Chdh, or choline dehydrogenase, is a transmembrane protein located in mitochondria. It is a key enzyme that catalyzes the oxidation of choline to betaine, playing a crucial role in this metabolic pathway. Betaine is an important methyl donor and organic osmolyte, and thus Chdh is vital for cellular physiology and metabolism. Additionally, Chdh is involved in mitochondrial autophagy (mitophagy) after mitochondrial damage [1,3].

In a Chdh knockout (KO) mouse model, deletion of Chdh did not affect fetal viability, growth, or survival of the mice. However, only one of eleven Chdh -/- males was able to reproduce, as loss of CHDH activity led to decreased testicular betaine and increased choline and PCho concentrations. The impaired fertility was due to diminished sperm motility in Chdh -/- males, along with abnormal mitochondrial morphology in their sperm. ATP content, total mitochondrial dehydrogenase activity, and inner mitochondrial membrane polarization were all significantly reduced in sperm from Chdh -/- animals. Mitochondrial changes were also detected in liver, kidney, heart, and testis tissues [2].

In conclusion, Chdh is essential for the conversion of choline to betaine and for maintaining normal mitochondrial function and sperm motility. The Chdh KO mouse model has revealed its significance in male fertility and mitochondrial-related functions in various tissues, providing valuable insights into potential disease mechanisms related to Chdh dysfunction, such as infertility [2].