High glucose stimulates cell proliferation and Collagen IV production in rat mesangial cells through inhibiting AMPK-KATP signaling.

PURPOSE: The present study investigated the putative mechanisms underlying effects of KATP channel on high glucose (HG)-induced mesangial cell proliferation and tissue inhibitors of metalloproteinases (TIMP)-2 and Collagen IV production. METHODS: Rat mesangial cells were subjected to whole cell patch clamp to record the KATP channel currents under high glucose (HG, 30 mM) condition. Cell proliferation was measured using a CCK-8 assay. The production of TIMP-2 and Collagen IV and AMP-activated protein kinase (AMPK)-signaling pathway activity was assessed by ELISA and Western blotting, respectively. AMPK agonist (AICAR) was used to analyze the role of this kinase. The expression of KATP subunit (Kir6.1, Kir6.2, SUR1, SUR2A and SUR2B) was examined using quantitative real-time PCR (RT-PCR). RESULTS: We found that HG was significant decreases in the expression of Kir6.1, SUB2A and SUB2B, three subunits of KATP, TIMP-2 production, KATP channel activity and AMPK activity, while it promoted the cell proliferation and Collagen IV production in rat mesangial cells. Pretreatment with KATP selective opener (diazoxide, DZX) significantly inhibited HG-induced mesangial cell proliferation, Collagen IV production and decrease in KATP channel activity in rat mesangial cells, which were reversed by pretreatment of 5-hydroxydecanoate, a selective inhibitor of KATP. Moreover, AICAR pretreatment inhibited HG-induced decrease in KATP channel activity. CONCLUSIONS: Taken together, activating AMPK-KATP signaling may protect against HG-induced mesangial cell proliferation and Collagen IV production, and, thereby, provides new insights into the molecular mechanisms underlying early diabetic nephropathy (DN).

Receptor for advanced glycation end as drug targets in diabetes-induced skin lesion.

The involvement of the receptor for advanced glycation end (RAGE) in different diseases has been reviewed in great detail, previously, but the effects of diabetic drugs on RAGE-induced skin lesion during long course diabetes remains poorly understood. In the present study, we have shown that RAGE was overexpressed in both diabetic rats and human keratinocytes (HaCaT cells). Cell cycle arrest and apoptosis as well as alternations of relative protein levels were also found in diabetic rats and HaCaT cells with overexpression of RAGE that were rectified by metformin (Met) treatment. Moreover, overexpression of RAGE was also found to induce secretions of TNF-α, IL-1ß, IL-6, ICAM-1 and COX-2 in HaCaT cells, and Met treatment corrected these inflammatory factor secretions. In addition, treatment with Met markedly reduced RAGE overexpression-induced p38 and NF-κB activation. Taken together, the findings of the present study have demonstrated, for the first time that Met protects HaCaT cells against diabetes-induced injuries and inflammatory responses through inhibiting activated RAGE.

Transplantation of betatrophin-expressing adipose-derived mesenchymal stem cells induces ß-cell proliferation in diabetic mice.

Recent progress in regenerative medicine has suggested that mesenchymal stem cell (MSC)-based therapy is a novel potential cure for diabetes. Betatrophin is a newly identified hormone that can increase the production and expansion of insulin-secreting ß-cells when administered to mice. In this study, we evaluated the effect of betatrophin overexpression by human adipose-derived MSCs (ADMSCs) by in vitro experiments, as well as following their transplantation into a mice with streptozotocin (STZ)-induced diabetes. The overexpression of betatrophin did not affect the ADMSCs in terms of proliferation, differentiation and morphology. However, the co-culture of human islets with ADMSCs overexpressing betatrophin (ADMSCs-BET) induced islet proliferation, ß-cell specific transcription factor expression, and the islet production of insulin under the stimulation of glucose or KCl and Arg. In addition, ADMSCs-BET enhanced the anti-inflammatory and anti-apoptotic effects of the co-cultured islets compared with ADMSCs cultured alone. In mice with STZ-induced diabetes, the transplantation of ADMSCs-BET ameliorated the hyperglycemia and weight loss associated with STZ-induced diabetes; ADMSCs-BET also significantly enhanced the ratio of ß-cells per islet compared to the transplantation of ADMSCs alone. Thus, our study demonstrates a novel strategy for inducing ß-cell regeneration. ADMSCs-BET may replace insulin injections by increasing the number of endogenous insulin-producing cells in patients with diabetes. This combined strategy of ADMSC transplantation and gene therapy may prove to be a useful therapy for the treatment of diabetes.

CD8(+) T cell-mediated cytotoxicity toward Schwann cells promotes diabetic peripheral neuropathy.

BACKGROUND: Damage to Schwann cells has been reported in the development of diabetic peripheral neuropathy (DPN), but how Schwann cells are damaged has not been elucidated. METHODS: The highly expressed proteins in the PBMC of DPN patients were identified through MALDI-TOF/TOF and SELDI protein chip technology. The expression levels of CXCR3 were detected by qPCR and flow cytometric analysis. Transwell migration assay was to investigate the migration of CD8(+) T cells. Western-blot analysis was to detect the levels of p38 MAP kinases pathway related proteins and TNF-α, FasL, and PDL1. RESULTS: Two highly expressed proteins, CXCR3 and p38, were identified. Under high glucose conditions, CXCR3 was elevated in CD8(+) T cells via the activation of p38 MAP kinases. Moreover, CXCL9, CXCL10, and CXCL11 expression were induced in Schwann cells, leading to the recruitment and infiltration of CD8(+) T cells into DPN tissues. Further study demonstrated that Schwann cells promoted activation of CD8(+) T cells and induced expression of TNF-α, FasL, and PDL1 on CD8(+) T cells, in return, CD8(+) T cells induced obvious apoptosis of Schwann cells. CONCLUSION: Our study indicates that CD8(+) T cells mediate cytotoxicity toward Schwann cells and play an important role in the development of DPN.

XRCC1 gene polymorphisms and the risk of differentiated thyroid carcinoma (DTC): a meta-analysis of case-control studies.

BACKGROUND: Previous studies investigating the association between X-ray repair cross-complementing group 1 (XRCC1) polymorphisms and thyroid cancer risk have yielded inconsistent results. This meta-analysis was performed to derive a more precise estimation of the relationship between three XRCC1 polymorphisms and thyroid cancer risk. METHODS/PRINCIPAL FINDINGS: PubMed and EMBASE database were systematically searched to identify relevant studies. 10 publications were selected for this meta-analysis, including 11 studies for Arg399Gln polymorphism (1726 cases and 3774 controls), 7 studies for Arg194Trp polymorphism (1037 cases and 2487 controls) and 8 studies for Arg280His polymorphism (1432 cases and 3356 controls). The results in total population did not show any significant association between these three polymorphisms and the risk of DTC for all genetic models. However, when stratified by ethnicity, the results showed that Arg280His polymorphism was associated with an increased risk of DTC among Caucasians (Arg/His vs. Arg/Arg: OR = 1.45, 95% CI = 1.09-1.93; dominant model: OR = 1.43, 95% CI = 1.08-1.89; additive model: OR = 1.38, 95% CI = 1.05-1.80), whereas individuals carrying Arg/His genotype have a significantly reduced risk of DTC among Asians (Arg/His vs. Arg/Arg: OR = 0.71, 95% CI = 0.51-0.98). We also detected that 399Gln variant allele carriers might presented an overall decreased risk of DTC in mixed population. Furthermore, subgroup analyses by histological subtype revealed that Arg194Trp polymorphism was significantly associated with reduced risk for papillary thyroid carcinoma (PTC) (dominant model: OR = 0.71, 95% CI = 0.50-0.99). CONCLUSIONS: This meta-analysis suggests that Arg280His polymorphism might contribute to the susceptibility of DTC among Caucasians, whereas it might provide protective effects in Asians against the risk of DTC. Additionally, our results support the protective role of Arg194Trp polymorphism in developing PTC, and show evidence of an association between Arg399Gln polymorphism and decreased risk of DTC in mixed population.

Association of two polymorphisms within and near SOCS3 gene with obesity in three nationalities in Xinjiang province of China.

AIM: SOCS3 gene plays an important role in the pathogenesis of obesity in animal models, but the data from human studies are relatively limited. To address this issue, a genetic association analysis on nationalities with different genetic background living in the similar environmental conditions was performed. METHODS: Two thousand seven hundred eleven subjects were randomly recruited from the Kazakh, Uygur and Han nationalities in Xinjiang of China. SNP polymorphisms rs4969168 and rs9892622 within or near the SOCS3 gene were genotyped using TaqMan-MGB™ assay. Association study between the two polymorphisms and obesity-related traits (body mass index [BMI]; waist-to-hip ratio [WHR]; weight; height, waist, and hip measurements) was conducted. RESULTS: Significant association was found between rs4969168 and the obesity-related traits, including BMI (25.32 ± 3.49 kg/m(2) for AA, 24.60 ± 3.70 kg/m(2) for AG, 24.39 ± 3.42 kg/m(2) for GG, P=0.042), weight (65.58 ± 11.42 kg for AA, 63.50 ± 11.30 kg for AG, 62.00 ± 10.78 kg for GG, P=0.011) in the Han nationality, but not in the Kazakh or Uygur nationalities. Rs9892622 was significantly associated with BMI, WHR, and WAIST in the Uygur males. Rs9892622 was also associated with BMI in Kazakh males. Linear regression analysis verified the above findings. However, neither of the two polymorphisms was associated with obesity-related traits in the total population. CONCLUSION: The polymorphism rs4969168 within or near the SOCS3 gene has a significant effect in the Han nationality, while rs9892622 was associated with obesity in Uygur and Kazakh nationalities in Xinjiang of China.

Serum biomarker of diabetic peripheral neuropathy indentified by differential proteomics.

At least one in four diabetic patients is affected by peripheral neuropathy. In this study, the MALDI-TOF-MS mass spectra of peptides and proteins were generated following WCX CLINPROT bead fractionation of 39 diabetic peripheral neuropathy (DPN), 39 diabetes mellitus (DM), and 35 control (CON) serum samples. The spectra were analyzed statistically using flexAnalysisTM and Clin-ProtTM bioinformatics software. Identification of the selected markers was performed and affinity bead-purified plasma protein was subjected to LTQ Orbitrap XL MS/MS analysis followed by Mascot identification of the peptide sequences. 89 differentially expressed peaks of serum proteins were identified. 17, 10 and 4 most significant peaks between CON vs. DM, CON vs. DPN, DM vs. DPN, respectively, were selected out using the ClinProTool software package and used to train a Supervised Neural Network. A veracity rate of 100% was obtained for all sets. Following this analysis, a 6631-Da marker was identified as a fragment of the Apolipoprotein C-I precursor. The peptides identified may have clinical utility as surrogate markers for detection and classification of DM and DPN.

Mechanistic study of endogenous skin lesions in diabetic rats.

Pathological and physiological changes in dermal tissue in a rat model of diabetes mellitus (DM) were investigated. Sixteen male 8-week-old Sprague-Dawley rats were randomized into two groups of eight, the DM group (Group DM) and the normal control group (Group (NC) normal control). Group DM rats were injected with streptozotocin (STZ) intraperitoneally at a dose of 65 mg/kg body weight. Group NC rats were injected with the same volume of citric acid buffer. All rats were sacrificed 12 weeks later. The impact of exposure to (AGE) advanced glycation end products-modified human serum albumin (AGE-HSA) on epidermal cells and ECV304 cells was evaluated in cell culture experiments. The diabetic rats exhibited changes in skin tissue, including a decrease in thickness, disappearance of the multilayer epithelium structure, degeneration of collagen fibres and an increase in the infiltration of inflammatory cells, in addition to a significant increase in skin glucose and AGEs. Moreover, diabetic rats had increased plasma glycosylated protein (GSP) and malondialdehyde (MDA) and decreased plasma glutathione (GSH). The percentage of epidermal cells in S phase was similar between the two group rats; however, there was a marked decrease in the G2/M phase in Group DM. Additionally, exposure of ECV304 cells to AGE-HSA led to a time-dependent and dose-dependent increase in apoptosis. Therefore, the high glucose in the skin tissue, coupled with the accumulation of toxic substances such as AGEs, promote the dysfunction of dermal cells and/or the matrix. This may be a significant mechanism of diabetes-induced early-stage endogenous skin damage.

[Study on the biological function of dermal fibroblasts in the wounds of diabetic and non-diabetic rats with deep burns].

OBJECTIVE: To explore the changes of the biological function of dermal fibroblasts (FBs) in the wounds of diabetic and non-diabetic burned rats and the pathogenesis of impaired wound healing in diabetes. METHODS: 80 Sprague-Dawley (SD) rats weighing 220 g were randomly divided into control and STZ-induced diabetic groups, and then deep partial thickness scald involving 10% TBSA was reproduced in the two groups. The diabetic groups were randomized into pre-scalding, post-scalding day (PSD 3), PSD 7, PSD 14 and PSD 21 groups, with 6 rats in each group. Controls were also randomized into 5 groups. Skin specimens from the wound were harvested at each time point. Cell cycles of FBs were analyzed with flow cytometry. The amount of hydroxyproline in the skin tissue was assessed on 0, 3, 7, 14, and PSD 21. The type I and III collagens were determined by ELISA. The expression of alpha-SMA in the dermal fibroblasts of each group was assessed by immunohistochemistry method. Transmission electron microscopy was used to observe the ultrastructure changes of FBs. RESULTS: Compared with that in the normal rats, the percentage of the cells in G(0)/G(1) phase in the DM group was evidently lower on PSD 0 (65.79 +/- 5.24 vs 82.43 +/- 9.68, P < 0.01). After the scalding, the percentage of the cells in G(0)/G(1) phase in DM group was significantly higher (70.00 +/- 4.27 vs 42.04 +/- 12.96, on PSD 3, P < 0.01), meanwhile the percentage of S phase was remarkably lower than those in C group on 3, 7, 14, 21PSD (P < 0.05, P < 0.01). The amount of hydroxyproline in the diabetic skin tissue was obviously lower than those of the responding control groups before (0.72 +/- 0.06 vs 1.42 +/- 0.28, P < 0.01) and after burn injury (P < 0.01). Furthermore, the rate of I/III collagen on 7, 14 and PSD 21 was much higher in DM group than that in C group (P < 0.01). The expression of alpha-SMA in DM groups on PSDS 3, 7, 14 and PSD 21 was evidently lower than those of the controls (levels 10.28 +/- 3.99, C group 28.42 +/- 2.73, on PSD 14, P < 0.01), although that inclined to be heightened after burn injury. Ultrastructure changes of FBs in the wounds of diabetic rats could be observed, such as the outstretched endoplasmic reticulum, un development of Golgi's body, lackness of microtubule and microfilament, a sharp increase of cytolysosomes, and so on. CONCLUSION: The FB proliferation in the diabetic skin is abnormal, the synthetical ability of collagen is weakened, the expression of alpha-SMA is insufficient, the microtubule and microfilament is lack, and the number of cytolysosomes increases. The pathogenesis of impaired-wound healing in diabetics might be related with the above mentioned factors.

[Amelioration of latent skin lesions in streptozotocin-induced diabetic rats by insulin].

OBJECTIVE: To explore the latent skin lesions in streptozotocin-induced diabetic rats and the mechanism of insulin prevention. METHODS: 81 male Sprague-Dawley (SD) rats were randomized into control (C, n = 27) and STZ-induced diabetic groups (n = 54), and then the diabetic rats were randomized into 2 groups: Group A group (n = 27) that was treated with insulin enough to control the high concentration of blood glucose strictly, and Group B group (n = 27) in which insulin was given too nut not sufficient to control the high blood glucose. Twenty-seven normal rats were used as controls. Four, eight, and twelve weeks after STZ-induction, skin specimens from the back were collected to undergo hematoxylin-eosin staining and histological examination. The skin glucose content was measured by Beckman's autoanalyzer. The skin advanced glycation end products (AGEs) concentration was assessed by fluorescence spectrophotometry and immunohistochemistry. The ultrastructure changes of skin microvessel were observed by electron microscopy. RESULTS: Twelve weeks after the establishment of the DM model the skin thickness of Group B was decreased, the features of multilayer epithelium structure disappeared in epidermis, and part of the collagen fibers in dermis became atrophic, swollen and degenerated, infiltration of inflammatory cells to different degrees was found, and subcutaneous fat showed progressive atrophy or disappeared. However, such changes were not detected in Group A. The skin glucose contents of Group B at different time points were all higher than those of Group A and Group (all P < 0.01) without a significant difference between Groups A and C. The fluorescence values of skin collagen extracts of Groups A and B were significantly higher than that of normal rats. The 8-week fluorescence value of skin collagen extracts of Groups B was 34 U/mg +/- 4 U/mg, significantly higher than that of Group A (29 U/mg +/- 3 U/mg, P < 0.05). The 12-week fluorescence value of skin collagen extracts of Groups B was 41 U/mg +/- 4 U/mg, significantly higher than that of Group A (32 U/mg +/- 4 U/mg, P < 0.05). The 8-week AGEs positive expression rate of Group B was 32% +/- 4%, significantly higher than that of Group A (25% +/- 5%, P < 0.05), and the 12-week AGEs positive expression rate of Group B was 39% +/- 5%, significantly higher than that of Group A (27% +/- 4%, P < 0.05). Degeneration of endothelial cells and thickening of basement membrane were more markedly in Group B than in Group A. CONCLUSION: Accumulation of AGEs in skin and high concentration of glucose are important causes of diabetic skin complications. Insulin application at the early stage postpones the course of diabetic skin lesions with the possible mechanisms of lowering the high glucose, inhibiting AGEs synthesis, and blocking the action of AGEs.

[Proliferation-inhibiting effect of advanced glycation end products modified human serum albumin to vascular endothelial cell ECV304].

OBJECTIVE: To study the proliferation-inhibiting and apoptosis-inducing effects of advanced glycation end products (AGE) modified human serum albumin (AGE-HSA) on human vein endothelial cells. METHODS: Human umbilical vein endothelial cells ECV304 were cultured in vitro with AGE-HSA of the concentrations of 12.5, 25, 50, 100, and 200 micro g/ml for 6, 12, 24, or 48 hour, then 20 micro l of 5 mg/ml MTT were added and the optical density (OD) at each time point was determined. Another ECV304 cells were cultured with AGE-HAS for 2, 4, or 8 days and then were stained with trypan blue to calculate the number of dead cells so as to calculate the proliferation-inhibiting rate. Another ECV304 cells were cultured with AGE-HAS for 6, 12, 24, or 48 hours and then stained with annexin V Fitc and propidium iodide (PI). Flow cytometry was used to calculate the annexin V Fitc positive cells (early and middle stage apoptotic cells) and Annexin V Fitc/PL positive cells (late apoptotic cells). Inverted microscope, transmission electron microscope, and fluorescence microscope were used to observe the histological changes of apoptotic cells. FCV304 cells incubated with HSA of the above-mentioned and without addition of the other agents concentrations were used as controls. RESULTS: The OD values of ECV304 cells cultured for 48 h with low concentrations (12.5, 25, and 50 micro g/ml) of AGE-HSA were not significantly different from those of the control (1.104 +/- 0.080, 1.098 +/- 0.097 and 1.059 +/- 0.122 VS. 1.159 +/- 0.088, all P > 0.05). The OD values of ECV304 cells cultured with low concentrations of AGE-HSA for 4 days and 6 days were significantly lower than those in the control group. The OD values of ECV304 cells cultured with high concentrations (100 and 200 micro g/ml) of AGE-HSA for 6 - 48 hours decreased to 0.117 +/- 0.033 and 0.081 +/- 0.020 in comparison with that of the control group (P < 0.01). Flow cytometry and fluorescence microscopy showed higher proportions of apoptotic cells among the ECV304 cells cultured with high concentrations of AGE-HAS than among the control cells at each time point (P < 0.01). The numbers of cells in the control group exponentially increased after culture for 2, 4, and 6 days. The number of cells cultured with low concentrations of AGE-HAS for 2 days was not significantly different from that of the control group (P > 0.05), however, the numbers of cells cultured with low concentrations of AGE-HAS for 4 and 6 days were significantly lower than those of the control group (both P < 0.01). The numbers of cells cultured with 100 or 200 micro g/ml AGE-HAS for 2 days were significantly lower than those of the control group (both P < 0.01) with a proliferation-inhibiting rate of 39.56% +/- 2.82% and 60.32% +/- 4.51% respectively. The apoptotic rates in cells cultured with low concentrations of AGE-HAS for 48 hours were not significantly different from those in the control group. The apoptotic rates in cells cultured with 100 or 200 micro g/ml AGE-HAS for 6, 12, 24, or 48 hours were significantly higher than those in the control group (all P < 0.01). The apoptotic rates in 200 micro g/ml group at different time points were significantly higher than those in the 100 micro g/ml group (P < 0.05 or 0.01). The apoptotic rate and number of apoptotic cells increased along with the increase of culture time and concentration of AGE-HAS. Microscopy showed morphological changes among the cells cultured with 100 micro g/ml AGE-HAS for 6, 12, 24, and 48 hours and the numbers of apoptotic cells, mainly late apoptotic cells, and dead cells increased remarkably since the cells were cultured for 48 hours. CONCLUSION: AGE-HSA inhibits the proliferation of vascular endothelial cells and induces apoptosis in dose and time dependent manner. AGE modification-induced pathobiological cascade may be involved in the pathogenesis of impaired wound healing in diabetes by the mechanism of angiogenesis retardation.