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Aim To examine the mechanism of action of γ-aminobutyric acid (GABA) on β-cell proliferation and investigate if co-treatment with Ly49, a novel GABA type A receptor positive allosteric modulator (GABAA -R PAM), amplifies this effect. Methods Human or mouse islets were co-treated for 4-5 days with GABA and selected receptor or cell signalling pathway modulators. Immunofluorescence was used to determine protein co-localization, cell number or proliferation, and islet size. Osmotic minipumps were surgically implanted in mice to assess Ly49 effects on pancreatic β-cells. Results Amplification of GABAA -R signalling enhanced GABA-stimulated β-cell proliferation in cultured mouse islets. Co-treatment of GABA with an inhibitor specific for PI3K, mTORC1/2, or p70S6K, abolished GABA-stimulated β-cell proliferation in mouse and human islets. Nuclear p-AktSer473 and p-p70S6KThr421/Ser424 expression in pancreatic β-cells was increased in GABA-treated mice compared with vehicle-treated mice, an effect augmented with GABA and Ly49 co-treatment. Mice co-treated with GABA and Ly49 exhibited enhanced β-cell area and proliferation compared with GABA-treated mice. Furthermore, S961 injection (an insulin receptor antagonist) resulted in enhanced plasma insulin in GABA and Ly49 co-treated mice compared with GABA-treated mice. Importantly, GABA co-treated with Ly49 increased β-cell proliferation in human islets providing a potential application for human subjects. Conclusions We show that GABA stimulates β-cell proliferation via the PI3K/mTORC1/p70S6K pathway in both mouse and human islets. Furthermore, we show that Ly49 enhances the β-cell regenerative effects of GABA, showing potential in the intervention of diabetes.

γ-Aminobutyric acid (GABA) administration has been shown to increase β-cell mass, leading to a reversal of type 1 diabetes in mice. Whether GABA has any effect on β cells of healthy and prediabetic/glucose-intolerant obese mice remains unknown. In the present study, we show that oral GABA administration ( ad libitum) to mice indeed increased pancreatic β-cell mass, which led to a modest enhancement in insulin secretion and glucose tolerance. However, GABA treatment did not further increase insulin-positive islet area in high fat diet-fed mice and was unable to prevent or reverse glucose intolerance and insulin resistance. Mechanistically, whether in vivo or in vitro, GABA treatment increased β-cell proliferation. In vitro, the effect was shown to be mediated via the GABAA receptor. Single-cell RNA sequencing analysis revealed that GABA preferentially up-regulated pathways linked to β-cell proliferation and simultaneously down-regulated those networks required for other processes, including insulin biosynthesis and metabolism. Interestingly, single-cell differential expression analysis revealed GABA treatment gave rise to a distinct subpopulation of β cells with a unique transcriptional signature, including urocortin 3 ( ucn3), wnt4, and hepacam2. Taken together, this study provides new mechanistic insight into the proliferative nature of GABA but suggests that β-cell compensation associated with prediabetes overlaps with, and negates, its proliferative effects.-Untereiner, A., Abdo, S., Bhattacharjee, A., Gohil, H., Pourasgari, F., Ibeh, N., Lai, M., Batchuluun, B., Wong, A., Khuu, N., Liu, Y., Al Rijjal, D., Winegarden, N., Virtanen, C., Orser, B. A., Cabrera, O., Varga, G., Rocheleau, J., Dai, F. F., Wheeler, M. B. GABA promotes β-cell proliferation, but does not overcome impaired glucose homeostasis associated with diet-induced obesity.

The International Diabetic Federation estimated that 415 million adults currently have diabetes and 318 million adults had impaired glucose tolerance, putting them at high risk of developing diabetes in the future. In Type 1 Diabetes (T1D), the β cells are lost because of autoimmune reactions. Although islet transplantation has been a promising therapy for T1D, it is greatly limited by pancreatic donors. Here, we describe a protocol to generate glucose- responsive pancreatic β-like (GRPβ-L) cells from human-induced pluripotent stem (iPS) cells. We recapitulate in vivo pancreas development by in vitro induction of differentiating human (iPS) cells with stage-specific signaling molecules and proteins. Inhibition of Tyrosine Kinase receptor AXL, TGF-β, and Notch signaling pathways in the final stage of the five-stage protocol could efficiently generate GRPβ-L from the endocrine progenitor. Differentiation of human iPS cells through the protocol could result in functional GRPβ-L cells, which could be used in pharmaceutical and β cell biology studies. © 2018 by John Wiley & Sons, Inc.

SummaryObjective To measure a profile of hormones in a group of elite athletes. Increasing awareness of the widespread use of hormones as performance-enhancing agents focusses attention on what may be considered as normal in this unusual group. Design Blood samples were obtained from 813 volunteer elite athletes from a cross-section of 15 sporting categories. An endocrine profile was measured on a subset of 693. Participants Volunteer elite athletes. Samples were drawn within two hours of an event at a major national or international competition. Measurements Demographics and hormone profiles were obtained on 454 male and 239 female elite athletes. Results Hormone profiles showed significant differences in 19 of the 24 measured variables between sexes and between all of the 15 sporting disciplines in men and 11 out of 24 in women. 16·5% of men had low testosterone levels, whereas 13·7% of women had high levels with complete overlap between the sexes. Women had a lean body mass 85% that of men – sufficient to account for sex differences in performance. There were highly significant correlations between many of the measured hormones. Conclusions Hormone profiles from elite athletes differ from usual reference ranges. Individual results are dependent on a number of factors including age, gender and physique. Differences in profiles between sports suggest that an individual's profile may contribute to his/her proficiency in a particular sport. The IOC definition of a woman as one who has a ‘normal’ testosterone level is untenable.

Urtica Dioica (UD) is a plant shown to reduce blood glucose levels upon oral ingestion; however, neither its active component nor its mechanism of action has been identified. One active fraction of this extract, termed UD-1, was separated by molecular sieve column chromatography and purified by high performance liquid chromatography (HPLC). While UD-1 did not stimulate insulin secretion in glucose-responsive MIN6 clonal beta-cells, chronic exposure (24 h) significantly enhanced glucose uptake (∼1.5-fold) in L6-GLUT4myc myoblast cells. Using HPLC and MALDI-TOF, we further purified the UD-1 fraction into two fractions termed UD-1A and UD-1B. Computational and structural analyses strongly suggested that the antidiabetic component of UD-1 was due to one or more structurally related cyclical peptides that facilitate glucose uptake by forming unique glucose permeable pores. The structure and function of these glucose-conducting pores are discussed herein. Copyright © 2009 John Wiley & Sons, Ltd.

It is well known that zinc is required in pancreatic beta-cells in the process of insulin biosynthesis and the maturation of insulin secretory granules. In fact, the zinc level in pancreatic islets is amongst the highest in the body and reduction in its levels in the pancreas has been associated with diabetes. High concentrations of zinc can also be toxic because of enhanced oxidative damage. The link between zinc, diabetes and islet dysfunction has recently been reiterated by genomewide association studies that identified an islet cell membrane zinc transporter, SLC30A8 (ZnT8), as one of the risk loci for type 2 diabetes. Here we explore the importance of both zinc and ZnT8 to islet biology and whole body glucose homeostasis.

Background and purpose: Some non-steroidal anti-inflammatory drugs (NSAIDs) incidentally induce hypoglycemia, which is often seen in diabetic patients receiving sulphonylureas. NSAIDs influence various ion channel activities, thus they may cause hypoglycemia by affecting ion channel functions in insulin secreting beta cells. This study investigated the effects of the NSAID meclofenamic acid (MFA) on the electrical excitability and the secretion of insulin from pancreatic beta cells. Experimental approach: Using patch clamp techniques and insulin secretion assays, the effects of MFA on the membrane potential and transmembrane current of INS-1 cells, and insulin secretion were studied. Key results: Under perforated patch recordings, MFA induced a rapid depolarization in INS-1 cells bathed in low (2.8mM), but not high (28mM) glucose solutions. MFA, as well as acetylsalicylic acid (ASA) and flufenamic acid (FFA), excited the cells by inhibiting ATP-sensitive potassium channels (KATP). In whole cell recordings, KATP conductance consistently appeared when intracellular ATP was diluted. Intracellular glibenclamide prevented the development of KATP activity, whereas intracellular MFA had no effect. At low glibenclamide concentrations, MFA induced additional inhibition of the KATP current. Live cell Ca2+ imaging displayed that MFA elevated intracellular Ca2+ at low glucose concentrations. Furthermore, MFA dose-dependently increased insulin release under low, but not high, glucose conditions. Conclusions and Implications: MFA blocked KATP through an extracellular mechanism and thus increased insulin secretion. As some NSAIDs synergistically inhibit KATP activity together with sulphonylureas, the risk of NSAID-induced hypoglycemia should be considered when glucose-lowering compounds are administered. British Journal of Pharmacology (2007) 151, 483–493; doi:10.1038/sj.bjp.0707259

Cytokines are multifunctional proteins that play a critical role in cellular communication and activation. Cytokines have been classified as being proinflammatory (T helper 1, Th1) or antiinflammatory (T helper 2, Th2) depending on their effects on the immune system. However, cytokines impact a variety of tissues in a complex manner that regulates inflammation, cell death, and cell proliferation and migration as well as healing mechanisms. Ethanol (alcohol) is known to alter cytokine levels in a variety of tissues including plasma, lung, liver, and brain. Studies on human monocyte responses to pathogens reveal ethanol disruption of cytokine production depending upon the pathogen and duration of alcohol consumption, with multiple pathogens and chronic ethanol promoting inflammatory cytokine production. In lung, cytokine production is disrupted by ethanol exacerbating respiratory distress syndrome with greatly increased expression of transforming growth factor b (TGFb). Alcoholic liver disease involves an inflammatory hepatitis and an exaggerated Th1 response with increases in tumor necrosis factor a (TNFa). Recent studies suggest that the transition from Th1 to Th2 cytokines contribute to hepatic fibrosis and cirrhosis. Cytokines affect the brain and likely contribute to changes in the central nervous system that contribute to long-term changes in behavior and neurodegeneration. Together these studies suggest that ethanol disruption of cytokines and inflammation contribute in multiple ways to a diversity of alcoholic pathologies.

We report the encapsulation of MIN6 cells, a pancreatic β-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at ∼30°C, gels were formed that exhibit mechanical integrity, and are stable in H2O, PBS and complete DMEM with negligible mass loss at 37°C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37°C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 µm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes. Biotechnol. Bioeng. 2007;96: 146–155. © 2006 Wiley Periodicals, Inc.

Mechanical properties of Nicalon-fiber-reinforced silicon carbide matrix composites were evaluated, in flexure, at various temperatures ranging from ambient to 1300°C. First matrix cracking stress ranged from 250 to 280 MPa and was relatively insensitive to test temperature. The measured ultimate strength showed a small increase from a room-temperature value of 370 to 460 MPa at 800°C. Beyond 800°C, however, strength dropped to as low as 280 MPa at 1300°C. This decrease in ultimate strength at elevated temperatures is believed to be partly due to degradation of in situ Nicalon fiber strength. Scanning electron microscopy was employed to evaluate the in situ Nicalon fiber strengths via fracture mirror size measurements. Degradation of Nicalon fiber strength is attributed to thermal damage and to structural changes to the fiber at elevated temperatures. Measured values of ultimate strength of the composites were compared with predictions made on the basis of in situ fiber strength characteristics and an available analytical model.

Recently, it was demonstrated that liver injury and TNF-alpha production as a result of endotoxin (lipopolysaccharide, LPS) were attenuated by feeding animals a diet enriched with glycine. This phenomenon was shown to be a result of, at least in part, activation of a chloride channel in Kupffer cells by glycine, which hyperpolarizes the cell membrane and blunts increases in intracellular calcium concentrations ([Ca(2+)](i)) similar to its action in the neuron. It is well known that hepatotoxicity due to LPS has a neutrophil-mediated component and that activation of neutrophils is dependent on increases in [Ca(2+)](i). Therefore, the purpose of this study was to determine if glycine affected agonist-induced increases in [Ca(2+)](i) in rat neutrophils. The effect of glycine on increases in [Ca(2+)](i) elicited either by the bacterial-derived peptide formyl-methionine-leucine-phenylalanine (FMLP) or LPS was studied in individual neutrophils using Fura-2 and fluorescence microscopy. Both FMLP and LPS caused dose-dependent increases in [Ca(2+)](i), which were maximal at 1 microM FMLP and 100 microgram/ml LPS, respectively. LPS increased intracellular calcium in the presence and absence of extracellular calcium. Glycine blunted increases in [Ca(2+)](i) in a dose-dependent manner with an IC(50) of approximately 0.3 mM, values only slightly higher than plasma levels. Glycine was unable to prevent agonist-induced increases in [Ca(2+)](i) in chloride-free buffer. Moreover, strychnine (1 microM), an antagonist of the glycine-gated chloride channel in the central nervous system, reversed the effects of glycine (1 mM) on FMLP- or LPS-stimulated increases in [Ca(2+)](i). To provide hard evidence for a glycine-gated chloride channel in the neutrophil, the effect of glycine on radioactive chloride uptake was determined. Glycine caused a dose-dependent increase in chloride uptake into neutrophils with an ED(50) of approximately 0.4 mM, an effect also prevented by 1 microM strychnine. Glycine also significantly reduced the production of superoxide anion from FMLP-stimulated neutrophils. Taken together, these data provide clear evidence that neutrophils contain a glycine-gated chloride channel that can attenuate increases in [Ca(2+)](i) and diminish oxidant production by this important leukocyte.

Summary OBJECTIVE Evidence is accumulating that the nocturnal increase in melatonin may influence pituitary hormone secretion. The aim of this study was to determine the effect of exogenous melatonin, in concencetrations spanning the physiological range, on the release of pituitary hormones in man during daylight hours DESIGN A double blind, randomized, crossover study. SUBJECTS Eight healthy male volunteers with a mean age of 21 6 0·5 years were studied on four occasions, observations being made after the adminstration of melatonin in doses of 0·05, 0·5 or 5·0 mg or placebo. They refrained from taking heavy exercise, alcohol and from smoking for 24 h prior to the study. MEASUREMENTS Serum cortisol, growth hormone, prolactin and plasma oxytocin, vasopressin, sodium, osmolality and packed cell volume were measured in samples taken at 30 minutes intervals for 150 minutes after the administration of melatonin. RESULTS Melatonin produced dose-dependent changes in circulating concentrations of oxytocin and vasopressin, the 0·5 mg dose being stimulatory, while 5·0 mg was inhibitory. These two doses stimulated growth hormone release, while there was no significant effect on prolactin or cortisol release. CONCLUSIONS These results confirm that the nocturnal increase in melatonin could contribute to the patterns of oxytocin, vasopressin and growth hormone release seen over 24 h.

Objective Vasopressin oxytocin and melatonin have been reported to be influenced by ovarian steroids. The neurohypophysial hormones have also been shown to display a diurnal pattern of secretion in men. We therefore studied the diurnal pattern of neurohypophysial hormone and melatonin secretion in premenopausal women and in women on oral contraceptives. Design Healthy normally cycling premenopausal women were studied over 24 hours during the mid-follicular and midluteal phases of the menstrual cycle. Healthy premenopausal women on oral contraceptives were studied over 24 hours at similar times. Subjects Eight healthy normally cycling women and 7 healthy premenopausal women on oral contraceptives. Measurements Plasma vasopressin oxytocin and melatonin were measured by radioimmunoassay. Results Vasopressin concentrations and its nocturnal peak were highest in the follicular phase of the natural menstrual cycle and attenuated in the women on oral contraceptives. Oxytocin concentrations did not vary between the two phases of the menstrual cycle but increased on oestrogen administration. Overall melatonin secretion was augmented in the women on oral contraceptives. Conclusions Vasopressin release and its nocturnal peak were greatest in the follicular phase of the menstrual cycle while melatonin secretion was augmented in the women on oral contraception. (authors)

OBJECTIVE The relationship between the pineal gland and pituitary function remains controversial, while the role of melatonin in the adaptation of the organism to the light-dark cycle of the environment is becoming increasingly recognized. The aim of this study was to investigate the effect of a manipulation of the melatonin rhythm on pituitary hormone secretion in man. DESIGN Double-blind controlled clinical study. SUBJECTS Ten adult healthy male volunteers, aged 21-33 years, were studied on two occasions: once after the administration of melatonin 5 mg orally for 4 days at 1700 hours and once after the administration of placebo, at similar times. On the day of each study the subjects undertook their normal duties but refrained from taking heavy exercise, from smoking and drinking alcohol. MEASUREMENTS Serum cortisol, growth hormone, prolactin and plasma vasopressin, oxytocin, melatonin, sodium, potassium, osmolality and packed cell volume were measured over the following 24 hours. RESULTS The cortisol peak was advanced and prolactin release increased after melatonin administration, while growth hormone was not affected. Vasopressin and oxytocin levels were found to increase during the night in the control study, but the period of the nocturnal increase in vasopressin concentrations was reduced after the administration of melatonin and the nocturnal increase of oxytocin was absent. CONCLUSION Altering the melatonin rhythm may affect neuroendocrine function, influencing the nocturnal pattern of neurohypophysial hormone secretion, augmenting prolactin release and advancing the peak of cortisol release.

OBJECTIVE Exposure to bright light inhibits melatonin secretion in man. As the relationship between melatonin and pituitary function remains controversial, we investigated the effect of altering the melatonin rhythm by bright light during the early hours of darkness on pituitary hormone secretion in man. DESIGN The investigation took the form of a randomized controlled clinical trial. SUBJECTS Ten adult healthy male volunteers, who were non-smokers and aged 21–33 years, were studied on two occasions: once during exposure to bright light from 2000 h to 0200 h and once during exposure to normal room lighting over the same period. On each day of the study, the subjects were allowed to sleep after lights were switched off at 0200 h. Observations were also performed when subjects were exposed to normal room lighting from 2000 h to 2400 h, thereafter being allowed to sleep. On each study day the subjects undertook their normal duties but refrained from taking heavy exercise and drinking alcohol. MEASUREMENTS Serum cortisol, GH and PRL, plasma vasopressin, oxytocin, melatonin, sodium, potassium and osmolality and packed cell volume were measured over 24 hours. RESULTS Bright light delayed the nocturnal melatonin peak by 2 hours and resulted in a decrease in cortisol concentrations. Growth hormone levels decreased but subsequently there was a significantly greater nocturnal increase. The PRL peak was delayed and nocturnal vasopressin concentrations were lower in both the studies where subjects were exposed to a modified sleep schedule. CONCLUSION Exposure to bright light during the early hours of darkness delays the nocturnal melatonin peak and alters cortisol, GH, PRL and nocturnal vasopressin secretion, while modification of the sleep pattern decreases vasopressin concentrations and alters its nocturnal peak.

OBJECTIVE Acne vulgaris is androgen dependent but the hormonal mechanisms are unclear. Although there have been many studies of serum hormones in women with acne there are few studies in men and the results are conflicting. We have therefore carried out a further study in men. DESIGN AND PATIENTS Fifty men with acne vulgaris were age-matched against 50 normal men. MEASUREMENTS Serum levels of dehydroepiandrosterone sulphate (DHEAS), 17 alpha-hydroxyprogesterone, 11-deoxycortisol, androstenedione and testosterone were measured by radioimmunoassay, sex hormone binding globulin (SHBG) by immunoradiometric assay and LH, FSH and oestradiol by automated ELISA. RESULTS The acne patients had higher levels of androstenedione, median 7.35 nmol/l, (interquartile range 2-7) vs 6.05 (2.3), P = 0.004; testosterone, 21.7 nmol/l (7.5) vs 17.55 (7.7), P = 0.04; and free androgen index (FAI) 78.26 (40) vs 65.06 (20), P = 0.007, but also had higher levels of 11-deoxycortisol, 13.65 nmol/l (4.3) vs 12.0 (4.3), P = 0.022. The LH, FSH, 17 alpha-hydroxyprogesterone, DHEAS, oestradiol and SHBG levels were not significantly different. Examination of the Spearman rank correlation coefficient matrices for the serum levels of 17 alpha-hydroxyprogesterone, androstenedione and 11-deoxycortisol showed that the strongest correlation was between androstenedione and 11-deoxycortisol. CONCLUSION Although there was overlap between the results of the acne patients and controls the acne patients tended to have higher levels of androstenedione, testosterone, free androgen index and 11-deoxycortisol. The higher levels of 11-deoxycortisol are suggestive of 11 beta-hydroyxlase dysfunction which could be due to a primary adrenal defect or a consequence of raised androgens. Also, a pathway between androstenedione and 11-deoxycortisol has been described in sheep and, although unsubstantiated in man, requires consideration.

A patient with a primary oral epidermoid carcinoma with presumed neck metastasis is presented who at operation was found to have a cervical mucoepidermoid carcinoma arising in the wall of a benign cyst. The case for considering this tumor a primary branchioma of mucoepidermoid type is presented, and the criteria for making the diagnosis of branchiogenic carcinoma are discussed.