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1.
Porcine leptin inhibits lipogenesis in porcine adipocytes 总被引：6，自引：0，他引：6
Ramsay TG 《Journal of animal science》2003,81(12):3008-3017
The present study examined whether recombinant porcine leptin alters lipid synthesis in porcine adipocytes. The stromal-vascular cell fraction of neonatal pig subcutaneous adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. These cells were seeded on 25-cm2 tissue culture flasks and proliferated to confluency in 10% (vol/vol) fetal bovine serum in Dulbecco's modified Eagle medium/F12 (DMEM/F12, 50:50). Cultures were differentiated using 2.5% pig serum (vol/vol), 10 nM insulin, 100 nM hydrocortisone. After 7 d of lipid filling, cultures were washed free of this medium, incubated overnight in DMEM/F12 containing 2% pig serum (vol/vol), and then used for experiments. Acute experiments assessed U-(14)C-glucose or 1-(14)C-palmitate metabolism in cultures exposed to porcine leptin (0 to 1,000 ng/mL medium) for 4 h. Chronic experiments used cultures incubated with 0 to 1,000 ng porcine leptin/mL medium for 44 h before measurements of U-(14)C-glucose and 1-(14)C-palmitate oxidation and incorporation into lipid. Another experiment examined whether chronic leptin treatment alters insulin responsiveness by including insulin (10 nM) with incubations containing leptin. Leptin had no acute effects on glucose oxidation or conversion to lipid (P > 0.05). Acute leptin treatment decreased palmitate incorporation into lipids up to 45% (P < 0.05). Chronic leptin exposure decreased glucose oxidation (21%), total lipid synthesis (18%), and fatty acid synthesis (23%) at 100 ng/mL medium (P < 0.05). Insulin increased rates of glucose oxidation, total lipid, and fatty acid synthesis (P < 0.05); however, chronic exposure to 10 ng leptin/mL medium decreased the effectiveness of 10 nM insulin to affect these measures of glucose metabolism by approximately 18 to 46% (P < 0.05). Higher concentrations of leptin inhibited all effects of insulin on glucose metabolism (P < 0.05). Chronic exposure to leptin increased palmitate oxidation by 36% (P < 0.05). Chronic leptin exposure decreased palmitate incorporation into total lipids by 40% at 100 ng/mL medium (P < 0.05). Lipoprotein lipase activity was not affected (P > 0.05) by leptin. These data indicate that leptin functions to promote partitioning of energy away from lipid accretion within porcine adipose tissue by inhibiting glucose oxidation and lipogenesis indirectly, by decreasing insulin-mediated stimulation of lipogenesis, and by stimulating fatty acid oxidation while inhibiting fatty acid esterification. 相似文献
2.
We determined the effects of short-term fasting and refeeding on temporal changes in plasma concentrations of leptin, insulin, insulin-like growth factor- 1 (IGF-1), growth hormone (GH), glucose, and nonesterified fatty acids (NEFA), in early lactating cows, non-lactating pregnant cows, and postpubertal heifers. In experiment 1, Holstein cows in early lactation were either fed ad libitum (Control, n=5) or feed deprived for 48 h (Fasted, n=6). Plasma leptin, insulin, and glucose concentrations rapidly declined (P<0.05) within 6h, and IGF-1 by 12h, but all these variables sharply returned to control levels (P>0.10) within 2h of refeeding. Plasma NEFA and GH concentrations were elevated (P<0.05) by 4 and 36 h of fasting and returned to control levels (P>0.10) by 8 and 24h after refeeding, respectively. In experiment 2, four ruminally cannulated pregnant non-lactating Holstein cows were used in a cross-over design and were fasted for 48 h (Fasted) or fasted with partial evacuation of rumen contents (Fasted-Evac). The plasma variables measured did not differ (P>0.10) between Fasted and Fasted-Evac cows. Plasma leptin, insulin, and IGF-1 concentrations were reduced by 10, 6, and 24h of fasting, respectively, in Fasted-Evac cows; and these variables were reduced by 24h in Fasted cows (P<0.05). Plasma glucose levels were reduced (P<0.05) by 48 h of fasting in both groups of fasted animals. Plasma NEFA and GH levels were increased (P<0.05) by 12 and 48 h of fasting, respectively. In experiment 3, postpubertal Holstein heifers were either fed ad libitum (Control, n=4) or feed deprived for 72 h (Fasted, n=5). Concentrations of leptin, insulin, IGF-1, and glucose in plasma were reduced (P<0.05) by 24, 10, 24, and 48 h of fasting, respectively. Plasma NEFA concentrations increased (P<0.05) by 4h, of fasting while GH levels were not significantly (P>0.10) affected by fasting. Collectively, our data provide evidence that plasma leptin concentrations are reduced with short-term fasting and rebound on refeeding in dairy cattle with the response dependent on the physiological state of the animals. Compared to the rapid induction of hypoleptinemia with fasting of early lactation cows, the fasting-induced hypoleptinemia was delayed in non-lactating cows and postpubertal heifers. 相似文献
3.
瘦素（ｌｅｐｔｉｎ）是１４６个氨基酸组成的分子量为１４６ｋＤａ的多肽,由脂肪细胞所分泌。瘦素作为内分泌因子,通过阿片促黑激素皮质素原（ＰＯＭＣ）和神经多肽Ｙ（ＮＰＹ）影响丘脑下部（ＧｎＲＨ）释放,从而影响着生殖激素的产生和释放,动物初情期的发动伴随着瘦素水平的不断提高,成年动物繁殖功能的维持也有赖于瘦素发挥作用。瘦素对性腺和垂体的作用机理尚不明确。 相似文献
4.
Propionate was recently shown to increase leptin synthesis in rodents. To determine if a similar effect occurs in ruminants, propionate was administered to lactating dairy cows. In experiment 1, 31 cows were given an intrajugular Na propionate bolus (1,040 micromol/kg body weight), increasing plasma propionate from 160 to 5,680 microM and plasma insulin from 6.8 to 77.8 microIU/mL. Plasma leptin concentration decreased from 2.11 ng/mL before bolus to 1.99 ng/mL after dosing (P<0.05) with no differences in leptin concentrations at 20, 50, and 100 min post-bolus (P>0.10). In experiment 2, 12 cows were used in a duplicated 6 x 6 Latin square experiment to assess the dose-response effect of ruminal propionate infusion on plasma leptin concentration. Sodium propionate was infused at rates of 0, 260, 520, 780, 1040, or 1,300 mmol/h, while total short-chain fatty acid infusion rate was held constant at 1,300 mmol/h by addition of Na acetate to the infusate. Coccygeal blood was sampled following 18 h of infusion. Increasing the rate of propionate infusion linearly increased plasma propionate concentration from 180 to 330 microM (P<0.001) and plasma insulin concentration from 6.7 to 9.1 microIU/mL (P<0.05). There was a quadratic response in plasma leptin concentration (P=0.04) with a maximum at 780 mmol/h propionate, but leptin concentrations increased by no more than 8% relative to the 0 mmol/h propionate infusion. Leptin concentrations were correlated with insulin concentrations but not with propionate concentrations in plasma. Propionate is not a physiological regulator of leptin secretion in lactating dairy cows. 相似文献
5.
Ramsay TG 《Journal of animal science》2005,83(9):2066-2074
The present study was designed to determine whether porcine leptin can alter the proliferation and differentiation of the porcine preadipocyte. The stromal vascular cell fraction of neonatal pig s.c. adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. For differentiation studies, cells were seeded on six-well tissue culture plates and proliferated to confluency in 10% (vol/vol) fetal bovine serum (FBS) in Dulbecco's modified Eagle medium/F12 (DMEM/F12; 50:50). Cultures were differentiated using 2.5% pig serum (vol/vol) and recombinant porcine leptin at concentrations of 0 to 1,000 ng/mL alone or in combination with porcine insulin (100 nM), dexamethasone (1 microM), or IGF-1 (250 ng/mL). After 7 d of lipid filling, cultures were harvested for analysis of sn-glycerol 3 phosphate dehydrogenase (GPDH) and lipoprotein lipase (LPL). The GPDH and LPL activities are measures of preadipocyte differentiation. Data were corrected for protein content of the cultures. For proliferation experiments, 24 h after seeding cells with 10% FBS in DMEM/F12 in 25-cm2 tissue culture flasks, cells were switched to 5% FBS and supplemented with 0 to 1,000 ng of porcine leptin or 1,000 ng of murine leptin. Cell proliferation was measured by 3H-thymidine incorporation in preconfluent cultures over 24 h on d 4 of culture. At confluency, cells were switched to a medium to promote differentiation and lipid filling (2.5% pig serum, 100 nM insulin, 1 microM dexamethasone) for 7 d. Cells were harvested from the flasks and adipocytes were separated from stromal cells by Percoll gradient centrifugation. In a series of experiments, leptin alone or in combination with insulin, dexamethasone, or IGF-I did not affect differentiation as measured by the activity of GPDH and LPL. Leptin at any concentration did not inhibit differentiation induced by insulin, dexamethasone, or IGF-I; however, leptin at 1,000 ng/mL stimulated a 30% increase in preadipocyte proliferation (P = 0.007; n = 6) and a 27% increase in stromal cell proliferation (P < 0.001; n = 6). These results indicate that, at most, porcine leptin may contribute to the recruitment of new adipocytes within the adipose tissue. 相似文献
6.
Leucine metabolism in comparison to glucose, and with substrate and insulin supplementation, were studied in bovine adipose tissue slices obtained from the tailhead region. In addition, leucine metabolism by isolated adipocytes in a Krebs-Ringer bicarbonate (KRB) buffer was compared to metabolism in Medium-199. Slices oxidized leucine and incorporated the amino acid into cellular protein and lipid, though at much lower rates than for glucose. Glucose addition increased leucine oxidation and its incorporation into lipid but did not affect protein synthesis. Insulin, up to 100 ng/ml, had no effect. Isolated cells convened a higher proportion of the leucine utilized to lipid, and less to protein, than did slices. Absolute rates of oxidation and lipid synthesis were lower, and protein synthesis higher, for Medium-199 than for KRB. Of the total leucine utilized, conversion to lipid represented the largest percentage in both buffers. Insulin had no effect in either buffer system. Bovine adipose tissue, the major site of fatty acid synthesis in this species, was found to both oxidize leucine, and utilize the amino acid for synthesis of cellular components. The isolated adipocyte, free of connective tissue, directs this “ketogenic” amino acid primarily towards lipid synthesis, by mechanisms which appear to be insulin insensitive in the adult bovine, as studied under short-term, in-vitro conditions. 相似文献
7.
Ramsay TG 《Journal of animal science》2003,81(12):3046-3051
This study evaluated the potential mechanism(s) by which leptin treatment inhibits loss of muscle mass with fasting. Cultures of C2C12 myoblasts were differentiated into myotubes with 5% (vol/vol) horse serum in Dulbecco's modified Eagle's medium/F12. These myotubes were used to assess 3H-tyrosine incorporation and release following incubation with recombinant porcine leptin (0 to 500 ng/mL). Protein synthesis in myotubes, as measured by 3H-tyrosine incorporation, was not affected by leptin treatment (P > 0.05). Protein breakdown in C2C12 myotubes, as measured by 3H-tyrosine release, was inhibited by leptin treatment. A leptin concentration of 0.5 ng/mL was sufficient to inhibit 3H-tyrosine release by 3.5% (P < 0.05); 50 ng/mL produced a maximal inhibition of 10.2% (P < 0.05). Dexamethasone (1 microM) was used to maximally stimulate protein breakdown. Leptin (50 ng/mL leptin) decreased dexamethasone-induced 3H-tyrosine release by 32% (P < 0.05). The inhibition of 3H-tyrosine release in C2C12 myotubes suggests that leptin produces a protein-sparing effect in vitro by inhibiting protein breakdown. Fatty acid metabolism also was investigated because fatty acids are a major energy source for muscle during periods of reduced intake, as occurs with leptin treatment. Acute (4 h) and chronic (24 h) exposures to porcine leptin (0 to 500 ng/mL) were used to evaluate 14C-palmitate oxidation. Acute leptin treatment had no effect (P > 0.05) on palmitate metabolism. Chronic leptin exposure resulted in up to a 26% increase in palmitate oxidation (P < 0.05). The stimulation of fatty acid oxidation with chronic leptin treatment suggests that leptin spares other energy sources in muscle from oxidation during periods of a leptin-induced decrease in feed intake. 相似文献
8.
本研究利用重组瘦蛋白进行动物饲养试验,研究了重组瘦蛋白对猪内分泌代谢和胴体品质的影响。结果表明,在腹腔注射0.5和1.0 mg/kg体重重组瘦蛋白后,血清胰岛素含量从注射7 d后开始降低,并且一直持续到试验结束,其中7~21 d显著低于对照组,降低的幅度为12%~20%(P<0.05);血清T3含量在注射后7~14 d和28~42 d有显著提高(P<0.05);T4含量在注射后7~21 d差异显著(P<0.05);GH含量在注射后7~28 d显著高于对照组,提高的幅度为9%~25%(P<0.05);血清IGF-Ⅰ含量在注射后7~21 d显著高于对照组,提高的幅度为9%~16%(P<0.05);同时,腹腔注射0.5和1.0 mg/kg体重重组瘦蛋白与对照组相比,胴体瘦肉率提高6.70%和7.30%(P<0.05);脂肪率降低16.00%和18.75%(P<0.05);背膘厚降低18.14%和23.01%(P<0.05);板油重降低22.95%和24.59%(P<0.05)。可见,腹腔注射不同剂量的重组瘦蛋白后在一定时间内对猪内分泌有不同程度的调节作用,重组瘦蛋白可显著提高猪肉的瘦肉率,降低脂肪率、背膘厚和板油重,从而起到了调节猪胴体品质的作用。 相似文献
9.
Porcine leptin alters insulin inhibition of lipolysis in porcine adipocytes in vitro 总被引：5，自引：0，他引：5
Ramsay TG 《Journal of animal science》2001,79(3):653-657
The present study determined whether porcine leptin can alter the lipolytic rate in porcine adipocytes produced in vitro. The stromal-vascular cell fraction of neonatal subcutaneous adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. These stromal-vascular cells were seeded on 25-cm2 tissue culture flasks and proliferated to confluency in 10% fetal bovine serum in DMEM/F12 (50:50). Cultures were differentiated using 2% pig serum + 10 mM isobutyl methylxanthine + 1 microM dexamethasone for 48 h. This medium was replaced with 5% pig serum + 1 microM insulin to promote lipid filling of adipocytes for 7 d. Adipocyte-containing cultures were incubated overnight in serum-free medium and then used for experiments. Acute experiments assessed lipolysis in cultures exposed to porcine leptin (0 to 1,000 ng/mL medium) for 2 h. Chronic experiments used cultures incubated with 100 ng porcine leptin/mL of medium for 72 h prior to lipolysis measurements. Direct effects of leptin were examined by incubating cultures in DMEM/F12, 25 mM HEPES, 3% bovine serum albumin, 20 mU of adenosine deaminase/mL of medium in the presence of 0 to 1,000 ng of porcine leptin/mL of medium. Indirect effects of leptin were examined using the same incubation medium but also supplemented with 1 microM isoproterenol +/- 10 nM insulin in the presence of 0 to 1,000 ng of porcine leptin/mL of medium. Media glycerol concentration was measured at the end of 2-h incubations. Acute leptin exposure induced up to a 76% increase in lipolysis (P < 0.05) but had no effect on insulin's inhibition of lipolysis. Chronic exposure to leptin produced up to a 56% increase in lipolysis (P < 0.05) and reduced insulin's inhibition ofisoproterenol-stimulated lipolysis by up to 31% (P < 0.05). These data demonstrate leptin functions to promote the partitioning of energy away from lipid accretion within porcine adipose tissue by promoting lipolysis directly and indirectly by reducing insulin-mediated inhibition of lipolysis. 相似文献
10.
Stimulation of lipogenesis by insulin in swine adipose tissue: antagonism by porcine growth hormone 总被引：1，自引：0，他引：1
The effects of physiological (1, 10 ng/ml) and pharmacological (1,000 ng/ml) concentrations of insulin (INS) and porcine growth hormone (pGH) on lipid metabolism were determined in short-term (2 h) and long-term (26, 50 h) incubations of swine adipose tissue. The short-term effects of three different commercial sources of bovine serum albumin (BSA) on adipose tissue metabolism were also evaluated. Two of the three BSA preparations were found to be unsuitable for inclusion in the short-term incubation buffer because they caused a stimulation of lipid synthesis in adipose tissue and masked the stimulatory effects of insulin. Physiological concentrations of insulin stimulated glucose metabolism in 2-h incubations by 100% in adipose tissue from 80-kg swine. After a 26-h incubation period, INS maintained rates of glucose metabolism at levels comparable to maximally stimulated rates in fresh tissue. Insulin also enhanced glucose metabolism following 50-h incubations; however, rates were less than for 2- or 26-h incubations. Glucose metabolism was also stimulated in adipose tissue from 127-kg swine when incubated for 2 h with INS; however, INS responsiveness declined with increasing body weight. Lipogenesis and glucose oxidation were partially maintained by INS using tissue from the heavier swine. A pharmacological but not physiological concentration of pGH stimulated glucose metabolism in short-term incubations by 50% in adipose tissue from 80-kg swine, and by 10% in adipose tissue from 127-kg swine. Long-term culture of adipose tissue in the presence of pGH had no effect on glucose metabolism. Physiological levels of pGH directly antagonized the stimulation of glucose metabolism by INS in short- and long-term incubations. In summary, these results are the first to establish that swine adipose tissue is quite sensitive to insulin and that pGH directly antagonizes insulin action. 相似文献
11.
The effects of leptin on the release of luteinizing hormone (LH), growth hormone (GH) and prolactin (PRL) were studied in cultured bovine anterior pituitary (AP) cells in vitro. The AP cells were obtained from fully‐fed Japanese Black steers and were incubated for 3 h with 10?13 to 10?7 mol/L of leptin after incubating in Dulbecco's modified Eagle's Medium for 3 days. Leptin significantly increased the concentration of LH in the culture medium by 45 and 44% at doses of 10?8 and 10?7 mol/L, respectively, compared with the controls (P < 0.05). Leptin significantly increased the concentration of GH in the culture medium by 14 and 12% at doses of 10?8 and 10?7 mol/L, respectively (P < 0.05). Leptin also significantly increased the concentration of PRL in the culture medium by 26% compared with the controls at a dose of 10?7 mol/L (P < 0.05). These results show that leptin stimulates the release of LH, GH and PRL by acting directly on bovine AP cells from fully‐fed steers. 相似文献
12.
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14.
The objective was to determine the effect of central infusion of insulin and (or) glucose on hypothalamic expression of leptin receptor and pituitary secretion of LH in the ewe. Twenty-two ovariectomized ewes (32 wk of age) were fitted with two lateral cerebroventricular (LCV) cannulae and fed 33% of NRC requirements for 8 wk. Ewes (n> or =5/group) were then infused, via LCV cannulae, with artificial cerebrospinal fluid (aCSF) or aCSF containing physiological concentrations of insulin (INS), glucose (GLU), or INS + GLU; the mass of each increasing linearly from Day 0 (mass = 0 units/h) to Day 8 (mass of INS = 80 mIU/hr and GLU = 10 mg/hr). Jugular serum was collected every 12 min for 4 hr on Days 0, 2, and 4. Ewes treated with INS or INS + GLU had greater (P<0.06) mean concentrations of LH than aCSF treated ewes on Day 2 (13.8+/-1.8 and 12.5+/-1.3 > 8.0+/-3.3 ng/ml). Furthermore, on Day 4, concentrations of LH in INS treated ewes exceeded that (P<0.07) of aCSF treated ewes (14.8+/-2.0 > 7.4+/-3.0 ng/ml). Expression of NPY mRNA did not differ between treatments (P = 0.87). Leptin receptor mRNA expression was dramatically reduced (P<0.0002) in INS+GLU versus aCSF treated ewes. These data provide evidence to suggest that insulin may be an important component of hypothalamic mechanisms regulating secretion of LH and expression of leptin receptors in undernourished ruminants. 相似文献
15.
Gordon ME McKeever KH Betros CL Manso Filho HC 《Veterinary journal (London, England : 1997)》2007,173(3):532-540
Six Standardbred (STB) mares (11+/-2 years, 521+/-77 kg; means+/-SD) performed an exercise trial (EX) where they underwent an incremental exercise test (GXT) as well as a parallel control trial (CON) to test the hypothesis that short-term, high intensity exercise would alter plasma concentrations of glucose, leptin, adiponectin, ghrelin, insulin and cortisol. Plasma samples were taken before (0 min), during (last 10s at 6, 8m/s, and the velocity eliciting VO(2max)), and after exercise (2, 10, 30, 60 min; 12 and 24h post-GXT). A second set of blood samples was collected before and after an afternoon meal given at 1515 h (at 1500, 1514, 1530, and 1545 h). Data were analyzed using ANOVA for repeated measures and Tukey's test. During the GXT, there were no changes (P>0.05) in the plasma concentrations of glucose, leptin, adiponectin or ghrelin. However, there was a 29% increase (P<0.05) in mean plasma cortisol concentration and a 35% decrease (P<0.05) in mean plasma insulin concentration. Substantial increases (P<0.05) in the mean plasma concentrations of glucose and cortisol of 36% and 102%, respectively, were seen in the EX trial during the first 60 min post-GXT. Plasma leptin concentration, measured at the 24h post-GXT time point, was 20% lower (P<0.05) during the EX trial compared with the parallel time point in the standing control (CON) trial. Plasma ghrelin concentration was 37% lower (P<0.05) in the EX trial compared with CON before and after the afternoon meal, but was 43% higher (P<0.05) 12h post-GXT. There were no differences between EX and CON for plasma concentrations of insulin or adiponectin during recovery. It was concluded that short-term high intensity exercise alters plasma leptin and ghrelin concentrations in STB mares post-exercise, which may signal the exercised animals to alter energy intake. 相似文献
16.
Caperna TJ Shannon AE Poch SM Garrett WM Richards MP 《Domestic animal endocrinology》2005,29(4):582-592
A study was conducted to elucidate hormonal control of leptin receptor gene expression in primary cultures of porcine hepatocytes. Hepatocytes were isolated from pigs (52 kg) and seeded into collagen-coated T-25 flasks. Monolayer cultures were established in medium containing fetal bovine serum for 1 day and switched to a serum-free medium for the remainder of the 3-day culture period. To establish basal conditions hepatocytes were maintained in serum-free William's E medium containing 10 nM dexamethasone and 1 ng/ml insulin. For the final 24 h, insulin (1 or 100 ng/ml) or glucagon (100 ng/ml), were added in the presence or absence of 100 nM triiodothyronine (T3). RNA was extracted and quantitative RT-PCR was performed with primers specific for the long form and total porcine leptin receptors. Leptin receptor expression was calculated relative to co-amplified 18S rRNA. Expression of the long form of the leptin receptor was confirmed under basal conditions. Insulin, glucagon and synthetic human proteins (ghrelin and GLP-1) at 100 ng/ml had no influence on leptin receptor expression; the addition of T3 was associated with a marked increase (P < 0.001) in expression of total and long forms of the leptin receptor by 1.6 and 2.4-fold, respectively. Addition of leptin to cells which were pre-treated with T3 for 24 h (to up-regulate leptin receptor expression), confirmed the lack of a direct effect of leptin on glucagon-induced glycogen turnover and cAMP production. These data suggest that porcine hepatocytes may be insensitive to leptin stimulation even when leptin receptor expression is enhanced by T3. 相似文献
17.
Kadokawa H Aikawa K Kimura K Blache D Williams IH Martin GB 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2007,69(3):225-231
Leptin secretion by adipose tissue is involved in many physiological control systems, including those that determine growth, development, body composition, milk production, and reproductive function. In the adipocyte of monogastric animals, malonyl CoA (coenzyme A) seems to link the flux of energy substrates to the control of leptin production. In this study, we tested this for ruminants by examining the effect of cerulenin, an inhibitor of de novo fatty acid synthesis at the step from malonyl CoA to palmitate, on leptin production by cultured bovine adipocytes derived from intermuscular fat. Purified preadipocytes were obtained by the ceiling culture method, and adipogenic media were used to induce their differentiation into adipocytes. We found that leptin concentrations increased significantly with time in culture, and with increases in glucose concentration. Addition of 2-deoxy-D-glucose to the medium, a competitive inhibitor of glucose transport and metabolism, suppressed leptin secretion. In media with high glucose concentrations, cerulenin enhanced leptin secretion. We conclude that, as in monogastrics, malonyl CoA may play a key role in the control of leptin secretion in ruminants. 相似文献
18.
Mammary uptake of nutrients is dependent on their availability in the circulation but the role of hormones in that process is not known. Arteriovenous differences (AVD) of glucose and key hormones across the mammary glands were therefore determined in sows fed varying levels of protein. Sixteen lactating sows (four/dietary treatment) were fed a 7.8, 13.0, 18.2 or 23.5% crude protein (CP) isocaloric diet throughout lactation and their litters were standardized to 11 pigs within 48 h of birth. The anterior main mammary vein and a carotid artery were cannulated on day 4+/-1 of lactation and blood samples were collected every 30 min over 6h on days 10, 14, 18 and 22 of lactation to measure glucose, insulin, IGF-I, and prolactin (PRL) concentrations. Amino acid data from these sows were previously published and used here to determine residual correlations. Dietary treatments had no effect on any of the insulin or PRL variables measured (P>0.1) and, on day 18 only, IGF-I AVD was greater (P=0.05) for sows on the 23.5% compared to the 18.2% diet. On days 18 and 22, sows fed the 13% CP diet had greater arterial, venous and AVD glucose concentrations than sows fed other diets (P<0.05). Total arterial amino acid concentrations were correlated to arterial insulin (P<0.001) and PRL (P<0.05) concentrations, but not to those of IGF-I (P>0.1). Mammary AVD for total (P<0.001) and essential amino acids (P<0.05) were correlated to arterial concentrations of insulin, but not to those of IGF-I (P>0.1) or PRL (P>0.1). Mammary AVD of both total (P<0.01) and essential (P<0.05) amino acids were also correlated to mammary PRL AVD. In conclusion, dietary protein level did not affect mammary AVD and circulating lactogenic hormone concentrations. Yet, amino acid utilization by the sow mammary gland seems to be regulated via both circulating insulin concentrations and PRL binding to and uptake by porcine mammary cells. 相似文献
19.
为研究日粮中添加藤茶提取物对不同体重阶段猪生长性能、血液生化指标、抗氧化活性的影响,本研究选用平均初始体重为30 kg的三元杂交(杜×长×大)去势公猪90头,随机分成3个处理,分别为对照组(CON组,饲喂基础日粮)、植物精油复合物组(A组,基础日粮中添加0.03%植物精油复合物)和藤茶提取物组(B组,基础日粮中添加0.03%藤茶提取物),根据不同体重阶段(30～50、50～75、75～100 kg及100 kg～出栏)饲喂不同阶段的基础日粮,每次换料前及试验结束时称重采血,分析不同体重阶段添加0.03%藤茶提取物对猪生长性能、血液生化指标、抗氧化活性的影响。结果表明:与CON组相比,添加0.03%藤茶提取物显著提高了30～75 kg猪的平均日采食量(ADFI)和平均日增重(ADG)(P<0.05);显著降低了30～50 kg猪血清乳酸(LA)含量(P<0.05);显著提高了50～75 kg猪血液胰岛素(INS)浓度(P<0.05),但对血糖(GLU)浓度无显著影响(P>0.05);显著提高了75～100 kg猪GLU浓度(P<0.05),INS浓度有升高趋势(P>0.05),乳酸脱氢酶(LDH)含量显著降低(P<0.05);各体重阶段血清生长激素(GH)含量均有升高趋势(P>0.05)。B组猪血清总超氧化物岐化酶(T-SOD)活力、丙二醛(MDA)含量、谷胱甘肽过氧化物酶(GSH-Px)活力、总抗氧化能力(TAOC)在各体重阶段与CON组相比均无显著差异(P>0.05)。与A组相比,添加0.03%藤茶提取物显著提高了30～100 kg猪的ADFI(P<0.05),显著降低了30～50 kg猪血清LA含量(P<0.05),且显著提高了50 kg以上体重阶段猪血清GSH-Px活力(P<0.05)。综合试验结果,添加0.03%藤茶提取物可促进30～75 kg猪生长代谢,在一定程度改善50～100 kg猪的血糖代谢,且添加藤茶提取物效果优于添加等量植物精油复合物。 相似文献
20.
Szkudelska K Nogowski L Nowicka E Szkudelski T 《Journal of animal physiology and animal nutrition》2007,91(3-4):91-99
Naringenin is a bioactive flavanone involved in the inhibition of drug metabolism which exhibits antioxidant, anti-inflammatory and anticancerogenic properties and which recently appeared to be a factor mitigating the hyperlipidaemic effects in rats and rabbits. In the performed experiment, the effect of naringenin, administered intragastrically (50 mg/kg) for 2 weeks to normal and ethanol drinking rats, on insulin and leptin levels and on some metabolic parameters was investigated. Naringenin did not change the hormone levels in any group of rats. Blood glucose, triglyceride, total, esterified and free cholesterol and high-density lipoprotein-cholesterol concentrations were also unaffected by this compound. Only free fatty acids were elevated after the naringenin treatment in the water-drinking rats. In spite of unchanged glucose and insulin concentrations in blood, the tested flavanone reduced the glucose/insulin ratio in ethanol-receiving rats. Liver triglycerides, elevated due to ethanol ingestion, were partially normalized by naringenin. Other tested parameters like liver glycogen and cholesterol, muscle triglycerides and glycogen were not altered in any group of rats. The influence of naringenin (62.5, 125, 250 and 500 microM) on basal and insulin-stimulated glucose conversion to lipids (lipogenesis) as well as on basal and epinephrine-stimulated glycerol release (lipolysis) in the isolated rat adipocytes was also tested. The basal and the stimulated lipogenesis tended to be decreased in the presence of the flavanone (250 microM). This inhibitory effect intensified and was statistically significant at the highest concentration of naringenin. The tested compound did not evoke any effect on basal lipolysis while the epinephrine-stimulated process was limited at the highest concentration of the flavanone. Naringenin (62.5, 125, 250 and 500 microM) had no effect on leptin secretion from the isolated rat adipocytes. Results obtained in our studies demonstrate that naringenin exerts a very weak influence on carbohydrate and lipid metabolism of normal and ethanol-consuming rats and on metabolism of isolated rat adipocytes. 相似文献