Adherence to Mediterranean diet and advanced glycation endproducts in patients with diabetes

BACKGROUND In recent years,American Diabetes Association started to strongly advocate the Mediterranean diet(MD)over other diets in patients with diabetes mellitus(DM)because of its beneficial effects on glycemic control and cardiovascular(CV)risk factors.Tissue levels of advanced glycation endproducts(AGEs)emerged as an indicator of CV risk in DM.Skin biopsy being invasive,the use of AGE Reader has been shown to reflect tissue AGEs reliably.AIM To examine the association between adherence to MD and AGEs in patients with DM type II.METHODS This cross-sectional study was conducted on 273 patients with DM type II.A survey questionnaire was composed of 3 separate sections.The first part of the questionnaire included general data and the habits of the participants.The second part aimed to assess the basic parameters of participants’diseases and associated conditions.The third part of the questionnaire was the Croatian version of the 14-item MD service score(MDSS).AGEs levels and associated CV risk were measured using AGE Reader(DiagnOptics Technologies BV,Groningen,The Netherlands).RESULTS A total of 27(9.9%)patients fulfilled criteria for adherence to MD,with a median score of 8.0(6.0-10.0).Patients with none/limited CV risk had significantly higher percentage of MD adherence in comparison to patients with increased/definite CV risk(15.2%vs 6.9%,P=0.028),as well as better adherence to guidelines for nuts(23.2%vs 12.6%,P=0.023)and legumes(40.4%vs 25.9%,P=0.013)consumption.Higher number of patients with glycated hemoglobin(HbA1c)<7%adhered to MD when compared to patients with HbA1c>7%(14.9%vs 7.3%,P=0.045).Moreover,those patients followed the MDSS guidelines for eggs(33.0%vs 46.8%,P=0.025)and wine(15.6%vs 29.8%,P=0.006)consumption more frequently.MDSS score had significant positive correlation with disease duration(r=0.179,P=0.003)and negative correlation with body mass index(BMI)values(r=-0.159,P=0.008).In the multiple linear regression model,BMI(β±SE,-0.09±0.04,P=0.037)and disease duration(β±SE,0.07±0.02,P<0.001)remained significant independent correlates of the MDSS score.Patients with HbA1c>7%think that educational programs on nutrition would be useful for patients in significantly more cases than patients with HbA1c<7%(98.9%vs 92.6%,P=0.009).CONCLUSION Although adherence to MD was very low among people with diabetes,we demonstrated that adherence to MD is greater in patients with lower CV risk,longer disease duration,and well-controlled glycaemia.

Influence of tonifying kidney recipe on advanced glycation endproducts and lipid peroxidation in ovariectomized rats

BACKGROUND： Previous studies have demonstrated that reduced estrogen levels may accelerate the formation of advanced glycation endproducts （AGE） in brain tissue, raise the concentration of lipid peroxidation products in vivo, and speed up deterioration of learning and memory. A tonifying kidney recipe is hypothesized to improve the ability of learning and memory in ovariectomized rats by downregulating AGE and lipid peroxidation products. OBJECTIVE： To simulate a postmenopausal state, bilateral ovariectomy （OVX） was performed in rats, and the effects of tonifying kidney recipe （TKR） on AGE and lipid peroxidation in the rat cerebral cortex, hippocampus, and blood serum levels was measured. In addition, the effects on learning and memory were evaluated, and the effect of AGE -specific inhibitor aminoguanidine （AG） was compared with TKR. DESIGN, TIME AND SETTING： A randomized, in vivo, control experiment was performed at the scientific research center （Provincial Key Laboratory） in the Fourth Hospital of Hebei Medical University （Shijiazhuang, Hebei Province, China） from May 2005 to January 2007. MATERIALS： Forty healthy, adult, female, Sprague Dawley rats were used for this study. TKR was composed of prepared rehmannia rhizome, epimedium herb, desert-living cistanche, and Szechwan lovage rhizome, which were provided by Shijiazhuang Medical Materials Company （China）. A TKR extraction was prepared for further use. AG was provided by Sigma （USA）. Forty rats were randomly divided into four groups： sham, OVX, AG, and TKR, with 10 rats in each group. METHODS： The rat ovaries were resected in the OVX, AG, and TKR groups, whereas the same volume of fat was resected in the sham group. At four weeks after OVX, the AG group received 1% AG water solution by lavage; the TKR group was administrated by lavage once per day at a dose of 6.3 g （crude drug）/kg; OVX and sham groups received equal volumes of tap water. MAIN OUTCOME MEASURES： Learning and memory behavior of rats was tested in a Y-electric maze 16 weeks after the OVX procedure. The contents of advanced glycation endproducts in the rat cerebral cortex, hippocampus, serum, and urine were detected by competitive ELISA and spectrofluorophotometer. The contents of lipid peroxidation in rat serum, cerebral cortex, and hippocampus were assayed using a biochemical method. RESULTS： Compared with the sham group, serum content of advanced glycation endproducts in the OVX group was significantly increased, and lipid peroxidation content increased in cerebral cortex, hippocampus, and serum （t = 3.04-4.22, P 〈 0.05 0.01）. Both AG and TKR decreased the amount of AGE in cerebral cortex and serum （t = 2.53, 3.64, P 〈 0.05, 0.01）, increased AGE urine content （t = 3.25 4.87, P 〈 0.01）, and decreased lipid peroxidation content in cerebral cortex, hippocampus, and serum （t = 2.80 3.70, P 〈 0.05 0.01）. In comparison to the OVX and sham groups, the correct escape rate in the Y-electric maze was significantly increased （t = 3.46, 3.28, P 〈 0.01）, and escape latency was significantly decreased （t=3.12, 2.48 P 〈 0.05） in the AG and TKR groups, which indicated that both AG and TKR improved learning and memory The OVX group had a significantly lower correct escape compared with the sham group （t = 4.21, P 〈 0.01 ）.CONCLUSION： The tonifying kidney recipe decreased deposition of advanced glycation endproducts and lipid peroxidation in ovariectomized rats, and concomitantly improved learning and memory. The effect of TKR was equal to that of AG.

Role of the receptor for advanced glycation end products in hepatic fibrosis

AIM： To study the role of advanced glycation end products （AGE） and their specific receptor （RAGE） in the pathogenesis of liver fibrogenesis. METHODS： In vitro RAGE expression and extracellular matrix-related gene expression in both rat and human hepatic stellate cells （HSC） were measured after stimulation with the two RAGE ligands, advanced glycation end product-bovine serum albumin （AGE- BSA） and N＇-（carboxymethyl） lysine （CML）-BSA, or with tumor necrosis factor-α （TNF-α）. In vivo RAGE expression was examined in models of hepatic fibrosis induced by bile duct ligation or thioacetamide. The effects of AGE-BSA and CML-BSA on HSC proliferation, signal transduction and profibrogenic gene expression were studied in vitro. RESULTS： In hepatic fibrosis, RAGE expression was enhanced in activated HSC, and also in endothelial cells, inflammatory cells and activated bile duct epithelia. HSC expressed RAGE which was upregulated after stimulation with AGE-BSA, CML-BSA, and TNF-α.RAGE stimulation with AGE-BSA and CML-BSA did not alter HSC proliferation, apoptosis, fibrogenic signal transduction and fibrosis- or fibrolysis-related gene expression, except for marginal upregulation of procollagen α1（ I ） mRNA by AGE-BSA. CONCLUSION： Despite upregulation of RAGE in activated HSC, RAGE stimulation by AGE does not alter their fibrogenic activation. Therefore, RAGE does not contribute directly to hepatic fibrogenesis.

Injury of cortical neurons is caused by the advanced glycation end products-mediated pathway

Advanced glycation end products lead to cell apoptosis, and cause cell death by increasing endoplasmic reticulum stress. Advanced glycation end products alone may also directly cause damage to tissues and cells, but the precise mechanism remains unknown. This study used primary cultures of rat cerebral cortex neurons, and treated cells with different concentrations of glycation end products （50, 100, 200, 400 mg/L）, and with an antibody for the receptor of advanced glycation end products before and after treatment with advanced glycation end products. The results showed that with increasing concentrations of glycation end products, free radical content increased in neurons, and the number of apoptotic cells increased in a dose-dependent manner. Before and after treatment of advanced glycation end products, the addition of the antibody against advanced glycation end-products markedly reduced hydroxyl free radicals, malondialdehyde levels, and inhibited cell apoptosis. This result indicated that the antibody for receptor of advanced glycation end-products in neurons from the rat cerebral cortex can reduce glycation end product-induced oxidative stress damage by suppressing glycation end product receptors. Overall, our study confirms that the advanced glycation end products-advanced glycation end products receptor pathway may be the main signaling pathway leading to neuronal damage.

MK615 decreases RAGE expression and inhibits TAGE-induced proliferation in hepatocellular carcinoma cells

AIM:To investigate the proliferative effect of advanced glycation end-products(AGEs) and the role of their cellular receptor(RAGE) on hepatocellular carcinoma(HCC) cells,and the inhibitory effects of MK615,an extract from Japanese apricot,against AGEs were also evaluated.METHODS:Two HCC cell lines,HuH7 and HepG2,were used.Expression of RAGE was investigated by poly-merase chain reaction,Western blotting,and flow cytemetry(FACS).The effect of MK615 on RAGE expression was also evaluated by FACS.The proliferative effects of a control(unglycated bovine serum albumin),glucosederived AGEs(Glc-AGE),and glyceraldehyde-derived AGEs(Glycer-AGE),and the anti-proliferative effect of MK615 against AGEs,were evaluated using MTT assays.RESULTS:Expression of RAGE was confirmed at both the mRNA and protein levels in both HuH7 and HepG2.FACS revealed that the level of RAGE expression was higher in HuH7 than in HepG2.Treatment with 0.1 μg/mL MK615 decreased the expression level of RAGE from 24.3% to 3.7% in HuH7 and from 6.2% to 4.8% in HepG2.The growth indices for the control,Glc-AGE,and Glycer-AGE were 1.06 ± 0.08,0.99 ± 0.04,and 1.38 ± 0.05,respectively,in HuH7(P = 0.037),and were 1.03 ± 0.04,1.04 ± 0.03,and 1.07 ± 0.05,respectively,in HepG2(P > 0.05).When the cells were cultured simultaneously with Glycer-AGE and MK615,MK615 abrogated the proliferative effect of Glycer-AGE in HuH7.CONCLUSION:Only Glycer-AGE has a proliferative effect on HuH7,which expresses a higher level of RAGE.MK615 suppresses the proliferative effect of GlycerAGE on HuH7 by decreasing the expression of RAGE.

Effect of Aβ protein on inhibiting proliferation and promoting apoptosis of retinal pigment epithelial cells

AIM： To identify the effect and regulatory mechanism of amyloid β （Aβ） protein on retinal pigment epithelial （RPE） cells in cell proliferation and apoptosis, and clarify Aβ role in the pathogenesis of age-related macular degeneration （AMD）. METHODS： The model of Aβ25-35 protein cytotoxicity in RPE cell was successfully established to investigate the effect of Aβ protein on RPE cells in vitro. Based on Aβ protein, the specific inhibitors （HY-50682 or BAY11-7082） or activating agent （lipopolysaccharide） was used to analyze the regulatory mechanism of Aβ protein to RPE cells on cell proliferation and apoptosis by flow cytometry, real-time polymerase chain reaction, Western blotting, enzyme-linked immunosorbent assay and dual-luciferase reporter gene assay. RESULTS： The number of RPE cells, treated with Aβ25-35 from 0.3 to 60 μmol/L, significantly reduce （P〈0.01）, and had the dose-dependent effect. Aβ protein 60 μmol/L inhibits the G1/S phase transition （P〈0.01） and down-regulated cyclin E mRNA level （P〈0.01）. Similarly, Aβ25-35 induced a significant increase of cell apoptosis, accompanied by the significantly higher level of activated caspase 3 protein. Furthermore, nuclear factor-kappaB （NF-κB） activity and hosphorylated Iκ-Ba level would significantly lower in treated RPE cells. Using specific inhibitors or activating agent based on the Aβ, the cell numbers, NF-κB activity, phosphorylated Iκ-Ba level, receptor for advanced glycation endproducts （RAGE） gene expression levels, cyclin E mRNA level and activated caspase 3 level had accordingly changed by different methods, confirming that RAGE/NF-κB signaling pathway involved in the regulation of Aβ protein on RPE cell apoptosis and proliferation. CONCLUSION： Aβ protein inhibits cell proliferation and activates apoptosis via inactivation of the RAGE/NF-κB signaling pathway in RPE cell.

A physically active lifestyle is related to a lower level of skin autofluorescence in a large population with chronic-disease(LifeLines cohort)

Background:Physical activity(PA)has substantial health benefits and is important in combatting chronic diseases,which have been associated with elevated levels of advanced glycation endproducts(AGEs).AGEs play a role in the aging process,and an association between PA and AGEs has been reported.We aimed to investigate the relationship between PA and AGE accumulation in a general population and in a population with chronic diseases.Methods:This large cross-sectional population study used data from adult participants in the LifeLines project,with participant information drawn from the LifeLines database as well data from patients with diabetes mellitus or renal and/or cardiovascular diseases.Tissue AGE accumulation was assessed non-invasively by skin-autofluorescence(SAF)using an AGE reader(DiagnOptics Technologies BV,Groningen,the Netherlands).PA was assessed using the short questionnaire to assess health-enhancing physical activity(SQUASH).Multivariate linear regression analyses were adjusted for age,body mass index,sex,and smoking status.Results:Data from 63,452 participants(general population n=59,177,chronic disease n=4275)were analyzed.The general population was significantly younger(43.58±11.77 years,mean±SD)and had significantly lower SAF(1.90±0.42 arbitrary units(AU))compared to the population with chronic disease(age:55.51±12.07 years;SAF:2.27±0.51 AU).In the group with chronic disease,more hours of moderate to vigorous physical activities per week were associated with lower SAF(β=-0.002,95%confidence interval(95%CI):-0.002 to-0.001).For the general population,there was no association between hours of moderate to vigorous activity and SAF(β=3.2×10^(-5),95%CI:0.000-0.001,p=0.742).However,there was an association in the general population between total hours of PA per week and SAF(β=4.2×10^(-4),95%CI:0.000-0.001,p<0.001),but this association was not found in the chronic disease population(β=-3.2×10^(-4),95%CI:-0.001 to 0.000,p=0.347).Conclusion:Our study demonstrates that an inverse relationship exists between PA and AGE accumulation in the population with chronic disease.More hours of moderate to vigorous activity is associated a significantly decreased SAF.More PA is associated a lower SAF,even after for the established predictors(age,body mass index,smoking status,and sex).Our findings could help to promote health and prolong longevity.

Schisandrol A protects AGEs-induced neuronal cells death by allosterically targeting ATP6V0d1 subunit of V-ATPase

Diabetes have been shown to cause progressive neuronal injury with pain and numbness via advanced glycation end-products(AGEs)-induced neuronal cell apoptosis;however, the valuable drug targets for diabetic neuropathy have been poorly reported so far. In this study, we discovered a natural small-molecule schisandrol A(SolA) with significant protective effect against AGEs-induced neuronal cell apoptosis. ATP6V0D1, a major subunit of vacuolar-type ATPase(V-ATPase) in lysosome was identified as a crucial cellular target of SolA. Moreover, SolA allosterically mediated ATP6V0D1 conformation via targeting a unique cysteine 335 residue to activate V-ATPase-dependent lysosomal acidification.Interestingly, SolA-induced lysosome pH downregulation resulted in a mitochondrial-lysosomal crosstalk by selectively promoting mitochondrial BH3-only protein BIM degradation, thereby preserving mitochondrial homeostasis and neuronal cells survival. Collectively, our findings reveal ATP6V0D1 is a valuable pharmacological target for diabetes-associated neuronal injury via controlling lysosomal acidification, and also provide the first small-molecule template allosterically activating V-ATPase for preventing diabetic neuropathy.