👤 Daisuke Usui

s: Cholesteryl ester transfer protein (CETP) inhibition has long been attracting a lot of attention if it could reduce the risk for coronary artery disease (CAD). A previous study has demonstrated that protein-truncating variants (PTVs) were associated with lower risk for CAD, which was dependent on lower LDL cholesterol in general population. We tested this hypothesis among Japanese heterozygous FH (HeFH) patients whose CAD risk was extremely high. We investigated the clinical data of 2344 patients diagnosed with HeFH (mean age = 50 years, males = 1,174, median LDL cholesterol = 244 mg/dL) who were examined for their genotype of CETP and phenotypes, including the presence of CAD from 1990 to 2024 at Kanazawa University Hospital. We investigated whether PTVs of the CETP were associated with plasma lipid levels and CAD among patients with HeFH. We identified 42 patients (1.8 %) with a PTV of CETP in HeFH patients. Compared with non-carriers, carriers of a PTV of CETP had higher HDL cholesterol (effect size, 17.6 mg/dL; 95 % confidence interval [CI], 11.4 to 23.8; P < 0.001), lower LDL cholesterol (-15.4 mg/dL; 95 % CI, -24.5 to -6.3; P < 0.001), and lower lipoprotein (a) [Lp(a)] (-7.8 mg/dL; 95 % CI, -12.5 to -2.5; P < 0.001). CETP PTV carrier status was associated with reduced risk for CAD (odds ratio, 0.64; 95 % CI, 0.38 to 0.90; P < 0.001). PTVs of CETP were significantly associated with higher HDL cholesterol, lower LDL cholesterol, lower Lp(a), and lower risk for CAD among patients with HeFH. Show less

Unimolecular peptide-based dual agonists against glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) have been gaining much attention recently as novel antidiabetic agents that can potentially control glycemia and bodyweight. Although GLP-1 and GIP both enhance insulin secretion and subsequently ameliorate postprandial glucose excursion, most research has focused on GLP-1R as a therapeutic target for type 2 diabetes. This is partly because the effects of GIPR activation on glycemia and bodyweight have been controversial. GIPR-deficient mice showed impaired glucose tolerance with reduced β-cell function and resistance to high-fat diet-induced obesity, whereas GIPR agonists improved glycemia and prevented high-fat diet-induced obesity in mice. Conflicting results in mice might be explained by pharmacological levels of GIP signal in the central nervous systems decreasing food intake and overcoming the obesogenic effects of GIP at physiological levels in adipose tissues. Thus, GIPR activation at pharmacological levels might result in bodyweight reduction. Indeed, bodyweight reduction by GIPR/GLP-1R dual agonists was greater than GLP-1R single agonists in individuals with type 2 diabetes. Thus, GLP-1R/GIPR dual agonists can add additional therapeutic efficacy to tailored diabetes care, especially among obese individuals with type 2 diabetes. However, caution should be exercised as to whether or not these drugs are appropriate for the management of Asian type 2 diabetes patients, which are primarily characterized by non-obesity and impaired β-cell function, as well as in that of elderly adults with type 2 diabetes, who tend to develop sarcopenia and frailty as a result of poor energy intake. Show less

Class III phosphoinositide 3-kinase (PIK3C3 or mammalian vacuolar protein sorting 34 homolog, Vps34) regulates vesicular trafficking, autophagy, and nutrient sensing. Recently, we reported that PIK3C3 is expressed in mouse cerebral cortex throughout the developmental process, especially at early embryonic stage. We thus examined the role of PIK3C3 in the development of the mouse cerebral cortex. Acute silencing of PIK3C3 with in utero electroporation method caused positional defects of excitatory neurons during corticogenesis. Time-lapse imaging revealed that the abnormal positioning was at least partially because of the reduced migration velocity. When PIK3C3 was silenced in cortical neurons in one hemisphere, axon extension to the contralateral hemisphere was also delayed. These aberrant phenotypes were rescued by RNAi-resistant PIK3C3. Notably, knockdown of PIK3C3 did not affect the cell cycle of neuronal progenitors and stem cells at the ventricular zone. Taken together, PIK3C3 was thought to play a crucial role in corticogenesis through the regulation of excitatory neuron migration and axon extension. Meanwhile, when we performed comparative genomic hybridization on a patient with specific learning disorders, a 107 Kb-deletion was identified on 18q12.3 (nt. 39554147-39661206) that encompasses exons 5-23 of PIK3C3. Notably, the above aberrant migration and axon growth phenotypes were not rescued by the disease-related truncation mutant (172 amino acids) lacking the C-terminal kinase domain. Thus, functional defects of PIK3C3 might impair corticogenesis and relate to the pathophysiology of specific learning disorders and other neurodevelopmental disorders. Acute knockdown of Class III phosphoinositide 3-kinase (PIK3C3) evokes migration defects of excitatory neurons during corticogenesis. PIK3C3-knockdown also disrupts axon outgrowth, but not progenitor proliferation in vivo. Involvement of PIK3C3 in neurodevelopmental disorders might be an interesting future subject since a deletion mutation in PIK3C3 was detected in a patient with specific learning disorders (SLD). Show less

The establishment of neuronal polarity is necessary for proper neuronal wiring. Semaphorin3A (Sema3A), originally identified as a repulsive axon guidance molecule, exerts a wide variety of biological functions through signaling pathways including sequential phosphorylation of collapsin response mediator protein by cyclin-dependent kinase-5 (Cdk5) and glycogen synthase kinase-3β (GSK3β). Sema3A acts on its receptor neuropilin-1 to regulate axonal transport. To delineate mechanism by which Sema3A induces axonal transport, we investigate whether GSK3β is involved in mediating Sema3A-induced axonal transport. 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione, an inhibitor of GSK3β, suppressed Sema3A-induced antero- and retrograde axonal transport. Introduction of either GSK3β mutants, GSK3β-L128A or K85M, suppressed Sema3A-induced axonal transport. On the other hand, introduction of GSK3β-R96A did not affect the Sema3A effect, suggesting that unprimed substrates are primarily involved in Sema3A-induced axonal transport. Overexpression of a partial fragment of frequently rearranged in advanced T-cell lymphomas 1 (FRATtide), which interferes the interaction between GSK3β and Axis inhibitor-1 (Axin-1), also suppressed Sema3A-induced transport. siRNA knockdown of Axin-1, an unprimed substrate of GSK3β, suppressed Sema3A-induced antero- and retrograde axonal transport. These results indicate that GSK3β and Axin-1 are involved in Sema3A-induced bidirectional axonal transport. This finding should provide a clue for understanding of mechanisms of a wide variety of biological activities of Sema3A. Show less

Semaphorin3A (Sema3A) exerts a wide variety of biological functions by regulating reorganization of actin and tubulin cytoskeletal proteins through signaling pathways including sequential phosphorylation of collapsin response mediator protein 1 (CRMP1) and CRMP2 by cyclin-dependent kinase-5 and glycogen synthase kinase-3β (GSK3β). To delineate how GSK3β mediates Sema3A signaling, we here determined the substrates of GSK3β involved. Introduction of either GSK3β mutants, GSK3β-R96A, L128A, or K85M into chick dorsal root ganglion (DRG) neurons suppressed Sema3A-induced growth cone collapse, thereby suggesting that unprimed as well as primed substrates are involved in Sema3A signaling. Axin-1, a key player in Wnt signaling, is an unprimed substrate of GSK3β. The phosphorylation of Axin-1 by GSK3β accelerates the association of Axin-1 with β-catenin. Immunocytochemical studies revealed that Sema3A induced an increase in the intensity levels of β-catenin in the DRG growth cones. Axin-1 siRNA knockdown suppressed Sema3A-induced growth cone collapse. The reintroduction of RNAi-resistant Axin-1 (rAxin-1)-wt rescued the responsiveness to Sema3A, while that of nonphosphorylated mutants, rAxin S322A/S326A/S330A and T485A/S490A/S497A, did not. Sema3A also enhanced the colocalization of GSK3β, Axin-1, and β-catenin in the growth cones. The increase of β-catenin in the growth cones was suppressed by the siRNA knockdown of Axin-1. Furthermore, either Axin-1 or β-catenin RNAi knockdown suppressed the internalization of Sema3A. These results suggest that Sema3A induces the formation of GSK3β/Axin-1/β-catenin complex, which regulates signaling cascade of Sema3A via an endocytotic mechanism. This finding should provide clue for understanding of mechanisms of a wide variety of biological functions of Sema3A. Show less

To determine the significance of anti-U1 RNP antibodies in the cerebrospinal fluid (CSF) of patients with systemic lupus erythematosus (SLE) or mixed connective tissue disease (MCTD) who have central neuropsychiatric SLE (NPSLE). The frequency of antinuclear antibodies including anti-U1 RNP antibodies in the sera and CSF of 24 patients with SLE and 4 patients with MCTD, all of whom had neuropsychiatric syndromes, was determined using an RNA immunoprecipitation assay and an enzyme-linked immunosorbent assay. The frequency of anti-U1 RNP antibodies in the CSF of patients with central NPSLE was examined, and the anti-U1 RNP index ([CSF anti-U1 RNP antibodies/serum anti-U1 RNP antibodies]/[CSF IgG/serum IgG]) was compared with CSF interleukin-6 (IL-6) levels and the albumin quotient (Qalb, an indicator of blood-brain barrier damage). CSF and serum antibodies against U1-70K, U1-A, and U1-C, including autoantigenic regions, were examined, and the U1-70K, U1-A, and U1-C indices as well as the anti-U1 RNP index were calculated. CSF anti-U1 RNP antibodies with an increased anti-U1 RNP index showed 64.3% sensitivity and 92.9% specificity for central NPSLE. The anti-U1 RNP index did not correlate with CSF IL-6 levels or the Qalb. The anti-U1-70K index was higher than the anti-U1-A and anti-U1-C indices in the CSF of anti-U1 RNP antibody-positive patients with central NPSLE. The major autoantigenic region for CSF anti-U1-70K antibodies appeared to be localized in U1-70K amino acid 141-164 residue within the RNA-binding domain. The frequency of anti-U1 RNP antibodies in the CSF and the anti-U1 RNP index are useful indicators of central NPSLE in anti-U1 RNP antibody-positive patients. The predominance of anti-U1-70K antibodies in CSF suggests intrathecal anti-U1 RNP antibody production. Show less

DEC1 (BHLHB2/Stra13/Sharp2)-a basic helix-loop-helix transcription factor-is known to be involved in various biological phenomena including clock systems and metabolism. In the clock systems, Dec1 expression is dominantly up-regulated by CLOCK : BMAL1 heterodimer, and it exhibits circadian rhythm in the suprachiasmatic nucleus (SCN)-the central circadian pacemaker-and other peripheral tissues. Recent studies have shown that the strong circadian rhythmicity of Dec1 in the SCN was abolished by Clock mutation, whereas that in the liver was affected, but not abolished, by Clock mutation. Moreover, feeding conditions affected hepatic Dec1 expression, which indicates that Dec1 expression is closely linked with the metabolic functions of the liver. Among ligand-activated nuclear receptors examined, LXRalpha and LXRbeta with T0901317-agonist for LXR-were found to be potent enhancers for Dec1 promoter activity, and a higher expression level of LXRalpha protein was detected in the liver than in the kidney and heart. T0901317 increased the levels of endogenous Dec1 transcript in hepatoma cells. Chromatin immunoprecipitation assay indicated that LXRalpha bound to the Dec1 promoter, and an LXRalpha-binding site was identified. These observations indicate that hepatic DEC1 mediates the ligand-dependent LXR signal to regulate the expression of genes involved in the hepatic clock system and metabolism. Show less

Axin, a negative regulator of the Wnt signaling pathway, forms a complex with glycogen synthase kinase-3beta (GSK-3beta), beta-catenin, adenomatous polyposis coli (APC) gene product, and Dvl, and it regulates GSK-3beta-dependent phosphorylation in the complex and the stability of beta-catenin. Using yeast two-hybrid screening, we found that regulatory subunits of protein phosphatase 2A, PR61beta and -gamma, interact with Axin. PR61beta or -gamma formed a complex with Axin in intact cells, and their interaction was direct. The binding site of PR61beta on Axin was different from those of GSK-3beta, beta-catenin, APC, and Dvl. Although PR61beta did not affect the stability of beta-catenin, it inhibited Dvl- and beta-catenin-dependent T cell factor activation in mammalian cells. Moreover, it suppressed beta-catenin-induced axis formation and expression of siamois, a Wnt target gene, in Xenopus embryos, suggesting that PR61beta acts either at the level of beta-catenin or downstream of it. Taken together with the previous observations that PR61 interacts with APC and functions upstream of beta-catenin, these results demonstrate that PR61 regulates the Wnt signaling pathway at various steps. Show less