Effects of sphingomyelin on aberrant colonic crypt foci development, colon crypt cell proliferation and immune function in an aging rat tumor model

Dietary Sphingolipids Contribute to Health via Intestinal Maintenance

As sphingolipids are constituents of the cell and vacuole membranes of eukaryotic cells, they are a critical component acquired from our daily diets. In the present review, we highlight the knowledge regarding how dietary sphingolipids affect our health, particularly our intestinal health. Animal- and plant-derived foods contain, respectively, sphingomyelin (SM) and glucosylceramide (GlcCer) as their representative sphingolipids, and the sphingoid base as a specific structure of sphingolipids also differs depending upon the source and class. For example, sphingosine is predominant among animal sphingolipids, and tri-hydroxy bases are present in free ceramide (Cer) from plants and fungi. Dietary sphingolipids exhibit low absorption ratios; however, they possess various functions. GlcCer facilitates improvements in intestinal impairments, lipid metabolisms, and skin disorders, and SM can exert both similar and different effects compared to those elicited by GlcCer. We discuss the digestion, absorption, metabolism, and function of sphingolipids while focused on the structure. Additionally, we also review old and new classes in the context of current advancements in analytical instruments.

Sphingolipids in food and their critical roles in human health

Sphingolipids (SLs) are ubiquitous structural components of cell membranes and are essential for cell functions under physiological conditions or during disease progression. Abundant evidence supports that SLs and their metabolites, including ceramide (Cer), ceramide-1-phosphate (C1P), sphingosine (So), sphingosine-1-phosphate (S1P), are signaling molecules that regulate a diverse range of cellular processes and human health. However, there are limited reviews on the emerging roles of exogenous dietary SLs in human health. In this review, we discuss the ubiquitous presence of dietary SLs, highlighting their structures and contents in foodstuffs, particularly in sea foods. The digestion and metabolism of dietary SLs is also discussed. Focus is given to the roles of SLs in both the etiology and prevention of diseases, including bacterial infection, cancers, neurogenesis and neurodegenerative diseases, skin integrity, and metabolic syndrome (MetS). We propose that dietary SLs represent a "functional" constituent as emerging strategies for improving human health. Gaps in research that could be of future interest are also discussed.

Quantitative profiling of sphingolipids in wild Cordyceps and its mycelia by using UHPLC-MS

In the present study, 101 sphingolipids in wild Cordyceps and its five mycelia were quantitatively profiled by using a fully validated UHPLC-MS method. The results revealed that a general rank order for the abundance of different classes of sphingolipids in wild Cordyceps and its mycelia is sphingoid bases/ceramides > phosphosphingolipids > glycosphingolipids. However, remarkable sphingolipid differences between wild Cordyceps and its mycelia were observed. One is that sphingoid base is the dominant sphingolipid in wild Cordyceps, whereas ceramide is the major sphingolipid in mycelia. Another difference is that the abundance of sphingomyelins in wild Cordyceps is almost 10-folds higher than those in most mycelia. The third one is that mycelia contain more inositol phosphorylceramides and glycosphingolipids than wild Cordyceps. Multivariate analysis was further employed to visualize the difference among wild Cordyceps and different mycelia, leading to the identification of respective sphingolipids as potential chemical markers for the differentiation of wild Cordyceps and its related mycelia. This study represents the first report on the quantitative profiling of sphingolipids in wild Cordyceps and its related mycelia, which provided comprehensive chemical evidence for the quality control and rational utilization of wild Cordyceps and its mycelia.

Sphingolipids in colon cancer

Colorectal cancer is one of the major causes of death in the western world. Despite increasing knowledge of the molecular signaling pathways implicated in colon cancer, therapeutic outcomes are still only moderately successful. Sphingolipids, a family of N-acyl linked lipids, have not only structural functions but are also implicated in important biological functions. Ceramide, sphingosine and sphingosine-1-phosphate are the most important bioactive lipids, and they regulate several key cellular functions. Accumulating evidence suggests that many cancers present alterations in sphingolipids and their metabolizing enzymes. The aim of this review is to discuss the emerging roles of sphingolipids, both endogenous and dietary, in colon cancer and the interaction of sphingolipids with WNT/β-catenin pathway, one of the most important signaling cascades that regulate development and homeostasis in intestine. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

The natural antioxidant rosmarinic acid spontaneously penetrates membranes to inhibit lipid peroxidation in situ

Exogenous molecules from dietary sources such as polyphenols are very efficient in preventing the alteration of lipid membranes by oxidative stress. Among the polyphenols, we have chosen to study rosmarinic acid (RA). We investigated the efficiency of RA in preventing lipid peroxidation and in interacting with lipids. We used liposomes of 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) to show that RA was an efficient antioxidant. By HPLC, we determined that the maximum amount of RA associated with the lipids was ~1 mol%. Moreover, by using Langmuir monolayers, we evidenced that cholesterol decreases the penetration of RA. The investigation of transferred lipid/RA monolayers by atomic force microscopy revealed that 1 mol% of RA in the membrane was not sufficient to alter the membrane structure at the nanoscale. By fluorescence, we observed no significant modification of membrane permeability and fluidity caused by the interaction with RA. We also deduced that RA molecules were mainly located among the polar headgroups of the lipids. Finally, we prepared DLPC/RA vesicles to evidence for the first time that up to 1 mol% of RA inserts spontaneously in the membrane, which is high enough to fully prevent lipid peroxidation without any noticeable alteration of the membrane structure due to RA insertion.

Abnormal Savda Munziq, an Herbal Preparation of Traditional Uighur Medicine, May Prevent 1,2-dimethylhydrazine-Induced Rat Colon Carcinogenesis

The study tried to assess the chemoprotective effect of abnormal Savda Munziq (ASMq) on 1,2-dimethylhydrazine (DMH)-induced rat colon carcinogenesis. Male F344 rats were randomized into eight groups: Group 1 was served as control, no DMH injection was given and treated daily with normal saline. Rats in Groups 2–8 were given a single intraperitoneal injection of DMH (20 mg/kg body weight) at the beginning of the study. Group 2 was served as negative control, administered with normal saline until the end of the experiment after the single DMH injection. Groups 3–5 were served as pretreatment group, administered with ASMq ethanol extract at 400, 800 and 1600 mg/kg body weight, respectively, until the 45th day, continued by normal saline administration for another 45 days. Groups 6–8 were served as the treatment group, administered with normal saline for the first 45 days from the day of DMH injection, ASMq ethanol extract at three different doses to be administered until the end of the second 45th day. All rats were sacrificed at 91st day and the colons were analyzed for aberrant crypt foci (ACF) formation and crypt multiplicity. Results showed that ASMq ethanol extract reduced the number of ACF, AC and crypt multiplicity significantly (P < .05). It suggested that ASMq ethanol extract had chemoprotective effects on DMH-induced colon carcinogenesis, by suppressing the development of preneoplastic lesions, and probably exerted protection against the initiation and promotion steps of colon carcinogenesis.

Suppression of intestinal inflammation and inflammation-driven colon cancer in mice by dietary sphingomyelin: importance of peroxisome proliferator-activated receptor γ expression

Inflammation of the gastrointestinal tract increases the risk of developing colon cancer especially in younger adults. Dietary compounds are not only associated with the etiology of inflammation and colon cancer but also in their prevention. Sphingolipid metabolites have been shown to play a role in the initiation and perpetuation of inflammatory responses. In the present study, we investigated the suppression of dextran sodium sulfate-induced colitis and azoxymethane-induced colon cancer by dietary sphingomyelin (SM) in mice that lack functional peroxisome proliferator-activated receptor γ (PPAR-γ) in intestinal epithelial and immune cells. Dietary SM decreased disease activity and colonic inflammatory lesions in mice of both genotypes but more efficiently in mice expressing PPAR-γ. The increased survival and suppression of tumor formation in the SM-fed mice appeared to be independent of PPAR-γ expression in immune and epithelial cells. Using a real-time polymerase chain reaction array, we detected an up-regulation in genes involved in Th1 (interferon γ) and Th17 (interleukin [IL]-17 and IL-23) responses despite the reduced inflammation scores. However, the genes involved in Th2 (IL-4, IL-13 and IL-13ra2) and Treg (IL-10rb) anti-inflammatory responses were up-regulated in a PPAR-γ-dependent manner. In line with the PPAR-γ dependency of our in vivo findings, treatment of RAW macrophages with sphingosine increased the PPAR-γ reporter activity. In conclusion, dietary SM modulated inflammatory responses at the early stages of the disease by activating PPAR-γ, but its anticarcinogenic effects followed a PPAR-γ-independent pattern.

Anticarcinogenic efficacy of phytic acid extracted from rice bran on azoxymethane-induced colon carcinogenesis in rats

This study is carried out to determine the potential of phytic acid extracted from rice bran in the suppression of colon carcinogenesis induced by azoxymethane (AOM) in rats. Seventy-two male Sprague-Dawley rats were divided into 6 groups with 12 rats in each group. The intended rats for cancer treatment received two intraperitoneal injections of AOM in saline (15mg/kg bodyweight) over a 2-week period. The treatments of phytic acid were given in two concentrations: 0.2% (w/v) and 0.5% (w/v) during the post-initiation phase of carcinogenesis phase via drinking water. The colons of the animals were analyzed for detection and quantification of aberrant crypt foci (ACF) after 8 weeks of treatment. The finding showed treatment with 0.2% (w/v) extract phytic acid (EPA) gave the greatest reduction in the formation of ACF. In addition, phytic acid significantly suppressed the number of ACF in the distal, middle and proximal colon as compared to AOM alone (p<0.05). For the histological classification of ACF, treatment with 0.5% (w/v) commercial phytic acid (CPA) had the highest percentage (71%) of non-dysplastic ACF followed by treatment with 0.2% (w/v) EPA (61%). Administration of phytic acid also reduced the incidence and multiplicity of total tumors even though there were no significant differences between groups. In conclusion, this study found the potential value of phytic acid extracted from rice bran in reducing colon cancer risk in rats.

The potential of sphingomyelin as a chemopreventive agent in AOM-induced colon cancer model: wild-type and p53+/- mice

A protective effect of sphingolipids on colorectal cancer (CRC) has been reported in certain mouse strains. It is unknown if sphingolipids are protective in a p53 deficiency mouse model of CRC. This study investigated the effect of sphingomyelin (SM) on intestinal sphingomyelinase (SMase) activity, colonic epithelial biology and azoxymethane (AOM)-induced CRC. Groups of wild-type (C57BL/6J) and p53+/- mice were fed 0.1% SM diet for 4 wk, administered a single AOM injection and then killed 6 h later to measure apoptosis and proliferation. Separately, both mouse types were fed 0.05% SM diet, administered three AOM injections and killed 33-38 wk later to measure tumour formation. SM significantly increased SMase activity and reduced proliferation (p < 0.05) in wild-type and p53+/- mice. SM did not regulate baseline apoptosis, apoptotic response to AOM or apoptosis in tumours, nor did it restore defective apoptosis in p53+/- mice. There was a nonsignificant trend to reduced tumour incidence with SM in wild-type (p = 0.15) and p53+/- (p = 0.12) mice. In conclusion, while increasing intestinal SMase activity and suppressing proliferation, SM did not promote any form of apoptosis and failed to achieve significant protection in these mice. Further investigation to understand the variable effect of SM in preventing CRC is warranted.

Intestinal immunity of rats with colon cancer is modulated by oligofructose-enriched inulin combined with Lactobacillus rhamnosus and Bifidobacterium lactis

Probiotics (PRO) are known to modulate immunity in animals and human subjects and to inhibit colon carcinogenesis in experimental models, but the effects of synbiotics (SYN) are not well understood. Therefore, the effects of PRO (Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12), PRE (inulin-based enriched with oligofructose, 100 g/kg) and SYN (combination of PRO and PRE) on the immune system of rats were investigated in the azoxymethane (AOM)-induced colon cancer model. After 33 weeks, rats with and without AOM treatment were killed and immune cells were isolated from spleen, mesenterial lymph nodes (MLN) and Peyer's patches (PP). AOM treatment significantly reduced natural killer (NK) cell-like cytotoxicity in control rats and in PRO- and PRE-supplemented rats. SYN supplementation prevented the AOM-induced suppression of NK cell-like cytotoxicity in PP compared with control rats (P<0.01). SYN and PRE supplementation stimulated IL-10 production in PP in these rats (P<0.01) and in MLN of rats not treated with AOM (P<0.05). Interferon-gamma production in PP was decreased by PRO supplementation (PRO and SYN groups combined; P<0.05). Proliferative responsiveness of lymphocytes (PP) from AOM-treated rats was suppressed in SYN-supplemented rats (P<0.01). Overall, SYN supplementation in carcinogen-treated rats primarily modulated immune functions in the PP, coinciding with a reduced number of colon tumours. PRE and PRO provided in combination as SYN may contribute to the suppression of colon carcinogenesis by modulating the gut-associated lymphoid tissue.

Effects of adlay on azoxymethane-induced colon carcinogenesis in rats

Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) is a grass crop used in traditional Chinese medicine and as a nutritious food. It has been reported that adlay has anti-inflammatory and anti-tumor activity. Cyclooxygenase-2 (COX-2) is an inducible enzyme functionally related to both inflammation and colon carcinogenesis and is the target of many chemopreventive agents. This study investigated the effect of adlay on colon carcinogenesis and COX-2 expression. In a short-term experiment, male F344 rats were fed diets containing different doses of dehulled adlay and received the colon-specific carcinogen, azoxymethane (AOM), by intraperitoneal injection. All rats were killed after 5 weeks of feeding, and the colons were examined for the preneoplastic lesion, aberrant crypt foci (ACF). Dietary dehulled adlay at levels of 10%, 20%, or 40% significantly reduced the numbers of ACF and aberrant crypts. Dehulled adlay reduced the number of ACF of different sizes but did not affect the crypt multiplicity. Most ACF were found in the middle and distal colons; dehulled adlay significantly suppressed the formation of ACF in the middle colon. In a long-term experiment, male F344 rats were fed diets containing different doses of dehulled adlay and injected with AOM. All rats were killed after 52 weeks of feeding, and colons were examined for tumors and COX-2 protein expression. The results indicated that dehulled adlay did not inhibit colon tumors in spite of a slight suppressing effect in the proximal colon. Rats fed diets containing 20% dehulled adlay had less COX-2 protein expression in both proximal and distal colon tumors. The inconsistent effects between COX-2 protein expression and tumor outcome may be due to regional differences in the colon and the malignancy of the tumors. These findings suggest that dehulled adlay suppresses early events in colon carcinogenesis but not the formation of tumors.

Aberrant crypt foci and beta-catenin accumulated crypts; significance and roles for colorectal carcinogenesis

Preneoplastic or precancerous lesions in the large bowel have been characterized in terms of morphology and histochemical phenotype. However, the detailed histogenesis and relation of particular lesions to malignancies has not yet to be unequivocally clarified. Aberrant crypt foci (ACF), identified in whole-mount preparations of colonic mucosa in rodents and also recognized in human colon, are now frequently used as effective surrogate biomarkers for experimentally detection of chemopreventive agents against colorectal cancers, but the preneoplastic or precancerous nature of ACF in rodents and humans still remains inconclusive. Relatively recently, early appearing beta-catenin accumulated crypts (BCAC) have been described in en face preparations of colonic mucosa in rodents which differ from ACF in many features. BCAC are suggested to be premalignant rather than preneoplastic. The pathological significance of both lesions, including their advantages and disadvantages as surrogate end points for large bowel neoplasms, and roles in colorectal carcinogenesis are discussed here.

Interaction of conjugated linoleic acid, sphingomyelin, and butyrate on formation of colonic aberrant crypt foci and immune functions in rats

This study was designed to investigate possible additive or synergistic action among sphingomyelin (SPH), cis-9,trans-11-conjugated linoleic acid (CLA), and butyrate (BTY) against colon cancer and modulation of immune functions in vivo in male Sprague-Dawley rats. Each of the 5 groups of rats was fed either 35 mg SPH, 100 mg CLA, or 100 mg BTY/kg body weight, a combination of the 3 compounds at the same doses, or none of the compounds, for 7 wk. Rats were injected with azoxymethane, a colon carcinogen, to induce the formation of aberrant crypt foci, preneoplastic lesions of colon cancer. Parameters measured included number and multiplicity (number of crypts per focus) of aberrant crypts, immune functions such as innate immunity (natural killer cell cytotoxicity), humoral immunity (development of antibodies), and cell-mediated immunity (delayed-type hypersensitivity). Results show that the groups treated with SPH, CLA, and BTY individually had significantly higher natural killer cell (NK) cytotoxicity than the group treated with all compounds. The CLA group also had significantly higher NK activity than the control group. This study shows that the three compounds may not act additively or synergistically either to inhibit the development of aberrant crypts or to enhance immune functions. In fact, exposure to the combined compounds may be antagonistic to enhancement of NK function by the individual chemicals.