| Background and Aims: Nonalcoholic fatty liver disease (NAFLD),whose disease spectrum including simple fatty liver (SFL), nonalcoholicsteatohepatitis (NASH) and its related fibrosis and cirrhosis, has beengradually becoming one of the most significant public health issues withthe improvement of living standards and the change of lifestyle. It is wellaccepted that inflammatory response is the key rate-limiting step whenSFL develops into NASH and leptin resistance could speed up theoccurrence and progress of NASH. As a natural regulatory factor ofenergy metabolism, galanin plays an opposite role against leptin in variousbiological functions. What is more, galanin serves as a regulatory factor ofinflammatory response as well. Upfront study found that in the early stageof pre-SFL, SFL and NASH, there existed a dynamic change of serumgalanin in the aninmal model of NAFLD. And our research is aimed to explore the impact of galanin on the occurrence and development ofNASH, trying to offer a new theraputic target of NAFLD.Methods: Fourty healthy male C57BL/6mice aged7~8weeks wereallowed to acclimate for10days after arrival with free access to water anda standard chow diet. Then the mice were assigned randomly to threegroups, including control, model and intervention group. Control groupwas fed standard diet; model group and intervention group were fed highfat and high cholesterol diet from beginning to end. The animal bodyweight were recorded weekly and the food assumption per2-week.8weeks after initiation of the experimental diets, all animals receivedsubcutaneous injection of galanin solution (8ug/100g body weight) or thesame amount of Phosphate-Buffered Saline (PBS) once per day. After13weeks of dietary exposure, mice were were sacrificed by cervicaldislocation after overnight fasting and tissues (blood, liver, adipose tissue)were isolated. Paraffin-embedded liver sections were stained withhematoxylin-eosin (HE) and CD68, then histological steatosis andinflammation were assessed. Quantitative real-time PCR was performed todetect relative gene expression：monocyte chemotactic protein (MCP)-1,CD68, chemokine receptor (CCR)-5，tumor necrosis factor (TNF)-, sterolregulatory binding protein (SREBP)-1c, peroxisome proliferator-activated receptor (PPAR)-γ, Ob-Rb. Serum cholesterol, triglycerides, alanineaminotransferase (ALT) and fasting blood glucose (FBG) were tested bybiochemical analyzer; serum galanin, leptin, insulin and MCP-1weremeasured by enzyme-linked immuno sorbent assays (ELISAs).Results: Relative to control group, model and intervention group hadhigher body weight and liver index (p<0.01); the histological evaluation ofthe model mice liver revealed significant steatosis and different extent ofinflammation, with higher NAFLD activity score (NAS) and highercounting of CD68positive cells compared to control group[(4.83±0.34) vs0;(3.62±4.51) vs (0.88±1.14)/hp, p<0.01]; relative to control group, theserological study of model group showed that the serum ALT [(81.60±7.38vs3.30±0.34) U/L, p<0.01], TG [(0.66±0.09) vs (0.35±0.03)mmol/L, p<0.05], TC [(4.41±0.15) vs (3.30±0.34) mmol/L, p<0.01],MCP-1[(73.36±3.35) vs (57.98±1.82) pg/ml, p<0.05], insulin [(1.473±0.09) vs (1.16±0.09) ng/ml, p<0.05] and leptin [(19.42±2.13) vs (6.27±1.16) ng/ml, p<0.01] comparatively elevated; the relative mRNAexpression of CD68, MCP-1, CCR5, TNF-, SREBP-1c and PPAR-γ inthe liver tissue of model group were higher (p<0.05for all) while theOb-Rb mRNA expression was lower than those of control group (p<0.05).Relative to model group, the body weight and liver index of the intervention group had no significant difference; however, the histologicalevaluation of the intervention group revealed lower inflammation score[(0.27±0.12) vs (0.92±0.19)，p<0.01] and lower counting of CD68positivecells [(0.84±1.23) vs (3.62±4.51)/hp, p<0.01] than those of model group;the serological study showed intervention group had decreased seruminsulin [(1.16±0.12) vs (1.47±0.09) ng/ml, p<0.05] and MCP-1levels[(56.88±2.03) vs (73.36±3.35) pg/ml, p<0.01] compared to model groupand had no significant difference compared to control group; unexpectedly,the serum TG level of intervention group significantly elevated comparedto either control group [(1.26±0.10) vs (0.35±0.03) mmol/L, p<0.01] ormodel group [(1.26±0.10) vs (0.66±0.09) mmol/L, p<0.01]; meanwhilethe intervention of galanin made no difference in leptin level betweenmodel and intervention group; intervention group had lower relativemRNA expression of MCP-1, CCR5, TNF-and CD68than those ofmodel group (p<0.05for all), and among all these proinflamatory genehad one and only one higher TNF-mRNA expression (p<0.05) than thatof control group; in addition, intervention group had higher SREBP-1cand PPAR-γ than those of control group and had no difference with thoseof model group; notably, the Ob-Rb mRNA expression of interventiongroup was surprisingly higher than that of model group and normal group. Conclusions: Galanin remarkably alleviated the inflammationresponse in the mice liver with NASH induced by high fat and highcholesterol diet, via reducing the infiltration of Kupffer cells, decreasingthe expression and secretion of the proinflammatory cytokines andup-regulating leptin receptor expression resulting in improved leptinresistance. In conclusion, galanin may play a significant role in inhibitingthe inflammation response in liver and the progress of NASH. |
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