Background. Kidney preservation techniques, such as hypothermic machine perfusion (HMP), improve graft outcomes in deceased-donor kidney transplantation by pausing graft metabolism and ameliorated ischemia–reperfusion injury (IRI) but do not completely eliminate injury. Alkaline phosphatase (ALP) has been postulated to reduce IRI-induced kidney injury through the conversion of extracellular adenosine triphosphate into adenosine. This study aimed to evaluate whether ALP offers protection during deceased-donor kidney storage. Methods. Sixteen abattoir porcine kidneys (8 ALP and 8 with placebo) were procured after euthanization and exposed to 30 min of warm ischemia followed by 24 h of HMP or static cold storage (SCS). Reperfusion was partly simulated by 240 min of normothermic machine perfusion (NMP). Throughout NMP, we obtained functional, biochemical, and histological parameters. Results. Significantly lower urine production accompanied by lower perfusate pCO2 and higher pH were observed in the ALP group throughout NMP. At the end of NMP, intracellular ATP reserves and oxygen consumption were significantly higher in the ALP-treated group. Metabolomics analysis with principal component analysis demonstrated significant differences between the ALP and placebo groups in glycolysis and mitochondrial metabolites, along with a significantly attenuated rise in perfusate lactate dehydrogenase levels. Conclusions. ALP supplementation during HMP was associated with lower urine production and energetic stress, with a shift toward less metabolic dysfunction and graft injury by the end of NMP. Our findings suggest an improvement in the early metabolic incompetency that characterizes delayed graft function in humans. Further research should elucidate whether these findings result in enhancement of graft functionality after transplantation.
ABSTRACT An individual's resonance frequency (RF) is considered the optimal breathing rate for eliciting cardiovascular and autonomic benefits and is often used to guide home breathing practice. However, evidence on the stability of RF over time is scarce. Previous research reported poor 1 week test–retest reliability in a small sample. The present study aimed to replicate and extend these findings in a larger community sample while adhering to an RF determination pro. Fifty‐one participants completed a 1‐week test–retest assessment of RF. Group‐level RF remained stable, but individual‐level stability was low (ICC = 0.10), with approximately 25% of participants showing differences larger than 0.5 breaths per minute. Trend‐level associations indicated that higher physical activity and more use of acceptance and self‐support emotion regulation skills were linked to smaller RF test–retest variability. This study demonstrates that resonance frequency breathing is not equally stable across individuals, with a substantial subset showing meaningful shifts over just 1 week. By identifying lifestyle and emotion regulation factors linked to greater stability, our findings challenge the assumption that a single RF assessment is sufficient. This work advances the field by highlighting when individualized RF may (and may not) offer added value in practice. These findings suggest that RF is not uniformly stable across individuals, raising questions about the necessity and clinical relevance of repeated or individualized RF assessment. Future research should examine for whom RF remains stable and whether tailoring breathing rates provides measurable physiological or clinical benefits.
