The Dipeptidyl Peptidase 4 Substrate CXCL12 Has Opposing Cardiac Effects in Young Mice and Aged Diabetic Mice Mediated by Ca2+ Flux and Phosphoinositide 3-Kinase γ

Prognostic significance of plasma SDF-1 in acute ischemic stroke patients with diabetes mellitus: the CATIS trial

BACKGROUND AND OBJECTIVES

Evidence on the associations between baseline stromal cell-derived factor (SDF)-1 and clinical outcomes in acute ischemic stroke patients is lacking. The present study aimed to examine the relationship between plasma SDF-1 levels and clinical outcomes based on a large multicenter study of the China Antihypertensive Trial in Acute Ischemic Stroke (CATIS).

METHODS

Secondary analysis was conducted among 3,255 participants from the CATIS trial with a baseline measurement of plasma SDF-1 levels. We evaluated the associations between plasma SDF-1 levels and one-year recurrent stroke, cardiovascular events, and all-cause mortality using Cox regression models. We further investigated the prognostic effect of SDF-1 on clinical outcomes in patients with different characteristics.

RESULTS

Higher plasma SDF-1 levels were not associated with recurrent stroke, cardiovascular events, and all-cause mortality at one-year after ischemic stroke (all P trend ≥ 0.05). There were significant interactions between plasma SDF-1 levels and history of diabetes mellitus on recurrent stroke (P = 0.005), cardiovascular events (P = 0.007) and all-cause mortality (P = 0.04) at one year. In patients with diabetes mellitus, plasma SDF-1 was significantly associated with an increased risk of recurrent stroke and cardiovascular events after adjustment for confounders. For example, 1-SD higher log-SDF-1 was associated with a hazard ratio (95% confidence interval) of 1.65 (1.18-2.32) for recurrent stroke and 1.47 (1.08-1.99) for the cardiovascular events, but not all-cause mortality 1.36 (0.96-1.93) at one year. However, there were no associations between plasma SDF-1 and clinical outcomes in patients without diabetes mellitus (all P > 0.05). The addition of plasma SDF-1 to the conventional risk factors model significantly improved the risk prediction of all outcomes. Similarly, findings between elevated SDF-1 levels and two-year outcomes were found only in patients with diabetes mellitus.

CONCLUSIONS

Elevated plasma SDF-1 was significantly associated with an increased risk of recurrent stroke and cardiovascular events only in ischemic patients with diabetes mellitus.

Cardiovascular Effects of Incretin-Based Therapies: Integrating Mechanisms With Cardiovascular Outcome Trials

As the worldwide prevalence of diabetes and obesity continues to rise, so does the risk of debilitating cardiovascular complications. Given the significant association between diabetes and cardiovascular risk, the actions of glucose-lowering therapies within the cardiovascular system must be clearly defined. Incretin hormones, including GLP-1 (glucagon-like peptide 1) and GIP (glucose-dependent insulinotropic polypeptide), are gut hormones secreted in response to nutrient intake that maintain glycemic control by regulating insulin and glucagon release. GLP-1 receptor agonists (GLP-1Ras) and dipeptidyl peptidase 4 inhibitors (DPP-4is) represent two drug classes used for the treatment of type 2 diabetes mellitus (T2DM) that improve glucose regulation through stimulating the actions of gut-derived incretin hormones or inhibiting their degradation, respectively. Despite both classes acting to potentiate the incretin response, the potential cardioprotective benefits afforded by GLP-1Ras have not been recapitulated in cardiovascular outcome trials (CVOTs) evaluating DPP-4is. This review provides insights through discussion of clinical and preclinical studies to illuminate the physiological mechanisms that may underlie and reconcile observations from GLP-1Ra and DPP-4i CVOTs. Furthermore, critical knowledge gaps and areas for further investigation will be emphasized to guide future studies and, ultimately, facilitate improved clinical management of cardiovascular disease in T2DM.

Pyridostigmine Protects Against Diabetic Cardiomyopathy by Regulating Vagal Activity, Gut Microbiota, and Branched-Chain Amino Acid Catabolism in Diabetic Mice

The disruption of gut microbes is associated with diabetic cardiomyopathy, but the mechanism by which gut microbes affect cardiac damage remains unclear. We explored gut microbes and branched-chain amino acid (BCAA) metabolite catabolism in diabetic cardiomyopathy mice and investigated the cardioprotective effect of pyridostigmine. The experiments were conducted using a model of diabetic cardiomyopathy induced by a high-fat diet + streptozotocin in C57BL/6 mice. The results of high-throughput sequencing showed that diabetic cardiomyopathy mice exhibited decreased gut microbial diversity, altered abundance of the diabetes-related microbes, and increased abundance of the BCAA-producing microbes Clostridiales and Lachnospiraceae. In addition, diabetes downregulated tight junction proteins (ZO-1, occludin, and claudin-1) and increased intestinal permeability to impair the intestinal barrier. These impairments were accompanied by reduction in vagal activity that manifested as increased acetylcholinesterase levels, decreased acetylcholine levels, and heart rate variability, which eventually led to cardiac damage. Pyridostigmine enhanced vagal activity, restored gut microbiota homeostasis, decreased BCAA-producing microbe abundance, and improved the intestinal barrier to reduce circulating BCAA levels. Pyridostigmine also upregulated BCAT2 and PP2Cm and downregulated p-BCKDHA/BCKDHA and BCKDK to improve cardiac BCAA catabolism. Moreover, pyridostigmine alleviated abnormal mitochondrial structure; increased ATP production; decreased reactive oxygen species and mitochondria-related apoptosis; and attenuated cardiac dysfunction, hypertrophy, and fibrosis in diabetic cardiomyopathy mice. In conclusion, the gut microbiota, BCAA catabolism, and vagal activity were impaired in diabetic cardiomyopathy mice but were improved by pyridostigmine. These results provide novel insights for the development of a therapeutic strategy for diabetes-induced cardiac damage that targets gut microbes and BCAA catabolism.

The Dipeptidyl Peptidase-4 Inhibitor Linagliptin Directly Enhances the Contractile Recovery of Mouse Hearts at a Concentration Equivalent to that Achieved with Standard Dosing in Humans

Despite a similar mechanism of action underlying their glucose-lowering effects in type 2 diabetes, dipeptidyl peptidase-4 (DPP-4) inhibitors have diverse molecular structures, raising the prospect of agent-specific, glucose-independent actions. To explore the issue of possible DPP-4 inhibitor cardiac heterogeneity, we perfused different DPP-4 inhibitors to beating mouse hearts ex vivo, at concentrations equivalent to peak plasma levels achieved in humans with standard dosing. We studied male and female mice, young non-diabetic mice, and aged diabetic high fat diet-fed mice and observed that linagliptin enhanced recovery after ischemia-reperfusion, whereas sitagliptin, alogliptin, and saxagliptin did not. DPP-4 transcripts were not detected in adult mouse cardiomyocytes by RNA sequencing and the addition of linagliptin caused ≤0.2% of cardiomyocyte genes to be differentially expressed. In contrast, incubation of C166 endothelial cells with linagliptin induced cell signaling characterized by phosphorylation of Akt and endothelial nitric oxide synthase, whereas the nitric oxide (NO) donor, S-nitroso-N-acetylpenicillamine increased serine 16 phosphorylation of the calcium regulatory protein, phospholamban in cardiomyocytes. Furthermore, linagliptin increased cardiomyocyte cGMP when cells were co-cultured with C166 endothelial cells, but not when cardiomyocytes were cultured alone. Thus, at a concentration comparable to that achieved in patients, linagliptin has direct effects on mouse hearts. The effects of linagliptin on cardiomyocytes are likely to be either off-target or indirect, mediated through NO generation by the adjacent cardiac endothelium.

CXC chemokine ligand 12 (CXCL12) in atherosclerosis: An underlying therapeutic target

CXC chemokine ligand 12 (CXCL12) is a specific chemokine ligand and plays a significant role in cell chemotaxis. Upon binding to CXC chemokine receptor 4 (CXCR4) or CXCR7, CXCL12 can activate different signaling cascades to regulate cell proliferation, migration, and metabolism. CXCL12 exerts a pro-atherogenic action by aggravating multiple pathogenesis of atherogenesis, including dyslipidemia, inflammation, neointima hyperplasia, angiogenesis, and insulin resistance. Serum CXCL12 levels are also markedly increased in patients with atherosclerosis-associated disease. The present review focuses on recent advances in CXCL12 research in the pathogenesis of atherosclerosis together with its clinical values. This may provide insight into potential novel therapies for atherosclerosis.

Empagliflozin Improves Diastolic Function in a Nondiabetic Rodent Model of Heart Failure With Preserved Ejection Fraction

Recent studies send an unambiguous signal that the class of agents known as sodium-glucose-linked co-transporter-2 inhibitors (SGLT2i) prevent heart failure hospitalization in patients with type 2 diabetes. However, the mechanisms remain unclear. Herein the authors utilize a rodent model of heart failure with preserved ejection fraction (HFpEF), and demonstrate that treatment with the SGLT2i empagliflozin, reduces left ventricular mass, improving both wall stress and diastolic function. These findings extend the observation that the main mechanism of action of empagliflozin involves improved hemodynamics (i.e., reduction in preload and afterload) and provide a rationale for upcoming trials in patients with HFpEF irrespective of glycemic status.

Linagliptin Effects on Heart Failure and Related Outcomes in Individuals With Type 2 Diabetes Mellitus at High Cardiovascular and Renal Risk in CARMELINA

BACKGROUND

Individuals with type 2 diabetes mellitus are at increased risk for heart failure (HF), particularly those with coexisting atherosclerotic cardiovascular disease and/or kidney disease. Some but not all dipeptidyl peptidase-4 inhibitors have been associated with increased HF risk. We performed secondary analyses of HF and related outcomes with the dipeptidyl peptidase-4 inhibitor linagliptin versus placebo in CARMELINA (The Cardiovascular and Renal Microvascular Outcome Study With Linagliptin), a cardiovascular outcomes trial that enrolled participants with type 2 diabetes mellitus and atherosclerotic cardiovascular disease and/or kidney disease.

METHODS

Participants in 27 countries with type 2 diabetes mellitus and concomitant atherosclerotic cardiovascular disease and/or kidney disease were randomized 1:1 to receive once daily oral linagliptin 5 mg or placebo, on top of standard of care. All hospitalization for HF (hHF), cardiovascular outcomes, and deaths were prospectively captured and centrally adjudicated. In prespecified and post hoc analyses of HF and related events, Cox proportional hazards models adjusting for region and baseline history of HF were used. Recurrent hHF events were analyzed using a negative binomial model. In a subset of participants with left ventricular ejection fraction captured within the year before randomization, HF-related outcomes were assessed in subgroups stratified by left ventricular ejection fraction > or ≤50%.

RESULTS

CARMELINA enrolled 6979 participants (mean age, 65.9 years; estimated glomerular filtration rate, mL/min per 1.73m2; hemoglobin A1c, 8.0%; 62.9% men; diabetes mellitus duration, 14.8 years), including 1873 (26.8%) with a history of HF at baseline. Median follow-up was 2.2 years. Linagliptin versus placebo did not affect the incidence of hHF (209/3494 [6.0%] versus 226/3485 [6.5%], respectively; hazard ratio [HR], 0.90; 95% CI, 0.74-1.08), the composite of cardiovascular death/hHF (HR, 0.94; 95% CI, 0.82-1.08), or risk for recurrent hHF events (326 versus 359 events, respectively; rate ratio, 0.94; 95% CI, 0.75-1.20). There was no heterogeneity of linagliptin effects on hHF by history of HF at baseline, baseline estimated glomerular filtration rate or urine albumin-creatinine ratio, or prerandomization left ventricular ejection fraction.

CONCLUSIONS

In a large, international cardiovascular outcome trial in participants with type 2 diabetes mellitus and concomitant atherosclerotic cardiovascular disease and/or kidney disease, linagliptin did not affect the risk of hHF or other selected HF-related outcomes, including among participants with and without a history of HF, across the spectrum of kidney disease, and independent of previous left ventricular ejection fraction.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01897532.