Diet and risk of ethanol-induced hepatotoxicity: carbohydrate-fat relationships in rats

Abstract

Nutritional status is a primary factor in the effects of xenobiotics and may be an important consideration in development of safety standards and assessment of risk. One important xenobiotic consumed daily by millions of people worldwide is alcohol. Some adverse effects of ethanol, such as alcohol liver disease, have been linked to diet. For example, ethanol-induced hepatotoxicity in animal models requires diets that have a high percentage of the total calories as unsaturated fat. However, little attention has been given to the role of carbohydrates (or carbohydrate to fat ratio) in the effects of this important xenobiotic on liver injury. In the present study, adult male Sprague-Dawley rats (8-10/group) were infused (intragastrically) diets high in unsaturated fat (25 or 45% total calories), sufficient protein (16%) and ethanol (38%) in the presence or absence of adequate carbohydrate (21 or 2.5%) for 42-55 days (d). Animals infused ethanol-containing diets adequate in carbohydrate developed steatosis, but had no other signs of hepatic pathology. However, rats infused with the carbohydrate-deficient diet had a 4-fold increase in serum ALT levels (p < 0.05), an unexpectedly high (34-fold) induction of hepatic microsomal CYP2E1 apoprotein (p < 0.001), and focal necrosis. The strong positive association between low dietary carbohydrate, enhanced CYP2E1 induction and hepatic necrosis suggests that in the presence of low carbohydrate intake, ethanol induction of CYP2E1 is enhanced to levels sufficient to cause necrosis, possibly through reactive oxygen species and other free radicals generated by CYP2E1 metabolism of ethanol and unsaturated fatty acids.

Effects of N-acetylcysteine on ethanol-induced hepatotoxicity in rats fed via total enteral nutrition

“…2 and Table 2. As described previously, rats infused ethanol as part of low carbohydrate TEN diets developed micro-and macrovesicular steatosis, inflammatory infiltrates, and occasional foci of necrosis and this was accompanied by 2-to 3-fold increases in serum ALT [19][20][21][22]31]. Dietary supplementation with NAC provided partial protection against ALT release which was decreased (P < 0.05) in the NAC + EtOH compared to the EtOH group.…”

“…Liver microsomes were prepared by differential ultracentrifugation and p-nitrophenol hydroxylation was measured as described previously [19]. Carbon tetrachloride-dependent lipid peroxidation was measured as described by Johansson and Ingelman-Sundberg [28].…”

“…Carbon tetrachloride-dependent lipid peroxidation was measured as described by Johansson and Ingelman-Sundberg [28]. CYP2E1 apoprotein expression was measured by Western blot as described previously [19] using a rabbit polyclonal antibody raised against purified rat CYP2E1. Intracellular soluble antioxidant capacity was measured in protein-precipitated liver cytosol using the oxygen radical absorbance capacity (ORAC) assay [29,30].…”

“…with no prior knowledge of the treatment groups. Scoring was based on a scale encompassing 1 (baseline) to 4 (most extensive) as described elsewhere [19]. Steatosis was scored as the percentage of parenchymal cells containing fat (micro-or macrosteatosis) as <25% = 1, 25-50% = 2; 50-75% = 3; >75% = 4.…”

“…We have developed a total enteral nutrition (TEN) model in which ethanol is also infused intragastrically, but in which ethanol substitututes for carbohydrate as part of an isocaloric diet. In this model, development of ALD (steatohepatitis accompanied by focal necrosis) above and beyond simple steatosis is dependent upon low dietary carbohydrate content (≤5% total calories) and high polyunsaturated dietary fatty acids (PUFA) (high PUFA/carbohydrate ratio) [19,20]. Moreover, in this later model, ALD develops without significant elevations in endotoxin [21,22].…”