Effect of long-acting somatostatin analog (SMS 201-995) on high glomerular filtration rate in insulin dependent diabetic patients.

Increased glomerular filtration rate (GFR) is considered to be a determinant factor in the pathogeny of diabetic nephropathy. In this study we analyzed the effect of a long-acting somatostatin analog (SMS 201-995) on high GFR in type I diabetes patients. Five subjects were involved in a cross-over double blind study. All the patients had a high GFR (205 +/- 18 ml/min/1.73 m2). They were randomly submitted to a 10-hour night i.v. infusion of SMS 201-995 at a rate of 8 g/min and placebo. GFR was measured using a blood 99mTc-DTPA decay curve during the last hour of infusion. After 10-hour SMS 201-995 treatment, no statistical change was observed in GFR. However, a slight decrease was noted in four of the five subjects (183.07 +/- 22.31 vs 202.83 +/- 13.23 ml/min/1.73 m2). GFR was higher only for the patient who presented with a mild hypoglycemic reaction during the infusion, which may increase glomerular filtration by itself. All the other parameters measured remained unchanged.

Inter and intra individual variability of acute insulin response during intravenous glucose tolerance tests.

To analyze the inter- and intra-individual variability of acute insulin response to intravenous glucose (AIRG), 41 healthy volunteers underwent an intravenous glucose tolerance test (IVGTT) and 29 of them a second IVGTT 1 to 9 months later. Basal glycemic, insulin (IRI), and C-peptide values were similar for both IVGTTs. Different indices were used to estimate AIRG. A great inter-individual variability of AIRG (CV around 60%) was detected. AIRGs were not statistically different between the two IVGTTs, and the within-subject variation was fair at the group level (CVs approximately 30%). However, individual coefficients of variation ranged from 2 to 60% between the two tests. Moreover, subjects considered as "low" responders during test 1, returned to "normal" values during test 2. Conversely, other subjects dropped to a "low" response in IVGTT 2. Insulin peak (IRI max) occurred between 1 and 3 minutes after glucose infusion in 85% of the control population, but time points of IRI max were different for 45% of the population between the two IVGTTs. These results suggest that AIRG during IVGTTs are reproducible at the group level, but that AIRG has to be interpreted with caution in individual early detection of pre-insulin-dependent diabetes mellitus because inter- and intra-individual variability could be high even for some normal subjects.