Lack of adverse health effects following 30-weeks of dietary exposure to acrylamide at low doses in male F344 rats

AbstractUnderstanding the health hazards following exposure to food-borne acrylamide, especially at low levels typified by human diets, is an ongoing food safety issue. We recently published results from a study that aimed to understand the effects of acrylamide short-term exposure at doses known to cause tumors in rodents, demonstrating that a number of key toxicological end points were altered by acrylamide exposure. Additionally, we reported that at much lower doses for 30 weeks of exposure, dietary acrylamide was ‘not a complete carcinogen’ to the colon in an organ-specific rodent carcinogenesis study but acted as a co-carcinogen along with azoxymethane (AOM, a colon-specific carcinogen). Here, we present toxicological data from a sub-set of this long-term exposure study from animals that received saline (instead of AOM). Briefly, male F344 rats were randomized to receive acrylamide at 0.5, 1.0 and 2.0mg/kg diet (∼0.02, 0.04, and 0.09mg/kg BW/day, respectively) or no acrylamide (control), for 30 weeks; all rats were then euthanized and their tissues harvested and processed for toxicological evaluation. We report that at the doses tested, acrylamide did not cause any changes in general well-being, body weight or food intake. Similarly, acrylamide did not cause any biologically relevant change in parameters associated with immunophenotyping, serum biochemistry or hematology. Histopathology assessment of tissues showed no changes except in the testis, where non-specific mild lesions were observed in all the groups, inclusive of the controls. No neuropathological effects of acrylamide were observed in the brain and nerve tissues. Together, these results suggest that acrylamide administered to rats through the diet at low doses for 30 weeks did not cause any toxicologically relevant changes. Given that the doses of acrylamide in the current study are low and are comparable to human dietary exposure, this null-effect study provides data that contribute to the body of scientific evidence relevant to understanding the health effects of acrylamide

Lack of adverse health effects following 30-weeks of dietary exposure to acrylamide at low doses in male F344 rats

AbstractUnderstanding the health hazards following exposure to food-borne acrylamide, especially at low levels typified by human diets, is an ongoing food safety issue. We recently published results from a study that aimed to understand the effects of acrylamide short-term exposure at doses known to cause tumors in rodents, demonstrating that a number of key toxicological end points were altered by acrylamide exposure. Additionally, we reported that at much lower doses for 30 weeks of exposure, dietary acrylamide was ‘not a complete carcinogen’ to the colon in an organ-specific rodent carcinogenesis study but acted as a co-carcinogen along with azoxymethane (AOM, a colon-specific carcinogen). Here, we present toxicological data from a sub-set of this long-term exposure study from animals that received saline (instead of AOM). Briefly, male F344 rats were randomized to receive acrylamide at 0.5, 1.0 and 2.0mg/kg diet (∼0.02, 0.04, and 0.09mg/kg BW/day, respectively) or no acrylamide (control), for 30 weeks; all rats were then euthanized and their tissues harvested and processed for toxicological evaluation. We report that at the doses tested, acrylamide did not cause any changes in general well-being, body weight or food intake. Similarly, acrylamide did not cause any biologically relevant change in parameters associated with immunophenotyping, serum biochemistry or hematology. Histopathology assessment of tissues showed no changes except in the testis, where non-specific mild lesions were observed in all the groups, inclusive of the controls. No neuropathological effects of acrylamide were observed in the brain and nerve tissues. Together, these results suggest that acrylamide administered to rats through the diet at low doses for 30 weeks did not cause any toxicologically relevant changes. Given that the doses of acrylamide in the current study are low and are comparable to human dietary exposure, this null-effect study provides data that contribute to the body of scientific evidence relevant to understanding the health effects of acrylamide

Exposure to a northern contaminant mixture (NCM) alters hepatic energy and lipid metabolism exacerbating hepatic steatosis in obese JCR rats.

Non-alcoholic fatty liver disease (NAFLD), defined by the American Liver Society as the buildup of extra fat in liver cells that is not caused by alcohol, is the most common liver disease in North America. Obesity and type 2 diabetes are viewed as the major causes of NAFLD. Environmental contaminants have also been implicated in the development of NAFLD. Northern populations are exposed to a myriad of persistent organic pollutants including polychlorinated biphenyls, organochlorine pesticides, flame retardants, and toxic metals, while also affected by higher rates of obesity and alcohol abuse compared to the rest of Canada. In this study, we examined the impact of a mixture of 22 contaminants detected in Inuit blood on the development and progression of NAFLD in obese JCR rats with or without co-exposure to 10% ethanol. Hepatosteatosis was found in obese rat liver, which was worsened by exposure to 10% ethanol. NCM treatment increased the number of macrovesicular lipid droplets, total lipid contents, portion of mono- and polyunsaturated fatty acids in the liver. This was complemented by an increase in hepatic total cholesterol and cholesterol ester levels which was associated with changes in the expression of genes and proteins involved in lipid metabolism and transport. In addition, NCM treatment increased cytochrome P450 2E1 protein expression and decreased ubiquinone pool, and mitochondrial ATP synthase subunit ATP5A and Complex IV activity. Despite the changes in mitochondrial physiology, hepatic ATP levels were maintained high in NCM-treated versus control rats. This was due to a decrease in ATP utilization and an increase in creatine kinase activity. Collectively, our results suggest that NCM treatment decreases hepatic cholesterol export, possibly also increases cholesterol uptake from circulation, and promotes lipid accumulation and alters ATP homeostasis which exacerbates the existing hepatic steatosis in genetically obese JCR rats with or without co-exposure to ethanol

Pathways of hepatic cholesterol and Coenzyme Q₁₀ (CoQ10) biosynthesis in liver.

<p>Pathways of hepatic cholesterol and Coenzyme Q₁₀ (CoQ10) biosynthesis in liver.</p

Contaminant levels (ng/g wt) in the sera of obese JCR rats treated with vehicle (V) or high dose (H) NCM with (E) or without (W) co-exposure to ethanol.

<p>n = 7–8, means ±SEM, 2-way ANOVA with Tukey's post-hoc test.</p>a<p>denotes statistically significant difference between vehicle (V) control and high dose (H) groups at p<0.05.</p><p>Contaminant levels (ng/g wt) in the sera of obese JCR rats treated with vehicle (V) or high dose (H) NCM with (E) or without (W) co-exposure to ethanol.</p

NCM exposure increases hepatic creatine kinase activity and total ATPase activity, which is associated with decreases in hepatic ABCA1, CD36, and L-FABP protein expression and circulating levels of cholesterol and triglycerides.

<p><b>A</b>). Measurement of the specific activities of pyruvate kinase, creatine kinase, and total MDR ATPases in liver homogenate. For pyruvate kinase, activities were ascertained by measuring the consumption of NADH. Creatine kinase activities were measured by ADP production. <i>n</i> = 5, means ±SEM. Total MDR ATPases activities were measured using BD Gentest ATPase Assay kit. <b>B</b>) Immunoblot analysis of ABCA1 and ApoB-100 protein levels. Membranes were stripped and probed for GAPDH. Blots were quantified using ImageJ software and values were normalized to GAPDH loading control levels. <i>n</i> = 3, means ±SEM. <b>C</b>) Hepatic CD36 and L-FABP levels were measured using ELISA kits from MyBioSource. <i>n</i> = 6, means±SEM. <b>D</b>) Serum cholesterol and triglycerides levels were measured using the Hitachi Model 917 Multichannel Analyzer. <i>n</i> = 5, means ±SEM. Two-way ANOVA with Tukey's post-hoc test. *, **, and *** denotes P<0.05, 0.01 and 0.001 respectively. * denotes statistical comparison between vehicle control (V) and high dose (H) and ^# denotes statistical comparison between water (W) and ethanol (E) treated groups. OWV; obese water vehicle, OWH; obese water high dose, OEV; obese ethanol vehicle, OEH; obese ethanol high dose.</p

Lipid contents and contaminant levels (ng/g wt) in the liver of obese JCR rats dosed with vehicle or NCM and treated with or without ethanol.

<p><i>n</i> = 7–8, means ± SEM, 2-way ANOVA with Tukey's post-hoc test.</p>a<p>denotes statistically significant difference between vehicle (V) control and high dose (H) groups at p<0.001.</p>b<p>denotes statistically significant difference between OWV and OEV, and between OWH and OEH groups at p<0.001.</p><p>Lipid contents and contaminant levels (ng/g wt) in the liver of obese JCR rats dosed with vehicle or NCM and treated with or without ethanol.</p