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Biomedical subjects

M V Taglietti

Publications and source records attributed to M V Taglietti.

8 recordsLinked to original sources
PubMed1999

Reversal of diabetes in mice by implantation of human fibroblasts genetically engineered to release mature human insulin.

Autoimmune destruction of pancreatic beta cells in type I, insulin-dependent diabetes mellitus (IDDM) results in the loss of endogenous insulin secretion, which is incompletely replaced by exogenous insulin administration. The functional restoration provided by allogeneic beta-cell transplantation is limited by adverse effects of immunosuppression. To pursue an insulin replacement therapy based on autologous, engineered human non-beta cells, we generated a retroviral vector encoding a genetically modified human proinsulin, cleavable to insulin in non-beta cells, and a human nonfunctional cell surface marker. Here we report that this vector efficiently transduced primary human cells, inducing the synthesis of a modified proinsulin that was processed and released as mature insulin. This retrovirally derived insulin displayed in vitro biological activity, specifically binding to and phosphorylation of the insulin receptor, comparable to human insulin. In vivo, the transplantation of insulin-producing fibroblasts reverted hyperglycemia in a murine model of diabetes, whereas proinsulin-producing cells were ineffective. These results support the possibility of developing insulin production machinery in human non-beta cells for gene therapy of IDDM.

Animals↗
PubMed1999

Insulin secretory patterns and blood glucose homeostasis after islet allotransplantation in IDDM patients: comparison with segmental- or whole-pancreas transplanted patients through a long term longitudinal study.

IDDM patients undergoing islet, segmental pancreas or whole pancreas allotransplantation were studied at regular intervals after surgery (3-6 months, 1, 2, 3 and 4 years) to evaluate glycometabolic control (24 h metabolic profile, OGTT) and serum free insulin response to insulinogenic stimuli (arginine, IVGTT). Patients received the same immunosuppressive therapy, based on cyclosporin, steroids and azathioprine. Islet transplanted patients showed: 1) an early peak of insulin secretion after arginine, that was maintained up to 4 years; 2) an early, but low peak of insulin secretion after IVGTT, which was lost at 3 years, despite evidence that islets were still functioning (insulin independence with normal HbAlc levels); 3) a diabetic-like response to OGTT at 3 months, which improved at 2 years (IGT response); 4) fasting euglycemia with mild and reversible post-prandial hyperglycemia during the 24 h metabolic profile, which was maintained for up to 2 years. Insulin secretory patterns of islet transplanted patients were similar to segmental pancreas transplanted patients, and lower than whole pancreas transplanted patients. The reduced beta cell mass transplanted and the functional denervation of the transplanted islets seem to be the major determinants of this behaviour.

Adult↗
PubMed1998

Long-term in vitro exposure to high glucose increases proinsulin-like-molecules release by isolated human islets.

The aim of this study was to determine the effect of long-term in vitro exposure to high glucose on the release and content of proinsulin and insulin in human islets. After 48 h culture in CMRL medium at 5.5 mM (control islets) and 16.7 mM glucose (experimental islets), islets were perifused and acutely stimulated with 16.7 mM glucose, followed by 3.3 mM glucose. Compared with control islets, experimental islets showed a higher basal release of true insulin and proinsulin-like-molecules (PLM), with no increase of true insulin and PLM release in response to 16.7 mM glucose, and a paradoxical true insulin release in response to 3.3 mM glucose; the PLM/total insulin ratio increased significantly after 16.7 mM glucose. Moreover these islets showed a decreased true insulin content and an increased PLM/total insulin ratio. Quantitative ultrastructural analysis of granules, supported by double gold immunostaining with monoclonal antibodies against proinsulin and insulin, showed an increased proinsulin to insulin ratio in beta-cells from experimental islets. These data support in vitro what was recently shown in vivo, and further confirm that culture in high glucose is a useful tool to mimic the effect of in vivo chronic hyperglycemia on human beta-cell function.

Adult↗
PubMed1997

Islet transplantation in IDDM patients.

This single-centre study investigated parameters that positively correlated with the success rate after islet allotransplantation in insulin-dependent diabetic (IDDM) patients. Twenty-one intrahepatic, fresh islet transplantations were performed in 20 IDDM patients (one patient had two transplants), after or simultaneous with kidney transplantation. The correlation between number and purity of transplanted islets and final outcome was investigated. One patient died of a cardiac arrest several hours after islet transplantation; this patient was not included in the follow-up analysis. Three patients (15%) experienced acute, irreversible, early failure of islet function, which was considered as a 'presumed rejection'. Nine patients (45%) achieved either complete insulin-independence (seven cases) or a reduction (> 50%) of exogenous insulin requirement (two cases), with sustained serum C-peptide secretion (0.89 +/- 0.04 nmol/l; duration: 21 +/- 7 months, range 2-58 months). Liver biopsy, performed 3 years after transplantation in one successful case, showed normal islets within the hepatic parenchyma. Eight cases (40%) did not show any metabolic effect of islet transplantation, with low serum C-peptide levels ('presumed function exhaustion'). Metabolic investigations performed in successful cases showed an early phase of insulin release after arginine, mild and reversible postprandial hyperglycaemia and normal HbA1c levels. Success of islet transplantation positively correlates with the number (p < 0.05) of the transplanted islets. Islet transplantation is a safe procedure, with 45% success rate, in terms of insulin-independence or relevant reductions of exogenous insulin requirement, although success can be transient.

Adult↗
PubMed1996

Deranged platelet calcium homeostasis in diabetic patients with end-stage renal failure. A possible link to increased cardiovascular mortality?

OBJECTIVE: Platelet hyperfunction is a typical feature of the prothrombotic state that frequently complicates the natural history of diabetes. In uremia, a bleeding diathesis is present, which principally involves the primary phase of hemostasis. Thus, in patients with uremia of diabetic origin, the infrequent coexistence of two opposite alterations of hemostasis takes place. In patients with uremia, an increased incidence of cardiovascular events and related mortality is observed. This phenomenon is greatly amplified in uremia of diabetic origin. Calcium homeostasis is a critical aspect of platelet function, which has recently become available in human diseases. The aim of this study was to evaluate calcium homeostasis in platelets from patients with uremia of diabetic and nondiabetic origin. RESEARCH DESIGN AND METHODS: We evaluated, by means of Fura 2, the intracellular concentration of ionized calcium ([Ca2+]i) in platelets from 18 patients with uremia of diabetic origin, 12 patients with uremia of nondiabetic origin and 16 healthy control subjects [Ca2+]i was evaluated in resting conditions and after stimulation with 0.05, 0.1, 0.5 U/ml thrombin. RESULTS: Platelets from uremic patients with diabetes had higher resting [Ca2+]i than both control subjects (P = 0.01) and uremic patients without diabetes (P = 0.001). Similarly, after stimulation with thrombin, the absolute increase of [Ca2+]i was higher (P < 0.05) in platelets from uremic patients with diabetes compared with both control subjects and uremic patients without diabetes. The relative increase of [Ca2+]i was higher (P < 0.05) than normal in platelets from uremic patients after weak or intermediate strength thrombin. No correlation were present between [Ca2+]i values and other clinical and laboratory variables potentially associated with platelet hyperfunction. CONCLUSIONS: Diabetes and uremia in combination further deteriorate the abnormal platelet calcium homeostasis observed in uremia.

Biomarkers↗
PubMedDate not supplied

Lessons from in vitro perifusion of pancreatic islets isolated from 80 human pancreases.

We report the average insulin response to acute glucose measured by in vitro perifusion of pancreatic islets isolated from 80 consecutive human organs. Different perifusion parameters were considered [basal release, stimulation index (SI), time to peak, incremental area under the curve delta-AUC alpha)], and the correlation among them was determined. SI positively correlated with delta-AUC alpha (p < 0.001, r = 0.80) while negatively with time to peak (p < 0.05, r = -0.23). We also evaluated several variables of the isolation procedure that might affect responsiveness to glucose by human islets. Sex and age of pancreas donors, cold ischemia time, duration of the digestion, collagenase concentration, and lot characteristics (collagenase, trypsin, clostripain, and proteases activity), and final islet yield were considered. Multivariate regression analysis showed only an independent association between SI and the concentration of collagenase (p = 0.01).

Adolescent↗
PubMedDate not supplied

[Pregnancy during nephropathy].

We illustrate two cases of pregnancy complicated by previously onset chronic nephropathy. In spite of two completely different pathogenetic mechanisms for chronic renal insufficiency (IgA nephropathy in one case and vescico-ureteral reflux in the other), renal function at the beginning of the pregnancy was similar and only partially impaired. In either case the pregnancy lowered by 50% the residual glomerular filtration rate. Only minimum recovery was observed during several months of follow-up.

Adult↗