Lipogenesis by in vitro liver and adipose tissue preparations from neonatal swine

Application of partition coefficient methods to predict tissue:plasma affinities in common farm animals: Influence of ionisation state

Tissue affinities are conventionally determined from in vivo steady-state tissue and plasma or plasma-water chemical concentration data. In silico approaches were initially developed for preclinical species but standardly applied and tested in human physiologically-based kinetic (PBK) models. Recently, generic PBK models for farm animals have been made available and require partition coefficients as input parameters. In the current investigation, data for species-specific tissue compositions have been collected, and prediction of chemical distribution in various tissues of livestock species for cattle, chicken, sheep and swine have been performed. Overall, tissue composition was very similar across the four farm animal species. However, small differences were observed in moisture, fat and protein content in the various organs within each species. Such differences could be attributed to factors such as variations in age, breed, and weight of the animals and general conditions of the animal itself. With regards to the predictions of tissue:plasma partition coefficients, 80 %, 71 %, 77 % of the model predictions were within a factor 10 using the methods of Berezhkovskiy (2004), Rodgers and Rowland (2006) and Schmitt (2008). The method of Berezhkovskiy (2004) was often providing the most reliable predictions except for swine, where the method of Schmitt (2008) performed best. In addition, investigation of the impact of chemical classes on prediction performance, all methods had very similar reliability. Notwithstanding, no clear pattern regarding specific chemicals or tissues could be detected for the values predicted outside a 10-fold change in certain chemicals or specific tissues. This manuscript concludes with the need for future research, particularly focusing on lipophilicity and species differences in protein binding.

Abomasal infusion of arginine stimulates SCD and C/EBPß gene expression, and decreases CPT1ß gene expression in bovine adipose tissue independent of conjugated linoleic acid

Based on previous research with bovine peadipocytes, we hypothesized that infusion of arginine into the abomasum of Angus steers stimulates stearoyl-CoA desaturase (SCD) gene expression in bovine subcutaneous (s.c.) adipose tissue, and that this would be attenuated by conjugated linoleic acid (CLA). Growing Angus steers were infused abomasally with L-arginine 50 g/day; n = 13; provided as L-arginine HCl) or L-alanine (isonitrogenous control, 100 g/day; n = 11) for 14 days. For the subsequent 14 days, half of the steers in each amino acid group were infused with CLA (100 g/day). Body weight gain and average daily gain were unaffected (P > 0.15) by infusion of arginine or CLA into the abomasum. The plasma concentrations of cis-9, trans-11 and trans-10, cis-12 CLA were increased CLA infusion (P = 0.001) and infusion of arginine increased plasma arginine (P = 0.01). Compared with day 0, fatty acid synthase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase enzyme activities in s.c. adipose tissue increased by day 14 in steers infused with either alanine or arginine (all P < 0.01). NADP-MDH activity was higher (P = 0.01) in steers infused with arginine than in steers infused with arginine plus CLA by day 28, but lipid synthesis in vitro from glucose and acetate was unaffected by infusion of either arginine or CLA (P > 0.40). By day 28, C/EBPβ and SCD gene expression was higher, and CPT1β gene expression was lower, in s.c. adipose tissue of steers infused with arginine than in steers infused with alanine (±CLA) (P = 0.05). CLA decreased adipose tissue oleic acid (18:1n-9) in alanine- or arginine-infused steers (P = 0.05), although CLA had no effect on SCD gene expression. The data indicate that supplemental arginine promotes adipogenic gene expression and may promote lipid accumulation in bovine adipose tissue. L-Arginine may beneficially improve beef quality for human consumption.

Energy dense, protein restricted diet increases adiposity and perturbs metabolism in young, genetically lean pigs

Animal models of obesity and metabolic dysregulation during growth (or childhood) are lacking. Our objective was to increase adiposity and induce metabolic syndrome in young, genetically lean pigs. Pre-pubertal female pigs, age 35 d, were fed a high-energy diet (HED; n = 12), containing 15% tallow, 35% refined sugars and 9.1–12.9% crude protein, or a control corn-based diet (n = 11) with 12.2–19.2% crude protein for 16 wk. Initially, HED pigs self-regulated energy intake similar to controls, but by wk 5, consumed more (P<0.001) energy per kg body weight. At wk 15, pigs were subjected to an oral glucose tolerance test (OGTT); blood glucose increased (P<0.05) in control pigs and returned to baseline levels within 60 min. HED pigs were hyperglycemic at time 0, and blood glucose did not return to baseline (P = 0.01), even 4 h post-challenge. During OGTT, glucose area under the curve (AUC) was higher and insulin AUC was lower in HED pigs compared to controls (P = 0.001). Chronic HED intake increased (P<0.05) subcutaneous, intramuscular, and perirenal fat deposition, and induced hyperglycemia, hypoinsulinemia, and low-density lipoprotein hypercholesterolemia. A subset of HED pigs (n = 7) was transitioned back to a control diet for an additional six weeks. These pigs were subjected to an additional OGTT at 22 wk. Glucose AUC and insulin AUC did not improve, supporting that dietary intervention was not sufficient to recover glucose tolerance or insulin production. These data suggest a HED may be used to increase adiposity and disrupt glucose homeostasis in young, growing pigs.

Carnitine palmitoyltransferase I control of acetogenesis, the major pathway of fatty acid {beta}-oxidation in liver of neonatal swine

To examine the regulation of hepatic acetogenesis in neonatal swine, carnitine palmitoyltransferase I (CPT I) activity was measured in the presence of varying palmitoyl-CoA (substrate) and malonyl-CoA (inhibitor) concentrations, and [1-(14)C]-palmitate oxidation was simultaneously measured. Accumulation rates of (14)C-labeled acetate, ketone bodies, and citric acid cycle intermediates within the acid-soluble products were determined using radio-HPLC. Measurements were conducted in mitochondria isolated from newborn, 24-h (fed or fasted), and 5-mo-old pigs. Acetate rather than ketone bodies was the predominant radiolabeled product, and its production increased twofold with increasing fatty acid oxidation during the first 24-h suckling period. The rate of acetogenesis was directly proportional to CPT I activity. The high activity of CPT I in 24-h-suckling piglets was not attributable to an increase in CPT I gene expression, but rather to a large decrease in the sensitivity of CPT I to malonyl-CoA inhibition, which offset a developmental decrease in affinity of CPT I for palmitoyl-CoA. Specifically, the IC(50) for malonyl-CoA inhibition and K(m) value for palmitoyl-CoA measured in 24-h-suckling pigs were 1.8- and 2.7-fold higher than measured in newborn pigs. The addition of anaplerotic carbon from malate (10 mM) significantly reduced (14)C accumulation in acetate (P < 0.003); moreover, the reduction was much greater in newborn (80%) than in 24-h-fed (72%) and 5-mo-old pigs (55%). The results demonstrate that acetate is the primary product of hepatic mitochondrial beta-oxidation in Sus scrofa and that regulation during early development is mediated primarily via kinetic modulation of CPT I.

Comparison of pig, sheep and chicken SCD5 homologs: Evidence for an early gene duplication event

Stearoyl-CoA desaturase (SCD) catalyzes the desaturation of saturated fatty acyl-CoA substrates at the delta-9 position. Multiple SCD isoforms are well characterized in rodents, especially in mice, where four isoforms have been described. In humans and cows, two SCD isoforms have been described: SCD1, which is a homolog of murine SCD1, and SCD5, which appears to be a distinct SCD gene rather than an ortholog of any of the four murine isoforms. In this paper, we describe for the first time SCD5 homologs in sheep, pigs and chickens. The SCD5 nucleotide sequences have notably higher GC content than SCD1 sequences, and the predicted protein sequences lack N-terminal PEST sequences typically found in SCD1 proteins. Similar to humans and bovines, the mRNA expression of sheep and pig SCD5 is greatest in the brain, and the mRNA expression of chicken SCD5 is greatest in the pancreas and brain. In contrast, SCD1 expression was found to be highest in adipose tissue in pigs and sheep, and liver in the chicken. This is the first report of an SCD5 homolog in a non-mammalian species, and suggests that SCD5 may be the result of an early gene duplication event that occurred before the divergence of mammals.

Protein and enery relationships in the broiler chicken 12. Dietary protein and triidothyronine (T3) effects on the response of broilers to isoproterenol and cyclic adenosine monophosphate in vitro

Indian River male broiler chickens (7-d-old) were fed on diets containing 120, 210 or 300 g crude protein/kg + 0 or 1 mg triiodothyronine (T3)/kg diet (Expt 1) and 120, 150, 180 or 210 g crude protein/kg +0 or 1 mg T3/kg diet (Expt 2) to determine the effects of crude protein level and T3on growth and metabolism. Body composition of chickens was determined by a combination of dissection of muscle and abdominal fat pads, and chemical extraction (Expt 1).In vitrolipogenesis (IVL) was determined in both experiments by incubating liver explants for 2 h at 37° in the presence of 10-4M-dibutyryl cyclic AMP (cAMP) or 10-5M isoproterenol (ISO) and 10-2M-[2-14C]acetate. Acetate incorporation into total lipid was an indication of IVL. Activity ratios for each of these additions relative to control (?cAMP?ISO) were calculated to ascertain basal ν. inhibited rates of IVL. The relative muscle mass was increased by increasing crude protein from 120 to 210 g/kg diet but not from 210 to 300 g/kg diet. Dietary T3decreased total body lipid regardless of the dietary crude-protein level. Increasing dietary crude protein decreased (P<0.05) basal IVL (?cAMP? ISO) but not IVL (+ cAMP). Dietary T3decreased basal IVL in birds fed on the diets containing 120 and 210 g crude protein/kg but had little effect on the two inhibited states of lipogenesis (+ cAMP or +ISO). The component of lipogenesis sensitive toin vitroinhibition is also the component under dietary control.

Comparative aspects of lipid metabolism: impact on contemporary research and use of animal models

The emerging obesity crisis and consequent concerns for corrective measures and appropriate public policy have stimulated research into causes, prevention, remediation, and health consequences of obesity and associated maladies. Such research areas include eating behavior, appetite control, and food intake regulation as well as the regulation of lipid metabolism, cardiovascular function, endocrine function, and dyslipidemia states utilizing various animal models and cell culture systems. Although the liver has a central role in lipid/fatty acid synthesis and glucose is the precursor for de novo fatty acid synthesis in rodents and humans, in many other species, adipose tissues are the primary sites of lipogenesis. In addition, many species utilize acetic acid as a precursor for fatty acid synthesis. This fundamental difference in the site of fatty acid synthesis and the pattern of consequent lipid trafficking influences overall animal lipid metabolism and the role of regulatory hormones and transcription factors. Researchers utilizing various animal species in targeted biomedical research should be aware of these species differences when interpreting their data. In addition, many animal species are used for food production, recreational, and companion purposes. Understanding the lipid metabolism regulatory mechanisms of such species from a comparative perspective is important for the proper nutrition and health of these animals.

Fatty acids modulate porcine adipocyte differentiation and transcripts for transcription factors and adipocyte-characteristic proteins*

Porcine stromal-vascular cells (S/V cells) differentiate into adipocytes in vitro when presented with appropriate hormones and growth factors. Porcine S/V cells were differentiated in vitro in serum-free media with or without fatty acids to determine the effect of fatty acids on differentiation and on transcripts for peroxisome proliferator-activated receptor gamma (PPARgamma), CCAAT/enhancer binding protein alpha (C/EBPalpha), lipoprotein lipase (LPL) and adipocyte fatty acid binding protein (aP2). Differentiation was measured by Oil Red O staining and transcript concentrations were measured by Northern analysis using porcine riboprobes. Addition of 100 µM oleic acid (C18:1) for 5 days increased differentiation and the mRNA levels for PPARgamma, C/EBPalpha, LPL and aP2. Other medium- and long-chain fatty acids were less active. Adipocyte differentiation and transcript concentrations for PPARgamma, C/EBPalpha, LPL and aP2 were increased by C18:1 in a dose-related manner. Differentiation was greater at 10 days than at 5 days than at 1 day, and C18:1 increased differentiation at each time. Transcript concentrations were increased by C18:1 at 1 and 5 days, but not at 10 days. These results suggest that the main effect of C18:1 is on regulating gene expression (an acute or drug-like effect) rather than changing the membrane fluidity as a result of changing membrane fatty acid composition (a chronic or nutrient-like effect). Taken together, these results indicate that selected fatty acids modulate porcine adipocyte differentiation and transcripts for adipocyte differentiation-related proteins such as PPARgamma, C/EBPalpha, LPL and aP2.

The effect of lecithin supplementation on plasma choline concentrations during a marathon

BACKGROUND

Previous studies have shown that plasma and urinary free choline concentrations decrease significantly during a marathon, and that these decreases may be associated with decreased performance.

OBJECTIVE

In a pilot study, we sought to determine whether lecithin supplementation prior to a marathon would maintain plasma free and urinary choline concentrations and improve performance versus placebo.

METHODS

12 accomplished marathon runners, males (7) and females (5), 21 to 50 years of age were randomized to receive lecithin (4 capsules BID; PhosChol 900) or placebo beginning one day prior to the 2000 Houston-Methodist Health Care Marathon. The lecithin supplement provided approximately 1.1 g of choline on a daily basis (2.2 g total). Runners estimated finish time based on recent performance and training. Fasting, pre- and post-marathon plasma and a five-hour urine collection were analyzed for free choline and plasma for phospholipid-bound choline. Pre-race predicted, as well as the actual finish time, were recorded.

RESULTS

All subjects completed the marathon. Plasma free choline decreased significantly in the placebo group and increased significantly in the lecithin group (9.6 +/- 3.6 to 7.0 +/- 3.6 nmol/mL vs. 8.0 +/- 1.2 to 11.7 +/- 3.6 nmol/mL, p = 0.001 for the delta between groups). No significant changes in plasma phospholipid-bound choline concentration were observed. There was a non-significant decrease in urine free choline in both groups. Actual finish time was 256.3 +/- 46.3 minutes for the lecithin group vs. 240.8 +/- 62.0 for the placebo group and the actual:predicted time was 1.03 +/- 0.06 (lecithin) and 1.07 +/- 0.08 (placebo), p = 0.36.

CONCLUSION

Short-term lecithin supplementation prior to a marathon maintains normal plasma free choline concentration during the race, but failed to improve performance.

Plasma free, phospholipid-bound and urinary free choline all decrease during a marathon run and may be associated with impaired performance

BACKGROUND

Previous investigations have shown that plasma free choline decreases during long distance running.

OBJECTIVE

This study was undertaken to determine if body choline status changes during a marathon run and whether performance is thereby adversely affected.

DESIGN

Twenty-three accomplished marathon runners 25 to 49 years of age were studied before and after the 1997 Houston-Methodist Marathon. Fasting blood and five-hour urine samples were obtained in the morning, 14 days prior to the race, immediately after the race and approximately 48 hours after completion of the race. Runners were asked to predict their finish times two weeks prior to the race. Performance was indicated by the ratio of predicted to actual time.

RESULTS

Both plasma free and phospholipid-bound choline concentrations as well as urinary free choline concentration decreased immediately following the race (19.2+/-4.5 to 14.6+/-4.2 nmol/mL, p=0.005, and 2565.2+/-516.4 to 2403.4+/-643.0 nmol/mL, p=0.068, respectively) and, except for the phospholipid-bound choline, rebounded towards baseline after 48 hours (15.6+/-3.2 and 2299.9+/-426.7 nmol/mL), although plasma concentrations remained significantly below baseline. Plasma free and phospholipid-bound choline concentrations were significantly correlated (r=0.46, p=0.0001), although urinary free choline concentration was not correlated with either. There was no correlation between plasma free, phospholipid-bound or urinary free choline concentration and actual finish time or the ratio of predicted to actual finish time. However, the percent decrease in urinary free choline concentration was significantly correlated with the ratio of predicted to actual time (r=0.47, p=0.036). No relationship was seen between this ratio and the percent decrease in either plasma free or phospholipid-bound choline concentrations immediately after the race.

CONCLUSION

Our finding of both decreased free and phospholipid-bound choline suggests the decrease in choline status is related to accelerated choline metabolism or enhanced choline uptake by tissues rather than decreased hepatic choline release. The role of choline supplementation during endurance running requires further investigation.

Starvation depresses acylglycerol biosynthesis in bovine subcutaneous but not intramuscular adipose tissue homogenates

The primary objective of this study was to document the effects of starvation on acylglycerol biosynthesis in homogenates of intramuscular and subcutaneous adipose tissues. Adipose tissue samples were obtained from 8th-13th thoracic rib sections from 12 Angus cattle (six steers plus six heifers). Three steers and three heifers were starved for 72 h prior to slaughter while the remainder were slaughtered 4 h after food was withheld. Fat-free 700 x g centrifugal fractions were used to measure the esterification of radiolabeled sn-glycerol 3-phosphate (G-3-P) into acylglycerols at 1.0 mM palmitic or stearic acid, or 0.2 mM oleic, linoleic, or alpha-linolenic acid. There were significant tissue x fatty acid interactions for rates of incorporation into diacylglycerols and triacylglycerols; in subcutaneous, but not intramuscular homogenates, palmitic > stearic = oleic = linoleic = alpha-linolenic acid. Subcutaneous homogenates incorporated a greater percentage of G-3-P into triacylglycerols, and a lesser percentage into phospholipid, than intramuscular homogenates (P < 0.05). In intramuscular homogenates, the primary product of G-3-P esterification to saturated fatty acids was phospholipids. When unsaturated fatty acid served as substrates, triacylglycerols and phospholipids were produced in equal proportions in intramuscular homogenates, and triacylglycerols were the predominant product in subcutaneous homogenates. Intramuscular adipose tissue homogenates exhibited no response to starvation, whereas triacylglycerol and diacylglycerol synthesis was depressed by approximately 50% in subcutaneous adipose tissue homogenates. Similarly, phosphatidic phosphohydrolase activity, initially greater in subcutaneous than in intramuscular adipose tissue, was decreased by approximately 50% by starvation in subcutaneous adipose tissue, but not in intramuscular adipose tissue. We conclude that differences in rates of diacylglycerol and triacylglycerol biosynthesis, and response to starvation, between intramuscular and subcutaneous adipose tissues were due to dissimilarities in the activity of phosphatidic phosphohydrolase.

Effect of low-fat colostrum on fat accretion and lipogenic enzyme activities in adipose tissue in the 1-day-old pig

Fat accretion, body fatty acid (FA) composition and adipose tissue lipogenic enzyme activities were determined in 1-day-old piglets fed during the first day of life sow colostrum that was either normal (control) or low in fat and high in lactose, galactose or glucose as the sole source of carbohydrate. Malic enzyme activity did not change during the first postnatal day while increases (P < 0.01) were found for glucose-6-phosphate dehydrogenase and acetyl-CoA-carboxylase. However, fat accretion was closely dependent on the amount of ingested fat and FA composition of piglets indicates a shift toward that of colostrum, the extent of which was dependent on the amount of ingested fat. Plasma glucose and insulin levels were the highest (P < 0.01) in piglets fed the colostrum high in glucose and plasma free fatty acid (FFA) levels were the lowest (P < 0.01) in piglets fed the low-fat, high-carbohydrate colostra. Liver weight and glycogen concentration were higher (P < 0.01) in piglets fed the colostra low in fat and high in carbohydrate than in those on the control colostrum. It is suggested that synthesis of fatty acids from carbohydrate is negligible in the newborn pig even in the presence of high plasma insulin and low plasma FFA levels. The metabolic fate of carbohydrate is discussed.

Is the lipolytic response in porcine adipose tissue slices equivalent to the lipolytic response in isolated adipocytes?

1. In most cases, when isolated adipocytes and adipose tissue slices from the same animal were stimulated with various lipolytic agents (adrenergic agonists, theophylline, adenosine deaminase), the qualitative response was similar. 2. There were, however, numerous exceptions; e.g. quinterenol did not affect isolated adipocytes whereas it was a partial agonist for adipose slices from the same animal. 3. The adipocytes present in slices were larger than those isolated from slices by collagenase digestion. 4. Isolated adipocytes were not more sensitive than tissue slices to stimulation by lipolytic agents.

Characterization of lipogenic and lipolytic activity, muscle tissue composition, and DNA and RNA levels of broilers eating ad libitum or severely restricted at an early age

Four experiments were conducted to characterize the rates of lipogenic and lipolytic activities and the composition and DNA and RNA concentrations in muscle tissue of broilers that were feed restricted at an early age. In all experiments, feed restriction (40 kcal/day per bird) was initiated at 4 days of age with ad libitum consumption of feed resuming at either 11 (Experiments 1 and 2) or 10 (Experiments 3 and 4) days of age. Female chicks in Experiment 1 were feed restricted at the same level from 4 to 9 days of age. Birds consuming feed ad libitum served as controls in all experiments. Broilers restricted for 7 days had significantly lower plasma very low density plus low density lipoproteins (VLDL+LDL) than the ad libitum birds at 49 days of age in Experiments 1 and 2. However, the reverse was observed at 28 days of age, as plasma triglycerides and lipoproteins and lipogenesis were greater in restricted chicks when compared with controls. No significant differences were observed in plasma triglycerides at 49 days of age or lipolysis, DNA and RNA concentrations, muscle protein, and muscle fat at 28 days of age between restricted and ad libitum broilers. Results from these studies indicate that early feed restriction may have induced a metabolic shift in restricted broilers that increased lipogenesis at 28 days of age, followed by a partitioning of excess nutrients to support anabolic activity at market age.

Effects of warm exposure on adipose tissue and muscle metabolism in growing pigs

1. Forty-eight pigs weaned at 3 weeks old and acclimated to the experimental temperatures for 2 weeks before the start of the experiment, were fed ad lib and used between 9 and 33 kg live weight to determine the effects of warm exposure (31.5 vs 18.5 degrees C) on adipose tissue and muscle metabolism. 2. Warm exposure induced a decline in the lipid content (P less than 0.01) of backfat whereas degree of saturation (P less than 0.05) and adipocytes size were increased (P less than 0.05). 3. At 31.5 degrees C, as compared to 18.5 degrees C, activities of malic enzyme and glucose-6-phosphate dehydrogenase were depressed by an average 33% in backfat (P less than 0.01) and 23% in leaf fat (P less than 0.05) while lipoprotein-lipase activity was stimulated by 60% (P less than 0.01) in leaf fat. 4. In warm conditions, the activities of the enzymes indicative of oxidative and glycolytic metabolism in muscle, i.e. lactate dehydrogenase, beta-hydroxyacyl coenzyme-A dehydrogenase, citrate synthase and cytochrome oxidase, were reduced in the longissimus dorsi muscle (P less than 0.05) and to a lesser extent in the trapezius muscle. 5. At 31.5 degrees C, pigs exhibit lower average plasma levels of insulin, T3 and T4 than those maintained at 18.5 degrees C.

Protein and energy relations in the broiler chicken. Chronic or acute effects of alternating protein or intermittent feeding regimens on broiler lipid metabolism

1. Broiler chickens growing from 7 to 28 d of age were given: (1) a 210 g protein/kg control diet for the entire experimental period, (2) an intermittent feeding regimen (210 g protein/kg diet for either 1 or 2 d followed by a 1 d fast), or (3) a daily change in the dietary protein level from 120 to 300 g/kg diet. Treatment variables examined were lipogenesis and glucose production in vitro, and circulating concentrations of insulin, triiodothyronine (T3) and thyroxine (T4) to determine the effects of chronic or acute dietary treatments. 2. Giving the 300 g protein/kg diet or withholding feed for 1 d decreased (P less than 0.05) lipogenesis in vitro compared with controls. 3. Giving the 120 g protein/kg diet or refeeding with a 210 g protein/kg diet for 1 or 2 d increased (P less than 0.05) lipogenesis in vitro compared with controls. Glucose production was affected in the same manner. 4. Fasting decreased (P less than 0.05) plasma insulin and T3 and increased T4. Both refeeding and a low-protein diet increased T3. Refeeding increased and a low-protein diet decreased insulin. 5. Chronic use (7-28 d of age) of either an alternating protein or intermittent feeding regimen caused greater responses compared with acute bouts (single cycle) of either of the regimens.

Comparison between constant-protein, calorie-restricted and protein-restricted, calorie-restricted diets on growth, in vitro lipogenesis and plasma growth hormone, thyroxine, triiodothyronine and somatomedin-C (Sm-C) of young chickens

1. We studied the effects of calorie-restricted, constant-protein and calorie-restricted, protein-restricted diets on growth and in vitro metabolism of male chickens from select (Cobb Line 500) and byproduct (Cobb female line) lines of broiler chickens. 2. Chickens consumed 40, 60, 80 or 100% of a prescribed formula for dietary energy (body weight in g0.70 x 16.7 kJ) in the presence of set (CEP) or varied dietary protein (VEP). 3. Chickens fed VEP were heavier (P less than 0.05) at all energy intakes than chickens fed CEP. Slope analysis of data for in vitro lipogenesis showed a significant difference between the two treatment series. 4. Plasma growth hormone was inversely related (P less than 0.05) to Sm-C. Growth hormone levels were greater in chickens on a low plane of energy nutrition (40%) than on the maximum plane (100%). 5. Plasma Sm-C levels (pooled across energy series) were greater in the select than in the byproduct line. There were no differences in plasma T3 between the two lines. There was a significant increase (P less than 0.05) in T3 and a decrease in the T4/T3 ratio accompanying an increase in dietary energy. 6. Restricting dietary carbohydrate and protein compromises anabolic processes more than restricting carbohydrate alone.

Influence of minor plant constituents on porcine hepatic lipid metabolism. Impact on serum lipids

The effects of plant constituents on lipid metabolism were examined in swine that had been fed for 4 weeks a standard diet containing, in addition, (per kg diet) 3.15 g of the methanol serial solvent fraction garlic bulbs or 3.5 g of the petroleum ether solubles high-protein barley flour or 5 mg of the plant growth regulator, AMO 1618. All treatments suppressed 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and cholesterol 7 alpha-hydroxylase activities. Modest increases in serum triglycerides were associated with significantly increased hepatic lipogenic activities in response to all treatments except that of the barley extract. The methanol solubles of a second lot of garlic were fractionated by HPLC and tested in an avian hepatocyte system. One component, an isoprenoid metabolite, MW 358, suppressed HMG-CoA reductase.

Some regulatory aspects of thermogenesis in cold-exposed piglets

1. Thermoregulatory mechanisms were studied in weaned piglets fed ad libitum for 3 weeks at 12 or 23 degrees C. 2. Cold-adapted pigs maintained a growth rate and a carcass composition similar to the control ones, while increasing food intake by 20% (P less than 0.05). 3. Lipoprotein lipase activity was increased (P less than 0.05) by cold exposure in white adipose tissue (WAT) and heart. A large enhancement of lipogenesis was observed in WAT and to a lesser extent in the liver while WAT composition did not change significantly in the cold. 4. Cytochrome oxydase activity was increased in liver (30%), perirenal fat (40%) and interscapular muscle (75%) of cold-exposed pigs. 5. Plasma levels of thyroid hormones (TSH, T3, T4) were increased in the cold. 6. Mechanisms and locations of heat production are discussed.

Lipogenesis and lipolysis in normal and dwarf chickens from lines selected for high and low body weight

Lipogenic and lipolytic comparisons were made among normal and dwarf adult males from both high-weight (HW) and low-weight (LW) selected lines. Six nonfasted birds from each of the four populations were sacrificed, and in vitro lipogenesis and lipolysis were measured in liver, adipose, and bone tissue. Also determined were activities of acetyl CoA carboxylase (E.C.6.4.1.2), NADP-malate dehydrogenase (E.C.1.1.1.40), ATP-citrate lyase (E.C.4.1.3.8), and plasma-free fatty acids (FFA). In comparison with the HW chickens, the LW males tended to exhibit higher activities of lipogenic enzymes, a greater capacity to incorporate acetate-1-14C into liver slices, an increased mobilization of FFA from adipose tissue, and high concentrations of FFA in plasma. The results indicated that the maintenance of increased postmaturational body fat associated with selection for high body weight was primarily the result of decreased lipolysis rather than enhanced lipogenesis. Effects of the dwarf allele on lipogenesis and lipolysis were not clear. Acetate incorporation into bone tissue was substantially higher than for adipose tissue, suggesting that bone may be an important site of lipogenesis in the fowl.

Metabolic fate of non-esterified fatty acids in isolated hepatocytes from newborn and young pigs. Evidence for a limited capacity for oxidation and increased capacity for esterification

In hepatocytes isolated from 48 h-old starved of suckling newborn pigs or from 15-day-old starved piglets, the rate of ketogenesis from oleate or from octanoate is very low. This is not due to an inappropriate fatty acid uptake by the isolated liver cells, but results from a limited capacity for fatty acid oxidation. Some 80-95% of oleate taken up is converted into esterified fats, whatever the age or the nutritional conditions. Three lines of indirect evidences suggest that fatty acid oxidation is not controlled primarily by malonyl-CoA concentration in newborn pig liver. Firstly, the addition of glucagon does not increase fatty acid oxidation or ketogenesis. Secondly, the rate of lipogenesis is very low in isolated hepatocytes from newborn pigs. Thirdly, the rates of oxidation and ketogenesis from octanoate are also decreased in isolated hepatocytes from newborn and young piglets. The huge rate of esterification of fatty acids in the liver of the newborn pigs probably represents a species-specific difference in intrahepatic fatty acid metabolism.

Effects of cereals and culture filtrate of Trichoderma viride on lipid metabolism of swine

Swine were fed corn- or barley-based diets with, or without, culture filtrate (CF) of Trichoderma viride for 21 days. Weight gains were nonsignificantly but slightly increased by CF. The activities of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7 alpha-hydroxylase, acetyl-CoA carboxylase (ACX), fatty acid synthetase (FAS) and other lipogenic enzymes in several tissues were determined. Significant decreases in the activities of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase in all tissues of swine fed the CF-diets were observed. The major site for the regulation of cholesterol biosynthesis was adipose tissue followed by the intestine, liver, lung and muscle in order of activity. The concentrations of cholesterol in serum and muscle were decreased 27% and 23%, respectively, by CF. ACX and FAS activities increased ca. 2-fold when CF was fed with either of the cereal-based diets. The major sites for fatty acid synthesis was the adipose tissue and, to a lesser extent, the liver. Very low rates of synthesis were detected in intestine, lung and muscle. Similar distributions of activities were found for related lipogenic enzymes.

Cholesterol and fatty acid synthesis in swine

In incubation studies with swine tissue slices, acetate-1-14C or glucose-U-14C as substrates were incorporated more readily into fatty acids and cholesterol in adipose tissue than other tissues tested. Cholesterol and fatty acid synthesizing acitivity was substantial in the small intestine. When acetate was available, liver, small intestine, and adipose tissue were important sites for cholesterol synthesis. Heart and aortic tissue had marginal levels of cholesterol synthesizing ability. Lipogenesis in adult swine liver, heart, and aortic tissue was extremely low. As in tissue slices, incorporation of acetyl-1-14C CoA into fatty acids by adipose homogenates indicated high lipogenic activity. Subcellular fractionations of heart and aortic tissue indicated that the heart microsomal fraction had the highest lipogenic activity as measured by the incroporation of acetyl-4-14C CoA into fatty acids. In adult swine adipose tissue, the incorporation of glucose-U-14C into fatty acid was higher than its incorporation into glyceride-glycerol. The synthesis of glyceride-glycerol from glucose-U-14C or acetate-1-14C in liver was higher than for fatty acid synthesis. The acitivity of acetyl CoA carboxylase, fatty acid synthetase, citrate cleavage enzyme, nicotinamide adenine dinucleotide phosphat-malate dehydrogenase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase was considerably higher in adipose tissue than in other tissues tested, paralleling its high lipogenic capacity.