Alkaline sphingomyelinase (NPP7) promotes cholesterol absorption by affecting sphingomyelin levels in the gut: A study with NPP7 knockout mice

We previously showed that dietary sphingomyelin (SM) inhibited cholesterol absorption in animals. The key enzyme hydrolyzing SM in the gut is alkaline sphingomyelinase (alk-SMase, nucleotide pyrophosphatase/phosphodiesterase 7). Here using the fecal dual-isotope ratio method we compared cholesterol absorption in the wild-type (WT) and alk-SMase knockout (KO) mice. The animals were fed an emulsion containing [14C]cholesterol and [3H]sitosterol. The radioactivities in the lipids of the fecal samples collected 4, 8, and 24 h thereafter were determined, and the ratio of 14C/3H was calculated. We found that the fecal [14C]cholesterol recovery in the KO mice was significantly higher than in the WT mice. A maximal 92% increase occurred 8 h after feeding. Recovery of [3H]sitosterol did not differ between the two groups. Accordingly, the 14C-to-3H ratio of fecal lipids was 133% higher at 8 h and 75% higher at 24 h in the KO than in the WT mice. Decreased [14C]cholesterol was also found in the serum of the KO mice 4 h after feeding. Supplement of SM in the emulsion reduced the differences in fecal [14C]cholesterol recovery between the WT and KO mice because of a greater increase of [14C]cholesterol recovery in the WT mice. Without treatment, the KO mice had significantly higher SM levels in the intestinal content and feces, but not in the intestinal mucosa or serum. The expression of Niemann-Pick C1 like 1 protein in the small intestine was not changed. In conclusion, alk-SMase is a physiological factor promoting cholesterol absorption by reducing SM levels in the intestinal lumen.

Pretreatment with the probiotic VSL#3 delays transition from inflammation to dysplasia in a rat model of colitis-associated cancer

Evidence supports involvement of microflora in the transition of chronic inflammation to neoplasia. We investigated the protective efficacy of the probiotic VSL#3 in a model of colitis-associated colorectal cancer. Chronic colitis was induced in Sprague-Dawley rats by administration of trinitrobenzene sulfonic acid (TNBS), followed 6 wk later by systemic reactivation. To induce colitis-associated dysplasia and cancer, the animals received TNBS (intravenously) twice a week for 10 wk. One group received VSL#3 in drinking water from 1 wk before colitis induction until death. The colons were examined for damage and presence of dysplasia or cancer. Samples were analyzed for cell proliferation and apoptosis, vitamin D receptor (VDR) expression, angiogenic factors, and presence of alkaline sphingomyelinase or phosphatase. Microbial community composition was evaluated by terminal restriction fragment-length polymorphism analysis of the bacterial 16S rRNA gene. None of the probiotic-treated animals developed carcinoma, and no high-grade dysplasia was found in either the proximal or mid colon. In contrast, 29% of the animals in the control group developed carcinoma in one or more regions of the colon. VSL#3-treated animals had significantly less damage than the vehicle treated-controls in all areas of the colon, and this correlated with decreased richness and diversity of the mucosally adherent microbiota. Treatment with the probiotic increased the antiangiogenic factor angiostatin, VDR expression, and alkaline sphingomyelinase. We concluded that pretreatment with the probiotic VSL#3 can attenuate various inflammatory-associated parameters, delaying transition to dysplasia and cancer, thus offering its potential therapeutic use in patients with long-standing colitis.

Effect of probiotic treatment on the transition from chronic colonic inflammation to dysplasia and cancer.

385 Background: Effective prevention of colitis-associated cancer still needs to be achieved. There is evidence that the microflora plays an important role in the progression of chronic inflammation to neoplastic transformation, so the aim of this study was to evaluate the potential efficacy of the probiotic VSL#3 in preventing this transition. Methods: Chronic colitis was induced in male Sprague Dawley rats by the administration of trinitrobenzene sulfonic acid (TNBS; 30 mg in 50% ethanol ic), followed six weeks later by reactivation with TNBS (5 mg/kg iv) for 3 days. To induce colitis-associated dysplasia and cancer the animals then received TNBS (iv) twice a week for ten weeks. One group of rats received the probiotic in drinking water (VSL#3; ∼5 billion cfu /100 gram body weight) from 1 week prior to initial colitis induction until the time of sacrifice (n = 22-23/group). After sacrifice the colons were removed and analyzed for total macroscopic damage, microscopic damage and presence of dysplasia or cancer. Tissue and serum samples were analyzed for cell proliferation and apoptosis, angiogenic factors and presence of alkaline sphingomyelinase. Results: Those animals receiving the probiotic had significantly less macroscopic and microscopic damage than the vehicle treated-controls in all areas of the colon (p < 0.05). Pathological analysis revealed that 29% of the vehicle treated animals developed carcinoma, which was confined to the proximal region. None of the probiotic treated animals developed carcinoma. Treatment with the probiotic caused a significant shift to a less severe diagnosis with no high-grade dysplasia found in either the proximal or midcolon. Treatment with the probiotic reduced crypt cell proliferation by 22% as assessed by measurement of BrdU incorporation in comparison with the vehicle treated group. Levels of the antiangiogenic factor angiostatin were higher in the probiotic treated animals (5-fold), as were serum levels of alkaline sphingomyelinase (2-fold). Conclusions: Treatment with the probiotic VSL#3 can delay the transition of chronic inflammation to dysplasia and cancer via effects on processes such as modulation of cell proliferation and angiogenesis. No significant financial relationships to disclose.