Conditions: Healthy Volunteers Diabetes Mellitus, Type 1
Keywords: dihydrotetrabenazine beta cell mass diabetes mellitus
Allocation: NON_RANDOMIZED | Intervention model: PARALLEL
Enrollment: 23
Healthy volunteers: yes

Brief summary:
Type 1 diabetes mellitus (T1DM) develops when there is impaired insulin production due to loss of insulin producing cells (beta cells). The amount of insulin that can be produced is imperfectly correlated with beta cell mass (BCM). The development of a reliable method to noninvasively quantify the total amount of insulin producing beta cells would be of great benefit by providing an important endpoint for the development of new treatments of diabetes. The investigators have previously identified a specific marker on islet cells called vesicular monoamine transporter 2 (VMAT2) that the investigators now propose to use in positron emission tomography (PET) scanning to determine islet beta cell mass. The PET radiopharmaceutical 18 F-fluoropropyl(FP)-dihydrotetrabenazine(DTBZ) has been used previously in human subjects without adverse effects. It has shown promise in differentiating type 1 diabetes and non-diabetes. The investigators now hypothesize that repeat PET scans will be reproducible in the same subject. Subjects with normal BCM will be recruited from among normal weight non-diabetic people with plasma insulin levels within the normal range. Subjects with predicted reduced BCM will be recruited from among patients with T1DM who have low or non-measurable insulin levels. Two PET scan measurements will be taken in each subject and the amount of VMAT2 in the pancreas will be and compared for reproducible findings. Biochemical testing will also be performed and compared to PET scans as a potential indirect marker of beta cell mass.

Detailed description:
Diabetes results when the insulin secretory capacity of the beta cell population is lost or severely compromised.Plasma insulin levels have been used as a surrogate marker of beta cell mass (BCM) but insulin levels often do not correlate well. A "gold standard of measurement" to obtain BCM would be of great value. The aim of the proposed study is to evaluate an islet imaging technique using PET scanning to directly measure BCM and thus provide valuable information for monitoring disease progress and response to therapy in people with diabetes and in people at high risk for diabetes. Type 1 diabetes (T1DM) occurs when the beta cells are selectively destroyed by a T cell mediated autoimmune process. People at high risk for developing T1DM, such as first degree relatives of patients with T1DM, can sometimes be identified before the disease develops by measuring autoantibodies to beta cells, however this test is neither sensitive nor specific. Little is known about the natural history of BCM, turnover and cell lifetime, or the course of inflammation in diabetes. This is principally because the pancreas is a highly heterogeneous organ that is difficult to biopsy without significant complications, and BCM only comprises 1 to 2% of the total volume. Accurate assessment of BCM in human diabetes is limited to autopsy studies, which usually suffer from inadequate clinical information; thus, the development of non-invasive means of BCM measurement could be important for interventional therapies of T1DM, islet regeneration/stem cell therapy and islet transplantation.

Arms:
arm 1: Pancreatic 18 F-FP-DTBZ uptake will be measured with PET scanning in healthy controls: subjects with predicted normal BCM (healthy, normal weight, non-diabetic individuals who have stimulated insulin and c-peptide levels within the normal range). arm 2: Pancreatic 18 F-FP-DTBZ uptake will be measured with PET scanning in patients with longstanding T1D: subjects with predicted reduced beta cell mass (subjects with established T1DM who have low or no measurable stimulated insulin and c-peptide levels).

Interventions: intervention 1: 18 F-FP-DTBZ intervention 2: PET Scanning
Intervention descriptions: intervention 1: The drug, no carrier added \[18 F\]-FP-DTBZ, is formulated in 5% (v/v) ethanol in 0.9% sterile saline solution to produce \[18 F\]-FP-DTBZ for injection. Subjects will receive a single i.v. administration of no more than 7.6 millicuries (mCi) of \[18 F\]-FP-DTBZ for injection immediately prior to imaging. The specific activity at time of injection will less than 1.0 mCi/microgram and thus for a 7.6 mCi dose the maximal mass dose will be less than 10 microgram. intervention 2: Individuals will be imaged continuously (i.e. dynamically) for 2 hours.

Protocol document: