Biological Characteristics And Its Possible Mechanism Of Adult Catch-up Growth Rats

Objective:Our aim was to observe the dynamic changes of biological characteristics in rats of catch-up growth in adult (CUGA).Methods:Male Sprague-Dawley rats were randomly divided into 10 groups:RN groups including caloric restriction group (R4) and catch-up growth groups (RN1, RN2, RN4, RN8; refeeding for 1,2,4,8 weeks individually after caloric restriction for 4 weeks); NC groups (age-matched controls) of the five groups mentioned above. The animal model of catch-up growth was built by way of refeeding after caloric restriction as scheduled. Body length, weight, caloric intake and the mass of subcutaneous, epididymal and perirenal adipose tissue were measured and Lee index, body fat percentage and food efficiency were analyzed in this study.Results:Compared with their NC groups, (1) the body length and weight of all catch-up growth rats were significantly lower in RN groups notwithstanding a rapid growth after refeeding; (2) the Lee index and food efficiency were transiently higher while refeeding for 1,2 weeks; (3) the body fat percentage of visceral adipose tissue was greater after a dramatic increase in the early 2-week refeeding period.Conclusion:The animal model of CUGA achieved by refeeding after malnutrition manifested rapid growth after growth retardation, transiently increased food efficiency and a faster growth rate of visceral adipose tissue versus body weight after refeeding. Objective:This study was designed to explore the metabolic changes resulting from catch-up growth in adult (CUGA) rats induced by varying types of nutrition promotion after undernutrition.Methods:The CUGA models were developed on rats refed on intakes of normal chow (RNs) or high-fat diet (RHs) after a period of caloric restriction. The body weight, body length, Lee index, fasting plasma lipids, blood glucose, insulin, body fat percentage of different sites, intramuscular and intrahepatic lipid content were determined. The insulin sensitivity were evaluated by hyperinsulinemic-euglycemic clamp in conscious rats based on tail artery and vein catheterization technique.Results:The growth of the rats measured by body weight and length stagnated during caloric restriction, and then rapidly accelerated following refeeding. CUGA resulted in an increase in intramuscular and intrahepatic lipid content, visceral fat deposition and insulin resistance, which is consistant with a transient rise in food efficiency during the early stage of refeeding. Additionally, ectopic lipid deposition, visceral fat accumulation and insulin resistance was more severe in RHs than RNs.Conclusions:The findings in the present study suggest that CUGA induced by rapid nutrition promotion could result in persistent lipid overaccumulation (increased visceral fat and ectopic lipid deposition) and drastic systemic insulin resistance. The effects of CUGA on metabolic characteristics are dependent on the type of diet which is used for refeeding, especially on the amount of fat intake. Objective:The purpose of this part was to investigate the probable mechanism of visceral fat accumulation and systemic insulin resistance in adult catch-up growth rats.Methods:Male Sprague-Dawley rats were randomly divided into 6 groups:caloric restriction group (R4, caloric restriction for 4 weeks) and normal controls for 4 weeks (NC4); catch-up growth groups refed with normal chow (RN4; refeeding for 4 weeks after caloric restriction for 4 weeks), catch-up growth groups refed with high-fat diet (RH4; refeeding for 4 weeks after caloric restriction for 4 weeks), normal chow or high-fat diet controls for 8 weeks (NC4). The animal model of catch-up growth was built by way of refeeding after caloric restriction as scheduled. Plasma corticosterone,11 beta-hydroxysteroid dehydrogenase type 1(11β-HSD1) mRNA expression level in adipose tissue (AT) and skeletal muscle (SkM), insulin signaling and 2-deoxyglucose uptake during hyperinsulinemic euglycemic clamp in SkM, were measured. Body fat percentage and systemic insulin sensitivity were analyzed as well.Results:Compared with their NC groups, (1) plasma corticosterone, 11β-HSD1 mRNA expression level in AT and SkM were significantly higher in RN4 and RH4 rats; (2) the Ser473 phosphorylation of PKB and 2-deoxyglucose uptake in SkM during the clamp remarkably decreased in RN4 and RH4 groups; (3) the body fat percentage of visceral adipose tissue were greater and the systemic insulin sensitivity were impaired in RN4 and RH4 animals; (4).the changes in RH4 rats mentioned above are more severe than that in RN4 rats. Conclusion:Catch-up growth rats is characterized by visceral fat accumulation and insulin resistance, which is associated with increased systemic and local (AT and SkM) stress and impaired insulin sensitivity in SkM. The latter might be of utmost importance in the etiology of visceral adiposity and insulin resistance in catch-up growth animals.