New research monitoring the effects of islet cell transplantation resulted in near-normal metabolic control and decreased hypoglycemia. Islet cell transplantation, which has been used experimentally to treat type 1 diabetes, places cells from an organ donor into the pancreas of a person with type 1 diabetes. Islets are cells found in clusters throughout the pancreas. The islets themselves contain beta cells, which make insulin, the hormone that helps the body use glucose for energy.
During the 18-month study, physicians used a continuous glucose monitoring system (CGMS) to monitor the effects of the islet cell transplant procedure on patients with type 1 diabetes. The results were intriguing.
"We did find CGMS to be useful in telling us how well our patients were doing after transplantation," Lisa Gorn, DO, from the Diabetes Research Institute at the University of Miami, in Florida, said during her presentation. "It was also useful in telling us when our patients were not doing well after transplantation."
For the study, glycemic control was assessed in 25 patients with type 1 diabetes — 12 underwent islet transplantation (ITx group) and 13 were controls. In all patients, weight, body mass index, insulin use, hemoglobin A1c (HbA1c), 90-minute glucose after a mixed-meal tolerance test, and fasting C-peptide/glucose ratio (CPGR) were monitored.
Mean interstitial glucose, standard deviation, glucose variability, and time in hyperglycemia (% glucose tolerance [GT] > 140 mg/dL), hypoglycemia (%GT < 54 mg/dL), and normoglycemia (%GT between 54 and 140 mg/dL) were measured in 72-hour periods with CGMS, in the control group at baseline and in the ITx group at 3, 6, 9, 12, 15, and 18 months after transplantation; these measurements were analyzed as indicators of graft dysfunction. Linear mixed-model regressions were assessed if CGMS findings at the time of graft dysfunction were significantly different than those at preceding time points.
At all time points except at 3 and 15 months, mean interstitial glucose and glucose variability were significantly lower in the ITx group than in the control group. At all time points, the percentage of time in hypoglycemia was significantly lower in the ITx group than in the control group.
In the ITx group, there was no association between insulin use and time in hypoglycemia. Time in normoglycemia was higher in the ITx group than in the control group at all times except at 15 months. Time in hyperglycemia was significantly lower at 6, 9, 12, and 18 months in the ITx group than in the control group. HbA1C, 90-minute glucose, and CPGR were significantly better at all time points after transplantation. Mean interstitial glucose, standard deviation, glucose variability, and percent time in hyperglycemia were indicators of graft dysfunction, and increased by 19.4 mg/dL,15.1 mg/dL,19.8 mg/dL, and 19.4%, respectively, when graft dysfunction occurred.
"This could be the gold standard — but with some modifications to it,” said Rhoda Cobin, MD, a clinical professor of medicine at Mount Sinai Medical Center in New York, and a past president of the American Association of Clinical Endocrinologists. Dr. Cobin was not involved in the study.
American Association of Clinical Endocrinologists 17th Annual Meeting and Clinical Congress: Abstract 225. Presented May 16, 2008.