Renal Function in Aged C57BL/6J Mice Is Impaired by Deposition of Age-Related Apolipoprotein A-II Amyloid Independent of Kidney Aging.

Spontaneous and age-related amyloidosis has been reported in C57BL/6J mice. However, the biochemical characteristics of age-related amyloidosis remain unclear. Herein, the age-related prevalence of amyloidosis, the types of amyloid fibril proteins, and the effects of amyloid deposition were investigated in renal function in C57BL/6J mice. The results obtained revealed a high incidence of amyloidosis in C57BL/6J mice originating from The Jackson Laboratory as well as the deposition of large amounts of amyloid in the glomeruli of aged mice. The amyloid fibril protein was identified as wild-type apolipoprotein A-II (ApoA-II). Induction of amyloid deposition in 40-week-old mice, equivalent to that of spontaneous development in 80-week-old mice, to rule out the effects of aging, revealed subsequent damage to kidney function by amyloid deposits. Furthermore, amyloid deposition in the mesangial region decreased podocyte density, compromised foot processes, and led to the accumulation of fibroblast growth factor 2 in glomeruli. Collectively, these results suggest that ApoA-II deposition is a general pathology in aged C57BL/6J mice and is dependent on supplier colonies. Therefore, the effects of age-related amyloid deposition need to be considered in research on aging in mice.

Enterocolic granulomatous phlebitis associated with epidermal growth factor-containing fibulin-like extracellular matrix protein 1 deposition and focal amyloid properties: A case report.

A woman in her 60s with rheumatoid arthritis was admitted with fever and abdominal pain. Laparoscopic examination with the differential diagnosis of peritoneal neoplasm and infection revealed granulomatous phlebitis in the resected greater omentum. Amorphous eosinophilic deposits observed in the resected tissue exhibited focal, weak positivity for Congo red but were strongly positive for thioflavin S, confirming their focal amyloid properties. Marked degeneration of elastic fibers was also evident. Electron microscopy revealed deposits around the affected elastic fibers. Immunohistochemistry revealed the deposition of epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) along with T-cell-predominant lymphocytic inflammation. The definitive diagnosis was granulomatous enterocolic lymphocytic phlebitis (ELP) associated with EFEMP1 deposition exhibiting focal amyloid properties (EFEMP1/AEFEMP1), supported by proteomics analysis. This type of vasculitis is similar to amyloid-ß-related angiitis of the central nervous system. Thus, we speculate that granulomatous ELP also results from an immune response that recognizes EFEMP1/AEFEMP1 deposits as foreign material and attempts to remove them. Confirmation of EFEMP1/AEFEMP1 deposition with Congo red staining is challenging, particularly in the presence of inflammation, and warrants comprehensive evaluation.

Amyloid-Forming Corpora Amylacea and Spheroid-Type Amyloid Deposition: Comprehensive Analysis Using Immunohistochemistry, Proteomics, and a Literature Review.

This study aimed to elucidate the similarities and differences between amyloid-forming corpora amylacea (CA) in the prostate and lung, examine the nature of CAs in cystic tumors of the atrioventricular node (CTAVN), and clarify the distinctions between amyloid-forming CA and spheroid-type amyloid deposition. We conducted proteomics analyses using liquid chromatography-tandem mass spectrometry with laser microdissection and immunohistochemistry to validate the characteristics of CAs in the lung and prostate. Our findings revealed that the CAs in these organs primarily consisted of common proteins (ß2-microglobulin and lysozyme) and locally produced proteins. Moreover, we observed a discrepancy between the histopathological and proteomic analysis results in CTAVN-associated CAs. In addition, while the histopathological appearance of the amyloid-forming CAs and spheroid-type amyloid deposits were nearly identical, the latter deposition lacked ß2-microglobulin and lysozyme and exhibited evident destruction of the surrounding tissue. A literature review further supported these findings. These results suggest that amyloid-forming CAs in the lung and prostate are formed through a shared mechanism, serving as waste containers (wasteosomes) and/or storage for excess proteins (functional amyloids). In contrast, we hypothesize that while amyloid-forming CA and spheroid-type amyloid deposits are formed, in part, through common mechanisms, the latter are pathological.

Anterior horn damage in brachial multisegmental amyotrophy with superficial siderosis and dural tear: an autopsy case report.

BACKGROUND: Patients with superficial siderosis (SS) rarely show brachial multisegmental amyotrophy with ventral intraspinal fluid collection accompanied with dural tear. CASE PRESENTATION: We describe spinal cord pathology of a 58-year-old man who developed brachial multisegmental amyotrophy with ventral intraspinal fluid collection from the cervical to lumbar spinal levels accompanied with SS, dural tear, and snake-eyes appearance on magnetic resonance imaging (MRI). Radiological and pathological analyses detected diffuse and prominent superficial deposition of hemosiderin in the central nervous system. Snake-eyes appearance on MRI expanded from the C3 to C7 spinal levels without apparent cervical canal stenosis. Pathologically, severe neuronal loss at both anterior horns and intermediate zone was expanded from the upper cervical (C3) to middle thoracic (Th5) spinal gray matter, and these findings were similar to compressive myelopathy. CONCLUSION: Extensive damage of the anterior horns in our patient may be due to dynamic compression induced by ventral intraspinal fluid collection.

Light and heavy chain deposition disease with focal amyloid deposition diagnosed with mass spectrometry: a case report.

BACKGROUND: Light and heavy chain deposition disease (LHCDD) is a rare condition characterised by the deposition of immunoglobulin components in the kidneys. Similarly, Amyloidosis is also caused by the deposition of light chain and/or heavy chain components of immunoglobulins which are folded into amyloid fibrils characterised by Congophilic deposits that exhibit apple-green birefringence under polarised light. Only a handful of reports describing LHCDD with amyloid fibril deposition have been previously published, however, none have characterized the composition of the deposited immunoglobulin components via mass spectrometry. CASE PRESENTATION: We report a case of a 79-year-old Japanese woman with nephrotic syndrome. Bone marrow aspiration revealed a slight proliferation of plasma cells (under 10%). Immunofluorescence assessment of renal biopsy showed amyloid-like deposits in the glomerulus that were positive for IgA and kappa. Further, the Congo red staining of the deposits was faintly positive, and only a slight birefringence was detected. Electron microscopy confirmed fine fibrillar structures and non-amyloid deposits. Finally, mass spectrometry revealed that the deposits were composed of abundant amounts of light chain with small amounts of heavy chain. Therefore, the patient was diagnosed with LHCDD and focal amyloid deposition. Chemotherapy was subsequently initiated, which resulted in haematological and renal response. Under polarised light, faint birefringence with Congo red staining and periodic acid-methenamine silver positivity indicated that the deposits were mostly non-amyloid fibrils with a small component of amyloid fibrils. Generally, the diagnosis of heavy- and light-chain amyloidosis is defined by greater heavy chain deposition compared to the light chain. However, in our case, contrary to the definition, the light-chain deposition was far greater than that of the heavy-chain. CONCLUSIONS: This is the first case of LHCDD with focal amyloid deposition diagnosed by analysing the glomerular deposits by mass spectrometry.

Variables for differential diagnosis of familial Mediterranean fever: multiple correspondence analysis of a large Japanese cohort.

OBJECTIVES: We investigated differential diagnoses that should be noted with familial Mediterranean fever (FMF) and useful variables for differentiation in a large Japanese cohort. METHODS: Patients aged ≥13 years who were clinically suspected of having FMF by Livneh criteria were studied 1 year after MEFV genetic testing. Patients ultimately diagnosed with other diseases were studied, and the association among each disease, patient characteristics, and clinical variables were analyzed using multiple correspondence analysis. RESULTS: In total, 504 patients were included in this study; 34 (6.7%) were diagnosed with a disease other than FMF. The most common diagnosis was Behçet's disease, followed by periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome, inflammatory bowel disease, myelodysplastic syndromes (MDS), and infectious diseases. Although none of the non-FMF patients had exon 10 variants, some responded to colchicine treatment. Multiple correspondence analysis suggested that atypical symptoms such as stomatitis were associated with Behçet's disease and PFAPA syndrome, whereas characteristic situations such as disease onset ≥40 years were associated with MDS and infectious diseases. CONCLUSION: Careful follow-ups and reanalysis of the diagnosis should be performed for patients with atypical findings and no exon 10 variants, even if their symptoms meet the clinical criteria for FMF.

Analysis of daily energy, protein, fat, and carbohydrate intake in citrin-deficient patients: Towards prevention of adult-onset type II citrullinemia.

Patients with citrin deficiency during the adaptation/compensation period exhibit diverse clinical features and have characteristic diet of high protein, high fat, and low carbohydrate. Japanese cuisine typically contains high carbohydrate but evaluation of diet of citrin-deficient patients in 2008 showed a low energy intake and a protein:fat:carbohydrate (PFC) ratio of 19:44:37, which indicates low carbohydrate consumption rate. These findings prompted the need for diet intervention to prevent the adult onset of type II citrullinemia (CTLN2). Since the publication of the report about 10 years ago, patients are generally advised to eat what they wish under active dietary consultation and intervention. In this study, citrin-deficient patients and control subjects living in the same household provided answers to a questionnaire, filled-up a maximum 6-day food diary, and supplied physical data and information on medications if any. To study the effects of the current diet, the survey collected data from 62 patients and 45 controls comparing daily intakes of energy, protein, fat, and carbohydrate. Food analysis showed that patient's energy intake was 115% compared to the Japanese standard. The confidence interval of the PFC ratio of patients was 20-22:47-51:28-32, indicating higher protein, higher fat and lower carbohydrate relative to previous reports. The mean PFC ratio of female patients (22:53:25) was significantly different from that of male patients (20:46:34), which may explain the lower frequency of CTLN2 in females. Comparison of the present data to those published 10 years ago, energy, protein, and fat intakes were significantly higher but the amount of carbohydrate consumption remained the same. Regardless of age, most patients (except for adolescents) consumed 100-200 g/day of carbohydrates, which met the estimated average requirement of 100 g/day for healthy individuals. Finally, patients were generally not overweight and some CTLN2 patients were underweight although their energy intake was higher compared with the control subjects. We speculate that high-energy of a low carbohydrate diet under dietary intervention may help citrin-deficient patients attain normal growth and prevent the onset of CTLN2.

Development of diagnostic antibodies against immunoglobulin heavy chain variable region for heavy chain amyloidosis (AH amyloidosis).

It is difficult to diagnose immunoglobulin heavy chain amyloidosis (AH amyloidosis) without proteomic analysis due to no useful diagnostic antibodies. The aim of this study was to develop diagnostic antibodies available to immunohistochemistry and immunoblotting. Two rabbit anti-heavy chain variable region antibodies were generated and evaluated in immunohistochemical studies performed on 11 AH amyloidosis patients and 64 patients with other systemic amyloidoses. Additionally, immunoblotting was performed using extracted amyloid protein from one patient and serum samples from two patients with AH amyloidosis. Immunohistochemical analysis generated a positive outcome in 10 of 11 AH amyloidosis patients (sensitivity 90.9%). While positive staining was also observed in 9 of 64 non-AH amyloidosis patients (specificity 85.9%), substitution of the blocking agent reversed the positive reactivity in 5 of 9 patients. Amyloid protein band was clearly detected via immunoblotting analysis, and protein bands with similar molecular weights of amyloid protein were observed in serum samples from patients with AH amyloidosis. The two antibodies may represent a powerful diagnostic tool for AH amyloidosis. In addition, our data revealed the existence of amyloidogenic variable region fragments in the serum of patients, suggesting their potential as diagnostic markers for AH amyloidosis.

Distribution of amyloidosis subtypes based on tissue biopsy site - Consecutive analysis of 729 patients at a single amyloidosis center in Japan.

This study was performed to elucidate the distribution of amyloidosis subtypes based on tissue biopsy site. Samples obtained from 729 consecutive patients with amyloidosis were analyzed by immunohistochemical staining (IHC) and supplemental mass spectrometry (MS). The correlations between the type of organs from which samples were obtained and amyloidosis subtypes were investigated retrospectively. Among the patients, 95.1% were diagnosed by IHC and 4.9% were diagnosed by MS. The distribution of amyloidosis subtypes was as follows: AL, 59.1%; ATTR, 32.9%; AA, 4.0%; AH, 1.4%; Aß2M, 0.8%; and others, 0.9%. AL was the most common subtype in most organs, including the liver, lung, kidney, lower urinary tract, bone marrow, gastrointestinal tract, and skin/subcutaneous tissue. ATTR was the most common subtype in the heart, carpal tunnel, and peripheral nerves. AH was the second most common subtype in renal biopsy. Three or more amyloidosis subtypes were detected in each organ. In conclusion, AL was the most common subtype in most biopsy sites except the heart, carpal tunnel, and peripheral nerve, in which ATTR was more common. Because several types of amyloidogenic protein were detected in each organ, amyloid typing must be pursued, no matter the site from where biopsy was obtained.

Triggering factors for febrile attacks in Japanese patients with familial Mediterranean fever.

OBJECTIVES: We occasionally encounter patients with familial Mediterranean fever (FMF) whose attacks are triggered by specific factors; however, information regarding these factors is limited. Our purpose was to identify the factors that trigger febrile attacks in Japanese patients with FMF. METHODS: Our retrospective study included 372 patients (229 women, 143 men) with FMF, who were diagnosed between April 2007 and June 2018. We retrospectively investigated clinical features, genetic variants, and the factors that the patients perceived to have triggered their attacks. Patients completed a questionnaire that included the following triggering factors, anxiety, psychological stress, tiredness, excitement, environmental change, and menstruation. RESULTS: Of 372 patients, 180 (49.4%) reported some triggering factors. Psychological stress and tiredness were commonly reported factors regardless of sex; however, menstruation (39.7%, n=91) was the most commonly reported triggering factor in female patients with FMF. Menstrual-related patients had a younger age of onset and diagnosis, a higher frequency of peritonitis, and a higher rate of patients with endometriosis compared with the non-menstrual-related patients. CONCLUSIONS: Gaining an understanding of these triggering factors could help to reduce attacks and educate the patients. Clinicians may need to consider FMF for patients who have fever and serositis that occurs with every menstrual period.

Late-onset familial Mediterranean fever in Japan.

Objectives: Most patients with familial Mediterranean fever (FMF) have their first attack at age < 20 years. Information about late-onset (age ≥40 years) FMF is limited. We aimed to evaluate the demographic, clinical, and genetic characteristics of late-onset FMF patients in the Japanese population.Methods: We retrospectively analyzed 292 patients with FMF. Patients were divided into three groups according to age of disease onset: Group I, ≤19 years; Group II, 20-39 years; and Group III, ≥40 years.Results: Of 292 patients, 44 (15.1%) experienced their first attack at age ≥40 years. While high fever (97.7%) and arthritis (45.5%) were common symptoms in Group III patients, peritonitis (40.9%) and pleuritis (25.0%) were significantly lower than in other groups. The frequency of patients carrying p.M694I (18.2%), which is the most representative mutation in Japan, was significantly lower in Group III than in Group I. The response to colchicine therapy was good (95.1%) and similar in all groups.Conclusions: In Japan, more patients than expected had late-onset FMF. They had a milder form of disease, with less frequent peritonitis and pleuritis. The response to colchicine treatment was good. Clinicians should consider FMF for patients with unexplained recurrent febrile episodes, regardless of age.

A case of spheroid-type localized lactoferrin amyloidosis in the bronchus.

We report a case of localized bronchial lactoferrin amyloidosis. A 47-year-old man presented with a complaint of persistent dry cough for two months. Chest computed-tomography revealed a calcification shadow of the right main bronchus; hence, a biopsy was performed, showing layered spheroid-type eosinophilic deposits in the bronchial wall. These deposits were positive for Congo red staining, exhibiting apple-green birefringence under polarized light. In addition, an electron microscopic examination demonstrated that this layered structure was formed by very thin cord-like amyloid deposits. By proteomics analysis using liquid chromatography-tandem mass spectrometry and immunohistochemistry, we confirmed that the deposited amyloid was composed of lactoferrin. While lactoferrin is known to be a precursor protein of localized corneal and seminal vesicle amyloidosis, localized lactoferrin amyloidosis of the bronchus has not been reported in the English literature. Our pathological findings suggested that localized lactoferrin amyloidosis may be caused by long-term tissue damage, and the characteristic spheroid-type appearance is thought to be associated with unique, thin cord-like amyloid deposits.

Usefulness of gastroduodenal biopsy in the differential diagnosis of systemic AH amyloidosis from systemic AL amyloidosis.

AIMS: The aim of this study is to examine the usefulness of gastroduodenal biopsy for the detection of immunoglobulin (Ig) heavy-chain amyloid deposition. Ig heavy-chain amyloidosis (AH amyloidosis) is Ig-related amyloidosis classified together with Ig light-chain amyloidosis (AL amyloidosis). Compared with AL amyloidosis, patients with AH amyloidosis exhibit a better prognosis and they may not need an aggressive treatment. Thus, the accurate diagnosis is essential for management of Ig-related amyloidosis patients. For the definite diagnosis of AH amyloidosis, biochemical analyses are usually needed. However, these analyses are not widely available. Therefore, the characteristic deposition pattern of AH amyloidosis in routine histopathological examination of biopsy specimens, such as gastrointestinal biopsy, if present, may help in the selection of cases for further biochemical analyses. METHODS AND RESULTS: Gastroduodenal biopsy specimens obtained from three cases of biochemically confirmed AH amyloidosis and 21 cases of immunohistochemically confirmed AL amyloidosis were examined, and the following distinctive histopathological features of AH amyloidosis were pointed out: (i) AH amyloid deposition was detectable with Congo red staining in the gastroduodenal biopsy specimens; and (ii) AH amyloid deposition was observed characteristically on the capillary wall of duodenal villi (dotted line-like deposition in the villi), and this pattern was not observed in AL amyloidosis. CONCLUSION: These findings help to select cases for biochemical analyses for definite diagnosis of AH amyloidosis, and may lead to the accumulation of cases and improve our understanding of systemic AH amyloidosis.

Visualization of multiple organ amyloid involvement in systemic amyloidosis using 11C-PiB PET imaging.

PURPOSE: To investigate the utility of Pittsburgh compound B (PiB) positron emission tomography (PET) imaging for evaluating whole-body amyloid involvement in patients with systemic amyloidosis. METHODS: Whole-body 11C-PiB PET was performed in seven patients with systemic immunoglobulin light-chain (AL) amyloidosis, seven patients with hereditary transthyretin (ATTRm) amyloidosis, one asymptomatic TTR mutation carrier and three healthy controls. The correlations between clinical organ involvement, radiological 11C-PiB uptake and histopathological findings were analysed for each organ. RESULTS: Organ involvement on 11C-PiB PET imaging showed good correlations with the clinical findings for the heart and stomach. Abnormal tracer uptake was also observed in the spleen, lachrymal gland, submandibular gland, sublingual gland, lymph node, brain, scalp, extraocular muscles, nasal mucosa, pharynx, tongue and nuchal muscles, most of which were asymptomatic. Physiological tracer uptake was universally observed in the urinary tract (kidney, renal pelvis, ureter and bladder) and enterohepatic circulatory system (liver, gallbladder, bile duct and small intestine) in all participants. Most of the patients and one healthy control subject showed asymptomatic tracer uptake in the lung and parotid gland. The peripheral nervous system did not show any tracer uptake even in patients with apparent peripheral neuropathy. Histological amyloid deposition was confirmed in biopsied myocardium and gastric mucosa where abnormal 11C-PiB retention was observed. CONCLUSIONS: 11C-PiB PET imaging can be used clinically in the systemic evaluation of amyloid distribution in patients with AL and ATTRm amyloidosis. Quantitative analysis of 11C-PiB PET images may be useful in therapy evaluation and will reveal whether amyloid clearance is correlated with clinical response.

Medium-chain triglycerides supplement therapy with a low-carbohydrate formula can supply energy and enhance ammonia detoxification in the hepatocytes of patients with adult-onset type II citrullinemia.

Citrin, encoded by SLC25A13, constitutes the malate-aspartate shuttle, the main NADH-shuttle in the liver. Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). Citrin deficiency is predicted to impair hepatic glycolysis and de novo lipogenesis, resulting in hepatic energy deficit. Secondary decrease in hepatic argininosuccinate synthetase (ASS1) expression has been considered a cause of hyperammonemia in CTLN2. We previously reported that medium-chain triglyceride (MCT) supplement therapy with a low-carbohydrate formula was effective in CTLN2 to prevent a relapse of hyperammonemic encephalopathy. We present the therapy for six CTLN2 patients. All the patients' general condition steadily improved and five patients with hyperammonemic encephalopathy recovered from unconsciousness in a few days. Before the treatment, plasma glutamine levels did not increase over the normal range and rather decreased to lower than the normal range in some patients. The treatment promptly decreased the blood ammonia level, which was accompanied by a decrease in plasma citrulline levels and an increase in plasma glutamine levels. These findings indicated that hyperammonemia was not only caused by the impairment of ureagenesis at ASS1 step, but was also associated with an impairment of glutamine synthetase (GS) ammonia-detoxification system in the hepatocytes. There was no decrease in the GS expressing hepatocytes. MCT supplement with a low-carbohydrate formula can supply the energy and/or substrates for ASS1 and GS, and enhance ammonia detoxification in hepatocytes. Histological improvement in the hepatic steatosis and ASS1-expression was also observed in a patient after long-term treatment.

One novel and two uncommon MEFV mutations in Japanese patients with familial Mediterranean fever: a clinicogenetic study.

Familial Mediterranean fever (FMF) is an autoinflammatory disease caused by mutations in the MEFV gene and characterized by recurrent episodes of fever and polyserositis. To date, over 317 MEFV mutations have been reported, only nine of which account for almost all Japanese patients with FMF. Therefore, the prevalence of rare MEFV variants and their clinical characteristics remains unclear. This study identified MEFV mutations previously unreported in the Japanese population and described their clinical features. We performed MEFV genetic testing in 488 Japanese patients with clinically suspected FMF. Of these patients, we retrospectively analyzed three patients with novel or very uncommon MEFV mutations. In all patients, the clinical diagnosis of FMF was made according to Tel-Hashomer's criteria. One novel missense mutation (N679H) and two rare mutations (T681I and R410H) were identified in the MEFV gene. These mutations were found in compound heterozygous or complex genotypes with other known mutations in exons 1 or 2. According to clinical images, all three patients exhibited typical FMF symptoms. A number of patients with FMF caused by novel or uncommon MEFV variants might exist in the Japanese population; therefore, careful genetic testing is required for accurate diagnosis of this curable genetic disorder.

AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition; a case mimicking AHL amyloidosis.

BACKGROUND: Immunoglobulin heavy-and-light-chain amyloidosis (AHL amyloidosis) is a newly established disease entity where both the immunoglobulin heavy-chain and light-chain compose amyloid fibrils. The immunoglobulins responsible for the amyloid fibrils are generally identified by immunostaining and/or laser microdissection-liquid chromatography-tandem mass spectrometry (LMD-LC-MS/MS). However, both techniques do not biochemically differentiate immunoglobulins that formed amyloid fibrils from non-responsible immunoglobulins. CASE PRESENTATION: We herein report a case of 67-year-old female patient with renal amyloidosis due to lymphoplasmacytic lymphoma secreting monoclonal immunoglobulin M (IgM)-kappa. Renal immunostaining monotypically positive for IgM-kappa and LMD-LC-MS/MS identification of mu heavy-chain and kappa light-chain were consistent with the diagnosis of AHL amyloidosis. In order to confirm that both the immunoglobulin heavy-chain and light-chain were forming amyloid fibrils, we performed LC-MS/MS of renal amyloid fibrils isolated by the traditional amyloid purification method. The additional LC-MS/MS identified kappa light-chain only without any heavy-chain component. These results were suggestive that amyloid fibrils were composed by kappa light-chain only and that the mu heavy-chain identified by immunostaining and LMD-LC-MS/MS was derived from the non-specific co-deposition of monoclonal IgM-kappa. CONCLUSION: The case was AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition. While immunostaining and LMD-LC-MS/MS are irreplaceable techniques to classify amyloidosis, confident exclusion of the present condition should be required to diagnose AHL amyloidosis.

Hereditary Fibrinogen Aα-Chain Amyloidosis in Asia: Clinical and Molecular Characteristics.

Hereditary fibrinogen Aα-chain amyloidosis (Aα-chain amyloidosis) is a type of autosomal dominant systemic amyloidosis caused by mutations in fibrinogen Aα-chain gene (FGA). Patients with Aα-chain amyloidosis have been mainly reported in Western countries but have been rarely reported in Asia, with only five patients with Aα-chain amyloidosis being reported in Korea, China, and Japan. Clinically, the most prominent manifestation in Asian patients with Aα-chain amyloidosis is progressive nephropathy caused by excessive amyloid deposition in the glomeruli, which is similar to that observed in patients with Aα-chain amyloidosis in Western countries. In molecular features in Asian Aα-chain amyloidosis, the most common variant, E526V, was found in only one Chinese kindred, and other four kindred each had a different variant, which have not been identified in other countries. These variants are located in the C-terminal region (amino acid residues 517-555) of mature Aα-chain, which was similar to that observed in patients with Aα-chain amyloidosis in other countries. The precise number of Asian patients with Aα-chain amyloidosis is unclear. However, patients with Aα-chain amyloidosis do exist in Asian countries, and the majority of these patients may be diagnosed with other types of systemic amyloidosis.

Steatogenesis in adult-onset type II citrullinemia is associated with down-regulation of PPARα.

SLC25A13 (citrin or aspartate-glutamate carrier 2) is located in the mitochondrial membrane in the liver and its genetic deficiency causes adult-onset type II citrullinemia (CTLN2). CTLN2 is one of the urea cycle disorders characterized by sudden-onset hyperammonemia due to reduced argininosuccinate synthase activity. This disorder is frequently accompanied with hepatosteatosis in the absence of obesity and ethanol consumption. However, the precise mechanism of steatogenesis remains unclear. The expression of genes associated with fatty acid (FA) and triglyceride (TG) metabolism was examined using liver samples obtained from 16 CTLN2 patients and compared with 7 healthy individuals. Although expression of hepatic genes associated with lipogenesis and TG hydrolysis was not changed, the mRNAs encoding enzymes/proteins involved in FA oxidation (carnitine palmitoyl-CoA transferase 1α, medium- and very-long-chain acyl-CoA dehydrogenases, and acyl-CoA oxidase 1), very-low-density lipoprotein secretion (microsomal TG transfer protein), and FA transport (CD36 and FA-binding protein 1), were markedly suppressed in CTLN2 patients. Serum concentrations of ketone bodies were also decreased in these patients, suggesting reduced mitochondrial ß-oxidation activity. Consistent with these findings, the expression of peroxisome proliferator-activated receptor α (PPARα), a master regulator of hepatic lipid metabolism, was significantly down-regulated. Hepatic PPARα expression was inversely correlated with severity of steatosis and circulating ammonia and citrulline levels. Additionally, phosphorylation of c-Jun-N-terminal kinase was enhanced in CTLN2 livers, which was likely associated with lower hepatic PPARα. Collectively, down-regulation of PPARα is associated with steatogenesis in CTLN2 patients. These findings provide a novel link between urea cycle disorder, lipid metabolism, and PPARα.

Mechanism for increased hepatic glycerol synthesis in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double-knockout mouse: Urine glycerol and glycerol 3-phosphate as potential diagnostic markers of human citrin deficiency.

The mitochondrial aspartate-glutamate carrier isoform 2 (citrin) and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) double-knockout mouse has been a useful model of human citrin deficiency. One of the most prominent findings has been markedly increased hepatic glycerol 3-phosphate (G3P) following oral administration of a sucrose solution. We aimed to investigate whether this change is detectable outside of the liver, and to explore the mechanism underlying the increased hepatic G3P in these mice. We measured G3P and its metabolite glycerol in plasma and urine of the mice under various conditions. Glycerol synthesis from fructose was also studied using the liver perfusion system. The citrin/mGPD double-knockout mice showed increased urine G3P and glycerol under normal, fed conditions. We also found increased plasma glycerol under fasted conditions, while oral administration of different carbohydrates or ethanol led to substantially increased plasma glycerol. Fructose infusion to the perfused liver of the double-knockout mice augmented hepatic glycerol synthesis, and was accompanied by a concomitant increase in the lactate/pyruvate (L/P) ratio. Co-infusion of either pyruvate or phenazine methosulfate, a cytosolic oxidant, with fructose corrected the high L/P ratio, leading to reduced glycerol synthesis. Overall, these findings suggest that hepatic glycerol synthesis is cytosolic NADH/NAD(+) ratio-dependent and reveal a likely regulatory mechanism for hepatic glycerol synthesis following a high carbohydrate load in citrin-deficient patients. Therefore, urine G3P and glycerol may represent potential diagnostic markers for human citrin deficiency.