👤 Takumi Sugawara

Melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor expressed in the hypothalamus, playing a key role in regulating feeding behavior and energy homeostasis. MC4R is integral to the POMC-MC4R and leptin-MC4R pathways, which control food intake and body weight. Mutations in the POMC gene lead to severe early-onset obesity and increased food consumption. Recently, glucagon-like peptide-1 (GLP-1) analogs, including semaglutide, tirzepatide, and retatrutide, have been explored as potential anti-obesity therapies. This study aimed to assess and compare the efficacy of these GLP-1 analogs in MC4R knockout (KO) mice, which are deficient in the POMC-MC4R pathway. GLP-1 analogs were administered for 21 days to MC4R KO mice and compared their efficacy. The percentage of body weight reduction was 19.7 ± 4.1% for semaglutide, 31.6 ± 7.6% for tirzepatide, and 24.1 ± 5.8% for retatrutide. Body composition analysis, including fat and lean mass, was performed using the Echo-MRI system, revealing significant suppression of both fat and lean mass by all three GLP-1 analogs. Furthermore, GLP-1 analogs improved plasma insulin levels, HOMA-IR, cholesterol levels, and markers of liver damage (AST and ALT), as well as reduced liver hypertrophy. While GLP-1 analogs suppressed genes related to fatty acid synthesis, they had no significant effect on inflammation-related gene expressions. Additionally, GLP-1 analogs reduced energy expenditure, with only tirzepatide showing a significant decrease in the respiratory quotient (RQ) in MC4R KO mice. Our findings demonstrate that all three GLP-1 analogs, semaglutide, tirzepatide, and retatrutide, exhibit significant anti-obesity effects in MC4R KO mice. These results suggest that GLP-1 analogs may provide an effective treatment option for patients with MC4R-POMC pathway deficiencies. Moreover, the efficacy of these drugs in MC4R KO mice aligns with clinical studies, indicating that MC4R KO mice serve as a reliable animal model for obesity research. Show less

Metabolic dysfunction-associated steatotic liver disease (MASLD) can progress to steatohepatitis (MASH), which is closely associated with obesity and insulin resistance. Resmetirom, and semaglutide, have been shown to have therapeutic effects in clinical studies. We compared these mechanisms in western diet (WD)-fed melanocortin 4 receptor knockout (MC4R-KO) mice, a human MASH pathology model. Male MC4R-KO mice were fed WD for 6 weeks starting from 22 weeks of age for disease induction and were administered drugs for 7 weeks with WD feeding, for a total duration of 13 weeks. Both resmetirom and semaglutide treatments for 7 weeks substantially improved these parameters. Although resmetirome and semaglutide improved liver hydroxyproline deposition and total fat mass, semaglutide markedly suppressed total lean mass. Moreover, resmetirom enhanced oxygen consumption, whereas semaglutide reduced energy expenditure. Histopathological evaluation showed that resmetirom significantly and semaglutide tended to improve liver steatosis score. On the fibrosis score, semaglutide significantly reduced it. Resmetirom and semaglutide have different mechanisms of action against MASH. Similar to clinical evidence, semaglutide treatment, might cause muscle mass reduction due to food intake suppression. This is the first study to simultaneously compare the effects of resmetirom and semaglutide on MASH phenotypes and reveal the differences on their mechanisms of action in WD-fed MC4R-KO mice. Show less

We aimed to clarify the relationship between apolipoprotein C3 (apo-C3) and the vascular composition of lesion plaque in stable coronary disease (SCD) before percutaneous coronary intervention (PCI), and to investigate major adverse cardiovascular events (MACEs) within 4 years. Data of 98 consecutive patients with SCD who underwent PCI between November 1, 2012, and March 10, 2015, were analyzed. Laboratory and virtual histology-intravascular ultrasound (VH-IVUS) examinations of culprit lesions were conducted before PCI. Patients were divided according to median apo-C3 into low apo-C3 (≤ 8.5 mg/dL) and high apo-C3 (> 8.5 mg/dL) groups. VH-IVUS data indicated that the percentage of necrotic core volume (%NC) was significantly higher in the high apo-C3 group than in the low apo-C3 group. Moreover, the %NC significantly correlated with the apo-C3 level (R = 0.2109, P = 0.037). Kaplan-Meier curve analysis revealed that freedom from MACEs exhibited a greater decrease in the high apo-C3 group than in the low apo-C3 group, and in the high %NC group than in the low %NC group. Multivariate Cox hazards analysis showed that the %NC and high apo-C3 were independent predictors of 4 year MACEs. Apo-C3 may be a useful marker of future MACEs in patients with SCD after PCI and contribute to %NC growth. Show less

Ornithine transcarbamylase deficiency (OTCD) is an X-linked disorder. Several male patients with OTCD suffer from severe hyperammonemic crisis in the neonatal period, whereas others develop late-onset manifestations, including hyperammonemic coma. Females with heterozygous pathogenic variants in the Show less

Urea cycle disorders (UCDs) are inherited metabolic diseases that lead to hyperammonemia with variable clinical manifestations. Using data from a nationwide study, we investigated the onset time, gene variants, clinical manifestations, and treatment of patients with UCDs in Japan. Of the 229 patients with UCDs diagnosed and/or treated between January 2000 and March 2018, identified gene variants and clinical information were available for 102 patients, including 62 patients with ornithine transcarbamylase (OTC) deficiency, 18 patients with carbamoyl phosphate synthetase 1 (CPS1) deficiency, 16 patients with argininosuccinate synthetase (ASS) deficiency, and 6 patients with argininosuccinate lyase (ASL) deficiency. A total of 13, 10, 4, and 5 variants in the OTC, CPS1, ASS, and ASL genes were respectively identified as novel variants, which were neither registered in ClinVar databases nor previously reported. The onset time and severity in patients with UCD could be predicted based on the identified gene variants in each patient from this nationwide study and previous studies. This genetic information may help in predicting the long-term outcome and determining specific treatment strategies such as liver transplantation in patients with UCDs. Show less

Carbohydrate response element binding protein (ChREBP), a glucose responsive transcription factor, mainly regulates expression of genes involved in glucose metabolism and lipogenesis. Recently, ChREBP is speculated to be involved in the onset and progression of diabetic nephropathy (DN). However, there exists no report regarding the localization and function of ChREBP in the kidney. Therefore, we analyzed the localization of Chrebp mRNA expression in the wild type (WT) mice kidney using laser microdissection method, and observed its dominant expression in the proximal tubules. In diabetic mice, mRNA expression of Chrebp target genes in the proximal tubules, including Chrebpβ and thioredoxin-interacting protein (Txnip), significantly increased comparing with that of WT mice. Co-overexpression of ChREBP and its partner Mlx, in the absence of glucose, also increased TXNIP mRNA expression as well as high glucose in human proximal tubular epithelial cell line HK-2. Since TXNIP is well known to be involved in the production of reactive oxygen species (ROS), we next examined the effect of ChREBP/Mlx co-overexpression, in the absence of glucose, on ROS production in HK-2 cells. Interestingly, ChREBP/Mlx co-overexpression also induced ROS production significantly as well as high glucose. Moreover, both high glucose-induced increase of TXNIP mRNA expression and ROS production were abrogated by ChREBP small interfering RNA transfection. Taken together, high glucose-activated ChREBP in the renal proximal tubules induce the expression of TXNIP mRNA, resulting in the production of ROS which may cause renal tubular damage. It is therefore speculated that ChREBP is involved in the onset and progression of DN. Show less

Heparan sulfate (HS), a linear polysaccharide, is involved in diverse biological functions of various tissues. HS is expressed in pancreatic β-cells and may be involved in β-cell functions. However, the importance of HS for β-cell function remains unknown. Here, we generated mice with β-cell-specific deletion of Ext1 (βExt1CKO), which encodes an enzyme essential for HS synthesis, to investigate the detailed roles of HS in β-cell function. βExt1CKO mice decreased body weights compared with control mice, despite increased food intake. Additionally, βExt1CKO mice showed impaired glucose tolerance associated with decreased insulin secretion upon glucose challenge. Glucose-induced insulin secretion (GIIS) from isolated βExt1CKO islets was also significantly reduced, highlighting the contribution of HS to insulin secretion and glucose homeostasis. The gene expression essential for GIIS was decreased in βExt1CKO islets. Pdx1 and MafA were downregulated in βExt1CKO islets, indicating that HS promoted β-cell development and maturation. BrdU- or Ki67-positive β-cells were reduced in βExt1CKO pancreatic sections, suggesting the involvement of HS in the proliferation of β-cells. Moreover, insufficient vascularization in βExt1CKO islets may contribute to central distribution of α-cells. These data demonstrate HS plays diverse roles in β-cells, and that loss of HS leads to insufficient insulin secretion and dysregulation of glucose homeostasis. Show less

To identify key oncogenes and proteins that are controlled by the microRNA miR-29 family (miR-29a, miR-29b and miR-29c) in renal cell carcinoma pathogenesis. Genome-wide gene expression and in silico database analyses were carried out. The Cancer Genome Atlas database was used to investigate the clinical significance of gene expression data in renal cell carcinoma patients. Loss-of-function assays were applied to investigate the function of target genes. We identified 47 possible target genes that might be regulated by the miR-29 family in renal cell carcinoma cells. Among the targets of the miR-29 family, high expression of 10 genes (ADAMTS14, TRIB13, SERPINH1, FCGR1B, COL1A1, LAIR2, WISP2, TREM1, TNKS1BP1 and GBP2) significantly predicted poor patient prognosis (P < 0.001). SERPINH1 was directly regulated by the miR-29 family, and its overexpression was detected in renal cell carcinoma surgical specimens and tyrosine kinase inhibitor failure autopsy specimens. High expression of SERPINH1 was significantly associated with tumor stage, pathological grade and poor prognosis (P < 0.0001). Knockdown assays showed that its expression enhanced cancer cell migration and invasive abilities. Genes regulated by the anti-tumor miR-29 family are closely involved in the molecular pathogenesis of renal cell carcinoma. Our approach based on anti-tumor microRNAs might contribute to the development of new diagnostic markers and therapeutic strategies. Show less

Dietary polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA), improve lipid metabolism and contribute to the prevention of vascular diseases such as atherosclerosis. However, EPA in the diet is easily oxidized at room temperature and several types of oxidized EPA (OEPA) derivatives are generated. To compare the efficiencies of OEPAs on lipid metabolism with EPA, human hepatocellular liver carcinoma cell line (HepG2) was treated with EPA or OEPAs and their effects on lipid metabolism related genes were studied. OEPAs more potently suppressed the expression of sterol-responsive element-binding protein (SREBP)-1c, a major transcription factor that activates the expression of lipogenic genes, and its downstream target genes than did EPA under conditions of lipid synthesis enhanced by T0901317, a synthetic liver X receptor (LXR) agonist. Furthermore, PGC-1β, a coactivator of both LXRα and SREBP-1, was markedly down-regulated by OEPAs compared with EPA. The treatment of OEPAs also significantly down-regulated the expression of glycerol-3-phosphate acyltransferase (GPA), the initiating enzyme in triacylglycerol (TG) synthesis, more than EPA. Therefore, the advantageous effects of OEPAs on cardiovascular diseases might be due to their SREBP-1c, PGC-1β and GPA mediated ameliorating effects. Show less