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Exercise increases tryptophan availability to the brain in older men age 57-70 years.

Abstract

PURPOSE

Many aspects of serotonergic activity, both central and peripheral in origin, undergo significant changes with human aging. These alterations might predispose elderly people to develop mood disorders. Because previous work showed that increasing the peripheral availability of tryptophan (TRP) to the brain holds antidepressant properties, this study evaluated whether TRP availability to the brain is increased during prolonged exercise in older men.

METHODS

Nineteen males age 64 ± 3 yr completed a treadmill exercise bout at an HR eliciting ∼68% V˙O(2peak) for 60 min. Fasting blood was collected at rest, after 30 and 60 min of exercise, and at 90 min (after exercise). Branched-chain amino acids (BCAA), total and free TRP, prolactin, ammonia, nonesterified fatty acids, glucose, and lactate were measured.

RESULTS

Changes in free TRP/BCAA ratio and prolactin were used as peripheral proxies of central serotonin synthesis rate and activity. The free TRP/BCAA ratio observed at baseline was increased by 102% after 1 h of exercise (P < 0.0001) and remained elevated after exercise (78% above baseline, P < 0.001). The free TRP portion in serum increased from 2.8 ± 0.7 to 5.7 ± 1.8 μmol·L⁻¹ after 1 h of exercise (P < 0.001) and was strongly correlated with plasma nonesterified fatty acid contents (r₁₇ = 0.887, P < 0.0001, all time points). Serum prolactin was significantly elevated after 1 h of exercise (8.6 ± 2.4 μg·L⁻¹, P < 0.001) and was positively correlated with free TRP/BCAA ratio (r₁₆ = 0.48, P < 0.05, all time points).

CONCLUSIONS

These results concur with previous observations in younger men and unveil that significant elevations in TRP availability to the brain are encountered during sustained exercise in older men. These results provide support to the hypothesis that increases in serotonin synthesis and activity might be involved in the antidepressant effect of exercise in the elderly.

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  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    Research Centre on Aging, University Institute of Geriatrics of Sherbrooke, Sherbrooke, Quebec, Canada.

    ,

    Source

    MeSH

    Aged
    Amino Acids, Branched-Chain
    Ammonia
    Biomarkers
    Blood Glucose
    Body Composition
    Brain
    Exercise
    Exercise Test
    Fatty Acids, Nonesterified
    Humans
    Lactates
    Linear Models
    Male
    Middle Aged
    Prolactin
    Tryptophan

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22051569

    Citation

    Melancon, Michel O., et al. "Exercise Increases Tryptophan Availability to the Brain in Older Men Age 57-70 Years." Medicine and Science in Sports and Exercise, vol. 44, no. 5, 2012, pp. 881-7.
    Melancon MO, Lorrain D, Dionne IJ. Exercise increases tryptophan availability to the brain in older men age 57-70 years. Med Sci Sports Exerc. 2012;44(5):881-7.
    Melancon, M. O., Lorrain, D., & Dionne, I. J. (2012). Exercise increases tryptophan availability to the brain in older men age 57-70 years. Medicine and Science in Sports and Exercise, 44(5), pp. 881-7. doi:10.1249/MSS.0b013e31823ede8e.
    Melancon MO, Lorrain D, Dionne IJ. Exercise Increases Tryptophan Availability to the Brain in Older Men Age 57-70 Years. Med Sci Sports Exerc. 2012;44(5):881-7. PubMed PMID: 22051569.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Exercise increases tryptophan availability to the brain in older men age 57-70 years. AU - Melancon,Michel O, AU - Lorrain,Dominique, AU - Dionne,Isabelle J, PY - 2011/11/5/entrez PY - 2011/11/5/pubmed PY - 2012/8/21/medline SP - 881 EP - 7 JF - Medicine and science in sports and exercise JO - Med Sci Sports Exerc VL - 44 IS - 5 N2 - PURPOSE: Many aspects of serotonergic activity, both central and peripheral in origin, undergo significant changes with human aging. These alterations might predispose elderly people to develop mood disorders. Because previous work showed that increasing the peripheral availability of tryptophan (TRP) to the brain holds antidepressant properties, this study evaluated whether TRP availability to the brain is increased during prolonged exercise in older men. METHODS: Nineteen males age 64 ± 3 yr completed a treadmill exercise bout at an HR eliciting ∼68% V˙O(2peak) for 60 min. Fasting blood was collected at rest, after 30 and 60 min of exercise, and at 90 min (after exercise). Branched-chain amino acids (BCAA), total and free TRP, prolactin, ammonia, nonesterified fatty acids, glucose, and lactate were measured. RESULTS: Changes in free TRP/BCAA ratio and prolactin were used as peripheral proxies of central serotonin synthesis rate and activity. The free TRP/BCAA ratio observed at baseline was increased by 102% after 1 h of exercise (P < 0.0001) and remained elevated after exercise (78% above baseline, P < 0.001). The free TRP portion in serum increased from 2.8 ± 0.7 to 5.7 ± 1.8 μmol·L⁻¹ after 1 h of exercise (P < 0.001) and was strongly correlated with plasma nonesterified fatty acid contents (r₁₇ = 0.887, P < 0.0001, all time points). Serum prolactin was significantly elevated after 1 h of exercise (8.6 ± 2.4 μg·L⁻¹, P < 0.001) and was positively correlated with free TRP/BCAA ratio (r₁₆ = 0.48, P < 0.05, all time points). CONCLUSIONS: These results concur with previous observations in younger men and unveil that significant elevations in TRP availability to the brain are encountered during sustained exercise in older men. These results provide support to the hypothesis that increases in serotonin synthesis and activity might be involved in the antidepressant effect of exercise in the elderly. SN - 1530-0315 UR - https://www.unboundmedicine.com/medline/citation/22051569/Exercise_increases_tryptophan_availability_to_the_brain_in_older_men_age_57_70_years_ L2 - http://Insights.ovid.com/pubmed?pmid=22051569 DB - PRIME DP - Unbound Medicine ER -