Further delineation of auriculocondylar syndrome based on 14 novel cases and reassessment of 25 published cases.

Auriculocondylar syndrome (ACS) is a rare craniofacial disorder characterized by mandibular hypoplasia and an auricular defect at the junction between the lobe and helix, known as a "Question Mark Ear" (QME). Several additional features, originating from the first and second branchial arches and other tissues, have also been reported. ACS is genetically heterogeneous with autosomal dominant and recessive modes of inheritance. The mutations identified to date are presumed to dysregulate the endothelin 1 signaling pathway. Here we describe 14 novel cases and reassess 25 published cases of ACS through a questionnaire for systematic data collection. All patients harbor mutation(s) in PLCB4, GNAI3, or EDN1. This series of patients contributes to the characterization of additional features occasionally associated with ACS such as respiratory, costal, neurodevelopmental, and genital anomalies, and provides management and monitoring recommendations.

Divergent variant patterns among 19 patients with Rubinstein-Taybi syndrome uncovered by comprehensive genetic analysis including whole genome sequencing.

Rubinstein-Taybi syndrome (RSTS) is characterized by dysmorphic facial features, broad thumbs, and intellectual disability. CREB-binding protein (CREBBP) or E1A-binding protein P300 (EP300) are causative genes. To elucidate the underlying genetic and genomic architecture related to the RSTS phenotype, we performed comprehensive genetic analysis targeting CREBBP and/or EP300 in 22 clinically diagnosed patients. During the 11-year study period, we used several analysis methods including high-resolution melting, array-based comparative genomic hybridization, panel-based exome sequencing, whole exome sequencing, and whole genome sequencing (WGS). We identified the causative variants in 19 patients (86.3%), but they were variable and complex, so we must combine multiple analysis methods. Notably, we found genetic alterations in the non-coding regions of two patients (10.5%, 2/19): scattered deletions including a partial 5'-untranslated region of CREBBP in one patient (all coding exons were intact), and a deep 229-bp intronic deletion in another patient, resulting in a splicing error. Furthermore, we identified rare clinical findings: two patients with an EP300 variant showed abnormal development of the neural tube, and one patient with a CREBBP variant had anorectal atresia with a cloaca. Our findings expand the allelic heterogeneity of RSTS, underscore the utility of comprehensive genetic analysis, and suggest that WGS may be a practical diagnostic strategy.

Intake of Carbohydrate to Fiber Ratio Is a Useful Marker for Metabolic Syndrome in Patients with Type 2 Diabetes: A Cross-Sectional Study.

BACKGROUND/AIMS: The effect of low carbohydrate diet on human health is still controversial. Whole grain, which is carbohydrate rich in fiber, has protective effects on human health. Thus, we assumed that intake of carbohydrate to fiber ratio has an important role in human health. METHODS: This is a post-hoc analysis of a cross-sectional study of 164 patients with type 2 diabetes. Habitual food and nutrient intake were assessed and estimated by a self-administered diet history questionnaire. Intake of carbohydrate to fiber ratio was defined as carbohydrate (g)/fiber intake (g). Logistic regression analyses were performed to reveal the association between intake of carbohydrate to fiber ratio and metabolic syndrome (MetS). RESULTS: Intake of carbohydrate to fiber ratio has closely associated with metabolic parameters, including triglycerides (r = 0.21, p = 0.007) and high-density lipoprotein cholesterol (r = -0.23, p = 0.003). Intake of carbohydrate to fiber ratio was associated with MetS (OR 1.06 [95% CI 1.00-1.13], p = 0.047) after adjusting for covariates, whereas carbohydrate intake (1.00 [0.99-1.01], p = 0.752) or carbohydrate energy/total energy (1.00 [0.94-1.07], p = 0.962) was not associated with MetS. CONCLUSIONS: Intake of carbohydrate to fiber ratio was associated with MetS, whereas carbohydrate intake was not.

Current status of non-invasive prenatal testing in Japan.

AIM: The purpose of this study was to report the 3-year experience of a nationwide demonstration project to introduce non-invasive prenatal testing (NIPT) of maternal plasma for aneuploidy, and review the current status of NIPT in Japan. METHODS: Tests were conducted to detect aneuploidy in high-risk pregnant women, and adequate genetic counseling was provided. The clinical data, test results, and pregnancy outcomes were recorded. We discuss the problems of NIPT on the basis of published reports and meta-analyses. RESULTS: From April 2013 to March 2016, 30 613 tests were conducted at 55 medical sites participating in a multicenter clinical study. Among the 30 613 women tested, 554 were positive (1.81%) and 30 021 were negative (98.1%) for aneuploidy. Of the 289, 128, and 44 women who tested positive for trisomies 21, 18, and 13, respectively, and underwent definitive testing, 279 (96.5%), 106 (82.8%), and 28 (63.6%) were determined to have a true-positive result. For the 13 481 women with negative result and whose progress could be traced, two had a false-negative result (0.02%). The tests were performed on the condition that a standard level of genetic counseling be provided at hospitals. CONCLUSION: Here, we report on the 3-year nationwide experience with NIPT in Japan. It is important to establish a genetic counseling system to enable women to make informed decisions regarding prenatal testing. Moreover, a welfare system is warranted to support women who decide to give birth to and raise children with chromosomal diseases.

An oxidized/reduced state of plasma albumin reflects malnutrition due to an insufficient diet in rats.

We examined whether protein- and food-intake restrictions modulate the oxidized/reduced state of plasma albumin in Sprague-Dawley rats. Rats were fed a 3%, 5%, 10% or 20% casein diet for 2 weeks. The plasma albumin concentration significantly decreased with decreasing protein intake. However, no significant difference in plasma albumin concentration was seen between rats fed the 5% or 10% casein diet. In rats fed the 5% casein diet, the percentage of mercaptalbumin within total plasma albumin was significantly lower and that of nonmercaptalbumin-1 was significantly higher than in rats fed the 10% casein diet. In experiments with food-intake restriction for 2 weeks, rats were fed 50% or 75% of the amount of a 20% casein diet consumed by control rats. The percentage of mercaptalbumin was significantly lower and that of nonmercaptalbumin-2 was significantly higher in rats with food-intake restriction than in control rats. When rats with malnutrition were refed with the 20% casein diet ad libitum, the percentage of mercaptalbumin rapidly increased. The change in the percentage of mercaptalbumin was correlated with the plasma transthyretin concentration. These results indicate that the oxidized/reduced state of plasma albumin may be applied as a sensitive marker of nutritional status reflecting dietary pattern.

Urinary pH reflects dietary acid load in patients with type 2 diabetes.

Dietary acid load is important information, however, survey of food intake needs time and skill. Therefore, it is difficult to survey food intake from all patients. It remains to be elucidated the association between dietary acid load and urinary pH in patients with type 2 diabetes. In this cross-sectional study of 173 patients, we investigated the relationship between urinary pH and dietary acid load, assessed with potential renal acid load. Habitual food and nutrient intake was assessed by a self-administered diet history questionnaire. Urinary pH was negatively correlated with potential renal acid load (r = -0.24, p = 0.002). Multivariate regression analysis revealed that potential renal acid load (standardized regression coefficient = -0.21, p = 0.036) was associated with urinary pH after adjusting for covariates. In addition, according to the receiver operator characteristic analysis, the optimal cut-off point of urinary pH for high dietary acid load, defined as potential renal acid load over 7.0 mEq/day was 5.7 (area under the receiver operator characteristic curve 0.63 (95% CI 0.54-0.71), sensitivity = 0.56, specificity = 0.70, p = 0.004). Urinary pH was associated with dietary acid load in patients with type 2 diabetes. We suggest that urinary pH can be a practical screening marker for dietary acid load in patients with type 2 diabetes.

Comparisons of dietary intake in Japanese with non-alcoholic fatty liver disease and type 2 diabetes mellitus.

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial disease that involves a complex interaction between genetics, diet, and lifestyle, all of which combine to form the NAFLD phenotype. In Japan, medical nutrition therapy for NAFLD has not yet been established, so NAFLD patients are instructed in the dietary modifications used for type 2 diabetes mellitus (T2DM). Because points of difference may exist in the effects of dietary choices on NAFLD and T2DM, the present study aimed to compare and assess the dietary intake of Japanese individuals with NAFLD and T2DM. This cross-sectional study involved 219 patients (77 NAFLD subjects; 33 males, 44 females; 142 T2DM subjects: 76 males, 66 females) aged 40-79 years. Dietary intake was assessed using a validated self-administered diet history questionnaire. Among the results, the most notable in NAFLD patients relative to T2DM patients were: 1) the low intake of vegetables that can reduce the overall energy density; 2) the high consumption of fruits and confectionery containing simple carbohydrates such as fructose; and 3) BMI may be higher. We demonstrated differences in dietary selection between the two groups. NAFLD patients were more likely to have dietary habits that promote fat accumulation in the body.

Additional patients with 4q deletion: Severe growth delay and polycystic kidney disease associated with 4q21q22 loss.

BACKGROUND: To the best of our knowledge, this is the third report concerning 4q21q22 deletions. In this report, we describe the cases of two girls with 4q deletion and polycystic kidney disease. G-banding confirmed the deletion in one patient but not in the other. METHODS: We describe the cases of two girls with 4q deletion and polycystic kidney disease. Chromosomal deletions were mapped to 4q21-22. One patient had a simple 4q contiguous gene deletion, whereas the other patient had a complicated chromosomal rearrangement. In patient 1, a smaller part of the 4q deletion was translocated to the 3p region. RESULTS: Fifty-four genes and 72 genes were deleted in patients 1 and 2, respectively. In both patients, 52 genes were consistently deleted. CONCLUSION: The present two patients had a similar phenotype, including severe growth and developmental retardation, and a characteristic facial appearance. The loss of RPKG2 and RASGEF1B causes severe growth defect. PKD2 loss causes kidney cysts.

Differing phenotypes of Moyamoya disease in a familial case involving heterozygous c.14429G > A variant in RNF213.

Moyamoya disease (MMD) is a chronic steno-occlusive arteriopathy involving the development of abnormal collateral vessels. Ring finger protein (RNF213) on the 17q25.3 locus was identified as an MMD-susceptibility gene in East Asian populations. We report a 5-year-old Japanese boy diagnosed with cerebral infarction and unilateral MMD. Magnetic resonance angiography (MRA) showed severe stenosis of the left internal carotid artery (ICA), terminal portion of the left ICA, and left origin of the posterior cerebral artery. Genetic testing indicated a heterozygous c.14429G > A (formerly described as c.14576G > A) variant in RNF213. The boy's mother had no neurological symptoms, but sequencing of RNF213 showed the same variant, and MRA indicated stenosis of the terminal bilateral ICA. This is the first report, to our knowledge, of different MMD phenotypes in a familial case involving the same heterozygous c.14429G > A variant in RNF213. Genetic testing for RNF213 is suggested for family member screening.

Autism spectrum disorders and hyperactive/impulsive behaviors in Japanese patients with Prader-Willi syndrome: a comparison between maternal uniparental disomy and deletion cases.

This study aims to compare maternal uniparental disomy 15 (mUPD) and a paternal deletion of 15q11-13 (DEL) of Prader-Willi syndrome (PWS) in regard to autism spectrum disorders (ASD). Forty-five Japanese individuals with PWS were recruited from a single recruitment center. The participants consisted of 22 children (aged from 6 to 12) and 23 adolescents (aged from 13 to 19). Six children and seven adolescents were confirmed as having mUPD. Sixteen children and 16 adolescents were confirmed as having DEL. Under blindness to the participants' genotypes, a single psychologist carried out behavioral and psychological assessments, including the Wechsler Intelligence Scales, Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS), and ADHD-Rating Scale-IV (ADHD-RS-IV). Two comparisons were made: one between mUPD and DEL children and another between mUPD and DEL adolescents. In children, no significant differences were found between mUPD and DEL participants in terms of autistic (PARS childhood, P = 0.657) and impulsive behaviors (ADHD-RS-IV hyperactive/impulsive, P = 0.275). In adolescents, mUPD patients showed significantly more autistic symptomatology (PARS adolescent, P = 0.027) and significantly more impulsive behavior (ADHD-RS-IV hyperactive/impulsive, P = 0.01) than DEL patients. Our findings about Japanese PWS patients were consistent with previous researches from western countries not focused on Asian patients, indicating that mUPD cases would be more prone to ASD than DEL cases, regardless of ethnoregional differences. In addition, our data suggested that the behavioral difference between mUPD and DEL cases in terms of autistic and impulsive symptoms tend to be unrecognizable in their childhood.

QOL in caregivers of Japanese patients with Prader-Willi syndrome with reference to age and genotype.

This study aimed to measure quality of life (QOL) of the primary family caregivers for patients with Prader-Willi syndrome (PWS). Comparisons were made between caregivers' QOL in regard to their dependents' genotype and age group. The participants with PWS consisted of 22 children (aged from 6 to 12 years) and 23 adolescents (aged from 13 to 19 years), including 6 children and 7 adolescents with maternal uniparental disomy (mUPD) and 16 children and 16 adolescents with deletion (DEL). The QOL of the primary family caregiver for each patient was assessed using the Japanese version of the WHOQOL-BREF. To examine the effect that age (children vs. adolescents) and genotype (DEL vs. mUPD) have on the QOL of caregivers, a two-way ANOVA was conducted, followed by the Bonferroni procedure to test the simple main effects. The two age groups and the two genotypes of PWS were used as independent variables and the total QOL of caregivers as a dependent variable. The two-way ANOVA (F(1, 41) = 6.98, P < 0.05), followed by the Bonferroni procedure, showed the following: the total QOL of caregivers of DEL adolescents showed little difference from that with DEL children, but the QOL of caregivers for mUPD adolescents was shown to be lower than that with mUPD children along with that of caregivers with DEL adolescents. There is hence a growing tendency for the deterioration in the QOL of caregivers to manifest itself later in the patients' adolescence, found mainly with mUPD patients.

Testosterone replacement therapy to improve secondary sexual characteristics and body composition without adverse behavioral problems in adult male patients with Prader-Willi syndrome: an observational study.

Prader-Willi syndrome (PWS), a complex genetic disorder, arises from suppressed expression of paternally inherited imprinted genes on chromosome 15q11-q13. Characteristics include short stature, intellectual disability, behavioral problems, hypogonadism, obesity, and reduced bone and muscle mass. Testosterone replacement (TR) remains controversial due to concerns regarding behavioral problems. To evaluate the effects of TR on secondary sexual characteristics, body composition, and behavior in adult males with PWS, 22 male PWS patients over the age of 16 with behavioral scores of less than grade 4 on the Modified Overt Aggression Scale (MOAS) underwent monthly intramuscular TR (125 mg). Pubertal change, body composition and behavior were evaluated before and after 24 months of therapy. Serum testosterone, LH, and FSH did not change. Increased pubic hair was observed in 16 of 22 patients (72.7%). Percent body fat decreased from 47.55 ± 2.06% to 39.75 ± 1.60% (n = 18) (P = 0.018). Bone mineral density increased from 0.8505 ± 0.0426 g/cm(2) to 0.9035 ± 0.0465 g/cm(2) (n = 18) (P = 0.036), and lean body mass increased from 18093.4 ± 863.0 g to 20312.1 ± 1027.2 g (n = 18) (P = 0.009). The MOAS was unchanged, from 4.5 ± 2.0 at the beginning of the study to 3.0 ± 1.7 at the end of study indicating no increase in aggression. No behavioral problems were observed. Based on this pilot study, TR with 125 mg monthly is a potentially safe and useful intervention for adult males with PWS.

Further characterization of atypical features in auriculocondylar syndrome caused by recessive PLCB4 mutations.

Auriculocondylar syndrome (ACS) is a branchial arch syndrome typically inherited in an autosomal dominant fashion. Patients with ACS display the following core symptoms with varying severity: a specific malformation of the external ear, known as a "question mark ear," micrognathia and mandibular condyle hypoplasia. Recently, phospholipase C, ß 4 (PLCB4) mutations were identified as the major cause of autosomal dominant ACS, with mutations of the PLCB4 catalytic domain predicted to have a dominant negative effect. In addition, one ACS patient born to related parents harbored a homozygous partial deletion of PLCB4, and presented with ACS plus central apnea and macropenis; these features had not been previously reported in association with ACS. His parents, each with a heterozygous partial PLCB4 deletion, were phenotypically normal, suggesting autosomal recessive inheritance of ACS, with complete loss of function of PLCB4 predicted in the patient. We herein describe two brothers with ACS caused by compound heterozygous splice site mutations in PLCB4. The patients were born to the same unrelated and healthy parents, with each parent harboring one of the mutations, indicating autosomal recessive ACS. Both patients reported here had mixed apneas, gastrointestinal transit defects and macropenis, in addition to typical craniofacial features of ACS. This is the first example of ACS caused by compound heterozygous splice site mutations in PLCB4, the second autosomal recessive case of ACS confirmed by molecular analysis, and strengthens the link between complete loss of function of PLCB4 and extra-craniofacial features.

Spread of X-chromosome inactivation into chromosome 15 is associated with Prader-Willi syndrome phenotype in a boy with a t(X;15)(p21.1;q11.2) translocation.

X-chromosome inactivation (XCI) is an essential mechanism in females that compensates for the genome imbalance between females and males. It is known that XCI can spread into an autosome of patients with X;autosome translocations. The subject was a 5-year-old boy with Prader-Willi syndrome (PWS)-like features including hypotonia, hypo-genitalism, hypo-pigmentation, and developmental delay. G-banding, fluorescent in situ hybridization, BrdU-incorporated replication, human androgen receptor gene locus assay, SNP microarrays, ChIP-on-chip assay, bisulfite sequencing, and real-time RT-PCR were performed. Cytogenetic analyses revealed that the karyotype was 46,XY,der(X)t(X;15)(p21.1;q11.2),-15. In the derivative chromosome, the X and half of the chromosome 15 segments showed late replication. The X segment was maternal, and the chromosome 15 region was paternal, indicating its post-zygotic origin. The two chromosome 15s had a biparental origin. The DNA methylation level was relatively high in the region proximal from the breakpoint, and the level decreased toward the middle of the chromosome 15 region; however, scattered areas of hypermethylation were found in the distal region. The promoter regions of the imprinted SNRPN and the non-imprinted OCA2 genes were completely and half methylated, respectively. However, no methylation was found in the adjacent imprinted gene UBE3A, which contained a lower density of LINE1 repeats. Our findings suggest that XCI spread into the paternal chromosome 15 led to the aberrant hypermethylation of SNRPN and OCA2 and their decreased expression, which contributes to the PWS-like features and hypo-pigmentation of the patient. To our knowledge, this is the first chromosome-wide methylation study in which the DNA methylation level is demonstrated in an autosome subject to XCI.

Scoliosis in Prader-Willi syndrome: effect of growth hormone therapy and value of paravertebral muscle volume by CT in predicting scoliosis progression.

Growth hormone (GH) therapy is now widely given to Prader-Willi syndrome (PWS) patients to encourage growth in body height and to prevent obesity. Scoliosis, one of the complications in this syndrome, is thought to be accelerated in parallel with a rapid increase in body height, especially during adolescence. To determine whether GH therapy aggravates scoliosis and to identify any factor which might predict the progression of scoliosis, we studied 35 (22 males and 13 female) PWS patients between the ages of 2-16 years on GH therapy whose scoliosis was followed with spinal X-rays every 6 months. Thirteen (37.1%) of 35 patients had scoliosis with a Cobb angle of over 10°. Scoliosis was unchanged in five patients (14.3%), became worse in six (17.1%) and improved in two (5.7%). All 22 (62.9%) of 35 patients who did not have scoliosis did not develop scoliosis with GH therapy. Since abnormal paraspinal muscle development was thought to induce scoliosis, we measured cross-sectional areas of paraspinal muscles by using one slice CT scan at the level of the umbilicus at the level of L4. Since there was a delay in the increase in total paravertebral muscle area and prolonged asymmetry in patients with progressive scoliosis, both were thought to be useful predictors of progressive scoliosis in PWS patients with GH therapy.

An Evaluation of the Protein Requirements of Japanese Young Men by Consuming Two Types of Dairy Proteins Using the Indicator Amino Acid Oxidation Method.

The indicator amino acid oxidation method is a relatively new method for determining protein requirements. Our hypothesis was that the protein requirement of the casein-whey protein mixture (70% casein and 30% whey protein) was lower than the protein requirement of plain casein, because casein and whey proteins compensate for the lack of the first-limiting amino acids. The optimal mixing ratio was determined based on the amino acid scoring pattern which is used to calculate the digestible indispensable amino acid score. In this study, digestibility was not considered to determine the optimal mixing ratio because dairy protein is a good source of digestible protein. This study aimed to evaluate the protein requirements of Japanese young men by consuming casein and casein-whey protein mixture. Ten healthy young men (22±0.2 y old) participated in 12 experiments according to a graded protein intake (0.5, 0.7, 0.9, 1.0, 1.2, 1.4 g/kg/d) of casein and casein-whey protein mixture. The mean protein requirement was calculated as the breakpoint of breath 13CO2 enrichment using change-point regression models. The mean protein requirements of Japanese young men by consuming casein and casein-whey protein mixture were estimated to be 1.00 g/kg/d and 0.90 g/kg/d, respectively. These estimated requirements were consistent with the protein quality expected from the amount of the first-limiting amino acids. The indicator amino acid oxidation method may be useful to evaluate protein quality.

Actin and Vimentin proteins with N-terminal deletion detected in tumor-bearing rat livers induced by intraportal-vein injection of Ha-ras-transfected rat liver cells.

The introduction of the tumorigenic v-Ha-ras oncogene-transformed rat liver epithelial cells (WBras), which is deficient in gap junctional intercellular communication (GJIC), into F344 rats, induces significant formation of hepatocellular tumors. GJIC plays a major role in maintaining tissue homeostasis. Using this in vivo tumor model system, we used 2-dimensional electrophoresis with isoelectric focusing in the first dimension and SDS-PAGE in the second dimension to globally identify proteins that are uniquely expressed in the livers of WBras-treated rats as compared to the sham control. Immunoblotting was used to identify Ras and Connexin43, which were the positive and negative marker proteins, respectively, of the introduced WBras cells. As predicted, immunoblotting indicated that the whole liver of tumor-bearing animals exhibited a decreased level of Connexin43 and an increased level of Ras. Connexin43 and GJIC were expressed and functional in normal liver, but not in the tumor. In addition to these 2 markers, an additional 4 proteins exhibited decreased levels and 2 proteins exhibited increased levels in the livers of tumor-bearing animals. N-Terminal sequencing analysis was used to identify these proteins, which were glucose-regulated protein 78, 2 isoforms of heat shock protein 60, and the beta-chain of ATP synthase for the down regulated proteins, and beta-Actin with a 46 amino acid deletion from its N-terminus and Vimentin with a 71 amino acid deletion from its N-terminus for the up regulated proteins. These data offer potentially new markers of liver tumorigenicity, particularly, Vimentin. (

Polypyrimidine tract-binding protein is involved in regulation of albumin synthesis in response to food intake.

Our recent study demonstrates that polypyrimidine tract-binding protein (PTB), which is a sequence specific RNA-binding protein, attenuates albumin synthesis in a cell-free translation system. In this study, the effects of food intake on regulation of albumin synthesis through binding of PTB to albumin messenger RNA (mRNA) were investigated. Rats were divided into 1 of 3 groups: fed; fasted for 36 h; or fasted for 36 h and then refed for 24 h. No significant differences in albumin mRNA levels were found among fed, fasted and refed rats. However, a decrease in the proportion of albumin mRNA associated with polysomes was identified in fasted rats. Furthermore, UV-cross linking analysis demonstrated that levels of albumin mRNA-PTB complex were increased in liver extracts from fasted rats. No significant differences in PTB levels in liver homogenate were found among the experimental groups. However, PTB level in the cytoplasmic fraction was higher in fasted rats than in fed rats. In refed rats, PTB level in the cytoplasmic fraction returned to a level comparable to that in fed rats, but was inhibited by treatment with rapamycin, a mammalian target of rapamycin (mTOR) inhibitor. These results suggest that localization of PTB is regulated by food intake through mTOR signaling, and alterations in level of albumin mRNA-PTB complex play a role in mediating the effects of food intake on albumin synthesis in the rat liver.

Dietary cystine is important to maintain plasma mercaptalbumin levels in rats fed low-protein diets.

The oxidized/reduced state of plasma albumin in rats is influenced by the quantity of dietary protein. However, the effects of the protein quality on the oxidized/reduced state of plasma albumin are not clear. We hypothesized that the quality of dietary protein might modulate the oxidized/reduced state of plasma albumin. The aim of the present study was to examine whether the amino acid composition of dietary protein modulates the oxidized/reduced state of plasma albumin in rats. Male Sprague-Dawley rats were fed low-protein diets containing 5% casein (CA), 5% egg white (EW), or 6% wheat gluten (WG) for 2 weeks. The plasma albumin concentration gradually decreased in rats fed each diet; however, there was no significant difference among the groups. In rats fed the 5% CA diet, the percentage of mercaptalbumin within the total plasma albumin was significantly lower than in those fed the EW or WG diet. Compared with EW or WG, CA contains lower amounts of glycine and cystine. In rats fed a 5% CA diet supplemented with cystine, the percentage of mercaptalbumin was significantly higher than that in rats fed a 5% CA diet supplemented with glycine. The expression of hepatic eukaryotic initiation factor 4E-binding protein 1 was significantly lower in rats fed the cystine-supplemented diet than in those fed the glycine-supplemented diet. These results suggest that dietary protein with a high cystine content maintains plasma mercaptalbumin levels in rats fed low-protein diets.