ABC | Volume 114, Nº1, January 2019

Original Article Alegre et al. Açaí and myocardial ischemia-reperfusion in rats Arq Bras Cardiol. 2020; 114(1):78-86 Figure 3 – Isolated heart study after global myocardial ischemia-reperfusion. Panel A: C: control group; A: açaí group. Initial volume represents the volume inside the balloon when diastolic pressure was zero; +dP/dt: left ventricular pressure development rate; -dP/dt: left ventricular pressure decrease rate; *different from group C (p = 0.025). Panel B: Relationship between diastolic pressure and volume. The area under the curve and inclination were similar between the groups. 180 140 120 100 80 60 40 20 0 180 140 120 100 80 60 40 20 0 4000 3000 2000 1000 0 2500 2000 1000 1500 500 0 C A C A C A C A * Initial volume (microL) Maximum systolic pressure (mmHg) Maximum + dP/dt (mmHg/s) Maximum – dP/dt (mmHg/s) A 30 25 20 15 10 5 0 0.10 0.12 0.14 0.16 0.18 Volume (mL) Diastolic pressure (mmHg) B Control group Açai group group A presented higher antioxidants enzymes activity in addition to lower concentration of myocardial lipid hydroperoxide. Lipid hydroperoxide is a marker of oxidative damage and is originated from the oxidative lesion of membrane lipids. Membrane lesion can lead to disturbances in permeability, alteration of the ionic flow and DNA, and impairment of extracellular matrix components. 31 In relation to the proteins involved in the regulation of the oxidative stress pathway, the mechanisms by which phenolic dietary compounds act in the prevention of degenerative pathologies have been partially studied. The complex interactions between these dietary molecules and their molecular targets activate signaling pathways of the cellular response, including the NF- κ B, Nrf2, SIRT1, and FOXO1. 32-34 NF- κ B is considered an important transcriptional factor related to oxidative stress. Açaí treatment inhibited NF-kB activation in astrocytes cell culture, 35,36 inhibited NF-kB phosphorylation in microglial cells 37 and down-regulated gene expression of NF-kB in colon myofibroblasts cell culture. 38 Similarly, Nrf2 is an important regulator of antioxidant enzymes production. In response to oxidative stress, Nrf2 dissociates from the Keap1 protein and migrates to the cell nucleus, where it stimulates the production of antioxidant enzymes. 39 Myocardial ischemia promotes increased protein expression of Nrf2 40 and the effect of açaí on Nrf2 expression was verified in an astrocyte culture study in which the fruit reduced the protein expression of Nrf2. 41 However, in another study, also with astrocyte culture, açaí administration increased Nrf2 expression, 36 showing that the effects of açaí on Nrf2 are not completely understood. Another cellular balance regulator is the SIRT1 protein, which can act on apoptosis, mitochondrial biogenesis, inflammation, glucose and lipid metabolism, autophagy and adaptations to cellular stress through the deacetylation of target proteins such as NF-kB and FOXO1. When acetylated by SIRT1, FOXO1 leads to increased expression of gluconeogenic genes. 33 Increased transcriptional activity of FOXO1 also increases the gene expression of catalase and superoxide dismutase. 34 To the best of our knowledge, there are no studies that evaluated the effect of açai on FOXO1 and SIRT1 protein expression. In the normal adult heart, approximately 95% of ATP production is derived from mitochondrial oxidative phosphorylation. The adult heart normally obtains 50–70% of its ATP from fatty acid β -oxidation instead of glucose oxidation. 42 The flavin adenine dinucleotide and nicotinamide 83