Annelies Bunschoten

Meat consumption, cigarette smoking, and genetic susceptibility in the etiology of colorectal cancer: results from a Dutch prospective study

Objective: We evaluated the effect of meat consumption and cigarette smoking in combination with N-acetyltransferases 1 and 2 (NAT1 and NAT2), and glutathione S-transferase M1 (GSTM1) genotypes on colorectal cancer. Methods: From a Dutch prospective study, after 8.5 years of follow-up, data of 102 incident colorectal cancer cases and a random sample of 537 controls frequency-matched for gender and age were analyzed. Baseline information on dietary and smoking habits, as well as blood samples for DNA isolation and genotyping, were available. Results: Red meat intake increased colorectal cancer risk among men (OR 2.7; 95% CI 1.1–6.7 highest vs. lowest intake), whereas poultry and fish decreased risk among women (OR 0.5; 95% CI 0.2–1.07). Cigarette smoking for at least 16 years increased colorectal cancer risk among former smokers only (OR 2.7; 95% CI 1.0–7.4), compared to those having smoked for 15 years or less. NAT1 and NAT2 polymorphisms did not significantly modify these associations. High consumption of poultry and fish was inversely associated with colorectal cancer only in the presence of GSTM1. Conclusions: In this study meat consumption and former long-term smoking were associated with colorectal cancer. Associations of colorectal cancer with different types of meat were modified by gender and GSTM1 genotype.

Risk of colorectal adenomas in relation to meat consumption, meat preparation, and genetic susceptibility in a Dutch population.

AbstractObjective: We studied the association between meat consumption and colorectal adenomas, and potential influence of genetic susceptibility to heterocyclic aromatic amines (HCAs) formed during meat cooking at high temperatures. Methods: We studied HCA concentration in relation to preparation habits among 63 volunteers. Associations of meat consumption, meat preparation habits, and genetic susceptibility with colorectal adenoma risk were investigated among 431 adenoma cases and 433 polyp-free controls recruited at endoscopy. Participants completed a meat consumption and preparation questionnaire and provided blood for DNA isolation. Polymorphisms of N-acetyltransferases (NAT) 1 and 2, sulfotransferase (SULT) 1A1, and glutathione-S-transferases (GST) M1 and T1 were determined. Results: HCAs were present in habitually prepared meat, although meat consumption (7 versus5x/week) did not increase the risk of colorectal adenomas (odds ratio (OR) 1.2, 95% confidence interval (CI) 0.8–1.9). Also, presumed unfavorable preparation habits (e.g., use of lid, preference for darkly browned meat) did not increase adenoma risk (OR 0.8 and 0.9, respectively). Only the combination of NAT2 slow acetylation and frequent meat consumption (>5x/week) slightly increased adenoma risk (OR 1.6, 95% CI 1.1–2.3). Conclusions: In this Dutch population, unfavorable meat consumption and preparation habits did not increase colorectal adenoma risk, and these associations were not influenced by relevant genetic polymorphisms.

Effect of SULT1A1 and NAT2 genetic polymorphism on the association between cigarette smoking and colorectal adenomas

Cigarette smoke contains polycyclic hydrocarbons and arylamines that may both be activated by sulfotransferase, encoded by SULT1A1. A genetic polymorphism leads to an Arg213His substitution, thereby decreasing enzyme activity and stability and might thus modify the association between smoking and colorectal adenomas. We investigated this in a Dutch case‐control study. Additionally, we evaluated potential roles of epoxide hydrolase (EPHX), N‐acetyltransferases (NAT1 and NAT2) and glutathione S‐transferases (GSTM1 and GSTT1). The data analysis included 431 adenoma cases and 432 polyp‐free controls (54% women; mean age, 54.6 years) enrolled at endoscopy in 8 Dutch hospitals between 1997 and 2000. All participants provided data on smoking habits and blood for DNA isolation. Genotyping was performed using appropriate polymerase chain reaction‐restriction fragment length polymorphism procedures. Multivariate models included age, sex, endoscopy indication, consumption of snacks and alcohol and, if appropriate, daily smoking dose or smoking duration. Smoking increased colorectal adenoma risk, most importantly by duration. Smoking for more than 25 years more than doubled adenoma risk (OR = 2.4, 95% CI = 1.4–4.1) compared to never smoking. Combinations of SULT1A1 fast sulfation (*1/*1) and of NAT2 slow acetylation with smoking resulted in a 4 times higher risk of adenomas compared to never smokers with other inherited gene variants, although there was no statistically significant effect modification. We found no clear effects of the other genetic polymorphisms on the association between smoking and adenomas. We conclude that smoking increases risk of colorectal adenomas and that SULT1A1 and NAT2 only modestly modify this association.

Quercetin induces hepatic lipid omega-oxidation and lowers serum lipid levels in mice.

Elevated circulating lipid levels are known risk factors for cardiovascular diseases (CVD). In order to examine the effects of quercetin on lipid metabolism, mice received a mild-high-fat diet without (control) or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Gas chromatography and 1H nuclear magnetic resonance were used to quantitatively measure serum lipid profiles. Whole genome microarray analysis of liver tissue was used to identify possible mechanisms underlying altered circulating lipid levels. Body weight, energy intake and hepatic lipid accumulation did not differ significantly between the quercetin and the control group. In serum of quercetin-fed mice, triglycerides (TG) were decreased with 14% (p<0.001) and total poly unsaturated fatty acids (PUFA) were increased with 13% (p<0.01). Palmitic acid, oleic acid, and linoleic acid were all decreased by 9–15% (p<0.05) in quercetin-fed mice. Both palmitic acid and oleic acid can be oxidized by omega (ω)-oxidation. Gene expression profiling showed that quercetin increased hepatic lipid metabolism, especially ω-oxidation. At the gene level, this was reflected by the up-regulation of cytochrome P450 (Cyp) 4a10, Cyp4a14, Cyp4a31 and Acyl-CoA thioesterase 3 (Acot3). Two relevant regulators, cytochrome P450 oxidoreductase (Por, rate limiting for cytochrome P450s) and the transcription factor constitutive androstane receptor (Car; official symbol Nr1i3) were also up-regulated in the quercetin-fed mice. We conclude that quercetin intake increased hepatic lipid ω-oxidation and lowered corresponding circulating lipid levels, which may contribute to potential beneficial effects on CVD.

Induction of lipid oxidation by polyunsaturated fatty acids of marine origin in small intestine of mice fed a high-fat diet

BackgroundDietary polyunsaturated fatty acids (PUFA), in particular the long chain marine fatty acids docosahexaenoic (DHA) and eicosapentaenoic (EPA), are linked to many health benefits in humans and in animal models. Little is known of the molecular response to DHA and EPA of the small intestine, and the potential contribution of this organ to the beneficial effects of these fatty acids. Here, we assessed gene expression changes induced by DHA and EPA in the wildtype C57BL/6J murine small intestine using whole genome microarrays and functionally characterized the most prominent biological process.ResultsThe main biological process affected based on gene expression analysis was lipid metabolism. Fatty acid uptake, peroxisomal and mitochondrial beta-oxidation, and omega-oxidation of fatty acids were all increased. Quantitative real time PCR, and -in a second animal experiment- intestinal fatty acid oxidation measurements confirmed significant gene expression differences and showed in a dose-dependent manner significant changes at biological functional level. Furthermore, no major changes in the expression of lipid metabolism genes were observed in the colon.ConclusionWe show that marine n-3 fatty acids regulate small intestinal gene expression and increase fatty acid oxidation. Since this organ contributes significantly to whole organism energy use, this effect on the small intestine may well contribute to the beneficial physiological effects of marine PUFAs under conditions that will normally lead to development of obesity, insulin resistance and diabetes.

Preservation of Metabolic Flexibility in Skeletal Muscle by a Combined Use of n-3 PUFA and Rosiglitazone in Dietary Obese Mice

Insulin resistance, the key defect in type 2 diabetes (T2D), is associated with a low capacity to adapt fuel oxidation to fuel availability, i.e., metabolic inflexibility. This, in turn, contributes to a further damage of insulin signaling. Effectiveness of T2D treatment depends in large part on the improvement of insulin sensitivity and metabolic adaptability of the muscle, the main site of whole-body glucose utilization. We have shown previously in mice fed an obesogenic high-fat diet that a combined use of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and thiazolidinediones (TZDs), anti-diabetic drugs, preserved metabolic health and synergistically improved muscle insulin sensitivity. We investigated here whether n-3 LC-PUFA could elicit additive beneficial effects on metabolic flexibility when combined with a TZD drug rosiglitazone. Adult male C57BL/6N mice were fed an obesogenic corn oil–based high-fat diet (cHF) for 8 weeks, or randomly assigned to various interventions: cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids (cHF+F), cHF with 10 mg rosiglitazone/kg diet (cHF+ROSI), cHF+F+ROSI, or chow-fed. Indirect calorimetry demonstrated superior preservation of metabolic flexibility to carbohydrates in response to the combined intervention. Metabolomic and gene expression analyses in the muscle suggested distinct and complementary effects of the interventions, with n-3 LC-PUFA supporting complete oxidation of fatty acids in mitochondria and the combination with n-3 LC-PUFA and rosiglitazone augmenting insulin sensitivity by the modulation of branched-chain amino acid metabolism. These beneficial metabolic effects were associated with the activation of the switch between glycolytic and oxidative muscle fibers, especially in the cHF+F+ROSI mice. Our results further support the idea that the combined use of n-3 LC-PUFA and TZDs could improve the efficacy of the therapy of obese and diabetic patients.

Peanut butter intake, GSTM1 genotype and hepatocellular carcinoma: a case-control study in Sudan

AbstractObjective: Hepatocellular carcinoma (HCC) is one of the major cancers in the world. In Sudan the incidence is thought to be high and increasing. This study aims to assess the association between peanut butter intake, as a source of aflatoxins, and the GSTM1 genotype in the etiology of HCC. Method: A case–control study was conducted among 150 patients and 205 controls from two regions in Sudan. Food habits with special reference to peanut butter consumption, as well as peanut storage systems, have been investigated, as well as confounders such as hepatitis, drinking and smoking habits, and demographic characteristics. GSTM1 genotype was assessed in DNA extracted from blood samples (110 cases, 189 controls). Results: A positive association was observed for highest vs. lowest quartile of peanut butter intake, humid storage system and HCC, with ORs (95% CI) being 3.0 (1.6–5.5) and 1.6 (1.1–2.5) respectively. The positive association with peanut butter intake was essentially limited to subjects with GSTM1 null genotype with OR for highest vs. lowest quartile 16.7 (2.7–105). Conclusion: Peanut butter consumption has been identified as a strong risk factor of HCC in a region with endemic aflatoxin contamination in Sudan and was essentially limited to subjects with the GSTM1 null genotype.

Effects of a high-fat, low- versus high-glycemic index diet: retardation of insulin resistance involves adipose tissue modulation

Beneficial effects of low glycemic index (GI) diets in rodents have been studied using healthy low‐fat diets, while the effects might be different on high‐fat diets inducing progression of insulin resistance. We fed C57BL/6J male mice high‐fat low/ high‐GI (LGI/HGI) diets for 13 wk. Glucose and insulin tolerance and serum substrates, including adipokines, were measured longitudinally. The LGI group showed a significantly higher glucose tolerance from wk 2 onwards, which was supported by lower serum insulin and free fatty acids levels at 8 wk, and a tendency for lower leptin levels, while resistin levels remained similar. At 11 wk, when differences in serum resistin started to increase, differences in serum insulin were diminished. Although food intake was similar throughout the study, body weights and epididymal adipose tissue mass became significantly lower in the LGI group at necropsy. Several serum substrates and adipose tissue leptin mRNA levels, as analyzed by Q‐PCR, were, again, significantly lower, whereas adiponectin mRNA levels were higher. Taken together, an LGI high‐fat diet maintains higher glucose tolerance and insulin sensitivity via adipose tissue modulation solely because of a difference in the type of carbohydrate, supporting a nutritional approach in the fight against insulin resistance.—Van Schothorst, E. M., Bunschoten, A., Schrauwen, P., Mensink, R. P., Keijer, J. Effects of a high‐fat, low versus high glycemic index diet: retardation of insulin resistance involves adipose tissue modulation. FASEB J. 23, 1092–1101 (2009)

Dietary restriction of mice on a high-fat diet induces substrate efficiency and improves metabolic health

High energy intake and, specifically, high dietary fat intake challenge the mammalian metabolism and correlate with many metabolic disorders such as obesity and diabetes. However, dietary restriction (DR) is known to prevent the development of metabolic disorders. The current western diets are highly enriched in fat, and it is as yet unclear whether DR on a certain high-fat (HF) diet elicits similar beneficial effects on health. In this research, we report that HF-DR improves metabolic health of mice compared with mice receiving the same diet on an ad libitum basis (HF-AL). Already after five weeks of restriction, the serum levels of cholesterol and leptin were significantly decreased in HF-DR mice, whereas their glucose sensitivity and serum adiponectin levels were increased. The body weight and measured serum parameters remained stable in the following 7 weeks of restriction, implying metabolic adaptation. To understand the molecular events associated with this adaptation, we analyzed gene expression in white adipose tissue (WAT) with whole genome microarrays. HF-DR strongly influenced gene expression in WAT; in total, 8643 genes were differentially expressed between both groups of mice, with a major role for genes involved in lipid metabolism and mitochondrial functioning. This was confirmed by quantitative real-time reverse transcription-PCR and substantiated by increase in mitochondrial density in WAT of HF-DR mice. These results provide new insights in the metabolic flexibility of dietary restricted animals and suggest the development of substrate efficiency.

Transcriptome analysis in benefit-risk assessment of micronutrients and bioactive food components

The establishment of functional effects due to variation in concentrations of micronutrients in our diet is difficult since they are often not immediately recognized as being healthy or unhealthy. Indeed, effects induced by micronutrients are hard to identify and therefore the establishment of the recommended daily intake, the optimal intake and the upper limit pose a challenge. For bioactive food components this is even more complicated. Whole-genome transcriptome analysis is highly suitable to obtain unbiased information on potential affected biological processes on a whole-genome level. Here, we will describe and discuss several aspects of transcriptome analysis in benefit-risk assessment, including effect size, sensitivity and statistical power, that have to be taken into account to faithfully identify functional effects of micronutrients and bioactive food components.