Publications by authors named "Hiroyo Ota"

Sleep apnea syndrome (SAS) exposes cells throughout the body to intermittent hypoxia (IH). Intermittent hypoxia is a risk factor not only for hypertension and insulin resistance but also for vascular dysfunction. We have reported correlations between IH, insulin resistance and hypertension.

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Sleep apnoea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]) and is a risk factor for insulin resistance/Type 2 diabetes. The induction of insulin resistance in skeletal muscle is a key phenomenon to develop diabetes. However, the mechanisms linking IH stress and insulin resistance remain elusive.

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Article Synopsis
  • Intermittent hypoxia (IH) from sleep apnea syndrome (SAS) causes repeated cycles of low oxygen that impact cells, leading to oxidative stress and inflammation, which are linked to metabolic syndrome and disorders like type 2 diabetes and hypertension.
  • The review highlights research on how IH affects gene expression in various cells, including neurons and pancreatic β cells, to understand its role in metabolic issues.
  • It also examines the connection between IH-induced metabolic disorders and the development of dementia, emphasizing the need to understand the direct and indirect pathways leading to cognitive decline.
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Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]), and is a risk factor for cardiovascular disease (CVD) and insulin resistance/Type 2 diabetes. However, the mechanisms linking IH stress and CVD remain elusive. We exposed rat H9c2 and mouse P19.

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Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia, IH), and it is a risk factor for cardiovascular disease (CVD) and insulin resistance/type 2 diabetes. However, the mechanisms linking IH stress and CVD remain elusive. We exposed rat H9c2 and mouse P19.

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Sleep apnea syndrome (SAS), characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia (IH)), is a risk factor for hypertension and insulin resistance. We report a correlation between IH and insulin resistance/diabetes. However, the reason why hypertension is induced by IH is elusive.

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Sleep apnea syndrome (SAS) is a breathing disorder characterized by recurrent episodes of upper-airway collapse, resulting in intermittent hypoxia (IH) during sleep. Experimental studies with animals and cellular models have indicated that IH leads to attenuation of glucose-induced insulin secretion from pancreatic β cells and to enhancement of insulin resistance in peripheral tissues and cells, such as the liver (hepatocytes), adipose tissue (adipocytes), and skeletal muscles (myocytes), both of which could lead to obesity. Although obesity is widely recognized as a major factor in SAS, it is controversial whether the development of SAS could contribute directly to obesity, and the effect of IH on the expression of appetite regulatory genes remains elusive.

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Sleep apnea syndrome (SAS) is a prevalent disorder characterized by recurrent apnea or hypoxia episodes leading to intermittent hypoxia (IH) and arousals during sleep. Currently, the relationship between SAS and metabolic diseases is being actively analyzed, and SAS is considered to be an independent risk factor for the development and progression of insulin resistance/type 2 diabetes (T2DM). Accumulating evidence suggests that the short cycles of decreased oxygen saturation and rapid reoxygenation, a typical feature of SAS, contribute to the development of glucose intolerance and insulin resistance.

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Sleep apnea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]), and it is a known risk factor for hypertension. The upregulation of the renin-angiotensin system has been reported in IH, and the correlation between renin and CD38 has been noted. We exposed human HEK293 and mouse As4.

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Preeclampsia/hypertensive disorders of pregnancy (PE/HDP) is a serious and potentially life-threatening disease. Recently, PE/HDP has been considered to cause adipose tissue inflammation, but the detailed mechanism remains unknown. We exposed human primary cultured adipocytes with serum from PE/HDP and healthy controls for 24 h, and analyzed mRNA expression of several adipokines, cytokines, and ligands of the receptor for advanced glycation endproducts (RAGE).

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Sleep apnea syndrome (SAS) is a very common disease involving intermittent hypoxia (IH), recurrent symptoms of deoxygenation during sleep, strong daytime sleepiness, and significant loss of quality of life. A number of epidemiological researches have shown that SAS is an important risk factor for insulin resistance and type 2 diabetes mellitus (DM), which is associated with SAS regardless of age, gender, or body habitus. IH, hallmark of SAS, plays an important role in the pathogenesis of SAS and experimental studies with animal and cellular models indicate that IH leads to attenuation of glucose-induced insulin secretion from pancreatic β cells and to enhancement of insulin resistance in peripheral tissues and cells, such as liver (hepatocytes), adipose tissue (adipocytes), and skeletal muscles (myocytes).

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Obstructive sleep apnea (OSA) causes many systemic disorders via mechanisms related to sympathetic nerve activation, systemic inflammation, and oxidative stress. OSA typically shows repeated sleep apnea followed by hyperventilation, which results in intermittent hypoxia (IH). IH is associated with an increase in sympathetic activity, which is a well-known pathophysiological mechanism in hypertension and insulin resistance.

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Sleep apnea syndrome (SAS), characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]), is a risk factor for insulin resistance. Recently, IH is considered to independently cause adipose tissue inflammation/dysfunction, leading to worsening insulin resistance; however, the detailed mechanism remains unknown. We exposed mouse 3T3-L1 and human SW872 adipocytes to experimental IH or normoxia for 24 h, and analyzed mRNA expression of several adipokines.

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Article Synopsis
  • Sleep apnea patients experience intermittent hypoxia (IH) during sleep, which affects the expression of appetite-regulating peptides in the body.
  • A study found that IH significantly increased the mRNA levels and concentrations of appetite-inhibiting gut hormones such as PYY, GLP-1, and NTS in specific human and mouse cell lines.
  • The research suggests that IH may reduce appetite by altering chromatin structure in enteroendocrine cells, demonstrating a potential anorexigenic effect on the enteric nervous system.
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Sleep apnea syndrome (SAS) is characterized by intermittent hypoxia (IH) during sleep. SAS and obesity are strongly related to each other. Here, we investigated the effect of IH on the expression of major appetite regulatory genes in human neuronal cells.

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Sleep apnea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]) and is a risk factor for insulin resistance/type 2 diabetes. However, the mechanisms linking IH stress and insulin resistance remain elusive. We exposed human hepatocytes (JHH5, JHH7, and HepG2) to experimental IH or normoxia for 24 h, measured mRNA levels by real-time reverse transcription polymerase chain reaction (RT-PCR), and found that IH significantly increased the mRNA levels of () - a hepatokine - and () - one of (Regenerating gene) family.

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Article Synopsis
  • Recent studies indicate a connection between advanced glycation end products (AGE) and hydroquinone (HQ) in the development of age-related macular degeneration (AMD), but the exact mechanism remains unclear.
  • This study found that HQ significantly reduces the number of viable human retinal pigment epithelial (RPE) cells through apoptosis, while AGE counters this effect by boosting DNA replication without affecting apoptosis.
  • Additionally, the research identified that HQ increases VEGF secretion, and combining HQ with AGE further elevates this response, implying that SP1 plays a critical role in regulating gene expression related to AMD development.
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Reg (Regenerating gene) gene was originally isolated from rat regenerating islets and its encoding protein was revealed as an autocrine/paracrine growth factor for β cells. Rat Reg gene is activated in inflammatory conditions for β cell regeneration. In human, although five functional REG family genes (REG Iα, REG Iβ, REG III, HIP/PAP, and REG IV) were isolated, their expressions in β cells under inflammatory conditions remained unclear.

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Article Synopsis
  • Researchers are exploring the possibility of curing diabetes using non-pancreatic cells, specifically fetal liver cells (hepatocytes).
  • They found that mouse fetal liver expresses insulin mRNAs and proteins, alongside transcription factors like NeuroD/Beta2 and MafA that are key in insulin production.
  • The study indicates that manipulating these transcription factors in fetal hepatocytes could lead to the development of insulin-producing β cells, offering a potential new treatment for diabetes.
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Aims: Although accumulating evidence suggests the associations between sleep apnea syndrome (SAS) and type 2 diabetes, the direct effect of intermittent hypoxia (IH) on pancreatic β cell proliferation remains a missing piece of the puzzle.

Main Methods: Rat RINm5F β cells, hamster HIT-T15 β cells, and human 1.1B4 β cells were exposed to normoxia (21% O2, 5% CO2, and balance N2), to sustained hypoxia (SH: 1% O2, 5% CO2, and balance N2), or to intermittent hypoxia (IH: 64 cycles of 5 min SH and 10 min normoxia) for 24 h.

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Obstructive sleep apnea is characterized by intermittent hypoxia (IH), and associated with cardiovascular diseases, such as stroke and heart failure. These cardiovascular diseases have a relation to atherosclerosis marked by the proliferation of vascular smooth muscle cells (VSMCs). In this study, we investigated the influence of IH on cultured rat aortic smooth muscle cell (RASMC).

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Reg (regenerating gene) product, Reg protein, is induced in pancreatic β-cells and acts as autocrine/paracrine growth factor for regeneration via the cell surface Reg receptor. However, high concentrations of Reg I protein induced β-cell apoptosis. In the present study, we found that hepatocyte growth factor (HGF) attenuated the β-cell apoptosis induced by the high concentrations of Reg I protein and that the combined stimulation of interleukin-6 (IL-6) and dexamethasone (Dx) induced the accumulation of HGF mRNA as well as Reg I mRNA in β-cells.

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Article Synopsis
  • Sleep apnea syndrome (SAS) leads to decreased oxygen levels during sleep, causing daytime sleepiness and negatively affecting quality of life, with connections to type 2 diabetes independent of obesity measurements.
  • Research involved exposing hamster β-cells and rat islets to intermittent hypoxia (IH) to assess its impact on glucose-induced insulin secretion (GIS) and related gene expression.
  • Findings showed that IH treatment reduced GIS without changing certain insulin-related mRNA levels, suggesting that IH stress directly affects GIS by lowering levels of the CD38 gene.
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  • Cyclic ADP-ribose (cADPR) is a key messenger that helps increase calcium (Ca²⁺) levels in cells, particularly influencing insulin secretion in pancreatic islets.
  • Researchers isolated a new type of ryanodine receptor (the islet-type RyR) from the RyR2 gene, which is created through a process called alternative splicing.
  • When comparing the islet-type RyR2 with the traditional RyR2, the islet-type showed enhanced response to cADPR, suggesting it plays a unique role in calcium signaling across different tissues.
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