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Objective: Neuropathy is a frequent and severe complication of diabetes. Multiple metabolic defects in type 2 diabetic patients result in oxidative injury of dorsal root ganglia (DRG) neurons. Our previous work focused on hyperglycemia clearly demonstrates induction of mitochondrial oxidative stress and acute injury in DRG neurons; however, this mechanism is not the only factor that produces neuropathy in vivo. Dyslipidemia also correlates with the development of neuropathy, even in pre-diabetic patients. This study was designed to explore the contribution of dyslipidemia in neuropathy.Research Design and Methods: Mice (n = 10) were fed a control (10% kcal %fat) or high-fat (45% kcal %fat) diet to explore the impact of plasma lipids on the development of neuropathy. We also examined oxidized lipid-mediated injury in cultured DRG neurons from adult rat using oxidized LDLs (oxLDLs).Results: Mice on a high-fat diet have increased oxLDLs and systemic and nerve oxidative stress. They develop nerve conduction velocity (NCV) and sensory deficits prior to impaired glucose tolerance. In vitro, oxLDLs lead to severe DRG neuron oxidative stress via interaction with the receptor lectin-like oxLDL receptor (LOX)-1 and subsequent NAD(P)H oxidase activity. Oxidative stress resulting from oxLDLs and high glucose is additive.Conclusions: Multiple metabolic defects in type 2 diabetes directly injure DRG neurons through different mechanisms that all result in oxidative stress. Dyslipidemia leads to high levels of oxLDLs that may injure DRG neurons via LOX-1 and contribute to the development of diabetic neuropathy. [ABSTRACT FROM AUTHOR]

Analysis of pulmonary arterial hypertension patients in Scotland across 20 years supports a recent French study suggesting there is no protective effect from obesity for this disease, in contrast to emerging evidence from the USA and China http://bit.ly/34WCZ7W., Competing Interests: Conflict of interest: L.L. McLean reports that he received a Summer Studentship Award 2016 from the British Lung Foundation during the conduct of the study. Conflict of interest: K. Pellino has nothing to disclose. Conflict of interest: M. Brewis has nothing to disclose. Conflict of interest: A. Peacock has nothing to disclose. Conflict of interest: M. Johnson has nothing to disclose. Conflict of interest: A.C. Church has nothing to disclose., (Copyright ©ERS 2019.)

Insulin resistance (IR) is the major feature of metabolic syndrome, including type 2 diabetes. IR studies are mainly focused on peripheral tissues, such as muscle and liver. There is, however, little knowledge about IR in neurons. In this study, we examined whether neurons develop IR in response to hyperinsulinemia. We first examined insulin signaling using adult dorsal root ganglion neurons as a model system. Acute insulin treatment resulted in time- and concentration-dependent activation of the signaling cascade, including phosphorylation of the insulin receptor, Akt, p70S6K, and glycogen synthase kinase-3β. To mimic hyperinsulinemia, cells were pretreated with 20 nM insulin for 24 h and then stimulated with 20 nM insulin for 15 min. Chronic insulin treatment resulted in increased basal Akt phosphorylation. More importantly, acute insulin stimulation after chronic insulin treatment resulted in blunted phosphorylation of Akt, p70S6K, and glycogen synthase kinase-3β. Interestingly, when the cells were treated with phosphatidylinositol 3-kinase pathway inhibitor, but not MAPK pathway inhibitor, chronic insulin treatment did not block acute insulin treatment-induced Akt phosphorylation. Insulin-induced Akt phosphorylation was lower in dorsal root ganglion neurons from BKS-db/db compared with control BKS-db+ mice. This effect was age dependent. Our results suggest that hyperinsulinemia cause IR by disrupting the Akt-mediated pathway. We also demonstrate that hyperinsulinemia increases the mitochondrial fission protein dynamin-related protein 1. Our results suggest a new theory for the etiology of diabetic neuropathy, i.e. that, similar to insulin dependent tissues, neurons develop IR and, in turn, cannot respond to the neurotrophic properties of insulin, resulting in neuronal injury and the development of neuropathy.

Mitochondria are key regulators of cellular energy and are the focus of a large number of studies examining the regulation of mitochondrial dynamics and biogenesis in healthy and diseased conditions. One approach to monitoring mitochondrial biogenesis is to measure the rate of mitochondrial DNA (mtDNA) replication. We developed a sensitive technique to visualize newly synthesized mtDNA in individual cells to study mtDNA replication within subcellular compartments of neurons. The technique combines the incorporation of 5-bromo-2-deoxyuridine (BrdU) and/or 5-ethynyl-2'-deoxyuridine (EdU) into mtDNA, together with a tyramide signal amplification protocol. Employing this technique, we visualized and measured mtDNA biogenesis in individual cells. The labeling procedure for EdU allows for more comprehensive results by allowing the comparison of its incorporation with other intracellular markers, because it does not require the harsh acid or enzyme digests necessary to recover the BrdU epitope. In addition, the utilization of both BrdU and EdU permits sequential pulse-chase experiments to follow the intracellular localization of mtDNA replication. The ability to quantify mitochondrial biogenesis provides an essential tool for investigating the alterations in mitochondrial dynamics involved in the pathogenesis of multiple cellular disorders, including neuropathies and neurodegenerative diseases.