scholarly journals Glucose- and insulin-independent induction of ATP citrate lyase in primary cultures of rat hepatocytes

1983 ◽  
Vol 212 (1) ◽  
pp. 65-71 ◽  
Author(s):  
N R Katz ◽  
S Giffhorn
Keyword(s):  
Enzyme Activity ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Enzyme Protein ◽  
Atp Citrate Lyase ◽  
Adult Rats ◽  
Parallel Increase ◽  
Citrate Lyase ◽  
Initial Decrease ◽  
Translational Level

ATP citrate lyase, which is involved in the translocation of the lipogenic precursor acetyl-CoA from mitochondria to cytosol, was studied in primary cultures of hepatocytes from adult rats. After an initial decrease at the first day of culture the enzyme activity was nearly constant during the following days. It could be enhanced between 24h and 48 h in culture about 1.5-fold by elevation of the insulin concentration to 10-7mol/1.22-fold by elevation of the glucose concentration from 5 to 25 mmol/l and 3.5-fold by simultaneous elevation of insulin and glucose. The increase of activity was about linear with time for 24 h and could be blocked by cycloheximide, which inhibits protein synthesis at the translational level. Both observations suggest that the enhancement of activity was due to induction rather than to activation by interconversion. The glucose-dependent induction was furthermore evidenced by immunotitration which indicated a parallel increase of activity and enzyme protein.

scholarly journals Glucose-dependent induction of acetyl-CoA carboxylase in rat hepatocyte cultures

1984 ◽  
Vol 221 (2) ◽  
pp. 343-350 ◽  
Author(s):  
S Giffhorn ◽  
N R Katz
Keyword(s):  
Enzyme Activity ◽  
Enzyme Level ◽  
Enzyme Synthesis ◽  
Acetyl Coa Carboxylase ◽  
Enzyme Protein ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Adult Rats ◽  
Hepatocyte Cultures

The carbohydrate-dependent long-term regulation of acetyl-CoA carboxylase was studied in primary hepatocyte cultures from adult rats. (1) The enzyme activity was increased 2-fold either by elevation of the glucose concentration to 20mM or by enhancement of the insulin concentration to 0.1 microM. Simultaneous increases in glucose and insulin resulted in a 5-fold increase in the enzyme activity. (2) As shown by immunochemical titration, the enhancement of the enzyme activity was due to an increase in the enzyme protein. (3) Incorporation of [35S]methionine and immunoprecipitation of the enzyme revealed that the increase in enzyme protein was due to an increased rate of enzyme synthesis. The rate of enzyme degradation remained essentially unchanged. (4) The glucose- and insulin-dependent induction of acetyl-CoA carboxylase was prevented by the addition of alpha-amanitin (10 microM) or cordycepin (10 microM), indicating a transcriptional regulation of the enzyme level. (5) The parallel induction of acetyl-CoA carboxylase and of ATP citrate lyase indicates a co-ordinate long-term regulation of lipogenic enzymes.

INDUCTION BY GONADAL HORMONES OF HEPATIC LIPOGENIC ENZYME ACTIVITY IN IMMATURE PULLETS

1974 ◽  
Vol 61 (1) ◽  
pp. 29-43 ◽  
Author(s):  
D. BALNAVE ◽  
J. PEARCE
Keyword(s):  
Enzyme Activity ◽  
Corn Oil ◽  
Specific Activity ◽  
Liver Lipid ◽  
Lipogenic Enzyme ◽  
Atp Citrate Lyase ◽  
Liver Lipid Content ◽  
Hormone Administration ◽  
Citrate Lyase ◽  
Specific Activities

SUMMARY The effect of gonadal hormone administration on hepatic lipogenic enzyme activity, and some physiological parameters was investigated in immature pullets. Pullets (aged 4 weeks) were allocated to treatment groups and received intramuscular injections of oestradiol, testosterone, progesterone or oestradiol + testosterone (all in 0·3 ml corn oil) or corn oil alone (control group). There was no evidence of any hormone-induced changes in the specific activity of hepatic ATP-citrate lyase 1, 3, 6 and 12 h after hormone administration. NADP-malate dehydrogenase exhibited significant variations in specific activity over this period of time and it is probable that these changes reflected an increased requirement for NADPH for synthetic purposes in hormone-treated birds. The effect of 1, 2, 4 and 9 days of hormone administration was also investigated. In testosterone-treated birds there were significant increases in the specific activities of both lipogenic enzymes after 1 day of hormone treatment whereas for birds receiving oestradiol the maximum specific activities were found on the second day. Similarly, the liver lipid content of oestradioltreated birds showed a substantial increase on day 2. After 9 days of hormone administration no significant differences in the specific activity of ATP-citrate lyase were observed between treatments but the specific activity of NADP-malate dehydrogenase was significantly reduced in oestradiol- or mixed hormone-treated birds; it is possible that the reduced enzyme activity is associated with a reduced requirement for NADPH and in this connexion there were no further increases in liver lipid content or liver weight after 4 days of hormone administration. The liver RNA:DNA ratio tended to be greatest in birds receiving oestradiol or oestradiol + testosterone. Studies utilizing inhibitors of RNA and protein synthesis showed that such compounds abolished the increases in lipogenic enzyme activity following hormone administration suggesting that these increases were hormone-induced effects. These results are discussed in relation to the effects of the various hormones on liver lipid metabolism and also in relation to the situation in the mature laying hen.

scholarly journals Genetic control of metabolism: enzyme studies of the obese and adipose mutants in the mouse

1972 ◽  
Vol 20 (1) ◽  
pp. 51-64 ◽  
Author(s):  
Grahame Bulfield
Keyword(s):  
Enzyme Activity ◽  
Malate Dehydrogenase ◽  
Primary Lesion ◽  
Gas Liquid Chromatography ◽  
Wild Type ◽  
Atp Citrate Lyase ◽  
Citrate Lyase ◽  
Lyase Activity ◽  
Metabolism Enzyme ◽  
Pheno Type

SUMMARYThe activity of several enzymes has been determined in the livers of homozygous obese and adipose mice, their normal litter-mates, and phenocopies induced in normal mice by aurothioglucose (ATG) injections.Obese, adipose and ATG mice had higher activities of ATP citrate lyase, malic enzyme (NADP malate dehydrogenase) and pyruvate kinase than normal mice. Heterozygote activities are indistinguishable from wild-type. There was no difference between normal and fat litter-mates in the activity of malate dehydrogenase (NAD-linked), lactate dehydrogenase, isocitrate dehydrogenase and fumarase.Crosses between mice doubly heterozygous for roth the ad and ob genes produced offspring that were only ‘fat’ or ‘normal’ and no offspring could be phenotypically recognized as the double mutant, either physically or in terms of ATP citrate lyase activity.Gas–liquid chromatography of the fatty acids of the depot fat showed no differences between any of the types of litter-mate.The alterations found in enzyme activity in obese and adipose mice are compared to several other enzyme activity differences reported in the literature for obese mice. These are discussed in relation to genetical criteria that may be estarlished to assess, from quantitative data, whether an enzyme is the site of the primary lesion in a mutant pheno-type. Some general observations are made on genetics and the control of metabolism.

scholarly journals An investigation of lipogenic and glycolytic enzyme activity in the liver of sexually immature and mature domestic fowl

1971 ◽  
Vol 123 (5) ◽  
pp. 717-719 ◽  
Author(s):  
J. Pearce
Keyword(s):  
Enzyme Activity ◽  
Significant Variation ◽  
Egg Production ◽  
Liver Lipid ◽  
Laying Hen ◽  
Glycolytic Enzyme ◽  
Egg Laying ◽  
Atp Citrate Lyase ◽  
Liver Lipid Content ◽  
Citrate Lyase

In the non-laying pullet and the cockerel it was observed that there was no significant variation in the activities of ATP citrate lyase and `malic' enzyme whereas in the laying hen there was a significantly greater activity of both these enzymes. Parallel increases in liver lipid content in the laying hen were also observed. Three glycolytic enzymes, phosphofructokinase, fructose diphosphate aldolase and pyruvate kinase, did not exhibit any significant variation in enzyme activity with the onset of egg laying. These results are discussed in relation to the hormonal status of the birds and also the demands of egg production for lipid.

scholarly journals Ethanol modulation of the hormonal and nutritional regulation of glucose 6-phosphate dehydrogenase activity in primary cultures of rat hepatocytes

1984 ◽  
Vol 217 (2) ◽  
pp. 543-549 ◽  
Author(s):  
D S Kelley ◽  
R F Kletzien
Keyword(s):  
Enzyme Activity ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Fold Increase ◽  
Defined Medium ◽  
Nutritional Regulation ◽  
G6pdh Activity ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Dose Dependent ◽  
Permissive Role

The hormonal and nutritional regulation of glucose 6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) was studied in primary cultures of rat hepatocytes maintained in a chemically defined medium. Inoculation of hepatocytes from starved rats into primary cultures resulted in a 4-5-fold increase in G6PDH activity in 48 h in the absence of hormones. Parallel cultures treated simultaneously with glucocorticoids and insulin exhibited a 12-15-fold increase during the same time. Glucocorticoids by themselves did not elevate G6PDH activity, whereas insulin alone significantly stimulated enzyme activity. Thus the glucocorticoids acted in a ‘permissive’ role to amplify the insulin stimulation of G6PDH. Elevated concentrations of glucose in the culture medium increased enzyme activity in both the control cultures and those treated with hormones. Ethanol was found to potentiate G6PDH activity in cultures treated with glucocorticoids and insulin. The effect of ethanol was time- and dose-dependent. These results establish that insulin, glucocorticoids, glucose and ethanol interact in some undefined manner to regulate hepatic G6PDH activity.

scholarly journals Changes in hepatic lipogenesis during development of the rat

1967 ◽  
Vol 105 (2) ◽  
pp. 717-722 ◽  
Author(s):  
C B Taylor ◽  
E. Bailey ◽  
W Bartley
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Malic Enzyme ◽  
Female Rats ◽  
Male Rats ◽  
Acetate Incorporation ◽  
Atp Citrate Lyase ◽  
Citrate Lyase ◽  
Malic Enzyme Activity ◽  
Glucose 6 Phosphate Dehydrogenase

1. Changes in the activities of ATP citrate lyase, ‘malic’ enzyme, glucose 6-phosphate dehydrogenase, pyruvate kinase and fructose 1,6-diphosphatase, and in the ability to incorporate [1−14C]acetate into lipid have been measured in the livers of developing rats between late foetal life and maturity. 2. In male rats the activities of those systems directly or indirectly concerned in lipogenesis (acetate incorporation into lipid, ATP citrate lyase and glucose 6-phosphate dehydrogenase) fall after birth and are maintained at a low value until weaning. After weaning these activities rise to a maximum between 30 and 40 days and then decline, reaching adult values at about 60 days. ‘Malic’ enzyme activity follows a similar course, except that none could be detected in the foetal liver. Pyruvate kinase activity is lower in foetal than in adult livers and rises to slightly higher than the adult value in the post-weaning period. Fructose 1,6-diphosphatase activity rises from a very low foetal value to reach a maximum at about 10 days but falls rapidly after weaning to reach adult values at about 30 days. 3. Weaning rats on to a high-fat diet caused the low activities of acetate incorporation, ATP citrate lyase, glucose 6-phosphate dehydrogenase and pyruvate kinase, characteristic of the suckling period, to persist. ‘Malic’ enzyme and fructose 1,6-diphosphatase activities were not altered appreciably. 4. No differences could be detected in hepatic enzyme activities between males and females up to 35 days, but after this time female rats gave higher values for acetate incorporation, glucose 6-phosphate dehydrogenase activity and ‘malic’ enzyme activity. 5. The results are discussed in relation to changes in alimentation and hormonal influences.

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