Deciphering Tacrolimus-Induced Toxicity in Pancreatic β Cells

Area of Science:

• Endocrinology
• Immunology
• Molecular Biology

Background:

• Type 2 diabetes mellitus (T2DM) involves dysfunctional beta cell transcription factors like FoxO1 and MafA.
• Posttransplant diabetes mellitus shares similarities with T2DM, arising from insulin resistance and immunosuppressants, particularly calcineurin inhibitors (CNIs).

Purpose of the Study:

• To investigate the impact of tacrolimus (TAC), cyclosporine A (CsA), and metabolic stressors on beta cell function.
• To compare the effects of TAC and CsA on beta cell transcription factors and insulin secretion in vitro and in vivo.

Main Methods:

• Insulinoma beta cells and pancreata from Zucker rats were exposed to glucose, palmitate, TAC, and CsA.
• Changes in nuclear transcription factors (FoxO1, MafA), insulin content, insulin secretion, calcineurin, and NFAT were analyzed.

Main Results:

• Glucose plus palmitate increased nuclear FoxO1 and decreased nuclear MafA; TAC exacerbated these changes.
• Both TAC and CsA reduced insulin content, but TAC also affected insulin secretion.
• TAC withdrawal or switching to CsA reversed TAC-induced changes; TAC potentiates glucolipotoxicity more than CsA.

Conclusions:

• Tacrolimus potentiates glucolipotoxicity in beta cells, likely through shared pathways of dysfunction, leading to more severe beta cell impairment than CsA.
• The diabetogenic effect of CNIs may involve calcineurin-NFAT pathway inhibition, but this doesn't fully explain TAC's stronger impact.
• TAC-induced beta cell dysfunction appears to be potentially reversible.