A novel homozygous missense mutation in PNPLA2 in a patient manifesting primary triglyceride deposit cardiomyovasculopathy

Primary triglyceride deposit cardiomyovasculopathy (P-TGCV), caused by a rare genetic mutation in PNPLA2 encoding adipose triglyceride lipase (ATGL), exhibits severe cardiomyocyte steatosis and heart failure. Here, we report the case of a 51-year-old man with P-TGCV homozygous for a novel PNPLA2 mutation (c.446C > G, P149R) in the catalytic domain of ATGL. Analyses of endomyocardial biopsy specimens and in vitro expression experiments showed mutant protein expression with conserved lipid binding, but reduced lipolytic activity, indicating mutation pathogenicity.

Rocuronium priming for tracheal intubation in COVID-19 patients

Priming doses of non-depolarising neuromuscular blocking drugs given before administration of anaesthetic agents have been used to hasten the onset of neuromuscular blockade. In the settings of coronavirus disease 2019 (COVID-19), this could be used to reduce the apnoeic, and potentially aerosol-generating, window. To our knowledge, we report the first cases of tracheal intubation with rocuronium for COVID-19 using the priming principle. Both patients needed their tracheas intubated for severe hypoxia using a rapid sequence induction technique with a priming dose of rocuronium. Despite adequate pre-oxygenation a sudden, unexpected fall in arterial oxygen saturations was observed in both patients after administration of a priming dose of 2 mg of rocuronium. Clinicians should consider this possible risk associated with priming doses of neuromuscular blocking drugs in the management of patients with respiratory failure due to COVID-19.

Triglyceride deposit cardiomyovasculopathy: a rare cardiovascular disorder

Triglyceride deposit cardiomyovasculopathy (TGCV) is a phenotype primarily reported in patients carrying genetic mutations in PNPLA2 encoding adipose triglyceride lipase (ATGL) which releases long chain fatty acid (LCFA) as a major energy source by the intracellular TG hydrolysis. These patients suffered from intractable heart failure requiring cardiac transplantation. Moreover, we identified TGCV patients without PNPLA2 mutations based on pathological and clinical studies. We provided the diagnostic criteria, in which TGCV with and without PNPLA2 mutations were designated as primary TGCV (P-TGCV) and idiopathic TGCV (I-TGCV), respectively. We hereby report clinical profiles of TGCV patients. Between 2014 and 2018, 7 P-TGCV and 18 I-TGCV Japanese patients have been registered in the International Registry. Patients with I-TGCV, of which etiologies and causes are not known yet, suffered from adult-onset severe heart disease, including heart failure and coronary artery disease, associated with a marked reduction in ATGL activity and myocardial washout rate of LCFA tracer, as similar to those with P-TGCV. The present first registry-based study showed that TGCV is an intractable, at least at the moment, and heterogeneous cardiovascular disorder.

Genetic basis of early-onset, maturity-onset diabetes of the young-like diabetes in Japan and features of patients without mutations in the major MODY genes: Dominance of maternal inheritance

BACKGROUND

Causative mutations cannot be identified in the majority of Asian patients with suspected maturity-onset diabetes of the young (MODY).

OBJECTIVES

To elucidate the genetic basis of Japanese patients with MODY-like diabetes and gain insight into the etiology of patients without mutations in the major MODY genes.

SUBJECTS

A total of 263 Japanese patients with early-onset, non-obese, MODY-like diabetes mellitus referred to Osaka City General Hospital for diagnosis.

METHODS

Mutational analysis of the four major MODY genes (GCK, HNF1A, HNF4A, HNF1B) by Sanger sequencing. Mutation-positive and mutation-negative patients were further analyzed for clinical features.

RESULTS

Mutations were identified in 103 (39.2%) patients; 57 mutations in GCK; 29, HNF1A; 7, HNF4A; and 10, HNF1B. Contrary to conventional diagnostic criteria, 18.4% of mutation-positive patients did not have affected parents and 8.2% were in the overweight range (body mass index [BMI] >85th percentile). HOMA-IR at diagnosis was elevated (>2) in 15 of 66 (22.7%) mutation-positive patients. Compared with mutation-positive patients, mutation-negative patients were significantly older (P = 0.003), and had higher BMI percentile at diagnosis (P = 0.0006). Interestingly, maternal inheritance of diabetes was significantly more common in mutation-negative patients (P = 0.0332) and these patients had significantly higher BMI percentile as compared with mutation-negative patients with paternal inheritance (P = 0.0106).

CONCLUSIONS

Contrary to the conventional diagnostic criteria, de novo diabetes, overweight, and insulin-resistance are common in Japanese patients with mutation-positive MODY. A significant fraction of mutation-negative patients had features of early-onset type 2 diabetes common in Japanese, and non-Mendelian inheritance needs to be considered for these patients.

Cholesterol Metabolism Is Enhanced in the Liver and Brain of Children With Citrin Deficiency

CONTEXT

Citrin-deficient infants present neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), which resolves at 12 months. Thereafter, they have normal liver function associated with hypercholesterolemia, and a preference for lipid-rich carbohydrate-restricted diets. However, some develop adult-onset type II citrullinemia, which is associated with metabolic abnormalities.

OBJECTIVES

To identify the causes of hypercholesterolemia in citrin-deficient children post-NICCD.

DESIGN AND SETTING

We determined the concentrations of sterol markers of cholesterol synthesis, absorption, and catabolism by liquid chromatography-electrospray ionization-tandem mass spectrometry and evaluated serum lipoprotein profiles.

SUBJECTS

Twenty citrin-deficient children aged 5 to 13 years and 37 age-matched healthy children.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Relationship between serum lipoproteins and sterol markers of cholesterol metabolism.

RESULTS

The citrin-deficient group had a significantly higher high-density lipoprotein cholesterol (HDL-C) concentration than did the control group (78 ± 11 mg/dL vs 62 ± 14 mg/dL, P < 0.001), whereas the two groups had similar low-density lipoprotein cholesterol and triglyceride concentrations. The concentrations of markers of cholesterol synthesis (lathosterol and 7-dehydrocholesterol) and bile acids synthesis (7α-hydroxycholesterol and 27-hydroxycholesterol) were 1.5- to 2.8-fold and 1.5- to 3.9-fold, respectively, higher in the citrin-deficient group than in the control group. The concentration of 24S-hydroxycholesterol, a marker of cholesterol catabolism in the brain, was 2.5-fold higher in the citrin-deficient group. In both groups, the HDL-C concentration was significantly positively correlated with that of 27-hydroxycholesterol, the first product of the alternative bile acid synthesis pathway.

CONCLUSIONS

HDL-C and sterol marker concentrations are elevated in citrin-deficient children post-NICCD. Moreover, cholesterol synthesis and elimination are markedly enhanced in the liver and brain of citrin-deficient children.

Serum Amino Acid Profiling in Citrin-Deficient Children Exhibiting Normal Liver Function During the Apparently Healthy Period

BACKGROUND

Citrin (mitochondrial aspartate-glutamate transporter) deficiency causes the failures in both carbohydrate-energy metabolism and the urea cycle, and the alterations in the serum levels of several amino acids in the stages of newborn (NICCD) and adult (CTLN2). However, the clinical manifestations are resolved between the NICCD and CTLN2, but the reasons are still unclear. This study evaluated the serum amino acid profile in citrin-deficient children during the healthy stage.

METHODS

Using HPLC-MS/MS analysis, serum amino acids were evaluated among 20 citrin-deficient children aged 5-13 years exhibiting normal liver function and 35 age-matched healthy controls.

RESULTS

The alterations in serum amino acids characterized in the NICCD and CTLN2 stages were not observed in the citrin-deficient children. Amino acids involved in the urea cycle, including arginine, ornithine, citrulline, and aspartate, were comparable in the citrin-deficient children to the respective control levels, but serum urea was twofold higher, suggestive of a functional urea cycle. The blood sugar level was normal, but glucogenic amino acids and glutamine were significantly decreased in the citrin-deficient children compared to those in the controls. In addition, significant increases of ketogenic amino acids, branched-chain amino acids (BCAAs), a valine intermediate 3-hydroxyisobutyrate, and β-alanine were also found in the citrin-deficient children.

CONCLUSION

The profile of serum amino acids in the citrin-deficient children during the healthy stage showed different characteristics from the NICCD and CTLN2 stages, suggesting that the failures in both urea cycle function and energy metabolism might be compensated by amino acid metabolism.

SYNOPSIS

In the citrin-deficient children during the healthy stage, the characteristics of serum amino acids, including decrease of glucogenic amino acids, and increase of ketogenic amino acids, BCAAs, valine intermediate, and β-alanine, were found by comparison to the age-matched healthy control children, and it suggested that the characteristic alteration of serum amino acids may be resulted from compensation for energy metabolism and ammonia detoxification.

Treatment with medium chain fatty acids milk of CD36-deficient preschool children

OBJECTIVE

CD36 deficiency is characterized by limited cellular long chain fatty acid uptake in the skeletal and cardiac muscles and often causes energy crisis in these muscles. However, suitable treatment for CD36 deficiency remains to be established. The aim of this study was to evaluate the clinical and metabolic effects of medium chain triacylglycerols (MCTs) in two CD36-deficient preschool children who often developed fasting hypoglycemia and exercise-induced myalgia.

METHODS

Fasting blood glucose, total ketone bodies, and free fatty acids were examined and compared for usual supper diets and for diets with replacement of one component with 2 g/kg of 9% MCT-containing milk (MCT milk). Changes in serum creatine kinase and alanine aminotransferase levels, resulting from replacement of glucose water intake with 1 g/kg of MCT milk and determined by using bicycle pedaling tasks, were examined and compared. Hypoglycemic and/or myalgia episodes in daily life were also investigated.

RESULTS

Biochemically, participants' blood glucose and total ketone bodies levels after overnight fasting substantially increased after dietary suppers containing MCT milk. Increases in serum creatine kinase and alanine aminotransferase levels resulting from the bicycle pedaling task were suppressed by MCT milk. Hypoglycemia leading to unconsciousness and tachycardia before breakfast decreased after introduction of dietary suppers containing MCT milk. Occurrence of myalgia in the lower limbs also decreased after intakes of MCT milk before long and/or strenuous exercising.

CONCLUSION

Our results suggest that MCTs can prevent fasting hypoglycemia and exercise-induced myalgia in CD36-deficient young children.

Diagnosis of congenital hyperinsulinism: Biochemical profiles during hypoglycemia

OBJECTIVES

To define the ranges of biochemical markers during hypoglycemia for the diagnosis of congenital hyperinsulinism (CHI), using high sensitivity insulin assays.

SUBJECTS

A total of 298 patients with CHI and 58 control patients with non-hyperinsulinemic hypoglycemia, who were diagnosed after 2007.

METHODS

The levels of biochemical markers (glucose, insulin, β-hydroxybutyrate [BHB], free fatty acids [FFA], lactate, ammonia) at the time of hypoglycemia were analyzed along with the maximal glucose infusion rate (GIR) to maintain euglycemia and clinical outcomes.

RESULTS

Median levels of blood glucose in patients with CHI and in controls were 30 and 46 mg/dL, while insulin levels were 9.90 and undetectable (<.5) μU/mL, respectively. Similarly, median levels of BHB were 17.5 and 3745 µmol/L, and those of FFA were 270.5 and 2660 µmol/L, respectively. For patients after 5 months, cutoffs of insulin >1.25 μU/mL, BHB < 2000 µmol/L, and FFA < 1248 µmol/L predicted CHI with sensitivities of 97.5, 96.2, and 95.2% and specificities of 84.2, 89.3, and 92.3%, respectively. Maximal GIR in the CHI groups tended to decrease with age. In addition, decreased gestational age, low birth weight, and elevated lactate at hypoglycemia were significantly more common in patients who were off treatment within 100 days without pancreatectomy.

CONCLUSIONS

After introduction of high-sensitive assays, the diagnostic value of insulin was improved, allowing for more efficient cutoffs to be set for diagnosis of CHI. Premature birth, low birth weight and elevated lactate might be helpful in predicting early remission of hypoglycemia.

Newly developed selective immunoinactivation assay revealed reduction in adipose triglyceride lipase activity in peripheral leucocytes from patients with idiopathic triglyceride deposit cardiomyovasculopathy

Triglyceride deposit cardiomyovasculopathy (TGCV) is a rare and newly identified disease among patients requiring cardiac transplantation. TGCV is characterized by cardiomyocyte steatosis and triglyceride (TG)-deposit atherosclerosis, resulting from the abnormal intracellular metabolism of TG. TGCV is classified into primary and idiopathic types. Primary TGCV carries ultra-rare genetic mutations in the adipose triglyceride lipase (ATGL), a rate-liming enzyme that hydrolyzes intracellular TG in adipose and non-adipose tissues. Idiopathic TGCV, first identified among autopsied individuals with diabetes mellitus (DM) with severe heart diseases, shows no ATGL mutations and its causes and underlying mechanisms are still unknown. TGCV is difficult to diagnose in daily clinics, thereby demanding feasible diagnostic procedures. We aimed to develop an assay to measure ATGL activity using peripheral leucocytes. Human his6-ATGL was expressed in COS1 cells, purified to homogeneity, and used to raise a polyclonal antibody neutralizing TG-hydrolyzing activity of ATGL. We developed a selective immunoinactivation assay (SIIA) for the quantitation of ATGL activity in cell lysates of leucocytes by the antibody neutralizing ATGL activities. ATGL activity was measured in 13 idiopathic TGCV patients, with two patients with primary TGCV as the negative control. Healthy (non-DM) and DM controls without heart diseases were also subjected. The developed SIIA assay revealed significant reduction in ATGL activity in leucocytes from patients with idiopathic TGCV who did not carry ATGL mutations as compared with non-DM and DM controls. Thus, ATGL in leucocytes may be an important biomarker for the diagnosis of TGCV and our assay may provide insights into pathophysiology and elucidate the underlying mechanism of TGCV and related disorders.

Assessment of ATP8B1 Deficiency in Pediatric Patients With Cholestasis Using Peripheral Blood Monocyte-Derived Macrophages

Progressive familial intrahepatic cholestasis type 1 (PFIC1), a rare inherited recessive disease resulting from a genetic deficiency in ATP8B1, progresses to liver failure. Because of the difficulty of discriminating PFIC1 from other subtypes of PFIC based on its clinical and histological features and genome sequencing, an alternative method for diagnosing PFIC1 is desirable. Herein, we analyzed human peripheral blood monocyte-derived macrophages (HMDM) and found predominant expression of ATP8B1 in interleukin-10 (IL-10)-induced M2c, a subset of alternatively activated macrophages. SiRNA-mediated depletion of ATP8B1 in IL-10-treated HMDM markedly suppressed the expression of M2c-related surface markers and increased the side scatter (SSC) of M2c, likely via impairment of the IL-10/STAT3 signal transduction pathway. These phenotypic features were confirmed in IL-10-treated HMDM from four PFIC1 patients with disease-causing mutations in both alleles, but not in those from four patients with other subtypes of PFIC. This method identified three PFIC1 patients in a group of PFIC patients undiagnosed by genome sequencing, an identical diagnostic outcome to that achieved by analysis of liver specimens and in vitro mutagenesis studies. In conclusion, ATP8B1 deficiency caused incomplete polarization of HMDM into M2c. Phenotypic analysis of M2c helps to identify PFIC1 patients with no apparent disease-causing mutations in ATP8B1.

•

ATP8B1, a causal gene of PFIC1, was expressed in IL-10-induced M2c, a subset of alternatively activated macrophages.

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ATP8B1 deficiency caused incomplete polarization of HMDM into M2c, likely via impairment of IL-10/STAT3 signaling.

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Phenotypic analysis of M2c helps to discriminate PFIC1 from other pediatric liver diseases undiagnosed by genomic analysis.

PFIC1, a rare inherited recessive disease resulting from a genetic deficiency in ATP8B1, progresses to liver failure. PFIC1 shares many clinical and histological features with other subtypes of PFIC, but differs in its therapeutic options. Because genome sequencing in patients with a clinical diagnosis of PFIC cannot always identify disease-causing mutations, an alternative method for diagnosing PFIC1 is desirable. We identified expression of ATP8B1 in IL-10-induced M2c, a subset of macrophages, and demonstrated its contribution to normal phenotypic expression of M2c. The phenotypic analysis of M2c helps to discriminate PFIC1 from other pediatric liver diseases undiagnosed by genomic analysis.

Blood asymmetric dimethylarginine and nitrite/nitrate concentrations in short-stature children born small for gestational age with and without growth hormone therapy

Objective

To investigate the basal amino acid metabolism and impact of growth hormone (GH) therapy in short-stature children born small for gestational age (short SGA children).

Methods

In this age-matched case-control study, the basal blood levels of amino acids, asymmetric dimethylarginine (ADMA), and nitrite/nitrate (NOx) were compared between 24 short SGA children and 25 age-matched normal children. Changes in these parameters were assessed for 12 months in 12 short SGA children initiating GH therapy (Group A) and 12 age-matched short SGA children without GH therapy (Group B).

Results

The arginine levels were significantly lower in the short SGA than in normal children. The ADMA levels were significantly higher and NOx levels were significantly lower in the short SGA than normal children. In Group A, the ADMA level was significantly lower and NOx level was significantly higher at 6 months than at baseline. At 12 months, the ADMA level in Group A began to increase, but the NOx level remained the same. Group B showed no significant changes.

Conclusions

This study is the first to show that ADMA is promoted and nitric oxide is suppressed in short SGA children and that GH therapy affects the production of ADMA and nitric oxide.

Circulating tricarboxylic acid cycle metabolite levels in citrin-deficient children with metabolic adaptation, with and without sodium pyruvate treatment

Citrin deficiency causes adult-onset type II citrullinemia (CTLN-2), which later manifests as severe liver steatosis and life-threatening encephalopathy. Long-standing energy deficit of the liver and brain may predispose ones to CTLN-2. Here, we compared the energy-driving tricarboxylic acid (TCA) cycle and fatty acid β-oxidation cycle between 22 citrin-deficient children (age, 3-13years) with normal liver functions and 37 healthy controls (age, 5-13years). TCA cycle analysis showed that basal plasma citrate and α-ketoglutarate levels were significantly higher in the affected than the control group (p<0.01). Conversely, basal plasma fumarate and malate levels were significantly lower than those for the control (p<0.001). The plasma level of 3-OH-butyrate derived from fatty acid β-oxidation was significantly higher in the affected group (p<0.01). Ten patients underwent sodium pyruvate therapy. However, this therapy did not correct or attenuate such deviations in both cycles. Sodium pyruvate therapy significantly increased fasting insulin secretion (p<0.01); the fasting sugar level remained unchanged. Our results suggest that citrin-deficient children show considerable deviations of TCA cycle metabolite profiles that are resistant to sodium pyruvate treatment. Thus, long-standing and considerable TCA cycle dysfunction might be a pivotal metabolic background of CTLN-2 development.

Hepatic aberrant glycosylation by N-acetylglucosaminyltransferase V accelerates HDL assembly

Glycosylation is involved in various pathophysiological conditions. N-Acetylglucosaminyltransferase V (GnT-V), catalyzing β1-6 branching in asparagine-linked oligosaccharides, is one of the most important glycosyltransferases involved in cancer and the immune system. Recent findings indicate that aberrant N-glycan structure can modify lipid metabolism. In this study, we investigated the effects of aberrant glycosylation by GnT-V on high-density lipoprotein cholesterol (HDL) assembly. We used GnT-V transgenic (Tg) mice and GnT-V Hep3B cell (human hepatoma cell line) transfectants. The study also included 96 patients who underwent medical health check-ups. Total serum cholesterol levels, particularly HDL-cholesterol (HDL-C) levels, were significantly increased in Tg vs. wild-type (WT) mice. Hepatic expression of apolipoprotein AI (ApoAI) and ATP-binding cassette subfamily A member 1 (ABCA1), two important factors in HDL assembly, were higher in Tg mice compared with WT mice. ApoAI and ABCA1 were also significantly elevated in GnT-V transfectants compared with mock-transfected cells. Moreover, ApoAI protein in the cultured media of GnT-V transfectants was significantly increased. Finally, we found a strong correlation between serum GnT-V activity and HDL-C concentration in human subjects. Multivariate logistic analyses demonstrated that GnT-V activity was an independent and significant determinant for serum HDL-C levels even adjusted with age and gender differences. Further analyses represented that serum GnT-V activity had strong correlation especially with the large-size HDL particle concentration. These findings indicate that enhanced hepatic GnT-V activity accelerated HDL assembly and could be a novel mechanism for HDL synthesis.

Successful treatment with 4-phenylbutyrate in a patient with benign recurrent intrahepatic cholestasis type 2 refractory to biliary drainage and bilirubin absorption

AIM

Benign recurrent intrahepatic cholestasis type 2 (BRIC2) is caused by mutations in ABCB11, a gene encoding the bile salt export pump (BSEP) that mediates biliary bile salt secretion, and presents with repeated intermittent cholestasis with refractory itching. Currently, no effective medical therapy has been established. We previously provided experimental and clinical evidence suggesting the therapeutic potential of 4-phenylbutyrate (4PB) for the cholestatic attacks of BRIC2.

METHODS

After examining the potential therapeutic use of 4PB treatment by in vitro studies, a patient with BRIC2 was treated p.o. with 4PB at gradually increasing doses (200, 350, and 500 mg/kg per day) for 4 months. Biochemical, histological and clinical data were collected.

RESULTS

The patient was diagnosed with BRIC2 because he had non-synonymous mutations (c.1211A>G [p.D404G] and 1331T>C [p.V444A]) in ABCB11, reduced hepatocanalicular expression of BSEP and low biliary bile salt concentrations. In vitro analysis showed that 4PB treatment partially restored the decreased expression of BSEP caused by p.D404G mutation. During the first 2 months of 4PB therapy at 200 and 350 mg/kg per day, the patient had no relief from his symptoms. No beneficial effect was observed after additional treatment with bilirubin absorption and endoscopic nasobiliary drainage. However, after starting treatment at a dose of 500 mg/kg per day, the patient's liver function tests and intractable itching were markedly improved. No apparent side-effects were observed during or after 4PB therapy. The symptoms relapsed within 1.5 months after cessation of 4PB therapy.

CONCLUSION

4PB therapy would have a therapeutic effect on the cholestatic attacks of BRIC2.

ApoE4 Determines the Reduction in LDL-C After GH Replacement Therapy in Children With an Idiopathic GH Deficiency

CONTEXT

GH activates the expression of low-density lipoprotein (LDL) receptors, leading to decreased LDL-cholesterol (LDL-C). Apolipoprotein (apo) E4 carriers suppress LDL receptor expression, rendering high LDL-C concentrations.

OBJECTIVES

We examined whether GH-deficient children carrying apoE4 exhibited a greater reduction in LDL-C after GH replacement therapy.

DESIGN AND SETTING

We determined lipoprotein profiles after 0, 4, and 12 months of GH treatment in children with an idiopathic GH deficiency. We compared the effects of GH treatment on LDL-C by apoE phenotype.

SUBJECTS

In total, 66 children with idiopathic GH deficiency and 89 healthy children were classified into subgroups according to apoE phenotype.

INTERVENTION

The intervention included GH replacement therapy for 12 months.

MAIN OUTCOME MEASURES

The relationship between apoE phenotype and reduced LDL-C induced by GH treatment was measured.

RESULTS

Concentrations of LDL-C and apoB were highest in the apoE4/3 group (n = 13), second highest in the apoE3/3 group (n = 46), and lowest in the apoE3/2 group (n = 7), whereas apoE concentrations were highest in the apoE3/2 group and lowest in the apoE4/3 group. The apoE4/3 group had significantly reduced LDL-C and apoB concentrations at months 4 and 12, whereas the apoE3/3 and apoE3/2 groups showed no changes. LDL-C concentrations did not differ among the three groups after 12 months. The trend in apoE concentration did not change among the groups.

CONCLUSIONS

Children with a GH deficiency carrying apoE4 had higher baseline LDL-C concentrations and experienced a greater reduction in LDL-C after GH replacement therapy than those without apoE4.

Abnormalities in chromosome 6q24 as a cause of early-onset, non-obese, non-autoimmune diabetes mellitus without history of neonatal diabetes

AIMS

Abnormalities in the imprinted locus on chromosome 6q24 are the most common causes of transient neonatal diabetes mellitus (6q24-related transient neonatal diabetes). 6q24-Related transient neonatal diabetes is characterized by the patient being small-for-gestational age, diabetes mellitus at birth, spontaneous remission within the first few months and frequent recurrence of diabetes after childhood. However, it is not clear whether individuals with 6q24 abnormalities invariably develop transient neonatal diabetes. This study explored the possibility that 6q24 abnormalities might cause early-onset, non-autoimmune diabetes without transient neonatal diabetes.

METHODS

The 6q24 imprinted locus was screened for abnormalities in 113 Japanese patients with early-onset, non-obese, non-autoimmune diabetes mellitus who tested negative for mutations in the common maturation-onset diabetes of the young (MODY) genes and without a history of transient neonatal diabetes. Positive patients were further analysed by combined loss of heterozygosity / comparative genomic hybridization analysis and by microsatellite analysis. Detailed clinical data were collected through the medical records of the treating hospitals.

RESULTS

Three patients with paternal uniparental isodisomy of chromosome 6q24 were identified. None presented with hyperglycaemia in the neonatal period. Characteristically, these patients were born small-for-gestational age, representing 27.2% of the 11 patients whose birth weight standard deviation score (SDS) for gestational age was below -2.0.

CONCLUSIONS

Abnormalities in the imprinted locus on chromosome 6q24 do not necessarily cause transient neonatal diabetes. Non-penetrant 6q24-related diabetes could be an underestimated cause of early-onset, non-autoimmune diabetes in patients who are not obese and born small-for-gestational age.

Coronary triglyceride deposition in contemporary advanced diabetics

It is of importance to clarify pathophysiology of diabetic heart diseases such as heart failure and coronary artery disease. We reported a novel clinical phenotype called triglyceride deposit cardiomyovasculopathy (TGCV), showing aberrant TG accumulation in both coronary arteries and myocardium, in a cardiac transplant recipient. Here, we examined autopsied diabetics for TG deposition in cardiovasculature. Consecutive series of hearts from advanced diabetes mellitus (DM) subjects (DM group: DMG, n = 20) and those from age- and sex-matched non-diabetic controls (non DM group: NDMG, n = 20) were examined. The diagnostic criteria of 'advanced DM' was made based on 2014 Clinical Practice Recommendations proposed by the American Diabetes Association. The mean duration of DM was 15.8 years. All DMG suffered from heart diseases including coronary artery diseases and 14 subjects had multi-vessel disease. Tissue TG contents were measured biochemically. Coronary arterial TG contents was significantly higher in DMG compared with NDMG. Spatial distribution of TG in transverse sections of coronary arteries showed TG deposition mainly in smooth muscle cells by Imaging Mass Spectrometry. Abundant TG deposition in coronary artery might be associated with advanced DM.

Molecular and clinical characterization of glucokinase maturity-onset diabetes of the young (GCK-MODY) in Japanese patients

AIMS

To investigate the molecular and clinical characteristics of the largest series of Japanese patients with glucokinase maturity-onset diabetes of the young (GCK-MODY), and to find any features specific to Asian people.

METHODS

We enrolled 78 Japanese patients with GCK-MODY from 41 families (55 probands diagnosed at the age of 0-14 years and their 23 adult family members). Mutations were identified by direct sequencing or multiplex ligation-dependent probe amplification of all exons of the GCK gene. Detailed clinical and laboratory data were collected on the probands using questionnaires, which were sent to the treating physicians.　Data on current clinical status and HbA1c levels were also collected from adult patients.

RESULTS

A total of 35 different mutations were identified, of which seven were novel. Fasting blood glucose and HbA1c levels of the probands were ≤9.3 mmol/l and ≤56 mmol/mol (7.3%), respectively, and there was considerable variation in their BMI percentiles (0.4-96.2). In total, 25% of the probands had elevated homeostatic assessment of insulin resistance values, and 58.3% of these had evidence of concomitant Type 2 diabetes in their family. The HbA1c levels for adults were slightly higher, up to 61 mmol/mol (7.8%). The incidence of microvascular complications was low. Out of these 78 people with GCK-MODY and 40 additional family members with hyperglycaemia whose genetic status was unknown, only one had diabetic nephropathy.

CONCLUSIONS

The molecular and clinical features of GCK-MODY in Japanese people are similar to those of other ethnic populations; however, making a diagnosis of GCK-MODY was more challenging in patients with signs of insulin resistance.

Intractable itch relieved by 4-phenylbutyrate therapy in patients with progressive familial intrahepatic cholestasis type 1

Background

Progressive familial intrahepatic cholestasis type 1 (PFIC1), an inherited liver disease caused by mutations in ATP8B1, progresses to severe cholestasis with a sustained intractable itch. Currently, no effective therapy has been established for PFIC1. Decreased function of the bile salt export pump (BSEP) in hepatocytes is suggested to be responsible for the severe cholestasis observed in PFIC1. We found a previously unidentified pharmacological effect of 4-phenylbutyrate (4PB) that increases the expression and function of BSEP. Here, we tested 4PB therapy in three patients with PFIC1.

Methods

The therapeutic potency of 4PB in these patients was tested by oral administration of this drug with gradually increasing dosage (200, 350, and 500 mg/kg/day) for 6 months. Biochemical, histological, and clinical data were collected.

Results

4PB therapy had no beneficial effect on the patients’ liver functions, as assessed by biochemical and histological analyses, despite an increase in hepatic BSEP expression. However, therapy with 4PB at a dosage of 350 or 500 mg/kg/day significantly relieved the intractable itch. Serum levels of potential pruritogens in cholestasis were much higher than the reference ranges during the 4PB therapy.

Conclusions

4PB therapy may be a new medication for patients with intractable cholestatic pruritus and may improve quality of life for patients and their families.

Peripheral leukocyte anomaly detected with routine automated hematology analyzer sensitive to adipose triglyceride lipase deficiency manifesting neutral lipid storage disease with myopathy/triglyceride deposit cardiomyovasculopathy

Adipose triglyceride lipase (ATGL) deficiency manifesting neutral lipid storage disease with myopathy/triglyceride deposit cardiomyovasculopathy presents distinct fat-containing vacuoles known as Jordans' anomaly in peripheral leucocytes. To develop an automatic notification system for Jordans' anomaly in ATGL-deficient patients, we analyzed circulatory leukocyte scattergrams on automated hematology analyzer XE-5000. The BASO-WX and BASO-WY values were found to be significantly higher in patients than those in non-affected subjects. The two parameters measured by automated hematology analyzer may be expected to provide an important diagnostic clue for homozygous ATGL deficiency.

Selective evaluation of high density lipoprotein from mouse small intestine by an in situ perfusion technique

The small intestine (SI) is the second-greatest source of HDL in mice. However, the selective evaluation of SI-derived HDL (SI-HDL) has been difficult because even the origin of HDL obtained in vivo from the intestinal lymph duct of anesthetized rodents is doubtful. To shed light on this question, we have developed a novel in situ perfusion technique using surgically isolated mouse SI, with which the possible filtration of plasma HDL into the SI lymph duct can be prevented. With the developed method, we studied the characteristics of and mechanism for the production and regulation of SI-HDL. Nascent HDL particles were detected in SI lymph perfusates in WT mice, but not in ABCA1 KO mice. SI-HDL had a high protein content and was smaller than plasma HDL. SI-HDL was rich in TG and apo AIV compared with HDL in liver perfusates. SI-HDL was increased by high-fat diets and reduced in apo E KO mice. In conclusion, with our in situ perfusion model that enables the selective evaluation of SI-HDL, we demonstrated that ABCA1 plays an important role in intestinal HDL production, and SI-HDL is small, dense, rich in apo AIV, and regulated by nutritional and genetic factors.

Improved liver function and relieved pruritus after 4-phenylbutyrate therapy in a patient with progressive familial intrahepatic cholestasis type 2

To examine the effects of 4-phenylbutyrate (4PB) therapy in a patient with progressive familial intrahepatic cholestasis type 2. A homozygous c.3692G>A (p.R1231Q) mutation was identified in ABCB11. In vitro studies showed that this mutation decreased the cell-surface expression of bile salt export pump (BSEP), but not its transport activity, and that 4PB treatment partially restored the decreased expression of BSEP. Therapy with 4PB had no beneficial effect for 1 month at 200 mg/kg/day and the next month at 350 mg/kg/day but partially restored BSEP expression at the canalicular membrane and significantly improved liver tests and pruritus at a dosage of 500 mg/kg/day. We conclude that 4PB therapy would have a therapeutic effect in patients with progressive familial intrahepatic cholestasis type 2 who retain transport activity of BSEP per se.

Disease-associated marked hyperalphalipoproteinemia

Marked hyperalphalipoproteinemia (HAL) is a heterogeneous syndrome. To clarify the pathophysiological significance of HAL, we compared clinical profiles between marked HAL subjects with and without cholesteryl ester transfer protein (CETP) deficiency. CETP deficiency was associated with cardiovascular diseases and strokes in the HAL population, particularly in female. HAL women without CETP deficiency tended to have higher prevalence with cancer history. HAL may not always be a longevity marker, but be sometimes accompanied with pathological conditions.

Genetic mutations in adipose triglyceride lipase and myocardial up-regulation of peroxisome proliferated activated receptor-γ in patients with triglyceride deposit cardiomyovasculopathy

Adipose triglyceride lipase (ATGL, also known as PNPLA2) is an essential molecule for hydrolysis of intracellular triglyceride (TG). Genetic ATGL deficiency is a rare multi-systemic neutral lipid storage disease. Information regarding its clinical profile and pathophysiology, particularly for cardiac involvement, is still very limited. A previous middle-aged ATGL-deficient patient in our institute (Case 1) with severe heart failure required cardiac transplantation (CTx) and exhibited a novel phenotype, "Triglyceride deposit cardiomyovasculopathy (TGCV)". Here, we tried to elucidate molecular mechanism underlying TGCV. The subjects were two cases with TGCV, including our second case who was a 33-year-old male patient (Case 2) with congestive heart failure requiring CTx. Case 2 was homozygous for a point mutation in the 5' splice donor site of intron 5 in the ATGL, which results in at least two types of mRNAs due to splicing defects. The myocardium of both patients (Cases 1 and 2) showed up-regulation of peroxisome proliferated activated receptors (PPARs), key transcription factors for metabolism of long chain fatty acids (LCFAs), which was in contrast to these molecules' lower expression in ATGL-targeted mice. We investigated the intracellular metabolism of LCFAs under human ATGL-deficient conditions using patients' passaged skin fibroblasts as a model. ATGL-deficient cells showed higher uptake and abnormal intracellular transport of LCFA, resulting in massive TG accumulation. We used these findings from cardiac specimens and cell-biological experiments to construct a hypothetical model to clarify the pathophysiology of the human disorder. In patients with TGCV, even when hydrolysis of intracellular TG is defective, the marked up-regulation of PPARγ and related genes may lead to increased uptake of LCFAs, the substrates for TG synthesis. This potentially vicious cycle of LCFAs could explain the massive accumulation of TG and severe clinical course for this rare disease.

Optimal serum phenylalanine for adult patients with phenylketonuria

High serum phenylalanine in adult patients with phenylketonuria (PKU) causes neuropsychological and psychosocial problems that can be resolved by phenylalanine-restricted diet. Therefore, PKU patients must continue to adhere to phenylalanine-restricted diet for life, although the optimal serum phenylalanine level in later life has yet to be established. The purpose of this review was to establish the optimal serum phenylalanine level in later life of PKU patients. We evaluated oxidative stress status, nitric oxide metabolism, cholesterol-derived oxysterols, vitamin D and bone status, and magnetic resonance imaging (MRI) in adult PKU patients according to serum phenylalanine level. Oxidative stress increased markedly at serum phenylalanine of 700-800 μmol/L. Serum phenylalanine higher than 700-850 μmol/L correlated with the disturbance of nitric oxide regulatory system. Adult PKU patients had poor vitamin D status and exhibited predominance of bone resorption over bone formation. In the brain, the levels of 24S-hydroxycholesterol, a marker of brain cholesterol elimination, were low at serum phenylalanine levels exceeding 650 μmol/L. MRI studies showed high signal intensity in deep white matter on T2-weighted and FLAIR images of PKU patients with serum phenylalanine greater than 500 μmol/L, with decreased apparent diffusion coefficients. Changes in most parameters covering the entire body organs in adult PKU were almost acceptable below 700-800 μmol/L of phenylalanine level. However, the optimal serum phenylalanine level should be 500 μmol/L or less in later life for the brain to be safe.

Immunological detection of large oxidized lipoproteins in hypertriglyceridemic serum

BACKGROUND

Triglyceride-rich, low-density lipoproteins (TG-rich LDL) have been reported as an oxidized lipoprotein species in patients with severe liver disease. Using TG-rich LDL as an immunogen, we obtained a monoclonal antibody (G11-6) that reacted with TG-rich LDL from patients with liver disease and with metal-oxidized LDL only in the early process of the oxidation reaction. This study determined the G11-6-reactive lipoproteins in hypertriglyceridemic serum.

METHODS

Serum samples from healthy volunteers (n = 12) and hypertriglyceridemic patients (n = 9) were fractionated by gel filtration and subjected to a sandwich enzyme-linked immunosorbent assay (ELISA) using G11-6 and polyclonal anti-apolipoprotein B antibodies.

RESULTS

Small LDL and larger lipoproteins reacted with G11-6. G11-6-reactive small LDL was identified in both the healthy subjects and hypertriglyceridemic patients, whereas G11-6-reactive larger lipoproteins were found only in the hypertriglyceridemic patients.

CONCLUSIONS

G11-6 is a useful tool for detecting increased large oxidized lipoproteins in hypertriglyceridemic patients.

Characteristics of NO cycle coupling with urea cycle in non-hyperammonemic carriers of ornithine transcarbamylase deficiency

Urea cycle deficient patients with prominent hyperammonemic often exhibit abnormal production of nitric oxide (NO), which reduces vascular tone, along with amino acid abnormalities. However, information related to the metabolic changes in heterozygotes of ornithine transcarbamylase deficiency (OTCD) lacking overt hyperammonemia is quite limited. We examined vascular mediators and amino acids in non-hyperammonemic heterozygotes. Twenty-four heterozygous OTCD adult females without hyperammonemic bouts, defined as non-hyperammonemic carriers, were enrolled. We measured blood amino acids constituting urea cycle and nitric oxide (NO) cycle. Blood concentrations of nitrate/nitrite (NOx) as stable NO-metabolites, asymmetric dimethylarginine (ADMA) inhibiting NO synthesis, and endothelin-1 (ET-1) raising vascular tone were also determined. NOx concentrations were significantly lower in non-hyperammonemic carriers (p < 0.01). However, ADMA and ET-1 levels in this group were comparable to those in the age-matched control group. Arginine and citrulline levels were also significantly lower in non-hyperammonemic carriers than in controls (p < 0.01). Of the 24 non-hyperammonemic carriers, 10 often developed headaches. Their daily NOx and arginine levels were significantly lower than those in headache-free carriers (p < 0.05). In three carriers receiving oral l-arginine, blood NOx concentrations were significantly higher. In two of those three, the occurrence of headaches was decreased. These results suggest that NO cycle coupling with the urea cycle is altered substantially even in non-hyperammonemic OTCD carriers, predisposing them to headaches.

Efficacy and safety of long-term, continuous subcutaneous octreotide infusion for patients with different subtypes of KATP-channel hyperinsulinism

OBJECTIVE

To evaluate the efficacy of long-term, continuous, subcutaneous octreotide infusion for congenital hyperinsulinism caused by mutations in the KATP-channel genes, KCNJ11 and ABCC8.

PATIENTS

Fifteen Japanese patients with diazoxide-unresponsive, KATP-channel hyperinsulinism.

METHODS

Molecular diagnoses were made by sequencing and multiple ligation-dependent probe amplification analysis. In patients with paternally inherited, monoallelic mutations, 18F-DOPA PET scans were performed to determine the location of the lesion. The patients were treated with continuous, subcutaneous octreotide infusion at a dosage of up to 25 μg/kg/day, using an insulin pump to maintain blood glucose levels higher than 3.33 mmol/l. Additional treatments (IV glucose, glucagon or enteral feeding) were administered as needed. The efficacy of the treatment was assessed in patients who received octreotide for 4 months to 5.9 years.

RESULTS

Three patients had biallelic mutations, and 12 had monoallelic, paternally inherited mutations. Four patients with monoallelic mutations showed diffuse 18F-DOPA uptake, whereas seven patients showed focal uptake. Octreotide was effective in all the patients. The patients with biallelic mutations required a higher dosage (17-25 μg/kg/day), and two patients required additional treatments. By contrast, the patients with monoallelic mutations required a lower dosage (0.5-21 μg/kg/day) irrespective of the PET results and mostly without additional treatments. Treatment was discontinued in three patients at 2.5, 3.3 and 5.9 years of age, without psychomotor delay. Except for growth deceleration at a higher dosage, no significant adverse effects were noted.

CONCLUSIONS

Long-term, continuous, subcutaneous octreotide infusion is a feasible alternative to surgery especially for patients with monoallelic KATP-channel mutations.

Sustained high plasma mannose less sensitive to fluctuating blood glucose in glycogen storage disease type Ia children

Plasma mannose is suggested to be largely generated from liver glycogen-oriented glucose-6-phosphate. This study examined plasma mannose in glycogen storage disease type Ia (GSD Ia) lacking conversion of glucose-6-phosphate to glucose in the liver. We initially examined fasting--and postprandial 2 h--plasma mannose and other blood carbohydrates and lipids for seven GSD Ia children receiving dietary interventions using cornstarch and six healthy age-matched children. Next, one-day successive intra-individual parameter changes were examined for six affected and two control children. Although there were no significant differences in fasting--and postprandial 2 h--glucose and insulin levels, the mannose level of the affected group was invariably much higher than that of the control group (p < 0.001): the fasting level of the affected group was about two-fold that of the control group; the postprandial-2 h level remained almost unchanged in the affected group, although it was one-half of the fasting level in the control group. Inter-individual analyses revealed that the GSD Ia group mannose level was significantly and positively correlated with lactate and triglycerides levels at both time points (p < 0.01). In each control, mannose levels fluctuated greatly, maintaining strong and significant negative correlations with glucose and insulin levels (p < 0.001). Correlations were lower or nonexistent in GSD Ia children. In individuals with high lactate and triglycerides levels, strikingly high mannose levels never changed against glucose and insulin fluctuations. Plasma mannose is less sensitive to blood glucose and insulin in GSD Ia children. Its basal level and the fluctuation pattern differ by their metabolic activity.

Oxysterol changes along with cholesterol and vitamin D changes in adult phenylketonuric patients diagnosed by newborn mass-screening

BACKGROUND

Phenylketonuria (PKU) possibly leads to hypocholesterolemia and lowered vitamin D (VD) status. Metabolism of oxysterols linking with those of cholesterol and VD has never been examined in PKU.

METHODS

Blood oxysterols along with blood phenylalanine, lipids and VD were examined for 33 PKU adults aged 21-38 years and 20 age-matched healthy controls.

RESULTS

Total- and low-density cholesterols, and 25-hydroxy VD(3) were decreased significantly in the PKU group (cholesterols, 10% decrease; 25-hydroxy VD(3) 35% decrease vs. the control group). 24S-hydroxycholesterol (24S-OHC) eliminating brain cholesterol, and 27-OHC and 7α-hydroxycholesterol (7α-OHC) representing peripheral and hepatic cholesterol elimination, respectively, were significantly decreased in PKU group: 24S-OHC, 25% decrease, p<.01; 27-OHC and 7α-OHC, 35-40% decrease, p<.001. 7β-Hydroxycholesterol (7β-OHC) reflecting oxidative stress was increased significantly in PKU group (p<.05). 7α-OHC and 27-OHC levels in PKU group always showed similar values, regardless of other parameters while the 24S-OHC and 7β-OHC levels decreased and increased, respectively, showing significant correlations with phenylalanine level (p<.005). 27-OHC level showed a significant positive correlation with the 25-hydroxy VD(3) level in this group (p<.001).

CONCLUSION

Blood oxysterol changes predominate over blood cholesterol changes and influence on VD status in adult PKU patients.

Fatty liver and anti-oxidant enzyme activities along with peroxisome proliferator-activated receptors γ and α expressions in the liver of Wilson's disease

BACKGROUND

The mechanisms of liver damage and steatosis in Wilson's disease (WD) presenting accumulation of copper generating oxidants remain unclear. Recent studies have shown that peroxisome proliferator-activated receptors (PPARs), in particular PPARs α and γ, regulate fat content of the liver together with the anti-oxidant and anti-inflammation systems. However, such PPARs have never been studied in WD.

METHODS

We examined PPARs along with the liver damage and steatosis of WD using liver specimens from affected patients exhibiting mild liver damage (group I, n = 5), moderate or greater liver damage (group II, n = 10) and fulminant hepatic failure (group III, n = 5), and from asymptomatic carriers (group H, n = 4).

RESULTS

PPAR α expression was increased over the control levels in groups H and I but was decreased in groups II and III in parallel with the progression of liver damage (group H = I>II>III). PPAR γ expression was inversely increased (group H<I<II<III). Mn-dependent superoxide dismutase (Mn-SOD), CuZn-SOD, and catalase activities were decreased in the affected three groups, and were increased in group H. Among group II exhibiting substantial inter-individual variances in parameters, the severity of steatosis showed a significant positive correlation with PPAR γ expression (p<0.001) but not PPAR α expression. CuZn-SOD activity was positively correlated with PPARα expression (p<0.05) but not PPAR γ expression.

CONCLUSION

These results suggest that changes of PPARs γ and α are associated with the steatosis and the impairment of anti-oxidant system in the liver of WD.

Novel monoclonal antibody recognizing triglyceride-rich oxidized LDLs associated with severe liver disease and small oxidized LDLs in normal subjects

Background

Triglyceride-rich low-density lipoproteins (TG-rich LDLs) in the plasma of patients with severe liver disease are reported to change macrophages into foam cells in vitro.

Methods

Male BALB/c mice were immunized with TG-rich LDLs isolated from the plasma of a patient with severe liver disease. The resulting monoclonal antibody (G11-6) was used in a sandwich enzyme-linked immunosorbent assay (ELISA) in combination with polyclonal anti-apolipoprotein B antibodies. The time course of copper-mediated LDL oxidation was monitored using this ELISA. The results were compared with those of the two commercial ELISAs for oxidized LDLs using DLH or ML25, thiobarbituric acid reactive substances and the optical absorbance for the conjugated dienes generated in lipid peroxides. Furthermore, the lipoprotein fractions separated by gel filtration were tested with this ELISA in healthy volunteers ( n = 11) and patients ( n = 3) with liver disease.

Results

G11-6 reacted with oxidized LDLs during only the early phase of copper oxidation, being distinct from the other monoclonal antibodies and methods. G11-6 was confirmed to react with TG-rich LDLs in patients, while it reacted with small LDL particles in normal controls.

Conclusions

The monoclonal antibody G11-6 is useful for detecting oxidized small LDLs in normal controls and oxidized TG-rich LDLs in patients with severe liver disease.

AP2 adaptor complex mediates bile salt export pump internalization and modulates its hepatocanalicular expression and transport function

The bile salt export pump (BSEP) mediates the biliary excretion of bile salts and its dysfunction induces intrahepatic cholestasis. Reduced canalicular expression of BSEP resulting from the promotion of its internalization is one of the causes of this disease state. However, the molecular mechanism underlying BSEP internalization from the canalicular membrane (CM) remains unknown. We have shown previously that 4-phenylbutyrate (4PBA), a drug used for ornithine transcarbamylase deficiency (OTCD), inhibited internalization and subsequent degradation of cell-surface-resident BSEP. The current study found that 4PBA treatment decreased significantly the expression of α- and μ2-adaptin, both of which are subunits of the AP2 adaptor complex (AP2) that mediates clathrin-dependent endocytosis, in liver specimens from rats and patients with OTCD, and that BSEP has potential AP2 recognition motifs in its cytosolic region. Based on this, the role of AP2 in BSEP internalization was explored further. In vitro analysis with 3×FLAG-human BSEP-expressing HeLa cells and human sandwich-culture hepatocytes indicates that the impairment of AP2 function by RNA interference targeting of α-adaptin inhibits BSEP internalization from the plasma membrane and increases its cell-surface expression and transport function. Studies using immunostaining, coimmunoprecipitation, glutathione S-transferase pulldown assay, and time-lapse imaging show that AP2 interacts with BSEP at the CM through a tyrosine motif at the carboxyl terminus of BSEP and mediates BSEP internalization from the CM of hepatocytes.

CONCLUSION

AP2 mediates the internalization and subsequent degradation of CM-resident BSEP through direct interaction with BSEP and thereby modulates the canalicular expression and transport function of BSEP. This information should be useful for understanding the pathogenesis of severe liver diseases associated with intrahepatic cholestasis.

Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

BACKGROUND

In Asians, mutations in the known maturity-onset diabetes of the young (MODY) genes have been identified in only <15% of patients. These results were obtained mostly through studies on adult patients.

OBJECTIVE

To investigate the molecular basis of Japanese patients with pediatric-onset MODY-type diabetes.

SUBJECTS

Eighty Japanese patients with pediatric-onset MODY-type diabetes.

METHODS

Mitochondrial 3243A>G mutation was first tested by the polymerase chain reaction restriction fragment length polymorphism analysis for maternally inherited families. Then, all coding exons and exon-intron boundaries of the HNF1A, HNF1B, GCK, and HNF4A genes were amplified from genomic DNA and directly sequenced. Multiplex ligation-dependent probe amplification analysis was also performed to detect whole-exon deletions.

RESULTS

After excluding one patient with a mitochondrial 3243A>G, mutations were identified in 38 (48.1%) patients; 18 had GCK mutations, 11 had HNF1A mutations, 3 had HNF4A mutations, and 6 had HNF1B mutations. In patients aged <8 yr, mutations were detected mostly in GCK at a higher frequency (63.6%). In patients >9 yr of age, mutations were identified less frequently (45.1%), with HNF1A mutations being the most frequent. A large fraction of mutation-negative patients showed elevated homeostasis model assessment (HOMA) insulin-resistance and normal HOMA-β indices. Most of the HNF1B mutations were large deletions, and, interestingly, renal cysts were undetectable in two patients with whole-gene deletion of HNF1B.

CONCLUSION

In Japanese patients with pediatric-onset MODY-type diabetes, mutations in known genes were identified at a much higher frequency than previously reported for adult Asians. A fraction of mutation-negative patients presented with insulin-resistance and normal insulin-secretory capacities resembling early-onset type 2 diabetes.

Cross-sectional study of bone metabolism with nutrition in adult classical phenylketonuric patients diagnosed by neonatal screening

The mechanism underlying the development of osteopenia or osteoporosis in longstanding phenylketonuria (PKU) remains to be clarified. We investigated the details of bone metabolism in 21 female and 13 male classical PKU patients aged 20-35 years. Vitamin D (VD), parathyroid hormone (PTH), bone turnover markers, and daily nutrient intake were examined. The patients had lower daily energy and protein intake than did the age-matched controls (22 women, 14 men), but their respective fat, VD, and calcium intake did not differ. Serum 1,25-dihydroxy VD and 25-hydroxy VD levels in female and male patient groups were significantly higher and lower than those in respective control groups (females, P < 0.001; males, P < 0.05 and P < 0.01, respectively). Serum intact PTH levels were significantly higher in the female patient group (P < 0.05). Urinary calcium levels in the patient groups were significantly higher than those of the control subjects (females, P < 0.001; males, P < 0.05). Bone resorption markers were significantly higher in patients than in controls, although bone formation markers were not different. Patient serum levels of osteoprotegerin-inhibiting bone resorption were significantly lower (females, P < 0.001; males, P < 0.01). None of the bone parameters correlated significantly with serum phenylalanine or nutrient intake. PKU patients exhibited lower VD status and more rapid bone resorption despite normal calcium-VD intakes.

Experimental evidence that phenylalanine is strongly associated to oxidative stress in adolescents and adults with phenylketonuria

Few studies have looked at optimal or acceptable serum phenylalanine levels in later life in patients with phenylketonuria (PKU). This study examined the oxidative stress status of adolescents and adults with PKU. Forty PKU patients aged over fifteen years were enrolled, and were compared with thirty age-matched controls. Oxidative stress markers, anti-oxidant enzyme activities in erythrocytes, and blood anti-oxidant levels were examined. Nitric oxide (NO) production was also examined as a measure of oxidative stress. Plasma thiobarbituric acid reactive species and serum malondialdehyde-modified LDL levels were significantly higher in PKU patients than control subjects, and correlated significantly with serum phenylalanine level (P<0.01). Plasma total anti-oxidant reactivity levels were significantly lower in the patient group, and correlated negatively with phenylalanine level (P<0.001). Erythrocyte superoxide dismutase and catalase activities were higher and correlated significantly with phenylalanine level (P<0.01). Glutathione peroxidase activity was lower and correlated negatively with phenylalanine level (P<0.001). The oxidative stress score calculated from these six parameters was significantly higher in patients with serum phenylalanine of 700-800 μmol/l. Plasma anti-oxidant substances, beta-carotene, and coenzyme Q(10) were also lower (P<0.001), although the decreases did not correlate significantly with the phenylalanine level. Serum nitrite/nitrate levels, as stable NO products, were higher together with low serum asymmetric dimethylarginine, as an endogenous NO inhibitor. Oxidative stress status is closely linked with serum phenylalanine levels. Phenylalanine level in should be maintained PKU below 700-800 μmol/l even in adult patients.

CD36 deficiency predisposing young children to fasting hypoglycemia

Fatty acid (FA) β-oxidation defects cause hypoglycemia. Our aim was to determine if CD36--a membrane transporter for long-chain FAs--deficiency predisposes children to hypoglycemia. After overnight fasting, we measured parameters for carbohydrate and FA metabolisms at 12-, 14-, and 16-hour fasting points in 51 preschool children with histories of episodic hypoglycemia and 49 age-matched healthy controls. Simultaneously, the expressions of CD36 on platelets and monocytes were examined to determine the phenotypes. Six of the 51 hypoglycemic children and none of the 49 control children were diagnosed as having type I CD36 deficiency. Four and 3 children were diagnosed as having type II CD36 deficiency, respectively. Hypoglycemia was often recurrent in the type I CD36 group. At any fasting point, the type I CD36 group showed significantly lower blood glucose and insulin concentrations than the other groups: glucose, P < .001 vs control group and P < .01 or P < .001 vs type II/wild-type CD36 hypoglycemic groups; insulin, P < .001 vs control group and P < .01 vs type II/wild-type CD36 hypoglycemic groups. Free FA concentration in the type I group was always 1.5- to 2.0-fold higher than that in the other groups, whereas the total ketone body concentration was consistently about two thirds of that in the other groups. Among the type II, wild-type, and control groups, there were no significant differences in the parameters except that the wild-type group showed significantly lower FFA concentration (P < .05). These results suggested that type I CD36 deficiency but not type II CD36 deficiency predisposes preschool children to hypoglycemia.

Molecular and clinical analysis of Japanese patients with persistent congenital hyperinsulinism: predominance of paternally inherited monoallelic mutations in the KATP channel genes

BACKGROUND

Preoperative identification of the focal form of congenital hyperinsulinism is important for avoiding unnecessary subtotal pancreatectomy. However, neither the incidence nor the histological spectrum of the disease is known for Japanese patients.

AIMS

The aim of the study was to elucidate the molecular and histological spectrum of congenital hyperinsulinism in Japan.

SUBJECTS

Thirty-six Japanese infants with persistent congenital hyperinsulinism were included in the study.

METHODS

All exons of the ATP-sensitive potassium channel (K(ATP) channel) genes (KCNJ11 and ABCC8), the GCK gene, and exons 6 and 7 and 10-12 of the GLUD1 gene were amplified from genomic DNA and directly sequenced. In patients with K(ATP) channel mutations, the parental origin of each mutation was determined, and the results were compared with the histological findings of surgically treated patients. In one of the patients with scattered lesions, islets were sampled by laser capture microdissection for mutational analysis.

RESULTS

Mutations were identified in 24 patients (66.7%): five in GLUD1 and 19 in the K(ATP) channel genes. Sixteen had a paternally derived, monoallelic K(ATP) channel mutation predictive of the focal form. In 10 patients who underwent pancreatectomy, the molecular diagnosis correctly predicted the histology, more accurately than [18F]-3,4-dihydroxyphenylalanine positron emission tomography scans. Three patients showed focal lesions that occupied larger areas of the pancreas. Preferential loss of the maternal allele was observed in these islets.

CONCLUSION

The majority of the Japanese patients with K(ATP) channel hyperinsulinism (84.2%) demonstrated paternally inherited monoallelic mutations that accurately predicted the presence of the focal form.

Favorable effect of 4-phenylacetate on liver functions attributable to enhanced bile salt export pump expression in ornithine transcarbamylase-deficient children

4-Phenylbutyrate (4-PB) acting against hyperammonemia has been administered to patients with urea cycle defects. Results of our recent experiments using animals and cultured cells strongly suggest that this agent enhances the function of bile salt export pump/ATP binding cassette B11 (BSEP/ABCB11) promoting bile acid excretion from hepatocytes to bile canaliculi, although it has not been confirmed in humans. Considering that 4-PB is converted easily into 4-phenylacetate (4-PA) in the liver, such an effect of 4-PB might occur through 4-PA. We performed retrospective analyzes of the effects of 4-PA on the liver functions of three ornithine transcarbamylase (OTC)-deficient female children receiving 4-PA. Two of the three received intravenous administration of 4-PA only at episodic periods of hyperammonemia; the remaining one received it orally at intercurrent periods. Soon after 4-PA administration, the serum total bile acid level was decreased to one-half or one-third of pre-treatment levels, but it returned to the basal levels within one month after 4-PA discontinuation. Other serum parameters for cholestasis such as gamma-glutamyl transferase also decreased markedly. Concomitantly, alanine aminotransferase and aspartate amino transferase levels decreased significantly. Western blot analyzes of the liver samples revealed that the 4-PA administration enhanced BSEP/ABCB11 protein expressions in the membranous fraction of liver cells, although the liver BSEP/ABCB11 messenger RNA level remained unchanged. These results suggest that 4-PA enhanced liver BSEP/ABCB11 function and thereby improved liver functions in OTC-deficient children. For treatment of liver disorders requiring enhancement of BSEP function, 4-PA might be a candidate.

Altered metabolisms of mediators controlling vascular function and enhanced oxidative stress in asymptomatic children with congenital portosystemic venous shunt

Children with congenital portosystemic venous shunt (PSVS) are at risk for developing pulmonary hypertension, irrespective of the severity of portal hypertension or liver damage. Altered metabolisms of nitric oxide (NO) and endothelin-1 (ET-1), which are linked with oxidative stress and control vascular tone, might contribute to the vascular disturbance. This study examined 14 children (aged 1-5 years) with congenital PSVS lacking major liver damage and portal hypertension. Serum levels of nitrite/nitrate (NOx) as stable metabolites of NO, and of asymmetric dimethylarginine (ADMA) as an endogenous NO synthase inhibitor were determined, along with the plasma level of ET-1. Oxidative stress, which might affect the production of such mediators, was also examined using specific urinary and blood markers. The NOx levels were significantly lower in affected children than in the age-matched control group, although ET-1 levels were significantly higher than the control levels. In the affected children, the ADMA levels and ADMA/NOx ratios were higher, respectively, by 30% and 130% and showed significant positive correlations with the shunt ratios. Oxidative stress markers, including plasma thiobarbiturate reactive substances and urinary acrolein-lysine and 8-hydroxy-2'-deoxyguanosine, were significantly higher in affected children than in the control group, consistent with them being subjected to enhanced oxidative stress. These results suggest the presence of altered metabolisms of vascular mediators and enhanced oxidative stress in asymptomatic preschool children with congenital PSVS.

Children's toxicology from bench to bed--Liver Injury (3): Oxidative stress and anti-oxidant systems in liver of patients with Wilson disease

The role of oxidative stress in the pathogenesis of liver disease in Wilson disease (WD), a genetic disorder characterized by excess hepatic deposition of copper, which generates free radicals, remains unclear. This study investigates oxidative stress on the liver and hepatic anti-oxidant responses in WD using liver specimens from affected patients showing mild liver damage (group I, n = 3), moderate or greater liver damage (group II, n = 5) and fulminant hepatic failure (group III, n = 5), and from asymptomatic carriers (n = 2). Decreased ratios of reduced glutathione (GSH) to oxidized glutathione (GSSG) and increased thiobarbituric acid reactive substance (TBARS), a lipid peroxidation product, were found in every affected patient, especially in groups II and III patients. Activities and protein expressions of Mn-dependent superoxide dismutase (Mn-SOD), CuZn-SOD, and catalase were decreased in all patients, especially in group III patients. Glutathione peroxidase activity was decreased only in group III patients. Asymptomatic carriers without any clinical manifestations showed normal TBARS level and GSH/GSSG ratio with increases in both GSH and GSSG levels. Their CuZn-SOD, Mn-SOD and catalase activities were increased. These results suggest that excessive copper-derived oxidants contribute to development and progression of liver disease in WD.