Skeletal muscle contraction kinetics and AMPK responses are modulated by the adenine nucleotide degrading enzyme AMPD1

AMP deaminase 1 (AMPD1; AMP → IMP + NH3) deficiency in skeletal muscle results in an inordinate accumulation of AMP during strenuous exercise, with some but not all studies reporting premature fatigue and reduced work capacity. To further explore these inconsistencies, we investigated the extent to which AMPD1 deficiency impacts skeletal muscle contractile function of different muscles and the [AMP]/AMPK responses to different intensities of fatiguing contractions. To reduce AMPD1 protein, we electroporated either an inhibitory AMPD1-specific miRNA encoding plasmid or a control plasmid, into contralateral EDL and SOL muscles of C57BL/6J mice (n = 48 males, 24 females). After 10 days, isolated muscles were assessed for isometric twitch, tetanic, and repeated fatiguing contraction characteristics using one of four (None, LOW, MOD, and HIGH) duty cycles. AMPD1 knockdown (∼35%) had no effect on twitch force or twitch contraction/relaxation kinetics. However, during maximal tetanic contractions, AMPD1 knockdown impaired both time-to-peak tension (TPT) and half-relaxation time (½ RT) in EDL, but not SOL muscle. In addition, AMPD1 knockdown in EDL exaggerated the AMP response to contractions at LOW (+100%) and MOD (+54%) duty cycles, but not at HIGH duty cycle. This accumulation of AMP was accompanied by increased AMPK phosphorylation (Thr-172; LOW +25%, MOD +34%) and downstream substrate phosphorylation (LOW +15%, MOD +17%). These responses to AMPD1 knockdown were not different between males and females. Our findings demonstrate that AMPD1 plays a role in maintaining skeletal muscle contractile function and regulating the energetic responses associated with repeated contractions in a muscle- but not sex-specific manner.NEW & NOTEWORTHY AMP deaminase 1 (AMPD1) deficiency has been associated with premature muscle fatigue and reduced work capacity, but this finding has been inconsistent. Herein, we report that although AMPD1 knockdown in mouse skeletal muscle does not change maximal isometric force, it negatively impacts muscle function by slowing contraction and relaxation kinetics in EDL muscle but not SOL muscle. Furthermore, AMPD1 knockdown differentially affects the [AMP]/AMPK responses to fatiguing contractions in an intensity-dependent manner in EDL muscle.

CITIZENS OBTAINING PSYCHOSOCIAL SUPPORT DURING THE COVID-19 PANDEMIC IN UKRAINE: A CROSS-SECTIONAL STUDY

OBJECTIVE

The aim: To investigate the obtaining of psychosocial support by citizens during the COVID-19 pandemic in Ukraine using a cross-sectional study assessing the socio-demographic characteristics of the respondents.

PATIENTS AND METHODS

Materials and methods: It was developed and used the authors' questionnaire "Socio-psychological support during the COVID-19 pandemic in Ukraine". Data processing used Nonparametric Mann-Whitney analysis of variance and one-way Kruskal-Wallis analysis of variance (SPSS 26.0).

RESULTS

Results: The study was conducted from October 2020 to May 2021 and sampled 100 individuals. Significant differences in the studied features are revealed. Gender: women have a more prosperous and broader range of contacts to discuss fears and anxieties during quarantine; suffer more from emotional loss; have more need to be heard and to be taken care of, with no criticism; are more experienced in professional psychological help obtaining; communicate with internal migrants more often. Age: young respondents (19-24 y.o.) suffer more from pandemic losses in the areas of spirituality and friendship; however, more often and more effectively use the means of online psychological support; older respondents are more likely to receive support from an important community and through meditation. Living conditions: living alone, citizens experience more pandemic stress, suffer from losses in personal life and friendship, and consider participation in challenge activities as the most convenient form of support. Place of residence: living in the rural areas is associated with a narrow circle of citizens' contacts to discuss their plans for leisure; more significant damage from pandemic losses in health; lack of support in the form of understanding themselves and their conditions. Education: higher education affects a broader circle of communication; more minor financial losses; willingness to share traumatic stories for art therapy. Financial satisfaction promotes the exchange of ideas between users of online psychological support.

CONCLUSION

Conclusions: The identified conditionality of psychosocial support obtaining by socio-demographic indicators can be used in the development of psychosocial support interventions during a pandemic for Ukrainian citizens by the public and private sectors, particularly in creating specialized smartphone applications, adapting playback theatre in the online space, creating gender-sensitive online programs to integrate IDPs into local communities.