Sustained and selective suppression of intestinal cholesterol synthesis by Ro 48-8071, an inhibitor of 2,3-oxidosqualene:lanosterol cyclase, in the BALB/c mouse

Abstract

The small intestine plays a fundamentally important role in regulating whole body cholesterol balance and plasma lipoprotein composition. This is articulated through the interplay of a constellation of genes that ultimately determines the net amount of chylomicron cholesterol delivered to the liver. Major advances in our insights into regulation of the cholesterol absorption pathway have been made using genetically manipulated mouse models and agents such as ezetimibe. One unresolved question is how a sustained pharmacological inhibition of intestinal cholesterol synthesis in vivo may affect cholesterol handling by the absorptive cells. Here we show that the lanosterolcyclase inhibitor, Ro 48-8071, when fed to BALB/c mice in a chow diet (20 mg/day/kg body weight), leads to a rapid and sustained inhibition (>50%) of cholesterol synthesis in the whole small intestine. Sterol synthesis was also reduced in the large intestine and stomach. In contrast, hepatic cholesterol synthesis, while markedly suppressed initially, rebounded to higher than baseline rates within 7 days. Whole body cholesterol synthesis, fractional cholesterol absorption, and fecal neutral and acidic sterol excretion were not consistently changed with Ro 48-8071 treatment. There were no discernible effects of this agent on intestinal histology as determined by H&E staining and the level of Ki67, an index of proliferation. The mRNA expression for multiple genes involved in intestinal cholesterol regulation including NPC1L1 was mostly unchanged although there was a marked rise in the mRNA level for the PXR target genes CYP3A11 and CES2A.

Statins increase hepatic cholesterol synthesis and stimulate fecal cholesterol elimination in mice

“…Intestinal synthesis was increased much less. These results are in accordance with the study of Chuang et al (51) who have measured an increase in acute cholesterol synthesis in BALB/c mice treated with simvastatin. Interestingly, Freeman et al (52) showed that lovastatin reduced HMGCR activity in human intestinal biopsies.…”

Impact of physiological levels of chenodeoxycholic acid supplementation on intestinal and hepatic bile acid and cholesterol metabolism in Cyp7a1-deficient mice

“…Relative mRNA levels in individual animals were determined by expressing the amount of mRNA found relative to that obtained for Cyp7a1 +/+ mice fed the basal diet alone (all studies with males), or the basal diet enriched with cholesterol (studies with females), which in each case was arbitrarily set at 1.0. The primer sequences used to measure RNA levels for all genes have been reported in two earlier publications [31, 38]. The names of all genes studied are as follows; Cyp7a1, Cholesterol 7α-hydroxylase; Cyp27a1, Sterol 27-hydroxylase; Cyp39a1, Oxysterol 7α-hydroxylase; Cyp7b1, Oxysterol 7α-hydroxylase; Cyp8b1, Sterol 12α-hydroxylase; Abca1, ATP binding cassette member A1; Abcb11, Bile salt export pump (Bsep); Abcg5, ATP-binding cassette G5; Fabp6, Ileal bile acid binding protein (Ibabp); Fgf15, Fibroblast growth factor 15; Hmgcs, Hydroxymethylglutaryl coenzyme A synthase; Npc1l1, Niemann-Pick Type C1 -like 1; and Nr0b2, Short heterodimer partner (Shp).…”

Quantitation of the rates of hepatic and intestinal cholesterol synthesis in lysosomal acid lipase-deficient mice before and during treatment with ezetimibe

“…mRNA levels were measured by real-time qPCR using an ABI Prism 7900 Sequence Detection System. The primer sequences used to measure the mRNA levels for genes of specific interest are given in earlier publications [23, 41, 43]. All analyses were determined by the comparative cycle number at threshold method with cyclophilin as the internal control [44].…”