Chemical range recognized by the ligand-binding domain in a representative amino acid-sensing taste receptor, T1r2a/T1r3, from medaka fish

Taste receptor type 1 (T1r) proteins are responsible for recognizing nutrient chemicals in foods. In humans, T1r2/T1r3 and T1r1/T1r3 heterodimers serve as the sweet and umami receptors that recognize sugars or amino acids and nucleotides, respectively. T1rs are conserved among vertebrates, and T1r2a/T1r3 from medaka fish is currently the only member for which the structure of the ligand-binding domain (LBD) has been solved. T1r2a/T1r3 is an amino acid receptor that recognizes various l-amino acids in its LBD as observed with other T1rs exhibiting broad substrate specificities. Nevertheless, the range of chemicals that are recognized by T1r2a/T1r3LBD has not been extensively explored. In the present study, the binding of various chemicals to medaka T1r2a/T1r3LBD was analyzed. A binding assay for amino acid derivatives verified the specificity of this protein to l-alpha-amino acids and the importance of alpha-amino and carboxy groups for receptor recognition. The results further indicated the significance of the alpha-hydrogen for recognition as replacing it with a methyl group resulted in a substantially decreased affinity. The binding ability to the protein was not limited to proteinogenic amino acids, but also to non-proteinogenic amino acids, such as metabolic intermediates. Besides l-alpha-amino acids, no other chemicals showed significant binding to the protein. These results indicate that all of the common structural groups of alpha-amino acids and their geometry in the l-configuration are recognized by the protein, whereas a wide variety of alpha-substituents can be accommodated in the ligand binding sites of the LBDs

Effect of Hemodialysis on Plasma Glucose Profile and Plasma Level of Liraglutide in Patients with Type 2 Diabetes Mellitus and End-Stage Renal Disease: A Pilot Study

The effect of hemodialysis on the plasma glucose profile and liraglutide level after liraglutide injection was investigated in patients with diabetes and end-stage renal disease (ESRD). Either 0.6 mg or 0.9 mg liraglutide was subcutaneously administered daily to 10 Japanese type 2 diabetic patients with ESRD. Hemodialysis was conducted on days 1 and 3. Plasma liraglutide and glucose concentrations were measured by enzyme-linked immunosorbent assay and a continuous glucose monitoring system, respectively. The safety profile of liraglutide was also assessed. Hemodialysis had no effect on the pharmacokinetic parameters of liraglutide in patients with diabetes and ESRD; the maximum plasma concentration (Cmax), tmax, area under the concentration-time curve (AUC), and CL/f were unaltered. Similarly, hemodialysis did not affect the mean or minimum glucose levels, AUC, or duration of hyperglycemia (>180 mg/dL) and hypoglycemia (<70 mg/dL) following liraglutide administration. However, significant increases in mean amplitude of glycemic excursions (MAGE) and standard deviation (SD) as markers of glucose fluctuation, and the maximum glucose level were observed during hemodialysis. No adverse events, including hypoglycemia, were observed after liraglutide injection, either off-hemodialysis (day 2) or on-hemodialysis (day 3). Liraglutide was well tolerated in patients with type 2 diabetes and ESRD undergoing hemodialysis. The present results suggested that hemodialysis did not affect the pharmacokinetic profile of liraglutide or most glycemic indices, with the exception of MAGE, SD, and the maximum glucose level. These results suggested that it may be possible to use liraglutide during hemodialysis for diabetes with ESRD, without dose adjustment. Trial Registration UMIN Clinical Trials Registry (UMIN-CTR) UMIN000010159.\ud \u

Hydro-acoustic methods as a practical tool for cartography of seagrass beds

Cartography of seagrass beds is very important for management and conservation of sound littoral ecosystems and sustainable fisheries in the coastal waters. The cartographical methods to map spatial distribution of seagrass beds are reviewed. They are classified into two categories. One is a direct method by visual observation and the other is an indirect method using a remote sensing apparatus. Indirect methods are divided into optical or hydro-acoustic methods. Indirect methods require sea truth by direct methods. Optical methods are image analysis of aerial photography or satellite imagery. They are effective for mapping broad areas but limited to shallow waters due to light attenuation in waters. Hydro-acoustic methods such as an echosounder and a side scan sonar have no limitation of turbidity. The echosounder is practical to map vertically density and height distributions of seagrass beds. The side scan sonar and multi-beam sonar are appropriate for mapping broad horizontal distributions. Coupling of several indirect mapping methods is more useful than using only one method

Isogenic pairs of induced-pluripotent stem-derived endothelial cells identify DYRK1A/PPARG/EGR1 pathway is responsible for Down syndrome-associated pulmonary hypertension

Down syndrome (DS) is the most prevalent chromosomal disorder associated with a higher incidence of pulmonary arterial hypertension (PAH). The dysfunction of vascular endothelial cells (ECs) is known to cause pulmonary arterial remodeling in PAH, although the physiological characteristics of ECs harboring trisomy 21 (T21) are still unknown. In this study, we analyzed the human vascular ECs by utilizing the isogenic pairs of T21-induced pluripotent stem cells (iPSCs) and corrected disomy 21 (cDi21)-iPSCs. In T21-iPSC-derived ECs, apoptosis and mitochondrial reactive oxygen species (mROS) were significantly increased, and angiogenesis and oxygen consumption rate (OCR) were significantly impaired as compared with cDi21-iPSC-derived ECs. The RNA-sequencing identified that EGR1 on chromosome 5 was significantly upregulated in T21-ECs. Both EGR1 suppression by siRNA and pharmacological inhibitor could recover the apoptosis, mROS, angiogenesis, and OCR in T21-ECs. Alternately, the study also revealed that DYRK1A was responsible to increase EGR1 expression via PPARG suppression, and that chemical inhibition of DYRK1A could restore the apoptosis, mROS, angiogenesis, and OCR in T21-ECs. Finally, we demonstrated that EGR1 was significantly upregulated in the pulmonary arterial ECs from lung specimens of a patient with DS and PAH. In conclusion, DYRK1A/PPARG/EGR1 pathway could play a central role for the pulmonary EC functions and thus be associated with the pathogenesis of PAH in DS.Suginobe Hidehiro, Ishida Hidekazu, Ishii Yoichiro, et al. Isogenic pairs of induced-pluripotent stem-derived endothelial cells identify DYRK1A/PPARG/EGR1 pathway is responsible for Down syndrome-associated pulmonary hypertension. Human Molecular Genetics 163, 1163 (2023); https://doi.org/10.1093/hmg/ddad162

Impaired Relaxation in Induced Pluripotent Stem Cell-Derived Cardiomyocytes with Pathogenic TNNI3 Mutation of Pediatric Restrictive Cardiomyopathy

Wang R., Hasegawa M., Suginobe H., et al. Impaired Relaxation in Induced Pluripotent Stem Cell-Derived Cardiomyocytes with Pathogenic TNNI3 Mutation of Pediatric Restrictive Cardiomyopathy. Journal of the American Heart Association 13, e032375 (2024); https://doi.org/10.1161/JAHA.123.032375.BACKGROUND: Restrictive cardiomyopathy (RCM) is characterized by impaired diastolic function with preserved ventricular contraction. Several pathogenic variants in sarcomere genes, including TNNI3, are reported to cause Ca²⁺ hypersensitivity in cardiomyocytes in overexpression models; however, the pathophysiology of induced pluripotent stem cell (iPSC)-derived cardiomyocytes specific to a patient with RCM remains unknown. METHODS AND RESULTS: We established an iPSC line from a pediatric patient with RCM and a heterozygous TNNI3 missense variant, c.508C>T (p.Arg170Trp; R170W). We conducted genome editing via CRISPR/Cas9 technology to establish an isogenic correction line harboring wild type TNNI3 as well as a homozygous TNNI3-R170W. iPSCs were then differentiated to cardio-myocytes to compare their cellular physiological, structural, and transcriptomic features. Cardiomyocytes differentiated from heterozygous and homozygous TNNI3-R170W iPSC lines demonstrated impaired diastolic function in cell motion analyses as compared with that in cardiomyocytes derived from isogenic-corrected iPSCs and 3 independent healthy iPSC lines. The intracellular Ca²⁺ oscillation and immunocytochemistry of troponin I were not significantly affected in RCM-cardiomyocytes with either heterozygous or homozygous TNNI3-R170W. Electron microscopy showed that the myofibril and mitochondrial structures appeared to be unaffected. RNA sequencing revealed that pathways associated with cardiac muscle development and contraction, extracellular matrix-receptor interaction, and transforming growth factor-β were altered in RCM-iPSC-derived cardiomyocytes. CONCLUSIONS: Patient-specific iPSC-derived cardiomyocytes could effectively represent the diastolic dysfunction of RCM. Myofibril structures including troponin I remained unaffected in the monolayer culture system, although gene expression profiles associated with cardiac muscle functions were altered

Clinical Outcomes and Genetic Analyses of Restrictive Cardiomyopathy in Children

BACKGROUND: Restrictive cardiomyopathy in children is rare and outcomes are very poor. However, little information is available concerning genotype-outcome correlations. METHODS: We analyzed the clinical characteristics and genetic testing, including whole exome sequencing, of 28 pediatric restrictive cardiomyopathy patients who were diagnosed from 1998 to 2021 at Osaka University Hospital in Japan. RESULTS: The median age at diagnosis (interquartile range) was 6 (2.25-8.5) years. Eighteen patients received heart transplantations and 5 patients were on the waiting list. One patient died while waiting for transplantation. Pathologic or likely-pathogenic variants were identified in 14 of the 28 (50%) patients, including heterozygous TNNI3 missense variants in 8 patients. TNNT2, MYL2, and FLNC missense variants were also identified. No significant differences in clinical manifestations and hemodynamic parameters between positive and negative pathogenic variants were detected. However, 2- and 5-year survival rates were significantly lower in patients with pathogenic variants (50% and 22%) compared with survival in patients without pathogenic variants (62% and 54%; P=0.0496, log-rank test). No significant differences were detected in the ratio of patients diagnosed at nationwide school heart disease screening program between positive and negative pathogenic variants. Patients diagnosed by school screening showed better transplant-free survival compared with patients diagnosed by heart failure symptoms (P=0.0027 in log-rank test). CONCLUSIONS: In this study, 50% of pediatric restrictive cardiomyopathy patients had pathogenic or likely-pathogenic gene variants, and TNNI3 missense variants were the most frequent. Patients with pathogenic variants showed significantly lower transplant-free survival compared with patients without pathogenic variants.Ishida H., Narita J., Ishii R., et al. Clinical Outcomes and Genetic Analyses of Restrictive Cardiomyopathy in Children. Circulation: Genomic and Precision Medicine 16, 382 (2023); https://doi.org/10.1161/CIRCGEN.122.004054