Toll-like receptor 4 (TLR4) is known to contribute to the modulation of insulin resistance and systemic inflammation seen in obesity and the metabolic syndrome. The present study was performed to investigate the fertility competence of TLR4 knock out male mice (TLR4 mice) on a high-fat diet (HFD), compared to a normal-chow diet (NCD). The controls included wildtype (WT) mice fed on a HFD or NCD. Six-week-old male mice were fed with either a NCD or HFD for 20 weeks. Body and organ weights, serum levels of glucose, triglycerides and hepatoxicity, sperm quality and spermatogenesis were observed after the sacrifice. Also, randomly selected male mice were mated with virgin female mice after feeding of 19 weeks. The weight of the body and organs increased in WT and TLR4 mice on a HFD compared to those of mice on a NCD. The weights of the reproductive organs did not vary among the treatment groups. The motility and concentration of the epididymal spermatozoa decreased in both WT and TLR4 mice fed a HFD. The pregnancy rate and litter size declined in the HFD-fed WT mice compared to the HFD-fed TLR4 mice. In conclusion, the HFD alters energy and steroid metabolism in mice, which may lead to male reproductive disorders. However, fertility competence was somewhat restored in HFD-fed TLR4 male mice, suggesting that the TLR4 is involved in testis dysfunction due to metabolic imbalance.

INTRODUCTION
MATERIALS AND METHODS
    Intake of normal and high-fat diet (HFD) by male mice
    Breeding
    Examination of organs and epididymal spermatozoa
    Analysis of glucose, cholesterol, and triglyceride concentrations in the serum
    Hepatotoxicity assessment
    Analysis of sperm quality
    Histological assessment
    Statistical analysis
RESULTS
DISCUSSION

• Eun Young Oh(Laboratory of Veterinary Virology, College of Veterinary Medicine, Chungbuk National University, Cheongju 28644, Korea)
• Sang-Myeong Lee(Laboratory of Veterinary Virology, College of Veterinary Medicine, Chungbuk National University, Cheongju 28644, Korea) Corresponding author
• Malavige Romesha Chandanee(Department of Agricultural Education, College of Education, Sunchon National University, Suncheon 57922, Korea)
• Wijesooriya Mudhiyanselage Nadeema Dissanayake(Department of Agricultural Education, College of Education, Sunchon National University, Suncheon 57922, Korea)
• Young-Joo Yi(Department of Agricultural Education, College of Education, Sunchon National University, Suncheon 57922, Korea) Corresponding author