Maca has been reported to alleviate male menopause symptoms in humans and experimental animals; however, its mechanism of action in improving male menopause has not been clearly identified. This study aimed to investigate the mechanism of action of gelatinized maca in improving male menopause by analyzing serum testosterone, testicular androgen receptor (AR) expression, and testicular oxidation-antioxidation balance. Gelatinized maca was administered orally to aged male C57BL/6 mice at three doses (500, 1,000, and 1,500 mg/kg/day) for 28 consecutive days. Serum biochemical analysis showed an increase in serum hydroxysteroid 17-beta-dehydrogenase 13 (HSD17β13) concentration at 1,500 mg/kg/day and a decrease in serum sex hormone-binding globulin (SHBG) concentration at ≥ 1,000 mg/kg/day. Gelatinized maca administration also resulted in the increased expression levels of testicular AR and cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) at 1,500 mg/kg/day. Oxidative stress analysis showed an increase in testicular superoxide dismutase and glutathione reductase activities and a decrease in testicular malondialdehyde at 1,500 mg/kg/day. In conclusion, gelatinized maca administration to aged male mice increased HSD17β13, AR and CREB expression, and antioxidant capacity and decreased serum SHBG. The results of the present study suggest that gelatinized maca may be a useful substance that can help alleviate male menopause symptoms.

Abstract
Introduction
Materials and Methods
    1. Experimental animals and laboratory environment
    2. Test substance and treatment
    3. Test groups and dose selection
    4. Clinical observation and body weight
    5. Necropsy and gross pathology
    6. Measurement of serum HSD17β13, SHBG, andtestosterone
    7. Quantitative reverse transcription polymerase chainreaction (qRT-PCR)
    8. Measurement of testicular oxidative stress
    9. Statistical analysis
Results and Discussion
    1. Effect of gelatinized maca on clinical signs andbody weight
    2. Effect of gelatinized maca on gross pathology
    3. Effect of gelatinized maca on serum testosterone,HSD17β13, and SHBG
    4. Effect of gelatinized maca on AR, CREB, andNF-kB expression
    5. Effect of gelatinized maca on testicularoxidation-antioxidation balance
Acknowledgment
References

• Jong Choon Kim(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea) Corresponding author
• In Sik Shin(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea)
• Chang Jong Moon(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea)
• Sin Hyang Park(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea)
• So Won Pak(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea)
• Woong Il Kim(Professor, College of Veterinary Medicine and BK21 FOUR Program, Chonnam National University, Gwangju 61186, Korea)
• Gwang Seop Jo(Team leader, Safety Evaluation Center, DT&CRO, Yongin 17042, Korea)