Biology subjects

Lim, E. W.

Publications and source records attributed to Lim, E. W..

3 recordsLinked to original sources

bioRxiv2021

Metabolic adaptation to progressive mitochondrial dysfunction in aging POLGD257A mice

A decline in mitochondrial function is associated with neurodegeneration and aging. Progressive mitochondrial defects have diverse metabolic consequences that could drive some of the pathophysiological changes that occur with aging. Here, we comprehensively characterized metabolic alterations in PolgD257A mitochondrial DNA mutator mice. Plasma alanine increased dramatically with time, with lactate and other organic acids accumulating to a lesser extent. These changes were reflective of increased glycolysis, rapid gluconeogenesis, and hypoglycemia. Tracing with [15N]ammonium revealed impairment of the urea cycle and diversion to purine catabolism. We also measured alterations in the lipidome, observing a general reduction in canonical lipids and the accumulation of 1-deoxysphingolipids, which are synthesized from alanine via promiscuous serine palmitoyltransferase activity. Consistent with 1-deoxysphingolipids association with peripheral neuropathy, PolgD257A mice exhibited thermal hypoalgesia. These results highlight the distinct changes that occur in carbon and nitrogen metabolism upon mitochondrial impairment and key metabolic mechanisms which can drive aging-associated neuropathy.

biochemistry↗

bioRxiv2020

A Small Molecule Fluorogenic Probe for the Detection of Sphingosine in Living Cells

ABSTRACTThe single-chained sphingolipid sphingosine is an essential structural lipid and signaling molecule. Abnormal sphingosine metabolism is observed in several diseases, including cancer, diabetes, and Alzheimer’s. Despite its biological importance, there are a lack of tools for detecting sphingosine in living cells. This is likely due to the broader challenge of developing highly selective and live-cell compatible affinity probes for hydrophobic lipid species. In this work, we have developed a small molecule fluorescent turn-on probe for labeling sphingosine in living cells. This probe utilizes a selective reaction between sphingosine and salicylaldehyde esters to fluorescently label sphingosine molecules. We demonstrate that this probe exhibits a dose-dependent response to sphingosine and is able to detect endogenous pools of sphingosine. Using our probe, we successfully detected sphingosine accumulation in live Niemann-Pick type C1 (NPC1) patient cells, a lipid transport disorder in which increased sphingosine mediates disease progression. This work provides a simple and accessible method for the detection of sphingosine and should facilitate study of this critical signaling lipid in biology and disease.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biochemistry↗

bioRxiv2019

Serine and glycine are essential for human muscle progenitor cell population expansion

Skeletal muscle regeneration is reliant on a population of muscle specific adult stem cells (muscle progenitor cells; MPCs). During regeneration, the MPC population undergoes a transient and rapid period of population expansion, which is necessary to repair damaged myofibers and restore muscle homeostasis. Much research has focused on the age-related accumulation of negative regulators of regeneration, while the age-related decline of nutrient and metabolic determinants of the regenerative process needs examination. We hypothesized that older individuals, a population that is at risk for protein malnutrition, have diminished availability of amino acids that are necessary for MPC function. Here, we identified that levels of the non-essential amino acid serine are reduced in the skeletal muscle of healthy, older individuals. Furthermore, using stable-isotope tracing studies, we demonstrate that primary, human MPCs (hMPCs) exhibit a limited capacity for de novo biosynthesis of serine and the closely related amino acid glycine. We identified that serine and glycine are essential for hMPC proliferation and, therefore, population expansion. Serine and glycine were necessary to support synthesis of the intracellular antioxidant glutathione, and restriction of serine and glycine was sensed in an EIF2-dependent manner resulting in cell cycle arrest in G0/G1. In conclusion, we elucidate that, despite an absolute requirement of serine/glycine for hMPC proliferation, availability of serine in the skeletal muscle microenvironment is limited to the hMPCs of healthy older adults and is a likely underlying mechanism for impaired skeletal muscle regeneration with advancing age.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC=\"FIGDIR/small/833798v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (32K):\norg.highwire.dtl.DTLVardef@438298org.highwire.dtl.DTLVardef@32f66dorg.highwire.dtl.DTLVardef@1d08aeeorg.highwire.dtl.DTLVardef@511c7f_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

cell biology↗