Effects of Tortoise-Shell Glue on Rat Oligoasthenospermia Model
Oligoasthenospermia (OA), characterized by reduced sperm count, concentration, and motility, is a leading cause of male infertility, affecting approximately 5% of reproductive-aged couples globally. Despite its prevalence, the etiology and mechanisms underlying OA remain poorly understood, necessitating innovative therapeutic approaches. Traditional Chinese medicine (TCM) has historically employed natural substances, such as tortoise-shell glue (TSG), to address conditions linked to energy deficiency or “Qi” imbalance. In TCM theory, “Qi” parallels the biological role of mitochondria, the cellular powerhouses critical for sperm motility and function. This study investigated the therapeutic potential of TSG in a rat model of OA, focusing on its effects on sperm parameters, testosterone levels, testicular histology, and mitochondrial function.
Establishment of the OA Model and Experimental Design
The OA model was induced in male Sprague Dawley rats (10 weeks old, 200 ± 20 g) through daily intragastric administration of 330 mg·kg⁻¹·day⁻¹ L-thyroxine for 20 days. L-thyroxine, a thyroid hormone, was selected based on prior evidence linking hyperthyroidism to reduced sperm motility and fertility. After model induction, rats were divided into seven groups (n=4 per group):
- Normal control: Saline administration for 50 days.
- OA model (Model): L-thyroxine for 20 days followed by saline for 30 days.
- Low-TSG: OA + 1.0 g/kg TSG daily.
- Medium-TSG: OA + 1.5 g/kg TSG daily.
- High-TSG: OA + 2.0 g/kg TSG daily.
- Levocarnitine: OA + 330 mg/kg levocarnitine daily (positive control).
- TSG + Levocarnitine: OA + 2.0 g/kg TSG + 330 mg/kg levocarnitine daily.
TSG, sourced from Hunan Dongjian Pharmaceutical Co., Ltd., and levocarnitine, a clinically proven sperm-quality enhancer, were administered intragastrically for 30 days post-OA induction.
TSG Restores Sperm Quality and Testosterone Levels
Sperm parameters, including curvilinear velocity (VCL), motility, and concentration, were severely impaired in the OA model group. Rats treated with L-thyroxine exhibited a 40–50% reduction in sperm motility (P < 0.05 vs. normal controls) and a sperm concentration of <12 × 10⁶/mL, consistent with clinical OA criteria. Medium- and high-TSG treatments significantly reversed these effects:
- High-TSG restored sperm motility to near-normal levels (32% increase vs. model group, P < 0.05), comparable to levocarnitine.
- TSG + Levocarnitine achieved the highest sperm concentration (28 × 10⁶/mL vs. 18 × 10⁶/mL in levocarnitine alone, P < 0.05), demonstrating synergistic effects.
Testosterone levels, critical for spermatogenesis, were reduced by 35% in OA rats (P < 0.05 vs. normal). Medium- and high-TSG doses elevated testosterone by 25% and 30%, respectively (P < 0.05 vs. model), with the combination group showing the most robust recovery (95% of normal levels).
Histological Protection of Testicular Architecture
Testicular histology in OA rats revealed structural degeneration, including shrunken seminiferous tubules, disorganized epithelium, and reduced spermatogenic cell density. TSG treatment dose-dependently ameliorated these changes:
- Low-TSG partially preserved tubule integrity but showed residual epithelial disruption.
- High-TSG restored near-normal tubule morphology and spermatogenic cell density.
- TSG + Levocarnitine exhibited the most pronounced protection, with seminiferous tubules indistinguishable from normal controls.
Mitochondrial Functional Recovery
Mitochondrial dysfunction, a hallmark of OA, was assessed via mitochondrial permeability transition pore (mPTP) activity and respiratory complex assays. L-thyroxine-induced OA caused mPTP hyperactivation, leading to mitochondrial membrane depolarization and impaired respiratory chain activity (Complexes I–IV reduced by 40–60%, P < 0.05 vs. normal). TSG treatment counteracted these effects:
- High-TSG normalized mPTP closure and increased Complex I–IV activities by 30–45% (P < 0.05 vs. model).
- TSG + Levocarnitine achieved near-complete restoration of mitochondrial function, exceeding levocarnitine alone (e.g., Complex III activity: 85% vs. 70% recovery, P < 0.05).
Western blot analysis of mitochondrial proteins further validated these findings. OA rats showed suppressed expression of voltage-dependent anion channel (VDAC) and adenine nucleotide translocase (ANT), key regulators of mPTP. High-TSG upregulated VDAC and ANT by 2.1-fold and 1.8-fold, respectively (P < 0.05 vs. model), aligning with improved mitochondrial integrity.
Mechanistic Insights and Therapeutic Implications
The study highlights mitochondria as central targets in TSG’s therapeutic action. By stabilizing mPTP and enhancing respiratory complex activity, TSG mitigates oxidative stress and apoptosis in spermatogenic cells, thereby preserving sperm production and motility. The synergy between TSG and levocarnitine suggests complementary mechanisms: levocarnitine enhances fatty acid oxidation for energy production, while TSG directly bolsters mitochondrial resilience.
Limitations and Future Directions
While promising, the study’s small sample size (n=4 per group) and reliance on a single OA model (hyperthyroidism-induced) limit generalizability. Future investigations should explore TSG’s efficacy in other OA models, such as oxidative stress- or infection-induced infertility, and incorporate larger cohorts. Additionally, isolating bioactive components of TSG could refine its therapeutic application and elucidate molecular targets.
Conclusion
This study demonstrates that TSG, particularly at high doses, effectively restores sperm quality, testosterone levels, and testicular structure in L-thyroxine-induced OA rats. Its mitochondrial protective effects, synergizing with conventional therapies like levocarnitine, position TSG as a viable adjunct or alternative for male infertility treatment. These findings bridge TCM principles with modern biomedicine, underscoring mitochondria as a nexus for therapeutic innovation in reproductive health.
doi.org/10.1097/CM9.0000000000001658
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