Markers of oxidative stress in obese men with and without hypertension

Whole-body oxidative stress reduction during testosterone therapy in aging men: A randomized placebo-controlled trial

BACKGROUND

Testosterone replacement therapy in aging men increases lean body mass and decreases whole-body fat. The safety of testosterone replacement therapy concerning cardiovascular disease is unresolved and assessment of whole-body oxidative stress may contribute to future decision making.

OBJECTIVES

To determine whole-body oxidative stress during testosterone replacement therapy and placebo in aging men and evaluate if a change in oxidative stress was mediated by changed body composition.

MATERIALS AND METHODS

This was a double-blinded, randomized, placebo-controlled study for 24 weeks in 38 men aged 60-78 years with bioavailable testosterone <7.3 nmol/L and waist circumference ≥94 cm who were randomized to testosterone replacement therapy (testosterone gel) (N = 20) or placebo (N = 18). At baseline and after 24 weeks, whole-body oxidative stress was assessed by oxidized derivatives of nucleic acids, 8-oxoguanosine and 8-oxo-2'-deoxyguanosine in 24-h urine samples by ultra-performance liquid chromatography tandem mass spectrometry. Lean body mass and whole-body fat were measured by dual X-ray absorptiometry. Subcutaneous and visceral adipose tissue were estimated by magnetic resonance imaging. Testosterone replacement therapy versus placebo was compared by Mann-Whitney tests on ∆-values (24-0 weeks).

RESULTS

Baseline age was 67 (64-72) years (median [interquartile range]), body mass index 29.8 (26.6-33.3) kg/m2 , waist 107 (99-117) cm, and bioavailable testosterone 4.7 (3.7-5.9) nmol/L. During testosterone replacement therapy, 8-oxoguanosine in 24-h urine samples decreased from 21.6 (19.8; 27.7) nm to 15.0 (12.2; 18.8) nm (p = 0.038 vs. placebo), lean body mass increased (p < 0.01) and whole-body fat (p = 0.02) and subcutaneous adipose tissue (p < 0.01) decreased. 8-Oxoguanosine in 24-h urine samples was inversely associated with Δ-lean body mass (ρ = -0.38, p = 0.03), which remained significant after adjusting for Δ-total testosterone. 8-Oxo-2'-deoxyguanosine in 24-h urine samples was unchanged (p = 0.06) during testosterone replacement therapy and Δ-8-oxo-2'-deoxyguanosine in 24-h urine samples was associated with Δ-whole-body fat (kg) (ρ = 0.47, p < 0.01). Δ-Values of oxidative stress biomarkers were not associated with Δ-fasting insulin or Δ-homeostatic model assessment of insulin resistance.

DISCUSSION

Oxidative stress decreased during testosterone replacement therapy compared to placebo, which could be mediated by changed body composition.

CONCLUSION

Whole-body oxidative stress decreased during 24 weeks of testosterone replacement therapy in aging men.

The Role of Oxidative Stress Enhanced by Adiposity in Cardiometabolic Diseases

Cardiometabolic diseases (CMDs), including cardiovascular disease (CVD), metabolic syndrome (MetS), and type 2 diabetes (T2D), are associated with increased morbidity and mortality. The growing prevalence of CVD is mostly attributed to the aging population and common occurrence of risk factors, such as high systolic blood pressure, elevated plasma glucose, and increased body mass index, which led to a global epidemic of obesity, MetS, and T2D. Oxidant–antioxidant balance disorders largely contribute to the pathogenesis and outcomes of CMDs, such as systemic essential hypertension, coronary artery disease, stroke, and MetS. Enhanced and disturbed generation of reactive oxygen species in excess adipose tissue during obesity may lead to increased oxidative stress. Understanding the interplay between adiposity, oxidative stress, and cardiometabolic risks can have translational impacts, leading to the identification of novel effective strategies for reducing the CMDs burden. The present review article is based on extant results from basic and clinical studies and specifically addresses the various aspects associated with oxidant–antioxidant balance disorders in the course of CMDs in subjects with excess adipose tissue accumulation. We aim at giving a comprehensive overview of existing knowledge, knowledge gaps, and future perspectives for further basic and clinical research. We provide insights into both the mechanisms and clinical implications of effects related to the interplay between adiposity and oxidative stress for treating and preventing CMDs. Future basic research and clinical trials are needed to further examine the mechanisms of adiposity-enhanced oxidative stress in CMDs and the efficacy of antioxidant therapies for reducing risk and improving outcome of patients with CMDs.

Effects of 2-Year Nutritional and Lifestyle Intervention on Oxidative and Inflammatory Statuses in Individuals of 55 Years of Age and over at High Cardiovascular Risk

Obesity and overweight are disorders with high impact on the morbidity and mortality of chronic diseases, such as type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD). We aim to assess the effects of 2-year nutritional and lifestyle intervention on oxidative and inflammatory status in individuals of 55 years of age and over at high CVD risk. Participants (n = 100 individuals of 55 years of age and over living in the Balearic Islands, Spain) were randomized into control and intervention group. Anthropometric and haematological parameters, blood pressure and physical activity were measured before and after the intervention. Oxidative and inflammatory biomarkers in plasma, urine, peripheral blood mononuclear cells (PBMCs) and neutrophils were determined. A higher reduction in abdominal obesity, blood pressure and triglycerides levels was observed after a 2-year intervention. An improvement of oxidative stress and proinflammatory status was demonstrated with a significant reduction in myeloperoxidase, xanthine oxidase, malondialdehyde and monocyte chemoattractant protein-1 (MCP1) levels, and an increase in polyphenols in plasma was observed. A decrease in reactive oxygen species production in PBMCs and neutrophils levels after zymosan and lipopolysaccharide activation was found in the intervention group with respect to the control group. The intervention with hypocaloric Mediterranean Diet and customized physical activity improves oxidative stress and proinflammatory status and could contribute to decreasing the CVD risk.

Urinary Oxidative Damage Markers and Their Association with Obesity-Related Metabolic Risk Factors

Oxidative damage and inflammation are possible mechanisms linking obesity to diabetes and related complications. This study investigates the levels of oxidative damage markers in the urine of community free-living subjects with increased prevalence of obesity. Methods: Participants were assessed regarding clinical, anthropometric, and physical activity data at baseline and at 6 months. Blood and urine samples were taken for the measurements of oxidative markers in urine ((glutathione (GSH), thiobarbituric acid reactive substances (TBARS), pteridine, 8-isoprostane and 8-hydroxy-2′-deoxyguanosine (8-OH-dG)), metabolic and inflammatory markers, and related biochemical variables in the blood. Univariate and multiple regression analyses were used to assess the association between oxidative markers and other clinical prognostic indicators. Results: Overall, 168 participants with a complete 6-month follow-up with a mean (±SD) age of 41 ± 12 (119 (71%) females) were included in the study. In multiple regression analysis, log-transformed urinary pteridine levels were significantly correlated with log-transformed urinary GSH, 8-isoprostane, and TBARS after adjusting for urinary creatinine at both baseline and follow-up. Significant correlations were also found between oxidative damage markers and cardiovascular disease risk factors, including systolic blood pressure, HbA1c, plasma glucose, us-C-reactive proteins, total cholesterol, and HDL. Higher TBARS levels were found in males and diabetic subjects, with lower GSH in diabetic hypertensive and obese subjects, but the latter result did not reach statistical significance. We found nonsignificantly higher TBARS, 8-isoprostane, and pteridine levels in smokers compared to those in nonsmokers. All measured urinary oxidative damage markers levels were higher in obese subjects compared with normal-weight subjects, but results did not reach statistical significance. Conclusion: we found significant associations between urinary oxidative damage and metabolic risk factors, and higher levels of urinary oxidative damage markers in diabetic, hypertensive, smoker, and male subjects.

Biology of aging: Oxidative stress and RNA oxidation

The prevalence of aged people has increased rapidly in recent years and brings profound demographic changes worldwide. The multi-level progression of aging occurs at diverse stages of complexity, from cell to organ systems and eventually to the human as a whole. The cellular and molecular damages are usually regulated by the cells; repair or degrade mechanisms. However, these mechanisms are not entirely functional; their effectiveness decreases with age due to influence from endogenous sources like oxidative stress, which all contribute to the aging process. The hunt for novel strategies to increase the man's longevity since ancient times needs better understandings of the biology of aging, oxidative stress, and their roles in RNA oxidation. The critical goal in developing new strategies to increase the man's longevity is to compile the novel developed knowledge on human aging into a single picture, preferably able to understand the biology of aging and the contributing factors. This review discusses the biology of aging, oxidative stress, and their roles in RNA oxidation, leading to aging in humans.

Oxidative stress and obesity

Obesity is a disease of excessive accumulation of adipose tissue due to an increased energy intake which is disproportionate to the energy expenditure in the body. The visceral adipose tissue in the obese accumulated in that way increases the risk of developing a number of metabolic and cardiovascular diseases. Disorders such as diabetes, dyslipidemia, inflammation, endothelial dysfunction and mitochondria can contribute to the development of oxidative stress, which is especially pronounced in the abdominal type of obesity. Obesity can induce systemic oxidative stress through a variety of biochemical mechanisms. Although ROS is generated in a large number of cells, mitochondria play a significant role in their intracellular production through the process of oxidative phosphorylation of the respiratory chain, and in fatty acid oxidation reactions. Oxidative stress is a unique link between the various molecular disorders present in the development of insulin resistance that plays a key role in the pathogenesis and progression of chronic metabolic, proinflammatory diseases. The progression of insulin resistance is also affected by inflammation. Both of these can be the cause and the consequence of obesity. The synthesis of the inflammatory mediators is induced by oxidative stress, thus bringing the inflammation and the oxidative stress into a very significant relation. This review aims to highlight recent findings on the role of oxidative stress in the pathogenesis of obesity, with special reference to the mechanisms that explain its occurrence.

Redox changes in obesity, metabolic syndrome, and diabetes

"Life is an instantaneous encounter of circulating matter and flowing energy" (Jean Giaja, Serbian physiologist), is one of the most elegant definitions not only of life but the relationship of redox biology and metabolism. Their evolutionary liaison has created inseparable yet dynamic homeostasis in health, which, when disrupted, leads to disease. This interconnection is even more pertinent today, in an era of increasing metabolic diseases of epidemic proportions such as obesity, metabolic syndrome, and diabetes. Despite great advances in understanding the molecular mechanisms of redox and metabolic regulation, we face significant challenges in preventing, diagnosing, and treating metabolic diseases. The etiological association and temporal overlap of these syndromes present significant challenges for the discrimination of appropriate clinical biomarkers for diagnosis, treatment, and outcome prediction. These multifactorial, multiorgan metabolic syndromes with complex etiopathogenic mechanisms are accompanied by disturbed redox equilibrium in target tissues and circulation. Free radicals and reactive species are considered both a causal factor and a consequence of disease status. Thus, determining the subtypes and levels of free radicals and reactive species, oxidatively damaged biomolecules (lipids, proteins, and nucleic acids) and antioxidant defense components as well as redox-sensitive transcription factors and fluxes of redox-dependent metabolic pathways will help define existing and establish novel redox biomarkers for stratifying metabolic diseases. This review aims to discuss diverse redox/metabolic aspects in obesity, metabolic syndrome, and diabetes, with the imperative to help establish a platform for emerging and future redox-metabolic biomarkers research in precision medicine. Future research warrants detailed investigations into the status of redox biomarkers in healthy subjects and patients, including the use of emerging 'omic' profiling technologies (e.g., redox proteomes, lipidomes, metabolomes, and transcriptomes), taking into account the influence of lifestyle (diet, physical activity, sleep, work patterns) as well as circadian ~24h fluctuations in circulatory factors and metabolites.

Higher systemic oxidatively generated DNA and RNA damage in patients with newly diagnosed bipolar disorder and their unaffected first-degree relatives

BACKGROUND

Prior studies in bipolar disorders (BD) have suggested that oxidative stress and cellular ageing play a key role in the pathophysiology of BD. Nevertheless, oxidative stress has not been investigated in patients with newly diagnosed BD and in their unaffected first-degree relatives (UR), compared with healthy control individuals (HC).

METHODS

We investigated the level of systemic oxidative damage to DNA and RNA measured by urinary excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) levels, respectively, in 360 patients with newly diagnosed BD, 92 of their UR and 197 HC.

RESULTS

Independent of lifestyle and demographic variables, levels of both 8-oxoGuo and 8-oxodG was 17.1% (B = 1.171, 95%CI = 1.125-1.219, p < 0.001) and 21.2% (B = 1.212, 95%CI = 1.145-1.283, p < 0.001) higher, respectively, in patients with BD compared with HC and 13.3% (B = 1.133, 95%CI = 1.069-1.200, p < 0.001) and 26.6% (B = 1.266, 95%CI = 1.167-1.374, p < 0.001) higher, respectively, in UR compared with HC. Neither 8-oxoGuo nor 8-oxodG levels differed between patients with BD and UR. These findings were replicated in patients in full or partial remission and were consistent both in BD type I and II.

CONCLUSION

Overall, the findings of higher oxidative stress in patients with newly diagnosed BD and their UR suggest that systemic nucleoside damage by oxidative stress is present prior to onset and in the early stages of BD thereby potentially representing trait markers of BD.

Recent progress in the LC-MS/MS analysis of oxidative stress biomarkers

The presence of a dynamic and balanced equilibrium between the production of reactive oxygen (ROS) and nitrogen (RNS) species and the in-house antioxidant defense mechanisms is characteristic for a healthy body. During oxidative stress (OS), this balance is switched to increased production of ROS and RNS, exceeding the capacity of physiological antioxidant systems. This can cause damage to biological molecules, leading to loss of function and even cell death. Nowadays, there is increasing scientific and clinical interest in OS and the associated parameters to measure the degree of OS in biofluids. An increasing number of reports using LC-MS/MS methods for the analysis of OS biomarkers can be found. Since bioanalysis is usually complicated by matrix effects, various types of cleanup procedures are used to effectively separate the biomarkers from the matrix. This is an essential part of the analysis to prepare a reproducible and homogenous solution suitable for injection onto the column. The present review gives a summary of the chromatographic methods used for the determination of OS biomarkers in both urine and plasma, serum, and whole blood samples. The first part mainly describes the biological background of the different OS biomarkers, while the second part reports examples of chromatographic methods for the analysis of different metabolites connected with OS in biofluids, covering a period from 2015 till early 2020. The selected examples mainly include LC-MS/MS methods for isoprostanes, oxidized proteins, oxidized lipoproteins, and DNA/RNA biomarkers. The last part explains the clinical relevance of this review.

Reduction of oxidative stress on DNA and RNA in obese patients after Roux-en-Y gastric bypass surgery-An observational cohort study of changes in urinary markers

Increased oxidative stress in obesity and diabetes is associated with morbidity and mortality risks. Levels of oxidative damage to DNA and RNA can be estimated through measurement of 8-oxo-7,8-dihydro-2´-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) in urine. Both markers have been associated with type 2 diabetes, where especially 8-oxoGuo is prognostic for mortality risk. We hypothesized that Roux-en-Y gastric bypass (RYGB) surgery that has considerable effects on bodyweight, hyperglycemia and mortality, might be working through mechanisms that reduce oxidative stress, thereby reducing levels of the urinary markers. We used liquid chromatography coupled with tandem mass spectrometry to analyze the content of 8-oxodG and 8-oxoGuo in urinary samples from 356 obese patients treated with the RYGB-procedure. Mean age (SD) was 44.2 (9.6) years, BMI was 42.1 (5.6) kg/m2. Ninety-six (27%) of the patients had type 2 diabetes. Excretion levels of each marker before and after surgery were compared as estimates of the total 24-hour excretion, using a model based on glomerular filtration rate (calculated from cystatin C, age, height and weight), plasma- and urinary creatinine. The excretion of 8-oxodG increased in the first months after RYGB. For 8-oxoGuo, a gradual decrease was seen. Two years after RYGB and a mean weight loss of 35 kg, decreased hyperglycemia and insulin resistance, excretion levels of both markers were reduced by approximately 12% (P < 0.001). For both markers, mean excretion levels were about 30% lower in the female subgroup (P < 0.0001). Also, in this subgroup, excretion of 8-oxodG was significantly lower in patients with than without diabetes. We conclude, that oxidative damage to nucleic acids, reflected in the excretion of 8-oxodG and 8-oxoGuo, had decreased significantly two years after RYGB-indicating that reduced oxidative stress could be contributing to the many long-term benefits of RYGB-surgery in obesity and type 2 diabetes.

Increased Oxidative Stress Underlies Abnormal Pain Threshold in a Normoglycemic Japanese Population

Normal-high HbA1c levels are a risk factor for attenuated pain sensation in normoglycemic subjects. It is unclear, however, what mechanisms underlie the pathogenesis of attenuated pain sensation in such a population. We, therefore, explored the relationship between oxidative stress (OS) and pain sensation in a rural Japanese population. A population-based study of 894 individuals (average age 53.8 ± 0.5 years) and 55 subjects with impaired fasting glucose (IFG) were enrolled in this study. Individuals with diabetes were excluded. Relationships between pain threshold induced by intraepidermal electrical stimulation (PINT) and clinico-hematological parameters associated with OS were evaluated. Univariate linear regression analyses revealed age, BMI, HbA1c, the OS biomarker urine 8-hydroxy-2'-deoxyguanosine (8-OHdG), systolic blood pressure, and decreased Achilles tendon reflex on the PINT scores. Adjustments for age, gender, and multiple clinical measures confirmed a positive correlation between PINT scores and urine 8-OHdG (β = 0.09, p < 0.01). Urine 8-OHdG correlated positively with higher HbA1c levels and age in the normoglycemic population. Unlike in the normoglycemic population, both inflammation and OS were correlated with elevated PINT scores in IFG subjects. OS may be a major contributing factor to elevated PINT scores in a healthy Japanese population.

Urinary markers of nucleic acid oxidation increase with age, obesity and insulin resistance in Danish children and adolescents

PURPOSE

Oxidative stress may play an important role in childhood obesity and increased cardiometabolic risk. 8-oxo-7,8-dihydroguanosine (8-oxoGuo) from oxidation of RNA and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) from oxidation of DNA are excreted into urine and function as biomarkers for oxidative stress reflecting the modification rate of nucleic acids by oxidation. This study investigates the associations between urinary markers of nucleic acid oxidation and Body Mass Index (BMI), age, sex and cardiometabolic risk factors in children and adolescents with and without obesity.

METHODS

We studied 543 children and adolescents from an obesity clinic cohort (n = 418) and a population-based cohort (n = 125), all aged 6-18 years. Anthropometrics, urine and blood samples were collected. A validated liquid chromatography-tandem mass spectrometry method was used to measure the nucleic acid oxidation markers.

RESULTS

Compared with the population-based cohort, children and adolescents in the obesity clinic cohort had higher calculated 24-h excretion of 8-oxoGuo (p = 0.045) and 8-oxodG (p = 0.014) adjusted for basal metabolic rate. Both oxidation markers were positively associated with age and female sex (all p < 0.002). In the obesity clinic cohort the RNA oxidation marker 8-oxoGuo correlated with serum insulin (rho = 0.18, p = <.001) and insulin resistance (rho = 0.19, p = <.001).

CONCLUSIONS

Childhood obesity associate with higher urinary excretion of nucleic acid oxidation biomarkers, and increase with age throughout childhood, mirroring the obesity- and age-related increase shown in adults. Finally, children with obesity and insulin resistance had higher RNA oxidation markers than children with obesity and no insulin resistance, supporting a possible link between oxidative stress and the pathogenesis of cardiometabolic risk including type 2 diabetes.

Recent Advances: Molecular Mechanism of RNA Oxidation and Its Role in Various Diseases

Compared with the research on DNA damage, there are fewer studies on RNA damage, and the damage mechanism remains mostly unknown. Recent studies have shown that RNA is more vulnerable to damage than DNA when the cells are exposed to endogenous and exogenous insults. RNA injury may participate in a variety of disease occurrence and development. RNA not only has important catalytic functions and other housekeeping functions, it also plays a decisive role in the translation of genetic information and protein biosynthesis. Various kinds of stressors, such as ultraviolet, reactive oxygen species and nitrogen, can cause damage to RNA. It may involve in the development and progression of diseases. In this review, we focused on the relationship between the RNA damage and disease as well as the research progress on the mechanism of RNA damage, which is of great significance for the pathogenesis, diagnosis, and treatment of related diseases.

Oxidatively generated modifications to nucleic acids in vivo: Measurement in urine and plasma

BACKGROUND

The oxidized guanine nucleosides, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo), derived from DNA and RNA, respectively, were used to investigate the importance of oxidative stress to nucleic acids in vivo. High urinary excretion of 8-oxodG is associated with cancer development, whereas high urinary excretion of 8-oxoGuo is associated with mortality in type 2 diabetes. Like creatinine, these small water-soluble molecules are not reabsorbed in the kidney. Therefore, 8-oxo nucleoside/creatinine reciprocal concentration ratios are identical in plasma and urine. The total amount of 8-oxo guanine nucleosides excreted by the kidneys is the product of plasma concentration and glomerular filtration rate.

METHODS

With relevant equations and an estimated glomerular filtration rate, the 24-h urinary excretion of 8-oxodG and 8-oxoGuo was calculated in 2679 subjects with type 2 diabetes, displaying good correlation with the measured urinary 8-oxo nucleoside/creatinine ratio: DNA oxidation r = 0.86 and RNA oxidation r = 0.84 (p < 0.05 for both).

RESULTS

Survival analyses based on the quartiles of the 8-oxodG/creatinine ratio and the quartiles of calculated 24-h urinary excretion rate of the 2679 subjects gave similar hazard ratio estimates for death due to all causes. This finding was similar for the 8-oxoGuo hazard ratio estimates.

CONCLUSIONS

This study shows that oxidatively generated modifications to DNA and RNA in vivo can be measured using 1) a spot urine sample, normalized to urinary creatinine, 2) 24-h urine, or 3) a single plasma sample based on concentrations of 8-oxo nucleoside and creatinine and glomerular filtration rate.

Elevated levels of 8-oxoGuo and 8-oxodG in individuals with severe mental illness - An autopsy-based study

Elevated systemic oxidative stress levels of 8-oxoGuo and 8-oxodG have been reported in individuals with severe mental illness (SMI). As no previous studies have addressed the link between local levels of 8-oxoGuo and 8-oxodG in the central nervous system (CNS), measured in cerebrospinal fluid (CSF), and urinary systemic levels, we employed autopsy-based material to elucidate this aspect. Additionally, we investigated the impact of 8-oxoGuo and 8-oxodG levels on the prevalence of somatic co-morbidities. Based on post mortem samples from deceased individuals with SMI (N = 107), we found significantly elevated urinary levels of both 8-oxoGuo and 8-oxodG compared to mentally healthy living controls. While we found an association between urinary and CSF 8-oxodG levels (r = 0.50, P < 0.001), a similar correlation was not evident for 8-oxoGuo (r = 0.15, P = 0.16). Additionally, the two r-values were significantly different (P < 0.001). Neither marker in urine or CSF was associated with obesity-related variables, metabolic syndrome or type 2 diabetes. The post mortem interval did not affect the results, but the agonal phase seemingly introduced bias. This study provided novel insights into the cellular oxidative stress levels in individuals with SMI. We demonstrated that increased oxidative stress locally and systemically is correlated and is a clear phenomenon in SMI. Although post mortem measurements contain some weaknesses, our study indicates DNA as the main site of oxidative stress modifications in the CNS in SMI. This may provide novel opportunities for treatment modalities. Additionally, our study demonstrated the applicability of post mortem material investigating systemic and local 8-oxoGuo and 8-oxodG levels.

DNA damage in obesity: Initiator, promoter and predictor of cancer

Epidemiological evidence linking obesity with increased risk of cancer is steadily growing, although the causative aspects underpinning this association are only partially understood. Obesity leads to a physiological imbalance in the regulation of adipose tissue and its normal functioning, resulting in hyperglycaemia, dyslipidaemia and inflammation. These states promote the generation of oxidative stress, which is exacerbated in obesity by a decline in anti-oxidant defence systems. Oxidative stress can have a marked impact on DNA, producing mutagenic lesions that could prove carcinogenic. Here we review the current evidence for genomic instability, sustained DNA damage and accelerated genome ageing in obesity. We explore the notion of genotoxicity, ensuing from systemic oxidative stress, as a key oncogenic factor in obesity. Finally, we advocate for early, pre-malignant assessment of genome integrity and stability to inform surveillance strategies and interventions.

Impact of obesity and overweight on DNA stability: Few facts and many hypotheses

Health authorities are alarmed worldwide about the increase of obesity and overweight in the last decades which lead to adverse health effects including inflammation, cancer, accelerated aging and infertility. We evaluated the state of knowledge concerning the impact of elevated body mass on genomic instability. Results of investigations with humans (39 studies) in which DNA damage was monitored in lymphocytes and sperm cells, are conflicting and probably as a consequence of heterogeneous study designs and confounding factors (e.g. uncontrolled intake of vitamins and minerals and consumption of different food types). Results of animal studies with defined diets (23 studies) are more consistent and show that excess body fat causes DNA damage in multiple organs including brain, liver, colon and testes. Different molecular mechanisms may cause genetic instability in overweight/obese individuals. ROS formation and lipid peroxidation were found in several investigations and may be caused by increased insulin, fatty acid and glucose levels or indirectly via inflammation. Also reduced DNA repair and formation of advanced glycation end products may play a role but more data are required to draw firm conclusions. Reduction of telomere lengths and hormonal imbalances are characteristic for overweight/obesity but the former effects are delayed and moderate and hormonal effects were not investigated in regard to genomic instability in obese individuals. Increased BMI values affect also the activities of drug metabolizing enzymes which activate/detoxify genotoxic carcinogens, but no studies concerning the impact of these alterations of DNA damage in obese individuals are available. Overall, the knowledge concerning the impact of increased body weight and DNA damage is poor and further research is warranted to shed light on this important issue.

Cardiovascular and All-Cause Mortality Risk Associated With Urinary Excretion of 8-oxoGuo, a Biomarker for RNA Oxidation, in Patients With Type 2 Diabetes: A Prospective Cohort Study

OBJECTIVE

Cardiovascular mortality risk remains high among patients with type 2 diabetes. Oxidative stress indicated by high urinary excretion of the biomarker for RNA oxidation, 8-oxo-7,8-dihydroguanosine (8-oxoGuo), is associated with an increased risk of death in newly diagnosed and treated patients. We assessed whether 8-oxoGuo is associated with specific cardiovascular and all-cause mortality risk.

RESEARCH DESIGN AND METHODS

Urinary biomarkers for nucleic acid oxidation were measured in a cohort of patients with type 2 diabetes aged ≥60 years (n = 1,863), along with biochemical measurements, questionnaire findings, and Central Person Registry information to estimate the hazard ratios (HRs) for log2-transformed RNA oxidation using Cox regression.

RESULTS

During the 5-year follow-up, 173 of 1,863 patients had died (9.3%), including 73 patients who died of cardiovascular disease (42.2%). Doubling of RNA oxidation was associated with an HR of all-cause mortality of 2.10 (95% CI 1.63-2.71; P < 0.001) and an HR of cardiovascular death of 1.82 (95% CI 1.20-2.77; P = 0.005) after multiple adjustments. The 5-year absolute risks (ARs) of all-cause mortality (AR 13.9 [95% CI 10.8-17.0] vs. AR 6.10 [95% CI 4.00-8.30]) and cardiovascular mortality (AR 5.49 [95% CI 3.44-7.55] vs. AR 3.16 [95% CI 1.59-4.73]) were approximately two times higher in the highest quartile of RNA oxidation than in the lowest quartile.

CONCLUSIONS

We conclude that high RNA oxidation is associated with all-cause and cardiovascular mortality risk in patients with type 2 diabetes. Targeting oxidative stress via interventions with long-term follow-up may reveal the predictive potential of the biomarker 8-oxoGuo.

The effect of smoking on the urinary excretion of 8-oxodG and 8-oxoGuo in patients with type 2 diabetes

Over the past decades, attention has been paid to understanding the impact of oxidative stress and related modifications of DNA and RNA on various human health risks. A recent meta-analysis comprising 1915 smokers and 3462 non-smokers found a significantly higher level of DNA oxidation measured as urinary 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) excretion in smokers compared with non-smokers in a healthy population. We aimed to investigate if an increased urinary excretion of 8-oxodG in smokers versus never smokers and former smokers could be verified in a population with type 2 diabetes. Additionally, we measured RNA oxidation levels through urinary excretion of 8-oxo-7, 8-dihydroguanosine (8-oxoGuo). Our study included urinary samples from 2721 type 2 diabetic patients, analyzed using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Logistic regression was used to examine the relationship between daily smokers (n = 462) versus former (n = 1341) and never smokers (n = 918) regarding the RNA and DNA oxidation, respectively. We did not find any significant effect of smoking on urinary excretion of 8-oxodG or 8-oxoGuo in our study. Due to a sparse study area, it is still too early to draw any conclusions on smoking and RNA-oxidation. Regarding DNA oxidation, our study suggests that the effect of smoking seen in healthy populations might be attenuated in patients with type 2 diabetes.