Low extracellular magnesium induces phenotypic and metabolic alterations in C2C12-derived myotubes

Magnesium (Mg) has a pivotal role in upholding skeletal muscle health and optimizing performance. Its deficiency decreases muscle strength, and an association has been reported between Mg intake and sarcopenia. To gain a comprehensive understanding of the repercussions arising from low Mg concentrations on muscle behavior, we employed an in vitro model utilizing C2C12-derived myotubes. Myotubes cultured in low Mg show a significant reduction of thickness and a concomitant down-regulation of myosin heavy chain (MyHC), Myog and Myomixer. In parallel, myotubes shape their metabolism. Glycolysis is inhibited and beta-oxidation increases. These metabolic changes are consistent with the increase of MyHC I (slow) vs. MyHC II (fast) expression. We identified an essential player in these changes, namely nitric oxide (NO), as the increase in NO production appeared to orchestrate the observed modifications in myotube behavior and metabolism under low Mg conditions. Understanding these underlying mechanisms may pave the way for targeted interventions to ameliorate muscle-related conditions associated with Mg deficiency and contribute to enhancing overall muscle health and function.

Cryopreserved placental biopsies maintain mitochondrial activity for high-resolution respirometry

BACKGROUND

High-resolution respirometry (HRR) of human biopsies can provide useful metabolic, diagnostic, and mechanistic insights for clinical research and comparative medical studies. Fresh tissues analysis offers the potential best condition, the drawback being the need to use them shortly after dissection for mitochondrial respiratory experiments. The development of effective long-term storage protocols for biopsies that allow the assessment of key Electron Transport System (ETS) parameters at later stages is thus a major need.

METHODS

We optimised a cryopreservation protocol that preserves mitochondrial membranes intactness, otherwise affected by direct tissue freezing. The protocol is based on a gradual freezing step from on-ice to liquid nitrogen and - 80 °C storage using a specific DMSO-based buffer.

RESULTS

Placenta is a suitable tissue to design and test the effectiveness of long-term storage protocols being metabolically active foetal tissue with mitochondrial dysfunctions contributing to placental disease and gestational disorders. Here we designed and tested the effectiveness of the cryopreservation protocol using human placenta biopsies; we measured the ETS activity by HRR of placenta specimens comparing fresh, cryopreserved, and snap frozen conditions.

CONCLUSIONS

By this protocol, Oxygen Consumption Rate (OCR) measurements of fresh and cryopreserved placental specimens are comparable whereas snap frozen procedure impairs mitochondrial activity.

The distribution of functional N-cycle related genes and ammonia and nitrate nitrogen in soil profiles fertilized with mineral and organic N fertilizer

Nitrogen transformation in soil is a complex process and the soil microbial population can regulate the potential for N mineralization, nitrification and denitrification. Here we show that agricultural soils under standard agricultural N-management are consistently characterized by a high presence of gene copies for some of the key biological activities related to the N-cycle. This led to a strong NO₃^- reduction (75%) passing from the soil surface (15.38 ± 11.36 g N-NO₃ kg^-1 on average) to the 1 m deep layer (3.92 ± 4.42 g N-NO₃ kg^-1 on average), and ensured low nitrate presence in the deepest layer. Under these circumstances the other soil properties play a minor role in reducing soil nitrate presence in soil. However, with excessive N fertilization, the abundance of bacterial gene copies is not sufficient to explain N leaching in soil and other factors, i.e. soil texture and rainfall, become more important in controlling these aspects.