Effect of probiotic supplementation on circadian clock in rats with fructose-induced non-alcoholic fatty liver disease

This study was conducted and planned in order to improve metabolic disorder by reprogramming the circadian clock in hepatocytes with an intervention in the intestine, using the gut microbiota-liver axis, by creating a non-alcoholic fatty liver model in rats. Twenty-seven Wistar-albino male rats were included in the study and their average weight was determined as 150 g (95-177) at the beginning of the study. The rats were then divided into 3 groups, standard feed+standard water [1. group (n:8)] and standard feed+fructose water [2. group [n:11) and 3. group (n:8)] for 13 weeks] were fed. After seven weeks, 3 rats from the 2nd group were slaughtered and when it was determined that liver fat was formed with pathological findings, 6-week probiotic supplementation with 2x109 cfu/day Lactobacillus rhamnosus GG (LGG) was started to the rats in the 3rd group and the other groups continued to be fed in the same way. The rats' fluid and food consumption, body weight, height and waist circumference measurements, biochemical findings (total cholesterol, GGT, LDH, ALT, AST, IL-6, IL-1β, zonulin, glutathione, superoxide dismutase, malondialdehyde and glutathione peroxidase), hormone (melatonin and insulin) and circadian clock gene levels (Bmal1, Clock, Rev-Erbα and Per2), and histopathological evaluation of the liver were performed. As a result of the study, NAS score of the YFD group (5,00) was significantly higher than the control group (0,00) and the YFD+probiotic group (3,00) (p<0.05). Compared to the control group (2,51%), the liver index of the YFD group (3,53%) was found to be significantly higher, while LGG supplementation decreased this value (3,01%). There was no significant difference between the groups for zonulin level and mRNA expression levels of circadian clock genes (p>0,05). However, fructose consumption increased circadian clock gene levels, while LGG reduced this effect. Melatonin levels were negatively correlated with Clock (r=-0.431; p=0.035), Rev-Erbα (r=-0.450; p=0.027) and Per2 (r=-0.410; p=0.045) genes. The MDA level was higher in the YFD (8,49 nmol/mL) and YFD+probiotic group (8,29 nmol/mL) than the control group (5,56 nmol/mL). LGG supplementation resulted in improvements in physiological parameters. The use of fructose increases oxidative stress, while the use of LGG reduces oxidative stress and destruction is observed less. Circadian clock gene levels increase in case of damage as in the YFD group, and these levels decrease with the use of LGG. The decrease in melatonin value causes an increase in circadian clock gene levels. In order to increase intestinal permeability in future studies, administering a high-fat diet with high fructose to rats or extending the experimental period or trying different strains; It is recommended to perform circadian clock locomotor activity test as well as mRNA levels of genes. In addition, it is recommended to try researches to determine the most suştable probiotic, prebiotic and symbiotic species as treatment approaches.