Proteomic and functional comparison between human induced and embryonic stem cells.

Human induced pluripotent stem cells (hiPSCs) have great potential to be used as alternatives to embryonic stem cells (hESCs) in regenerative medicine and disease modelling. In this study, we characterise the proteomes of multiple hiPSC and hESC lines derived from independent donors and find that while they express a near-identical set of proteins, they show consistent quantitative differences in the abundance of a subset of proteins. hiPSCs have increased total protein content, while maintaining a comparable cell cycle profile to hESCs, with increased abundance of cytoplasmic and mitochondrial proteins required to sustain high growth rates, including nutrient transporters and metabolic proteins.

PINK1 regulated mitophagy is evident in skeletal muscles.

PINK1, mutated in familial forms of Parkinson's disease, initiates mitophagy following mitochondrial depolarization. However, it is difficult to monitor this pathway physiologically in mice as loss of PINK1 does not alter basal mitophagy levels in most tissues. To further characterize this pathway , we used -QC mice in which loss of PINK1 was combined with the mitochondrial-associated POLG mutation.

Discovery of XL01126: A Potent, Fast, Cooperative, Selective, Orally Bioavailable, and Blood-Brain Barrier Penetrant PROTAC Degrader of Leucine-Rich Repeat Kinase 2.

Leucine-rich repeat kinase 2 (LRRK2) is one of the most promising targets for Parkinson's disease. LRRK2-targeting strategies have primarily focused on type 1 kinase inhibitors, which, however, have limitations as the inhibited protein can interfere with natural mechanisms, which could lead to undesirable side effects. Herein, we report the development of LRRK2 proteolysis targeting chimeras (PROTACs), culminating in the discovery of degrader XL01126, as an alternative LRRK2-targeting strategy.

Global ubiquitylation analysis of mitochondria in primary neurons identifies endogenous Parkin targets following activation of PINK1.

How activation of PINK1 and Parkin leads to elimination of damaged mitochondria by mitophagy is largely based on cell lines with few studies in neurons. Here, we have undertaken proteomic analysis of mitochondria from mouse neurons to identify ubiquitylated substrates of endogenous Parkin. Comparative analysis with human iNeuron datasets revealed a subset of 49 PINK1 activation–dependent diGLY sites in 22 proteins conserved across mouse and human systems.

Impact of Type II LRRK2 inhibitors on signaling and mitophagy.

Much effort has been devoted to the development of selective inhibitors of the LRRK2 as a potential treatment for LRRK2 driven Parkinson's disease. In this study, we first compare the properties of Type I (GSK3357679A and MLi-2) and Type II (GZD-824, Rebastinib and Ponatinib) kinase inhibitors that bind to the closed or open conformations of the LRRK2 kinase domain, respectively. We show that Type I and Type II inhibitors suppress phosphorylation of Rab10 and Rab12, key physiological substrates of LRRK2 and also promote mitophagy, a process suppressed by LRRK2.

Pharmacological rescue of impaired mitophagy in Parkinson's disease-related LRRK2 G2019S knock-in mice.

Parkinson's disease (PD) is a major and progressive neurodegenerative disorder, yet the biological mechanisms involved in its aetiology are poorly understood. Evidence links this disorder with mitochondrial dysfunction and/or impaired lysosomal degradation - key features of the autophagy of mitochondria, known as mitophagy. Here, we investigated the role of LRRK2, a protein kinase frequently mutated in PD, in this process in vivo.

IL-15 and PIM kinases direct the metabolic programming of intestinal intraepithelial lymphocytes.

Intestinal intraepithelial lymphocytes (IEL) are an abundant population of tissue-resident T cells that protect and maintain the intestinal barrier. IEL respond to epithelial cell-derived IL-15, which is complexed to the IL-15 receptor α chain (IL-15/Rα). IL-15 is essential both for maintaining IEL homeostasis and inducing IEL responses to epithelial stress, which has been associated with Coeliac disease.

Effects of Simvastatin on Lipid Metabolism in Wild-Type Mice and Mice with Muscle PGC-1α Overexpression.

Previous studies suggest that statins may disturb skeletal muscle lipid metabolism potentially causing lipotoxicity with insulin resistance. We investigated this possibility in wild-type mice (WT) and mice with skeletal muscle PGC-1α overexpression (PGC-1α OE mice). In WT mice, simvastatin had only minor effects on skeletal muscle lipid metabolism but reduced glucose uptake, indicating impaired insulin sensitivity.

Parkinson's disease and mitophagy: an emerging role for LRRK2.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects around 2% of individuals over 60 years old. It is characterised by the loss of dopaminergic neurons in the substantia nigra pars compacta of the midbrain, which is thought to account for the major clinical symptoms such as tremor, slowness of movement and muscle stiffness. Its aetiology is poorly understood as the physiological and molecular mechanisms leading to this neuronal loss are currently unclear.

Simvastatin Impairs Glucose Homeostasis in Mice Depending on PGC-1α Skeletal Muscle Expression.

Several studies showed an increased risk for diabetes with statin treatment. PGC-1α is an important regulator of muscle energy metabolism and mitochondrial biogenesis. Since statins impair skeletal muscle PGC-1α expression and reduced PGC-1α expression has been observed in diabetic patients, we investigated the possibility that skeletal muscle PGC1α expression influences the effect of simvastatin on muscle glucose metabolism.

Semi-automated quantitation of mitophagy in cells and tissues.

Mitophagy is a natural phenomenon and entails the lysosomal degradation of mitochondria by the autophagy pathway. In recent years, the development of fluorescent pH-sensitive mitochondrial reporters has greatly facilitated the monitoring of mitophagy by distinguishing between cytosolic mitochondria or those delivered to acidic lysosomes. We recently published the mito-QC reporter, which consists of a mitochondrial outer membrane-localised tandem mCherry-GFP tag.

PGC-1α plays a pivotal role in simvastatin-induced exercise impairment in mice.

Aim: Statins decrease cardiovascular complications, but can induce myopathy. Here, we explored the implication of PGC-1α in statin-associated myotoxicity.

Methods: We treated PGC-1α knockout (KO), PGC-1α overexpression (OE) and wild-type (WT) mice orally with 5 mg simvastatin kg  day for 3 weeks and assessed muscle function and metabolism.

Mechanisms of statin-associated skeletal muscle-associated symptoms.

Statins lower the serum low-density lipoprotein cholesterol and prevent cardiovascular events by inhibiting 3-hydroxy-3-methyl-glutaryl-CoA reductase. Although the safety of statins is documented, many patients ingesting statins may suffer from skeletal muscle-associated symptoms (SAMS). Importantly, SAMS are a common reason for stopping the treatment with statins.

PGC-1β modulates statin-associated myotoxicity in mice.

Statins inhibit cholesterol biosynthesis and lower serum LDL-cholesterol levels. Statins are generally well tolerated, but can be associated with potentially life-threatening myopathy of unknown mechanism. We have shown previously that statins impair PGC-1β expression in human and rat skeletal muscle, suggesting that PGC-1β may play a role in statin-induced myopathy.

Phosphorylation of Parkin at serine 65 is essential for its activation .

Mutations in PINK1 and Parkin result in autosomal recessive Parkinson's disease (PD). Cell culture and studies have elaborated the PINK1-dependent regulation of Parkin and defined how this dyad orchestrates the elimination of damaged mitochondria via mitophagy. PINK1 phosphorylates ubiquitin at serine 65 (Ser65) and Parkin at an equivalent Ser65 residue located within its N-terminal ubiquitin-like domain, resulting in activation; however, the physiological significance of Parkin Ser65 phosphorylation in mammals remains unknown.

Basal Mitophagy Occurs Independently of PINK1 in Mouse Tissues of High Metabolic Demand.

Dysregulated mitophagy has been linked to Parkinson's disease (PD) due to the role of PTEN-induced kinase 1 (PINK1) in mediating depolarization-induced mitophagy in vitro. Elegant mouse reporters have revealed the pervasive nature of basal mitophagy in vivo, yet the role of PINK1 and tissue metabolic context remains unknown. Using mito-QC, we investigated the contribution of PINK1 to mitophagy in metabolically active tissues.

Moderate Exercise Allows for shorter Recovery Time in Critical Limb Ischemia.

Whether and how moderate exercise might allow for accelerated limb recovery in chronic critical limb ischemia (CLI) remains to be determined. Chronic CLI was surgically induced in mice, and the effect of moderate exercise (training five times per week over a 3-week period) was investigated. Tissue damages and functional scores were assessed on the 4th, 6th, 10th, 20th, and 30th day after surgery.

IFN-β-induced reactive oxygen species and mitochondrial damage contribute to muscle impairment and inflammation maintenance in dermatomyositis.

Dermatomyositis (DM) is an autoimmune disease associated with enhanced type I interferon (IFN) signalling in skeletal muscle, but the mechanisms underlying muscle dysfunction and inflammation perpetuation remain unknown. Transcriptomic analysis of early untreated DM muscles revealed that the main cluster of down-regulated genes was mitochondria-related. Histochemical, electron microscopy, and in situ oxygraphy analysis showed mitochondrial abnormalities, including increased reactive oxygen species (ROS) production and decreased respiration, which was correlated with low exercise capacities and a type I IFN signature.

Comparative analysis of resuscitation using human serum albumin and crystalloids or 130/0.4 hydroxyethyl starch and crystalloids on skeletal muscle metabolic profile during experimental haemorrhagic shock in swine: A randomised experimental study.

Background: Protection against acute skeletal muscle metabolic dysfunction and oxidative stress could be a therapeutic target in volume expansion for severely bleeding patients.

Objectives: This experimental pilot study in swine aims at comparing 130/0.4 hydroxyethyl starch (HES) with 4% albumin along with crystalloid perfusion for first-line volume expansion in haemorrhagic shock with a particular emphasis on oxidative stress and muscular mitochondrial function.

Impaired Exercise Performance and Skeletal Muscle Mitochondrial Function in Rats with Secondary Carnitine Deficiency.

Purpose: The effects of carnitine depletion upon exercise performance and skeletal muscle mitochondrial function remain largely unexplored. We therefore investigated the effect of N-trimethyl-hydrazine-3-propionate (THP), a carnitine analog inhibiting carnitine biosynthesis and renal carnitine reabsorption, on physical performance and skeletal muscle mitochondrial function in rats.

Methods: Male Sprague Dawley rats were treated daily with water (control rats; n = 12) or with 20 mg/100 g body weight THP (n = 12) via oral gavage for 3 weeks.

Endothelial function does not improve with high-intensity continuous exercise training in SHR: implications of eNOS uncoupling.

Exercise training is a well-recognized way to improve vascular endothelial function by increasing nitric oxide (NO) bioavailability. However, in hypertensive subjects, unlike low- and moderate-intensity exercise training, the beneficial effects of continuous high-intensity exercise on endothelial function are not clear, and the underlying mechanisms remain unknown. The aim of this study was to investigate the impact of high-intensity exercise on vascular function, especially on the NO pathway, in spontaneous hypertensive rats (SHR).

Statins Trigger Mitochondrial Reactive Oxygen Species-Induced Apoptosis in Glycolytic Skeletal Muscle.

Aims: Although statins are the most widely used cholesterol-lowering agents, they are associated with a variety of muscle complaints. The goal of this study was to characterize the effects of statins on the mitochondrial apoptosis pathway induced by mitochondrial oxidative stress in skeletal muscle using human muscle biopsies as well as in vivo and in vitro models.

Results: Statins increased mitochondrial H2O2 production, the Bax/Bcl-2 ratio, and TUNEL staining in deltoid biopsies of patients with statin-associated myopathy.

High reactive oxygen species in fibrotic and nonfibrotic skin of patients with diffuse cutaneous systemic sclerosis.

Systemic sclerosis (SSc) is a chronic multisystemic connective tissue disease characterized by progressive fibrosis affecting skin and internal organs. Despite serious efforts to unveil the pathogenic mechanisms of SSc, they are still unclear. High levels of reactive oxygen species (ROS) in affected patients have been shown, and ROS are suggested to play a role in fibrosis pathogenesis.

Contractile function and energy metabolism of skeletal muscle in rats with secondary carnitine deficiency.

The consequences of carnitine depletion upon metabolic and contractile characteristics of skeletal muscle remain largely unexplored. Therefore, we investigated the effect of N-trimethyl-hydrazine-3-propionate (THP) administration, a carnitine analog inhibiting carnitine biosynthesis and renal reabsorption of carnitine, on skeletal muscle function and energy metabolism. Male Sprague-Dawley rats were fed a standard rat chow in the absence (CON; n = 8) or presence of THP (n = 8) for 3 wk.

Reductive stress impairs myoblasts mitochondrial function and triggers mitochondrial hormesis.

Even though oxidative stress damage from excessive production of ROS is a well known phenomenon, the impact of reductive stress remains poorly understood. This study tested the hypothesis that cellular reductive stress could lead to mitochondrial malfunction, triggering a mitochondrial hormesis (mitohormesis) phenomenon able to protect mitochondria from the deleterious effects of statins. We performed several in vitro experiments on L6 myoblasts and studied the effects of N-acetylcysteine (NAC) at different exposure times.