Extra-virgin olive oil ameliorates high-fat diet-induced seminal and testicular disorders by modulating the cholesterol pathway

Abstract

Background: Rabbits are sensitive to dietary cholesterol and rapidly develop hypercholesterolemia, leading to prominent subfertility. Sterol regulatory element-binding protein isoform 2 drives the intracellular cholesterol pathway in many tissues, including the testicles. Its abnormal regulation could be the mainly responsible for the failure of suppressing cholesterol synthesis in a cholesterol-enriched environment, ultimately leading to testicular and seminal alterations. However, extra-virgin olive oil consumption has beneficial properties that promote lowering of cholesterol levels, including the recovery of seminal parameters altered under a high-fat diet. Objectives: Our goal was to investigate the effects of high-fat diet supplementation with extra-virgin olive oil at the molecular level on rabbit testes, by analyzing sterol regulatory element-binding protein isoform 2 protein and its corresponding downstream effectors. Materials and methods: During 12 months, male rabbits were fed a control diet, high-fat diet, or 6-month high-fat diet followed by 6-month high-fat diet plus extra-virgin olive oil. Serum lipids, testosterone levels, bodyweight, and seminal parameters were tested. The mRNA and protein levels of sterol regulatory element-binding protein isoform 2, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, and low-density lipoprotein receptor were determined by semi-quantitative polymerase chain reaction and Western blotting techniques. The expression pattern of sterol regulatory element-binding protein isoform 2 protein in the rabbit testicles was studied by indirect immunofluorescence. In addition, testicular cholesterol was detected and quantified by filipin staining and gas chromatography. Results: The data showed that the addition of extra-virgin olive oil to high-fat diet reduced testicular cholesterol levels and recovered the expression of sterol regulatory element-binding protein isoform 2, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, and low-density lipoprotein receptor initially altered by the high-fat diet. Discussion and conclusions: The combination of high-fat diet with extra-virgin olive oil encourages testicular recovery by modifying the expression of the enzymes related to intracellular cholesterol management.