Abstract
Cholesterol and lipid homeostasis is important for male fecundity. However, the plasma total cholesterol level does not reflect sperm concentration and motility. Adipose tissue in mammals is the main tissue contributing to the dynamic equilibrium of lipid synthesis and catabolism. However, recent studies suggested that local lipolysis has an important role in male fertility. If so, which plasma lipid metabolism parameter reflects sperm concentration and motility? Leptin receptor-deficient db/db mice show hyperphagia, hyperglycemia, hypercholesterolemia, hypertriglyceridemia, morbid obesity and are reported to be infertile. Impairment of spermatogenesis and sperm motility in db/db mice was observed in our experiments. Medium-chain triglycerides (MCTs) are more quickly metabolized as fuel compared to long-chain triglycerides (LCTs). If the LCTs are replaced with MCTs in the diet, even in hyperphagia, does it affect spermatogenesis and sperm motility? In this study, we investigated the effect of a MCT replacement diet on sperm parameters using db/db mice. Six weeks of MCT replacement diet improved not only spermatogenesis but also the maturation processes in the epididymis for sperm to acquire the ability to move forward. Plasma chylomicron and large VLDL levels showed positive correlation with total and motile sperm concentrations. The MCT replacement diet could be an effective treatment for idiopathic non-obstructive oligozoospermia or asthenozoospermia men with low levels of chylomicron and large VLDL.