A long-standing aim in the setting of various pathologies including acute myocardial infarction, chronic kidney disease (CKD), and ischaemic stroke, has been to identify successful approaches to augment cellular and organ protection. Although the continual evolution and refinement of ideas over the past few decades has allowed the field to progress, we are yet to realise successful clinical translation of this concept. The 12th Hatter Cardiovascular Workshop identified a number of important points and key questions for future research relating to cardio- and neuro-protection and interorgan communication. Specific topics that were discussed include the ‘cardio-metabolic-renal’ axis of organ protection, the parasympathetic signalling hypothesis, the role of the coronary microvasculature in myocardial infarction, the RISK pathway of cardioprotection, extracellular vesicles and the way forward, the future for clinical studies of remote ischaemic conditioning, and new experimental models for cardio-oncology investigations.

The Hatter Cardiovascular Institute biennial workshop, originally scheduled for April 2020 but postponed for 2 years due to the Covid pandemic, was organised to debate and discuss the future of Remote Ischaemic Conditioning (RIC). This evolved from the large multicentre CONDI-2–ERIC–PPCI outcome study which demonstrated no additional benefit when using RIC in the setting of ST-elevation myocardial infarction (STEMI). The workshop discussed how conditioning has led to a significant and fundamental understanding of the mechanisms preventing cell death following ischaemia and reperfusion, and the key target cyto-protective pathways recruited by protective interventions, such as RIC. However, the obvious need to translate this protection to the clinical setting has not materialised largely due to the disconnect between preclinical and clinical studies. Discussion points included how to adapt preclinical animal studies to mirror the patient presenting with an acute myocardial infarction, as well as how to refine patient selection in clinical studies to account for co-morbidities and ongoing therapy. These latter scenarios can modify cytoprotective signalling and need to be taken into account to allow for a more robust outcome when powered appropriately. The workshop also discussed the potential for RIC in other disease settings including ischaemic stroke, cardio-oncology and COVID-19. The workshop, therefore, put forward specific classifications which could help identify so-called responders vs. non-responders in both the preclinical and clinical settings.

In the 25 years since the hypothesis was first described, therapeutic use of inhibitors of dipeptidyl peptidase-4 (DPP-4i) as a novel approach to the treatment of type 2 diabetes has become established widely, with several compounds now available to exemplify the class. Although the clinical profiles of members of the DPP-4i class have been reviewed extensively, the underlying pragmatic small molecular design and pharmaceutical properties of these agents have seldom been addressed in the context of establishment of the class as treatments for type 2 diabetes. Among the reasons contributing to the wide acceptance of DPP-4i as oral anti-hyperglycaemic therapy are: (i) the endocrine basis of their pharmacology; (ii) their chemical 'simplicity' and low molecular mass; (iii) their pharmacological selectivity for their target mechanism of action; (iv) the nature of physiologically relevant substrates for the enzyme; (v) their relative ease of formulation into tablets; (vi) their efficacy as glucose-lowering agents; (vii) their absorption, distribution, metabolism and elimination profiles; and (viii) their limited tolerability issues.

In the 30 years since the original description of ischaemic preconditioning, understanding of the pathophysiology of ischaemia/reperfusion injury and concepts of cardioprotection have been revolutionised. In the same period of time, management of patients with coronary artery disease has also been transformed: coronary artery and valve surgery are now deemed routine with generally excellent outcomes, and the management of acute coronary syndromes has seen decade on decade reductions in cardiovascular mortality. Nonetheless, despite these improvements, cardiovascular disease and ischaemic heart disease in particular, remain the leading cause of death and a significant cause of long-term morbidity (with a concomitant increase in the incidence of heart failure) worldwide. The need for effective cardioprotective strategies has never been so pressing. However, despite unequivocal evidence of the existence of ischaemia/reperfusion in animal models providing a robust rationale for study in man, recent phase 3 clinical trials studying a variety of cardioprotective strategies in cardiac surgery and acute ST-elevation myocardial infarction have provided mixed results. The investigators meeting at the Hatter Cardiovascular Institute workshop describe the challenge of translating strong pre-clinical data into effective clinical intervention strategies in patients in whom effective medical therapy is already altering the pathophysiology of ischaemia/reperfusion injury-and lay out a clearly defined framework for future basic and clinical research to improve the chances of successful translation of strong pre-clinical interventions in man.

The dipeptidyl peptidase-4 (DPP-4) inhibitor concept is an example of prospective drug design and development based upon a distinct endocrine hypothesis. The design of enzyme inhibitors is a pragmatic approach to drug design; being compatible with the identification and optimization of small molecules that have properties commensurate with oral administration, as well as acceptable drug metabolism, distribution and elimination characteristics. Glucagon-like peptide 1 (GLP-1), a hormone with a spectrum of favourable metabolic actions, including glucose-dependent stimulation of insulin and inhibition of glucagon secretion, provided the endocrine basis from which the idea of using DPP-4 inhibitors as anti-diabetic agents was developed. The origin of the DPP-4 inhibitor concept was inspired by the angiotensin-converting enzyme inhibitor approach, which succeeded in establishing a class of extensively used therapeutic agents for the treatment of cardiovascular disorders.

AIM:Recent studies suggest that the incretin concept is not restricted to glucose ingestion but relevant also after non-glucose macronutrient administration. We therefore hypothesized that raising incretin hormones reduces circulating glucose after both glucose and non-glucose macronutrient ingestion in healthy subjects. METHODS:Twelve healthy subjects received the dipeptidyl peptidase-4 inhibitor sitagliptin (100 mg) or placebo before ingestion of glucose, fat (olive oil) or protein mix in equicaloric amounts (8 kcal/kg) plus paracetamol (1.5 g). The 120-min areas under curve (AUC) of intact glucagon-like peptide-1 (GLP-1), glucose, insulin, C-peptide, glucagon and paracetamol, and model-derived insulin secretion rate (ISR), insulin sensitivity, insulin clearance and glucose absorption were measured. RESULTS:The increased plasma intact GLP-1 levels after each macronutrient was augmented by sitagliptin. This was associated with a robust lowering of glucose: glucose excursion after oral glucose was diminished, and glucose fell below baseline after oral fat and protein. In spite of lower glucose, AUCC -peptide and ISR did not differ significantly between sitagliptin and placebo after any macronutrient. AUCglucagon , insulin sensitivity and insulin clearance were also not different between sitagliptin and placebo. Glucose absorption after oral glucose was reduced by sitagliptin, whereas AUCparacetamol was not statistically different between sitagliptin and placebo. CONCLUSIONS:Physiological elevation of intact GLP-1 levels after ingestion of glucose and non-glucose macronutrients is robustly glucose-lowering in healthy subjects. Hence, the incretin concept is not restricted to glucose ingestion in normal physiology. The glucose-lowering action of sitagliptin at these low glucose levels in healthy subjects may have complex mechanisms, involving both islet-dependent and islet-independent mechanisms.

Diabetes, Obesity and MetabolismVolume 14, Issue 4 p. 383-384 Reply to: Ahren B et al. Mechanisms of action of the dipeptidyl peptidase-4 inhibitor vildagliptin in humans. Diabetes Obes Metab 2011; 13(9): 775–783 and Ahren B et al. Clinical evidence and mechanistic basis for vildagliptin's action when added to metformin. Diabetes Obes Metab 2011; 13(3): 193–203 R. D. Carr, Corresponding Author R. D. Carr MSD A/S, Ballerup, DenmarkMSD A/S, Lautrupbjerg 4, DK-2750 Ballerup, Denmark E-mail: richard.carr@merck.comSearch for more papers by this authorH. L. Katzeff, H. L. Katzeff Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorC. M. Alexander, C. M. Alexander Merck Inc, Upper Gwynedd, PA, USASearch for more papers by this authorJ. P. Berger, J. P. Berger Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorS. S. Xu, S. S. Xu Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorN. Thornberry, N. Thornberry Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this author R. D. Carr, Corresponding Author R. D. Carr MSD A/S, Ballerup, DenmarkMSD A/S, Lautrupbjerg 4, DK-2750 Ballerup, Denmark E-mail: richard.carr@merck.comSearch for more papers by this authorH. L. Katzeff, H. L. Katzeff Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorC. M. Alexander, C. M. Alexander Merck Inc, Upper Gwynedd, PA, USASearch for more papers by this authorJ. P. Berger, J. P. Berger Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorS. S. Xu, S. S. Xu Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this authorN. Thornberry, N. Thornberry Merck Research Laboratories, Rahway, NJ, USASearch for more papers by this author First published: 05 March 2012 https://doi.org/10.1111/j.1463-1326.2011.01542.xCitations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume14, Issue4April 2012Pages 383-384 RelatedInformation

Aim: Glucagon-like peptide-1 (GLP-1) is an incretin hormone that induces glucose-dependent insulin secretion and may have neurotrophic properties. Our aim was to identify the presence and activity of GLP-1 receptors (GLP-1Rs) in peripheral nerve and to assess the impact of GLP-1R agonists on diabetes-induced nerve disorders. Methods: Tissues were collected from streptozotocin-diabetic rats. GLP-1R function was assessed by incubating tissues from normal and diabetic rats with GLP-1R agonists and antagonists and measuring induction of ERK1/2 phosphorylation by Western blot. Streptozotocin-diabetic mice were also treated with the GLP-1R agonist exenatide for 8 weeks to assess the impact of GLP-1R signalling on peripheral nerve function and structure. Results: GLP-1R protein was detected in rat dorsal root ganglia and the neurons and Schwann cells of the sciatic nerve. Protein levels were not affected by streptozotocin-induced diabetes. GLP-1R agonists did not signal via ERK1/2 in sciatic nerve of normal rats. However, GLP-1R agonists significantly increased pERK1/2 levels in sciatic nerves from diabetic rats, indicating that GLP-1Rs are functional in this tissue. Exenatide treatment did not affect blood sugar, insulin levels or paw thermal response latencies in either control or diabetic mice. However, the reductions of motor nerve conduction velocity and paw intraepidermal fibre density seen in diabetic mice were attenuated by exenatide treatment. Conclusions: These data show that the peripheral nerve of diabetic rodents exhibits functional GLP-1R and suggest that GLP-1R-mediated ERK-signalling in sciatic nerve of diabetic rodents may protect large motor fibre function and small C fibre structure by a mechanism independent of glycaemic control.

Protein elicits a stronger early (30 min) glucose-dependent insulinotropic polypeptide (GIP) response than fat ingestion in lean individuals, with no difference in glucagon-like peptide-1 (GLP-1). We assessed the incretin hormone response to protein versus fat ingestion in obesity. Equicaloric (8 kcal/kg) fat (olive oil) or protein (whey protein) was ingested by non-diabetic obese male volunteers [body mass index (BMI) >30 kg/m2; n = 12] and plasma GIP and GLP-1 were determined. We found no difference in the early GIP or GLP-1 responses to fat versus protein. However, the total 300-min GIP response was greater after fat than after protein ingestion (20.3 ± 3.9 vs. 10.0 ± 2.8 nmol/l × min; p = 0.026), whereas the 300-min GLP-1 responses were the same. Thus, in obesity, protein and fat ingestion elicit similar early (30 min) incretin hormone responses, whereas 300-min GIP secretion is more pronounced after fat than protein ingestion.

Introduction & The incretin hormone glucagon-like peptide-1 (GLP-1) has a number of eff ects (reviewed in [1] ), which has made it a very attractive basis for the development of new therapies for type 2 diabetes. The eff ects include actions on the pancreatic islets as well as, for example, benefi cial actions on the cardiovascular system [2] . The native peptide is, however, not clinically useful due to its rapid cleavage in vivo by dipeptidyl peptidase-4 (DPP-4) [3] , whereby the peptide loses its insulinotropic action. By promoting the benefi cial eff ects of endogenous GLP-1, DPP-4 inhibitors have shown great therapeutic potential [4] , and therefore, have been implemented in the treatment of type 2 diabetes. DPP-4 is, however, not the only enzyme involved in the degradation of GLP-1. In vitro studies have shown that several enzymes located in the kidney brush border membrane are able to cleave GLP-1 [5] , and although they are probably not all relevant in the in vivo metabolism of GLP-1, studies have indicated that at least neutral endopeptidase 24.11 (NEP) seems to be of importance. NEP is widely distributed [6] , and is able to cleave GLP-1 at several sites in the mid-region and the COOH-terminal part of the peptide [7] . Furthermore, a physiological role of NEP in the degradation of GLP-1 has been demonstrated in the anaesthetized pig [8] . In the present study, we have investigated whether addition of a NEP inhibitor would potentiate the eff ect on glycemic control obtained with a DPP-4 inhibitor during 12 weeks of treatment in diabetic Goto – Kakizaki (GK)-rats. The GK-rat is a lean, polygenic model of type 2 diabetes, with impaired glucose-induced insulin secretion due to a decreased β -cell mass and moderate insulin resistance [9] . Materials and Methods & Animals The animal studies were conducted in accordance with international guidelines (National Institutes of Health publication no. 85-23, revised 1985, and Danish legislation governing animal experimentation, 1987), and were carried out after permission had been granted by the Animal Experiments Inspectorate, Ministry of Justice, Denmark. The study was performed in 10-weekold male GK-rats (Taconic, Ejby, Denmark) weighing around 300 g. Animals were handled regularly prior to and during the experimental period in order to accustom them and minimize any stress due to handling in the subsequent oral glucose tolerance tests (OGTT).

Altitude exposure has been associated with loss of appetite and weight loss in healthy humans. However, it remains unclear whether endocrine factors contribute to these changes. Leptin and Glucagon like peptide‐1 (GLP‐1) are peptide hormones which play a role in the regulation of appetite and metabolism. Leptin is also a hypoxia inducible gene, however, the influence of hypoxia on GLP‐1 is less clear. We sought to determine the influence of normobaric hypoxia on plasma leptin and GLP‐1 levels in 25 healthy humans (age=30±8 yrs, BMI=25±3 kg/m2). Subjects ingested a controlled meal during normoxia and following a 17‐hr exposure to normobaric hypoxia (12.5% FIO2) with assessment of plasma leptin before the meal and GLP‐1 pre‐meal, at 20 and 40min. post‐meal. Oxygen saturation (O2sats) values were monitored and recorded continuously during hypoxia and averaged 83±2% over the course of 17‐hrs. We found that hypoxia caused a significant elevation in plasma leptin levels (normoxia=4.9±0.8, hypoxia=7.7±1.5ng/mL, p<0.05), but no change in GLP‐1 values (baseline=15.7±0.9 vs. 15.9±0.7pmol/L, 20min post meal=21.7±0.9 vs. 21.8±1.2pmol.L, 40 minutes post meal=19.7±1.2 vs. 21.0±1.2pmol/L, for normoxia and hypoxia, respectively, p>0.05 normoxia vs. hypoxia at each point). There was a moderate correlation between O2sats and leptin over the 17hr exposure (r=0.45, p<0.05), but no relationship between O2sats and GLP‐1. These data suggest that changes in plasma leptin levels are associated with the degree of O2 desaturation with exposure to 12.5% FIO2 whereas, changes in GLP‐1 appear independent of changes in O2sats. HL71478, AHA 0410073Z.

Recent studies have suggested that sensory nerves may influence insulin secretion and action. The present study investigated the effects of resiniferatoxin (RTX) inactivation of sensory nerves (desensitization) on oral glucose tolerance, insulin secretion and whole body insulin sensitivity in the glucose intolerant, hyperinsulinemic, and insulin-resistant obese Zucker rat. After RTX treatment (0.05 mg/kg RTX sc given at ages 8, 10, and 12 wk), fasting plasma insulin was reduced (P < 0.0005), and oral glucose tolerance was improved (P < 0.005). Pancreas perfusion showed that baseline insulin secretion (7 mM glucose) was lower in RTX-treated rats (P = 0.01). Insulin secretory responsiveness to 20 mM glucose was enhanced in the perfused pancreas of RTX-treated rats (P < 0.005) but unaffected in stimulated, isolated pancreatic islets. At the peak of spontaneous insulin resistance in the obese Zucker rat, insulin sensitivity was substantially improved after RTX treatment, as evidenced by higher glucose infusion rates (GIR) required to maintain euglycemia during a hyperinsulinemic euglycemic (5 mU.kg(-1).min(-1)) clamp (GIR(60-120min): 5.97 +/- 0.62 vs. 11.65 +/- 0.83 mg.kg(-1).min(-1) in RTX-treated rats, P = 0.003). In conclusion, RTX treatment and, hence, sensory nerve desensitization of adult male obese Zucker rats improved oral glucose tolerance by enhancing insulin secretion, and, in particular, by improving insulin sensitivity.

Glucagon-like peptide 1 (GLP-1), a gut incretin hormone that stimulates insulin secretion, also activates antiapoptotic signaling pathways such as phosphoinositide 3-kinase and mitogen-activated protein kinase in pancreatic and insulinoma cells. Since these kinases have been shown to protect against myocardial injury, we hypothesized that GLP-1 could directly protect the heart against such injury via these prosurvival signaling pathways. Both isolated perfused rat heart and whole animal models of ischemia/reperfusion were used, with infarct size measured as the end point of injury. In both studies, GLP-1 added before ischemia demonstrated a significant reduction in infarction compared with the valine pyrrolidide (an inhibitor of its breakdown) or saline groups. This protection was abolished in the in vitro hearts by the GLP-1 receptor antagonist exendin (9-39), the cAMP inhibitor Rp-cAMP, the PI3kinase inhibitor LY294002, and the p42/44 mitogen-activated protein kinase inhibitor UO126. Western blot analysis demonstrated the phosphorylation of the proapoptotic peptide BAD in the GLP-1-treated groups. We show for the first time that GLP-1 protects against myocardial infarction in the isolated and intact rat heart. This protection appears to involve activating multiple prosurvival kinases. This finding may represent a new therapeutic potential for this class of drug currently undergoing clinical trials in the treatment of type 2 diabetes.

Although ATP-sensitive potassium (K(ATP)) channel openers, e.g., minoxidil and diazoxide, can induce hair growth, their mechanisms require clarification. Improved drugs are needed clinically. but the absence of a good bioassay hampers research. K(ATP) channels from various tissues contain subtypes of the regulatory sulfonylurea receptor, SUR, and pore-forming, K(+) inward rectifier subunits, Kir6.X, giving differing sensitivities to regulators. Therefore, the in vitro effects of established potassium channel openers and inhibitors (tolbutamide and glibenclamide), plus a novel, selective Kir6.2/SUR1 opener, NNC 55-0118, were assessed on deer hair follicle growth in serum-free median without streptomycin. Minoxidil (0.1-100 microM, p<0.001), NNC 55-0118 (1 mM, p<0.01; 0.1, 10, 100 microM, p<0.001), and diazoxide (10 microM, p<0.01) increased growth. Tolbutamide (1 mM) inhibited growth (p<0.001) and abolished the effect of 10 microM minoxidil, diazoxide and NNC 55-0118; glibenclamide (10 microM) had no effect, but prevented stimulation by 10 microM minoxidil. Phenol red stimulated growth (p<0.001), but channel modulator responses remained unaltered. Thus, deer follicles offer a practical, ethically advantageous in vitro bioassay that reflects clinical responses in vivo. The results indicate direct actions of K(ATP) channel modulators within hair follicles via two types of channels, with SUR 1 and SUR 2, probably SUR2B, sulfonylurea receptors.

OBJECTIVE:It has earlier been demonstrated that capsaicin-induced desensitization improves insulin sensitivity in normal rats. However, whether increased capsaicin-sensitive nerve activity precedes the onset of insulin resistance in diet-induced obesity--and therefore might be involved in the pathophysiology--is not known. Further, it is of relevance to investigate whether capsaicin desensitization improves glycaemic control even in obese individuals and we therefore chose the obese Zucker rats to test this.DESIGN AND METHODS:Plasma levels of calcitonin gene-related peptide (CGRP; a marker of sensory nerve activity) was assessed in 8-week-old Zucker rats. To investigate whether capsaicin desensitization (100 mg/kg at 9 weeks of age) would also ameliorate glycaemia in this non-diabetic model, we assessed oral glucose tolerance at 7 weeks after capsaicin.RESULTS:It was found that plasma CGRP levels were elevated in obese Zucker rats prior to the onset of obesity (16.1+/-3.4 pmol/l in pre-obese Zucker rats vs 6.9+/-1.1 pmol/l in lean littermates; P = 0.015) despite similar body weights. Furthermore, capsaicin desensitization reduced both fasting blood glucose (4.3+/-0.2 mmol/l vs 5.1+/-0.2 mmol/l in controls; P = 0.050) as well as the mean blood glucose level during an oral glucose tolerance test (OGTT) (6.8+/-0.3 mmol/l vs 8.6+/-0.5 mmol/l in control obese rats; P = 0.024) whereas the plasma insulin levels during the OGTT were unchanged. However this did not lead to an improvement in insulin resistance or to a reduction of tissue triglyceride accumulation in muscle or liver.CONCLUSION:We concluded that capsaicin-induced sensory nerve desensitization improves glucose tolerance in Zucker rats. Since, in this study, plasma CGRP levels, a marker of sensory nerve activity, were increased in the pre-obese rats, our data support the hypothesis that increased activity of sensory nerves precedes the development of obesity and insulin resistance in Zucker rats.