In vitro and in vivo suppression of gluconeogenesis by inhibition of pyruvate carboxylase

Bahl, Joseph J.; Matsuda, Masafumi; DeFronzo, Ralph A.; Bressler, Rubin

doi:10.1016/s0006-2952(96)00660-0

Cited by 64 publications

(48 citation statements)

References 40 publications

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“…On the other hand, triose phosphate and pentose cycling as well as transaldolase reactions could each contribute by approximately 2 % to overestimation of GNG from the C5:C2 ratio [40] but they should have no influence on 13 C NMR spectroscopy measurements [25]. Alternatively, NEFA could directly stimulate gluconeogenesis either by supplying the energy necessary for [41] or activating key enzymes of gluconeogenesis like pyruvate carboxylase, or both [42,43] or phosphoenolpyruvate carboxykinase [44].…”

Section: Resultsmentioning

confidence: 99%

Lipid-dependent control of hepatic glycogen stores in healthy humans

et al. 2001

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Increased endogenous glucose production (EGP) could contribute to fasting hyperglycaemia in Type II (non-insulin-dependent) diabetes mellitus and could result from increased rates of glycogenolysis or gluconeogenesis (GNG) AbstractAims/hypothesis. Non-esterified fatty acids and glycerol could stimulate gluconeogenesis and also contribute to regulating hepatic glycogen stores. We examined their effect on liver glycogen breakdown in humans.Methods. After an overnight fast healthy subjects participated in three protocols with lipid/heparin (plasma non-esterified fatty acids: 2.2 0.1 mol/l; plasma glycerol: 0.5 0.03 mol/l; n = 7), glycerol (0.4 0.1 mol/l; 1.5 0.2 mol/l; n = 5) and saline infusion (control; 0.5 0.1 mol/l; 0.2 0.02 mol/l; n = 7). Net rates of glycogen breakdown were calculated from the decrease of liver glycogen within 9 h using ), respectively. Conclusion/interpretation: An increase of non-esterified fatty acid leads to a pronounced inhibition of net hepatic glycogen breakdown and increases gluconeogenesis whereas glucose production does not differ from the control condition. We suggest that this effect is not due to increased availability of glycerol alone but rather to lipid-dependent control of hepatic glycogen stores. [Diabetologia (2001) 44: 48±54]

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Section: Resultsmentioning

confidence: 99%

Lipid-dependent control of hepatic glycogen stores in healthy humans

et al. 2001

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“…Throughout the study, we have used PAA, the most widely used inhibitor of pyruvate carboxylase; so far, effects of PAA other than on metabolism and insulin secretion have not been reported in beta cells [13,14]. However, we acknowledge that pharmacological inhibitors must be used with great caution, since non-specific effects can never be entirely excluded.…”

Section: Discussionmentioning

confidence: 99%

“…The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells as compared with islet non-beta-cells [11], and ∼40% of pyruvate entering the tricarboxylic acid cycle during glucose stimulation is carboxylated by pyruvate carboxylase [12], indicating a critical role of the enzyme. Indeed, inhibition of pyruvate carboxylase with phenylacetic acid (PAA) [13] decreases insulin secretion in INS-1 cells, 832/13 cells and rat islets [14][15][16]. PAA is metabolised to phenylacetyl-CoA intracellularly, and inhibits pyruvate carboxylase by competing with acetyl-CoA, a key regulator of the enzyme [17].…”

Section: Introductionmentioning

confidence: 99%

Anaplerosis via pyruvate carboxylase is required for the fuel-induced rise in the ATP:ADP ratio in rat pancreatic islets

et al. 2006

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Aims/hypothesis: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. Methods: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K + channel (K ATP -channel) conductance. Results: We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca 2+ -induced exocytosis and K ATP -channel conductance in single cells, were unaffected. Insulin secretion induced by α-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K ATP -independent actions of fuel secretagogues are operational, as well as the first and K ATPdependent phase. Conclusions/interpretation: Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion.

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“…The addition of DMM to our cell line most responsive to glucose, 832/13, nearly doubled insulin secretion at 12 mmol/l glucose and caused an increase in pyruvate cycling as measured by NMR (22). As a second test, phenylacetic acid (PAA), a well-known inhibitor of PC (17,26), was added to 832/13 cells in the presence of stimulatory glucose (12 mmol/l), resulting in a 50% inhibition of insulin secretion and a parallel decrease in pyruvate cycling (22). Remarkably, the data points created for 832/13 cells treated with DMM or PAA fell on the line relating pyruvate cycling and GSIS for the four independent INS-1Ϫderived cell lines (Fig.…”

Section: Application Of Nmr-based Metabolic Analysis To Glucose-respomentioning

confidence: 99%

Stimulus/Secretion Coupling Factors in Glucose-Stimulated Insulin Secretion

Newgard

Jensen

et al. 2002

Diabetes

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There is a growing appreciation for the complexity of the pathways involved in glucose-stimulated insulin secretion (GSIS) from pancreatic islet ␤-cells. In our laboratory, this has stimulated the development of an interdisciplinary approach to the problem. In this study, we review recent studies combining the tools of recombinant adenovirus for gene delivery, the development of novel cell lines that exhibit either robust or weak GSIS, and nuclear magnetic resonance imaging for metabolic fingerprinting of glucose-stimulated cells. Using these tools, we demonstrate a potentially important role for pyruvate carboxylase؊mediated pyruvate cycling pathways in the control of GSIS, and discuss potential coupling factors produced by such pathways. Diabetes 51 (Suppl. 3):S389 -S393, 2002 A fundamental property of pancreatic islet ␤-cells is their capacity to secrete insulin in response to changes in glucose concentrations. A complete understanding of the biochemical mechanism of glucose-stimulated insulin secretion (GSIS) would be extremely valuable for the development of new therapies for both major forms of diabetes. GSIS is perhaps the seminal example of metabolism as a signaling mechanism. However, unlike classic hormonal signaling pathways involving well-characterized receptors and transducing molecules (e.g., signaling by glucagon or ␤-adrenergic agonists), the full picture of metabolismbased signaling is not yet available. This is true in part because we are just beginning to realize that GSIS is likely to involve more than one, and perhaps several, signaling events that converge to activate exocytosis of insulincontaining secretory granules. The picture becomes even more complex when one considers the myriad of permissive, potentiating, and inhibitory agents that modulate the effects of glucose on insulin secretion.In light of this growing appreciation of the complexity of the problem, we and others have realized that an interdisciplinary approach may be required to fully understand ␤-cell function. The result is that a field that began with the application of tools of metabolic biochemistry, enzymology, and physiology, now welcomes investigators applying molecular biology, gene discovery, cell and developmental biology, and biophysical chemistry strategies. In this study, we present our version of a multidisciplinary approach to the understanding of GSIS, and summarize the insights that we have gained to date and hope to gain in the future. DEVELOPMENT OF TOOLS FOR STUDYING ␤-CELL FUNCTIONRecombinant adenovirus as a gene delivery tool. The use of a recombinant adenovirus for gene transfer into islet cells was first demonstrated in our laboratory in the early 1990s (1,2). Using this approach, genes can be delivered to isolated rat islets with a transfer efficiency of 70 -80%, and to insulinoma cell line models with an efficiency approaching 100% (1-3). This level of efficiency for gene transfer is required for testing the impact of specific genes on candidate signaling pathways, and has led to an approach in whic...

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In vitro and in vivo suppression of gluconeogenesis by inhibition of pyruvate carboxylase

Cited by 64 publications

References 40 publications

Lipid-dependent control of hepatic glycogen stores in healthy humans

Lipid-dependent control of hepatic glycogen stores in healthy humans

Anaplerosis via pyruvate carboxylase is required for the fuel-induced rise in the ATP:ADP ratio in rat pancreatic islets

Stimulus/Secretion Coupling Factors in Glucose-Stimulated Insulin Secretion

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