Curcumin, Alone or in Combination with Aminoguanidine, Increases Antioxidant Defenses and Glycation Product Detoxification in Streptozotocin-Diabetic Rats: A Therapeutic Strategy to Mitigate Glycoxidative Stress.

Both oxidative stress and the exacerbated generation of advanced glycation end products (AGEs) have crucial roles in the onset and progression of diabetic complications. Curcumin has antioxidant and antidiabetic properties; its combination with compounds capable of preventing the advanced glycation events, such as aminoguanidine, is an interesting therapeutic option to counteract diabetic complications. This study is aimed at investigating the effects of treatments with curcumin or aminoguanidine, alone or in combination, on metabolic alterations in streptozotocin-diabetic rats; the focus was mainly on the potential of these bioactive compounds to oppose the glycoxidative stress. Curcumin (90 mg/kg) or aminoguanidine (50 and 100 mg/kg), alone or in combination, slightly decreased glycemia and the biomarkers of early protein glycation, but markedly decreased AGE levels (biomarkers of advanced glycation) and oxidative damage biomarkers in the plasma, liver, and kidney of diabetic rats. Some novel insights about the in vivo effects of these bioactive compounds are centered on the triggering of cytoprotective machinery. The treatments with curcumin and/or aminoguanidine increased the activities of the antioxidant enzymes (paraoxonase 1, superoxide dismutase, and catalase) and the levels of AGE detoxification system components (AGE-R1 receptor and glyoxalase 1). In addition, combination therapy between curcumin and aminoguanidine effectively prevented dyslipidemia in diabetic rats. These findings demonstrate the combination of curcumin (natural antioxidant) and aminoguanidine (prototype therapeutic agent with anti-AGE activity) as a potential complementary therapeutic option for use with antihyperglycemic agents, which may aggregate beneficial effects against diabetic complications.

Hydrochlorothiazide and high-fat diets reduce plasma magnesium levels and increase hepatic oxidative stress in rats.

This study was designed to develop a rodent model of hydrochlorothiazide (HCTZ) toxicity by associating its intake with a high-fat (HF) diet. Rats were fed for 16 weeks with a control diet or with an HF diet supplemented or not with different doses of HCTZ. HCTZ, in a similar way to the HF diet, caused a significant increase in fructosamine levels. HCTZ and HF diet intake caused a significant reduction in magnesium and potassium levels, as well as an increase in lipid peroxidation and vitamin C in liver. Importantly, negative correlations were found between magnesium and glucose levels as well as between magnesium and fructosamine levels. The association between HCTZ and the HF diet caused additional worsening of biochemical parameters related to glucose homeostasis, and further increased hepatic oxidative stress. Our results suggest that chronic intake of HCTZ or an HF diet causes metabolic changes that are consistent with the development of insulin resistance. In addition, the association of an HF diet and HCTZ treatment can exacerbate some of these biochemical alterations, suggesting that this model might be useful for studying HCTZ metabolic toxicity.

Ozone oxidative post-conditioning in acute renal failure.

OBJECTIVES: The ischaemia-reperfusion process is largely mediated by reactive oxygen species. Taking into account that a transient and controlled administration of ozone is able to upregulate cellular antioxidant enzymes, a morphological, biochemical and functional renal study was performed in rats undergoing warm renal ischaemia. METHODS: Rats were divided into four groups. All except the negative controls underwent 60 min' bilateral renal ischaemia followed by 10 days' reperfusion. The positive control group received no further treatment. The ozone group received an ozone/oxygen mixture (ozone dose 0.5 mg/kg) immediately after the ischaemia and daily for the 10 days' reperfusion; the oxygen group were given the same concentration of oxygen alone (13 mg/kg). Biochemical parameters fructosamine, phospholipase A2, catalase, superoxide dismutase and thiobarbituric acid reactive substances were measured, as well as renal plasma flow and glomerular filtration rate. KEY FINDINGS: Renal plasma flow and glomerular filtration rate decreased significantly in the positive controls and the oxygen group whereas values in the ozone group were similar to those in the negative control group. With respect to the biochemical parameters, ozone maintained a homeostasis redox, with significant increases in catalase and superoxide dismutase activities and similar values for phospholipase A2 and fructosamine compared with the negative control group. Fewer morphological alterations were seen in kidneys from the ozone group. No advantages were obtained in the positive control and oxygen groups. CONCLUSIONS: The protective effect of ozone may be explained by upregulation of the antioxidant defence system and beneficial effects on blood circulation and in oxygen metabolism. Ozone treatment may represent a therapeutic approach for minimising renal damage after transplantation.

Lack of age-related increase in average glycemia in a non-Westernized sample of rural Yucatec Maya females.

Age-related decline in glucose processing and the associated progressively higher circulating glucose levels are considered well-established biological aging phenomena. However, their occurrence in non-Westernized populations characterized by less mechanization and dietary processing has not been well-studied. This research extends evaluation of lifestyle conditions of diet and physical activity beyond those of Westernized areas and examines aging patterns in blood glucose among rural Yucatec Maya. The purpose is to investigate whether deteriorating glucose processing is intrinsic to human aging, while controlling for body composition in a non-Westernized setting. Data were gathered from 60 nondiabetic Maya women, 40-85 years of age, living in 16 rural villages around Merida, Yucatan. Information regarding personal history, diet, and physical activity was collected through interviews. Body composition was assessed through anthropometric and derived indicators of body size, fat distribution, body mass index, intra-abdominal fat, and total fat and fat-free masses. Glycemia was measured through microvenous samples analyzed for glycated hemoglobin (HbA(1c)) and fructosamine, to demonstrate average circulating glucose under customary living conditions. As indicated by glycation, average glycemia is not higher in older Maya females (age group F for HbA(1c) = 0.88, P > 0.05; age group F for fructosamine = 0.38, P > 0.05). Further, correlations between age and HbA(1c) (r = -0.13, P > 0.05) and fructosamine (r = -0.10, P > 0.05) are negative and not significant. The absence of significant, positive age associations with HbA(1c) and fructosamine persists when effects of body composition are taken into account. Thus, decline in glucose regulation does not appear to be a feature of aging in this non-Westernized sample, suggesting that age-related deterioration in glucose processing is not universal among human populations. Results suggest that relationships of age with glycemia are linked to lifestyle differences.

Prevention of renal injury after induction of ozone tolerance in rats submitted to warm ischaemia.

On the basis that ozone (O3) can upregulate cellular antioxidant enzymes, a morphological, biochemical and functional renal study was performed in rats undergoing a prolonged treatment with O3 before renal ischaemia. Rats were divided into four groups: (1) control, a medial abdominal incision was performed to expose the kidneys; (2) ischaemia, in animals undergoing a bilateral renal ischaemia (30 min), with subsequent reperfusion (3 h); (3) O3 + ischaemia, as group 2, but with previous treatment with O3 (0.5 mg/kg per day given in 2.5 ml O2) via rectal administration for 15 treatments; (4) O2 + ischaemia, as group 3, but using oxygen (O2) alone. Biochemical parameters as fructosamine level, phospholipase A, and superoxide dismutases (SOD) activities, as well as renal plasma flow (RPF) and glomerular filtration rate (GFR), were measured by means of plasma clearance of p-amino-hippurate and inulin, respectively. In comparison with groups 1 and 3, the RPF and GFR were significantly decreased in groups 2 and 4. Interestingly, renal homogenates of the latter groups yielded significantly higher values of phospholipase A activity and fructosamine level in comparison with either the control (1) and the O3 (3) treated groups. Moreover renal SOD activity showed a significant increase in group 3 without significant differences among groups 1, 2 and 4. Morphological alterations of the kidney were present in 100%, 88% and 30% of the animals in groups 2, 4 and 3, respectively. It is proposed that the O3 protective effect can be ascribed to the substantial possibility of upregulating the antioxidant defence system capable of counteracting the damaging effect of ischaemia. These findings suggest that, whenever possible, ozone preconditioning may represent a prophylactic approach for minimizing renal damage before transplantation.

The effect of magnesium supplementation in increasing doses on the control of type 2 diabetes.

OBJECTIVE: Hypomagnesemia occurs in 25-38% of patients with type 2 diabetes. Several studies have suggested an association between magnesium (Mg) depletion and insulin resistance and/or reduction of insulin secretion in these cases. Our purpose was to evaluate if Mg supplementation (as magnesium oxide [MgO]) would improve metabolic control in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We studied 128 patients with type 2 diabetes (32 men, 96 women, aged 30-69 years), treated by diet or diet plus oral antidiabetic drugs, in the Bahia Federal University Hospital, Brazil. Patients at risk for hypomagnesemia or with reduced renal function were excluded. This study was a clinical randomized double-blind placebo-controlled trial. Patients received either placebo, 20.7 mmol MgO, or 41.4 mmol MgO daily (elementary Mg) for 30 days. Mg concentrations were measured in plasma, in mononuclear cells, and in 24-h urine samples. Fasting blood glucose, HbA1, and fructosamine were used as parameters of metabolic control. RESULTS: Of the patients, 47.7% had low plasma Mg, and 31.1% had low intramononuclear Mg levels. Intracellular Mg in patients with diabetes was significantly lower than in the normal population (62 blood donors; 1.4 +/- 0.6 vs. 1.7 +/- 0.6 micrograms/mg of total proteins). No correlation was found between plasma and intracellular Mg concentrations (r = -0.179; P = 0.15) or between Mg concentrations and glycemic control (r = -0.165; P = 0.12). Intracellular Mg levels were lower in patients with peripheral neuropathy than in those without (1.2 +/- 0.5 vs. 1.5 +/- 0.6 micrograms/mg). Similar findings were observed in patients with coronary disease (1.0 +/- 0.5 vs. 1.5 +/- 0.6 micrograms/mg). In the placebo and in the 20.7 mmol Mg groups, neither a change in plasma and intracellular levels nor an improvement in glycemic control were observed. Replacement with 41.4 mmol Mg tended to increase plasma, cellular, and urine Mg and caused a significant fall (4.1 +/- 0.8 to 3.8 +/- 0.7 mmol/l) in fructosamine (normal, 1.87-2.87 mmol/l). CONCLUSIONS: Mg depletion is common in poorly controlled patients with type 2 diabetes, especially in those with neuropathy or coronary disease. More prolonged use of Mg in doses that are higher than usual is needed to establish its routine or selective administration in patients with type 2 diabetes to improve control or prevent chronic complications.