Exercise and Neuromodulators: Choline and Acetyicholine in Marathon Runners L.A. Conlay2, L.A. Sabounjian3 ,R. J. Wurtman1 of Neuroendocrine Regulation, Massachusetts Institute of Technology 2Dept. of Anesthesia, Massachusetts General Hospital, Harvard Medical School 3lnterneuron Pharmaceuticals Incorporated
Abstract L. A. Conlay, L. A. Sabounjian andR. I Wurtman, Exercise and Neuromodulators: Choline and Acetyl-
choline in Marathon Runners. mt J Sports Med, Vol 13, Suppll,S141—S142, 1992.
Certain neurotransmitters (i.e., acetylcholine, catecholamines, and serotonin) are formed from dietary constituents (i.e., choline, tyrosine and tryptophan). Changing the consumption of these precursors alters release of their respective neurotransmitter products.
The neurotransmitter acetylcholine is released from the neuromuscular junction and from brain. It is formed from choline, a common constituent in fish, liver,
and eggs. Choline is also incorporated into cell membranes; membranes may likewise serve as an alternative choline source for acetylcholine synthesis.
A) reducing the choline concentration has been shown in vitro, to reduce acetylcholine release; B) we observe reductions in plasma choline in marathon runners (4) and in humans consuming a choline-free diet (5);
C) such reductions have been found to be associated with a slowing in transmission of the contraction-generating impulse across muscle (10).
Genera/concepts ofprecursor control The neurotransmitters acetylcholine, catecholamines, and serotonin are synthesized from precursors normally obtained from the diet (choline, tyrosine, and tryptophan, respectively). Moreover, the levels of these nutrients in the brain control the rates at which their neurotransmitter
In trained athletes, running a 26 km
products are synthesized. This dietary control of neu-
marathon reduced plasma choline by approximately 40%, from 14.1 to 8.4 uM. Changes of similar magnitude have been shown to reduce acetylcholine release from the neuromuscular junction in vivo. Thus, the reductions in plasma
into the brain; 2) the rate-limiting enzymes in the neu-
choline associated with strenuous exercise may reduce acetylcholine release, and could thereby affect endurance or performance. Key words
Choline, exercise, acetyicholine, lecithin, running
rotransmitter synthesis is possible because: 1) the biochemical precursors for this class of neurotransmitters readily gain entry
rotransmitter synthesis pathway are not saturated with precursor-substrate at physiologic concentrations; and 3) these neurotransmitters do not "feed-back" to inhibit their own synthesis (9). Thus, the consumption of additional precursor (i.e., choline, tyrosine, or tryptophan) can generate more of the re-
spective neurotransmitter product (i.e., acetylcholine, the catecholamines, or serotonin). The concentration of these precursors has been demonstrated to affect blood pressure, sleep, memory, pain, and mood (9). Consumption of the proper diet
could thus influence the athlete's performance, response to stress, decision-making ability, and level of fatigue.
Materials and Methods
Many neurotransmitters or neuromodulators influence an individual's ability to exercise via actions in both the peripheral and central nervous systems. Acetylcholine is perhaps the most familiar, since cholinergic neurons transmit signals for motor and preganglionic sympathetic fibers as well
Following approval by our institution's Committee on the Use of Humans as Experimental Subjects, qualified runners of the Boston Marathon consented for the study. Blood (10 ml) was collected before (between 9 and 11 am.)
and immediately after (2 to 4 p.m.) the Boston Marathon. Plasma was separated and assayed radioenzymatically for choline (5).
mt. J. SportsMed.13(1992) S141 —S142 GeorgThieme Verlag Stuttgart New York
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as for neurons in the central nervous system involving memory, awareness, and temperature regulation. Acetylcholine is synthesized from choline, a compound consumed in the diet (3). The choline/acetyicholine relationship is important during exercise because:
S142 mt. J. Sports Med. 13(1992)
u 15 C a)
05 a a
Fig. 1 Plasma choline concentrations in qualified runners completing the 1985 and 1986
Boston Marathons (p