Effects of Dietary Resistant Starch on the Wnt Signaling Pathway and Preneoplastic Cells in the Colons of Azoxymethane-Treated Rats.

Dietary resistant starch (RS) has been suggested to reduce colonic neoplasia. To determine the effects of digestion-resistant cornstarch on colonic carcinogenesis and Wnt signaling in azoxymethane (AOM)-treated F344 rats, diets containing naturally occurring RS from corn lines derived partially from Guat209 (GUAT), AR16035 (AR), or a hybrid (ARxGUAT), containing 34.5 ± 2.0, 0.2 ± 0.1, and 1.9 ± 0.1% RS, respectively, were fed at 55% of the diet. GUAT-fed rats had increased cecal content and tissue weight and decreased cecal pH compared with AR- or ARxGUAT-fed rats. Numbers of aberrant crypt foci (ACF) were not different among diet groups. Increased numbers of crypts/focus were observed in AOM-injected rats fed GUAT compared with rats fed other diets. ß-catenin mRNA expression of the crypts was significantly increased in GUAT-fed rats injected with AOM relative to those injected with saline. These findings suggest that selected dietary RSs may at some level further enhance colonocyte proliferation and differentiation in an AOM-treated colon.

Overexpression of ILK promotes temozolomide resistance in glioma cells.

The present study aimed to investigate whether overexpression of integrin-linked kinase (ILK) affects drug resistance to temozolomide (TMZ) in glioma cells. To do this, a plasmid containing the ILK gene was transfected into the SHG­44 human glioma cell line, and cells were subsequently cultured in the absence or presence of TMZ. The expression levels of ILK, multidrug resistance­associated protein (MRP) and multi­drug resistance protein (MDR) were assessed in these cells. Cell growth and apoptosis were measured by MTT and Hoechst staining, and flow cytometry, respectively. In addition, the expression levels of B­cell lymphoma 2 (Bcl­2) and Bcl­2­associated x protein (Bax), and caspase­3 activity, were evaluated. The ILK­overexpressing SHG­44 cell was successfully constructed, and demonstrated increased expression levels of ILK, MDR and MRP compared with untransfected cells. Cell growth in the ILK+TMZ group was significantly greater, and the percentage of apoptotic cells in the ILK+TMZ group was significantly reduced, compared with the p enhanced green fluorescent protein (EGFP)­C1+ TMZ empty vector control group. Expression levels of the anti­apoptotic protein Bcl­2 were significantly increased and those of the pro­apoptotic protein Bax were significantly decreased (P<0.01) in the ILK+TMZ group compared with the pEGFP­C1+TMZ group. In addition, the activity of caspase­3 in ILK+TMZ group was significantly decreased compared with the pEGFP­C1+TMZ group (P<0.01). Overexpression of ILK therefore promoted the proliferation of SHG­44 human glioma cells, reduced apoptosis and reduced sensitivity to TMZ via decreasing the activity of caspase­3.

High-resolution time-of-flight mass spectrometry fingerprinting of metabolites from cecum and distal colon contents of rats fed resistant starch.

Time-of-flight mass spectrometry along with statistical analysis was utilized to study metabolic profiles among rats fed resistant starch (RS) diets. Fischer 344 rats were fed four starch diets consisting of 55 % (w/w, dbs) starch. A control starch diet consisting of corn starch was compared against three RS diets. The RS diets were high-amylose corn starch (HA7), HA7 chemically modified with octenyl succinic anhydride, and stearic-acid-complexed HA7 starch. A subgroup received antibiotic treatment to determine if perturbations in the gut microbiome were long lasting. A second subgroup was treated with azoxymethane (AOM), a carcinogen. At the end of the 8-week study, cecal and distal colon content samples were collected from the sacrificed rats. Metabolites were extracted from cecal and distal colon samples into acetonitrile. The extracts were then analyzed on an accurate-mass time-of-flight mass spectrometer to obtain their metabolic profile. The data were analyzed using partial least-squares discriminant analysis (PLS-DA). The PLS-DA analysis utilized a training set and verification set to classify samples within diet and treatment groups. PLS-DA could reliably differentiate the diet treatments for both cecal and distal colon samples. The PLS-DA analyses of the antibiotic and no antibiotic-treated subgroups were well classified for cecal samples and modestly separated for distal colon samples. PLS-DA analysis had limited success separating distal colon samples for rats given AOM from those not treated; the cecal samples from AOM had very poor classification. Mass spectrometry profiling coupled with PLS-DA can readily classify metabolite differences among rats given RS diets.

Inhibition of azoxymethane-induced preneoplastic lesions in the rat colon by a cooked stearic acid complexed high-amylose cornstarch.

This study evaluated a novel stearic acid complexed high-amylose cornstarch (SAC) for the prevention of preneoplastic lesions in the colon of azoxymethane (AOM)-treated Fisher 344 rats fed resistant starches at 50-55% of the diet for 8 weeks. Uncooked SAC (r-SAC) diet was compared with raw normal-cornstarch diet (r-CS) or raw high-amylose cornstarch diet (r-HA), and water-boiled CS (w-CS) was compared with w-HA and w-SAC, respectively. w-SAC markedly reduced mucin-depleted foci (MDF) numbers compared with w-HA or w-CS. r-HA significantly decreased aberrant crypt foci (ACF) numbers compared with r-CS or r-SAC. Increased cecum weight and decreased cecum pH were observed in the SAC or HA groups. The highest amounts of total or individual short-chain fatty acids (SCFAs) in cecum and of butyrate or propionate in feces were observed in the AOM-treated w-SAC group. This study revealed the effectiveness of a novel resistant starch in inhibiting colonic preneoplastic lesions and the importance of high-moisture cooking on the suppression of colon carcinogenesis by this resistant starch.