Enzymes of glucose and fatty acid metabolism of liver, kidney, skeletal muscle, adipose tissue and mammary gland of lactating and non-lactating sheep

The effect of peak lactation on the activities of a number of enzymes of glucose and lipid metabolism of perirenal and subcutaneous adipose tissue, skeletal muscle, liver, kidney cortex and mammary parenchyma of sheep are described. Enzymes studied included hexokinase (glucose utilization), pyruvate carboxylase (gluconeogenesis), pyruvate dehydrogenase (glucose oxidation and production of acetyl CoA for fatty acid synthesis), acetyl CoA carboxylase (fatty acid synthesis) and glycerol-3-phosphate acyltransferase (fatty acid esterification). Major changes that were found include a decrease in activities of enzymes of fatty acid synthesis and esterification in adipose tissues, decreased activity of pyruvate dehydrogenase in muscle and adipose tissues and increased pyruvate carboxylase; there was no change in activities of enzyme of fatty acid esterification in liver. Activities of hexokinase, acetyl CoA carboxylase and glycerol-3-phosphate acyltransferase have been estimated per tissue; this shows the quantitative importance of limiting glucose utilization by muscle and of suppression of fatty acid synthesis in adipose tissue for efficient partitioning of nutrients for milk production.     

Acetyl-CoA carboxylase of sheep adipose tissue: problems of the assay and adaptation during fetal development

The rate of fatty acid synthesis of perirenal adipose tissue of fetal lambs decreased by 90% during the last month of gestation. There was also a 90% decrease in the activity of fatty acid synthetase during this period, but the activity of this enzyme exceeded lipogenic flux by a factor of 10. The activity of acetyl CoA carboxylase in the active state (initial activity) was very similar to the lipogenic flux in adipose tissue from lambs at 120 d of gestation; although activity decreased towards term, the decline was insufficient to account for the fall in rate of fatty acid synthesis. The study also shows that assay of acetyl CoA carboxylase in the active state of ovine adipose tissue and of caprine mammary gland requires the presence of citrate, thus differing from that for rat adipose tissue. Evidence that pyruvate carboxylase can interfere in the assay of acetyl CoA carboxylase also is presented.     

Acetyl-CoA carboxylase and fatty acid synthase activity and immunodetectable protein in adipose tissues of ruminants: effect of temperature and feeding level

To gain insights into the regulation of fat synthesis, we have investigated the effect of cold environmental exposure and feed restriction of sheep on activity and immunodetectable protein content of acetyl-CoA carboxylase (ACC) and fatty acid synthase in adipose tissue. Subcutaneous and mesenteric adipose tissues were collected at slaughter from sheep exposed to either cold (0+/-2 degrees C) or warm (23+/-2 degrees C) environment, and given either ad libitum or restricted access to feed for three 5-wk periods. Acetyl-CoA carboxylase was isolated from frozen adipose tissue samples and activity determined as the rate of incorporation of H14CO3- into acid stable malonyl-CoA. Cold exposure and feed restriction reduced (P < .05) ACC activity in the two adipose tissue depots. Western blot analysis with peroxidase-conjugated streptavidin showed that both adipose tissue depots express a single isoform of ACC. In s.c. adipose tissue, cold exposure increased (P < .05) ACC protein abundance, which is opposite to the change in activity. However, feed restriction reduced immunodetectable ACC protein. There was no significant effect of environment or feeding level on ACC protein abundance in mesenteric tissue. Fatty acid synthase activity determined in ammonium sulfate extract by measuring the malonyl-CoA- and acetyl-CoA-dependent oxidation of NADPH was decreased (P < .05) by feed restriction in both s.c. and mesenteric tissues. Cold exposure reduced fatty acid synthase activity in s.c. but not in mesenteric tissue. There was no effect of environment on fatty acid synthase protein abundance in either adipose tissue depot. However, feed restriction significantly reduced fatty acid synthase protein abundance in the two depots. The data suggest that feed restriction and exposure of ruminants to cold environmental conditions may significantly down-regulate the activity of key lipogenic enzymes.     

Effects of short-term infusion with propionate on the mRNA expression of a putative G-protein coupled receptor 41 (GPR41) in adipose tissue of goats

Short chain fatty acids (SCFA) represent the main source for energy supply in ruminants. Propionate up-regulates leptin synthesis through the G protein-coupled receptor 41 (GPR41) in mice but the importance of the GPR41 in ruminants is not yet clarified. Here we characterise the short-term effects of intravenously infused propionate on a putative GPR41 mRNA in goat adipose tissue. Castrated male goats (Capra hircus) received propionate infusion or NaCl solution with equivalent sodium content for 260 min. A putative GPR41 mRNA was quantified in subcutaneous and perirenal adipose tissue by real-time RT-PCR. The mRNA concentration of the putative GPR41 mRNA increased (p = 0.029) in subcutaneous but not in perirenal adipose tissue (p = 0.756) of propionate-infused animals versus the NaCl group. We hypothesise that the differential response of the putative GPR41 mRNA in subcutaneous versus perirenal adipose tissue towards short-term propionate infusion could be involved in a differential nutrient sensing of SCFA in the two adipose depots of goats.     

Effects of body condition score at parturition and postpartum supplemental fat on adipose tissue lipogenic activity of lactating beef cows

Three-year-old Angus x Gelbvieh beef cows nutritionally managed to achieve a BCS of 4 +/- 0.07 (479.3 +/- 36.3 kg of initial BW) or 6 +/- 0.07 (579.6 +/- 53.1 kg of initial BW) at parturition were used in a 2-yr experiment (n = 36/yr) to determine the effects of BCS at parturition and postpartum lipid supplementation on cow adipose tissue lipogenesis. Beginning 3 d postpartum, cows within each BCS were randomly assigned to be fed hay and a low-fat control supplement or supplements with either cracked high-linoleate safflower seeds or cracked high-oleate safflower seeds until d 60 of lactation. Diets were formulated to be isonitrogenous and isocaloric, and safflower seed diets provided 5% DMI as fat. Adipose tissue biopsies were collected near the tail-head region of cows on d 30 and 60 of lactation. Dietary treatment did not affect (P > or = 0.43) adipose tissue lipogenesis. Body condition score at parturition did not affect acetate incorporation into lipid (P = 0.53) or activity of acetyl CoA carboxylase (P = 0.77) or fatty acid synthase (P = 0.18). Lipoprotein lipase activity and palmitate incorporation into triacyl-glycerol tended to be greater (P = 0.06), and palmitate esterification into total acylglycerols was greater (P = 0.01) in cows with a BCS of 4 at parturition. Mean activity of acetyl-CoA carboxylase (P < 0.001), lipoprotein lipase (P = 0.01), and rate of palmitate incorporation into monoacylglycerol (P = 0.02), diacylglycerol (P = 0.001), triacylglycerol (P = 0.003), and total acylglycerols (P = 0.002) were greater at d 30 than d 60, suggesting a greater proclivity for fatty acid biosynthesis and esterification by adipose tissue at d 30 of lactation. Although dietary lipid supplementation did not affect adipose tissue lipogenesis, results suggest that cows with a BCS of 4 at parturition have a greater propensity to deliver exogenously derived fatty acids to the adipocyte surface and incorporate preformed fatty acids into acylglycerols as stored adipocyte lipid. Additionally, cows in early lactation seemed to be able to synthesize and incorporate more fatty acids into stored lipid than cows during peak lactation.     

Effects of dietary copper on the expression of lipogenic genes and metabolic hormones in steers

An experiment was conducted to determine the effects of Cu supplementation on performance, subcutaneous adipose tissue mRNA expression of acetyl CoA carboxylase (ACC), stearoyl CoA desaturase (SCD), uncoupling protein 2 (UCP2), and leptin in growing and finishing steers. Forty-eight purebred Angus steers were allotted to one of five treatments: 1) control (no supplemental Cu); 2) 10 mg Cu/kg DM from CuSO4; 3) 10 mg Cu/kg DM from a Cu amino acid complex (Availa Cu); 4) 20 mg Cu/kg DM from CuSO4; 5) 20 mg Cu/kg DM from Availa Cu. Steers were fed an alfalfa hay corn-based diet for 56 d (basal diet contained 7.1 mg Cu/kg DM) and switched to a high-concentrate diet for 144 d (basal diet contained 6.1 mg Cu/kg DM). Blood samples were obtained every 28 d throughout the entire experiment. On d 112 of the finishing period, subcutaneous adipose tissue biopsies were obtained from the tailhead of three animals per treatment and analyzed for ACC, SCD, UCP2, and leptin mRNA expression. Animal performance was not affected by Cu supplementation during the growing phase. Steers receiving 10 mg Cu/kg DM from Availa Cu had higher (P < 0.05) ending body weights and tended (P < 0.10) to have higher ADG than steers receiving 10 mg Cu/kg DM from CuSO4 during the finishing phase. Serum concentrations of nonesterified fatty acid and insulin were not affected by Cu supplementation. Steers receiving supplemental Cu tended (P < 0.11) to have less backfat relative to controls. However, dietary Cu did not influence the level of subcutaneous adipose tissue ACC and SCD mRNA. Neither UCP2 nor leptin gene expression was affected by Cu supplementation. These results indicate that dietary Cu supplementation (10 to 20 mg Cu/kg DM diet) may alter lipid metabolism of subcutaneous adipose tissue; however, it does not seem to affect expression of certain lipogenic genes.     

长期饲喂不同蛋白质水平饲粮对猪脂肪代谢相关基因表达的影响

本试验旨在研究长期饲喂不同蛋白质水平饲粮对猪脂肪代谢相关基因表达的影响。试验选用18头三元(杜×长×大)杂交28日龄断奶仔猪,随机分为3组,每组6个重复,每个重复1头。对照组[高粗蛋白质(HCP)组]采用符合NRC(2012)推荐营养需要的饲粮,试验组是根据NRC(2012)标准,在添加赖氨酸(Lys)、蛋氨酸(Met)、苏氨酸(Thr)、色氨酸(Try)4种必需氨基酸基础上,将饲粮蛋白质水平分别降低3%[中粗蛋白质(MCP)组]和6%[低粗蛋白质(LCP)组]。试验期125 d。结果表明:1)在肝脏中,与HCP组相比,LCP组显著降低脂肪酸合成相关基因乙酰辅酶A羧化酶(ACC)、脂肪酸合成酶(FAS)、苹果酸酶1(ME1)及锚蛋白1(ANK1)的基因表达量(P0.05);同时显著提高脂肪酸转运相关基因过氧化物酶体增殖物激活受体γ(PPARγ)及脂肪酸结合蛋白(FABP)的基因表达量(P0.05);而MCP组与HCP组相比,脂肪酸合成、转运相关基因表达量均无显著性差异(P0.05);与HCP组相比,MCP及LCP组均显著降低脂肪酸氧化分解相关基因、过氧化物酶体增殖物激活受体α(PPARα)、肉毒碱棕榈酰转移酶(CPT)的基因表达量(P0.05)。2)在背最长肌(LDM)中,MCP组中脂肪酸合成相关基因胆固醇调节元件结合蛋白(SREBP)、FAS、硬脂酰辅酶A去饱和酶(SCD)的基因表达量显著高于其他2组(P0.05);ACC及FABP在LCP组的基因表达量显著低于其他2组(P0.05);CPT基因表达量及LDM的肌内脂肪(IM F)含量在LCP及M CP组显著低于HCP组(P0.05)。3)肝脏和LDM中,各组甘油三酯脂酶(ATG L)及二烯酰辅酶A还原酶(DECR)基因表达量均无显著性差异(P0.05)。由此可见,在NRC(2012)基础上,适当的降低饲粮蛋白质水平(3%)可促进LDM中脂肪酸合成、转运相关基因的表达,但对肝脏中脂肪酸合成相关基因的表达无显著影响;适当的降低饲粮蛋白质水平(3%)可降低LDM及肝脏中脂肪酸氧化分解相关基因的表达,但并不增加LDM肌内脂肪含量。     

Effects of dietary energy level on lipid metabolism‐related gene expression in subcutaneous adipose tissue of Yellow breed × Simmental cattle

This study was conducted to estimate the effect of dietary energy level on lipid metabolism‐related gene expression of subcutaneous adipose tissue in Yellow breed × Simmental cattle. The experiment was conducted for 60 days. The results showed that final weight, average daily gain, average backfat thickness, (testicles + kidney + pelvic) fat percentage and subcutaneous fat percentage in the high and medium energy groups were significantly higher than in the low‐energy group but that the feed conversion ratio was significantly lower. The glucose, triglycerides, cholesterol, high‐density lipoprotein and low‐density lipoprotein in the high‐energy group were significantly higher than in the low‐energy group. With dietary energy increasing the activities of lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl‐CoA carboxylase (ACC) significantly increased, whereas hormone‐sensitive lipase (HSL) and carnitine palmitoyltransferase‐1 (CPT‐1) significantly diminished. Peroxisome proliferator‐activated receptor γ (PPARγ), LPL, FAS, sterol regulatory element binding protein 1 (SREBP‐1), ACC, stearoyl‐CoA desaturase (SCD) and adipocyte‐fatty acid binding proteins (A‐FABP) gene expression were significantly increased by dietary energy increasing, and HSL and CPT‐1 gene expression were significantly decreased. These results indicated that with dietary energy increasing, the subcutaneous fat accumulation mainly increased due to adipose tissue lipogenic gene expression and decreased lipolytic gene expression.     

Interactions between dietary fatty acids and hepatic gene expression in livers of pigs during the weaning period

The aim of the present study was to evaluate the impact of dietary fatty acids (FA) during the weaning period on expression of genes involved in the oxidation and metabolism of FA (peroxisome proliferator-activated receptor (PPAR-), stearoyl-CoA-desaturase (SCD), Δ6-desaturase (D6D), acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS)). Liver samples were obtained from littermates, either on day 28 of age just before weaning, or at day 56 after the 4 weeks ad lib. provision of 5% of either animal fat, fish oil or sunflower oil. In conclusion, genes involved in the regulation of FA conversion (SCD, D6D) were influenced by the n-6 to n-3 ratio, whereas the FA oxidation, as indicated by the expression of PPAR-, was highly likely regulated by the hepatic ratio between mono- and poly-unsaturated FA. Furthermore, weaning and/or age affected the hepatic expression of genes involved in FA synthesis and conversion, but not the expression of PPAR-.     

Maternal obesity upregulates fatty acid and glucose transporters and increases expression of enzymes mediating fatty acid biosynthesis in fetal adipose tissue depots

Maternal nutrient restriction leads to alteration in fetal adipose tissue, and offspring from obese mothers have an increased risk of developing obesity. We hypothesized that maternal obesity increases fetal adipogenesis. Multiparous ewes (Columbia/Rambouillet cross 3 to 5 yr of age) carrying twins were assigned to a diet of 100% (Control; CON; n = 4) or 150% (Obese; OB, n = 7) of NRC maintenance requirements from 60 d before conception until necropsy on d 135 of gestation. Maternal and fetal plasma were collected and stored at -80°C for glucose and hormone analyses. Fetal measurements were made at necropsy, and perirenal, pericardial, and subcutaneous adipose tissues were collected from 7 male twin fetuses per group and snap frozen at -80°C. Protein and mRNA expression of fatty acid translocase [cluster of differentiation (CD) 36], fatty acid transport proteins (FATP) 1 and 4, insulin-sensitive glucose transporter (GLUT-4), fatty acid synthase (FASN), and acetyl-coA carboxylase (ACC) was evaluated. Fetal weight was similar, but fetal carcass weight (FCW) was reduced (P < 0.05) in OB versus CON fetuses. Pericardial and perirenal adipose tissue weights were increased (P < 0.05) as a percentage of FCW in OB versus CON fetuses, as was subcutaneous fat thickness (P < 0.001). Average adipocyte diameter was greater (P < 0.01) in the perirenal fat and the pericardial fat (P = 0.06) in OB fetuses compared with CON fetuses. Maternal plasma showed no difference (P > 0.05) in glucose or other hormones, fetal plasma glucose was similar (P = 0.42), and cortisol, IGF-1, and thyroxine were reduced (P ≤ 0.05) in OB fetuses compared with CON fetuses. Protein and mRNA expression of CD 36, FATP 1 and 4, and GLUT-4 were increased (P ≤ 0.05) in all fetal adipose depots in OB versus CON fetuses. The mRNA expression of FASN and ACC was increased (P < 0.05) in OB vs. CON fetuses in all 3 fetal adipose tissue depots. Fatty acid concentrations were increased (P = 0.01) in the perirenal depot of OB versus CON fetuses, and specific fatty acid concentrations were altered (P < 0.05) in subcutaneous and pericardial adipose tissue because of maternal obesity. In conclusion, maternal obesity was associated with increased fetal adiposity, increased fatty acid and glucose transporters, and increased expression of enzymes mediating fatty acid biosynthesis in adipose depots. These alterations, if maintained into the postnatal period, could predispose the offspring to later obesity and metabolic disease.     

Expression of fat deposition and fat removal genes is associated with intramuscular fat content in longissimus dorsi muscle of Korean cattle steers

Intramuscular fat (IMF) in cattle is an important component of traits that influence meat quality. We measured carcass characteristics and gene expression in Korean steers to clarify the molecular mechanism(s) underlying IMF deposition in LM tissue by determining the correlation between IMF content and gene expression abundance and by developing models to predict IMF content using gene expression abundance. The deposition of IMF is determined by a balance between fat deposition and fat removal in the LM. We measured mRNA abundance of lipid metabolic genes including lipogenesis [acetyl CoA carboxylase (ACC), fatty acid synthase (FASN)], fatty lipid uptake [lipoprotein lipase (LPL), fatty acid translocase (CD36), fatty acid transport protein 1 (FATP1)], fatty acid esterification [glycerol-3-phosphate acyltransferase 1 (GPAT1), acylglycerol phosphate acyltransferase 1 (AGPAT1), diacylglycerol acyltransferase 1 (DGAT1), DGAT2], lipolysis [adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), monoglyceride lipase (MGL)], and fatty acid oxidation [carnitine palmitoyl transferase 1B, very long-chain acyl-CoA dehydrogenase (VLCAD), medium-chain acyl-CoA dehydrogenase (MCAD)] in the LM. The mRNA abundance of the GPAT1 gene showed the greatest correlation (r = 0.74; P < 0.001) with IMF content among 9 fat deposition genes. The gene expression abundance of other fat deposition genes including ACC, FASN, LPL, CD36, FATP1, AGPAT1, DGAT1, and DGAT2 also exhibited significant positive correlations (P < 0.05) with IMF content in the LM. Conversely, ATGL mRNA abundance showed the greatest negative correlation (r = -0.68; P < 0.001) with IMF content in the LM among 6 fat removal genes. The expression of other fat removal genes including MGL, VLCAD, and MCAD showed significant negative correlations (P < 0.05) with IMF content. Our findings show that the combined effects of increases in lipogenesis, fatty acid uptake, fatty acid esterification, and of decreases in lipolysis and fatty acid oxidation contribute to increasing IMF deposition in Korean steers. The multiple regression analysis revealed that the mRNA abundance of the GPAT1 gene in the LM was the first major variable predicting IMF content (54%) among 15 lipid metabolic genes. The second was mRNA abundance of ATGL (11%). In conclusion, these results suggest that GPAT1 and ATGL genes could be used as genetic markers to predict IMF deposition in the LM.     

Effects of perilla extract on productive performance, serum values and hepatic expression of lipid-related genes in Shaoxing ducks

1. The aim of this study was to identify the effect of perilla extract, a source of polyunsaturated fatty acids, on lipid metabolism and expression of lipid-related genes in livers of Shaoxing ducks. 2. Two hundred and forty 28-week-old laying ducks received a commercial diet with perilla extract added at 0 (control) or 200 mg/kg of feed. 3. Ducks fed on a diet with perilla extract had increased laying rates compared with control ducks. 4. Serum concentrations of triglycerides were reduced by perilla extract, while high-density lipoprotein cholesterol and total serum cholesterol increased. 5. The expression of genes involved in hepatic lipogenesis, sterol regulatory element-binding protein-1, acetyl CoA carboxylase, stearoyl CoA desaturase, fatty acid synthase, apolipoprotein B, and apolipoprotein very low density lipoprotein, were decreased in the perilla group. 6. The mRNA expression of peroxisome proliferators-activated receptor alpha and acyl-coenzyme A oxidase was enhanced following treatment with perilla extract, and a similar tendency was observed in the expression of liver fatty acid-binding protein. 7. The results show that a diet with 200 mg/kg perilla extract regulated fat metabolism of Shaoxing ducks by improving egg laying, altering serum lipid profiles, stimulating lipid catabolic gene expression and inhibiting lipogenic gene expression in the liver.     

The effect of anabolic implants on intramuscular lipid deposition in finished beef cattle

Two experiments were conducted to determine the effects of anabolic implants on performance, changes in ultrasound measurements, carcass quality, cellularity of i.m. and s.c. adipose depots, and mRNA expression of acetyl CoA carboxylase (ACC), stearoyl CoA desaturase (SCD), and lipoprotein lipase (LPL) in i.m. adipose tissue of finished beef cattle. Angus heifers (experiment 1: n = 10; 411 kg of BW) and steers (experiment 2: n = 18; 279 kg of BW) were randomly allotted as control (C) or implanted with Synovex-Plus (SP) at d 0 and midway through the finishing period. The cattle were fed a high-concentrate diet and were weighed at approximately 28-d intervals. Heifers and steers were finished for 108 and 133 d, respectively. At slaughter, a section of the LM (sixth to ninth rib) was removed, and i.m. adipose tissue was dissected for mRNA analysis. Subcutaneous and i.m. adipose tissues also were collected for determination of cellularity. At 48 h postmortem, carcass data were collected, and a steak (12th rib) was removed for analysis of lipid and fatty acid composition. Body weight did not differ (P > 0.10) between treatments until after reimplanting of the heifers (d 55) or steers (d 73). Average daily gain was 36 and 16% faster (P < or = 0.01) for implanted heifers and steers, respectively, compared with their control counterparts. Implanting resulted in larger (P < or = 0.10) HCW and LM area for heifers and steers. However, implanting did not affect (P > 0.10) dressing percent, fat thickness, percentage of KPH, yield grade, or marbling score. Intramuscular lipid content and concentrations of major fatty acids did not differ (P > 0.10) between treatments. Percentage of SC adipocytes was greater at larger diameters ( > 150 microm), whereas the majority of i.m. adipocytes were at small to middle diameters (50 to 150 microm). The number of i.m. adipocytes per gram of tissue was greater (P < 0.05) for SP than C and also were greater (P < 0.05) than the number of s.c. adipocytes in SP heifers. In experiment 2, adipocytes per gram of tissue tended to be greater (P = 0.07) for SP than C and were greater (P < 0.01) for i.m. than s.c. In experiment 1, average cell diameter and volume did not differ (P > 0.10) between treatments and tissues, but in experiment 2 both cellularity traits were greater (P < 0.01) for s.c. than for i.m.. Implanting did not alter mRNA expression of ACC, SCD, or LPL in i.m. adipose tissue. This study shows that anabolic implants do not appear to have direct effects on i.m. lipid deposition.     

饲粮添加锰对3~4月龄獭兔脂肪沉积和脂肪组织脂质代谢的影响

本试验旨在研究饲粮添加锰对生长獭兔脂肪组织脂质代谢的影响。选用初始体重相近、健康状况良好的3月龄獭兔200只,随机分为5组(每组40个重复,每个重复1只),分别饲喂在基础饲粮中添加0(对照)、5、10、20、40 mg/kg锰(以硫酸锰的形式)的试验饲粮。预试期7 d,正试期29 d。结果表明:1)与对照组相比,饲粮中添加10~20 mg/kg锰显著降低了肩胛脂肪沉积率(P<0.05),饲粮中添加5~40 mg/kg锰显著降低了胃周脂肪沉积率(P<0.05)。饲粮中锰添加水平对肾周脂肪沉积率没有显著影响(P>0.05)。2)饲粮中锰添加水平对肉碱脂酰转移酶2(CPT2)、激素敏感脂酶(HSL)和过氧化物酶体增殖物激活受体β(PPARβ)基因的表达量没有显著影响(P>0.05)。与对照组相比,饲粮中添加20~40 mg/kg锰显著降低了脂肪酸合成酶(FAS)基因的表达量(P<0.05);饲粮中添加20~40 mg/kg锰显著降低了乙酰辅酶A羧化酶(ACC)基因的表达量(P<0.05);饲粮中添加10~40 mg/kg锰显著提高了肉碱脂酰转移酶1(CPT1)基因的表达量(P<0.05);饲粮中添加10~20 mg/kg锰显著提高过氧化物酶体增殖物激活受体α(PPARα)基因的表达量(P<0.05)。综上所述,饲粮中添加锰影响了3~4月龄獭兔的脂肪沉积和脂肪组织脂质代谢,锰添加水平为20 mg/kg时,可以有效促进脂肪组织的氧化分解,抑制脂肪组织的合成,并能降低体脂肪的沉积率。     

Effects of epigallocatechin gallate on lipid metabolism and its underlying molecular mechanism in broiler chickens

The objective of this study was to investigate the effects of epigallocatechin gallate (EGCG) on fat metabolism and to establish the molecular mechanism of these effects in broilers. Seventy‐two 28‐day‐old male Ross 308 broiler chickens were divided into three groups with different levels of EGCG supplementation for 4 weeks: normal control (NC) group, L‐EGCG (a low‐level supplement of EGCG, 40 mg/kg body weight daily) and H‐EGCG (a high‐level supplement of EGCG, 80 mg/kg body weight daily). After 4 weeks of oral administration, EGCG significantly reduced the level of abdominal fat deposition in broilers. The serum triglycerides and low‐density lipoprotein cholesterol of chickens in H‐EGCG group were also significantly decreased compared with the NC group, and the high‐density lipoprotein cholesterol was notably increased at the same time. Moreover, the vital role of the liver and abdominal adipose tissue in lipid metabolism of poultry animals was examined through gene expression and enzyme activities related to fat anabolism and catabolism in these organs. Our data show that EGCG supplementation for 2 weeks significantly downregulated the expression of fatty acid synthesis and fat deposition‐related genes, and upregulated the expression of genes involved in fatty acid β‐oxidation and lipolysis genes. Simultaneously, the activities of hepatic fatty acid synthesis enzymes (fatty acid synthase and acetyl CoA carboxylase) were significantly decreased, and the activity of carnitine palmitoyl transferase‐1 was notably elevated. The results suggest that EGCG could alleviate fat deposition in broilers through inhibiting fat anabolism and stimulating lipid catabolism in broilers.