Glucose stimulation of the proinsulin synthesis in isolated pancreatic islets without increasing amount of proinsulin mRNA

Itoh, Nobuyuki; Sei, T. P.; Nose, Kiyoshi; Okamoto, Hiroshi

doi:10.1016/0014-5793(78)81136-3

Cited by 50 publications

(46 citation statements)

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“…Accounting for the reduced proinsulin mRNA concentration evident in the 10% remnant equivalent head, 90% pancreatectomy imposed demand for a greater than 10-fold increase in insulin production to achieve complete adaptation. An adaptation of this magnitude might have been anticipated on the basis of data from isolated rat islets, where significant short-term increases in insulin biosynthesis have been demonstrated (11)(12)(13)(14). A maximum 3.5-fold increase in proinsulin mRNA concentration was observed in this study at 3 wk after pancreatectomy, associated with a rise of proinsulin mRNA/ body weight to 40% of control.…”

Section: Discussionsupporting

confidence: 51%

“…In isolated pancreatic islets, measurements of isotope incorporation into insulin have revealed ability to modulate insulin biosynthesis with in vitro manipulation (11)(12)(13)(14), but applicability of these findings to synthesis in vivo is unclear. In rats given streptozotocin as neonates, examination of islets has shown increased [3H]leucine incorporation into insulin (15), but demonstration of reductions in pancreatic insulin content and in [3Hjleucine incorporation into proinsulin in vivo (16,17) have limited an interpretation ofthe islet findings.…”

Section: Introductionmentioning

confidence: 99%

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Modulation of proinsulin messenger RNA after partial pancreatectomy in rats. Relationships to glucose homeostasis.

Orland¹,

Chyn²,

Permutt³

1985

J. Clin. Invest.

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These studies of partial pancreatectomy assess pancreatic proinsulin messenger RNA (mRNA) levels as an index of in vivo insulin biosynthesis, and show relationships to glucose homeostasis. Rats were subjected to sham operation, 50% pancreatectomy (Px), or 90% Px, and were examined after 1, 3, or 14 wk. Proinsulin mRNA was measured by dot hybridization to complementary DNA. After 50% Px there was a nearly complete adaptation of proinsulin mRNA. After 90% Px a marked increase of proinsulin mRNA occurred, but it was insufficient and it was not maintained with time. The deficit in insulin production is related to development of hyperglycemia.Sham-operated controls showed no worsening of fasting or fed blood glucose or of intraperitoneal glucose tolerance within the period of observation. Total proinsulin mRNA and pancreatic insulin content rose in proportion to body weight. 50% PN produced no change from controls in body weight or blood glucose. The concentration of proinsulin mRNA in the 50% pancreatic remnant paralleled that of controls after 1 and 3 wk, but then increased after 14 wk, such that total proinsulin mRNA approached control levels. This adaptive response was reflected by changes in serum insulin, but not by pancreatic insulin content, which was only 30% of control after 14 wk. Intraperitoneal glucose tolerance was impaired mildly, and did not worsen with time after pancreatectomy.90% Px led to elevated fed blood glucose and reduced serum insulin after 3 wk, and fasting hyperglycemia was seen after 14 wk. Proinsulin mRNA concentration in the 10% pancreatic remnant showed an adaptive increase after 1 and 3 wk, such that total proinsulin mRNA reached 40% of control. After 14 wk, however, remnant proinsulin mRNA concentration was no longer increased; total proinsulin mRNA and pancreatic insulin content were severely reduced. Intraperitoneal glucose tolerance was impaired more dramatically than with the 50% Px animals, and worsened with time after operation.These observations indicate ability to increase proinsulin mRNA levels as an adaptation to pancreatectomy. Insufficiency of this adaptation is associated with the development of hyperglycemia, and the loss of this adaptation correlates with a worsening of glucose tolerance.

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Section: Discussionsupporting

confidence: 51%

Section: Introductionmentioning

confidence: 99%

Modulation of proinsulin messenger RNA after partial pancreatectomy in rats. Relationships to glucose homeostasis.

Orland¹,

Chyn²,

Permutt³

1985

J. Clin. Invest.

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“…However, the relative contribution of transcriptional versus post-transcriptional mechanisms to the control of insulin mRNA levels is under debate. According to the original view, insulin mRNA is a highly abundant messenger (6), which is not affected by short term glucose challenges (7), and therefore controlled to a large extent by changes in messenger stability (5). The half-life of insulin mRNA was assessed to be 29 h at a low glucose concentration and 77 h at a high glucose concentration (5).…”

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confidence: 99%

Control of Insulin mRNA Stability in Rat Pancreatic Islets

Tillmar

Carlsson

Welsh

2002

Journal of Biological Chemistry

147

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Stabilization of insulin mRNA in response to glucose is a significant component of insulin production, but the mechanisms governing this process are unknown. We presently observe that insulin mRNA is a highly abundant messenger and that the content of this mRNA is mainly controlled by changes in messenger stability. We also demonstrate specific binding of the polypyrimidine tract-binding protein to a pyrimidine-rich sequence located in the 3-untranslated region (3-UTR) of insulin mRNA. This binding was increased in vitro by dithiothreitol and in vivo by glucose. Inhibition of polypyrimidine tract-binding protein binding to the pyrimidinerich sequence by mutation of the core binding site resulted in a destabilization of a reporter gene mRNA. Thus, glucose-induced binding of polypyrimidine tractbinding protein to the 3-UTR of insulin mRNA could be a necessary event in the control of insulin mRNA levels.

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“…Further, more recently we have demonstrated that the induction of proinsulin synthesis by glucose in rat pancreatic islets is controlled at the translational level [8,9]. A detailed analysis of the regulation mechanism of the proinsulin induction requires the characterization and quantification of proinsulin mRNA.…”

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confidence: 99%

Purification and Characterization of Proinsulin mRNA from Rat B‐Cell Tumor

Itoh

Nose

Okamoto

1979

European Journal of Biochemistry

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Proinsulin mRNA was purified from rat B-cell tumor induced by streptozotocin and nicotinamide. The purification was achieved through the use of oligo(dT)-cellulose chromatography and sucrose gradient centrifugation. As judged by translational activity in a cell-free protein-synthesizing system of wheat germ, proinsulin mRNA was purified 362-fold from total nucleic acid of the B-cell tumor. Purified proinsulin mRNA migrated as a single symmetrical peak on sucrose gradient centrifugation and as a single band on polyacrylamide gel electrophoresis in the presence of formamide. The translation product of purified proinsulin mRNA in the cell-free protein-synthesizing system was found to be only preproinsulin, as analyzed by dodecylsulfate/polyacrylamide gel electrophoresis and immunoprecipitation.The molecular weight of proinsulin mRNA, determined by polyacrylamide gel electrophoresis in the presence of formamide, was approximately 200 000 (equivalent to approximately 570 nucleotides). Almost all of the proinsulin mRNA was bound to oligo(dT)-cellulose, and the translation of proinsulin mRNA in a cell-free protein-synthesizing system of wheat germ was completely inhibited by 7-methylguanosine 5'-phosphate. These results indicated that the nucleotide sequences in proinsulin mRNA consisted of 58 "/, translatable sequences and 42 % untranslatable sequences, presumably containing a capped structure, a 7-methylguanosine residue, at the 5' terminus and a poly(A) sequence at the 3' terminus.The translation product of purified proinsulin mRNA, preproinsulin, was found to consist of two types of preproinsulin I (57 %) and preproinsulin I1 (43 %). This result indicated that the isolated proinsulin mRNA consisted of two types of proinsulin I mRNA and proinsulin I1 mRNA in approximately equal amounts.Complementary DNA was synthesized with proinsulin mRNA as a template. From the experiment of hybridization kinetics under conditions of excess RNA, the ~g f l , Z of proinsulin mRNA was found to be 2.1 x moll-' s. This result also confirmed that proinsulin mRNA had been isolated in a high degree of purity.The investigation of the mechanisms controlling transcription and translation in eukaryotic cells have been facilitated by the isolation of specific mRNAs [I -31. Purified mRNA can be employed as a template for the synthesis of complementary DNA and in investigation of mRNA structure and function.In recent years several attempts have been carried out to isolate and characterize proinsulin mRNA from mammalian and fish pancreatic islets and from an X-ray-induced islet tumor. However, because of the limited availability of these materials, proinsulin mRNA has been only partially purified [4,5]. In the preceeding paper [6] we reported that the B-cell tumor -.Ahhreviutions. Hepes, 4-(2-hydroxyethyI)-l-piperazineethanesulphonic acid; Tos-Phe-CHzCI, L-1-tosylamido-2-phenylethyl chloromethyl ketone.induced by streptozotocin and nicotinamide can be used as a suitable material for isolation and purification of proinsulin mRNA, since the RNA fr...

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Glucose stimulation of the proinsulin synthesis in isolated pancreatic islets without increasing amount of proinsulin mRNA

Cited by 50 publications

References 23 publications

Modulation of proinsulin messenger RNA after partial pancreatectomy in rats. Relationships to glucose homeostasis.

Modulation of proinsulin messenger RNA after partial pancreatectomy in rats. Relationships to glucose homeostasis.

Control of Insulin mRNA Stability in Rat Pancreatic Islets

Purification and Characterization of Proinsulin mRNA from Rat B‐Cell Tumor

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