Phenylketonuria: reduced tyrosine brain influx relates to reduced cerebral protein synthesis

Table 1 Study cohort characteristics

Patient	Age (yrs)	Phe tolerance (mg/kg/day)	Plasma Phe (μmol/L)	Plasma Tyr (μmol/L)	k_2,1^a	k_3,2^b	k_1,2^c
1	16	28	233	66	0.055	1.06	0.073
2	23	11	358	37	0.037	0.48	0.064
3	23	12	361	32	0.046	0.71	0.077
4	24	16	373	35	0.041	0.46	0.070
5	26	31	375	47	0.031	0.50	0.052
6	25	27	405	49	0.031	0.47	0.069
7	23	20	411	87	0.037	0.70	0.072
8	21	18	477	31	0.034	0.42	0.061
9	22	32	546	42	0.033	0.54	0.057
10	25	13	565	76	0.028	0.78	0.047
11	20	19	586	38	0.039	0.55	0.085
12	24	17	632	61	0.023	0.50	0.055
13	21	15	805	35	0.027	0.36	0.066
14	27	23	825	49	0.021	0.32	0.060
15	47	14	1078	33	0.019	0.21	0.029
16	33	12	1362	37	0.021	0.34	0.049

Phe tolerance values were obtained at age 5 years. Patients 15 and 16 were treated from 6 and 9 years of age onward, respectively. In these patients, Phe tolerance was determined 6 months after treatment start. Phenylalanine and tyrosine plasma concentrations shown are baseline values. ^{a 11}C-Tyr transport from blood to brain (ml plasma/g brain tissue/min). ^b¹¹C-Tyr cerebral protein incorporation (nmol/g brain tissue/min). ^c¹¹C-Tyr transport from brain to blood (ml plasma/g brain tissue/min).

ISSN: 1750-1172