bims-glecem 2023-12-31 papers

Issue of 2023–12–31
four papers selected by
Dipsikha Biswas, Københavns Universitet

Histochem Cell Biol. 2023 Dec 26.

Optimization of PAS stain and similar Schiff's based methods for glycogen demonstration in liver tissue.

Yosef Mohamed-Azzam Zakout, Marwah Abdelrahman Abdellah, Masia Aldai Abdallah, Samah Abdelrahim Batran.

Demonstration of glycogen in tissue holds considerable diagnostic relevance across various pathological conditions, particularly in certain tumors. The histochemical staining of glycogen using methods utilizing Schiff's reagents is subject to influences arising from the type of fixative, fixation temperature, and oxidizing agents employed. This study aimed to assess diverse fixatives, fixation temperatures, and oxidizing agents, each with variable treatment durations, in conjunction with Schiff's reagent for optimal glycogen demonstration. Paraffin blocks derived from a rabbit's liver served as the experimental substrate, encompassing 340 paraffin sections subjected to different procedures. For tissues fixed at 4 °C, good staining outcomes, as determined by the periodic acid-Schiff (PAS) stain, were observed with 10% neutral buffered formalin (NBF), 80% alcohol, and Bouin's solution. Tissues fixed at room temperature (RT) demonstrated good PAS staining results with both 10% NBF and 80% alcohol. Notably, other oxidizing agents exhibited poor outcomes across all fixatives and fixation temperature, with two exceptions, as satisfactory staining results were obtained when using 5% chromic acid. Consequently, Both 10% NBF and 80% emerge as preferred fixatives of choice for glycogen demonstration when coupled with PAS stain. It is noteworthy that Bouin's solution could also provide good outcomes when fixation occurred at 4 °C.

Keywords: Fixation; Glycogen; Oxidizing agent; PAS

DOI: https://doi.org/10.1007/s00418-023-02261-x

FASEB J. 2024 Jan;38(1): e23392

Resistance-only and concurrent exercise induce similar myofibrillar protein synthesis rates and associated molecular responses in moderately active men before and after training.

Matthew J Lee, Nikeisha J Caruana, Nicholas J Saner, Jujiao Kuang, Tanner Stokes, Jonathan C McLeod, Sara Y Oikawa, David J Bishop, Jonathan D Bartlett, Stuart M Phillips.

Aerobic and resistance exercise (RE) induce distinct molecular responses. One hypothesis is that these responses are antagonistic and unfavorable for the anabolic response to RE when concurrent exercise is performed. This thesis may also depend on the participants' training status and concurrent exercise order. We measured free-living myofibrillar protein synthesis (MyoPS) rates and associated molecular responses to resistance-only and concurrent exercise (with different exercise orders), before and after training. Moderately active men completed one of three exercise interventions (matched for age, baseline strength, body composition, and aerobic capacity): resistance-only exercise (RE, n = 8), RE plus high-intensity interval exercise (RE+HIIE, n = 8), or HIIE+RE (n = 9). Participants trained 3 days/week for 10 weeks; concurrent sessions were separated by 3 h. On the first day of Weeks 1 and 10, muscle was sampled immediately before and after, and 3 h after each exercise mode and analyzed for molecular markers of MyoPS and muscle glycogen. Additional muscle, sampled pre- and post-training, was used to determine MyoPS using orally administered deuterium oxide (D2 O). In both weeks, MyoPS rates were comparable between groups. Post-exercise changes in proteins reflective of protein synthesis were also similar between groups, though MuRF1 and MAFbx mRNA exhibited some exercise order-dependent responses. In Week 10, exercise-induced changes in MyoPS and some genes (PGC-1ɑ and MuRF1) were dampened from Week 1. Concurrent exercise (in either order) did not compromise the anabolic response to resistance-only exercise, before or after training. MyoPS rates and some molecular responses to exercise are diminished after training.

Keywords: MPS; exercise order; glycogen; mRNA; signaling; training status

DOI: https://doi.org/10.1096/fj.202302024R

Am J Physiol Cell Physiol. 2023 Dec 25.

Potentiation of force by extracellular potassium is not dependent on muscle length in mouse EDL muscle.

Angelos Angelidis, Kristian Overgaard, Rene Vandenboom.

Increases in myofiber extracellular potassium with prolonged contractile activity can potentiate twitch force. Activity-dependent potentiation, another mechanism of force increase in skeletal muscle, has a strong dependence on muscle or sarcomere length. Thus, potassium-mediated twitch potentiation could also be length-dependent. However, this has not been previously investigated. To this end, we used isolated C57BL/6 mouse extensor digitorum longus (EDL) muscles and elicited twitches at 0.9 Lo, Lo and 1.1 Lo (Lo refers to optimal length) in normal (5 mM) and high (10 mM) potassium solutions. Potentiation magnitude was similar to previous observations and was not significantly different between lengths (0.9 Lo: 12.3 ± 4.4 %, Lo: 12.2 ± 3.6 %, 1.1 Lo: 11.8 ± 4.8 %, values are mean ± SD). Exposure to dantrolene sodium, a compound that attenuates calcium release, reduced twitch force across lengths by ~70%. When dantrolene-affected muscles were subsequently exposed to high potassium, potentiation was not significantly different than in the absence of the former. In total, these findings provide novel information on potassium-mediated twitch potentiation.

Keywords: elevated extracellular potassium; force potentiation; muscle length; skeletal muscle

DOI: https://doi.org/10.1152/ajpcell.00456.2023

Metabolism. 2023 Dec 26. pii: S0026-0495(23)00372-4. [Epub ahead of print] 155768

Impact of fasting on the AMPK and PGC-1α axis in rodent and human skeletal muscle: A systematic review.

K L Storoschuk, D Lesiuk, J Nuttall, M LeBouedec, A Khansari, H Islam, B J Gurd.

Based primarily on evidence from rodent models fasting is currently believed to improve metabolic health in via activation of the AMPK-PGC-1α axis in skeletal muscle. However, it is unclear whether the skeletal muscle AMPK-PGC-1α axis is activated by fasting in humans. The current systematic review examined the fasting response in skeletal muscle from 34 selected studies (7 human, 21 mouse, and 6 rat). From these studies, we gathered 38 unique data points related to AMPK and 47 related to PGC-1α. In human studies, fasting mediated activation of the AMPK-PGC-1α axis is largely absent. Although evidence does support fasting-induced activation of the AMPK-PGC-1α axis in rodent skeletal muscle, the evidence is less robust than anticipated. Our findings question the ability of fasting to activate the AMPK-PGC-1α axis in human skeletal muscle and suggest that the metabolic benefits of fasting in humans are associated with caloric restriction rather than the induction of mitochondrial biogenesis. Registration: https://doi.org/10.17605/OSF.IO/KWNQY.

Keywords: AMPK; Fasting; Mitochondrial biogenesis; PGC-1α

DOI: https://doi.org/10.1016/j.metabol.2023.155768