Chronic peptide-based GIP receptor inhibition exhibits modest glucose metabolic changes in mice when administered either alone or combined with GLP-1 agonism.

Combinatorial gut hormone therapy is one of the more promising strategies for identifying improved treatments for metabolic disease. Many approaches combine the established benefits of glucagon-like peptide-1 (GLP-1) agonism with one or more additional molecules with the aim of improving metabolic outcomes. Recent attention has been drawn to the glucose-dependent insulinotropic polypeptide (GIP) system due to compelling pre-clinical evidence describing the metabolic benefits of antagonising the GIP receptor (GIPR). We rationalised that benefit might be accrued from combining GIPR antagonism with GLP-1 agonism. Two GIPR peptide antagonists, GIPA-1 (mouse GIP(3-30)NH2) and GIPA-2 (NαAc-K10[γEγE-C16]-Arg18-hGIP(5-42)), were pharmacologically characterised and both exhibited potent antagonist properties. Acute in vivo administration of GIPA-1 during an oral glucose tolerance test (OGTT) had negligible effects on glucose tolerance and insulin in lean mice. In contrast, GIPA-2 impaired glucose tolerance and attenuated circulating insulin levels. A mouse model of diet-induced obesity (DIO) was used to investigate the potential metabolic benefits of chronic dosing of each antagonist, alone or in combination with liraglutide. Chronic administration studies showed expected effects of liraglutide, lowering food intake, body weight, fasting blood glucose and plasma insulin concentrations while improving glucose sensitivity, whereas delivery of either GIPR antagonist alone had negligible effects on these parameters. Interestingly, chronic dual therapy augmented insulin sensitizing effects and lowered plasma triglycerides and free-fatty acids, with more notable effects observed with GIPA-1 compared to GIPA-2. Thus, the co-administration of both a GIPR antagonist with a GLP1 agonist uncovers interesting beneficial effects on measures of insulin sensitivity, circulating lipids and certain adipose stores that seem influenced by the degree or nature of GIP receptor antagonism.

A dual apolipoprotein C-II mimetic-apolipoprotein C-III antagonist peptide lowers plasma triglycerides.

Recent genetic studies have established that hypertriglyceridemia (HTG) is causally related to cardiovascular disease, making it an active area for drug development. We describe a strategy for lowering triglycerides (TGs) with an apolipoprotein C-II (apoC-II) mimetic peptide called D6PV that activates lipoprotein lipase (LPL), the main plasma TG-hydrolyzing enzyme, and antagonizes the TG-raising effect of apoC-III. The design of D6PV was motivated by a combination of all-atom molecular dynamics simulation of apoC-II on the Anton 2 supercomputer, structural prediction programs, and biophysical techniques. Efficacy of D6PV was assessed ex vivo in human HTG plasma and was found to be more potent than full-length apoC-II in activating LPL. D6PV markedly lowered TG by more than 80% within a few hours in both apoC-II-deficient mice and hAPOC3-transgenic (Tg) mice. In hAPOC3-Tg mice, D6PV treatment reduced plasma apoC-III by 80% and apoB by 65%. Furthermore, low-density lipoprotein (LDL) cholesterol did not accumulate but rather was decreased by 10% when hAPOC3-Tg mice lacking the LDL-receptor (hAPOC3-Tg × Ldlr-/- ) were treated with the peptide. D6PV lowered TG by 50% in whole-body inducible Lpl knockout (iLpl-/- ) mice, confirming that it can also act independently of LPL. D6PV displayed good subcutaneous bioavailability of about 80% in nonhuman primates. Because it binds to high-density lipoproteins, which serve as a long-term reservoir, it also has an extended terminal half-life (42 to 50 hours) in nonhuman primates. In summary, D6PV decreases plasma TG by acting as a dual apoC-II mimetic and apoC-III antagonist, thereby demonstrating its potential as a treatment for HTG.

Endoscopic duodenal mucosal resurfacing improves glycaemic and hepatic indices in type 2 diabetes: 6-month multicentre results.

Insulin resistance is a core pathophysiological defect underscoring type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD). Both conditions improve with duodenal exclusion surgery. Duodenal mucosal resurfacing (DMR) is an endoscopic intervention developed to treat metabolic disease which has been shown to improve glycaemia in patients with poorly controlled T2DM. Herein, we aimed to further analyse the effects of DMR on hepatic and metabolic parameters in this patient cohort. METHODS: Eighty-five patients with T2DM who received endoscopic DMR treatment were enrolled from 5 centres and followed up for 6 months. We assessed safety in all patients. Efficacy was evaluated in patients who received at least 9 cm of duodenal ablation (n = 67). Endpoints included HbA1c, fasting plasma glucose, weight and aminotransferase levels. Metabolomic analysis was conducted in a subgroup (n = 14). Data were analysed using paired t test or ANOVA for repeated measures with Bonferroni correction and correction for initial weight loss if applicable. RESULTS: The DMR procedure was completed with no intraprocedural complications in the entire cohort. HbA1c was lower 6 months after DMR than at baseline (7.9 ± 0.2% vs. 9.0 ± 0.2% [mean ± SE], p ≪0.001). Fasting plasma glucose was also significantly lower 6 months after DMR compared to baseline (161 ± 7 mg/dl vs. 189 ± 6 mg/dl, p = 0.005). Body weight decreased slightly. At 6 months, alanine aminotransferase had decreased from 41 ± 3 IU/L to 29 ± 2 IU/L (p ≪0.001) and aspartate aminotransferase had decreased from 30 ± 2 IU/L to 23 ± 1 IU/L (p ≪0.001). Metabolomic analysis demonstrated that DMR had key lipid-lowering, insulin-sensitizing and anti-inflammatory effects, as well as increasing antioxidant capacity. Mean FIB-4 was also markedly decreased. CONCLUSION: Hydrothermal ablation of the duodenum by DMR elicits a beneficial metabolic response in patients with T2DM. DMR also improves hepatic indices, potentially through an insulin-sensitizing mechanism. These encouraging data deserve further evaluation in randomized controlled trials. LAY SUMMARY: Hydrothermal duodenal mucosal resurfacing (DMR) is an endoscopic technique designed to treat metabolic disease through ablation of the duodenal mucosa. DMR is a safe procedure which improves glycaemia and hepatic indices in patients with type 2 diabetes mellitus. DMR is an insulin-sensitizing intervention which can be complementary to lifestyle intervention approaches and pharmacological treatments aimed at preserving the pancreas and liver from failure. DMR is a potential therapeutic solution for patients with type 2 diabetes and fatty liver disease.

Novel exenatide analogs with peptidic albumin binding domains: potent anti-diabetic agents with extended duration of action.

The design, synthesis and pharmacology of novel long-acting exenatide analogs for the treatment of metabolic diseases are described. These molecules display enhanced pharmacokinetic profile and potent glucoregulatory and weight lowering actions compared to native exenatide. [Leu(14)]exenatide-ABD is an 88 residue peptide amide incorporating an Albumin Binding Domain (ABD) scaffold. [Leu(14)]exenatide-ABP is a 53 residue peptide incorporating a short Albumin Binding Peptide (ABP). [Leu(14)]exenatide-ABD and [Leu(14)]exenatide-ABP exhibited nanomolar functional GLP-1 receptor potency and were metabolically stable in vitro in human plasma and in a pancreatic digestive enzyme mixture. Both molecules displayed picomolar and nanomolar binding association with albumin across multiple species and circulating half lives of 16 and 11 hours, respectively, post a single IV dose in rats. Unlike exenatide, both molecules elicited robust glucose lowering when injected 1 day prior to an oral glucose tolerance test, indicative of their extended duration of action. [Leu(14)]exenatide-ABD was compared to exenatide in a Lep (ob/ob) mouse model of diabetes. Twice-weekly subcutaneously dosed [Leu(14)]exenatide-ABD displayed superior glucose lowering and weight loss in diabetic mice when compared to continuously infused exenatide at the same total weekly dose. A single oral administration of each molecule via an enteric coated capsule to cynomolgus monkeys showed superior pharmacokinetics for [Leu(14)]exenatide-ABD as compared to [Leu(14)]exenatide-ABP with detectable exposure longer than 14 days. These studies support the potential use of these novel long acting exenatide analogs with different routes of administration for the treatment of type 2 diabetes.

Bifunctional PEGylated exenatide-amylinomimetic hybrids to treat metabolic disorders: an example of long-acting dual hormonal therapeutics.

Peptide hybrids (phybrids) comprising covalently linked peptide hormones can leverage independent biological pathways for additive or synergistic metabolic benefits. PEGylation of biologics offers enhanced stability, duration, and reduced immunogenicity. These two modalities can be combined to produce long-acting therapeutics with dual pharmacology and enhanced efficacy. Compound 10 is composed of an exenatide (AC2993) analogue, AC3174, and an amylinomimetic, davalintide (AC2307), with an intervening 40 kD PEG moiety. It displayed dose-dependent and prolonged efficacy for glucose control and body weight reduction in rodents with superior in vitro and in vivo activities compared to those of a side-chain PEGylated phybrid 6. In diet-induced obese (DIO) rats, the weight-loss efficacy of 10 was similar to that of a combination of PEG-parents 3 and 4. A single dose of 10 elicited sustained body weight reduction in DIO rats for at least 21 days. Compound 10's terminal half-life of ~27 h should translate favorably to weekly dosing in humans.

Improved glucose control and reduced body weight in rodents with dual mechanism of action peptide hybrids.

Combination therapy is being increasingly used as a treatment paradigm for metabolic diseases such as diabetes and obesity. In the peptide therapeutics realm, recent work has highlighted the therapeutic potential of chimeric peptides that act on two distinct receptors, thereby harnessing parallel complementary mechanisms to induce additive or synergistic benefit compared to monotherapy. Here, we extend this hypothesis by linking a known anti-diabetic peptide with an anti-obesity peptide into a novel peptide hybrid, which we termed a phybrid. We report on the synthesis and biological activity of two such phybrids (AC164204 and AC164209), comprised of a glucagon-like peptide-1 receptor (GLP1-R) agonist, and exenatide analog, AC3082, covalently linked to a second generation amylin analog, davalintide. Both molecules acted as full agonists at their cognate receptors in vitro, albeit with reduced potency at the calcitonin receptor indicating slightly perturbed amylin agonism. In obese diabetic Lep(ob)/Lep (ob) mice sustained infusion of AC164204 and AC164209 reduced glucose and glycated haemoglobin (HbA1c) equivalently but induced greater weight loss relative to exenatide administration alone. Weight loss was similar to that induced by combined administration of exenatide and davalintide. In diet-induced obese rats, both phybrids dose-dependently reduced food intake and body weight to a greater extent than exenatide or davalintide alone, and equal to co-infusion of exenatide and davalintide. Phybrid-mediated and exenatide + davalintide-mediated weight loss was associated with reduced adiposity and preservation of lean mass. These data are the first to provide in vivo proof-of-concept for multi-pathway targeting in metabolic disease via a peptide hybrid, demonstrating that this approach is as effective as co-administration of individual peptides.

Diet-induced mouse model of fatty liver disease and nonalcoholic steatohepatitis reflecting clinical disease progression and methods of assessment.

Shortcomings of previously reported preclinical models of nonalcoholic steatohepatitis (NASH) include inadequate methods used to induce disease and assess liver pathology. We have developed a dietary model of NASH displaying features observed clinically and methods for objectively assessing disease progression. Mice fed a diet containing 40% fat (of which ∼18% was trans fat), 22% fructose, and 2% cholesterol developed three stages of nonalcoholic fatty liver disease (steatosis, steatohepatitis with fibrosis, and cirrhosis) as assessed by histological and biochemical methods. Using digital pathology to reconstruct the left lateral and right medial lobes of the liver, we made comparisons between and within lobes to determine the uniformity of collagen deposition, which in turn informed experimental sampling methods for histological, biochemical, and gene expression analyses. Gene expression analyses conducted with animals stratified by disease severity led to the identification of several genes for which expression highly correlated with the histological assessment of fibrosis. Importantly, we have established a biopsy method allowing assessment of disease progression. Mice subjected to liver biopsy recovered well from the procedure compared with sham-operated controls with no apparent effect on liver function. Tissue obtained by biopsy was sufficient for gene and protein expression analyses, providing the opportunity to establish an objective method of assessing liver pathology before subjecting animals to treatment. The improved assessment techniques and the observation that mice fed the high-fat diet exhibit many clinically relevant characteristics of NASH establish a preclinical model for identifying pharmacological interventions with greater likelihood of translating to the clinic.

Native chemical ligation derived method for recombinant peptide/protein C-terminal amidation.

C-terminal amidation is often a requisite structural feature for peptide hormone bio-activity. We report a chemical amidation method that converts peptide/protein thioesters into their corresponding C-terminal amides. The peptide/protein thioester is treated with 1-(2,4-dimethoxyphenyl)-2-mercaptoethyl auxiliary (1b) in a native chemical ligation (NCL) reaction to form an intermediate, which upon removal of the auxiliary with TFA, yields the peptide/protein amide. We have demonstrated the general utility of the approach by successfully converting several synthetic peptide thioesters to peptide amides with high conversion rates. Preliminary results of converting a recombinant peptide thioester to its amide form are also reported.

A sulfated, phosphorylated 7 kDa secreted peptide characterized by direct analysis of cell culture media.

An unusual sulfotyrosine-, phosphoserine-containing motif was mapped on a differentially post-translationally modified 60 residue antimicrobial neuroendocrine peptide called chrombacin. The study was performed by high resolution FT MS using complementary fragmentation techniques. The peptide was analyzed at low levels directly from cell culture media in contrast to previous reports that required extensive purification and proteolytic digestion. The sulfation site was not previously described nor predicted by informatic analysis of the peptide's precursor sequence.

Efficient high-throughput discovery of large peptidic hormones and biomarkers.

A novel approach is presented for the simultaneous identification and relative quantification of secreted peptides, particularly those that have been historically difficult to analyze in a concerted manner. Peptides exceeding 60 residues with various degrees of post-translational modification were identified on a liquid chromatographic time scale. The approach demonstrates high efficiency pattern-based recognition analysis of complex neuroendocrine peptide sets and enables rapid identification of biomarkers from biological material.

Mediation of spontaneous knee osteoarthritis by progressive chondrocyte ATP depletion in Hartley guinea pigs.

OBJECTIVE: Because articular chondrocytes reside in a hypoxic milieu, anaerobic glycolysis is central in generating ATP to support chondrocyte matrix synthesis and viability, with mitochondrial oxidative phosphorylation possibly providing physiologic reserve ATP generation. Nitric oxide (NO) potently suppresses mitochondrial oxidative phosphorylation. Because enhanced cartilage NO generation occurs in osteoarthritis (OA), we systematically tested for mitochondrial dysfunction in the pathogenesis of OA. METHODS: We assessed chondrocytes for ATP depletion and for in situ changes in mitochondrial ultrastructure prior to and during the evolution of spontaneous knee OA in male Hartley guinea pigs, a model in which chondrocalcinosis also supervenes. RESULTS: Spontaneous NO release from knee cartilage samples in organ culture doubled between ages 2 months and 8 months as knee OA developed. Concomitantly, chondrocyte intracellular ATP levels declined by approximately 50%, despite a lack of mitochondrial ultrastructure abnormalities in knee chondrocytes. As ATP depletion progressed with aging in knee chondrocytes, an increased ratio of lactate to pyruvate was observed, consistent with an adaptive augmentation of glycolysis to mitochondrial dysfunction. Furthermore, we observed progressive elevation of chondrocyte ATP-scavenging nucleotide pyrophosphatase/phosphodiesterase (NPP) activity and extracellular levels of the NPP enzymatic end product inorganic pyrophosphate (PPi), which stimulate chondrocalcinosis. CONCLUSION: Profound chondrocyte ATP depletion develops in association with heightened NO generation in guinea pig knee OA. Increased NPP activity and concordant increases in extracellular PPi, which are strongly associated with human aging-associated degenerative arthropathy and directly stimulate chondrocalcinosis, may be primarily driven by chondrocyte ATP depletion. Our findings implicate a decreased mitochondrial bioenergetic reserve as a pathogenic factor in both degenerative arthropathy and chondrocalcinosis in aging.

The subunit composition of the human NADH dehydrogenase obtained by rapid one-step immunopurification.

Defects of the NADH dehydrogenase complex are predominantly manifested in mitochondrial diseases and are significantly associated with the development of many late onset neurological disorders such as Parkinson's disease. Here we describe an immunocapture procedure for isolating this multisubunit membrane-bound complex from human tissue. Using small amounts of immunoisolated protein, one-dimensional and two-dimensional gel electrophoresis, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) peptide mass finger printing (PMF), and nanoflow liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS), we can resolve and identify the human homologues of 42 polypeptides detected so far in the more extensively studied beef heart complex I. These polypeptides include the GRIM-19 protein, which is claimed to be involved in apoptosis, a polypeptide first identified by gene screening as a neuronal protein, as well as a protein thought to be in differentiation linked processes. The concordance of data from human and bovine complex I isolated by different procedures adds to the certainty that these novel proteins of seemingly diverse function are a part of complex I.

A functionally active human F1F0 ATPase can be purified by immunocapture from heart tissue and fibroblast cell lines. Subunit structure and activity studies.

Human mitochondrial F(1)F(0) ATP synthase was isolated with a one-step immunological approach, using a monoclonal antibody against F(1) in a 96-well microplate activity assay system, to establish a method for fast high throughput screening of inhibitors, toxins, and drugs with very small amounts of enzyme. For preparative purification, mitochondria from human heart tissue as well as cultured fibroblasts were solubilized with dodecyl-beta-d-maltoside, and the F(1)F(0) was isolated with anti-F(1) monoclonal antibody coupled to protein G-agarose beads. The immunoprecipitated F(1)F(0) contained a full complement of subunits that were identified with specific antibodies against five of the subunits (alpha, beta, OSCP, d, and IF(1)) and by MALDI-TOF and/or LC/MS/MS for all subunits except subunit c, which could not be resolved by these methods because of the limits of detection. Microscale immunocapture of F(1)F(0) from detergent-solubilized mitochondria or whole cell fibroblast extracts was performed using anti-F(1) monoclonal antibody immobilized on 96-well microplates. The captured complex V displayed ATP hydrolysis activity that was fully oligomycin and inhibitor protein IF(1)-sensitive. Moreover, IF(1) could be co-isolated with F(1)F(0) when the immunocapture procedure was carried out at pH 6.5 but was absent when the ATP synthase was isolated at pH 8.0. Immunocaptured F(1)F(0) lacking IF(1) could be inhibited by more than 90% by addition of recombinant inhibitor protein, and conversely, F(1)F(0) containing IF(1) could be activated more than 10-fold by brief exposure to pH 8.0, inducing the release of inhibitor protein. With this microplate system an ATP hydrolysis assay of complex V could be carried out with as little as 10 ng of heart mitochondria/well and as few as 3 x 10(4) cells/well from fibroblast cultures. The system is therefore suitable to screen patient-derived samples for alterations in amount or functionality of both the F(1)F(0) ATPase and IF(1).

An alternative strategy to determine the mitochondrial proteome using sucrose gradient fractionation and 1D PAGE on highly purified human heart mitochondria.

An alternative strategy for mitochondrial proteomics is described that is complementary to previous investigations using 2D PAGE techniques. The strategy involves (a) obtaining highly purified preparations of human heart mitochondria using metrizamide gradients to remove cytosolic and other subcellular contaminant proteins; (b) separation of mitochondrial protein complexes using sucrose density gradients after solubilization with n-dodecyl-beta-D-maltoside; (c) 1D electrophoresis of the sucrose gradient fractions; (d) high-throughput proteomics using robotic gel band excision, in-gel digestion, MALDI target spotting and automated spectral acquisition; and (e) protein identification from mixtures of tryptic peptides by high-precision peptide mass fingerprinting. Using this approach, we rapidly identified 82 bona fide or potential mitochondrial proteins, 40 of which have not been previously reported using 2D PAGE techniques. These proteins include small complex I and complex IV subunits, as well as very basic and hydrophobic transmembrane proteins such as the adenine nucleotide translocase that are not recovered in 2D gels. The technique described here should also be useful for the identification of new protein-protein associations as exemplified by the validation of a recently discovered complex that involves proteins belonging to the prohibitin family.