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Douglas Paddon-Jones , Ph.D. Associate Professor, Physical Therapy and Internal Medicine

Protein Intake and the Preservation of Muscle Mass in Aging. Douglas Paddon-Jones , Ph.D. Associate Professor, Physical Therapy and Internal Medicine The University of Texas Medical Branch. Iowa Dietetic Association 2009. Overview. muscle protein metabolism – the science.

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Douglas Paddon-Jones , Ph.D. Associate Professor, Physical Therapy and Internal Medicine

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  1. ProteinIntake and the Preservation of Muscle Mass in Aging Douglas Paddon-Jones, Ph.D. Associate Professor, Physical Therapy and Internal Medicine The University of Texas Medical Branch Iowa Dietetic Association 2009

  2. Overview • muscle protein metabolism – the science • - healthy aging • physical inactivity • exercise • protein needs • translating science  clinical practice

  3. Hormones Muscle growth Synthesis Exercise Nutrition Balance Malnutrition Muscle loss Inactivity Breakdown Maintaining Muscle Mass Illness/Injury

  4. Fat Mass Lean Body Mass 35 55 30 50 25 (kg) 45 (kg) 20 40 15 35 10 30 5 20 30 40 50 60 70 80 20 30 40 50 60 70 80 Age (years) Age (years) Age and body composition

  5. Decreased muscle mass • lean body mass • strength • fat mass • power • visceral fat • walking speed • insulin resistance • risk of falls • type 2 diabetes • risk of fractures Frailty

  6. Dietary strategies to maintain muscle • Free-form amino acid supplements: • stimulate muscle anabolism • they are effective in all age groups • they can be used clinically

  7. How much protein are we getting ? Breakfast Lunch Dinner ? ? ?

  8. Muscle Protein Synthesis / Muscle Growth - protein ingestion - 0.14 0.12 0.1 Protein Synthesis (%/h) 0.08 ? Young Elderly 0.06 0.04 0.02 0 30 g protein Fasting Symons et. al. AJCN, 2007

  9. Young Old Protein Ingestion and Muscle Growth - a message of moderation - 0.14 0.12 0.1 0.08 Protein Synthesis (%/h) 0.06 0.04 0.02 0 Fasting Fasting 90 g protein 30 g protein ~1.2 g/kg/day for 180 lb individual

  10. Daily protein distribution - typical ? - maximum rate of protein synthesis Total Protein 90 g Anabolism 65 g 15 g 10 g Catabolism A skewed daily protein distribution fails to maximize potential for muscle growth

  11. Anabolism Catabolism Daily protein distribution - Optimal - maximum rate of protein synthesis Total Protein 90 g 30 g 30g 30 g Repeated maximal stimulation of protein synthesis increase / maintenance of muscle mass

  12. Protein + Exercise 0.18 0.16 0.14 0.12 0.1 Young Protein Synthesis (%/h) 0.08 Elderly 0.06 ? ? 0.04 0.02 0 Fasting Protein meal Protein + Exercise

  13. 100 90 % of Time 80 70 60 50 40 30 20 10 0 Inactive Low Activity (0 steps/min) (< 15 steps/min) Bed rest is a defacto treatment modality - if you’re hospitalized you will become inactive -

  14. Muscle Loss in Bedridden Elders - 10 Days of Inactivity/Bed rest - 250 Young 28 Days Bedrest Elderly 10 Days Bedrest 0 -250 ? -500 Loss of lean leg mass (g) 2% total lean leg mass -750 -1000 -1500 -2000 Paddon-Jones et. al. 2004 Kortebein et al. 2007

  15. Muscle Loss in Hospitalized Elders 250 Young 28 Days Inactivity Healthy Elders 10 Days Inactivity Elderly Inpatients ~ 3 days 0 -250 ? ? -500 Loss of lean leg mass (g) -750 -1000 -1500 2% total lean leg mass -2000

  16. Inactivity reduces the ability to build/repair proteins and muscle 0.1 0.09 0.08 0.07 * 0.06 Protein Synthesis (%/h) 0.05 0.04 0.03 0.02 0.01 0 Day 1 Day 10 24 h muscle protein synthesis during 10 day of inactivity in elders (stable isotope methodology) Kortebein et al. 2007

  17. What are our older inpatients eating ? per meal

  18. Can we reduce muscle loss associated with injury/inactivity using dietary protein ?

  19. Muscle Mass 0.6 0.4 0.2 Bedrest +Amino acids Bedrest Change in leg muscle mass (kg) 0 ? -0.2 -0.4 -0.6 Paddon-Jones et. al. 2004 Paddon-Jones et al, 2004

  20. Strength 5 Bedrest Bedrest +Amino acids 0 ? -5 Loss of 1RM Leg Extension strength (kg) -10 -15 -20 -25 Paddon-Jones et. al. 2004

  21. # Normal Diet + Amino Acids Normal Diet + Amino Acids Can protein also help elders? - 24 h muscle protein synthesis - 0.1 0.09 0.08 0.07 * 0.06 Protein Synthesis (%/h) 0.05 0.04 0.03 0.02 0.01 0 Normal Diet Normal Diet Day 10 Day 1

  22. Regular meals + Leucine 0.12 0.11 0.10 0.09 Protein synthesis: % / hr Post-absorptive 0.08 Post-prandial 0.07 ? 0.06 0.05 0 Day 1 Day 14 (pre) ( 2 weeks LEU)

  23. Summary • Muscle growth is a slow process, but atrophy can be exceedingly fast • The RDA for protein is not sufficient in many circumstances • Distribution of protein throughout the day plays a key role • ~ 30 g of protein maximally stimulates muscle protein synthesis • Hot topic: Leucine plays a key role • Moderation and common sense are still the key themes

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