Sleep and rhythm consequences of a genetically induced loss of serotonin

Abstract

Background: A genetic deficiency in sepiapterin reductase leads to a combined deficit of serotonin and dopamine. The motor phenotype is characterized by a dopa-responsive fluctuating generalized dystonia-parkinsonism. The non-motor symptoms are poorly recognized. In particular, the effects of brain serotonin deficiency on sleep have not been thoroughly studied.

Objective: We examine the sleep, sleep-wake rhythms, CSF neurotransmitters, and melatonin profile in a patient with sepiapterin reductase deficiency.

Patient: The patient was a 28-year-old man with fluctuating generalized dystonia-parkinsonism caused by sepiapterin reductase deficiency.

Methods: A sleep interview, wrist actigraphy, sleep log over 14 days, 48-h continuous sleep and core temperature monitoring, and measurement of CSF neurotransmitters and circadian serum melatonin and cortisol levels before and after treatment with 5-hydroxytryptophan (the precursor of serotonin) and levodopa were performed.

Results: Before treatment, the patient had mild hypersomnia with long sleep time (704 min), ultradian sleep-wake rhythm (sleep occurred every 11.8 +/- 5.3 h), organic hyperphagia, attentionlexecutive dysfunction, and no depression. The serotonin metabolism in the CSF was reduced, and the serum melatonin profile was flat, while cortisol and core temperature profiles were normal. Supplementation with 5-hydroxytryptophan, but not with levodopa, normalized serotonin metabolism in the CSF, reduced sleep time to 540 min, normalized the eating disorder and the melatonin profile, restored a circadian sleep-wake rhythm (sleep occurred every 24 +/- 1.7 h, P < 0.0001), and improved cognition.

Conclusion: In this unique genetic paradigm, the melatonin deficiency (caused by a lack of its substrate, serotonin) may cause the ultradian sleep-wake rhythm.

Figure 1

Biosynthesis of tetrahydrobiopterin, dopamine, serotonin

Figure 2

Sleep log before (A) and after treatment with 5–0H–tryptophan (B), with x axis for clock time, and y axis for week days. Note that the sleep/wake rhythm is ultradian (periodicity: 11.8 h) before treatment, and circadian (periodicity: 24 h) after treatment. Black bars = sleep period.

Figure 3

Hypnogram before (upper panel) and after treatment with 5–OH–tryptophan (lower panel) with x axis for clock time, and y axis for sleep stages

Figure 4

Plasma melatonin profile (pg/mL vs. clock time) before (dotted line) and after (plain line) treatment with 5–OH–tryptophan

Supplemental Figure 1

Serum cortisol profile (mcg/dL vs. clock time) before (dotted line) and after (plain line) treatment with 5-OH-tryptophan

Supplemental Figure 2

Core body temperature before (circles) and after (square points) treatment with 5–OH–tryptophan