The influence of dietary lipids on sperm and semen quality in rabbits

The relationship between obesity/hypercholesterolemia and the decrease in male fertility has been reported clinically and in experimental models. The effect of high cholesterol (chol) intake and its impact in different tissue/organs has also been described in several animal models. But few documents focus on the addition of natural products to food as a protective diet, in order to avoid sperm alterations. New Zealand male rabbits fed with a high-fat diet were associated with deleterious changes in semen and sperm cells. The reported alterations include: decreased semen volume and sperm count, and an increase in abnormal sperm morphology. In addition, diets rich in fat (fat of animal origin) also had an impact on cellular function, such as the functionality of sperm cells. Cholesterol is a key molecule in sperm life because it is involved in several steps of sperm physiology. Changes in the concentration and distribution of cholesterol in the sperm membrane lead to the alteration of the specific functions of sperm coupled to the membrane. Sperm motility, osmotic resistance of the membrane to hypo osmotic shock, sperm capacitation and induced acrosome reaction were significantly reduced; probably due to an increase in the cholesterol content of the membrane. Capacitation and acrosome reaction are sperm specific processes required for fertilizing the oocyte in vivo. During sperm capacitation several changes occur in the surface of the sperm, such as the reorganization of proteins and lipids of the membrane. It is likely that these changes result in the capacitated state that typically allows the sperm to bind the pellucid zone and immediately afterwards to acrosome react. The deleterious effects of high cholesterol could be attributable to defects in the seminiferous tubules, low efficient of the spermatogenetic epithelium and failed spermiogenesis. In morphological detailed analysis it was observed that manchette/acroplaxome arrangement was disrupted. The manchette is a three-dimensional complex of sperm-specific microtubules that normally pulls down both the acrosomal and nuclear rings towards the site of flagella implantation. Under the intake of fatty foods, these structures are asymmetrical generating an abnormal sperm head and the implantation of flagella outside the central axis of the sperm. Olive oil, a component of Mediterranean diet, has been proposed by several studies as a protective agent against vascular injury promoted by acquired hypercholesterolemia. Interheart studies, population studies and the use of animal models analyzed the negative effect of increased serum cholesterol and the corresponding protection by the administration of virgin olive oil. We took advantage of our established rabbit model to evaluate if the administration of olive oil can recover the semen and sperm parameters altered by the hypercholesterolemia acquired by the diet. Supplementation of the fatty diet with olive oil was found to improve not only serum cholesterol level but also semen quality, morphology and sperm function.