Dysfunction of cardiac ryanodine receptors in the metabolic syndrome

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Metabolic Syndrome Research

Background:

• Metabolic syndrome and prediabetes are associated with increased cardiovascular risk.
• Cardiac dysfunction can occur early in metabolic syndrome, but underlying mechanisms are not fully understood.
• Ryanodine receptor 2 (RyR2) plays a critical role in cardiac excitation-contraction coupling.

Purpose of the Study:

• To investigate the impact of prediabetic metabolic syndrome on cardiac RyR2 expression, phosphorylation, and binding affinity.
• To determine if alterations in RyR2 contribute to early cardiac dysfunction in a canine model of metabolic syndrome.

Main Methods:

• Utilized real-time PCR and Western blot to analyze RyR2 mRNA and protein expression in canine cardiac tissues.
• Assessed RyR2 functional integrity via phosphorylation at Ser2809 and [3H]ryanodine binding assays.
• Evaluated cardiac function using cardiac index measurements in exercising dogs.

Main Results:

• Chronically high-fat feeding significantly elevated RyR2 phosphorylation at Ser2809 in the left and right ventricles.
• RyR2 hyperphosphorylation correlated with decreased RyR2 binding affinity and reduced cardiac index in exercising dogs.
• No significant changes in RyR2 mRNA, protein expression, or atrial RyR2 properties were observed.

Conclusions:

• Alterations in RyR2 phosphorylation and binding affinity, not expression levels, are implicated in early cardiac dysfunction in metabolic syndrome.
• These RyR2 changes represent a potential mechanism contributing to cardiac issues in obesity and insulin resistance.
• Targeting RyR2 modulation may offer therapeutic strategies for preventing or treating metabolic syndrome-related heart disease.