Citrate Cleavage Enzyme Research Articles

The effect of immunocastration on adipose tissue deposition and composition in pigs

Immunocastrated pigs (IC) exhibit intensive fat deposition after immunisation, but the underlying mechanisms of intensified fat metabolism and deposition are not yet fully understood. Moreover, there is also a lack of comparative studies performed on IC, entire males (EM) and surgical castrates (SC). The main objective of our research was, therefore, to characterise the adipose tissue from the quantitative, histo-morphological and biochemical perspectives in IC 5 weeks after their immunisation in comparison to EM and SC. Immunocastrated pigs had an intermediate position in carcass fatness traits between EM (the leanest) and SC (the fattest). The histo-morphological traits of the subcutaneous adipose tissue of IC were similar to those of SC and differed from those of EM; i.e., they exhibited larger adipocytes in the outer backfat and a larger lobulus surface area in both backfat layers than EM. Intensive fat tissue development in IC was corroborated with higher activities of lipogenic enzymes (i.e., fatty acid synthase, malic enzyme, glucose 6-phosphate dehydrogenase, citrate cleavage enzyme), which was especially pronounced in the subcutaneous adipose tissue of IC (1.5- to 2.7-fold higher activity than in EM or SC). The fatty acid composition of the backfat in IC was similar to that in EM pigs. Both IC and EM exhibited less saturated and more polyunsaturated fatty acids than SC. In contrast, the fatty acid composition of the intramuscular fat of longissimus dorsi muscle in IC pigs was more similar to SC than to EM (higher monounsaturated and lower polyunsaturated fatty acid content in IC and SC than EM). In this study, it was demonstrated that immunocastration notably influenced lipid metabolism. This was shown by increased quantity of lipid depots and with changes in adipose tissue cellularity compared to EM, with changes in the fatty acid composition of the intramuscular fat and enhanced lipogenic activity compared to both EM and SC. These results provide new insights into the specificity of adipose tissue development and deposition in IC compared to EM and SC.

Effects of substituting dietary fish oil with crude palm oil and palm fatty acid distillate on growth, muscle fatty acid composition and the activities of hepatic lipogenic enzymes in snakehead (Channa striatus, Bloch 1793) fingerling

Three diets were formulated to be iso-nitrogenous (450 g kg−1), iso-lipidic (65 g kg−1) and iso-energetic (18.5 KJ g−1), varying only in their lipid sources and designated as 100% fish oil (FO), 100% crude palm oil (CPO) and 100% palm fatty acid distillate (PFAD). Feed were hand fed to homogenous groups of 12 Channa striatus fingerlings (mean weight 3.5 ± 0.3 g) per tank in triplicate for 12 weeks, in a recirculation system. The growth performance and feed intake in the CPO and PFAD treatments were significantly (P<0.05) higher than those in the fish fed the control diet (FO), respectively, whereas the feed conversion ratio was better in PFAD than that in the other treatments respectively. The biological indices monitored (hepatosomatic index and viscerosomatic index) as well as carcass yield did not vary significantly among all the treatments respectively. The muscle fatty acid (FA) profile of fish was influenced by the composition of the diets fed, whereas no differences were recorded in the activities of the hepatic lipogenic enzymes monitored (fatty acid synthetase, citrate cleavage enzyme and malic enzyme). Whole-body proximate composition analysis revealed that PFAD treatment, compared with others, contained significantly higher protein and ash, but lower lipid contents, although the muscle content of these nutrients was similar among all the treatments. Based on the results of this trial, CPO and PFAD could be used to partially substitute FO in the diet for C. striatus fingerling, to achieve good growth performance without any negative effects or compromising the muscle n-3 FA composition (especially in the docosa hexaenoic acid and eicosa pentaenoic acid content).

Effects of dietary myo-inositol or phytic acid on hepatic concentrations of lipids and hepatic activities of lipogenic enzymes in rats fed on corn starch or sucrose

This study was undertaken with growing rats to compare the effects of dietary 0.1% myo-inositol or 0.5% sodium phytate on the changes in the metabolism of hepatic lipids due to sucrose feeding. Liver weight, hepatic concentrations of total lipids and triglyceride, and hepatic activities of glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49), malic enzyme (ME, EC 1.1.1.40), fatty acid synthetase (FAS, EC 2.3.1.85), citrate cleavage enzyme (CCE, EC 4.1.3.8) and acetyl-CoA carboxylase (CBX, EC 6.4.1.2) were remarkably higher in rats fed on sucrose than in rats fed on corn starch for 12 or 13 days. Dietary myo-inositol and phytate significantly depressed the rises in liver weight, hepatic concentrations of total lipids and triglyceride, and hepatic activities of G6PD, ME, FAS and CCE due to sucrose feeding. These results suggested that dietary myo-inositol and phytate both can protect sucrose-fed animals against an accumulation of hepatic lipids, which might be at least in part ascribed to the depression in the hepatic lipogenesis.

The effect of gamma-hexachlorocyclohexane (lindane) on the activities of liver lipogenic enzymes and on serum lipids in rats.

The effect of dietary gamma-hexachlorocyclohexane (lindane) (50-350 ppm, 0.17-1.19 mumol/kg chow) on the activity of enzymes of lipogenesis, viz., fatty acid synthase (FAS; EC 2.3.1.85), citrate cleavage enzyme (CCE; EC 4.1.3.8), malic enzyme (ME; EC 1.1.1.40), glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (PGDH; EC 1.1.1.44), and on serum lipid levels, was investigated in livers of 35-day-old male Wistar rats. Lindane (150 ppm) caused a substantial decline of enzyme activities within the first 24 h of treatment. The decrease was transient, however, and enzyme activities subsequently recovered despite continuation of lindane feeding. The recovery of enzyme activities was comparatively fast in the case of ME, G6PDH and PGDH, but very slow with FAS and CCE. Activities of lipogenic enzymes decrease when animals are starved, and increase much beyond prestarvation levels upon subsequent refeeding. Lindane in the refeeding diet blunted this overshoot of FAS and CCE activities in a dose-dependent manner. In contrast, activities of Me, G6PDH and PGDH responded to low dietary lindane concentrations with a substantial stimulation of the increase of activity, whereas at high lindane concentrations the overshoot was inhibited. According to their responses to lindane exposure, liver lipogenic enzymes could be grouped into 2 categories with FAS and CCE representing one and ME, G6PDH and PGDH representing the other group. Polychlorinated biphenyls (PCBs) in the diet caused basically opposite changes of the activities of the lipogenic enzymes. Co-administration of lindane and PCBs resulted in an apparent cancellation of effects, suggesting that lindane and PCBs affect fatty acid synthesis at opposite points.(ABSTRACT TRUNCATED AT 250 WORDS)

Zinc deficiency and activities of lipogenic and glycolytic enzymes in liver of rats fed coconut oil or linseed oil

In previous studies, zinc-deficient rats force-fed a diet with coconut oil as the major dietary fat developed a fatty liver, whereas zinc-deficient rats force-fed a diet with linseed oil did not. The present study was conducted to elucidate the reason for this phenomenon. In a bifactorial experiment, rats were fed zinc-adequate or zinc-deficient diets containing either a mixture of coconut oil (70 g/kg) and safflower oil (10 g/kg) ("coconut oil diet") or linseed oil (80 g/kg) ("linseed oil diet") as a source of dietary fat, and activities of lipogenic and glycolytic enzymes in liver were determined. In order to ensure adequate food intake, all the rats were force-fed. Zinc-deficient rats on the coconut oil diet developed a fatty liver, characterized by elevated levels of triglycerides with saturated and monounsaturated fatty acids. These rats also had markedly elevated activities of the lipogenic enzymes acetyl-CoA carboxylase, fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and citrate cleavage enzyme, whereas activities of malic enzyme and glycolytic enzymes were not different compared with zinc-adequate rats on the coconut oil diet. In contrast, rats receiving the linseed oil diet had similar triglyceride concentrations regardless of zinc status, and activities of lipogenic enzymes and glycolytic enzymes were not different between the two groups. Zinc-deficient rats fed either type of dietary fat exhibited statistically significant correlations between activities of FAS, G6PDH, 6PGDH and concentrations of saturated and monounsaturated fatty acids in liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary gamma-linolenic acid-enriched oil reduces body fat content and induces liver enzyme activities relating to fatty acid beta-oxidation in rats.

The objectives of this study were to examine the effects of dietary gamma-linolenic acid-enriched oil extracted from fungi on rat body composition and on the various enzyme activities relating to fat metabolism in the liver. The oil contained 25.3 g gamma-linolenic acid/100 g fatty acids. The levels of gamma-linolenic acid-enriched oil in the diets were 0, 1.5 and 4%, to give 0, 2.88 and 7.68 g gamma-linolenic acid/kg diet. The control diet contained 8% soybean oil. The rats were given free access to these diets for 4 wk. Body weight gain was less in the gamma-linolenic acid oil-fed groups than in the control group, although food intake was similar among the three groups. Absolute and relative carcass fat weights were significantly lower in the gamma-linolenic acid oil-fed groups than in the control group. Carcass protein and water contents were not different among the three groups, although values were slightly greater than controls in gamma-linolenic acid-fed groups when expressed relative to body weight. Plasma total cholesterol and free fatty acid concentrations generally were lower in the gamma-linolenic acid oil-fed groups than in the control group. In the liver, there were no significant differences in activities of malic enzyme and citrate cleavage enzyme among the three groups. However, the activities of carnitine palmitoyl-transferase and peroxisomal beta-oxidation were significantly higher in the gamma-linolenic acid oil-fed groups than in the control group. These results clearly demonstrate that dietary gamma-linolenic acid oil reduces body fat content and facilitates fatty acid beta-oxidation in the liver.

Influence of dietary medium- and long-chain triglycerides on fat deposition and lipogenic enzyme activities in rats.

The present study investigates fat deposition, variances of fatty acid (FA) composition, and lipogenic enzyme activities through dietary medium- and long-chain triglyceride (MCT and LCT) supplementation in growing rats. Eighteen male Wistar rats were divided into three groups and fed isocalorically for 4 weeks with control (based on AIN 76), MCT (C8:0 26%), or LCT (corn oil 25%) diets. Compared to the control group with 0.28 +/- 0.01, feed efficiency was lower in the MCT rats and greater in the LCT rats (0.24 +/- 0.01 and 0.33 +/- 0.01, respectively). Weights of perirenal and epididymal adipose tissue pads of the MCT rats were similar to those of the control group, but were significantly lower than those of the LCT group. Whole-body carcass components data of MCT rats showed the decrease in moisture and protein contents compared to those of control and LCT rats. Fat content of LCT rats was 25-30% higher than those of the MCT and control group. Glucose-6-phosphate dehydrogenase, citrate cleavage enzyme, and malic enzyme activities of liver and epididymal adipose tissue were markedly low in LCT rats. In the MCT group, however, lipogenic enzyme activities were not suppressed, and malic enzyme activity was drastically increased. FA composition of whole-body triglycerides and epididymal adipose tissue in MCT rats showed that C16:0 and C16:1 levels were higher than those of the LCT rats. In contrast, FA composition of the LCT group presented high C18:2 content.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes of lipogenic enzyme activities and lipogenesis in brown adipose tissue and liver of the rat

1. 1. Brown adipose tissue (BAT) and liver lipogenesis in vivo estimated by using 3H 2O as tracer was very low and did not change significantly between 10 and 20 days after birth. Lipogenesis increased dramatically in both tissues by weaning at 20 days, peaking between 25 and 30 days of age. Since that time the rate of fatty acid synthesis in BAT decreased gradually to reach adult level after 2 months, whereas in the liver there was a sharp decrease of lipogenesis. 2. 2. The activities of fatty acid synthase, citrate cleavage enzyme, malic enzyme and glucose 6-phosphate dehydrogenase essentially followed a similar course of developmental changes as lipogenesis. 3. 3. In contrast to the enzymes listed above NADP-linked isocitrate dehydrogenase remained unaltered over the period studied, whereas lactate and malate dehydrogenases exhibited very high activity at 10 days after birth and from then decreased to reach adult level at the age of about 20 days. 4. 4. The data obtained indicate that no substantial differences could be detected in the developmental pattern of lipogenesis and lipogenic enzyme activities between BAT and liver up to 30 days of age but after this time these processes were not co-ordinated in both tissues. Beyond this time the BAT was charaterized by a much higher rate of lipogenesis than the liver. 5. 5. The results are discussed in terms of the nutrient changes and the relationship between thermogenesis and lipogenesis in BAT.

Effect of Liver Denervation on Compensatory Changes in Food Intake, Body Composition and Hepatic Enzyme Induction after Food Restriction in Rats

The mechanisms involved in the recovery of body fat and liver metabolism after food restriction and refeeding are not understood. This study's aim was to determine the need for hepatic neural input for the compensatory changes in food intake, body composition and hepatic lipogenic enzymes seen upon realimentation after energy restriction. Rats underwent total surgical hepatic denervation or had sham operations. One group of sham-operated and denervated rats was fed a semipurified diet ad libitum; a second group was restricted to 40% ad libitum levels for 7 d, then given free access to food during a 2-d refeeding period. Body fat content and body fat recovery rate from below "set point" were not altered by hepatic denervation. These observations do not rule out liver involvement because blood-borne factors communicating energy status information to the central nervous system could be released from the liver. The activities of hepatic enzymes--glucose-6-phosphate dehydrogenase, malic enzyme and citrate cleavage enzyme--were stimulated at least twofold by restriction and refeeding when compared to ad libitum feeding. Hepatic denervation had no effect on basal enzyme levels in ad libitum-fed animals or on elevated enzyme activity induced by refeeding after food restriction. This study clearly demonstrates that hepatic innervation is not essential for energy balance and body composition regulation. The induction of lipogenic enzymes by food restriction and refeeding does not depend on central nervous system input to the liver.

Metabolism of cis-12-octadecadienic acid and trans-9, trans-12-octsidecadienoic acid and their influence on lipogenic enzyme activities in mouse liver

High carbohydrate (65% glucose) diets containing cis-12-octadecenoic acid (12 c-18:1) or trans-9, trans-12-octadecadienoic acid (9 t,12 t-18:2) were fed to weanling mice to investigate the influence of fatty acid structure on six hepatic enzyme activities involved in lipid metabolism. Results with these diets were compared to those with diets containing no fatty acids, saturated fatty acids; cis-9-octadecenoic acid (9 c-18: l) and cis-9, cis-12-octadecadienoic acid (9 c,12 c-18:2). These comparisons show saturated fatty acids, 9 c-18:1, 12 c-18:1, and 9 t,12 t-8:2, had little or no influence on the activity levels of fatty acid synthetase, malic enzyme (EC 1.1.1.40)citrate cleavage enzyme (EC 4.1.3.8), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and acetyl-CoA carboxylase (EC 6.4.1.2). Neither 12 c-18:1 nor 9 t,12 t-18:2 produced the dramatic enzyme-lowering effect exhibited by the diet containing 9 c,12 c-18:2 when compared to the diet devoid of fat. Thus, both the 9 and 12 bonds must be present in the same molecule. Also, at least one and probably both bonds must be in the cis configuration to depress liver enzyme activities. Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were both used for analysis of the methyl esters derived from the hepatic lipids. The GC and GC-MS data provided (a) direct evidence for incorporation of both isomers into hepatic lipids and (b) indirect evidence that 9 t,12 t-18:2 lowered liver Δ 9-desaturase activity. In addition, since these products were found in the complex liver lipids, there is no doubt that the various enzymes concerned with activation and acylation utilize both of these isomeric fatty acids as substrates.

Effects of Pantethine Supplementation to Diets with Different Energy Cereals on Hepatic Lipogenesis of Laying Hens

Effects on dietary pantethine supplementation on hepatic lipid accumulation and on the activities of lipogenic-related enzymes in the liver were studied in Single Comb White Leghorn laying hens fed isocaloric and isonitrogenous diets containing corn or barley as the carbohydrate source. Addition of 200 ppm pantethine to the corn-soy (CS) basal diet significantly reduced abdominal fat weight, liver triglyceride, as well as total cholesterol and 17β-estradiol concentrations in the plasma. Activities of citrate cleavage enzyme (EC 4.1.3.8; CCE) and fatty acid synthetase (FAS) in the liver were significantly reduced when the CS basal diet was supplemented with pantethine, but the activities of nicotinamide adenine dinucleotide phosphate-malate dehydrogenase (EC 1.1.1.40; NADP-MDH) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PDH), were not significantly affected. However, liver triglyceride, total cholesterol, and 17β-estradiol concentrations in plasma as well as the activities of CCE, FAS, and NADP-MDH in liver were significantly lower in laying hens fed the barley-soy (BS) basal diet than in those fed the CS basal diet. Pantethine supplementation to the BS diet failed to show any significant effect on liver triglyceride content and on the hepatic activities of lipogenic-related enzymes. There were no significant differences in liver weight, rate of egg production, and egg weight among dietary treatments, these results suggest that dietary pantethine is effective in reducing the accumulation of liver and abdominal fat in laying hens fed a CS diet.

Circadian Changes in Serum and Liver Metabolites and Liver Lipogenic Enzymes in Ad Libitum- and Meal-Fed, Lean and Obese Zucker Rats

Circadian rhythms were studied in ad libitum- and meal-fed Zucker rats. Lean and obese female rats were fed ad libitum or in a single meal from 1400–1800 for 12 d. Both groups of ad libitum-fed rats exhibited a nocturnal feeding pattern; obese rats ate more than the lean rats during the light and dark parts of the cycle. After 12 d, groups of rats were killed at 4-h intervals over a 24-h period, inclusively, and the presence of circadian rhythms was evaluated for the serum metabolites, liver constituents and the liver lipogenic enzymes. The obese ad libitum-fed rats demonstrated rhythms for serum triglycerides, serum cholesterol, liver protein and glycogen, and the activities of fatty acid synthetase, citrate cleavage enzyme (EC 4.1.3.8), and glucose-6-P dehydrogenase (EC 1.1.1.49). Meal feeding the obese rats modified the rhythms for serum cholesterol, liver glycogen and the activities of glucose-6-P dehydrogenase, and citrate cleavage enzyme and a rhythm was established for serum glucose. The feeding schedule did not cue a rhythm for serum tir-glycerides and phosphogluconate dehydrogenase (EC 1.1.1.44) or modify the rhythm for liver protein. The lean ad libitum-fed rats displayed rhythms for all the measured parameters except serum glucose. Feeding-cued rhythms for all metabolites except serum cholesterol were observed when the lean rats were meal-fed. These data suggest that the rhythms of the ad libitum-fed obese rats may not be similar to those observed in the lean rat. Yet, changing the feeding schedule may be important in establishing rhythm patterns that will alter the anabolic profile characteristic of the Zucker obese rat.

Effect of the peroxisomal proliferator di(2-ethylhexyl)phthalate on component reactions of the rat hepatic microsomal fatty acid chain elongation system and on other hepatic lipogenic enzymes

The feeding of 2% di(2-ethylhexyl)phthalate (DEHP) to rats increased the hepatic microsomal elongation of palmitoyl-CoA by about twofold, while those of palmitoleoyl-CoA and γ-linolenoyl-CoA decreased to 83 and 63%, respectively, of the control values. When component reactions of the elongation pathway were measured, it was observed that only the activity of condensing enzyme was increased by twofold, while those of β-ketostearoyl-CoA reductase, β-hydroxypalmitoyl-CoA dehydrase, and trans-2-hexadecenoyl-CoA reductases were not affected. Furthermore, the time course for induction of both condensation and elongation of palmitoyl-CoA was similar. In vitro addition of DEHP had no effect on either condensation or elongation. Thus, these results indicate that the peroxisomal proliferator induces only the condensing enzyme which is the regulatory and rate-limiting step of elongation sequence. The DEHP treatment also markedly enhanced the cytosolic NADPH-generating activities of glucose-6-PO 4 dehydrogenase (2.2-fold) and malic enzyme (7.3-fold). Unexpectedly, the activities of fatty acid synthetase and citrate cleavage enzyme were unaffected. These results are discussed in light of the fact that these lipogenic enzymes are coordinatively induced by diet or hormones.

Changes in the activities of hepatic lipogenic-related enzymes and in the concentrations of various plasma and liver lipid fractions in hens before and after the onset of laying.

The changes in the concentrations of various plasma and liver lipid fractions, plasma E2 and corticosterone, and hepatic lipogenic related enzyme (LRE) activities, were determined. The relationships between the concentrations of these plasma hormones and hepatic lipoge-nesis around the onset of egg production were elucidated.E2 concentration rose gradually as the hens advanced in age, reaching a peak at the age of 150 days which was the period immediately before the onset of egg laying. Triglyceride, NEFA, total cholesterol and phospholipid levels in the plasma remained relatively constant between 90 and 140 days of age. These rose rapidly as the birds neared the age of 150 days, and reached their peaks immediately before the onset of laying. These values decre-ased, and then remained stable, upon the onset of egg production; nevertheless, even at their reduced levels, they were still comparatively higher than these obtained during the 90-140 days of pre-ovulation period.Hepatic triglyceride content rose gradually and simulataneously with the aging of the hens and reached a peak immediately before the onset of laying. It decreased when the egg laying set in, but remained at a relatively higher level thereafter.The activities of hepatic LREs increased gradually as the hens advanced in age. Fatty acid synthetase reached a peak at 130 days of age and citrate cleavage enzyme and NADP-malate dehydro-genase, 140 days of age.Statistically significant positive correlations were observed between plasma E2 concentra-tion and the grouped parameters of abdominal fat weight (P<0.01), hepatic triglyceride content (P<0.01), concentrations of various plasma lipid fractions (P<0.01), and activities of fatty acid synthetase (P<0.05), NADP-malate dehydrogenase (P<0.05) and citrate cle-avage enzyme (P<0.05) in the liver of hens.

Lipogenesis and Lipolysis in Fed and Fasted Chicks from High and Low Body Weight Lines

Lipogenic and lipolytic capacities were examined in fasted and nonfasted 28-day-old chicks from high-weight (HW) and low-weight (LW) selected lines. Lipogenesis was assessed in liver and bone (sternum) tissues through the activities of malic enzyme (EC 1.1.1.40), citrate cleavage enzyme (EC 4.1.3.8), and acetyl coenzyme A carboxylase (EC 6.4.1.2), as well as through the in vitro incorporation of acetate-1-14C into liver and bone lipid fractions. Lipolysis was estimated through the in vitro release of free fatty acids (FFA) from abdominal adipose tissue and through plasma FFA.Fasting depressed lipogenesis and increased lipolysis. Regardless of the feeding state, LW chicks exhibited higher lipogenic and lipolytic capacities than their HW counterparts, suggesting that lipid degradation may be relatively more important than synthesis in determining net fat deposition. In addition, the incorporation of radioactive acetate into bone lipid was associated with detectable activity of lipogenic enzymes, providing further evidence that the skeleton is an important site of lipogenesis in the chicken.

Chronic hyperinsulinemia in the fetal rhesus monkey: Effects of physiologic hyperinsulinemia on fetal substrates, hormones, and hepatic enzymes

Chronic fetal hyperinsulinemia, similar to that found in human infants of diabetic mothers, was produced in fetal rhesus monkeys during the latter third of gestation. Fetal plasma glucose and amino acid concentrations were found to be inversely logarithmically correlated with plasma insulin concentration. Fetal plasma glucagon concentrations were suppressed by hyperinsulinemia. Fetal plasma erythropoietin concentrations were increased by hyperinsulinemia in a dose/response manner. The activity of the hepatic gluconeogenic enzymes glucose-6-phosphatase and total phosphoenolpyruvate carboxykinase were reduced by hyperinsulinemia. Fatty acid synthase complex activity was, in contrast, increased by hyperinsulinemia while citrate cleavage enzyme and glucose-6-phosphate dehydrogenase were only increased when supraphysiologic hyperinsulinemia was produced. This model provides an opportunity to study the metabolic effects of hyperinsulinemia separate from those of hyperglycemia on the primate fetus, making it a useful model for the study of fetal pathologic conditions in diabetic pregnancies.

Characterization of Plasma Hormone Levels and Lipogenic Enzyme Activity in Chickens Divergently Selected for Oxygen Consumption

The bases for differences in growth and metabolism of lines previously selected for divergence in O2 consumption in comparison to a randombred control population were studied. Body weights, carcass fat, plasma growth hormone (GH), triiodothyronine (T3), thyroxine (T4), malic enzyme, and citrate cleavage enzyme activities were determined. The early growth of the low O2 birds was greater than the high O2 birds, whereas the growth rate of the control population was intermediate to, but not statistically different from, the two O2 lines. Six-week body weights did not differ between the lines. Percent fat of the high O2 birds was less than the other two lines at 1 and 2 weeks of age but greater than the low O2 birds at 3 weeks of age. Percent fat did not differ between the lines at 6 weeks. Plasma T4 levels differed between the lines only at Day 1, when the control population exhibited greater T4 levels than the O2 lines. Plasma T3 levels were lower in the high O2 chicks in comparison to only the control chicks at 0, 1, and 2 weeks of age. No line differences in T3 levels were detected at 3 or 6 weeks. From 1 to 3 weeks, GH levels were greater in the low O2 birds than the high O2, while the control birds had GH levels intermediate to the O2 lines. By 6 weeks, the O2 lines had similar GH levels, but these levels were lower than those of the controls. No consistent line differences in malic enzyme or citrate cleavage enzyme activities were observed.

Hormone and Lipogenic Enzyme Response of the Heterozygous dw Chick to Dietary Protein Level

The growth and lipogenic responses of broiler progeny from normal (DωDω♂, Dω-♀) and dwarf (Dωdω♂, Dω-*♀) dams to high and low dietary protein were studied. Body weight gains for the DωDω compared to Dωdω male progeny were greater from week 1 to 3, but less from week 7 to 8 and were similar for Dω-* and Dω- females. No significant effects of progeny genotype and no diet × genotype interactions were observed for feed conversion, carcass nitrogen or fat, abdominal fat, growth hormone, triiodothyronine (T3) or thyroxine (T4). Hepatic malic enzyme was elevated in DωDω male progeny compared to Dωdω males, regardless of diet, and was greater in Dω- females than in Dω-* only in response to low dietary protein. Citrate cleavage enzyme was greater in Dω-* than in Dω- females. Low protein resulted in elevated lipogenic enzyme activities, which were more pronounced in progeny of normal dams. A positive relationship observed between malic enzyme activity and T3 levels for all progeny not carrying the dw gene suggests that although circulating levels of thyroid hormones did not differ between genotypes, the cellular response to these hormones was affected by the presence of the dω gene.

Development of fatty acid-synthetic capacity in interscapular brown adipose tissue during suckling in genetically obese Zucker rats.

The development of the lipogenic capacity in brown adipose tissue was studied in suckling lean (Fa/fa) and obese (fa/fa) Zucker pups aged from 7 to 22 days. In both lean and obese pups, activities of the two key lipogenic enzymes, fatty acid synthetase and acetyl-CoA carboxylase, and of citrate cleavage enzyme rose from the early to the late suckling period. Compared with lean pups, 7-day-old fa/fa pups showed a 35% increase in fat accumulation in interscapular brown adipose tissue and a 25% increase in fatty acid synthetase activity. By 10 days of age, fat deposition, lipogenesis in vivo (assessed by the incorporation of 3H from 3H2O into fatty acids) and fatty acid synthetase activity were 1.5-2-fold higher in pre-obese than in lean pups. Compared with lean pups, the increased lipogenesis in vivo observed in brown adipose tissue of 10-day-old pre-obese pups could not entirely account for the difference in fat deposition observed in this tissue, suggesting that additional mechanisms are at play to explain the increased fat content of this tissue.

Effect of specific dietary fatty acids on lipogenesis in the livers and mammary glands of lactating mice.

The effects of linoleic, linolenic and columbinic acids fed as 4% of a high carbohydrate (50% glucose) diet on the activities and the amounts of several enzymes associated with fatty acid synthesis in livers and mammary glands of lactating mice were compared with those for stearic and oleic acids. Fatty acid synthesis, measured in vivo, was significantly lower in livers of mice ingesting all 3 polyunsaturated fatty acids (PUFA), whereas in mammary glands synthesis was lower only in mice receiving columbinic acid. The activities of fatty acid synthetase (FAS) and acetyl CoA carboxylase were significantly reduced in liver by all 3 PUFA, as wee activities of glucose-6-phosphate dehydrogenase, malic enzyme (ME) and citrate cleavage enzyme (CCE), also associated with lipogenesis. In mammary gland, on the other hand, the activities of these enzymes were unaffected by dietary PUFA. The tissue contents of FAS, ME and CCE, measured by rocket immunoelectrophoresis, were found to be significantly reduced in liver by linoleate, linolenate and columbinate but were not significantly altered in mammary gland. The decrease in hepatic lipogenesis observed was principally due to a decrease in the amounts of these enzymes induced by the dietary PUFA but the inhibition in mammary gland caused by columbinate could not be accounted for by a reduction in enzyme contents and therefore may be due to allosteric effects which occur when fatty acid synthesis is measured with 3H2O. The fatty acid composition in liver and mammary gland of dams and in liver and kidney of pups completely reflected dietary fatty acids. Columbinate made up ca. 20% of the total fatty acids in both tissues of the columbinic acid-fed mice and ca. 15% in the pup tissues. This suggests that columbinate is incorporated into milk lipids of dams and is easily absorbed by pups. The elevated ratios of 16/16:1 and 18/18:1 in liver and mammary gland of dams and liver and kidney of the pups from dams fed linoleate, linolenate and columbinate suggest that each of these polyunsaturated fatty acids in the diet can inhibit the activity of delta 9 desaturase.