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Ashley M Bommarito Chemistry Department East Stroudsburg University
A Brief Look into the Biochemistry of Fasting, Starvation & Anorexia Nervosa Ashley M Bommarito Chemistry Department East Stroudsburg University
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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Metabolism Set of chemical reactions that occur in organisms to maintain life Two categories Catabolism – “Destructive metabolism” Anabolism – “Constructive metabolism” Organized into metabolic pathways Enzymes couple energy-requiring reactions with energy-releasing reactions Only focusing on humans and similar mammals
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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General Catabolism 3 main stages
Food broken down to smaller components; occurs outside cells Digestive enzymes: proteases, glycoside hydrolases, lipases Smaller molecules taken into cells; broken down more Acetyl Coenzyme A (acetyl-CoA), releases some energy Acetyl group oxidized to H2O and CO2 Via citric acid cycle and electron transport chain Coenzyme NAD+ NADH; releases much more energy
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TCA Cycle Overview
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Metabolism Catabolism and Anabolism always coexist
One process may dominate over the other Awake: catabolism Sleep: anabolism With regular rest and healthy diet – balanced
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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Fasting, Starvation & Anorexia Nervosa
Voluntarily abstaining from all or most food Starvation Extended fasting Involuntary Anorexia Poor appetite, due to many causes Anorexia Nervosa Eating disorder – low body weight, distorted body image Some food is still eaten, often only certain “categories”
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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General Effects Inadequate carbohydrate consumption
Body shifts to catabolic state Body’s materials broken down – provides glucose to maintain life Only materials required for survival are generated Catabolism > anabolism
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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Specific Effects – Amino Acids
Alanine level decline Alanine to Pyruvate ratio downshift Increase in oxidation of Alanine to obtain Pyruvate
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Specific Effects – Amino Acids
Alanine Oxygen Carbon Hydrogen Nitrogen Pyruvate Oxygen Carbon Hydrogen
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Specific Effects – Amino Acids
Glutamate level decline Glutamate to α-ketoglutarate ratio downshift Oxidation of Glutamate increase
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Specific Effects – Amino Acids
Glutamate Oxygen Carbon Hydrogen Nitrogen α-ketoglutarate Oxygen Carbon Hydrogen
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Specific Effects : Pyruvate
Influx of carbons from acetyl CoA versus influx of carbons from pyruvate 14H: double 66H: triple PEP carboxykinase vs. TCA cycle flux Seven-fold higher, 18H fast Pyruvate recycling vs TCA cycle flux Five-fold higher, 18H fast
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Specific Effects – Pyruvate
Oxygen Carbon Hydrogen Acetyl CoA Oxygen Carbon Hydrogen Sulfur CoA
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Oxygen Carbon Hydrogen Oxaloacetate Oxygen Carbon Hydrogen
Pyruvate Oxygen Carbon Hydrogen Oxaloacetate Oxygen Carbon Hydrogen PEP Phosphoenolpyruvate Oxygen Carbon Hydrogen Phosphorous Glucose Oxygen Carbon Hydrogen
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Outline Metabolism Fasting, Starvation & Anorexia Effects Summary
Catabolism Fasting, Starvation & Anorexia Effects General Specifics Summary
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Summary Metabolism – usually well balanced cycles
Catabolism – break down, provides energy Fasting, Starvation & Anorexia – Different forms of malnutrition Effects - Body must adapt, still requires glucose for some cells while other cells can use different energy forms General – Body shifts to catabolic state Specifics – Amino Acids (ex, alanine & glutamate) from muscles used to propel TCA cycle & fund glucose requirements
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