Circulating long-chain acylcarnitine concentrations are not affected by exercise training in pregnant women with obesity

Authors: ALLMAN, BRITTANY - Arkansas Children'S Nutrition Research Center (ACNC); SPRAY, BEVERLY - Arkansas Children'S Hospital; LAN, RENNY - University Arkansas For Medical Sciences (UAMS); ANDRES, ALINE - University Arkansas For Medical Sciences (UAMS); BORSHEIM, ELISABET - University Arkansas For Medical Sciences (UAMS)

Submitted to: Journal of Applied Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2022
Publication Date: 1/6/2022
Citation: Allman, B.R., Spray, B.J., Lan, R.S., Andres, A., Borsheim, E. 2022. Circulating long-chain acylcarnitine concentrations are not affected by exercise training in pregnant women with obesity. Journal of Applied Physiology. https://doi.org/10.1152/japplphysiol.00712.2021.
DOI: https://doi.org/10.1152/japplphysiol.00712.2021

Interpretive Summary: Pregnant women that have problems controlling blood glucose produce markers of an imbalance between supply of fat circulating in the blood and the usage of fat in the cells, called acylcarnitines. Even though exercise is known to help control blood glucose and decrease acylcarnitines, the effect of exercise on these markers has not been looked at in pregnancy. Therefore, we wanted to determine the effect of exercise during pregnancy in non-active women with obesity on acylcarnitine changes throughout pregnancy. We thought that exercise would decrease acylcarnitines throughout gestation compared to a non-exercise group. The exercise group exercised three times per week from about 13 weeks until close to giving birth. Exercise training involved cardio exercise, resistance exercise, and stretching. At about 12 weeks and 36 weeks of pregnancy, we measured acylcarnitines in the blood, in addition to insulin and glucose to determine insulin resistance. We also measured resting metabolism to study which fuels (fats, carbohydrates) were used at rest. We found that the exercise group improved all their fitness outcomes and had a greater increase in the use of carbohydrates as fuel throughout pregnancy compared to the non-exercise group. However, exercise did not affect any other metabolism measures or any of the acylcarnitines. When we just looked at how these markers changed throughout pregnancy, and did not compare groups, the acylcarnitines decreased, whereas insulin resistance, resting energy expenditure, and the use of fat as fuel increased throughout pregnancy. Therefore, moderate intensity exercise during pregnancy in obese women does not impact the balance between fat supply and fat need, meaning that the movement of fuel with exercise during pregnancy is not negatively impacted.

Technical Abstract: The purpose of this study was to determine the effect of exercise during pregnancy in sedentary women with obesity on longitudinal changes long-chain acylcarnitine (LC-AC) concentrations. We hypothesized that exercise training would significantly decrease circulating LC-ACs throughout gestation compared to a non-exercise control group. Obese but otherwise healthy pregnant women (n = 80, mean +/- SD; BMI: 36.9 +/- 5.7 kg/m2) were randomized into an exercise (n = 40, aerobic/resistance 3x/week, ~13th gestation week until birth) or a non-exercise control (n = 40) group. At gestation week 12.2 +/- 0.5 and 36.0 +/- 0.4, a submaximal exercise test was conducted, and indirect calorimetry was used to measure absolute and relative resting energy expenditure (REE), fat oxidation (FatOx), and carbohydrate oxidation (CHOOx), as well as respiratory exchange ratio (RER) at rest. Fasting blood samples were collected and analyzed for LC-AC concentrations. Blood glucose and insulin concentrations were also determined from which the homeostatic model assessment of insulin resistance (HOMA2-IR) was calculated. The exercise group displayed an improvement in all performance variables, and a greater increase in resting carbohydrate oxidation throughout pregnancy compared to the control group (P = 0.047). Exercise training did not affect any other parameters of resting metabolism or circulating LC-AC. LC-ACs decreased during gestation (combined groups, P < 0.001), whereas HOMA2-IR (P = 0.002), absolute REE (P < 0.001), relative REE (kcal/kg-1/d-1, P = 0.008), and FatOx (P = 0.037) increased during gestation. In summary, a moderate intensity exercise intervention during pregnancy in obese women did not alter LC-ACs concentrations versus control, indicating that the balance between LCFA availability and oxidation neither improved nor worsened with an exercise intervention.