NMR Metabolomic Analysis of Fecal Water from Subjects on a Vegetarian Diet

Abstract

Plant based food contains a multiplicity of bioactive phytochemicals. These compounds are believed to contribute to the cancer protective effect of a diet high in fruit and vegetables.1,2) One group of phytochemicals is the cyclooxygenase-2 (COX-2) inhibitors, which potentially can act as preventive agents against colon cancer. Such compounds and their derivatives may pass through the digestive system and reach the colon where they exert chemopreventive effects.The water fraction of feces (fecal water) is believed to be in direct contact with the colonocytes, and its composition appears to be important for a healthy environment in the colon.3) It is believed that the fecal water composition roughly reflects the food intake and that it contains a mixture of compounds that may prevent and promote cancer development. A favorable change in the composition of fecal water would consequently decrease the risk of developing colon cancer.4) Fecal water is nowadays a common tool used in human intervention studies. It is used to test cellular responses in vitro in cell systems. [5][6][7][8] Such studies have shown that fecal water can modulate several cellular parameters such as genotoxicity, proliferation and apoptosis, all of which are relevant for tumorigenesis. [9][10][11] Other human intervention studies have indicated that it is possible to alter the pH and the composition of bile acids in fecal water with a change in the diet. 3,12) Another parameter that can be modulated by fecal water is the colonic COX-2 enzyme. We have recently shown that fecal waters from human volunteers inhibit COX-2 protein expression and prostaglandin E 2 (PGE 2 ) production in colonic cells. 13)COX-2 is the inducible form of two isoforms of cyclooxygenases, and it catalyzes the production of prostaglandins. This enzyme is not normally expressed in the colon, but it can be induced by growth factors, cytokines, tumor necrosis factor and lipopolysaccharides in situations of stress. [14][15][16] An over expression of COX-2 protein and an increased production of prostaglandins have been reported in patients with colon cancer, [17][18][19] and inhibition of the COX-2 enzyme has been a drug target over the past fifteen years. Today, there are several specific COX-2 inhibitors available on the market, but some of these synthetic drugs were recently reported to have severe side effects on the cardiovascular system. 20,21) To characterize a complex mixture of metabolites such as fecal water, a comprehensive metabolite profiling method is required. Metabolomic profiling of complex extracts is not an easy task to perform since they usually display a wide range of structural diversity. Of the possible analytical methods used in metabolomics, NMR provides a rapid, reproducible method well suited for identification of many metabolites and it has several advantages compared to other methods. It is not only the high information content of the resulting spectra for chemical structures but also the convenience in practical aspects such as high reproducibilit...

Approaches that ascertain the role of dietary compounds in colonic cancer cells

“…Colonic derivatives of the flavonoids in the colon were detected at concentrations up to two orders of magnitude higher than these of their precursors; thus, the total monophenolic acids reached up to 740.7 mol and the total nonphenolic aromatic acids, 1.5 mmol [48] . Recent analyses of fecal water have confirmed the prevalence of the phenolic and non-phenolic aromatic acids in fecal water [28,54] . Therefore, our question of how polyphenols and their metabolites modulate the activity of butyrate may need to be re-stated to how the activity of butyrate is affected by high levels of monophenolic and nonphenolic acids.…”

“…To date, there are two approaches that address these problems: (1) performing analyses with the aqueous phase of feces (fecal water); and (2) utilizing in vitro GI models. The first approach is justified by the fact that the colonic epithelium is exposed to the fecal matter in vivo [48,[51][52][53][54] and that fecal water affects the growth of colonocytes more effectively than components of the solid phase of feces [52,53] . Gas chromatography and mass spectrometry analyses of the fecal water of healthy volunteers have identified and quantified the flavonoids and their derivatives in the colon [48] .…”

Targeting Colon Drug Delivery by Natural Products

“…It has been shown that intact fecal water (water phase) samples from human volunteers significantly decreased prostaglandin production and COX-2 expression in colonic cells. NMR spectroscopy and multivariate data analysis were later used for further analysis of the composition of the fecal waters and to trace the COX-2 inhibiting activity [18,19]. The wealth of different natural products with experimentally demonstratedCOX inhibitory effects and an urge to understand and characterize their structural diversity was the starting point for the application of chirography in our natural products research.…”

In vitro Analysis of the Impact of Enrofloxacin Residues on the Human Intestinal Microbiota Using 1H-NMR Spectroscopy

“…Metabolite profiling of fecal extracts is not a simple analysis since feces are a complex mixture of digested and undigested food, bacterial fermentation products and metabolites, human cells and secretions, and microorganisms. Nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis is a powerful technique that has been used to characterize the compositional metabolic profiles of feces [Bezabeh et al, 2009;de Graaf et al, 2010;Han et al, 2010;Jacobs et al, 2008;Monleon et al, 2009;Pettersson et al, 2008;Romick-Rosendale et al, 2009;Yap et al, 2008]. However, there are few studies on metabolomic approaches in feces that take account of the metabolic changes that occur during exposure to antibiotics and evaluate the effects of antimicrobial residues on the intestinal microbiota [Romick-Rosendale et al, 2009;Swann et al, 2011].…”