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Hypercholesterolemia induces differential expression of rabbit apolipoprotein A and C genes
P Crespo1, J M Ordovás, M Albajar
1Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain.
Abstract:
We have compared steady-state mRNA levels of apolipoproteins AI, AII, AIV, CI, CII and CIII in liver and small intestine of rabbits fed on a cholesterol-rich diet for up to 16 weeks. Apolipoprotein (apo) AIV mRNA was detected in both liver and small intestine, while apo AII was not detected in either organ. Apo CI, apo CII and apo CIII were expressed only in liver and apo AI mRNA was detected only in small intestine. In small intestine, apo AIV and apo AI mRNA levels increased to a maximum at the 4th and 12th week of treatment, respectively. In liver there was a parallel increase in the mRNA levels of apo AIV, apo CI, apo CII and apo CIII, with maximum levels after 4 weeks of treatment. A 3-fold increase was found in apo CII and apo CIII hepatic transcription rates between hypercholesterolemic and control rabbits after 4 weeks of treatment, no longer detectable after 8 weeks. However, no changes were found in apo AIV and apo CI transcription rates. Changes in apolipoprotein mRNA levels were accompanied by changes in plasma lipoprotein levels. Overall, these changes correlate well with the variations detected in the expression of the different apolipoprotein genes. Our results indicate that dietary cholesterol plays an important role in the regulation of these genes and that this regulation is tissue dependent.
Insights
Dietary cholesterol impacts apolipoprotein gene expression differently in rabbit liver and small intestine. These changes in apolipoprotein (apo) mRNA levels correlate with plasma lipoprotein variations, showing tissue-specific regulation.
Area of Science:
- Lipid metabolism and gene expression
- Molecular biology of apolipoproteins
- Nutritional biochemistry
Background:
- Apolipoproteins are crucial for lipoprotein metabolism.
- Dietary cholesterol influences lipid homeostasis.
- Tissue-specific gene regulation is key in metabolic processes.
Purpose of the Study:
- To investigate the effect of a cholesterol-rich diet on apolipoprotein mRNA levels in rabbit liver and small intestine.
- To determine the temporal changes in gene expression over 16 weeks.
- To correlate changes in apolipoprotein mRNA with plasma lipoprotein levels.
Main Methods:
- Comparison of steady-state mRNA levels of various apolipoproteins (AI, AII, AIV, CI, CII, CIII) in liver and small intestine.
- Analysis of apolipoprotein mRNA levels in rabbits fed a cholesterol-rich diet for up to 16 weeks.
- Measurement of hepatic transcription rates for specific apolipoproteins.
- Assessment of plasma lipoprotein levels.
Main Results:
- Apolipoprotein (apo) AIV mRNA found in both organs; apo AII mRNA not detected.
- Specific apolipoprotein mRNA expression patterns observed: apo CI, CII, CIII in liver; apo AI in small intestine.
- Small intestine showed increased apo AIV and apo AI mRNA levels at 4 and 12 weeks, respectively.
- Liver exhibited parallel increases in apo AIV, CI, CII, and CIII mRNA levels peaking at 4 weeks.
- Hepatic transcription rates for apo CII and apo CIII increased significantly at 4 weeks but diminished by 8 weeks.
- No changes in apo AIV and apo CI transcription rates were observed.
- Changes in apolipoprotein mRNA levels corresponded with alterations in plasma lipoprotein profiles.
Conclusions:
- Dietary cholesterol significantly regulates apolipoprotein gene expression.
- The regulation of these genes is dependent on the specific tissue (liver vs. small intestine).
- Observed changes in gene expression and plasma lipoproteins highlight the complex interplay in lipid metabolism.
- This study provides insights into the tissue-specific adaptive responses to dietary cholesterol challenges.