How to interpret the role of SDF-1α on diabetic complications during therapy with DPP-4 inhibitors

Incretins and microvascular complications of diabetes: neuropathy, nephropathy, retinopathy and microangiopathy

Glucagon-like peptide-1 receptor agonists (GLP-1RAs, incretin mimetics) and dipeptidyl peptidase-4 inhibitors (DPP-4is, incretin enhancers) are glucose-lowering therapies with proven cardiovascular safety, but their effect on microvascular disease is not fully understood. Both therapies increase GLP-1 receptor agonism, which is associated with attenuation of numerous pathological processes that may lead to microvascular benefits, including decreased reactive oxygen species (ROS) production, decreased inflammation and improved vascular function. DPP-4is also increase stromal cell-derived factor-1 (SDF-1), which is associated with neovascularisation and tissue repair. Rodent studies demonstrate several benefits of these agents in the prevention or reversal of nephropathy, retinopathy and neuropathy, but evidence from human populations is less clear. For nephropathy risk in human clinical trials, meta-analyses demonstrate that GLP-1RAs reduce the risk of a composite renal outcome (doubling of serum creatinine, eGFR reduction of 30%, end-stage renal disease or renal death), whereas the benefits of DPP-4is appear to be limited to reductions in the risk of albuminuria. The relationship between GLP-1RAs and retinopathy is less clear. Many large trials and meta-analyses show no effect, but an observed increase in the risk of retinopathy complications with semaglutide therapy (a GLP-1RA) in the SUSTAIN-6 trial warrants caution, particularly in individuals with baseline retinopathy. Similarly, DPP-4is are associated with increased retinopathy risk in both trials and meta-analysis. The association between GLP-1RAs and peripheral neuropathy is unclear due to little trial evidence. For DPP-4is, one trial and several observational studies show a reduced risk of peripheral neuropathy, with others reporting no effect. Evidence in other less-established microvascular outcomes, such as microvascular angina, cerebral small vessel disease, skeletal muscle microvascular disease and autonomic neuropathies (e.g. cardiac autonomic neuropathy, gastroparesis, erectile dysfunction), is sparse. In conclusion, GLP-1RAs are protective against nephropathy, whereas DPP-4is are protective against albuminuria and potentially peripheral neuropathy. Caution is advised with DPP-4is and semaglutide, particularly for patients with background retinopathy, due to increased risk of retinopathy. Well-designed trials powered for microvascular outcomes are needed to clarify associations of incretin therapies and microvascular diseases.

Dipeptidyl Peptidase-4 Inhibitors versus Other Antidiabetic Drugs Added to Metformin Monotherapy in Diabetic Retinopathy Progression: A Real World-Based Cohort Study

BACKGROUND

To investigate the effects of dipeptidyl peptidase-4 inhibitor (DPP4i) as add-on medications to metformin on progression of diabetic retinopathy (DR) in patients with type 2 diabetes mellitus, compared with sulfonylurea (SU) or thiazolidinedione (TZD).

METHODS

We identified 4,447 patients with DPP4i, 6,136 with SU, and 617 with TZD in addition to metformin therapy from the database of Korean National Health Insurance Service between January 2013 and December 2015. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) for DR progression. The progression of DR was defined by the procedure code of panretinal photocoagulation, intravitreal injection or vitrectomy; or the addition of diagnostic code of vitreous hemorrhage, retinal detachment, or neovascular glaucoma.

RESULTS

The age and sex-adjusted HR of DR progression was 0.74 for DPP4i add-on group compared with SU add-on group (95% confidence interval [CI], 0.62 to 0.89). This lower risk of DR progression remained significant after additional adjustments for comorbidities, duration of metformin therapy, intravitreal injections and calendar index year (HR, 0.80; 95% CI, 0.66 to 0.97).

CONCLUSION

This population-based cohort study showed that the use of DPP4i as add-on therapy to metformin did not increase the risk of DR progression compared to SU.

Cardiovascular events, diabetes and guidelines: the virtue of simplicity

Cardiovascular (CV) events or their minor syndromes, as various forms of ischemia, are medical emergencies that do not allow enough time for a guiding anamnesis or proper clinical examination, and lead to relying on Treatment Guidelines, but in many situations it is appropriate to deviate from them. Pathological studies have associated 75% of coronary artery events with atherosclerotic plaque rupture; it is now known that rupture alone is not enough for obstruction or occlusion of the vessel lumen. Concomitant conditions are required for the clinical manifestation of cardiovascular disease, including prothrombogenic and dysfunctional endothelium, less fibrinolytic capacity to protect it, increased platelet activation, increased adrenergic tone, microcirculation vasoconstriction, and other countless factors that contribute to thrombus formation, causing ischemia or infarction. But in most cases, repair of plaque rupture and re endothelization of the lesion are asymptomatic and silent. Atherosclerotic process is a chronic and progressive immune inflammation. Most of the therapeutic indications include statins, which cause side effects in 10% of patients, with a range varying between 7 and 21%, according to different authors. Many investigators have proved that statin use contribute to the genesis of diabetes, reports vary between 1 and 46%, where marked elevation of blood glucose fasting levels and glycosylated hemoglobin have been observed, be it by increased tissue resistance to insulin or by reduced β-cell insulin secretion. Physicians should base their indications on the recommendations provided by Guidelines, but they should not forget that every patient is different, and they should not get confused due to lack of time in an emergency nor be influenced by the latest publications or techniques until they have been properly tested.

Effects of SGLT2 Inhibitors on Circulating Stem and Progenitor Cells in Patients With Type 2 Diabetes

CONTEXT

Reduction in the levels of circulating stem cells (CSCs) and endothelial progenitor cells (EPCs) predicts development or progression of microangiopathy and macroangiopathy in patients with type 2 diabetes (T2D).

OBJECTIVE

We tested whether treatment with sodium glucose cotransporter-2 (SGLT2) inhibitors affected the levels of CSCs and EPCs.

DESIGN

A randomized trial of dapagliflozin vs placebo with open-label extension, and an open-label observational study of empagliflozin treatment.

SETTING

Tertiary referral diabetes outpatient clinic.

PATIENTS

Patients with T2D aged 18 to 75 years.

INTERVENTION

Dapagliflozin at 10 mg vs placebo (n = 31); empagliflozin at 10 mg (n = 15).

MAIN OUTCOME MEASURES

We measured CSCs (CD34+) and EPCs (CD34+KDR+) by flow cytometry at baseline, at 12 weeks, and after the extension period.

RESULTS

After 12 weeks, CSCs declined nonsignificantly in the dapagliflozin group, remained stable in the placebo group, and the change from baseline was not significantly different between the two groups. EPCs declined nonsignificantly in the dapagliflozin group, increased nonsignificantly in the placebo group, and the change from baseline was significantly different between the two groups. After an open-label extension period of about 1.5 years, CSCs remained stable over time, whereas EPCs significantly increased in patients who received dapagliflozin. In all patients, irrespectively of treatment, EPCs increased significantly from baseline to the end of observation, concomitantly with improvement in HbA1c. In a cohort of 15 patients who received open-label empagliflozin for 12 weeks, CSCs declined nonsignificantly, whereas EPCs remained stable.

CONCLUSION

SGLT2 inhibitors do not significantly increase CSCs or EPCs. Thus, cardiovascular protection by SGLT2 inhibitors may not directly involve stem/progenitor cells.

The effect of DPP-4 inhibition to improve functional outcome after stroke is mediated by the SDF-1α/CXCR4 pathway

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are approved drugs for the treatment of hyperglycemia in patients with type 2 diabetes. These effects are mainly mediated by inhibiting endogenous glucagon-like peptide-1 (GLP-1) cleavage. Interestingly, gliptins can also improve stroke outcome in rodents independently from GLP1. However, the underlying mechanisms are unknown. Stromal cell-derived factor-1α (SDF-1α) is a DPP-4 substrate and CXCR4 agonist promoting beneficial effects in injured brains. However, SDF-1α involvement in gliptin-mediated neuroprotection after ischemic injury is unproven. We aimed to determine whether the gliptin linagliptin improves stroke outcome via the SDF-1α/CXCR4 pathway, and identify additional effectors behind the efficacy.

METHODS

Mice were subjected to stroke by transient middle cerebral artery occlusion (MCAO). linagliptin was administered for 3 days or 3 weeks from stroke onset. The CXCR4-antagonist AMD3100 was administered 1 day before MCAO until 3 days thereafter. Stroke outcome was assessed by measuring upper-limb function, infarct volume and neuronal survival. The plasma and brain levels of active GLP-1, GIP and SDF-1α were quantified by ELISA. To identify additional gliptin-mediated molecular effectors, brain samples were analyzed by mass spectrometry.

RESULTS

Linagliptin specifically increased active SDF-1α but not glucose-dependent insulinotropic peptide (GIP) or GLP-1 brain levels. Blocking of SDF-1α/CXCR4 pathway abolished the positive effects of linagliptin on upper-limb function and histological outcome after stroke. Moreover, linagliptin treatment after stroke decreased the presence of peptides derived from neurogranin and from an isoform of the myelin basic protein.

CONCLUSIONS

We showed that linagliptin improves functional stroke outcome in a SDF-1α/CXCR4-dependent manner. Considering that Calpain activity and intracellular Ca²⁺ regulate neurogranin and myelin basic protein detection, our data suggest a gliptin-mediated neuroprotective mechanism via the SDF-1α/CXCR4 pathway that could involve the regulation of Ca²⁺ homeostasis and the reduction of Calpain activity. These results provide new insights into restorative gliptin-mediated effects against stroke.

The role of dipeptidylpeptidase-4 inhibitors in management of cardiovascular disease in diabetes; focus on linagliptin

Multiple population based analyses have demonstrated a high incidence of cardiovascular disease (CVD) and cardiovascular (CV) mortality in subjects with T2DM that reduces life expectancy by as much as 15 years. Importantly, the CV system is particularly sensitive to the metabolic and immune derangements present in obese pre-diabetic and diabetic individuals; consequently, CV dysfunction is often the initial CV derangement to occur and promotes the progression to end organ/tissue damage in T2DM. Specifically, diabetic CVD can manifest as microvascular complications, such as nephropathy, retinopathy, and neuropathy, as well as, macrovascular impairments, including ischemic heart disease, peripheral vascular disease, and cerebrovascular disease. Despite some progress in prevention and treatment of CVD, mainly via blood pressure and dyslipidemia control strategies, the impact of metabolic disease on CV outcomes is still a major challenge and persists in proportion to the epidemics of obesity and diabetes. There is abundant pre-clinical and clinical evidence implicating the DPP-4-incretin axis in CVD. In this regard, linagliptin is a unique DPP-4 inhibitor with both CV and renal safety profiles. Moreover, it exerts beneficial CV effects beyond glycemic control and beyond class effects. Linagliptin is protective for both macrovascular and microvascular complications of diabetes in preclinical models, as well as clinical models. Given the role of endothelial-immune cell interactions as one of the key events in the initiation and progression of CVD, linagliptin modulates these cell–cell interactions by affecting two important pathways involving stimulation of NO signaling and potent inhibition of a key immunoregulatory molecule.