Effects of empagliFlozin on myocardIal metabOlic Rate of glucosE Estimated Through 18FDG PET (FIORE Study)

Diabetes mellitus type 2 (T2DM) is the most common metabolic disease and its prevalence is rapidly increasing. T2DM is a chronic disease that affects over 451 million people in the world and this number is expected to increase over the years and it is estimated that in 2045 there will be in the world over 693 million patients with T2DM. Diabetes is an independent risk factor for ischemic heart disease (CAD), stroke and peripheral artery disease and cardiovascular diseases are the main cause of mortality and morbidity in patients with diabetes. It is estimated that subjects with T2DM have a risk of cardiovascular events same as those of non-diabetic subjects with a previous cardiovascular event and several epidemiological studies have reported that the incidence of fatal and nonfatal coronary events in patients with T2DM is 1.5 to 3-4 times higher than non-diabetics of the same age.

Many studies showed that, in diabetic subjects, improved plasma glucose is associated with a reduction in microvascular complications. Instead, is not completely shown that a reduction of plasma glucose result in a reduction of cardiovascular events. In fact, although it was noted that, in subjects with T2DM, good control glyco-metabolic is associated with modest cardiovascular benefits in the long term, however, the intensive treatment hypoglycemic agent or the use of antidiabetic drugs is often associated with adverse events cardiovascular.

Recently, it was approved for the treatment of T2DM a new class of drugs, inhibitors of sodium glucose cotransporter type 2 (SGLT-2), that work by blocking the renal glucose reabsorption, causing glycosuria. SGLT-2 inhibitors have a good safety profile, are effective in reducing HbA1c regardless of the duration of diabetes and the degree of beta-cell dysfunction and insulin resistance and exhibit a low risk of hypoglycemia. In addition, the loss of glucose renal induced by SGLT2 inhibitors is associated with modest weight loss and reduction in blood pressure. Pre clinical studies showed that SGLT2 inhibitors, through a reduction in glucose toxicity, determine an improvement in insulin resistance liver and muscle and a restoration of first and second phase insulin secretion. The improvement of β-cell function and insulin sensitivity, assessed by indexes derived from OGTT, was obtained in subjects with T2DM, even after a single dose of empagliflozin, selective SGLT2 inhibitor. There are few data on the changes in insulin sensitivity, assessed by hyperinsulinemic euglycemic clamp, and insulin secretion, estimated by intravenous glucose test tolerance (IVGTT), induced by SGLT2 inhibitor. It was shown that, in subjects with T2DM at high cardiovascular risk, treatment with empagliflozin in addition to standard therapy was associated with a significant reduction of the composite cardiovascular endpoint, consisting of cardiovascular death, non-fatal myocardial infarction and non-fatal stroke, compared to placebo. In addition, treatment with empagliflozin in addition to standard therapy determined in a significant reduction in cardiovascular mortality, mortality from all causes and hospitalization for heart failure compared to placebo. It is not completely known the mechanism through which treatment with empagliflozin is associated to an improvement of cardiovascular outcomes. Growing evidences suggest that empagliflozin performs positive cardiovascular effects through a reduction in blood pressure, an improvement in arterial stiffness, a reduction in body weight and visceral adiposity. Recently, it was shown that in nondiabetic porcine model with heart failure, the treatment with empagliflozin was associated with a switch of myocardial fuel utilization from glucose uptake toward uptake of ketone bodies and free fatty acid, thereby improving myocardial energetics, enhancing LV systolic function, and ameliorating adverse LV remodeling.

Myocardial positron emission tomography (PET) with 18F-Fluorodeoxyglucose (18F-FDG), a widely used glucose analogue, in combination with the euglycemic-hyperinsulinemic clamp is considered the gold standard to measure myocardial metabolic rate of glucose under standardized experimental conditions. In this study we hypothesize that empagliflozin may determine beneficial cardiovascular effects reducing myocardial metabolic rate of glucose assessed by hyperinsulinemic euglycemic clamp 18F-FDG PET scans in patients with type 2 diabetes with no history of coronary heart disease, compared to treatment with glimepiride, both add on metformin.

Study design

13 subjects with T2DM, poorly controlled on metformin monotherapy, and without a history of ischemic heart disease, will be treated with empagliflozin for 26 weeks and will be compared with a group of 13 subjects with T2DM, poorly controlled on metformin monotherapy, and without a history of ischemic heart disease, treated with glimepiride (both in addition to metformin) for 26 weeks. At the end of 26 weeks of treatment, subjects belonging to the first group will be shifted to glimepiride therapy, while subjects belonging to the second group will be shifted to empagliflozin treatment for 26 weeks. All subjects, then, will control themselves.

Schematic overview of the study timeline

Visit 1 Screening (week -1): Clinical examination, vital signs (systolic and diastolic blood pressure and pulse), anthropometric measures, HbA1c, FPG, haematology and biochemistry, pro-BNP, high sensitivity C-reactive protein (hsCRP), troponin T, renal function, albumin/creatinine ratio (ACR), evaluation criteria for inclusion and exclusion, electrocardiogram (ECG), echocardiogram, Holter ECG.

Visit 2 Randomization (week 0 baseline): Hyperinsulinemic euglycemic clamp combined with 18F-FDG PET. Assignment two treatment arms randomly with ratio of 1: 1. Beginning of treatment with empagliflozin 10 mg/day in one arm and the other glimepiride.

Visit 3 (week 4): Clinical examination, security monitoring (systolic and diastolic blood pressure), hypoglycemia and adverse events evaluation

Visit 4 (week 8): Clinical examination, security monitoring (ECG (assessment of P Wave, QRS Complex, QT Interval), systolic and diastolic blood pressure), hypoglycemia and adverse events evaluation

Visit 5 (week 12): Clinical examination, security monitoring, hypoglycemia and adverse events evaluation

Visit 6 (week 26): Clinical examination, vital signs (systolic and diastolic blood pressure and pulse), anthropometric measures, haematology and biochemistry, pro-BNP, high sensitivity C-reactive protein (hsCRP), troponin T, renal function, ACR, ECG, echocardiogram, Holter ECG

Visit 7 (week 26+ 1 day): Hyperinsulinemic euglycemic clamp combined with 18F-FDG PET (shift of the treatment groups).

Visit 8 (week 30): Clinical examination, security monitoring (systolic and diastolic blood pressure), hypoglycemia and adverse events evaluation

Visit 9 (week 34): Clinical examination, security monitoring (ECG, blood pressure), hypoglycemia and adverse events evaluation

Visit 10 (week 40): Clinical examination, security monitoring, hypoglycemia and adverse events evaluation

Visit 11 (week 52): Clinical examination, vital signs, anthropometric measures, haematology and biochemistry, pro-BNP, high sensitivity C-reactive protein (hsCRP), troponin T, renal function, ACR, ECG, echocardiogram, Holter ECG.

Visit 12 (week 52 + 1 day): Hyperinsulinemic euglycemic clamp combined with 18F-FDG PET

Hyperinsulinemic euglycemic clamp combined with 18F-FDG-PET scan for assessment of peripheral insulin sensitivity and myocardial glucose uptake.

Myocardial metabolic rate of glucose (Global MRGlu - mmol/min/100mg) will be measured by 18F-FDG-PET acquired in the course of euglycemic hyperinsulinemic clamp as previously described. Subjects will be received a priming dose of insulin (Humulin R 100UI/ml; Eli Lilly) during the initial 10 min to acutely raise the desired levels of plasma insulin, followed by continuous insulin infusion fixed at 40 mU/m2 x min. The blood glucose level will be maintained constant at 90 mg/dl for the next 120 min by infusing 20% glucose at varying rates according to blood glucose measurements performed at 5-min intervals (mean coefficient of variation of blood glucose was <4%). Glucose metabolized by the whole body (M) will be calculated as the mean rate of glucose infusion measured during the last 60 minutes of the clamp examination (steady state) and was expressed as milligrams per minute per kilogram fat-free mass (MFFM).

The 18F-FDG PET imaging procedure will be performed on a hybrid PET/CT scanner (GE Discovery ST8- 2D PET scanner), starting 60 minutes after the insulin infusion. 60-min dynamic acquisition will be started simultaneously with the intravenous injection of 370 MBq18F-FDG and the insulin-glucose infusion will be continued during entire PET acquisition. The estimation of myocardial MRGlu will be performed using a Patlak compartmental modelling, a widely diffuse technique provided by a graphical tool specific for cardiac images analysis (PCARD) in PMOD Software platform (Version 3.806). PCARD allows to measure the global MRGlu as well as the segmental myocardial glucose uptake by using a segmentation algorithm to divide myocardium into standard 17 segments model according to ASNC (American Society of Nuclear Cardiology) guideline and the American Heart Association (AHA).

Sample size

The "Sample Size" in the study is of 26 subjects (13 subjects per group). The same result has been calculated considering a significant reduction in group Empagliflozin of 40 % in myocardial metabolic rate of glucose estimated through 18F-FGD-PET, compared to a change in the treatment arm glimepiride of 15% and assuming a standard deviation of 5%, a "dropout" of 10%, with a power of 85% and an alpha error of 0.05%, using the power calculation available at the following website https://clincalc.com/Stats/SampleSize.aspx.

The randomization of the subjects will be done using the program "Research Randomizer (www.randomizer.org). The subjects will be allocated to one of two arms of the study (1 = Treatment Empagliflozin; 2 = Treatment Glimepriride;) according to the outline generated by the program indicated above and attached to the protocol.

Safety assessment

During the course of the present study all adverse events (including hypoglycemic episodes), both those suspected to be study drug-related and those not suspected to be related to study medications, will be collected.