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Objective: To investigate the effect of intravenous insulin therapy combined with nicotinamide in the metabolic control and beta-cell function of newly diagnosed type 1 diabetic subjects in comparison with intensive insulin therapy and nicotinamide alone.Research Design and Methods: A total of 34 newly diagnosed type 1 diabetic patients were included. After the correction of initial metabolic disturbances, subjects were randomly assigned to the following three groups within 72 h after admission: 1) intensive insulin therapy + placebo (C) (n = 12); 2) intensive insulin therapy + nicotinamide, 700 mg three times a day (NIC) (n = 11); and 3) 72-h intravenous insulin followed by intensive insulin therapy + nicotinamide, 700 mg three times a day (NIV) (n = 11). The subjects were monitored for 12 months. GAD, tyrosine phosphatase antibodies, and insulin autoantibodies were measured. C-peptide was measured basally and after 2, 4, 6, 8, and 10 min of 1 mg intravenous glucagon. HbA1c, glucagon, and antibody measurements were determined initially and at 1, 3, 6, 9, and 12 months.Results: HbA1c values declined to normal after treatment was initiated in all groups and remained not significantly different during the follow-up period. We did not find differences between experimental (NIC and NIV) and placebo (C) groups in terms of beta-cell function, considering basal or glucagon-stimulated C-peptide (maximal stimulated C-peptide and area under the curve [AUC] of C-peptide) values during the follow-up period. After pooling data from the NIC and NIV groups (both including nicotinamide) and comparing it with data from the C group, the results remained unchanged. At diagnosis, GAD positivity was observed in 10 of 12, 8 of 11, and 10 of 11 subjects (NS) in the C, NIC, and NIV groups, respectively, and IA2 positivity was observed in 3 of 12, 4 of 11, and 4 of 11 subjects (NS) in the C, NIC, and NIV groups, respectively. Antibody titers displayed a similar behavior in all groups during the follow-up period.Conclusions: Our pilot study failed to demonstrate that the addition of 72-h intravenous insulin and nicotinamide to conventional intensive insulin therapy produces any beneficial effect in newly diagnosed type 1 diabetic subjects in terms of beta-cell function and metabolic control. [ABSTRACT FROM AUTHOR]