Changes in the activities of the enzymes of hepatic fatty acid oxidation during development of the rat.
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ABSTRACT:
SUBMITTER: Foster PC
PROVIDER: S-EPMC1172675 | biostudies-other | 1976 Jan
REPOSITORIES: biostudies-other
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Project description:The liver is critical for maintaining systemic energy balance during starvation. To understand the role of hepatic fatty acid ?-oxidation on this process, we generated mice with a liver-specific knockout of carnitine palmitoyltransferase 2 (Cpt2(L-/-)), an obligate step in mitochondrial long-chain fatty acid ?-oxidation. Fasting induced hepatic steatosis and serum dyslipidemia with an absence of circulating ketones, while blood glucose remained normal. Systemic energy homeostasis was largely maintained in fasting Cpt2(L-/-) mice by adaptations in hepatic and systemic oxidative gene expression mediated in part by Ppar? target genes including procatabolic hepatokines Fgf21, Gdf15, and Igfbp1. Feeding a ketogenic diet to Cpt2(L-/-) mice resulted in severe hepatomegaly, liver damage, and death with a complete absence of adipose triglyceride stores. These data show that hepatic fatty acid oxidation is not required for survival during acute food deprivation but essential for constraining adipocyte lipolysis and regulating systemic catabolism when glucose is limiting.
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Project description:ObjectivesShcKO mice have low body fat and resist weight gain on a high fat diet, indicating that Shc proteins may influence enzymes involved in ?-oxidation. To investigate this idea, the activities of ?-oxidation and ketone body metabolism enzymes were measured.MethodsThe activities of ?-oxidation enzymes (acyl-CoA dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and ketoacyl-CoA thiolase) in liver and hindlimb skeletal muscle, ketolytic enzymes (acetoacetyl-CoA thiolase, ?-hydroxybutyrate dehydrogenase and 3-oxoacid-CoA transferase) in skeletal muscle, and ketogenic enzymes (acetoacetyl-CoA thiolase and ?-hydroxybutyrate dehydrogenase) in liver were measured from wild-type and ShcKO mice.ResultsThe activities of ?-oxidation enzymes were increased (P<.05) in the ShcKO compared to wild-type mice in the fasted but not the fed state. In contrast, no uniform increases in the ketolytic enzyme activities were observed between ShcKO and wild-type mice. In liver, the activities of ketogenic enzymes were increased (P<.05) in ShcKO compared to wild-type mice in both the fed and fasted states. Levels of phosphorylated hormone sensitive lipase from adipocytes were also increased (P<.05) in fasted ShcKO mice.ConclusionThese studies indicate that the low Shc levels in ShcKO mice result in increased liver and muscle ?-oxidation enzyme activities in response to fasting and induce chronic increases in the activity of liver ketogenic enzymes. Decreases in the level of Shc proteins should be considered as possible contributors to the increase in activity of fatty acid oxidation enzymes in response to physiological conditions which increase reliance on fatty acids as a source of energy.
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Project description:The concentration of hepatic fatty acid-binding protein was determined in the livers of rats at various stages of development from foetus to young adult. Fatty acid-binding protein concentrations were determined by quantifying the fluorescence enhancement on the binding of the fluorescent probe 11-(dansylamino)-undecanoic acid. A 20-fold increase in the concentration of the protein was observed between the foetus and adult, and this increase was confirmed by immuno-blotting. No other protein in the 14,000-Mr range was observed in the foetus. Possible alternative fatty acid-binding proteins could not be detected in h.p.l.c.-fractionated foetal cytosol by the fluorescence-enhancement method.
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Project description:In response to infection, patients with inborn errors of metabolism may develop a functional deterioration termed metabolic decompensation. The biochemical hallmarks of this disruption of metabolic homeostasis are disease specific and may include acidosis, hyperammonemia or hypoglycemia. In a model system previously published by our group, we noted that during influenza infection, mice displayed a depression in hepatic mitochondrial enzymes involved in nitrogen metabolism. Based on these findings, we hypothesized that this normal adaptation may extend to other metabolic pathways, and as such, may impact various inborn errors of metabolism. Since the liver is a critical organ in inborn errors of metabolism, we carried out untargeted metabolomic profiling of livers using mass spectrometry in C57Bl/6 mice infected with influenza to characterize metabolic adaptation. Pathway analysis of metabolomic data revealed reductions in CoA synthesis, and long chain fatty acyl CoA and carnitine species. These metabolic adaptations coincided with a depression in hepatic long chain β-oxidation mRNA and protein. To our surprise, the metabolic changes observed occurred in conjunction with a hepatic innate immune response, as demonstrated by transcriptional profiling and flow cytometry. By employing an immunomodulation strategy to deplete Kupffer cells, we were able to improve the expression of multiple genes involved in β-oxidation. Based on these findings, we are the first to suggest that the role of the liver as an immunologic organ is central in the pathophysiology of hepatic metabolic decompensation in inborn errors of metabolism due to respiratory viral infection.
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Project description:This SuperSeries is composed of the SubSeries listed below.
2021-06-29 | GSE179053 | GEO
Project description:Fatty-acids (FAs) are required in the diet of many animals throughout their life. However, the mechanisms involved in the perception of and preferences for dietary saturated and unsaturated FAs (SFAs and UFAs, respectively) remain poorly explored, especially in insects. Using the model species Drosophila melanogaster, we measured the responses of wild-type larvae and adults to pure SFAs (14, 16, and 18 carbons) and UFAs (C18 with 1, 2, or 3 double-bonds). Individual and group behavioral tests revealed different preferences in larvae and adults. Larvae preferred UFAs whereas SFAs tended to induce both a strong aversion and a persistent aggregation behavior. Adults generally preferred SFAs, and laid more eggs and had a longer life span when ingesting these substances as compared to UFAs. Our data suggest that insects can discriminate long-chain dietary FAs. The developmental change in preference shown by this species might reflect functional variation in use of FAs or stage-specific nutritional requirements, and may be fundamental for insect use of these major dietary components.
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Project description:Peroxisome proliferator-activated receptor ? (PPAR?) belongs to the nuclear receptor family and is involved in metabolic diseases. Although PPAR? is known to attenuate hepatic lipid deposition, its mechanism remains unclear. Here, we show that PPAR? is a potent stimulator of hepatic autophagic flux. The expression levels of PPAR? and autophagy-related proteins were decreased in liver tissues from obese and ageing mice. Pharmacological and adenovirus-mediated increases in PPAR? expression and activity were achieved in obese transgenic db/db and high fat diet-fed mice. Using genetic, pharmacological and metabolic approaches, we demonstrate that PPAR? reduces intrahepatic lipid content and stimulates ?-oxidation in liver and hepatic cells by an autophagy-lysosomal pathway involving AMPK/mTOR signalling. These results provide novel insight into the lipolytic actions of PPAR? through autophagy in the liver and highlight its potential beneficial effects in NAFLD.
| S-EPMC6393554 | biostudies-literature
Project description:Hepatic steatosis is associated with detrimental metabolic phenotypes including enhanced risk for diabetes. Stearoyl-CoA desaturases (SCDs) catalyze the synthesis of MUFAs. In mice, genetic ablation of SCDs reduces hepatic de novo lipogenesis (DNL) and protects against diet-induced hepatic steatosis and adiposity. To understand the mechanism by which hepatic MUFA production influences adipose tissue stores, we created two liver-specific transgenic mouse models in the SCD1 knockout that express either human SCD5 or mouse SCD3, that synthesize oleate and palmitoleate, respectively. We demonstrate that hepatic de novo synthesized oleate, but not palmitoleate, stimulate hepatic lipid accumulation and adiposity, reversing the protective effect of the global SCD1 knockout under lipogenic conditions. Unexpectedly, the accumulation of hepatic lipid occurred without induction of the hepatic DNL program. Changes in hepatic lipid composition were reflected in plasma and in adipose tissue. Importantly, endogenously synthesized hepatic oleate was associated with suppressed DNL and fatty acid oxidation in white adipose tissue. Regression analysis revealed a strong correlation between adipose tissue lipid fuel utilization and hepatic and adipose tissue lipid storage. These data suggest an extrahepatic mechanism where endogenous hepatic oleate regulates lipid homeostasis in adipose tissues.
| S-EPMC4306685 | biostudies-literature
Project description: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-(14)C]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.
| S-EPMC1198369 | biostudies-other
Project description:1. In the absence of added carnitine pronounced changes occur during development, in the degradation of [U-(14)C]palmitate to (14)C-labelled acid-soluble material (predominantly ketone bodies) and (14)CO(2) by liver homogenates. The formation of both products by liver homogenates of 5-day-old rats is considerably higher than in foetal livers. This high value is maintained during the suckling period and falls after weaning to adult values which are similar to those of the foetus. Addition of carnitine stimulates production of acid-soluble material throughout development. The effect of added carnitine on CO(2) production varies with age, stimulating in foetal and post-weaning age groups but inhibiting during the suckling period. 2. The degradation of [U-(14)C]palmitate to acid-soluble material and CO(2) by heart homogenates also varies during development. Formation of both products is highest 5 days after birth and thereafter decreases steadily to adult values. Addition of carnitine stimulates the production of both CO(2) and acid-soluble material at all ages. 3. The activity of carnitine palmitoyltransferase in liver increased after birth to reach maximum activity at 2-5 days of age. Thereafter the activity of the enzyme decreased until day 15 of life and then remained constant until day 30, decreasing after this time to adult values which were about one half of the foetal liver activities.
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