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Am J Physiol Gastrointest Liver Physiol (September 4, 2008). doi:10.1152/ajpgi.90376.2008
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Submitted on June 15, 2008
Revised on August 17, 2008
Accepted on August 29, 2008

Modulation of intestinal cholesterol absorption by high glucose levels: impact on cholesterol transporters, regulatory enzymes and transcription factors

Zaava Ravid1, Moise Bendayan2, Edgard Delvin3, Alain T Sané1, Mounib Elchebly1, Julie Lafond4, Marie Lambert1, Geneviève Mailhot1, and Emile Levy5*

1 Université de Montréal
2 Universite Montr
3 Universit de Montral
4 Universite du Quebec a Montreal
5 CHU Sainte-Justine

* To whom correspondence should be addressed. E-mail: emile.levy{at}recherche-ste-justine.qc.ca.

Growing evidence suggests that the small intestine may contribute to excessive postprandial lipemia, which is highly prevalent in insulin-resistant/type 2 diabetic individuals and substantially increases the risk of cardiovascular disease. The aim of the present study was to determine the role of high glucose levels on intestinal cholesterol absorption, cholesterol transporter expression, enzymes controlling cholesterol homeostasis and the status of transcription factors. To this end, we employed highly differentiated and polarized cells (20 days of culture), plated on permeable polycarbonate filters. In the presence of [14C]-cholesterol, glucose at 25 mM stimulated cholesterol uptake compared to Caco-2/15 cells supplemented with 5 mM glucose (P<0.04). Because combination of 5 mM glucose with 20 mM of the structurally related mannitol or sorbitol did not change cholesterol uptake, we conclude that extracellular glucose concentration is uniquely involved in the regulation of intestinal cholesterol transport. The high concentration of glucose enhanced the protein expression of the critical cholesterol transporter NPC1L1 and that of CD36 (P<0.02) and concomitantly decreased SR-BI protein mass (P<0.02). No significant changes were observed in the protein expression of ABCA1 and ABCG8, which act as efflux pumps favoring cholesterol export out of absorptive cells. At the same time, HMG-CoA reductase activity was decreased (P<0.007), whereas ACAT activity remained unchanged. Finally, increases were noted in the transcription factors LXR{alpha}, LXR{beta}, PPAR{beta} and PPAR{gamma} along with a drop in the protein expression of SREBP-2. Collectively, our data indicate that glucose at high concentrations may regulate intestinal cholesterol transport and metabolism in Caco-2/15 cells, thus suggesting a potential influence on the cholesterol absorption process in type 2 diabetes.







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