日粮鱼油对高脂日粮饲喂小鼠发情周期和机体产热的影响

本研究旨在探讨鱼油对高脂日粮饲喂小鼠发情周期和机体代谢产热的影响。试验选用36只4周龄C57BL/6 J雌性小鼠，随机分成3组（n=12）：对照组、高脂组和高脂+鱼油组。对照组饲喂标准啮齿动物饲料（AIN-93G），高脂组和高脂+鱼油组分别饲喂高脂日粮（脂肪提供60%能量）和添加5%鱼油（等能替代猪油）的高脂日粮。试验期间，对小鼠体组成（12周龄）、整体代谢（16周龄）、褐色脂肪温度（18周龄）、体核温度（直肠温度，18周龄）和发情周期（20周龄）等进行检测。试验结束后，眼球采血分离血清，检测促卵泡激素（follicle-stimulating hormone，FSH）和雌二醇（estradiol，E2）的水平。此外，采集皮下脂肪、腹部脂肪和肩胛间褐色脂肪，称重并使用Western blot检测脂肪组织中产热相关基因的蛋白表达（UCP1、Cyto C），使用实时荧光定量PCR检测褐色脂肪组织中产热基因的mRNA表达（UCP1， PRDM16，PGC1α，Cidea，Elovl3）。结果显示，与对照组相比，高脂日粮显著增加了小鼠的体脂含量（12周龄）及皮下和腹部脂肪的沉积量（21周龄）（P<0.05），而添加鱼油显著降低了高脂饮食引起的体脂含量增加（P<0.05）。另外，高脂日粮导致小鼠的发情周期紊乱，伴随着周期延长、发情期缩短，以及血清中FSH和E2的水平降低（P<0.05），而添加鱼油可缓解高脂日粮导致的小鼠发情周期紊乱，提高血清中FSH和E2的水平（P<0.05）。同时，添加鱼油可增加高脂饲喂小鼠肩胛间褐色脂肪（interscapular brown adipose tissue，iBAT）和腹股沟白色脂肪（inguinal white adipose tissue，iWAT）中产热相关基因的表达（P<0.05），进而促进iBAT激活/产热和iWAT褐色化。结果提示，日粮鱼油可缓解高脂日粮导致的发情周期紊乱，可能与BAT激活和WAT褐色化造成的机体代谢产热增强有关。

Effects of Dietary Fish Oil on Estrous Cycles and Body Heat Production in Mice Fed High-fat Diets

This study aimed to investigate the effects of dietary fish oil on estrous cycles and body heat production of mice fed high-fat diets (HFD). Thirty-six C57BL/6 J female mice at 4-week-old were randomly divided into 3 groups (n=12):control group, HFD group and HFD + fish oil group, respectively. The control group was fed with a standard rodent chow diet (AIN-93G). The HFD group and HFD + fish oil group were fed HFD (60% energy from fat) without or with 5% fish oil (equally replace lard energy), respectively. During the trial, the mice were used for various examinations, including body composition (12-week-old), body energy metabolism (16-week-old), brown adipose tissue(BAT) temperature (18-week-old), body core temperature (rectum temperature, 18-week-old) and estrous cycles (20-week-old). At the end of the experiment, the blood sample was collected from eye sockets, and the serum was isolated for examination of follicle-stimulating hormone (FSH) and estradiol (E2). In addition, the subcutaneous fat, abdominal fat and interscapular BAT were collected, weighed and used for detection of the protein expression of genes related to thermogenic program in adipose tissues (UCP1, Cyto C) by Western blot, and the mRNA expression of genes related to thermogenic program in brown adipose tissues (UCP1, PRDM16, PGC1α, Cidea, Elovl3) by real-time fluorescence quantitative PCR. The results showed that HFD induced a significant increase in body fat content (12-week-old), and subcutaneous fat and abdominal fat mass (21-week-old) compared with the control diet (P<0.05). Notably, the HFD-induced increase of fat content was significantly reduced by fish oil supplementation (P<0.05). In addition, HFD led irregular estrous cycles, with prolonged cycle duration and shortened estrus period, and decreased the level of FSH and E2 in serum (P<0.05). However, the HFD-induced estrous cycle irregularity of mice was alleviated by fish oil supplementation and the level of FSH and E2 in serum was increased (P<0.05). Meanwhile, fish oil supplementation increased BAT activation/thermogenesis and promoted white adipose tissue(WAT) browning in HFD-fed mice, with enhanced the expression of thermogenic marker genes in interscapular brown adipose tissue (iBAT) and inguinal white adipose tissue (iWAT) (P<0.05). These findings suggest that dietary fish oil can alleviate HFD-induced estrous cycle irregularity, possibly associate with enhanced body thermogenesis via BAT activation and WAT browning.