Dyslipidemia impairs mitochondrial trafficking and function in sensory neurons

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154247/1/fsb2fj201700206r.pd

Tubulin involvement in Bortezomib peripheral neurotoxicity

Axonal transport of mitochondria (Mt) controlled by specialized motor and docking proteins that distribute Mt throughout the axon where they provide energy for metabolic and synaptic activity is a vulnerable target in neuronal pathology (1). Bortezomib (BZ) is a proteasome inhibitor active in multiple myeloma (2). One of its key toxicities is painful peripheral neuropathy (BIPN), which frequently requires treatment discontinuation (3). BIPN is dose-related and predominantly sensory, resulting from axonal degeneration. Recent results indicate that BZ modifies axonal tubulin dynamic and we hypothesize that BZ alters fast axonal transport. Here we studied using time-lapse imaging the effect of different BZ concentration on axonal Mt transport in isolated dorsal root ganglion (DRG) neurons from adult male mice. We used kymograph to quantify the total number of Mt and to discriminate antero and retrogradely moving Mt from stationary Mt. Twenty-four hours of BZ treatment (0.1 to 15 µM) induced a dose-dependent reduction in Mt trafficking. Moreover, BZ had no impact on MT motion directions, but it induced a progressive reduction of both anterograde and retrograde axonal transport velocities. These events were associated with increase in tubulin polymerization and of MAP2 expression, but they occurred only after 72h of chronic BZ treatment. We have developed an in vitro model of BIPN demonstrating that transport impairment is already present before evident tubulin polymerization, suggesting that transport deficit represents an early stage of axonal dysfunction. Perpetuated transport dysfunction could impair distal organelle supply and play a critical role in advanced stages of BIPN.This work was supported by the University of Milan-Bicocca and University of Michigan research grant

Electrostatic and Hydrophobic Interactions Mediate Single-Stranded DNA Recognition and <i>Acta2</i> Repression by Purine-Rich Element-Binding Protein B

Myofibroblast differentiation is characterized by an increased level of expression of cytoskeletal smooth muscle α-actin. In human and murine fibroblasts, the gene encoding smooth muscle α-actin (<i>Acta2</i>) is tightly regulated by a network of transcription factors that either activate or repress the 5′ promoter–enhancer in response to environmental cues signaling tissue repair and remodeling. Purine-rich element-binding protein B (Purβ) suppresses the expression of <i>Acta2</i> by cooperatively interacting with the sense strand of a 5′ polypurine sequence containing an inverted MCAT <i>cis</i> element required for gene activation. In this study, we evaluated the chemical basis of nucleoprotein complex formation between the Purβ repressor and the purine-rich strand of the MCAT element in the mouse <i>Acta2</i> promoter. Quantitative single-stranded DNA (ssDNA) binding assays conducted in the presence of increasing concentrations of monovalent salt or anionic detergent suggested that the assembly of a high-affinity nucleoprotein complex is driven by a combination of electrostatic and hydrophobic interactions. Consistent with the results of pH titration analysis, site-directed mutagenesis revealed several basic amino acid residues in the intermolecular (R267) and intramolecular (K82 and R159) subdomains that are essential for Purβ transcriptional repressor function in <i>Acta2</i> promoter–reporter assays. In keeping with their diminished <i>Acta2</i> repressor activity in fibroblasts, purified Purβ variants containing an R267A mutation exhibited reduced binding affinity for purine-rich ssDNA. Moreover, certain double and triple-point mutants were also defective in binding to the <i>Acta2</i> corepressor protein, Y-box-binding protein 1. Collectively, these findings establish the repertoire of noncovalent interactions that account for the unique structural and functional properties of Purβ

Plasma lipid metabolites associate with diabetic polyneuropathy in a cohort with type 2 diabetes

ObjectiveThe global rise in type 2 diabetes is associated with a concomitant increase in diabetic complications. Diabetic polyneuropathy is the most frequent type 2 diabetes complication and is associated with poor outcomes. The metabolic syndrome has emerged as a major risk factor for diabetic polyneuropathy; however, the metabolites associated with the metabolic syndrome that correlate with diabetic polyneuropathy are unknown.MethodsWe conducted a global metabolomics analysis on plasma samples from a subcohort of participants from the Danish arm of Anglo‐Danish‐Dutch study of Intensive Treatment of Diabetes in Primary Care (ADDITION‐Denmark) with and without diabetic polyneuropathy versus lean control participants.ResultsCompared to lean controls, type 2 diabetes participants had significantly higher HbA1c (p = 0.0028), BMI (p = 0.0004), and waist circumference (p = 0.0001), but lower total cholesterol (p = 0.0001). Out of 991 total metabolites, we identified 15 plasma metabolites that differed in type 2 diabetes participants by diabetic polyneuropathy status, including metabolites belonging to energy, lipid, and xenobiotic pathways, among others. Additionally, these metabolites correlated with alterations in plasma lipid metabolites in type 2 diabetes participants based on neuropathy status. Further evaluating all plasma lipid metabolites identified a shift in abundance, chain length, and saturation of free fatty acids in type 2 diabetes participants. Importantly, the presence of diabetic polyneuropathy impacted the abundance of plasma complex lipids, including acylcarnitines and sphingolipids.InterpretationOur explorative study suggests that diabetic polyneuropathy in type 2 diabetes is associated with novel alterations in plasma metabolites related to lipid metabolism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/167813/1/acn351367_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/167813/2/acn351367.pd

Plasma lipid metabolites associate with diabetic polyneuropathy in a cohort with type 2 diabetes

ObjectiveThe global rise in type 2 diabetes is associated with a concomitant increase in diabetic complications. Diabetic polyneuropathy is the most frequent type 2 diabetes complication and is associated with poor outcomes. The metabolic syndrome has emerged as a major risk factor for diabetic polyneuropathy; however, the metabolites associated with the metabolic syndrome that correlate with diabetic polyneuropathy are unknown.MethodsWe conducted a global metabolomics analysis on plasma samples from a subcohort of participants from the Danish arm of Anglo‐Danish‐Dutch study of Intensive Treatment of Diabetes in Primary Care (ADDITION‐Denmark) with and without diabetic polyneuropathy versus lean control participants.ResultsCompared to lean controls, type 2 diabetes participants had significantly higher HbA1c (p = 0.0028), BMI (p = 0.0004), and waist circumference (p = 0.0001), but lower total cholesterol (p = 0.0001). Out of 991 total metabolites, we identified 15 plasma metabolites that differed in type 2 diabetes participants by diabetic polyneuropathy status, including metabolites belonging to energy, lipid, and xenobiotic pathways, among others. Additionally, these metabolites correlated with alterations in plasma lipid metabolites in type 2 diabetes participants based on neuropathy status. Further evaluating all plasma lipid metabolites identified a shift in abundance, chain length, and saturation of free fatty acids in type 2 diabetes participants. Importantly, the presence of diabetic polyneuropathy impacted the abundance of plasma complex lipids, including acylcarnitines and sphingolipids.InterpretationOur explorative study suggests that diabetic polyneuropathy in type 2 diabetes is associated with novel alterations in plasma metabolites related to lipid metabolism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/167813/1/acn351367_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/167813/2/acn351367.pd