Abstract
Context
There is evidence demonstrating variation in insulin sensitivity across the menstrual cycle. However, to date, research has yielded inconsistent results.
Objective
This study investigated variation in insulin sensitivity across the menstrual cycle and associations with BMI, physical activity and cardiorespiratory fitness.
Design
Data from 1906 premenopausal women in NHANES cycles 1999-2006 were analysed.
Main outcome measures
Menstrual cycle day was assessed using questionnaire responses recording days since last period. Rhythmic variation of plasma glucose, triglyceride and insulin, homeostatic model of insulin resistance (HOMA-IR) and adipose tissue insulin resistance index (ADIPO-IR) across the menstrual cycle were analysed using cosinor rhythmometry. Participants were assigned low or high categories of BMI, physical activity and cardiorespiratory fitness and category membership included in cosinor models as covariates.
Results
Rhythmicity was demonstrated by a significant cosine fit for glucose (p= 0.014) but not triglyceride (p= 0.369), insulin (p= 0.470), HOMA-IR (p=0.461) and ADIPO-IR (p= 0.335). When covariates were included, rhythmicity was observed when adjusting for: 1. BMI: glucose (p< 0.001), triglyceride (p< 0.001), insulin (p< 0.001), HOMA-IR (p< 0.001) and ADIPO-IR (p< 0.001); 2. Physical activity: glucose (p< 0.001), triglyceride (p= 0.006) and ADIPO-IR (p= 0.038); 3. Cardiorespiratory fitness: triglyceride (p= 0.041), insulin (p= 0.002), HOMA-IR (p= 0.004) and ADIPO-IR (p= 0.004). Triglyceride amplitude, but not acrophase, was greater in the high physical activity category compared to low (p=0.018).
Conclusions
Rhythmicity in insulin sensitivity and associated metabolites across the menstrual cycle are modified by BMI, physical activity and cardiorespiratory fitness.
Cyclic changes in lipoprotein and apolipoprotein levels during the menstrual cycle in healthy premenopausal women on a controlled diet.
