Loganin alleviates testicular damage and germ cell apoptosis induced by AGEs upon diabetes mellitus by suppressing the RAGE/p38MAPK/NF‐κB pathway

Diabetes mellitus (DM) damages male reproduction at multiple levels, such as endocrine secretion, spermatogenesis and penile erection. We herein investigated the protective effects and mechanism of loganin targeting the advanced glycation end products (AGEs)/receptor for AGEs (RAGE)/p38 mitogen‐activated protein kinase (p38MAPK)/NF‐κB signalling pathway. Loganin relieved the general DM symptoms and decreased the blood glucose level of KK‐Ay DM mice. Haematoxylin‐eosin staining demonstrated that loganin ameliorated testicular histology and function and enhanced the activities of testis‐specific markers lactate dehydrogenase (LDH), acid phosphatase (ACP) and gamma‐glutamyl transferase (γ‐GT). Loganin also showed evident anti‐oxidative stress, anti‐apoptotic and anti‐inflammatory effects on DM‐induced reproductive damage by restoring glutathione (GSH) level and superoxide dismutase (SOD) activity, as well as reducing reactive oxygen species (ROS) level and Bax/Bcl‐2 ratio in vivo and in vitro. Western blotting exhibited that loganin significantly inhibited the AGEs/RAGE/p38MAPK/NF‐κB signalling pathway. Acridine orange and ethidium bromide staining (AOEB) and Western blotting showed that loganin in combination with inhibitors of RAGE, p38MAPK and NF‐κB exerted stronger anti‐apoptotic effects on AGE‐induced GC‐2 cell damage compared with loganin alone. In conclusion, loganin can protect against DM‐induced reproductive damage, probably by suppressing the AGEs/RAGE/p38MAPK/NF‐κB pathway.