Age-dependent changes of serum oxygen radical scavenger capacity and haemoglobin glycosylation in non-insulin-dependent diabetic patients

Selenoprotein H suppresses cellular senescence through genome maintenance and redox regulation

Oxidative stress and persistent DNA damage response contribute to cellular senescence, a degeneration process critically involving ataxia telangiectasia-mutated (ATM) and p53. Selenoprotein H (SelH), a nuclear selenoprotein, is proposed to carry redox and transactivation domains. To determine the role of SelH in genome maintenance, shRNA knockdown was employed in human normal and immortalized cell lines. SelH shRNA MRC-5 diploid fibroblasts under ambient O2 displayed a distinct profile of senescence including β-galactosidase expression, autofluorescence, growth inhibition, and ATM pathway activation. Such senescence phenotypes were alleviated in the presence of ATM kinase inhibitors, by p53 shRNA knockdown, or by maintaining the cells under 3% O2. During the course of 5-day recovery, the induction of phospho-ATM on Ser-1981 and γH2AX by H2O2 treatment (20 μm) subsided in scrambled shRNA but exacerbated in SelH shRNA MRC-5 cells. Results from clonogenic assays demonstrated hypersensitivity of SelH shRNA HeLa cells to paraquat and H2O2, but not to hydroxyurea, neocarzinostatin, or camptothecin. While SelH mRNA expression was induced by H2O2 treatment, SelH-GFP did not mobilize to sites of oxidative DNA damage. The glutathione level was lower in SelH shRNA than scrambled shRNA HeLa cells, and the H2O2-induced cell death was rescued in the presence of N-acetylcysteine, a glutathione precursor. Altogether, SelH protects against cellular senescence to oxidative stress through a genome maintenance pathway involving ATM and p53.

Oxidative stress: Does it play a role in the genesis of early glycated proteins?

Glycation and oxidative stress are two important processes known to play a key role in complications of many pathophysiological processes. The two traditional factors found to modulate the early glycation of proteins are the prevailing concentration of glucose and half life of the protein. But evidences in the literature have documented an increased glycated protein levels in some non-diabetic pathological states. So it stands to reason that hyperglycemia, while clearly the culprit in diabetes, is not the complete answer to the etiology of increased early glycated products in non-diabetic conditions. A common denominator in all these above mentioned non-diabetic pathological conditions is oxidative stress. Collective evidences from the literature reveal that malondialdehyde, reduced glutathione, vitamin C, vitamin E and drugs with antioxidant properties mitigate the process of protein glycation. Taking all the above factors into account, we hypothesis that oxidative stress either via increasing reactive oxygen species or by depleting the antioxidants may modulate the genesis of early glycated proteins in vivo.

Mangifera indica L. (Vimang) Protection against Serum Oxidative Stress in Elderly Humans

BACKGROUND

We searched for the protective effect of a natural extract from stem bark of Mangifera indica L. extract (Vimang) on age-related oxidative stress.

METHODS

Healthy subjects were classified in two groups, elderly (>65 years) and young group (<26 years). The elderly group received a daily dose of 900 mg of extract (three coated Vimang tablets, 300 mg each, before meals) for 60 days. Serum concentration of lipid peroxides, serum peroxidation potential, extracellular superoxide dismutase activity (EC-SOD), glutathione status (GSH, GSSG, GSSG/GSH ratio)) and total antioxidant status (TAS) were determined before (both experimental groups) and 15, 30, and 60 days after treatment (only elderly group). We confirmed the existence of an age-associated oxidative stress in human serum as documented by an age-related increase in serum lipoperoxides and GSSG and a decrease in serum antioxidant capacity and EC-SOD activity.

RESULTS

Vimang tablet supplementation increased EC-SOD activity (p <0.01) and serum TAS (p <0.01). It also decreased serum thiobarbituric reactive substances (p <0.01) and GSSG levels (p <0.05). We suggested that the antioxidant components of the extract could have been utilized by the cells (especially blood and endothelial cells), sparing the intra- and extracellular antioxidant system and increasing serum peroxil scavenging capacity, thus preventing age-associated increase in GSH oxidation and lipoperoxidation.

CONCLUSIONS

Vimang tablets prevent age-associated oxidative stress in elderly humans, which could retard the onset of age-associated disease, improving the quality of life for elderly persons.

Reassessing the increased glycation of hemoglobin in nondiabetic chronic renal failure patients: a hypothesis on the role of lipid peroxides

BACKGROUND

Glycated hemoglobin (HbA(1C)) is considered clinically useful for assessing long-term integrated control of blood glucose in diabetes. However, an increased HbA(1C) concentration has been documented in chronic renal failure (CRF) patients without any history of diabetes. Collective evidences reveal that lipid peroxidation (MDA) can modulate protein glycation. We evaluated the relationship between glycated hemoglobin (HbA(1C)) and lipid peroxidation in non-diabetic CRF patients.

METHODS

Twenty-eight nondiabetic CRF and 23 age- and sex-matched healthy subjects were enrolled for this study. Plasma urea, creatinine, lipid peroxides, fasting glucose and HbA(1C) were analyzed in both the groups. The in-vitro effect of MDA on glycation of hemoglobin was studied by incubating healthy erythrocytes with either 5 or 50 mmol/l glucose concentration.

RESULTS

The percentage of HbA(1C) concentrations and plasma malondialdehyde (MDA) were significantly increased in CRF patients compared to control subjects. When the effects of uremia and blood glucose on the concentration of HbA(1C) was refuted by partial correlation analysis, MDA was found to be a significant determinant of HbA(1C) (r=0.41, p=0.04) in patients with renal failure. In-vitro incubation of RBC with glucose along with MDA was found to enhance the process of hemoglobin glycation.

CONCLUSION

Our results suggest that lipid peroxidation per se can contribute to glycation of hemoglobin, warranting extra-precaution in interpreting HbA(1C) as a measure of glycemic control in CRF.

The use of pholasin as a probe for the determination of plasma total antioxidant capacity

BACKGROUND AND OBJECTIVES

Total antioxidant capacity (TAC) reflects the capacity of plasma, or other body fluid, to resist oxidation. The aim of the present study was to assess the prognostic value of Pholasin as a probe for the determination of plasma TAC.

DESIGN AND METHODS

Plasma samples either oxidised using the free radical generator 2'-azobis-(2-amidinopropane) hydrochloride (AAPH) at 60 degrees C for 180 min or obtained from diabetic (type 1 and type 2) patients (n = 61 and 124, respectively) with or without polyneuropathy (PN) and/or cardiovascular autonomic neuropathy (CAN) and control subjects (n = 70) were analysed for TAC status. TAC was assessed using two versions of Analysis By Emitted Light (ABEL) tests including quenching of Pholasin chemiluminescence (QPC) with peroxynitrite (ONOO(-)-QPC) and with superoxide anion (O2(-)-QPC).

RESULTS

The utilisation of AAPH to induce peroxyl radical mediated plasma oxidation produced a significant decrease in TAC as assessed by ONOO(-)-QPC and O2(-)-QPC assays in a time-dependent manner. Type 1 and type 2 diabetic patients without PN and/or CAN had lower TAC (ONOO(-)-QPC and O2(-)-QPC) than in control subjects. Further alterations in TAC were noted in the presence of PN and/or CAN. Correlations were found between TAC (ONOO(-)-QPC and O2(-)-QPC) values on duration of diabetes and neurological impairment score-lower limb (NIS-LL) in type 1 diabetic patients.

CONCLUSIONS

This study has established that the ONOO(-)-QPC and O2(-)-QPC versions of the ABEL test fulfil the criteria in terms of simplicity, sensitivity and reliability for the measurement of plasma TAC. These biomarkers may prove useful in studies evaluating the impact of therapeutic drugs or antioxidant interventions aimed at delaying the onset of complications in clinical conditions associated with oxidative stress.

A different approach to analyzing age-related HbA1c values in non-diabetic subjects

Using appropriate statistical tests and taking into account the analytical performance of hemoglobin A1c (HbA1c) measurements, is it useful to establish HbA1c age-related values in non-diabetic subjects? Non-diabetic subjects (n=135, 72 women and 63 men) from the neuromuscular department of the Pitié-Salpétrière Hospital (Paris) were involved in our study. Subjects were divided into two groups related to age: 51 patients under 50 years old and 84 subjects aged 50 years or more. Fasting plasma glucose and HbA1c measurements were respectively performed by enzymatic assay using the hexokinase method and high-performance liquid chromatography based on the ion exchange methodology with high precision. We first checked the normality of HbA1c distribution using the Kolmogorov-Smirnov test. Then we compared mean HbA1c in the two age subgroups using the Student's t test. Mean HbA1c was significantly (p<0.0001) higher in the subgroup aged 50 years or more (mean HbA1c=5.2%) than in younger subjects (mean HbA1c=5.0%). Then plots were drawn to check the relationship between HbA1c and age. Under the hypothesis of linearity, determination coefficients (R2) were calculated. However, considering their low values, this hypothesis must be rejected and other factors than age must be retained to explain HbA1c variability.

Oxidative and antioxidative status in pregnant women with either gestational or type 1 diabetes

OBJECTIVES

To evaluate oxidative and antioxidative status in pregnant diabetic women between 26 and 32 weeks of gestation.

DESIGN AND METHODS

Free and total malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and vitamins A and E were determined in plasma and erythrocytes of 54 pregnant women. Among these, 27 were diabetics with either gestational diabetes mellitus (GDM), sub-group I, or previous insulin-dependent diabetes mellitus (type 1 diabetes), sub-group II. The other 27 patients were controls. Fasting plasma glucose and HbA(1c) levels were determined in all women.

RESULTS

HbA(1c) levels, plasma-, and erythrocyte-free MDA levels were significantly higher in all diabetic women and in both sub-groups than in controls. Plasma vitamin E and erythrocyte vitamin A levels were significantly lower in all diabetic women than in controls. Moreover, GPX and SOD activities were significantly reduced in all diabetic women, GPX in both sub-groups and SOD only in type 1 diabetes.

CONCLUSIONS

The increased oxidative stress we demonstrated in pregnant women with previous type 1 diabetes or with GDM should be monitored by strictly controlling blood glucose during pregnancy with stringent recommendations and perhaps antioxidant supplementation.