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Background: Polycystic ovary syndrome’s (PCOS) main feature is hyperandrogenism, which is linked to a higher risk of metabolic disorders in women. Gene expression analyses in adipose tissue and skeletal muscle reveal dysregulated metabolic pathways in women with PCOS, but these differences do not necessarily lead tochanges in protein levels and biological function. Methods: To advance our understanding of the molecular alterations in PCOS, we performed global proteomic and phosphorylation site analysis using tandem mass spectrometry. Adipose tissue and skeletal muscle were collected at baseline from 10 women with and without PCOS, and in women with PCOS after 5 weeks of treatment with electrical stimulation. Results: Perilipin-1, a protein that typically coats the surface of lipid droplets in adipocytes, was increased whereas proteins involved in muscle contraction and type I muscle fiber function were downregulated in PCOS muscle. Proteins in the thick and thin filaments had many altered phosphorylation sites, indicating differences in protein activity and function. The upregulated proteins in muscle post treatment were enriched in pathways involved in extracellular matrix organization and wound healing, which may reflect a protective adaptation to repeated contractions and tissue damage due to needling. A similar, albeit less pronounced, upregulation in extracellular matrix organization pathways was also seen in adipose tissue. Conclusions: Our results suggest that hyperandrogenic women with PCOS have higher levels of extramyocellular lipids and fewer oxidative insulin-sensitive type I muscle fibers. These could be key factors leading insulin resistance in PCOS muscle while electric stimulation-induced tissue remodeling may be protective., CC BY 4.0 DEED5 January 2024Corresponding author: Anna Benrick, University of Gothenburg, Institute of Neuroscience and Physiology, Department of Physiology, Box 432, 405 30 Gothenburg, Sweden. Phone: +46 (0)709490148. E-mail: anna.benrick@gu.seFunding: A.B. holds funding from the Swedish Research Council (2020-02485), E.SV. holds funding from the Swedish Research Council (2022-00550), the Novo Nordisk Foundation (NNF22OC0072904), and I.W.A. holds funding from the Swedish Research Council (2020-01463), Mary von Sydow Foundation, Diabetes Wellness Sverige, and EFSD//European Research Programme on ‘New Targets for Diabetes or Obesity-related Metabolic Diseases’ supported by MSD 2022, and J.N. holds funding from IngaBritt and Arne Lundberg Research Foundation.Manuskript i medRxiv: DOI: 10.1101/2023.03.08.23286896

Background Patients with breast cancer exhibit muscle weakness, which is associated with increased mortality risk and reduced quality of life. Muscle weakness is experienced even in the absence of loss of muscle mass in breast cancer patients, indicating intrinsic muscle dysfunction. Physical activity is correlated with reduced cancer mortality and disease recurrence. However, the molecular processes underlying breast cancer-induced muscle weakness and the beneficial effect of exercise are largely unknown. Methods Eight-week-old breast cancer (MMTV-PyMT, PyMT) and control (WT) mice had access to active or inactive in-cage voluntary running wheels for 4 weeks. Mice were also subjected to a treadmill test. Muscle force was measured ex vivo. Tumour markers were determined with immunohistochemistry. Mitochondrial biogenesis and function were assessed with transcriptional analyses of PGC-1 alpha, the electron transport chain (ETC) and antioxidants superoxide dismutase (Sod) and catalase (Cat), combined with activity measurements of SOD, citrate synthase (CS) and beta-hydroxyacyl-CoA-dehydrogenase (beta HAD). Serum and intramuscular stress levels were evaluated by enzymatic assays, immunoblotting, and transcriptional analyses of, for example, tumour necrosis factor-alpha (TNF-alpha) and p38 mitogen-activated protein kinase (MAPK) signalling. Results PyMT mice endured shorter time and distance during the treadmill test (similar to 30%, P < 0.05) and ex vivo force measurements revealed similar to 25% weaker slow-twitch soleus muscle (P < 0.001). This was independent of cancer-induced alteration of muscle size or fibre type. Inflammatory stressors in serum and muscle, including TNF-alpha and p38 MAPK, were higher in PyMT than in WT mice (P < 0.05). Cancer-induced decreases in ETC (P < 0.05, P < 0.01) and antioxidant gene expression were observed (P < 0.05). The exercise intervention counteracted the cancer-induced muscle weakness and was accompanied by a le

Phosphorylase is one of the most carefully studied proteins in history, but knowledge of its regulation during intense muscle contraction is incomplete. Tyrosine nitration of purified preparations of skeletal muscle phosphorylase results in inactivation of the enzyme and this is prevented by antioxidants. Whether an altered redox state affects phosphorylase activity and glycogenolysis in contracting muscle is not known. Here, we investigate the role of redox state in control of phosphorylase and glycogenolysis in isolated mouse fast-twitch (extensor digitorum longus, EDL) and slow-twitch (soleus) muscle preparations during repeated contractions. Exposure of crude muscle extracts to H2O2 had little effect on phosphorylase activity. However, exposure of extracts to peroxynitrite (ONOO-), a nitrating/oxidizing agent, resulted in complete inactivation of phosphorylase (half maximal inhibition at ~200 µM ONOO-), which was fully reversed by the presence of an ONOO-scavanger, dithiothreitol (DTT). Incubation of isolated muscles with ONOO- resulted in nitration of phosphorylase and marked inhibition of glycogenolysis during repeated contractions. ONOO- also resulted in large decreases in high-energy phosphates (ATP and phosphocreatine) in the rested state and following repeated contractions. These metabolic changes were associated with decreased force production during repeated contractions (to ~60% of control). In contrast, repeated contractions did not result in nitration of phosphorylase, nor did DTT or the general antioxidant N-acetylcysteine alter glycogenolysis during repeated contractions. These findings demonstrate that ONOO- inhibits phosphorylase and glycogenolysis in living muscle under extreme conditions. However, nitration does not play a significant role in control of phosphorylase and glycogenolysis during repeated contractions.

The hypoxia-inducible nuclear-encoded mitochondrial protein NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) has been demonstrated to decrease oxidative phosphorylation and production of reactive oxygen species in neonatal cardiomyocytes, brain tissue and hypoxic domains of cancer cells. Prolonged local hypoxia can negatively affect skeletal muscle size and tissue oxidative capacity. Although skeletal muscle is a mitochondrial rich, oxygen sensitive tissue, the role of NDUFA4L2 in skeletal muscle has not previously been investigated. Here we ectopically expressed NDUFA4L2 in mouse skeletal muscles using adenovirus-mediated expression and in vivo electroporation. Moreover, femoral artery ligation (FAL) was used as a model of peripheral vascular disease to induce hind limb ischemia and muscle damage. Ectopic NDUFA4L2 expression resulted in reduced mitochondrial respiration and reactive oxygen species followed by lowered AMP, ADP, ATP, and NAD(+) levels without affecting the overall protein content of the mitochondrial electron transport chain. Furthermore, ec-topically expressed NDUFA4L2 caused a similar to 20% reduction in muscle mass that resulted in weaker muscles. The loss of muscle mass was associated with increased gene expression of atrogenes MurF1 and Mul1, and apoptotic genes caspase 3 and Bax. Finally, we showed that NDUFA4L2 was induced by FAL and that the Ndufa4l2 mRNA expression correlated with the reduced capacity of the muscle to generate force after the ischemic insult. These results show, for the first time, that mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force. Specifically, induced NDUFA4L2 reduces mitochondrial activity leading to lower levels of important intramuscular metabolites, including adenine nucleotides and NAD(+), which are hallmarks of mitochondrial dysfunction and hence shows that dysfunctional mitochondrial activity may drive muscle wasting., Funding agencies:Strategic research program in Diabetes at Karolinska InstitutetSigrid Juselius FoundationChina Scholarship Council