Amiloride derivatives enhance insulin release in pancreatic islets from diabetic mice

Gunawardana, Subhadra C.; Head, W. Steven; Piston, David W.

doi:10.1186/1472-6823-5-9

Cited by 8 publications

(19 citation statements)

References 25 publications

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“…In certain idiopatic type 2 diabetic mouse models, misregulation of acidification has been shown to occur in the islets of Langerhans (42). To our knowledge, this is the first time a putative cause of acidification impairment resulting in a type 2 diabetes-like phenotype in mouse has been described.…”

Section: Discussionmentioning

confidence: 84%

Role of furin in granular acidification in the endocrine pancreas: Identification of the V-ATPase subunit Ac45 as a candidate substrate

Louagie

Taylor

Flamez

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Furin is a proprotein convertase which activates a variety of regulatory proteins in the constitutive exocytic and endocytic pathway. The effect of genetic ablation of fur was studied in the endocrine pancreas to define its physiological function in the regulated secretory pathway. Pdx1-Cre/loxP furin KO mice show decreased secretion of insulin and impaired processing of known PC2 substrates like proPC2 and proinsulin II. Both secretion and PC2 activity depend on granule acidification, which was demonstrated to be significantly decreased in furin-deficient ␤ cells by using the acidotrophic agent 3-(2,4-dinitroanilino)-3 amino-N-methyldipropylamine (DAMP). Ac45, an accessory subunit of the proton pump V-ATPase, was investigated as a candidate substrate. Ac45 is highly expressed in islets of Langerhans and furin was able to cleave Ac45 ex vivo. Furthermore, the exact cleavage site was determined. In addition, reduced regulated secretion and proinsulin II processing could be obtained in the insulinoma cell line ␤TC3 by downregulation of either furin or Ac45. Together, these data establish an important role for furin in regulated secretion, particularly in intragranular acidification most likely due to impaired processing of Ac45.endoprotease ͉ insulin ͉ islets of Langerhans ͉ proton pump ͉ proprotein convertase

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Section: Discussionmentioning

confidence: 84%

Role of furin in granular acidification in the endocrine pancreas: Identification of the V-ATPase subunit Ac45 as a candidate substrate

Louagie

Taylor

Flamez

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The number of times each experiment was repeated with islets from different mice is shown as n. Culture of islets. For imaging experiments, islets were cultured using methods developed in our lab, as previously described (19,20). Culture dishes (35 mm) with glass-bottomed wells (Mat-Tek) were used.…”

Section: Methodsmentioning

confidence: 99%

“…Several previous studies (16 -18) and our preliminary work have shown that mouse islets do not normally exhibit TDP. However, we recently demonstrated that TDP can be enabled/unmasked in mouse islets under certain conditions (19,20). Such conditions are provided by prior treatment with dimethylamiloride (DMA), which is associated with a sustained decrease in islet intracellular pH (pH i ) and an increase in the levels of cellular reducing equivalents (19).…”

mentioning

confidence: 99%

“…Such conditions are provided by prior treatment with dimethylamiloride (DMA), which is associated with a sustained decrease in islet intracellular pH (pH i ) and an increase in the levels of cellular reducing equivalents (19). DMA treatment enables glucose to induce TDP in mouse islets in which it is normally absent (19,20) and magnifies the TDP normally present in rat islets (21). Since DMA alone does not stimulate insulin release, we postulated that the DMA-induced increase of reducing equivalents is more likely to represent NADPHϩH ϩ (NADPH) rather than NADHϩH ϩ (NADH) (22).…”

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confidence: 99%

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Mechanisms of Time-Dependent Potentiation of Insulin Release

et al. 2006

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Time-dependent potentiation (TDP) of insulin release is normally absent in mice. However, we recently demonstrated that TDP occurs in mouse islets under conditions of forced decrease of intracellular pH (pH i ) associated with elevated NADPH؉H ؉ (NADPH) levels. Hence, TDP in mouse islets may be kept suppressed by neuronal nitric oxide (NO) synthase (nNOS), an NADPH-utilizing enzyme with alkaline pH optimum. To determine the role of nNOS in the suppression of TDP in mouse islets, glucose-induced TDP was monitored in mouse islets in which nNOS activity had been genetically removed or chemically inhibited and compared with the TDP response in wild-type mouse islets with and without forced intracellular acidification. Genetic deletion of nNOS was provided by an nNOS knockout (NOS-KO) mouse model, B6 -129S4-Nos1tm1Plh /J. To explore how nNOS inhibits TDP, we compared pH i and NADPH levels in wild-type and NOS-KO islets and monitored TDP with various components of the nNOS reaction added. Glucose normally does not produce TDP in wildtype mouse islets except under forced intracellular acidification. Remarkably, glucose produced strong TDP in NOS-KO islets and in wild-type islets treated with nNOS inhibitors. TDP in NOS-KO islets was not inhibited by the addition of NO, and NOS-KO islets exhibited a lower pH i than wild-type islets. The addition of arginine to wild-type islets also enabled glucose to induce TDP. Our results show that nNOS activity contributes to the absence of TDP in mouse islets putatively through depletion of intracellular arginine.

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“…Derivatives of amiloride have been reported to increase insulin secretion from β-cells in vitro and in vivo (30,31). In contrast, no association between propafenone and insulin secretion has been previously reported.…”

Section: Discussionmentioning

confidence: 80%

Disease allele-dependent small-molecule sensitivities in blood cells from monogenic diabetes

Shaw

Blodgett²,

Maggie³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Even as genetic studies identify alleles that influence human disease susceptibility, it remains challenging to understand their functional significance and how they contribute to disease phenotypes. Here, we describe an approach to translate discoveries from human genetics into functional and therapeutic hypotheses by relating human genetic variation to small-molecule sensitivities. We use small-molecule probes modulating a breadth of targets and processes to reveal disease allele-dependent sensitivities, using cells from multiple individuals with an extreme form of diabetes (maturity onset diabetes of the young type 1, caused by mutation in the orphan nuclear receptor HNF4α). This approach enabled the discovery of small molecules that show mechanistically revealing and therapeutically relevant interactions with HNF4α in both lymphoblasts and pancreatic β-cells, including compounds that physically interact with HNF4α. Compounds including US Food and Drug Administration–approved drugs were identified that favorably modulate a critical disease phenotype, insulin secretion from β-cells. This method may suggest therapeutic hypotheses for other nonblood disorders.

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Amiloride derivatives enhance insulin release in pancreatic islets from diabetic mice

Cited by 8 publications

References 25 publications

Role of furin in granular acidification in the endocrine pancreas: Identification of the V-ATPase subunit Ac45 as a candidate substrate

Role of furin in granular acidification in the endocrine pancreas: Identification of the V-ATPase subunit Ac45 as a candidate substrate

Mechanisms of Time-Dependent Potentiation of Insulin Release

Disease allele-dependent small-molecule sensitivities in blood cells from monogenic diabetes

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