Conditions: Type 2 Diabetes Mellitus Bone Remodeling
Keywords: Type 2 diabetes exenatide Byetta
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 14
Healthy volunteers: yes

Brief summary:
The purpose of this study is to determine changes in bone turnover markers and calcitonin following the initiation of exenatide compared to placebo in postmenopausal women wtih type 2 diabetes.

Hypothesis 1a: Bone resorption (measured by osteocalcin and bone-specific alkaline phosphatase) will be lower and bone formation (measured by type I collagen crosslinked aminoterminal peptide in urine (Urine NTX)) will be higher when subjects are treated with exenatide compared to when subjects are treated with placebo.

Hypothesis 1b: Calcitonin levels will not vary significantly between periods of treatment with exenatide vs. placebo.

Detailed description:
Patients with Type 2 Diabetes Mellitus (T2DM) are at an increased risk of fracture, despite having bone mineral density (BMD) levels similar to age and sex matched cohorts. Recent studies have indicated that changes in incretin (INtestinal seCRETion of INsulin) hormones in the setting of T2DM may play a role in bone metabolism. Two of these incretin hormones, gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), have been shown to be involved in bone turnover regulation, in addition to their effect in increasing insulin secretion and decreasing glucagon secretion in a glucose-dependent manner. In addition, the rise in glucagon-like peptide-2 (GLP-2) in the postprandial state has been found to have a direct effect on reduced bone resorption in a non-fasting state and treatment with GLP-2 improved BMD in postmenopausal women. Due to their glucose lowering effects, incretin hormones have been a therapeutic target for the treatment of T2DM through GLP-1 receptor agonists (i.e. exenatide) or inhibition of incretin hormone metabolism via dipeptidyl peptidase 4 (DPP-4)inhibitors. The GLP-1 receptor analog exenatide leads to an approximate 13-fold increased GLP-1 effect compared to approximate doubling of incretin hormone levels with current DDP-4 inhibitors. In rodent models, calcitonin levels rise significantly following treatment with GLP-1 receptor agonists, leading to c-cell hyperplasia. However, review of calcitonin changes in humans and cynomolgus monkeys treated with GLP-1 receptor agonists have not shown similar results.

Arms:
arm 1: Study participants in phase1 will receive the study drug, exenatide, at a dose of 5mg subcutaneously twice daily 30 minutes before meals for one month. During the second month of the study, the dose of exenatide will be increased to 10mg subcutaneously twice daily before meals for one month. During the third month of the study, no study medication will be given and this will serve as a "wash out" period prior to the second phase of the study (placebo). During the fourth and fifth months, study participants will get placebo alternatives to exenatide 5mg and exenatide 10mg, respectively, subcutaneously twice daily before meals. arm 2: Study participants in phase1 will receive the saline placebo, at a dose of 5mcg subcutaneously twice daily 30 minutes before meals for one month. During the second month of the study, the saline placebo will be increased to 10mcg subcutaneously twice daily before meals for one month. During the third month of the study, no treatment will be given and this will serve as a "wash out" period prior to the second phase of the study. During the fourth month study participants will receive Exenatide 5mcg twice daily with meals. During the fifth month, study participants will receive exenatide 10mcg, subcutaneously twice daily before meals.

Interventions: intervention 1: exenatide intervention 2: Saline
Intervention descriptions: intervention 1: exenatide 5mcg sq twice daily for one month and exenatide 10mcg twice daily for month 2. The 3rd month is a washout period. Month 4 and 5 saline placebo is given as 5mcg and 10mcg respectively. intervention 2: Month 1 and 2 saline placebo is given as a low and high dose respectively. The 3rd month is a washout period. Month 4 exenatide 5mcg sq twice daily and for month 5 exenatide 10mcg twice daily is administered.

Protocol document: