A Polymorphism of the Gene Encoding AMPD1: Clinical Impact and Proposed Mechanisms in Congestive Heart Failure

The Association of Genetic Markers Involved in Muscle Performance Responding to Lactate Levels during Physical Exercise Therapy by Nordic Walking in Patients with Long COVID Syndrome: A Nonrandomized Controlled Pilot Study

Several genetic markers have shown associations with muscle performance and physical abilities, but the response to exercise therapy is still unknown. The aim of this study was to test the response of patients with long COVID through an aerobic physical therapy strategy by the Nordic walking program and how several genetic polymorphisms involved in muscle performance influence physical capabilities. Using a nonrandomized controlled pilot study, 29 patients who previously suffered from COVID-19 (long COVID = 13, COVID-19 = 16) performed a Nordic walking exercise therapy program for 12 sessions. The influence of the ACE (rs4646994), ACTN3 (rs1815739), AMPD1 (rs17602729), CKM (rs8111989), and MLCK (rs2849757 and rs2700352) polymorphisms, genotyped by using single nucleotide primer extension (SNPE) in lactic acid concentration was established with a three-way ANOVA (group × genotype × sessions). For ACE polymorphism, the main effect was lactic acid (p = 0.019). In ACTN3 polymorphism, there were no main effects of lactic acid, group, or genotype. However, the posthoc analysis revealed that, in comparison with nonlong COVID, long COVID increased lactic acid concentrations in Nordic walking sessions in CT and TT genotypes (all p < 0.05). For AMPD1 polymorphism, there were main effects of lactic acid, group, or genotype and lactic acid × genotype or lactic acid × group × genotype interactions (all p < 0.05). The posthoc analysis revealed that, in comparison with nonlong COVID, long COVID increased lactic acid concentrations in Nordic walking sessions in CC and CT genotypes (all p < 0.05). Physical therapy strategy through Nordic walking enhanced physical capabilities during aerobic exercise in post-COVID19 patients with different genotypes in ACTN3 c.1729C>T and AMPD1 c.34C>T polymorphisms. These findings suggest that individuals who reported long COVID who presumably exercised less beforehand appeared to be less able to exercise, based on lactate levels, and the effect of aerobic physical exercise enhanced physical capabilities conditioned by several genetic markers in long COVID patients.

Surface AMP deaminase 2 as a novel regulator modifying extracellular adenine nucleotide metabolism

Adenine nucleotides represent crucial immunomodulators in the extracellular environment. The ectonucleotidases CD39 and CD73 are responsible for the sequential catabolism of ATP to adenosine via AMP, thus promoting an anti-inflammatory milieu induced by the "adenosine halo". AMPD2 intracellularly mediates AMP deamination to IMP, thereby both enhancing the degradation of inflammatory ATP and reducing the formation of anti-inflammatory adenosine. Here, we show that this enzyme is expressed on the surface of human immune cells and its predominance may modify inflammatory states by altering the extracellular milieu. Surface AMPD2 (eAMPD2) expression on monocytes was verified by immunoblot, surface biotinylation, mass spectrometry, and immunofluorescence microscopy. Flow cytometry revealed enhanced monocytic eAMPD2 expression after TLR stimulation. PBMCs from patients with rheumatoid arthritis displayed significantly higher levels of eAMPD2 expression compared with healthy controls. Furthermore, the product of AMPD2-IMP-exerted anti-inflammatory effects, while the levels of extracellular adenosine were not impaired by an increased eAMPD2 expression. In summary, our study identifies eAMPD2 as a novel regulator of the extracellular ATP-adenosine balance adding to the immunomodulatory CD39-CD73 system.

AMPD1 polymorphism and response to regadenoson

AIMS

 AMPD1 c.34C > T (rs17602729) polymorphism results in AMPD1 deficiency. We examined the association of AMPD1 deficiency and variability of hemodynamic response to regadenoson.

SUBJECTS & METHODS

Genotyping for c.34C>T was performed in 267 patients undergoing regadenoson cardiac stress testing.

RESULTS

Carriers of c.34C >T variant exhibited higher relative changes in systolic blood pressure (SBP) compared with wild-type subjects ([%] SBP change to peak: 12 ± 25 vs 5 ± 13%; p = 0.01) ([%] SBP change to nadir: -3 ± 15 vs -7 ± 11%; p = 0.04). Change in heart rate was similar between groups, but side effects were more common in carriers of the variant (+LR = 4.2; p = 0.04).

CONCLUSION

AMPD1 deficiency may be involved in the modulation of regadenoson's systemic effects.

Inhibition of AMP deaminase as therapeutic target in cardiovascular pathology

AMP deaminase (AMPD; EC 3.5.4.6) catalyzes hydrolysis of the amino group from the adenine ring of AMP resulting in production of inosine 5'-monophosphate (IMP) and ammonia. This reaction helps to maintain healthy cellular energetics by removing excess AMP that accumulates in energy depleted cells. Furthermore, AMPD permits the synthesis of guanine nucleotides from the larger adenylate pool. This enzyme competes with cytosolic 5'-nucleotidases (c5NT) for AMP. Adenosine, a product of c5NT is a vasodilator, antagonizes inotropic effects of catecholamines and exerts anti-platelet, anti-inflammatory and immunosuppressive activities. The ratio of AMPD/c5NT defines the amount of adenosine produced in adenine nucleotide catabolic pathway. Inhibition of AMPD could alter this ratio resulting in increased adenosine production. Besides the potential effect on adenosine production, elevation of AMP due to inhibition of AMPD could also lead to activation of AMP regulated protein kinase (AMPK) with myriad of downstream events including enhanced energetic metabolism, mitochondrial biogenesis and cytoprotection. While the benefits of these processes are well appreciated in cells such as skeletal or cardiac myocytes its role in protection of endothelium could be even more important. Therapeutic use of AMPD inhibition has been limited due to difficulties with obtaining compounds with adequate characteristics. However, endothelium seems to be the easiest target as effective inhibition of AMPD could be achieved at much lower concentration than in the other types of cells. New generation of AMPD inhibitors has recently been established and its testing in context of endothelial and organ protection could provide important basic knowledge and potential therapeutic tools.

AMP deaminase 1 gene polymorphism and heart disease-a genetic association that highlights new treatment

Nucleotide metabolism and signalling is directly linked to myocardial function. Therefore analysis how diversity of genes coding nucleotide metabolism related proteins affects clinical progress of heart disease could provide valuable information for development of new treatments. Several studies identified that polymorphism of AMP deaminase 1 gene (AMPD1), in particular the common C34T variant of this gene was found to benefit patients with heart failure and ischemic heart disease. However, these findings were inconsistent in subsequent studies. This prompted our detailed analysis of heart transplant recipients that revealed diverse effect: improved early postoperative cardiac function associated with C34T mutation in donors, but worse 1-year survival. Our other studies on the metabolic impact of AMPD1 C34T mutation revealed decrease in AMPD activity, increased production of adenosine and de-inhibition of AMP regulated protein kinase. Thus, genetic, clinical and biochemical studies revealed that while long term attenuation of AMPD activity could be deleterious, transient inhibition of AMPD activity before acute cardiac injury is protective. We suggest therefore that pharmacological inhibition of AMP deaminase before transient ischemic event such as during ischemic heart disease or cardiac surgery could provide therapeutic benefit.