1. Investigación

Caloric restriction (CR) improves endothelial function through the upregulation of adenosine monophosphateactivated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS). Moreover, hydrogen peroxide (H2O2) is upregulated in yeast subjected to CR. Our aim was to assess if mild short-term CR increases vascular H2O2 formation as a link with AMPK and eNOS activation. Twelve-week old Zucker obese (fa/fa) and control Zucker lean male rats were fed a standard chow either ad libitum (AL, n=10) or with a 20% CR (CR, n=10) for two weeks. CR significantly improved relaxation to ACh in fa/fa rats because of an enhanced endogenous production of H2O2 in aortic rings (H2O2 levels fa/faAL=0.5±0.05 nmol/mg vs. H2O2 levels fa/faCR=0.76±0.07 nmol/mg protein; p<0.05). Expression of mitochondrial superoxide dismutase (Mn-SOD) and total SOD activity were increased in aorta from fa/fa animals after CR. In cultured aortic endothelial cells, serum deprivation or 2-deoxy-D-glucose induced a significant increase in: i) superoxide anion and H2O2 levels, ii) p-AMPK/AMPK and p-eNOS/eNOS expression and iii) nitric oxide levels. This effect was reduced by catalase and strongly inhibited by Ca2+/calmodulin-dependent kinase II (CamkII) silencing. In conclusion, we propose that mild short-term CR might be a trigger of mechanisms aimed at protecting the vascular wall by the increase of H2O2, which then activates AMPK and nitric oxide release, thus improving endothelium-dependent relaxation. In addition, we demonstrate that CAMKII plays a key role in mediating CRinduced AMPK activation through H2O2 increase.

The activation of endoplasmic reticulum (ER) stress and a reduction of AMP-dependent protein kinase (AMPK) phosphorylation have been described in obesity. We hypothesize that a moderate caloric restriction (CR) might contribute to reducing ER stress and increasing AMPK phosphorylation in peripheral tissues from genetically obese Zucker fa/fa rats and in peripheral blood mononuclear cells (PBMCs). Zucker Lean and Zucker fa/fa rats were fed with chow diet either ad libitum (AL) (C, as controls) or 80% of AL (CR) for 2 weeks, giving rise to four experimental groups: Lean C, Lean CR, fa/fa C and fa/fa CR. CR significantly increased AMPK phosphorylation in the liver, perirenal adipose tissue (PRAT) and PBMCs from fa/fa rats but not in the subcutaneous AT (SCAT), suggesting a reduced response of SCAT to CR. Liver samples of fa/fa rats exhibited an increased mRNA expression of PERK, EIF-2α, XBP-1(s), Chop and caspase 3, which was significantly reduced by CR. PRAT exhibited an overexpression of Edem and PDIA-4 in fa/fa rats, but only PDIA-4 expression was reduced by CR. eIF-2α phosphorylationwas significantly increased in all studied tissues fromfa/fa rats and reduced by CR. A negative correlationwas detected between p-AMPK and p-eIF-2α in the liver, PRAT and PBMCs from fa/fa rats but not in SCAT. This study shows that a moderate CR reduces ER stress and improves AMPK phosphorylation in several peripheral tissues and in circulating PBMCs, suggesting that alterations observed in PBMCs could reflect metabolic alterations associated with obesity. © 2020 Elsevier Inc. All rights reserved.