Loss of coupling between calcium influx, energy consumption and insulin secretion associated with development of hyperglycaemia in the UCD-T2DM rat model of type 2 diabetes

Rountree, Austin M.; Reed, Benjamin J.; Cummings, Bethany P.; Jung, Seung‐Ryoung; Stanhope, Kimber L.; Graham, James L.; Griffen, Steven C.; Hull, Rebecca L.; Havel, Peter J.; Sweet, Ian R.

doi:10.1007/s00125-012-2808-6

Cited by 19 publications

(16 citation statements)

References 37 publications

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“…This signaling machinery is dysfunctional in diabetes (type 2 and pre-type 1) [8–14], making the understanding of β-cell bioenergetic function and dysfunction vital for understanding and treating diabetes. In T2D, ΔψM in β-cells becomes less sensitive to changes in blood glucose [16,46–48] by unknown mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Positive Feedback Amplifies the Response of Mitochondrial Membrane Potential to Glucose Concentration in Clonal Pancreatic Beta Cells

Gerencser

Mookerjee

Jastroch

et al. 2017

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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Analysis of the cellular mechanisms of metabolic disorders, including type 2 diabetes mellitus, is complicated by the large number of reactions and interactions in metabolic networks. Metabolic control analysis with appropriate modularization is a powerful method for simplifying and analyzing these networks. To analyze control of cellular energy metabolism in adherent cell cultures of the INS-1 832/13 pancreatic β-cell model we adapted our microscopy assay of absolute mitochondrial membrane potential (ΔψM) to a fluorescence microplate reader format, and applied it in conjunction with cell respirometry. In these cells the sensitive response of ΔψM to extracellular glucose concentration drives glucose-stimulated insulin secretion. Using metabolic control analysis we identified the control properties that generate this sensitive response. Force-flux relationships between ΔψM and respiration were used to calculate kinetic responses to ΔψM of processes both upstream (glucose oxidation) and downstream (proton leak and ATP turnover) of ΔψM. The analysis revealed that glucose-evoked ΔψM hyperpolarization is amplified by increased glucose oxidation activity caused by factors downstream of ΔψM. At high glucose, the hyperpolarized ΔψM is stabilized almost completely by the action of glucose oxidation, whereas proton leak also contribute to the homeostatic control of ΔψM at low glucose. These findings suggest a strong positive feedback loop in the regulation of β-cell energetics, and a possible regulatory role of proton leak in the fasting state. Analysis of islet bioenergetics from published cases of type 2 diabetes suggests that disruption of this feedback can explain the damaged bioenergetic response of β-cells to glucose.

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Section: Discussionmentioning

confidence: 99%

Positive Feedback Amplifies the Response of Mitochondrial Membrane Potential to Glucose Concentration in Clonal Pancreatic Beta Cells

Gerencser

Mookerjee

Jastroch

et al. 2017

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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“…Whole pancreas sections were then digitized (Nanozoomer Digital Pathology system, Hamamatsu Corporation, Bridgewater, NJ). For each section, total pancreas tissue and insulin-positive areas were determined automatically based on pixel value and density (Visiopharm software, Hoersholm, Denmark) and verified by manual examination of segmented images, as we have done previously (Rountree, et al 2013). Beta cell area was expressed as insulin-positive area/total tissue area (%).…”

Section: Methodsmentioning

confidence: 99%

High fat feeding unmasks variable insulin responses in male C57BL/6 mouse substrains

Hull

Willard

Struck

et al. 2017

Journal of Endocrinology

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Mouse models are widely used for elucidating mechanisms underlying type 2 diabetes. Genetic background profoundly affects metabolic phenotype; therefore selecting the appropriate model is critical. While variability in metabolic responses between mouse strains is now well-recognized, it also occurs within C57BL/6 mice, of which several substrains exist. This within-strain variability is poorly understood, and could emanate from genetic and/or environmental differences. To better define the within-strain variability, we performed the first comprehensive comparison of insulin secretion from C57BL/6 substrains 6J, 6JWehi, 6NJ, 6NHsd, 6NTac and 6NCrl. In vitro, glucose-stimulated insulin secretion correlated with Nnt mutation status, wherein responses were uniformly lower in islets from C57BL/6J versus C57BL/6N mice. In contrast, in vivo insulin responses following 18 weeks of low fat feeding showed no differences among any of the six substrains. When challenged with a high fat diet for 18 weeks, C57BL/6J substrains responded with a similar increase in insulin release. However, variability was evident among C57BL/6N substrains. Strikingly, 6NJ mice showed no increase in insulin release after high fat feeding, contributing to the ensuing hyperglycemia. The variability in insulin responses among high fat-fed C57BL/6N mice could not be explained by differences in insulin sensitivity, body weight, food intake or beta-cell area. Rather, as yet unidentified genetic and/or environmental factor(s) are likely contributors. Together, our findings emphasize that caution should be exercised in extrapolating data from in vitro studies to the in vivo situation, and inform on selecting the appropriate C57BL/6 substrain for metabolic studies.

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“…Decreased expression levels and enzymatic activities of select glycolytic, tricarboxylic acid (TCA) cycle and oxidative phosphorylation components have been reported in T2D human islets (8,11,12), but not in all cases (13), and maximal capacity of respiration was not decreased (14). Impaired glucoseevoked hyperpolarization of the mitochondrial membrane potential (⌬M) in diabetic islets from humans and from rodent models (13,15,16) has been suggested by qualitative measurements. However, the specific cause of this attenuation is unknown.…”

mentioning

confidence: 91%

Bioenergetic Analysis of Single Pancreatic β-Cells Indicates an Impaired Metabolic Signature in Type 2 Diabetic Subjects

Gerencser

2015

Endocrinology

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Impaired activation of mitochondrial energy metabolism by glucose has been demonstrated in type 2 diabetic β-cells. The cause of this dysfunction is unknown. The aim of this study was to identify segments of energy metabolism with normal or with altered function in human type 2 diabetes mellitus. The mitochondrial membrane potential (ΔψM), and its response to glucose, is the main driver of mitochondrial ATP synthesis and is hence a central mediator of glucose-induced insulin secretion, but its quantitative determination in β-cells from human donors has not been attempted, due to limitations in assay technology. Here, novel fluorescence microscopic assays are exploited to quantify ΔψM and its response to glucose and other secretagogues in β-cells of dispersed pancreatic islet cells from 4 normal and 3 type 2 diabetic organ donors. Mitochondrial volume densities and the magnitude of ΔψM in low glucose were not consistently altered in diabetic β-cells. However, ΔψM was consistently less responsive to elevation of glucose concentration, whereas the decreased response was not observed with metabolizable secretagogue mixtures that feed directly into the tricarboxylic acid cycle. Single-cell analysis of the heterogeneous responses to metabolizable secretagogues indicated no dysfunction in relaying ΔψM hyperpolarization to plasma membrane potential depolarization in diabetic β-cells. ΔψM of diabetic β-cells was distinctly responsive to acute inhibition of ATP synthesis during glucose stimulation. It is concluded that the mechanistic deficit in glucose-induced insulin secretion and mitochondrial hyperpolarization of diabetic human β-cells is located upstream of the tricarboxylic acid cycle and manifests in dampening the control of ΔψM by glucose metabolism.

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Loss of coupling between calcium influx, energy consumption and insulin secretion associated with development of hyperglycaemia in the UCD-T2DM rat model of type 2 diabetes

Cited by 19 publications

References 37 publications

Positive Feedback Amplifies the Response of Mitochondrial Membrane Potential to Glucose Concentration in Clonal Pancreatic Beta Cells

Positive Feedback Amplifies the Response of Mitochondrial Membrane Potential to Glucose Concentration in Clonal Pancreatic Beta Cells

High fat feeding unmasks variable insulin responses in male C57BL/6 mouse substrains

Bioenergetic Analysis of Single Pancreatic β-Cells Indicates an Impaired Metabolic Signature in Type 2 Diabetic Subjects

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