Km mice

KM mice (18–22 g) with half males and half females were purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. Water and foods were plentiful and free to the animals. Meanwhile, the room temperature (25 ± 2 °C) and humidity (50 ± 5%) were stable coupled with a 12 h light/dark cycle. This study was carried out in accordance with the recommendations of the Principles of Laboratory Animals and the related ethical regulations of Beijing University of Chinese Medicine. The protocol was approved by the ‘Affidavit of Approval of Animal Ethical and Welfare of BUCM’ (No.4-2017010103-10043, 27 September 2017, Beijing University of Chinese Medicine).

KM mice were purchased from the Vital River Laboratories (Beijing, China) and randomly divided into 4 groups. Animals (n = 10 per group, ♀ × 5, ♂ × 5) were treated intraperitoneally with a single dose of 1000, or 500, or 250 mg/kg CA, and saline was used as a control. Mouse survival and body weight changes were examined daily for all groups for 7 days. Next, 200 µL blood samples were collected from each mouse via retro-orbital bleeding, and levels of ALT, AST, BUN, and CRE in serum were detected.

The male KM mice (n = 40, 6–7 weeks) were from Vital River Laboratory Animal Technology Co., Ltd., (Beijing, China). They were raised in cages with a room temperature of 22 ± 2 °C and a humidity of 55 ± 5% for 12 h of light/dark cycle. The experiment was designed and modified from the previous description [19 (link)]. All mice had free access to water and food for the first week to acclimatize to the environment. After seven days, the mice were divided into five groups (n = 8 per group), including the normal control group (NC), model group (M), L. paracasei JY062 group (JY), L. gasseri JM1 group (JM), and the combination group (MIX) (L. paracasei JY062: L. gasseri JM1 = 1:2). All groups of mice except the NC group were given 5 mg/(kg·d) body weight of loperamide by continuous gavage for 7 days. At this time, mice in the NC group were continuously gavaged with equal amounts of PBS. Then, mice of JY, JM and MIX groups were intragastrically administered L. paracasei JY062, L. gasseri JM1, and the combination with 5 × 10⁹ CFU/mL, at a dose of 10 mg/(kg·d) body weight for two weeks, respectively, whereas those of the NC and M groups were intragastrically administered PBS with an equal dose. Mice were anesthetized by intraperitoneal injection of ketamine and diazepam before sacrifice at the end of the experiment.

Female 3‐week‐old and 8‐month‐old female KM mice were purchased from Vital River Laboratory Animal Technology Co., Ltd (Beijing, China). The 8‐month‐old female mice were raised in the specific pathogen‐free laboratory for more than 8 months. Before the experiment, the 3‐week‐old mice were acclimated to the laboratory environment for 1 week. The age of old and young mice used in this study was approximately 16 months old and 4 weeks old, respectively. The laboratory environment was maintained with a 12 h:12 h light/dark cycle, and the temperature (22–24 °C) and humidity (50–60%) were under control. The procedures of oocyte collecting were approved by the Animal Care and Use Committee of the Sixth Affiliated Hospital, Sun Yat‐sen University (Guangzhou, China), with the ethical approval numbers IACUC‐2021101102 and IACUC‐2020053102.