Mitochondrial Energy Metabolism:

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Clare Douglas
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1 Mitochondrial Energy Metabolism: How Fa8y Acids and Other Fuels Keep Our Bodies Running David M. Koeller, MD Professor of Pediatrics Director, CDRC Metabolic Clinic

2 What is Energy?

3 What is Energy?

4 What is Energy?

5 What is Energy?

6 Putting the Sun s Energy to work When you burn wood you release the solar energy stored in the chemical bonds of the wood Burning wood in the air is very inefficient, Oxygen is consumed, and the only products are CO 2 and H 2 O, heat and light

7 Putting the Sun s Energy to work When we burn foods we also consume oxygen and release CO 2 and H 2 O, but we do it in very small steps and capture the energy released in order to do work. There is also heat generated, which helps maintain our body temperature. We have ways to reduce the efficiency of how we burn fuel to create more heat. Animals that hibernate are really good at this!

8 What form of energy do we use? ATP: Adenosine Triphosphate 1 2 3

9 Conversion of ATP to ADP releases energy, which we use to do work ATP ADP We use energy from food to convert ADP back to ATP

10 Energy Metabolism The process by which the energy (calories) in fats, sugars, and proteins is converted into ATP

11 Energy Metabolism

12 Most ATP is made in Mitochondria

13 Mitochondria Have Many Functions Energy production Fatty acid oxidation, ketogenesis

14 Fatty Acid Oxidation Fatty acid oxidation produces acetyl-coa CPT1 CPT2 TFP SCAD MCAD VLCAD TFP LCHAD TFP

15 Mitochondria Have Many Functions Energy production Fatty acid oxidation Krebs citric acid cycle Acetyl-CoA from fatty acids, protein, and glucose Electron transport = Oxidative Phosphorylation The source of most of our ATP

16 Still Awake? Summary: We burn fats, protein, and sugar in the mitochondrion All of these fuels produce Acetyl-Coa Acetyl-CoA is used to make ATP

17 Humans are Flex Fuel Vehicles!

18 What determines what we use for fuel? Real Estate Broker: Location, Location, Location Heart, Brain, Liver, Muscles, etc. Stock Broker: Timing is everything How long since you last ate?

19 Discuss how FAO fits into the big picture of mitochondrial metabolism. Discuss fuel utilization in fed and fasting state and how FAO fits into the big picture.

20 Glucose sources during fasting 40 Glucose used grams/hour Glycogen Gluconeogenesis 0 MEAL Hours Days Glucose Source Consuming Tissues Primary brain fuel Exogenous All Glucose

21 40 Glucose used grams/hour Glycogen Gluconeogenesis 0 MEAL Hours Days Glucose Source Consuming Tissues Primary brain fuel Glycogen Gluconeogenesis All but muscle and liver Glucose

22 40 Glucose used grams/hour Glycogen Gluconeogenesis 0 MEAL Hours Days Glucose Source Consuming Tissues Primary brain fuel Gluconeogenesis Glycogen All but muscle and liver Glucose

23 Prolonged Fasting 40 Glucose used grams/hour Glycogen Gluconeogenesis 0 MEAL Hours Days Glucose Source Consuming Tissues Primary brain fuel Gluconeogenesis Brain, blood cells, medullary kidney Glucose

24 Summary During fasting the blood glucose level is initially maintained by release of glucose from the liver (glycogen) As we run out of glycogen we maintain the blood glucose level by making glucose from amino acids (protein) and other compounds The energy to make glucose comes from burning fatty acids, which also generates ketones that are used as an alternative fuel by some tissues (flex fuel) The inability to burn fats (fatty acid oxidation disorder) impairs ketone and glucose production during fasting, resulting in an energy shortage to the brain and other tissues

25 What about muscles? The muscles also have flexibility in fuel usage, but it is dependent on the type and amount of activity, not the length of fasting Sustained isometric contractions without significant muscle shortening such as carrying heavy objects and skiing, as well as short bursts of activity such as weight lifting, are primarily fueled by ATP made directly from glucose Dynamic contractions - brief and repetitive contractions with muscle shortening, such as walking, running, and swimming, are highly aerobic and fueled by ATP made from fats and glucose

26 Whole body carbohydrate (CHO) and fat oxidation rates during cycling exercise at 60% of peak capacity 2003 by American Physiological Society

27 The second wind comes when we start burning fat in our muscles

28 Carbohydrate reduces fat oxidation during exercise Rate of fat oxidation

29 Conclusions Fats, sugars, and protein can all be used by the mitochondria to produce ATP (energy) What we use depends on what is available (length of fasting), and the type of tissue Carbohydrates and some fats (MCT) can be used as alternative muscle fuels during exercise

30 Questions?

Cellular Respiration Harvesting Chemical Energy ATP

Cellular Respiration Harvesting Chemical Energy ATP 2009-2010 Ch.8.3 Section Objectives: Compare and contrast cellular respiration and fermentation. Explain how cells obtain energy from cellular respiration.