Shilajit Mitigates Diabetes-Induced Testicular Dysfunction in Mice: A Modulation in Insulin Sensitivity, Germ Cell-Junctional Dynamics, and Oxido-Apoptotic Status

Abstract

Diabetes is a chronic metabolic condition that causes testicular damage by high oxidative stress, rendering 35% of afflicted people infertile. Shilajit is a traditional Indian medicine known for its antioxidant, antidiabetic, and aphrodisiac properties. However, its effectiveness on diabetes-induced testicular dysfunction remains unclear. Therefore, the current investigation aimed to determine whether Shilajit could restore testicular functions in diabetic mice. Two days postpartum male Parkes mice received a single intraperitoneal injection of streptozotocin (STZ) (90 mg/kg BW) to induce diabetes. Three months postinjection, the effects of daily Shilajit (100 and 200 mg/kg BW) treatment were evaluated for one spermatogenic cycle in adult diabetic mice, using Empagliflozin (10 mg/kg BW) as a positive control. In STZ-induced diabetic mice, testicular functions were compromised due to disruptions in testosterone biosynthesis, changes in germ-cell ratios, and increased oxidative stress and apoptosis. Shilajit restored glycemic status in diabetic mice by significantly decreasing serum glucose, insulin level, and homeostasis model assessment of insulin resistance (HOMA-IR) value while increasing insulin sensitivity. These effects were comparable to those observed with conventional antidiabetic medication Empagliflozin. Further, Shilajit stimulates steroidogenesis and germ cell dynamics of diabetic mice by increasing the activity of StAR, 3β-HSD, and 17β-HSD enzymes and 1C:2C, 4C:S-Ph, and 1C:4C germ cell ratios, respectively. Shilajit also improves blood–testis barrier (BTB) functioning by increasing expression of ZO-1, Connexin-43, N-Cadherin, and β-catenin as well as oxidative status and apoptosis by modulating NF-E2–related factor 2 (Nrf-2)/heme oxygenase 1 (HO-1) signaling and Bax/Bcl-2 ratio. Subsequently, Shilajit improved the histoarchitecture of testis and epididymis in diabetic mice and recovered both qualitative and quantitative sperm parameters, as seen by higher percentages of sperm motility, viability, and normal sperm morphology as well as increased sperm numbers in cauda epididymis. In summary, Shilajit restores glycemic status, increases insulin sensitivity, stimulates steroidogenesis, and improves testicular functions through Sertoli cell and Nrf-2/HO-1 signaling in STZ-induced diabetic mice.