Conditions such as metabolic syndrome, diabetes mellitus and obesity affect the electrical activity of the heart. Their relationship and consequences are analyzed through animal models by students of the Institute of Physiology and the Faculty of Medicine of the Meritorious Autonomous University of Puebla (BUAP), led by Dr. Julián Torres Jácome.

Daniela Bernabé Sánchez and Marissa Limón Cantú, students of the Master’s Degree in Physiological Sciences, study the electrical alterations of the ventricle and atrium of the heart, in animal models with metabolic syndrome and with a diet high in sugars and carbohydrate. As in humans, these animal models, present increased weight and abdominal circumference, damage to certain organs, sleep disturbances and symptoms of depression.

José Alonso Romero, from the Master of Medical Sciences of the Faculty of Medicine, studies a genetically modified model with type 2 diabetes mellitus.

Metabolic syndrome causes atrial arrhythmias

Due to changes in lifestyle and diet, based on intake of fast food and many carbohydrates, metabolic syndrome is a growing condition.

The International Diabetes Federation estimates that a quarter of the world’s population has this disorder, although the prevalence ranges from less than 10 percent to 84 percent. This condition increases the risk of suffering from type 2 diabetes mellitus and cardiovascular disease (mainly atrial arrhythmias).

It was previously believed that these supraventricular or atrial arrhythmias were benign and the human being could live with them. Recent studies show the opposite: they increase the risk of sudden death, because the heart contracts irregularly and oxygen does not reach the tissues.

In the Laboratory of Cardiovascular Pathophysiology, of the Institute of Physiology of the BUAP, Marissa Limón Cantú analyzes the changes in the electrical activity of the atria of the heart, a cavity little studied and without a broad description, since the existing data is not sufficient to determine the origin of arrhythmias.

In his research, Limón Cantú details that alterations of the atrial part were found in electrocardiograms performed on people with metabolic syndrome: extensions of variability of a wave called P and the interval of this signal until the beginning of the Q wave.

These modifications are also sought in the electrocardiograms and tissues of animal models. “In the rat with metabolic syndrome, we expect to see these action potentials altered alike –recording the electrical activity of a stable cell.”

Obesity causes more arrhythmias

Romero works with a genetically modified model with type 2 diabetes mellitus (Zucker rat), with three months of life (age of 17 years in humans) and fed a high fat diet.

“In this model, the presence of ventricular extrasystoles (additional heartbeat triggered by an abnormal electrical activation that originates in the ventricles earlier than a normal heartbeat would occur) and an arrhythmia called torsade de pointes (ventricular tachycardia resulting in sudden death),” he said.

Therefore, with his research, Romero shows that obesity generates more changes in the ventricular heart rate and even fatal arrhythmias, compared to diabetes.

Ventricle Study

The work of Bernabé Sánchez focuses on the study of the ventricle, the lower heart cavity, with emphasis on the papillary muscles. In previous work, she reports that the electrical activity of this area was measured by means of action potentials. There, a difference was observed between control rats and those with metabolic syndrome, specifically in an area of ​​action potential known as repolarization.

Each zone of the heart is influenced by the activity and presence of different ions. On the electrocardiogram, the student noticed an elongation of six milliseconds in the QT interval, which indicates the activity of the ventricles. “From there it could be assumed that there will be changes in action potentials and, therefore, a decrease or increase in repolarizing potassium currents,” he says.

Methodology

The methodology is the same for the three works. The animal model emulates the development of a child towards adulthood. The study rats reach two months of age weighing between 250 and 280 grams. The lot is divided into two groups: control and induction to metabolic syndrome.

The induction process, Daniela Bernabé explained, involves adding 20 percent of sugar to the water they drink. This liquid is compared to drinking soda every day. The food is the same for both groups. However, “with the passage of time we observe that the specimens prefer sugar water, instead of food. They stop eating, but keep getting fat. ”

From the induction, this group is subdivided into animals with two months of intake of sugar water and one more, with six months of the same treatment. After the first period (two months of induction), an electrocardiogram is recorded in vivo to see the presence of arrhythmias and lengthening between intervals.

Subsequently, morphometric and metabolic parameters are taken, such as length, waist, glucose concentration, cholesterol and triglyceride levels, plasma sample and abdominal circumference.

On the other hand, in the six-month model with metabolic syndrome there are specimens without weight gain and others with considerable obesity. However, the latter have fewer alterations at the electrical level, compared to the former. “Although they do not gain weight, there are alterations caused by the high intake of sugars,” Bernabé Sánchez said.

 

Source: Ciencia MX