In a new study, researchers investigated the mortality and respiration rates of RNA virus-infected male fruit flies and how aging impacts these outcomes and measurements.
RNA viruses are responsible for approximately 70% of emerging infectious diseases in humans, according to a 2020 report by the National Academy of Medicine. Examples of RNA viruses include: influenza, hepatitis C, HIV, measles, zika, ebola, poliovirus, rhinovirus, rabies, and SARS-CoV-2—the virus responsible for the COVID-19 pandemic. After infection with an RNA virus, significant changes can take place in the host’s metabolism. While it is clear that disease tolerance declines as humans age, it is not yet clear how aging affects virus-induced changes in metabolism.
“Virus-induced metabolic reprogramming could impact infection outcomes, however, how this is affected by aging and impacts organismal survival remains poorly understood.”
In a new study, researchers Eli Hagedorn, Dean Bunnell, Beate Henschel, Daniel L. Smith Jr., Stephanie Dickinson, Andrew W. Brown, Maria De Luca, Ashley N. Turner, and Stanislava Chtarbanova from the University of Alabama, Indiana University, University of Arkansas for Medical Sciences, Arkansas Children’s Research Institute, and Jacksonville State University examined how an RNA virus can affect the respiration rate in male fruit flies (Drosophila melanogaster), both young and old. On March 22, 2023, their research paper was published in Aging’s Volume 15, Issue 6, entitled, “RNA virus-mediated changes in organismal oxygen consumption rate in young and old Drosophila melanogaster males.”
An organism’s metabolism depends on oxygen to produce energy. An efficient immune system depends, in part, on energy from the body’s metabolism to fuel it. Paradoxically, decreased metabolism, or hypometabolism, is a survival strategy that promotes disease tolerance in response to infection. In this study, the researchers used oxygen consumption rate (OCR) to indirectly measure changes in metabolism before and after RNA viral infection. The team infected male fruit flies with the RNA virus Flock House virus (FHV), and documented their oxygen consumption rate and/or mortality times at different time intervals after infection.
“As the exact mechanisms by which hypometabolism promotes tolerance are not fully understood, D. melanogaster could serve as an excellent model to dissect the genetic and molecular bases of this process.”
After the first 72-hours post-infection, FHV appeared to modulate respiration in all flies, but age did not appear to have a significant effect on OCR. However, over the course of the three-day experiment, the longitudinal assessment showed that OCR in young flies progressively and significantly decreased, while OCR in aged flies remained constant. The researchers found that the OCR at 24-hours varied in response to both experimental treatment and survival status. FHV-injected flies that died prior to 48- or 72-hours had a lower OCR compared to survivors at 48-hours.
“Our results show that FHV infection significantly reduces organismal OCR compared to Tris-injected controls; however, we did not observe a significant change in OCR with aging. Interestingly, flies that died prior to 48-hours post-treatment measurements exhibited a significantly lower OCR at 24 h post-treatment compared to survivors. These findings suggest that the host’s metabolic profile could influence the outcome of viral infections.”
In conclusion, RNA viruses pose a significant threat to human health, causing numerous emerging infectious diseases. The impact of these viruses on the host’s metabolism, particularly in relation to aging, remains poorly understood. The recent study by Hagedorn et al. sheds light on the interaction between RNA viruses, metabolism and aging by examining the effects of the Flock House virus on the respiration rate of male fruit flies. The findings suggest that this infection can modulate the host’s OCR, and that the metabolic profile of the host could influence the outcome of viral infections. The authors suggest that further research is needed to determine the precise mechanisms by which RNA viruses affect metabolic rate and to explore the potential for interventions to modulate metabolic rate and improve healthspan and lifespan.
“Older flies exhibit impaired disease tolerance to FHV , and here we show that metabolic rate depression does not occur in older flies in response to FHV in the first three days following treatment. It is therefore possible that as is the case in mammals, flies employ hypometabolism as a survival strategy that is part of a disease tolerance mechanism. It would be interesting in the future to test this hypothesis by comparing OCR in tolerance mutant flies such as the G9a mutants.”
Click here to read the full research paper published by Aging.
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