Search PubMed⌕ Search

Biomedical subjects

U Di Mario

Publications and source records attributed to U Di Mario.

At least 91 records · Page 5Linked to original sources
PubMed1993

D-lysine reduces the non-enzymatic glycation of proteins in experimental diabetes mellitus in rats.

D-Lysine, the non-physiological isomer of L-lysine, can competitively reduce protein non-enzymatic glycation in vitro. To study the effect of D-lysine in vivo, 6-8-week old Sprague-Dawley rats with streptozotocin-induced diabetes mellitus were treated from diagnosis for 45 days with two daily subcutaneous injections of D-lysine (0.5 g.ml-1.day-1). Another group of diabetic rats was only injected with equal volumes of physiological saline (0.9% NaCl). Glycated haemoglobin was measured by ion exchange chromatography, and glycated serum and lens proteins by boronate affinity gel chromatography. Serum and urinary creatinine concentrations were evaluated by the alkaline-picrate reaction. Urinary lysine concentrations at mid- and end-study were evaluated by cation exchange chromatography. Blood glucose concentrations, serum creatinine levels and creatinine clearances, measured at the end of the study, were similar in both diabetic groups (> 22.0 mmol/l, < or = 106 mumol/l and approximately 0.02 ml/s, respectively). Urinary lysine concentration in D-lysine-treated diabetic animals was more than 50-fold higher than in placebo-treated diabetic rats. In D-lysine-treated vs placebo-treated diabetic animals, a statistically significant reduction was found in the levels of glycated haemoglobin (stable HbA1; mean +/- SD = 3.00 +/- 0.74% vs 4.02 +/- 0.46%, p < 0.05; labile HbA1 = 3.92 +/- 0.89% vs 5.84 +/- 0.61%, p < 0.005), glycated serum proteins (1.40 +/- 0.47% vs 2.52 +/- 1.15%, p < 0.05) and glycated lens proteins (4.90 +/- 0.96% vs 5.98 +/- 0.65%, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A charge selectivity impairment in protein permselectivity is present in type 2 diabetes.

A possible loss in kidney charge permselectivity of proteins before any manifestation of nephropathy has been sought in type 2 (non-insulin-dependent) diabetes by assessing the clearances of proteins differing in charge and/or size (anionic and cationic immunoglobulins, albumin). Eighty-five consecutive outpatients with type 2 diabetes were studied and compared with 101 normal subjects. Of the patients, 14.1% were microalbuminuric and 2.3% macroalbuminuric. A significant increase in protein clearances was observed in diabetic patients in comparison with normal subjects: the median of albumin clearance was 0.09 ml/min, interquartile range (IR) 0.04-0.31 (P < 0.01 vs normals); that of anionic immunoglobulins (IgG4) 0.02 ml/min, IR 0.04-0.05 (P < 0.005 vs normals); and that of neutral/cationic immunoglobulins (IgG) 0.13 ml/min, IR 0.07-0.19 (P < 0.01 vs normals). The anionic/cationic immunoglobulin ratio median was 0.22, IR 0.11-0.43, and exceeded the upper limit of normal values in 29.4% of all patients. IgG4 clearance was positively correlated with albumin clearance (r = 0.72) and with IgG clearance (r = 0.98). Nevertheless anionic immunoglobulin clearance was increased in a number of patients (17.3%) with normal IgG excretion and even in patients (15.1%) with normal albumin clearance. Clearances of IgG4 and IgG, but not that of albumin, were correlated with the duration of diabetes. Thus, an increased anionic/cationic IgG ratio in type 2 diabetes highlights a charge selectivity defect in protein permselectivity; this selective proteinuria may reflect more accurately than does microalbuminuria an early kidney abnormality in this form of diabetes.

Adult↗
PubMed1993

High glucose inhibits cytosolic calcium signaling in cultured rat mesangial cells.

Glomerular vasodilatation in the early stages of type I diabetes mellitus apparently results from arteriolar insensitivity to vasoconstrictors. Since cytosolic free calcium ([Ca2+]i) is a major signaling mechanism for smooth muscle contraction, we studied whether growth of smooth muscle-like rat glomerular mesangial cells in media with high glucose concentration affects [Ca2+]i responses to vasoconstrictors. In cells grown for five days in 22 mM glucose, we observed blunted responsiveness to three structurally unrelated vasoconstrictors that elevate [Ca2+]i via a phospholipase C-dependent mechanism, angiotensin II, prostaglandin F2 alpha, and arginine vasopressin. Inhibition of [Ca2+]i responses was not due to an osmotic effect of high glucose, since it was not mimicked by hypertonic mannitol. While the size of intracellular Ca2+ pools was unaffected by elevated glucose, Na+/Ca2+ exchange was markedly inhibited, thus ruling out both impaired filling of Ca2+ stores and enhanced counter-regulatory mechanisms. Impaired myoinositol transport or intracellular sorbitol accumulation were not responsible for the effects of high glucose, since supplementation of media with myo-inositol or with the aldose reductase inhibitor. Alcon 1576, failed to reverse insensitivity to vasoconstrictors. On the other hand, down-regulation or pharmacological inhibition of protein kinase C completely reversed the effects of high glucose, thus indicating involvement of this signal transduction pathway. These data suggest a possible intracellular mechanism for the impaired vascular sensitivity underlying early renal hemodynamic changes in diabetes mellitus.

Animals↗
PubMed1993

Pancreatic gangliosides delay the onset of insulitis and hyperglycaemia in the low-dose streptozotocin mouse model.

Gangliosides have been shown to modulate autoimmune phenomena in experimental diabetes. The effects of a pancreatic ganglioside preparation or of a commercial brain ganglioside mixture on the insulitis and blood glucose levels in the low-dose streptozotocin mouse model of diabetes have been investigated. Fifty-five C57BL/6J male mice were grouped as follows: Group 1 (n = 20) was injected intraperitoneally with repeated low doses of streptozotocin; Group 2 (n = 10) received streptozotocin as above but was also injected with a pancreatic ganglioside preparation equivalent to 2 micrograms sialic acid 2 h before each streptozotocin dose; Group 3 (n = 15) received streptozotocin and brain-derived gangliosides in the same dose as that of pancreatic gangliosides; Group 4 (n = 10) consisted of normal animals. Half of the mice were killed on day 12 and the others on day 24 from the beginning of treatment. On day 12, among the streptozotocin-injected animals only those treated with pancreatic gangliosides remained normoglycaemic, whereas on day 24 all streptozotocin mice were hyperglycaemic. Such a result paralleled the data pertaining to insulitis scores. In conclusion, pancreatic gangliosides have a short-term protective role on the development of diabetes in the low-dose streptozotocin model, an effect therefore linked to tissue-related differences in the glycosphingolipid composition.

Animals↗
PubMed1992

Diabetes-related autoantibodies do appear in children with coeliac disease.

Humoral immune factors related to type 1 diabetes have been investigated in children with coeliac disease. Anti-insulin (IAAb), immunoglobulin (alpha IgAb), islet cell (ICA) and glucagon autoantibodies were examined in 15 children with coeliac disease at diagnosis (group 1), in 15 children with coeliac disease following a gluten-free diet (group 2) and in 30 control patients (groups 3 and 4). IAAb were present in 27% of group 1 and in 20% of group 2 patients and alpha IgAb were significantly increased in group 1 and 2 patients; two patients in group 2 were positive for ICA; none of the coeliac disease patients were positive for anti-glucagon antibodies. The levels of anti-gliadin antibodies in group 1 were positively correlated with those of alpha IgAb. Coeliac disease-related HLA antigens were not correlated with antibody presence. The presence of diabetes-related humoral immune factors in coeliac disease raises the question as to whether or not they are predictive of subclinical pancreatic damage or whether they are simply indicators of a more general autoimmune diathesis.

Adolescent↗
PubMed1992

Selective decrement of anionic immunoglobulin clearance after induced renal hemodynamic changes in diabetic patients.

The charge permselectivity of proteins was evaluated in diabetic patients after systemic and renal hemodynamic changes induced by an intravenous injection of an angiotensin-converting enzyme inhibitor (captopril) or of clonidine. Anionic immunoglobulin clearance (IgG4) was compared with that of total immunoglobulins, which have the same size but are mostly cationic, and of albumin. Ten type I hypertensive diabetic patients (group 1), 10 type 2 hypertensive diabetic patients (group 2), 5 type 1 normotensive diabetic patients (group 3), 10 subjects with essential hypertension (group 4), and 7 normal volunteers (group 5) received an intravenous injection of captopril (25 mg/100 ml in 5 min). Twelve of the hypertensive diabetic patients underwent a second provocative test with clonidine (150 micrograms/100 ml) (group 6) or placebo (100 ml saline) (group 7) with the same procedure. None of the patients had clinical nephropathy or other disorders. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured before and during the tests. A significant decrease in diastolic blood pressure was observed in groups 1, 2, 4, and 6, together with an increase in the GFR and RPF values in groups 1, 2, 3, and 4 only, as well as a decrease in renal vascular resistances in groups 1, 2, 3, 4, and 6. Both clearances and fractional clearances of IgG4 and IgG decreased after captopril in groups 1 and 2.2+ The decrease in IgG4 clearance was correlated to that of renal vascular resistances in group 1 patients. A significant decrease in the anionic-cationic immunoglobulin ratio (IgG4/IgG) was observed in groups 1, 2, and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Pancreatic islet ganglioside expression in nonobese diabetic mice: comparison with C57BL/10 mice and changes after autoimmune beta-cell destruction.

Recent observations have shown that the presumed target antigen of cytoplasmic islet cell antibodies (ICA) has properties of a monosialo-ganglioside migrating between GM2 and GM1 standards (GM2-1) and that ICA binding is higher in nonobese diabetic (NOD) than in C57BL/10SnJ mouse pancreatic frozen sections. This study aimed to characterize the ganglioside expression in NOD mouse islets in comparison with the control C57BL/10SnJ strain, taking into account possible sex differences, variations with age, and changes after autoimmune beta-cell destruction. Thus, acidic glycolipid composition was analyzed 1) in isolated islets from 11-week-old female and male NOD mice and age-matched female and male C57BL/10SnJ mice, and 2) in whole pancreas of both NOD and control mouse strains at different ages (4, 8, and 18 weeks) and of female NOD mice before and after diabetes onset. The acidic glycolipid GM2-1 is expressed in isolated female NOD islets, male NOD islets, and C57BL/10SnJ mouse islets, but quantitative analysis showed an increased amount of GM2-1 in NOD vs. C57BL/10 islets. GM3 is a ganglioside fraction expressed in female and male NOD mice and not in the C57BL/10 strain, whereas GD3 characterizes the C57BL/10 strain islets. GM2-1 is the sole ganglioside fraction in the whole pancreas to clearly decrease with age in the NOD mouse, and diabetes onset in this strain is associated with a significant decrease in the expression of this component as well as of GM3, whereas other pancreatic ganglioside (GD3, GD1a, and GT1b) levels did not significantly decrease; no age-related ganglioside change was observed in the C57BL/10SnJ mouse. Interestingly, the observed increased ICA binding in NOD islets is paralleled by the increased expression of GM2-1 islet ganglioside, and beta-cell destruction in NOD mice is associated with a significant decrease in the amount of this ganglioside in the pancreas.

Age Factors↗
PubMed1991

Charge selectivity of proteinuria in type I diabetes explored by Ig subclass clearance.

To investigate the role of protein charge in early diabetic proteinuria, the clearance of proteins differing in charge and/or size (anionic and cationic Igs, albumin) was evaluated in 98 insulin-dependent (type I) diabetic patients selected as a representative sample of the 418 patients attending our clinics. Of the patients, 12.9% were microalbuminuric and 4.8% were macroalbuminuric. Anionic and total IgG clearances were significantly increased in 30.6 and 12.2% of patients and were correlated with duration of disease. Anionic IgG4 clearances were increased in patients (9.2%) with normal IgG excretion, suggesting that charge-selectivity impairment is responsible for protein loss. Anionic Ig clearances were also higher in some patients (14.3%) with normal albumin clearance, probably as a result of different glomerular filtration and/or tubular reabsorption. The anionic-cationic IgG clearance ratio tended to increase in parallel with albumin clearance, but once above macroalbuminuric levels, it tended to fall again, indicating the concomitant presence of size-selectivity loss. The anionic IgG clearance and the anionic-cationic IgG ratio, in addition to albumin excretion, may be valuable in assessing early kidney protein charge-selectivity impairment and better characterizing normoalbuminuric patients and those in the preclinical stage of diabetic nephropathy.

Adult↗
PubMed1991

Advanced nonenzymatic glycation endproducts (AGE): their relevance to aging and the pathogenesis of late diabetic complications.

Several studies in the last decade have highlighted the importance of the hexose sugars and especially glucose, as being responsible for alterations to living protein and other molecules. The phenomenon of nonenzymatic glycation--by which the carbonyl group of glucose can directly condense with a free amino group--may be relevant for the process of aging and for the pathogenesis of late diabetic complications. Thus life-long exposure to normoglycemia in non diabetic subjects or a shorter exposure but continued association with a hyperglycemic milieu, as in diabetes mellitus, have both been shown to lead to the formation and accumulation of irreversible and highly reactive advanced glycation endproducts (AGE) over long-lived, fundamental molecules such as the constituents of arterial wall collagen, basement membranes, nerve myelin, DNA and others. For example, the introduction of foreign AGE groups into proteins might alter their tertiary structure and therefore modify their function or activity. By increasing protein-to-protein cross-links AGE could reduce protein turnover, with consequential increases in levels of modified and thus less reactive molecules. Moreover, AGE could initiate an immune response with the production of specific antibodies. Reducing the extent of nonenzymatic glycation could effectively reduce the accumulation of AGE. Many authors are experimenting with methods to achieve this aim. Amongst the products tested are aspirin and aminoguanidine which compete with glucose for the same protein amino group. D-lysine is also being investigated on the principle that by reacting with glucose in circulation, it could effectively prevent it from reaching the amino group on the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Anionic versus cationic immunoglobulin clearance in normal subjects: a novel approach to the evaluation of charge permselectivity.

The excretion of proteins differing in charge (the different immunoglobulin subclasses) and/or size (albumin, immunoglobulins) were investigated in normal subjects in a number of physiological conditions aiming at the evaluation of renal charge permselectivity. In 101 randomly selected normal subjects the urinary excretion rates of albumin, IgG4 (anionic proteins) and of total IgG (mostly cationic) were evaluated in basal conditions; the protein/creatinine urinary ratio and protein clearances were assessed in part of them. In addition, the intra- and interday variations of protein excretion were evaluated. Protein clearances were measured in a sample group after standardized physical exercise, after an amino acid load, and in orthostatism. Albumin, IgG4 and IgG were assayed using sensitive methods developed in our laboratories. The excretion rate values of albumin, IgG4 and total IgG (median, interquartile range) were 4.36 micrograms/min, (2.58-6.59), 4.25 ng/min (2.6-7.6), and 1.47 micrograms/min (0.85-2.44), respectively. The clearances of the three proteins (mean +/- SD) were 0.13 +/- 0.07, 0.017 +/- 0.012 and 0.14 +/- 0.08 ml/min x 10(-3), respectively. The IgG4/IgG ratio averaged 0.1 and was always below 0.25. Protein excretion rates showed a noticeable variation during the day and from day to day. Physical exercise, the change of posture and the amino acid load significantly increased proteinuria but did not significantly modify the anionic/cationic immunoglobulin ratio. Thus, the anionic/cationic immunoglobulin ratio of about one tenth, substantially stable during dynamic tests, in normal subjects may be considered an index of physiological renal protein charge permselectivity.

Adolescent↗
PubMed1990

Autoantibodies to insulin do appear in non-diabetic patients with autoimmune disorders: comparison with anti-immunoglobulin antibodies and other autoimmune phenomena.

Insulin- and anti-immunoglobulin-antibodies have been recently reported in pre-diabetic subjects: the former has been proposed as a predictive marker of Type I diabetes in non-diabetic-subjects. To evaluate the diabetes-related specificity of these antibodies, the presence of insulin autoantibodies, using a recently developed and highly sensitive competitive radioimmune assay, and of anti-immunoglobulin antibodies together with that of immune complexes and of other autoantibodies has been investigated in patients with organ- or non-organ-specific autoimmune diseases. One hundred and eleven serum samples were assayed from patients with Graves' disease, primary hypothyroidism, chronic autoimmune thyroiditis, Addison's disease, chronic autoimmune hepatitis, pernicious anemia, lupus erythematosus, and rheumatoid arthritis, together with 45 serum samples from normal subjects. From patients with autoimmune diseases, 32.4% of all sera revealed values of insulin autoantibodies above the limit of positivity (p less than 0.001); anti-immunoglobulin antibodies were present in 4.1% of patients (NS); immune complexes were found in 19.5% (NS) of all patients, but in 38% of patients with Graves' disease and chronic hepatitis (p less than 0.02). There was a trend for multiple autoantibody positivity to be associated with high levels of insulin autoantibodies (p less than 0.05). Thus, whereas contrary to expectation anti-immunoglobulin antibodies are not associated with non-diabetes-related autoimmune diseases, increased humoral immunoresponsiveness to endogenous insulin appears to be related to autoimmunity in general rather than restricted to Type I diabetes.

Adult↗
PubMed1989

New parameters to monitor the progression of diabetic nephropathy.

The possible differential elimination of the anionic IgG4 and of the other cationic IgG molecules whose pH differs but whose other characteristics are similar, has been hypothesized as a possibly useful parameter in monitoring preclinical diabetic nephropathy. An enzyme-linked immunosorbent assay method has been developed, based on a sandwich technique with subclass-specific antiimmunoglobulin monoclonal antibodies, which detects about 2 ng/mL IgG4. A sensitive radioimmunoassay method has been used to detect IgG. Normoalbuminuric, microalbuminuric, and macroalbuminuric patients, together with normal control subjects, were included in the cross-sectional study. Whereas IgG levels were elevated, as expected, in macroalbuminuric patients, it was interesting to note that IgG4, but not total IgG, levels were elevated in microalbuminuric patients. The IgG4/IgG ratio was increased almost to the same extent in microalbuminuric and macroalbuminuric patients. These findings are strongly in favor of the selective elimination of the acid medium-sized protein, IgG4, in incipient diabetic nephropathy. The measurement of immunoglobulin subclasses in the urine appears to be a promising parameter to characterize and subgroup diabetic patients with preclinical diabetic nephropathy.

Adolescent↗
PubMed1989

Humoral and cellular immunological factors as possible markers of clinical relapse in HLA-typed Graves' patients followed with time.

Humoral and cellular immune factors were studied in 33 newly diagnosed Graves' patients at diagnosis and in 12 of these patients at regular intervals thereafter. All the patients were treated with carbimazole for 15 months (initially 60 mg and then 20 mg supplemented with L-Thyroxine). The incidence of relapse after treatment was 42%. Thyrotropin receptor antibodies (TRAb), T-cell subsets, K and NK cells and mononuclear cells expressing surface antigen markers of different activation were evaluated respectively by the use of a radioimmunoassay and a panel of monoclonal antibodies. Patients in the follow-up study were HLA-A, B, C and D typed. TRAb levels (91%) and levels of 4F2-positive cells (73%) and class II-positive lymphocytes (69.6%) were significantly increased in newly diagnosed Graves' patients in comparison with normal controls, whereas CD8 cells were significantly decreased. There was a significant inverse correlation between the increase in 4F2-positive cells and TRAb values. In the follow-up study both humoral and cellular immunological parameters showed a wide variation in levels, but TRAb, 4F2 and L243 values declined on average with respect to diagnosis. After 15 months some patients still showed abnormal values of activated T cells and TRAb values. All patients who relapsed (42%) after medical treatment showed a significant increase of 4F2-positive cells, and some of TRAb, some time before the appearance of clinical symptoms. Finally, no correlation was found between HLA type and relapse of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Evidence for an immune-mediated mechanism in food-induced migraine from a study on activated T-cells, IgG4 subclass, anti-IgG antibodies and circulating immune complexes.

Various immunological studies have revealed controversial outcomes on pathogenetic mechanisms of food-induced migraine. In order to better define the immune status of this disease we studied 21 patients for circulating immune complexes (CIC). Six out of them were also studied for lymphocyte subpopulations, IgG4 and anti-IgG antibodies, before (TO), 4 hours after (T4), and 72 hours after (T72) a specific challenge with 250 ml of milk. The ClqSp assay was used to determine CIC. Lymphocyte subpopulations were defined by the following monoclonal antibodies (Mab): OKT3, OKT4, OKT8, 4F2, H366, TAC, 5E9, L.243 and DA6.231. IgG4 subclass was assessed by using a mouse specific Mab. Anti-IgG antibodies were determined by using HPLC. The result showed an increased incidence of CIC (28.6%) when compared to the control group (10%). Total T-cells (OKT3+) showed a marked increase at T4 (p less than 0.01) and a subsequent decrease at T72 (p less than 0.02). Interestingly, T-activated cells (4F2+ and TAC+) showed a parallel trend at T4 (respectively p less than 0.02 and less than 0.01) and a subsequent decrease at T72 only for the Tac+ cells (p less than 0.05). Also K and NK cells (H366+) showed an early increase at T4 (p less than 0.05). No significant variation was observed in the study of the expression of DR antigens (L.243 and DA6.231) at the three times. IgG4 and anti-IgG antibodies values showed no variation in their time-course.+

Adolescent↗
PubMed1989

Nonenzymic glycation of isolated human glomerular basement membrane changes its physicochemical characteristics and binding properties.

The chronic hyperglycemia in diabetes mellitus enhances the nonenzymic glycation of structural proteins possibly increasing the formation of highly reactive advanced glycation end products (AGE). These protein changes might be involved in tissue-damaging mechanisms leading to diabetic complications, including diabetic nephropathy. To simulate these events, an in vitro model, based on isolated human glomerular basement membrane (hGBM), has been developed. In this study we have investigated the extent of AGE formation and the binding changes induced by the nonenzymic glycation of hGBM. An enriched fraction of hGBM was isolated from normal human kidneys and glycated in vitro by incubation with glucose (500 mmol/l) at 37 degrees C for 10 days. The presence of AGE was investigated by two methods - spectrofluorescence and the diazonium salt reaction - both specific for this type of chemical entity. The binding capacity of glycated hGBM was tested by a 10-day incubation with human insulin, albumin, immunoglobulin G and fibrinogen. Higher relative spectrofluorescence values at 440 nm emission (20.0 +/- 2.0 vs. 12.5 +/- 5.0) and higher absorbance values at 492 nm (0.798 +/- 0.063 vs. 0.429 +/- 0.228) indicated the presence of increased levels of AGE in glycated vs. native hGBM. Insulin and the three proteins were bound to hGBM in increased amounts after its glycation (p less than 0.05). The results obtained in this in vitro model confirm that enhanced nonenzymic glycation of hGBM induces the formation of AGE and possibly, through these compounds, alters its physicochemical and binding properties. This reaction might contribute to the mechanisms eventually leading to diabetic nephropathy.

Basement Membrane↗