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

Spontaneous Diabetes in Hemizygous Human Amylin Transgenic Mice That Developed Neither Islet Amyloid nor Peripheral Insulin Resistance

OBJECTIVES—We sought to 1) Determine whether soluble-misfolded amylin or insoluble-fibrillar amylin may cause or result from diabetes in human amylin transgenic mice and 2) determine the role, if any, that insulin resistance might play in these processes

Putovanje kroz interakcije proteinskih kinaza aktiviranih mitogenima i okratoksina A

Ochratoxin A (OTA) is a ubiquitous mycotoxin with potential nephrotoxic, carcinogenic, and cytotoxic action. It has been proposed that OTA might be involved in the development of Balkan endemic nephropathy, which is associated with an increased risk of urinary tract tumours, and of other forms of interstitial nephritis. Cell susceptibility to OTA mainly depends on mycotoxin concentrations, duration of exposure, and intracellular molecular and genetic context. OTA can affect a cell by stimulating or inhibiting certain signalling pathways such as mitogen-activated protein kinase (MAPK). Three major mammalian MAPKs have been described: extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. All MAPKs regulate diverse cellular programmes, but in most cases ERKs have been linked to cell survival, while JNKs, and p38 MAPKs have been implicated in cell death by apoptosis. This review looks into OTA-mediated MAPK activation and its effects.Okratoksin A (OTA) posvuda je prisutan mikotoksin za koji se smatra da je potencijalno nefrotoksičan i karcinogen, a može uzrokovati i smrt stanice. OTA se smatra mogućim uzročnikom balkanske endemske nefropatije koju karakterizira povećani rizik od razvoja tumora mokraćnog sustava te različitih drugih vrsta intersticijskog nefritisa. Osjetljivost stanice naspram OTA ovisi ponajprije o koncentraciji mikotoksina, vremenu izloženosti i o unutarstaničnome molekularnom i genskom sklopu. OTA može djelovati na stanicu tako što potiče ili inhibira određene signalne putove u stanici poput puta proteinskih kinaza aktiviranih mitogenima (MAPK). Tri glavne MAPK u sisavaca su proteinska kinaza regulirana izvanstaničnim signalima (ERK), kinaza koja fosforilira N-kraj transkripcijskog faktora c-Jun (JNK) i p38 MAPK. Svi članovi porodice MAPK reguliraju različite stanične programe, s time da ERK najčešće stimuliraju preživljavanje stanica, dok JNK i p38 MAPK najčešće uzrokuju umiranje stanica apoptozom. U ovome smo preglednom članku prikazali na koji način stanice odgovaraju na aktivaciju MAPK koju potiče OTA

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

Characterisation of the PTEN inhibitor VO-OHpic

PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a phosphatidylinositol triphosphate 3-phosphatase that counteracts phosphoinositide 3-kinases and has subsequently been implied as a valuable drug target for diabetes and cancer. Recently, we demonstrated that VO-OHpic is an extremely potent inhibitor of PTEN with nanomolar affinity in vitro and in vivo. Given the importance of this inhibitor for future drug design and development, its mode of action needed to be elucidated. It was discovered that inhibition of recombinant PTEN by VO-OHpic is fully reversible. Both Km and Vmax are affected by VO-OHpic, demonstrating a noncompetitive inhibition of PTEN. The inhibition constants Kic and Kiu were determined to be 27 ± 6 and 45 ± 11 nM, respectively. Using the artificial phosphatase substrate 3-O-methylfluorescein phosphate (OMFP) or the physiological substrate phosphatidylinositol 3,4,5-triphosphate (PIP3) comparable parameters were obtained suggesting that OMFP is a suitable substrate for PTEN inhibition studies and PTEN drug screening