An in vivo analysis of pancreatic protein and insulin biosynthesis in a rat model for non-insulin-dependent diabetes.

Permutt, M. A.; Kakita, Keiji; Malinas, P; Karl, Irene E.; Bonner-Weir, Susan; Weir, Gordon C.; Giddings, Stephen J.

doi:10.1172/jci111337

Cited by 42 publications

(41 citation statements)

References 46 publications

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“…Modulation of proinsulin mRNA concentration has been shown in studies assessing the physiologic regulation of insulin production (17)(18)(19)(20)(21)(22). A correlation has been shown in rats between pancreatic proinsulin mRNA concentration and rates of in vivo incorporation of [3Hjleucine into proinsulin, showing comparable ability to assess rates of insulin biosynthesis (16,17). A correlation between tissue mRNA levels and protein synthetic rates also has been shown for other protein systems in vitro (23,24) and in vivo (25,26).…”

Section: Introductionmentioning

confidence: 80%

“…Parallel measurement of these two parameters in 100 g male Sprague-Dawley rats has shown tight correlation in estimating a twofold reduction of insulin biosynthesis imposed by neonatal streptozotocin treatment (16,17), and in assessing a twofold augmentation of insulin biosynthesis apparent in normal and streptozotocin-treated rats given pharmacologic doses of dexamethasone for 4 d (17). Contrary to the results of short-term labeling studies in isolated pancreatic islets (I1), the in vivo data did not show an important independent contribution of translational activity to insulin biosynthesis under the conditions specified.…”

Section: Discussionmentioning

confidence: 99%

“…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%

“…Measurement of proinsulin messenger RNA (mRNA)' has conveyed potential for estimating in vivo capacity to produce insulin (16,17). Modulation of proinsulin mRNA concentration has been shown in studies assessing the physiologic regulation of insulin production (17)(18)(19)(20)(21)(22).…”

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: Introductionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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“…Although there were minor differences in early insulin responses, overall the responses were comparable. It has never been easy to assess insulin producing capacity in vivo (25). Both brothers are lean, whereas the diabetic sisters are obese.…”

Section: Discussionmentioning

confidence: 99%

A variant insulin promoter in non-insulin-dependent diabetes mellitus.

Olansky¹,

Welling²,

Giddings³

et al. 1992

J. Clin. Invest.

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To test the hypothesis that alterations in regulatory regions of the insulin gene occur in a subset of patients with non-insulindependent diabetes mellitus (NIDDM), the promoter region was studied by polymerase chain reaction (PCR) amplification directly from genomic DNA, followed by high-resolution polyacrylamide gel electrophoresis under nondenaturing conditions. By using this method a previously identified HincII polymorphism (GTIGAC to GTTGAG at position -56) in American Blacks was readily detected, indicating that single base changes could be observed. In the course of screening the insulin promoter from 40 American Black subjects with NIDDM, an apparent larger allele was found in two individuals. Both patients were shown to have in addition to a normal allele, a larger allele containing an 8-bp repeat, TGGTCTAA from positions -322 to -315 of the insulin promoter.To facilitate rapid screening for the 8-bp repeat, a high-resolution agarose gel electrophoretic analysis was adopted. DNA from American Black NIDDM subjects (a = 100) and nondiabetic subjects (a = 100) was PCR amplified and analyzed. The 8-bp repeat was present in five NIDDM subjects, and one nondiabetic subject. DNA from Mauritius Creoles, also of African ancestry, was analyzed, and the 8-bp repeat was present in 3 of 41 NIDDM subjects, and 0 of 41 nondiabetic subjects. Analysis of glucose metabolism in three presumed normal sibs of an NIDDM patient with an 8-bp repeat revealed that one sib had overt diabetes, and two sibs were glucose intolerant, but there was no consistent segregation of the insulin promoter variant with the diabetes phenotype. The variant promoter was not present in 35 Caucasian NIDDM patients or in 40 Pima Indians.To test the biological consequences of the 8-bp repeat sequence in the insulin promoter, a normal and variant promoter were subcloned into a luciferase plasmid, and reporter gene activity assessed by transient transfection into mouse insulinoma (ITC1) and hamster insulinoma (HIT) cells. The promoter activity of the variant allele was found to be reduced to 37.9 ± 10.3% of the activity of the normal promoter in HIT cells (P < 0.01, n = 4), and 49.1 ± 6.4% infTCl cells (P < 0.01, n = 6). These data thus suggest that a naturally occurring vari-

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Insulin Gene Expression and Biosynthesis

Poitout¹,

Stein²,

Rhodes³

2003

International Textbook of Diabetes Mellitus

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The insulin gene is expressed specifically and at very high levels in pancreatic β‐cells. Most of its tissue‐specific expression and metabolic regulation are conferred by approximately 340 bp upstream of the transcription initiation site. Several glucose‐responsive elements have been identified within this region, and physiological regulation of insulin gene expression relies on the cooperative and synergistic interactions between DNA‐binding factors and coactivators. Glucose is the major regulator of insulin gene expression. It activates transcription and stabilizes insulin mRNA. In addition, insulin gene expression is stimulated by glucagon‐like peptide 1, growth hormone, and lactogenic hormones, and inhibited by epinephrine, somatostatin, glucagon, and leptin. In type 2 diabetes, chronic elevations of blood glucose and fatty acid levels impair insulin gene expression. Under most circumstances, the production of insulin is also highly regulated at the translational level. Indeed, this is the predominant control mechanism in the β‐cell whereby intracellular insulin stores are efficiently maintained in the short term. Essentially, translation of the preproinsulin mRNA template to preproinsulin protein occurs in a fashion typical of most eukaryotic mRNAs. In general, nutrients that stimulate insulin secretion, of which glucose is the most physiologically relevant, also stimulate proinsulin biosynthesis at the translational level. Recently, it has been shown that specific control of glucose‐induced proinsulin biosynthesis in the β‐cell resides in cis ‐elements in the 5′‐ and 3′‐untranslated regions of preproinsulin mRNA itself. After proinsulin is translocated into the lumen of the rough endoplasmic reticulum, correctly folded proinsulin can then be delivered in transport vesicles to the cis ‐Golgi apparatus in an ATP‐dependent process. The major site for processing of the proinsulin to biologically active insulin is the immature granule compartment of the β‐cell. Production of insulin occurs via limited proteolysis of the proinsulin precursor molecule, which is catalyzed by two endopeptidases, proprotein convertase 2 (PC2) and proprotein convertase 3 (PC3) (also known as PC‐1), and an exopeptidase, carboxypeptidase‐H (CP‐H). Similar to their deleterious effects on insulin gene expression, chronic hyperglycemia and hyperlipidiemia impair proinsulin biosynthesis.

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An in vivo analysis of pancreatic protein and insulin biosynthesis in a rat model for non-insulin-dependent diabetes.

Cited by 42 publications

References 46 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.

A variant insulin promoter in non-insulin-dependent diabetes mellitus.

Insulin Gene Expression and Biosynthesis

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