Preneoplastic cells switch to Warburg metabolism from their inception exposing multiple vulnerabilities for targeted elimination

Otto Warburg described tumour cells as displaying enhanced aerobic glycolysis whilst maintaining defective oxidative phosphorylation (OXPHOS) for energy production almost 100 years ago 1,2. Since then, the ‘Warburg effect’ has been widely accepted as a key feature of rapidly proliferating cancer cells 3,4,5. What is not clear is how early “Warburg metabolism” initiates in cancer and whether changes in energy metabolism might influence tumour progression ab initio. We set out to investigate energy metabolism in HRASG12V driven preneoplastic cell (PNC) at inception, in a zebrafish skin PNC model. We find that, within 24 hours of HRASG12V induction, PNCs upregulate glycolysis and blocking glycolysis reduces PNC proliferation, whilst increasing available glucose enhances PNC proliferation and reduces apoptosis. Impaired OXPHOS accompanies enhanced glycolysis in PNCs, and a mild complex I inhibitor, metformin, selectively induces apoptosis and suppresses proliferation of PNCs. Enhanced mitochondrial fragmentation might be underlining impaired OXPHOS and block mitochondrial fragmentation triggers PNC apoptosis. Our data indicate that altered energy metabolism is one of the earliest events upon oncogene activation in somatic cells, which allows a targeted and effective PNC elimination

Sideroflexin 3 is an α-synuclein-dependent mitochondrial protein that regulates synaptic morphology

α-Synuclein plays a central role in Parkinson's disease, where it contributes to the vulnerability of synapses to degeneration. However, the downstream mechanisms through which α-synuclein controls synaptic stability and degeneration are not fully understood. Here, comparative proteomics on synapses isolated from α-synuclein(-/-) mouse brain identified mitochondrial proteins as primary targets of α-synuclein, revealing 37 mitochondrial proteins not previously linked to α-synuclein or neurodegeneration pathways. Of these, sideroflexin 3 (SFXN3) was found to be a mitochondrial protein localized to the inner mitochondrial membrane. Loss of SFXN3 did not disturb mitochondrial electron transport chain function in mouse synapses, suggesting that its function in mitochondria is likely to be independent of canonical bioenergetic pathways. In contrast, experimental manipulation of SFXN3 levels disrupted synaptic morphology at the Drosophila neuromuscular junction. These results provide novel insights into α-synuclein-dependent pathways, highlighting an important influence on mitochondrial proteins at the synapse, including SFXN3. We also identify SFXN3 as a new mitochondrial protein capable of regulating synaptic morphology in vivo.</p

COMPLEMENT FACTOR B IS A DETERMINANT OF BOTH METABOLIC AND CARDIOVASCULAR FEATURES OF METABOLIC SYNDROME

CFB (complement factor B) is elevated in adipose tissue and serum from patients with type 2 diabetes mellitus and cardiovascular disease, but the causal relationship to disease pathogenesis is unclear. Cfb is also elevated in adipose tissue and serum of the spontaneously hypertensive rat, a well-characterized model of metabolic syndrome. To establish the role of CFB in metabolic syndrome, we knocked out the Cfb gene in the spontaneously hypertensive rat. Cfb−/− rats showed improved glucose tolerance and insulin sensitivity, redistribution of visceral to subcutaneous fat, increased adipocyte mitochondrial respiration, and marked changes in gene expression. Cfb−/− rats also had lower blood pressure, increased ejection fraction and fractional shortening, and reduced left ventricular mass. These changes in metabolism and gene expression, in adipose tissue and left ventricle, suggest new adipose tissue-intrinsic and blood pressure-independent mechanisms for insulin resistance and cardiac hypertrophy in the spontaneously hypertensive rat. In silico analysis of the human CFB locus revealed 2 cis-regulated expression quantitative trait loci for CFB expression significantly associated with visceral fat, circulating triglycerides and hypertension in genome-wide association studies. Together, these data demonstrate a key role for CFB in the development of spontaneously hypertensive rat metabolic syndrome phenotypes and of related traits in humans and indicate the potential for CFB as a novel target for treatment of cardiometabolic disease

Repurposing dichloroacetate for the treatment of women with endometriosis

Endometriosis is a chronic pain condition affecting ∼176 million women worldwide. It is defined by the presence of endometrium-like tissue (lesions) outside the uterus, most commonly on the pelvic peritoneum. There is no cure for endometriosis. All endometriosis drug approvals to date have been contraceptive, limiting their use in women of child-bearing age. We have shown that human peritoneal mesothelial cells (HPMCs) recovered from the pelvic peritoneum of women with endometriosis exhibit significantly higher glycolysis, lower mitochondrial respiration, decreased enzymatic activity of pyruvate dehydrogenase (PDH), and increased production of lactate compared to HPMCs from women without disease. Transforming growth factor-β1 (TGF-β1) is elevated in the peritoneal fluid from women with endometriosis, and exposure of HPMCs to TGF-β1 exacerbates this abnormal phenotype. Treatment of endometriosis HPMCs with the pyruvate dehydrogenase kinase (PDK) inhibitor/PDH activator dichloroacetate (DCA) normalizes HPMC metabolism, reduces lactate secretion, and abrogates endometrial stromal cell proliferation in a coculture model. Oral DCA reduced peritoneal fluid lactate concentrations and endometriosis lesion size in a mouse model. These findings provide the rationale for targeting metabolic processes as a noncontraceptive treatment for women with endometriosis either as a primary nonhormonal treatment or to prevent recurrence after surgery

Genomic loci mispositioning in Tmem120a knockout mice yields latent lipodystrophy

Little is known about how the observed fat-specific pattern of 3D-spatial genome organisation is established. Here we report that adipocyte-specific knockout of the gene encoding nuclear envelope transmembrane protein Tmem120a disrupts fat genome organisation, thus causing a lipodystrophy syndrome. Tmem120a deficiency broadly suppresses lipid metabolism pathway gene expression and induces myogenic gene expression by repositioning genes, enhancers and miRNA-encoding loci between the nuclear periphery and interior. Tmem120a(−/−) mice, particularly females, exhibit a lipodystrophy syndrome similar to human familial partial lipodystrophy FPLD2, with profound insulin resistance and metabolic defects that manifest upon exposure to an obesogenic diet. Interestingly, similar genome organisation defects occurred in cells from FPLD2 patients that harbour nuclear envelope protein encoding LMNA mutations. Our data indicate TMEM120A genome organisation functions affect many adipose functions and its loss may yield adiposity spectrum disorders, including a miRNA-based mechanism that could explain muscle hypertrophy in human lipodystrophy

Strain-specificity in the hydrogen sulphide signalling network following dietary restriction in recombinant inbred mice

Modulation of the ageing process by dietary restriction (DR) across multiple taxa is well established. While the exact mechanism through which DR acts remains elusive, the gasotransmitter hydrogen sulphide (H2S) may play an important role. We employed a comparative-type approach using females from three ILSXISS recombinant inbred mouse strains previously reported to show differential lifespan responses following 40% DR. Following long-term (10 months) 40% DR, strain TejJ89—reported to show lifespan extension under DR—exhibited elevated hepatic H2S production relative to its strain-specific ad libitum (AL) control. Strain TejJ48 (no reported lifespan effect following 40% DR) exhibited significantly reduced hepatic H2S production, while H2S production was unaffected by DR in strain TejJ114 (shortened lifespan reported following 40% DR). These differences in H2S production were reflected in highly divergent gene and protein expression profiles of the major H2S production and disposal enzymes across strains. Increased hepatic H2S production in TejJ89 mice was associated with elevation of the mitochondrial H2S-producing enzyme 3-mercaptopyruvate sulfurtransferase (MPST). Our findings further support the potential role of H2S in DR-induced longevity and indicate the presence of genotypic-specificity in the production and disposal of hepatic H2S in response to 40% DR in mice

Hepatic hydrogen sulfide levels are reduced in mouse model of Hutchinson-Gilford progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) is a rare human disease characterised by accelerated biological ageing. Current treatments are limited, and most patients die before 15 years of age. Hydrogen sulfide (H2S) is an important gaseous signalling molecule that it central to multiple cellular homeostasis mechanisms. Dysregulation of tissue H2S levels is thought to contribute to an ageing phenotype in many tissues across animal models. Whether H2S is altered in HGPS is unknown. We investigated hepatic H2S production capacity and transcript, protein and enzymatic activity of proteins that regulate hepatic H2S production and disposal in a mouse model of HGPS (G609G mice, mutated Lmna gene equivalent to a causative mutation in HGPS patients). G609G mice were maintained on either regular chow (RC) or high fat diet (HFD), as HFD has been previously shown to significantly extend lifespan of G609G mice, and compared to wild type (WT) mice maintained on RC. RC fed G609G mice had significantly reduced hepatic H2S production capacity relative to WT mice, with a compensatory elevation in mRNA transcripts associated with several H2S production enzymes, including cystathionine-γ-lyase (CSE). H2S levels and CSE protein were partially rescued in HFD fed G609G mice. As current treatments for patients with HGPS have failed to confer significant improvements to symptoms or longevity, the need for novel therapeutic targets is acute and the regulation of H2S through dietary or pharmacological means may be a promising new avenue for research

Mitochondrial dysfunction and mitophagy blockade contribute to renal osteodystrophy in chronic kidney disease-mineral bone disorder

Chronic kidney disease–mineral and bone disorder (CKD-MBD) presents with extra-skeletal calcification and renal osteodystrophy (ROD). The origins of ROD likely lie with elevated uremic toxins and/or an altered hormonal profile but the cellular events responsible remain unclear. Here, we report that stalled mitophagy contributes to mitochondrial dysfunction in bones of a CKD-MBD mouse model, and also human CKD-MBD patients. RNA-seq analysis exposed an altered expression of genes associated with mitophagy and mitochondrial function in tibia of CKD-MBD mice. The accumulation of damaged osteocyte mitochondria and the expression of mitophagy regulators, p62/SQSTM1, ATG7 and LC3 was inconsistent with functional mitophagy, and in mito-QC reporter mice with CKD-MBD, there was a 2.3-fold increase in osteocyte mitolysosomes. Altered expression of mitophagy regulators in human CKD-MBD bones was also observed. To determine if uremic toxins were possibly responsible for these observations, indoxyl sulfate treatment of osteoblasts revealed mitochondria with distorted morphology and whose membrane potential and oxidative phosphorylation were decreased, and oxygen-free radical production increased. The altered p62/SQSTM1 and LC3-II expression was consistent with impaired mitophagy machinery and the effects of indoxyl sulfate were reversible by rapamycin. In conclusion, mitolysosome accumulation from impaired clearance of damaged mitochondria may contribute to the skeletal complications, characteristic of ROD. Targeting mitochondria and the mitophagy process may therefore offer novel routes for intervention to preserve bone health in patients with ROD. Such approaches would be timely as our current armamentarium of anti-fracture medications has not been developed for, or adequately studied in, patients with severe CKD-MBD

Bioenergetic status modulates motor neuron vulnerability and pathogenesis in a zebrafish model of spinal muscular atrophy

Degeneration and loss of lower motor neurons is the major pathological hallmark of spinal muscular atrophy (SMA), resulting from low levels of ubiquitously-expressed survival motor neuron (SMN) protein. One remarkable, yet unresolved, feature of SMA is that not all motor neurons are equally affected, with some populations displaying a robust resistance to the disease. Here, we demonstrate that selective vulnerability of distinct motor neuron pools arises from fundamental modifications to their basal molecular profiles. Comparative gene expression profiling of motor neurons innervating the extensor digitorum longus (disease-resistant), gastrocnemius (intermediate vulnerability), and tibialis anterior (vulnerable) muscles in mice revealed that disease susceptibility correlates strongly with a modified bioenergetic profile. Targeting of identified bioenergetic pathways by enhancing mitochondrial biogenesis rescued motor axon defects in SMA zebrafish. Moreover, targeting of a single bioenergetic protein, phosphoglycerate kinase 1 (Pgk1), was found to modulate motor neuron vulnerability in vivo. Knockdown of pgk1 alone was sufficient to partially mimic the SMA phenotype in wild-type zebrafish. Conversely, Pgk1 overexpression, or treatment with terazosin (an FDA-approved small molecule that binds and activates Pgk1), rescued motor axon phenotypes in SMA zebrafish. We conclude that global bioenergetics pathways can be therapeutically manipulated to ameliorate SMA motor neuron phenotypes in vivo

Mitochondrial bioenergetic deficits in C9orf72 amyotrophic lateral sclerosis motor neurons cause dysfunctional axonal homeostasis

ARM is a Lady Edith Wolfson Clinical Fellow and is jointly funded by the Medical Research Council (MRC) and the Motor Neurone Disease Association (MR/R001162/1). He also acknowledges support from the Rowling Scholars scheme, administered by the Anne Rowling Regenerative Neurology Clinic (ARRNC), University of Edinburgh, and a seedcorn grant from The Chief Scientist Office and the RS Macdonald Charitable Trust via the Scottish Neurological Research Fund, administered by the University of St Andrews. JMG is funded by a starter grant for clinical lecturers from the Academy of Medical Sciences. CS is supported by a Medical Research Council grant (MR/L016400/1). NMM was funded by a Wellcome Trust New Investigator Award (100981/Z/13/Z). RNC and NMM are funded by a Diabetes UK grant (17/0005697). The Hardingham and Chandran laboratories are supported by the Euan MacDonald Centre for Motor Neurone Disease Research, and the UK Dementia Research Institute (DRI), which receives its funding from UK DRI Ltd, funded by the MRC, Alzheimer's Society and Alzheimer's Research UK. SC also acknowledges funding from the ARRNC, My Name’5 Doddie Foundation, and an MRC Dementias Platform UK Stem Cell Partnership grant (MR/N013255/1). BTS is a Rowling-DRI Fellow.Peer reviewedPublisher PD