Dietary Fibre Supplementation Improves Semen Production by Increasing Leydig Cells and Testosterone Synthesis in a Growing Boar Model.

Yan Lin,Lujie Li,Yong Zhuo,Shengyu Xu,Jian Li,Junjie Zhang,Zhengfeng Fang,Caimei Wu,Bin Feng,De Wu,Lianqiang Che

doi:10.3389/fvets.2022.850685

Abstract

Testicular development is imperative to spermatogenesis, and pre-puberty is the key period for testis development. This study, therefore, investigated the effects of fibre supplementation on testis development and its possible mechanism in a growing boar model. Thirty Yorkshire boars were randomly divided into a control group (Control) and a fibre group (Fibre) from day 0 to 90 after weaning, with three pigs per pen and five pens per treatment. Blood and testes were collected for analysis. Dietary fibre supplementation had no significant effect on growth performance, testicular volume, or libido but increased the semen production of boars. Boars fed with fibre had lower serum cholesterol (CHO) and low-density lipoprotein (LDL) levels compared to those on the Control diet; however, testicular CHO, triglyceride (TG), and LDL concentration in the Fibre group were significantly higher than the Control group (P < 0.01). Testicular histological analysis showed that seminiferous tubules and testicular germ cells of 120-day-old boars were densely arranged in the Fibre group, and the number of Leydig cells was significantly higher than that of the Control group (P < 0.001). Furthermore, the diet supplemented with fibre significantly decreased leptin, leptin receptor (Leptor), and luteinising hormone (LH) concentrations in boar serum (P < 0.05), whereas follicle-stimulating hormone (FSH) and testosterone concentrations were significantly increased (P < 0.05). Meanwhile, the expression of AMH, AMHR2, and SYCP3 genes related to proliferation and differentiation, and hormone-related genes STAR and SOCS3, were significantly up-regulated (P < 0.05). OCCLUDIN expression was up-regulated, whereas CDH2 expression was down-regulated. In conclusion, increased fibre intake during the pre-puberty period in growing boar is crucial for Leydig cell proliferation, up-regulating the expression of genes related to hormone synthesis and thereby promoting the secretion of testosterone and semen production.

Highlights

We found that a total dietary fibre (TDF) difference of approximately 1.5–2.5% had no significant effect on the growth performance of growing boars
Our results showed that the increase in fibre intake in growing boars promoted the proliferation of Leydig cells and increased the levels of T and folliclestimulating hormone (FSH), implying that fibre supplementation improves testicular development, which is beneficial to spermatogenesis in adulthood
We found that increased fibre intake significantly increased the boar testicular cholesterol and T levels but reduced the serum cholesterol and T levels

Summary

Introduction

The testis is an important sexual organ in male animals. In humans and other male mammals, such as rats and boars, testicular development directly affects semen quality [1, 2], which is crucial for reproduction. Testicular development mainly occurs in the seminiferous tubules, including the proliferation of Sertoli, germ, and Leydig cells. Human testes mainly develop during childhood (2–11 years) and adolescence (2–14 years) [3]. From 2–8 years of age, the number of germ cells increases by 3 to 6 times, and testis volume, testis weight, Sertoli cells, and testosterone levels in the testes gradually increase [4]; subsequently, the spermatogonial cells proliferate rapidly. During the pre-puberty period, the number of germ cells increases, and boars nearly reach sexual maturity at approximately 120–150 days. Testicular development during the growing period is very important for later spermatogenesis

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Conclusion