The Effects of Anthocyanins on Atherosclerosis Risks in The Metabolic Syndrome Population and Diabetic Endothelial Cells

Abstract

Metabolic syndrome (MetS) is a collection of metabolic risk factors associated with an increased risk of developing atherosclerosis. Reducing levels of modifiable atherogenic risk factors is an essential goal in the prevention of atherosclerosis. Since there is an established relationship between metabolic syndrome, oxidative stress, chronic inflammation and cardiovascular disease, the first study focused on demonstrating these links. Therefore, this research focuses on a sedentary population who work under conditions that predispose them to risk factors of metabolic syndrome and who are likely to develop atherosclerosis ultimately. Accordingly, a comprehensive evaluation of metabolic syndrome risk factors was conducted on 79 transport drivers. The clinical examination collected anthropometric data and blood biochemistry results. Daily step counts calculated by the Fitbit over seven days were also used to monitor their activity trends over time. Health assessments were conducted at the beginning of the study. The results showed that 68% (n = 51) of participants were recorded as having three or more risk factors which can contribute to MetS including obesity, hyperglycaemia, lipid profile abnormalities, blood pressure, hyperuricemia and markers of inflammation. This study also demonstrated that there are interconnections between oxidative stress and chronic inflammation with MetS components highlighting the role of oxidative stress and inflammation in metabolic syndrome and atherosclerosis. It could be suggested that the potential use of anthocyanins as antioxidants and with anti-inflammatory properties as an alternative approach for the prevention and management of atherosclerosis in MetS population. Initially, the use of an in vitro model of endothelial cells can offer valuable mechanistic insights into the development and progression of inflammatory conditions that provide an efficient platform for product screening before conducting a human intervention trial. Based on findings from the literature review, it is hypothesised that anthocyanin might exert protective effects on healthy human aortic endothelial cells against inflammation and oxidative stress in vitro. The second study aimed to examine and compare the abilities of healthy and diabetic human aortic endothelial cells to incorporate anthocyanins’ potential benefits against hydrogen peroxide (H2O2) as an oxidative stressor and lipopolysaccharide (LPS) to induce inflammation. Cultured Primary Human Aortic Endothelial Cells (HAEC) and Diseased-(type II diabetic) Aortic Endothelial Cells (D-HAEC) were exposed to oxidative stress by H2O2 (75 μM) and LPS (1μg/ml) and were treated with the anthocyanin (AC, 50 μl/ml). The results showed that anthocyanins might be responsible for protecting that aortic endothelial cells against inflammatory insult. These findings may have important implications for preserving endothelial cell function and preventing the initiation of endothelial cell damage that leads to platelets activation and coagulation associated with endothelial dysfunction. Finally, based on the in vitro finding, the last chapter aimed to investigate the antithrombotic effects of same berry-derived anthocyanin supplements on biomarkers of atherosclerosis, platelet function, and the expression of pro-atherogenic genes in a population with metabolic syndrome. A total of 55 participants in two groups of Normal and MetS (age 25-75y) were given 320 mg anthocyanin supplements twice daily for four weeks in a clinical trial. The effects of berry-derived supplementation were examined on features of metabolic syndrome, including fasting blood glucose, lipid profile, inflammatory markers, oxidative stress marker (uric acid), platelet surface markers, and the expression of pro-atherogenic genes. The results showed that anthocyanin consumption for four weeks significantly decreased the average fasting blood glucose (FBG) level by 13.3 % in the MetS group. Similarly, significant reductions were observed in triglyceride (24.9%) and low-density lipoprotein (LDL) (33.1%) levels in the MetS group compared with the Normal group (P ≤ 0.05). Anthocyanin supplementation also caused a reduction (18%) in high sensitivity C-reactive protein (hs-CRP), an inflammatory biomarker, with no significant difference in the Normal group. There was a positive correlation between decreased hs-CRP values and the levels of LDL-C and FBG in the MetS group (P ≤ 0.05). Anthocyanin supplements also decreased ADP-induced platelet activation configuration expressed as P-selectin by 40%. The data here revealed that anthocyanin intake showed an inhibitory effect on the gene expression of proinflammatory cytokines, including interleukin (IL)-1A, tumour necrosis factor-alpha (TNF-α) and interleukin (IL)-6, as well as endothelial cell adhesion molecule-1 (ECAM-1) and cyclooxygenase (COX)-2, with stimulatory effects on the expression of superoxide dismutase (SOD) and Peroxisome proliferator-activated receptor gamma (PPRAG). Thus, these findings suggest that short-term consumption of anthocyanin supplements may have atheroprotective effects through the inhibition of chronic inflammation and platelet activation and improvement of MetS components.