Carbohydrate diet-induced changes in very low density lipoprotein composition and structure

Area of Science:

• Lipid metabolism
• Nutritional biochemistry
• Atherosclerosis research

Background:

• High carbohydrate diets are known to influence plasma lipoprotein profiles.
• Very low-density lipoprotein (VLDL) particles are central to triglyceride transport.
• The liver's role in producing diet-altered VLDL requires clarification.

Purpose of the Study:

• To determine if the liver is the source of diet-induced VLDL changes.
• To characterize the composition and structure of VLDL secreted by the liver under high carbohydrate conditions.
• To investigate the impact of diet on hepatic VLDL secretion and postsecretory processing.

Main Methods:

• Rats were fed high carbohydrate or control diets.
• Plasma and liver VLDL composition was analyzed using radioimmunoassay, chromatography, and electrophoresis.
• In vitro liver perfusion was used to study VLDL secretion.
• Lipid and apoprotein levels (ApoA-I, ApoB, ApoC, ARP) were quantified.

Main Results:

• High carbohydrate feeding led to larger, triglyceride-enriched VLDL particles in plasma and liver perfusates.
• Hepatic VLDL secretion increased in triglyceride content but not in absolute apoprotein B secretion.
• Alterations in apoprotein composition, particularly increased ApoC and shifts in ApoC-III isoforms, were observed in both plasma and hepatic VLDL.
• Discrepancies in apoprotein composition between plasma and perfusate VLDL suggest postsecretory modifications.

Conclusions:

• The liver is a significant source of the altered VLDL particles observed in plasma following high carbohydrate diets.
• Diet-induced changes in hepatic VLDL composition are largely mirrored in the circulation.
• Postsecretory processing and metabolism play a role in the final composition of circulating VLDL, particularly concerning apoprotein content.