Telomere shortening: a marker of atherosclerosis?

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Differential gene expression of NADPH oxidase (p22phox) and hemoxygenase-1 in patients with Type 2 diabetes and microangiopathy

Aims: While the downstream effects of increased reactive oxygen species (ROS) in the pathogenesis of diabetes were well studied, only a few studies have explored the cellular sources of ROS. We examined whether protection against oxidative stress is altered in patients with diabetes and microangiopathy by examining changes in NADPH oxidase (p22phox) and hemoxygenase‐1 (HO‐1) levels. Methods: NADPH oxidase (p22phox) and HO‐1 gene expression were probed by RT‐PCR using leucocytes from patients with Type 2 diabetes without (n = 19) and with microangiopathy (n = 20) and non‐diabetic subjects (n = 17). Levels of lipid peroxidation as measured by thiobarbituric reactive substances (TBARS) and protein carbonyl content (PCO) were determined by fluorimetric and spectrophotometric methods, respectively. Results: p22phox gene expression (mean ± se) was significantly (P < 0.05) higher in diabetic patients with (0.99 ± 0.04) and without microangiopathy (0.86 ± 0.05) compared with control subjects (0.66 ± 0.05). Consistent with the mRNA data, the p22phox protein expression and NADPH oxidase activity was also increased in cells from diabetic patients compared with control subjects. However, HO‐1 gene expression was significantly (P < 0.05) lower in patients with (0.73 ± 0.03) and without microangiopathy (0.85 ± 0.02) compared with control subjects (1.06 ± 0.03). The mean (± se) levels of TBARS were significantly (P < 0.05) higher in diabetic patients with (14.36 ± 1.3 nm/ml) and without microangiopathy (12.20 ± 1.3 nm/ml) compared with control subjects (8.58 ± 0.7 nm/ml). The protein carbonyl content was also significantly (P < 0.05) higher in diabetic patients with (1.02 ± 0.04 nmol/mg protein) and without microangiopathy (0.84 ± 0.06 nmol/mg protein) compared with control subjects (0.48 ± 0.02 nmol/mg protein). In diabetic subjects, increased p22phox gene expression was negatively correlated with HO‐1 and positively correlated with TBARS, PCO, HbA1c and diabetes duration. In contrast, HO‐1 gene expression was correlated negatively with p22phox, TBARS, PCO, HbA1c and diabetes duration. Conclusion: Our results indicate that increased oxidative damage is seen in Asian Indians with Type 2 diabetes and microangiopathy and is associated with increased NADPH oxidase (p22phox) and decreased HO‐1 gene expression

Association of telomere shortening with impaired glucose tolerance and diabetic macroangiopathy

Objective: Shortening of telomere length has been reported in several conditions including Type 2 diabetes and atherosclerosis. The aims of this study were (1) to assess whether telomere shortening occurs at the stage of pre-diabetes, i.e., impaired glucose tolerance (IGT) and (2) whether telomere shortening was greater in Type 2 diabetic subjects with atherosclerotic plaques. Methods: Subjects with impaired glucose tolerance (IGT) (n = 30), non-diabetic control subjects (n = 30), Type 2 diabetic patients without (n = 30) and with atherosclerotic plaques (n = 30) were selected from the Chennai Urban Rural Epidemiology Study (CURES), an ongoing epidemiological population-based study. Southern-blot analysis was used to determine mean terminal restriction fragment (TRF) length, a measure of average telomere size, in leukocyte DNA. Levels of thiobarbituric acid reactive substances (TBARS), protein carbonyl content (PCO) and high sensitive C-reactive protein (hs-CRP) were measured by standard methodologies. Carotid intima-media thickness (IMT) was assessed by high resolution B-mode ultrasonography. Results: The mean (±S.E.) TRF lengths were significantly lower in IGT subjects (6.97 ± 0.3 kb; p = 0.002) and lower still in Type 2 diabetic subjects without plaques (6.21 ± 0.2; p = 0.0001) and lowest in Type 2 diabetic subjects with atherosclerotic plaques (5.39 ± 0.2; p = 0.0001) when compared to control subjects (8.7 ± 0.5). In IGT subjects, TRF length was positively correlated to HDL cholesterol and negatively correlated to glycated hemoglobin (HbA1c), TBARS, PCO, HOMA-IR and IMT. In multiple linear regression analysis, presence of diabetes, HDL cholesterol and increased TBARS levels appear as significant determinants of telomere shortening. Conclusion: Telomere shortening is seen even at the stage of IGT. Among subjects with Type 2 diabetes, those with atherosclerotic plaques had greater shortening of telomere length compared to those without plaques

Telomere shortening & metabolic/vascular diseases

Telomeres are specialized DNA-protein structures located at the ends of eukaryotic chromosomes whose length is progressively reduced in most somatic cells during ageing. Over the past decade, emerging evidence has shown that the telomeres are essential regulators of cellular life span and chromosome integrity in a dynamic fashion. By inducing genomic instability, replicative senescence and apoptosis, shortening of telomeres is thought to contribute to organismal ageing. While the aetiology of cardiovascular diseases and diabetes represent a complex interaction between various risk factors overlaid on different genetic backgrounds, the conventional risk factors often did not explain the inter-individual variability related to predisposition of disease states. This underscores the need for biological indicators of ageing in evaluating the aetiology of several age-related disorders, and recent studies indicate that telomere length could qualify as an ideal marker of biological ageing. Short telomeres have been detected in senescent endothelial cells and vascular smooth muscle cells from human atherosclerotic plaque as well as in myocardial tissue from patients with end-stage heart failure and cardiac hypertrophy. In addition, telomere shortening has been demonstrated in WBCs from patients with coronary heart disease, premature myocardial infarction, hypertension and diabetes mellitus. In this review, we discuss the telomere hypothesis of ageing as well as human studies that address the role of telomeres in cardiovascular, diabetes and other cardio-metabolic pathologies

Oxidative DNA damage and augmentation of poly(ADP-ribose) polymerase/nuclear factor-kappa B signaling in patients with Type 2 diabetes and microangiopathy

Although oxidative stress and the subsequent DNA damage is one of the obligatory signals for poly(ADP-ribose) polymerase (PARP) activation and nuclear factor-kappa B (NFκB) alterations, these molecular aspects have not been collectively examined in epidemiological and clinical settings. Therefore, this study attempts to assess the oxidative DNA damage and its downstream effector signals in peripheral blood lymphocytes from Type 2 diabetes subjects without and with microangiopathy along with age-matched non-diabetic subjects. The basal DNA damage, lipid peroxidation and protein carbonyl content were significantly (p < 0.05) higher in patients with and without microangiopathy compared to control subjects. Formamido Pyrimidine Glycosylase (FPG)-sensitive DNA strand breaks which represents reliable indicator of oxidative DNA damage were also significantly (p < 0.001) higher in diabetic patients with (19.41 ± 2.5) and without microangiopathy (16.53 ± 2.0) compared to control subjects (1.38 ± 0.85). Oxidative DNA damage was significantly correlated to poor glycemic control. PARP mRNA expression and PARP activity were significantly (p < 0.05) increased in cells from diabetic patients with (0.31 ± 0.03 densitometry units; 0.22 ± 0.02 PARP units/mg protein, respectively) and without (0.35 ± 0.02; 0.42 ± 0.05) microangiopathy compared to control (0.19 ± 0.02; 0.11 ± 0.02) subjects. Diabetic subjects with and without microangiopathy exhibited a significantly (p < 0.05) higher (80%) NFκB binding activity compared to control subjects. In diabetic patients, FPG-sensitive DNA strand breaks correlated positively with PARP gene expression, PARP activity and NFκB binding activity. This study provides a comprehensive molecular evidence for increased oxidative stress and genomic instability in Type 2 diabetic subjects even prior to vascular pathology and hence reveals a window of opportunity for early therapeutic intervention

Elevated unmethylated and methylated insulin DNA are unique markers of A + β + ketosis prone diabetes

A + β + ketosis prone diabetes (KPD) is associated with slowly progressive autoimmune beta cell destruction. Plasma unmethylated and methylated insulin DNA (biomarkers of ongoing beta cell damage and systemic inflammation, respectively) were elevated in A + β + KPD compared to all other KPD subgroups

Curcumin-induced inhibition of cellular reactive oxygen species generation: novel therapeutic implications

There is evidence for increased levels of circulating reactive oxygen species (ROS) in diabetics, as indirectly inferred by the findings of increased lipid peroxidation and decreased antioxidant status. Direct measurements of intracellular generation of ROS using fluorescent dyes also demonstrate an association of oxidative stress with diabetes. Although phenolic compounds attenuate oxidative stress-related tissue damage, there are concerns over toxicity of synthetic phenolic antioxidants and this has considerably stimulated interest in investigating the role of natural phenolics in medicinal applications. Curcumin (the primary active principle in turmeric, Curcuma longa Linn.) has been claimed to represent a potential antioxidant and antiinflammatory agent with phytonutrient and bioprotective properties. However there are lack of molecular studies to demonstrate its cellular action and potential molecular targets. In this study the antioxidant effect of curcumin as a function of changes in cellular ROS generation was tested. Our results clearly demonstrate that curcumin abolished both phorbol-12 myristate-13 acetate (PMA) and thapsigargin-induced ROS generation in cells from control and diabetic subjects. The pattern of these ROS inhibitory effects as a function of dose-dependency suggests that curcumin mechanistically interferes with protein kinase C (PKC) and calcium regulation. Simultaneous measurements of ROS and Ca2+ influx suggest that a rise in cytosolic Ca2+ may be a trigger for increased ROS generation. We suggest that the antioxidant and antiangeogenic actions of curcumin, as a mechanism of inhibition of Ca2+ entry and PKC activity, should be further exploited to develop suitable and novel drugs for the treatment of diabetic retinopathy and other diabetic complications

Omega Production in pp Collisions

A model-independent irreducible tensor formalism which has been developed earlier to analyze measurements of $\vec{p}\vec{p}\to pp \pi^\circ$, is extended to present a theoretical discussion of $\vec{p}\vec{p}\to pp \omega$ and the polarization of $\omega$ in $pp\to pp \vec{\omega}$. The recent measurement of unpolarized differential cross section for $pp\to pp \omega$ is analyzed using this theoretical formalism.Comment: 5 pages (double column), no figures, uses revtex

Biomarkers of oxidative stress: methods and measures of oxidative DNA damage (COMET assay) and telomere shortening

Oxidative stress is fast becoming the nutritional and medical buzzword for the twenty-first century. The theoretical importance of oxidative stress in diabetes is highlighted by its potential double impact on metabolic dysfunction on one hand and the vascular system on the other hand. The new concept of oxidative stress, being an important trigger in the onset and progression of diabetes and its complications, emphasizes the need for measurement of markers of oxidation to assess the degree of oxidative stress. While we have been routinely measuring biomarkers in our molecular epidemiology projects, here we discuss the utility of two assays, (a) DNA damage assessment by COMET measurement and (b) telomere length measurement. As DNA damage is efficiently repaired by cellular enzymes, its measurement gives a snapshot view of the level of oxidative stress. The protocol allows for measurement of oxidative DNA damage (FPG-sensitive DNA strand breaks). Telomere length measured by Southern blotting technique allows one to estimate the chronic burden of oxidative stress at the molecular level and is now considered as biomarker of biological aging