Zucker lean

Five-week-old male ZDF (n = 40) rats and age-matched male Zucker lean (ZL; n = 10) rats from Charles River Laboratory (Beijing, China) were maintained on the vitamin D-deficient Purina 5008 chow (500 IU vitamin D3/kg) and tap water ad libitum. Animals were kept on a regular 12:12 h light-dark cycle at a controlled temperature (22 ± 2°C) and relative humidity (55 ± 5%). All experimental procedures involving animals complied with the Regulations on the Administration of Laboratory Animals in China and were approved by the Animal Ethical Committee of Tongji Medical College (Approval NO. S432).

The Ethics Committee from Comunidad de Madrid (PROEX 079/19) approved the protocol for animal experimentation. Animals were treated according to the European (2010/63/EU) and Spanish (RD 53/2013) legislation on care and use of experimental animals.
Male Zucker diabetic fatty rats (ZDF) and their Zucker lean (ZL) controls were purchased from Charles River Laboratories (L’arbresle, France) at 11 weeks of age. All animals were acclimated under standard controlled conditions (21 ± 1 °C; 50–60% humidity and 12 h day/night cycle). One week later, ZDF rats were randomly sorted into two groups; the first one received a standard AIN-93G diet (ZDF) and the second one received a cocoa–carob blend (CCB)-rich diet (10%) (ZDF-CCB). The ZL nondiabetic group received the standard AIN-93G diet (ZL). Animals were given ad libitum access to food and water. At 24 weeks of age (12 weeks of supplementation), animals were sacrificed, and blood samples were collected for biochemical analysis. The entire colon was rapidly resected for histological and biochemical analyses. One day before the sacrifice, fresh fecal samples were collected using abdominal massage in sterilized tubes and immediately frozen in liquid nitrogen and stored at −80 °C for further analyses.

Six-week-old male Zucker lean (ZL) and Zucker diabetic fatty (ZD) rats were purchased from Charles River Laboratories (Wilmington, MA, USA). Rats were housed in a temperature-controlled room with a 12 : 12-hour light-dark cycle and free access to Purina 5008 rat chow and water. Blood glucose was monitored using the Accu-chek glucometer by tail-vein blood sampling. In a previous study in which we characterized the time course of blood glucose in this model [15 (link)], we showed that blood glucose of the ZD rats began to increase at week 8, reached a peak at week 12, and remained at this higher level thereafter. The rats were housed in the animal care facility at the Morehouse School of Medicine that is AAALAC accredited. All animal protocols were approved by the Institutional Animal Care and Use Committee and were in accordance with the requirements stated in the National Institutes of Health Guide for the Care and Use Laboratory Animals.
For fenofibrate treatment, 12-week-old Zucker rats were divided into 3 experimental groups: vehicle- (0.5% carboxymethylcellulose ig) treated ZL, vehicle-treated ZD, or fenofibrate- (150 mg/kg/day ig) treated ZD (F-ZD) rats for 10 weeks. For rosiglitazone treatment, 12-week-old ZD animals were treated with rosiglitazone (10 mg/kg/day in drinking water) or vehicles for 8 weeks.