High-fat diet alters gene expression in the liver and colon: links to increased development of aberrant crypt foci

Changes in the Fecal Metabolome Accompany an Increase in Aberrant Crypt Foci in the Colon of C57BL/6 Mice Fed with a High-Fat Diet

High-fat diet (HFD)-induced obesity is a risk factor for colon cancer. Our previous data show that compared to an AIN-93 diet (AIN), a HFD promotes azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation and microbial dysbiosis in C57BL/6 mice. To explore the underlying metabolic basis, we hypothesize that AOM treatment triggers a different fecal metabolomic profile in C57BL/6 mice fed the HFD or the AIN. We found that 65 of 196 identified metabolites were significantly different among the four groups of mice (AIN, AIN + AOM, HFD, and HFD + AOM). A sparse partial least squares discriminant analysis (sPLSDA) showed that concentrations of nine fecal lipid metabolites were increased in the HFD + AOM compared to the HFD, which played a key role in overall metabolome group separation. These nine fecal lipid metabolite concentrations were positively associated with the number of colonic ACF, the cell proliferation of Ki67 proteins, and the abundance of dysbiotic bacteria. These data suggest that the process of AOM-induced ACF formation may increase selective fecal lipid concentrations in mice fed with a HFD but not an AIN. Collectively, the accumulation of these critical fecal lipid species may alter the overall metabolome during tumorigenesis in the colon.

Obesity, the other pandemic: linking diet and carcinogenesis by epigenetic mechanisms

Both obesity and cancer are complex medical conditions that are considered public health problems. The influence of obesity on the predisposition to develop various types of cancer has been observed in a wide variety of studies. Due to their importance as public health problems, and the close relationship between both conditions, it is important to be able to understand and associate them mechanistically. In this review article, we intend to go a little further, by finding relationships between lifestyle, which can lead a person to develop obesity, and how it influences at the cellular and molecular level, affecting gene expression to favor signaling pathways or transcriptional programs involved in cancer. We describe how products of metabolism and intermediate metabolism can affect chromatin structure, participating in the regulation (or dysregulation) of gene expression, and we show an analysis of genes that are responsive to diets high in sugar and fat, and how their epigenetic landscape is altered.

Contributing factors common to COVID‑19 and gastrointestinal cancer

The devastating complications of coronavirus disease 2019 (COVID-19) result from the dysfunctional immune response of an individual following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events, ultimately leading to COVID-19. The authors have previously identified a number of contributing factors (CFs) common to myriad chronic diseases. Based on these observations, it was hypothesized that there may be a significant overlap between CFs associated with COVID-19 and gastrointestinal cancer (GIC). Thus, in the present study, a streamlined dot-product approach was used initially to identify potential CFs that affect COVID-19 and GIC directly (i.e., the simultaneous occurrence of CFs and disease in the same article). The nascent character of the COVID-19 core literature (~1-year-old) did not allow sufficient time for the direct effects of numerous CFs on COVID-19 to emerge from laboratory experiments and epidemiological studies. Therefore, a literature-related discovery approach was used to augment the COVID-19 core literature-based ‘direct impact’ CFs with discovery-based ‘indirect impact’ CFs [CFs were identified in the non-COVID-19 biomedical literature that had the same biomarker impact pattern (e.g., hyperinflammation, hypercoagulation, hypoxia, etc.) as was shown in the COVID-19 literature]. Approximately 2,250 candidate direct impact CFs in common between GIC and COVID-19 were identified, albeit some being variants of the same concept. As commonality proof of concept, 75 potential CFs that appeared promising were selected, and 63 overlapping COVID-19/GIC potential/candidate CFs were validated with biological plausibility. In total, 42 of the 63 were overlapping direct impact COVID-19/GIC CFs, and the remaining 21 were candidate GIC CFs that overlapped with indirect impact COVID-19 CFs. On the whole, the present study demonstrates that COVID-19 and GIC share a number of common risk/CFs, including behaviors and toxic exposures, that impair immune function. A key component of immune system health is the removal of those factors that contribute to immune system dysfunction in the first place. This requires a paradigm shift from traditional Western medicine, which often focuses on treatment, rather than prevention.

Azoxymethane Alters the Plasma Metabolome to a Greater Extent in Mice Fed a High-Fat Diet Compared to an AIN-93 Diet

Consumption of a high-fat diet (HFD) links obesity to colon cancer in humans. Our data show that a HFD (45% energy fat versus 16% energy fat in an AIN-93 diet (AIN)) promotes azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation in a mouse cancer model. However, the underlying metabolic basis remains to be determined. In the present study, we hypothesize that AOM treatment results in different plasma metabolomic responses in diet-induced obese mice. An untargeted metabolomic analysis was performed on the plasma samples by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). We found that 53 of 144 identified metabolites were different between the 4 groups of mice (AIN, AIN + AOM, HFD, HFD + AOM), and sparse partial least-squares discriminant analysis showed a separation between the HFD and HFD + AOM groups but not the AIN and AIN + AOM groups. Moreover, the concentrations of dihydrocholesterol and cholesterol were inversely associated with AOM-induced colonic ACF formation. Functional pathway analyses indicated that diets and AOM-induced colonic ACF modulated five metabolic pathways. Collectively, in addition to differential plasma metabolomic responses, AOM treatment decreases dihydrocholesterol and cholesterol levels and alters the composition of plasma metabolome to a greater extent in mice fed a HFD compared to the AIN.

Azoxymethane-Induced Colorectal Cancer Mice Treated with a Polyphenol-Rich Apple Extract Show Less Neoplastic Lesions and Signs of Cachexia

Obesity is considered a risk factor for the development of colorectal cancer. In rodents, high-fat (HF) diets are able to increase the formation of azoxymethane (AOM)-induced polyps. Polyphenol-rich apple extracts have antioxidant and anti-inflammatory activities and may induce an amelioration of the manifestations of colorectal cancer. Twenty-seven male Crl:CD-1 mice received AOM during four weeks and were subsequently divided into three groups fed a HF diet (n = 9 each group): a non-supplemented group, a second group supplemented with apple extract at 1%, and a third group supplemented with the same apple extract at 1.5%. Energy metabolism and the respiratory quotient were not affected by the supplementation with the apple extract. Although body weight was not affected by the treatment, the mice supplemented with the apple extract showed less signs of cachexia than the non-treated mice. In the intestine, the mice supplemented with the apple extract showed lower sucrase, dipeptidyl-peptidase IV, and aminopeptidase N activities, and less intestinal lesions (aberrant crypt foci and polyps). Administration of a polyphenol-rich apple extract reduces the number of neoplastic lesions in mice with AOM-induced colorectal cancer and contributes to preserve adipose tissue mass.

Colon Carcinogenesis: The Interplay Between Diet and Gut Microbiota

Colorectal cancer (CRC) incidence increases yearly, and is three to four times higher in developed countries compared to developing countries. The well-known risk factors have been attributed to low physical activity, overweight, obesity, dietary consumption including excessive consumption of red processed meats, alcohol, and low dietary fiber content. There is growing evidence of the interplay between diet and gut microbiota in CRC carcinogenesis. Although there appears to be a direct causal role for gut microbes in the development of CRC in some animal models, the link between diet, gut microbes, and colonic carcinogenesis has been established largely as an association rather than as a cause-and-effect relationship. This is especially true for human studies. As essential dietary factors influence CRC risk, the role of proteins, carbohydrates, fat, and their end products are considered as part of the interplay between diet and gut microbiota. The underlying molecular mechanisms of colon carcinogenesis mediated by gut microbiota are also discussed. Human biological responses such as inflammation, oxidative stress, deoxyribonucleic acid (DNA) damage can all influence dysbiosis and consequently CRC carcinogenesis. Dysbiosis could add to CRC risk by shifting the effect of dietary components toward promoting a colonic neoplasm together with interacting with gut microbiota. It follows that dietary intervention and gut microbiota modulation may play a vital role in reducing CRC risk.

Food-grade titanium dioxide (E171) induces anxiety, adenomas in colon and goblet cells hyperplasia in a regular diet model and microvesicular steatosis in a high fat diet model

Food-grade titanium dioxide (E171) is a white additive widely used in solid and liquid food products. There is still debate about E171 toxic effects after oral consumption since this additive is deposited in colon, liver, spleen, testis and brain. The consumption of E171 commonly occurs with Western diets that are characterized by a high fat content. Thus, E171 could worsen adverse effects associated with a high fat diet (HFD) such as anxiety, colon diseases and testicular damage. We aimed to evaluate the effects of E171 on anxiety-like behavior, colon, liver and testis and to analyze if the administration of a HFD could exacerbate adverse effects. E171 was administered at ~5 mg/kg_bw by drinking water for 16 weeks and mice were fed with a Regular Diet or a HFD. E171 promoted anxiety, induced adenomas in colon, goblet cells hypertrophy and hyperplasia and mucins overexpression, but had no toxic effects on testicular tissue or spermatozoa in regular diet fed-mice. Additionally, E171 promoted microvesicular steatosis in liver in HFD fed-mice and the only HFD administration decreased the spermatozoa concentration and motility. In conclusion, E171 administration increases the number of adenomas in colon, induces hypertrophy and hyperplasia in goblet cells and microvesicular steatosis.

Effects of high-fat diet and intestinal aryl hydrocarbon receptor deletion on colon carcinogenesis

Consumption of a high-fat diet has been associated with an increased risk of developing colorectal cancer (CRC). However, the effects of the interaction between dietary fat content and the aryl hydrocarbon receptor (AhR) on colorectal carcinogenesis remain unclear. Mainly known for its role in xenobiotic metabolism, AhR has been identified as an important regulator for maintaining intestinal epithelial homeostasis. Although previous research using whole body AhR knockout mice has revealed an increased incidence of colon and cecal tumors, the unique role of AhR activity in intestinal epithelial cells (IECs) and modifying effects of fat content in the diet at different stages of sporadic CRC development are yet to be elucidated. In the present study, we have examined the effects of a high-fat diet on IEC-specific AhR knockout mice in a model of sporadic CRC. Although loss of AhR activity in IECs significantly induced the development of premalignant lesions, in a separate experiment, no significant changes in colon mass incidence were observed. Moreover, consumption of a high-fat diet promoted cell proliferation in crypts at the premalignant colon cancer lesion stage and colon mass multiplicity as well as β-catenin expression and nuclear localization in actively proliferating cells in colon masses. Our data demonstrate the modifying effects of high-fat diet and AhR deletion in IECs on tumor initiation and progression.NEW & NOTEWORTHY Through the use of an intestinal-specific aryl hydrocarbon receptor (AhR) knockout mouse model, this study demonstrates that the expression of AhR in intestinal epithelial cells is required to reduce the formation of premalignant colon cancer lesions. Furthermore, consumption of a high-fat diet and the loss of AhR in intestinal epithelial cells influences the development of colorectal cancer at various stages.

Differences Between the Intestinal Lumen Microbiota of Aberrant Crypt Foci (ACF)-Bearing and Non-bearing Rats

BACKGROUND

Multiple factors including host-microbiota interaction could contribute to the conversion of healthy mucosa to sporadic precancerous lesions. An imbalance of the gut microbiota may be a cause or consequence of this process.

AIM

The goal was to investigate and analyze the composition of gut microbiota during the genesis of precancerous lesions of colorectal cancer.

METHODS

To analyze the composition of gut microbiota in the genesis of precancerous lesions, a rat model of 1, 2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) was established. The feces of these rats and healthy rats were collected for 16S rRNA sequencing.

RESULTS

The diversity and density of the rat intestinal microbiota were significantly different between ACF-bearing and non-bearing group. ACF were induced in rats treated with DMH and showed increased expression of the inflammatory cytokines IL-6, IL-8, and TNF-α. Firmicutes was the most predominant phylum in both ACF-bearing and non-bearing group, followed by Bacteroidetes. Interestingly, although the density of Bacteroidetes decreased from the fifth week to the 17th week in both groups, it was significantly reduced in ACF-bearing group at the 13th week (P < 0.01). At the genus level, no significant difference was observed in the most predominant genus, Lactobacillus. Instead, Bacteroides and Prevotella were significantly less abundant (P < 0.01), while Akkermansia was significantly more abundant (P < 0.05) in ACF-bearing group at the 13th week.

CONCLUSION

Imbalance of the intestinal microbiota existed between ACF-bearing and non-bearing rats, which could be used as biomarker to predict the genesis of precancerous lesions in the gut.

Effects of Grape Juice in Superoxide Dismutase and Catalase in Colorectal Cancer Carcinogenesis Induced by Azoxymethane

Background:

The intestinal mucosa is commonly exposed to oxidant nutrients and carcinogens, which can lead to the generation of free radicals. The antioxidants present in the diet assume great importance as possible protective agents, reducing the oxidative damage. In this way, we evaluated the antioxidant action of grape juice on preneoplastic lesions induced by azoxymethane (AOM) in Wistar rats.

Methods:

The colorectal carcinogenesis was induced by two intraperitoneal injections of 15mg/kg of AOM in Wistar rats. The animals were divided in 7 groups and treated with 1 and 2% concentrations of grape juice before and after carcinogen administration. After euthanasia, the expression of antioxidant enzymes catalase (CAT), copper-zinc superoxide dismutase (Cu/Zn-SOD) and manganese superoxide dismutase (Mn-SOD) CAT, SOD1 and SOD2 were evaluated by immunohistochemistry.

Results:

AOM decreased the expression of CAT and Mn-SOD enzymes, but not for Cu/Zn-SOD. We observed an increase expression of CAT and Mn-SOD after grape juice administration in some concentrations according to the time of administration of the grape juice before the carcinogen or just after the carcinogen.

Conclusion:

Our results suggest an independent action of each enzyme and a possible antioxidant action of the grape juice components in the diet being able to balance the body to neutralize the superoxide radicals and not leave them in the cell-damaging form.

Novel leptin OB3 peptide-induced signaling and progression in thyroid cancers: Comparison with leptin

Obesity results in increased secretion of cytokines from adipose tissue and is a risk factor for various cancers. Leptin is largely produced by adipose tissue and cancer cells. It induces cell proliferation and may serve to induce various cancers. OB3-leptin peptide (OB3) is a new class of functional leptin peptide. However, its mitogenic effect has not been determined. In the present study, because of a close link between leptin and the hypothalamic-pituitary-thyroid axis, OB3 was compared with leptin in different thyroid cancer cells for gene expression, proliferation and invasion. Neither agent stimulated cell proliferation. Leptin stimulated cell invasion, but reduced adhesion in anaplastic thyroid cancer cells. Activated ERK1/2 and STAT3 contributed to leptin-induced invasion. In contrast, OB3 did not affect expression of genes involved in proliferation and invasion. In vivo studies in the mouse showed that leptin, but not OB3, significantly increased circulating levels of thyrotropin (TSH), a growth factor for thyroid cancer. In summary, OB3 is a derivative of leptin that importantly lacks the mitogenic effects of leptin on thyroid cancer cells.

Colonic aberrant crypt formation accompanies an increase of opportunistic pathogenic bacteria in C57BL/6 mice fed a high-fat diet

The increasing worldwide incidence of colon cancer has been linked to obesity and consumption of a high-fat Western diet. To test the hypothesis that a high-fat diet (HFD) promotes colonic aberrant crypt (AC) formation in a manner associated with gut bacterial dysbiosis, we examined the susceptibility to azoxymethane (AOM)-induced colonic AC and microbiome composition in C57/BL6 mice fed a modified AIN93G diet (AIN, 16% fat, energy) or an HFD (45% fat, energy) for 14 weeks. Mice receiving the HFD exhibited increased plasma leptin, body weight, body fat composition and inflammatory cell infiltration in the ileum compared with those in the AIN group. Consistent with the gut inflammatory phenotype, we observed an increase in colonic AC, plasma interleukin-6, tumor necrosis factor-α, monocyte chemoattractant protein-1 and inducible nitric oxide synthase in the ileum of the HFD-AOM group compared with the AIN-AOM group. Although the HFD and AIN groups did not differ in bacterial species number, the HFD and AIN diets resulted in different bacterial community structures in the colon. The abundance of certain short-chain fatty acid (SCFA) producing bacteria (e.g., Barnesiella) and fecal SCFA (e.g., acetic acid) content were lower in the HFD-AOM group compared with the AIN and AIN-AOM groups. Furthermore, we identified a high abundance of Anaeroplasma bacteria, an opportunistic pathogen in the HFD-AOM group. Collectively, we demonstrate that an HFD promotes AC formation concurrent with an increase of opportunistic pathogenic bacteria in the colon of C57BL/6 mice.

Leptin OB3 peptide suppresses leptin-induced signaling and progression in ovarian cancer cells

BACKGROUND

Obesity and its comorbidities constitute a serious health burden worldwide. Leptin plays an important role in diet control; however, it has a stimulatory potential on cancer cell proliferation. The OB3 peptide, a synthetic peptide, was shown to be more active than leptin in regulating metabolism but with no mitogenic effects in cancer cells.

METHODS

In this study, we investigated the proliferative effects, gene expressions and signaling pathways modulated by leptin and OB3 in human ovarian cancer cells. In addition, an animal study was performed.

RESULTS

Leptin, but not OB3, induced the proliferation of ovarian cancer cells. Interestingly, OB3 blocked the leptin-induced proliferative effect when it was co-applied with leptin. Both leptin and OB3 activated the phosphatidylinositol-3-kinase (PI3K) signal transduction pathway. In addition, leptin stimulated the phosphorylation of signal transducer and activator of transcription-3 (STAT3) Tyr-705 as well as estrogen receptor (ER)α, and the expression of ERα-responsive genes. Interestingly, all leptin-induced signal activation and gene expressions were blocked by the co-incubation with OB3 and the inhibition of extracellular signal-regulated kinase (ERK)1/2. Coincidently, leptin, but not OB3, increased circulating levels of follicle-stimulating hormone (FSH) which is known to play important roles in the initiation and proliferation of ovarian cancer cells.

CONCLUSIONS

In summary, our findings suggest that the OB3 peptide may prevent leptin-induced ovarian cancer initiation and progression by disrupting leptin-induced proliferative signals via STAT3 phosphorylation and ERα activation. Therefore, the OB3 peptide is a potential anticancer agent that might be employed to prevent leptin-induced cancers in obese people.

Diets link metabolic syndrome and colorectal cancer development (Review)

Diets have been believed to be an important factor in the development of metabolic syndrome and colorectal cancer (CRC). In recent years, many studies have shown an intimate relationship between mucosal immunity, metabolism and diets, which has led to a greater understanding of the pathophysiology of metabolic syndrome and CRC development. Although the precise effects of diets on oncogenesis have not been compl-etely elucidated, microbiota changes and inflammation are believed to be important factors that influence the development of CRC. Moreover, increased release of pro-inflammatory cytokines and alteration of adipokine levels have been observed in patients with colorectal adenoma and/or CRC, and these all have been considered as the important mechanisms that link diets to the development of metabolic syndrome and CRC. Importantly, a high-fat, low-fiber diet is associated with dysbiosis, and as the gut signature becomes more important in metabolic syndrome and CRC, an increased understanding of diets on bacterial activity in the pathogenesis of metabolic syndrome and CRC will lead to new preventive and therapeutic strategies.

Weight loss following diet-induced obesity does not alter colon tumorigenesis in the AOM mouse model

Obesity presents a significant public health concern given its association with increased cancer incidence, unfavorable prognosis, and metastasis. However, there is very little literature on the effects of weight loss, following obesity, on risk for colon cancer or liver cancer. Therefore, we sought to study whether intentional weight loss through diet manipulation was capable of mitigating colon and liver cancer in mice. We fed mice with a high-fat diet (HFD) comprised of 47% carbohydrates, 40% fat, and 13% protein for 20 wk to mimic human obesity. Subsequently, azoxymethane (AOM) was used to promote colon and liver carcinogenesis. A subset of obese mice was then switched to a low-fat diet (LFD) containing 67.5% carbohydrate, 12.2% fat, and 20% protein to promote intentional weight loss. Body weight loss and excess fat reduction did not protect mice from colon cancer progression and liver dysplastic lesion in the AOM-chemical-cancer model even though these mice had improved blood glucose and leptin levels. Intentional weight loss in AOM-treated mice actually produced histological changes that resemble dysplastic alterations in the liver and presented a higher percentage of F4/80⁺CD206⁺ macrophages and activated T cells (CD4⁺CD69⁺) in the spleen and lymph nodes, respectively. In addition, the liver of AOM-treated mice exposed to a HFD during the entire period of the experiment exhibited a marked increase in proliferation and pNF-κB activation. Altogether, these data suggest that intentional weight loss following chemical-induced carcinogenesis does not affect colon tumorigenesis but may in fact negatively impact liver repair mechanisms.

Colonic inflammation accompanies an increase of β-catenin signaling and Lachnospiraceae/Streptococcaceae bacteria in the hind gut of high-fat diet-fed mice

Consumption of an obesigenic/high-fat diet (HFD) is associated with a high colon cancer risk and may alter the gut microbiota. To test the hypothesis that long-term high-fat (HF) feeding accelerates inflammatory process and changes gut microbiome composition, C57BL/6 mice were fed HFD (45% energy) or a low-fat (LF) diet (10% energy) for 36 weeks. At the end of the study, body weights in the HF group were 35% greater than those in the LF group. These changes were associated with dramatic increases in body fat composition, inflammatory cell infiltration, inducible nitric oxide synthase protein concentration and cell proliferation marker (Ki67) in ileum and colon. Similarly, β-catenin expression was increased in colon (but not ileum). Consistent with gut inflammation phenotype, we also found that plasma leptin, interleukin 6 and tumor necrosis factor α concentrations were also elevated in mice fed the HFD, indicative of chronic inflammation. Fecal DNA was extracted and the V1-V3 hypervariable region of the microbial 16S rRNA gene was amplified using primers suitable for 454 pyrosequencing. Compared to the LF group, the HF group had high proportions of bacteria from the family Lachnospiraceae/Streptococcaceae, which is known to be involved in the development of metabolic disorders, diabetes and colon cancer. Taken together, our data demonstrate, for the first time, that long-term HF consumption not only increases inflammatory status but also accompanies an increase of colonic β-catenin signaling and Lachnospiraceae/Streptococcaceae bacteria in the hind gut of C57BL/6 mice.

Bardoxolone Methyl Prevents High-Fat Diet-Induced Colon Inflammation in Mice

Obesity induces chronic, low-grade inflammation, which increases the risk of colon cancer. We investigated the preventive effects of Bardoxolone methyl (BARD) on high-fat diet (HFD)-induced inflammation in a mouse colon. Male C57BL/6J mice (n=7) were fed a HFD (HFD group), HFD plus BARD (10 mg/kg) in drinking water (HFD/BARD group), or normal laboratory chow diet (LFD group) for 21 weeks. In HFD mice, BARD reduced colon thickness and decreased colon weight per length. This was associated with an increase in colon crypt depth and the number of goblet cells per crypt. BARD reduced the expression of F4/80 and CD11c but increased CD206 and IL-10, indicating an anti-inflammatory effect. BARD prevented an increase of the intracellular pro-inflammatory biomarkers (NF-қB, p NF-қB, IL-6, TNF-α) and cell proliferation markers (Cox2 and Ki67). BARD prevented fat deposition in the colon wall and prevented microbial population changes. Overall, we report the preventive effects of BARD on colon inflammation in HFD-fed mice through its regulation of macrophages, NF-қB, cytokines, Cox2 and Ki67, fat deposition and microflora.

Dietary aloe vera gel powder and extract inhibit azoxymethane- induced colorectal aberrant crypt foci in mice fed a high- fat diet

Aloe vera gel exhibits protective effects against insulin resistance as well as lipid-lowering and anti-diabetic effects. The anti-diabetic compounds in this gel were identified as Aloe-sterols. Aloe vera gel extract (AVGE) containing Aloe-sterols has recently been produced using a new procedure. We previously reported that AVGE reduced large-sized intestinal polyps in Apc-deficient Min mice fed a high fat diet (HFD), suggesting that Aloe vera gel may protect against colorectal cancer. In the present study, we examined the effects of Aloe vera gel powder (AVGP) and AVGE on azoxymethane-induced colorectal preneoplastic aberrant crypt foci (ACF) in mice fed a HFD. Male C57BL/6J mice were given a normal diet (ND), HFD, HFD containing 0.5% carboxymethyl cellulose solution, which was used as a solvent for AVGE (HFDC), HFD containing 3% or 1% AVGP, and HFDC containing 0.0125% (H-) or 0.00375% (L-) AVGE. The number of ACF was significantly lower in mice given 3% AVGP and H-AVGE than in those given HFD or HFDC alone. Moreover, 3% AVGP, H-AVGE and L-AVGE significantly decreased the mean Ki-67 labeling index, assessed as a measure of cell proliferation in the colonic mucosa. In addition, hepatic phase II enzyme glutathione S-transferase mRNA levels were higher in the H-AVGE group than in the HFDC group. These results suggest that both AVGP and AVGE may have chemopreventive effects on colorectal carcinogenesis under the HFD condition. Furthermore, the concentration of Aloe-sterols was similar between 3% AVGP and H-AVGE, suggesting that Aloe-sterols were the main active ingredients in this experiment.

Obesity promotes colonic stem cell expansion during cancer initiation

There is an urgent need to elucidate the mechanistic links between obesity and colon cancer. Convincing evidence for the role of Lgr5(+) stem cells in colon tumorigenesis has been established; however, the influence of obesity on stem cell maintenance is unknown. We assessed the effects of high fat (HF) feeding on colonic stem cell maintenance during cancer initiation (AOM induced) and the responsiveness of stem cells to adipokine signaling pathways. The number of colonic GFP(+) stem cells was significantly higher in the AOM-injected HF group compared to the LF group. The Lgr5(+) stem cells of the HF fed mice exhibited statistically significant increases in cell proliferation and decreases in apoptosis in response to AOM injection compared to the LF group. Colonic organoid cultures from lean mice treated with an adiponectin receptor agonist exhibited a reduction in Lgr5-GPF(+) stem cell number and an increase in apoptosis; however, this response was diminished in the organoid cultures from obese mice. These results suggest that the responsiveness of colonic stem cells to adiponectin in diet-induced obesity is impaired and may contribute to the stem cell accumulation observed in obesity.

Leptin activation of mTOR pathway in intestinal epithelial cell triggers lipid droplet formation, cytokine production and increased cell proliferation

Accumulating evidence suggests that obesity and enhanced inflammatory reactions are predisposing conditions for developing colon cancer. Obesity is associated with high levels of circulating leptin. Leptin is an adipocytokine that is secreted by adipose tissue and modulates immune response and inflammation. Lipid droplets (LD) are organelles involved in lipid metabolism and production of inflammatory mediators, and increased numbers of LD were observed in human colon cancer. Leptin induces the formation of LD in macrophages in a PI3K/mTOR pathway-dependent manner. Moreover, the mTOR is a serine/threonine kinase that plays a key role in cellular growth and is frequently altered in tumors. We therefore investigated the role of leptin in the modulation of mTOR pathway and regulation of lipid metabolism and inflammatory phenotype in intestinal epithelial cells (IEC-6 cells). We show that leptin promotes a dose- and time-dependent enhancement of LD formation. The biogenesis of LD was accompanied by enhanced CXCL1/CINC-1, CCL2/MCP-1 and TGF-β production and increased COX-2 expression in these cells. We demonstrated that leptin-induced increased phosphorylation of STAT3 and AKT and a dose and time-dependent mTORC activation with enhanced phosphorilation of the downstream protein P70S6K protein. Pre-treatment with rapamycin significantly inhibited leptin effects in LD formation, COX-2 and TGF-β production in IEC-6 cells. Moreover, leptin was able to stimulate the proliferation of epithelial cells on a mTOR-dependent manner. We conclude that leptin regulates lipid metabolism, cytokine production and proliferation of intestinal cells through a mechanism largely dependent on activation of the mTOR pathway, thus suggesting that leptin-induced mTOR activation may contribute to the obesity-related enhanced susceptibility to colon carcinoma.

Fat, epigenome and pancreatic diseases. Interplay and common pathways from a toxic and obesogenic environment

The worldwide obesity epidemic is paralleled by a rise in the incidence of pancreatic disorders ranging from "fatty" pancreas to pancreatitis and cancer. Body fat accumulation and pancreatic dysfunctions have common pathways, mainly acting through insulin resistance and low-grade inflammation, frequently mediated by the epigenome. These mechanisms are affected by lifestyle and by the toxic effects of fat and pollutants. An early origin is common, starting in pediatric age or during the fetal life in response to nutritional factors, endocrine disruptor chemicals (EDCs) or parental exposure to toxics. A "fatty pancreas" is frequent in obese and is able to induce pancreatic damage. The fat is a target of EDCs and of the cytotoxic/mutagenic effects of heavy metals, and is the site of bioaccumulation of lipophilic and persistent pollutants related with insulin resistance and able to promote pancreatic cancer. Increased Body Mass Index (BMI) can act as independent risk factor for a more severe course of acute pancreatitis and obesity is also a well-known risk factor for pancreatic cancer, that is related with BMI, insulin resistance, and duration of exposure to the toxic effects of fat and/or of environmental pollutants. All these mechanisms involve gene-environment interactions through epigenetic factors, and might be manipulated by primary prevention measures. Further studies are needed, pointing to better assess the interplays of modifiable factors on both obesity and pancreatic diseases, and to verify the efficacy of primary prevention strategies involving lifestyle and environmental exposure to toxics.

Grape juice concentrate (G8000™) modulates apoptosis but not oxidative stress following rat colon carcinogenesis induced by azoxymethane

OBJECTIVES

The aim of this study was to evaluate if grape juice concentrate is able to protect against experimental colon carcinogenesis.

MATERIAL AND METHODS

For this purpose, a total of 35 male Wistar rats were randomly distributed into seven groups: G1: SHAM animals receiving only saline; G2: animals receiving 15 mg/kg azoxymethane (AOM); G3: animals receiving 1% grape juice concentrate 2 weeks before the administration of AOM; G4: animals receiving 2% grape juice concentrate 2 weeks before the administration of AOM; G5: animals receiving 1% grape juice concentrate 4 weeks after the last administration of AOM; G6: animals receiving 2% grape juice concentrate 4 weeks after the last administration of AOM; G7: animals receiving only 2% grape juice concentrate.

RESULTS

The group that received 2% grape juice concentrate before induction with AOM showed the decreased expression of Bcl-2 compared to those animals that were induced by AOM (positive control). Regarding Bax, animals that received grape juice at 2% decreased Bax immunoexpression when compared to AOM group. Furthermore, animals that intake grape juice at 1% after induced by AOM decreased Bax immunoexpression as well. 8-OHdGLI did not show significant statistically differences (p > 0.05) among groups.

CONCLUSION

In summary, our results demonstrate that grape juice is able to modulate rat colon carcinogenesis as a result of induction of apoptosis.

No effect of high fat diet-induced obesity on spontaneous reporter gene mutations in gpt delta mice

A large number of epidemiological studies have demonstrated that obesity is a risk factor for several human cancers. Several animal studies using rodents with diet-induced or genetic obesity have also demonstrated that obesity can promote tumor development. However, the effects of obesity on the early stages of carcinogenesis, and especially on the spontaneous occurrence of somatic gene mutations, remain unclear. To investigate the effects of obesity on the rate of spontaneous gene mutations, we performed reporter gene mutation assays in liver, kidney, and colon, organs in which obesity appears to be associated with cancer development on the basis of epidemiological or animal studies, in mice with high fat diet (HFD)-induced obesity. Six-week-old male and female C57BL/6 gpt delta mice were fed HFD or standard diet (STD) for 13 or 26 weeks. At the end of the experiments, reporter gene mutation assays of liver, kidney, and colon were performed. Final body weights and serum leptin levels of male and female mice fed HFD for 13 or 26 weeks were significantly increased compared with corresponding STD-fed groups. Reporter gene mutation assays of liver, kidney, and colon revealed that there were no significant differences in gpt or Spi- mutant frequencies between STD- and HFD-fed mice in either the 13-week or 26-week groups. These results indicate that HFD treatment and consequent obesity does not appear to influence the spontaneous occurrence of somatic gene mutations.

Nutrient-induced intestinal adaption and its effect in obesity

Obese and lean individuals respond differently to nutrients with changes in digestion, absorption and hormone release. This may be a result of differences in intestinal epithelial morphology and function driven by the hyperphagia or the type of diet associated with obesity. It is well known that the maintenance and growth of the intestine is driven by the amount of luminal nutrients, with high nutrient content resulting in increases in cell number, villi length and crypt depth. In addition, the type of nutrient appears to contribute to alterations in the morphology and function of the epithelial cells. This intestinal adaptation may be what is driving the differences in nutrient processing in lean versus obese individuals. This review describes how nutrients may be able to induce changes in intestinal epithelial cell proliferation, differentiation and function and the link between intestinal adaptation and obesity.

Risk of colonic cancer is not higher in the obese Lep(ob) mouse model compared to lean littermates

Epidemiological data suggest that obesity increases the risk of colorectal cancer in humans. Given that diet-induced obesity mouse models verified the epidemiological data, the present study aimed to determine whether obese C57BL/6J-Lep(ob) male mice (a different obesity in vivo model) were at greater risk of colonic cancer than their lean male littermates. Risk of colonic tumorigenesis was assessed by numbers of aberrant crypts, aberrant crypt foci and colonic tumors. Proliferation of the colonic epithelia was assessed histochemically following administration of BrdU. Availability of the procarcinogen, azoxymethane (AOM) to target tissues was assessed by quantifying via HPLC plasma AOM concentrations during the 60 min period following AOM injection. When obese and lean mice were injected with azoxymethane (AOM) at doses calculated to provide equivalent AOM levels per kg lean body mass, obese animals had significantly fewer aberrant crypts/colon and fewer aberrant crypt foci/colon than the lean animals. Tumors were identified in the colonic mucosa of lean (4 tumors in 14 mice) but not obese (0 tumors in 15 mice) mice. Colonic cell proliferation was not significantly different for obese and lean mice. Because these results were unexpected, plasma AOM concentrations were measured and were found to be lower in the obese than lean mice. When plasma AOM levels were comparable for the lean and obese mice, the Lep(ob) mice continued to have significantly fewer aberrant crypt foci/colon than the lean mice, but differences were not statistically different for aberrant crypts/colon. Interestingly, obese Lep(ob) mice did not exhibit increased risk of colonic cancer as expected. Instead, Lep(ob) mice exhibited equivalent or lower risk of colon cancer when compared to the lean group. These results taken together with in vivo results from diet-induced obesity studies, imply that leptin may be responsible for the increased risk of colon cancer associated with obesity.

Linking inflammation to tumorigenesis in a mouse model of high-fat-diet-enhanced colon cancer

Many observational epidemiologic studies suggest an association between high-fat-diet (HFD) and colon cancer risk. However, the lack of controlled experimental studies that examine this relationship and the mechanisms involved weaken the basis for inferring a causal relationship. Inflammation plays a role in colon cancer progression and HFDs have been reported to increase inflammation; however, the inflammatory effects of HFD in colon cancer have yet to be firmly established. We examined the effects of a novel HFD that closely mimics the standard American diet (12% and 40% of total caloric intake from saturated fat and total fat, respectively) on macrophage markers and inflammatory mediators in a mouse model of intestinal tumorigenesis and relate this to polyp characteristics as well as measures of adiposity. Male Apc(Min/+) mice (7-8/group) were fed a Control Diet (Con) or novel high-fat-diet (HFD) from 4 to 12weeks of age. Body weight and body composition were measured weekly and monthly, respectively. Intestinal tissue was analyzed for polyp burden (number and size). Gene expression of macrophage markers and inflammatory mediators were examined in the adipose tissue and polyps. The HFD increased the expression of macrophage markers and inflammatory mediators in the adipose tissue (F4/80, CD11c, TLR-4 and MCP-1) and tumor microenvironment (IL-12, MCP-1, IL-6 and TNF-α). As expected, the HFD increased body weight, body fat percent, fat mass and blood glucose (P<0.05), and was associated with an increase in the number of large polyps (P<0.05) but not total polyps. In summary, consumption of a HFD, similar in macronutrient composition to the standard American diet, altered the expression of macrophage phenotypic markers and inflammatory mediators in adipose tissue and intestinal polyps and this was associated with increased tumorigenesis.

Diet-induced obesity promotes colon tumor development in azoxymethane-treated mice

Obesity is an important risk factor for colon cancer in humans, and numerous studies have shown that a high fat diet enhances colon cancer development. As both increased adiposity and high fat diet can promote tumorigenesis, we examined the effect of diet-induced obesity, without ongoing high fat diet, on colon tumor development. C57BL/6J male mice were fed regular chow or high fat diet for 8 weeks. Diets were either maintained or switched resulting in four experimental groups: regular chow (R), high fat diet (H), regular chow switched to high fat diet (RH), and high fat diet switched to regular chow (HR). Mice were then administered azoxymethane to induce colon tumors. Tumor incidence and multiplicity were dramatically smaller in the R group relative to all groups that received high fat diet at any point. The effect of obesity on colon tumors could not be explained by differences in aberrant crypt foci number. Moreover, diet did not alter colonic expression of pro-inflammatory cytokines tumor necrosis factor-α, interleukin-6, interleukin-1β, and interferon-γ, which were measured immediately after azoxymethane treatment. Crypt apoptosis and proliferation, which were measured at the same time, were increased in the HR relative to all other groups. Our results suggest that factors associated with obesity – independently of ongoing high fat diet and obesity – promote tumor development because HR group animals had significantly more tumors than R group, and these mice were fed the same regular chow throughout the entire carcinogenic period. Moreover, there was no difference in the number of aberrant crypt foci between these groups, and thus the effect of obesity appears to be on subsequent stages of tumor development when early preneoplastic lesions transition into adenomas.

Molecular mechanisms of chemopreventive phytochemicals against gastroenterological cancer development

Cancer is one of the leading causes of death worldwide. Commonly used cancer treatments, including chemotherapy and radiation therapy, often have side effects and a complete cure is sometimes impossible. Therefore, prevention, suppression, and/or delaying the onset of the disease are important. The onset of gastroenterological cancers is closely associated with an individual’s lifestyle. Thus, changing lifestyle, specifically the consumption of fruits and vegetables, can help to protect against the development of gastroenterological cancers. In particular, naturally occurring bioactive compounds, including curcumin, resveratrol, isothiocyanates, (-)-epigallocatechin gallate and sulforaphane, are regarded as promising chemopreventive agents. Hence, regular consumption of these natural bioactive compounds found in foods can contribute to prevention, suppression, and/or delay of gastroenterological cancer development. In this review, we will summarize natural phytochemicals possessing potential antioxidant and/or anti-inflammatory and anti-carcinogenic activities, which are exerted by regulating or targeting specific molecules against gastroenterological cancers, including esophageal, gastric and colon cancers.