Search PubMed⌕ Search

Biomedical subjects

U Di Mario

Publications and source records attributed to U Di Mario.

At least 73 records · Page 4Linked to original sources
PubMed1997

Early, but not advanced, glomerulopathy is reversed by pancreatic islet transplants in experimental diabetic rats: correlation with glomerular extracellular matrix mRNA levels.

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.

Animals↗
PubMed1997

Autoimmune markers of diabetes in diabetic pregnancy.

Gestational diabetes mellitus (GDM) has been described in 1-3% of pregnancies and increases the risk (up to 60-70%) to subsequently developing an overt diabetes (generally of type 2 non insulin-dependent diabetes mellitus (NIDDM)). Several humoral autoimmune phenomena have been described in GDM: islet cell antibodies (ICA) have been found and it was shown that ICA+ patients tend to have a worse glucose tolerance. Recently, autoantibodies against glutamic acid decarboxylase (GAD), were detected in type 1 diabetic sera before or at the onset of the disease; these markers, as well as ICA and insulin antibodies, seem to have a predictive value for the onset of the disease. Aim of our study was to investigate the presence of GAD65 in 83 GDM, 79 NIDDM and 64 pregnant normal women in late gestation. GAD Ab positivity was found (0.035 index as limit) only in GDM and NIDDM (3.6% in GDM, 3.8% in NIDDM, and nothing in control women). These results indicate that GAD positivity in GDM overlaps that of NIDDM, suggesting that the two diabetic populations have the same predisposition to develop a type 1 diabetes mellitus, and likely they share the same disease. Further studies need to clarify whether this prevalence of GAD positivity may unmask type 1 diabetes in both GDM and NIDDM diabetic women.

Adult↗
PubMed1997

Target antigens in autoimmune diabetes: pancreatic gangliosides.

Type 1 diabetes mellitus is a disease caused by the autoimmune destruction of insulin-producing pancreatic beta-cells that takes place in genetically prodisposed individuals. Autoantibodies and autoreactive T lymphocytes reacting with islet target molecules or protein of glycolipid nature have been shown in the circulation of individuals and of animal models of type 1 diabetes (NOD mouse and BB rat) before and at the onset of the disease. As far as autoantigens of glycolipid nature is concerned, gangliosides such as GT3, GD3 and especially GM-1, have been shown to be target of autoantibodies associated to autoimmune diabetes. Of particular interest is the islet-specific monosialo-ganglioside GM2-1, which is target of an autoimmune response highly associated to future progression to diabetes development in first degree relatives of type 1 diabetic individuals. This molecule is recognized by IgG autoantibodies which have been detected before the appearance if clinical diabetes both in man and in the NOD mouse, representing a novel marker of beta-cell autoimmunity.

Animals↗
PubMed1996

Selection of phage-displayed peptides mimicking type 1 diabetes-specific epitopes.

Phage display technology represents a powerful tool for the identification of peptides reacting with disease-related antibodies present in human sera. The application of this technology to type 1 diabetes could provide a set of novel reagents for diabetes prediction and could also lead to the identification of novel autoantigens or even of environmental factors possibly causing the disease. In the present study, sera of prediabetic and high risk individuals were used to select candidate peptides from phage-displayed random peptide libraries. Diabetes specific phage clones were then identified from these through screening and counter screening, using sera from diabetic and non-diabetic individuals. The results presented in this paper demonstrate the feasibility of this methodology to identify peptides reacting preferentially with antibodies present in the serum of diabetic patients.

Adolescent↗
PubMed1996

Increased activity of the insulin-like growth factor system in mesangial cells cultured in high glucose conditions. Relation to glucose-enhanced extracellular matrix production.

Recent evidence suggests that several growth factors participate in diabetic glomerular disease by mediating increased extracellular matrix accumulation and altered cell growth and turnover leading to mesangial expansion. Transforming growth factor (TGF)-beta has been demonstrated to be upregulated both in vivo and in vitro, whereas studies on the activity of the renal insulin-like growth factor (IGF) system in experimental diabetes have provided conflicting results. We investigated the effects of prolonged exposure (4 weeks) of cultured human and rat mesangial cells to high (30 mmol/l) glucose vs iso-osmolar mannitol or normal (5.5 mmol/l) glucose levels on: 1) the autocrine/paracrine activity of the IGF system (as assessed by measuring IGF-I and II, IGF-I and II receptors, and IGF binding proteins); and, in parallel, on 2) TGF-beta 1 gene expression; 3) matrix production; and 4) cell proliferation. High glucose levels progressively increased the medium content of IGF-I and the mRNA levels for IGF-I and IGF-II, increased IGF-I and IGF-II binding and IGF-I receptor gene expression, and reduced IGF binding protein production. TGF-beta 1 transcripts and matrix accumulation and gene expression were increased in parallel, whereas cell proliferation was reduced. Iso-osmolar mannitol did not affect any of the above parameters. These experiments demonstrated that high glucose levels induce enhanced mesangial IGF activity, together with enhanced TGF-beta 1 gene expression, increased matrix production, and reduced cell proliferation. It is possible that IGFs participate in mediating diabetes-induced changes in matrix turnover leading to mesangial expansion, by acting in a paracrine/autocrine fashion within the glomerulus.

Animals↗
PubMed1996

Peripheral, but not central, nervous system abnormalities are reversed by pancreatic islet transplantation in diabetic Lewis rats.

Neuroelectrophysiological recordings represent a non-invasive and reproducible method of detecting central and peripheral nervous system alterations in diabetes mellitus. In order to evaluate whether the normalization of metabolic control obtained by pancreatic islet transplantation could reverse diabetic neuroelectrophysiological alterations, or prevent further deterioration, we used an experimental model in which pancreatic islets (n = 1200) were injected into the portal vein of inbred Lewis rats (used as islet donors as well as recipients). Islets were injected 4 months after diabetes induction, since previous work had shown functional but not morphological damage at the nervous tissue level at this stage of the disease. Visual (V), brainstem auditory (BA) and somatosensory (S) evoked potentials (EPs) were measured in streptozotocin-induced, islet-recipient diabetic rats (n = 7), streptozotocin-induced diabetic rats (n = 16) and non-diabetic control rats (n = 12). Metabolic parameters and electrophysiological recordings were evaluated before diabetes induction, before transplantation and 4 months later. After transplantation, glycaemic levels returned to normal values within 1 week and remained so until the end of the study, as confirmed by a normal oral glucose tolerance test and by an increase in body weight. Electrophysiological recordings were altered in diabetic animals before transplantation. Four months after transplantation EP recordings improved, with a detectable gradient from the peripheral to the central structures. SEPs were significantly improved in the peripheral tarsus-L6 tract and the L6-cortex tract (P < 0.005 and P < 0.01 versus diabetic rats) and were ameliorated without achieving statistical significance in the central L6-cortex tract. BAEP latency values tended to improve in transplanted rats, but the differences versus non-transplanted diabetic animals failed to reach significance. VEP values remained clearly pathological and even deteriorated after transplantation. These results show that normalization of metabolic control by pancreatic islet transplantation can reverse some of the already established neuroelectrophysiological alterations at the peripheral nervous system level, but does not affect other alterations at the central nervous system level.

Animals↗
PubMed1996

Antigenic determinants in type 1 diabetes mellitus. Review article.

Type 1 diabetes mellitus (IDDM) is a disease caused by the autoimmune destruction of insulin-producing pancreatic beta cells that takes place in genetically predisposed individuals. The results of the studies performed so far during the search for "the target antigen" in beta cell autoimmunity have indicated that, unlike many autoimmune disorders, type 1 diabetes appears to be the result of an autoimmune response to a multiplicity of autoantigens. Autoantibodies and autoreactive T lymphocytes reacting with islet target molecules of protein or glycolipid nature have been shown in the circulation of individuals and of animal models of type 1 diabetes (NOD mouse and BB rat) before and at the onset of the disease. In the present article we have reviewed the data available on the antigenic determinants in type 1 diabetes, with particular reference to those recognized by autoantibodies which represent the best available predictive marker of future disease development in large scale screening studies.

Animals↗
PubMed1996

Insulin-like growth factors I and II stimulate extracellular matrix production in human glomerular mesangial cells. Comparison with transforming growth factor-beta.

An enhanced paracrine/autocrine activity of the insulin-like growth factor (IGF) system within the glomerulus has been implicated together with up-regulation of transforming growth factor-beta (TGFbeta) in the pathogenesis of diabetic glomerular disease. This would imply their ability to modulate extracellular matrix (ECM) and cell turnover at the mesangial level, but the direct effects of IGFs on ECM production have not been demonstrated to date. These experiments in cultured human mesangial cells were aimed at assessing the effects of IGF-I and IGF-II, compared with those of TGFbeta, on 1) ECM medium accumulation and gene expression, and 2) total protein synthesis and cell proliferation. Human mesangial cells were grown to subconfluence, growth arrested for 48 h, and then exposed for 4-24 h to serum-free medium containing IGF-I (10(-7) - 10(-11) M), IGF-II (10(-7) - 10(-11) M), TGFbeta (10(-9) - 10(-11) M), or various combinations of two of these growth factors (10(-9)M). All three growth factors dose dependently increased ECM protein and messenger RNA levels. The combination of either IGF-I or IGF-II with TGFbeta, but not the two IGFs together, produced additive effects on matrix production. Total protein synthesis was also increased by IGF-I, IGF-II, and TGFbeta, although to a lesser extent than ECM production, whereas cell proliferation was enhanced by IGFs but not by TGFbeta. These results demonstrate that IGF-I and IGF-II are effective, although less potent than TGFbeta, in stimulating the production of the ECM components that accumulate in the mesangial region during the course of diabetic glomerular disease.

Cell Division↗
PubMed1996

Beta-cell markers and autoantigen expression by a human insulinoma cell line: similarities to native beta cells.

In the present study we have evaluated the expression of different beta-cell markers, islet molecules and auto-antigens relevant in diabetes autoimmunity by a human insulinoma cell line (CM) in order to define its similarities with native beta cells and to discover whether it could be considered as a model for studies on immunological aspects of Type 1 diabetes. First, the positivity of the CM cell line for known markers of neuroendocrine derivation was determined by means of immunocytochemical analysis using different anti-islet monoclonal antibodies including A2B5 and 3G5 reacting with islet gangliosides, and HISL19 binding to an islet glycoprotein. Secondly, the expression and characteristics of glutamic acid decarboxylase (GAD) and of GM2-1 ganglioside, both known to be islet autoantigens in diabetes autoimmunity and expressed by human native beta cells, were investigated in the CM cell line. The pattern of ganglioside expression in comparison to that of native beta cells was also evaluated. Thirdly, the binding of diabetic sera to CM cells reacting with islet cytoplasmic antigens (ICA) was studied by immunohistochemistry. The results of this study showed that beta cell markers identified by anti-islet monoclonal antibodies A2B5, 3G5 and HISL-19 are expressed by CM cells; similarly, islet molecules such as GAD and GM2-1 ganglioside are present and possess similar characteristics to those found in native beta cells; the pattern of expression of other gangliosides by CM cells is also identical to human pancreatic islets; beta cell autoantigen(s) reacting with antibodies present in islet cell antibodies (ICA) positive diabetic sera identified by ICA binding are also detectable in this insulinoma cell line. We conclude that CM cells show close similarities to native beta cells with respect to the expression of neuro-endocrine markers, relevant beta cell autoantigens in Type 1 diabetes (GAD, GM2-1, ICA antigen), and other gangliosides. Therefore, this insulinoma cell line may be considered as an ideal model for studies aimed at investigating autoimmune phenomena occurring in Type 1 diabetes.

Autoantigens↗
PubMed1996

Autoimmunity to the GM2-1 islet ganglioside before and at the onset of type I diabetes.

Recently, the GM2-1 pancreatic islet ganglioside, proposed as a potential autoantigen in type I diabetes autoimmunity, has been biochemically characterized and found to be a novel ganglioside structure. In the present study, we aimed to determine whether an autoimmune response toward this novel islet molecule is 1) present in type I diabetes and is specifically directed against this molecule and not to gangliosides in general and 2) predictive of disease in high-risk subjects. To this end, the following patients have been studied: 1) 24 newly diagnosed type I diabetic subjects, 20 islet cell autoantibody (ICA)-negative first-degree relatives of type I diabetic subjects, and 25 age-matched normal control individuals; and 2) 31 prospectively evaluated ICA+ first-degree relatives of type I diabetic subjects who were followed for up to 10 years, during which 14 of them developed type I diabetes. A direct assay for autoantibodies to GM2-1 and to other pancreatic gangliosides (GM3, GD3, GD1a) was developed using an indirect immunoperoxidase technique performed directly on thin layer chromatography plates. Anti-GM2-1 autoantibodies (all belonging to the IgG class) were expressed in a high percentage of newly diagnosed type I diabetic subjects (71%), while no significant difference was found in the expression of antibodies directed against other pancreatic gangliosides (GM3, GD3, GD1a) among the different groups studied. Anti-GM2-1 autoantibodies were also present in ICA+ relatives (64%) (P < 0.001 vs. control subjects and ICA-relatives): in this group, life table analysis of progression to diabetes showed that anti-GM2-1 autoantibodies were significantly (P < 0.001) associated with disease, occurring in all relatives developing type I diabetes within 5 years and thus identifying a cohort of ICA+ subjects with markedly increased diabetes risk.

Autoantibodies↗
PubMed1995

GM2-1 pancreatic islet ganglioside: identification and characterization of a novel islet-specific molecule.

Recent studies have indicated that GM2-1, a pancreatic islet monosialo-ganglioside, is an islet-specific component whose expression is metabolically regulable and represents one of the target antigens of cytoplasmic islet cell antibodies. In the present study we aimed to biochemically characterize this molecule using a panel of biochemical techniques including gas chromatography, thin layer chromatography, enzymatic digestion and mass spectrometry. GM2-1 ganglioside was extracted from human pancreas and purified by thin-layer chromatography. Fatty acids in the ceramide (the hydrophobic portion of the molecule), identified by gas chromatography ranged from C16:1 to C24:1. The oligosaccharide chain was enzymatically digested by the sequential application of various exoglycosidases (neuraminidase followed by beta-galactosidase, followed by beta-hexosaminidase) and characterized by gas chromatography identification of the liberated sugars. The following structure was deducted from enzymatic studies and confirmed by mass spectrometry analysis: N-acetyl neuraminic acid-galactose-galactosamine-galactosamine-glucose-ceramide. This is a novel ganglioside structure, not yet described, which shares characteristics with a neuronal glycolipid autoantigen: the LM1 ganglioside. Both GM2-1 and LM1 have a single sialic acid residue in the terminal position, the same migration position on thin layer chromatography and the same number of carbohydrate moieties. In conclusion, we have characterized a novel islet-specific ganglioside molecule with unusual characteristics, such as the terminal sialic acid and the galactosamine residues, which may facilitate both its antigenicity and its involvement in beta-cell autoimmunity.

Carbohydrate Sequence↗
PubMed1995

Anti-ganglioside antibodies in new onset type 1 diabetic patients and high risk subjects.

Insulin dependent (type 1) diabetes mellitus appears to be a genetically determined autoimmune disease. Gangliosides have been implicated in type 1 diabetes as antigenic determinants recognized by islet cell antibodies (ICA) and shown to be able to modulate autoimmune phenomena in experimental diabetes. In order to explore in type 1 diabetes the humoral immune reactivity against gangliosides, taking into account their pancreatic localization and molecular characteristics, antibodies to gangliosides GM3, GM2, GM1, GD3, GD1a, GD1b, and GT1b have been investigated in sera from new onset type 1 diabetics and relatives of type 1 diabetic patients with or without insulin (CIAA) and/or islet cell autoantibodies. Using a purposefully designed sensitive ELISA method we found that presence of antibodies directed against the pacreatic disialo-ganglioside GD3 in a significant percentage of newly diagnosed type 1 diabetics (p < 0.001 vs normal controls) but not in CIAA and/or ICA positive relatives of type 1 diabetics. These findings confirm the involvement of gangliosides in autoimmune phenomena related to type 1 diabetes and suggest disialo-ganglioside GD3 as target of a humoral immune response associated with the onset of insulin-dependent diabetes.

Adolescent↗
PubMed1994

Characteristics of proteinuria in experimental diabetes mellitus.

An impairment of protein charge selectivity has been invoked to explain the initial anionic proteinuria in diabetic nephropathy. The aims of this work were to investigate charge and size protein perm-selectivity abnormalities in experimental diabetes and to monitor these changes over time after diabetes induction. Diabetes was induced in 56 Sprague-Dawley male rats by streptozotocin; the control group was represented by 38 normal rats. Blood glucose, body weight, urine volumes, and proteinuria in 24-h urine collections were evaluated at 3, 6, 9, and 12 months of diabetes. The Bradford method and mono- and bidimensional gel electrophoresis were used to determine and characterize proteinuria. Body weight increase was lower (P < 0.05, P < 0.0001, P < 0.05 at 3, 6, and 12 months, respectively), urine volumes were greater (P < 0.001, P < 0.005, P < 0.05 at 6, 9, and 12 months, respectively) and the proteinuria was significantly increased (P < 0.05 at 3 months, P < 0.001 at 6 months, P < 0.01 at 9 months, and P < 0.05 at 12 months) in diabetic rats compared with the control group. When the charge and the size of urine proteins were considered, small (30 kDa) and anionic proteins were found to be mainly excreted in diabetic rats, at 3 months of the disease; at 6 months, higher amounts of albumin and cationic proteins with higher molecular weight (50 kDa) were also found in the urine; at 9 and 12 months the changes previously described were associated with an excretion of proteins weighing about 75 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1994

Arterial hypertension and microalbuminuria in IDDM: the Italian Microalbuminuria Study.

Arterial hypertension and poor glycaemic control are central to the development of microalbuminuria in insulin-dependent diabetes mellitus (IDDM). Recent consensus has established sensitive criteria for their detection and treatment, although the proportion of patients who may benefit is unclear. Between 1988 and 1990, we measured urinary albumin to creatinine concentration ratio (A/C) in 3,636 adult out-patients with IDDM of more than 3 years duration, serum creatinine under 133 mumol/l and who were not undergoing antihypertensive treatment. A/C indicating microalbuminuria (> or = 2.38/2.96 mg/mmol, male/female) was found in 620 of 3,451 patients without proteinuria, and associated with hypertension (blood pressure > or = 140 and/or 90 mmHg; p = 0.0016; rate: 39.6%), independent of diabetes duration (p = 0.0082) and male gender (p = 0.0350; relative risk = 1.16; 95% confidence interval: 1.01-1.32). Hypertension was less common among those with normal A/C (27.5%, p < 0.0001) but was positively related with diabetes duration. Of the 1,015 patients with A/C > or = 2.0 mg/mmol 529 were reexamined. Glycated haemoglobin levels exceeded 3 SD above the mean of normal in 84.3% of the 198 microalbuminuric patients (AER = 20-200 micrograms/min), but were comparably poor (79.2%) in normoalbuminuria. Duration of diabetes was inversely related to glycated haemoglobin only in microalbuminuria (0.05 < p < 0.1). Intervention to lower blood pressure remains mainly restricted to those patients with long-term diabetes and slower development of kidney disease. Near-normalisation of glycaemia remains the priority for the majority of patients with microalbuminuria.

Adolescent↗