Modeling and Evaluation of Murine Diabetic Cardiomyopathy Model

This protocol describes a method for inducing diabetic cardiomyopathy by combining high-fat diet feeding and streptozotocin injections. The goal is to provide a reliable framework for scientific research into diabetic cardiomyopathy and to explore potential clinical treatment applications. We developed a cost-effective and convenient method for creating diabetic cardiomyopathy in mice with enlarged, disorganized cardiomyocytes, myocardial fiber rupture, dissonation, myocardioal dysfunction, and reduced cardio function.

Compared to other methods, our protocol is cost-effective, efficient, and easier to operate by combining a high-fat diet and streptozotocin injections. The establishment of this model will better help us understand the mechanisms underlying the development and progression of diabetic cardiomyopathy. To begin, using a one-milliliter syringe, administer intraperitoneal injections of 30 milligrams per kilogram of streptozotocin, or STZ, daily for seven days to mice in the high-fat diet, or HFD/STZ group.

To measure blood glucose level, one week after the final injection, carefully position the mouse on a restraining device, ensuring its tail is fully extended outside. Thoroughly sanitize the blood collection site on the tail with a 70%alcohol swab. Next, insert the sharp-tipped needle into the tail vein, advancing from the tip toward the base to a depth of three to four millimeters.

Once the needle is positioned, gently squeeze the top of the tail to stimulate blood flow. Carefully apply the blood onto a test strip, allowing it to absorb fully. Wait for the glucose meter to display the blood glucose reading.

For the oral glucose tolerance test, or OGTT, fast each mouse overnight for 14 hours while allowing unrestricted access to water. Prepare approximately 10 milliliters of a 20%glucose solution. Administer a dosage of one gram per kilogram orally to each mouse during the OGTT.

Monitor blood glucose levels at zero, 15, 30, 60, and 120 minutes after glucose administration. Mice in the HFD/STZ group showed a peak in body weight at 12 weeks, significantly higher than the ND group. Following STZ administration, the HFD/STZ group's body weight decreased, while the ND group displayed a steady increase over 12 weeks.

The HFD/STZ group maintained significantly higher random blood glucose levels than the ND group throughout the feeding period. The OGTT curve was significantly higher for the HFD/STZ group than the ND group, with both groups peaking at 15 minutes before declining. Serum insulin levels in the ND group were initially higher than in the HFD group for the first 12 weeks, but reversed after STZ administration To conduct echocardiography assessments, placed the anesthetized mouse from the STZ/HFD or ND group on a heating pad.

Secure the mouse's claws to an electrode to ensure a stable supine position. Remove the mouse's fur from the chest using depilatory cream, then apply ultrasonic gel to the exposed chest area. To obtain an optimal left ventricle long axis view, place the 50 megahertz probe on the left side of the mouse's chest.

Rotate the probe counterclockwise between 15 degrees and 45 degrees relative to the left parasternal line, aligning the notch towards the right shoulder. Adjust the Z axis and Y axis to ensure a clear B-mode image. Next, press M-mode twice to display the measuring line.

Position the measuring line at the level of the papillary muscle, then measure at least three consecutive heartbeats for accuracy and tap save clip to save the cineloop in the series. Identify the end-systolic dimension at the phase aligned with the ECGT wave and the end-diastolic dimension at the phase aligned with the ECGR wave. Next, tilt the operating pad, lowering the upper left corner and raising the lower right corner.

Adjust the probe along the direction of the cardiac apex, parallel to the long axis of the heart, to obtain a transapical four-chamber view. After adjusting the volume and sampling direction, record mitral valve hemodynamic information to capture E and A wave measurements. Return the recovered mouse to the home cage, housed in a controlled environment with a 12 hour light-dark cycle at zero week and 12 week time points.

Hearts in the HFD/STZ group displayed systolic and diastolic dysfunction, with reduced amplitude in the interventricular septum and left ventricular posterior wall pulsation compared with the ND group.