Casein-induced hypercholesterolaemia in rabbits is calcium-dependent

Area of Science:

• Nutrition Science
• Biochemistry
• Animal Nutrition

Background:

• Dietary protein sources can influence lipid metabolism.
• Calcium intake is a known modulator of various physiological processes, including lipid absorption.
• The impact of different protein types and calcium levels on cholesterol homeostasis requires further investigation.

Purpose of the Study:

• To investigate the effects of casein versus soy protein on serum lipid profiles in rabbits.
• To determine the role of dietary calcium levels in modulating these protein-specific effects.
• To explore the relationship between phosphate absorption, fat excretion, and hypercholesterolemia.

Main Methods:

• Young male rabbits were fed semi-purified diets with casein or soy protein at normal and high calcium concentrations.
• Serum total and free cholesterol, and phospholipid levels were measured.
• Intestinal phosphate absorption and fecal fat excretion were assessed.
• Correlations between lipid parameters, phosphate absorption, and fat excretion were analyzed.

Main Results:

• Casein, compared to soy protein, elevated serum total and free cholesterol and the free cholesterol to phospholipid ratio at normal calcium levels.
• Casein increased intestinal phosphate absorption and decreased fecal fat excretion.
• Higher dietary calcium intake mitigated the casein-induced hypercholesterolemia and altered intestinal parameters.
• Calcium supplementation did not affect lipid parameters in rabbits fed soy protein.

Conclusions:

• The phosphorylation degree of casein may contribute to its hypercholesterolemic effect via the enterohepatic cycle of bile acids.
• Dietary calcium plays a significant role in modulating the effects of casein on lipid metabolism.
• Soy protein appears to have a different metabolic impact compared to casein, less influenced by calcium levels.