Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

Duée, Pierre‐Henri; Pégorier, Jean‐Paul; Quant, Patti A.; Herbin, Catherine; Kohl, Claude; Girard, Jean

doi:10.1042/bj2980207

Cited by 46 publications

(34 citation statements)

References 37 publications

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“…No significant interaction was found. As expected, BHB production was low as it is known that ketogenic capacity of liver from newborn pigs is much lower than in other mammalian species (Duée et al, 1994) and low ketone production persists in the adult pig (Duée et al, 1994). BHB levels in the present study were in the lower range to previously reported values for hepatocytes isolated from 60 kg pigs (Fernández-Fígares et al, 2004).…”

Section: Bhb Synthesiscontrasting

confidence: 50%

Metabolic differences in hepatocytes of obese and lean pigs

González-Valero

Rodríguez-López

Lachica

et al. 2014

Animal

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There are important differences in terms of metabolic activity, energy utilization and capacity of protein and fat deposition when Iberian and modern pigs are compared. Primary culture of hepatocytes was used to evaluate hepatic function and sensitivity to hormones between breeds without the interference of circulating blood factors. Hepatocytes were isolated from pure Iberian (n = 10) and Landrace (n = 8) pigs of similar BW (24.5 ± 12.1 and 32.9 ± 6.1 kg BW, respectively), by collagenase perfusion. Monolayers were established in medium containing fetal bovine serum for 1 day and switched to serum-free medium for the remainder of the culture period. Hepatocytes were maintained in William's E supplemented with β-mercaptoethanol (0.1 mM), glutamine (2 mM), antibiotics (gentamicin, penicillin, streptomycin and amphotericin B), dimethyl sulfoxide (1 µg/ml), dexamethasone (10 −8 M), insulin (0.173 and 17.3 nM) and glucagon (0.287, 2.87 and 28.7 nM) for 24 to 48 h. Gluconeogenesis (GNG), glycogen degradation, triglycerides (TG) content and esterification, β-hydroxybutyrate (BHB) synthesis, IGF-1 synthesis, albumin and urea synthesis were determined. Iberian pigs had greater capacity of GNG than Landrace (24%, P < 0.05), although no difference in glycogen degradation was found (P > 0.10). TG content and esterification tended to be lower in hepatocytes from Iberian compared with Landrace pigs (12% and 31%, respectively; 0.10 < P < 0.05). Furthermore, addition of free fatty acids (CLA or linoleic acid, 0.2 mM) increased TG content (64%, P < 0.001) although no difference between fatty acids was found. When free fatty acids were compared, a trend toward increased esterification (41%, P = 0.078) was found for CLA. Although glucagon stimulated and insulin inhibited BHB synthesis, no difference between breeds was found (P > 0.10). IGF-1 synthesis was diminished in hepatocytes from Iberian compared with Landrace pigs (16%, P < 0.05). On the contrary, rate of albumin synthesis was greater in Iberian compared with Landrace pigs (58%, P < 0.05). Finally, the capacity of urea synthesis was lower in hepatocytes of Iberian compared with Landrace pigs (37%, P < 0.05). When ammonia was added to the media, urea concentration increased (648%, 1108% and 2791% when 0 mM was compared with 2.5, 5 and 10 mM, respectively). Urea synthesis increased on increasing ammonia content (55% and 325% when 0 mM was compared with 5 and 10 mM, respectively; P < 0.0001). In conclusion, the genetic background accounts for important differences in protein and energy metabolism pathways found in primary culture of hepatocytes from lean and obese pigs.Keywords: hepatocytes, metabolism, pig ImplicationsSeveral studies have shown the existence of numerous dissimilarities in metabolic activity between Iberian and modern pig breeds that might be explained by genotypic differences. Primary hepatocyte cultures are a valuable tool to study specific metabolic liver functions, without the interference of changing levels of metabolites and hormones found in vivo. These...

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Section: Bhb Synthesiscontrasting

confidence: 50%

Metabolic differences in hepatocytes of obese and lean pigs

González-Valero

Rodríguez-López

Lachica

et al. 2014

Animal

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“…Fatty acids constitute about 60% of the total energy in porcine milk, and neonates rely heavily on fatty acids for survival [1]. Because piglets seem to have a limited mitochondrial P-oxidation of longchain fatty acids [3][4][5]20], a relatively large contribution of peroxisomal P-oxidation may act as a compensatory mechanism to use milk-derived fatty acids, which in porcine milk are almost exclusively long-chain fatty acids [25],…”

Section: ß-Oxidation In Piglet Livermentioning

confidence: 99%

“…Ketogenesis from fatty acids is a normal com ponent of the adaptations in neonates of rats and many other species [1], Recent evidence [2][3][4][5] from research using a variety of experi mental approaches has indicated that piglets have a limited ketogenic capacity relative to the adult rat which has been the most widely studied model. Because the mortality of pig lets and other neonates remains a major prob lem, an increased understanding of the meta bolic adaptations that occur after birth is im portant.…”

mentioning

confidence: 99%

Response of Hepatic Mitochondrial and Peroxisomal β-Oxidation to Increasing Palmitate Concentrations in Piglets

Yu¹,

Drackley²,

Odle³

et al. 1997

Neonatology

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Responses of total, mitochondrial, and peroxisomal β-oxidation to increasing [1-¹⁴C]-palmitate concentrations (0.02–1.0 mM) were measured in liver homogenates from neonatal pigs. Incubations were conducted in the absence (total β-oxidation) or presence (peroxisomal β-oxidation) of antimycin A and rotenone; mitochondrial β-oxidation was calculated as total minus peroxisomal oxidation. Total and mitochondrial β-oxidations were maximized at a palmitate concentration of 0.05 mM, whereas peroxisomal β-oxidation was maximized at 0.50 mM palmitate. Across concentrations, peroxisomal β-oxidation contributed 40–47% of total β-oxidation. An increased rate of CO₂ production and a greater ratio of CO₂ production to total mitochondrial β-oxidation as palmitate concentration increased suggested that the limited capacity for mitochondrial β-oxidation was attributable primarily to limited ketogenic capacity. Comparative observations in liver from adult rats showed that peroxisomal β-oxidation was maximized at 0.1 mM palmitate, but total and mitochondrial β-oxidation rates were not maximized even at 1 mM palmitate. At 1 mM palmitate, peroxisomal β-oxidation was 20% of total β-oxidation in adult rats and 37% in adult pigs. Therefore, the contribution of peroxisomal β-oxidation to total β-oxidation is highly dependent on substrate concentration and appears to be greater in adult pigs than in adult rats. The greater proportional contribution of peroxisomal β-oxidation in piglet liver might act as a compensatory mechanism for piglets to oxidize milk fatty acids.

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“…The attenuated activity of mHMGCS appears not to be associated with a low mRNA abundance but rather a low rate of translation (5). The physiological significance of the unique structure of hepatic CPT I is not known, but it was suggested that fatty acid oxidation in mitochondria may be limited in neonatal pigs due to the diminished ketogenic pathway (8). This prompted us to investigate the oxidation occurring in peroxisomes (which is usually considered an ancillary oxidative pathway to mitochondria oxidation), because acetate is reported to be the primary product of peroxisomal ␤-oxidation (18) due to the high level of short-chain acyl-CoA thioesterase (39).…”

mentioning

confidence: 99%

“…The porcine CPT I protein is a natural chimera of the more typical mammalian liver (L) and muscle (M)-CPT I isotypes, containing the L-CPT I binding site for acyl-CoA and the M-CPT I binding sites for carnitine and malonyl-CoA. Besides the unique structure of porcine CPT I, the activity of mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase (mHMGCS), the key enzyme regulating ketogenesis, is extremely low in suckling piglets, which results in the reduced ketogenesis (8). The attenuated activity of mHMGCS appears not to be associated with a low mRNA abundance but rather a low rate of translation (5).…”

mentioning

confidence: 99%

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

Lin

Shim

Odle

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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Lin X, Shim K, Odle J. Carnitine palmitoyltransferase I control of acetogenesis, the major pathway of fatty acid ␤-oxidation in liver of neonatal swine. Am J Physiol Regul Integr Comp Physiol 298: R1435-R1443, 2010. First published March 17, 2010 doi:10.1152/ajpregu.00634.2009.-To examine the regulation of hepatic acetogenesis in neonatal swine, carnitine palmitoyltransferase I (CPT I) activity was measured in the presence of varying palmitoyl-CoA (substrate) and malonyl-CoA (inhibitor) concentrations, and [1-14 C]-palmitate oxidation was simultaneously measured. Accumulation rates of 14 C-labeled acetate, ketone bodies, and citric acid cycle intermediates within the acid-soluble products were determined using radio-HPLC. Measurements were conducted in mitochondria isolated from newborn, 24-h (fed or fasted), and 5-mo-old pigs. Acetate rather than ketone bodies was the predominant radiolabeled product, and its production increased twofold with increasing fatty acid oxidation during the first 24-h suckling period. The rate of acetogenesis was directly proportional to CPT I activity. The high activity of CPT I in 24-h-suckling piglets was not attributable to an increase in CPT I gene expression, but rather to a large decrease in the sensitivity of CPT I to malonyl-CoA inhibition, which offset a developmental decrease in affinity of CPT I for palmitoyl-CoA. Specifically, the IC 50 for malonyl-CoA inhibition and Km value for palmitoyl-CoA measured in 24-h-suckling pigs were 1.8-and 2.7-fold higher than measured in newborn pigs. The addition of anaplerotic carbon from malate (10 mM) significantly reduced 14 C accumulation in acetate (P Ͻ 0.003); moreover, the reduction was much greater in newborn (80%) than in 24-h-fed (72%) and 5-mo-old pigs (55%). The results demonstrate that acetate is the primary product of hepatic mitochondrial ␤-oxidation in Sus scrofa and that regulation during early development is mediated primarily via kinetic modulation of CPT I. acetate; anaplerosis; carnitine palmitoyltransferase I activity; ketone bodies; mitochondria; Sus scrofa IT IS WELL ESTABLISHED THAT hepatic long-chain fatty acid oxidation is acutely controlled by a system in which carnitine palmitoyltransferase I (CPT I) is regulated allosterically by a change in malonyl-CoA concentration and/or the sensitivity to malonyl-CoA inhibition. This regulatory mechanism dictates fatty acid flux into mitochondria and controls the rates of ␤-oxidation and ketogenesis based on the animal's physiological status. The neonatal period represents a physiological state characterized by marked enhancement of fatty acid oxidation and ketogenesis. Both humans and rats present a significant hyperketonemia during the suckling period (40). Evidence confirms that the physiological hyperketonemia is a result of the high hepatic ketogenic rate in neonates consuming a diet (i.e., milk) that is high in fat and low in carbohydrate. In fact, more than 90% of the non-CO 2 carbon derived from fatty acid oxidation in liver homogenates is ketone bodies (21). Wh...

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Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

Cited by 46 publications

References 37 publications

Metabolic differences in hepatocytes of obese and lean pigs

Metabolic differences in hepatocytes of obese and lean pigs

Response of Hepatic Mitochondrial and Peroxisomal β-Oxidation to Increasing Palmitate Concentrations in Piglets

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

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