Search

Objectives We aimed to investigate the effect of iron deficiency on basal- and contraction-induced increases in muscle protein synthesis. Methods Four-wk-old male Sprague–Dawley rats were divided into three groups. The rats in two of the three groups had free access to a control diet (AD) or iron-deficient diet (ID) for 4 wk. The rats in the third group (CON) were pair-fed the control diet to the mean intake of the ID group. Results In comparison with the CON group, the ID group showed significantly lower hematocrit and hemoglobin concentrations, iron-containing protein levels, and total iron content in skeletal muscle, but non-iron-containing protein levels did not show any differences between the groups. Protein synthesis, measured by puromycin-labeled peptides, was lower in the ID group compared with the CON group in both basal- and contraction-stimulated states. The ID diet impaired the activation levels of signaling pathways involved in protein synthesis, such as ribosomal protein S6 and eukaryotic translation initiation factor 4E-binding protein 1. Furthermore, dietary iron deficiency decreased autophagy capacity, but did not affect the ubiquitinated protein content. Conclusions These results suggest that severe iron deficiency decreases not only basal but also muscle contraction-induced increases in protein synthesis due to, at least in part, downregulation of the protein synthesis signaling pathway in the skeletal muscle.

During lipolysis, triglyceride (TG) are hydrolyzed into a glycerol and fatty acids in adipocyte. A significant portion of the fatty acids are re-esterificated into TG, and this is a critical step in promoting lipolysis. Although glycerol-3-phosphate (G3P) is required for triglyceride synthesis in mammalian cell, the substrate for G3P synthesis during active lipolysis is not known. A recent study showed that the inhibition of glucose uptake reduces catecholamine-stimulated lipolysis, suggesting that glucose availability is important in lipolysis in adipocytes. We hypothesized that glucose might play an essential role in generating G3P and thereby promoting catecholamine-stimulated lipolysis in adipocytes. Therefore, we determined the effect of glucose availability on catecholamine-stimulated lipolysis in 3T3-L1 adipocytes and rat adipose tissue. 3T3-L1 adipocytes and rat epididymal fat pads were cultured in a medium with/without glucose during stimulation by isoproterenol. Glycerol release was higher when adipocytes were cultured in a glucose-containing medium than that in a medium without glucose. Measurement of glucose uptake during catecholamine-stimulated lipolysis showed a slight, but significant increase in glucose uptake. We also compared glucose metabolism-related protein, such as glucose transporter 4, hexokinase, glycerol-3-phosphate dehydrogenase and lipase contents between fat tissues that play a critical role in active lipolysis. Epididymal fat exhibited higher lipolytic activity than inguinal fat because of higher lipase and glucose metabolism-related protein contents. We demonstrated that catecholamine-stimulated lipolysis is enhanced in the presence of glucose, and suggests that glucose is one of the primary substrates for G3P in adipocytes during active lipolysis.

arXiv:2104.04948v1, et al., We present spectroscopic and photometric observations of 17 dwarf-nova superoutbursts obtained by KOOLS-IFU mounted on the 3.8 m telescope Seimei at the Okayama Observatory of Kyoto University and through the Variable Star Network collaboration (VSNET). Our spectroscopic observations for six outbursts were performed within 1 d of their optical peak. 11 objects (TCP J00590972+3438357, ASASSN-19ado, TCP J06073081−0101501, ZTF20aavnpug, ASASSN-19ady, MASTER OT J061642.05+435617.9, TCP J20034647+1335125, ASASSN-20kv, ASASSN-20kw, MASTER OT J213908.79+161240.2, and ASASSN-20mf) were previously unknown systems, and our observations enabled quick classification of their transient type. These results illustrate that the Seimei telescope has the capability to conduct quick follow-up observations of unknown transients. Our photometric observations yielded that 11 of the objects are WZ Sge-type dwarf novae and their candidates, and the other six are SU UMa-type dwarf novae and their candidates. The He ii 4686 Å emission line was clearly detected among ASASSN-19ado, TCP J06073081−0101501 and MASTER OT J213908.79+161240.2, the association of which with a spiral arm structure in an accretion disk has been suggested in previous studies. Our result suggests that a higher-inclination system shows a stronger emission line of He ii 4686 Å, as well as larger-amplitude early superhumps., Maeda acknowledges support from the Japan Society for the Promotion of Science (JSPS) KAKENHI grant JP18H05223, JP20H00174, and JP20H04737. U. Burgaz acknowledges the support provided by the Turkish Scientific and Technical Research Council (TÜBITAK2211C and 2214A). This work was supported by the project APVV-15-0458 “Interacting binaries - Key for the Understanding of the Universe”. This work was supported by the Slovak Research and Development Agency under the contract No. APVV15-0458 and by the Slovak Academy of Sciences grant VEGA No. 2/0030/21. The authors from Sternberg institute thank the Program of Development of Lomonosov MSU ‘Leading Scientific Schools’. A.A.B, N.P.I. and M.A.B. (SAI MSU) are supported by the Interdisciplinary Scientific and Educational School of Moscow University ’Fundamental and Applied Space Research’. This research was partly supported by the Slovak Academy of Sciences grant VEGA No. 2/0030/21.

Iron deficiency has been associated with obesity and related metabolic disorders. The aim of the present study was to evaluate the effect of iron deficiency on fat metabolism, particularly regarding the lipolytic activity, lipolysis‑related protein expression, and glucose utilization of adipocytes. Differentiated 3T3‑L1 adipocytes were incubated with an iron chelator, deferoxamine mesylate (DFO), for 48 h. Subsequently, basal and isoproterenol‑stimulated lipolytic activities, the proteins involved in lipolysis and glucose utilization were compared with a control (CON). The results revealed that treatment with DFO significantly decreased the free iron content but did not affect total protein and lipid contents in adipocytes. Iron deprivation caused a significant reduction in isoproterenol‑stimulated lipolysis, but not basal lipolysis. Lipolysis‑related proteins, including perilipin A, adipose triglyceride lipase, hormone sensitive lipase and comparative gene identification‑58, were decreased in the DFO compared with the CON group. Furthermore, glucose utilization, a major precursor of 3‑glycerol phosphate for micro‑lipid droplet synthesis during lipolysis and the expression of glucose transporter (GLUT) 4 were significantly lower in the DFO group when compared with the CON group. However, hypoxia‑inducible factor‑1α and GLUT1 expressions were upregulated in DFO‑treated adipocytes. In conclusion, the results indicated that low iron availability attenuated catecholamine‑stimulated lipolysis by downregulating lipolytic enzymes and glucose utilization in 3T3‑L1 adipocytes.