11FNTR342--AlcoholMetabolism

11FNTR342--AlcoholMetabolism - Alcohol Metabolism Reading:...

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Alcohol Metabolism Reading: Gropper 4 th ed, Ch 4, pp. 98–104 Gropper 5 th ed, Ch 5, pp. 170–173
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2 Objectives for today: Alcohol metabolism– the last macronutrient
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3 Alcohol Alcohol absorption and metabolism Effects of alcohol on absorption and metabolism of other macronutrients
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4 Alcohol characteristics Similarities: It’s a common dietary component Metabolized by oxidation Differences: It’s not a natural nutrient Calories are empty
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5 Alcohol characteristics cont… Ethanol (grain alcohol; ethyl alcohol; EtOH) CH 3 -CH 2 OH (C 2 H 6 O) Is not a carbohydrate Carbohydrate = C n (H 2 O) n Product of fermented sugars Drug/toxin, but least toxic of alcohols Metabolized by detoxification pathways Provides energy (~7 kcal/g) Unusual for a drug Can provide up to 50% of energy intake in alcoholics But alcoholics tend to lose weight when alcohol is substituted for carbohydrates
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6 Alcohol absorption Readily absorbed by stomach and intestines Passive diffusion Most (80%) absorbed in upper small intestine Food (especially lipids) in stomach delays emptying and slows absorption Completely miscible in water; transported in bloodstream Lipid soluble; diffuses into cells
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Alcohol Metabolism Effects: Diuresis: inhibits vasopressin (antidiuretic hormone, ADH) secretion from posterior pituitary gland Crosses blood-brain barrier; causes euphoria (through disinhibition), then depression of neural functions Detectable effects on motor coordination and judgment at <0.05% blood alcohol concentration (BAC) Depression of brainstem functions at ≈0.25% BAC Potentially fatal alcohol poisoning at 0.30-0.40% BAC LD50 = 0.40% BAC in adults 7
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Alcohol Metabolism Absorption rate faster than maximum metabolic rate Therefore, blood alcohol content rises with continued consumption BAC depends on : Amount and rapidity of consumption Weight/size Percent body fat Sex Tolerance (induction of metabolizing enzymes) 8
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9 Alcohol metabolism Step 1: Ethanol oxidized to acetaldehyde ADH or MEOS Step 2: Acetaldehyde oxidized to acetate ALDH Step 3: Acetate converted to acetyl CoA ACSS2 Acetyl CoA oxidized in the Krebs cycle or stored as triglycerides Two primary enzymatic systems oxidize ethanol to acetaldehyde Alcohol dehydrogenase (ADH) Microsomal ethanol oxidizing system (MEOS)
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10 Alcohol metabolism: ADH Alcohol dehydrogenase Found in liver and gastric mucosal cells Cytosolic enzyme; produces NADH (which can be shuttled to
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This note was uploaded on 11/25/2011 for the course NTR 342 taught by Professor Tillman during the Spring '09 term at University of Texas at Austin.

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11FNTR342--AlcoholMetabolism - Alcohol Metabolism Reading:...

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