[Effect of Rehmannia glutinosa Libosch water extraction on gene expression of proinsulin in type 2 diabetes mellitus rats].

OBJECTIVE: To investigate the mechanisms of treating 2-DM by Rehmannia glutinosa Libosch water extraction (RGLE). METHODS: The mRNA level of proinsulin in rats panreas tissue was examined by semi-quatitativa RT-PCR,and the protein was measured by SDS-PAGE. RESULTS: The mRNA and protein expressions of proinsulin in RGLE group were higher than those of diabetic model group (P<0.01). The levels of FPG decreased. FINS,IS, HbetaCI increased (P<0.01). CONCLUSION: It may be the mechanism how the RGLE to decline high FPG and cure the 2-DM.

C-peptide: much more than a byproduct of insulin biosynthesis.

OBJECTIVES: During the past decade, numerous studies in both humans and animals have demonstrated that C-peptide, although not influencing blood sugar control, might play a role in preventing and potentially reversing some of the chronic complications of type 1 diabetes. The aim of this paper is to present an up-to-date review of C-peptide, focusing on its role in insulin biosynthesis and in the classification of diabetes mellitus, as well as its potential clinical applications. METHODS AND RESULTS: The relevant literature cited in the MEDLINE database shows that the measurement of C-peptide production combined with screening for the presence of islet-cell and other autoantibodies seems to exert an important role in the accurate differentiation between patients with type 1 and type 2 diabetes. Also, both experimental and clinical data provide evidence suggesting that combined replacement of insulin and C-peptide has potential therapeutic value in patients with type 1 diabetes. CONCLUSIONS: Further study in this area is warranted, but the findings that pancreas transplants promote the reversal of diabetic neuropathy and stabilization of diabetic retinopathy and that both pancreas and islet transplants lead to the reversal of diabetic nephropathy lend credence to the concept that combined replacement of insulin and C-peptide may more effectively mitigate the inexorable progression of diabetes-related complications.

Effects of growth hormone in vitro on the glucose metabolism of fetal rat islet beta-cells.

This study was undertaken to investigate the effects of growth hormone (GH) on the in vitro maturation of the metabolism of fetal rat islets. For this purpose fetal islets were obtained from 21-day-old fetuses by mild collagenase digestion of the pancreas and cultured in RPMI 1640 supplemented with 10% fetal calf serum. After one day the medium was changed and supplemented with 1% fetal calf serum with or without GH (1 microgram/ml, human recombinant) and the islets cultured for another two days. Islets were then studied with regard to insulin secretion, (pro)insulin and total protein biosynthesis, glucose utilization and oxidation, thymidine incorporation, insulin and DNA contents and the contents of mRNAs for either insulin, adenine nucleotide translocator or cytochrome b. In addition, the activities of glucose phosphorylating enzymes and succinate-cytochrome c reductase were measured. Islets treated with GH showed increased insulin secretion in response to glucose, increased rates of glucose oxidation and utilization, increased thymidine incorporation and increased activities of succinate cytochrome c reductase and glucose phosphorylation at high glucose concentrations. There were, however, no changes in (pro)insulin and total protein biosynthesis, contents of insulin and DNA or the contents of any of the mRNAs. These combined data show that fetal beta-cells are sensitive to growth hormone with respect to glucose metabolism, insulin release and DNA replication. The increased rates of islet glucose phosphorylation may reflect glucokinase activity and explain part of the increased insulin responsiveness to glucose of the fetal rat beta-cell. These observations suggest that GH is of physiological significance for the maturation of the fetal beta-cell.

Expression of a human insulin transgene in cholinergic neurons of the mouse medial habenula.

We explored the possibility that an insulin gene deleted in its 5'-flanking region is expressed in adult mouse brain. We used three independent lines of mice carrying a human insulin transgene which included the insulin gene transcription unit flanked by 168 base pairs upstream and 5.5 kb downstream. Using a reverse transcription-polymerase chain reaction assay, human insulin mRNAs were detected in whole brain extracts. In all three lines, human insulin mRNAs were localized by in situ hybridization in a single cerebral site, the medial habenula. With a monoclonal antibody specific for human C-peptide and human proinsulin, labelling was restricted to a subset of habenular cholinergic neurons, with rare immunostained fibers. No labelling was observed in the projection fibers of the retroflexus fasciculus or in their axon terminals in the interpeduncular nucleus. Electron microscope studies suggested that the transgene expressing cells. These findings demonstrate that the human insulin transgene tested here includes a habenula specific promoter which could be useful for physiological and molecular studies on the habenula.

Preservation of glucose-responsive islet beta-cells during serum-free culture.

This study describes a serum-free medium in which adult rat islet beta-cells can be cultured in suspension for at least 9 days without a detectable loss in cell number or function. The medium is composed of Ham's F-10 with 10 mM glucose, 1% BSA, and 50 microM isobutylmethylxanthine. After 9 days of culture, beta-cell aggregates had preserved their initial DNA content, with more than 80% ultrastructurally intact cells. Their rates of glucose-inducible insulin synthesis (64 +/- 13 fmol/10(3) cells.2 h) and release (173 +/- 44 fmol/10(3) cells.2 h) were comparable to those previously determined in overnight cultured beta-cells. Their secretory response to 20 mM glucose plus 10(-8) M glucagon was biphasic and 10-fold elevated above the basal level. Their secretory and biosynthetic activities at basal (1.25 mM) glucose levels were significantly higher than after culture with serum. These elevated basal activities are attributed to a rise in the proportion of beta-cells with high content in pale secretory granules. Supplementing the serum-free medium with GH (1 micrograms/ml) plus glucagon (10(-8) M) further increased basal activities, leading to cellular degranulation and reduced hormone release after stimulation. Control cultures in Ham's F-10 with 10 mM glucose and 10% fetal calf serum reduced the initial DNA content by 40% and, consequently, the total amount of hormone synthesis and release. Surviving cells exhibited a lower secretory responsiveness than those recovered from serum-free medium; their lower basal activities coincided with an absence of cells with high content in pale granules. It is concluded that preservation of glucose-responsive beta-cells during suspension culture requires conditions that keep the cells recruited into glucose-dependent functions. Such a condition is achieved by the presently defined serum-free medium. It is characterized by the presence of a subpopulation of beta-cells with a high proportion of pale secretory granules.

Amino acids and human amniotic fluid increase DNA biosynthesis in pancreatic islets of adult mouse, but this effect is lost following exposure to streptozotocin.

The present study describes the effects of growth hormone (GH), amino acids, and human amniotic fluid on the function and replication of normal and SZ-treated adult mouse pancreatic islets. Thus, mouse islets were exposed in vitro to SZ or vehicle only, and maintained in culture for 7 days in RPMI 1640 containing 11.1 mM glucose and the different supplements described above. Supplementation with amino acids increased the insulin accumulation in the medium, DNA biosynthesis, and polyamine contents in the control islets. In the SZ-treated islets, amino acids increased insulin accumulation in the medium and polyamine contents, but not DNA biosynthesis. Culture of control islets in the presence of 10% human amniotic fluid increased the insulin accumulation in the medium, islet insulin content, total protein and (pro)insulin biosynthesis, and DNA biosynthesis. However, in the SZ-treated islets, the effects of human amniotic fluid were limited to an increase in insulin content and insulin accumulation in the medium. GH significantly increased insulin accumulation in the medium in control, but not SZ-treated islets. In both groups of islets, GH failed to induce a significant increase in thymidine incorporation. It is concluded that amino acids and human amniotic fluid are potent stimulators of DNA biosynthesis in adult mouse pancreatic beta cells, perhaps due to an increase in cellular polyamine contents. However, following exposure to streptozotocin, the islets are not anymore responsive to these stimulators of DNA biosynthesis.

Estudio sobre el mecanismo de accion del zincum metalico / Study about the action mode of the metallic zincum

El objeto de este estudio es presentar la revision documental de un medicamento homeopatico que se ha usado durante doscientos anos. Se trata de um oligoelemento, el zinc, que en los ultimos dieciocho anos ha sido profundamente estudiado en cuanto al aspecto bioquimico, farmacologico y principalmente la accion toxica en el organismo

Estudio sobre el mecanismo de accion del zincum metalico / Study about the action mode of the metallic zincum

El objeto de este estudio es presentar la revision documental de un medicamento homeopatico que se ha usado durante doscientos anos. Se trata de um oligoelemento, el zinc, que en los ultimos dieciocho anos ha sido profundamente estudiado en cuanto al aspecto bioquimico, farmacologico y principalmente la accion toxica en el organismo

Tissue culture of human fetal pancreas. Effects of nicotinamide on insulin production and formation of isletlike cell clusters.

Human fetal pancreas (HFP) is a potential source of beta-cells for transplantation to insulin-dependent diabetic patients. We have previously described a method for tissue culture of HFP that results in the in vitro development of isletlike cell clusters (ICCs) containing a minority of insulin-positive cells. Recently we found that nicotinamide, an inhibitor of poly(ADP-ribose) synthetase, induces an increased islet cell DNA replication both in vivo and in vitro. In this study, this culture technique was used to evaluate the effects of addition of 10 mM nicotinamide on HFP explants cultured in RPMI-1640 medium plus 10% human serum. ICCs developed in 11 of 19 consecutive cultures with nicotinamide increased the yield of ICCs by 40%. Also, the insulin content of ICCs increased approximately 50% with nicotinamide supplementation, although measurements of DNA indicated an unchanged number of cells in each ICC. Neither the rates of insulin release in response to 16.7 mM glucose plus 5 mM theophylline nor the (pro)insulin or total protein biosynthesis rates were affected by nicotinamide addition. The combined results of this study suggest that nicotinamide is useful for stimulating the formation of ICCs from HFP.