Antioxidants Complement the Requirement for Protein Chaperone Function to Maintain β-Cell Function and Glucose...

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Biology

Background:

• Proinsulin misfolding in the endoplasmic reticulum (ER) triggers cell death, but the mechanism is unclear.
• Beta-cell (β-cell) failure contributes to type 2 diabetes.
• ER stress and oxidative stress are implicated in β-cell dysfunction.

Purpose of the Study:

• To investigate the role of the ER co-chaperone P58(IPK)/DnajC3 in β-cell function and survival.
• To elucidate the mechanisms by which protein misfolding leads to β-cell failure.
• To explore potential therapeutic strategies for diabetes linked to ER stress.

Main Methods:

• Analysis of P58(IPK) knockout (P58(IPK-/-)) mice exhibiting diabetic phenotypes.
• Assessment of β-cell function, mass, oxidative stress, and apoptosis.
• Intervention studies using chemical chaperones, Chop deletion, and antioxidant/chaperone feeding.
• Evaluation of MafA localization and β-cell function in Akita mice with mutant proinsulin.

Main Results:

• P58(IPK-/-) mice developed diabetes due to decreased β-cell function and mass, with increased oxidative stress and cell death.
• Chemical chaperone treatment and Chop deletion ameliorated the diabetic phenotype in P58(IPK-/-) mice.
• Antioxidant feeding rapidly restored β-cell function and corrected MafA localization in P58(IPK-/-) mice.
• Antioxidant feeding preserved β-cell function in Akita mice, demonstrating a link between protein misfolding, oxidative stress, and apoptosis.

Conclusions:

• Defective protein folding in β-cells induces oxidative stress as a key signal for apoptosis in response to ER stress.
• Antioxidant feeding effectively restores β-cell function following ER molecular chaperone deletion.
• Antioxidant or chemical chaperone therapies represent promising approaches for managing type 2 diabetes.