The effects of garlic upon endothelial function, vascular inflammation, oxidative stress and insulin resistance in patients with type 2 diabetes at high cardiovascular risk: A double blind randomised placebo controlled trial
Student thesis: Doctoral Thesis
Background and aims Endothelial dysfunction, vascular inflammation and oxidative stress have been integrally linked to the pathogenesis of both type 2 diabetes and cardiovascular disease. Aged Garlic Extract (AGE), a potent antioxidant, has been shown in previous studies to attenuate these novel risk factors in a non-diabetic population. Aims This study tested the hypothesis that AGE may improve endothelial function , oxidative stress, vascular inflammation and insulin resistance in high risk cardiovascular subjects with type 2 diabetes (defined as >30% Cardiovascular risk over 10 yrs). Methods A double blind, placebo controlled cross-over study was performed in 26 type 2 diabetic patients who received 1200mg of AGE or placebo daily for 4 weeks with a 4 week washout period. Plasma HsCRP was measured as a marker of inflammation. TAOS,GSH/GSSG and LHP were measured as markers of oxidative stress/anti-oxidant defence. Insulin resistance was measured using the HOMA-IR method. Endothelial function was measured using change in the reflective index (RI) post salbutamol using digital photoplethysmography and urinary albumin/creatinine ratio was measured as a biochemical surrogate. Measurements were taken at baseline and after intervention with AGE or placebo. Results Of the 26 patients studied (Male 17, Female 9), mean age was 61 ± 8 yrs, HbA1c 7.2 ± 1.1%, BP 130/75 ± 15.9/9.8 mmHg, total cholesterol 4.2 ± 0.81 mmol/l, triglyceride 2.11 ± 1.51 mmol/l, HDL-cholesterol 1.04 ± 0.29 mmol/l. The majority of patients were being treated with metformin (59%), aspirin (50%) and statin (96%) therapy. 36% were treated with an ACEI. There were no changes in these therapies throughout the study. Treatment with AGE had no significant effect upon the above metabolic parameters including insulin resistance. Systolic blood pressure pre AGE 130 ± 15mmHg vs post AGE 130± 14mmHg. Total cholesterol pre AGE 4.2 ± 0.9 mmol/l vs post AGE 4.2 ± 0.8 mmol/l. Triglycerides pre AGE 1.4 IQ range 0.7 mmol/l vs post AGE 1.4 IQ range 0.8 mmol/l. HDL cholesterol pre AGE 1.0 ± 0.3 mmol/l vs post AGE 1.0 ± 0.3mmol/l. In addition, no statistically significant difference was found in plasma HsCRP (pre AGE: median 2.0mg/l, IQ range 0.8-2.7 vs post AGE: median 1.83mg/l, IQ range 1.1-3.2, p = 0.89) or urinary albumin/creatinine ratio (pre AGE: 0.55, IQ range 0.4-1.65 vs post AGE: 0.6, IQ range 0.47-1.5, p = 0.43) endothelial function (change in RI pre AGE: 6.5%, IQ range 2.75-11 vs post AGE: 6.5%, IQ range 2.75-13, p = 0.95) with AGE or placebo. Conclusion In this group of type 2 diabetic patients at high cardiovascular risk, 4 weeks treatment with AGE did not significantly improve endothelial function, vascular inflammation, oxidative stress or insulin resistance.
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