Phaseolus lunatus L. supplementation improved testicular structure and estradiol synthesis in protein-restricted rats

Context: Protein deficiency remains a critical concern in developing countries, with implications in many physiological aspects, including male fertility. Lima beans (Phaseolus lunatus; PL), a legume rich in protein and commonly consumed in Indonesia, may serve as a traditional plant-based alternative to support male reproductive health. Aims: To investigate the potential benefits of P. lunatus supplementation on testicular histology and hormonal profiles in protein-restricted rats. Methods: Male rats were fed a 12% protein-restricted diet for six weeks, followed by supplementation with 25% (PL25) or 50% (PL50) P. lunatus powder for another six weeks. Testicular structure was examined histologically under a microscope. In addition, serum levels of testosterone and estradiol, as well as the activity of androgen receptors (AR) and estrogen receptor-α (ER-α), were measured. Results: Protein restriction led to reduced testicular size, disrupted seminiferous tubule integrity, decreased sperm count, and a selective impairment of estradiol synthesis, accompanied by downregulation of AR and ER-α expression. Supplementation with PL50 significantly reversed these effects, improving testicular architecture, estradiol production, and receptor activity. Conclusions: P. lunatus supplementation shows potential in mitigating testicular damage and dysfunction induced by protein deficiency, possibly by restoring estrogen signaling and spermatogenesis. Further studies are required to elucidate the underlying mechanisms by which P. lunatus exerts its protective effects on the male reproductive system.