Dietary cholesterol affects chenodeoxycholic acid action on biliary lipids

Area of Science:

• Hepatology and Gastroenterology
• Biochemistry
• Lipid Metabolism

Background:

• Chenodeoxycholic acid (CDC) is a therapeutic agent for gallstone dissolution.
• Dietary cholesterol influences biliary lipid composition and may impact CDC efficacy.
• Hepatic hydroxymethylglutaryl coenzyme A reductase (HMG-CoAR) is a key enzyme in cholesterol synthesis.

Purpose of the Study:

• To investigate the impact of varying dietary cholesterol levels on CDC's ability to reduce biliary saturation.
• To assess how dietary cholesterol affects the activity of hepatic HMG-CoAR during CDC therapy.

Main Methods:

• Seventy-two hamsters were assigned to three dietary groups: high cholesterol, standard, or cholesterol-free.
• Animals received either CDC or no treatment for one month.
• Biliary lipids and hepatic HMG-CoAR activity were measured post-treatment.

Main Results:

• CDC significantly decreased the biliary saturation index (SI) in hamsters on high cholesterol and standard diets, but not on cholesterol-free diets.
• The SI was higher in CDC-treated hamsters on high cholesterol and cholesterol-free diets compared to the standard diet.
• CDC reduced HMG-CoAR activity across all diets, but this inhibition was less optimal on high cholesterol and cholesterol-free diets.

Conclusions:

• Dietary cholesterol plays a crucial role in optimizing CDC's inhibition of HMG-CoAR.
• Both high and cholesterol-free diets impede the maximal reduction of the biliary saturation index by CDC.
• Alterations in dietary cholesterol may contribute to the failure of CDC in gallstone dissolution therapy.