Dietary Amylopectin-amylose Starch Content Affects Lipid Metabolism In Weaned Pigs

The fat deposition is a fundamental mode of energy storing. The deposition quantity of animals body fat is a homeostasis, which includes fat intussuscept, the fatty acid synthesizes, the triglyceride (TG) synthesizes and break down. The fat biosynthesis and decomposition are complete through certain enzyme catalyses. The factors of affecting enzyme-catalyzed reactions as enzyme activity and the enzyme content, the regulation of glucose (GLU) and insulin (INS) and so on. All of that can affect the fat synthesis and break down. Carbohydrate mainly influence fat metabolism through the activity and expression of FAS, ACC and ATP-CL, which may regulate by certain hormone. A lot of research showed, high carbohydrate promoted fatty acid synthesis by increasing the expression and content of FAS and ACC. And this mechanism of action was in correlation to the transcription of key lipogenic enzyme gene. In this paper, three different sources starch was formulated three experimental diets, evaluated the ingredient composition and the contents of amylopectin-amylose in diets. Followed, weaned pigs were used as animal models for determining serum biochemical parameter, hormone concentration and key lipogenic gene expression to reveal lipometabolism discipline after intaking three different amylopectin-amylase starch diets. Besides, it also provides a reference for infant formula.1. Analyze the ingredient composition and contents of amylopectin-amylose starch in three dietary groups:maize starch group (MS), sticky rice starch group (SRS) and resistant starch group (RS). In dry matter basis, the total starch, CP, Ca and P nearly the same in three dietary groups, reaching the requirements recommended by NRC (1998).The amount of amylose and amylopectin accounted for 16.27% and 52.65% of total starch in MS group, respectively. SRS contained 100% of amylopectin and RS contains only 2.32% of amylose of total starch. 2. Eighteen weaned pigs at 28 d of age (BW=7.04±0.52 kg) were surgically fitted with a catheter in jugular vein, were randomly assigned to three dietary groups. representing MS group, SRS group and RS group, respectively. Venous blood samples were taken for determining postprandial serum concentration of glucose (GLU), triglyceride (TG), cholesterol (CHO), high density lipoproteins (HDL), low density lipoproteins (LDL) and activity of lipase (LPS) at different time points were measured. Results showed, in SRS group, the concentration of GLU was the highest and the rangeability of serum GLU level was the largest. So the supply efficiency of blood GLU was higher in SRS group than in two other groups because of high content of amylopectin. Besides, the postprandial serum concentration of TG, CHO and HDL, the activity of LPS and the range of variation of above parameters in pigs of SRS group were nearly all higher than those in MS and RS group. The postprandial serum concentration of LDL in pigs of MS group was higher than that in SRS and RS group. Make a conclusion, compared to MS and RS, intaking SRS may be more conducive to fat metabolism.3. The serous levels of of insulin (INS), growth hormone (GH), insulin growth factor-Ⅰ(IGF-Ⅰ) and glucagon at different time points were detected by radioimmunosive (RIA) assay to survey the change of hormone levels in weaned pigs after feeding different contents of amylopectin-amylose starch dietary. The results showed, in SRS group, the levels of hormone were the highest and the rangeability of hormone levels was the largest, consistenting with the fluctuation of GLU concentration. So may be the blood GLU play an intermediate role in regulating hormone levels.4. The special primers for FAS, ACC, ATP-CL and GAPDH were designed respectively according to the gene sequences reported previously in Genebank. Then total RNA was extracted from liver, adipose tissue and muscle of weaned pigs and the target gene mRNA amplified through real-time PCR with special primers to determine the key lipogenic enzyme gene expression. It is surveyed, the mRNA levels of FAS, ACC and ATP-CL in pigs of the SRS group were higher than those in the MS group, and those in the MS group were higher than in the RS group. This change was consistented with serum GLU and INS fluctuations. On the other hand, three gene expressions in white adipose tissue and liver were higher than in brown adipose tissue and myocardium, with tissue specificity. In a word, compared to MS and RS groups. SRS group with higher content of amylopectin were able to creat higher key lipogenic enzyme gene expressions in weaned pigs via the changes of postprandial serum GLU and INS levels, although the details of how this is achieved are not fully understood.