Lipid metabolism

1. Lipid metabolism • Lipid structure • Triglyeride (triacylglycerol) metabolism • Lipogenesis • Lipolysis • FFA oxidation • Fat metabolism during exercise • Training effects on fat metabolism

2. Lipid structure: FFA and glycerol Brooks et al.

3. Lipid structure: triglyceride Brooks et al. (Fig. 7-2)

4. Lipid structure: α-glycerophosphate Brooks et al. (Fig. 7-2)

5. TG metabolism Brooks et al. (Insert 7-1)

6. TG metabolism Brooks et al.

7. TG storage

8. TG/FFA fluxes Brooks et al.

9. Lipogenesis: FFA production from glucose

10. Lipogenesis Murray et al., Harper’s Biochemistry, Lange, 1996

11. Adipose tissue metabolism Murray et al., Harper’s Biochemistry, Lange, 1996

12. Lipolysis Murray et al., Harper’s Biochemistry, Lange, 1996

13. FFA oxidation Brooks et al.

14. β-oxidation Murray et al., Harper’s Biochemistry, Lange, 1996

15. FFA oxidation Brooks et al.

16. Plasma FFA and glycerol during exercise Brooks et al.

17. Substrate use during exercise Brooks et al., Physiology of Exercise, 2nd ed., Mayfield, 1996

18. Glucose-fatty acid cycle Brooks et al.

19. Glucose-fatty acid cycle Brooks et al.

20. FFA oxidation Brooks et al.

21. Training: plasma FFA and glycerol Brooks et al.

22. Training: FFA turnover and metabolism Friedlander et al., J Appl Physiol 86: 2097, 1999

23. Metabolic regulation: wrap-upPrimary control: Energy charge Murray et al., Harper’s Biochemistry, 24th ed., Lange, 1996

24. Metabolic regulation: wrap-upPrimary control: energy charge↓[ATP]/[ADP] → ↑[NAD+]/[NADH]↑[NAD+] allows increased activity of all the mitochondrial dehydrogenases (PDH, β-oxidation, Krebs cycle)

25. Below about 50% VO2max, FFA oxidation provides most of the energy with the exception of the always present low blood glucose oxidation rate – remember, there are no major “regulatory” enzymes in the muscle cell controlling the rate of FFA oxidation; the rate of oxidation is just dependent upon the [ADP], and hence, the [NAD+] Brooks et al., Physiology of Exercise, 2nd ed., Mayfield, 1996

26. Thus, at ≤50% VO2max, the following are relatively high: [ATP]/[ADP], [NADH]/[NAD+], [acetyl CoA]/[CoA], and [citrate]The following are relatively low: [AMP], [Pi], [NH4+], [plasma catechoamines]Under these conditions, CHO metabolism is low because of inhibition of the following reactions: phosphorylase, PFK, PDH Brooks et al., Physiology of Exercise, 2nd ed., Mayfield, 1996

27. When the maximal rate of FFA oxidation is surpassed above ~50% VO2max, the following more rapidly decrease: [ATP]/[ADP], [NADH]/[NAD+], [acetyl CoA]/[CoA], and [citrate]The following progressively increase: [AMP], [Pi], [NH4+], [plasma catechoamines]Under these conditions, CHO metabolism increases because of progressive removal of inhibition of phosphorylase, PFK, and PDH. Brooks et al., Physiology of Exercise, 2nd ed., Mayfield, 1996

28. Metabolic regulation: wrap-upPrimary control: energy charge[ ] in mM[ATP] [ADP] [AMP] 4.80 0.20 0.004 4.69 (↓2%) 0.30 (↑50%) 0.009 (↑125%) 4.48 (↓6%) 0.50 (↑150%) 0.02 (↑400%)