Effect of valsartan, an angiotensin II receptor blocker, on markers of oxidation and glycation in Japanese type 2 diabetic subjects: blood pressure-independent effect of valsartan

Benefits of Valsartan and Amlodipine in Lipolysis through PU.1 Inhibition in Fructose-Induced Adiposity

High fructose intake has been implicated in obesity and metabolic syndrome, which are related to increased cardiovascular mortality. However, few studies have experimentally examined the role of renin–angiotensin system blockers and calcium channel blockers (CCB) in obesity. We investigated the effects of valsartan (an angiotensin II receptor blocker) and amlodipine (a CCB) on lipolysis through the potential mechanism of PU.1 inhibition. We observed that high fructose concentrations significantly increased adipose size and triglyceride, monoacylglycerol lipase, adipose triglyceride lipase, and stearoyl-CoA desaturase-1 (SCD1), activating transcription factor 3 and PU.1 levels in adipocytes in vitro. Subsequently, PU.1 inhibitor treatment was able to reduce triglyceride, SCD1, and PU.1 levels. In addition, elevated levels of triglyceride and PU.1, stimulated by a high fructose concentration, decreased with valsartan and amlodipine treatment. Overall, these findings suggest that high fructose concentrations cause triacylglycerol storage in adipocytes through PU.1-mediated activation. Furthermore, valsartan and amlodipine treatment reduced triacylglycerol storage in adipocytes by inhibiting PU.1 activation in high fructose concentrations in vitro. Thus, the benefits of valsartan and amlodipine in lipolysis may be through PU.1 inhibition in fructose-induced adiposity, and PU.1 inhibition might have a potential therapeutic role in lipolysis in fructose-induced obesity.

Keap1/Nrf2/ARE signaling unfolds therapeutic targets for redox imbalanced-mediated diseases and diabetic nephropathy

Hyperglycemia/oxidative stress has been implicated in the initiation and progression of diabetic complications while the components of Keap1/Nrf2/ARE signaling are being exploited as therapeutic targets for the treatment/management of these pathologies. Antioxidant agents like drugs, nutraceuticals and pure compounds that target the proteins of this pathway and their downstream genes hold the therapeutic strength to put the progression of this disease at bay. Here, we elucidate how the modulation of Keap1/Nrf2/ARE had been exploited for the treatment/management of end-stage diabetic kidney complication (diabetic nephropathy) by looking into (1) Nrf2 nuclear translocation and phosphorylation by some protein kinases at specific amino acid sequences and (2) Keap1 downregulation/Keap1-Nrf2 protein-protein inhibition (PPI) as potential therapeutic mechanisms exploited by Nrf2 activators for the modulation of diabetic nephropathy biomarkers (Collagen IV, Laminin, TGF-β1 and Fibronectin) that ultimately lead to the amelioration of this disease progression. Furthermore, we brought to limelight the relationship between diabetic nephropathy and Keap1/Nrf2/ARE and finally elucidate how the modulation of this signaling pathway could be further explored to create novel therapeutic milestones.

Medications that cause weight gain and alternatives in Canada: a narrative review

BACKGROUND

The cause of the obesity epidemic is multifactorial, but may, in part, be related to medication-induced weight gain. While clinicians may strive to do their best to select pharmacotherapy(ies) that has the least negative impact on weight, the literature regarding the weight effects of medication is often limited and devoid of alternative therapies.

RESULTS

Antipsychotics, antidepressants, antihyperglycemics, antihypertensives and corticosteroids all contain medications that were associated with significant weight gain. However, there are several medication alternatives within the majority of these classes associated with weight neutral or even weight loss effects. Further, while not all of the classes of medication examined in this review have weight-favorable alternatives, there exist many other tools to mitigate weight gain associated with medication use, such as changes in dosing, medication delivery or the use of adjunctive therapies.

CONCLUSION

Medication-induced weight gain can be frustrating for both the patient and the clinician. As the use of pharmaceuticals continues to increase, it is pertinent for clinicians to consider the weight effects of medications prior to prescribing or in the course of treatment. In the case where it is not feasible to make changes to medication, adjunctive therapies should be considered.

Strategies to decrease oxidative stress biomarker levels in human medical conditions: A meta-analysis on 8-iso-prostaglandin F2α

The widespread detection of elevated oxidative stress levels in many medical conditions has led to numerous efforts to design interventions to reduce its effects. Efforts have been wide-ranging, from dietary changes to administration of antioxidants, supplements, e.g., omega-3-fatty acids, and many medications. However, there is still no systemic assessment of the efficacy of treatments for oxidative stress reduction across a variety of medical conditions. The goal of this meta-analysis is, by combining multiple studies, to quantitate the change in the levels of the popular oxidative stress biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) after a variety of treatment strategies in human populations. Nearly 350 unique publications with 180 distinct strategies were included in the analysis. For each strategy, the difference between pre- or placebo and post-treatment levels calculated using Hedges' g value of effect. In general, administration of antibiotics, antihyperlipidemic agents, or changes in lifestyle (g = - 0.63, - 0.54, and 0.56) had the largest effect. Administration of supplements, antioxidants, or changes in diet (g = - 0.09, - 0.28, - 0.12) had small quantitative effects. To fully interpret the effectiveness of these treatments, comparisons to the increase in g value for each medical condition is required. For example, antioxidants in populations with coronary artery disease (CAD) reduce the 8-iso-PGF2α levels by g = - 0.34 ± 0.1, which is quantitatively considered a small effect. However, CAD populations, in comparison to healthy populations, have an increase in 8-iso-PGF2α levels by g = 0.38 ± 0.04; therefore, the overall reduction of 8-iso-PGF2α levels is ≈ 90% by this treatment in this specific medical condition. In conclusion, 8-iso-PGF2α levels can be reduced not only by antioxidants but by many other strategies. Not all strategies are equally effective at reducing 8-iso-PGF2α levels. In addition, the effectiveness of any strategy can be assessed only in relation to the medical condition investigated.

Advanced Glycation End Products Predict Loss of Renal Function and Correlate With Lesions of Diabetic Kidney Disease in American Indians With Type 2 Diabetes

We examined associations of advanced glycation end products (AGEs) with renal function loss (RFL) and its structural determinants in American Indians with type 2 diabetes. Data were from a 6-year clinical trial that assessed renoprotective efficacy of losartan. Participants remained under observation after the trial concluded. Glomerular filtration rate (GFR) was measured annually. Kidney biopsies were performed at the end of the trial. Five AGEs were measured in serum collected at enrollment and at kidney biopsy. RFL was defined as ≥40% decline of measured GFR from baseline. Of 168 participants (mean baseline age 41 years, HbA_1c 9.2%, GFR 164 mL/min, and albumin-to-creatinine ratio 31 mg/g), 104 reached the RFL end point during median follow-up of 8.0 years. After multivariable adjustment, each doubling of carboxyethyl lysine (hazard ratio [HR] 1.60 [95% CI 1.08-2.37]) or methylglyoxal hydroimidazolone (HR 1.30 [95% CI 1.02-1.65]) concentration was associated with RFL. Carboxyethyl lysine, carboxymethyl lysine, and methylglyoxal hydroimidazolone correlated positively with cortical interstitial fractional volume (partial r = 0.23, P = 0.03; partial r = 0.25, P = 0.02; and partial r = 0.31, P = 0.003, respectively). Glyoxyl hydroimidazolone and methylglyoxal hydroimidazolone correlated negatively with total filtration surface per glomerulus (partial r = -0.26, P = 0.01; and partial r = -0.21, P = 0.046, respectively). AGEs improve prediction of RFL and its major structural correlates.

Eplerenone restores 24-h blood pressure circadian rhythm and reduces advanced glycation end-products in rhesus macaques with spontaneous hypertensive metabolic syndrome

Hypertension is often associated with metabolic syndrome (MetS), and serves as a risk factor of MetS and its complications. Blood pressure circadian rhythm in hypertensive patients has been suggested to contribute to cardiovascular consequences and organ damage of hypertension. But circadian changes of BP and their response to drugs have not been clearly investigated in non-human primates (NHPs) of MetS with hypertension. Here, we identified 16 elderly, hypertensive MetS rhesus monkeys from our in-house cohort. With implanted telemetry, we investigate BP changes and its circadian rhythm, together with the effect of antihypertensive drugs on BP and its diurnal fluctuation. MetS hypertensive monkeys displayed higher BP, obesity, glucose intolerance, and dyslipidemia. We also confirmed impaired 24-h BP circadian rhythm in MetS hypertensive monkeys. Importantly, Eplerenone, a mineralocorticoid receptor blocker, exerts multiple beneficial effects in MetS hypertensive monkeys, including BP reduction, 24-h BP circadian rhythm restoration, and decreased plasma concentration of inflammation factors and advanced glycation end-products. In summary, we identified a naturally-developed hypertensive MetS NHP model, which is of great value in the studies on pathogenesis of MetS-associated hypertension and development of novel therapeutic strategies. We also provided multiple novel mechanistic insights of the beneficial effect of Eplerenone on MetS with hypertension.

Soluble receptor for advanced glycation end products and increased aortic stiffness in the general population

It has been suggested that accumulation of advanced glycation end products (AGEs) is involved in several pathophysiological processes in the vessel wall. We hypothesized that low levels of the soluble receptor for AGEs (sRAGE) might be associated with increased arterial stiffness, a manifestation of vascular ageing in the general population. Using a cross-sectional design, we analyzed 1077 subjects from the Czech post-MONICA study. The aortic pulse wave velocity (aPWV) was measured using a Sphygmocor device. sRAGE concentrations were assessed in frozen samples using enzyme-linked immunosorbent assay methods (R&D Systems). aPWV significantly (P<0.0001) increased across the sRAGE quartiles. An aPWV of 1 m s(-1) was associated with a 37% increase in the risk of low sRAGE (<918 pg ml(-1), bottom quartile; P-value=0.018). In a categorized manner, subjects in the bottom sRAGE quartile had an odds ratio of an increased aPWV (⩾9.3 m s(-1)), adjusted for all potential confounders of 2.05 (95% confidence interval: 1.26-3.32; P=0.004), but this was only the case for non-diabetic hypertensive patients. In contrast, a low sRAGE was rejected as an independent predictor of an increased aPWV in normotensive or diabetic subjects using similar regression models. In conclusion, low circulating sRAGE was independently associated with increased arterial stiffness in a general population-based sample, but this was only observed in hypertensive non-diabetic patients.

Glycemic variability and oxidative stress: a link between diabetes and cardiovascular disease?

Diabetes is associated with a two to three-fold increase in risk of cardiovascular disease. However, intensive glucose-lowering therapy aiming at reducing HbA1c to a near-normal level failed to suppress cardiovascular events in recent randomized controlled trials. HbA1c reflects average glucose level rather than glycemic variability. In in vivo and in vitro studies, glycemic variability has been shown to be associated with greater reactive oxygen species production and vascular damage, compared to chronic hyperglycemia. These findings suggest that management of glycemic variability may reduce cardiovascular disease in patients with diabetes; however, clinical studies have shown conflicting results. This review summarizes the current knowledge on glycemic variability and oxidative stress, and discusses the clinical implications.

Impact of antibacterial drugs on human serum paraoxonase-1 (hPON1) activity: an in vitro study

OBJECTIVE

To investigate the in vitro effects of the antibacterial drugs, meropenem trihydrate, piperacillin sodium, and cefoperazone sodium, on the activity of human serum paraoxonase (hPON1).

METHODS

hPON1 was purified from human serum using simple chromatographic methods, including DEAE-Sephadex anion exchange and Sephadex G-200 gel filtration chromatography.

RESULTS

The three antibacterial drugs decreased in vitro hPON1 activity. Inhibition mechanisms meropenem trihydrate was noncompetitive while piperacillin sodium and cefoperazone sodium were competitive.

CONCLUSIONS

Our results showed that antibacterial drugs significantly inhibit hPON1 activity, both in vitro, with rank order meropenem trihydrate piperacillin sodium cefoperazone sodium in vitro.

Effects of valsartan on inflammatory and oxidative stress markers in hypertensive, hyperglycemic patients: an open-label, prospective study

BACKGROUND

Diabetes mellitus and hypertension are aggravated by activation of the renin-angiotensin system caused by increased oxygen stress and local inflammatory responses. Several studies have suggested that angiotensin II type 1 receptors can reduce inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], interleukin [IL]-6, IL-18, soluble vascular cell adhesion molecule [VCAM]-I, and l-selectin) and oxidative stress markers (urinary 8-hydroxy-7,8-dihydro-2'-deoxyguanosine [8-OHdG] and 8-epi-prostaglandin F2α [8-isoprostane]) in hypertensive patients.

OBJECTIVE

The aim of this study was to assess the effects of valsartan, an angiotensin II receptor blocker, on inflammatory and oxidative stress markers in hypertensive patients with mild diabetes or impaired glucose tolerance.

METHODS

In this open-label, prospective study, hypertensive patients aged >20 years with mild diabetes (requiring treatment by diet alone or an oral hypoglycemic), seen on an outpatient basis at the Division of Diabetes, Metabolism, and Endocrinology, Omori Hospital, Toyko, Japan, who were receiving a therapeutic dietary regimen for ≥1 month in the treatment of diabetes or hypertension, were eligible for enrollment. Blood pressure, inflammatory markers (hs-CRP, IL-6, IL-18, VCAM-1, and L-selectin), and oxidative stress markers (urinary 8-OHdG and 8-isoprostane) were monitored before treatment commencement with valsartan (40-80 mg/d) and after 3 months of treatment.

RESULTS

A total of 26 patients (18 men, 8 women; mean [SD] age, 57.7 [11.3] years; mean [SD] weight, 65.3 [13.1] kg) were enrolled in the study. After 3 months of treatment, patients' mean (SD) blood pressure had significantly decreased from 153.1 (11.2)/88.3 (11.4) to 143.7 (13.7)/85.2 (9.0) mm Hg (P < 0.05). Among the inflammatory and oxidative stress markers, hs-CRP, VCAM-1, and urinary 8-OHdG concentrations decreased significantly from 0.231 (0.199) to 0.134 (0.111) mg/dL (P = 0.043), 471.1 (193.9) to 403.2 (135.2) ng/mL (P = 0.012), and 12.12 (5.99) to 8.07 (3.36) ng/mg · creatinine (P = 0.001), respectively. The reductions in these markers were observed in patients regardless of whether or not their glycosylated hemoglobin (HbA1c) concentration improved (defined as a decrease of ≥1% in HbA1c).

CONCLUSION

This small, open-label, prospective study found that a 3-month treatment with valsartan was associated with a significant reduction of hs-CRP, VCAM-1, and urinary 8-OHdG concentrations independent of improvement in HbA1c concentration in these hypertensive patients with hyperglycemia.

Ramipril inhibits AGE-RAGE-induced matrix metalloproteinase-2 activation in experimental diabetic nephropathy

BACKGROUND

Advanced glycation end products (AGE)-receptor for AGE (RAGE) axis and renin-angiotensin system (RAS) play a role in diabetic nephropathy (DN). Matrix metalloproteinase-2 (MMP-2) activation also contributes to DN. However, the pathological interaction among AGE-RAGE, RAS and MMP-2 in DN remains unknown. We examined here the involvement of AGE and RAS in MMP-2 activation in streptozotocin (STZ)-induced diabetic rats and in AGE-exposed rat renal proximal tubular cells (RPTCs).

METHODS

Experimental diabetes was induced in 6-week-old male Sprague-Dawley (SD) rats by intravenous injection of STZ. Diabetic rats received ramipril (3 mg/kg body weight/day) or vehicle for 32 weeks. AGE-modified rat serum albumin (AGE-RSA) or RSA was intraperitoneally administrated to 6-week-old male SD rats for 16 weeks. RPTCs were stimulated with 100 μg/ml AGE-modified bovine serum albumin (AGE-BSA) or BSA in the presence or absence of 10(-7) M ramiprilat, an inhibitor of angiotensin-converting enzyme or 100 nM BAY11-7082, an IκB-α phosphorylation inhibitor.

RESULTS

AGE and RAGE expression levels and MMP-2 activity in the tubules of diabetic rats was significantly increased in association with increased albuminuria, all of which were blocked by ramipril. AGE infusion induced tubular MMP-2 activation and RAGE gene expression in SD rats. Ramiprilat or BAY11-7082 inhibited the AGE-induced MMP-2 activation or reactive oxygen species generation in RPTCs. Angiotensin II increased MMP-2 gene expression in RPTCs, which was blocked by BAY11-7082.

CONCLUSIONS

Our present study suggests the involvement of AGE-RAGE-induced, RAS-mediated MMP-2 activation in experimental DN. Blockade of AGE-RAGE axis by ramipril may protect against DN partly via suppression of MMP-2.

Current therapeutic interventions in the glycation pathway: evidence from clinical studies

The increased formation of advanced glycation endproducts (AGEs) constitutes a potential mechanism of hyperglycaemia-induced micro- and macrovascular disease in diabetes. In vitro and animal experiments have shown that various interventions can inhibit formation and/or actions of AGEs, in particular the specific AGE inhibitor aminoguanidine and the AGEs crosslink breaker alagebrium, and the B vitamins pyridoxamine and thiamine, and the latter's synthetic derivative, benfotiamine. The potential clinical value of these interventions, however, remains to be established. The present review provides, from the clinical point of view, an overview of current evidence on interventions in the glycation pathway relating to (i) the clinical benefits of specific AGE inhibitors and AGE breakers and (ii) the potential AGE-inhibiting effects of therapies developed for purposes unrelated to the glycation pathway. We found that safety and/or efficacy in clinical studies with the specific AGE inhibitor, aminoguanidine and the AGE breaker, alagebrium, appeared to be a concern. The clinical evidence on the potential AGE-inhibiting effects of B vitamins is still limited. Finally, current evidence for AGE inhibition by therapies developed for purposes unrelated to glycation is limited due to a large heterogeneity in study designs and/or measurement techniques, which have often been sub-optimal. We conclude that, clinical evidence on interventions to inhibit formation and/or action of AGEs is currently weak and unconvincing.

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.

Relationship between the receptor occupancy profile and pleiotropic effects of angiotensin II receptor blockers

AIM

To investigate whether (i) angiotensin receptor occupying profiles of angiotensin II receptor blockers (ARBs) vary among the drugs and (ii) such differences contribute to the degree of their pleiotropic effects.

METHODS

In a randomized, three phase crossover study, nine hypertensive patients received repeated doses (each recommended starting dose for 7 days and then each maximum recommended dose for 20 days) of irbesartan, valsartan and candesartan. The time course profiles and trough level of receptor occupancy were determined on days 7 and 28, respectively. The pleiotropic effect related parameters were measured on days 0 and 28 in each trial.

RESULTS

Of the pleiotropic effect related parameters investigated, urinary 8-isoprostane, fasting serum insulin and homeostasis model assessment of insulin resistance index were more suppressed after 4 weeks treatment with irbesartan than after candesartan and valsartan therapy, respectively. The maximum, area under the curve and trough values of receptor occupancy significantly differed between the ARBs [geometric mean (and 95% CI) of trough value 18.1 (12.9, 25.3) for irbesartan, 9.6 (6.0, 15.3) for valsartan and 5.5 (2.8, 10.8) for candesartan, respectively] and were negatively correlated with the change in urinary 8-isoprostane (r = -0.46 - -0.55, P < 0.05), but not the markers of insulin resistance (r = 0.02-0.15, P = 0.46-0.94).

CONCLUSIONS

Our results demonstrate that the receptor occupying profiles are different among the ARBs. This class of drugs might have both receptor occupancy dependent and independent pleiotropic effects.

Intramuscular injection of soluble receptor for advanced glycation endproducts expression vector prevents the development of streptozotocin-induced diabetes mellitus in rats on high fat diet

BACKGROUND

In order to study if advanced glycation endproducts (AGE) in high-temperature cooked high fat diet could be the cause of type 2 diabetes, a expressing vector encoding soluble form of receptor for AGE (sRAGE) was injected intramuscularly, and the incidence of streptozotocin (STZ)-induced diabetes mellitus in rats on high fat diet were observed.

METHODS

Rat sRAGE gene, cloned to a pLNCX(2) expression vector (pLNCX(2) -sRAGE), was injected into the hind leg muscles of Sprague-Dawley rats. Rats were fed with high fat diet for 8 weeks before pLNCX(2) -sRAGE injection (designed as T group), or pLNCX2 (as H group), and rats on normal chow (as N group). The diet remained the same until end of the study. Serum malondialdehyde (MDA) and superoxide dismutase (SOD) levels were studied in one serial of rats (n = 8) under the treatment of different vectors without STZ injection. For a second serial of study (n = 20), rats were injected with 30 mg/kg STZ intraperitoneally 2 weeks after the second injection of vectors, and tail blood glucose was detected 1 week later.

RESULTS

Malondialdehyde levels were found to be decreased 1 week after injection of sRAGE and lasted for at least 3 weeks after each injection. SOD activities were found to be increased slowly in the second week after each injection. As determined with fasting and random glycemia only two rats were in diabetic level (fasting glycemia ≥7.0 mmol/L and random glycemia ≥11.1 mmol/L) in T group while eight mice were in the diabetic level in H group.

CONCLUSIONS

Intramuscular injection of sRAGE decreases the MDA level and increases SOD activities, and decreases the STZ-induced incidence of diabetes in rats in high fat diet.

New and old mechanisms associated with hypertension in the elderly

Hypertension is a widely prevalent and important risk factor for cardiovascular diseases that increase with aging. The hallmark of hypertension in the elderly is increased vascular dysfunction. However, the molecular mechanisms by which increased blood pressure leads to vascular injury and impaired endothelial function are not well defined. In the present paper, we will analyze several mechanisms described in the scientific literature involved in hypertension in the elderly as endothelial dysfunction, increased oxygen delivery to tissues, inflammation, cellular apoptosis, and increased concentration of active metabolites. Also, we will focus on new molecular mechanisms involved in hypertension such as telomeres shortening, progenitor cells, circulating microparticles, and epigenetic factors that have appeared as possible causes of hypertension in the elderly. These molecular mechanisms may elucidate different origin for hypertension in the elderly and provide us with new targets for hypertension treatment.

Reduction of age-associated arterial wall changes by low-dose valsartan

BACKGROUND

Functional and morphological arterial wall impairment progresses with ageing. Angiotensin II in the arterial wall is involved in this process. Appropriate early intervention might theoretically slow the progress of age-related changes. Herein, we investigated a new approach to this issue: whether arterial wall changes present in middle-aged males could be reduced by low-dose valsartan intervention.

METHODS

Forty apparently healthy, middle-aged males (42.9 ± 0.9 years) were recruited for a double-blind randomized study and received either placebo or valsartan (20 mg daily) for 30 days. Brachial artery flow-mediated dilation (FMD), pulse wave velocity (PWV), and β-stiffness of the common carotid artery were measured using an Aloka alfa-10 Prosound with an integrated eTracking system at inclusion, after 30 days, and after 3 and 8 months.

RESULTS

Intervention resulted in FMD increase (154.2 ± 20.1 %; p < 0.001) and PWV and β-stiffness decrease compared to initial values (-6.9 ± 1.0 % and -13.2 ± 1.4 %; both p < 0.01) whereas values in the untreated group (p < 0.001 for all parameters) remained unchanged throughout the study. The advantageous effects decreased over the months following valsartan discontinuation, but were still significant after 3 months (largely in FMD and less in PWV and β-stiffness), and negligible after 8 months. The beneficial effects were ascribed to valsartan's pleiotropic effects, as no blood pressure changes were recorded.

CONCLUSIONS

We showed that age-related arterial wall changes in middle-aged males are reversible and could be reduced by a low-dose, short-term valsartan intervention. The new approach merits detailed investigation in future studies.

Role of advanced glycation end products (AGEs) and oxidative stress in vascular complications in diabetes

BACKGROUND

A non-enzymatic reaction between reducing sugars and amino groups of proteins, lipids and nucleic acids contributes to the aging of macromolecules, whose process has been known to progress at an accelerated rate under hyperglycemic and/or oxidative stress conditions. Over a course of days to weeks, early glycation products undergo further reactions such as rearrangements and dehydration to become irreversibly cross-linked, fluorescent protein derivatives termed advanced glycation end products (AGEs).

SCOPE OF REVIEW

In this paper, we review the role of AGE-oxidative stress axis and its therapeutic interventions in vascular complications in diabetes.

MAJOR CONCLUSIONS

AGEs elicit oxidative stress generation and subsequently cause inflammatory and thrombogenic reactions in various types of cells via interaction with a receptor for AGEs (RAGE), thereby being involved in vascular complications in diabetes. In addition, mitochondrial superoxide generation has been shown to play an important role in the formation and accumulation of AGEs under diabetic conditions. Further, we have recently found that a pathophysiological crosstalk between AGE-RAGE axis and renin-angiotensin system (RAS) could contribute to the progression of vascular damage in diabetes.

GENERAL SIGNIFICANCE

These observations suggest that inhibition of AGE-RAGE-oxidative stress axis or blockade of its interaction with RAS is a novel therapeutic strategy for preventing vascular complications in diabetes.

The three-gene paraoxonase family: physiologic roles, actions and regulation

The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. By far the most-studied member is PON1, a high-density lipoprotein-associated esterase/lactonase, also endowed with the capacity to hydrolyze organophosphates, but all the three proteins prevent oxidative stress and fight inflammation. They therefore seem central to a wide variety of human illnesses, including atherosclerosis, diabetes mellitus, mental disorders and inflammatory bowel disease. The major goal of this review is to highlight the regulation of each of the paraoxonase components by diverse nutritional molecules and pharmacological agents as well as a number of pathophysiological events, such as oxidative stress and inflammation. Considerable and detailed cell-based studies and animal model experiments have been provided to allow a thorough scrutiny of PON modulation, which will increase our understanding and ability to target these genes in order to efficiently increase their transcriptional activity and decrease the risks of developing different disorders.

Advanced glycation end products, oxidative stress and diabetic nephropathy

About 246 million people worldwide had diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end-stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)-oxidative stress system in diabetic nephropathy.

Advanced glycation end products, oxidative stress and diabetic nephropathy

About 246 million people worldwide have diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end-stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)-oxidative stress system in diabetic nephropathy.

Effect of rosuvastatin on concentrations of plasma lipids, urine and plasma oxidative stress markers, and plasma high-sensitivity C-reactive protein in hypercholesterolemic patients with and without type 2 diabetes mellitus: A 12-week, open-label, pilot study

BACKGROUND

Oxidative stress and inflammation of the arterial wall are now recognized as important factors in the progression of atherosclerosis. C-reactive protein (CRP) has been defined as a sensitive but not specific marker of inflammation. Statin therapy has been reported to decrease plasma high-sensitivity CRP (hs-CRP) concentration in hypercholesterolemic patients.

OBJECTIVE

The aim of this study was to examine the effect of rosuvastatin on concentrations of plasma lipids, urine and plasma oxidative stress markers, and plasma hs-CRP in hypercholesterolemic patients with and without type 2 diabetes mellitus.

METHODS

Patients with hypercholesterolemia with and without type 2 diabetes mellitus were enrolled in this pilot study after written informed consent was given. At baseline and after 12 weeks of open-label treatment with rosuvastatin 2.5 mg/d, concentrations of plasma lipids, urine and plasma oxidative stress markers, and plasma hs-CRP were measured. Urine 8-iso-prostaglandin F2α (8-iso-PGF2α) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentrations were also measured to asess whole-body oxidative stress. Plasma free-radical generation was estimated using a total reactive oxygen species (TROS) assay system. Adverse effects were assessed at each study visit (4-week intervals) through patient interviews and laboratory testing.

RESULTS

Thirty-five patients were enrolled with 1 dropping out prior to study completion; therefore, 34 patients (19 women, 15 men; mean [SE] age, 55.4 [13.6] years; range, 30-78 years) completed the study. Compared with baseline, significant decreases were found in serum concentrations of total cholesterol (TC) (252.3 [39.3] vs 187.8 [30.1] mg/dL; P < 0.001; Δ = 24.5%), LDL-C (162.0 [44.3] vs 98.5 [31.9] mg/dL; P < 0.001; Δ = 38.7%), and triglycerides (TG) (157.2 [93.6] vs 124.4 [69.9] mg/dL; P < 0.05; Δ = 11.7%) after 12 weeks of treatment with rosuvastatin. Serum HDL-C concentration did not change significantly from baseline (59.7 [20.5] vs 63.7 [19.3] mg/dL; Δ = 9.4%). The plasma LDL-C/HDL-C ratio decreased significantly after rosuvastatin treatment (3.03 [1.33] vs 1.72 [0.83]; P < 0.001; Δ = 43.2%). Compared with baseline, significant decreases were observed in urine concentrations of the oxidative stress markers after 12 weeks of rosuvastatin treatment: 8-iso-PGF2α (342.8 [154.3] vs 300.6 [101.2] pg/mg; P < 0.05) and 8-OHdG (11.1 [4.53] vs 8.1 [2.7] ng/mg; P < 0.01). TROS decreased significantly (182.3 [29.0] vs 157.6 [17.3] U; P < 0.001), and plasma hs-CRP concentration also decreased significantly (0.107 [0.100] vs 0.054 [0.033] mg/dL; P < 0.05). When the patients' results were assessed according to the presence or absence of type 2 diabetes mellitus, urine 8-iso-PGF2α concentration was significantly decreased from baseline only in the nondiabetic group. No adverse events were reported or observed during the course of the study.

CONCLUSION

Rosuvastatin treatment was associated with significant reductions in plasma concentrations of TC, LDL-C, and TG, urine and plasma oxidative stress markers, and plasma hs-CRP in these hypercholesterolemic patients.

Low-density lipoprotein levels are one of the independent determinants of circulating levels of advanced glycation end products in nondiabetic subjects

BACKGROUND

Nonenzymatic modification of proteins by reducing sugars leads to the formation of advanced glycation end products (AGEs), whose process has been reported to progress under diabetes. Recently, diet has been found to be a major environmental source of proinflammatory AGEs in humans. Further, fats or meat-derived products processed by high heat such as broiling have been shown to contain more AGEs than carbohydrates boiled for longer periods. Since circulating levels of low-density lipoprotein cholesterol (LDL-C) are also regulated by dietary cholesterol, it is conceivable that intake of cholesterol-rich foods could regulate serum levels of AGEs in humans. In this study, we investigated whether LDL-C levels are one of the independent determinants of circulating AGEs levels in a nondiabetic general population.

METHODS

A total of 170 nondiabetic Japanese subjects underwent a complete history, physical examination, determination of blood chemistries, and serum AGEs.

RESULTS

Univariate analysis showed that AGEs levels were associated with LDL-C (P < 0.05) and fasting plasma glucose levels (P < 0.05). By the use of multiple stepwise regression analyses, LDL-C (P < 0.01) and fasting plasma glucose levels (P < 0.05) remained significant and were independently related to AGEs levels (R2 = 0.069).

CONCLUSIONS

The present study is the first demonstration that LDL-C levels are one of the independent determinants of serum levels of AGEs in a nondiabetic general population. Intake of cholesterol-rich foods may regulate serum levels of AGEs in nondiabetic subjects.

Inhibitors of advanced glycation end products (AGEs): potential utility for the treatment of cardiovascular disease

Accelerated atherosclerosis and microvascular complications are the leading causes of coronary heart disease, stroke, blindness, and end-stage renal failure, which could account for disabilities and high mortality rates in patients with diabetes. Recent clinical studies have substantiated the concept of "hyperglycemic memory" in the pathogenesis of cardiovascular disease (CVD) in diabetes. Indeed, the Diabetes Control and Complications Trial-Epidemiology of Diabetes Interventions and Complications (DCCT-EDIC) Research, has revealed that intensive therapy during the DCCT reduces the risk of cardiovascular events by about 50% in type 1 diabetic patients 11 years after the end of the trial. Among various biochemical pathways activated under diabetic conditions, the process of formation and accumulation of advanced glycation end products (AGEs) and their mode of action are most compatible with the theory "hyperglycemic memory." Further, there is a growing body of evidence that AGEs play an important role in CVD in diabetes. These observations suggest that the inhibition of AGEs formation may be a promising target for therapeutic intervention in diabetic vascular complications. Therefore, in this article, we review several agents with inhibitory effects on AGEs formation and their therapeutic implications in CVD in diabetes.