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            C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)

Lu, Danhong; Mulder, Hindrik; Zhao, Piyu; Burgess, Shawn C.; Jensen, Mette V.; Kamzolova, Svetlana V.; Newgard, Christopher B.; Sherry, A. Dean

doi:10.1073/pnas.052005699

Cited by 251 publications

(281 citation statements)

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“…Furthermore, these clones are characterized by similar insulin content (12). However, significant differences in tricarboxylic acid cycle fluxes are evident that could be attributed to an accelerated anaplerotic pyruvate cycling pathway in glucose-responsive 832/13 cells (13). These characteristic differences were found to correlate with the altered GSIS in 832/2 versus 832/13 cells.…”

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confidence: 64%

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Malmgren

Nicholls

Taneera

et al. 2009

Journal of Biological Chemistry

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101

116

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The biochemical mechanisms underlying glucose-stimulated insulin secretion from pancreatic ␤-cells are not completely understood. To identify metabolic disturbances in ␤-cells that impair glucose-stimulated insulin secretion, we compared two INS-1-derived clonal ␤-cell lines, which are glucose-responsive (832/13 cells) or glucose-unresponsive (832/2 cells). To this end, we analyzed a number of parameters in glycolytic and mitochondrial metabolism, including mRNA expression of genes involved in cellular energy metabolism. We found that despite a marked impairment of glucose-stimulated insulin secretion, 832/2 cells exhibited a higher rate of glycolysis. Still, no glucoseinduced increases in respiratory rate, ATP production, or respiratory chain complex I, III, and IV activities were seen in the 832/2 cells. Instead, 832/2 cells, which expressed lactate dehydrogenase A, released lactate regardless of ambient glucose concentrations. In contrast, the glucose-responsive 832/13 line lacked lactate dehydrogenase and did not produce lactate. Accordingly, in 832/2 cells mRNA expression of genes for glycolytic enzymes were up-regulated, whereas mitochondria-related genes were down-regulated. This could account for a Warburg-like effect in the 832/2 cell clone, lacking in 832/13 cells as well as primary ␤-cells. In human islets, mRNA expression of genes such as lactate dehydrogenase A and hexokinase I correlated positively with HbA 1c levels, reflecting perturbed long term glucose homeostasis, whereas that of Slc2a2 (glucose transporter 2) correlated negatively with HbA 1c and thus better metabolic control. We conclude that tight metabolic regulation enhancing mitochondrial metabolism and restricting glycolysis in 832/13 cells is required for clonal ␤-cells to secrete insulin robustly in response to glucose. Moreover, a similar expression pattern of genes controlling glycolytic and mitochondrial metabolism in clonal ␤-cells and human islets was observed, suggesting that a similar prioritization of mitochondrial metabolism is required in healthy human ␤-cells. The 832 ␤-cell lines may be helpful tools to resolve metabolic perturbations occurring in Type 2 diabetes.Pancreatic ␤-cells regulate whole body metabolism by secreting the hormone insulin in response to raised levels of blood glucose. However, the mechanisms underlying glucosestimulated insulin secretion (GSIS) 2 are not completely understood. The main signaling event is believed to be the rise in the ATP:ADP ratio, mainly accounted for by mitochondria. This closes ATP-dependent K ϩ (K ATP ) channels, depolarizing the plasma membrane. In turn voltage-gated Ca 2ϩ channels open, allowing Ca 2ϩ to enter the cell, initiating exocytosis of insulincontaining vesicles (1, 2). In addition, there seem to be several other metabolic events that affect insulin secretion independent of K ATP channel activity (3, 4); among them are anaplerotic rate, levels of mitochondrial glutamate, and several other metabolic intermediates (1, 5-7).Pyruvate carboxylase (PC), catalyzing the carbo...

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confidence: 64%

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Malmgren

Nicholls

Taneera

et al. 2009

Journal of Biological Chemistry

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101

116

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“…Pancreatic beta cells have remarkably high anaplerotic activity [46,47] as a likely compensatory mechanism for important cataplerosis, i.e. leak out of the TCA cycle.…”

Section: Discussionmentioning

confidence: 99%

Insulin secretion profiles are modified by overexpression of glutamate dehydrogenase in pancreatic islets

Carobbio¹,

Ishihara²,

Fernández-Pascual

et al. 2004

Diabetologia

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Aims/hypothesis. Glutamate dehydrogenase (GDH) is a mitochondrial enzyme playing a key role in the control of insulin secretion. However, it is not known whether GDH expression levels in beta cells are ratelimiting for the secretory response to glucose. GDH also controls glutamine and glutamate oxidative metabolism, which is only weak in islets if GDH is not allosterically activated by L-leucine or (+/−)-2-aminobicyclo-[2,2,1]heptane-2-carboxylic acid (BCH). Methods. We constructed an adenovirus encoding for GDH to overexpress the enzyme in the beta-cell line INS-1E, as well as in isolated rat and mouse pancreatic islets. The secretory responses to glucose and glutamine were studied in static and perifusion experiments. Amino acid concentrations and metabolic parameters were measured in parallel.Results. GDH overexpression in rat islets did not change insulin release at basal or intermediate glucose (2.8 and 8.3 mmol/l respectively), but potentiated the secretory response at high glucose concentrations (16.7 mmol/l) compared to controls (+35%). Control islets exposed to 5 mmol/l glutamine at basal glucose did not increase insulin release, unless BCH was added with a resulting 2.5-fold response. In islets overexpressing GDH glutamine alone stimulated insulin secretion (2.7-fold), which was potentiated 2.2-fold by adding BCH. The secretory responses evoked by glutamine under these conditions correlated with enhanced cellular metabolism. Conclusions/interpretation. GDH could be rate-limiting in glucose-induced insulin secretion, as GDH overexpression enhanced secretory responses. Moreover, GDH overexpression made islets responsive to glutamine, indicating that under physiological conditions this enzyme acts as a gatekeeper to prevent amino acids from being inappropriate efficient secretagogues. [Diabetologia (2004) 47:266-276]

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“…The rate of pyruvate carboxylation correlates with the glucose concentration applied to pancreatic islets and thus is correlated with the rate of insulin secretion [5]. 13 C-NMR isoprotomer studies of glucose metabolism in clonal cell lines have also shown a correlation between insulin secretion and pyruvate flux through the pyruvate carboxylase reaction [8,9]. The purpose of anaplerosis in the beta cell is different from that in many other tissues which possess a high level of pyruvate carboxylase.…”

Section: Introductionmentioning

confidence: 99%

The role of rapid lipogenesis in insulin secretion: Insulin secretagogues acutely alter lipid composition of INS-1 832/13 cells

MacDonald

Dobrzyń

Ntambi

et al. 2008

Archives of Biochemistry and Biophysics

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Pancreatic beta cell mitochondria convert insulin secretagogues into products that support insulin exocytosis. We explored the idea that lipids are some of these products formed from acyl group transfer out of mitochondria to the cytosol, the site of lipid synthesis. There are two isoforms of acetyl-CoA carboxylase, the enzyme that forms malonyl-CoA from which C 2 units for lipid synthesis are formed. We found that ACC1, the isoform seen in lipogenic tissues, is the only isoform present in human and rat pancreatic islets and INS-1 832/13 cells. Inhibitors of ACC and fatty acid synthase inhibited insulin release in islets and INS-1 cells. Carbon from glucose and pyruvate were rapidly incorporated into many lipid classes in INS-1 cells. Glucose and other insulin secretagogues acutely increased many lipids with C 14 -C 24 chains including individual cholesterol esters, phospholipids and fatty acids. Many phosphatidylcholines and phosphatidylserines were increased and many phosphatidylinositols and several phosphatidylethanolamines were decreased. The results suggest that lipid remodeling and rapid lipogenesis from secretagogue carbon support insulin secretion.

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¹³ C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)

Cited by 251 publications

References 39 publications

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Insulin secretion profiles are modified by overexpression of glutamate dehydrogenase in pancreatic islets

The role of rapid lipogenesis in insulin secretion: Insulin secretagogues acutely alter lipid composition of INS-1 832/13 cells

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13 C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)

Cited by 251 publications

References 39 publications

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal β-Cells Is Required for Robust Insulin Secretion

Insulin secretion profiles are modified by overexpression of glutamate dehydrogenase in pancreatic islets

The role of rapid lipogenesis in insulin secretion: Insulin secretagogues acutely alter lipid composition of INS-1 832/13 cells

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¹³ C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS)