Disposition of [U-2H7]glucose into hepatic glycogen in rat and in seabass

Martins, Fátima O.; Rito, João; Jarak, Ivana; Viegas, Iván; Pardal, Miguel Ângelo; Macedo, M. Paula; Jones, John G.

doi:10.1016/j.cbpa.2013.07.002

Cited by 16 publications

(21 citation statements)

References 31 publications

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“…It also explains the high rates of futile glucose–G6P cycling observed under feeding conditions since both GK and G6Pase are active at the same time ( 13 , 32 , 45 ) . Metabolic fluxes obtained from 2 H NMR in the present study and other studies ( 46 ) associated with the lack of response observed in pyruvate kinase (present study), and PFK-1 ( 45 , 47 ) , located downstream of G6P in the glycolytic pathway, seem to support this assumption. Along with this futile cycling of glucose, the contribution of glycogen conversion to glucose via glycosidases ( EC 3.2.1, includes glucosidases, amylases and glycogen-debranching enzymes) is yet to be evaluated.…”

Section: Discussionsupporting

confidence: 88%

Contribution of dietary starch to hepatic and systemic carbohydrate fluxes in European seabass (Dicentrarchus labraxL.)

et al. 2015

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In the present study, the effects of partial substitution of dietary protein by digestible starch on endogenous glucose production were evaluated in European seabass (Dicentrarchus labrax). The fractional contribution of dietary carbohydrates v. gluconeogenesis to blood glucose appearance and hepatic glycogen synthesis was quantified in two groups of seabass fed with a diet containing 30 % digestible starch (DS) or without a carbohydrate supplement as the control (CTRL). Measurements were performed by transferring the fish to a tank containing water enriched with 5 % 2 H 2 O over the last six feeding days, and quantifying the incorporation of 2 H into blood glucose and hepatic glycogen by 2 H NMR. For CTRL fish, gluconeogenesis accounted for the majority of circulating glucose while for the DS fish, this contribution was significantly lower (CTRL 85 (SEM 4) % v. DS 54 (SEM 2) %; P,0·001). Hepatic glycogen synthesis via gluconeogenesis (indirect pathway) was also significantly reduced in the DS fish, in both relative (CTRL 100 (SEM 1) % v. DS 72 (SEM 1) %; P, 0·001) and absolute terms (CTRL 28 (SEM 1) v. DS 17 (SEM 1) mmol/kg per h; P,0·001). A major fraction of the dietary carbohydrates that contributed to blood glucose appearance (33 (SEM 1) % of the total 47 (SEM 2) %) had undergone exchange with hepatic glucose 6-phosphate. This indicated the simultaneous activity of hepatic glucokinase and glucose 6-phosphatase. In conclusion, supplementation of digestible starch resulted in a significant reduction of gluconeogenic contributions to systemic glucose appearance and hepatic glycogen synthesis. Key words:2 H 2 O: Gluconeogenesis: Endogenous glucose production: Glucokinase: Starch utilisationIn aquaculture, substituting costly fishmeal with less expensive plant-derived carbohydrate (CHO) reduces feed input costs. The provision of dietary CHO to carnivorous fish such as the European seabass (Dicentrarchus labrax L.) may also have environmental benefits since CHO utilisation can potentially spare the catabolism of dietary amino acids to glucose and nitrogenous waste (1) . Dietary CHO influences growth, feed utilisation and deposition of nutrients according to species, quantity, origin and pre-treatment for improving digestibility (2 -4) . The effects of partial substitution of dietary protein by plant-derived CHO on food conversion efficiency and nutrient digestibility sources have been tested in seabass (5 -7) . In addition, its effects on energy retention and maintenance requirements (8) as well as the activity of key CHO-metabolising enzymes (6,9) have been studied. These studies have suggested that, on the one hand, carnivorous fish are able to up-regulate their capacity for hepatic glucose utilisation through the increased expression of gateway enzymes such as glucokinase when fed with a high-CHO diet. However, on the other hand, supplementation of fish feed with up to 30 % starch has not been shown to alter the overall protein efficiency ratio or nitrogen retention in seabass (7) . This is despite...

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Section: Discussionsupporting

confidence: 88%

Contribution of dietary starch to hepatic and systemic carbohydrate fluxes in European seabass (Dicentrarchus labraxL.)

et al. 2015

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“…Hepatic glycogen levels were also significantly different between fasted seabream and fasted seabass ( P < 0.0005, respectively). Compared to our previous study with 90 g fasted seabass 9 , liver glycogen levels were somewhat higher: 8.4 ± 0.5 g.100 g −1 liver in this study versus 6.6 ± 0.6 g.100 g −1 liver previously. From a comparison of hepatic glycogen levels in saline-injected versus glucose-injected seabass, the glucose load resulted in a significant increase in hepatic glycogen levels of fasted fish while it had no significant effects on glycogen levels of fed fish (Table 1 ).…”

Section: Resultscontrasting

confidence: 96%

“…In the 2 H NMR spectrum, the position 2 intensity appears to be less than that of position 5 - consistent with a previous seabass study of glycogen enrichment from 2 H 2 O 13 . This is due to a significant kinetic isotope effect that limits the exchange between the hydrogen 2 of G6P and body water 9 thereby decreasing the enrichment of this specific site from 2 H 2 O. The magnitude of this effect can be quantified from the analysis of glycogen 2 H-enrichment from [U- 2 H 7 ]glucose allowing the position 2 enrichment from 2 H 2 O to be corrected for incomplete exchange 9 (see Table 2 ).…”

Section: Resultsmentioning

confidence: 99%

“…To our knowledge, direct and indirect pathway contributions to hepatic glycogen synthesis following a glucose load have not been reported for any fish species. This setting is expected to maximize direct pathway activity due to the high availability of glucose that in turn promotes insulin secretion 8 and activation of hepatic glycogen synthesis 9 . A glucose load can be enriched with [U- 13 C 6 ]glucose whose incorporation into hepatic glycogen can be used to independently measure direct and indirect pathway contributions of the glucose load to glycogen synthesis 14 .…”

Section: Introductionmentioning

confidence: 99%

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Disposition of a Glucose Load into Hepatic Glycogen by Direct and Indirect Pathways in Juvenile Seabass and Seabream

Rito

Viegas

Pardal

et al. 2018

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In carnivorous fish, conversion of a glucose load to hepatic glycogen is widely used to assess their metabolic flexibility towards carbohydrate utilization, but the activities of direct and indirect pathways in this setting are unclear. We assessed the conversion of an intraperitoneal glucose load (2 g.kg−1) enriched with [U-13C6]glucose to hepatic glycogen in juvenile seabass and seabream. 13C-NMR analysis of glycogen was used to determine the contribution of the load to glycogen synthesis via direct and indirect pathways at 48-hr post-injection. For seabass, [U-13C6]glucose was accompanied by deuterated water and 2H-NMR analysis of glycogen 2H-enrichment, allowing endogenous substrate contributions to be assessed as well. For fasted seabass and seabream, 47 ± 5% and 64 ± 10% of glycogen was synthesized from the load, respectively. Direct and indirect pathways contributed equally (25 ± 3% direct, 21 ± 1% indirect for seabass; 35 ± 7% direct, 29 ± 4% indirect for seabream). In fasted seabass, integration of 2H- and 13C-NMR analysis indicated that endogenous glycerol and anaplerotic substrates contributed an additional 7 ± 2% and 7 ± 1%, respectively. In fed seabass, glucose load contributions were residual and endogenous contributions were negligible. Concluding, direct and indirect pathways contributed equally and substantially to fasting hepatic glycogen repletion from a glucose load in juvenile seabream and seabass.

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“…G-6-P, glucose-6-phosphate; Gly-3-P, glyceraldehyde-3-phosphate; DHAP, dihydroxyacetone phosphate; OA, oxaloacetate; PEP, phosphoenolpyruvate; AA, amino acids. stable isotope tracer methodologies, that are highly practical for juvenile fish raised in small recirculating systems in the research setting (Viegas et al, 2012(Viegas et al, , 2015(Viegas et al, , 2016Martins et al, 2013;Rito et al, 2018Rito et al, , 2019.…”

Section: Introductionmentioning

confidence: 99%

Limitations to Starch Utilization in Barramundi (Lates calcarifer) as Revealed by NMR-Based Metabolomics

et al. 2020

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Practical diets for commercial barramundi production rarely contain greater than 10% starch, used mainly as a binding agent during extrusion. Alternative ingredients such as digestible starch have shown some capacity to spare dietary protein catabolism to generate glucose. In the present study, a carnivorous fish species, the Asian seabass (Lates calcarifer) was subjected to two diets with the same digestible energy: Protein (P)-with high protein content (no digestible starch); and Starch (S)-with high digestible (pregelatinized) starch content. The effects of a high starch content diet on hepatic glycogen synthesis as well as the muscle and liver metabolome were studied using a complementary approach of 1 H and 2 H NMR. The hepatosomatic index was lower for fish fed high starch content diet while the concentration of hepatic glycogen was similar between groups. However, increased glycogen synthesis via the direct pathway was observed in the fish fed high starch content diet which is indicative of increased carbohydrate utilization. Multivariate analysis also showed differences between groups in the metabolome of both tissues. Univariate analysis revealed more variations in liver than in muscle of fish fed high starch content diet. Variations in metabolome were generally in agreement with the increase in the glycogen synthesis through direct pathway, however, this metabolic shift seemed to be insufficient to keep the growth rate as ensured by the diet with high protein content. Although liver glycogen does not make up a substantial quantity of total stored dietary energy in carnivorous fish, it is a key regulatory intermediate in dietary energy utilization.

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Disposition of [U-2H7]glucose into hepatic glycogen in rat and in seabass

Cited by 16 publications

References 31 publications

Contribution of dietary starch to hepatic and systemic carbohydrate fluxes in European seabass (Dicentrarchus labraxL.)

Contribution of dietary starch to hepatic and systemic carbohydrate fluxes in European seabass (Dicentrarchus labraxL.)

Disposition of a Glucose Load into Hepatic Glycogen by Direct and Indirect Pathways in Juvenile Seabass and Seabream

Limitations to Starch Utilization in Barramundi (Lates calcarifer) as Revealed by NMR-Based Metabolomics

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