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Journal of Inorganic Biochemistry Jun 2024Our prior studies have illustrated that the uracil ruthenium(II) diimino complex, [Ru(Hucp)Cl(PPh)] (1)...
Our prior studies have illustrated that the uracil ruthenium(II) diimino complex, [Ru(Hucp)Cl(PPh)] (1) (Hucp = 2,6-bis-((6-amino-1,3-dimethyluracilimino)methylene)pyridine) displayed high hypoglycemic effects in diet-induced diabetic rats. To rationalize the anti-diabetic effects of 1, three new derivatives have been prepared, cis-[Ru(bpy)(urdp)]Cl (2) (urdp = 2,6-bis-((uracilimino)methylene)pyridine), trans-[RuCl(PPh)(urdp)] (3), and cis-[Ru(bpy)(Hucp)](PF) (4). Various physicochemical techniques were utilized to characterize the structures of the novel ruthenium compounds. Prior to biomolecular interactions or in vitro studies, the stabilities of 1-4 were monitored in anhydrous DMSO, aqueous phosphate buffer containing 2% DMSO, and dichloromethane (DCM) via UV-Vis spectrophotometry. Time-dependent stability studies showed ligand exchange between DMSO nucleophiles and chloride co-ligands of 1 and 3, which was suppressed in the presence of an excess amount of chloride ions. In addition, the metal complexes 1 and 3 are stable in both DCM and an aqueous phosphate buffer containing 2% DMSO. In the case of compounds 2 and 4 with no chloride co-ligands within their coordination spheres, high stability in aqueous phosphate buffer containing 2% DMSO was observed. Fluorescence emission titrations of the individual ruthenium compounds with bovine serum albumin (BSA) showed that the metal compounds interact non-discriminately within the protein's hydrophobic cavities as moderate to strong binders. The metal complexes were capable of disintegrating mature amylin amyloid fibrils. In vivo glucose metabolism studies in liver (Chang) cell lines confirmed enhanced glucose metabolism as evidenced by the increased glucose utilization and glycogen synthesis in liver cell lines in the presence of complexes 2-4.
Topics: Rats; Animals; Coordination Complexes; Serum Albumin, Bovine; Ruthenium; Dimethyl Sulfoxide; Hypoglycemic Agents; Chlorides; Diabetes Mellitus, Experimental; Pyridines; Peptides; Ruthenium Compounds; Glucose; Phosphates; Antineoplastic Agents; Ligands
PubMed: 38554578
DOI: 10.1016/j.jinorgbio.2024.112541 -
ACS Chemical Neuroscience Apr 2024Amylin is a neuroendocrine hormone with a potential role in addictive disorders, including alcohol use disorder (AUD). In addition to reducing appetitive behavior,...
Amylin is a neuroendocrine hormone with a potential role in addictive disorders, including alcohol use disorder (AUD). In addition to reducing appetitive behavior, amylin has been shown to affect alcohol-related behaviors in rodents. Delineating the biobehavioral correlates of amylin in relation to alcohol seeking and consumption has the potential of identifying new treatment targets for AUD, yet additional translational and human research is needed.
Topics: Humans; Alcoholism; Islet Amyloid Polypeptide; Behavior, Addictive; Ethanol; Peptide Hormones
PubMed: 38551493
DOI: 10.1021/acschemneuro.4c00133 -
Pflugers Archiv : European Journal of... May 2024The American Diabetes Association guidelines (2021) confirmed the importance of raising public awareness of diabetes-induced cognitive impairment, highlighting the links...
Liraglutide versus pramlintide in protecting against cognitive function impairment through affecting PI3K/AKT/GSK-3β/TTBK1 pathway and decreasing Tau hyperphosphorylation in high-fat diet- streptozocin rat model.
The American Diabetes Association guidelines (2021) confirmed the importance of raising public awareness of diabetes-induced cognitive impairment, highlighting the links between poor glycemic control and cognitive impairment. The characteristic brain lesions of cognitive dysfunction are neurofibrillary tangles (NFT) and senile plaques formed of amyloid-β deposition, glycogen synthase kinase 3 beta (GSK3β), and highly homologous kinase tau tubulin kinase 1 (TTBK1) can phosphorylate Tau proteins at different sites, overexpression of these enzymes produces extensive phosphorylation of Tau proteins making them insoluble and enhance NFT formation, which impairs cognitive functions. The current study aimed to investigate the potential contribution of liraglutide and pramlintide in the prevention of diabetes-induced cognitive dysfunction and their effect on the PI3K/AKT/GSK-3β/TTBK1 pathway in type 2 diabetic (T2D) rat model. T2D was induced by administration of a high-fat diet for 10 weeks, then injection of a single dose of streptozotocin (STZ); treatment was started with either pramlintide (200 μg/kg/day sc) or liraglutide (0.6 mg/kg/day sc) for 6 weeks in addition to the HFD. At the end of the study, cognitive functions were assessed by novel object recognition and T-maze tests. Then, rats were sacrificed for biochemical and histological assessment of the hippocampal tissue. Both pramlintide and liraglutide treatment revealed equally adequate control of diabetes, prevented the decline in memory function, and increased PI3K/AKT expression while decreasing GSK-3β/TTBK1 expression; however, liraglutide significantly decreased the number of Tau positive cells better than pramlintide did. This study confirmed that pramlintide and liraglutide are promising antidiabetic medications that could prevent associated cognitive disorders in different mechanisms.
Topics: Animals; tau Proteins; Rats; Glycogen Synthase Kinase 3 beta; Liraglutide; Diet, High-Fat; Male; Cognitive Dysfunction; Proto-Oncogene Proteins c-akt; Phosphatidylinositol 3-Kinases; Phosphorylation; Signal Transduction; Diabetes Mellitus, Experimental; Islet Amyloid Polypeptide; Hypoglycemic Agents; Rats, Sprague-Dawley; Streptozocin; Diabetes Mellitus, Type 2
PubMed: 38536493
DOI: 10.1007/s00424-024-02933-0 -
Proteins Mar 2024Human islet amyloid polypeptide (amylin or hIAPP) is a 37 residue hormone co-secreted with insulin from β cells of the pancreas. In patients suffering from type-2...
Human islet amyloid polypeptide (amylin or hIAPP) is a 37 residue hormone co-secreted with insulin from β cells of the pancreas. In patients suffering from type-2 diabetes, amylin self-assembles into amyloid fibrils, ultimately leading to the death of the pancreatic cells. However, a research gap exists in preventing and treating such amyloidosis. Plumbagin, a natural compound, has previously been demonstrated to have inhibitory potential against insulin amyloidosis. Our investigation unveils collapsible regions within hIAPP that, upon collapse, facilitates hydrophobic and pi-pi interactions, ultimately leading to aggregation. Intriguingly plumbagin exhibits the ability to bind these specific collapsible regions, thereby impeding the aforementioned interactions that would otherwise drive hIAPP aggregation. We have used atomistic molecular dynamics approach to determine secondary structural changes. MSM shows metastable states forming native like hIAPP structure in presence of PGN. Our in silico results concur with in vitro results. The ThT assay revealed a striking 50% decrease in fluorescence intensity at a 1:1 ratio of hIAPP to Plumbagin. This finding suggests a significant inhibition of amyloid fibril formation by plumbagin, as ThT fluorescence directly correlates with the presence of these fibrils. Further TEM images revealed disappearance of hIAPP fibrils in plumbagin pre-treated hIAPP samples. Also, we have shown that plumbagin disrupts the intermolecular hydrogen bonding in hIAPP fibrils leading to an increase in the average beta strand spacing, thereby causing disaggregation of pre-formed fibrils demonstrating overall disruption of the aggregation machinery of hIAPP. Our work is the first to report a detailed atomistic simulation of 22 μs for hIAPP. Overall, our studies put plumbagin as a potential candidate for both preventive and therapeutic candidate for hIAPP amyloidosis.
PubMed: 38497314
DOI: 10.1002/prot.26682 -
Peptides Jun 2024Amylin, a pancreatic hormone, is well-established to suppress feeding by enhancing satiation. Pramlintide, an amylin analog that is FDA-approved for the treatment of...
Amylin, a pancreatic hormone, is well-established to suppress feeding by enhancing satiation. Pramlintide, an amylin analog that is FDA-approved for the treatment of diabetes, has also been shown to produce hypophagia. However, the behavioral mechanisms underlying the ability of pramlintide to suppress feeding are unresolved. We hypothesized that systemic pramlintide administration in rats would reduce energy intake, specifically by reducing meal size. Male rats were given b.i.d. administration of intraperitoneal pramlintide or vehicle for 1 week, and chow intake, meal patterns, and body weight were monitored throughout the test period. Consistent with our hypothesis, pramlintide decreased chow intake mainly via suppression of meal size, with corresponding reductions in meal duration on several days. Fewer effects on meal number or feeding rate were detected. Pramlintide also reduced weight gain over the 1-week study. These results highlight that the behavioral mechanisms by which pramlintide produces hypophagia are similar to those driven by amylin itself, and provide important insight into the ability of this pharmacotherapy to promote negative energy balance over a period of chronic administration.
Topics: Animals; Islet Amyloid Polypeptide; Male; Rats; Feeding Behavior; Eating; Rats, Sprague-Dawley; Body Weight; Energy Intake
PubMed: 38493922
DOI: 10.1016/j.peptides.2024.171197 -
Biochemical Pharmacology May 2024Leptin is a hormone that is secreted by adipocytes in proportion to adipose tissue size, and that informs the brain about the energy status of the body. Leptin acts... (Review)
Review
Leptin is a hormone that is secreted by adipocytes in proportion to adipose tissue size, and that informs the brain about the energy status of the body. Leptin acts through its receptor LepRb, expressed mainly in the hypothalamus, and induces a negative energy balance by potent inhibition of feeding and activation of energy expenditure. These actions have led to huge expectations for the development of therapeutic targets for metabolic complications based on leptin-derived compounds. However, the majority of patients with obesity presents elevated leptin production, suggesting that in this setting leptin is ineffective in the regulation of energy balance. This resistance to the action of leptin in obesity has led to the development of "leptin sensitizers," which have been tested in preclinical studies. Much research has focused on generating combined treatments that act on multiple levels of the gastrointestinal-brain axis. The gastrointestinal-brain axis secretes a variety of different anorexigenic signals, such as uroguanylin, glucagon-like peptide-1, amylin, or cholecystokinin, which can alleviate the resistance to leptin action. Moreover, alternative mechanism such as pharmacokinetics, proteostasis, the role of specific kinases, chaperones, ER stress and neonatal feeding modifications are also implicated in leptin resistance. This review will cover the current knowledge regarding the interaction of leptin with different endocrine factors from the gastrointestinal-brain axis and other novel mechanisms that improve leptin sensitivity in obesity.
Topics: Humans; Infant, Newborn; Adipose Tissue; Energy Metabolism; Hypothalamus; Leptin; Obesity
PubMed: 38490517
DOI: 10.1016/j.bcp.2024.116129 -
The Journal of Headache and Pain Mar 2024The upper cervical dorsal root ganglia (DRG) are important for the transmission of sensory information associated with the back of the head and neck, contributing to...
BACKGROUND
The upper cervical dorsal root ganglia (DRG) are important for the transmission of sensory information associated with the back of the head and neck, contributing to head pain. Calcitonin receptor (CTR)-based receptors, such as the amylin 1 (AMY) receptor, and ligands, calcitonin gene-related peptide (CGRP) and amylin, have been linked to migraine and pain. However, the contribution of this system to nociception involving the cervical DRG is unclear. Therefore, this study aimed to determine the relative distribution of the CTR, CGRP, and amylin in upper cervical DRG.
METHODS
CTR, CGRP, and amylin immunofluorescence was examined relative to neural markers in C1/2 DRG from male and female mice, rats, and human cases. Immunofluorescence was supported by RNA-fluorescence in situ hybridization examining amylin mRNA distribution in rat DRG.
RESULTS
Amylin immunofluorescence was observed in neuronal soma and fibres. Amylin mRNA (Iapp) was also detected. Amylin and CGRP co-expression was observed in 19% (mouse), 17% (rat), and 36% (human) of DRG neurons in distinct vesicle-like neuronal puncta from one another. CTR immunoreactivity was present in DRG neurons, and both peptides produced receptor signalling in primary DRG cell cultures. CTR-positive neurons frequently co-expressed amylin and/or CGRP (66% rat; 84% human), with some sex differences.
CONCLUSIONS
Amylin and CGRP could both be local peptide agonists for CTR-based receptors in upper cervical DRG, potentially acting through autocrine and/or paracrine signalling mechanisms to modulate neuron function. Amylin and its receptors could represent novel pain targets.
Topics: Rats; Female; Male; Humans; Mice; Animals; Calcitonin Gene-Related Peptide; Receptors, Calcitonin; Ganglia, Spinal; Islet Amyloid Polypeptide; In Situ Hybridization, Fluorescence; Pain; RNA, Messenger
PubMed: 38481170
DOI: 10.1186/s10194-024-01744-z -
Chemistry (Weinheim An Der Bergstrasse,... May 2024Novel fluorinated foldamers based on aminomethyl-1,4-triazolyl-difluoroacetic acid (1,4-Tz-CF) units were synthesized and their conformational behaviour was studied by...
Novel fluorinated foldamers based on aminomethyl-1,4-triazolyl-difluoroacetic acid (1,4-Tz-CF) units were synthesized and their conformational behaviour was studied by NMR and molecular dynamics. Their activity on the aggregation of the human islet amyloid polypeptide (hIAPP) amyloid protein was evaluated by fluorescence spectroscopy and mass spectrometry. The fluorine labelling of these foldamers allowed the analysis of their interaction with the target protein. We demonstrated that the preferred extended conformation of homotriazolamers of 1,4-Tz-CF unit increases the aggregation of hIAPP, while the hairpin-like conformation of more flexible heterotriazolamers containing two 1,4-Tz-CF units mixed with natural amino acids from the hIAPP sequence reduces it, and more efficiently than the parent natural peptide. The longer heterotriazolamers having three 1,4-Tz-CF units adopting more folded hairpin-like and ladder-like structures similar to short multi-stranded β-sheets have no effect. This work demonstrates that a good balance between the structuring and flexibility of these foldamers is necessary to allow efficient interaction with the target protein.
Topics: Islet Amyloid Polypeptide; Humans; Triazoles; Molecular Dynamics Simulation; Halogenation; Protein Aggregates
PubMed: 38478740
DOI: 10.1002/chem.202303887 -
Molecular Pharmacology Apr 2024Dual amylin and calcitonin receptor agonists (DACRAs) show promise as efficacious therapeutics for treatment of metabolic disease, including obesity. However,...
Development of a Novel Assay for Direct Assessment of Selective Amylin Receptor Activation Reveals Novel Differences in Behavior of Selective and Nonselective Peptide Agonists.
Dual amylin and calcitonin receptor agonists (DACRAs) show promise as efficacious therapeutics for treatment of metabolic disease, including obesity. However, differences in efficacy in vivo have been observed for individual DACRAs, indicating that detailed understanding of the pharmacology of these agents across target receptors is required for rational drug development. To date, such understanding has been hampered by lack of direct, subtype-selective, functional assays for the amylin receptors (AMYRs). Here, we describe the generation of receptor-specific assays for recruitment of Venus-tagged Gs protein through fusion of luciferase to either the human calcitonin receptor (CTR), human receptor activity-modifying protein (RAMP)-1, RAMP1 (AMYR), human RAMP2 (AMYR), or human RAMP3 (AMYR). These assays revealed a complex pattern of receptor activation by calcitonin, amylin, or DACRA peptides that was distinct at each receptor subtype. Of particular note, although both of the CT-based DACRAs, sCT and AM1784, displayed relatively similar behaviors at CTR and AMYR, they generated distinct responses at AMYR and AMYR. These data aid the rationalization of in vivo differences in response to DACRA peptides in rodent models of obesity. Direct assessment of the pharmacology of novel DACRAs at AMYR subtypes is likely to be important for development of optimized therapeutics for treatment of metabolic diseases. SIGNIFICANCE STATEMENT: Amylin receptors (AMYRs) are important obesity targets. Here we describe a novel assay that allows selective functional assessment of individual amylin receptor subtypes that provides unique insight into the pharmacology of potential therapeutic ligands. Direct assessment of the pharmacology of novel agonists at AMYR subtypes is likely to be important for development of optimized therapeutics for treatment of metabolic diseases.
Topics: Humans; Receptors, Calcitonin; Receptor Activity-Modifying Proteins; Receptors, Islet Amyloid Polypeptide; Islet Amyloid Polypeptide; Receptors, Peptide; Membrane Proteins; Intracellular Signaling Peptides and Proteins; Neuropeptides; Obesity; Metabolic Diseases
PubMed: 38458773
DOI: 10.1124/molpharm.123.000865 -
Frontiers in Immunology 2024There is accumulating evidence that pathogenic T cells in T1D recognize epitopes formed by post-translational modifications of β-cell antigens, including hybrid insulin...
There is accumulating evidence that pathogenic T cells in T1D recognize epitopes formed by post-translational modifications of β-cell antigens, including hybrid insulin peptides (HIPs). The ligands for several CD4 T-cell clones derived from the NOD mouse are HIPs composed of a fragment of proinsulin joined to peptides from endogenous β-cell granule proteins. The diabetogenic T-cell clone BDC-6.9 reacts to a fragment of C-peptide fused to a cleavage product of pro-islet amyloid polypeptide (6.9HIP). In this study, we used a monoclonal antibody (MAb) to the 6.9HIP to determine when and where HIP antigens are present in NOD islets during disease progression and with which immune cells they associate. Immunogold labeling of the 6.9HIP MAb and organelle-specific markers for electron microscopy were employed to map the subcellular compartment(s) in which the HIP is localized within β-cells. While the insulin B9-23 peptide was present in nearly all islets, the 6.9HIP MAb stained infiltrated islets only in NOD mice at advanced stages of T1D development. Islets co-stained with the 6.9HIP MAb and antibodies to mark insulin, macrophages, and dendritic cells indicate that 6.9HIP co-localizes within insulin-positive β-cells as well as intra-islet antigen-presenting cells (APCs). In electron micrographs, the 6.9HIP co-localized with granule structures containing insulin alone or both insulin and LAMP1 within β-cells. Exposing NOD islets to the endoplasmic reticulum (ER) stress inducer tunicamycin significantly increased levels of 6.9HIP in subcellular fractions containing crinosomes and dense-core granules (DCGs). This work demonstrates that the 6.9HIP can be visualized in the infiltrated islets and suggests that intra-islet APCs may acquire and present HIP antigens within islets.
Topics: Animals; Mice; Mice, Inbred NOD; Diabetes Mellitus, Type 1; Islets of Langerhans; Peptides; Insulin-Secreting Cells; Antigens
PubMed: 38455055
DOI: 10.3389/fimmu.2024.1348131