佐久間 一基

AGPAT2 (1-acyl-sn-glycerol-3-phosphate-acyltransferase-2) converts lysophosphatidic acid (LPA) into phosphatidic acid (PA), and mutations of the AGPAT2 gene cause the most common form of congenital generalized lipodystrophy which leads to steatohepatitis. The underlying mechanism by which AGPAT2 deficiency leads to lipodystrophy and steatohepatitis has not been elucidated. We addressed this question using an antisense oligonucleotide (ASO) to knockdown expression of Agpat2 in the liver and white adipose tissue (WAT) of adult male Sprague-Dawley rats. Agpat2 ASO treatment induced lipodystrophy and inflammation in WAT and the liver, which was associated with increased LPA content in both tissues, whereas PA content was unchanged. We found that a controlled-release mitochondrial protonophore (CRMP) prevented LPA accumulation and inflammation in WAT whereas an ASO against glycerol-3-phosphate acyltransferase, mitochondrial (Gpam) prevented LPA content and inflammation in the liver in Agpat2 ASO-treated rats. In addition, we show that overnutrition, due to high sucrose feeding, resulted in increased hepatic LPA content and increased activated macrophage content which were both abrogated with Gpam ASO treatment. Taken together, these data identify LPA as a key mediator of liver and WAT inflammation and lipodystrophy due to AGPAT2 deficiency as well as liver inflammation due to overnutrition and identify LPA as a potential therapeutic target to ameliorate these conditions.

Fructose-1,6-bisphosphatase (FBPase) deficiency, caused by an FBP1 mutation, is an autosomal recessive disorder characterized by hypoglycemic lactic acidosis. Due to the rarity of FBPase deficiency, the mechanism by which the mutations cause enzyme activity loss still remains unclear. Here we identify compound heterozygous missense mutations of FBP1, c.491G>A (p.G164D) and c.581T>C (p.F194S), in an adult patient with hypoglycemic lactic acidosis. The G164D and F194S FBP1 mutants exhibit decreased FBP1 protein expression and a loss of FBPase enzyme activity. The biochemical phenotypes of all previously reported FBP1 missense mutations in addition to G164D and F194S are classified into three functional categories. Type 1 mutations are located at pivotal residues in enzyme activity motifs and have no effects on protein expression. Type 2 mutations structurally cluster around the substrate binding pocket and are associated with decreased protein expression due to protein misfolding. Type 3 mutations are likely nonpathogenic. These findings demonstrate a key role of protein misfolding in mediating the pathogenesis of FBPase deficiency, particularly for Type 2 mutations. This study provides important insights that certain patients with Type 2 mutations may respond to chaperone molecules.

Adipose tissues accumulate excess energy as fat and heavily influence metabolic homeostasis. O-linked N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation), which involves the addition of N-acetylglucosamine to proteins by O-GlcNAc transferase (Ogt), modulates multiple cellular processes. However, little is known about the role of O-GlcNAcylation in adipose tissues during body weight gain due to overnutrition. Here, we report on O-GlcNAcylation in mice with high-fat diet (HFD)-induced obesity. Mice with knockout of Ogt in adipose tissue achieved using adiponectin promoter-driven Cre recombinase (Ogt-FKO) gained less body weight than control mice under HFD. Surprisingly, Ogt-FKO mice exhibited glucose intolerance and insulin resistance, despite their reduced body weight gain, as well as decreased expression of de novo lipogenesis genes and increased expression of inflammatory genes, resulting in fibrosis at 24 weeks of age. Primary cultured adipocytes derived from Ogt-FKO mice showed decreased lipid accumulation. Both primary cultured adipocytes and 3T3-L1 adipocytes treated with OGT inhibitor showed increased secretion of free fatty acids. Medium derived from these adipocytes stimulated inflammatory genes in RAW 264.7 macrophages, suggesting that cell-to-cell communication via free fatty acids might be a cause of adipose inflammation in Ogt-FKO mice. In conclusion, O-GlcNAcylation is important for healthy adipose expansion in mice. Glucose flux into adipose tissues may be a signal to store excess energy as fat.NEW & NOTEWORTHY We evaluated the role of O-GlcNAcylation in adipose tissue in diet-induced obesity using adipose tissue-specific Ogt knockout mice. We found that O-GlcNAcylation in adipose tissue is essential for healthy fat expansion and that Ogt-FKO mice exhibit severe fibrosis upon long-term overnutrition. O-GlcNAcylation in adipose tissue may regulate de novo lipogenesis and free fatty acid efflux to the degree of overnutrition. We believe that these results provide new insights into adipose tissue physiology and obesity research.

AIMS/HYPOTHESIS: Athletes exhibit increased muscle insulin sensitivity, despite increased intramuscular triacylglycerol content. This phenomenon has been coined the 'athlete's paradox' and is poorly understood. Recent findings suggest that the subcellular distribution of sn-1,2-diacylglycerols (DAGs) in the plasma membrane leading to activation of novel protein kinase Cs (PKCs) is a crucial pathway to inducing insulin resistance. Here, we hypothesised that regular aerobic exercise would preserve muscle insulin sensitivity by preventing increases in plasma membrane sn-1,2-DAGs and activation of PKCε and PKCθ despite promoting increases in muscle triacylglycerol content. METHODS: C57BL/6J mice were allocated to three groups (regular chow feeding [RC]; high-fat diet feeding [HFD]; RC feeding and running wheel exercise [RC-EXE]). We used a novel LC-MS/MS/cellular fractionation method to assess DAG stereoisomers in five subcellular compartments (plasma membrane [PM], endoplasmic reticulum, mitochondria, lipid droplets and cytosol) in the skeletal muscle. RESULTS: We found that the HFD group had a greater content of sn-DAGs and ceramides in multiple subcellular compartments compared with the RC mice, which was associated with an increase in PKCε and PKCθ translocation. However, the RC-EXE mice showed, of particular note, a reduction in PM sn-1,2-DAG and ceramide content when compared with HFD mice. Consistent with the PM sn-1,2-DAG-novel PKC hypothesis, we observed an increase in phosphorylation of threonine1150 on the insulin receptor kinase (IRKT1150), and reductions in insulin-stimulated IRKY1162 phosphorylation and IRS-1-associated phosphoinositide 3-kinase activity in HFD compared with RC and RC-EXE mice, which are sites of PKCε and PKCθ action, respectively. CONCLUSIONS/INTERPRETATION: These results demonstrate that lower PKCθ/PKCε activity and sn-1,2-DAG content, especially in the PM compartment, can explain the preserved muscle insulin sensitivity in RC-EXE mice.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, in which prognosis is determined by liver fibrosis. A common variant in hydroxysteroid 17-beta dehydrogenase 13 (HSD17B13, rs72613567-A) is associated with a reduced risk of fibrosis in NAFLD, but the underlying mechanism(s) remains unclear. We investigated the effects of this variant in the human liver and in Hsd17b13 knockdown in mice by using a state-of-the-art metabolomics approach. We demonstrate that protection against liver fibrosis conferred by the HSD17B13 rs72613567-A variant in humans and by the Hsd17b13 knockdown in mice is associated with decreased pyrimidine catabolism at the level of dihydropyrimidine dehydrogenase. Furthermore, we show that hepatic pyrimidines are depleted in two distinct mouse models of NAFLD and that inhibition of pyrimidine catabolism by gimeracil phenocopies the HSD17B13-induced protection against liver fibrosis. Our data suggest pyrimidine catabolism as a therapeutic target against the development of liver fibrosis in NAFLD.

The microRNA (miR) miR-874, a potential tumour suppressor, causes cell death via target gene suppression in various cancer types. Mevalonate pathway inhibition also causes cell death in breast cancer. However, the relationship between the mevalonate pathway and miR-874-induced apoptosis or its association with the tumour suppressor p53 has not been elucidated. We identified phosphomevalonate kinase (PMVK), a key mevalonate pathway enzyme, and sterol regulatory element-binding factor 2 (SREBF2), the master cholesterol biosynthesis regulator, as direct miR‑874 targets. Next-generation sequencing analysis revealed a significant miR-874-mediated downregulation of PMVK and SREBF2 gene expression and p53 pathway enrichment. Luciferase reporter assays showed that miR-874 directly regulated PMVK and SREBF2. miR-874-induced apoptosis was p53 dependent, and single-cell RNA sequencing analysis demonstrated that miR-874 transfection resulted in apoptosis and p53 pathway activation. Downregulation of PMVK expression also caused cell cycle arrest and p53 pathway activation, which was rescued by geranylgeranyl pyrophosphate (GGPP) supplementation. Analysis of The Cancer Genome Atlas (TCGA) database indicated a negative correlation between miR-874 and PMVK expression and between miR-874 and SREBF2 expression. These findings suggest that miR-874 suppresses the mevalonate pathway by targeting SREBF2 and PMVK, resulting in GGPP depletion, which activates the p53 pathway and promotes cycle arrest or apoptosis.

The liver stores glycogen and releases glucose into the blood upon increased energy demand. Group 2 innate lymphoid cells (ILC2) in adipose and pancreatic tissues are known for their involvement in glucose homeostasis, but the metabolic contribution of liver ILC2s has not been studied in detail. Here we show that liver ILC2s are directly involved in the regulation of blood glucose levels. Mechanistically, interleukin (IL)-33 treatment induces IL-13 production in liver ILC2s, while directly suppressing gluconeogenesis in a specific Hnf4a/G6pc-high primary hepatocyte cluster via Stat3. These hepatocytes significantly interact with liver ILC2s via IL-13/IL-13 receptor signaling. The results of transcriptional complex analysis and GATA3-ChIP-seq, ATAC-seq, and scRNA-seq trajectory analyses establish a positive regulatory role for the transcription factor GATA3 in IL-13 production by liver ILC2s, while AP-1 family members are shown to suppress IL-13 release. Thus, we identify a regulatory role and molecular mechanism by which liver ILC2s contribute to glucose homeostasis.

コルチゾール産生腫瘍では、PRKACA、Wnt、GNAS変異などが知られているが、分子生物学的全容は解明されていない。今回、クッシング症候群(CS)とサブクリニカルクッシング症候群(SCS)の特性を知るために、原発性アルドステロン症(APA)症例を比較対照としてシングルセル解析を行った。対象は、当院で2020～2021年に副腎腫瘍摘出術を施行され病理診断されたCS 2例、SCS 5例、APA 5例とした。全ての摘出副腎組織から得られた細胞をクラスター分析した結果、23のクラスターに分類することができた。各クラスターがそれぞれどのような細胞集団であるのか、細胞マーカを用いて同定し、それらを分離することで、副腎皮質細胞のみを抽出することができた。腫瘍部における各細胞集団の割合をみると、腫瘍部であっても腫瘍コンテンツは約35%にとどまることが分かった。副腎皮質細胞と同定された細胞群をサブクラスタリング解析すると、SCS腫瘍細胞が多くを占めるサブクラスターや、APA細胞が多くを占めるサブクラスターが存在し、サブクラスターごとにCYP11B1やCYP17A1の発現パターンが異なっていた。

当院でオシロドロスタットを投与した副腎性クッシング症候群3例の治療成績を報告した。原疾患の内訳は副腎腺腫が2例、PMAHが1例であった。投与期間は3ヵ月～1年6ヵ月で、3例とも尿中コルチゾール排泄量が速やかに減少し、正常化した。副腎腺腫の2例に対してはオシロドロスタット投与後に副腎摘除術を行い、完治した。

INTRODUCTION: Poor medication adherence and disordered eating are major self-care problems in patients with type 2 diabetes that worsen glycemic control and increase the risk of developing severe diabetes complications. Affective temperament, which remains mostly unchanged throughout life, is speculated to predict poor treatment response and high comorbidity. The aim of this study was to explore the link between affective temperament and poor glycemic control due to insufficient self-care. METHODS: This single-center case-control study involved 77 outpatients divided into the 'poor glycemic control' group (n = 52) and the 'better glycemic control' group (n = 25) based on their mean glycated hemoglobin (HbA1c) levels over the past 12 months. All participants underwent one-on-one interviews during which they completed the following psychometric questionnaires: (1) the Mini-International Neuropsychiatric Interview 5.0.0; (2) the Temperament Evaluation of Memphis, Pisa, and San Diego Auto-questionnaire; (3) a researcher-designed single question for assessing subclinical stress-induced overeating; and (4) the Morisky Medication Adherence Scale. The difference between two continuous independent variables was determined using Student's t test. Discrete variables were compared using the Chi-square (χ2) or Fisher's exact test. Multiple testing corrections were performed using the false discovery rate. RESULTS: Those outpatients in the poor glycemic control group exhibited significantly more stress-induced overeating (χ2 = 1.14, q statistic = 0.040) and poor medication adherence (t = 3.70, q = 0.034) than those in the better glycemic control group. However, there were no significant differences between the two groups in terms of affective temperaments, clinical eating disorders, or diabetes-specific distress. Patients with stress-induced overeating (t = - 2.99, p = 0.004) and poor medication adherence (t = - 4.34, p = 0.000) exhibited significantly higher scores for cyclothymic temperament than their counterparts. CONCLUSION: Cyclothymic temperament is significantly associated with disordered eating and/or poor medication adherence in patients with type 2 diabetes and is possibly linked to poor glycemic control.

Rathke's cleft cyst (RCC) is a common incidental tumor in the hypothalamic-pituitary region. Some reports have shown that the clinical symptoms and endocrine functions of symptomatic RCCs are temporarily improved by glucocorticoid administration. However, it is still unknown whether glucocorticoid treatment is effective for symptomatic RCCs according to long-term observations. In this study, we describe the long-term clinical outcomes of two cases of glucocorticoid-treated biopsy-proven secondary hypophysitis caused by RCCs. We summarize the symptoms, imaging findings, and endocrine evaluations of two symptomatic RCC patients with concomitant hypophysitis before and after prednisolone treatment. In both evaluated cases, visual impairments and altered endocrine parameters were present due to chiasm and stalk compression; these outcomes improved after shrinkage of RCCs in response to prednisolone administration, and partial recovery of anterior pituitary hormone secretion was observed. However, in both cases, the deficits in anterior pituitary hormone secretion recurred, possibly due to persistent inflammatory infiltration in the RCCs and pituitary glands. After relapse of hypophysitis, anterior hormone secretion did not fully recover. In our cases of secondary hypophysitis caused by RCCs, prednisolone administration had an early effect of cyst shrinkage, followed by partial improvements in clinical symptoms and pituitary functions. However, long-term observation showed that prednisolone treatment did not contribute to complete improvement in anterior pituitary hormone dysfunction.

<title>Abstract</title> p53 is mutated more than half of human cancers, and mutant p53, a gain of function, can actively have functional consequences with tumorigenesis. However, its action of molecular mechanisms, particularly in vivo conditions, has not been fully are clarified. Here, we generated KO and KI (R280K) breast cancer cell lines for p53 using CRISPR/Cas9 system, and then performed a three-dimensional culture model. We found that the introduction of mutant p53 was solely able to mediate the transformation to poor architectural structure. Interestingly, our findings in statin-effect along with cholesterol synthesis pathway, especially isoprenoid dependency, revealed that this pathway is necessary and sufficient for the regulation of malignant architecture in SREBP2-dependent manner with cooperatively being controlled by mutant p53 on 3D-cultured breast cancer. Furthermore, in accordance with the malignancy progresses, SREBP2 was accumulated in nuclear and nuclear membrane portion with enhancement in malignant formation. In addition, we found that mutant p53 interacts with SREBP2, and consistently mutant p53 was associated with DHCR7 promoter in parallel with binding pattern of SREBP2. Thus, our results provide the novel insight into the mutant p53, a gain of function, and its linkage to poor architectural structure in 3D-cultured breast cancer cells via SREBP2-dependent isoprenoids regulation as potential therapeutic targets.

<title>Abstract</title> Iron is an essential cofactor for many proteins that function in electron transport or oxygen transport as heme or iron-sulfur cluster. On the contrary, iron also has the potential to cause oxidative damage if not carefully regulated and when in labial iron excess. Clinical studies show that elevated serum ferritin levels are observed in most patients with type 2 diabetes and non-alcoholic fatty liver disease (NAFLD). In this context, p53 is shown to induces some mitochondrial iron regulatory genes. The role of crosstalk between p53 and iron metabolism has not been sufficiently examined in the pathogenesis of diabetes and NAFLD. Here, we examined the role of ferredoxin reductase (FDXR), a key mitochondrial regulator for iron metabolism, as p53-inducible gene with focusing on the hepatocyte and liver. We confirmed that p53 induced FDXR expression in HepG2 cells and SKEHP1 cells. Biochemical analysis demonstrated that FDXR regulated ROS levels via iron metabolism. In vivo analysis, high-fat diet activated the p53-FDXR pathway in mice liver. We generated transgene expression in mice liver using adenovirus infection carrying shRNA or CRISPR Cas9 system. Treatment with the FDXR knockdown increased hepatic iron content and aggravated glucose intolerance. Besides, forkhead box protein O1 (FOXO1), a key transcriptional factor that induces phosphoenolpyruvate carboxylase and glucose-6-phosphatase increased ratio of nuclear localization, indicating hepatic gluconeogenesis activation. Consistently, biochemical analysis in HepG2 cells demonstrated that FDXR regulated insulin-dependent FOXO1 nuclear exclusion through oxidative stress. In conclusion, p53-inducible FDXR regulates iron metabolism and oxidative stress. FDXR inhibits iron accumulation and oxidative stress in liver and links to suppression of hepatic gluconeogenesis via insulin-dependent FOXO1 nuclear exclusion. The results of this study provide important new insights into relationship between iron metabolism and glucose metabolism as well as potentially identify novel therapeutic targets for the treatment of diabetes and NAFLD.

OBJECTIVE: Accurate assessment and localization of aldosterone-producing adenomas (APAs) are essential for the treatment of primary aldosteronism (PA). Although adrenal venous sampling (AVS) is the standard method of reference for subtype diagnosis in PA, controversy exists concerning the criteria for its interpretation. This study aims to determine better indicators that can reliably predict subtypes of PA. METHOD: Retrospective, single-cohort analysis including 209 patients with PA who were subjected to AVS. Eighty-two patients whose plasma aldosterone concentrations (PAC) were normalized after surgery were histopathologically or genetically diagnosed with APA. The accuracy of image findings was compared to AVS results. Receiver operating characteristic (ROC) curve analysis between the operated and the no-apparent laterality groups was performed using AVS parameters and loading test for diagnosis of PA. RESULT: Agreement between image findings and AVS results was 56.3%. ROC curve analysis revealed that the lateralization index (LI) after adrenocorticotropin stimulation cutoff was 2.40, with 98.8% sensitivity and 97.1% specificity. The contralateral suppression index (CSI) cutoff value was 1.19, with 98.0% sensitivity and 93.9% specificity. All patients over the LI and CSI cutoff values exhibited unilateral subtypes. Among the loading test, the best classification accuracy was achieved using the PAC reduction rate after a saline infusion test (SIT) >33.8%, which yielded 87.2% sensitivity or a PAC after a SIT <87.9 pg/mL with 86.2% specificity for predicting bilateral PA. CONCLUSION: The combined criteria of the PAC reduction rate and PAC after the SIT can determine which subset of patients with APA who should be performed AVS for validation.

Context: Necrolytic migratory erythema (NME) occurs in approximately 70% of patients with glucagonoma syndrome. Excessive stimulation of metabolic pathways by hyperglucagonemia, which leads to hypoaminoacidemia, contributes to NME pathogenesis. However, the molecular pathogenesis of glucagonoma and relationships between metabolic abnormalities and clinical symptoms remain unclear. Patient: A 53-year-old woman was referred to our hospital with a generalized rash and weight loss. NME was diagnosed by histopathological examination of skin biopsy tissue. Laboratory tests revealed diabetes, hyperglucagonemia, marked insulin resistance, severe hypoaminoacidemia, ketosis, and anemia. Enhanced computed tomography scans detected a 29-mm pancreatic hypervascular tumor, which was eventually diagnosed as glucagonoma. Preoperative treatment with octreotide long-acting release reduced the glucagon level, improved the amino acid profile, and produced NME remission. Surgical tumor excision normalized the metabolic status and led to remission of symptoms, including NME. Interventions: Whole-exome sequencing (WES) and subsequent targeted capture sequencing, followed by Sanger sequencing and pyrosequencing, identified biallelic alteration of death-domain associated protein (DAXX) with a combination of loss of heterozygosity and frameshift mutations (c.553_554del:p.R185fs and c.1884dupC:p.C629fs) in the glucagonoma. Consistently, immunohistochemistry confirmed near-absence of DAXX staining in the tumor cells. Tumor expression of glucagon and somatostatin receptor subtype 2 and 3 messenger RNA was markedly upregulated. Conclusions: This is a report of glucagonoma with biallelic inactivation of DAXX determined by WES. The tumor manifested as glucagonoma syndrome with generalized NME. This case showed the relationship between hypoaminoacidemia and NME status. Further investigations are required to elucidate the underlying mechanisms of NME onset and glucagonoma tumorigenesis.