Lactate production is a prioritized feature of adipocyte metabolism

Adipose tissue is essential for whole-body glucose homeostasis, with a primary role in lipid storage. It has been previously observed that lactate production is also an important metabolic feature of adipocytes, but its relationship to adipose and whole-body glucose disposal remains unclear. Therefore, using a combination of metabolic labeling techniques, here we closely examined lactate production of cultured and primary mammalian adipocytes. Insulin treatment increased glucose uptake and conversion to lactate, with the latter responding more to insulin than did other metabolic fates of glucose. However, lactate production did not just serve as a mechanism to dispose of excess glucose, because we also observed that lactate production in adipocytes did not solely depend on glucose availability and even occurred independently of glucose metabolism. This suggests that lactate production is prioritized in adipocytes. Furthermore, knocking down lactate dehydrogenase specifically in the fat body of Drosophila flies lowered circulating lactate and improved whole-body glucose disposal. These results emphasize that lactate production is an additional metabolic role of adipose tissue beyond lipid storage and release

Characterization of Trafficking Regulator of GLUT4-1 (TRARG1)

Insulin resistance is a precursor of most metabolic diseases including Type 2 diabetes, and is largely recapitulated by impaired insulin-stimulated glucose transport mediated by the glucose transporter, GLUT4. However, understanding precisely how insulin orchestrates regulation of GLUT4 traffic at the various transport steps, has been a longstanding puzzle. GLUT4 storage vesicles (GSVs) are specialized intracellular storage compartment of GLUT4 and translocate to the plasma membrane (PM) in response to insulin stimulation. In pursuit of novel proteins regulating GLUT4 traffic, our laboratory performed proteomic studies of GSVs purified from adipocytes and uncovered TRARG1 as a novel positive regulator of insulin-stimulated GLUT4 trafficking. To elucidate the mechanism(s) by which TRARG1 functions, I began with demonstrating that TRARG1 contains a single transmembrane domain (TMD) and one re-entrant loop, with a cytosolic N-terminus, contrary to the consensus predicted topology. Mass spectrometry (MS) analysis revealed a range of post-translational modifications (PTMs) on TRARG1, including phosphorylation. Examination of MS analysis of insulin-regulated protein phosphorylation in 3T3-L1 adipocytes and biochemical validation suggested that TRARG1 dephosphorylation by insulin is PI3K/Akt-dependent. Furthermore, TRARG1 is a novel substrate of the protein kinase GSK3. TRARG1 protein-protein interaction analysis revealed that insulin-mediated TRARG1 dephosphorylation regulates its binding to a range of proteins including Bcl9l. These findings have elucidated novel functions of TRARG1 in that it is predicted to function at multiple steps along the GLUT4 trafficking pathway as well as other functions thought to interact with GLUT4 trafficking. These latter include the Wnt-β-catenin signalling pathway which may regulate insulin sensitivity. My studies have revealed many novel functions of TRARG1 and highlighted this to be a key mediator of GLUT4 trafficking in fat cells

The role of lipid droplet associated proteins in inherited human disorders.

Publication status: PublishedProteins which associate with the surface of lipid droplets are intimately involved in the regulation of the droplets. Several human inherited disorders have now been linked to loss- and, in some cases, likely gain-of-function mutations in the genes encoding these proteins. These are summarised in this Graphical Review

Coal content recognition method of coal-rock mixture based on phase difference detectio

In view of problems of long measuring time and big error existed in current coal content recognition methods of coal-rock mixture, a coal content recognition method of coal-rock mixture based on phase difference detection was proposed. Relationship between coal content of coal-rock mixture and capacitance was gotten through experiment, parameters of phase difference detection circuit were chosen reasonably, and relationship between phase difference and the coal content was analyzed through numerical simulation and circuit simulation. The results show that coal content is lower than the minimum coal content threshold of coal mining when phase difference is positive, and coal content is higher than the minimum coal content threshold of coal mining when phase difference is negative, which indicate whether coal content achieves the minimum coal content threshold of coal mining can be judged accurately through detecting positive or negative of phase difference

A high-content endogenous GLUT4 trafficking assay reveals new aspects of adipocyte biology

Insulin-induced GLUT4 translocation to the plasma membrane in muscle and adipocytes is crucial for whole-body glucose homeostasis. Currently, GLUT4 trafficking assays rely on overexpression of tagged GLUT4. Here we describe a high-content imaging platform for studying endogenous GLUT4 translocation in intact adipocytes. This method enables high fidelity analysis of GLUT4 responses to specific perturbations, multiplexing of other trafficking proteins and other features including lipid droplet morphology. Using this multiplexed approach we showed that Vps45 and Rab14 are selective regulators of GLUT4, but Trarg1, Stx6, Stx16, Tbc1d4 and Rab10 knockdown affected both GLUT4 and TfR translocation. Thus, GLUT4 and TfR translocation machinery likely have some overlap upon insulin-stimulation. In addition, we identified Kif13A, a Rab10 binding molecular motor, as a novel regulator of GLUT4 traffic. Finally, comparison of endogenous to overexpressed GLUT4 highlights that the endogenous GLUT4 methodology has an enhanced sensitivity to genetic perturbations and emphasises the advantage of studying endogenous protein trafficking for drug discovery and genetic analysis of insulin action in relevant cell types

Circ_005077 accelerates myocardial lipotoxicity induced by high-fat diet via CyPA/p47PHOX mediated ferroptosis

Abstract The long-term high-fat diet (HFD) can cause myocardial lipotoxicity, which is characterized pathologically by myocardial hypertrophy, fibrosis, and remodeling and clinically by cardiac dysfunction and heart failure in patients with obesity and diabetes. Circular RNAs (circRNAs), a novel class of noncoding RNA characterized by a ring formation through covalent bonds, play a critical role in various cardiovascular diseases. However, few studies have been conducted to investigate the role and mechanism of circRNA in myocardial lipotoxicity. Here, we found that circ_005077, formed by exon 2–4 of Crmp1, was significantly upregulated in the myocardium of an HFD-fed rat. Furthermore, we identified circ_005077 as a novel ferroptosis-related regulator that plays a role in palmitic acid (PA) and HFD-induced myocardial lipotoxicity in vitro and in vivo. Mechanically, circ_005077 interacted with Cyclophilin A (CyPA) and inhibited its degradation via the ubiquitination proteasome system (UBS), thus promoting the interaction between CyPA and p47phox to enhance the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase responsible for ROS generation, subsequently inducing ferroptosis. Therefore, our results provide new insights into the mechanisms of myocardial lipotoxicity, potentially leading to the identification of a novel therapeutic target for the treatment of myocardial lipotoxicity in the future

Polycystin-2 is an essential ion channel subunit in the primary cilium of the renal collecting duct epithelium

Mutations in the polycystin genes, PKD1 or PKD2, results in Autosomal Dominant Polycystic Kidney Disease (ADPKD). Although a genetic basis of ADPKD is established, we lack a clear understanding of polycystin proteins’ functions as ion channels. This question remains unsolved largely because polycystins localize to the primary cilium – a tiny, antenna-like organelle. Using a new ADPKD mouse model, we observe primary cilia that are abnormally long in cells associated with cysts after conditional ablation of Pkd1 or Pkd2. Using primary cultures of collecting duct cells, we show that polycystin-2, but not polycystin-1, is a required subunit for the ion channel in the primary cilium. The polycystin-2 channel preferentially conducts K+ and Na+; intraciliary Ca2+, enhances its open probability. We introduce a novel method for measuring heterologous polycystin-2 channels in cilia, which will have utility in characterizing PKD2 variants that cause ADPKD

Simple routes from natural graphite to graphite foams: Preparation, structure and properties

Graphite foams were prepared using foaming method and template method with nature flake graphite powder as main raw materials, sucrose as a foaming agent or binder, as well sodium chloride as a template. The compositions, microstructure, thermal properties and mechanical performance of the fabricated graphite foams were investigated by X-ray fluorescence spectrometer, scanning electron microscope, laser thermal conductivity meter, and electronic universal testing machine, respectively. The results show that water in binder played an important role in forming process of graphite foams. Graphite foams with controllable pore structure can be obtained by template method. The porosity of graphite foams increased with increasing the concentration of templating agent. With a fixed concentration of the templating agent the thermal diffusivity of the foams deceased with increasing the concentration of binder. Moreover, the obtained graphite foams has a minimum density of 288 kg/m (3), a maximum porosity of 78% and a maximum thermal diffusivity of 7.14 x 10(-6) m(2)/s. Two binding models of graphite foams prepared using template method has been proposed in the first time. This work provided an optimized processing for graphite foams with simple preparation, low-cost recyclable raw materials, and a promising thermal management material for many applications. (C) 2019 Elsevier Ltd. All rights reserved