Decrease of the inhibition of lipid peroxidation by glutathione-dependent system in erythrocytes of non-insulin dependent diabetics

Alzheimer's Disease in Diabetic Patients: A Lipidomic Prospect

Diabetes Mellitus (DM) and Alzheimer's disease (AD) have been two of the most common chronic diseases affecting people worldwide. Type 2 DM (T2DM) is a metabolic disease depicted by insulin resistance, dyslipidemia, and chronic hyperglycemia while AD is a neurodegenerative disease marked by Amyloid β (Aβ) accumulation, neurofibrillary tangles aggregation, and tau phosphorylation. Various clinical, epidemiological, and lipidomics studies have linked those diseases claiming shared pathological pathways raising the assumption that diabetic patients are at an increased risk of developing AD later in their lives. Insulin resistance is the tipping point beyond where advanced glycation end (AGE) products and free radicals are produced leading to oxidative stress and lipid peroxidation. Additionally, different types of lipids are playing a crucial role in the development and the relationship between those diseases. Lipidomics, an analysis of lipid structure, formation, and interactions, evidently exhibits these lipid changes and their direct and indirect effect on Aβ synthesis, insulin resistance, oxidative stress, and neuroinflammation. In this review, we have discussed the pathophysiology of T2DM and AD, the interconnecting pathological pathways they share, and the lipidomics where different lipids such as cholesterol, phospholipids, sphingolipids, and sulfolipids contribute to the underlying features of both diseases. Understanding their role can be beneficial for diagnostic purposes or introducing new drugs to counter AD.

The effect of gamma radiation on the lipid profile of irradiated red blood cells

An investigation into the effects of irradiation and of the storage time on aging and quality are a relevant issue to ensure the safety and the efficiency of irradiation in the prevention of transfusion-associated graft-versus-host disease (TA-GVHD). In this work, the biochemical properties and alterations presented by erythrocyte membranes, up to 28-days post-irradiation, with a dose of 25 Gy, were studied as a function of storage and post-irradiation time. There was a considerable variation in the total of phospholipid content, when comparing the control and irradiated samples, mostly from the third day onwards; and at the same time, the effect occurred as a function on the storage time of blood bags. The levels of total cholesterol decreased 3-9 days after irradiation. TBARS levels were increased after irradiation and 7 days of storage, but no increment of catalase activity was observed after the irradiation. Furthermore, the protein profile was maintained throughout the irradiation and storage time, until the 21st day, with the presence of a protein fragmentation band of around 28 kDa on the 28th day. In conclusion, although gamma irradiation is the main agent for the prevention of TA-GVHD, a better understanding of the physical and biochemical properties of erythrocytes are necessary to better assess their viability, and to be able to issue more secure recommendations on the shelf life of blood bags, and the safe use of the irradiated red cells therein.

Therapeutic impact of leptin on diabetes, diabetic complications, and longevity in insulin-deficient diabetic mice

OBJECTIVE

The aim of the current study was to evaluate the long-term effects of leptin on glucose metabolism, diabetes complications, and life span in an insulin-dependent diabetes model, the Akita mouse.

RESEARCH DESIGN AND METHODS

We cross-mated Akita mice with leptin-expressing transgenic (LepTg) mice to produce Akita mice with physiological hyperleptinemia (LepTg:Akita). Metabolic parameters were monitored for 10 months. Pair-fed studies and glucose and insulin tolerance tests were performed. The pancreata and kidneys were analyzed histologically. The plasma levels and pancreatic contents of insulin and glucagon, the plasma levels of lipids and a marker of oxidative stress, and urinary albumin excretion were measured. Survival rates were calculated.

RESULTS

Akita mice began to exhibit severe hyperglycemia and hyperphagia as early as weaning. LepTg:Akita mice exhibited normoglycemia after an extended fast even at 10 months of age. The 6-h fasting blood glucose levels in LepTg:Akita mice remained about half the level of Akita mice throughout the study. Food intake in LepTg:Akita mice was suppressed to a level comparable to that in WT mice, but pair feeding did not affect blood glucose levels in Akita mice. LepTg:Akita mice maintained insulin hypersensitivity and displayed better glucose tolerance than did Akita mice throughout the follow-up. LepTg:Akita mice had normal levels of plasma glucagon, a marker of oxidative stress, and urinary albumin excretion rates. All of the LepTg:Akita mice survived for >12 months, the median mortality time of Akita mice.

CONCLUSIONS

These results indicate that leptin is therapeutically useful in the long-term treatment of insulin-deficient diabetes.

Lipid peroxidation alterations in type 2 diabetic patients

It was studied that type 2 diabetes mellitus is connected with increased plasma lipid peroxidation (lipid peroxidation expressed as malondialdehyde). This review aimed to evaluate the state of lipid peroxidation among type 2 diabetic subjects. Present finding showed that lipid peroxidation increased in type 2 diabetes mellitus. Increased lipid peroxidation maybe is associated with some diseases such as cancer, cardiovascular diseases and diabetes mellitus. Lipid peroxidation has an important role in the pathogenesis and the complications of diabetes. Antioxidants have been found to prevent the progression and occurrence of diabetes. There are several mechanisms that may cause lipid peroxidation affront in diabetic subjects, although, their precise contributions are not completely clear. We proposed that production of free radicals can be reduced by preventing high blood glucose levels and by the control of instabilities in blood glucose levels. A contributor to these instabilities in blood glucose is glycaemic control by using of fast blood sugar test. Furthermore, the earlier assessment of the advancement of diabetes that firmly control of blood glucose can be obtained; the greater will be the decrease in diabetic complications. Patients with type 2 diabetes may have very high physiological antioxidants requirements.

Elevation of plasma lipid peroxides in non-insulin dependent diabetics with multiple lacunar infarcts

Our purpose was to determine whether lipid peroxides are elevated in the plasma of patients with non-insulin dependent diabetes with multiple lacunar infarcts as detected by magnetic resonance imaging (MRI), and to confirm whether peroxide levels correlate with glycemic controls and blood lipid levels. The level of lipid peroxide (measured as thiobarbituric acid reactive substances (TBARS)) was measured in 23 healthy controls and 28 diabetics showing normal MRI findings and 22 diabetics with multiple lacunar infarcts. These groups were age-matched. In patients with multiple lacunar infarcts, systolic blood pressure, diastolic blood pressure and TBARS levels were significantly higher than in diabetics without such infarcts (p < 0.05). When the diabetic patients were divided into two groups according to the presence or absence of hypertriglyceridemia or hyperglycemia, in both groups plasma TBARS levels in patients with multiple lacunar infarcts were significantly higher than in patients without such infarcts. Multivariate analysis showed systolic blood pressure and plasma TBARS levels to be independent predictors of multiple lacunar infarcts. Among diabetics, total plasma TBARS levels were positively correlated with fasting blood glucose, HbA1c and triglyceride levels, but not with total cholesterol levels and age. In conclusion plasma lipid peroxides were elevated in diabetics with multiple lacunar lesions, and are related to the metabolic imbalance of plasma glucose and lipids.

Effect of glycemic control, race (white versus black), and duration of diabetes on reduced glutathione content in erythrocytes of diabetic patients

We designed this study to examine whether uncontrolled hyperglycemia, duration of diabetes, or race (black v white) have any effect on glutathione levels in erythrocytes of type I diabetic patients. Hyperglycemia was assessed by measuring the level of hemoglobin A1c (HbA1c). Results show that erythrocytes of diabetic patients have a significantly lower glutathione level compared with those of age-matched normal subjects (P < .004). We found a significant negative correlation (r = -.59, P < .001) between the degree of hyperglycemia and the level of reduced glutathione (GSH) in erythrocytes of diabetic patients. There was no significant relationship (r = -.29, P > .12) between the level of GSH in erythrocytes and the duration of diabetes. Erythrocytes of black diabetic patients had significantly lower levels of GSH (P < .05) than those of white diabetic patients. Using erythrocytes as a model, this study suggests that a lower level of GSH may have a role in the cellular damage and impaired insulin secretion in uncontrolled diabetic patients.

Effect of insulin on impaired antioxidant activities in aortic endothelial cells from diabetic rabbits

The defense system of aortic endothelial cells against oxidative stress was studied in alloxan-induced diabetic rabbits, and the effect of insulin on the antioxidant activities was estimated. Endothelial cells were prepared from 10 diabetic rabbits, 18 diabetic rabbits treated with insulin, and 10 age-matched controls after 17 days of diabetes. These cells were used for the estimation of glutathione (GSH) levels and its related enzyme activities. The antioxidant activities in these endothelial cells from diabetic rabbits were compared with those from control subjects. The concentration of GSH decreased in diabetic rabbits (1.6 +/- 0.2 nmol/mg protein [mean +/- SD] v 3.7 +/- 0.6 nmol/mg protein). Decreases in the activities of Cu, Zn-superoxide dismutase (Cu,Zn-SOD) (62.7 +/- 11.0 U/mg protein v 172.9 +/- 20.2 U/mg protein), catalase (7.6 +/- 2.1 U/mg protein v 12.3 +/- 3.2 U/mg protein), and GSH peroxidase (134.0 +/- 27.0 mU/mg protein v 179.1 +/- 26.2 mU/mg protein) were observed. The activities of other GSH-related enzymes such as GSH S-transferase or GSH reductase did not change in endothelial cells from diabetic rabbits. Most of these antioxidant activities were prevented when diabetic rabbits were treated with insulin (1 to 2 U/kg/d). These antioxidant activities were also determined in the diabetic liver and kidney. Similar decreases in the cellular defense activities and prevention of the decrease in activities by insulin were observed in the diabetic liver, while these antioxidant enzyme activities in the kidney were resistant to diabetic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative stress. Biochemistry and human disease

The early involvement of free radicals in the evolution of life may explain their ubiquitous presence and vital physiological role. Imbalance between protection against free radicals and their generation, explains the likely association of various diseases with toxic oxygen species. An elaborate defence system against oxygen-free radicals exists. The effects of oxidative stress are manifold. Direct demonstration of oxygen radicals in intact biological systems is difficult. Frequently, effect-related measurements are used in this respect. The clinical conditions adult respiratory distress syndrome and multiple organ failure, reflex sympathetic dystrophy and sugar cataract are discussed and the role of oxygen radicals in the aetiology of these diseases are described.