Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Sexual Dysfunction in Diabetic Patients: Τhe Role of Advanced Glycation End Products

Sexual dysfunction is a common but underestimated disorder of diabetic patients of both genders, entailing specific and complex pathogenesis and severely affecting reproductive health and quality of life. Hyperglycemia, dyslipidemia, hypertension, obesity, aging, and psychological factors underlie its pathogenesis. A large body of evidence indicates that advanced glycation end products and oxidative stress have a distinct impact on the pathogenesis of diabetes and its complications, including hypogonadism, which is closely related to sexual dysfunction. Advanced glycation end products seem to affect sexual function either directly by accumulation in various regions of the reproductive system and/or correlation or indirectly through oxidative stress induction via several mechanisms. They are also involved in the pathogenesis of diabetic complications, which are related to sexual dysfunction. Herein, we review the issue of sexual dysfunction in diabetic males and females, with special emphasis on the impact of advanced glycation end products in the pathogenesis of sexual dysfunction, the relationship of advanced glycation end products with low testosterone levels in diabetic subjects, which account for the proportion of disorder and the available therapeutic interventions.

Arterial stiffness and the non-dipping pattern in type 1 diabetes males with and without erectile dysfunction

Arterial stiffness (AS) and non-dipping pattern are early predictors of cardiovascular diseases but are not used in clinical practice. We aimed to assess if AS and the non-dipping pattern are more prevalent in the erectile dysfunction (ED) group than in the non-ED group among subjects with type 1 diabetes (T1DM). The study group consisted of adults with T1DM. Aortic pulse wave velocity (PWV Ao)-a marker of increased AS, central systolic blood pressure, and heart rate (HR) were measured with a brachial oscillometric device (Arteriograph 24). Erectile dysfunction (ED) was assessed by the International Index of Erectile Function-5. A comparison between the groups with and without ED was performed. Of 34 investigated men with T1DM, 12 (35.3%) suffered from ED. The group with ED had higher mean 24 h HR (77.7 [73.7-86.5] vs 69.9 [64.0-76.8]/min; p = 0.04, nighttime PWV Ao (8.1 [6.8-8.5] vs 6.8 [6.1-7.5] m/s; p = 0.015) and prevalence of non-dipping SBP Ao pattern (11 [91.7] vs 12 [54.5]%; p = 0.027) than individuals without ED. The presence of ED detected a central non-dipping pattern with a sensitivity of 47.8% and a specificity of 90.9%. The central non-dipping pattern was more prevalent and the nighttime PWV was higher in T1DM subjects with ED than in those without ED.

Saxagliptin alleviates erectile dysfunction through increasing stromal cell-derived factor-1 in diabetes mellitus

BACKGROUND

Diabetes mellitus-induced erectile dysfunction (DMED) is one of the complications of diabetes and has a poor response to phosphodiesterase type 5 inhibitor, the first-line treatment for ED. Saxagliptin (Sax), a dipeptidyl peptidase-4 inhibitor (DPP-4i), has been officially used in the treatment of type 2 diabetes. Stromal cell-derived factor-1 (SDF-1) is one of the important substrates of DPP-4, and has been proven to be beneficial for several DM complications. However, it is unknown whether Sax contributes to the management of DMED.

OBJECTIVES

To explore the effect and possible underlying mechanisms of Sax in the treatment of DMED.

METHODS

The model of DM was established by intraperitoneal injection of streptozotocin. All rats were divided into three groups (n = 8 per group): control group, DMED group and DMED+Sax group. In cellular experiments, the corpus cavernosum smooth muscle cells (CCSMCs) were exposed to high glucose (HG), and treated with Sax and AMD3100 (SDF-1 receptor inhibitor). The penile tissue and CCSMCs were harvested for detection.

RESULTS

We found that erectile function was impaired in DMED rats compared with the control group, which was partially relieved by Sax. Decreased expression of DPP-4 and increased level of SDF-1 were also observed in DMED+Sax group, together with elevation of PI3K/AKT pathway and inhibition of endothelial dysfunction, oxidative stress and apoptosis in corpus cavernosum. Moreover, Sax could also regulate oxidative stress and apoptosis in CCSMCs under HG condition, which was blocked in part by AMD3100.

CONCLUSION

Sax could alleviate DMED through increasing SDF-1 and PI3K/AKT pathway, in company with moderation of endothelial dysfunction, oxidative stress and apoptosis. Our findings indicated that DPP-4 is may be beneficial to the management of DMED.

Engineered Adipose-Derived Stem Cells Overexpressing RXFP1 via CRISPR Activation Ameliorate Erectile Dysfunction in Diabetic Rats

Due to the high incidence of diabetes mellitus (DM) and poor response to the first-line treatment of DM-induced erectile dysfunction (DMED), new therapeutic strategies for DMED are needed. Adipose-derived stem cell (ADSC) transplantation is considered a promising treatment modality for DMED but is limited by poor survival and efficacy after transplantation. In this study, we aimed to increase the therapeutic effect of DMED by overexpressing the relaxin family peptide receptor 1 (RXFP1) using a clustered regularly interspaced short palindromic repeats activation (CRISPRa) system in ADSCs. Two lentiviruses carrying the CRISPRa system transfected ADSCs to overexpress RXFP1 (RXFP1-ADSCs). The intracavernous injection of ADSCs was performed in DMED rats induced by the intraperitoneal injection of streptozotocin. Four weeks after transplantation, we measured erectile function and collected specimens of the corpus cavernosum for follow-up detection. The results showed that ADSCs improved erectile function in diabetic rats, and the RXFP1-ADSCs were more significant. We detected reduced levels of oxidative stress, apoptosis and fibrosis together with relative normalization of endothelial and smooth muscle cell function in the penis after ADSC transplantation. RXFP1-ADSCs had more potent efficacy in the above alterations compared to negative control ADSCs due to the high levels of survival and paracrine capacity in RXFP1-ADSCs. The results revealed that RXFP1-ADSC transplantation could partially preserve erectile function in DMED rats associated with the regulation of oxidative stress, apoptosis, fibrosis and endothelial and smooth muscle cell dysfunction. RXFP1 may be the new target for the genetic modification of ADSCs, which benefits the management of DMED.

Association between Advanced Glycation End-Products, Carotenoids, and Severe Erectile Dysfunction

PURPOSE

To investigate the association between skin advanced glycation end-products (AGEs) levels, blood antioxidative vitamin and carotenoid concentrations, and severe erectile dysfunction (ED) in community-dwelling men.

MATERIALS AND METHODS

This cross-sectional study used the 5-Item International Index of Erectile Function to identify 335 community-dwelling men with ED. The accumulation of skin AGEs was assessed noninvasively by measuring skin autofluorescence. Background-adjusted multivariable logistic regression analyses using the inverse probability of treatment weighting method were performed to evaluate the effects of AGEs, vitamins, and carotenoids on severe ED. Moreover, multiple linear regression analyses were performed to assess the association between skin AGEs levels and serum carotenoid concentrations.

RESULTS

The median age of study participants was 57 years. Of the 335 men, 289 (86.3%) and 46 (13.7%) were classified into the mild/moderate and severe ED groups, respectively. Multivariable analyses revealed that skin AGEs levels, blood vitamins C and E, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, total lycopene, and cis-lycopenes concentrations were significantly associated with severe ED, whereas all-trans lycopene concentrations were not. In the multiple linear regression analyses, serum zeaxanthin concentrations were negatively and significantly correlated with skin AGEs levels.

CONCLUSIONS

Higher skin AGEs levels and lower blood antioxidative vitamin and carotenoid concentrations were significantly associated with severe ED. Serum zeaxanthin levels were negatively and significantly correlated with skin AGEs levels, suggesting the possible effects of zeaxanthin on ED by decreasing tissue AGEs levels.

The role of microRNAs in erectile dysfunction: From pathogenesis to therapeutic potential

Erectile dysfunction (ED) is a common male sexual dysfunction disease, and it was predicted that the number of ED patients worldwide will reach 322 million by 2025. However, the pathogenesis of ED is complex and the current treatment options are still limited, so it is urgent to explore new treatment strategies. Recent studies have shown that microRNAs (miRNAs) play an important role in ED, and these single-stranded non-coding small RNA molecules are involved in key pathophysiological processes in the occurrence and development of ED. Therefore, miRNAs have remarkable potential as therapeutic targets in ED. Here, this review introduces the physiological basis of erectile function and the pathophysiological changes in ED and summarizes the current knowledge on the expression, biological functions, and molecular mechanisms of miRNAs in ED, especially the potential of miRNA-targeted therapies to improve ED. This review will provide a comprehensive view of the role of miRNAs in the pathogenesis of ED and the potential value of miRNAs in the treatment of ED.

A novel role of Nano selenium and sildenafil on streptozotocin-induced diabetic nephropathy in rats by modulation of inflammatory, oxidative, and apoptotic pathways

AIMS

The present study aimed to investigate the effect of nano selenium, sildenafil, and their combination on inflammation, oxidative stress, and apoptosis in streptozotocin-induced diabetic nephropathy in rats. Herein, a new anti-inflammatory pathway for sildenafil as a high-mobility group box (HMGB1) inhibitor was proposed using the molecular docking technique.

MATERIALS AND METHODS

Rats were divided into 7 groups: normal control, control nano selenium, control sildenafil, control diabetic, diabetic+ nano selenium, diabetic+ sildenafil, diabetic+ nano selenium+ sildenafil. The effects of drugs were evaluated by measuring serum urea, creatinine, lactate dehydrogenase (LDH), levels of tumor necrosis factor-alpha (TNF-α), Interleukin 1 beta (IL-1β), HMGB1, receptor advanced glycation end product (RAGE), malondialdehyde (MDA), thioredoxin reductase (TrxR) by biochemical assays, nuclear factor-kappa b (NF-κB), toll-like receptor (TLR4) by immunohistochemistry, gene expressions of caspase 3 and monocyte chemoattractant protein (MCP-1) besides histopathological investigations of renal cells.

KEY FINDINGS

Results showed beneficial effects of 8 weeks of treatment by nano selenium and sildenafil supported by improvement in kidney function, histopathological changes, and reduction in all of these parameters. These results supported molecular docking that indicated sildenafil had a high binding score and interactions with the HMGB1 receptor.

SIGNIFICANCE

The current study demonstrated a renoprotective effect of nano‑selenium and sildenafil by interfering at multiple pathways, especially the HMGB1/NF-κB signaling pathway.

Cysteine-Rich Whey Protein Isolate (CR-WPI) Ameliorates Erectile Dysfunction by Diminishing Oxidative Stress via DDAH/ADMA/NOS Pathway

Nitric oxide synthase- (NOS-) dependent endothelial dysfunction induced by oxidative stress (OS) is assumed to play a pivotal role in the pathogenesis and progression of diabetes mellitus-related erectile dysfunction (DMED). Cysteine-rich whey protein isolate (CR-WPI) is a widely used protein supplement and has been confirmed to reduce reactive oxygen species (ROS) by increasing cellular antioxidant glutathione (GSH). However, it is currently unknown whether CR-WPI elicits therapeutic effects in DMED. Here, we provide diabetic rats with CR-WPI to determine its effect on DMED and the underlying mechanisms. The results suggest that CR-WPI supplementation increased GSH biosynthesis and reduced ROS content and simultaneously upregulated the dimethylarginine dimethylaminohydrolase (DDAH)/asymmetrical dimethylarginine (ADMA)/nitric oxide synthase (NOS) metabolic pathway. Evaluation of intracavernous pressure (ICP) also showed an improvement of penile erectile function in CR-WPI-treated rats. The results of the vitro cell culture showed that glutathione pretreatment protected corpus cavernosum smooth muscle cells (CCSMC) from H₂O₂-induced apoptosis by decreasing Caspase 9 and Caspase 3 expressions. These results augur well for the potential therapeutic application of dietary CR-WPI supplementation for treating diabetic erectile dysfunction.

The therapeutic effect of ALT-711 on erectile function in rats treated with high-level AGEs (advanced glycation end products) containing diet

To investigate, if advanced glycation end products (AGEs) are involved in erectile dysfunction (ED) and also ALT-711, a cross-link breaker of AGEs, has the therapeutic potential against the development of ED in rats treated with high concentrated AGEs including food. For this purpose, 30 male Harlan Spraque-Dawley rats randomly were divided into three groups; (1) control rats treated with regular diet, (2) rats treated with high-level of AGE specific diet for 6 months, and (3) rats having AGE-diet treated with ALT-711 for the final 3 months of 6 months of AGE-diet period. Erectile response to cavernosal nerve stimulation (CNS), protein expression of neuronal nitric oxide synthase (nNOS) and levels of AGEs, Malondialdehyde (MDA), cyclic guanosine monophosphate (cGMP) were determined in penile tissues. Erectile responses to CNS and penile nNOS and cGMP content were significantly reduced, while AGEs and MDA were elevated in penises of Group-2. Treatment with ALT-711 reversed ED and depletion of both nNOS and cGMP. Additionally, ALT-711 treatment reduced penile tissue AGEs and MDA expression. In present study: rats without any co-morbidity such as diabetes mellitus (DM) and chronic renal failure (CRF) were treated with high-level AGEs containing food. Our results suggest that ALT-711 may be an interesting and promising approach in the treatment of AGEs-related ED.

Sodium 4-phenylbutyrate inhibits protein glycation

The production and accumulation of advanced glycation end-products (AGEs) are hypothesized to have a causal role in the development of the complications associated with aging and lifestyle-related diseases, such as diabetes, atherosclerosis and hyperlipidemia. Therefore, it is important to reduce the production and accumulation of AGEs. In the present study, the ability of sodium 4-phenylbutyrate (PBA) on inhibition of glycation was assessed. In vitro, PBA inhibited the glycation of albumin and collagen by up to 42.1 and 36.9%, respectively. Furthermore, when spontaneously diabetic KK mice were administered PBA (20 mg/day) or vehicle orally, glycosuria developed rapidly in the control mice, but after 6 weeks, only one treated mouse was glycosuric. In addition, the weight gain and HbA1c levels were significantly lower in the treated mice compared with the untreated mice (weight gain, 36.0 g vs. 39.4 g, P<0.01; HbA1C level, 3.96 vs. 4.78%, P<0.01; respectively). These results suggested that PBA also inhibited glycation in vivo. Further studies are required to determine whether PBA may be effective for the therapy or prevention of aging or lifestyle-related diseases caused by the accumulation of AGEs. The method of administration and the side-effects of PBA have already been established as PBA is already used clinically. Therefore, the repurposing of PBA for reducing AGE levels may be a potential option to reduce complications associated with aging.

Liraglutide Ameliorates Erectile Dysfunction via Regulating Oxidative Stress, the RhoA/ROCK Pathway and Autophagy in Diabetes Mellitus

Background

Erectile dysfunction (ED) occurs more frequently and causes a worse response to the first-line therapies in diabetics compared with nondiabetic men. Corpus cavernosum vascular dysfunction plays a pivotal role in the occurrence of diabetes mellitus ED (DMED). The aim of this study was to investigate the protective effects of glucagon-like peptide-1 (GLP-1) analog liraglutide on ED and explore the underlying mechanisms in vivo and in vitro.

Methods

Type 1 diabetes was induced in rats by streptozotocin, and the apomorphine test was for screening the DMED model in diabetic rats. Then they were randomly treated with subcutaneous injections of liraglutide (0.3 mg/kg/12 h) for 4 weeks. Erectile function was assessed by cavernous nerve electrostimulation. The corpus cavernosum was used for further study. In vitro, effects of liraglutide were evaluated by primary corpus cavernosum smooth muscle cells (CCSMCs) exposed to low or high glucose (HG)-containing medium with or without liraglutide and GLP-1 receptor (GLP-1R) inhibitor. Western blotting, fluorescent probe, immunohistochemistry, and relevant assay kits were performed to measure the levels of target proteins.

Results

Administration of liraglutide did not significantly affect plasma glucose and body weights in diabetic rats, but improved erectile function, reduced levels of NADPH oxidases and ROS production, downregulated expression of Ras homolog gene family (RhoA) and Rho-associated protein kinase (ROCK) 2 in the DMED group dramatically. The liraglutide treatment promoted autophagy further and restored expression of GLP-1R in the DMED group. Besides, cultured CCSMCs with liraglutide exhibited a lower level of oxidative stress accompanied by inhibition of the RhoA/ROCK pathway and a higher level of autophagy compared with HG treatment. These beneficial effects of liraglutide effectively reversed by GLP-1R inhibitor.

Conclusion

Liraglutide exerts protective effects on ED associated with the regulation of smooth muscle dysfunction, oxidative stress and autophagy, independently of a glucose- lowering effect. It provides new insight into the extrapancreatic actions of liraglutide and preclinical evidence for a potential treatment for DMED.

Effects of Orally Consumed Rosa damascena Mill. Hydrosol on Hematology, Clinical Chemistry, Lens Enzymatic Activity, and Lens Pathology in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is a multisystemic metabolic disorder that may affect the eyes, kidneys, vessels, and heart. Chronic hyperglycemia causes non-enzymatic glycation of proteins and elevation of the polyol pathway resulting in oxidative stress that damages organs. The current study aimed to investigate the dose-dependent effects of orally consumed Rosa damascena Mill. hydrosol on hematology, clinical biochemistry, lens enzymatic activity, and lens pathology in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced into male Sprague-Dawley rats by intraperitoneal administration of STZ (40 mg/kg body weight). Rose hydrosols containing 1515 mg/L and 500 mg/L total volatiles (expressed as citronellol) were introduced to rats orally for 45 days. Consumption of 1515 mg/L volatile containing rose hydrosol successfully ameliorated hematologic, hepatic, and renal functions. Hydrosols also attenuated hyperglycemia and decreased the advanced glycation end-product formation in a dose-dependent manner. Rose hydrosol components significantly increased the lens enzymatic activities of glutathione peroxidase and decreased the activity of aldose reductase to prevent cataractogenesis. Histopathological examinations of rat lenses also indicated that increasing the dose of rose hydrosol had a protective effect on lenses in diabetic conditions. Additionally, in silico modeling of aldose reductase inhibition with rose hydrosol volatiles was carried out for extrapolating the current study to humans. The present results suggest that rose hydrosol exerts significant protective properties in diabetes mellitus and has no toxic effect on all studied systems in healthy test groups.

Early administration of phosphodiesterase 5 inhibitors after induction of diabetes in a rat model may prevent erectile dysfunction

BACKGROUND

The possible role of phosphodiesterase 5 inhibitors (PDE5Is) in prevention of negative effect of diabetes mellitus (DM) on erectile function is not well settled.

OBJECTIVES

To investigate the effect of early administration of vardenafil on erectile function, cavernosal structure, and genes expression in a rat model of DM.

MATERIALS AND METHODS

This experimental study was carried out at Suez Canal University's research laboratory. This study was conducted on a total of 60 adult male Albino Wistar rats, aged 60-80 days and weighing an average of 200 g. Rats were equally divided into six groups of 10 rats each: Group I (sham); Group II (DM with no treatment); Groups III, IV, V, and VI received vardenafil started at day 1, week 4, week 8, and week 12 after induction of DM, respectively. Functional study assessment of all groups was performed before euthanization, and then tissues were harvested for histopathological, ultrastructural, and molecular examinations.

RESULTS

There was a significant difference of intracavernosal pressure between early (94 ± 2.18) and late (40.5 ± 1.94) treatment groups (p = 0.011). Histopathological and ultrastructural changes of DM with no treatment and late treatment groups showed distorted cavernous architecture and extensive fibrosis. There was significant difference of smooth muscle to collagen ratio between early and late treatment groups (p = 0.035). There was significant upregulation of nNOS(p = 0.021) and iNOS (p = 0.047) in early vs. late treatment group. The difference was insignificant in eNOS (p = 0.386) or TGF-β1(p = 0.149).

DISCUSSION AND CONCLUSION

Early treated rats with vardenafil had preserved erection and normal cavernosal structure, ultrastructure and gene expression of iNOS, nNOS, eNOS, and TGF-β1. Quantification of gene expression would improve our knowledge regarding cytokines expression and molecular background of DM-associated ED. Clinical application of this result may encourage early administration of PDE5I to prevent deleterious effects of DM on erectile function in newly diagnosed DM patients with probable uncontrolled blood glucose.

In vitro antioxidant, anti-glycation and immunomodulation activities of fermented blue-green algae Aphanizomenon flos-aquae

To clarify the antioxidant, anti-glycation and immunomodulatory capacities of fermented blue-green algae Aphanizomenon flos-aquae (AFA), hot aqueous extract suspensions made from 10% AFA were fermented by Lactobacillus plantarum AN7 and Lactococcus lactis subsp. lactis Kushiro-L2 strains isolated from a coastal region of Japan. The DPPH and O₂^- radical scavenging capacities and Fe-reducing power were increased in the fermented AFA. The increased DPPH radical scavenging capacity of the fermented AFA was fractionated to mainly < 3 kDa and 30-100 kDa. The increased O₂^- radical scavenging capacities were fractionated to mainly < 3 kDa. Anti-glycation activity in BSA-fructose model rather than BSA-methylglyoxal model was increased by the fermentation. The increased anti-glycation activity was fractionated to mainly 30-100 kDa. The NO concentration in the murine macrophage RAW264.7 culture media was high with the fermented AFA. The increased immunomodulation capacity was also fractionated to mainly 30-100 kDa. These results suggest that the fermented AFA is a more useful material for health foods and supplements.

Glycated proteins in nutrition: Friend or foe?

Advanced glycation end products (AGEs) are formed in in vivo, and accumulate in tissues and body fluids during ageing. Endogenous AGE-modified proteins show altered structure and function, and may interact with receptor for AGEs (RAGE) resulting in production of reactive oxygen species, inflammatory, atherogenic and diabetogenic responses. AGEs are also formed in thermally processed foods. Studies in rodents document that dietary AGEs are partially absorbed into circulation, and accumulate in different tissues. Knowledge on the health effects of high dietary intake of AGEs is incomplete and contradictory. In this overview we discuss the data from experimental and clinical studies, either those supporting the assumption that restriction of dietary AGEs associated with health benefits, or data suggesting that dietary intake of AGEs associates with positive health outcomes. We polemicize whether the effects of exaggerated intake or restriction of highly thermally processed foods might be straightforward interpreted as the effects of AGEs-rich vs. AGEs-restricted diets. We also underline the lack of studies, and thus a poor knowledge, on the effects of different single chemically defined AGEs administration, concurrent intake of different dietary AGEs, of load with dietary AGEs corresponding to the habitual diet in humans, and on those of dietary AGEs in vulnerable populations, such as infants and particularly elderly.

Diagnosis of erectile dysfunction can be used to improve screening for Type 2 diabetes mellitus

AIMS

To assess the diagnostic accuracy of four undiagnosed Type 2 diabetes mellitus risk scores accounting for erectile dysfunction status.

METHODS

This was a population-based cross-sectional study. Type 2 diabetes was defined according to a oral glucose tolerance test and self-reported physician diagnosis. Erectile dysfunction was defined according to the answer to the question, 'Have you had difficulties obtaining an erection in the last 6 months?' (yes/no). The risk scores used were the FINDRISC, LA-FINDRISC, American Diabetes Association score and the Peruvian Risk Score. A Poisson regression model was fitted to assess the association between Type 2 diabetes and erectile dysfunction. The area under the receiver-operating characteristic curve was estimated overall and by erectile dysfunction status.

RESULTS

A total of 799 men with a mean (sd) age of 48.6 (10.7) years were included in the study. The overall prevalence of Type 2 diabetes was 9.3%. Compared with healthy men, men with Type 2 diabetes had 2.71 (95% CI 1.57-4.66) higher chances of having erectile dysfunction. Having excluded men aware of Type 2 diabetes status (N=38), the area under the receiver-operating characteristic curve of three of the risk scores (not the American Diabetes Association score) improved among those who had erectile dysfunction in comparison with those who did not; for example, the area under the receiver-operating characteristic curve of the LA-FINDRISC score was 89.6 (95% CI 78.7-99.9) in men with erectile dysfunction and 76.5 (95% CI 68.5-84.4) overall.

CONCLUSIONS

In a population-based study, erectile dysfunction was more common in men with Type 2 diabetes than in the otherwise healthy men. Screening for erectile dysfunction before screening for Type 2 diabetes seems to improve the accuracy of well-known risk scores for undiagnosed Type 2 diabetes.

Cavernosal hydrogen sulfide levels are associated with nitric oxide and hemeoxygenase levels in diabetic rats

Penile erection is a neuromuscular event modulated by psyche, hormones as well as neurotransmitters. This pre-clinical study aimed to assess hydrogen sulfide (H₂S) relationship with nitric oxide (NO) and hemeoxygenase (HO) in the cavernous tissues of diabetic rats. Overall, 90 adult male rats were investigated (6 groups, n = 15 each). They were subdivided into the following groups; untreated rats, rats treated with H₂S donor/inhibitor, induced diabetic rats, diabetic rats treated with H₂S donor/inhibitor. At the 6th week, the rats were killed to assess cavernous tissue cGMP, NO, H₂S, HO enzyme activity levels. The rats treated with H₂S donor showed increased mean cavernous tissue cGMP, NO, H₂S, and HO enzyme activity levels whereas induced diabetic rats and rats treated with H₂S inhibitor showed significant decreases in these parameters compared with the untreated rats. On the other hands, diabetic rats treated with H₂S donor showed elevated mean cavernous tissue cGMP, NO, H₂S, and HO enzyme activity levels whereas diabetic rats treated with H₂S inhibitor showed significant decreases in these parameters compared with diabetic rats. Cavernous tissue H₂S levels exhibited significant positive correlations with the cavernous tissue levels cGMP, NO, and HO enzyme activity levels. From these results, it could be concluded that cavernous tissues H₂S plays a role of male sexual health by affecting cavernous tissues NO and HO enzyme activity in general and in diabetics in particular.

Protective effect of exendin-4 treatment on erectile dysfunction induced by chronic methylglyoxal administration in rats

OBJECTIVE

The aim of this study was to investigate the effect of chronic exendin-4 (Ex-4) treatment on corpus cavernosum (CC) dysfunction in methylglyoxal (MGO) administered rats.

METHODS

Male rats were divided into four groups as control, MGO (75 mg/kg/day in drinking water for 12 weeks), MGO + low-dose Ex-4 (0.1 μg/kg twice daily subcutaneously for 12 weeks concomitant with MGO), and MGO + high-dose Ex-4 (1 μg/kg twice daily subcutaneously for 12 weeks concomitant with MGO). Nitric oxide (NO)-mediated endothelium-dependent and neurogenic CC relaxations were evaluated by acetylcholine (ACh) and electrical field stimulation (EFS), respectively. Apoptosis was determined by TUNEL. Endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS), NADPH oxidase subunit gp91phox (NOX2), and Rho kinase (ROCK2) expressions in CC were investigated by immunohistochemistry. Levels of the malondialdehyde (MDA) and advanced oxidation protein products (AOPP) were also measured.

RESULTS

In MGO administered rats, both endothelium-dependent and neurogenic CC relaxations were significantly impaired as compared to controls. Apoptotic cell death and levels of MDA and AOPP increased significantly in MGO administered rats. eNOS and p-eNOS expressions decreased significantly in MGO group, while gp91phox expressions increased significantly. The diminished relaxation in response to ACh or EFS as well as the changes in expression of proteins in MGO groups were significantly improved by exendin-4 treatment. TUNEL-positive cells, and levels of MDA and AOPP in MGO group rats were also significantly reduced by exendin-4.

CONCLUSION

Exendin-4 treatment improves NO-mediated CC relaxations in MGO administered rats probably by inhibiting NADPH oxidase.

Icariside II ameliorates endothelial dysfunction by regulating the MAPK pathway via miR-126/SPRED1 in diabetic human cavernous endothelial cells

Aim

The aim of the study was to investigate whether miR-126, a regulator of MAPK signaling via targeting sprouty-related EVH1 domain-containing protein 1 (SPRED1) mRNA, is involved in the process by which icariside II (ICA II) ameliorates endothelial dysfunction in human cavernous endothelial cells (hCECs) exposed to a diabetic-like environment.

Materials and methods

Primary hCECs were isolated and divided into three groups, normal control, diabetes mellitus (DM), and DM treated with ICA II. The cell proliferation and migration abilities of the hCECs were examined. The expression levels of endothelial-related microRNAs and relative target mRNAs (SPRED1, phosphoinositol-3 kinase regulatory subunit 2, and vascular cell adhesion molecule 1) of miR-126 were determined by real-time PCR. The protein expression of endothelial nitric oxide synthase, receptor for advanced glycation end products, and SPRED1, and MAPK signaling activities was determined by Western blot analysis. In addition, miR-126 agomir and antagomir were used for transfection into hCECs to further testify the association between miR-126 and its targeting mRNA SPRED1.

Results

hCECs induced with glucose plus advanced glycation end product-BSA showed a significant decrease in endothelial nitric oxide synthase, Ki-67, and miR-126 expression; a downregulated cell migration ability and an increased receptor for advanced glycation end products level. ICA II could partially reverse these changes. SPRED1 mRNA showed a contrary tendency with the miR-126-3p changes. The level of SPRED1 protein increased after the hCECs were induced with glucose plus advanced glycation end product-BSA, and ICA II could rescue its aberrant expression. In addition, the MAPK pathway was downregulated in the hCECs under diabetic conditions, and ICA II could partially enhance its signaling activities. miR-126 was obviously downregulated, and SPRED1 was accordingly upregulated after miR-126 antagomir transfection, while ICA II treatment could recover the expressions of both miR-126 and SPRED1. Moreover, the upregulation of miR-126 and the inhibition of SPRED1 were noticed in the diabetic hCECs by further transfection with miR-126 agomir.

Conclusion

ICA II could ameliorate endothelial dysfunction by regulating the MAPK pathway via miR-126/SPRED1 in hCECs exposed to a diabetic-like environment, and ICA II might be a protective agent for endothelial function in diabetic ED.

Salidroside Protects Against Advanced Glycation End Products-Induced Vascular Endothelial Dysfunction

Background

Salidroside, the major active compound in Rhodiola, has been reported to provide beneficial effects on cardiovascular diseases, but its effects on diabetes-induced vascular endothelial dysfunction are less known. Here, we examined the protective effects of salidroside on endothelial function in diabetes and explored the potential underlying mechanism.

Material/Methods

First, we assessed the endothelium-dependent relaxation response to acetylcholine, with or without salidroside treatment, in aortas isolated from Sprague-Dawley rats. Then, cell viability, oxidative biomarkers, and protein expression were tested to determine the effect of salidroside treatment on human umbilical vein endothelial cells (HUVECs) in vitro.

Results

Advanced glycation end product (AGE)-induced endothelial dysfunction was significantly improved by salidroside treatment (P<0.05), as shown by a reduced relaxation response to the vasodilator acetylcholine. Further, incubation with salidroside restored NO levels and reduced reactive oxygen species formation in AGE-stimulated HUVECs in a concentration-dependent manner (P<0.05). We also showed that nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) and nuclear factor kappa B (NF-κB) signaling was critical for the salidroside-mediated beneficial regulation.

Conclusions

Our results demonstrate that salidroside protects against AGE-induced endothelial dysfunction, and its effects may be in part attributed to the induction of HO-1 and attenuation of phosphorylated NF-κB p65.

TNF-α antagonism with etanercept enhances penile NOS expression, cavernosal reactivity, and testosterone levels in aged rats

Erectile dysfunction (ED) has been reported to be associated with inflammation. This study investigated the effects of tumor necrosis factor alpha (TNF-α) inhibitor etanercept on penile neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) expressions, testosterone concentrations, neurogenic and endothelium-dependent relaxations of corpus cavernosum (CC), and circulating and cavernosal levels of inflammatory markers in aged rats. Animals were separated into control, aged, and etanercept-treated aged groups. Aged rats displayed significantly increased serum and cavernosal TNF-α, C-reactive protein (CRP), monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule (ICAM-1) levels, and decreased penile nNOS and eNOS expressions and serum testosterone levels compared with controls. In etanercept-treated aged group, NOS expressions were similar to that of the control group. The circulating and cavernosal concentrations of TNF-α, CRP, MCP-1, ICAM-1, and testosterone were also normalized by etanercept. Neurogenic and endothelium-dependent relaxant responses significantly decreased in aged rats and etanercept treatment markedly improved these relaxation responses. Our findings indicate that aging decreases penile NOS expression, neurogenic and endothelium-dependent relaxations of CC, and also suppresses serum testosterone levels by inducing inflammatory response that may contribute to the development of ED. TNF-α antagonism may be a novel strategy to treat aging-associated ED.

Erectile Dysfunction: An Underestimated Presentation in Patients with Diabetes Mellitus

INTRODUCTION

Erectile dysfunction (ED) is a common complication of diabetes mellitus. ED, like other sexual disorders, is often under-reported and under-diagnosed, as talking about sex is considered a taboo in our society.

METHODOLOGY

All the male patients with diabetes mellitus (with or without active complaints of ED) attending Medicine or Psychiatry OPD of the institute during the study period were enrolled in the study. They were investigated for their body-mass index (BMI), blood sugar and lipid profile; and were assessed on HAM-D, General Health Questionnaire-30, IIEF, sex myth checklist and QOL Instrument for Indian Diabetes Patients (QOLID).

RESULT AND DISCUSSION

In the present study, a total of 138 diabetic patients were assessed, and those with severe ED were found to have poor glycemic control, worse lipid profile, higher body mass index, later age of onset, and longer duration of untreated diabetes as compared to non-ED patients. ED patients also scored higher on depression rating scale, had poorer general health and quality of life (QOL). Early attention to ED in diabetic patients can improve general health and QOL of the sufferers.

CONCLUSION

DM patients with poor glycemic control and advanced age have a higher propensity of developing severe ED, which further deteriorates the already compromised health & QOL.

Protective effects of physiological testosterone on advanced glycation end product‑induced injury in human endothelial cells

The effect of testosterone, a sex steroid, on endothelial cells is controversial as it is uncertain if it has a protective effect on them. Whether physiological testosterone can inhibit the deleterious effects of advanced glycation end products (AGEs) on endothelial cells remains to be elucidated. The present study focused on elucidating the effect of testosterone on the injury of endothelial cells induced by AGEs. Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and treated with AGEs in the presence or absence of various concentrations of testosterone. The cell viability in each group was measured using an MTS assay. Early-stage apoptosis was detected using flow cytometry with Annexin V-fluorescein isothiocyanate/propidium iodide double staining, and the expression levels of apoptosis-associated proteins, B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and caspase-3, were determined using western blot analysis. Oxidative stress and pro-inflammatory parameters in the medium were evaluated using an enzyme-linked immunosorbent assay. The MTS results showed that AGEs significantly decreased the proliferation of HUVECs, whereas a physiological concentration of testosterone alleviated this damage. Physiological concentrations of testosterone protected the HUVECs from AGE-induced apoptosis, mediated by caspase-3 and Bax/Bcl-2. In addition, treatment of the HUVECs with AGEs caused a significant decrease in anti-oxidative parameters, but increased the concentrations of malondialdehyde and tumor necrosis factor-α. The activation of Janus kinase 2 and signal transducer and activator of transcription 3 was significantly increased by incubation with AGEs. However, pre-incubation with a physiological concentration of testosterone attenuated these changes. Therefore, the data obtained in the present study established the potential role of physiological testosterone in ameliorating AGE-induced damage in HUVECs.

Skin autofluorescence (a marker for advanced glycation end products) and erectile dysfunction in diabetes

AIM

Although diabetes-related erectile dysfunction (ED) has many etiological factors, little is known about the putative pathophysiological role of advanced glycation end products (AGEs). Skin autofluorescence is a noninvasive marker of AGEs. Recent studies have evidenced a relationship between skin autofluorescence and several complications of diabetes. We hypothesized that AGEs (assessed by skin autofluorescence) are associated with ED in diabetes patients.

METHODS

Between March 2014 and April 2015, 42 patients with type 1 diabetes (T1D) and 44 patients with type 2 diabetes (T2D) were consecutively enrolled in a descriptive, cross-sectional study and compared to 54 healthy controls. ED was evaluated via the 5-item version of the International Index of Erectile Function (IIEF-5). Skin autofluorescence was measured on the volar aspect of the arm with an AGE-Reader.

RESULTS

Patients with diabetes had a mean±standard deviation age of 50±15 and a mean duration of diabetes of 16±12years. Skin autofluorescence was strongly and significantly correlated with the IIEF-5 score in the T1D subgroup (r=-0.52; P=0.004), the T2D subgroup (r=-0.32; P<0.03) and in the whole group of diabetic patients (r=-0.49; P<0.0001). In multivariate analyses that controlled for potentially confounding clinical and biochemical factors, only skin autofluorescence was still significantly correlated with the IIEF-5 score (P<0.0001). A receiver operating characteristic analysis revealed that a skin autofluorescence value ≥3.2AU determined severe ED with a sensitivity of 60% and a specificity of 87% in diabetic patients.

CONCLUSION

Skin autofluorescence is significantly associated with ED in diabetes, independently of classical confounding factors.

Prevalence of Sexual Dysfunction and Associated Risk Factors in Middle-Aged and Elderly Korean Men in Primary Care

Although several studies have individually investigated the risk factors for erectile dysfunction (ED), premature ejaculation (PE), and late-onset hypogonadism (LOH), few studies have considered ED, PE, and LOH as categories of sexual dysfunction (SD) within the same population. We therefore aimed to investigate the prevalence of SD and its associated risk factors among men in primary care. Study participants were enrolled by 18 family physicians from 15 hospital-based family practices in Korea between August 2010 and May 2011. Participants answered a questionnaire regarding their demographic characteristics and lifestyle factors as well as the Korean versions of the Androgen Deficiency in the Aging Male, the International Index of Erectile Function, and the Premature Ejaculation Diagnostic Tool questionnaires. SD prevalence was 64.9% among study participants who were ≥ 40 years of age. ED prevalence was 43.7%, PE prevalence was 38.6%, and LOH prevalence was 16.8%. SD prevalence was significantly associated with increased age, overweight, hypertension, diabetes, and depression. These findings highlight the importance of screening questions for SD in primary care, especially among older male patients with the identified risk factors.

Effects of prolonged ingestion of epigallocatechin gallate on diabetes type 1-induced vascular modifications in the erectile tissue of rats

Diabetes Mellitus type 1 is a metabolic disease that predisposes to erectile dysfunction, partly owing to structural and molecular changes in the corpus cavernosum (CC) vessels. The aim of this study was to determine the effects of early treatment with the antioxidant epigallocatechin gallate (EGCG) in cavernous diabetes-induced vascular modifications. Diabetes was induced in two groups of young Wistar rats; one group was treated with EGCG for 10 weeks. A reduction in smooth muscle content was observed in the CC of diabetic rats, which was significantly attenuated with EGCG consumption. No differences were observed among groups, neither in the expression of VEGF assayed by western blotting nor in the immunofluorescent labeling of vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2). VEGFR2 was restricted to the endothelium, whereas VEGF and VEGFR1 co-localized in the smooth muscle layer. With regard to the Angiopoietin/Tie-2 system, no quantitative differences in Angiopoietin 1 were observed among the experimental groups. Ang1 localization was restricted to the smooth muscle layer, and receptor Tie2 and Angiopoietin 2 were both expressed in the endothelium. In brief, our results suggest that EGCG consumption prevented diabetes-induced loss of cavernous smooth muscle but does not affect vascular growth factor expression in young rats.

Antioxidant Potential and Ability of Phloroglucinol to Decrease Formation of Advanced Glycation End Products Increase Efficacy of Sildenafil in Diabetes-Induced Sexual Dysfunction of Rats

INTRODUCTION

Diabetes-induced sexual dysfunction is associated with an increase in oxidative stress. Scavengers of reactive oxygen species (ROS) have been shown to reduce oxidative stress and aid in the management of sexual dysfunction in diabetes.

AIM

The aim of the study was to test the hypothesis that antioxidant, which scavenge ROS and reduce formation of advanced glycation end products (AGEs), can potentiate efficacy of phosphodiesterase type 5 inhibitors in diabetes-induced sexual dysfunction that is associated with oxidative stress.

MATERIALS AND METHODS

Effect of phloroglucinol and sildenafil on serum glucose level, sexual function, penile smooth muscle : collagen ratio, and phenylephrine precontracted corpus cavernosum smooth muscle (CCSM) was studied. The ability of phloroglucinol to reduce the formation of AGEs and its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) was also evaluated.

MAIN OUTCOME MEASURES

Antioxidant potential of phloroglucinol was studied in addition to its effect on diabetes-induced sexual dysfunction in presence and absence of sildenafil.

RESULTS

Phloroglucinol (50 mg/kg, p.o.) significantly decreased serum glucose level and increased sexual function in streptozotocin-induced diabetic rats when compared with diabetic control rats. Sildenafil (5 mg/kg, p.o.) had no effect on glycemia but significantly increased sexual function of diabetic rats. Coadministration of phloroglucinol increased the efficacy of sildenafil by improving sexual function. Treatment of diabetic rats with phloroglucinol + sildenafil maintained smooth muscle : collagen levels similar to that of normal rat penile tissue. Phloroglucinol decreased formation of AGEs and significantly scavenged DPPH radical activity in vitro. Sildenafil relaxed isolated CCSM of normal rat and diabetic rat significantly, but phloroglucinol did not show any significant effect. Phloroglucinol also inhibited human CYP3A4 enzyme activity in vitro.

CONCLUSION

Phloroglucinol coadministration increases efficacy of sildenafil in diabetes-induced sexual dysfunction. However, further studies are required to ascertain the benefits of phloroglucinol owing to its undesirable CYP3A4 inhibition activity.

Basic Science Evidence for the Link Between Erectile Dysfunction and Cardiometabolic Dysfunction

INTRODUCTION

Although clinical evidence supports an association between cardiovascular/metabolic diseases (CVMD) and erectile dysfunction (ED), scientific evidence for this link is incompletely elucidated.

AIM

This study aims to provide scientific evidence for the link between CVMD and ED.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current literature on basic scientific support for a mechanistic link between ED and CVMD, and deficiencies in this regard with a critical assessment of current preclinical models of disease.

RESULTS

A link exists between ED and CVMD on several grounds: the endothelium (endothelium-derived nitric oxide and oxidative stress imbalance); smooth muscle (SM) (SM abundance and altered molecular regulation of SM contractility); autonomic innervation (autonomic neuropathy and decreased neuronal-derived nitric oxide); hormones (impaired testosterone release and actions); and metabolics (hyperlipidemia, advanced glycation end product formation).

CONCLUSION

Basic science evidence supports the link between ED and CVMD. The Committee also highlighted gaps in knowledge and provided recommendations for guiding further scientific study defining this risk relationship. This endeavor serves to develop novel strategic directions for therapeutic interventions.

Penile Dimensions of Diabetic and Nondiabetic Men With Erectile Dysfunction: A Case-Control Study

This study aimed to report penile dimensions in diabetic and nondiabetic men with erectile dysfunction (ED) and correlate their dimensions with other study variables. A case-control study was designed through retrospective data analysis of diabetic and nondiabetic patients consulting for ED and a control group ( n = 105, each group). Study data retrieved included history, clinical evaluation, and penile dimensions (pendulous length [PL], total length [TL], and circumference [CF]) at flaccid and erect states. Results identified that patients had lower values (mean, cm) for almost all penile dimensions. The diabetic patients identified significant differences in most dimensions, whether in flaccid (PL: 7.46 vs. 7.51 and 7.81, p = .11; TL: 11.8 vs. 12.77 and 12.88, p = .000; CF: 8.84 vs. 9.1 and 9.14, p = .016) or erect state (PL: 9.66 vs. 9.61 and 10, p = .092; TL: 13.96 vs. 14.88 and 15.04, p = .000; CF: 11.56 vs. 12.06 and 11.92, p = .018) as compared with the nondiabetic patients and controls, respectively. No significant correlation was detected between the dimensions and age, durations of diabetes and ED, or erectile function scores. In conclusion, diabetic and nondiabetic patients with ED presented, in varying degrees, significant decline in their penile dimensions, and this was more prevalent in diabetic patients. As changes in penile size could be a silent corollary of comorbidities, monitoring the changes in penile dimensions should be an important component of the clinical checkup of any patient with ED, especially a diabetic patient.

Distribution of advanced glycation end products and their receptor in the stomach of diabetic rats

AIM: To observe the distribution of advanced glycation end products (AGEs) and their receptor (RAGE) in the stomach of diabetic rats.

METHODS: Diabetes mellitus (DM) and control (CON) rats were reared for eight weeks. Fasting plasma glucose (FPG), glycated serum protein (GSP) and gastric layer thickness were measured. The expression of AGEs and RAGE was detected by immunohistochemical staining.

RESULTS: The thickness of the mucosa (781.47 μm ± 137.82 μm vs 709.85 μm ± 169.41 μm) and submucosa (233.39 μm ± 134.05 μm vs 109.32 μm ± 44.43 μm) increased significantly in the DM group compared with the CON group (P < 0.05). The expression of AGEs and RAGE in the mucosa (5.66 ± 1.90 vs 2.25 ± 0.52, 2.79 ± 0.54 vs 1.70 ± 0.30) and muscle (37.37 ± 7.38 vs 24.32 ± 4.02, 4.26 ± 0.80 vs 3.59 ± 0.37) layers of the stomach was significantly higher in the DM group than in the CON group (P < 0.05).

CONCLUSION: The expression of AGEs and RAGE is up-regulated in the stomach of diabetic rats. The increased levels of AGE and RAGE in gastric tissue may contribute to diabetic gastrointestinal dysfunction.

Impact of ER stress-regulated ATF4/p16 signaling on the premature senescence of renal tubular epithelial cells in diabetic nephropathy

Premature senescence is an important event during diabetic nephropathy (DN) progression. Here, we investigated the role of endoplasmic reticulum (ER) stress-regulated activation of transcription factor 4 (ATF4)/p16 signaling in the premature senescence of renal tubular epithelial cells (RTECs) during DN development. In the renal tissues of Type 2 DN patients, we detected an increased number of senescent cells; elevated deposition of advanced glycation end products (AGEs); upregulated expression of ER stress marker, glucose-regulated protein 78; as well as overexpression of ATF4 and p16. Similarly, these phenomena were also observed in cultured mouse RTECs following AGE treatment. Interestingly, AGE-induced p16 expression and premature senescence were successfully attenuated by ER stress inhibitor and ATF4 gene silencing. Moreover, AGE-induced premature senescence was mimicked by ER stress inducers and ATF4 overexpression, while suppressed by p16 gene silencing. In addition, ER stress inducers can augment ATF4 expression. Therefore, our results demonstrate that the ER stress-regulated ATF4/p16 pathway is involved in the premature senescence of RTECs during DN progression.

A comprehensive review of urologic complications in patients with diabetes

Diabetes Mellitus (DM) is a chronic disease characterized by hyperglycemia, as a result of abnormal insulin production, insulin function, or both. DM is associated with systemic complications, such as infections, neuropathy and angiopathy, which involve the genitourinary tract. The three most significant urologic complications include: bladder cystopathy, sexual dysfunction and urinary tract infections. Almost half of the patients with DM have bladder dysfunction or cystopathy, which can be manifested in women as hypersensitivity (in 39-61% of the diabetic women) or neurogenic bladder. In males it can be experienced as lower urinary tract symptoms (in 25% of diabetic males with a nearly twofold increased risk when seen by age groups). Additionally, an increased prostate volume affects their micturition as well as their urinary tract. Involving sexual dysfunction in women, it includes reduced libido, decreased arousal, clitoral erectile dysfunction and painful or non-sensitive intercourse; and in diabetic males it varies from low libido, ejaculatory abnormalities and erectile dysfunction. Globally, sexual disorders have a prevalence of 18-42%. Erectile dysfunction is ranked as the third most important complication of DM. Urinary tract infections are observed frequently in diabetic patients, and vary from emphysematous infections, Fournier gangrene, staghorn infected lithiasis to repetitive bacterial cystitis. The most frequent finding in diabetic women has been lower urinary tract infections. Because of the high incidence of obesity worldwide and its association with diabetes, it is very important to keep in mind the urologic complication associated with DM in patients, in order to better diagnose and treat this population.

Effects of puerarin in STZ-induced diabetic rats by oxidative stress and the TGF-β1/Smad2 pathway

The present study aimed to investigate the effects of pueraria on streptozotocine (STZ)-induced renal damage and its possible mechanisms. Wistar rats were randomly divided into five groups: the normal control group, diabetes untreated model group, two dosages (140 and 200 mg per kg bw per day) of puerarin treatment groups and a positive control group. Rats were studied 30 days after the STZ treatment, and the diabetes untreated model group presented significantly higher kidney index, blood glucose, triglyceride (TG), total cholesterol (TC), malondialdehyde (MDA), interferon-γ (IFN-γ), and IFN-γ/IL-4 levels, lower body weight, fasting blood insulin (FPI), IL-4, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and nitric oxide (NO) levels and worse renal function (higher blood urea nitrogen (BUN), serum creatinine (SCr), urine protein (UP) levels and glomerular extracellular matrix (relative area)) compared with the normal control group (p < 0.05). Furthermore, RT-FQ-PCR and western blot analyses showed that TGF-β1, Smad2, CTGF and FN protein and mRNA expression was significantly increased in the diabetes untreated model group compared with the normal control group. In contrast, the puerarin treatment dose-dependently significantly decreased the kidney index, blood glucose, TG, TC, MDA, IFN-γ, and IFN-γ/IL-4 levels, increased the body weight, FPI, IL-4, SOD, CAT, GSH-Px and NO levels and improved the renal function (lower BUN, SCr, UP levels and glomerular extracellular matrix (relative area)) in puerarin treatment groups (p < 0.05). In addition, the mRNA and protein expression of TGF-β1, Smad2, CTGF and FN was downregulated. It can be concluded that puerarin exerted its anti-diabetic effect on the STZ-treated rats through the inhibition of the TGF-β1/Smad2 pathway.

Advanced glycation end products inhibit intracellular calcium concentration in colon smooth muscle cells in a protein kinase C-dependent manner

AIM: To investigate the effect of advanced glycation end products (AGEs) on intracellular calcium concentration in isolated colonic smooth muscle cells and the possible mechanisms involved.

METHODS: Colonic smooth muscle cells were isolated from normal adult rats, and immumofluorescence staining for α-actin was used to identify smooth muscle cells. The responsiveness of colonic smooth muscle cells to AGEs was measured by confocal laser scanning microscopy. Intracellular Ca²⁺ concentration ([Ca²⁺]i) was determined by Fluo3/AM based digital microfluorimetric measurement. Protein kinase C (PKC) activity was detected by PKC activity assay. PKC inhibitor chelerythrine was used to examine the role of PKC in AGEs-mediated inhibition of [Ca²⁺]i in colonic smooth muscle cells.

RESULTS: Colonic smooth muscle cells were successfully isolated from normal rats and identified by immunofluorescence staining. AGEs inhibited [Ca²⁺]i in a concentration-dependent manner. AGEs at a concentration of 50 or 100 µg/mL significantly inhibited the mean [Ca²⁺]i compared with the control group (56.7% ± 3.6%, 78.6% ± 5% vs 99.6% ± 3.1%, P < 0.05, P < 0.01). PKC activity increased in SMCs treated with 50 µg/mL or 100 µg/mL of AGEs compared with the control group. Pretreatment with chelerythrine (1 µmol/L) reduced AGEs-mediated inhibition of [Ca²⁺]i (70.7% ± 3.7% vs 87.1% ± 2.5%, P < 0.05).

CONCLUSION: AGEs inhibit [Ca²⁺]i in colonic smooth muscle cells in a PKC-dependent manner.

Lipocalin-2 elicited by advanced glycation end-products promotes the migration of vascular smooth muscle cells

Advanced glycation end-products (AGEs) play key roles in the development of diabetic vascular complications by activating the proliferation and migration of vascular smooth muscle cells. Here, we identified an increase of the migratory properties of human aortic smooth muscle cells (HASMC) through AGE-induced expression of lipocalin-2 (LCN2). Because the AGE-elicited expression of LCN2 was diminished by an antibody against the AGE receptor (RAGE), diphenylene iodonium (DPI), N-acetyl cysteine, LY294002, and SP600125, we suggest that AGEs enhance the expression of LCN2 via a RAGE-NADPH oxidase-reactive oxygen species pathway, leading to the phosphorylation of PI3K-Akt and JNK in HASMCs. In addition, a chromatin immunoprecipitation assay and promoter assay revealed that CCAAT/enhancer binding protein β is crucial for AGE-induced expression of LCN2. However, any other AGE-related signaling pathway, including ERK1/2, p38, NF-κB, and AP-1, did not affect the AGE- induced expression of LCN2. Knockdown of LCN2 expression by shRNA showed that AGE-elicited LCN2 expression enhanced the invasive and migratory properties of HASMCs, but showed no effect on cell proliferation. Considering the importance of HASMC migration in the development of atherosclerosis, our study provides a novel insight into diabetic vascular complications.

Modulation of liver function, antioxidant responses, insulin resistance and glucose transport by Oroxylum indicum stem bark in STZ induced diabetic rats

A decoction of stem bark of Oroxylum indicum Vent. (OI) is taken (2-3 times/day) by the tribal people of Sikkim, India to treat diabetes but scientific validation of its overall potential is lacking. Present study was aimed to assess in vitro antihyperglycemic activity of standardized OI extract using inhibition of α-glucosidase, BSA glycation and enhancement of insulin sensitivity. Antidiabetic and antioxidant modulatory effects of OI extract along with the blood biomarkers of toxic response were studied in streptozotocin (STZ) induced diabetic rats. In vitro analysis showed strong antioxidant capacity of OI -and potential to inhibit BSA glycation and α-glucosidase activity which was comparable to standard counterparts. Extract also improved insulin sensitivity in mature 3T3-L1 adipocytes. In vivo effects of OI extract (oral 250 mg/kg b.wt.) on STZ induced type II diabetic rats normalized the antioxidant status (p≤0.01). Analysis of blood biomarkers of toxic response indicated its safety. Lowering of total cholesterol and HDL levels (p≤0.05) and restoration of glycated Hb (p≤0.01) were also found in OI treated diabetic rats. HOMA-IR, QUICKI analysis along with area under the curve analysis showed the capacity of OI extract to enhance the insulin sensitivity significantly (p≤0.01) which was confirmed by increased GLUT-4 translocation in skeletal muscles.

Carbonyl stress in aging process: role of vitamins and phytochemicals as redox regulators

There is a growing scientific agreement that the cellular redox regulators such as antioxidants, particularly the natural polyphenolic forms, may help lower the incidence of some pathologies, including metabolic diseases like diabetes and diabesity, cardiovascular and neurodegenerative abnormalities, and certain cancers or even have anti-aging properties. The recent researches indicate that the degree of metabolic modulation and adaptation response of cells to reductants as well as oxidants establish their survival and homeostasis, which is linked with very critical balance in imbalances in cellular redox capacity and signaling, and that might be an answer the questions why some antioxidants or phytochemicals potentially could do more harm than good, or why some proteins lose their function by increase interactions with glyco- and lipo-oxidation mediates in the cells (carbonyl stress). Nonetheless, pursue of healthy aging has led the use of antioxidants as a means to disrupt age-associated physiological dysfunctions, dysregulated metabolic processes or prevention of many age-related diseases. Although it is still early to define their exact clinical benefits for treating age-related disease, a diet rich in polyphenolic or other forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders. It is now clear that any deficiency in antioxidant vitamins, inadequate enzymatic antioxidant defenses can distinctive for many age-related disease, and protein carbonylation can used as an indicator of oxidative stress associated diseases and aging status. This review examines antioxidant compounds and plant polyphenols as redox regulators in health, disease and aging processes with hope that a better understanding of the many mechanisms involved with these distinct compounds, which may lead to better health and novel treatment approaches for age-related diseases.