The major goal in the treatment of type 2 diabetes mellitus is to control the hyperglycaemia characteristic of the disease. However, treatment with common therapies such as insulin or insulinotrophic ...sulphonylureas (SU), while effective in reducing hyperglycaemia, may impose a greater risk of hypoglycaemia, as neither therapy is self‐regulated by ambient blood glucose concentrations. Hypoglycaemia has been associated with adverse physical and psychological outcomes and may contribute to negative cardiovascular events; hence minimization of hypoglycaemia risk is clinically advantageous. Stimulation of insulin secretion from pancreatic β‐cells by glucagon‐like peptide 1 receptor (GLP‐1R) agonists is known to be glucose‐dependent. GLP‐1R agonists potentiate glucose‐stimulated insulin secretion and have little or no activity on insulin secretion in the absence of elevated blood glucose concentrations. This ‘glucose‐regulated’ activity of GLP‐1R agonists makes them useful and potentially safer therapeutics for overall glucose control compared to non‐regulated therapies; hyperglycaemia can be reduced with minimal hypoglycaemia. While the inherent mechanism of action of GLP‐1R agonists mediates their glucose dependence, studies in rats suggest that SUs may uncouple this dependence. This hypothesis is supported by clinical studies showing that the majority of events of hypoglycaemia in patients treated with GLP‐1R agonists occur in patients treated with a concomitant SU. This review aims to discuss the current understanding of the mechanisms by which GLP‐1R signalling promotes insulin secretion from pancreatic β‐cells via a glucose‐dependent process.
We present an approach for estimating and correcting Mie scattering occurring in infrared spectra of single cells, at diffraction limited probe size, as in synchrotron based microscopy. The Mie ...scattering is modeled by extended multiplicative signal correction (EMSC) and subtracted from the vibrational absorption. Because the Mie scattering depends non-linearly on α, the product of the radius and the refractive index of the medium/sphere causing it, a new method was developed for estimating the Mie scattering by EMSC for unknown radius and refractive index of the Mie scatterer. The theoretically expected Mie contributions for a range of different α values were computed according to the formulae developed by Van de Hulst (1957). The many simulated spectra were then summarized by a six-dimensional subspace model by principal component analysis (PCA). This subspace model was used in EMSC to estimate and correct for Mie scattering, as well as other additive and multiplicative interference effects. The approach was applied to a set of Fourier transform infrared (FT-IR) absorbance spectra measured for individual lung cancer cells in order to remove unwanted interferences and to estimate ranges of important α values for each spectrum. The results indicate that several cell components may contribute to the Mie scattering.
•Amylin, a 37 amino acid peptide pancreatic hormone co-secreted with insulin, normalizes the altered eating patterns induced by chronic psychological stress in the rat.•Amylin might mitigate other ...neurobehavioral states associated with chronic psychological stress and, therefore, administration of amylin analogues could provide relief from stress-related conditions like anxiety and depression.•Our newly reported findings support a potential for peripherally administered amylin analogues to access stress-related pathways and benefit pathways that regulate memory, emotion, and mood.
Amylin, a 37 amino acid peptide pancreatic hormone co-secreted with insulin, normalizes the altered eating patterns induced by chronic stress in the rat. Because these stress-induced changes are driven, in part, by brain corticotropin-releasing factor and corticosterone, and because alterations in the activity of these molecules and the stress system are commonly associated with neuropsychiatric diseases like anxiety, depression, and schizophrenia, we hypothesized that amylin might mitigate behavioral states associated with stress. Therefore, we tested the effects of rat amylin in rodent-based behavioral assays sensitive to neuropsychiatric drugs, including anxiolytic, antidepressant, antipsychotic, and cognitive enhancing drugs: stress-induced hyperthermia (SIH); marble burying; elevated plus maze (EPM)), forced swim test (FST), pre-pulse inhibition, and phencyclidine-induced locomotion. To assess the neural underpinnings of amylin's anxiolytic-like effects, we examined the effect of amylin on SIH after lesioning the area postrema (AP), which mediates amylin's metabolic effects. Amylin injection (IP, 0.1, 1.0, & 10 mg/kg) significantly (P < 0.05) decreased SIH (97% below vehicle) and AP lesions inhibited this effect. Amylin also reduced marble burying (72% below vehicle), but had no effect in the EPM. Together, these effects suggest anxiolytic-like activity or potential. Amylin injection also enhanced cognitive performance in the novel object recognition test. When administered continuously by implanted osmotic pumps, amylin (300 mg/kg/d) blocked SIH when tested at 1 and 4 weeks. Compared to vehicle, amylin infusion (1 and 3 mg/kg/d) reduced the time immobile in the FST (P < 0.05; 30% below vehicle), suggesting antidepressant-like potential. Although further testing is needed, our findings support a potential for peripherally administered amylin to access and benefit pathways that regulate memory, emotion, and mood.
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Objective: The current set of studies describe the in vivo metabolic actions of the novel amylin-mimetic peptide davalintide (AC2307) in rodents and compares these effects with those of the native ...peptide. Research design and methods: The anti-obesity effects of davalintide were examined after intraperitoneal injection or sustained peripheral infusion through subcutaneously implanted osmotic pumps. The effect of davalintide on food intake after lesioning of the area postrema (AP) and neuronal activation as measured by c-Fos, were also investigated. Results: Similar to amylin, davalintide bound with high affinity to amylin, calcitonin and calcitonin gene-related peptide receptors. Acutely, davalintide displayed greater suppression of dark-cycle feeding and an extended duration of action compared with amylin (23 versus 6 h). Davalintide had no effect on locomotor activity or kaolin consumption at doses that decreased food intake. Davalintide-induced weight loss through infusion was dose dependent, durable up to 8 weeks, fat-specific and lean-sparing, and was associated with a shift in food preference away from high-fat (palatable) chow. Metabolic rate was maintained during active weight loss. Both davalintide and amylin failed to suppress food intake after lesioning of the AP and activated similar brain nuclei, with davalintide displaying an extended duration of c-Fos expression compared with amylin (8 versus 2 h). Conclusion: Davalintide displayed enhanced in vivo metabolic activity over amylin while retaining the beneficial properties possessed by the native molecule. In vitro receptor binding, c-Fos expression and AP lesion studies suggest that the metabolic actions of davalintide and amylin occur through activation of similar neuronal pathways.
There is growing evidence that peptidic glucagon-like peptide-1 receptor agonists (GLP-1RA), such as exenatide, may provide useful therapeutic options for treatment of feline diabetes. However, ...because such drugs are administered subcutaneously, it is desirable that they be long-acting and not require frequent injections. We have developed a chemically controlled delivery system to support half-life extension of peptidic therapeutics. Here, the peptide is covalently attached to hydrogel microspheres by a self-cleaving β-eliminative linker; after subcutaneous injection of the microspheres, the peptide is slowly released from the depot to the systemic circulation. Using this technology, we developed a delivery system that supports once-monthly administration of a stable exenatide analog, Gln28exenatide, in rodents (Schneider, et al, ACS Chem Biol 12, 2107 to 2116, 2017). The purposes of the present study were a) to demonstrate pharmacokinetic and pharmacodynamic similarities of the deamidation-sensitive GLP-1RA exenatide and the closely related, more stable Gln28exenatide and b) to develop a long-acting GLP-1RA in cats. The results show that exenatide and Gln28exenatide injected intravenously or subcutaneously at 10 μg/kg have nearly identical pharmacokinetics in the cat—both having elimination half-lives of ∼40 min—but subcutaneously administered Gln28exenatide has superior bioavailability—93% for Gln28exenatide vs 52% for exenatide. The results also show that exenatide and Gln28exenatide have similar insulinotropic activities in the cat during a high-dose intravenous glucose tolerance test; they increased the area under the curve (AUC) for insulin to a similar extent but had no effect on glucose AUC. Finally, subcutaneous injection of a microsphere-Gln28exenatide conjugate containing an appropriate self-cleaving linker in the cat provides plasma Gln28exenatide with a half-life of about 40 d vs 40 min with the injected free peptide. Hence, the large body of information available for exenatide can be used to facilitate clinical development of Gln28exenatide as a treatment for feline diabetes, and the microsphere-Gln28exenatide conjugate is quite suitable for once-monthly subcutaneous administration of the peptide in the cat.
•Glucagon-like peptide-1 receptor agonists (GLP-1RAs) may be effective in treating feline diabetes.•A stable exenatide analog shows favorable pharmacokinetic and pharmacodynamic effects in cats.•A hydrogel drug delivery system allows monthly subcutaneous delivery of GLP-1RAs in cats.•We propose a patient-selection protocol for treatment of diabetes in cats with a GLP-1RA.
Exenatide (exendin-4) is an incretin mimetic currently marketed as an antidiabetic agent for patients with type 2 diabetes. In preclinical models, a reduction in body weight has also been shown in ...low-fat-fed, leptin receptor-deficient rodents.
To more closely model the polygenic and environmental state of human obesity, we characterized the effect of exenatide on food intake and body weight in high-fat-fed, normal (those with an intact leptin signaling system) rodents. As glucagon-like peptide-1 receptor agonism has been found to elicit behaviors associated with visceral illness in rodents, we also examined the effect of peripheral exenatide on kaolin consumption and locomotor activity.
High-fat-fed C57BL/6 mice and Sprague-Dawley rats were treated with exenatide (3, 10 and 30 microg/kg/day) for 4 weeks via subcutaneously implanted osmotic pumps. Food intake and body weight were assessed weekly. At 4 weeks, body composition and plasma metabolic profiles were measured. Kaolin consumption and locomotor activity were measured in fasted Sprague-Dawley rats following a single intraperitoneal injection of exenatide (0.1-10 microg/kg). Exenatide treatment in mice and rats dose-dependently decreased food intake and body weight; significant reductions in body weight gain were observed throughout treatment at 10 and 30 microg/kg/day (P<0.05). Decreased body weight gain was associated with a significant decrease in fat mass (P<0.05) with sparing of lean tissue. Plasma cholesterol, triglycerides and insulin were also significantly reduced (P<0.05). Exenatide at 10 microg/kg significantly reduced food intake (P<0.05) but failed to induce kaolin intake. In general, locomotor activity was reduced at doses of exenatide that decreased food intake, although a slightly higher dose was required to produce significant changes in activity.
Systemic exenatide reduces body weight gain in normal, high-fat-fed rodents, a model that parallels human genetic variation and food consumption patterns, and may play a role in metabolic pathways mediating food intake.
Peptide YY (PYY) is a 36 amino-acid peptide secreted from ileal L cells following meals. The cleaved subpeptide PYY3-36 is biologically active and may constitute the majority of circulating PYY-like ...immunoreactivity. The peptide family that includes PYY, pancreatic peptide and neuropeptide Y is noted for its orexigenic effect following intracerebroventricular administration.
To investigate the effects of peripheral (intraperitoneal and chronic subcutaneous) infusions of PYY3-36 on food intake, body weight and glycemic indices.
Food intake was measured in normal mice and in several rodent models of obesity and type II diabetes. In marked contrast to the reported central orexigenic effects, in the present study, PYY3-36 acutely inhibited food intake by up to 45%, with an ED(50) of 12.5 microg/kg in fasted female NIH/Swiss mice. A 4-week infusion reduced weight gain in female ob/ob mice, without affecting the cumulative food intake. In diet-induced obese male mice, PYY3-36 infusion reduced cumulative food intake, weight gain and epididymal fat weight (as a fraction of carcass) with similar ED(50)'s (466, 297 and 201 microg/kg/day, respectively) and prevented a diet-induced increase in HbA1c. Infusion at 100 microg/kg/day for 8 weeks in male fa/fa rats reduced the weight gain (288+/-11 vs 326+/-12 g in saline-infused controls; P<0.05), similar to effects in a pair-fed group. In female ob/ob and db/db mice, there was no acute effect of PYY3-36 on plasma glucose concentrations. In male diabetic fatty Zucker rats, PYY3-36 infused for 4 weeks reduced HbA1c and fructosamine (ED(50)'s 30 and 44 microg/kg/day).
Peripheral PYY3-36 administration reduced the food intake, body weight gain and glycemic indices in diverse rodent models of metabolic disease of both sexes. These findings justify further exploration of the potential physiologic and therapeutic roles of PYY3-36.
This study compares in vitro effects of exendin-4 and glucagon-like peptide (GLP)-1 on basal and glucose-stimulated insulin release from isolated rat islets and in vivo insulinotropic actions of ...exendin-4 and GLP-1 after an intravenous glucose challenge in rats. In static incubation of isolated islets, changing ambient glucose concentration from 3 mmol/L to 10 mmol/L stimulated insulin secretion 9.8 ± 1.3-fold. The addition of exendin-4 or GLP-1 (1 nmol/L to 1 μmol/L) increased glucose-stimulated insulin secretion up to 5.8 ± 1.6-fold and 3.3 ± 1.0-fold, respectively, over basal rates (defined as no hormones added, 3 mmol/L glucose) and 19.6 ± 2.3-fold and 15.0 ± 3.1-fold at 10 mmol/L glucose. In dynamically perfused isolated islets exposed to 7.5 mmol/L glucose, insulin secretion increased 6.4 ± 1.5-fold, and exendin-4 (20 nmol/L) or GLP-1 (20 nmol/L) increased this similarly by up to 13.5 ± 2.8 and 12.7 ± 3.9-fold,respectively. Anesthetized rats administered 5.7 mmol/kg intravenous glucose increased plasma insulin concentration 3.0-fold. Infusion of exendin-4 or GLP-1 increased this to a maximum of 7.6-fold and 5.3-fold, respectively. As with isolated islet studies, in vivo dose responses and concentration responses with exendin-4 and GLP-1 were bell-shaped. When insulinotropic effects were mapped onto the steady-state plasma concentrations associated with these infusion rates, both peptides exhibited bell-shaped concentration responses with peak insulinotropic effects occurring with plasma peptide concentrations of approximately 1 nmol/L in this model. In summary, exendin-4 and GLP-1 exhibited similar insulinotropic potencies (median effective dose ED50) when assessed on a concentration basis in in vitro and in vivo models, while exendin-4 exhibited greater efficacy (maximum response).
White blister rust, caused by the oomycete Albugo candida, is a widespread disease of Brassica crops. The Brassica relative Arabidopsis thaliana uses the paired immune receptor complex CSA1-CHS3/DAR4 ...to resist Albugo infection. The CHS3/DAR4 sensor NLR, which functions together with its partner, the helper NLR CSA1, carries an integrated domain (ID) with homology to DA1 peptidases. Using domain swaps with several DA1 homologs, we show that the LIM-peptidase domain of the family member CHS3/DAR4 functions as an integrated decoy for the family member DAR3, which interacts with and inhibits the peptidase activities of the three closely related peptidases DA1, DAR1, and DAR2. Albugo infection rapidly lowers DAR3 levels and activates DA1 peptidase activity, thereby promoting endoreduplication of host tissues to support pathogen growth. We propose that the paired immune receptor CSA1-CHS3/DAR4 detects the actions of a putative Albugo effector that reduces DAR3 levels, resulting in defense activation.
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•Plant NLR immune receptors integrate domains (IDs) from diverse protein families•Such IDs detect actions of pathogen effectors and mount defense responses•Oomycete effectors activate DA1 LIM-peptidases to promote pathogen growth•LIM-peptidase IDs detect this activation and trigger defense responses
The DA1 family of LIM-peptidases modulates plant cell proliferation. Gu et al. show that in susceptible hosts, oomycete effectors activate DA1 to facilitate pathogen growth by reducing levels of DAR3, which inhibits DA1. In resistant plants, effector activity is detected by a DAR3-like integrated domain to induce cell death.
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