The effects of garlic extract upon endothelial function, vascular inflammation, oxidative stress and insulin resistance in adults with type 2 diabetes at high cardiovascular risk. A pilot double blind randomized placebo controlled trial

Abstract

Background and aimsEndothelial 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. AimsThis 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. MethodsA double blind, placebo controlled crossover pilot study was performed in 26 subjects with type 2 diabetes who received 1200mg of AGE or placebo daily for 4weeks with a 4week washout period. Plasma HsCRP was measured as a marker of inflammation. Plasma TAOS, blood GSH/GSSG and plasma LHP were measured as markers of oxidative stress/anti-oxidant defense. 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. ResultsOf the 26 patients studied (male 17, female 9), age was 61±8years (mean±1 SD), HbA1c 7.2±1.1%, BP 130/75±15.9/9.8mmHg, total cholesterol 4.2±0.81mmol/l, triglyceride 2.11±1.51mmol/l, and HDL cholesterol 1.04±0.29mmol/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. Treatment with AGE also had no significant effect on markers of endothelial function (plethysmography), oxidative stress (TAOS, GSH/GSSG, LHP) or inflammation (HsCRP). ConclusionIn this group of type 2 diabetic patients at high cardiovascular risk, 4weeks treatment with AGE did not significantly improve endothelial function, vascular inflammation, oxidative stress or insulin resistance.