Safety and efficacy of once-daily HU6 versus placebo in people with non-alcoholic fatty liver disease and high BMI: a randomised, double-blind, placebo-controlled, phase 2a trial.

BACKGROUND: HU6 is a controlled metabolic accelerator that is metabolised in the liver to the mitochondrial uncoupler 2,4-dinitrophenol and increases substrate utilisation so that fat and other carbon sources are oxidised in the body rather than accumulated. We aimed to assess the safety and efficacy of HU6 compared with placebo in people with non-alcoholic fatty liver disease (NAFLD) and high BMI. METHODS: This randomised, double-blind, placebo-controlled, phase 2a trial was done at a single community site in the USA. Adults (aged 28-65 years) with a BMI of 28-45 kg/m2, a FibroScan controlled attenuation parameter score of more than 270 decibels per metre, and at least 8% liver fat by MRI-proton density fat fraction (MRI-PDFF) were randomly assigned (1:1:1:1) to receive, under fasting conditions, either once-daily HU6 100 mg, HU6 300 mg, HU6 450 mg, or matching placebo by oral administration for 61 days. Randomisation was blocked (groups of four) and stratified by baseline glycated haemoglobin (<5·7% vs ≥5·7%; 39 mmol/mol). All participants and study personnel involved with outcome assessments were masked to treatment assignment. The primary endpoint was the relative change in liver fat content from baseline to day 61, as assessed by MRI-PDFF, and was analysed in the full analysis set (FAS), which comprised all participants who were randomly assigned, received at least one dose of treatment, and had less than 4·5 kg of weight gain or weight loss from the time of screening to day 1 of treatment. The safety population included all participants who were randomly assigned and received at least one dose of study drug. This study was registered at ClinicalTrials.gov, NCT04874233, and is complete. FINDINGS: Between April 28, 2021, and Nov 29, 2021, 506 participants were assessed for eligibility and 80 adults (39 [49%] women and 41 [51%] men) were enrolled and randomly assigned to placebo (n=20), HU6 150 mg (n=20), HU6 300 mg (n=21), or HU6 450 mg (n=19). One participant in the HU6 450 mg group was excluded from the FAS due to weight gain. Relative mean change in liver fat content from baseline to day 61 was -26·8% (SD 17·4) for the HU6 150 mg group, -35·6% (13·8) for the HU6 300 mg group, -33·0% (18·4) for the HU6 450 mg group, and 5·4% (19·8) for the placebo group. Three people treated with HU6 (two treated with 150 mg and one treated with 300 mg) and two people treated with placebo discontinued treatment due to treatment-emergent adverse events (TEAEs). No serious TEAEs were reported. In those treated with HU6, flushing (19 [32%] participants), diarrhoea (15 [25%] participants), and palpitations (seven [12%] participants) were the most frequently reported TEAEs (in the placebo group, two [10%] participants had flushing, none had diarrhoea, and one [5%] had palpitations). There were no deaths. INTERPRETATION: HU6 could be a promising pharmacological agent for treating patients with obesity and NAFLD and its metabolic complications. FUNDING: Rivus Pharmaceuticals.

Mitochondrial Dysfunction in Alzheimer's Disease and the Rationale for Bioenergetics Based Therapies.

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder characterized by the progressive loss of cholinergic neurons, leading to the onset of severe behavioral, motor and cognitive impairments. It is a pressing public health problem with no effective treatment. Existing therapies only provide symptomatic relief without being able to prevent, stop or reverse the pathologic process. While the molecular basis underlying this multifactorial neurodegenerative disorder remains a significant challenge, mitochondrial dysfunction appears to be a critical factor in the pathogenesis of this disease. It is therefore important to target mitochondrial dysfunction in the prodromal phase of AD to slow or prevent the neurodegenerative process and restore neuronal function. In this review, we discuss mechanisms of action and translational potential of current mitochondrial and bioenergetic therapeutics for AD including: mitochondrial enhancers to potentiate energy production; antioxidants to scavenge reactive oxygen species and reduce oxidative damage; glucose metabolism and substrate supply; and candidates that target apoptotic and mitophagy pathways to remove damaged mitochondria. While mitochondrial therapeutic strategies have shown promise at the preclinical stage, there has been little progress in clinical trials thus far.

RhTFAM treatment stimulates mitochondrial oxidative metabolism and improves memory in aged mice.

Mitochondrial function declines with age in postmitotic tissues such as brain, heart and skeletal muscle. Despite weekly exercise, aged mice showed substantial losses of mtDNA gene copy numbers and reductions in mtDNA gene transcription and mitobiogenesis signaling in brain and heart. We treated these mice with weekly intravenous injections of recombinant human mitochondrial transcription factor A (rhTFAM). RhTFAM treatment for one month increased mitochondrial respiration in brain, heart and muscle, POLMRT expression and mtDNA gene transcription in brain, and PGC-1 alpha mitobiogenesis signaling in heart. RhTFAM treatment reduced oxidative stress damage to brain proteins, improved memory in Morris water maze performance and increased brain protein levels of BDNF and synapsin. Microarray analysis showed co-expression of multiple Gene Ontology families in rhTFAM-treated aged brains compared to young brains. RhTFAM treatment reverses age-related memory impairments associated with loss of mitochondrial energy production in brain, increases levels of memory-related brain proteins and improves mitochondrial respiration in brain and peripheral tissues.

P2Y12 receptor expression is a critical determinant of functional responsiveness to ATX's MORFO domain.

In the central nervous system, the formation of the myelin sheath and the differentiation of the myelinating cells, namely oligodendrocytes, are regulated by complex signaling networks that involve purinergic receptors and the extracellular matrix. However, the exact nature of the molecular interactions underlying these networks still needs to be defined. In this respect, the data presented here reveal a signaling mechanism that is characterized by an interaction between the purinergic P2Y(12) receptor and the matricellular extracellular matrix protein autotaxin (ATX), also known as ENPP2, phosphodiesterase-Iα/ATX, or lysoPLD. ATX has been previously described by us to mediate intermediate states of oligodendrocyte adhesion and to enable changes in oligodendrocyte morphology that are thought to be crucial for the formation of a fully functional myelin sheath. This functional property of ATX is mediated by ATX's modulator of oligodendrocyte remodeling and focal adhesion organization (MORFO) domain. Here, we show that the expression of the P2Y(12) receptor is necessary for ATX's MORFO domain to exert its effects on differentiating oligodendrocytes. In addition, our data demonstrate that exogenous expression of the P2Y(12) receptor can render cells responsive to the known effects of ATX's MORFO domain, and they identify Rac1 as an intracellular factor mediating the effect of ATX-MORFO-P2Y(12) signaling on the assembly of focal adhesions. Our data further support the idea that a physical interaction between ATX and the P2Y(12) receptor provides the basis for an ATX-MORFO-P2Y(12) signaling axis that is crucial for mediating cellular states of intermediate adhesion and morphological/structural plasticity.

Collagen XIII induced in vascular endothelium mediates alpha1beta1 integrin-dependent transmigration of monocytes in renal fibrosis.

Alport syndrome is a common hereditary basement membrane disorder caused by mutations in the collagen IV α3, α4, or α5 genes that results in progressive glomerular and interstitial renal disease. Interstitial monocytes that accumulate in the renal cortex from Alport mice are immunopositive for integrin α1ß1, while only a small fraction of circulating monocytes are immunopositive for this integrin. We surmised that such a disparity might be due to the selective recruitment of α1ß1-positive monocytes. In this study, we report the identification of collagen XIII as a ligand that facilitates this selective recruitment of α1ß1 integrin-positive monocytes. Collagen XIII is absent in the vascular endothelium from normal renal cortex and abundant in Alport renal cortex. Neutralizing antibodies against the binding site in collagen XIII for α1ß1 integrin selectively block VLA1-positive monocyte migration in transwell assays. Injection of these antibodies into Alport mice slows monocyte recruitment and protects against renal fibrosis. Thus, the induction of collagen XIII in endothelial cells of Alport kidneys mediates the selective recruitment of α1ß1 integrin-positive monocytes and may potentially serve as a therapeutic target for inflammatory diseases in which lymphocyte/monocyte recruitment involves the interaction with α1ß1 integrin.

Lysophosphatidic acid can support the formation of membranous structures and an increase in MBP mRNA levels in differentiating oligodendrocytes.

During development, differentiating oligodendrocytes progress in distinct maturation steps from premyelinating to myelinating cells. Such maturing oligodendrocytes express both the receptors mediating signaling via extracellular lysophosphatidic acid (LPA) and the major enzyme generating extracellular LPA, namely phosphodiesterase-Ialpha/autotaxin (PD-Ialpha/ATX). However, the biological role of extracellular LPA during the maturation of differentiating oligodendrocytes is currently unclear. Here, we demonstrate that application of exogenous LPA induced an increase in the area occupied by the oligodendrocytes' process network, but only when PD-Ialpha/ATX expression was down-regulated. This increase in network area was caused primarily by the formation of membranous structures. In addition, LPA increased the number of cells positive for myelin basic protein (MBP). This effect was associated by an increase in the mRNA levels coding for MBP but not myelin oligodendrocyte glycoprotein (MOG). Taken together, these data suggest that LPA may play a crucial role in regulating the later stages of oligodendrocyte maturation.

Phosphodiesterase-Ialpha/autotaxin's MORFO domain regulates oligodendroglial process network formation and focal adhesion organization.

Development of a complex process network by maturing oligodendrocytes is a critical but currently poorly characterized step toward myelination. Here, we demonstrate that the matricellular oligodendrocyte-derived protein phosphodiesterase-Ialpha/autotaxin (PD-Ialpha/ATX) and especially its MORFO domain are able to promote this developmental step. In particular, the single EF hand-like motif located within PD-Ialpha/ATX's MORFO domain was found to stimulate the outgrowth of higher order branches but not process elongation. This motif was also observed to be critical for the stimulatory effect of PD-Ialpha/ATX's MORFO domain on the reorganization of focal adhesions located at the leading edge of oligodendroglial protrusions. Collectively, our data suggest that PD-Ialpha/ATX promotes oligodendroglial process network formation and expansion via the cooperative action of multiple functional sites located within the MORFO domain and more specifically, a novel signaling pathway mediated by the single EF hand-like motif and regulating the correlated events of process outgrowth and focal adhesion organization.

Phosphodiesterase-Ialpha/autotaxin (PD-Ialpha/ATX): a multifunctional protein involved in central nervous system development and disease.

Phosphodiesterase-Ialpha/autotaxin (PD-Ialpha/ATX) was originally identified as a cell-motility-stimulating factor secreted by a variety of tumor cells. Thus, studies related to its potential functional roles have traditionally focused on tumorigenesis. PD-Ialpha/ATX's catalytic activity, initially defined as nucleotide pyrophosphatase/phosphodiesterase, was soon recognized as being necessary for its tumor cell-motility-stimulating activity. However, only the discovery of PD-Ialpha/ATX's identity with lysophospholipase D, an extracellular enzyme that converts lysophosphatidylcholine into lysophosphatidic acid (LPA) and potentially sphingosylphosphoryl choline into sphingosine 1-phosphate (S1P), revealed the actual effectors responsible for PD-Ialpha/ATX's ascribed motogenic functions, i.e., its catalytic products. PD-Ialpha/ATX has also been detected during normal development in a number of tissues, in particular, the central nervous system (CNS), where expression levels are high. Similar to tumor cells, PD-Ialpha/ATX-expressing CNS cells secrete catalytically active PD-Ialpha/ATX into the extracellular environment. Thus, it appears reasonable to assume that PD-Ialpha/ATX's CNS-related functions are mediated via lysophospholipid, LPA and potentially S1P, signaling. However, recent studies identified PD-Ialpha/ATX as a matricellular protein involved in the modulation of oligodendrocyte-extracellular matrix interactions and oligodendrocyte remodeling. This property of PD-Ialpha/ATX was found to be independent of its catalytic activity and to be mediated by a novel functionally active domain. These findings, therefore, uncover PD-Ialpha/ATX, at least in the CNS, as a multifunctional protein able to induce complex signaling cascades via distinct structure-function domains. This Mini-Review describes PD-Ialpha/ATX's multifunctional roles in the CNS and discusses their potential contributions to CNS development and pathology.

Neurotoxic nitric oxide rapidly depolarizes and permeabilizes mitochondria by dynamically opening the mitochondrial transition pore.

Exposure of SH-SY5Y neuroblastoma or rat cortical neurons to diethylenetriamine-NO (DETA-NO) rapidly depolarized mitochondria. In SH-SY5Y DETA-NO activated caspase 3 and produced cell death. Mitochondrial depolarization in SH-SY5Y was visualized both with JC-1 accumulation and as dequenching of calcein fluorescence in mitochondria initially loaded with calcein-AM and tetramethylrhodamine methyl ester (TMRM). Calcein/TMRM-visualized mitochondrial depolarization was prevented by cyclosporin A (CsA) or approximately two-fold increased levels of BclXL protein. Dynamic imaging of mitochondrial potential (Deltapsi M) with TMRM showed that DETA-NO induced cycles of mitochondrial depolarization/repolarization ("flickering"). Fifteen-30 min of DETA-NO exposure caused high-frequency flickering with small peak size; 2 h of DETA-NO produced large peaks with prolonged depolarization. NO-induced flickering but not that from Bax was blocked by the calcium uniporter antagonist Ru360. Our findings show rapid-onset, dynamic regulation of Deltapsi M by NO, implying that neuroprotective therapies for brain ischemia target cell death processes downstream of effects of NO on mitochondria.

Interactions among nitric oxide and Bcl-family proteins after MPP+ exposure of SH-SY5Y neural cells I: MPP+ increases mitochondrial NO and Bax protein.

We studied effects of methylpyridinium ion (MPP(+)) on apoptosis, cell death and regulation of Bcl-2-family proteins in SH-SY5Y neuroblastoma cells. MPP(+) increased intracellular accumulation of DNA-histone complexes as a measure of apoptosis and decreased intracellular calcein fluorescence as a measure of cell death. If ATP synthesis was supported, MPP(+) caused apoptosis in rho(0) cells devoid of electron transport function. Caspase inhibition blocked apoptosis but not cell death caused by MPP(+). MPP(+) increased levels of Bax, Bcl-2 and Bcl-X(L) proteins approximately 2-fold over 24 hr, with Bax increases occurring first; Bax did not increase in rho(0) cells. The Bax increase, but not that of Bcl-2 or Bcl-X(L), was dependent on nitric oxide (NO) and seemed post-transcriptional. DAF-FM imaging revealed increased mitochondrial NO within hours of exposure to MPP(+). Western blots showed a constitutive approximately 130 kD protein that stained for NOS-2, consistent with reports of mitochondrial nitric oxide synthase (mtNOS). MPP(+) caused a NO-dependent release of cytochrome C into cytoplasm. MPP(+) increases mitochondrial NO levels and causes a NO-dependent increase in Bax protein, providing a mechanism for NOS-and Bax-dependency of MPTP neurotoxicity in vivo and implicating locally produced NO as a signaling molecule used by mitochondria to manipulate cell death cascades.

Interactions among nitric oxide and Bcl-family proteins after MPP+ exposure of SH-SY5Y neural cells II: exogenous NO replicates MPP+ actions.

In the preceding companion article, we showed that the neurotoxin methylpyridinium (MPP(+)) increases mitochondrial nitric oxide (NO), causes a post-transcriptional, NO-dependent increase in Bax protein and produces caspase-dependent apoptosis and caspase-independent cell death. In the present study, we show that exogenous NO replicates these findings. The long-term NO generator diethylenetriamine-NO (DETA-NO) reproduced the post-transcriptional Bax protein increase, but did not increase Bcl-2 or Bcl-X(L) proteins. Like MPP(+), DETA-NO caused an early decrease in Bcl-2 mRNA, did not increase Bax protein in rho(0) cells and caused caspase- and cycloheximide-dependent apoptosis and caspase-independent cell death. We developed cell lines with inducible overexpression of Bcl proteins, at levels relevant to those we found in cells exposed to MPP(+) or DETA-NO. Inducible overexpression ( approximately 2-fold) of Bcl-2 or Bcl-X(L) proteins reduced MPP(+) or NO-induced apoptosis but did not affect cell death. Inducible Bax overexpression ( approximately 5-fold) slightly increased cell death. Our results show that exogenous NO mimics actions of MPP(+) on SH-SY5Y neuroblastoma cells and supports the mediation of MPP(+) neurotoxicity by NO generated intracellularly in mitochondria.

Methylpyridinium (MPP(+))- and nerve growth factor-induced changes in pro- and anti-apoptotic signaling pathways in SH-SY5Y neuroblastoma cells.

The parkinsonian neurotoxin methylpyridinium (MPP(+)) mimics the neuropathology of Parkinson's disease (PD) and likely kills neurons by inhibiting complex I of the electron transport chain and increasing oxidative stress. We examined the time course of activation/inactivation of multiple pro- and anti-apoptotic signaling pathways in MPP(+)-induced apoptotic death of SH-SY5Y neuroblastoma cells. We found an early increase and later decrease of transcriptional activity of the generally anti-apoptotic nuclear factor kappa-beta (NF-kappa B) and early increases in activating phosphorylation of the anti-apoptotic upstream kinase protein kinase B (PKB, also known as AKT). Sequestration-inducing phosphorylation of pro-apoptotic BAD protein increased early then declined. A small biphasic increase in the generally pro-apoptotic p38 kinase activity paralleled the biphasic rise in NF-kappa B-mediated transcription. Inhibition of p38 kinase with 5 micro M SB203540, inhibition of MEK-ERK with 50 micro M U0126, or inhibition of phosphatidylinositol-3-kinase (PI3K) with 10 micro M LY294002 reduced cell viability by 4, 18 or 37%, respectively, after 24 h. All three kinase inhibitors increased cell death in response to 24 h of MPP(+), with the greatest effect shown by LY294002. Nerve growth factor (NGF) caused an early increase in activating phosphorylation of PKB/AKT and MEK-ERK and increased cell survival during MPP(+) exposure. We found that acute MPP(+) exposure activates multiple interacting death- and survival-promoting pathways. Survival-promoting MEK-ERK and PI3K pathways contribute to viability during MPP(+) exposure, both are activated by NGF, and loss of PI3K-mediated signaling and NF-kappa B-mediated transcription may commit cells irreversibly to apoptosis in this model. It remains unknown to what extent these signaling pathways modulate dopamine neuronal death in PD.