Teratospermia (ejaculation of ≥ 60% structurally abnormal spermatozoa) is prevalent among felids facing extinction risk, including the cheetah. This trait also occurs in certain domestic cat populations, providing a valuable research model. Multiple components of sperm function are disrupted in teratospermic cats, and even structurally normal spermatozoa from these ejaculates may be functionally compromised. Teratospermic ejaculates are highly sensitive to damage during cryopreservation, limiting the success of genome resource banking programs for species conservation. Although both teratospermia and cryopreservation are linked to disruptions in multiple energy-dependent sperm processes, the metabolism of these cells has not been investigated. This project explored how cellular metabolism of domestic cat and cheetah spermatozoa is influenced by species physiology, teratospermia, and sperm cryopreservation.
The project scope was divided into four studies that collectively examined the two main energy-producing pathways in spermatozoa, i.e., glycolysis and oxidative phosphorylation. Each study compared three animal populations: normospermic cat, teratospermic cat, and cheetah. First, rates of glycolytic and oxidative substrate utilization were correlated to standard metrics of sperm function. Second, the influence of exogenous substrate availability and glycolytic enzyme activity was investigated. Third, mitochondrial activity and the role of oxidative metabolism were assessed. Lastly, sperm metabolic function was examined after cryopreservation and postthaw processing.enzyme activity was essential for sperm function, but, unexpectedly, the importance of this pathway appeared to be linked to glycerol rather than glucose metabolism. Sperm oxidative metabolism was severely compromised in the cheetah, and comparison with the teratospermic cat proved this defect to be species-specific. Spermatozoa from both species experienced metabolic damage during cryopreservation. Post-thaw processing recovered a metabolicallynormal sperm subpopulation in the cat, but cheetah spermatozoa remained functionally compromised. Collectively, these studies provided key insight into metabolism and cryosensitivity of felid spermatozoa and highlighted the importance of domestic animal models for wildlife research.
Patterns of substrate utilization were similar in spermatozoa of the cat and cheetah, including an unexpected lack of glucose uptake. However, rates of sperm pyruvate uptake and lactate production were reduced in the teratospermic cat and cheetah compared to the normospermic cat. Lactate production predicted ejaculate quality in each study. Glycolyti
