Showing papers by "Garth J. S. Cooper published in 2015"
TL;DR: A comprehensive, system-wide analysis of the PNS of a rodent model of diabetic neuropathy suggests that the most severe molecular consequences of diabetes in the nervous system present in the SN, the region most affected by neuropathy.
Abstract: High glucose levels in the peripheral nervous system (PNS) have been implicated in the pathogenesis of diabetic neuropathy (DN). However, our understanding of the molecular mechanisms that cause the marked distal pathology is incomplete. We performed a comprehensive, system-wide analysis of the PNS of a rodent model of DN. We integrated proteomics and metabolomics from the sciatic nerve (SN), the lumbar 4/5 dorsal root ganglia (DRG), and the trigeminal ganglia (TG) of streptozotocin-diabetic and healthy control rats. Even though all tissues showed a dramatic increase in glucose and polyol pathway intermediates in diabetes, a striking upregulation of mitochondrial oxidative phosphorylation and perturbation of lipid metabolism was found in the distal SN that was not present in the corresponding cell bodies of the DRG or the cranial TG. This finding suggests that the most severe molecular consequences of diabetes in the nervous system present in the SN, the region most affected by neuropathy. Such spatial metabolic dysfunction suggests a failure of energy homeostasis and/or oxidative stress, specifically in the distal axon/Schwann cell-rich SN. These data provide a detailed molecular description of the distinct compartmental effects of diabetes on the PNS that could underlie the distal-proximal distribution of pathology.
75 citations
TL;DR: Brain urea metabolism is a target for generating novel monitoring/imaging strategies and/or therapeutic interventions aimed at ameliorating the impact of HD in patients, and hypothesize that defective brain Urea metabolism could play a substantive role in the pathogenesis of neurodegeneration, perhaps via defects in osmoregulation or nitrogen metabolism.
57 citations
TL;DR: Two analogues of insulin glargine containing a 1,4-disubstituted 1,2,3-triazole group in place of the CysA7-CysB7 disulfide bond were prepared using CuAAC click chemistry to efficiently join the peptide chains, suggesting that maintaining a precise inter-chain distance is critical to the structure of the insulin hormone.
Abstract: Two analogues of insulin glargine containing a 1,4-disubstituted 1,2,3-triazole group in place of the CysA7–CysB7 disulfide bond were prepared using CuAAC click chemistry to efficiently join the peptide chains. The resulting insulin analogues were analysed by circular dichroism spectroscopy to assess whether this modification compromised the folding pattern of the native form. Investigations, including an in vivo murine study, revealed that these analogues were not biologically active and that the structures were significantly unfolded, an outcome which suggests that maintaining a precise inter-chain distance is critical to the structure of the insulin hormone.
30 citations
TL;DR: The findings identify A20 as a mediator of adiponectin anti-inflammatory action in WAT and a potential target for mitigating obesity-related pathology.
Abstract: Obesity is a major risk factor for metabolic disease, with white adipose tissue (WAT) inflammation emerging as a key underlying pathology. We detail that mice lacking Reverbα exhibit enhanced fat storage without the predicted increased WAT inflammation or loss of insulin sensitivity. In contrast to most animal models of obesity and obese human patients, Reverbα(-/-) mice exhibit elevated serum adiponectin levels and increased adiponectin secretion from WAT explants in vitro, highlighting a potential anti-inflammatory role of this adipokine in hypertrophic WAT. Indeed, adiponectin was found to suppress primary macrophage responses to lipopolysaccharide and proinflammatory fatty acids, and this suppression depended on glycogen synthase kinase 3β activation and induction of A20. Attenuated inflammatory responses in Reverbα(-/-) WAT depots were associated with tonic elevation of A20 protein and ex vivo shown to depend on A20. We also demonstrate that adipose A20 expression in obese human subjects exhibits a negative correlation with measures of insulin sensitivity. Furthermore, bariatric surgery-induced weight loss was accompanied by enhanced WAT A20 expression, which is positively correlated with increased serum adiponectin and improved metabolic and inflammatory markers, including C-reactive protein. The findings identify A20 as a mediator of adiponectin anti-inflammatory action in WAT and a potential target for mitigating obesity-related pathology.
29 citations
TL;DR: Metal measurements in defatted-dried liver samples reveal that most essential metals were actually normal and indicate specific lowering of copper in ob/ob mice, consistent with hepatic copper deficiency, which can provide a model useful for the study of copper regulation in NAFLD and NASH.
24 citations
TL;DR: An innovative new strategy for data dependent acquisition (DDA) for on-line MS/MS data acquisition in parallel to full-scan metabolite profiling on LTQ-Orbitrap mass spectrometers is proposed and demonstrated, for the first time, that the integrated application of both CID and higher-energy collisional dissociation ion activation methods provide complementary information and increases the number of unique metabolites for which MS/ MS data is acquired.
Abstract: The annotation and identification of metabolites is a current bottleneck in non-targeted metabolomics studies. Although accurate measurement of m/z is applied routinely in UPLC–MS applications to putatively annotate metabolites, the acquisition of MS/MS or MS
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data is required to deduce structural information, further reducing the chemical search-space and providing greater confidence in metabolite annotation by comparison to mass spectral databases. Here we propose an innovative new strategy for data dependent acquisition (DDA) for on-line MS/MS data acquisition in parallel to full-scan metabolite profiling on LTQ-Orbitrap mass spectrometers. We recommend the application of different and integrated DDA MS/MS experiments to increase the coverage of unique metabolites for which MS/MS data were acquired. We demonstrate, for the first time, that the integrated application of both CID and higher-energy collisional dissociation ion activation methods, multiple different activation energies and narrow precursor ion m/z ranges of 100 or 300 for acquisition of MS/MS spectra provide complementary information and increases the number of unique metabolites for which MS/MS data is acquired. The strategies herein provide a different approach for data acquisition to increase the number of unique MS/MS mass spectra acquired for metabolite annotation purposes in non-targeted metabolomics studies. MS/MS data are available on request from the corresponding author.
24 citations
TL;DR: Evidence is provided for an adaptive proteinase response in diabetic kidneys, affected by excessive collagen-CML formation and decreased collagen digestibility, using the Cu(II)selective chelator, triethylenetetramine (TETA) as a treatment option to rectify collagen metabolism in diabetes independent of alterations in blood glucose levels.
21 citations
TL;DR: Many of the observed protein changes are consistent with known molecular perturbations in the ascending aorta that occur in response to hypercholesterolemia, e.g. elevation of tissue levels of apolipoproteins, extracellular matrix adhesion proteins, glycolytic enzymes, heat shock proteins and proteins involved in immune defense.
16 citations
TL;DR: It is shown that there are two distinct sites to which copper can bind at a location in the C-terminal 5 amino acids of the peptide, and this interaction is not observed under standard mass spectrometry (acidic) conditions but is present at physiological pH values.
14 citations
TL;DR: Potentiometric titration showed that introduction of this AGE increased the capacity of the host-peptide to bind Cu(II), and this result was confirmed by mass spectrometric characterisation of the AGE-modified peptide-Cu(II) system.
Abstract: Emerging evidence indicates that levels of advanced glycation end-products (AGEs) correlate with age- and diabetes-related organ damage and may play a causative role in such damage. Increased chelation of Cu(II) ions appears to play an important role in this process, however, the precise relationship between formation of AGEs and accumulation of Cu(II) is yet to be determined. The interaction between AGEs and Cu(II) has been investigated using a collagenous peptide that has been site-specifically modified by a key AGE. Potentiometric titration showed that introduction of this AGE increased the capacity of the host-peptide to bind Cu(II). This result was confirmed by mass spectrometric characterisation of the AGE-modified peptide-Cu(II) system.
13 citations
TL;DR: PHs and LHs are both required for physiological adiponectin production and in particular are essential for the formation/secretion of the high molecular-weight (HMW) isoforms.
TL;DR: Rat GRPP and rGRPP‐LP did not affect glucose output from the liver, but both elicited potent inhibition of glucose‐stimulated insulin secretion from the rat pancreas, suggesting they may be novel regulators of insulin secretion.
Abstract: Peptides derived from the glucagon gene Gcg, for example, glucagon and glucagon-like peptide 1 (GLP-1), act as physiological regulators of fuel metabolism and are thus of major interest in the pathogenesis of diseases, such as type-2 diabetes and obesity, and their therapeutic management. Glicentin-related pancreatic polypeptide (GRPP) is a further, 30 amino acid Gcg-derived peptide identified in human, mouse, rat, and pig. However, the potential glucoregulatory function of this peptide is largely unknown. Here, we synthesized rat GRPP (rGRPP) and a closely related peptide, rat GRPP-like peptide (rGRPP-LP), and investigated their actions in the liver and pancreas of adult male rats by employing isolated-perfused organ preparations. Rat GRPP and rGRPP-LP did not affect glucose output from the liver, but both elicited potent inhibition of glucose-stimulated insulin secretion (GSIS) from the rat pancreas. This action is unlikely to be mediated by glucagon or GLP-1 receptors, as rGRPP and rGRPP-LP did not stimulate cyclic adenosine monophosphate (cAMP) production from the glucagon or GLP-1 receptors, nor did they antagonize glucagon- or GLP-1-stimulated cAMP-production at either receptor. GRPP and GRPP-LP may be novel regulators of insulin secretion, acting through an as-yet undefined receptor.
TL;DR: Abnormalities of selenium but not of copperhomeostasis may contribute to tissue fibrosis in SSc.
Abstract: Abnormalities of selenium but not of copperhomeostasis may contribute to tissue fibrosis inSSc.
TL;DR: In this paper, the effect of Cu homeostasis on cardiac function was investigated in diabetic and non-diabetic control rats with TETA-selective chelator infusion in the coronary arteries.
TL;DR: It is reported for the first time that NIH-3T3 fibroblasts, which are generally considered to be non-adipogenic, can be converted into mature adipocytes by treatment with a defined hormone mixture comprising EGF, HGF, Dex, and insulin.
Abstract: Obesity is accompanied by an increase in the size and the number of adipocytes. As adipocytes are thought to differentiate from pre-adipocytes, we postulate that non-adipogenic fibroblasts contribute to adipocyte formation under certain conditions such as obesity. We report for the first time that NIH-3T3 fibroblasts, which are generally considered to be non-adipogenic, can be converted into mature adipocytes by treatment with a defined hormone mixture comprising EGF (epidermal growth factor), HGF (hepatocyte growth factor), Dex (dexamethasone) and insulin. Furthermore, NIH-3T3 cells transplanted into obese immunodeficient NOD/SCID (non-obese diabetic/severe combined immunodeficient) mice formed adipocytes in vivo. Interestingly, the mixture elicited conversion of NIH-3T3 cells directly into adipocytes without a preceding pre-adipocyte stage. Functional analysis revealed that each component of the mixture was necessary for the induction of adipogenesis, including Dex which inhibited the cell proliferation stimulated by EGF. Upon profiling the signalling pathways employed by EGF and HGF, we found STAT5 (signal transducer and activator of transcription 5) signalling to be activated, predominantly at the levels of both transcription and post-translational modification. Inhibition of the STAT5 pathway, either by genetic knockdown or a specific pharmacological agent, blocked adipogenesis in NIH-3T3 cells. Taken together, these data not only establish a newly recognized grouping of factors that can induce trans-differentiation of non-adipogenic fibroblasts into adipocytes, but also give us a greater understanding of obesity.
TL;DR: A liquid chromatography-tandem mass spectrometry method that enables selective detection and semiquantitation of the highly related IGF-II and vesiculin molecules and shows utility for detecting and differentiating active peptides that are highly related and of low abundance.
Abstract: The search for an islet β-cell growth factor has been a key objective in recent diabetes research, because the ability to regenerate and/or protect the functioning β-cell population in patients could result in a great advancement for diabetes treatment. IGF-I and IGF-II are known to play crucial roles in fetal growth and prenatal development, and there is growing evidence that IGF-II increases β-cell proliferation and survival in vitro and in vivo. A search for the source of IGF-II–like immunoreactivity in isolated β-cell secretory granules from the murine cell line βTC6-F7 revealed a novel 2-chain IGF-II–derived peptide, which we named vesiculin and which has been shown to be a full insulin agonist. Here, we present a liquid chromatography–tandem mass spectrometry method that enables selective detection and semiquantitation of the highly related IGF-II and vesiculin molecules. We have used this method to measure these 2 peptides in conditioned media from 2 β-cell lines, produced under increasing glucose ...