 24 % lower in the carotid and 47 % lower in the MCA (p < 0.05). For old CR, EDD was not different from young in the carotid artery (p > 0.05), but was 25 % lower than young in the MCA (p < 0.05). EDD was not different between groups after NO synthase inhibition with N(ω)-nitro-L-arginine methyl ester in the carotid artery or MCA. Superoxide production by the carotid artery and MCA was greater in old AL compared with young and old CR (p < 0.05). In the carotid, incubation with the superoxide scavenger TEMPOL improved EDD for old AL (p > 0.05), with no effect in young or old CR (p > 0.05). In the MCA, incubation with TEMPOL or the NADPH oxidase inhibitor apocynin augmented EDD in old AL (p < 0.05), but reduced EDD in young and old CR (p < 0.05). Thus, age-related endothelial dysfunction is prevented by lifelong CR completely in conduit arteries, but only partially in cerebral resistance arteries. These benefits of lifelong CR on EDD result from lower oxidative stress and greater NO bioavailability.

Fig. 1

Endothelium-dependent dilation (EDD) to acetylcholine (ACh) in the absence or presence of nitric oxide synthase inhibitor N^ω-nitro-l-arginine methyl ester (l -NAME) measured by pressure myography in carotid (a) and middle cerebral arteries (MCA, b) from young, old ad libitum fed (AL), and old lifelong calorically restricted (CR) mice (n = 5–16 per group). Endothelium-independent dilation to sodium nitroprusside in carotid arteries (c) and MCAs (d) from young, old AL, and old CR mice (n = 5–9 per group). Significance marks denote a time by group interaction or main effect for group from repeated-measures ANOVA analyses. *p < 0.05 vs. young ACh alone, †p < 0.05 vs. old AL ACh alone, ‡p < 0.05 vs. old CR ACh alone. Values are mean±SEM

Fig. 2

Maximal response to acetylcholine in carotid and middle cerebral arteries (MCA) from young, old ad libitum fed (AL), and old lifelong calorically restricted (CR) mice (n = 9–16 per group). Each maximal response was normalized to the mean response of the young group for that artery. †p < 0.05 vs. old AL carotid, ‡p < 0.05 vs. old CR carotid. Values are mean±SEM

Fig 3

Superoxide production measured by electron paramagnetic resonance using a CMH spin probe in carotid arteries (a) and middle cerebral arteries (MCA, b) from young, old ad libitum fed (AL), and old lifelong calorically restricted (CR) mice (n = 4–8 group^-1). Representative spectra shown below each bar (scale for all carotid spectra is intensity:-1.0 to 1.0; scale for all MCA spectra is intensity: -0.4 to 0.4). *p < 0.05 vs. young, †p < 0.05 vs. old AL. Values are mean±SEM

Fig. 4

Carotid artery EDD to acetylcholine (ACh) in the absence or presence of superoxide dismutase mimetic TEMPOL, alone or in combination with NOS inhibitor N^ω-nitro-l-arginine methyl ester (l -NAME), measured by pressure myography in arteries from young (a), old ad libitum fed (AL, b), and old lifelong calorically restricted (CR, c) mice (n = 4-12 per group). Significance marks denote a time by condition interaction or main effect for condition from repeated-measures ANOVA analyses. *p < 0.05 vs. young ACh alone, †p < 0.05 vs. old AL ACh alone, ‡p < 0.05 vs. old CR ACh alone, §p < 0.05 vs. young ACh with TEMPOL, ‖ p < 0.05 vs. old AL ACh with TEMPOL, ¶p < 0.05 vs. old CR ACh with TEMPOL. Values are mean±SEM

Fig. 5

Middle cerebral artery (MCA) EDD to acetylcholine (ACh) in the absence or presence of superoxide dismutase mimetic TEMPOL, alone or in combination with NOS inhibitor N^ω-nitro-l-arginine methyl ester (l -NAME), measured by pressure myography in arteries from young (a), old ad libitum fed (AL, b), and old lifelong calorically restricted (CR, c) mice (n = 3–16 per group). Significance marks denote a time by condition interaction or main effect for condition from repeated-measures ANOVA analyses. *p < 0.05 vs. young ACh alone, †p < 0.05 vs. old AL ACh alone, ‡p < 0.05 vs. old CR ACh alone, ‖p < 0.05 vs. old AL ACh with TEMPOL. Values are mean±SEM

Fig. 6

Maximal middle cerebral artery (MCA) EDD to acetylcholine (ACh) in the absence or presence of NADPH oxidase inhibitor apocynin (APO), alone or in combination with NOS inhibitor N^ω-nitro-l-arginine methyl ester (l -NAME), measured by pressure myography in arteries from young, old ad libitum fed (AL), and old lifelong calorically restricted (CR) mice (n = 3–16 per group). *p < 0.05 vs. young ACh alone, †p < 0.05 vs. old AL ACh alone, ‡p < 0.05 vs. old CR ACh alone, ‖p < 0.05 vs. old AL ACh with APO, ¶p < 0.05 vs. old CR ACh with APO. Values are mean±SEM

Fig. 7

Change in diameter in response to exogenous nicotinamide adenine dinucleotide phosphate (NADPH) in the carotid (a) and middle cerebral arteries (MCA, b) from young, old ad libitum fed (AL), and old lifelong calorically restricted (CR) mice (n = 5–11 per group). Values are mean±SEM