Increased visceral fat mass and insulin signaling in colitis-related colon carcinogenesis model mice. Chem Biol Interact. 2010;183:271-275. [PMID: 19931517 DOI: 10.1016/j.cbi.2009.11.014]

An Overview of Molecular Profiles in Ulcerative Colitis-Related Cancer

Ulcerative colitis (UC) is an independent risk factor of colorectal cancer (CRC). Both genetic and epigentic events induce a unique molecular profile during the development from UC to UC-related CRC (UCRC). These molecular changes play varied roles in DNA repair, immune response, cell metabolism, and interaction with the microbiota during the carcinogenesis process. This review will systmatically discuss the molecular characteristics of UCRC and point out the future perspectives in this research field.

Garcinol suppresses inflammation-associated colon carcinogenesis in mice

SCOPE

Garcinol is a polyisoprenylated benzophenone derivative isolated from the fruit rind of Garcinia indica and has exhibited chemopreventive effects on azoxymethane)-induced colonic aberrant crypt foci in mice. In this study, we investigated whether garcinol protects against dextran sulfate sodium (DSS) induced colitis/inflammation and azoxymethane/DSS-induced inflammation-related colon tumorigenesis in male ICR mice. We also aimed to delineate the possible molecular mechanisms responsible for these effects.

METHODS AND RESULTS

Treatment with garcinol prevented shortening of the colon length and the formation of aberrant crypt foci and improved the inflammation score in the mouse colon stimulated by DSS. Moreover, administration of garcinol markedly decreased DSS-induced inducible nitric oxide synthase, cyclooxygenase-2, and proliferating cell nuclear antigen protein expression. The dietary administration of garcinol effectively reduced the tumor size and incidence in the mouse colon. Western blot and immunohistochemical analysis revealed that administration of garcinol significantly downregulated cyclooxygenase-2, cyclin D1, and vascular endothelial growth factor expression via inhibition of the extracellular signal-regulated protein kinase 1/2, phosphatidylinositol 3 kinase/Akt/p70 ribosomal S6 kinase, and Wnt/β-catenin signaling pathways.

CONCLUSION

Our results suggest that garcinol may merit further clinical investigation as a chemoprophylactic food that helps prevent colitis-associated colon cancer.

Cytosolic malic enzyme 1 (ME1) mediates high fat diet-induced adiposity, endocrine profile, and gastrointestinal tract proliferation-associated biomarkers in male mice

BACKGROUND

Obesity and associated hormonal disturbances are risk factors for colon cancer. Cytosolic Malic Enzyme (ME1) generates NADPH used for lipogenesis in gastrointestinal (GI), liver and adipose tissues. We have reported that inclusion of soy protein isolate (SPI) in the diet lowered body fat content and colon tumor incidence of rats fed AIN-93G diet, while others have demonstrated SPI inhibition of rat hepatic ME1 expression. The present study examined the individual and combined effects of dietary SPI and absence of ME1 on: 1) serum concentrations of hormones implicated in colon cancer development, 2) expression of lipogenic and proliferation-associated genes in the mouse colon and small intestine, and 3) liver and adipose expression of lipogenic and adipocytokine genes that may contribute to colon cancer predisposition.

METHODS

Weanling wild type (WT) and ME1 null (MOD-1) male mice were fed high-fat (HF), iso-caloric diets containing either casein (CAS) or SPI as sole protein source for 5 wks. Somatic growth, serum hormone and glucose levels, liver and adipose tissue weights, GI tissue parameters, and gene expression were evaluated.

RESULTS

The MOD-1 genotype and SPI-HF diet resulted in decreases in: body and retroperitoneal fat weights, serum insulin, serum leptin, leptin/adiponectin ratio, adipocyte size, colon mTOR and cyclin D1 mRNA abundance, and jejunum FASN mRNA abundance, when compared to WT mice fed CAS-HF. Regardless of diet, MOD-1 mice had reductions in liver weight, liver steatosis, and colon crypt depth, and increases in adipose tissue expression of IRS1 and IRS2, compared to WT mice. SPI-HF diet reduced ME1 gene expression only in retroperitoneal fat.

CONCLUSIONS

Data suggest that the pharmacological targeting of ME1 or the inclusion of soy protein in the diet may provide avenues to reduce obesity and its associated pro-tumorigenic endocrine environment and improve insulin sensitivity, potentially disrupting the obesity-colon cancer connection.

Metabonomic variations associated with AOM-induced precancerous colorectal lesions and resveratrol treatment

Resveratrol (Res), 3,5,4'-trihydroxy-trans-stilbene, is an antioxidant found in the skin of red grapes and in several other plants. This phenolic compound has been recently reported to possess cancer chemopreventive activity that inhibits the process of carcinogenesis. However, the mechanisms underlying its anticancer effects remain largely unresolved. In this study, we investigated the chemoprotective effects of dietary Res in an azoxymethane (AOM) induced precancerous colorectal lesion model in male Wistar rats. The metabolic alterations in urine, sera, and colonic tissues of experimental rats perturbed by AOM intervention as well as the Res treatment were measured by a gas chromatography time-of-flight mass spectrometry (GC-TOFMS) analysis. Significant alterations of metabolites were observed in AOM group in urine, sera, and colonic tissues, which were attenuated by Res treatment and concurrent with the histopathological improvement with significantly decreased aberrant crypt foci (ACF) incidence. Representative metabolites include depleted glucose, β-hydroxybutyrate (ketone body), hypoxanthine, and elevated branched chain amino acids (isoleucine and valine) and tryptophan in colonic tissue, as well as elevated serum aminooxyacetate and urinary 4-hydroxyphenylacetate and xanthurenate. These metabolic changes suggest that the preventive effect of Res is associated with attenuation of impaired glucose and lipid metabolism and elevated protein breakdown in colonic tissues from AOM-exposed rats. It also appears that Res induced significant metabolic alterations independent of the AOM-induced metabolic changes. The significantly altered metabolites identified in Res-AOM group relative to AOM group include arachidonate, linoleate, glutamate, docosahexaenoate, palmitelaidate, 2-aminobutyrate, pyroglutamate, and threonate, all of which are involved in inflammation and oxidation processes. This suggests that Res exerts the chemopreventive effects on ACF formation by anti-inflammatory and antioxidant mechanisms in addition to amelioration of AOM-induced mitochondrial disruption.

Differential effects of energy balance on experimentally-induced colitis

AIM: To characterize the influence of diet-induced changes in body fat on colitis severity in SMAD3-/- mice.

METHODS: SMAD3-/- mice (6-8 wk of age) were randomly assigned to receive a calorie restricted (30% of control; CR), control (CON), or high fat (HF) diet for 20 wk and were gavaged with sterile broth or with Helicobacter hepaticus (H. hepaticus) to induce colitis. Four weeks after infection, mice were sacrificed and the cecum and colons were processed for histological evaluation.

RESULTS: Dietary treatment significantly influenced body composition prior to infection (P < 0.05), with CR mice having less (14% ± 2%) and HF-fed mice more body fat (32% ± 7%) compared to controls (22% ± 4%). Differences in body composition were associated with alterations in plasma levels of leptin (HF > CON > CR) and adiponectin (CON > HF ≥ CR) (P < 0.05). There were no significant differences in colitis scores between CON and HF-fed mice 4 wk post-infection. Consistent with this, differences in proliferation and inflammation markers (COX-2, iNOS), and infiltrating cell types (CD3⁺ T lymphocytes, macrophages) were not observed. Unexpectedly, only 40% of CR mice survived infection with H. hepaticus, with mortality observed as early as 1 wk following induction of colitis.

CONCLUSION: Increased adiposity does not influence colitis severity in SMAD3-/- mice. Importantly, caloric restriction negatively impacts survival following pathogen challenge, potentially due to an impaired immune response.

Early lesion formation in colorectal carcinogenesis is associated with adiponectin status whereas neoplastic lesions are associated with diet and sex in C57BL/6J mice

Adiponectin is an antiinflammatory and insulin-sensitizing hormone that is decreased in obesity. Although controversial, it has been suggested that decreased adiponectin contributes to colorectal cancer risk in obesity. To further investigate the role of adiponectin in obesity-linked colorectal carcinogenesis, we used male and female adiponectin knockout (KO) and wild-type (Wt) C57BL/6J mice. Tumorigenesis was induced in all mice with the combined treatment of azoxymethane (AOM) and dextran sodium sulfate (DSS). Following AOM/DSS treatment, mice were fed a low-fat control (LFC), or high-fat lard (HFL) diet for 7 1/2 wk. KO mice developed fewer total lesions than Wt mice, males developed fewer lesions than females, and mice fed the HFL diet developed fewer lesions than those fed the LFC diet. Early lesion multiplicity was influenced by genotype, whereas advanced lesion development was influenced by sex and diet. Moreover, lesion types were differentially correlated with serum adipokines and colon gene expression of adiponectin receptors, insulin receptor, and toll-like receptor 4. These data suggest that in the AOM/DSS model of carcinogenesis, adiponectin functions to promote early lesion development whereas sex and diet are important regulators of advanced lesion development through pathways involved in inflammation and insulin signaling.

Effects of diet-induced obesity on colitis-associated colon tumor formation in A/J mice

OBJECTIVE

Studies have indicated that obesity is associated with a higher risk of colorectal cancer. This study was performed to determine the effect of diet-induced obesity on the formation of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colon tumors and to identify adiposity-related mechanisms.

METHODS

Male A/J mice were placed on either a high-fat diet (HFD; 45% of total calories from fat) or a normal diet (ND; 15% of calories from fat) for 12 weeks. To induce colon tumors, AOM was administered at a dose of 10 mg/kg body weight, followed by two cycles of DSS supply.

RESULTS

Study results indicated that the HFD group had twofold higher numbers of colonic tumors, as compared with the ND group. The HFD group also had significantly increased body weight and epididymal fat weight, which were associated with increases of serum insulin, insulin-like growth factor-1, leptin, epididymal fat pad leptin mRNA and colonic leptin receptor (Ob-R) mRNA. Animals on HFD showed higher expressions of Ob-R, insulin receptor, phosphorylated Akt, phosphorylated extracellular signal-regulated kinases, Bcl-xL and Cyclin D1 proteins in the colon.

CONCLUSION

The results suggest that HFD-induced obesity facilitates colon tumor formation, possibly by regulating downstream targets of circulating adiposity-related factors via receptor-mediated signaling of the phosphatidylinositol 3-kinase/Akt pathway.