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A wave of Foxp3 + regulatory T cell accumulation in the neonatal liver plays unique roles in maintaining self-tolerance. Cell Mol Immunol 2019; 17:507-518. [PMID: 31171863 DOI: 10.1038/s41423-019-0246-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/15/2019] [Indexed: 12/24/2022] Open
Abstract
Newborn animals require tightly regulated local and systemic immune environments to govern the development and maturation of multiple organs/tissues even though the immune system itself is far from mature during the neonatal period. Regulatory T cells (Tregs) are essential for maintaining immune tolerance/homeostasis and modulating inflammatory responses. The features of Tregs in the neonatal liver under steady-state conditions are not well understood. The present study aimed to investigate the phenotype, functions, and significance of neonatal Tregs in the liver. We found a wave of thymus-derived Treg influx into the liver during 1-2 weeks of age. Depletion of these Tregs between days 7 and 11 after birth rapidly resulted in Th1-type liver inflammation and metabolic disorder. More Tregs in the neonatal liver than in the spleen underwent MHC II-dependent activation and proliferation, and the liver Tregs acquired stronger suppressive functions. The transcriptomic profile of these neonatal liver Tregs showed elevated expression of PPARγ and T-bet and features of Tregs that utilize lipid metabolic machinery and are capable of regulating Th1 responses. The accumulation of Tregs with unique features in the neonatal liver is critical to ensure self-tolerance and liver maturation.
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Epigenetic Switching and Neonatal Nutritional Environment. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1012:19-25. [PMID: 29956191 DOI: 10.1007/978-981-10-5526-3_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The hepatic metabolic function changes sequentially during early life in mammals to adapt to the drastic changes in the nutritional environment. Accordingly, hepatic fatty acid β-oxidation is activated after birth to produce energy from breast milk lipids. De novo lipogenesis is induced upon the onset of oral intake, when the major nutritional source switches to carbohydrate. However, how a particular metabolic pathway is activated during the liver maturation is poorly understood. We found that the expression of glycerol-3-phosphate acyltransferase 1 (GPAT1), a rate-limiting enzyme of de novo hepatic lipogenesis, is epigenetically regulated in the mouse liver by DNA methylation. In the neonatal liver, DNA methylation of the GPAT1 gene (Gpam) promoter, which is likely to be induced by DNA methyltransferase (Dnmt) 3b, inhibited the recruitment of sterol regulatory element-binding protein-1c (SREBP-1c), whereas in the adult, decreased DNA methylation resulted in active chromatin conformation, allowing the recruitment of SREBP-1c. Maternal nutritional environment affects the DNA methylation status in the Gpam promoter, GPAT1 expression, and triglyceride content in the liver of the offspring. We also found DNA demethylation and increased mRNA expression of the fatty acid β-oxidation genes in the postnatal mouse liver. The DNA demethylation is specifically induced in the lactation period. Analysis of mice deficient in the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) and maternal administration of a PPARα ligand during the gestation and lactation periods reveals that the DNA demethylation is PPARα-dependent. These findings indicate the gene- and lifestage-specific DNA demethylation of a particular metabolic pathway in the neonatal liver to adapt the marked changes in nutritional environment in early life.
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Renaud HJ, Cui YJ, Lu H, Zhong XB, Klaassen CD. Ontogeny of hepatic energy metabolism genes in mice as revealed by RNA-sequencing. PLoS One 2014; 9:e104560. [PMID: 25102070 PMCID: PMC4125194 DOI: 10.1371/journal.pone.0104560] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/14/2014] [Indexed: 12/18/2022] Open
Abstract
The liver plays a central role in metabolic homeostasis by coordinating synthesis, storage, breakdown, and redistribution of nutrients. Hepatic energy metabolism is dynamically regulated throughout different life stages due to different demands for energy during growth and development. However, changes in gene expression patterns throughout ontogeny for factors important in hepatic energy metabolism are not well understood. We performed detailed transcript analysis of energy metabolism genes during various stages of liver development in mice. Livers from male C57BL/6J mice were collected at twelve ages, including perinatal and postnatal time points (n = 3/age). The mRNA was quantified by RNA-Sequencing, with transcript abundance estimated by Cufflinks. One thousand sixty energy metabolism genes were examined; 794 were above detection, of which 627 were significantly changed during at least one developmental age compared to adult liver. Two-way hierarchical clustering revealed three major clusters dependent on age: GD17.5–Day 5 (perinatal-enriched), Day 10–Day 20 (pre-weaning-enriched), and Day 25–Day 60 (adolescence/adulthood-enriched). Clustering analysis of cumulative mRNA expression values for individual pathways of energy metabolism revealed three patterns of enrichment: glycolysis, ketogenesis, and glycogenesis were all perinatally-enriched; glycogenolysis was the only pathway enriched during pre-weaning ages; whereas lipid droplet metabolism, cholesterol and bile acid metabolism, gluconeogenesis, and lipid metabolism were all enriched in adolescence/adulthood. This study reveals novel findings such as the divergent expression of the fatty acid β-oxidation enzymes Acyl-CoA oxidase 1 and Carnitine palmitoyltransferase 1a, indicating a switch from mitochondrial to peroxisomal β-oxidation after weaning; as well as the dynamic ontogeny of genes implicated in obesity such as Stearoyl-CoA desaturase 1 and Elongation of very long chain fatty acids-like 3. These data shed new light on the ontogeny of homeostatic regulation of hepatic energy metabolism, which could ultimately provide new therapeutic targets for metabolic diseases.
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Affiliation(s)
- Helen J. Renaud
- Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Yue Julia Cui
- Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Hong Lu
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York, United States of America
| | - Xiao-bo Zhong
- Department of Pharmaceutical Sciences, University of Connecticut School of Pharmacy, Storrs, Connecticut, United States of America
| | - Curtis D. Klaassen
- College of Medicine, University of Kansas, Kansas City, Kansas, United States of America
- * E-mail:
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Ehara T, Kamei Y, Takahashi M, Yuan X, Kanai S, Tamura E, Tanaka M, Yamazaki T, Miura S, Ezaki O, Suganami T, Okano M, Ogawa Y. Role of DNA methylation in the regulation of lipogenic glycerol-3-phosphate acyltransferase 1 gene expression in the mouse neonatal liver. Diabetes 2012; 61:2442-50. [PMID: 22721968 PMCID: PMC3447899 DOI: 10.2337/db11-1834] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 04/19/2012] [Indexed: 12/17/2022]
Abstract
The liver is a major organ of lipid metabolism, which is markedly changed in response to physiological nutritional demand; however, the regulation of hepatic lipogenic gene expression in early life is largely unknown. In this study, we show that expression of glycerol-3-phosphate acyltransferase 1 (GPAT1; Gpam), a rate-limiting enzyme of triglyceride biosynthesis, is regulated in the mouse liver by DNA methylation, an epigenetic modification involved in the regulation of a diverse range of biological processes in mammals. In the neonatal liver, DNA methylation of the Gpam promoter, which is likely to be induced by Dnmt3b, inhibited recruitment of the lipogenic transcription factor sterol regulatory element-binding protein-1c (SREBP-1c), whereas in the adult, decreased DNA methylation resulted in active chromatin conformation, allowing recruitment of SREBP-1c. Maternal overnutrition causes decreased Gpam promoter methylation with increased GPAT1 expression and triglyceride content in the pup liver, suggesting that environmental factors such as nutritional conditions can affect DNA methylation in the liver. This study is the first detailed analysis of the DNA-methylation-dependent regulation of the triglyceride biosynthesis gene Gpam, thereby providing new insight into the molecular mechanism underlying the epigenetic regulation of metabolic genes and thus metabolic diseases.
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Affiliation(s)
- Tatsuya Ehara
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
- Functional Food Research Department, Food Science and Technology Institute, Morinaga Milk Industry Co., Ltd., Kanagawa, Japan
| | - Yasutomi Kamei
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Organ Network and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Mayumi Takahashi
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Xunmei Yuan
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Sayaka Kanai
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Erina Tamura
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Miyako Tanaka
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Organ Network and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tomomi Yamazaki
- Nutritional Science Program, National Institute of Health and Nutrition, Tokyo, Japan
| | - Shinji Miura
- Nutritional Science Program, National Institute of Health and Nutrition, Tokyo, Japan
| | - Osamu Ezaki
- Nutritional Science Program, National Institute of Health and Nutrition, Tokyo, Japan
| | - Takayoshi Suganami
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Masaki Okano
- Laboratory for Mammalian Epigenetic Studies, Center for Developmental Biology, RIKEN, Kobe, Japan
| | - Yoshihiro Ogawa
- Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
- Department of Molecular Endocrinology and Metabolism, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
- Global Center of Excellence Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
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Bernard A, Rigault C, Mazue F, Le Borgne F, Demarquoy J. L-carnitine supplementation and physical exercise restore age-associated decline in some mitochondrial functions in the rat. J Gerontol A Biol Sci Med Sci 2008; 63:1027-33. [PMID: 18948552 DOI: 10.1093/gerona/63.10.1027] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In mammals, during the aging process, an atrophy of the muscle fibers, an increase in body fat mass, and a decrease in skeletal muscle oxidative capacities occur. Compounds and activities that interact with lipid oxidative metabolism may be useful in limiting damages that occur in aging muscle. In this study, we evaluated the effect of L-carnitine and physical exercise on several parameters related to muscle physiology. We described that supplementing old rats with L-carnitine at 30 mg/kg body weight for 12 weeks (a) allowed the restoration of L-carnitine level in muscle cells, (b) restored muscle oxidative activity in the soleus, and (c) induced positive changes in body composition: a decrease in abdominal fat mass and an increase in muscle capabilities without any change in food intake. Moderate physical exercise was also effective in (a) limiting fat mass gain and (b) inducing an increase in the capacities of the soleus to oxidize fatty acids.
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Affiliation(s)
- Arnaud Bernard
- INSERM, U866, Université de Bourgogne, 6 boulevard Gabriel, 21000 Dijon, France
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6
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Rigault C, Le Borgne F, Georges B, Demarquoy J. Ghrelin reduces hepatic mitochondrial fatty acid beta oxidation. J Endocrinol Invest 2007; 30:RC4-8. [PMID: 17556859 DOI: 10.1007/bf03346290] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ghrelin is a 28-amino-acid peptide secreted during starvation by gastric cells. Ghrelin physiologically induces food intake and seems to alter lipid and glucid metabolism in several tissues such as adipose tissue and liver. Liver has a key position in lipid metabolism as it allows the metabolic orientation of fatty acids between oxidation and esterification. We investigated the effects of peripheral ghrelin administration on 2 crucial parameters of fatty acid oxidation: the levocarnitine (L-carnitine)-dependent entry of the fatty acids in the mitochondria and the mitochondrial fatty acid oxidation. Ghrelin was either given to rats prior to the hepatocyte preparation and culture or used to treat hepatocytes prepared from control animals. Direct incubation of ghrelin to raw hepatocytes did not induce any change in the studied parameters. In hepatocytes prepared from 3 nmol ghrelin-treated rats, a 44% reduction of the mitochondrial fatty acid oxidation while no alteration of the L-carnitine-related parameters were observed. These results suggested (a) that ghrelin has no direct effect on liver, and (b) that when administrated to a whole organism, ghrelin may alter the lipid metabolism and the energy balance through a marked decrease in liver fatty acid oxidation.
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Affiliation(s)
- C Rigault
- INSERM, Faculty of Sciences Gabriel, Metabolic and Nutritional Biochemics (LBMN), University of Burgundy, Dijon, France
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Lin X, Odle J. Changes in kinetics of carnitine palmitoyltransferase in liver and skeletal muscle of dogs (Canis familiaris) throughout growth and development. J Nutr 2003; 133:1113-9. [PMID: 12672928 DOI: 10.1093/jn/133.4.1113] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This study was conducted to investigate developmental changes in the kinetics of carnitine palmitoyltransferase (CPT) within hepatic and skeletal muscle tissues of the canine species. Carnitine concentrations, CPT activity and the apparent K(m) for carnitine were measured in tissue homogenates from dogs in six age categories: newborn; 24-h-old; 3-, 6- and 9-wk-old; and adult. Hepatic CPT activity was low at birth, increased by 100% during the suckling period (P < 0.05) and then declined after weaning to adult levels. In contrast, CPT activity in muscle continued to increase with age, reaching adult levels after 9 wk. Congruent with CPT activity, nearly identical concentration profiles of liver and muscle acylcarnitines were observed. The apparent K(m) of hepatic CPT for carnitine also paralleled the increase in CPT activity during the suckling period; however, free and total liver carnitine concentrations declined by 50% during this time (P < 0.05). Beginning at 3 wk of age, the hepatic concentration of free carnitine was at or below the apparent K(m) of CPT for carnitine. A similar relationship existed in muscle of young dogs, but in adults, the free carnitine concentration was markedly increased and exceeded the apparent K(m) by 5-fold. Collectively, we infer that fatty acid oxidation capacity increases rapidly after birth in the canine, after ontogenic increases in CPT activity. Furthermore, based on the relatively low tissue carnitine concentrations when compared with the apparent carnitine K(m) of CPT, we suggest that carnitine may have an important role in the regulation of fatty acid oxidation and that increased dietary carnitine may improve fatty acid oxidative capacity in developing dogs.
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Affiliation(s)
- Xi Lin
- Department of Animal Science, North Carolina State University, Raleigh 27695-7621, USA
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8
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Plonné D, Schulze HP, Kahlert U, Meltke K, Seidolt H, Bennett AJ, Cartwright IJ, Higgins JA, Till U, Dargel R. Postnatal development of hepatocellular apolipoprotein B assembly and secretion in the rat. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31513-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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9
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Bremer J. The biochemistry of hypo- and hyperlipidemic fatty acid derivatives: metabolism and metabolic effects. Prog Lipid Res 2001; 40:231-68. [PMID: 11412891 DOI: 10.1016/s0163-7827(01)00004-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A selection of amphipatic hyper- and hypolipidemic fatty acid derivatives (fibrates, thia- and branched chain fatty acids) are reviewed. They are probably all ligands for the peroxisome proliferation activation receptor (PPARalpha) which has a low selectivity for its ligands. These compounds give hyper- or hypolipidemic responses depending on their ability to inhibit or stimulate mitochondrial fatty acid oxidation in the liver. The hypolipidemic response is explained by the following metabolic effects: Lipoprotein lipase is induced in liver where it is normally not expressed. Apolipoprotein CIII is downregulated. These two effects in liver lead to a facilitated (re)uptake of chylomicrons and VLDL, thus creating a direct transport of fatty acids from the gut to the liver. Fatty acid metabolizing enzymes in the liver (CPT-I and II, peroxisomal and mitochondrial beta-oxidation enzymes, enzymes of ketogenesis, and omega-oxidation enzymes) are induced and create an increased capacity for fatty acid oxidation. The increased oxidation of fatty acids "drains" fatty acids from the body, reduces VLDL formation, and ultimately explains the antiadiposity and improved insulin sensitivity observed after administration of peroxisome proliferators.
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Affiliation(s)
- J Bremer
- Institute of Medical Biochemistry, University of Oslo, Pb 1112 Blindern, 0317, Oslo, Norway
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Lane RH, Kelley DE, Gruetzmacher EM, Devaskar SU. Uteroplacental insufficiency alters hepatic fatty acid-metabolizing enzymes in juvenile and adult rats. Am J Physiol Regul Integr Comp Physiol 2001; 280:R183-90. [PMID: 11124150 DOI: 10.1152/ajpregu.2001.280.1.r183] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple adult morbidities are associated with intrauterine growth retardation (IUGR) including dyslipidemia. We hypothesized that uteroplacental insufficiency and subsequent IUGR in the rat would lead to altered hepatic fatty acid metabolism. To test this hypothesis, we quantified hepatic mRNA levels of acetyl-CoA carboxylase (ACC), carnitine palmitoyltransferase (CPTI), the beta-oxidation-trifunctional protein (HADH), fasting serum triglycerides, and hepatic malonyl-CoA levels at different ages in control and IUGR rats. Fetal gene expression of all three enzymes was decreased. Juvenile gene expression of CPTI and HADH continued to be decreased, whereas gene expression of ACC was increased. Serum triglycerides were unchanged. A sex-specific response was noted in the adult rats. In males, serum triglycerides, hepatic malonyl-CoA levels, and ACC mRNA levels were significantly increased, and CPTI and HADH mRNA levels were significantly decreased. In contrast, the female rats demonstrated no significant changes in these variables. These results suggest that uteroplacental insufficiency leads to altered hepatic fatty acid metabolism that may contribute to the adult dyslipidemia associated with low birth weight.
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Affiliation(s)
- R H Lane
- Department of Pediatrics, University of California Los Angeles School of Medicine, Mattel Children's Hospital at UCLA, Los Angeles, California 90095, USA.
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11
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Cohen I, Girard J, Prip-Buus C. Biogenesis of the rat liver mitochondrial carnitine palmitoyltransferase I. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 466:1-16. [PMID: 10709623 DOI: 10.1007/0-306-46818-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme et Développement CNRS UPR1524, Meudon, France
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12
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Lionetti L, Iossa S, Liverini G, Brand MD. Changes in the hepatic mitochondrial respiratory system in the transition from weaning to adulthood in rats. Arch Biochem Biophys 1998; 352:240-6. [PMID: 9587412 DOI: 10.1006/abbi.1998.0579] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study we investigated the changes in the hepatic mitochondrial respiratory system in the transition from weaning to adulthood in the rat. We conceptually divided the system into blocks of reactions that produced or consumed mitochondrial membrane potential and then measured the kinetic responses of these blocks of reactions to changes in this potential in isolated liver mitochondria from 25- and 60-day-old rats using succinate as substrate. Moreover, we considered the mitochondrial membrane potential producers to be divided into blocks of reactions that reduced or oxidized ubiquinone-2 (Q-2) and then measured the kinetic responses of these two blocks to changes in Q-2 redox state as well as the flux control coefficients and the cytochrome content. We found that adult rats exhibited significantly higher state 3 respiratory rates with increased kinetic response of the substrate oxidation pathway to the mitochondrial membrane potential, slightly decreased activity of the phosphorylating system, increased kinetic responses of both Q-2 reducers and oxidizers to Q-2 redox state, and increased cytochrome content. Our results indicate that important changes in the hepatic mitochondrial respiratory system occur in the transition from weaning to adulthood in rats.
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Affiliation(s)
- L Lionetti
- Department of General and Environmental Physiology, University of Naples, Italy
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Iossa S, Mollica MP, Lionetti L, Barletta A, Liverini G. Rat liver mitochondrial respiratory capacities in the transition from weaning to adulthood. Mech Ageing Dev 1998; 100:59-66. [PMID: 9509395 DOI: 10.1016/s0047-6374(97)00124-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the present study we investigated the changes in hepatic mitochondrial function in the transition from weaning to adulthood in the rat. We measured mitochondrial respiration using FAD- and NAD-linked substrates in 25 and 60 day old rats. The results show that adult rats exhibited significantly higher respiratory rates with all the substrates used except pyruvate. Our results indicate that the transition from weaning to adulthood induces important changes in hepatic mitochondrial function.
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Affiliation(s)
- S Iossa
- Department of General and Environmental Physiology, University of Naples Federico II, Italy.
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14
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Abstract
The in vitro and in vivo effects of lovastatin on fatty acid metabolism were studied in isolated rat hepatocytes. When added in vitro to cell incubations, lovastatin stimulated de novo fatty acid synthesis and acetyl-CoA carboxylase activity, whereas fatty acid synthase activity was unaffected. Lovastatin depressed palmitate, but not octanoate, oxidation. This may be attributed to the lovastatin-induced increase in intracellular malonyl-CoA levels, as no concomitant change of carnitine palmitoyltransferase I (CPT-I) specific activity was detected. Lovastatin had no effect on the synthesis and secretion of triacylglycerols and phospholipids in the form of very low density lipoproteins (VLDL). When rats were fed a diet supplemented with 0.1% (w/w) lovastatin for one week, both acetyl-CoA carboxylase activity and de novo fatty acid synthesis were reduced compared to pair-fed controls, whereas fatty acid synthase activity was unaffected. Palmitate oxidation was enhanced in the lovastatin-fed group. There was an increase in CPT-I activity but no change in intracellular concentration of malonyl-CoA. Lovastatin feeding had no significant effect either on the esterification of exogenous palmitic acid into both cellular and VLDL triacylglycerols and phospholipids or on hepatic lipid accumulation. The in vitro and in vivo effects of lovastatin were not significantly different between periportal and perivenous hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Guzmán
- Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, Madrid, Spain
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Guzmán M, Geelen MJ. Regulation of fatty acid oxidation in mammalian liver. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1167:227-41. [PMID: 8097629 DOI: 10.1016/0005-2760(93)90224-w] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- M Guzmán
- Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, Madrid, Spain
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16
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Skrede S, Bremer J. Acylcarnitine formation and fatty acid oxidation in hepatocytes from rats treated with tetradecylthioacetic acid (a 3-thia fatty acid). BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1167:189-96. [PMID: 8466948 DOI: 10.1016/0005-2760(93)90161-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In livers of rats fed a single morning dose of 100 mg tetradecylthioacetic acid (TTA) total long-chain acyl-CoA increased significantly to 3 times control levels within 6 h, then the level declined almost to control value within the next morning. Hepatic malonyl-CoA was reduced 75% 6 h after TTA treatment. From 6 to 24 h malonyl-CoA increased about 10-fold to about 3 times that of controls. Paradoxically there was nearly a 2-fold higher oxidation of both [1-14C]palmitic acid (0.5 mM) and [1-14C]oleic acid (0.5 mM) in hepatocytes isolated from rats 24 h after TTA treatment compared to controls. After 6 h, when malonyl-CoA was at a minimum in vivo, fatty acid oxidation in cells was not increased. Acylcarnitine formation in digitonin permeabilized hepatocytes isolated 24 h after administration of TTA was increased both in the absence and in the presence of malonyl-CoA. At 24 h peroxisomal palmitoyl-CoA oxidase activity was not increased. The results suggest that an increased CPT activity and increased acylcarnitine formation in the presence of malonyl-CoA is a delayed response to increased acyl-CoA levels. Furthermore, in hepatocytes isolated after 24 h incorporation of [1-14C]oleic acid into triacylglycerols was significantly reduced. The data show that in hepatocytes isolated from rats 24 h after administration of a single dose of TTA, there is a diversion of hepatic acyl-CoA from synthesis of triacylglycerols into beta-oxidation in the mitochondria.
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Affiliation(s)
- S Skrede
- Institute of Medical Biochemistry, University of Oslo, Norway
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17
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Quant PA, Robin D, Robin P, Girard J, Brand MD. A top-down control analysis in isolated rat liver mitochondria: can the 3-hydroxy-3-methylglutaryl-CoA pathway be rate-controlling for ketogenesis? BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1156:135-43. [PMID: 8427872 DOI: 10.1016/0304-4165(93)90128-u] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We incubated isolated liver mitochondria with palmitoyl-CoA, 2,4-dinitrophenol and malonate. Under these conditions all the flux of carbon from palmitoyl-CoA was directed towards acetoacetate synthesis. We measured the rate of acetyl-CoA formation from palmitoyl-CoA (by measuring the rate of oxygen consumption) and the rate of acetoacetate production from acetyl-CoA at three different acetyl-CoA/CoA ratios. Using the top-down approach of metabolic control analysis we calculated the control over ketogenesis exerted by (a) the conversion of extramitochondrial palmitoyl-CoA to intramitochondrial acetyl-CoA and by (b) the conversion of acetyl-CoA to acetoacetate (the 'HMG-CoA pathway'). The overall flux control coefficients of the groups of enzymes involved in (a) and (b) over ketogenesis were 0.28 and 0.72, respectively. Our results show that it is possible for significant control to be exerted over ketogenesis by the enzymes of the HMG-CoA pathway.
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Affiliation(s)
- P A Quant
- Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, Centre National de la Recherche Scientifique, Meudon-Bellevue, France
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18
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Abstract
Metabolic control analysis (MCA) has provided the language and framework for quantitative study of control over flux, or over metabolites, by individual enzymes of a pathway. By contrast, top-down control analysis (TDCA) yields an immediate overview of the control structure of the whole system of interest, giving information about the control exercised by large sections of complex pathways. Unlike MCA, TDCA does not rely on the use of specific inhibitors or genetic manipulation to determine control coefficients. The method and an application of TDCA to ketogenesis are described.
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Affiliation(s)
- P A Quant
- Department of Biochemistry, University of Cambridge, UK
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Prip-Buus C, Bouthillier-Voisin AC, Kohl C, Demaugre F, Girard J, Pegorier JP. Evidence for an impaired long-chain fatty acid oxidation and ketogenesis in Fao hepatoma cells. ACTA ACUST UNITED AC 1992; 209:291-8. [PMID: 1356769 DOI: 10.1111/j.1432-1033.1992.tb17288.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Fatty acid metabolism has been studied in Fao rat hepatoma cells. In basal conditions of culture, [1-14C]oleate is mainly esterified (85% of oleate uptake) in Fao cells, phospholipids being the most important esterified products (60% of oleate esterified). Addition of N6,O2'-dibutyryl-adenosine 3',5'-monophosphate (0.1 mM) in Fao cells does not change the metabolic fate of oleate whereas it induces gluconeogenesis and phosphoenolpyruvate carboxykinase mRNA accumulation. It is shown that the limitation of oleate oxidation is located at the level of the entry into mitochondria since octanoate is actively oxidized in Fao cells. Neither the activities of carnitine palmitoyltransferase (CPT) I and II nor the CPT II protein amount are affected by cAMP addition. The limitation of oleate oxidation in Fao cells results from (a) a high rate of lipogenesis and a high malonyl-CoA concentration, (b) a CPT I very sensitive to malonyl-CoA inhibition. The presence of an active oleate oxidation in mitochondria isolated from Fao cells confirms that CPT I is the limiting step of oleate oxidation. Moreover, Fao cells are unable to perform ketogenesis. This particular feature results from a specific deficiency in mitochondrial hydroxymethylglutaryl-CoA synthase protein, activity and gene expression. The metabolic characteristics observed in Fao cells could be a common feature in hepatoma cell lines with regard to the low capacity for long-chain fatty acid oxidation and ketone body production observed in the rat H4IIE and the human HepG2 cells.
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Affiliation(s)
- C Prip-Buus
- Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, Meudon-Bellevue, France
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Pénicaud L, Robin D, Robin P, Kandé J, Picon L, Girard J, Ferré P. Effect of insulin on the properties of liver carnitine palmitoyltransferase in the starved rat: assessment by the euglycemic hyperinsulinemic clamp. Metabolism 1991; 40:873-6. [PMID: 1861636 DOI: 10.1016/0026-0495(91)90018-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effect of insulin on the properties of liver carnitine palmitoyltransferase I (CPT I) was assessed in conscious starved rats with the euglycemic hyperinsulinemic clamp. A 24-hour clamp was necessary to fully reverse the effect of starvation on liver malonyl-CoA concentration, CPT I maximal activity, and apparent km and Ki for malonyl-CoA. Since glucagon was not decreased during the clamp, insulin is the major factor involved in the regulation of CPT I.
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Affiliation(s)
- L Pénicaud
- Centre de Recherche sur la Nutrition, CNRS, Meudon-Bellevue, France
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21
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Pauly DF, Kirk KA, McMillin JB. Carnitine palmitoyltransferase in cardiac ischemia. A potential site for altered fatty acid metabolism. Circ Res 1991; 68:1085-94. [PMID: 2009609 DOI: 10.1161/01.res.68.4.1085] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The sensitivity of carnitine palmitoyl coenzyme A (CoA) transferase I to inhibition of its activity by malonyl-CoA is progressively reduced in mitochondria isolated from ischemic cardiac cells as blood flow decreases to 30% or less of the preocclusion flow. The activity of carnitine palmitoyl-CoA transferase I in mitochondria isolated from nonischemic cardiac cells demonstrates incomplete inhibition, even at high concentrations of malonyl-CoA. Kinetic analyses of these data gave results most consistent with the expression of two overt enzyme activities: one activity that is sensitive to inhibition by malonyl-CoA and one activity that demonstrates little or no sensitivity to such inhibition. The decrease in malonyl-CoA-sensitive activity associated with ischemia results from a 13% decrease in the activity of the sensitive component and a corresponding 13% increase in the activity of the insensitive component. Decreased sensitivity of ischemic carnitine palmitoyl-CoA transferase I to inhibition by malonyl-CoA, together with potential fluctuations in the content of malonyl-CoA in tissue, would increase the synthesis of palmitoylcarnitine during ischemia and facilitate return to the use of fatty acid as a preferred metabolic fuel on reperfusion. This apparent conversion occurs concomitantly with a decrease in the free protein thiol content of the mitochondrial membranes isolated from ischemic cardiac cells. Treatment of the mitochondria from ischemic cardiac cells with dithiothreitol in vitro partially reverses the loss in sensitivity to malonyl-CoA, suggesting the possible role of thiol oxidation in the altered metabolism of ischemic mitochondria. Western blot analysis of these mitochondria using an antibody against carnitine palmitoyltransferase II purified from beef heart demonstrates a 68-kDa protein, which under ischemic conditions apparently is decreased by 2 kDa. These results are more indicative of a modification in protein folding of carnitine palmitoyltransferase than proteolytic changes during ischemia.
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Affiliation(s)
- D F Pauly
- Department of Medicine, University of Alabama, Birmingham
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Guzmán M, Castro J. Alterations in the regulatory properties of hepatic fatty acid oxidation and carnitine palmitoyltransferase I activity after ethanol feeding and withdrawal. Alcohol Clin Exp Res 1990; 14:472-7. [PMID: 2378434 DOI: 10.1111/j.1530-0277.1990.tb00506.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of prolonged ethanol feeding on the regulatory properties of both hepatic fatty acid oxidation and carnitine palmitoyltransferase I activity (CPT-I) were studied in rats fed a high-fat diet containing 36% of total calories as ethanol (ethanol group) or an isocaloric amount of carbohydrate (control group). Prolonged ethanol feeding progressively decreased CPT-I activity and increased enzyme sensitivity and sensitization to inhibition by malonyl-CoA in liver mitochondria. Similarly, long-term ethanol feeding progressively increased the sensitivity of CPT-I, as well as that of fatty acid oxidation, to inhibition by 4-hydroxyphenylglyoxylate. Short-term addition of ethanol or acetaldehyde to the incubations markedly increased the sensitivity of CPT-I to inhibition by malonyl-CoA in a subsequent assay in hepatocytes isolated from ethanol-treated rats, but not in cells from control animals. This effect may be mediated by the ethanol- or acetaldehyde-induced increase of intracellular malonyl-CoA levels. The present results show that ethanol feeding to rats leads to profound alterations in the regulatory properties of hepatic CPT-I, which seem to be determinant for the decreased capacity of fatty acid oxidation by the liver in this state. Nevertheless, all the above-mentioned alterations of the fatty acid oxidative system were reversible, disappearing after 2 to 4 days of ethanol withdrawal.
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Affiliation(s)
- M Guzmán
- Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, Madrid, Spain
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McGarry JD, Woeltje KF, Kuwajima M, Foster DW. Regulation of ketogenesis and the renaissance of carnitine palmitoyltransferase. DIABETES/METABOLISM REVIEWS 1989; 5:271-84. [PMID: 2656156 DOI: 10.1002/dmr.5610050305] [Citation(s) in RCA: 239] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- J D McGarry
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas
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