Catechins, the major polyphenolic compounds in green tea, exert vascular protective effects through multiple mechanisms, including antioxidative, anti-hypertensive, anti-inflammatory, antiproliferative, anti-thrombogenic, and lipid lowering effects.
- Tea catechins present antioxidant activity by scavenging free radicals, chelating redox active transition-metal ions, inhibiting redox active transcription factors, inhibiting pro-oxidant enzymes and inducing antioxidant enzymes thereby reducing surrogate markers of atherosclerosis and lipid peroxidation, particularly low-density lipoprotein (LDL) oxidation and malondialdehyde concentrations.
- Tea catechins inhibit the key enzymes involved in lipid biosynthesis and reduce intestinal lipid absorption, thereby improving blood lipid profile.
- Catechins regulate vascular tone by activating endothelial nitric oxide.
- Catechins prevent vascular inflammation that plays a critical role in the progression of atherosclerotic lesions. The antiinflammatory activities of catechins may be due to their suppression of leukocyte adhesion to endothelium and subsequent transmigration through inhibition of transcriptional factor NF-kB-mediated production of cytokines and adhesion molecules both in endothelial cells and inflammatory cells.
- Catechins inhibit proliferation of vascular smooth muscle cells by interfering with vascular cell growth factors involved in atherogenesis.
- Catechins suppress platelet adhesion, thereby inhibiting thrombogenesis. Taken together, catechins may be novel plantderived small molecules for the prevention and treatment of cardiovascular diseases
Lipid peroxidation
Inami et al. evaluated the effect of catechin (from green tea) intake on the lipid profile and plasma oxidized LDL. The study population consisted of 40 healthy adult volunteers (10 men, 30 women). The subjects were randomly divided into two groups, a catechin group (n = 29) and a control group (n = II). Plasma oxidized LDL was significantly decreased after catechin administration (from 9.56 +/9.2 to 7.76 +/- 7.7 U/mL, p = 0.005), while plasma LDL-C, triglyceride, and HDL-C concentrations did not change. Catechin decreased the plasma oxidized LDL concentration without significant change in plasma LDL concentration.
Cholesterol and triglyceride levels
Hsu et al. examined the effect of green tea extract (GTE) on obese women in a randomized, double-blind, placebo-controlled clinical trial order to explore the relationship between GTE and obesityrelated hormone peptides. Seventy-eight of 100 obese women aged between 16 and 60 years with BMI>27 kg/m2 and who had not received any other weight control maneuvers within the last 3 months completed this study. The subjects were randomly divided into Groups A (41 individuals who received GTE) and B (37 individuals) who took cellulose as a placebo, one capsule (400mg) three times each day for 12 weeks. There was a 0.3% reduction in body weight (0.15 kg) after 12 weeks of treatment with GTE. Within group comparison revealed that the GTE group had significant reduction in LDL-cholesterol and triglyceride, and marked increase in the level of HDL-cholesterol, adiponectin and ghrelin. On the other hand, the placebo group showed significant reduction in triglyceride only, and a marked increase in the level of ghrelin alone.
Effects on blood pressure
Nantz et al. studied the effects of a standardized and defined decaffeinated green tea (Camellia sinensis) on blood pressure, serum lipids, oxidative stress, and markers of chronic inflammation in a randomized, double-blind, placebo-controlled, parallel study involving I I I healthy adult volunteers aged 21-70 y, The researchers administered a standardized capsule of Camellia sinensis compounds (CSC) twice a day. After 3 wk, CSC lowered systolic and diastolic blood pressures by 5 and 4 mmHg, respectively. After 3 mo, systolic blood pressure remained significantly lower. Camellia sinensis compounds lowered serum amyloid-alpha by 42% and malondialdehyde by 11.9%. In men, there were 10- and 9-mg/dL reductions in total LDL cholesterol, respectively. In all subjects with a baseline LDL cholesterol level >99 mg/dL, there was 9 mg/dL lowering of total and LDL cholesterol.