Anti-oxidative effects of pomegranate juice (PJ) consumption by diabetic patients on serum and on macrophages
Introduction
Diabetes mellitus is increasing worldwide, resulting from the interaction of obesity, inflammation and hyperglycemia. Both type I and type II diabetes are powerful and independent risk factors for coronary artery disease, stroke and peripheral arterial disease [1], [2], and atherosclerosis accounts for 80% of all deaths among diabetic patients. Prolonged exposure to hyperglycemia is now recognized as a major risk factor in the pathogenesis of atherosclerosis in diabetes [3]. Animal and human studies elucidated three major mechanisms for the pathological alterations observed in diabetic vasculature, i.e. non-enzymatic glycosylation of proteins and lipids which can interfere with their normal function, cellular protein kinase C (PKC) activation and oxidative stress [3], [4]. Diabetic patients may be highly prone to oxidative stress because hyperglycemia depletes natural anti-oxidants and facilitates the production of free radicals [5], [6]. Thus, anti-oxidants treatment in diabetes could be beneficial [7]. Indeed, it was shown that alpha-tocopherol or red wine supplementation to diabetic patients significantly reduced serum oxidative stress [8], [9]. Furthermore, tea catechins were able to protect diabetic erythrocytes from tert-buthyl hydroperoxide-induced oxidative stress [10]. Pomegranate juice (PJ) possesses impressive anti-oxidative properties due to its polyphenolics, tannins and anthocyanins [11], [12]. We have previously demonstrated that consumption of PJ by humans for a period of 1 year significantly reduced the oxidation of both LDL and HDL [13]. Furthermore, in patients with carotid artery stenosis that consumed PJ for 3 years, we demonstrated reduced oxidative stress in their blood, and a decreased atherosclerotic lesion size [14].
Macrophages play a major role in the early stages of atherogenesis [15]. Recent studies that were performed in control subjects or in diabetic patients’ monocytes–macrophages demonstrated that high glucose levels can lead to macrophage foam cell formation by several mechanisms including: increased cholesterol synthesis [16], altered expression and secretion of lipoprotein lipase [17], monocytes PKC activation [18] and up-regulation of an oxidized LDL (LOX-1) receptor [19], or scavenger receptors [20]. Recently, we have shown increased oxidative stress and increased uptake of Ox-LDL also in peritoneal macrophages from streptozotocin-induced diabetic mice, as well as in vitro, in cells that were incubated with high glucose levels [21].
The diabetic patients avoid sugar-containing juices, such as grape juice, which can worsen their diabetic conditions. In the present study, we questioned whether PJ (which contains 10% sugars and potent polyphenols anti-oxidants) consumption by diabetic patients also worsen diabetes and its oxidative complications.
Section snippets
Subjects
Ten male healthy subjects (controls) and 10 male non-insulin dependent diabetes mellitus (NIDDM) patients (age 35–71 years old, mean age 50 ± 10) participated in the study. The controls were non-smokers, with no diabetes (glucose levels below 100 mg% and hemoglobin A1c levels were in the range of 4.8–6.2%), hypertension or coronary artery disease, and they did not take any medications. The diabetes mellitus duration in the patients was 4–10 years, glucose levels above 160 mg%, hemoglobin A1c in the
Effect of PJ consumption by diabetic patients on serum biochemical parameters
Serum total cholesterol and LDL cholesterol levels in the patients were similar to that of the controls. In contrast, serum triglyceride levels were significantly higher by 2.8-fold in the patients versus controls, whereas HDL-cholesterol levels were significantly decreased by 28% (Table 1). PJ consumption by the patients did not affect these parameters (Table 1). As PJ contains sugars we first questioned the effect of PJ consumption by the patients on serum diabetic parameters: glucose,
Discussion
The present study demonstrated that pomegranate juice consumption by diabetic patients (as previously shown for healthy subjects and atherosclerotic patients) did not worsen the diabetic parameters, but rather resulted in anti-atherogenic effects with a significant reduction in oxidative stress in the patients’ serum and monocytes–macrophages, as well as in macrophage uptake of Ox-LDL.
Diabetic patients versus control healthy subjects have significant high serum triglyceride levels and low
Acknowledgment
This study was supported by a grant from the Russell Berrie Foundation, and D-Cure, Diabetes Care in Israel.
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