Molecular mechanisms of insulin resistance in chronic kidney disease

Area of Science:

• Metabolic disorders
• Nephrology
• Molecular biology

Background:

• Insulin resistance is characterized by reduced organ sensitivity to insulin, leading to metabolic defects.
• It is prevalent in chronic kidney disease (CKD) and associated with minimally increased serum creatinine.
• Key signaling pathways involve insulin receptor substrate-1 (IRS-1) phosphorylation and activation of PI3K and Akt.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying insulin resistance in CKD and related conditions.
• To identify the role of reduced Akt phosphorylation (p-Akt) in metabolic dysfunction.
• To explore the contribution of E3 ubiquitin ligases and the ubiquitin-proteasome system (UPS) in IRS-1 degradation.

Main Methods:

• Analysis of insulin signaling pathways, including insulin receptor auto-phosphorylation, IRS-1, PI3K, and Akt.
• Assessment of p-Akt levels as an indicator of insulin resistance.
• Investigation of E3 ubiquitin ligase activity and its role in IRS-1 ubiquitination and degradation via the UPS.

Main Results:

• Low levels of p-Akt were identified as a marker for insulin resistance and associated metabolic defects.
• CKD and other conditions (inflammation, oxidative stress, metabolic acidosis, aging, excess angiotensin II) reduce p-Akt.
• E3 ubiquitin ligases activate in these conditions, leading to IRS-1 ubiquitination and subsequent degradation by the UPS.

Conclusions:

• IRS-1 degradation due to E3 ubiquitin ligase activation suppresses insulin-induced signaling, causing insulin resistance.
• Understanding these mechanisms is crucial for developing therapeutic strategies for metabolic disturbances in CKD patients.
• Targeting the UPS or E3 ligases may offer novel approaches to combat insulin resistance.