| Backgroud: Obesity and its relating factors become a studying focus in the world. The mechanism of obesity development is highly complex. Long-term high-fat diet is one of vitally influencing factors. Apolipoprotein (apo) A-Ⅳ is the only glycoprotein synthesized by the human intestine and hypothalamus that is markly stimulated by fat absorption. It is a short-term satiety factor, which plays an important role in the regulation of food intake and bodyweight gain. Thus, Future studies of mechanisms regulating apo A-Ⅳ synthesis by lipid absorption, PYY, leptin, chronic consumption of a high-fat diet, and other currently unknown factors will pose both a challenge and reward to investigators in their search to attain a greater understanding of obesity development.Objective: To obtain the elementary physiological parameter of serum apoA-Ⅳ levels in Chinese, investigate effects of age, gender, adipose, lipids, fasting glucose, chronic and acute diet, serum leptin levels as well as other currently unknown factors on serum apoA-Ⅳ levels, and further illustrate the regulation of food intake and energy homeostasis.Methods: 389 subjects aged 7-70 years were drawn from Zibo and Jinan city in Shandong Province. The serum apoA-Ⅳ concentrationes were measured by enzyme-linked immunosorbant assays (ELISA). Fasting serum lipids, glucose, and leptin were detected as well. Body indexes were measured by body composition analyzar. In addition, diet intake and life styles were reflected from food frequency survey and 3-day food record. Statistical analyses were performed with SPSS 12.0.Results: 1. The mean serum apoA-IV concentration in 389 subjects was 13.66±8.26 mg/dl,and it was 14.86±8.80mg/dl in male, 13.08±7.95mg/dl in female. There was nosignificant gender difference in apoA-Ⅳ concentrations for all subjects. The apoA-Ⅳ levels of urban residents (17.10±7.40 mg/dl) were significantly higher than those of rural ones (10.82±7.86 mg/dl) (P<0.01). There was no significant difference between the non-obese serum apoA-Ⅳ levels (14.04±8.46 mg/dl) and obese ones (12.83±7.67 mg/dl). Analyses for the transformed logarithm for leptin and apoA-Ⅳ were presented because their concentrations were not distributed normally.2. There was no correlation between apoA-Ⅳ and age (r=0.039, p>0.05). After adjustment for area, apoA-Ⅳ concentrations were positivly correlated with age of all subjects(r=0.139, p<0.05).3. A weakly negative correlation trend was noted between apoA-Ⅳ and BMI, skinfold, percent body fat, obesity, WHR, but there was no statistical significance.4. Serum apoA-Ⅳ levels were absolutely correlated with TC, HDL-c, apoA-I, fasting plasma glucose. Positive correlation was observed between apoA-Ⅳ and TC, HDL-c, apoA-I in females, only fasting plasma glucose in males. There was no relation between apoA-Ⅳ and TG level for all subjects, as well as men and women.5. A weakly negative correlation trend was observed between apoA-Ⅳ and leptin, however, there was no statistical significance. But serum apoA-Ⅳ levels of the very high-leptin group were significantly lower than those of low-leptin group (P<0.05).6. Serum apoA-Ⅳ levels were negatively correlated with long-term fat intake, dietary fiber, carbohydrate, and protein intake. ApoA-Ⅳ levels were positively correlated with acute cholesterol and protein intake.7. Humans chronically consuming a high-fat diet initially developed significantly lower serum apoA-Ⅳ levels than those of a chronic low-fat diet. Serum apoA-Ⅳ levels of an acute high-fat diet were higher than those of an acute low-fat diet, but no statistical significance was seen. For humans with a chronic low-fat diet, a three-day high-fat diet resulted in elevated apoA-Ⅳ levels as compared with athree-day low-fat diet. However, for those with a chronic high-fat diet, apoA-Ⅳ levels of a three-day high-fat diet were lower than those of a three-day low-fat diet. Both were no statistical significance. After adjustment for chronic fat intake, the correlation between apoA-Ⅳ levels and acute fat intake was not observed. 8. Stepwise multiple liner regression analysis was revealed that area, long-term fat intake, and fasting glucose levels had significant effects on normal population serum apoA-Ⅳ levels. Conclusion:1. There is no significant effect of gender, smoking, and alcohol intake on serum apoA-Ⅳ levels.2. ApoA-Ⅳ levels are significantly and positively correlated with age in all subjects after adjusted for area.3. BMI, and percent body fat are not the primary factors to affect serum apoA-Ⅳ levels.4. ApoA-Ⅳ levels are positively correlated with TC, HDL-c, apoA-I, fasting plasma glucose. There is no correlation with TG.5. Serum apoA-Ⅳ levels of the very high-leptin group were significantly lower than those of low-leptin group.6. Serum apoA-Ⅳ levels of long-term high-fat diet were significantly lower than those of long-term low-fat diet, however, acute high-fat intake has a weakly increased effect on serum apoA-Ⅳ levels, which are significantly affected by long-term high-fat intake.
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