*4.4. Animals and Diet*

Forty-five eight-week-old male Kunming mice were raised in an experimental environment and subjected to a light–dark cycle at 23 ± 1 ◦C for 12 h. During the week of domestication, the animals were given normal lab feed and free water. Mice were randomly divided into blank control group (BC), negative control group (NC), positive control group (PC) (VC, 100 mg/kg), low-dose group (LD) (UPE, dose of 50 mg/kg), and high-dose group (HD) (UPE, dose of 300 mg/kg), with 9 mice in each group. Mice in NC group, PC group, LD group, and HD group were subcutaneously injected with D-Gal at a dose of 400 mg/kg, and mice in BC group were injected with 0.9% normal saline for 10 weeks. Starting from week 7, the LD group and HD group were intragastrically given UPE at the corresponding dose, while the PC group was intragastrically given VC once a day for 4 consecutive weeks. The BC and NC groups were given the same volume of distilled water. The experiment design was approved by the Animal Care and Use Committee of Ocean University of China (certificate no. SYXK2012014).

#### *4.5. Body Weight Measurement*

The mice were weighed every 2 days. On the last day of the experimental period, after 8–12 h of fasting, the mice were sacrificed under ether narcotization. The kidney was isolated and weighed to calculate the organ coefficient, using the following formula:

Coefficient (mg/g) = organ weight (mg)/body weight (g).

#### *4.6. Serum Indexes Analysis*

Blood samples were collected from the eye socket and centrifuged at 4 ◦C and 3000 rpm for 30 min, and the serum was stored at −80 ◦C. The contents of Scr, BUN, and Cys-c were determined.
