Biology subjects

Venckunas, T.

Publications and source records attributed to Venckunas, T..

5 recordsLinked to original sources

bioRxiv2025

Antioxidant supplementation blunts the proteome response to three weeks of sprint interval training preferentially in human type 2 muscle fibres

Sprint interval training (SIT) is a time-efficient type of endurance training that involves large type 2 muscle fibre recruitment. Effiective antioxidant supplementation may mitigate positive training adaptations by limiting the oxidant challenge. Our aim was to test whether SIT affiects type 2 more than type 1 muscle fibres, and whether the training response is mitigated by antioxidant treatment. Young men performed three SIT sessions (6 x 30 s all-out cycling) per week for three weeks while treated with antioxidants (vitamin C, 1 g/day; vitamin E, 235 mg/day) or placebo. Vastus lateralis biopsies were taken to measure (i) activation of genes for reactive oxygen/nitrogen species (ROS) sensors and inflammatory mediators with quantitative RT PCR and (ii) fibre type-specific proteome adaptations using mass spectrometry-based proteomics. Vitamin treatment decreased the upregulation of genes for ROS sensors and inflammatory regulators during the first SIT session. The three weeks of SIT caused generally larger proteome adaptations in type 2 than in type 1 fibres, and this included larger increases in abundance of proteins involved in mitochondrial energy production. Vitamin treatment blunted the SIT-induced proteome adaptations, whereas it did not affiect the training-induced improvement in maximal cycling performance. In conclusion, (i) the large type 2 fibre recruitment and resulting proteome adaptations are instrumental to the effiectiveness of SIT, and (ii) antioxidant supplementation counteracts positive muscular adaptations to SIT, which would blunt any improvement in submaximal endurance performance, whereas it does not affiect the improvement in maximal cycling performance, where O2 delivery to muscle would be limiting.

physiology↗

bioRxiv2024

alpha-Actinin-3 deficiency protects from the effects of acute cold exposure through altered skeletal muscle Ca2+ and OXPHOS signaling.

Summary / AbstractA nonsense polymorphism in the ACTN3 gene (R577X, rs1815739) results in the loss of the fast skeletal muscle fiber protein -actinin-3 in an estimated 1.5 billion humans worldwide. Homozygosity for this common polymorphism (ACTN3 577XX) does not cause disease but is detrimental to sprint performance in elite athletes. Recently, we reported that ACTN3 577XX humans and Actn3 knockout mice show improved cold tolerance. This was not due to an increase in brown adipose tissue activity or a greater muscle shivering response, but was associated with an increased abundance of slow myosin heavy chain muscle fibers in XX individuals, which in turn increased muscle tone to improve cold tolerance. Using the Actn3 knockout mouse we have now analyzed the molecular and physiological impacts of acute cold exposure (4{degrees}C, for 5 hours) on skeletal muscle. In addition, we used statistical inference of publicly available archaic (Neanderthal and Denisovan) and modern human DNA data to estimate the age of the ACTN3 X-allele and to identify a novel haplotype associated with this variant that provides support for genetic selection in some populations of modern humans. Our results indicate that skeletal muscle of Actn3 knockout mice exhibit higher mitochondrial oxidative phosphorylation abundance and activity than wild-type controls. Following acute cold exposure, we identified reductions in gene ontology pathways associated with metabolism and protein breakdown, which impact muscle mass loss and improved muscle fatigue resistance. Together this provides further evidence for improved cold tolerance in Actn3 knockout mice and ACTN3 577XX individuals. Furthermore, we confirm that the X-allele first appeared in modern humans [~]135,000 years ago, with this variant increasing in frequency in European and Asian populations from as early as 42,000 years ago, which aligns with modern human migration out of Africa. Taken together these data provide additional molecular and functional evidence for a protective advantage of -actinin-3 deficiency following cold exposure, highlighting the importance of skeletal muscle in mammalian thermogenesis and its potential role in the evolution of modern-day humans.

cell biology↗

bioRxiv2023

Zfp697 is an RNA-binding protein that regulates skeletal muscle inflammation and regeneration.

Muscular atrophy is a mortality risk factor that happens with disuse, chronic disease, and aging. Recovery from atrophy requires changes in several cell types including muscle fibers, and satellite and immune cells. Here we show that Zfp697/ZNF697 is a damage-induced regulator of muscle regeneration, during which its expression is transiently elevated. Conversely, sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Myofiber-specific Zfp697 ablation hinders the inflammatory and regenerative response to muscle injury, compromising functional recovery. We uncover Zfp697 as an essential interferon gamma mediator in muscle cells, interacting primarily with ncRNAs such as the pro-regenerative miR-206. In sum, we identify Zfp697 as an integrator of cell-cell communication necessary for tissue regeneration. One Sentence SummaryZfp697 is necessary for interferon gamma signaling and muscle regeneration.

physiology↗

bioRxiv2022

Skeletal muscle hypertrophy rewires glucose metabolism in mice: an experimental investigation and systematic review

BackgroundProliferating cancer cells shift their metabolism toward glycolysis even in the presence of oxygen to especially generate glycolytic intermediates as substrates for anabolic reactions. We hypothesize that a similar metabolic remodeling occurs during skeletal muscle hypertrophy. MethodsWe used mass spectrometry in hypertrophying C2C12 myotubes in vitro and plantaris mice muscle in vivo and assessed metabolomic changes and the incorporation of [U-13C6]glucose tracer. We performed enzyme inhibition of the key serine synthesis pathway enzyme phosphoglycerate dehydrogenase (Phgdh) for further mechanistic analysis and conducted a systematic review to align any changes in metabolomics during muscle growth with published findings. Finally, UK Biobank was used to link the findings to population level. ResultsThe metabolomics analysis in myotubes revealed IGF-1 induced altered metabolite concentrations in anabolic pathways such as in the pentose phosphate (ribose-5-phosphate/ribulose-5-phosphate: +40%; p=0.01) and serine synthesis pathway (serine: - 36.8%; p=0.009). Like the hypertrophy-stimulation with IGF-1 in myotubes in vitro, the concentration of the dipeptide L-carnosine was decreased by 26.6% (p=0.001) during skeletal muscle growth in vivo. However, phosphorylated sugar (glucose-6-phosphate, fructose-6-phosphate or glucose-1-phosphate) decreased by 32.2% (p=0.004) in the overloaded muscle in vivo, while increased in the IGF-1 stimulated myotubes in vitro. The systematic review revealed that 10 metabolites linked to muscle hypertrophy were directly associated with glycolysis and its interconnected anabolic pathways. We demonstrated that labelled carbon from [U-13C6]glucose is increasingly incorporated by [~]13% (p=0.001) into the non-essential amino acids in hypertrophying myotubes, which is accompanied by an increased depletion of media serine (p=0.006). The inhibition of Phgdh suppressed muscle protein synthesis in growing myotubes by 58.1% (p<0.001) highlighting the importance of the serine synthesis pathway for maintaining muscle size. Utilizing data from the UK Biobank (n=450,243), we then discerned genetic variations linked to the serine synthesis pathway (PHGDH and PSPH) and to its downstream enzyme (SHMT1), revealing their association with appendicular lean mass in humans (p<5.0e-8). ConclusionUnderstanding the mechanisms that regulates skeletal muscle mass will help in developing effective treatments against muscle weakness. Our results provide evidence for metabolic rewiring of glycolytic intermediates into anabolic pathways during muscle growth, such as in the serine synthesis.

molecular biology↗

bioRxiv2020

Loss of α-actinin-3 during human evolution provides superior cold resilience and muscle heat generation

The fast skeletal muscle protein -actinin-3 is absent in 1.5 billion people worldwide due to homozygosity for a nonsense polymorphism in the ACTN3 gene (R577X) 1. The prevalence of the 577X allele increased as modern humans moved to colder climates, suggesting a link between -actinin-3 deficiency and improved cold tolerance 1,2. Here, we show that humans lacking -actinin-3 (XX) are superior in maintaining core body temperature during cold-water immersion due to changes in skeletal muscle thermogenesis. Muscles of XX individuals displayed a shift towards more slow-twitch isoforms of myosin heavy chain (MyHC) and sarcoplasmic reticulum (SR) proteins, accompanied by altered neuronal muscle activation resulting in increased tone rather than overt shivering 3,4. Experiments on Actn3 knockout mice showed no alterations in brown adipose tissue (BAT) properties that could explain the improved cold tolerance in XX individuals. Thus, this study provides a clear mechanism for the positive selection of the ACTN3 X-allele in cold climates and supports a key thermogenic role of skeletal muscle during cold exposure in humans.

genetics↗