Insulin signaling is mediated via a network of protein phosphorylation. Dysregulation of this network is central to obesity, type 2 diabetes and metabolic syndrome. Here we investigate the role of phosphatase binding protein Alpha4 (α4) that is essential for the serine/threonine protein phosphatase 2A (PP2A) in insulin action/resistance in adipocytes. Unexpectedly, adipocyte-specific inactivation of α4 impairs insulin-induced Akt-mediated serine/threonine phosphorylation despite a decrease in the protein phosphatase 2A (PP2A) levels. Interestingly, loss of α4 also reduces insulin-induced insulin receptor tyrosine phosphorylation. This occurs through decreased association of α4 with Y-box protein 1, resulting in the enhancement of the tyrosine phosphatase protein tyrosine phosphatase 1B (PTP1B) expression. Moreover, adipocyte-specific knockout of α4 in male mice results in impaired adipogenesis and altered mitochondrial oxidation leading to increased inflammation, systemic insulin resistance, hepatosteatosis, islet hyperplasia, and impaired thermogenesis. Thus, the α4 /Y-box protein 1(YBX1)-mediated pathway of insulin receptor signaling is involved in maintaining insulin sensitivity, normal adipose tissue homeostasis and systemic metabolism.
Bubbles with a diameter of 1 to 100 μm are defined as microbubbles (hereinafter, this is called "MB"), and are used for floatation separation because of their adhesion to suspended substances. However, there are few research reports on floatation separation, and standardization for device design has not been performed, so improving the efficiency of floatation separation devices has become an issue. Therefore, in this study, the experiments were carried out to clarify the floatation separation characteristics by microbubbles as a basic research of floatation separation by microbubbles. In the experiment, the soft flour was used as a suspended substance, and as basic characteristics, the state of adhesion with microbubbles, the relationship with bubble diameter, and the rising velocity rate were measured. In addition, as the actual floating separation performance, the concentration time with each initial concentration was investigated. The conclusions are as follows: About 60% of the adhered form of the microbubbles and the soft flour was observed as a form in which a single microbubble adhered to the soft flour. The number of microbubbles with a bubble diameter of 80-90 μm was attached in the case of single microbubble attachment to flour is large. In the floating separation characteristics, floatation the soft flour concentration in the tank decreases sharply at the short time, and then gradually decreases. The higher the initial concentration, the longer the processing time required to reach the target concentration, but the tendency of the concentration decrease was the same. The final concentration remains around 20 ppm in all experimental conditions. These results are important for standardization of floatation separation characteristics in the future.
Insulin and IGF1 signaling through the PI3K/AKT and MAPK/ERK pathways are essential for maintenance of brown and white adipose tissues (BAT and WAT), as shown by our previous results using adipocyte-specific and inducible IR/IGF1R knockout mice (Ai-DKO). Here, through a research to screen the genes essential for adipose tissues maintenance in WAT and BAT using Ai-DKO mice, we identified a reduction of α4, a protein phosphatase protector which regulate phosphorylation state, in Ai-DKO BAT. shRNA-mediated α4 knockdown (KD) altered insulin-stimulated phosphorylation status in BAT; decreased IRβ (Y1162/1163), IRS1 (Y612) and Akt (S473), with a mild change in ERK1/2 (T202/Y204) but increased ribosomal S6 protein (S235/236), suggesting α4 reduces S6 phosphorylation state via a unique pathway. Next, to investigate the impact of α4 in vivo, we created inducible adipocyte-specific α4 KO (Ai-α4 KO) mice with tamoxifen-inducible Cre-ERT2 transgene. Once induced α4 KO in adipocytes, the mice revealed extensive losses of adipocytes in SC-WAT and BAT depots with increased apoptotic cell death. Ai-α4 KO mice showed cold intolerance, severe diabetes, ectopic lipid accumulation in the liver, and pancreatic islet hyperplasia. RNA-seq showed a marked reduction of genes associated with mitochondrial fatty acid oxidation and increases with inflammatory cytokine pathways in Ai-α4 KO SC-WAT and BAT. WAT and BAT mass can recover after a few months in Ai-α4KO. Interestingly, lipidomics analysis displayed that the regenerated adipocytes showed unique lipid content in the Ai-α4KO. Thus, our model demonstrates that the tuning of phosphorylation status for insulin-dependent signaling by α4 is critical for maintaining and regeneration of white and brown adipose tissues. Disclosure M. Sakaguchi: None. S. Okagawa: None. Y. Okubo: None. S. Kitano: None. M. Igata: None. T. Kondo: None. E. Araki: Advisory Panel; Self; Abbott. Speaker’s Bureau; Self; ARKRAY, Astellas Pharma Inc., AstraZeneca, Eli Lilly Japan K.K., Merck & Co., Inc., Novo Nordisk Inc., WebMD LLC. Other Relationship; Self; Kowa Company, Ltd., Mitsubishi Tanabe Pharma Corporation, Novartis Pharma K.K., Sumitomo Dainippon Pharma Co., Ltd., Takeda Pharmaceutical Company Limited. Funding Japan Society for the Promotion of Science; Merck Sharp & Dohme Foundation; Takeda Foundation; Boehringer Ingelheim; Eli Lilly and Company
Insulin and IGF1 signaling initiate Tyr phosphorylation of IR/IGF1R and adaptor IRSs, leading to Ser/Thr phosphorylation of PI3K/AKT and MAPK/ERK pathways essential for the maintenance of brown and white adipose tissues (BAT and WAT). Lack of insulin-signaling in adipose tissues caused metabolic disease in mice with hyperglycemia, hyperlipidemia, and fatty liver, but the mice recovered adipose tissues by regenerating adipocytes. We addressed the mechanism of how adipose tissues regenerate using adipocyte-specific and inducible IR/IGF1R knockout mice (Ai-DKO). We identified a reduction of protein phosphatase protector, α4, which can regulate Ser/Thr phosphorylation of down-stream insulin signaling. shRNA-mediated α4 knockdown (KD) in BAT affected not only insulin-stimulated down-stream Ser/Thr phosphorylation of AKT (S473) but also affected up-stream Tyr phosphorylation of IRβ (Y1162/1163) and IRS1 (Y612). Proteomics analysis of α4-binding molecule identified Y-box protein 1 (YBX1), which functions as a transcription factor for Tyr phosphatase PTP1B. We observed increased PTP1B expression in α4-KO preadipocytes. As the impact of α4 in vivo, inducible adipocyte-specific α4 KO (Ai-α4 KO) mice with tamoxifen-inducible Cre-ERT2 transgene showed cold intolerance, diabetes, ectopic lipid accumulation in the liver, and pancreatic islet hyperplasia, with an increase of C18: 0-ceramide in WAT and BAT. RNA-seq showed a marked reduction of genes associated with mitochondrial fatty acid oxidation and the increases in inflammatory cytokine pathways in Ai-α4 KO WAT and BAT, implicating the cause of fat tissue loss was the increased adipocyte apoptosis. The α4 to PTP1B loop is critical for fat tissue maintenance by regulating IR tyrosine phosphorylation. Disclosure M. Sakaguchi: None. S. Okagawa: None. Y. Okubo: None. K. Fukuda: None. M. Igata: None. J. Kawashima: None. T. Kondo: None. E. Araki: Other Relationship; Self; Daiichi Sankyo Company, Limited, Eli Lilly Japan K. K., Mitsubishi Tanabe Pharma Corporation, MSD K. K., Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk Pharma Ltd., Sanofi K. K., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Co., Speaker’s Bureau; Self; Astellas Pharma Inc., AstraZeneca K. K., Kowa Company, Ltd. Funding Japan Society for the Promotion of Science; Merck Sharp & Dohme Corp; Takeda Foundation
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