Prenatal Exercise and Glucose Regulation

Overview

Gestational diabetes mellitus (GDM) is the most common disease during pregnancy and is characterized by an inability to regulate blood glucose (sugar) levels because of resistance to the hormone, insulin, which is responsible for getting glucose out of the blood. Aerobic training (AT, "cardio," for example: walking) is commonly used to regulate blood glucose levels in similar populations, like diabetics, but another form of exercise known as resistance training (RT, for example: weightlifting), has shown to be just as effective. Further, exercise intensity, regardless of the type, is directly proportional to blood glucose control. However, no study has compared AT and RT exercise modalities or intensity on blood glucose regulation in GDM, even though women with GDM share a similar insulin resistant phenotype as diabetics. Therefore, long-term objective of this study is to compare the effects of exercise type and intensity on glucose regulation and insulin sensitivity after four acute exercise sessions: low intensity RT (LOW-RT), low intensity AT (LOW-AT), moderate intensity RT (MOD-RT), moderate intensity AT (MOD-AT). Researchers will address the following aims: Specific Aim 1: Determine the impact of exercise type and intensity on glucose regulation using continuous glucose monitoring during- and for 24 hours after four acute exercise sessions: LOW-RT, LOW-AT, MODRT, and MOD-AT. Researchers hypothesize that RT and moderate intensity will elicit better glucose control compared to AT and low intensity, respectively. Specific Aim 2: Determine the impact of exercise type and intensity on insulin sensitivity by quantifying the quantitative insulin-sensitivity check index (QUICKI) before and after four acute exercise sessions: LOWRT, LOW-AT, MOD-RT, and MOD-AT. Researchers hypothesize that RT and moderate intensity will elicit greater insulin sensitivity compared to AT and low intensity, respectively.

Gestational diabetes mellitus (GDM) is defined as an inability to manage blood glucose (sugar) levels that is first diagnosed during pregnancy and poses a significant threat to the mom and baby. Even so, current pharmacological treatment strategies may not affect the root cause of the problem (reduced sensitivity to insulin) in the same way that other adjuvant therapies, like exercise, do. In fact, exercise has been coined as "medicine" in many professional organizations because of its regenerative nature, owing to its ability to improve physiological outcomes just like pharmacological treatments. As such, exercise prescription, like drug prescription, must be specific and consider several key variables, such as those described in the FITT principle for exercise: frequency (how often), intensity (how hard), time (how many minutes), and type (which kind of exercise). Although resistance training (RT, a type of exercise) and higher intensities of exercise are tremendously influential on insulin sensitivity and consequent glucose regulation in populations with similar physiological burdens as GDM (e.g., type 2 diabetes mellitus), no study to date has thoroughly explored the impact of these variables in GDM. Furthermore, in general, prenatal exercise recommendations prescribing FITT are for the very general health of the mom and baby. However, "general health" tends to be quite myopic for a population such as GDM, whose characteristic physiological issue is insulin insensitivity, which thus should be the main target. Therefore, a major obstacle in the field of prenatal exercise is determining what FITT exercise prescription is optimal for insulin sensitivity and glucose regulation in GDM, and not simply overall health (again, much like medicine). In effect, my long-term goal is to determine the appropriate FITT prescription for optimal insulin sensitivity and glucose regulation in GDM. My central hypothesis is that the current FITT prescription for prenatal exercise in GDM grossly underestimates what is needed for optimal insulin sensitivity and glucose regulation. To begin testing my hypothesis, in the proposed study, I will seek to address two aims: Specific Aim 1: Determine the impact of exercise type (resistance training \[RT\], aerobic training \[AT\]) and intensity (low, moderate) on glucose regulation in GDM by assessing real-time blood glucose levels using continuous glucose monitoring (CGM) during and for 24 hours after an acute bout of exercise in four conditions: low intensity RT (LOW-RT), low intensity AT (LOW-AT), moderate intensity RT (MOD-RT), and moderate intensity AT (MOD-AT). The hypothesis is that MOD-RT will elicit the most optimal glucose regulation throughout the 24-hour window, followed by MOD-AT, then LOW-RT, and finally LOW-AT. Specific Aim 2: Determine the impact of exercise type (RT, AT) and intensity (low, moderate) on insulin sensitivity in GDM by calculating the quantitative insulin-sensitivity check index (QUICKI) using blood glucose levels before and after an acute bout of exercise in four conditions: LOW-RT, LOW-AT, MOD-RT, and MODAT. The hypothesis is that MOD-RT will elicit the greatest change in insulin sensitivity, followed by MOD-AT, then LOW-RT, and finally LOW-AT. This data could be immensely informative for prescribing exercise for optimal metabolic health in GDM and could therefore be used to manage acute changes in glucose levels in this population. For example, if the hypothesis of this study is confirmed, this may mean that if a woman with GDM has a brief episode of high glucose levels (e.g., after a high-sugar meal), she may be "prescribed" a form of RT at a certain intensity to get her glucose levels back to baseline, instead of-/in concert with- pharmacological approaches, therefore, effectively using specific exercise prescription as a form of medicine. In the future, I plan to determine the optimal prescription of the other FITT variables (frequency and time) for optimizing glucose regulation in GDM. Then I will use this exercise prescription in a long-term exercise training study in GDM and examine the impacts on both the mom and baby.