Rapid and transient oxygen consumption increase following acute HDAC/KDAC inhibition in Drosophila tissue

Abstract

Epigenetic deregulation, such as the reduction of histone acetylation levels, is thought to be causally linked to various maladies associated with aging. Consequently, histone deacetylase inhibitors are suggested to serve as epigenetic therapy by increasing histone acetylation. However, previous work suggests that many non-histone proteins, including metabolic enzymes, are also acetylated and that post transitional modifications may impact their activity. Furthermore, deacetylase inhibitors were recently shown to impact the acetylation of a variety of proteins. By utilizing a novel technique to measure oxygen consumption rate from whole living tissue, we demonstrate that treatment of whole living fly heads by the HDAC/KDAC inhibitors sodium butyrate and Trichostatin A, induces a rapid and transient increase of oxygen consumption rate. In addition, our study indicates that the rate increase is markedly attenuated in midlife fly head tissue. Overall, our data suggest that HDAC/KDAC inhibitors may induce enhanced mitochondrial activity in a rapid manner. This observed metabolic boost provides further, but novel evidence, that treating various maladies with deacetylase inhibitors may be beneficial.

Measuring and Interpreting Oxygen Consumption Rates in Whole Fly Head Segments

“…However, based on our observations, automatically using the AKOS algorithm may give misleading, if not opposite results for the correct OCR. Such artefacts can be generated in conditions of a highly consuming sample which reaches anoxia 13,22 . For example, the addition of sodium butyrate (SB), a KDAC inhibitor, transiently changes the dynamics of the oxygen levels ( Figure 3A).…”

“…Finally, a critical step is choosing the correct algorithm to analyze the samples. As we have demonstrated, the default AKOS algorithm yielded a misleading and sometimes opposing calculation in samples that consumed oxygen at high rates 13 . We therefore stress the importance of checking the raw data for oxygen levels and comparing the resulting OCR.…”

“…Furthermore, the isolation process is long and may result in loss of relevant protein posttranslational modifications which regulate mitochondrial function 9,10,11 . Moreover, it has been shown that isolated mitochondria do not consistently represent whole tissue metabolic rates 12,13 . Such cellular biological complexity could be viewed as, 'the whole is greater than the sum of its parts', i.e., mitochondria may display different metabolic rates inside a complex cell compared with their metabolic rate when isolated.…”

“…In this study, we have used a similar setup to enable the measurement of whole OCR from whole living and non-mobile Drosophila 22 . This technique also offers a secondary advantage in measuring the impact of various drugs on metabolic activity in a whole segment, without having to pass through the digestive system barrier 13,22 . For example, it was previously demonstrated that direct injection of lysine deacetylase inhibitor (KDACi), a drug believed to alter epigenetic mechanism in the brain, resulted in an improved memories formation 23 .…”

Epigenetic mechanisms related to cognitive decline during aging

“…Accordingly, the administration of sodium butyrate and TSA caused a rapid increase in oxygen consumption rate (OCR) in Drosophila via non‐histone protein acetylation suggesting that HDAC inhibition is able to increase metabolic activity by enhancement of mitochondrial function. HDACi treatment was less effective on midlife flies, which might be due to the fact that these have already elevated OCR and thus their metabolic range is resistant to further augment (Becker, Nogueira, Klima, Angelis, & Peleg, ). In contrast to class I and class II‐HDACs, the levels of Sirtuin 1 (SIRT1), a class III deacetylase, were found to decline with aging in brain (Quintas, Solis, Diez‐Guerra, Carrascosa, & Bogonez, ; Sommer et al, ), other tissues and in senescent cells (Gong et al, ; Sasaki, Maier, Bartke, & Scrable, ).…”