Food supplementation with rice bran enzymatic extract prevents vascular apoptosis and atherogenesis in ApoE-/- mice

Atherosclerosis is associated with reduced mononuclear cell (MNC) telomere length, and senescent cells have been detected in atherosclerotic plaques. Rice bran is a source of gamma-oryzanol, phytosterols and tocols with potential lipid-lowering, antioxidant and anti-inflammatory activities. Here, we tested the hypothesis that rice bran enzymatic extract (RBEE) impacts on apoptosis, telomere length and atherogenesis in mice. Seven-week-old male ApoE-/- mice were fed high-fat diet (HFD) or isocaloric HFD supplemented with 5 % (w/w) RBEE for 23 weeks. Wild-type mice of the same age were kept under standard diet as controls. RBEE treatment reduced total cholesterol (19.24 +/- 1.63 vs 24.49 +/- 1.71 mmol/L) and triglycerides (1.13 +/- 0.18 vs 1.75 +/- 0.22 mmol/L) and augmented HDL-cholesterol (1.86 +/- 0.20 vs 1.07 +/- 0.20 mmol/L). RBEE attenuated macrophage infiltration by 56.69 +/- 4.65 % and plaque development (7737 +/- 836 vs 12,040 +/- 1001 mu m(2)) in the aortic sinus. In the aorta, RBEE treatment reduced expression of the apoptosis pathway components p16, p53 and bax/bcl-2 ratio. RBEE prevented apoptosis of aortic endothelial cells (2.81 +/- 0.71-1.14 +/- 0.35 apoptotic nuclei/ring for ApoE-/- HFD and ApoE-/- HFD 5 % RBEE, respectively). In contrast, MNC of RBEE-fed mice exhibited enhanced apoptosis marker expression with increased p53 and bax/bcl-2 protein levels. Compared to WT, ApoE-/- mice on HFD were characterized by significant telomere shortening in aorta (11 +/- 2 %) and MNC (73 +/- 7 %), which was reduced by supplementation with RBEE (aorta: 40 +/- 7 %; MNC: 105 +/- 10 %). Expression of telomere repeat-binding factor 2 was increased in RBEE-fed mice. Long-term food supplementation with RBEE lowers cholesterol and prevents atherosclerotic plaque development in ApoE-/- mice. Differential regulation of vascular and MNC apoptosis and senescence were identified as potential mechanisms.