GIPR Agonism Enhances TZD-Induced Insulin Sensitivity in Obese IR Mice

Recent studies have found that glucose-dependent insulinotropic polypeptide receptor (GIPR) agonism can enhance the metabolic efficacy of glucagon-like peptide-1 receptor agonist treatment by promoting both weight-dependent and -independent improvements on systemic insulin sensitivity. These findings have prompted new investigations aimed at better understanding the broad metabolic benefit of GIPR activation. Herein, we determined whether GIPR agonism favorably influenced the pharmacologic efficacy of the insulin-sensitizing thiazolidinedione (TZD) rosiglitazone in obese insulin-resistant (IR) mice. Genetic and pharmacological approaches were used to examine the role of GIPR signaling on rosiglitazone-induced weight gain, hyperphagia, and glycemic control. RNA sequencing was conducted to uncover potential mechanisms by which GIPR activation influences energy balance and insulin sensitivity. In line with previous findings, treatment with rosiglitazone induced the mRNA expression of the GIPR in white and brown fat. However, obese GIPR-null mice dosed with rosiglitazone had equivalent weight gain to that of wild-type (WT) animals. Strikingly, chronic treatment of obese IR WT animals with a long-acting GIPR agonist prevented rosiglitazone-induced weight-gain and hyperphagia, and it enhanced the insulin-sensitivity effect of this TZD. The systemic insulin sensitization was accompanied by increased glucose disposal in brown adipose tissue, which was underlined by the recruitment of metabolic and thermogenic genes. These findings suggest that GIPR agonism can counter the negative consequences of rosiglitazone treatment on body weight and adiposity, while improving its insulin-sensitizing efficacy at the same time.

ARTICLE HIGHLIGHTS

Chronic high-rate pacing induces heart failure with preserved ejection fraction-like phenotype in Ossabaw swine

The lack of pre-clinical large animal models of heart failure with preserved ejection fraction (HFpEF) remains a growing, yet unmet obstacle to improving understanding of this complex condition. We examined whether chronic cardiometabolic stress in Ossabaw swine, which possess a genetic propensity for obesity and cardiovascular complications, produces an HFpEF-like phenotype. Swine were fed standard chow (lean; n = 13) or an excess calorie, high-fat, high-fructose diet (obese; n = 16) for ~ 18 weeks with lean (n = 5) and obese (n = 8) swine subjected to right ventricular pacing (180 beats/min for ~ 4 weeks) to induce heart failure (HF). Baseline blood pressure, heart rate, LV end-diastolic volume, and ejection fraction were similar between groups. High-rate pacing increased LV end-diastolic pressure from ~ 11 ± 1 mmHg in lean and obese swine to ~ 26 ± 2 mmHg in lean HF and obese HF swine. Regression analyses revealed an upward shift in LV diastolic pressure vs. diastolic volume in paced swine that was associated with an ~ twofold increase in myocardial fibrosis and an ~ 50% reduction in myocardial capillary density. Hemodynamic responses to graded hemorrhage revealed an ~ 40% decrease in the chronotropic response to reductions in blood pressure in lean HF and obese HF swine without appreciable changes in myocardial oxygen delivery or transmural perfusion. These findings support that high-rate ventricular pacing of lean and obese Ossabaw swine initiates underlying cardiac remodeling accompanied by elevated LV filling pressures with normal ejection fraction. This distinct pre-clinical tool provides a unique platform for further mechanistic and therapeutic studies of this highly complex syndrome.

Preclinical Characterization of LY3209590, a Novel Weekly Basal Insulin Fc-fusion Protein

The benefit of once-weekly basal insulin is less frequent dosing, which has the potential to reduce the barrier to injection therapy and impact patient activation, adherence/compliance, quality of life, and outcomes. Basal Insulin Fc (BIF, LY3209590, or insulin efsitora alfa) is a once-weekly basal insulin in clinical testing for type 1 and type 2 diabetes mellitus. BIF is comprised of a novel single-chain variant of insulin fused to a human IgG2 Fc domain using a peptide linker. The in vitro binding affinity of BIF for the human insulin receptor (IR) was two orders of magnitude weaker relative to human insulin. BIF stimulated IR phosphorylation in cells with reduced potency, yet full agonism, and exhibited a significantly faster dephosphorylation kinetic profile than human insulin or AspB10 insulin. BIF stimulated de novo lipogenesis in 3T3-L1 adipocytes and cell proliferation in SAOS-2 and H4IIE cells with {greater than or equal to}70-fold reduction in in vitro potency compared to human insulin. BIF possessed markedly reduced binding to hIGF-1R making definitive measurements unattainable. In vivo pharmacology studies using streptozotocin-treated diabetic rats demonstrated a significant decrease in blood glucose compared to vehicle-treated animals 24h post-injection, persisting through 336h following subcutaneous administration. In streptozotocin-treated rats, BIF reached T_max at 48h and possessed a clearance rate of ~0.85 mL/hr/kg, with a t_1/2 of ~120h following subcutaneous administration. These results demonstrate BIF has an in vitro pharmacological profile similar to native insulin, with significantly reduced potency and an extended time-action profile in vivo that supports QW dosing in humans. Significance Statement BIF is a novel basal insulin Fc-fusion protein designed for once-weekly dosing. In this study we demonstrate that BIF has an in vitro pharmacological profile similar to human insulin, but with weaker potency across assays for IR binding and activity. BIF has a PD and PK profile in STZ-treated rats supportive of weekly dosing in humans.

Acute SGLT-2i treatment improves cardiac efficiency during myocardial ischemia independent of Na+/H+ exchanger-1

AIMS

Sodium glucose co-transporter 2 inhibitors (SGLT2i) demonstrate cardioprotective benefits independent of a glucose lowering effect including preservation of cardiac function during a myocardial ischemia. Sodium‑hydrogen exchanger-1 (NHE-1), has been hypothesized to contribute to the cardiac effects of SGLT2i. We characterized the beneficial effects of acute pre-ischemia exposure to SGLT2i and explored the possibility that these effects are explained by NHE-1 inhibition.

METHODS AND RESULTS

Swine were anesthetized and instrumented for invasive hemodynamic measurements After baseline data collection, swine received a 15-30 min intravenous infusion of vehicle (DMSO), the SGLT2i canagliflozin (~1 mg/kg), or the NHE-1 inhibitor cariporide (~0.03 mg/kg) ending immediately prior to occlusion of the left circumflex artery. Measurements were obtained at baseline, during a 60-min complete occlusion of the circumflex coronary artery, and during a 2-h reperfusion period. Blood pressure, heart rate, left anterior descending artery flow, and associated myocardial oxygen consumption were unaffected by acute pre-treatment with canagliflozin or cariporide during ischemia and reperfusion. Acute pre-ischemic treatment with canagliflozin significantly increased diastolic filling and stroke work, producing a rightward shift in the Frank-Starling relationship, and also improved cardiac work efficiency relative to untreated control hearts during ischemia. Effects of NHE-1 inhibition with cariporide were modest and dissimilar. Examination of AP-1 cells transfected with wild-type NHE-1 and iPSC-derived cardiomyocytes confirmed dose-dependent-inhibition of NHE-1 activity by cariporide, while canagliflozin had no significant effect on NHE-1 activity.

CONCLUSION

Acute pre-treatment with SGLT2i produces cardioprotective effects during ischemia, including improved work efficiency. These effects are not explained by NHE-1 inhibition.

TRANSLATIONAL PERSPECTIVE

SGLT2 inhibitors have been shown to improve cardiac outcomes in patient including reducing myocardial infarction incidence and mortality. The mechanism(s) explaining this effect are not clear. This manuscript demonstrates a protective effect from acute SGLT2i exposure, as short as 15 min, prior to experimental infarction in swine. These effects were independent of NHE1 inhibition. These observations suggest that SGLT2 inhibitors can confer cardioprotective effects on a very short time scale. It is possible that such effects provide an ongoing contribution to ischemic protection even in the setting of chronic treatment.

Pharmacological Evaluation of a Pegylated Urocortin-1 Peptide in Experimental Autoimmune Disease Models

Urocortin-1 (UCN1) is a member of the corticotropin releasing hormone (CRH) family of peptides that acts through CRH-receptor 1 (CRHR1) and CRH-receptor 2 (CRHR2). UCN1 can induce adrenocorticotropin hormone (ACTH) and downstream glucocorticoids through CRHR1 and promote beneficial metabolic effects through CRHR2. UCN1 has a short half-life and has been shown to improve experimental autoimmune disease. A pegylated UCN1 peptide (PEG-hUCN1) was generated to extend half-life and was tested in multiple experimental autoimmune disease models and in healthy mice to determine effects on corticosterone induction, autoimmune disease, and glucocorticoid induced adverse effects. Cardiovascular effects were also assessed by telemetry. PEG-hUCN1 demonstrated a dose dependent 4-to-6-fold elevation of serum corticosterone and significantly improved autoimmune disease comparable to prednisolone in several experimental models. In healthy mice, PEG-hUCN1 showed less adverse effects compared to corticosterone treatment. PEG-hUCN1 peptide induced an initial 30% reduction in blood pressure that was followed by a gradual and sustained 30% increase in blood pressure at the highest dose. Additionally, an adeno-associated viral 8 (AAV8) UCN1 was used to assess adverse effects of chronic elevation of UCN1 in wild type and CRHR2 knockout mice. Chronic UCN1 expression by an AAV8 approach in wild type and CRHR2 knockout mice demonstrated an important role of CRHR2 in countering the adverse metabolic effects of elevated corticosterone from UCN1. Our findings demonstrate that PEG-hUCN1 shows profound effects in treating autoimmune disease with an improved safety profile relative to corticosterone and that CRHR2 activity is important in metabolic regulation. Significance Statement This study reports the generation and characterization of a pegylated UCN1 peptide and the role of CRHR2 in UCN1-induced metabolic effects. The potency/selectivity, pharmacokinetic properties, pharmacodynamic effects and efficacy in four autoimmune models and safety profiles are presented. This pegylated UCN1 shows potential for treating autoimmune diseases with reduced adverse effects compared to corticosterone treatment. Continuous exposure to UCN1 through an AAV8 approach demonstrates some glucocorticoid mediated adverse metabolic effects that are exacerbated in the absence of the CRHR2 receptor.

Preclinical Characterization of Once Weekly Basal Insulin Fc (BIF)

Weekly basal insulin injections may increase treatment adherence in subjects with diabetes and an appropriately engineered weekly basal insulin may reduce daily pharmacokinetic (PK)/pharmacodynamic (PD) fluctuations compared to currently available daily basal insulins. Therefore, a weekly insulin has the potential to not only ease the burden of insulin therapy, but also improve outcomes for subjects with diabetes in a real-world setting. Basal insulin Fc (BIF, LY3209590) is an insulin Fc-fusion protein in clinical testing as a once weekly treatment for type 1 and type 2 diabetes mellitus (T1DM, T2DM). BIF is comprised of a human single-chain insulin fused to a human IgG2 Fc domain through a peptide linker. The in vitro evaluation determined that BIF exhibited reduced insulin receptor (IR) potency with full agonism, selectivity against human insulin-like growth factor-1 receptor (hIGF-1R), and functional properties similar to native human insulin. The binding affinity of BIF for hIR isoform A, Ki = 25 nM (SEM = 4, n=10), and hIR isoform B, Ki = 26 nM (SEM = 4, n=10), was more than two orders of magnitude weaker than human insulin. BIF stimulated IR phosphorylation in cells with reduced potency, but full agonism, and showed a significantly faster hIR dephosphorylation profile than either human insulin or AspB10 insulin. BIF stimulated de novo lipogenesis in 3T3-L1 adipocytes and cell proliferation in SAOS-2 and H4IIE cells with at least a 70-fold reduction in potency compared to human insulin. BIF possessed markedly reduced binding and activation of hIGF-1R making definitive mitogenic measurements unattainable. In preclinical in vivo pharmacology studies using streptozotocin (STZ)-treated diabetic rats, a statistically significant decrease in blood glucose compared to vehicle-treated animals was seen 24 hours post-injection and persisted through 336 hours post-injection following a single subcutaneous administration (30 nmol/kg) of BIF. In STZ-treated rats, BIF reached a Tmax at 48 hours, possessed an apparent clearance rate of ~0.85 mL/hr/kg, and t1/2 of ~120 hrs. Collectively, these results demonstrate that BIF possesses selective IR agonism with a pharmacological profile similar to native insulin, however with a significantly reduced potency, and a significantly extended time action profile in preclinical animal models supporting once weekly testing in the clinic.

Distinct hemodynamic responses to (pyr)apelin-13 in large animal models

This study tested the hypothesis that (pyr)apelin-13 dose-dependently augments myocardial contractility and coronary blood flow, irrespective of changes in systemic hemodynamics. Acute effects of intravenous (pyr)apelin-13 administration (10 to 1,000 nM) on blood pressure, heart rate, left ventricular pressure and volume, and coronary parameters were measured in dogs and pigs. Administration of (pyr)apelin-13 did not influence blood pressure (P = 0.59), dP/dt_max (P = 0.26), or dP/dt_min (P = 0.85) in dogs. However, heart rate dose-dependently increased > 70% (P < 0.01), which was accompanied by a significant increase in coronary blood flow (P < 0.05) and reductions in left ventricular end-diastolic volume and stroke volume (P < 0.001). In contrast, (pyr)apelin-13 did not significantly affect hemodynamics, coronary blood flow, or indexes of contractile function in pigs. Furthermore, swine studies found no effect of intracoronary (pyr)apelin-13 administration on coronary blood flow (P = 0.83) or vasorelaxation in isolated, endothelium-intact (P = 0.89) or denuded (P = 0.38) coronary artery rings. Examination of all data across (pyr)apelin-13 concentrations revealed an exponential increase in cardiac output as peripheral resistance decreased across pigs and dogs (P < 0.001; R² = 0.78). Assessment of the Frank-Starling relationship demonstrated a significant linear relationship between left ventricular end-diastolic volume and stroke volume across species (P < 0.001; R² = 0.70). Taken together, these findings demonstrate that (pyr)apelin-13 does not directly influence myocardial contractility or coronary blood flow in either dogs or pigs.NEW & NOTEWORTHY Our findings provide much needed insight regarding the pharmacological cardiac and coronary effects of (pyr)apelin-13 in larger animal preparations. In particular, data highlight distinct hemodynamic responses of apelin across species, which are independent of any direct effect on myocardial contractility or perfusion.

Disentangling the Gordian knot of local metabolic control of coronary blood flow

Recognition that coronary blood flow is tightly coupled with myocardial metabolism has been appreciated for well over half a century. However, exactly how coronary microvascular resistance is tightly coupled with myocardial oxygen consumption (MV̇o₂) remains one of the most highly contested mysteries of the coronary circulation to this day. Understanding the mechanisms responsible for local metabolic control of coronary blood flow has been confounded by continued debate regarding both anticipated experimental outcomes and data interpretation. For a number of years, coronary venous Po₂ has been generally accepted as a measure of myocardial tissue oxygenation and thus the classically proposed error signal for the generation of vasodilator metabolites in the heart. However, interpretation of changes in coronary venous Po₂ relative to MV̇o₂ are quite nuanced, inherently circular in nature, and subject to confounding influences that remain largely unaccounted for. The purpose of this review is to highlight difficulties in interpreting the complex interrelationship between key coronary outcome variables and the arguments that emerge from prior studies performed during exercise, hemodilution, hypoxemia, and alterations in perfusion pressure. Furthermore, potential paths forward are proposed to help to facilitate further dialogue and study to ultimately unravel what has become the Gordian knot of the coronary circulation.

Inhibition of sodium-glucose cotransporter-2 preserves cardiac function during regional myocardial ischemia independent of alterations in myocardial substrate utilization

The goal of the present study was to evaluate the effects of SGLT2i on cardiac contractile function, substrate utilization, and efficiency before and during regional myocardial ischemia/reperfusion injury in normal, metabolically healthy swine. Lean swine received placebo or canagliflozin (300 mg PO) 24 h prior to and the morning of an invasive physiologic study protocol. Hemodynamic and cardiac function measurements were obtained at baseline, during a 30-min complete occlusion of the circumflex coronary artery, and during a 2-h reperfusion period. Blood pressure, heart rate, coronary flow, and myocardial oxygen consumption were unaffected by canagliflozin treatment. Ventricular volumes remained unchanged in controls throughout the protocol. At the onset of ischemia, canagliflozin produced acute large increases in left ventricular end-diastolic and systolic volumes which returned to baseline with reperfusion. Canagliflozin-mediated increases in end-diastolic volume were directly associated with increases in stroke volume and stroke work relative to controls during ischemia. Canagliflozin also increased cardiac work efficiency during ischemia relative to control swine. No differences in myocardial uptake of glucose, lactate, free fatty acids or ketones, were noted between treatment groups at any time. In separate experiments using a longer 60 min coronary occlusion followed by 2 h of reperfusion, canagliflozin increased end-diastolic volume and stroke volume and significantly diminished myocardial infarct size relative to control swine. These data demonstrate that SGLT2i with canagliflozin preserves cardiac contractile function and efficiency during regional myocardial ischemia and provides ischemia protection independent of alterations in myocardial substrate utilization.

Local metabolic hypothesis is not sufficient to explain coronary autoregulatory behavior

The local metabolic hypothesis proposes that myocardial oxygen tension determines the degree of autoregulation by increasing the production of vasodilator metabolites as perfusion pressure is reduced. Thus, normal physiologic levels of coronary venous PO₂, an index of myocardial oxygenation, are proposed to be required for effective autoregulation. The present study challenged this hypothesis through determination of coronary responses to changes in coronary perfusion pressure (CPP 140-40 mmHg) in open-chest swine in the absence (n = 7) and presence of euvolemic hemodilution (~ 50% reduction in hematocrit), with (n = 5) and without (n = 6) infusion of dobutamine to augment MVO₂. Coronary venous PO₂ decreased over similar ranges (~ 28-15 mmHg) as CPP was lowered from 140 to 40 mmHg in each of the groups. However, coronary venous PO₂ was not associated with changes in coronary blood flow (r = - 0.11; P = 0.29) or autoregulatory gain (r = - 0.29; P = 0.12). Coronary zero-flow pressure (Pzf) was measured in 20 mmHg increments and determined to be directly related to vascular resistance (r = 0.71; P < 0.001). Further analysis demonstrated that changes in coronary blood flow remained minimal at Pzf > 20 mmHg, but progressively increased as Pzf decreased below this threshold value (r = 0.68; P < 0.001). Coronary Pzf was also positively correlated with autoregulatory gain (r = 0.43; P = 0.001). These findings support that coronary autoregulatory behavior is predominantly dependent on an adequate degree of underlying vasomotor tone, independent of normal myocardial oxygen tension.

Progressive Renal Disease Established by Renin-Coding Adeno-Associated Virus-Driven Hypertension in Diverse Diabetic Models

Progress in research and developing therapeutics to prevent diabetic kidney disease (DKD) is limited by a lack of animal models exhibiting progressive kidney disease. Chronic hypertension, a driving factor of disease progression in human patients, is lacking in most available models of diabetes. We hypothesized that superimposition of hypertension on diabetic mouse models would accelerate DKD. To test this possibility, we induced persistent hypertension in three mouse models of type 1 diabetes and two models of type 2 diabetes by adeno-associated virus delivery of renin (ReninAAV). Compared with LacZAAV-treated counterparts, ReninAAV-treated type 1 diabetic Akita/129 mice exhibited a substantial increase in albumin-to-creatinine ratio (ACR) and serum creatinine level and more severe renal lesions. In type 2 models of diabetes (C57BKLS db/db and BTBR ob/ob mice), compared with LacZAAV, ReninAAV induced significant elevations in ACR and increased the incidence and severity of histopathologic findings, with increased serum creatinine detected only in the ReninAAV-treated db/db mice. The uninephrectomized ReninAAV db/db model was the most progressive model examined and further characterized. In this model, separate treatment of hyperglycemia with rosiglitazone or hypertension with lisinopril partially reduced ACR, consistent with independent contributions of these disorders to renal disease. Microarray analysis and comparison with human DKD showed common pathways affected in human disease and this model. These results identify novel models of progressive DKD that provide researchers with a facile and reliable method to study disease pathogenesis and support the development of therapeutics.

Elevated levels of Interleukin (IL)-33 induce bone pathology but absence of IL-33 does not negatively impact normal bone homeostasis

Interleukin (IL)-33 is a member of the IL-1 family. IL-33 effects are mediated through its receptor, ST2 and IL-1RAcP, and its signaling induces the production of a number of pro-inflammatory mediators, including TNFα, IL-1β, IL-6, and IFN-γ. There are conflicting reports on the role of IL-33 in bone homeostasis, with some demonstrating a bone protective role for IL-33 whilst others show that IL-33 induces inflammatory arthritis with concurrent bone destruction. To better clarify the role IL-33 plays in bone biology in vivo, we studied IL-33 KO mice as well as mice in which the cytokine form of IL-33 was overexpressed. Mid-femur cortical bone mineral density (BMD) and bone strength were similar in the IL-33 KO mice compared to WT animals during the first 8months of life. However, in the absence of IL-33, we observed higher BMD in lumbar vertebrae and distal femur in female mice. In contrast, overexpression of IL-33 resulted in a marked and rapid reduction of bone volume, mineral density and strength. Moreover, this was associated with a robust increase in inflammatory cytokines (including IL-6 and IFN-γ), suggesting the bone pathology could be a direct effect of IL-33 or an indirect effect due to the induction of other mediators. Furthermore, the detrimental bone effects were accompanied by increases in osteoclast number and the bone resorption marker of C-terminal telopeptide collagen-I (CTX-I). Together, these results demonstrate that absence of IL-33 has no negative consequences in normal bone homeostasis while high levels of circulating IL-33 contributes to pathological bone loss.

Three different consecutive manifestations of morphoeic BCC in the same patient: presenting first as ectropion, then entropion, and finally medial canthal dystopia with epicanthus inversus

Morpheaform basal cell carcinoma (BCC) can cause diagnostic difficulty due to an atypical clinical presentation. Successful treatment requires a high index of clinical suspicion together with an early confirmatory biopsy. We present the case of an 81-year-old lady with a delayed diagnosis of morphoeic BCC due to an unusual presentation of evolving lid malposition, and we highlight the limitations of a punch biopsy in diagnosing atypical lesions. An appropriate biopsy technique is vital, with consideration for repeat biopsies when necessary, especially if the clinical picture is changing over time.

Nasal secretions from patients with polyps and healthy individuals, collected with a new aspiration system: evaluation of total protein and immunoglobulin concentrations

This study was designed, first, to test a new system for aspiration of human nasal secretions and, secondly, to evaluate protein and immunoglobulin concentrations in these secretions at different levels of secretory activity. The direct aspiration system combines the advantages of minimal irritation of the nasal mucosa with the facility to determine concentrations per gram of secretion. The total protein and immunoglobulin concentrations were inversely related to the amount of secretion obtained. Variations in fluid secretion throughout the day may be responsible for this relationship. The inverse relationship was much more significant in patients with nasal polyps, in which much higher concentrations were found, than in healthy subjects. Ratios of immunoglobulin to total protein were independent of the amount of secretion obtained. Compared to the controls, the ratios of IgM and IgG to protein in the secretions of the patients were significantly increased. The secretory immunoglobulin A to total protein ratios were only slightly higher in the patients' secretions.

Two deaths resulting from apparent parenteral injection of strychnine

Large amounts of strychnine were found in the bodies of two drug abusers, presumable as a result of injection of "street drugs" adulterated with strychnine. Current therapeutic research with this drug, if widely accepted into medical practice, may lead to its greater availability and hence an increased poisoning incidence potential.