Abstract
Malnutrition is present in chronic alcoholics. However, how moderate alcohol consumption affects the absorption of nutrients like glutamine has not been investigated. Glutamine, an amino acid, is vital to gastrointestinal health. Glutamine is absorbed via sodium-dependent glutamine co-transport (B0AT1; SLC6A19) along the brush border membrane of absorptive villus cells. Rat intestinal epithelial cells (IEC-18) and sixteen-week-old Sprague Dawley rats were administered the equivalent of a 0.04% blood alcohol content of ethanol (8.64 mM; 2 g/kg) to investigate the effect of moderate alcohol on sodium-glutamine co-transport. Sodium-dependent 3H-glutamine uptakes were performed to measure B0AT1 activity. Inorganic phosphate was measured as a function of Na-K-ATPase activity. Protein expression was analyzed by immunohistochemical and Western blot analysis. Ethanol significantly inhibited sodium-dependent glutamine absorption and Na-K-ATPase activity in enterocytes in vitro and ex vivo. Kinetic studies suggested that the mechanism of inhibition was due to decreased maximal rate of uptake (Vmax) of the B0AT1 co-transporter, corresponding to decreased B0AT1 protein expression and secondary to an inhibited sodium-gradient at the cellular level in vitro and ex vivo. In all, moderate ethanol significantly inhibited glutamine absorption at the level of decreased B0AT1 expression at the brush border membrane and a reduced sodium gradient, which may contribute to malnutrition present in chronic alcoholics.
Highlights
According to the National Institute of Alcohol Abuse and Alcoholism, over 15 million adults in the United States have an alcohol use disorder
3H-glutamine uptakes with and Sodium-dependent glutamine activity inhibited was determined without a sodium-free in control ethanol-treated ratswith
This study demonstrated that there was an inhibition in the Na-K-ATPase activity in villus cells from Sprague Dawley (SD) rats and in IEC-18 cells exposed to moderate ethanol
Summary
Chronic alcohol use, defined by binge drinking five or more days per month, has many well documented negative consequences including an increased risk for cancer, cardiovascular disease, liver disease and malnutrition [1,2]. This increased risk of malnutrition was demonstrated in 1984, when studies conducted by the Veterans Health Administration Cooperative. The absorption of over 20 nutrients have been shown to be affected by chronic alcohol consumption including proteins, carbohydrates, such as glucose [5,6,7,8], lipids [9], as well as vitamins such as vitamin B12 [4] and vitamin C [10].
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