Novel factors modulating human ß-cell proliferation.

ß-Cell dysfunction in type 1 and type 2 diabetes is accompanied by a progressive loss of ß-cells, and an understanding of the cellular mechanism(s) that regulate ß-cell mass will enable approaches to enhance hormone secretion. It is becoming increasingly recognized that enhancement of human ß-cell proliferation is one potential approach to restore ß-cell mass to prevent and/or cure type 1 and type 2 diabetes. While several reports describe the factor(s) that enhance ß-cell replication in animal models or cell lines, promoting effective human ß-cell proliferation continues to be a challenge in the field. In this review, we discuss recent studies reporting successful human ß-cell proliferation including WS6, an IkB kinase and EBP1 inhibitor; harmine and 5-IT, both DYRK1A inhibitors; GNF7156 and GNF4877, GSK-3ß and DYRK1A inhibitors; osteoprotegrin and Denosmab, receptor activator of NF-kB (RANK) inhibitors; and SerpinB1, a protease inhibitor. These studies provide important examples of proteins and pathways that may prove useful for designing therapeutic strategies to counter the different forms of human diabetes.

beta-cell-specific deletion of the Igf1 receptor leads to hyperinsulinemia and glucose intolerance but does not alter beta-cell mass.

Regulation of glucose homeostasis by insulin depends on the maintenance of normal beta-cell mass and function. Insulin-like growth factor 1 (Igf1) has been implicated in islet development and differentiated function, but the factors controlling this process are poorly understood. Pancreatic islets produce Igf1 and Igf2, which bind to specific receptors on beta-cells. Igf1 has been shown to influence beta-cell apoptosis, and both Igf1 and Igf2 increase islet growth; Igf2 does so in a manner additive with fibroblast growth factor 2 (ref. 10). When mice deficient for the Igf1 receptor (Igf1r(+/-)) are bred with mice lacking insulin receptor substrate 2 (Irs2(-/-)), the resulting compound knockout mice show a reduction in mass of beta-cells similar to that observed in pancreas of Igf1r(-/-) mice (ref. 11), suggesting a role for Igf1r in growth of beta-cells. It is possible, however, that the effects in these mice occur secondary to changes in vascular endothelium or in the pancreatic ductal cells, or because of a decrease in the effects of other hormones implicated in islet growth. To directly define the role of Igf1, we have created a mouse with a beta-cell-specific knockout of Igf1r (betaIgf1r(-/-)). These mice show normal growth and development of beta-cells, but have reduced expression of Slc2a2 (also known as Glut2) and Gck (encoding glucokinase) in beta-cells, which results in defective glucose-stimulated insulin secretion and impaired glucose tolerance. Thus, Igf1r is not crucial for islet beta-cell development, but participates in control of differentiated function.

Added value of the measles-rubella supplementary immunization activity in reaching unvaccinated and under-vaccinated children, a cross-sectional study in five Indian districts, 2018-20.

INTRODUCTION: Supplementary immunization activities (SIAs) aim to interrupt measles transmission by reaching susceptible children, including children who have not received the recommended two routine doses of MCV before the SIA. However, both strategies may miss the same children if vaccine doses are highly correlated. How well SIAs reach children missed by routine immunization is a key metric in assessing the added value of SIAs. METHODS: Children aged 9 months to younger than 5 years were enrolled in cross-sectional household serosurveys conducted in five districts in India following the 2017-2019 measles-rubella (MR) SIA. History of measles containing vaccine (MCV) through routine services or SIA was obtained from documents and verbal recall. Receipt of a first or second MCV dose during the SIA was categorized as "added value" of the SIA in reaching un- and under-vaccinated children. RESULTS: A total of 1,675 children were enrolled in these post-SIA surveys. The percentage of children receiving a 1st or 2nd dose through the SIA ranged from 12.8% in Thiruvananthapuram District to 48.6% in Dibrugarh District. Although the number of zero-dose children prior to the SIA was small in most sites, the proportion reached by the SIA ranged from 45.8% in Thiruvananthapuram District to 94.9% in Dibrugarh District. Fewer than 7% of children remained measles zero-dose after the MR SIA (range: 1.1-6.4%) compared to up to 28% before the SIA (range: 7.3-28.1%). DISCUSSION: We demonstrated the MR SIA provided considerable added value in terms of measles vaccination coverage, although there was variability across districts due to differences in routine and SIA coverage, and which children were reached by the SIA. Metrics evaluating the added value of an SIA can help to inform the design of vaccination strategies to better reach zero-dose or undervaccinated children.

Modulation of ß-cell function: a translational journey from the bench to the bedside.

Both decreased insulin secretion and action contribute to the pathogenesis of type 2 diabetes (T2D) in humans. The insulin receptor and insulin signalling proteins are present in the rodent and human ß-cell and modulate cell growth and function. Insulin receptors and insulin signalling proteins in ß-cells are critical for compensatory islet growth in response to insulin resistance. Rodents with tissue-specific knockout of the insulin receptor in the ß-cell (ßIRKO) show reduced first-phase glucose-stimulated insulin secretion (GSIS) and with aging develop glucose intolerance and diabetes, phenotypically similar to the process seen in human T2D. Expression of multiple insulin signalling proteins is reduced in islets of patients with T2D. Insulin potentiates GSIS in isolated human ß-cells. Recent studies in humans in vivo show that pre-exposure to insulin increases GSIS, and this effect is diminished in persons with insulin resistance or T2D. ß-Cell function correlates to whole-body insulin sensitivity. Together, these findings suggest that pancreatic ß-cell dysfunction could be caused by a defect in insulin signalling within ß-cell, and ß-cell insulin resistance may lead to a loss of ß-cell function and/or mass, contributing to the pathophysiology of T2D.

Growth factor signalling in the regulation of α-cell fate.

Glucagon plays critical roles in regulating glucose homeostasis, mainly by counteracting the effects of insulin. Consequently, the dysregulated glucagon secretion that is evident in type 2 diabetes has significant implications in the pathophysiology of the disease. Glucagon secretion from pancreatic α-cells has been suggested to be modulated by blood glucose, signals from the nervous system and endocrine components. In addition to these regulators, intraislet factors acting in a paracrine manner from neighbouring ß-cells are emerging as central modulator(s) of α-cell biology. One of the most important of these paracrine factors, insulin, modulates glucagon secretion. Indeed, the α-cell-specific insulin receptor knockout (αIRKO) mouse manifests hypersecretion of glucagon in the postprandial stage and exhibits defective secretion in fasting-induced hypoglycaemia, together mimicking the α-cell defects observed in type 2 diabetes. Interestingly, αIRKO mice display a progressive increase in ß-cell mass and a concomitant decrease in α-cells. Lineage trace analyses reveal that the new ß-cells originate, in part, from the insulin receptor-deficient α-cells indicating a critical role for α-cell insulin signalling in determining ß-cell origin. Our studies also reveal that glucagon-like peptide-1 (GLP-1) treatment of αIRKO mice suppresses glucagon secretion despite absence of functional insulin receptors precluding a role for insulin in GLP-1 action on α-cells in this model. These findings highlight the significance of insulin signalling in the regulation of α-cell biology.

The roles of telomeres and telomerase in beta-cell regeneration.

Telomerase is a specialized reverse transcriptase that is responsible for extending and preserving the end of the chromosomes (telomeres). Telomerase plays a key role in regulating the lifespan of mammalian cells and is involved in critical aspects of cellular ageing processes. In this review, we will briefly summarize our current understanding of the functions of telomeres, telomerase and their regulation. Considering that compensatory islet hyperplasia and beta-cell regeneration play important roles in the prevention and/or delay of the onset of overt diabetes, we will also examine current literature regarding the effects of diabetes on telomere shortening and provide insights from our own studies on the role of telomerase in beta-cell regeneration.

Differential expression of cell cycle proteins during ageing of pancreatic islet cells.

One of the major challenges for developmental biologists and investigators in the field of diabetes over the last few decades has been to dissect the origin of pancreatic endocrine cells and to accurately understand the mechanisms that regulate islet cell regeneration. While significant advances have been made recently, there continues to be a paucity of knowledge regarding the growth factor signalling pathways that directly regulate the proteins involved in islet cell cycle control. We will discuss recent work in these areas and provide insights from our studies into age-dependent alterations in the expression of growth factor signalling proteins and cell cycle proteins in islet cells.

Inheritance of pollen-less anthers and "thrum" and "pin" flowers in periwinkle.

Two mutants, 1 with small, pollen-less anthers (OR-EA) and another with "pin" flowers (EMS 13-2), in contrast to "thrum" flowers found in normal periwinkle (Catharanthus roseus) plants, were isolated after induced mutagenesis in strain OR and cultivar, "Dhawal," respectively. Inheritance of these 2 traits, pollen-less anthers, and pin flowers was studied by crossing the mutants with their respective parental strains. Segregation ratios observed in F(2) and testcross generations of the cross OR-EA x OR suggested that the pollen-less anthers trait was determined by duplicate recessive genes. Data obtained from F(2) and F(3) generations of the cross involving mutant EMS 13-2 with pin flowers and its parental variety Dhawal, suggested that production of pin (mutant) and thrum (normal) flowers was under the control of inhibitory epistatic interaction between 2 independently inherited genes.

Altered function of insulin receptor substrate-1-deficient mouse islets and cultured beta-cell lines.

Insulin receptor substrate-1 (IRS-1) is pivotal in mediating the actions of insulin and growth factors in most tissues of the body, but its role in insulin-producing beta islet cells is unclear. Freshly isolated islets from IRS-1 knockout mice and SV40-transformed IRS-1-deficient beta-cell lines exhibit marked insulin secretory defects in response to glucose and arginine. Furthermore, insulin expression is reduced by about 2-fold in the IRS-1-null islets and beta-cell lines, and this defect can be partially restored by transfecting the cells with IRS-1. These data provide evidence for an important role of IRS-1 in islet function and provide a novel functional link between the insulin signaling and insulin secretion pathways. This article may have been published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.

Possible evidence for endogenous production of a novel galanin-like peptide.

Galanin mRNA and peptide are not detectable in normal islets. We studied the effect of galanin antagonists on insulin secretion in the rat beta cell line, RIN5AH, and in perifused rat islets. In RIN cell membranes galanin and its antagonists showed high affinity for 125I-galanin binding sites [Kd: (galanin) 0.03+/-0.01; Ki for galanin antagonists: (C7) 0.12+/- 0.02, (M35) 0.21+/-0.04, and (M40) 0.22+/-0.03 nM, mean+/- SEM, n = 4]. Galanin (1 microM) inhibited glucose-induced insulin release in islets (control 21.2+/-1.5 vs. galanin 4.5+/-0.2 fmol/islet per min, P < 0.001, n = 6) and RIN5AH cells (control 0.26+/-0.01 vs. galanin 0.15+/-0.02 pmol/10(6) cells per h, P < 0.001, n = 9). In RIN5AH cells, all antagonists blocked the inhibitory effects of galanin and stimulated insulin release in the absence of galanin. C7 and M40 (1 microM) alone significantly stimulated glucose-induced insulin secretion. Purified porcine galanin antibody (GAb) enhanced glucose-induced insulin release from islets (control 100+/- 16.3% vs. GAb 806.1+/-10.4%, P < 0.001, n = 6), and RIN5AH cells (control 100+/-9.6% vs. GAb 149+/-6.8%, P < 0. 01, n = 6). Western blotting of dexamethasone-treated islet extracts using GAb showed a specific band of similar molecular weight to porcine galanin not detected using a rat specific galanin antibody. One possible explanation for these results is the presence of an endogenous galanin-like peptide.

Leptin rapidly suppresses insulin release from insulinoma cells, rat and human islets and, in vivo, in mice.

Obesity is associated with diabetes, and leptin is known to be elevated in obesity. To investigate whether leptin has a direct effect on insulin secretion, isolated rat and human islets and cultured insulinoma cells were studied. In all cases, mouse leptin inhibited insulin secretion at concentrations within the plasma range reported in humans. Insulin mRNA expression was also suppressed in the cultured cells and rat islets. The long form of the leptin receptor (OB-Rb) mRNA was present in the islets and insulinoma cell lines. To determine the significance of these findings in vivo, normal fed mice were injected with two doses of leptin. A significant decrease in plasma insulin and associated rise in glucose concentration were observed. Fasted normal and leptin receptor-deficient db/db mice showed no response to leptin. A dose of leptin, which mimicked that found in normal mice, was administered to leptin-deficient, hyperinsulinemic ob/ob mice. This caused a marked lowering of plasma insulin concentration and a doubling of plasma glucose. Thus, leptin has a powerful acute inhibitory effect on insulin secretion. These results suggest that the action of leptin may be one mechanism by which excess adipose tissue could acutely impair carbohydrate metabolism.

Exploring inter-organ crosstalk to uncover mechanisms that regulate ß-cell function and mass.

Impaired ß-cell function and insufficient ß-cell mass compensation are twin pathogenic features that underlie type 2 diabetes (T2D). Current therapeutic strategies continue to evolve to improve treatment outcomes in different ethnic populations and include approaches to counter insulin resistance and improve ß-cell function. Although the effects of insulin secretion on metabolic organs such as liver, skeletal muscle and adipose is directly relevant for improving glucose uptake and reduce hyperglycemia, the ability of pancreatic ß-cells to crosstalk with multiple non-metabolic tissues is providing novel insights into potential opportunities for improving ß-cell function and/or mass that could have beneficial effects in patients with diabetes. For example, the role of the gastrointestinal system in the regulation of ß-cell biology is well recognized and has been exploited clinically to develop incretin-related antidiabetic agents. The microbiome and the immune system are emerging as important players in regulating ß-cell function and mass. The rich innervation of islet cells indicates it is a prime organ for regulation by the nervous system. In this review, we discuss the potential implications of signals from these organ systems as well as those from bone, placenta, kidney, thyroid, endothelial cells, reproductive organs and adrenal and pituitary glands that can directly impact ß-cell biology. An added layer of complexity is the limited data regarding the relative relevance of one or more of these systems in different ethnic populations. It is evident that better understanding of this paradigm would provide clues to enhance ß-cell function and/or mass in vivo in the long-term goal of treating or curing patients with diabetes.

A model to explore the interaction between muscle insulin resistance and beta-cell dysfunction in the development of type 2 diabetes.

Type 2 diabetes is a polygenic disease characterized by defects in both insulin secretion and insulin action. We have previously reported that isolated insulin resistance in muscle by a tissue-specific insulin receptor knockout (MIRKO mouse) is not sufficient to alter glucose homeostasis, whereas beta-cell-specific insulin receptor knockout (betaIRKO) mice manifest severe progressive glucose intolerance due to loss of glucose-stimulated acute-phase insulin release. To explore the interaction between insulin resistance in muscle and altered insulin secretion, we created a double tissue-specific insulin receptor knockout in these tissues. Surprisingly, betaIRKO-MIRKO mice show an improvement rather than a deterioration of glucose tolerance when compared to betaIRKO mice. This is due to improved glucose-stimulated acute insulin release and redistribution of substrates with increased glucose uptake in adipose tissue and liver in vivo, without a significant decrease in muscle glucose uptake. Thus, insulin resistance in muscle leads to improved glucose-stimulated first-phase insulin secretion from beta-cells and shunting of substrates to nonmuscle tissues, collectively leading to improved glucose tolerance. These data suggest that muscle, either via changes in substrate availability or by acting as an endocrine tissue, communicates with and regulates insulin sensitivity in other tissues.

Microsurgical anatomy of the middle cerebral artery.

BACKGROUND: The microsurgical anatomy of the middle cerebral artery (MCA) is of particular interest to the cerebrovascular surgeon. The purpose of this study was to define the microsurgical anatomy of the MCA and its various branches in the Indian population. METHODS: Ten MCAs were studied from five cadaveric brain specimens. The authors studied the outer diameter, length, branches, perforators and site of these on the main trunk (M1), the division of the main trunk, the secondary trunks and their various cortical branches using the operating microscope under 5-20x magnification. RESULTS: The outer diameter of the MCA main trunk ranges from 2.5 to 4 mm with a mean of 3.35 mm. The superolateral branches consisted of polar temporal artery and anterior temporal artery that had a common origin and sometimes the uncal artery or the accessory uncal artery. Perforators or lenticulostriate arteries were seen in the inferomedial surface all along the length of M1. Eight bifurcations and two trifurcations were noted. Cortical branches and their origin are discussed. CONCLUSION: Although the microsurgical anatomy of the MCA in Indian population correlated with the findings in the western literature, some structural and statistical variations were noted.

A study of leucorrhoea in reproductive age group women of Nagpur City.

A community based cross-sectional study was conducted in reproductive age group women in an urban community of Nagpur, to assess the prevalence of leucorrhoea and the factors influencing the same in these women. The study participants included 506 females, out of which 149 were unmarried and 357 were married. Detailed history and clinical examination was done in all the females including gynecological examination in all the married females. Leucorrhoea was present in 139 (27.47%) females. Leucorrhoea was found significantly more in married females as compared to unmarried (p < 0.001), pregnant as compared to non-pregnant (OR = 2.10, 95% C.I. = 1.02-4.32), and women of lower socioeconomic status (p < 0.001), women with high parity (p < 0.001). Use of Cu-T was not associated with Leucorrhoea (p > 0.05).

Pyroglutamyl-phenylalanyl-proline amide attenuates thyrotropin-releasing hormone-stimulated insulin secretion in perifused rat islets and insulin-secreting clonal beta-cell lines.

TRH immunoreactivity has been detected in the pancreas of man and rat and localized to the islets of Langerhans. We studied the effect of synthetic TRH and the related tripeptide pyroglutamyl-phenylalanyl-proline amide (EFP) on isolated perifused rat islets and the glucose-responsive clonal cell lines HIT-T15 and RIN5AH. TRH at 10 nM potentiated [0.5 +/- 0.1 (control) vs. 0.8 +/- 0.1 (TRH) pmol/10(6) cells per 120 min; mean +/- SEM; n = 6; P < 0.001; n = 15], whereas EFP from 1 nM upwards suppressed glucose-stimulated insulin secretion [0.8 +/- 0.1 (control) vs. 0.5 +/- 0.1 (EFP) pmol/10(6) cells per 120 min; P < 0.001; n = 12) in the cell lines. Further, EFP reversed TRH-stimulated insulin release. Similar responses were observed in perifused isolated rat islets at the tested dose of 1 microM. Gel permeation chromatography of rat adult and neonatal whole pancreas, isolated islets, and HIT cell extracts demonstrated the elution of total TRH-like immunoreactivity (t-TRH-LI) in the same position as synthetic TRH. Cation exchange analysis of the t-TRH-LI from rat adult pancreas and HIT cell extracts showed that neutral TRH-like peptides corresponding to synthetic EFP were also present. Reverse-phase fast protein liquid chromatographic analysis of t-TRH-LI in the unbound fraction of these extracts subjected to anion exchange columns, also demonstrated peaks corresponding to synthetic EFP. We conclude that TRH potentiates, whereas EFP inhibits, glucose-stimulated insulin release in isolated perifused islets and the cell lines. In addition, EFP reversed the stimulatory effect of TRH. The presence of EFP-LI in rat adult and neonatal pancreas and HIT cell extracts suggests it may contribute in the modulation of pancreatic endocrine function.

The influence of different methods on basal metabolic rate measurements in human subjects.

While collating basal metabolic rate (BMR) measurements made worldwide it becomes important to know how different instruments compare with each other and whether errors in methodology could account for the differences in BMRs measured. BMRs of 34 healthy individuals were measured by using five different instruments in various combinations. Results show that energy outputs were comparable between the oxylog. Hartmann and Braun Metabolator, ventilated tent and hood, and whole-body indirect calorimeter: small differences, if any, were not statistically significant. However, significant interactions existed between subjects with the ventilated tent and hood and calorimeter when measurements were taken in subjects who were unaccustomed to the apparatus. When converting O2-consumption measurements to energy output, some instruments make assumptions that introduce a variable error in the final result, which may lead to systematic errors during the compilation of large databases of human BMRs.

Investigation of the effects of antisense oligodeoxynucleotides to islet amyloid polypeptide mRNA on insulin release, content and expression.

We have investigated the effects of antisense oligodeoxynucleotides (oligos) to islet amyloid polypeptide (IAPP) mRNA on the expression and secretion of IAPP and insulin, in the clonal beta-cell line HIT-T15. Phosphorothioate-modified oligos were cytotoxic compared with phosphodiester (D)-oligos. Of the nine oligos tested using a lipofection reagent, O3, a 30-mer D-oligo complementary to a sequence downstream of the IAPP initiation codon, showed a significant dose-dependent suppression of IAPP mRNA, with a 42% decrease at 7.5 microM, compared with a scrambled (MSO3) control oligo (n = 3, P < 0.01). A subsequent 89% suppression of IAPP release was observed in the 4-h period following antisense treatment (1.78 +/- 0.13 (MSO3) vs 0.19 +/- 0.14 (O3) pmol/10(6) cells per 240 min, n = 7, P < 0.01). A significant increase in insulin mRNA (100 +/- 10% (MSO3) vs 124 +/- 8% (O3), n = 3, P < 0.05) and insulin content (13.0 +/- 0.9 (MSO3) vs 17.4 +/- 1.4 (O3) pmol/10(6) cells, n = 7, P = 0.028) was observed following treatment with O3 at 7.5 microM. O8, a 20-mer D-oligo directed to a region of IAPP mRNA further downstream than O3, also showed a decrease in IAPP mRNA and peptide release and an increase in insulin content. No significant changes were observed in the expression and release of the unrelated beta-cell peptide, neuropeptide Y. We thus show a suppression of synthesis and release of IAPP in HIT-T15 cells using antisense oligos. The associated increase in insulin mRNA and content in these cells after treatment with IAPP antisense oligos is in accord with an inhibitor action of IAPP on insulin availability.

A 67 kDa protein mediates pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-stimulated insulin secretion in a hamster clonal beta-cell line.

Insulin secretion is regulated by neural and neurohormonal factors. The report of nerves releasing pituitary adenylate cyclase-activating polypeptide (PACAP)--a 38 amino acid peptide--in the endocrine pancreas, suggests it may be important in modulating insulin release. We therefore carried out receptor-binding studies on membranes prepared from the glucose-responsive clonal beta-cell line HIT-T15, and also examined the effects of PACAP38, PACAP27--a C-terminal truncated form of the peptide--and vasoactive intestinal peptide (VIP) on insulin and islet amyloid polypeptide (IAPP) release. We showed by chemical cross-linking that PACAP and VIP stimulate secretion from the clonal cells by binding to a receptor with a molecular weight of 67 kDa (n = 4). Binding was saturable when membranes were incubated with 125I-PACAP27 (Kd 1.2 +/- 0.2 nM; Bmax 415.7 +/- 35.3 fmol/mg; n = 4) or 125I-VIP (Kd 1.3 +/- 0.3 nM; Bmax 354.8 +/- 42.8 fmol/mg; n = 4). We also demonstrated an increase in glucose-stimulated insulin (PACAP27, 366.6 +/- 25.8%; PACAP38, 389.9 +/- 13.4%; VIP, 342.6 +/- 16.1% of control; all at 1 microM, P < 0.01 vs control) and IAPP release (PACAP27, 236.9 +/- 26.2%; PACAP38, 226.5 +/- 10.9%; VIP, 242.9 +/- 15.8% of control; all at 1 microM, P < 0.01 vs control). Incubation of the cells with these peptides, for a duration of 12 h, in the presence of 5.5 mM glucose, did not alter the expression of insulin or IAPP. These findings suggest that PACAP and VIP stimulate secretion of insulin and IAPP by binding to a 67 kDa protein on clonal beta-cells and do not alter the transcription of insulin and IAPP under the conditions tested.

Glibenclamide but not other sulphonylureas stimulates release of neuropeptide Y from perifused rat islets and hamster insulinoma cells.

We have studied the effects of first and second generation sulphonylureas on the release of insulin and neuropeptide tyrosine (NPY) from hamster insulinoma tumour (HIT T15) cells and isolated rat islets. In the presence of 5.5 mmol/l glucose all sulphonylureas stimulated insulin release from the HIT cells (P<0.01 ANOVA, n> or =4) but only glibenclamide (GLIB, 10 micromol/l) stimulated the release of NPY (mean+/-s.e.m. control 11.1+/-1.3 vs GLIB 28.4+/-4.1 fmol/h per 10(6) cells, P<0001, n=16). In isolated perifused rat islets both glibenclamide (10 micromol/l) (control 3.5+/-0.3 vs GLIB 6. 3+/-0.2 fmol/min per islet, P<0.01, n=6) and tolbutamide (50 micromol/l) (control 4.7+/-0.1 vs TOLB 6.7+/-0.3 fmol/min per islet, P<0.01, n=6) enhanced glucose (8 mmol/l)-stimulated insulin release. However, only glibenclamide stimulated the release of NPY from the islets (control 3.4+/-0.8 vs GLIB 24.5+/-5 attomol/min per islet, P<0.01, n=6). Similar results were obtained in islets isolated from dexamethasonetreated rats. Glibenclamide treatment of HIT cells showed a prompt insulin release (10 min) while NPY secretion was slower (60 min), suggesting that internalization of the sulphonylurea is required to stimulate NPY release. Glibenclamide, the most common oral therapeutic agent in type 2 diabetes mellitus, is associated with release of the autocrine insulin secretion inhibitor, NPY.