Conclusions
Our results suggest that plasma FFA availability is an important regulator of diurnal expression patterns of PDK4, and we identify a novel interaction between plasma FFA and cellular diurnal rhythms in regulating substrate metabolism.
Methods
We analyzed peripheral blood mononuclear cells (PBMCs), subcutaneous adipose tissue, and plasma samples obtained serially during 24 hours from metabolically healthy women (n = 10) and evaluated the interrelationships among PDK4, plasma FFA, and clock genes. We also determined the potential mechanisms responsible for PDK4 transcriptional regulation by using primary human PBMCs and adipocytes.
Objective
We tested the hypothesis that the diurnal expression pattern of pyruvate dehydrogenase kinase 4 (PDK4), a key metabolic enzyme involved in fuel switching between glucose and free fatty acids (FFAs), is associated with plasma FFA concentration and clock genes. Design and
Results
We found that PDK4 diurnal expression patterns were similar in PBMCs and adipose tissue (ρ = 0.84, P < 0.001). The diurnal variation in PBMC PDK4 expression correlated more strongly with plasma FFA and insulin (ρ = 0.86 and 0.63, respectively, both P < 0.001) concentrations than clock genes. Data obtained from primary culture experiments demonstrated that FFAs directly induced PDK4 gene expression, at least in part through activation of peroxisome proliferator-activated receptor α. Conclusions: Our results suggest that plasma FFA availability is an important regulator of diurnal expression patterns of PDK4, and we identify a novel interaction between plasma FFA and cellular diurnal rhythms in regulating substrate metabolism.
Trial registration
ClinicalTrials.gov NCT02011581 NCT02093572.