ASHLEY M BOMMARITOCHEMISTRY DEPARTMENT

EAST STROUDSBURG UNIVERSITY

A Brief Look into the Biochemistry of Fasting,

Starvation & Anorexia Nervosa

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

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 reactionsOnly focusing on humans and similar

mammals

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

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

TCA Cycle Overview

http://www.dnatube.com/video/278/Citric-Acid--TCA--Krebs-Cycle

Metabolism

Catabolism and Anabolism always coexistOne process may dominate over the other

Awake: catabolism Sleep: anabolism

With regular rest and healthy diet – balanced

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

Fasting, Starvation & Anorexia Nervosa

Fasting 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”

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

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

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

Specific Effects – Amino Acids

Alanine level decline

Alanine to Pyruvate ratio downshift

Increase in oxidation of Alanine to obtain Pyruvate

PyruvateOxygen Carbon Hydrogen

AlanineOxygen Carbon Hydrogen

Nitrogen

Specific Effects – Amino Acids

Glutamate level decline

Glutamate to α-ketoglutarate ratio downshift

Oxidation of Glutamate increase

Specific Effects – Amino Acids

GlutamateOxygen Carbon Hydrogen

Nitrogen

α-ketoglutarateOxygen Carbon Hydrogen

Specific Effects – Amino Acids

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

Specific Effects – Pyruvate

PyruvateOxygen Carbon Hydrogen

Acetyl CoAOxygen Carbon Hydrogen

Sulfur CoA

PyruvateOxygen Carbon Hydrogen Oxaloacetate

Oxygen Carbon Hydrogen

PEP

GlucoseOxygen Carbon Hydrogen

PhosphoenolpyruvateOxygen Carbon Hydrogen

Phosphorous

Outline

Metabolism Catabolism

Fasting, Starvation & AnorexiaEffects

General Specifics

Summary

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