Differential effects of omega-3 fatty acid docosahexaenoic acid and palmitate on the circadian transcriptional profile of clock genes in immortalized hypothalamic neurons

Abstract

Diets high in saturated fatty acids (SFAs) are associated with the development of circadian dysregulation, obesity, and Type 2 diabetes mellitus. Conversely, polyunsaturated fatty acids (PUFAs) have recently been identified to improve insulin sensitivity, reduce weight gain, and relieve obesity-induced inflammation. While saturated fatty acids, such as the prevalent dietary fatty acid palmitate, have been implicated in circadian disruption, there is a paucity of studies regarding the effects of PUFAs on circadian parameters. Therefore, the immortalized murine neuronal model, mHypoE-37, was utilized to examine the effects of the SFA palmitate and omega-3 PUFA docosahexaenoic acid (DHA) on circadian rhythms. The mHypoE-37 neurons express the core clock genes, Bmal1, Per2, and Rev-erbα, in a circadian manner. 25 μM of palmitate significantly increased the transcriptional expression of Bmal1, without altering the expression of inflammatory markers TLR4, IκBα, and IL-6, nor the orexigenic neuropeptide AgRP, suggesting that the observed disruption of the molecular clock is the result of a mechanism distinct from that of hypothalamic cellular inflammation. Furthermore, treatment with the PUFA DHA resulted in alterations in the circadian expression profile of Bmal1, although differentially from the effects of palmitate. In the presence of DHA, the disruptive effects of palmitate on Bmal1 were less pronounced, suggesting a protective effect of DHA. These studies are the first to identify the potential for omega-3 PUFAs to protect against palmitate-mediated dysregulation of circadian parameters and will ultimately improve the understanding of circadian control mechanisms.

Palmitate Induces an Anti-Inflammatory Response in Immortalized Microglial BV-2 and IMG Cell Lines that Decreases TNFα Levels in mHypoE-46 Hypothalamic Neurons in Co-Culture

“…A final concentration of 50 µM was prepared by diluting the stock solution in pre-warmed (37°C) media with 5% FBS as a carrier. This methodology was developed, and certified [14, 29], to avoid potential LPS contamination in BSA-conjugated palmitate. This was still an issue even with “endotoxin-free” BSA where we previously found that the BSA alone had an effect on cellular cytokine expression.…”

A rotating light cycle promotes weight gain and hepatic lipid storage in mice

“…Alternatively, meal composition may affect the molecular clock system (39). In cell line studies, it has been demonstrated that the fatty acid palmitate can alter circadian expression of clock genes (19,23). This is supported by an in vivo study demonstrating that 3 days on a HFD are sufficient to alter expression of mouse hepatic clock genes, suggesting that the HFD rather than the development of obesity initiates circadian reprogramming (17).…”

Nutrient Sensing Systems in Fish: Impact on Food Intake Regulation and Energy Homeostasis

“…The ability of other classes of LCFA differing in the length of their acyl chain and/or in their degree of unsaturation to elicit the activation of these systems has been scarcely assessed to date. The available studies in mammals indicate that neither saturated fatty acids like palmitate (C16:0) nor the presence of two (such as in linoleate, C18:2 n-6) or three (such as in docosahexanoate, C22:6 n-3) double bonds activate fatty acid sensing systems (Gomez-Pinilla and Ying, 2010; Ross et al, 2010; Schwinkendorf et al, 2011; Greco et al, 2014). …”