11 research outputs found
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 ÂľM) 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
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Gut microbiota in a mouse model of obesity and peripheral neuropathy associated with plasma and nerve lipidomics and nerve transcriptomics
Background
Peripheral neuropathy (PN) is a common complication in obesity, prediabetes, and type 2 diabetes, though its pathogenesis remains incompletely understood. In a murine high-fat diet (HFD) obesity model of PN, dietary reversal (HFD-R) to a low-fat standard diet (SD) restores nerve function and the nerve lipidome to normal. As the gut microbiome represents a potential link between dietary fat intake and nerve health, the current study assessed shifts in microbiome community structure by 16S rRNA profiling during the paradigm of dietary reversal (HFD-R) in various gut niches. Dietary fat content (HFD versus SD) was also correlated to gut flora and metabolic and PN phenotypes. Finally, PN-associated microbial taxa that correlated with the plasma and sciatic nerve lipidome and nerve transcriptome were used to identify lipid species and genes intimately related to PN phenotypes.
Results
Microbiome structure was altered in HFD relative to SD but rapidly reversed with HFD-R. Specific taxa variants correlating positively with metabolic health associated inversely with PN, while specific taxa negatively linked to metabolic health positively associated with PN. In HFD, PN-associated taxa variants, including Lactobacillus, Lachnoclostridium, and Anaerotruncus, also positively correlated with several lipid species, especially elevated plasma sphingomyelins and sciatic nerve triglycerides. Negative correlations were additionally present with other taxa variants. Moreover, relationships that emerged between specific PN-associated taxa variants and the sciatic nerve transcriptome were related to inflammation, lipid metabolism, and antioxidant defense pathways, which are all established in PN pathogenesis.
Conclusions
The current results indicate that microbiome structure is altered with HFD, and that certain taxa variants correlate with metabolic health and PN. Apparent links between PN-associated taxa and certain lipid species and nerve transcriptome-related pathways additionally provide insight into new targets for microbiota and the associated underlying mechanisms of action in PN. Thus, these findings strengthen the possibility of a gut-microbiome-peripheral nervous system signature in PN and support continuing studies focused on defining the connection between the gut microbiome and nerve health to inform mechanistic insight and therapeutic opportunities.
Video Abstrac
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 Îą-actin. In
human and murine fibroblasts, the gene encoding smooth muscle Îą-actin
(<i>Acta2</i>) is tightly regulated by a network of transcription
factors that either activate or repress the 5Ⲡpromoterâenhancer
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 5Ⲡpolypurine 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> promoterâreporter 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 AngloâDanishâDutch study of Intensive Treatment of Diabetes in Primary Care (ADDITIONâDenmark) 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 AngloâDanishâDutch study of Intensive Treatment of Diabetes in Primary Care (ADDITIONâDenmark) 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