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  • Effective and safe gene-based delivery of GLP-1 using chitosanplasmid-DNA therapeutic nanocomplexes in an animal model of type 2 diabetes. 21412280

    Glucagon-like peptide-1 (GLP-1) is an incretin hormone that regulates blood glucose level post-prandially. It has been proposed that GLP-1 can be used in type 2 diabetes (T2D) mellitus treatment because of its insulinotropic action. Despite its remarkable advantages, GLP-1 suffers the disadvantage of an extremely short half-life owing to its degradation by the dipeptidyl peptidase IV protease. One way of overcoming this drawback is GLP-1 gene delivery. Here we show effective and safe gene-based delivery of GLP-1 using chitosan/plasmid-DNA therapeutic nanocomplexes (TNCs) in Zucker diabetic fatty (ZDF) animal model of T2D. The expression plasmid fused the GLP-1 gene to a Furin cleavage site was driven by a cytomegalovirus promoter/enhancer. TNCs were prepared by mixing this plasmid with chitosans of specific molecular weight (MW), degree of deacetylation (DDA) and ratio of chitosan amine to DNA phosphate (N:P ratio). Animals injected with the TNC chitosan 92-10-5 (DDA-MW-N:P) showed GLP-1 plasma levels of about fivefold higher than that in non-treated animals and the insulinotropic effect of recombinant GLP-1 was shown by a threefold increase in plasma insulin concentration when compared with untreated animals. Intraperitoneal glucose tolerance tests revealed an efficacious decrease of blood glucose compared with controls for up to 24 days after treatment, where injections of this formulation allowed near-normalization of blood glucose level. TNCs composed of specific chitosans and GLP-1-expressing plasmid constructs showed an impressive ability to harness the profound therapeutic potential of GLP-1 for the treatment of T2D mellitus.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Comparison of mRNA for IGFs and their binding proteins in the oviduct during the peri-oestrous period between dairy heifers and lactating cows. 21730111

    The oviduct provides the environment to support gamete maturation, fertilisation and early embryo development. As there is a high incidence of early embryonic death in lactating dairy cows, this study compared expression of IGF family members in the oviduct between lactating Holstein-Friesian dairy cows (n=16, 81±2.4 days in milk) and nulliparous heifers (n=16, age 1.6±0.07 years) at three stages of the oestrous cycle: A) newly selected dominant follicle in the luteal phase, B) follicular phase before the LH surge and C) pre-ovulatory phase after the LH surge. Expression of IGF1, IGF2, IGF binding protein 2 (IGFBP2), IGFBP3 and IGFBP6 mRNA was determined in the ampulla of the oviduct. Oviduct side (ipsilateral or contralateral) with respect to the dominant follicle did not affect gene expression. Expression of IGF1 and all three IGFBPs increased significantly between the luteal and the pre-ovulatory phases, with no further significant alteration post-LH surge. Concentrations of circulating IGF1 were higher in heifers than in cows, as was the mRNA expression of IGF1, IGFBP3 and IGFBP6. The pre-LH surge rise in IGFBP2 mRNA was only observed in heifers. IGF2 expression was not influenced by either age or stage of cycle. These three IGFBPs are generally considered to inhibit IGF action. These results indicate tight regulation of IGF bioavailability in the oviductal environment around oestrus, with pronounced differences between cows and heifers, which are likely to influence early embryonic development. Further studies are required to assess the implications for embryo survival.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • Design and evaluation of oral bioadhesive controlled release formulations of miglitol, intended for prolonged inhibition of intestinal alpha-glucosidases and enhancement ... 19563873

    Alpha-glucosidase enzyme is present ubiquitously throughout the lumen of the small intestine. It is responsible for the breakdown of complex into simple carbohydrates. alpha-Glucosidase inhibitors such as miglitol, are drugs that have greater affinity towards this enzyme in comparison to carbohydrates. Miglitol regulates the postprandial glucose levels directly by inhibiting the enzyme reversibly and also indirectly by including the secretion of glucagon like peptide-1 (GLP-1). The aims of this study were (i) to design a controlled release (CR) mucoadhesive (in the intestine) formulation of miglitol which would inhibit the alpha-glucosidase enzyme for a longer duration of time (in comparison to the non-controlled release (IR) formulation) thus reducing the dosing frequency, and also controlling the postprandial glucose levels more effectively over a longer period of time; (ii) to assess the effect of different formulation parameters on the release of miglitol in vitro from the CR pellets; (iii) to evaluate the mucoadhesion of pellets in the intestine ex vivo; (iv) to study the effect of formulation parameters on plasma GLP-1 levels; and (v) to find out the effect of formulations on postprandial glucose levels. The data obtained was analysed to find out whether there was a correlation between these different parameters. Four controlled release formulations (CR1, CR2, CR3 and CR4) of miglitol comprising of multilayered pellets were designed successfully. The CR4 formulation containing 30% of 20 cps of ethyl cellulose (the retarding layer of the formulation) displayed slowest release of miglitol in vitro in comparison to other formulations. We designed an ex vivo experimental setup for studying the mucoadhesion of the pellets in the lumen of the intestine. Results indicated that amongst all of the adherent pellets, 5% were found to be adhering in the duodenal region, 61% in the jejunum, 32% in the ileum and 2% in the colon. Two of the controlled release formulations CR1 and CR4 were evaluated in vivo in dogs. Both the formulations displayed significantly higher and more prolonged (greater AUC) levels of GLP-1 in comparison to either the placebo or the immediate release (IR) formulations. They even displayed a significantly better control of postprandial glucose in comparison to either placebo or IR formulations. However, a comparison between the two controlled release formulations (CR1 and CR4) revealed that the plasma GLP-1 (AUC by CR1=63.1+/-1.32 and CR4=66.2+/-0.82) and postprandial glucose values due to both the formulations were rather similar despite their differences in in vitro release as well as pharmacokinetic profiles (plasma miglitol AUC of CR1=16.17+/-4.11 and CR4=27.17+/-4.33).
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • Targeting enteral endocrinal L-cells with dietary carbohydrates, by increasing the availability of miglitol in the intestinal lumen, leads to multi-fold enhancement of pl ... 21126213

    The principle aim of this study was to design a controlled release (CR), bioadhesive formulation of miglitol (in form of pellets) which would regulate the post-prandial glucose levels via reversible inhibition of α-glucosidase enzyme as well as by modulating the glucagon-like peptide-1 (GLP-1) pathway in non-diabetic canines. A multilayered pellet formulation which was both bioadhesive (because of hydroxy propyl methyl cellulose polymer) and CR (because of the ethyl cellulose layer) was formulated. We report a novel finding that the CR formulation of miglitol (S3) induced a 2.2-fold elevation in the C(max) as well as the overall AUC(0-24) of GLP-1 values in comparison to the non-CR (immediate release (IR) formulation). The S3 formulation also resulted in better, steady, and prolonged control of glucose levels over a time period of 7 h in comparison to the IR formulation possibly due to combination of both, prolonged inhibition of the α-glucosidase enzyme and enhanced plasma GLP-1 levels. The S3 formulation was stable with no changes in the dissolution profiles at both of the stability conditions tested, 25°C/60% RH and 40°C/75% RH. Aqueous polymeric coating of the pellets (in contrast to coating using organic solvents) resulted morphologically in a uniform polymeric film and also releases profiles with lower burst effect. Curing played a significant role in determining release profile of the pellets, prepared by aqueous polymeric coating method.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • Meal-contingent intestinal lymph sampling from awake, unrestrained rats. 22513747

    Standard procedures for intestinal lymph collection involve continuous, quantitative drainage of the lymph fluid in anesthetized or restrained animals that are often euthanized within 48 h. We here describe a novel technique for the nonocclusive cannulation of the major intestinal lymph duct in rats that allows for repetitive in vivo sampling of intestinal lymph from unrestrained, awake, and ad libitum-fed animals. The distinctive feature of this novel technique is that a 5- to 7-mm long piece of Vialon tubing (OD/ID: 0.8/0.7 mm) with a small hole in its wall is first implanted into the major intestinal lymph duct for stabilization. The tapered tip (OD: ≈0.1 mm) of the catheter is then inserted into the hole of the tubing and fixed in place with a polyamid suture and a drop of tissue glue. In our hands, catheters implanted this way remain patent for up to 6 wk after surgery. In an initial experiment we collected lymph from six adult rats before (0) and 15, 30, 45, 60, 75, 90, 120, and 180 min (120 μl, each) after the onset of isocaloric (12.5 kcal) low-fat (LF) or high-fat (HF) test meals and measured active glucagon-like peptide-1 (GLP-1). Intestinal lymphatic GLP-1 concentration increased (P < 0.05) from ≈4 pmol/l (0 min) to a peak of 33 ± 6 (means ± SE) or 22 ± 4 pmol/l at 15 (HF) or 30 min (LF) after meal onset and gradually returned to baseline levels by 180 min. With this new technique fewer animals are required to generate physiologically relevant data for various aspects of gastrointestinal physiology that involve the lymphatic system. Furthermore, the advantage of this system is that the animal can act as its own control when the effect of different experimental protocols is tested.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • Compensation for obesity-induced insulin resistance in dogs: assessment of the effects of leptin, adiponectin, and glucagon-like peptide-1 using path analysis. 21474268

    The hormonal mediators of obesity-induced insulin resistance and compensatory hyperinsulinemia in dogs have not been identified. Plasma samples were obtained after a 24-h fast from 104 client-owned lean, overweight, and obese dogs. Plasma glucose and insulin concentrations were used to calculate insulin sensitivity and β-cell function with the use of the homeostasis model assessment (HOMA(insulin sensitivity) and HOMA(β-cell function), respectively). Path analysis with multivariable linear regression was used to identify whether fasting plasma leptin, adiponectin, or glucagon-like peptide-1 concentrations were associated with adiposity, insulin sensitivity, and basal insulin secretion. None of the dogs were hyperglycemic. In the final path model, adiposity was positively associated with leptin (P < 0.01) and glucagon-like peptide-1 (P = 0.04) concentrations. No significant total effect of adiposity on adiponectin in dogs (P = 0.24) was observed. If there is a direct effect of leptin on adiponectin, then our results indicate that this is a positive relationship, which at least partly counters a negative direct relationship between adiposity and adiponectin. Fasting plasma leptin concentration was directly negatively associated with fasting insulin sensitivity (P = 0.01) and positively associated with β-cell function (P < 0.01), but no direct association was observed between adiponectin concentration and either insulin sensitivity or β-cell function (P = 0.42 and 0.11, respectively). We conclude that dogs compensate effectively for obesity-induced insulin resistance. Fasting plasma leptin concentrations appear to be associated with obesity-associated changes in insulin sensitivity and compensatory hyperinsulinemia in naturally occurring obese dogs. Adiponectin does not appear to be involved in the pathophysiology of obesity-associated changes in insulin sensitivity.Copyright © 2011 Elsevier Inc. All rights reserved.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • The effect of multidisciplinary lifestyle intervention on the pre- and postprandial plasma gut Peptide concentrations in children with obesity. 22363876

    Objective. This study aims to evaluate the effect of a multidisciplinary treatment of obesity on plasma concentrations of several gut hormones in fasting condition and in response to a mixed meal in children. Methods. Complete data were available from 36 obese children (age 13.3 ± 2.0 yr). At baseline and after the 3-month multidisciplinary treatment, fasting and postprandial blood samples were taken for glucose, insulin, ghrelin, peptide YY (PYY), and glucagon-like peptide 1 (GLP-1). Results. BMI-SDS was significantly reduced by multidisciplinary treatment (from 4.2 ± 0.7 to 4.0 ± 0.9, P < .01). The intervention significantly increased the area under the curve (AUC) of ghrelin (from 92.3 ± 18.3 to 97.9 ± 18.2 pg/L, P < .01), but no significant changes were found for PYY or GLP-1 concentrations (in fasting or postprandial condition). The insulin resistance index (HOMA-IR) remained unchanged as well. Conclusion. Intensive multidisciplinary treatment induced moderate weight loss and increased ghrelin secretion, but serum PYY and GLP-1 concentrations and insulin sensitivity remained unchanged.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA

  • Beneficial effects of exendin-4 on experimental polyneuropathy in diabetic mice. 21810596

    The therapeutic potential of exendin-4, an agonist of the glucagon-like peptide-1 receptor (GLP-1R), on diabetic polyneuropathy (DPN) in streptozotocin (STZ)-induced diabetic mice was investigated.The presence of the GLP-1R in lumbar dorsal root ganglion (DRG) was evaluated by immunohistochemical analyses. DRG neurons were dissected from C57BL6/J mice and cultured with or without Schwann cell-conditioned media in the presence or absence of GLP-1 (7-37) or exendin-4. Then neurite outgrowth was determined. In animal-model experiments, mice were made diabetic by STZ administration, and after 12 weeks of diabetes, exendin-4 (10 nmol/kg) was intraperitoneally administered once daily for 4 weeks. Peripheral nerve function was determined by the current perception threshold and motor and sensory nerve conduction velocity (MNCV and SNCV, respectively). Sciatic nerve blood flow (SNBF) and intraepidermal nerve fiber densities (IENFDs) also were evaluated.The expression of the GLP-1R in DRG neurons was confirmed. GLP-1 (7-37) and exendin-4 significantly promoted neurite outgrowth of DRG neurons. Both GLP-1R agonists accelerated the impaired neurite outgrowth of DRG neurons cultured with Schwann cell-conditioned media that mimicked the diabetic condition. At the doses used, exendin-4 had no effect on blood glucose or HbA(1c) levels. Hypoalgesia and delayed MNCV and SNCV in diabetic mice were improved by exendin-4 without affecting the reduced SNBF. The decreased IENFDs in sole skins of diabetic mice were ameliorated by exendin-4.Our findings indicate that exendin-4 ameliorates the severity of DPN, which may be achieved by its direct actions on DRG neurons and their axons.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Decreased glucagon-like peptide 1 release after weight loss in overweight/obese subjects. 15897480

    OBJECTIVE: Postprandial glucagon-like peptide 1 (GLP-1) release seems to be attenuated in obese subjects. Results on whether weight loss improves GLP-1 release are contradictory. The aim of this study was to further investigate the effect of weight loss on basal and postprandial GLP-1 release in overweight/obese subjects. RESEARCH METHODS AND PROCEDURES: Thirty-two overweight/obese subjects participated in a repeated measurement design before (BMI, 30.3 +/- 2.8 kg/m2; waist circumference, 92.6 +/- 7.8 cm; hip circumference, 111.1 +/- 7.4 cm) and after a weight loss period of 6 weeks (BMI, 28.2 +/- 2.7 kg/m2; waist circumference, 85.5 +/- 8.5 cm; hip circumference, 102.1 +/- 9.2 cm). During weight loss, subjects received a very-low-calorie diet (Optifast) to replace three meals per day. Subjects came to the laboratory fasted, and after a baseline blood sample, received a standard breakfast (1.9 MJ). Postprandially, blood samples were taken every one-half hour relative to intake for 120 minutes to determine GLP-1, insulin, glucose, and free fatty acids from plasma. Appetite ratings were obtained with visual analog scales. RESULTS: After weight loss, postprandial GLP-1 concentrations at 30 and 60 minutes were significantly lower than before weight loss (p 0.05). Glucose concentrations were also lower, and free fatty acids were higher compared with before weight loss. Ratings of satiety were increased, and hunger scores were decreased after weight loss (p 0.05). DISCUSSION: In overweight/obese subjects, GLP-1 concentrations after weight loss were decreased compared with before weight loss, and nutrient-related stimulation was abolished. This might be a response to a proceeding negative energy balance. Satiety and GLP-1 seem to be unrelated in the long term.
    Document Type:
    Reference
    Product Catalog Number:
    EGLP-35K
    Product Catalog Name:
    Glucagon Like Peptide-1 (Active) ELISA