Autonomic Nervous System and Exercise In Gestational Diabetes

Gestational diabetes (GDM) is one of the earliest signs for increased risk of developing CVD. In addition to this independent association, GDM increases CVD risk through type 2 diabetes. The physiological basis for his disease progression is not yet fully understood. Increasing evidence exists on interplay of insulin resistance and subclinical inflammation, and more recently on unbalance of the autonomic nervous system.

There is unequivocal evidence that increased physical activity and regular exercise can prevent risk factors that give rise to cardiovascular complications. According to a recent meta-analysis, exercise started before and continued throughout pregnancy may lead to marked GDM risk reduction. Unfortunately, exercise in most lifestyle studies is usually unstructured or unsupervised or does not meet current guidelines. There is also a significant gap in our understanding of how to target, deliver and prescribe the beneficial type of exercise to patients at risk in the community.

Sixty women planning pregnancy with BMI equal or over 30 and/or history of GDM will be recruited and randomized to an individual exercise arm (n=20), a general exercise arm (n=20) and a control arm (n=20). General intervention group will receive general exercise and dietary counselling whereas a personal exercise and dietary programs will be planned for individualized exercise group. Those randomized to the control arm will receive no dietary and exercise information. All subjects will be followed by diabetes nurses every 3 months as follows: at the time of recruitment, after 3 months intervention period, int the 1st, 2nd and 3rd trimester of pregnancy and 6 weeks, 6 months and 1 year postpartum. The following measurements will be performed at every visit:blood pressure, weight, waist-to-hip ratio, glucose homeostasis (2-h OGTT, Pf- insulin, Pf- glucose, insulin resistance (Homa-IR), GHbA1c, lipids (total cholesterol, LDL, HDL, triglycerides), inflammatory markers (sCRP,S-amyloid A, IL-1 and 6, alpha 1-glycoprotein, SHBG), adipokines (endothelin, adrenomedullin, adiponectin),dipeptidyl peptidase-4 (DPP-4), atrial natriuretic peptides (ANP, proBNP).For all study participants, 15 D and EDPS questionnaires are used for assessment of quality of life and mental health. Registered costs of the intervention will be calculated for cost-effectiveness analysis.

Both endurance and strength training will be included in the exercise program of the individual exercise study group. Heart rate will be monitored with heart rate belt and registered in internet-based exercise diary which can be instantly followed by the exercise professionals. This information will be used for fine-tuning of their exercise prescription during the intervention period. Diet and weight target will be planned individually by a dietician. Actualized diet will be registered in an internet-based diary instantly followed by the study dietician who will guide the subjects personally by e-mail and suggest further dietary changes if needed.

All subjects will perform an exercise test in the beginning of the study and after 3 months intervention with a step incremental protocol on a cycle ergometer until volitional fatigue. Extensive and advanced technologies will be used to monitor exercise responses, including breath-by-breath ventilation and alveolar gas exchange; exercise ECG; impedance cardiography; automatic arterial blood pressure; analysis system for heart rate variability and blood pressure variability, baroreflex sensitivity, muscle electrical activity, arterial O2 saturation and local cerebral and muscle tissue oxygenation with near-infrared spectroscopy. The autonomic nervous system measurements, including 24 hour ECG monitoring, heart rate variability assessment with controlled breathing rate, the orthostatic test and a 5 min handgrip test, will be performed during another visit to the laboratory. Total haemoglobin mass and blood volume will be determined by carbonmonoxy rebreathing method.