Abstract
Purpose :
Taurin depletion due to mutations of the transmembrane taurine transporter (TAUT) causes early-onset retinal degeneration (EOSRD). We recently presented data on two brothers with EOSRD with a homozygous mutation in SLC6A6 which codes for TAUT (PMID 31345061). Cardiomyopathy, liver disease, and neurologic abnormalities, reported in addition to EOSRD in Slc6a6 knock-out mice and two humans, were excluded in the two patients reported here.
Here we report on the development of ophthalmological parameters in these patients under taurine supplementation which was reported to reduce taurine depletion in an independent report (PMID 31903486).
Methods :
Our patients received 100 mg/kg/day taurine nutrient over two years, and taurine levels in blood and urine were monitored. Ophthalmological parameters during the two year observation period were best corrected visual acuity (BCVA), Goldmann perimetry (GVF), and Spectral-Domain Optical Coherence Tomography (SD-OCT). Cardiac status was examined by ECG recording and ultrasound.
Results :
Before treatment, taurine serum levels were very low (0.5 mg/l and 1 mg/l resp. norm value 12 mg/l). After the first intake, an immediate rise up to a ten times of normal occurred within one hour, declining slowly thereafter. Splitting the daily taurin dose in two leveled the mean taurine concentration at normal blood levels throughout 24 hours. No extraocular symptoms were identified before supplementation started, and no side effects due to taurine increase were observed.
During the two years of observation, BCVA fluctuated around 0.8 logMAR and 1.6 logMAR for the two brothers, respectively. GVF (target V/4e) declined from 10 deg. to 5 deg. in the older patient, whereas in the younger brother, it remained between 20 deg. and 10 deg. with a temporal bridge to 60–80 deg. Severely reduced thickness of the photoreceptor-related layers as observed by SD-OCT remained stable. The cardiac status remained unaffected during the observation period.
Conclusions :
Substitution of taurine in these two brothers normalized serum levels. Whether the slow decline of BCVA and GVF is a success of this treatment requires further observation and/or a more precise differentiation from the natural course.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.