Review Question - QID 109975

This patient who presents with polydipsia, polyphagia, and polyuria has developed diabetes after being placed on a post-transplantation drug, most likely tacrolimus, which is associated with an increased risk of developing diabetes. Tacrolimus functions by binding to FKBP-12 to inhibit calcineurin.

Tacrolimus, also known as FK506, is an immunosuppresive drug that is given for maintenance of prophylaxis against transplant rejection. It provides this function by serving as a calcineurin inhibitor after binding the intracellular FKBP-12 protein. Since calcineurin is responsible for activating the transcription of interleukin 2, tacrolimus impairs IL-2 production and release. IL-2 is a major activation and survival factor for T-cells so this decrease in the production of IL-2 functions as a powerful immunosuppressant. Side effects of tacrolimus include nephrotoxicity, neurotoxicity, and an increased risk of developing diabetes.

Incorrect Answers:
Answer 1: Binding to cyclophilin D to inhibit calcineurin is the mechanism of action for cyclosporine, which is associated with neurotoxicity, hirsutism, gingival hyperplasia but not diabetes.

Answer 3: Inosine monophosphate dehydrogenase inhibitor is the mechanism of action for mycophenolate mofetil, which is associated with gastrointestinal upset, hypertension, and pancytopenia but not development of diabetes.

Answer 4: Conversion into 6-mecaptopurine is the mechanism of action for azathioprine, which is associated with pancytopenia but not development of diabetes.

Answer 5: Targeting the α-chain of the IL-2 receptor is the mechanism of action for basiliximab, which is associated with edema, tremor, and hypertension but not development of diabetes.

Bullet Summary:
Tacrolimus leads to immunosuppression by binding with FKBP-12 to inhibit calcineurin and increases the risk of developing diabetes.