Emixustat reduces metabolic demand of dark activity in the retina

Ryo Kubota*, David J. Calkins, Susan H. Henry, Robert A. Linsenmeier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


PURPOSE. In the dark, photoreceptor outer segments contain high levels of cyclic guanosine 30-50 monophosphate (cGMP), which binds to ion channels, holding them open and allowing an influx of cations. Ion pumping activity, which balances cation influx, uses considerable amounts of adenosine triphosphate (ATP) and oxygen. Light reduces cation influx and thereby lowers metabolic demand. Blood vessels are compromised in the diabetic retina and may not be able to meet the higher metabolic demand in darkness. Emixustat is a visual cycle modulator (VCM) that reduces chromophore levels and, therefore, may mimic light conditions. We evaluated the effect of emixustat on oxygen consumption and cation influx in dark conditions. METHODS. Cation influx was measured in rats using Mn-magnetic resonance imaging (MEMRI). Retinal oxygen profiles were recorded to evaluate oxygen consumption. In the MEMRI protocol, animals were treated with either emixustat or vehicle. In the oxygen protocol, animals were untreated or treated with emixustat. RESULTS. In vehicle-treated animals, cation channel activity increased in the dark. Emixustat treatment reduced cation channel activity; activity was comparable to vehicle-treated controls in light conditions. In vehicle-treated animals, minimum retinal oxygen tension decreased as the retina recovered from a photobleach, indicating that more oxygen was being consumed. Emixustat treatment prevented the decrease in oxygen pressure after photobleach. CONCLUSIONS. Emixustat reduced the cation influx and retinal oxygen consumption associated with dark conditions. VCMs are a promising potential treatment for ischemic retinal neovascularization, such as that in diabetic retinopathy.

Original languageEnglish (US)
Pages (from-to)4924-4930
Number of pages7
JournalInvestigative Ophthalmology and Visual Science
Issue number14
StatePublished - Nov 1 2019


  • Dark adaptation
  • Emixustat
  • Retina

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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