Dietary Intake Of Flavonoids And HDL- And LDL- Cholesterol In Two Black Ethnicities With And Without Type 2 Diabetes

摘要

Flavonoids are a class of over 6,500 plant metabolites that have been associated with reduced mortality from cardiovascular disease. A cross-sectional analysis of dietary flavonoids and serum cholesterol in 507 Blacks with and without type 2 diabetes (258 Haitian-Americans and 249 African-Americans) showed differences by ethnicity and diabetes status. Haitian-Americans consumed more of most flavonoids as compared to African-Americans. Individuals with type 2 diabetes consumed less of most flavonoids as compared to those without diabetes. Flavonoids were differentially associated with low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL) by diabetes status. Flavanones were associated with lower LDL for participants without diabetes and higher LDL for those with diabetes, independent of ethnicity and adjusted for age, gender, cholesterol medications, daily energy, dietary fat, body mass index (BMI), and smoking. Flavan-3-ols were positively related to LDL while polyflavonoids (theaflavin and polymers, proanthocyanidins) were inversely related to LDL for the group without diabetes only. Higher anthocyanidins and flavan-3-ols and lower polyflavonoids were associated with higher HDL (same adjustments) for those without diabetes, whereas no flavonoids were associated with HDL for individuals with type 2 diabetes. Introduction Flavonoids (bioflavonoids) are a diverse group of more than 6500 polyphenols (phenyl benzopyrans)1 which function as phytochemicals. Flavonoids are secondary plant metabolites found primarily in fruits, vegetables and seeds and are generally classified into categories based on their chemical structure. There is a lack of consensus for some of the flavonoid-subgroups. This may be due to the fact that subclasses of flavonoids are differentiated on the basis of the number and nature of substituent groups attached to the rings.2 Isoflavones have been considered a separate category and the distinction of polyflavonoid is not always made.3 Classification by the degree of unsaturation and degree of oxidation of the three carbon segment results in the following major classes: flavones, isoflavones, flavonols, anthocyanidins (or anthocyanins), flavanones, flavan-3-ols, chalcones and aurones.1 It has been demonstrated throughout the literature that diets high in plant-based foods are protective against the development of cardiovascular disease, diabetes and cancer and that flavonoids have been thought to contribute to the protective role.4,5 Flavonoids incorporated in the diet exhibit several biological effects, such as anti-oxidant and anti-inflammatory properties.6 Flavan-3-ols and proanthocyanidins have been associated with reduction of risk for cardiovascular disease by increasing the release of endothelial nitric oxide and inducing vasodilatation.7,8 The antioxidant property of dietary flavonoids may be of particular benefit to persons with diabetes since their hyperglycemic condition depletes natural anti-oxidants and may result in oxidative stress.9 and references therein Dietary flavonoids (flavonols and flavones) were inversely related to mortality from coronary heart disease for a five-year cohort of N=805 men aged 65-84 years.10 Dietary anthocyanidins and flavanones decreased coronary heart disease deaths, but not stroke, in post-menopausal women (N=34,492).11 Reduction of cardiovascular risk and mortality by dietary flavonoids may be attributed, in part, to the oxidation and serum levels of LDL. Although there is evidence that certain flavonoids improve cholesterol in numerous animal models, the pathways by which the categories of flavonoids may help prevent or improve lipid profile in humans is unclear. Based on animal studies, flavanones may have biochemical effects that result in hypolipdemic properties such as inhibiting cholesterol acyltransferase activities in the liver and upregulating LDL receptors.12 A proposed mechanism of dietary flavonoids resulting in lower seru