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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study, we investigated 1) whether long-term restoration of euglycemia by means of pancreatic islet transplants is capable of preventing and/or reversing renal functional and structural alterations in an experimental model of insulin-deficient diabetes, and 2) whether changes in extracellular matrix (ECM) and cell turnover at the glomerular level and biochemical abnormalities associated with hyperglycemia correlate with the renal outcome after transplantation. Male Lewis rats, rendered diabetic by intravenous injection of streptozotocin, underwent homologous islet transplantation via the portal vein at 2 weeks (study A), at 4 months (study B), and at 8 months (study C) after the induction of diabetes and killed 12 months after transplantation in study A and 4 months after transplantation in studies B and C. Age-matched nondiabetic and untreated diabetic rats were used as control animals and were studied at 4, 8, and 12 months. In the untreated diabetic animals, metabolic derangement was associated with increased erythrocyte polyol and fructose levels, tail-tendon content of advanced glycation end products (AGEs), total proteinuria, albuminuria, kidney weight, and mean glomerular volume as well as with marked glomerular and extraglomerular lesions. Glomerular gene expression for the ECM components fibronectin and collagen IV and for TGF-beta was also increased, whereas glomerular cell proliferation was unaffected by diabetes. In study A, changes in renal function and structure observed in diabetic rats at 12 months were completely prevented by successful islet transplants. In study B, all functional and structural abnormalities detected in diabetic rats at 4 months of disease duration were virtually reversed by 4 months of euglycemia in transplanted animals, whereas they progressed further in untreated diabetic rats. In study C, the course of functional and structural changes observed in untreated diabetic rats was not reversed by islet transplantation. Likewise, tissue AGE accumulation and particularly upregulation of glomerular ECM and transforming growth factor (TGF)-beta gene expression, which are believed to play a role in the pathogenesis of altered renal function and structure in diabetes, were normalized in transplanted rats from study A and study B, but not in those from study C. These experiments show that restoration of euglycemia by islet transplants is capable of preventing experimental diabetic glomerulopathy and reversing early changes in renal function and structure induced by diabetes. In a later phase of the disease, when glomerular matrix gene expression becomes independent of hyperglycemia, possibly because of the persistent increase in tissue AGE accumulation, metabolic control is not capable of reversing renal abnormalities.
Diabetes 1997 Jul
PMID:Early, but not advanced, glomerulopathy is reversed by pancreatic islet transplants in experimental diabetic rats: correlation with glomerular extracellular matrix mRNA levels. 920 Jun 56

A new type of CD4+ T cell clone (NY4.2) isolated from pancreatic islet-infiltrated lymphocytes of acutely diabetic non-obese diabetic (NOD) mice prevents the development of insulin-dependent diabetes mellitus (IDDM) in NOD mice, as well as the recurrence of autoimmune diabetes in syngeneic islet-transplanted NOD mice. It has been demonstrated that the cytokine TGF-beta, secreted from the cells of this clone, is the substance which prevents autoimmune IDDM. This investigation was initiated to determine the molecular role TGF-beta plays in the prevention of autoimmune IDDM by determining its effect on IL-2-induced signal transduction in Con A-activated NOD mouse splenocytes and HT-2 cells. First, we determined whether TGF-beta, secreted from NY4.2 T cells, inhibits IL-2-dependent T cell proliferation in HT-2 cells (IL-2-dependent T cell line) and NOD splenocytes. We found that TGF-beta suppresses IL-2-dependent T cell proliferation. Second, we determined whether TGF-beta inhibits the activation of Janus kinases (JAKs), as well as signal transducers and activators of transcription (STAT) proteins, involved in an IL-2-induced signalling pathway that normally leads to the proliferation of T cells. We found that TGF-beta inhibited tyrosine phosphorylation of JAK1, JAK3, STAT3 and STAT5 in Con A blasts from NOD splenocytes and HT-2 cells. Third, we examined whether TGF-beta inhibits the cooperation between STAT proteins and mitogen-activated protein kinase (MAPK), especially extracellular signal-regulated kinase 2 (ERK2). We found that TGF-beta inhibited the association of STAT3 and STAT5 with ERK2 in Con A blasts from NOD splenocytes and HT-2 cells. On the basis of these observations, we conclude that TGF-beta may interfere with signal transduction via inhibition of the IL-2-induced JAK/STAT pathway and inhibition of the association of STAT proteins with ERK2 in T cells from NOD splenocytes, resulting in the inhibition of IL-2-dependent T cell proliferation. TGF-beta-mediated suppression of T cell activation may be responsible for the prevention of effector T cell-mediated autoimmune IDDM in NOD mice by TGF-beta-producing CD4+ suppressor T cells.
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PMID:Molecular role of TGF-beta, secreted from a new type of CD4+ suppressor T cell, NY4.2, in the prevention of autoimmune IDDM in NOD mice. 921 58

Oral administration of antigen leads to systemic immune unresponsiveness. Low dose oral tolerance generates regulatory cells which, when triggered in an antigen-specific manner, suppress inflammatory responses. We have previously shown that oral administration of an organ-specific antigen, porcine insulin, protects against diabetes development in the NOD mouse. In the present study we extend these observations to the B-chain of insulin, a 30-amino-acid peptide which has now been shown by others to contain the immunogenic epitope. Oral administration of the B-chain slowed diabetes development in a co-transfer model in which cells from B-chain-fed animals were co-transferred with diabetogenic cells (P=0.02). Further exposure to antigen via feeding of the co-transfer recipient animals not only slowed diabetes development but prevented diabetes in some animals (P=0.01). In vitro proliferation of popliteal lymph node cells from fed and immunized animals was suppressed in an antigen-specific manner when cells were restimulated with the fed antigen. When those cells were cultured and restimulated in vitro with the B-chain of insulin, we also observed a decrease in IFN-gamma expression and an increase in IL-4, TGF-beta and IL-10 expression. These results demonstrate that an orally protective epitope resides in the B-chain of insulin and that refeeding following adoptive transfer enhances protection. Finally, the orally administered antigen is associated with a decrease in Th1 responses and an increase in Th2 responses to the insulin B-chain.
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PMID:Oral administration of the immunodominant B-chain of insulin reduces diabetes in a co-transfer model of diabetes in the NOD mouse and is associated with a switch from Th1 to Th2 cytokines. 923 97

Chronic hyperglycemia may cause growth factor alterations that are likely to participate in tissue remodeling typical for diabetic late complications. However, few details of such events are known. The ocular vitreous fluid allows studies of growth factor levels in human eyes (after vitrectomy). The vitreous is highly inert and protected by the blood-retina barrier and thus probably reflects growth factor production by the normal retina. Vitreous from patients with proliferative diabetic retinopathy (PDR) was compared with vitreous obtained from patients with nonproliferative eye disease and with vitreous from patients without diabetes but with marked neovascular proliferations due to ischemia. This design permits us to distinguish diabetes-related from non-diabetes-related alterations. Insulin-like growth factor I (IGF-I), IGF-II, IGF binding protein 2 (IGFBP-2), and IGFBP-3 were elevated 3- to 13-fold in nondiabetic retinal ischemia and 1.5- to 3-fold in PDR, indicating that the changes were not restricted to diabetes. These changes may partially be explained by leakage of serum into the vitreous, since IGFs and IGFBPs are 20- to 50-fold higher in serum than in vitreous, and vitreous protein content was 1.5-fold elevated in PDR subjects and 5-fold in ischemia patients compared with control subjects. TGF-beta is a proposed antiangiogenic factor in the eye. TGF-beta2 was the predominant subtype in vitreous, and its total amount was not altered in PDR patients. More importantly, the active fraction of TGF-beta was decreased by 30 and 70% in PDR and nondiabetic retinal ischemia patients, respectively. Since plasmin may control TGF-beta activation, the serum protein alpha2-antiplasmin was measured and found to be significantly elevated to 150 and 250% of control values in PDR and ischemia patients, respectively. Thus, influx of serum proteins due to microvascular disturbances and hypoxia is proposed as a possible cause for vitreous alterations of IGF-I and of active TGF-beta. These changes seem to occur late in the sequence of events leading to PDR and are not specific for diabetes, but they were also observed in other diseases characterized by retinal hypoxia.
Diabetes 1997 Sep
PMID:Growth factor alterations in advanced diabetic retinopathy: a possible role of blood retina barrier breakdown. 928 95

Oxidant stress and a reduction in antioxidant status, including reduced plasma and tissue ascorbic acid content, occur in diabetic patients and experimental models of diabetes. In this study, the effects of treatment of streptozotocin diabetic rats for 2 mo with vitamin C (10 g/kg body wt/d) or dietary vitamin E (200 mg/kg body wt/d) in the drinking water on urinary albumin excretion, glomerular transforming growth factor (TGF)-beta content, and glomerular size were examined. Treatment of diabetic rats with vitamin C or E had no effect on blood glucose levels compared with that in untreated diabetics (453 +/- 28 g/dl +/- SEM). Body weight, BP, and creatinine clearance rates were not significantly different among the study groups. Kidney weight was significantly higher in all of the diabetic groups compared with age-matched control rats. Treatment with vitamin C, but not vitamin E, significantly reduced kidney weight compared with that in untreated diabetic rats. Immunohistochemical staining for TGF-beta was 2.5-fold higher in glomeruli of cortical sections from untreated diabetic rats versus control rats. Treatment with vitamin C or E prevented the increase in glomerular TGF-beta immunoreactivity. Glomerular volume was also significantly increased (twofold) in kidneys of untreated diabetic rats compared with control rats, as assessed by light microscopy. Treatment with vitamin C prevented and treatment with vitamin E reduced the increase in glomerular volume. Treatment with vitamin C also prevented the sevenfold increase in albumin clearance otherwise seen in untreated diabetic rats. By contrast, treatment with vitamin E had no effect on albumin clearance despite reductions in glomerular size and TGF-beta. Renal cortical vitamin E and plasma, but not renal cortical vitamin C, were reduced in diabetic rats versus control rats. Supplementation of diabetic rats with vitamin C markedly increased plasma and renal cortical vitamin C content to values greater than those in control rats. Supplementation with vitamin E increased renal cortical vitamin E content by 50% compared with values in control rats and also increased plasma and renal cortical vitamin C. These results support the potential utility of antioxidant treatment for the prevention of renal injury in diabetes.
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PMID:Effects of supplementation with vitamin C or E on albuminuria, glomerular TGF-beta, and glomerular size in diabetes. 929 32

In mammals, insulin signalling regulates glucose transport together with the expression and activity of various metabolic enzymes. In the nematode Caenorhabditis elegans, a related pathway regulates metabolism, development and longevity. Wild-type animals enter the developmentally arrested dauer stage in response to high levels of a secreted pheromone, accumulating large amounts of fat in their intestines and hypodermis. Mutants in DAF-2 (a homologue of the mammalian insulin receptor) and AGE-1 (a homologue of the catalytic subunit of mammalian phosphatidylinositol 3-OH kinase) arrest development at the dauer stage. Moreover, animals bearing weak or temperature-sensitive mutations in daf-2 and age-1 can develop reproductively, but nevertheless show increased energy storage and longevity. Here we show that null mutations in daf-16 suppress the effects of mutations in daf-2 or age-1; lack of daf-16 bypasses the need for this insulin receptor-like signalling pathway. The principal role of DAF-2/AGE-1 signalling is thus to antagonize DAF-16. daf-16 is widely expressed and encodes three members of the Fork head family of transcription factors. The DAF-2 pathway acts synergistically with the pathway activated by a nematode TGF-beta-type signal, DAF-7, suggesting that DAF-16 cooperates with nematode SMAD proteins in regulating the transcription of key metabolic and developmental control genes. The probable human orthologues of DAF-16, FKHR and AFX, may also act downstream of insulin signalling and cooperate with TGF-beta effectors in mediating metabolic regulation. These genes may be dysregulated in diabetes.
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PMID:The Fork head transcription factor DAF-16 transduces insulin-like metabolic and longevity signals in C. elegans. 935 26

We studied the urinary excretion of transforming growth factor-beta 1 (TGF-beta 1), platelet-derived growth factor-BB (PDGF) and fibronectin (FN) in 104 patients (52 normoalbuminuric, 24 microalbuminuric, and 28 with overt diabetic nephropathy) with insulin-dependent diabetes mellitus (IDDM) of a long duration and in 30 non-diabetic controls. IDDM patients had higher urinary excretion of TGF-beta 1, PDGF and FN compared to controls. Urinary excretion of TGF-beta 1 and PDGF was elevated in all IDDM subgroups, while FN excretion was significantly increased only in patients with macroalbuminuria. Urinary excretion of TGF-beta 1 and FN did not differ between normoalbuminuric IDDM patients with long duration of diabetes, a group at low risk of ever developing diabetic nephropathy, and IDDM patients with incipient or overt diabetic nephropathy. Excretion of PDGF was significantly higher in patients with micro- and macroalbuminuria compared to normoalbuminuric patients, but there was a considerable overlap between the groups. In conclusion, although longitudinal follow-up studies are needed to further clarify the issue, our results in long-standing IDDM do not support a hypothesis of urinary excretion of TGF-beta 1, PDGF or FN to predict development of diabetic nephropathy.
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PMID:Urinary excretion of TGF-beta 1, PDGF-BB and fibronectin in insulin-dependent diabetes mellitus patients. 940 57

Albumin modified by Amadori glucose adducts, formed in increased amounts in diabetes, stimulates collagen IV production and gene expression in renal glomerular mesangial cells, and induces mesangial matrix accumulation accompanied by increased mRNA encoding alpha 1 (IV) collagen and fibronectin in diabetic animals. These effects contribute to the pathogenesis of diabetic nephropathy, and resemble biologic activities of the cytokine TGF-beta 1, which also has been causally implicated in diabetic renal disease. We postulated that Amadori-modified glycated albumin modulates TGF-beta 1 expression in mesangial cells, and that TGF-beta 1 participates in mediating the glycated albumin-induced increases in mesangial cell matrix production. To test this hypothesis, we measured mRNA encoding TGF-beta 1, the TGF-beta Type II receptor and fibronectin, a key matrix component of the TGF-beta 1 tissue response, after incubation of mesangial cells with glycated albumin. Steady state levels of the mRNAs encoding for these proteins were stimulated when mesangial cells were cultured in the presence of albumin containing Amadori glucose adducts compared with levels in cells cultured with the nonglycated, glucose-free counterpart. The glycated protein-induced changes in mRNA expression were observed with concentrations of glycated albumin encompassing those found in clinical specimens and in media containing physiologic (5.5 mM) glucose concentrations, indicating that they were due to the glucose-modified protein and not to a hyperglycemic milieu. Further, they were accompanied by increased translated fibronectin protein, which was prevented with TGF-beta neutralizing antibody, as was the glycated albumin-induced increase in fibronectin mRNA. The findings indicate that Amadori-modified glycated albumin stimulates mesangial cell TGF-beta 1 gene expression by mechanisms that are operative under normoglycemic conditions. These data provide the first link between elevated glycated serum albumin concentrations and increased TGF-beta 1 bioactivity in the pathogenesis of mesangial matrix accumulation in diabetes.
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PMID:Glycated albumin stimulates fibronectin gene expression in glomerular mesangial cells: involvement of the transforming growth factor-beta system. 950 8

Administration of TNF-alpha to autoimmune diabetes-prone nonobese diabetic mice and biobreeding rats inhibits diabetes development; however, the mechanism(s) of diabetes prevention by TNF-alpha has not been established. We used the model of syngeneic islet transplantation into diabetic nonobese diabetic mice to study the effects of TNF-alpha administration on the types of mononuclear cells and cytokines expressed in the islet grafts and on autoimmune diabetes recurrence. Twice daily i.p. injections of TNF-alpha (20 microg/day) from day 1 to day 30 after islet transplantation significantly prolonged islet graft survival; thus, 70% (16 of 23) of mice treated with TNF-alpha were normoglycemic at 30 days after islet transplantation compared with none (0 of 14) of vehicle-treated control mice. Islet grafts and spleens from TNF-alpha-treated mice at 10 days after islet transplantation contained significantly fewer CD4+ and CD8+ T cells, and significantly decreased mRNA levels of type 1 cytokines (IFN-gamma, IL-2, and TNF-beta) than islet grafts and spleens from control mice. Regarding type 2 cytokines, IL-4 mRNA levels were not changed significantly in islet grafts or spleens of TNF-alpha-treated mice, whereas IL-10 mRNA levels were decreased significantly in islet grafts of TNF-alpha-treated mice and not significantly changed in spleens. TGF-beta mRNA levels in islet grafts and spleens were similar in TNF-alpha-treated and control mice. These results suggest that TNF-alpha partially protects beta cells in syngeneic islet grafts from recurrent autoimmune destruction by reducing CD4+ and CD8+ T cells and down-regulating type 1 cytokines, both systemically and locally in the islet graft.
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PMID:TNF-alpha down-regulates type 1 cytokines and prolongs survival of syngeneic islet grafts in nonobese diabetic mice. 955 Apr 35

Subcutaneous insulin treatment of young diabetes prone BB rats has been shown previously to suppress the development of autoimmune diabetes. In this study the hypothesis was tested that exogenous insulin may deviate the autoimmune process by acting on the Th1/Th2 cytokine balance in the pancreas. BB rats were implanted with pellets which continuously released insulin, at 50 d of age. Three weeks later cytokine mRNA expression in the pancreas and insulitis score were determined. While in control BB rats high levels of IFNgamma mRNA were detectable by RT-PCR, insulin treatment almost completely suppressed IFNgamma mRNA levels without concomitant upregulation of counterregulatory IL-10 and TGFbeta gene expression. Insulin also suppressed gene expression of inducible nitric oxide synthase. Mean insulitis scores were decreased after insulin treatment. We conclude that the protective effects of insulin treatment may not be due to the induction of protective Th2 immune reactivity but to general downregulation of immune activation in the pancreas, and hence also of Th1 autoimmunity.
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PMID:Insulin therapy of prediabetes suppresses TH1 associated gene expression in BB rat pancreas. 955 50


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