REmodelling in Diabetic CardiOmapathy: Gender Response to PDE5i InhibiTOrs

DCM is yet unclear and gender differences at baseline and a specific treatment have not been indicated. The study aims to characterize DCM, measuring molecular and neuroendocrine assessment to relate cardiac kinetic. The investigators will perform a randomized, placebo-controlled, double-blind study enrolling 120 diabetic patients with DCM, to evaluate gender responses to 5 months of PDE5Ai. The study will describe gender differences in DCM features. The proposed research will test whether PDE5Ai could become a new target for antiremodeling drugs and to discover a molecular pathways affected by this class of drugs and a network of circulating markers for the early diagnosis, monitoring and treatment of DCM.

In vitro studies have shown that phosphodiesterase 5 overexpression reduces cGMP levels and exacerbates remodeling. The investigators already studied the effects of 3-months daily Inhibition of cGMP hydrolysis through a phosphodiesterase 5A inhibitor (PDE5i) on cardiac remodeling in a cohort of asymptomatic, middle-aged men with type 2 diabetes mellitus (T2DM). CMR imaging revealed that diabetic cardiomyopathy in these patients produced an uncoupling in left ventricular contraction between longitudinal strain, which is reduced, and cardiac axial rotation, which is increased. Characterized DCM at early asymptomatic stages in men, we identified two circulating markers, TGF-beta and MCP-1 increased and significantly related to cardiac kinetic parameters. Then, the investigators found that long-term PDE5i restored coupling by reducing torsion and improving strain. It also reduced the ratio of left ventricular mass to end-diastolic volume that is increased in the presence of concentric hypertrophy. Circulating markers TGF-beta and MCP-1, significantly decreased after PDE5i vs. Placebo.These data suggest that phosphodiesterase 5 inhibition could work as an antiremodeling drug by acting directly on cardiac tissue, independently of other secondary vascular, endothelial, or metabolic effects.

However, these data need to be validated on a wide sample, for a longer duration of treatment, and including women, because of their high vulnerability to diabetic damage with preferential evolution in chronic heart failure, compared to males that frequently have ischemic complications.

T2DM is also considered a state of persistent inflammation that likely plays a role in development cardiovascular disease. Some studies have suggested that inflammation may impair the tissue repair process in diabetes, which appears delayed, unsupervised, and associated with higher levels of circulating classical monocytes.

The interaction between angiogenic cells and the endothelium is still critical for inflammatory cells to move and home in specific tissue sites in various pathological conditions. The Tie2 receptor is highly enriched in the endothelium and actively signals vascular quiescence. It is also expressed by in a unique subset of monocytes, Tie2-expressing monocytes (TEMs), which have been considered crucial for tissue remodeling and repair. Tie2 is stimulated by angiopoietin-1 (Ang1), a protein secreted by peri-endothelial cells and platelets. In the context of inflammation, a paralog of Ang1 called Ang2 competitively inhibits Tie2, normal endothelialcell function depends in part on a tightly regulated balance between Ang1 and Ang2. There is evidence of angiopoietin deregulation T2DM.

Several studies demonstrate that PDE5 inhibitors, have cardioprotective effects in different conditions, particularly in in diabetes. PDE5is reduce circulating inflammatory cytokines, protect against tissue damage, exert an anti-inflammatory response, preserve endothelial cell function and increase angiogenic mediators, including Ang1 in mouse models. The PDE5is also improves metabolism and these effects are extended to adipose tissue function.

Another diabetic complication is Diabetic polyneuropathy (DPN). DPN is characterized by loss and degeneration of neurons, Schwann cells, and neuronal fibers resulting in slowing of nerve conduction velocities.

cGMP is involved in the regulation of many neural functions, including neurotransmission, long term potentiation, gene expression, and even neurotoxicity and neurodegeneration. Hyperglycemia up-regulates PDE-5 in Schwann cells and reduces their proliferation and migration. Schwann cells play an important role in regenerating the peripheral nervous system by their capacity to proliferate, migrate, and secrete numerous factors that control nerve regeneration. Decreased proliferation of Schwann cells has also been demonstrated in both human and experimental models of diabetes. Therefore, reduction of cGMP levels by hyperglycemia suppresses Schwann cell proliferation and migration. Elevation of cGMP by blockage of PDE5 with sildenafil completely abolished and reverses the effect of hyperglycemia on Schwann cells in mice.

These changes are accompanied by change in serum neurotropic factors that are witnesses of active remodeling and regeneration at the neuronal level. Many studies in diabetic mice demonstrated that cGMP induces Schwann cells to synthesize nerve growth factor (NGF), neurotropic 3 (NT3) and BDNF.

One third of diabetes patients suffers from diabetic nephropathy (DN), a leading cause of end-stage renal disease. To date, effective treatment in halting or reversing the natural progression of DN remains uncertain. The pathophysiology is multifactorial and the molecular pathways involved are complex. Glomerular endothelial cell injury plays a major role in the development and progression of diabetic kidney disease, that is considered the result of converging hemodynamic and metabolic insults.

In kidney PDE5 is expressed in the glomeruli, mesangial cells, cortical tubules, inner medullary collecting duct and plays a critical role in the regulation of excretory function. In diabetes, glomerular cGMP production is decreased, PDE5 activity is increased and changes in the cGMP-NO pathway leads to a rise in intra-glomerular pressure.

PDE5 inhibitors may have an active role in the management of DN by reducing glomerulosclerosis and proteinuria and improving vascular inflammation and podocyte count in experimental diabetes models. These findings, together with the modulation of inflammatory and angiogenic mediators, and endothelial function in murine and human models, support the use of PDE5i to prevent complications of the diabetic kidney. Intriguingly, sildenafil, a potent PDE5i, was also associated with improved kidney function in patients with pulmonary arterial hypertension and in type-2 diabetes (T2DM) patients.

We hypothesize that:

• there are gender differences in left ventricular myocardial remodeling of T2DM patients detectable with tagged-CMR in terms of myocardial strain and ventricular torsion;
• gender-related features determine different cardiac response to PDE5i treatment detected by changes in ventricular contractility (strain and torsion on tagged-CMR);
• neuroendocrine (e.g. natriuretic peptides), metabolic markers, chemokines , circulating and cellular angiogenesis mediators might identify those asymptomatic patients at greatest risk of developing the diabetic complications (cardiomyopathy, neuropathy, nephropathy);
• neuroendocrine (e.g. natriuretic peptides), metabolic markers, chemokines , circulating and cellular angiogenesis mediators able to predict response to treatment with PDE5i and the evolution of diabetic complications;
• chronic treatment with PDE5i could restore or shut down neurological diabetic damage;
• chronic treatment with PDE5i could restore or shut down renal diabetic damage.

The aims of the study are:

Characterization of gender differences in DCM remodeling through a cluster of biomarkers indicative of the stage of the disease and CMR quantification of kinetic parameters (myocardial strain, ventricular torsion), fibrosis amount (T1-mapping technique).

Quantification of a cluster of biomarkers predictive of disease progression: metabolic and neuroendocrine markers, pro-fibrotic and pro-inflammatory circulating chemokines.

Evaluation of gender differences in the anti-remodeling effect of PDE5A inhibition in T2DM patients The investigators will perform a randomized, placebo-controlled, double-blind study enrolling 120 patients (females and males) with T2DM and diabetic cardiomyopathy. Patients will be randomized to treatment with PDE5Ai 20 mg / day or placebo for 5 consecutive months.

The outcomes will be evaluated before and 1 and 5 months after therapy.

Cardiovascular, endothelial and metabolic indices, and oxidative stress markers will be evaluated in all patients and related to CMR cardiac kinetic and metabolic parameters and fibrosis in order to identify:

• gender differences in kinetic parameters of left ventricle (end-diastolic volume, end-systolic volume, stroke volume, wall motion score index, myocardial strain, torsion angle, recoil rate with contraction dynamics);
• changes in myocardial fibrosis replacement amount (global contrast-enhanced T1 relaxation time, percentage of myocardial surface area, quantified by T1-mapping technique);

Diagnostic procedures will include:

• physical examination with measurement of anthropometric parameters (weight, waist circumference, hip circumference) and vital signs (blood pressure, heart rate);
• blood sampling for assessing glucose and lipid metabolism, liver, renal, hematopoietic and coagulative function, thyroid and androgen hormones, inflammatory parameters (cytokines, monocyte subpopulations);
• quantification of peripheral blood mononuclear cells (PBMC) subpopulations by flow cytometry;
• Circulating and cellular angiogenesis mediators assessment (angiogenic factors; cytokines, receptors and other angiogenic factors) by qRT-PCR and ELISA;
• SF36, FSFI (in women), IEFF e IPSS (in men) questionnaires, Infectious Diseases Questionnaire;
• cardiac exam, electrocardiogram and standard 2-D echocardiography with Tissue Doppler Imaging for diastolic function assessment and speckle tracking for cardiac kinetics measurement;
• assessment of body composition by a whole-body DEXA scan;
• magnetic resonance imaging (MRI) with contrast-enhanced cardiac tagging for evaluating kinetic parameters (torsion) and T1-mapping for assessing cardiac fibrosis;

Neurological examination to assess signs and symptoms related to polyneuropathy and autonomic neuropathy.

Specifically:

• evaluation of different sensitivity (diapason for vibratory, cotton wool for touch and pinprick for to pain);
• presence / reduction / absence of deep tendon reflexes;
• any motor deficits.

If any signs or symptoms consistent with diabetic neuropathy, to diagnosis confirm, these patients will undergo to a standard nerve conduction study for the large-caliber fibers (by registration of sensory potential stimulation from the sural, ulnar and radial nerve surface, and motors potential stimulation from peroneal and ulnar nerve). Those with large fiber neuropathy will be evaluate for small caliber fibers injuries with:

• evoked potentials laser;
• Quantitative Sensory Testing (QST);
• skin biopsy.
• renal doppler ultrasonography for the detection of possible renal complications through measurements of kidney volume and resistive index (RRI).