46 research outputs found
Amphibian host-defense peptides with potential for Type 2 diabetes therapy - an updated review
Investigations conducted since 2018 have identified several host-defense peptides present in frog skin secretions whose properties suggest the possibility of their development into a new class of agent for Type 2 diabetes (T2D) therapy. Studies in vitro have described peptides that (a) stimulate insulin release from BRIN-BD11 clonal β-cells and isolated mouse islets, (b) display β-cell proliferative activity and protect against cytokine-mediated apoptosis and (c) stimulate production of the anti-inflammatory cytokine IL-10 and inhibit production of the pro-inflammatory cytokines TNF-ι and IL-1β. Rhinophrynin-27, phylloseptin-3.2TR and temporin F are peptides with therapeutic potential. Studies in vivo carried out in db/db and high fat-fed mice have shown that twice-daily administration of [S4K]CPF-AM1 and [A14K]PGLa-AM1, analogs of peptides first isolated from the octoploid frog Xenopus amieti, over 28 days lowers circulating glucose and HbA1c concentrations, increases insulin sensitivity and improves glucose tolerance and lipid profile. Peptide treatment produced potentially beneficial changes in the expression of skeletal muscle genes involved in insulin signaling and islet genes involved in insulin secretion in these murine models of T2D. Lead compounds uncovered by the study of frog HDPs may provide a basis for the design of new types of agents that can be used, alone or in combination with existing therapies, for the treatment of T2D.
Functional Enhancement of Electrofusion-derived BRIN-BD11 Insulin-secreting Cells After Implantation into Diabetic Mice
Electrofusion-derived BRIN-BD11 cells are glucosesensitive
insulin-secreting cells which provide an
archetypal bioengineered surrogate β-cell for
insulin replacement therapy in diabetes mellitus,
5x106 BRIN-BD11 cells were implanted intraperitoneally
into severely hyperglycaemic (>24mmol/l)
streptozotocin-induced insulin-treated diabetic
athymic nude (nu/nu) mice. The implants reduced
hyperglycaemia such that insulin injections were
discontinued by 5â16 days (<17mmol/l) and normoglycaemia
(<9mmol/l) was achieved by 7â20
days. Implanted cells were removed after 28 days
and re-established in culture. After re-culture for 20
days, glucose-stimulated (16.7mmol/l) insulin
release was enhanced by 121% (p<0.001) compared
to non-implanted cells. Insulin responses to
glucagon-like peptide-1 (10â9mol/l), cholecystokinin-8 (10â8 mol/l) and L-alanine (10 mmol/l) were
increased by 32%, 31% and 68% respectively
(p<0.05â0.01). Insulin content of the cells was 148%
greater at 20 days after re-culture than before
implantation (p<0.001), but basal insulin release (at
5.6 mmol/l glucose) was not changed. After re-culture
for 40 days, insulin content declined to 68% of
the content before implantation (p<0.01), although
basal insulin release was unchanged. However, the
insulin secretory responses to glucose, glucagonlike
peptide-1, cholecystokinin-8 and L-alanine
were decreased after 40 days of re-culture to 65%,
72%, 73% and 42% respectively of the values before
implantation (p<0.05â0.01). The functional
enhancement of electrofusion-derived surrogate β-cells that were re-cultured for 20 days after implantation
and restoration of normoglycaemia indicates
that the in vivo environment could greatly assist β-cell engineering approaches to therapy for diabetes
In vitro and in vivo antihyperglycemic activity of the ethanol extract of Heritiera fomes bark and characterization of pharmacologically active phytomolecules
Objective -- This study aimed to demonstrate the mechanistic basis of Heritiera fomes, which has traditionally been used to treat diabetes. Methods -- Clonal pancreatic β-cells and primary islets were used to measure insulin release. 3T3-L1 cells were used to analyse insulin action, and in vitro systems were used to measure further glucose-lowering activity. In vivo assessment was performed on streptozotocin (STZ)-induced type-2 diabetic rats and reversed-phase-HPLC followed by liquid chromatography mass spectrometry (LC-MS) to detect bioactive molecules. Key findings -- Ethanol extract of Heritiera fomes (EEHF) significantly increased insulin release with stimulatory effects comparable to 1 ¾M glucagon-like peptide 1, which were somewhat reduced by diazoxide, verapamil and calcium-free conditions. Insulin release was stimulated by tolbutamide, isobutyl methylxanthine and KCl. EEHF induced membrane depolarization and increased intracellular Ca2+ levels. EEHF enhanced glucose uptake in 3T3L1 cells and decreased protein glycation. EEHF significantly inhibited postprandial hyperglycaemia following sucrose loading and inversely elevated unabsorbed sucrose concentration in the gut. It suppressed glucose absorption during in situ gut perfusion. Furthermore, EEHF improved glucose tolerance, plasma insulin and gut motility, and decreased plasma dipeptidyl peptidase IV activity. Procyanidins, epicatechin and proanthocyanidins were some of the identified bioactive constituents that may involve in β-cell actions. Conclusions -- This study provides some evidence to support the use of H. fomes as an antidiabetic traditional remedy
Antimicrobial, cytotoxic and insulinâreleasing activities of the amphibian hostâdefense peptide ocellatinâ3N and its Lâlysineâsubstituted analogs
The host-defense peptide ocellatin-3N (GIFDVLKNLAKGVITSLAS.NH2), first isolated from the Caribbean frog Leptodactylus nesiotus, inhibited growth of clinically relevant Gram-positive and Gram-negative bacteria as well as a strain of the major emerging yeast pathogen Candida parapsilosis. Increasing cationicity while maintaining amphipathicity by the substitution Asp(4)-> Lys increased potency against the microorganisms by between 4- and 16-fold (MIC <= 3 mu M) compared with the naturally occurring peptide. The substitution Ala(18)-> Lys and the double substitution Asp(4)-> Lys and Ala(18)-> Lys had less effects on potency. The [D4K] analog also showed 2.5- to 4-fold greater cytotoxic potency against non-small-cell lung adenocarcinoma A549 cells, breast adenocarcinoma MDA-MB-231 cells, and colorectal adenocarcinoma HT-29 cells (LC50 values in the range of 12-20 mu M) compared with ocellatin-3N but was less hemolytic to mouse erythrocytes. However, the peptide showed no selectivity for tumor-derived cells [LC50 = 20 mu M for human umbilical vein endothelial cells (HUVECs)]. Ocellatin-3N and [D4K]ocellatin-3N stimulated the release of insulin from BRIN-BD11 clonal beta-cells at concentrations >= 1 nM, and [A18K]ocellatin-3N, at concentrations >= 0.1 nM. No peptide stimulated the release of lactate dehydrogenase at concentrations up to 3 mu M, indicating that plasma membrane integrity had been preserved. The three peptides produced an increase in intracellular [Ca2+] in BRIN-BD11 cells when incubated at a concentration of 1 mu M. In view of its high insulinotropic potency and relatively low hemolytic activity, the [A18K] ocellatin analog may represent a template for the design of agents with therapeutic potential for the treatment of patients with type 2 diabetes
Evaluation of Antidiabetic Potential of Mangifera indica Leaf in Streptozotocin-Induced Type 2 Diabetic Rats: Focus on Glycemic Control and Cholesterol Regulation
Mangifera indica (Anacardiaceae family) is renowned for its diverse pharmacological properties, encompassing antidiabetic, antioxidant, and anti-inflammatory effects. The present study delves into the insulin-releasing and glucose-lowering potential of the ethanolic extract of Mangifera indica (EEMI) leaves in streptozotocin-induced type 2 diabetic (STZ-T2D) rats, concurrently investigating its phytoconstituents. EEMIâs effects on insulin secretion were measured using BRIN BD11 β-cells and isolated mouse islets. Its enzymatic inhibitory properties on carbohydrate digestion, and absorption, and free radicals were investigated using in vitro methods. In vivo parameters including the lipid profile and liver glycogen content were assessed in STZ-T2D rats. EEMI exhibited a dose-dependent increase in insulin secretion from clonal pancreatic BRIN BD11 β-cells and isolated mouse islets. EEMI inhibited starch digestion, glucose diffusion over time, and DPPH activity in vitro. In acute in vivo studies, EEMI improved food intake and oral glucose tolerance. Moreover, following 28 days of treatment with EEMI, a remarkable amelioration in body weight, fasting blood glucose, plasma insulin, liver glycogen content, total cholesterol, triglyceride, LDL, VLDL, and HDL levels was observed. Further phytochemical analysis with EEMI identified the presence of alkaloids, tannins, saponins, steroids, and flavonoids. The synergistic effects of EEMI, potentially attributable to naturally occurring phytoconstituents, hold promise for the development of enriched antidiabetic therapies, offering a promising avenue for the management of type 2 diabetes
Insulin secretory actions of polyphenols of <i>Momordica charantia</i> regulate glucose homeostasis in alloxan-induced type 2 diabetic rats
Objective Momordica charantia, commonly known as bitter gourd, is traditionally used as remedies for various diseases including diabetes. The main objective of this study is to investigate the in vitro and in vivo insulinotropic and anti-diabetic effects of an 80% ethanolic extract of Momordica charantia (EEMC) fruit, as well as the underlying molecular mechanism involved and preliminary phytochemical screening. Methods The insulin secretion was measured using clonal pancreatic BRIN-BD11 β-cells and isolated mouse islets. The ability of EEMC to inhibit carbohydrate digestive enzymes and glucose absorption and, scavenge free radicals were assessed via starch digestion, glucose diffusion and DPPH assay methods. The effects of EEMC on a variety of metabolic parameters were evaluated in alloxan-induced type 2 diabetic rats, including lipid profile. Finally, a preliminary phytochemical screening was conducted to identify the active phytoconstituents. Key findings EEMC increased insulin release through the KATP-dependent/cAMP pathway, which depolarizes the β-cell membrane and elevates intracellular calcium. It also inhibited glucose absorption and free radicals, suggesting its potential to delay gastric emptying, attenuate oxidative stress, and reduce inflammatory cytokines. In vivo studies showed that EEMC improves oral glucose tolerance, food intake, fasting blood glucose, plasma insulin, lipids, and promotes intestinal motility. The active phytoconstituents in EEMC, such as flavonoids, alkaloids, tannins, saponins, steroids, and glycosides, are likely responsible for these effects. Conclusion The antihyperglycemic properties of EEMC indicate that it might be a promising candidate for diabetes management. However, additional study into the application of Momordica charantia in type 2 diabetes is essential
Antidiabetic actions of ethanol extract of Camellia sinensis leaf ameliorates insulin secretion, inhibits the DPP-IV enzyme, improves glucose tolerance, and increases active GLP-1 (7â36) levels in high-fat-diet-fed rats
Camellia sinensis (green tea) is used in traditional medicine to treat a wide range of ailments. In the present study, the insulin-releasing and glucose-lowering effects of the ethanol extract of Camellia sinensis (EECS), along with molecular mechanism/s of action, were investigated in vitro and in vivo. The insulin secretion was measured using clonal pancreatic BRIN BD11 β cells, and mouse islets. In vitro models examined the additional glucose-lowering properties of EECS, and 3T3L1 adipocytes were used to assess glucose uptake and insulin action. Non-toxic doses of EECS increased insulin secretion in a concentration-dependent manner, and this regulatory effect was similar to that of glucagon-like peptide 1 (GLP-1). The insulin release was further enhanced when combined with isobutylmethylxanthine (IBMX), tolbutamide or 30 mM KCl, but was decreased in the presence of verapamil, diazoxide and Ca2+ chelation. EECS also depolarized the β-cell membrane and elevated intracellular Ca2+, suggesting the involvement of a KATP-dependent pathway. Furthermore, EECS increased glucose uptake and insulin action in 3T3-L1 cells and inhibited dipeptidyl peptidase IV (DPP-IV) enzyme activity, starch digestion and protein glycation in vitro. Oral administration of EECS improved glucose tolerance and plasma insulin as well as inhibited plasma DPP-IV and increased active GLP-1 (7â36) levels in high-fat-diet-fed rats. Flavonoids and other phytochemicals present in EECS could be responsible for these effects. Further research on the mechanism of action of EECS compounds could lead to the development of cost-effective treatments for type 2 diabetes
Esculentin-2CHa-Related Peptides Modulate Islet Cell Function and Improve Glucose Tolerance in Mice with Diet-Induced Obesity and Insulin Resistance
The frog skin host-defense peptide esculentin-2CHa (GFSSIFRGVA10KFASKGLGK
D20LAKLGVDLVA30CKISKQC) displays antimicrobial, antitumor, and immunomodulatory
properties. This study investigated the antidiabetic actions of the peptide and selected analogues.
Esculentin-2CHa stimulated insulin secretion from rat BRIN-BD11 clonal pancreatic
β-cells at concentrations greater than 0.3 nM without cytotoxicity by a mechanism involving
membrane depolarization and increase of intracellular Ca2+. Insulinotropic activity was
attenuated by activation of KATP channels, inhibition of voltage-dependent Ca2+ channels
and chelation of extracellular Ca2+. The [L21K], [L24K], [D20K, D27K] and [C31S,C37S]
analogues were more potent but less effective than esculentin-2CHa whereas the [L28K]
and [C31K] analogues were both more potent and produced a significantly (P < 0.001)
greater maximum response. Acute administration of [L28K]esculentin-2CHa (75 nmol/kg
body weight) to high fat fed mice with obesity and insulin resistance enhanced glucose tolerance
and insulin secretion. Twice-daily administration of this dose of [L28K]esculentin-
2CHa for 28 days had no significant effect on body weight, food intake, indirect calorimetry
or body composition. However, mice exhibited decreased non-fasting plasma glucose
(P < 0.05), increased non-fasting plasma insulin (P < 0.05) as well as improved glucose tolerance
and insulin secretion (P < 0.01) following both oral and intraperitoneal glucose
loads. Impaired responses of isolated islets from high fat fed mice to established insulin
secretagogues were restored by [L28K]esculentin-2CHa treatment. Peptide treatment was
accompanied by significantly lower plasma and pancreatic glucagon levels and normalization
of Îą-cell mass. Circulating triglyceride concentrations were decreased but plasma cholesterol
and LDL concentrations were not significantly affected. The data encourage further
investigation of the potential of esculentin-2CHa related peptides for treatment of patients
with type 2 diabetes