Gudca

Male C57BL/Ksj-db/db mice (35–45 g, 6–8 weeks old) and C57BL/Ksj-m/m mice (20-23 g, 6–8 weeks old) were purchased from Changzhou Cavens Model Animal Co.,Ltd with the permission number SCXK 2016–0010. After two weeks of adaptive feeding under a 12 h light/dark cycle at 21 ± 2°C with enough food and water, the mice were randomly divided into 3 groups. The study protocol followed international ethical guidelines and was approved by the Animal Care and Use Committee of Xinjiang Medical University.
The m/m mice (n = 10) and db/db mice (n = 10) were fed a standard chow diet and drinking water with vehicle for 8 weeks. At the same time, ten db/db mice were fed a standard chow diet and given 100 mg/kg/d GUDCA (Sigma-Aldrich, Cat# 06863) by gavage for 8 weeks. Weekly measurements of body weight, food and drink intake, and blood glucose were taken during experiments. Stool samples were collected during the last week and stored at−80°C until the analysis. All mice were fasted and water was available for 16 hours before death. The blood samples were collected and centrifuged at 3500rpm for 15 min at 4°C to obtain the serum. Liver, ileum, and white adipose were immediately collected after excision. The tissues were stored at−80°C until further analysis or in 4% paraformaldehyde and 2.5% glutaraldehyde for histological and transmission electron microscopy studies.

NCI-H716 cells (ATCC, CCL-251) was maintained in RPMI-1640 (Gibco, Life Technologies) supplemented with 10% fetal bovine serum, 2 mM L-Glutamine, 50 IU/mL penicillin and 50 μg/mL streptomycin in a humidified incubator at 37 °C, 5% of CO2. For GLP-1 secretion studies, 4 × 10⁵ NCI-H716 cells were incubated 24 h with appropriate concentration of CDCA, TCDCA, LCA, TLCA (all purchased from Aladdin Inc., China, with purity >99%) and GUDCA (Sigma-Aldrich) or vehicle. Supernatant was centrifuged and stored at −80 °C until used.
The NCI-H716 cell line is not listed in the International Cell Line Authentication Committee (ICLAC) database of commonly misidentified cell lines (http://iclac.org/databases/cross-contaminations). The cell line was obtained from American Type Culture Collection (ATCC, USA) and the cell line was authenticated using STR profiling, which confirmed its identity and purity.