Effect of red wheat, aleurone, and testa layers on colon cancer biomarkers, nitrosative stress, and gut microbiome composition in rats.

We previously found greater reduction of colon cancer (CC) biomarkers for red wheat compared to white wheat regardless of refinement state. In the present study we examined whether the phenolic-rich aleurone and testa layers are drivers of chemoprevention by red wheat and their influence on gut microbiota composition using a 1,2-dimethylhydrazine-induced CC rat model. Rats were fed a low-fat diet (16% of energy as fat), high-fat diet (50% of energy as fat), or high-fat diet containing whole red wheat, refined red wheat, refined white wheat, or aleurone- or testa-enriched fractions for 12 weeks. Morphological markers (aberrant crypt foci, ACF) were assessed after methylene blue staining and biochemical markers (3-nitrotyrosine [3-NT], Dclk1) by immunohistochemical determination of staining positivity within aberrant crypts. Gut microbiota composition was evaluated from 16S rRNA gene sequencing of DNA extracted from cecal contents. Relative to the high-fat diet, the whole and refined red wheat, refined white wheat, and testa-enriched fraction decreased ACF, while only the refined red wheat and aleurone-enriched fraction decreased 3-NT. No significant differences were observed for Dclk1. An increase in microbial diversity was observed for the aleurone-enriched fraction (ACE index) and whole red wheat (Inverse Simpson Index). The diet groups significantly modified overall microbiome composition, including altered abundances of Lactobacillus, Mucispirillum, Phascolarctobacterium, and Blautia coccoides. These results suggest that red wheat may reduce CC risk through modifications to the gut microbiota and nitrosative stress, which may be due, in part, to the influence of dietary fiber and the phenolic-rich aleurone layer.

Evaluation of Feeding Beta-Hydroxy-Beta-Methylbutyrate (HMB) to Mouse Dams during Gestation on Birth Weight and Growth Variation of Offspring.

This study was designed to determine if feeding ß-hydroxy-ß-methylbutyrate (HMB) to pregnant mice would improve birth weight uniformity and growth performance of offspring. Dams (Agouti Avy) were assigned to one of four treatments: control (CON; n = 13), low-level HMB (LL; 3.5 mg/g; n = 14), high-level HMB (HL; 35 mg/g; n = 15), and low-level pulse dose fed from gestational days 6 to 10 (PUL; 3.5 mg/g; n = 14). Randomly selected dams (n = 27) were euthanized on gestational day 18 to collect placentae and pup weights. The remaining dams gave birth and lactated for 28 days. Dams only received HMB during gestation. Dietary HMB did not influence the performance of dams. Dietary treatment during gestation did not affect litter size or birth weight of pups. Variation was not different among treatments in terms of birth weight of offspring. Placental weights were not affected by treatments. Overall, growth performance of offspring after weaning was similar among all treatments. Body composition of offspring at 5 and 8 weeks of age was similar regardless of HMB treatment during gestation. In conclusion, dietary HMB supplementation in pregnant mice did not affect birth weight, variations in birth weight, or growth performance of offspring.

Simple Nutrient-Based Rules vs. a Nutritionally Rich Plant-Centered Diet in Prediction of Future Coronary Heart Disease and Stroke: Prospective Observational Study in the US.

To better understand nutrition paradigm shift from nutrients to foods and dietary patterns, we compared associations of a nutrient-based blood cholesterol-lowering diet vs. a food-based plant-centered diet with risk of coronary heart disease (CHD) and stroke. Participants were 4701 adults aged 18-30 years and free of cardiovascular disease at baseline, followed for clinical events from 1985 and 86 to 2018. A plant-centered diet was represented by higher A Priori Diet Quality Score (APDQS). A blood cholesterol-lowering diet was represented by lower Keys Score. Proportional hazards regression was used to calculate hazard ratios (HR). Higher APDQS showed a nutrient-dense composition that is low in saturated fat but high in fiber, vitamins and minerals. Keys Score and APDQS changes were each inversely associated with concurrent plasma low-density lipoprotein cholesterol (LDL-C) change. Over follow-up, 116 CHD and 80 stroke events occurred. LDL-C predicted CHD, but not stroke. APDQS, but not Keys Score, predicted lower risk of CHD and of stroke. Adjusted HRs (95% CIs) for each 1-SD higher APDQS were 0.73 (0.55-0.96) for CHD and 0.70 (0.50-0.99) for stroke. Neither low dietary fat nor low dietary carbohydrate predicted these events. Our findings support the ongoing shift in diet messages for cardiovascular prevention.

Plant-Centered Diet and Risk of Incident Cardiovascular Disease During Young to Middle Adulthood.

Background The association between diets that focus on plant foods and restrict animal products and cardiovascular disease (CVD) is inconclusive. We investigated whether cumulative intake of a plant-centered diet and shifting toward such a diet are associated with incident CVD. Methods and Results Participants were 4946 adults in the CARDIA (Coronary Artery Risk Development in Young Adults) prospective study. They were initially 18 to 30 years old and free of CVD (1985-1986, exam year [year 0]) and followed until 2018. Diet was assessed by an interviewer-administered, validated diet history. Plant-centered diet quality was assessed using the A Priori Diet Quality Score (APDQS), in which higher scores indicate higher consumption of nutritionally rich plant foods and limited consumption of high-fat meat products and less healthy plant foods. Proportional hazards models estimated hazard ratios of CVD associated with both time-varying average APDQS and a 13-year change in APDQS score (difference between the year 7 and year 20 assessments). During the 32-year follow-up, 289 incident CVD cases were identified. Both long-term consumption and a change toward such a diet were associated with a lower risk of CVD. Multivariable-adjusted hazard ratio was 0.48 (95% CI, 0.28-0.81) when comparing the highest quintile of the time-varying average ADPQS with lowest quintiles. The 13-year change in APDQS was associated with a lower subsequent risk of CVD, with a hazard ratio of 0.39 (95% CI, 0.19-0.81) comparing the extreme quintiles. Similarly, strong inverse associations were found for coronary heart disease and hypertension-related CVD with either the time-varying average or change APDQS. Conclusions Consumption of a plant-centered, high-quality diet starting in young adulthood is associated with a lower risk of CVD by middle age.

A Plant-Centered Diet and Markers of Early Chronic Kidney Disease during Young to Middle Adulthood: Findings from the Coronary Artery Risk Development in Young Adults (CARDIA) Cohort.

BACKGROUND: Few studies have evaluated whether plant-centered diets prevent progression of early stage chronic kidney disease (CKD). OBJECTIVES: We examined the association between plant-centered diet quality and early CKD markers. METHODS: We prospectively examined 2869 black and white men and women in the Coronary Artery Risk Development in Young Adults Study free of diagnosed kidney failure in 2005-2006 [examination year 20 (Y20); mean age: 45.3 ± 3.6  y]. CKD marker changes from Y20 to 2015-2016 (Y30) were considered, including estimated glomerular filtration rate (eGFR; serum creatinine), urinary albumin-to-creatinine ratio (ACR), and both. Diet was assessed through interviewer-administered diet histories at Y0, Y7, and Y20, and plant-centered diet quality was quantified with the A Priori Diet Quality Score (APDQS). Linear regression models were used to examine the association of APDQS and subsequent 10-y changes in CKD markers. RESULTS: After adjustment for sociodemographic, behavioral, and diet factors, we found that higher APDQS was related to less adverse changes in CKD markers in the subsequent 10-y period. Compared with the lowest APDQS quintile, the highest quintile was associated with an attenuated increase in lnACR (-0.25 mg/g; 95% CI: -0.37, -0.13 mg/g; P-trend < 0.001), whereas the highest quintile was associated with an attenuated decrease in eGFR (4.45 mL·min-1·1.73 m-2; 95% CI: 2.46, 6.43 mL·min-1·1.73 m-2). There was a 0.50 lower increase in combined CKD markers [ln(ACR) z score - eGFR z score] when comparing the extreme quintiles. Associations remained similar after further adjustment for hypertension, diabetes, and obesity as potential mediating factors. The attenuated worsening CKD marker changes associated with higher APDQS strengthened across increasing initial CKD category; those with the best diet and microalbuminuria in Y10-Y20 returned to high normal albuminuria (all P-interaction < 0.001). CONCLUSIONS: Individuals who consumed plant-centered, high-quality diets were less likely to experience deterioration of kidney function through midlife, especially among participants with initial stage characterized as mild CKD.

Polylactose Exhibits Prebiotic Activity and Reduces Adiposity and Nonalcoholic Fatty Liver Disease in Rats Fed a High-Fat Diet.

BACKGROUND: Prebiotic dietary fibers change the intestinal microbiome favorably and provide a health benefit to the host. OBJECTIVES: Polylactose is a novel fiber, synthesized by extrusion of lactose. We evaluated its prebiotic activity by determining its fermentability, effect on the microbiota, and effects on adiposity and liver lipids in a diet-induced obesity animal model. METHODS: Male Wistar rats (4-5 wk old) were fed normal-fat (NF, 25% fat energy) or high-fat (HF, 51% fat energy) diets containing different fibers (6% fiber of interest and 3% cellulose, by weight), including cellulose (NFC and HFC, negative and positive controls, respectively), polylactose (HFPL), lactose matched to residual lactose in the HFPL diet, and 2 established prebiotic fibers: polydextrose (HFPD) and fructooligosaccharide (HFFOS). After 10 wk of feeding, organs were harvested and cecal contents collected. RESULTS: HFPL animals had greater cecum weight (3 times greater than HFC) and lower cecal pH (∼1 pH unit lower than HFC) than all other groups, suggesting that polylactose is more fermentable than other prebiotic fibers (HFPD, HFFOS; P < 0.05). HFPL animals also had increased taxonomic abundance of the probiotic species Bifidobacterium in the cecum relative to all other groups (P < 0.05). Epididymal fat pad weight was significantly decreased in the HFPL group (29% decrease compared with HFC) compared with all other HF groups (P < 0.05) and did not differ from the NFC group. Liver lipids and cholesterol were reduced in HFPL animals when compared with HFC animals (P < 0.05). CONCLUSIONS: Polylactose is a fermentable fiber that elicits a beneficial change in the gut microbiota as well as reducing adiposity in rats fed HF diets. These effects of polylactose were greater than those of 2 established prebiotics, fructooligosaccharide and polydextrose, suggesting that polylactose is a potent prebiotic.

A Shift Toward a Plant-Centered Diet From Young to Middle Adulthood and Subsequent Risk of Type 2 Diabetes and Weight Gain: The Coronary Artery Risk Development in Young Adults (CARDIA) Study.

OBJECTIVE: To examine the associations between change in plant-centered diet quality and type 2 diabetes risk and change in body size. RESEARCH DESIGN AND METHODS: A prospective study conducted in the U.S. enrolled adults ages 18-30 years in 1985-1986 (examination year [Y0]) and followed them through 2015-2016. We analyzed the associations between change in plant-centered diet quality over 20 years (Y0-Y20) and diabetes (Y20-30; n = 2,534) and change (Y0-Y20 and Y20-30) in BMI, waist circumference (WC), and weight (n > 2,434). Plant-centered diet quality was measured using the A Priori Diet Quality Score (APDQS); a higher score favors nutritionally rich plant foods. Cox regression models were used to assess diabetes risk, and linear regression models were used to examine change in body size. RESULTS: During a mean follow-up of 9.3 (± 1.7) years, 206 case subjects with incident diabetes were observed. In multivariable analysis, participants with the largest increase in APDQS over 20 years had a 48% (95% CI 0.31-0.85; P trend < 0.001) lower risk of diabetes over the subsequent 10 years compared with participants whose score remained stable. Each 1-SD increment in APDQS over 20 years was associated with lower gains in BMI (-0.39 kg/m2; SE 0.14; P = 0.004), WC (-0.90 cm; SE 0.27; P < 0.001) and weight (-1.14 kg; SE 0.33; P < 0.001) during the same period, but not with subsequent changes. CONCLUSIONS: Young adults who increased plant-centered diet quality had a lower diabetes risk and gained less weight by middle adulthood.

Colon Cancer Risk of a Westernized Diet Is Reduced in Mice by Feeding Cruciferous or Apiaceous Vegetables at a Lower Dose of Carcinogen but Not a Higher Dose.

Western-style diets (WD) are associated with greater risk of colon cancer. Exposure to 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), a food-borne carcinogen, is linked to increased colon cancer risk. In contrast, intake of apiaceous and cruciferous vegetables (APIs and CRUs) is associated with reduced risk. Here we evaluated effects of a WD alone or a WD containing API or CRU, relative to a purified diet (basal), on colon cancer risk in mice. All diets were fed at one of two concentrations of PhIP (100 or 400 ppm). The activity of the hepatic PhIP-activating enzyme, cytochrome P450 (CYP) 1A2, was examined at week 4 and colonic precancerous lesions (aberrant crypt foci, ACF) were enumerated at week 12. In low PhIP-fed groups, CYP1A2 activity was greater for CRU than all other groups, which did not differ from one another. WD had a significantly greater effect on the formation of ACF than the basal diet. In groups fed API or CRU, the ACF number was reduced to the level observed in the basal diet-fed group. In high PhIP-fed groups, all WD-based diets had greater CYP1A2 activity than the basal diet-fed group. Surprisingly, the basal diet group had more ACF than the WD group, and API and CRU groups did not differ from the WD alone group. Thus, at the lower dose of PhIP, the WD increased colon cancer risk in mice, compared to a purified diet, and APIs and CRUs reduced the risk of the WD. However, at the higher dose of PhIP, the enhancement of colon cancer risk by the WD was not evident, nor was the chemopreventive effect of these vegetables.

Apiaceous and Cruciferous Vegetables Fed During the Post-Initiation Stage Reduce Colon Cancer Risk Markers in Rats.

BACKGROUND: Vegetable consumption reduces colon cancer risk when fed in the initiation stage of carcinogenesis; however, the effect of vegetable consumption during the post-initiation stage has rarely been examined. OBJECTIVE: We investigated the chemopreventive effects of feeding apiaceous and cruciferous vegetables on colon cancer risk in the post-initiation stage. METHODS: Thirty male Wistar rats (∼5 wk, 92 g) were subcutaneously injected with 1,2-dimethylhydrazine 1 time/wk for 2 wk. One week after the last dose, rats were randomly assigned to 3 groups: the basal diet, an apiaceous vegetable-containing diet (API; 21% fresh wt/wt), or a cruciferous vegetable-containing diet (CRU; 21% fresh wt/wt). All diets contained ∼20% protein, 7% fat, and 63% digestible carbohydrate. Experimental diets were fed for 10 wk, after which colons were harvested. RESULTS: CRU reduced aberrant crypt foci (ACF) number compared to the basal group (P = 0.014) and API (P = 0.013), whereas API decreased the proportion of dysplastic ACF relative to the basal group (P < 0.05). Both CRU and API reduced doublecortin-like kinase 1-positive marker expression relative to basal by 57.9% (P = 0.009) and 51.4% (P < 0.02). The numbers of CD44-positive ACF did not differ between the groups. We identified 14 differentially expressed microRNAs (miRNAs). Of these, expression of 6 miRNAs were greater or tended to be greater (P ≤ 0.10) in one or both vegetable-containing groups compared to the basal group. Bioinformatic analysis of these expression changes in miRNA predicted a change in WNT/ß-catenin signaling, indicating downregulation of ß-catenin in the vegetable-fed groups. Consistent with this bioinformatics analysis, ß-catenin-accumulated ACF were decreased in CRU (93.1%, P = 0.012), but not in API (54.4%, P = 0.125), compared to the basal group. CONCLUSION: Both apiaceous and cruciferous vegetables, fed post-initiation, reduce colonic preneoplastic lesions as well as cancer stem cell marker expression in rats, possibly by suppressing oncogenic signaling through changes in miRNA expression.

Antioxidant capacity and phytochemical content of 16 sources of corn distillers dried grains with solubles (DDGS).

Corn distillers dried grains with solubles (DDGS) is a co-product of the fuel ethanol industry that is an excellent source of energy, digestible amino acids, and digestible phosphorus. However, the antioxidant capacity and phytochemical content of DDGS and how it is influenced by production parameters is unknown. Therefore, 16 DDGS samples obtained from different ethanol production plants in the U.S. were characterized for antioxidant capacity, vitamin E, xanthophylls, and ferulic acid content and compared with corn. The antioxidant capacity of DDGS samples, measured using the 2,2-diphenyl-l-picrylhydrazyl (DPPH) assay, varied almost 2 folds among samples, but in all cases was more than 3 times that of corn. All DDGS samples had a considerably greater concentration of tocopherols and tocotrienols (lipid-soluble antioxidants) than corn. However, the relative concentrations among the tocopherols and tocotrienols tended to be similar to corn. The xanthophyll lutein was present in all DDGS samples and in all cases exceeded the content in corn. Zeaxanthin was detected in most samples. The total ferulic acid content of the DDGS samples was almost 3-fold greater than corn, but, as in corn, almost all was present in a bound form. However, the concentration of unbound (free) ferulic acid was more than 3 times the concentration found in the corn sample. Thus, DDGS is a rich source of phytochemical compounds and may provide antioxidant and health benefits beyond its macronutrient composition. However, differences in processing can greatly influence the phytochemical content and quality of DDGS. In particular, thermal abuse due to excessive heat used in drying may lead to lipid oxidation products that may have deleterious effects when incorporated into feeds.

Apiaceous Vegetables and Cruciferous Phytochemicals Reduced PhIP-DNA Adducts in Prostate but Not in Pancreas of Wistar Rats.

We previously showed rats fed with apiaceous vegetables, but not with their putative chemopreventive phytochemicals, reduced colonic DNA adducts formed by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a dietary procarcinogen. We report here the effects of feeding apiaceous and cruciferous vegetables versus their purified predominant phytochemicals, either alone or combined, on prostate and pancreatic PhIP-DNA adduct formation. In experiment I, male Wistar rats received three supplemented diets: CRU (cruciferous vegetables), API (apiaceous vegetables), and CRU+API (both types of vegetables). In experiment II, rats received three diets supplemented with phytochemicals matched to their levels in the vegetables from experiment I: P + I (phenethyl isothiocyanate and indole-3-carbinol), FC (furanocoumarins; 5-methoxypsoralen, 8-methoxypsoralen, and isopimpinellin), and COMBO (P + I and FC combined). After 6 days of feeding, PhIP was injected (10 mg/kg body weight) and animals were killed on day 7. PhIP-DNA adducts were analyzed by LC-MS/MS. In prostate, PhIP-DNA adducts were reduced by API (33%, P < .05), P + I (45%, P < .001), and COMBO (30%, P < .01). There were no effects observed in pancreas. Our results suggest that fresh vegetables and purified phytochemicals lower PhIP-DNA adducts and may influence cancer risk.

Comparison of short- and long-term exposure effects of cruciferous and apiaceous vegetables on carcinogen metabolizing enzymes in Wistar rats.

Cruciferous and apiaceous vegetables may be chemopreventive due to their ability to modulate carcinogen-metabolizing enzymes but whether the effects on such enzymes are sustained over time is unknown. To examine the short- and long-term effects of the vegetables, rats were fed one of four diets for 7, 30, or 60 d: AIN-93G, CRU (21% cruciferous vegetables-fresh broccoli, green cabbage, watercress), API (9% apiaceous vegetables - fresh parsnips, celery), or API + CRU (10.5% CRU + 4.5% API). Although CRU increased activity and protein expression of cytochrome P450 (CYP) 1A1 and CYP1A2 after 7 d, only activity was sustained after 30 and 60 d. There was a trend towards an interaction between the length of feeding period and CRU for CYP1A1 activity; activity increased with greater time of feeding. API increased CYP1A2 activity but decreased sulfotransferase 1A1 activity after 7 d, although not at later times. Altogether, increased CYP1A activity by CRU was maintained with long term feeding while protein amount decreased, suggesting influence by mechanisms other than, or in addition to, transcriptional regulation. Thus, response patterns and interactions with length of feeding may differ, depending upon the types of vegetables and enzymes, requiring caution when interpreting the results of short-term feeding studies.

Phenethyl isothiocyanate and indole-3-carbinol from cruciferous vegetables, but not furanocoumarins from apiaceous vegetables, reduced PhIP-induced DNA adducts in Wistar rats.

SCOPE: We previously showed that apiaceous but not cruciferous vegetables reduced DNA adducts formed by 2-amino-1-methyl-6-phenylimidazo[4, 5-b]pyridine (PhIP) in rats. Here, we report the effects of the putative chemopreventive phytochemicals from these vegetables on PhIP metabolism and DNA adduct formation. METHODS AND RESULTS: Rats received three supplemented diets: P + I (phenethyl isothiocyanate and indole-3-carbinol), furanocoumarins (FC, 5-methoxypsoralen, 8-methoxypsoralen, and isopimpinellin), and combination (P + I and FC). Phytochemical supplementation matched the levels in vegetables fed in our previous study. After 6 days, rats were injected with PhIP (10 mg/kg body wt) and killed after 24-h urine collection. Compared to the control, P + I increased activity of hepatic cytochrome P450 (CYP) 1A1 (10.1-fold), CYP1A2 (3.62-fold), and sulfotransferase 1A1 (2.70-fold). The combination diet also increased CYP1A1 and CYP1A2 activity. Urinary metabolomics revealed that PhIP metabolite profiles generally agreed with biotransformation enzyme activities. P + I and combination diets reduced PhIP-DNA adducts by 43.5 and 24.1%, respectively, whereas FC had no effect on adducts, compared to the control diet. CONCLUSION: Effects of phytochemicals on metabolic outcomes and markers of carcinogenesis might differ from fresh vegetables, thus limiting the inferences that one can draw from the effects of purified phytochemicals on the health benefits of the vegetables from which they derive.

Comparative DNA adduct formation and induction of colonic aberrant crypt foci in mice exposed to 2-amino-9H-pyrido[2,3-b]indole, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, and azoxymethane.

Considerable evidence suggests that environmental factors, including diet and cigarette smoke, are involved in the pathogenesis of colon cancer. Carcinogenic nitroso compounds (NOC), such as N-nitrosodimethylamine (NDMA), are present in tobacco and processed red meat, and NOC have been implicated in colon cancer. Azoxymethane (AOM), commonly used for experimental colon carcinogenesis, is an isomer of NDMA, and it produces the same DNA adducts as does NDMA. Heterocyclic aromatic amines (HAAs) formed during the combustion of tobacco and high-temperature cooking of meats are also associated with an elevated risk of colon cancer. The most abundant carcinogenic HAA formed in tobacco smoke is 2-amino-9H-pyrido[2,3-b]indole (AαC), whereas 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) is the most potent carcinogenic HAA formed during the cooking of meat and fish. However, the comparative tumor-initiating potential of AαC, MeIQ, and AOM is unknown. In this report, we evaluate the formation of DNA adducts as a measure of genotoxicity, and the induction of colonic aberrant crypt foci (ACF) and dysplastic ACF, as an early measure of carcinogenic potency of these compounds in the colon of male A/J mice. Both AαC and AOM induced a greater number of DNA adducts than MeIQ in the liver and colon. AOM induced a greater number of ACF and dysplastic ACF than either AαC or MeIQ. Conversely, based on adduct levels, MeIQ-DNA adducts were more potent than AαC- and AOM-DNA adducts at inducing ACF. Long-term feeding studies are required to relate levels of DNA adducts, induction of ACF, and colon cancer by these colon genotoxicants.

Wheat Type (Class) Influences Development and Regression of Colon Cancer Risk Markers in Rats.

We previously found red wheat more effective than white wheat in reducing colon cancer risk in rats when fed during initiation and postinitiation stages. Here we examine the effect of wheat on colon cancer risk in early and late postinitiation stages in carcinogen-treated rats. Four groups were fed a basal diet, 1 group a red wheat diet, and 1 group a white wheat diet. After 6 wk, 1 basal, the red and white groups were killed (early postinitiation stage). Of the remaining basal groups, 1 continued on the basal diet, 1 was switched to red and another to white wheat for 8 more wk (late postinitiation stage). Red and white wheat significantly reduced morphological [aberrant crypt foci (ACF)] and biochemical (ß-catenin accumulated crypts) markers in both early and late postinitiation stages. Both wheat diets reduced dysplasia markers (sialomucin-expressing ACF and mucin depleted foci), compared to the basal diet, during the late postinitiation stage, but red wheat more so. Only red wheat significantly reduced the number of metallothionein-positive crypts, a stem cell mutation marker, in both stages. Overall, red wheat flour reduced risk markers more than white wheat flour, and this was more pronounced in the late post-initiation stage.

Apiaceous vegetable consumption decreases PhIP-induced DNA adducts and increases methylated PhIP metabolites in the urine metabolome in rats.

BACKGROUND: Heterocyclic aromatic amines, such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), are carcinogenic compounds produced during heating of protein-containing foods. Apiaceous vegetables inhibit PhIP-activating enzymes, whereas cruciferous vegetables induce both PhIP-activating and -detoxifying enzymes. OBJECTIVE: We investigated the effects of these vegetables, either alone or combined, on PhIP metabolism and colonic DNA adduct formation in rats. METHODS: Male Wistar rats were fed cruciferous vegetables (21%, wt:wt), apiaceous vegetables (21%, wt:wt), or a combination of both vegetables (10.5% wt:wt of each). Negative and positive control groups were fed an AIN-93G diet. After 6 d, all groups received an intraperitoneal injection of PhIP (10 mg · kg body weight(-1)) except for the negative control group, which received only vehicle. Urine was collected for 24 h after the injection for LC-tandem mass spectrometry metabolomic analyses. On day 7, rats were killed and tissues processed. RESULTS: Compared with the positive control, cruciferous vegetables increased the activity of hepatic PhIP-activating enzymes [39.5% and 45.1% for cytochrome P450 (CYP) 1A1 (P = 0.0006) and CYP1A2 (P < 0.0001), respectively] and of uridine 5'-diphospho-glucuronosyltransferase 1A (PhIP-detoxifying) by 24.5% (P = 0.0267). Apiaceous vegetables did not inhibit PhIP-activating enzymes, yet reduced colonic PhIP-DNA adducts by 20.4% (P = 0.0496). Metabolomic analyses indicated that apiaceous vegetables increased the relative abundance of urinary methylated PhIP metabolites. The sum of these methylated metabolites inversely correlated with colonic PhIP-DNA adducts (r = -0.43, P = 0.01). We detected a novel methylated urinary PhIP metabolite and demonstrated that methylated metabolites are produced in the human liver S9 fraction. CONCLUSIONS: Apiaceous vegetables did not inhibit the activity of PhIP-activating enzymes in rats, suggesting that the reduction in PhIP-DNA adducts may involve other pathways. Further investigation of the importance of PhIP methylation in carcinogen metabolism is warranted, given the inverse correlation of methylated PhIP metabolites with a biomarker of carcinogenesis and the detection of a novel methylated PhIP metabolite.

High-viscosity dietary fibers reduce adiposity and decrease hepatic steatosis in rats fed a high-fat diet.

Viscous dietary fiber consumption lowers the postprandial glucose curve and may decrease obesity and associated comorbidities such as insulin resistance and fatty liver. We determined the effect of 2 viscous fibers, one fermentable and one not, on the development of adiposity, fatty liver, and metabolic flexibility in a model of diet-induced obesity. Rats were fed a normal-fat (NF) diet (26% energy from fat), a high-fat diet (60% energy from fat), each containing 5% fiber as cellulose (CL; nonviscous and nonfermentable), or 5% of 1 of 2 highly viscous fibers-hydroxypropyl methylcellulose (HPMC; nonfermentable) or guar gum (GG; fermentable). After 10 wk, fat mass percentage in the NF (18.0%; P = 0.03) and GG groups (17.0%; P < 0.01) was lower than the CL group (20.7%). The epididymal fat pad weight of the NF (3.9 g; P = 0.04), HPMC (3.9 g; P = 0.03), and GG groups (3.6 g; P < 0.01) was also lower than the CL group (5.0 g). The HPMC (0.11 g/g liver) and GG (0.092 g/g liver) groups had lower liver lipid concentrations compared with the CL group (0.14 g/g liver). Fat mass percentage, epididymal fat pad weight, and liver lipid concentration were not different among the NF, HPMC, and GG groups. The respiratory quotient was higher during the transition from the diet-deprived to fed state in the GG group (P = 0.002) and tended to be higher in the HPMC group (P = 0.06) compared with the CL group, suggesting a quicker shift from fatty acid (FA) to carbohydrate oxidation. The HPMC group [15.1 nmol/(mg ⋅ h)] had higher ex vivo palmitate oxidation in muscle compared with the GG [11.7 nmol/(mg ⋅ h); P = 0.04] and CL groups [10.8 nmol/(mg ⋅ h); P < 0.01], implying a higher capacity to oxidize FAs. Viscous fibers can reduce the adiposity and hepatic steatosis that accompany a high-fat diet, and increase metabolic flexibility, regardless of fermentability.

Wheat color (class), not refining, influences colon cancer risk in rats.

Epidemiological studies suggest whole grain consumption is associated with decreased colon cancer risk. However, wheat classes differ in their usage, making the influence of wheat class (red vs. white) and state of refinement (whole vs. refined) difficult to separate, leading to potential confounding. Consequently, we examined the effect of wheat class and refining on colonic precancerous lesions (aberrant crypt foci; ACF) in carcinogen-treated rats. Diets contained wheat flour as whole soft white, refined soft white, whole hard red, or refined hard red. Feeding was begun 10 days prior to carcinogen treatment and continued for 9 wk. Hard red-fed groups had significantly fewer ACF than soft white-fed groups (25-32% reduction, P = 0.013). However, state of refinement had no significant effect on ACF number. Cecal contents supernatant oxygen radical absorbance capacity and fecal bile acid concentration were significantly greater in whole wheat-fed groups than refined wheat-fed groups and did not correlate with ACF number (increase of 21-22%, P < 0.001 and 55-56%, P < 0.001, respectively). Consequently, wheat class, not state of refinement, appears to influence colon cancer risk, with hard red wheat protective relative to soft white wheat. Thus, epidemiological associations of reduced colon cancer risk with whole grain consumption may actually reflect different wheat classes.

Malonylglucoside conjugates of isoflavones are much less bioavailable compared with unconjugated ß-glucosidic forms in rats.

Despite considerable interest in the physiologic effects of isoflavones, the in vivo bioavailability of the most common isoflavone forms, malonylglucoside conjugates, has not been determined. Differences in the bioavailability of malonylglucosides compared with the nonconjugated ß-glucoside forms may explain the inconsistent findings regarding the physiologic effects of isoflavones. Therefore, our objective was to determine the effect of malonyl- conjugation on isoflavone bioavailability in an animal model. Malonylgenistin and malonyldaidzin, and their corresponding nonconjugated glucosides, were extracted from soy grits and purified using liquid chromatography. Purity of the isolated forms was confirmed by nuclear magnetic resonance analysis. Male rats were gavaged with malonylgenistin, genistin, malonyldaidzin, or daidzin at a dose of 100 µmol/kg body weight. Blood and urine samples were collected at time intervals ranging from 0 to 48 h. Isoflavone metabolites in plasma and urine were determined using stable isotope dilution-liquid chromatography/mass spectrometry. Comparisons of pharmacokinetic variables were made between nonconjugated and conjugated glucosides and over time of plasma collection. The areas under the time-concentration curve of the metabolites in the plasma obtained after the administration of nonconjugated ß-glucosides were 1 to 6 times higher than those of their respective malonylglucosides (P ≤ 0.05). Additionally, maximum plasma concentration and urinary excretion of isoflavone metabolites were significantly higher (1-9 times; P ≤ 0.05) after the administration of nonconjugated ß-glucosides. To our knowledge, these results demonstrated, for the first time, that nonconjugated ß-glucosides are relatively more bioavailable than their respective malonylglucosides. These differences in the bioavailability of conjugated and nonconjugated ß-glucosides should be considered in future studies focused on the bioactivity of isoflavones.

The role of viscosity and fermentability of dietary fibers on satiety- and adiposity-related hormones in rats.

Dietary fiber may contribute to satiety. This study examined the effect of two dietary fiber characteristics, small intestinal contents viscosity and large intestinal fermentability, on satiety-and adiposity-related hormones in rats. Diets contained fiber sources that were non-viscous, somewhat viscous, or highly viscous, and either highly fermentable or non-fermentable, in a 2 × 3 factorial design. In the fed state (2 h postprandial), rats fed non-fermentable fibers had significantly greater plasma GLP-1 concentration than fermentable fibers. In the fasted state, among non-fermentable fibers, viscosity had no effect on GLP-1 concentration. However, among fermentable fibers, greater viscosity reduced GLP-1 concentration. Plasma peptide tyrosine tyrosine (PYY) concentrations in the fasted state were not influenced by the fermentability of the fiber overall, however animals consuming a fructooligosaccharide greater PYY concentration. In both the fed and fasted states, rats fed non-fermentable fibers had a significantly lower plasma ghrelin concentration than rats fed fermentable fibers. In the fasted state, rats fed non-fermentable fibers had a significantly lower plasma leptin concentration than rats fed fermentable fibers. Thus, fermentability and viscosity of dietary fiber interacted in complex ways to influence satiety- and adiposity-related plasma hormone concentrations. However, the results suggest that highly viscous, non-fermentable fibers may limit weight gain and reduce adiposity and non-fermentable fibers, regardless of viscosity, may promote meal termination.