👤 Shiori Kubota

Future directions in incretin research: Three major directions currently shape therapeutic innovation in incretin research: multi-receptor agonism, oral drug development, and mechanistic reappraisal of glucose-dependent insulinotropic polypeptide (GIP) physiology. These advances indicate that incretin-based therapies should be understood within an integrated enteroinsular network rather than through isolated hormone actions. DPP-4, dipeptidyl peptidase-4; GCGR, glucagon receptor; GIPR, GIP receptor; GLP-1, glucagon-like peptide-1; GLP-1R, GLP-1 receptor; T2D, type 2 diabetes. Show less

Dipeptidyl peptidase-4 (DPP-4) inhibitors enhance circulating levels of biologically intact incretins, yet the relative contribution of glucose-dependent insulinotropic polypeptide (GIP) to their metabolic effects remains incompletely understood. While glucagon-like peptide-1 (GLP-1) has long been emphasized in incretin biology, emerging evidence suggests important physiological roles for GIP. This study investigated whether endogenous GIP signaling is indispensable for the glucose-lowering and anti-obesity effects of DPP-4 inhibition. Male Gipr DPP-4 inhibition significantly improved glucose tolerance and attenuated body-weight gain in HFD-fed Gipr Endogenous GIP signaling is essential for both glucose-lowering and anti-obesity actions of DPP-4 inhibitors in mice. GLP-1 elevation alone is insufficient to compensate for GIP receptor deficiency. These findings refined the mechanistic understanding of DPP-4 inhibitors, highlighted the physiological importance of GIP, and suggested context-dependent metabolic actions of incretins. Show less

Obesity, a risk factor for atherosclerosis development and progression, is marked by excessive reactive oxygen species (ROS) production. We previously demonstrated that high-glucose (HG) conditions induce mitochondrial ROS (mtROS) production in aortic endothelial cells (ECs). However, the link between elevated mtROS levels in obesity and atherosclerosis progression remains unclear. This study aimed to investigate whether endothelial-specific mtROS suppression by overexpressing manganese superoxide dismutase (MnSOD) could attenuate atherosclerosis progression in high-fat diet (HFD)-induced obese apolipoprotein E-deficient (ApoE KO) mice. Atherosclerotic lesion formation did not differ significantly between normal chow-fed control ApoE KO mice and endothelial cell-specific MnSOD-overexpressing ApoE KO (eMnSOD-Tg/ApoE KO) mice. However, in HFD-fed groups, eMnSOD-Tg/ApoE KO mice exhibited reduced atherosclerotic lesion size, decreased relative ROS levels, and lower Our findings demonstrate that endothelial-specific MnSOD overexpression suppresses obesity-related atherosclerosis in ApoE KO mice. mtROS plays a pivotal role in obesity-associated atherosclerosis, and targeting endothelial mtROS may offer a therapeutic strategy for preventing vascular complications in obesity. Show less

Atherosclerosis is a chronic inflammatory disease wherein macrophage polarization critically influences lesion development. Dipeptidyl peptidase-4 (DPP4), a serine protease expressed on immune cells, has been implicated in vascular inflammation; however, its cell type-specific roles remain unclear. This study aimed to determine whether Dpp4 deficiency, particularly in hematopoietic cells, affects macrophage polarization and atherosclerosis progression. Using Apoe-knockout (ApoeKO) and Apoe- and Dpp4-double knockout mice as well as bone marrow transplantation models, we evaluated the impact of systemic and myeloid-specific Dpp4 deficiency on macrophage phenotype and atherogenesis. In bone marrow-derived macrophages, Dpp4 deficiency enhanced M2 marker expression (Arg1, Ym1, Mgl2, and Fizz1) and increased the proportion of CD206 Show less

Crohn's disease (CD) is a chronic inflammatory bowel disease with unknown etiology. Inflammatory chemical mediators synthesized from arachidonic acid, an n-6 polyunsaturated fatty acid (PUFA), have been shown to activate CD. Additionally, n-3 PUFAs are metabolized by the same enzyme as n-6 PUFAs and known to inhibit the arachidonic acid cascade. Our previous study noted that the presence of erythrocyte membrane fatty acids is a characteristic finding in Japanese CD patients. It was thus speculated that To investigate the relationship of Using previously reported findings regarding The presence of the rs174538 mutation in The rs174538 mutation alters the fatty acid profile through strong linkage to the Show less

Diabetes is an increasingly prevalent global disease and is often accompanied by sarcopenia, particularly in older adults. While insulin resistance is a well-known contributor to muscle loss in diabetes, the role of glucose signaling in diabetic skeletal muscle atrophy, particularly under insulin-deficient conditions, remains poorly understood. This study aimed to elucidate the pathophysiological role of the carbohydrate-responsive element-binding protein (ChREBP), a glucose-sensing transcription factor encoded by the Chrebp gene in mice, in diabetic sarcopenia by generating Chrebp-deficient, insulin-deficient Ins2Akita/+ mice. We evaluated Chrebp +/+, Chrebp -/-, Ins2Akita/+ /Chrebp +/+, and Ins2Akita/+ /Chrebp -/- mice for muscle strength, endurance, survival, body composition, and muscle histology. Skeletal muscles were analyzed for gene expressions related to anabolic and catabolic pathways. We found that Ins2Akita/+ /Chrebp -/- mice exhibited significant reductions in body weight, grip strength, survival, and skeletal muscle mass - particularly in the tibialis anterior, soleus, gastrocnemius, and quadriceps - compared to Ins2Akita/+ controls, despite similar hyperglycemia. Histological analysis revealed a smaller mean muscle fiber size and reduced cross-sectional area of type 2A and 2B fibers, without changes in fiber-type composition. Furthermore, Igf-1 expression was suppressed, while the atrophy marker Fbxo32/Atrogin-1 was upregulated. These findings demonstrate that Chrebp deletion exacerbates muscle atrophy and frailty in insulin-deficient mice, underscoring a key role for ChREBP-mediated glucose signaling in maintaining muscle mass under diabetic conditions. The Ins2Akita/+ /Chrebp -/- model provides a valuable platform for exploring diabetic sarcopenia mechanisms and potential therapeutic targets. Show less

The phase angle (PhA), assessed using bioelectrical impedance analysis (BIA), is becoming increasingly popular as an index of muscle quality associated with various health-related outcomes. This study aimed to clarify the relationship between PhA and sedentary behavior (SB), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA), which were objectively measured using accelerometers in older adults with disabilities requiring care. We recruited 90 older adults (39 men and 51 women, mean age of 78.7 ± 6.7 years) with disabilities under the long-term care insurance system. Skeletal muscle mass index (SMI) and PhA of the lower limbs were measured using a multifrequency BIA instrument. Daily durations of SB, LPA, and MVPA per day were measured using a triaxial accelerometer. Nutritional status was assessed using the long form of the Mini Nutritional Assessment (MNA). The MVPA duration was significantly associated with lower limb PhA after adjusting for age, sex, SB and LPA durations, MNA score, and medical history (p = 0.037), whereas SB and LPA durations were not associated with lower limb PhA. The duration of SB, LPA, and MVPA were not significantly associated with lower limb SMI, whereas the MNA score was. Lower limb PhA, but not lower limb SMI, was associated with MVPA duration, independent of nutritional status and medical history. Enhancing the duration of MVPA is needed to maintain the PhA and prevent further decline in physical function in older adults who require long-term care due to disabilities. Show less

Being overweight exacerbates various metabolic diseases, necessitating the identification of target molecules for obesity control. In the current study, we investigated common physiological features related to metabolism in mice with low weight gain: (1) G protein-coupled receptor, family C, group 5, member B-knockout; (2) gastric inhibitory polypeptide receptor-knockout; and (3) Iroquois-related homeobox 3-knockout. Moreover, we explored genes involved in metabolism by analyzing differentially expressed genes (DEGs) between low-weight gain mice and the respective wild-type control mice. The common characteristics of the low-weight gain mice were low inguinal white adipose tissue (iWAT) and liver weight despite similar food intake along with lower blood leptin levels and high energy expenditure. The DEGs of iWAT, epididymal (gonadal) WAT, brown adipose tissue, muscle, liver, hypothalamus, and hippocampus common to these low-weight gain mice were designated as candidate genes associated with metabolism. One such gene tetraspanin 7 (Tspan7) from the iWAT was validated using knockout and overexpressing mouse models. Mice with low Tspan7 expression gained more weight, while those with high Tspan7 expression gained less weight, confirming the involvement of the Tspan7 gene in weight regulation. Collectively, these findings suggest that the candidate gene list generated in this study contains potential target molecules for obesity regulation. Further validation and additional data from low-weight gain mice will aid in understanding the molecular mechanisms associated with obesity. Show less

Platelet-rich plasma (PRP), which is prepared by concentrating platelets in autologous blood, shows efficacy in chronic skin wounds via multiple growth factors. However, it exhibits heterogeneity across patients, leading to unstable therapeutic efficacy. Human induced pluripotent stem cell (iPSC)-derived megakaryocytes and platelets (iMPs) are capable of providing a stable supply, holding promise as materials for novel platelet concentrate-based therapies. In this context, we evaluated the effect of iMPs on wound healing and validated lyophilization for clinical applications. The growth factors released by activated iMPs were measured. The effect of the administration of iMPs on human fibroblasts and human umbilical vein endothelial cells (HUVECs) was investigated in vitro. iMPs were applied to dorsal skin defects of diabetic mice to assess the wound closure rate and quantify collagen deposition and angiogenesis. Following the storage of freeze-dried iMPs (FD-iMPs) for three months, the stability of growth factors and their efficacy in animal models were determined. Multiple growth factors that promote wound healing were detected in activated iMPs. iMPs specifically released FGF2 and exhibited a superior enhancement of HUVEC proliferation compared to PRP. Moreover, an RNA-seq analysis revealed that iMPs induce polarization to stalk cells and enhance ANGPTL4 gene expression in HUVECs. Animal studies demonstrated that iMPs promoted wound closure and angiogenesis in chronic wounds caused by diabetes. We also confirmed the long-term stability of growth factors in FD-iMPs and their comparable effects to those of original iMPs in the animal model. Our study demonstrates that iMPs promote angiogenesis and wound healing through the activation of vascular endothelial cells. iMPs exhibited more effectiveness than PRP, an effect attributed to the exclusive presence of specific factors including FGF2. Lyophilization enabled the long-term maintenance of the composition of the growth factors and efficacy of the iMPs, therefore contributing to stable supply for clinical application. These findings suggest that iMPs provide a novel treatment for chronic wounds. Show less

Because apolipoprotein-A2 (ApoA2), a key component of high-density lipoprotein cholesterol (HDL-C), lacks clear clinical significance, we investigated its impact on cardiovascular events in patients undergoing percutaneous coronary intervention (PCI). We examined 638 patients who underwent PCI with a new-generation drug-eluting stent for acute or chronic coronary syndrome and had their apolipoprotein levels measured between 2016 and 2021. The patients were divided into 2 groups based on the median serum ApoA2 values, and the incidence of major adverse cardiovascular events (MACE) was assessed. Of the 638 patients, 563 (88%) received statin treatment, with a median serum LDL-C level of 93 mg/dL. Furthermore, 137 patients (21.5%) experienced MACE, and Kaplan-Meier analysis revealed that the higher ApoA2 group had a significantly lower incidence of MACE than the lower ApoA2 group (30.9% vs. 41.6%). However, the other apolipoproteins, including ApoA1, ApoB, ApoC2, ApoC3, and ApoE, showed no significant differences in MACE. Multivariable Cox hazard analysis indicated that ApoA2 was an independent predictor of MACEs (hazard ratio, 0.666; 95% confidence interval, 0.465-0.954). Furthermore, ApoA2 levels exhibited the strongest inverse association with high-sensitivity C-reactive protein levels (r Among all the apolipoproteins, the serum ApoA2 level may be the strongest predictor of future cardiovascular events and prognosis in patients undergoing PCI. Show less

The epithelial-mesenchymal transition (EMT) is a phenomenon, in which epithelial cells acquire a mesenchymal cell phenotype. It is important during wound healing; however, chronic inflammation leads to excessive EMT and causes tissue barrier dysfunction with hyperplasia. EMT is induced by several cytokines, such as interleukin (IL)-4 and IL-13. Additionally, IL-4 and IL-13 are known to increase in atopic dermatitis (AD) characterized by intense itching and eczema. Therefore, we assumed that there was commonality between the respective EMT and AD phenotypes. Herein, we evaluated EMT marker expression in AD skin and demonstrated that EMT-maker Snai1 and Twist expression were increased in AD mice model and patients with AD. Moreover, the epithelial-marker keratin 5 and mesenchymal marker Vimentin were co-expressed in the skin epidermis of mice with AD, suggesting the existence of hybrid epithelial-mesenchymal (E/M) cells possessing both epithelial and mesenchymal characteristics. In fact, we found that ΔNp63a, a stabilizing factor for hybrid E/M cells, was upregulated in the skin epidermis of the AD model mouse. Interestingly, increased expression of EMT markers was observed even at a nonlesion site in a patient with AD without initial inflammation or scratching. Therefore, EMT-like phenomena may occur independently of wound healing in skin of patients with AD. Show less

Na Knockdown of ATP1A1 expression was performed in human CC cell lines HT29 and Caco2 using small interfering RNA. The roles of ATP1A1 in various biological processes of cells (i.e., proliferation, cell cycle, apoptosis, migration, and invasion) were assessed. Microarray analysis was utilized for gene expression profiling. Samples obtained from 200 patients with CC who underwent curative colectomy were analyzed through immunohistochemistry. ATP1A1 knockdown suppressed cell proliferation, migration, and invasion and induced apoptosis. The results of the microarray analysis revealed that the upregulated or downregulated gene expression in ATP1A1-depleted cells was related to the extracellular signal-regulated kinase 5 (ERK5) signaling pathway [epidermal growth factor receptor (EGFR), mitogen-activated protein kinase kinase 5 (MAP2K5), mitogen-activated protein kinase 7 (MAPK7), FOS, MYC, and BCL2 associated agonist of cell death (BAD)]. Immunohistochemical analysis demonstrated a correlation between ATP1A1 expression and pathological T stage (p = 0.0054), and multivariate analysis identified high ATP1A1 expression as an independent predictor of poor recurrence-free survival in patients with CC (p = 0.0040, hazard ratio: 2.807, 95% confidence interval 1.376-6.196). ATP1A1 regulates tumor progression through the ERK5 signaling pathway. High ATP1A1 expression is associated with poor long-term outcomes in patients with CC. Show less

Loss of epithelial integrity is associated with colorectal cancer (CRC) aggressiveness. Protein kinase C (PKC) is frequently implicated in human cancers, but the role of PKCγ in CRC remains poorly understood. Here, we show that PKCγ, a conventional PKC, is expressed in normal colonic epithelium, but this is lower in dedifferentiated CRC. PKCγ expression was downregulated by SNAI1 overexpression, and low PKCγ expression was associated with poor prognosis in patients with CRC. Transient or stable knockdown of PKCγ reduced E-cadherin expression in CRC cells. PKCγ knockdown enhanced proliferation, anchorage-independent cell growth, resistance to anti-cancer drugs, and Show less

Carbohydrate response element-binding protein (ChREBP) is critical in the regulation of fatty acid and triglyceride synthesis in the liver. Interestingly, Chrebp-/- mice show reduced levels of plasma cholesterol, which is critical for steroid hormone synthesis in adrenal glands. Furthermore, Chrebp mRNA expression was previously reported in human adrenal glands. Thus, it remains to be investigated whether ChREBP plays a role directly or indirectly in steroid hormone synthesis and release in adrenal glands. In the present study, we find that Chrebp mRNA is expressed in mouse adrenal glands and that ChREBP binds to carbohydrate response elements. Histological analysis of Chrebp-/- mice shows no adrenal hyperplasia and less oil red O staining compared with that in WT mice. In adrenal glands of Chrebp-/- mice, expression of Fasn and Scd1, two enzymes critical for fatty acid synthesis, was substantially lower and triglyceride content was reduced. Expression of Srebf2, a key transcription factor controlling synthesis and uptake of cholesterol and the target genes, was upregulated, while cholesterol content was not significantly altered in the adrenal glands of Chrebp-/- mice. Adrenal corticosterone content and plasma adrenocorticotropic hormone and corticosterone levels were not significantly altered in Chrebp-/- mice. Consistently, expression of genes related to steroid hormone synthesis was not altered. Corticosterone secretion in response to two different stimuli, namely 24-h starvation and cosyntropin administration, was also not altered in Chrebp-/- mice. Taking these results together, corticosterone synthesis and release were not affected in Chrebp-/- mice despite reduced plasma cholesterol levels. Show less

Consumer preference for slow-growing broiler chickens is rising because of increased demand for high-quality poultry products. Korat chicken (KRC) is a slow-growing chicken generated in Thailand. A goal of the KRC breeding program is to produce meat with a low purine content to benefit an aging population, without interfering with growth performance. Thus, this study aimed to investigate the effects of genes encoding melanocortin 4 receptor (MC4R), calpain 1 (CAPN1), and adenylosuccinate lyase (ADSL) on body weight, muscle fiber, and content of purine and its derivatives (i.e., adenine, guanine, hypoxanthine, and xanthine), to develop molecular markers for breeding programs. Genotypes of MC4R, CAPN1, and ADSL were obtained from 583 KRCs by PCR-single-strand conformation polymorphism. The body weight and purine contents of the KRCs were measured every 2 wk until the KRCs reached market weight at 10 wk of age. A significant association between the MC4R genotype and body weight at 2, 4, and 10 wk of age was detected. KRC possessing the BB genotype of CAPN1 showed significantly heavier body weight at 6 wk of age and guanine content at 4 wk of age, and a smaller muscle fiber diameter in the breast muscle at 10 wk of age, compared with those of the other genotypes. In addition, high expression levels of the CAPN1 and ADSL genes were detected in the breast muscle at 2 wk of age. Although higher purine contents were detected at a young age, no significant associations with the MC4R, CAPN1, and ADSL genes were detected. Our results indicate that MC4R and CAPN1 could be used as genetic markers for growth and meat quality in the slow-growing chicken breeding program. Show less

Multiple osteochondromas (MO; also referred to as hereditary multiple exostoses [HME] in the literature) is an autosomal dominant disorder characterized by benign, cartilage-capped bone tumors that grow from the metaphyses of long bones. Two genes are associated with this disease: EXT1 on 8q24.11-q24.13 and EXT2 on 11p12-p11. Mutations in EXT1 and EXT2 are found in 54-96% of patients with MO and are generally more frequent in EXT1 than in EXT2. We previously studied 43 Japanese families with MO using single-strand conformation polymorphism analysis for EXT1 and EXT2, and reported 23 families (54%) with mutations and 20 families (46%) with no mutations in these genes. Among the families with mutations, 17 families (40%) had mutations in EXT1, and 6 families (14%) had mutations in EXT2. Here we examined the same 43 Japanese families using denaturing high-performance liquid chromatography as an alternative technique. We detected five mutations, three of which are novel, in seven families in addition to the previously described mutations. In summary, we detected mutations in EXT1 or EXT2 in 30 (70%) out of 43 families. Our result suggests the presence of other gene(s) responsible for MO, at least in Japanese patients. Show less

Hereditary multiple exostoses (EXT) is an autosomal dominant bone disease characterized by the formation of cartilage-capped prominences. EXT is genetically heterogeneous with at least four chromosomal loci. Among the four loci, the exostosis type 1 gene (EXT1) and type 2 gene (EXT2) have been cloned. Previous studies have shown that disease-type-specific frequency of mutations is different among various ethnic populations. To determine those frequencies in the Japanese, we conducted a large-scale mutation screening on both genes. In 23 of 43 Japanese families examined, we found 21 different mutations, of which 18 are novel. Seventeen (40%) of the 23 families had a mutation in EXT1 and six (14%) had a mutation in EXT2, suggesting that the former mutations are more frequent than the latter in Japanese EXT families. Of the 17 families with EXT1 mutations, 13 had those causing premature termination of the EXT1 protein and four showed missense mutations, whereas five of the six families with EXT2 mutations had those causing premature termination and one showed missense mutation. Interestingly, all four EXT1 missense mutations occurred in an arginine residue at codon 340 (R340) that is known as a critical site for expression of heparan sulfate glycosaminoglycans, suggesting that the region encompassing the arginine residue may play an important role in the function of the EXT1 protein. These results expand our knowledge of the ethnic difference of EXT and the structure-function relationship of the EXT genes. Show less

Mice with a targeted mutation of the gastric inhibitory polypeptide (GIP) receptor gene (GIPR) were generated to determine the role of GIP as a mediator of signals from the gut to pancreatic beta cells. GIPR-/- mice have higher blood glucose levels with impaired initial insulin response after oral glucose load. Although blood glucose levels after meal ingestion are not increased by high-fat diet in GIPR+/+ mice because of compensatory higher insulin secretion, they are significantly increased in GIPR-/- mice because of the lack of such enhancement. Accordingly, early insulin secretion mediated by GIP determines glucose tolerance after oral glucose load in vivo, and because GIP plays an important role in the compensatory enhancement of insulin secretion produced by a high insulin demand, a defect in this entero-insular axis may contribute to the pathogenesis of diabetes. Show less