Effect of Tahini in Oxidative Stress and Endothelial Function in Diabetes

Cardiovascular disease (CVD), a cluster of disorders that affect heart and blood vessels, is the leading cause of morbidity and mortality around the world and is responsible for 17.9 million deaths annually worldwide. CVD includes coronary heart disease, peripheral arterial disease, cerebrovascular disease, rheumatic heart disease, congenital heart disease, deep vein thrombosis and pulmonary embolism. CVD risk factors can be modifiable (nutrition, physical activity, obesity, smoking, hyperlipidemia, hypertension and diabetes) and non-modifiable (age, gender, ethnicity, family history and socioeconomic status). Chronic exposure to CVD risk factors induces oxidative stress and promotes inflammation. In addition, endothelial cells in response to the inflammatory reaction secrete growth factors, leading to the destruction of vascular endothelium and promoting atherogenesis.

Oxidative stress refers to the imbalance between anti-oxidant and pro-oxidant compounds, with predominance of the pro-oxidant ones. These compounds are also called Reactive Oxygen Species (ROS) or free radicals and are unstable atoms or molecules. Their generation, as products of normal cellular metabolism, occurs naturally by endogenous sources (e.g. mitochondria, peroxisomes and endoplasmic reticulum) through enzymatic and non-enzymatic reactions. Furthermore, exogenous sources implicated in free radical production are air pollution, alcohol consumption, tobacco smoking, ultraviolet light exposure, industrial solvents and others. Free radical production is regulated by the well-organized human endogenous enzymatic and non-enzymatic antioxidant system, along with the exogenous antioxidants found in food. However, in some cases antioxidant system fails to eliminate ROS overproduction and can consequently induce serious damage to important for life biomolecules (DNA, lipids, proteins), leading to cell injury and death. Thus, ROS overproduction has been implicated in pathogenesis and complications of numerous diseases including diabetes, cardiovascular diseases, cancer, neurodegenerative diseases and chronic kidney disease.

Moreover, endothelium consists of a single layer of endothelial cells; it is the natural barrier between blood and tissues and also an endocrine organ. It plays a key role in vascular homeostasis by maintaining a balance between vasodilation and vasoconstriction. Moreover, vascular endothelium is responsible for fluid filtration, blood vessel tone, hormone trafficking, hemostasis, regulation of blood flow and growth of blood vessels. Thus, reductions in endothelial function are detrimental and predict and precede the development of overt CVD.

Sesame belongs to Pedaliaceae family and can be consumed in different forms such as seeds, oil or tahini, i.e., a 100 % peeled, ground and roasted sesame paste. Sesame seeds are rich in polyunsaturated fatty acids (PUFAs), proteins, vitamin E and lignans, such as sesamin, sesamolin and sesamol. Recent studies have highlighted the antioxidant, antihypertensive, hypolipidemic and appetite control properties of sesame seeds and sesame oil. Moreover, few studies have investigated the effect of sesame consumption on blood pressure, endothelial function and arterial stiffness in human population. According to a metanalysis, sesame consumed in form of seed, oil, capsule or bar decreased both systolic blood pressure (SBP) and diastolic blood pressure (DBP), while sesame oil consumption was found to improve endothelial function both in the postprandial state and after long term consumption in hypertensive men.

Regarding the consumption of tahini and its effect on human health, only a few studies are available in the current literature. The most recent of them have indicated that tahini consumption can lower blood pressure and pulse rate and improve endothelial function and glycemic response in healthy males postprandially. However, only two studies are available in the current literature concerning the effect on diabetes, one of them in patients with type 2 diabetes and one in diabetic animal model. Thus, the aim of the present study is to investigate the effect of tahini consumption on oxidative stress, blood pressure, endothelial function and arterial stiffness in patients with type 2 diabetes postprandially.

Inclusion criteria

• minimum period from diagnosis three years
• good glycemic control (HbA1c <7%)
• taking a stable anti-diabetic treatment for the last 3 months (anti-diabetic tablets only)

Exclusion criteria

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