Joachim Nielsen

NSAID ingestion augments training‐induced muscle hypertrophy and differentially affects muscle mRNA expression, but not strength gains, in trained men Abstract figure legend Schematic outlining the impact of NSAID ingestion on resistance exercise training-induced changes in muscle morphology, function and gene networks relative to placebo ingestion...

Hopefully of interest to scientists and exercise practitioners with and interest in muscle mass and functional gains in human volunteers. doi.org/10.1113/JP28...

@jphysiol.bsky.social

Principles of protein abundance regulation across single cells in a mammalian tissue Protein synthesis and clearance are major regulatory steps of gene expression, but their in vivo regulatory roles across the cells comprising complex tissues remains unexplored. Here, we systematicall...

This article is a homecoming for me.

As a PhD student, I focused on the growth-rate transcriptional regulation in yeast.

Now, ~ 20 years later, we report protein regulation scaling with the growth rates of single cells in mammalian tissues.

www.biorxiv.org/content/10.1...

RACMEM Debate: Is Human Energy Expenditure Constrained? | Javier Gonzalez Is human energy expenditure constrained? This hypothesis was proposed by Herman Pontzer, and has received widespread interest with coverage from mainstream media, podcasts, and even the RI Christmas ...

Is Human Energy Expenditure Constrained? I recently debated Herman Pontzer on this topic in Shenzhen, China.

My slides can be viewed here:

www.linkedin.com/posts/javier...

Manuscript now accepted! 🥳 @steffendanielle.bsky.social @valerioizzi.bsky.social @abigailmackey1.bsky.social @ismcopenhagen.bsky.social

Spatially distinct ECM-producing fibroblasts and myonuclei orchestrate early adaptation to mechanical loading in the human muscle-tendon unit

The Expanding Clinical and Genetic Spectrum of Muscle Glycogen Storage Disease 0, (GSD0B) Glycogen storage disorders are a group of genetic disorders affecting glucose homeostasis in the body. Muscular glycogen stores are essential for liberating glucose for energy supply during bursts of...

The Expanding Clinical and Genetic Spectrum of Muscle Glycogen Storage Disease 0, (GSD0B) - Donoghue - 2025 - American Journal of Medical Genetics Part A - Wiley Online Library onlinelibrary.wiley.com/doi/10.1002/...

Phosphorylation of RYR1 at Ser2902 decreases Ca2+ leak in skeletal muscle and susceptibility to malignant hyperthermia and heat stroke Reducing Ca2+ leak through mutant RYR1 prevents pathological heat production in skeletal muscle.

New #scisignal paper: Phosphorylation of RYR1 at Ser2902 decreases Ca2+ leak in skeletal muscle and susceptibility to malignant hyperthermia and heat stroke. #Myoblue tinyurl.com/bddss3j6

Cardiolipin dynamics promote membrane remodeling by mitochondrial OPA1 - Nature Communications This study reveals how cardiolipin governs mitochondrial morphology by modulating the activity of human OPA1 and how its replacement by monolyso-cardiolipin, as observed in Barth syndrome, impacts mitochondrial membrane-shaping mechanisms.

Excited to share that our paper on mitochondrial cardiolipin dynamics is published in @natcomms.nature.com today! We provide molecular explanations for unique aspects of mitochondrial morphology and the mechanisms underlying cardiolipin-related Barth Syndrome.
www.nature.com/articles/s41...

The data show that eight weeks of HIIT training led to a 7% increase in mitochondrial cristae density, demonstrating cristae plasticity.
Importantly, this plasticity was also observed in patients with type 2 diabetes, highlighting its relevance for metabolic health.

This level of precision was necessary to detect training-induced changes in cristae density, as previous data suggested expected increases of <10%. Even in athletes, cristae density is only ~25% higher than in untrained individuals.

In our previous studies, we used a cut-off of 8 profiles to achieve a coefficient of error of 0.10.
To improve precision, significantly more work (x5) was required, moving onto the flatter part of the curve where additional profiles yield marginal gains in accuracy.

Martin and Amalie manually analysed ~11,000 mitochondrial profiles for cristae density using classical stereology: counting intersections with cristae and points with mitochondria.
Each biopsy typically included >100 profiles, with a minimum cut-off of 49 profiles to ensure a CE ≤ 0.05.

Martin performed TEM imaging on 117 muscle biopsies (pre- and post-training), resulting in ~17,000 images.
These were analysed for mitochondrial and lipid droplet parameters, as published here: 🔗 10.1152/ajpcell.00470.2022 and 10.1113/JP284386

At that time, we had biopsies before and after 10 weeks of aerobic training but found no effect of training on cristae density, raising questions about its plasticity.

Until 2017, the prevailing consensus was that mitochondrial cristae density remained unchanged with training. However, in a cross-sectional study, we observed that endurance-trained athletes had a 25% higher cristae density compared to untrained individuals: 10.1113/JP273040

Mitochondrial cristae density is increased following high-intensity interval training in patients with type 2 diabetes Aims/hypothesis: Mitochondrial cristae architecture is a key determinant of oxidative capacity in skeletal muscle. While mitochondrial dysfunction is common in type 2 diabetes, it remains unclear whet...

Our new preprint!
Great effort by Martin de Almeida and Amalie Platz has led to the discovery that training increases mitochondrial cristae density.
www.biorxiv.org/cgi/content/...
Thanks to Niels Ørtenblad at SDU and Kurt Højlund and Maria Petersen at Steno Diabetes Center Odense.

🧵 Thread below…

Common and distinct roles of AMPKγ isoforms in small-molecule activator-stimulated glucose uptake in mouse skeletal muscle Objective: Small-molecule activators targeting the allosteric drug and metabolite (ADaM) site of AMPK enhance insulin-independent glucose uptake in skeletal muscle and lower glucose in preclinical mod...

Check out our latest preprint from the lab, spearheaded by researcher @itsmedipsikha.bsky.social , investigating the distinctive roles of regulatory gamma subunits of the AMPK protein complex in small molecule activator-stimulated skeletal muscle glucose uptake.
www.biorxiv.org/content/10.1...

Electron tomography reveals mitochondrial network and cristae remodelling during cell differentiation in the human placenta Mitochondria adapt their structure through fusion and fission, yet how their morphology and cristae architecture alter as cells differentiate remains unclear. The human placenta is an ideal model for ...

www.biorxiv.org/content/10.1...

Does biological sex impact the rate of intrinsic mitochondrial respiration in the presence of creatine in human skeletal muscle? Emily J. Ferguson (@queensuresearch.bsky.social) et al. investigate!

📜 buff.ly/46B6lzL

Mechanical Loading Induces the Longitudinal Growth of Muscle Fibers via an mTORC1-Independent Mechanism https://www.biorxiv.org/content/10.1101/2025.09.19.676647v1

Divergent Changes in Peak Fat Oxidation and Fatmax Following 3-Day Dietary Interventions Are Related to Muscle Glycogen Availability in Men

by Tarry, Vestergaard, Petersen, Olsen, Ingersen, Connor, Pilegaard, Dela, Larsen, Shaw, and Helge

onlinelibrary.wiley.com/share/CDCGW2...

Sarcopenia is accelerated loss of skeletal muscle mass and function commonly, but not exclusively, associated with advancing age. It is observed across many species including humans in whom it can lead to decline in physical function and mobility. https://www.nature.c...

Skeletal muscle Rac1 mediates exercise training adaptations towards muscle glycogen resynthesis and protein synthesis Long-term exercise training elicits tremendous health benefits; however, the molecular understanding is incomplete and identifying therapeutic targets…

Congrats to Steffen Raun, Lykke Sylow and Team for their new Redox Biology paper, "Skeletal muscle Rac1 mediates exercise training adaptations towards muscle glycogen resynthesis and protein synthesis", that included the CMR's Prof Paul Gregorevic
www.sciencedirect.com/science/arti...

🚨 The last paper of my PhD is out in @MSSE

Regular Long Runs and Higher Training Volumes are Associated with Better Running Economy Durability in Performance Matched Well-Trained Male Runners

🙏🏻 Rich Blagrove & Jonathan Folland

Temporary free download.

🔗 journals.lww.com/acsm-msse/ab...

🧵 1/7

Elegant study on glycogen using the one-legged exercise model:

Exercise- and diet-induced glycogen depletion impairs performance during one-legged constant-load, high-intensity exercise in humans

Thomassen, McKenna, Olmedillas, Wyckelsma, Bangsbo, Nordsborg
www.frontiersin.org/journals/phy...

Congratulations to Researcher @itsmedipsikha.bsky.social for being one of the recipients of the EFSD/Lilly Young Investigator Awards! We celebrated her achievement with some cakes and bubbles earlier 🥳 @easdnews.bsky.social @cbmr.science

www.europeandiabetesfoundation.org/recipients/e...

Join our PhD course in metabolism and EC coupling.
November 10-15. University of Southern Denmark.
Enrol here: www.sdu.dk/en/forskning...

New paper!

Do ketone esters affect post-exercise recovery?

doi.org/10.1007/s003...

#ketones #exercise #sports #nutrition #recovery

Glycogen metabolism in mouse embryonic Sertoli cells sustains the germ line through the lactate shuttle Metabolites are key regulators of cell fate decisions, epigenetic remodeling, and lineage commitment. While genetic pathways governing testis differentiation are well studied, the role of metabolism r...

www.biorxiv.org/content/10.1...

Muscle memory theory: A critical evaluation Click on the article title to read more.

“Muscle memory theory: A critical evaluation” in @JPhysiol led by postdoc Nate Serrano physoc.onlinelibrary.wiley.com/doi/10.1113/...

#Research by Léo Blervaque et al. examines #capillary-to-sarcolemma distance and location of cytochrome c oxidase, offering insights for maximal O2 uptake and muscle lactate release in trained athletes 🚴‍♂️ 🔎

📜 Read the study here: physoc.onlinelibrary.wiley.com/doi/10.1113/...