Tobacco smoke is a source of toxic reactive glycation products

AGEs and chronic subclinical inflammation in diabetes: disorders of immune system

Chronic subclinical inflammation represents a risk factor of type 2 diabetes and several diabetes complications, including neuropathy and atherosclerosis including macro-vasculopathy and micro-vasculopathy. However, the inflammatory response in the diabetic wound was shown to be remarkably hypocellular, unregulated and ineffective. Advanced glycation end products (AGEs) and one of its receptors, RAGE, were involved in inducing chronic immune imbalance in diabetic patients. Such interactions attracts immune cell into diffused glycated tissue and activates these cells to induce inflammatory damage, but disturbs the normal immune rhythm in diabetic wound. Traditional measurements of AGEs are high-performance liquid chromatography and immunohistochemistry staining, but their application faces the limitations including complexity, cost and lack of reproducibility. A new noninvasive method emerged in 2004, using skin autofluorescence as indicator for AGEs accumulation. It had been reported to be informative in evaluating the chronic risk of diabetic patients. Studies have indicated therapeutic potentials of anti-AGE recipes. These recipes can reduce AGE absorption/de novo formation, block AGE-RAGE interaction and arrest downstream signaling after RAGE activation.

Skin mirrors human aging

Abstract Aged skin exhibits disturbed lipid barrier, angiogenesis, production of sweat, immune functions, and calcitriol synthesis as well as the tendency towards development of certain benign or malignant diseases. These complex biological processes comprise endogenous and exogenous factors. Ethnicity also markedly influences the phenotype of skin aging. The theories of cellular senescence, telomere shortening and decreased proliferative capacity, mitochondrial DNA single mutations, the inflammation theory, and the free radical theory try to explain the biological background of the global aging process, which is mirrored in the skin. The development of advanced glycation end-products and the declining hormonal levels are major factors influencing intrinsic aging. Chronic photodamage of the skin is the prime factor leading to extrinsic skin aging. The deterioration of important skin functions, due to intrinsic and extrinsic aging, leads to clinical manifestations, which mirror several internal age-associated diseases such as diabetes, arterial hypertension and malignancies.

25-hydroxyvitamin d and advanced glycation endproducts in healthy and hypertensive subjects: are there interactions?

Advanced glycation endproducts (AGEs) accumulate during aging. Skin is the single organ of vitamin D synthesis, induced by ultraviolet B light. Accumulation of AGEs in the skin could interfere with synthesis of the vitamin, whereas the microinflammation and oxidative stress (associated with hypovitaminosis D) could amplify both the toxic effects of AGEs and their production. Clinical data on potential interactions between vitamin D3 deficiency and AGE accumulation are sparse. Here we investigated potential associations between levels of circulating vitamin D3 and those of AGEs in blood and skin with regard to markers of inflammation and oxidative stress in nondiabetic subjects. In a cross-sectional study, 146 subjects (119 healthy persons and 27 hypertensive patients; 73 male and 73 female; mean age, 57.0 ± 15.5 years) were included. Skin autofluorescence (SAF) and plasma levels of vitamin D3, AGE-associated fluorescence, high-sensitivity C-reactive protein level, and advanced oxidation protein products as well as renal function (estimated glomerular filtration rate) were determined. In a subgroup of 61 patients, N(ε)-carboxymethyllysine, soluble receptor of AGEs, and soluble vascular adhesion protein-1 were additionally analyzed. Vitamin D3 level averaged 22.5 ± 8.9 ng/mL. Prevalence of vitamin D insufficiency (20-29 ng/mL) was 43%, and that of deficiency (<20 ng/mL) 37%. The age-dependent rise in SAF was steeper in smokers and in subjects presenting arterial hypertension. No association between SAF and hypovitaminosis D was revealed. Among smokers, an inverse relationship manifested between vitamin D3 and plasma AGE-associated fluorescence as well as soluble vascular adhesion protein-1. Our data suggest that in nondiabetic adults, hypovitaminosis D does not enhance toxicity and accumulation of AGEs. Only in smokers interactions are conceivable.

Glycated Serum Albumin and AGE Receptors

In vivo modification of proteins by molecules with reactive carbonyl groups leads to intermediate and advanced glycation end products (AGE). Glucose is a significant glycation reagent due to its high physiological concentration and poorly controlled diabetics show increased albumin glycation. Increased levels of glycated and AGE-modified albumin have been linked to diabetic complications, neurodegeneration, and vascular disease. This review discusses glycated albumin formation, structural consequences of albumin glycation on drug binding, removal of circulating AGE by several scavenger receptors, as well as AGE-induced proinflammatory signaling through activation of the receptor for AGE. Analytical methods for quantitative detection of protein glycation and AGE formation are compared. Finally, the use of glycated albumin as a novel clinical marker to monitor glycemic control is discussed and compared to glycated hemoglobin (HbA1c) as long-term indicator of glycemic status.

Vascular Effects of Dietary Advanced Glycation End Products

Evidence has accumulated lately demonstrating that advanced glycation end products (AGEs) play an important role in the development of diabetic and cardiovascular complications as well as the development of other chronic diseases. AGEs originating from diet have a significant contribution to the AGEs body pool and therefore dietary interventions aiming at reducing AGEs load are believed to exert health promoting effects. This review summarizes the evidence from clinical studies regarding effects of dietary AGEs on the vascular system, highlighting also the different aspects of vascular tests. It also advocates an extension of dietary recommendations towards the promotion of cooking methods that reduce dietary AGEs in consumed foods.

Current perspectives on the health risks associated with the consumption of advanced glycation end products: recommendations for dietary management

Advanced glycation end products (AGEs) constitute a complex group of compounds produced endogenously during the aging process and under conditions of hyperglycemia and oxidative stress. AGEs also have an emerging exogenous origin. Cigarette smoke and diet are the two main exogenous sources of AGEs (glycotoxins). Modern Western diets are rich in AGEs which have been implicated in the pathogenesis of several metabolic and degenerative disorders. Accumulating evidence underlies the beneficial effect of the dietary restriction of AGEs not only in animal studies but also in patients with diabetic complications and metabolic diseases. This article reviews the evidence linking dietary glycotoxins to several disorders from diabetic complications and renal failure to liver dysfunction, female reproduction, eye and cognitive disorders as well as cancer. Furthermore, strategies for AGE reduction are discussed with a focus on dietary modification.

Antiglycation Activity of Iridoids and Their Food Sources

Iridoids are dietary phytochemicals that may have the ability to inhibit the formation of advanced glycation end products (AGEs). Three studies were conducted to investigate this anti-AGE potential. First, the inhibition of fluorescence intensity by food-derived iridoids, after 4 days of incubation with bovine serum albumin, glucose, and fructose, was used to evaluate in vitro antiglycation activity. Next, an 8-week open-label pilot study used the AGE Reader to measure changes in the skin autofluorescence of 34 overweight adults who consumed daily a beverage containing food sources of iridoids. Finally, a cross-sectional population study with 3913 people analyzed the relationship between daily iridoid intake and AGE accumulation, as measured by skin autofluorescence with the TruAge scanner. In the in vitro test, deacetylasperulosidic acid and loganic acid both inhibited glycation in a concentration-dependent manner, with respective IC₅₀ values of 3.55 and 2.69 mM. In the pilot study, average skin autofluorescence measurements decreased by 0.12 units (P < 0.05). The cross-sectional population survey revealed that, for every mg of iridoids consumed, there is a corresponding decline in AGE associated age of 0.017 years (P < 0.0001). These results suggest that consumption of dietary sources of iridoids may be a useful antiaging strategy.

The axis AGE-RAGE-soluble RAGE and oxidative stress in chronic kidney disease

Chronic kidney disease (CKD) has been shown to be associated with high oxidative stress and cardiovascular disease. In this chapter our focus will be on the role of advanced glycation end products (AGE) and their receptor, RAGE in CKD progression and their role on cardiovascular complications. We provide a succinct, yet comprehensive summary of the current knowledge, the challenges and the future therapeutic avenues that are stemming out from novel recent findings. We first briefly review glycation and AGE formation and the role of the kidney in their metabolism. Next, we focus on the RAGE, its signaling and role in oxidative stress. We address the possible role of soluble RAGEs as decoys and the controversy regarding this issue. We then provide the latest information on the specific role of both AGE and RAGE in inflammation and perpetuation of kidney damage in diabetes and in CKD without diabetes, which is the main purpose of the review. Finally, we offer an update on new avenues to target the AGE-RAGE axis in CKD.

Reprint of "accumulation of modified proteins and aggregate formation in aging"

Increasing cellular damage during the aging process is considered to be one factor limiting the lifespan of organisms. Besides the DNA and lipids, proteins are frequent targets of non-enzymatic modifications by reactive substances including oxidants and glycating agents. Non-enzymatic protein modifications may alter the protein structure often leading to impaired functionality. Although proteolytic systems ensure the removal of modified proteins, the activity of these proteases was shown to decline during the aging process. The additional age-related increase of reactive compounds as a result of impaired antioxidant systems leads to the accumulation of damaged proteins and the formation of protein aggregates. Both, non-enzymatic modified proteins and protein aggregates impair cellular functions and tissue properties by a variety of mechanisms. This is increasingly important in aging and age-related diseases. In this review, we will give an overview on oxidation and glycation of proteins and the function of modified proteins in aggregate formation. Furthermore, their effects as well as their role in aging and age-related diseases will be highlighted.

Advanced glycation end products: role in pathology of diabetic cardiomyopathy

Increasing evidence demonstrates that advanced glycation end products (AGEs) play a pivotal role in the development and progression of diabetic heart failure, although there are numerous other factors that mediate the disease response. AGEs are generated intra- and extracellularly as a result of chronic hyperglycemia. Then, following the interaction with receptors for advanced glycation end products (RAGEs), a series of events leading to vascular and myocardial damage are elicited and sustained, which include oxidative stress, increased inflammation, and enhanced extracellular matrix accumulation resulting in diastolic and systolic dysfunction. Whereas targeting glycemic control and treating additional risk factors, such as obesity, dyslipidemia, and hypertension, are mandatory to reduce chronic complications and prolong life expectancy in diabetic patients, drug therapy tailored to reducing the deleterious effects of the AGE-RAGE interactions is being actively investigated and showing signs of promise in treating diabetic cardiomyopathy and associated heart failure. This review shall discuss the formation of AGEs in diabetic heart tissue, potential targets of glycation in the myocardium, and underlying mechanisms that lead to diabetic cardiomyopathy and heart failure along with the use of AGE inhibitors and breakers in mitigating myocardial injury.

Acrolein-exposed normal human lung fibroblasts in vitro: cellular senescence, enhanced telomere erosion, and degradation of Werner's syndrome protein

BACKGROUND

Acrolein is a ubiquitous environmental hazard to human health. Acrolein has been reported to activate the DNA damage response and induce apoptosis. However, little is known about the effects of acrolein on cellular senescence.

OBJECTIVES

We examined whether acrolein induces cellular senescence in cultured normal human lung fibroblasts (NHLF).

METHODS

We cultured NHLF in the presence or absence of acrolein and determined the effects of acrolein on cell proliferative capacity, senescence-associated β-galactosidase activity, the known senescence-inducing pathways (e.g., p53, p21), and telomere length.

RESULTS

We found that acrolein induced cellular senescence by increasing both p53 and p21. The knockdown of p53 mediated by small interfering RNA (siRNA) attenuated acrolein-induced cellular senescence. Acrolein decreased Werner's syndrome protein (WRN), a member of the RecQ helicase family involved in DNA repair and telomere maintenance. Acrolein-induced down-regulation of WRN protein was rescued by p53 knockdown or proteasome inhibition. Finally, we found that acrolein accelerated p53-mediated telomere shortening.

CONCLUSIONS

These results suggest that acrolein induces p53-mediated cellular senescence accompanied by enhanced telomere attrition and WRN protein down-regulation.

Advanced glycation end products in the skin are enhanced in COPD

BACKGROUND

Cigarette smoking is the main cause of chronic obstructive pulmonary disease (COPD) inducing oxidative stress and local tissue injury, resulting in pulmonary inflammation. Advanced glycation end products (AGEs) are produced by glycation and oxidation processes and their formation is accelerated in inflammatory conditions. In this study we assessed whether AGE accumulation in the skin is elevated in COPD and associates with disease severity.

METHODS

202 mild-to-very-severe COPD patients and 83 old (40-75 years) and 110 young (18-40 years) healthy smokers and never-smokers were included. AGEs were measured by skin autofluorescence (SAF). Demographic variables, smoking habits, co-morbidities and lung function values were obtained.

RESULTS

COPD patients (FEV₁=55% predicted) had significantly higher SAF values than old and young healthy controls: 2.5 vs. 1.8 and 1.2 (arbitrary units, p<0.05). No differences in SAF values were found between GOLD stages I-IV (2.4, 2.3, 2.5, 2.5 respectively). Lower function (FEV₁/FVC, MEF₅₀/FVC, RV/TLC) and higher number of packyears were significantly associated with SAF (p<0.05).

CONCLUSIONS

SAF is increased in mild-to-very severe COPD patients compared with healthy controls. Interestingly, SAF was not associated with disease severity as values were comparable between different GOLD stages (stage I-IV) of COPD. This may suggest that AGEs play a role in the induction phase of COPD in susceptible smokers. Future studies should further investigate the mechanisms underlying AGEs formation and accumulation in COPD.

Normoglycemic diabetic nephropathy: the role of insulin resistance

The pathophysiology of diabetic nephropathy (DN) is complex and incompletely understood. Whereas hyperglycemia is clearly important, the role of insulin resistance (IR) is increasingly recognized. We present the case of a normotensive non-smoking obese woman with nephrotic syndrome who was found to have DN by biopsy. All measures of glucose metabolism, including fasting glucose, glycosylated hemoglobin, and oral glucose tolerance testing, were repeatedly normal with little exception. IR was documented, however, based on the presence of the metabolic syndrome and an elevated homeostasis model assessment of IR. We posit that this IR is central to the pathogenesis of our patient's lesion, and this may explain other cases of DN with normoglycemia. The literature supporting this concept is discussed.

Lifestyle and Advanced Glycation End Products (AGEs) Burden: Its Relevance to Healthy Aging

Uncontrolled continued exposure to oxidative stress is a precursor to many chronic diseases including cancer, diabetes, degenerative disorders and cardiovascular diseases. Of the many known mediators of oxidative stress, reactive oxygen species (ROS) and advanced glycation end products (AGEs) are the most studied. In the present review, we have summarized current data on the origin of circulating AGEs, discussed issues associated with reliable assessment of its steady state level, and changes in its level with age and select metabolic diseases. Lastly, we have made recommendations about life style changes that may decrease AGEs burden to promote healthy aging.

Accumulation of modified proteins and aggregate formation in aging

Increasing cellular damage during the aging process is considered to be one factor limiting the lifespan of organisms. Besides the DNA and lipids, proteins are frequent targets of non-enzymatic modifications by reactive substances including oxidants and glycating agents. Non-enzymatic protein modifications may alter the protein structure often leading to impaired functionality. Although proteolytic systems ensure the removal of modified proteins, the activity of these proteases was shown to decline during the aging process. The additional age-related increase of reactive compounds as a result of impaired antioxidant systems leads to the accumulation of damaged proteins and the formation of protein aggregates. Both, non-enzymatic modified proteins and protein aggregates impair cellular functions and tissue properties by a variety of mechanisms. This is increasingly important in aging and age-related diseases. In this review, we will give an overview on oxidation and glycation of proteins and the function of modified proteins in aggregate formation. Furthermore, their effects as well as their role in aging and age-related diseases will be highlighted.

Reference values of skin autofluorescence as an estimation of tissue accumulation of advanced glycation end products in a general Slovak population

AIMS

For decades, Slovakia has maintained a prominent place in mortality rates from cardiovascular diseases among European Union (EU-27) countries. Determination of skin autofluorescence serves as an estimate of tissue accumulation of advanced glycation end products--substances accumulating in tissues and body fluids that play a pathophysiological role in age-related diseases and their complications, such as diabetes.

METHODS

In 1385 apparently healthy Slovakian subjects aged from a few days old to 77 years, skin autofluorescence was determined using an advanced glycation end product reader and compared with reference data from Dutch Caucasians. The impact of the weekly frequency of recreational physical exercise on skin autofluorescence was investigated in the adults, and the impact of feeding regimen in the infants.

RESULTS

With the exception of 10- to 19-year-olds, Slovaks had lower skin autofluorescence values in comparison with the Dutch Caucasians. In healthy non-smokers, physical exercise for > 30 min/day performed ≥ 3 times/week was associated with lower skin autofluorescence levels. In infants, breastfeeding (advanced glycation end product-poor diet) was associated with lower skin autofluorescence levels in comparison with consumption of infant formulas (advanced glycation end product-rich diet).

CONCLUSIONS

Reference ranges of skin autofluorescence in Slovak Caucasians, detailed for paediatric age groups, are provided. Our data show that, in healthy adults, regular physical exercise associates with lower skin autofluorescence. Infants fed or weaned from infant formulas (advanced glycation end product-rich diet) have higher skin autofluorescence than their breast milk-consuming counterparts. It is unclear why Slovaks have lower skin autofluorescence compared with a Dutch population with lower cardiovascular mortality rates. Reference data on skin autofluorescence from diverse populations are needed for the precise clinical interpretation of skin autofluorescence measurements.

Diabetes, aging, and their tissue complications

The inactivation of NO by advanced glycation endproducts (AGEs), which accumulate on tissue proteins as a function of age and hyperglycemia, focused attention on the role of these ubiquitous posttranslational modifications in acquired impairments of vascular reactivity and other signaling processes. This observation occurred during a watershed period of basic and translational research in glycation that encompassed new pathologic phenomena and novel intervention strategies. How has the AGE paradigm for the tissue complications of aging and diabetes fared since the identification of the link between these glycation products and NO inactivation, and what lessons may be offered for future investigations?

Impact of smoking on microalbuminuria and urinary albumin creatinine ratio in non-diabetic normotensive smokers

Smoking is associated with an excessive morbidity and mortality from a variety of diseases. The aim of this study was to find out the effects of smoking on renal function study in non-diabetic, normotensive subjects. A community-based, prospective, cross-sectional cohort study was conducted on 120 subjects; 80 (66.66%) were smokers and 40 (33.33%) age matched non-smokers; with age range of 30 to 70 years. Measurement of fasting sugar, urea, creatinine, lipids and one time screening of urinary albumin and urinary creatinine was done. Smokers had significantly higher urinary albumin and albumin creatinine ratio (ACR) (52.84 ± 46.42 mg/L, 93.98 ± 78.68 μg/mg) than non-smokers (19.25 ± 7.77 mg/L, 18.99 ± 6.65 μg/mg), respectively (P =< 0.001, P =< 0.001). Microalbuminuria and urinary ACR level were directly related to the amount of smoking (pack-years). Among smokers, 73 (91.25%) had microalbuminuria (>20 mg/L) and 64 (80%) had increased urinary ACR (>30 μg/mg). Smoker had significantly lower high-density lipoprotein level (36.66 ± 10.28 mg/dl) compared to non-smokers (41.22 ± 11.72 mg/dl) (P = 0.031). Urea, creatinine, creatinine clearance, total cholesterol, low density lipoprotein, triglyceride levels were comparable (p = NS). In conclusion, smokers have a 4-fold higher prevalence of microalbuminuria than non-smokers.

Dicarbonyl stress and glyoxalases in ovarian function

The ovary is the main regulator of female fertility. Changes in maternal health and physiology can disrupt intraovarian homoeostasis thereby compromising oocyte competence and fertility. Research has only recently devoted attention to the involvement of dicarbonyl stress in ovarian function. On this basis, the present review focuses on clinical and experimental research supporting the role of dicarbonyl overload and AGEs (advanced glycation end-products) as key contributors to perturbations of the ovarian microenvironment leading to lower fertility. Particular emphasis has been given to oocyte susceptibility to methylglyoxal, a powerful glycating agent, whose levels are known to increase during aging and metabolic disorders. According to the literature, the ovary and the oocyte itself can rely on the glyoxalase system to counteract the possible dicarbonyl overload such as that which may occur in reproductive-age women and patients with PCOS (polycystic ovarian syndrome) or diabetes. Overall, although biochemical methods for proper evaluation of dicarbonyl stress in oocytes and the ovarian microenvironment need to be established, AGEs can be proposed as predictive markers and/or therapeutic targets in new strategies for improving reproductive counselling and infertility therapies.

Association of polymorphisms of the receptor for advanced glycation end products gene with COPD in the Chinese population

The receptor for advanced glycation end products (RAGE) is a cell surface molecule of the immunoglobulin superfamily that binds diverse endogenous ligands involved in the development of chronic diseases and inflammatory damage. A growing body of evidence has suggested that RAGE is involved in the development and progression of chronic obstructive pulmonary disease (COPD). The present study investigated the existence of an association among three polymorphisms (-374T/A, -429T/C, and G82S) of the RAGE gene with the risk of COPD in the Chinese population. The RAGE genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism in 216 patients with COPD and 239 age-matched healthy individuals. Our study demonstrated that the frequencies of the GS genotype and the S allele in the G82S mutation were significantly higher in COPD patients than in controls (odds ratios [OR]=1.70, 95% confidence interval [CI]: 1.15-2.50, p=0.0098 and OR=1.42, 95% CI: 1.06-1.91, p=0.023, respectively). Further stratification analysis by smoking status revealed that the presence of the GS genotype conferred a higher risk of developing COPD in current smokers (p=0.044). In contrast, mutations at -374T/A and -429T/C did not demonstrate any association with COPD, even after taking into account the patients' smoking history. Our study provides preliminary evidence that the G82S polymorphism in the RAGE gene is associated with an increased risk of COPD and that the GS genotype of the G82S variant is a risk factor for COPD in the Chinese population.

Role of advanced glycation end products in cellular signaling

Improvements in health care and lifestyle have led to an elevated lifespan and increased focus on age-associated diseases, such as neurodegeneration, cardiovascular disease, frailty and arteriosclerosis. In all these chronic diseases protein, lipid or nucleic acid modifications are involved, including cross-linked and non-degradable aggregates, such as advanced glycation end products (AGEs). Formation of endogenous or uptake of dietary AGEs can lead to further protein modifications and activation of several inflammatory signaling pathways. This review will give an overview of the most prominent AGE-mediated signaling cascades, AGE receptor interactions, prevention of AGE formation and the impact of AGEs during pathophysiological processes.

Advanced glycation end products (AGE) and diabetes: cause, effect, or both?

Despite new and effective drug therapies, insulin resistance (IR), type 2 diabetes mellitus (T2D) and its complications remain major medical challenges. It is accepted that IR, often associated with over-nutrition and obesity, results from chronically elevated oxidant stress (OS) and chronic inflammation. Less acknowledged is that a major cause for this inflammation is excessive consumption of advanced glycation end products (AGEs) with the standard western diet. AGEs, which were largely thought as oxidative derivatives resulting from diabetic hyperglycemia, are increasingly seen as a potential risk for islet β-cell injury, peripheral IR and diabetes. Here we discuss the relationships between exogenous AGEs, chronic inflammation, IR, and T2D. We propose that under chronic exogenous oxidant AGE pressure the depletion of innate defense mechanisms is an important factor, which raises susceptibility to inflammation, IR, T2D and its complications. Finally we review evidence on dietary AGE restriction as a nonpharmacologic intervention, which effectively lowers AGEs, restores innate defenses and improves IR, thus, offering new perspectives on diabetes etiology and therapy.

Maternal serum AGEs levels in pregnancies associated with neural tube defects

Advanced glycation end products (AGEs) plays an important role in diabetic embryopathy. AGE-mediated DNA damage could be a significant factor in the teratogenicity. The aim of the present study was to evaluate the association between the AGEs level and neural tube defects (NTDs) occurrence risk. Forty-eight mothers with NTD-affected pregnancies and 50 normal mothers were selected in this study. Blood were collected from the mothers and were assayed for serum AGEs, malondiadehyde (MDA) and hemoglobin A1c (HbA1c). Data were analyzed by logistic regression method. The study indicated that there were significant but modest lower prevalence for cases mothers on age, BMI and glucose levels compared with controls. NTD-affected mothers were significantly more likely to have higher AGEs levels (5.6±0.48 AU vs. 4.6±0.68 AU ρ<0.01) than controls. The AGEs levels were not correlated with MDA and HbA1c in NTDs mothers (r(2)=0.0006 p=0.8691 and r(2)=0.001 p=0.8172, respectively). The conclusion is that AGEs might be associated with NTDs occurrence.

Vascular effects of advanced glycation endproducts: Clinical effects and molecular mechanisms

The enhanced generation and accumulation of advanced glycation endproducts (AGEs) have been linked to increased risk for macrovascular and microvascular complications associated with diabetes mellitus. AGEs result from the nonenzymatic reaction of reducing sugars with proteins, lipids, and nucleic acids, potentially altering their function by disrupting molecular conformation, promoting cross-linking, altering enzyme activity, reducing their clearance, and impairing receptor recognition. AGEs may also activate specific receptors, like the receptor for AGEs (RAGE), which is present on the surface of all cells relevant to atherosclerotic processes, triggering oxidative stress, inflammation and apoptosis. Understanding the pathogenic mechanisms of AGEs is paramount to develop strategies against diabetic and cardiovascular complications.

Ethnic and gender differences in advanced glycation end products measured by skin auto-fluorescence

Background

Advanced glycation end products (AGEs) have been shown to be a predictor of cardiovascular risk in Caucasian subjects. In this study we examine whether the existing reference values are useable for non-Caucasian ethnicities. Furthermore, we assessed whether gender and smoking affect AGEs.

Methods

AGEs were determined by a non-invasive method of skin auto-fluorescence (AF). AF was measured in 200 Arabs, 99 South Asians, 35 Filipinos and 14 subjects of other/mixed ethnicity in the Qatar Metabolomics Study on Diabetes (QMDiab). Using multivariate linear regression analysis and adjusting for age and type 2 diabetes, we assessed whether ethnicity, gender and smoking were associated with AF.

Results

The mean AF was 2.27 arbitrary units (AU) (SD: 0.63). Arabs and Filipinos had a significant higher AF than the South Asian population (0.25 arbitrary units (AU) (95% CI: 0.11‒0.39), p = 0.001 and 0.34 (95% CI: 0.13‒0.55), p = 0.001 respectively). Also, AF was significantly higher in females (0.41 AU (95% CI: 0.29‒0.53), p < 0.001). AF associated with smoking (0.21 AU (95% CI: 0.01‒0.41), p = 0.04) and increased with the number of pack-years smoked (p = 0.02).

Conclusions

This study suggests that the existing reference values should take ethnicity, gender and smoking into account. Larger studies in specific ethnicities are necessary to create ethnic- and gender-specific reference values.

Advanced glycation end products and their relevance in female reproduction

STUDY QUESTION

Do advanced glycation end products (AGEs) and their receptors play a role in female reproduction?

SUMMARY ANSWER

AGEs might contribute to the etiology of polycystic ovary syndrome (PCOS) and infertility.

WHAT IS KNOWN ALREADY

The endogenous AGEs are produced in the body by chemical reactions. Exogenous sources of AGEs are diet and smoking. AGEs have been proposed to be among the main intermediaries involved in several diseases, such as metabolic syndrome, type 2 diabetes mellitus, cardiovascular disease, ovarian aging, inflammation, neurodegenerative disorders and PCOS.

STUDY DESIGN, SIZE, DURATION

A systematic review was performed for all available basic science and clinical peer-reviewed articles published in PubMed from 1987 to date. Abstracts of annual meetings of the Endocrine Society and American Society for Reproductive Medicine were also reviewed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 275 publications and scientific abstracts were identified from the initial search. Sixty-two papers and four published scientific abstracts were selected for full review. The main outcomes were the regulatory effects of AGEs on: (i) granulosa cells, adipocyte physiology, obesity and insulin resistance in women with PCOS and in polycystic ovary animal models and (ii) infertility and measures of ovarian reserve.

MAIN RESULTS AND THE ROLE OF CHANCE

There is an intricate relationship between the AGE-RAGE (receptor for AGEs) system and some aspects of PCOS, such as granulosa cell dysfunction, adipocyte pathophysiology, obesity and insulin resistance. Additionally, irregular ovarian AGE signaling might in part explain the abnormal ovarian histology observed in women with PCOS. The ovarian dysfunction due to AGEs in women without PCOS suggests a role for the AGE-RAGE system in the ovarian follicular environment, and might relate to assisted reproduction technology outcome and measures of ovarian reserve.

LIMITATIONS, REASONS FOR CAUTION

The body of literature currently available limits these findings. The results obtained from granulosa cell lines and animal models may not fully extrapolate to humans.

WIDER IMPLICATIONS OF THE FINDINGS

This review underscores a critical need to unveil the exact mechanistic actions of AGEs in reproductive physiology and more specifically the hypothalamic-pituitary-ovarian axis. AGE inhibitors might present an emerging therapeutic approach with significant applications in the context of PCOS and infertility.

STUDY FUNDING/COMPETING INTEREST(S)

American Society for Reproductive Medicine New Investigator Award and University of Vermont College of Medicine Internal Funds. No competing interests.

Influence of smoking and diet on glycated haemoglobin and 'pre-diabetes' categorisation: a cross-sectional analysis

BACKGROUND

The new HbA1c criteria for diagnosis of pre-diabetes have been criticised for misdiagnosis. It is possible that some elevation of HbA1c is not driven by hyperglycaemia. This study assesses associations of HbA1c, commonly assumed to relate solely to glucose concentration, with (i) smoking, a major source of reactive oxygen species (ROS) and (ii) fruit & vegetables consumption associated with improved redox status.

METHODS

One-way ANOVA, Chi-squared and multivariate linear regressions, adjusted for all known confounders were used to explore associations of HbA1c with self-reported smoking status and fruit & vegetables consumptions in the Scottish Health Surveys 2003-2010, among individuals without known diabetes and HbA1c < 6.5%.

RESULTS

Compared to non-smokers (n = 2831), smokers (n = 1457) were younger, consumed less fruit & vegetables, had lower physical activity levels, lower BMI, higher HbA1c and CRP (p < 0.05). HbA1c was higher in smokers by 0.25 SDs (0.08%), and 0.38 SDs higher (0.14%) in heavy smokers (>20 cigarettes/day) than non-smokers (p < 0.001 both). Smokers were twice as likely to have HbA1c in the 'pre-diabetic' range (5.7-6.4%) (p < 0.001, adj.model). Pre-diabetes and low grade inflammation did not affect the associations. For every extra 80 g vegetable portion consumed, HbA1c was 0.03 SDs (0.01%) lower (p = 0.02), but fruit consumption did not impact on HbA1c, within the low range of consumptions in this population.

CONCLUSION

This study adds evidence to relate smoking (an oxidative stress proxy) with protein glycation in normoglycaemic subjects, with implications for individuals exposed to ROS and for epidemiological interpretation of HbA1c.

Increased advanced glycation end-products (AGEs) assessed by skin autofluorescence in schizophrenia

BACKGROUND

Oxidative stress has been intensively studied as a key biochemical system in the pathophysiology of schizophrenia. However, little is known about the implication of oxidative stress in the development of physical illnesses in schizophrenia patients, who are characterized by high cardiovascular risk and decreased life expectancy. Advanced glycation end-products (AGEs) are considered to be markers of oxidative stress and are linked to the development of atherosclerosis.

METHODS

We investigated AGE levels determined by a noninvasive skin autofluorescence (skin AF) method (AGE-Reader™) in schizophrenia patients. Skin AF was assessed in 55 schizophrenia patients without diabetes or renal disease and 55 healthy controls matched for age, gender and smoking status. Nineteen of the 55 schizophrenia patients had a severe form of the disease (Kraepelinian schizophrenia).

RESULTS

Skin AF was significantly higher in schizophrenia patients compared to controls (2.46 ± 0.52 and 1.90 ± 0.21, respectively, p < 0.0001). Kraepelinian schizophrenia patients had significantly higher skin AF than non-Kraepelinian schizophrenia patients (p = 0.05).

CONCLUSIONS

This is the first study to demonstrate high AGE levels assessed by a noninvasive method in schizophrenia patients.

Arterial stiffness and wave reflections in relation to plasma advanced glycation end products in a Chinese population

BACKGROUND

Accumulation of advanced glycation end products (AGEs) in the human body might engender arterial stiffening. We investigated the relationship of plasma AGE concentration with arterial stiffness and wave reflections in a Chinese population.

METHODS

The study subjects were recruited from a newly established residential area in the suburb of Shanghai in 2009. Using the SphygmoCor system, we measured carotid-femoral pulse wave velocity (cfPWV) and central augmentation indices (cAI) and peripheral augmentation indices (pAI). Plasma AGE concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis.

RESULTS

The 1,051 study participants (mean age = 55.1±13.1 years) included 663 (63.1%) women, 390 (37.1%) hypertensive patients, and 90 (8.6%) diabetic or prediabetic subjects. Plasma AGE concentration was higher in men than women (5.62 vs. 5.07 μg/ml; P = 0.02) and with older age (r = 0.13 in both sexes; P ≤ 0.01) and higher serum total/high-density lipoprotein cholesterol ratio (r = 0.20 in men and r = 0.15 in women; P < 0.0001). In multiple regression analyses, plasma AGE concentration was significantly associated with cAI and pAI (1.9% and 4.0% increase per 10-time increase in plasma AGE concentration, respectively; P ≤ 0.02) but not with cfPWV (P = 0.62). However, there was significant (P = 0.001) interaction between plasma AGE concentration and age in relation to cfPWV. Only in subjects aged ≥70 years, cfPWV increased with higher levels of plasma AGE concentration (bottom vs. top quintile distributions = 8.10 vs. 8.90 m/s; P = 0.02).

CONCLUSIONS

AGEs accumulate with aging and high cholesterol and are associated with arterial wave reflections and, in an age-dependent manner, with arterial stiffness.

Advanced glycation end products and diabetic retinopathy

Studies have established hyperglycemia as the most important factor in the progress of vascular complications. Formation of advanced glycation end products (AGEs) correlates with glycemic control. The AGE hypothesis proposes that hyperglycemia contributes to the pathogenesis of diabetic complications including retinopathy. However, their role in diabetic retinopathy remains largely unknown. This review discusses the chemistry of AGEs formation and their patho-biochemistry particularly in relation to diabetic retinopathy. AGEs exert deleterious effects by acting directly to induce cross-linking of long-lived proteins to promote vascular stiffness, altering vascular structure and function and interacting with receptor for AGE, to induce intracellular signaling leading to enhanced oxidative stress and elaboration of key proinflammatory and prosclerotic cytokines. Novel anti-AGE strategies are being developed hoping that in next few years, some of these promising therapies will be successfully evaluated in clinical context aiming to reduce the major economical and medical burden caused by diabetic retinopathy.

Advanced glycation end-products, a pathophysiological pathway in the cardiorenal syndrome

The prevalence of heart failure (HF) is increasing. A distinction is made between diastolic HF (preserved left ventricular ejection fraction (LVEF)) and systolic HF (reduced LVEF). Advanced glycation end-products (AGEs) are crystallized proteins that accumulate during ageing, but are particularly increased in patients with diabetes mellitus and in patients with renal failure. Through the formation of collagen crosslinks, and by interaction with the AGE-receptor, which impairs calcium handling and increases fibrosis, AGE-accumulation has pathophysiologically been associated with the development of diastolic and renal dysfunction. Interestingly, diastolic dysfunction is a frequent finding in elderly patients, diabetic patients and in patients with renal failure. Taken together, this suggests that AGEs are related to the development and progression of diastolic HF and renal failure. In this review, the role of AGEs as a possible pathophysiological factor that link the development and progression of heart and renal failure, is discussed. Finally, the role of AGE intervention as a possible treatment in HF patients will be discussed.

Advanced glycation end products: Key players in skin aging?

Aging is the progressive accumulation of damage to an organism over time leading to disease and death. Aging research has been very intensive in the last years aiming at characterizing the pathophysiology of aging and finding possibilities to fight age-related diseases. Various theories of aging have been proposed. In the last years advanced glycation end products (AGEs) have received particular attention in this context. AGEs are formed in high amounts in diabetes but also in the physiological organism during aging. They have been etiologically implicated in numerous diabetes- and age-related diseases. Strategies inhibiting AGE accumulation and signaling seem to possess a therapeutic potential in these pathologies. However, still little is known on the precise role of AGEs during skin aging. In this review the existing literature on AGEs and skin aging will be reviewed. In addition, existing and potential anti-AGE strategies that may be beneficial on skin aging will be discussed.

The transcription levels of ABCA1, ABCG1 and SR-BI are negatively associated with plasma CRP in Chinese populations with various risk factors for atherosclerosis

ATP binding cassette transporters (ABCA1, ABCG1) and scavenger receptor class B type I (SR-BI) are the three most important cellular cholesterol transporters that may prevent atherogenesis. The aim of this study was to investigate whether they were altered in Chinese populations with various risk factors for atherosclerosis and their potential associations with C-reactive protein (CRP). Healthy female controls (n = 30) and populations with various risk factors for atherosclerosis, such as type 2 diabetes (n = 17), hypertension (n = 12), overweight/obesity (n = 10), incipient nephropathy (n = 10), postmenopausal women (n = 9), male (n = 19), ageing male (n = 22), or smoking (n = 16), were recruited. ABCA1, ABCG1 and SR-BI mRNA levels in peripheral monocytes was determined. ABCG1 was decreased in all the risk populations except ageing. ABCA1 was decreased in all the risk populations except diabetes and male. SR-BI was decreased in those with overweight/obesity and incipient nephropathy. Circulating CRP was increased almost in all the risk populations except in males. The levels of ABCA1, ABCG1 and SR-BI were reduced in those with subclinically high CRP, and negatively associated with CRP level. These data indicates that ABCA1, ABCG1, and SR-BI are reduced in various populations under subclinically inflammatory conditions, which may potentially lead to impairing reverse cholesterol transport and developing atherosclerosis.

Determinants of HbA1c in nondiabetic Dutch adults: genetic loci and clinical and lifestyle parameters, and their interactions in the Lifelines Cohort Study

OBJECTIVES

Glycated haemoglobin (HbA1c) is associated with cardiovascular disease risk in individuals without diabetes, and its use has been recommended for diagnosing diabetes. Therefore, it is important to gain further understanding of the determinants of HbA1c. The aim of this study was to investigate the effects of genetic loci and clinical and lifestyle parameters, and their interactions, on HbA1c in nondiabetic adults.

DESIGN

Population-based cohort study.

SETTING

Three northern provinces of the Netherlands.

SUBJECTS

A total of 2921 nondiabetic adults participating in the population-based LifeLines Cohort Study.

MEASUREMENTS

Body mass index (BMI), waist circumference, HbA1c, fasting plasma glucose (FPG) and erythrocyte indices were measured. Data on current smoking and alcohol consumption were collected through questionnaires. Genome-wide genotyping was performed, and 12 previously identified single-nucleotide polymorphisms (SNPs) were selected for replication and categorized as 'glycaemic' and 'nonglycaemic' SNPs according to their presumed mechanism(s) of action on HbA1c. Genetic risk scores (GRSs) were calculated as the sum of the weighted effect of HbA1c-increasing alleles.

RESULTS

Age, gender, BMI, FPG, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, current smoking and alcohol consumption were independent predictors of HbA1c, together explaining 26.2% of the variance in HbA1c, with FPG contributing 10.9%. We replicated three of the previously identified SNPs and the GRSs were also found to be independently associated with HbA1c. We found a smaller effect of the 'nonglycaemic GRS' in females compared with males and an attenuation of the effect of the GRS of all 12 SNPs with increasing BMI.

CONCLUSIONS

Our results suggest that a substantial portion of HbA1c is determined by nonglycaemic factors. This should be taken into account when considering the use of HbA1c as a diagnostic test for diabetes.

An emerging role of glucagon-like peptide-1 in preventing advanced-glycation-end-product-mediated damages in diabetes

Glucagon-like peptide-1 (GLP-1) is a gut hormone produced in the intestinal epithelial endocrine L cells by differential processing of the proglucagon gene. Released in response to the nutrient ingestion, GLP-1 plays an important role in maintaining glucose homeostasis. GLP-1 has been shown to regulate blood glucose levels by stimulating glucose-dependent insulin secretion and inhibiting glucagon secretion, gastric emptying, and food intake. These antidiabetic activities highlight GLP-1 as a potential therapeutic molecule in the clinical management of type 2 diabetes, (a disease characterized by progressive decline of beta-cell function and mass, increased insulin resistance, and final hyperglycemia). Since chronic hyperglycemia contributed to the acceleration of the formation of Advanced Glycation End-Products (AGEs, a heterogeneous group of compounds derived from the nonenzymatic reaction of reducing sugars with free amino groups of proteins implicated in vascular diabetic complications), the administration of GLP-1 might directly counteract diabetes pathophysiological processes (such as pancreatic β-cell dysfunction). This paper outlines evidence on the protective role of GLP-1 in preventing the deleterious effects mediated by AGEs in type 2 diabetes.

Oxidant stress and mitochondrial signaling regulate reversible changes of ERα expression and apoptosis in aging mouse glomeruli and mesangial cells

Estrogen actions are largely dependent on the intracellular estrogen receptor (ER) levels. During aging the decline of estrogens or ER leads to a loss in antiinflammatory protection and an increase in oxidant stress due to changes in mitochondrial function. Estrogens/ER may also coordinate signaling between the nucleus and mitochondria through ERK activation, which paradoxically decreases ER expression. The changes in ER expression and transcriptional activation that occur with aging as well as the mitochondria-to-nuclear signaling pathways have not been studied in the glomerulus. We found that ER expression and transcriptional activation decreased with age. Whereas ER levels decreased by greater than 90%, serum 17β-estradiol levels decreased by less than 30%, suggesting alternative mechanisms for ER decrease. Because we postulated that this was due in part to age-related oxidant stress, we treated mesangial cells (MCs) with ethidium bromide (EtBr) to deplete mitochondria. EtBr treatment resulted in decreased ERK activation and reactive oxygen species, which were associated with increased ERα expression and transcriptional activation in old MCs. EtBr treatment also decreased apoptosis and caspase-9 protein expression in old MCs. These data suggest that loss of several of the functions of 17β-estradiol during aging could be mainly due to decreased ERα expression, that the ER loss is reversible by reducing reactive oxygen species, and that mitochondrial retrograde signaling plays a role in this regulation.

RAGE: a new frontier in chronic airways disease

Asthma and chronic obstructive pulmonary disease (COPD) are heterogeneous inflammatory disorders of the respiratory tract characterized by airflow obstruction. It is now clear that the environmental factors that drive airway pathology in asthma and COPD, including allergens, viruses, ozone and cigarette smoke, activate innate immune receptors known as pattern-recognition receptors, either directly or indirectly by causing the release of endogenous ligands. Thus, there is now intense research activity focused around understanding the mechanisms by which pattern-recognition receptors sustain the airway inflammatory response, and how these mechanisms might be targeted therapeutically. One pattern-recognition receptor that has recently come to attention in chronic airways disease is the receptor for advanced glycation end products (RAGE). RAGE is a member of the immunoglobulin superfamily of cell surface receptors that recognizes pathogen- and host-derived endogenous ligands to initiate the immune response to tissue injury, infection and inflammation. Although the role of RAGE in lung physiology and pathophysiology is not well understood, recent genome-wide association studies have linked RAGE gene polymorphisms with airflow obstruction. In addition, accumulating data from animal and clinical investigations reveal increased expression of RAGE and its ligands, together with reduced expression of soluble RAGE, an endogenous inhibitor of RAGE signalling, in chronic airways disease. In this review, we discuss recent studies of the ligand-RAGE axis in asthma and COPD, highlight important areas for future research and discuss how this axis might potentially be harnessed for therapeutic benefit in these conditions.

Benfotiamine counteracts smoking-induced vascular dysfunction in healthy smokers

Background. Smoking induces endothelial dysfunction (ED) mainly by exacerbating oxidative stress (OS) and inflammation. Benfotiamine, a thiamine prodrug with high bioavailability, prevents nicotine-induced vascular dysfunction in rats. It remained unknown whether this effect also occurs in humans. Methods. Therefore, 20 healthy volunteers (mean age: 38 years) were investigated twice, 7–10 days apart in a randomized, cross-over, and investigator-blinded design. Vascular function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery and by measurements of the soluble vascular cell adhesion molecule (sVCAM)-1. Investigations were performed after an overnight fast as well as 20 minutes after one cigarette smoking. On another day, the same procedure was applied following a 3-day oral therapy with benfotiamine (1050 mg/day). Ten patients were randomized to start with smoking alone, and ten started with benfotiamine. Results. Results are expressed as (mean ± SEM). Smoking acutely induced a decrease in FMD by 50% (^∗∗P < 0.001 versus baseline) an effect significantly reduced by benfotiamine treatment to 25%^∗§ (^∗P < 0.05 versus baseline, ^§P < 0.05 versus smoking alone). Smoking-induced elevation in sVCAM-1 was also prevented by benfotiamine. The endothelium-independent vasodilatation remained unaltered between days. Conclusion. In healthy volunteers, smoking blunts vascular function mirrored by a decrease in FMD and an increase in sVCAM-1. Short-term treatment with benfotiamine significantly reduces these effects, showing protective vascular properties.

The effect of cigarette smoke extract on thrombomodulin-thrombin binding: an atomic force microscopy study

Cigarette smoking is a well-known risk factor for cardiovascular disease. Smoking can cause vascular endothelial dysfunction and consequently trigger haemostatic activation and thrombosis. However, the mechanism of how smoking promotes thrombosis is not fully understood. Thrombosis is associated with the imbalance of the coagulant system due to endothelial dysfunction. As a vital anticoagulation cofactor, thrombomodulin (TM) located on the endothelial cell surface is able to regulate intravascular coagulation by binding to thrombin, and the binding results in thrombosis inhibition. This work focused on the effects of cigarette smoke extract (CSE) on TM-thrombin binding by atomic force microscopy (AFM) based single-molecule force spectroscopy. The results from both in vitro and live-cell experiments indicated that CSE could notably reduce the binding probability of TM and thrombin. This study provided a new approach and new evidence for studying the mechanism of thrombosis triggered by cigarette smoking.

RAGE and tobacco smoke: insights into modeling chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by chronic airway inflammation and airspace remodeling, leading to airflow limitation that is not completely reversible. Smoking is the leading risk factor for compromised lung function stemming from COPD pathogenesis. First- and second-hand cigarette smoke contain thousands of constituents, including several carcinogens and cytotoxic chemicals that orchestrate chronic lung inflammation and destructive alveolar remodeling. Receptors for advanced glycation end-products (RAGE) are multi-ligand cell surface receptors primarily expressed by diverse lung cells. RAGE expression increases following cigarette smoke exposure and expression is elevated in the lungs of patients with COPD. RAGE is responsible in part for inducing pro-inflammatory signaling pathways that culminate in expression and secretion of several cytokines, chemokines, enzymes, and other mediators. In the current review, new transgenic mouse models that conditionally over-express RAGE in pulmonary epithelium are discussed. When RAGE is over-expressed throughout embryogenesis, apoptosis in the peripheral lung causes severe lung hypoplasia. Interestingly, apoptosis in RAGE transgenic mice occurs via conserved apoptotic pathways also known to function in advanced stages of COPD. RAGE over-expression in the adult lung models features of COPD including pronounced inflammation and loss of parenchymal tissue. Understanding the biological contributions of RAGE during cigarette smoke-induced inflammation may provide critically important insight into the pathology of COPD.

RAGE signaling by alveolar macrophages influences tobacco smoke-induced inflammation

Receptors for advanced glycation end-products (RAGE) are multiligand cell surface receptors of the immunoglobin family expressed by epithelium and macrophages, and expression increases following exposure to cigarette smoke extract (CSE). The present study sought to characterize the proinflammatory contributions of RAGE expressed by alveolar macrophages (AMs) following CSE exposure. Acute exposure of mice to CSE via nasal instillation revealed diminished bronchoalveolar lavage (BAL) cellularity and fewer AMs in RAGE knockout (KO) mice compared with controls. Primary AMs were obtained from BAL, exposed to CSE in vitro, and analyzed. CSE significantly increased RAGE expression by wild-type AMs. Employing ELISAs, wild-type AMs exposed to CSE had increased levels of active Ras, a small GTPase that perpetuates proinflammatory signaling. Conversely, RAGE KO AMs had less Ras activation compared with wild-type AMs after exposure to CSE. In RAGE KO AMs, assessment of p38 MAPK and NF-κB, important intracellular signaling intermediates induced during an inflammatory response, revealed that CSE-induced inflammation may occur in part via RAGE signaling. Lastly, quantitative RT-PCR revealed that the expression of proinflammatory cytokines including TNF-α and IL-1β were detectably decreased in RAGE KO AMs exposed to CSE compared with CSE-exposed wild-type AMs. These results reveal that primary AMs orchestrate CSE-induced inflammation, at least in part, via RAGE-mediated mechanisms.

Interplay between smoking-induced genotoxicity and altered signaling in pancreatic carcinogenesis

Despite continuous research efforts directed at early diagnosis and treatment of pancreatic cancer (PC), the status of patients affected by this deadly malignancy remains dismal. Its notoriety with regard to lack of early diagnosis and resistance to the current chemotherapeutics is due to accumulating signaling abnormalities. Hoarding experimental and epidemiological evidences have established a direct correlation between cigarette smoking and PC risk. The cancer initiating/promoting nature of cigarette smoke can be attributed to its various constituents including nicotine, which is the major psychoactive component, and several other toxic constituents, such as nitrosamines, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and polycyclic aromatic hydrocarbons. These predominant smoke-constituents initiate a series of oncogenic events facilitating epigenetic alterations, self-sufficiency in growth signals, evasion of apoptosis, sustained angiogenesis, and metastasis. A better understanding of the molecular mechanisms underpinning these events is crucial for the prevention and therapeutic intervention against PC. This review presents various interconnected signal transduction cascades, the smoking-mediated genotoxicity, and genetic polymorphisms influencing the susceptibility for smoking-mediated PC development by modulating pivotal biological aspects such as cell defense/tumor suppression, inflammation, DNA repair, as well as tobacco-carcinogen metabolization. Additionally, it provides a large perspective toward tumor biology and the therapeutic approaches against PC by targeting one or several steps of smoking-mediated signaling cascades.

Progression of periodontal destruction and the roles of advanced glycation end products in experimental diabetes

BACKGROUND

Progression of diabetes-associated periodontal destruction and the roles of advanced glycation end products (AGEs) are investigated.

METHODS

Diabetes was induced by streptozocotin injection, and periodontitis was induced via silk ligature placement with Porphyromonas gingivalis lipopolysaccharide injection in 64 Sprague-Dawley rats for 7 to 21 days. The quality of alveolar bone and attachment loss (AL) were measured by microcomputed tomography and histology. Destruction profiles were evaluated by histology, histochemistry, immunohistochemistry, and quantitative assessments of inflammatory cells, expression of receptors for AGEs (RAGE), tartrate-resistant acid phosphatase, and proliferating cell nuclear antigen.

RESULTS

Without periodontitis induction, there was no obvious morphologic change in the periodontium, although slight elevations of AGEs and RAGE levels were noted in animals with diabetes. In the group with experimental periodontitis, significant periodontal bone loss was noted in animals both with and without diabetes from day 7, with more progressive bone loss in animals with diabetes during days 14 to 21. Histologically, the disruption of attachment and inflammation were observed from day 7, but subsequently subsided in animals without diabetes. A stronger and more prolonged response with significant AL was observed in animals with diabetes. Stronger inflammation, attenuated and persistent resorptive activity, and weaker proliferating potential were demonstrated by animals with diabetes. AGE deposition and RAGE expression were noted in animals without diabetes but with periodontitis, although levels were considerably elevated in the later stages in animals with diabetes.

CONCLUSIONS

Diabetes augments periodontal destruction by reducing the proliferating capability and activating resorptive activities. Presence of the AGE-RAGE axis without diabetes implies that it is involved in the regulation of inflammation.

Role of advanced glycation endproducts and potential therapeutic interventions in dialysis patients

It has been nearly 100 years since the first published report of advanced glycation end products (AGEs) by the French chemist Maillard. Since then, our understanding of AGEs in diseased states has dramatically changed. Especially in the last 25 years, AGEs have been implicated in complications related to aging, neurodegenerative diseases, diabetes, and chronic kidney disease. Although AGE formation has been well characterized by both in vitro and in vivo studies, few prospective human studies exist demonstrating the role of AGEs in patients on chronic renal replacement therapy. As the prevalence of end-stage renal disease (ESRD) in the United States rises, it is essential to identify therapeutic strategies that either delay progression to ESRD or improve morbidity and mortality in this population. This article reviews the role of AGEs, especially those of dietary origin, in ESRD patients as well as potential therapeutic anti-AGE strategies in this population.

Effect of dietary advanced glycation end products on mouse liver

The exact pathophysiology of non-alcoholic steatohepatitis (NASH) is not known. Previous studies suggest that dietary advanced glycation end products (AGEs) can cause oxidative stress in liver. We aim to study the effects of dietary AGEs on liver health and their possible role in the pathogenesis of NASH.

METHODS

Two groups of mice were fed the same diet except the AGE content varied. One group was fed a high AGE diet and the second group was fed a regular AGE diet. Liver histology, alanine aminotransferase, aspartate aminotransferase, fasting glucose, fasting insulin, insulin resistance and glucose tolerance were assessed.

RESULTS

Histology revealed that neutrophil infiltration occurred in the livers of the high AGE group at week 26; steatosis did not accompany liver inflammation. At week 39 livers from both groups exhibited macro- or micro-steatosis, yet no inflammation was detected. Higher insulin levels were detected in the regular AGE group at week 26 (P = 0.034), compared to the high AGE group. At week 39, the regular AGE group showed higher levels of alanine aminotransferase (P<0.01) and aspartate aminotransferase (P = 0.02) than those of the high AGE group.

CONCLUSIONS

We demonstrate that a high AGE diet can cause liver inflammation in the absence of steatosis. Our results show that dietary AGEs could play a role in initiating liver inflammation contributing to the disease progression of NASH. Our observation that the inflammation caused by high AGE alone did not persist suggests interesting future directions to investigate how AGEs contribute to pro-oxidative and anti-oxidative pathways in the liver.