Ovarian Function Modulates the Effects of Long-Chain Polyunsaturated Fatty Acids on the Mouse Cerebral Cortex

Abstract

Different dietary ratios of n−6/n−3 long-chain polyunsaturated fatty acids (LC-PUFAs) may alter brain lipid profile, neural activity, and brain cognitive function. To determine whether ovarian hormones influence the effect of diet on the brain, ovariectomized and sham-operated mice continuously treated with placebo or estradiol were fed for 3 months with diets containing low or high n−6/n−3 LC-PUFA ratios. The fatty acid (FA) profile and expression of key neuronal proteins were analyzed in the cerebral cortex, with intact female mice on standard diet serving as internal controls of brain lipidome composition. Diets containing different concentrations of LC-PUFAs greatly modified total FAs, sphingolipids, and gangliosides in the cerebral cortex. Some of these changes were dependent on ovarian hormones, as they were not detected in ovariectomized animals, and in the case of complex lipids, the effect of ovariectomy was partially or totally reversed by continuous administration of estradiol. However, even though differential dietary LC-PUFA content modified the expression of neuronal proteins such as synapsin and its phosphorylation level, PSD-95, amyloid precursor protein (APP), or glial proteins such as glial fibrillary acidic protein (GFAP), an effect also dependent on the presence of the ovary, chronic estradiol treatment was unable to revert the dietary effects on brain cortex synaptic proteins. These results suggest that, in addition to stable estradiol levels, other ovarian hormones such as progesterone and/or cyclic ovarian secretory activity could play a physiological role in the modulation of dietary LC-PUFAs on the cerebral cortex, which may have clinical implications for post-menopausal women on diets enriched with different proportions of n−3 and n−6 LC-PUFAs.

Ovarian Hormone-Dependent Effects of Dietary Lipids on APP/PS1 Mouse Brain

“…Synapsins are a family of presynaptic proteins that play critical roles in synaptic development, neurotransmitter release, and neural plasticity through phosphorylation-dependent processes (Chi et al, 2003;Menegon et al, 2006;Giachello et al, 2010). Considering the roles of PI3K, PSD95, and synapsin, our results suggest that diets enriched in n-3 LC-PUFA and with different ratios of specific n-6 and n-3 PUFAs modulate the expression of key elements involved in neuroprotective signaling and synaptic transmission in AD mice, consistent with previous reports on the effects of DHA-enriched diets on hippocampal neuronal development (Cao et al, 2009), synaptic function (Cao et al, 2009), synaptic membrane proteins (Calon et al, 2004;Cansev et al, 2008;Sidhu et al, 2016;Herrera et al, 2018), and the restoration of neural plasticity and cognition after brain trauma (Wu et al, 2011). Our present findings indicate that two diets differing in their specific ARA, EPA, DPA, and DHA content, and in the n-6/n-3 PUFA ratio induce divergent changes in the lipidome of AD mouse brains.…”

“…We previously found that different concentrations of n-6 and n-3 LC-PUFAs in the diet are associated with differences in the total fatty acids (FAs), sphingolipids, and gangliosides in the female mouse cerebral cortex. Interestingly, these changes in the brain lipidome composition are partially dependent on the presence or absence of circulating ovarian hormones (Herrera et al, 2018). Furthermore, we also found that diet and ovarian function interact and affect the expression of several neuronal proteins as well as the APP levels in the brain.…”

“…How of the Interaction of the Different n-6/n-3 PUFA Ratios or n-3 LC-PUFA Content and the Gonadal Status Affects Hippocampal Accumulation of Amyloid Peptide Aβ 1 -40 in Female APP/PS1 Mouse Changes in the dietary DHA intake reduce the amyloid burden in the brain of AD mouse models (Lim et al, 2005;Green et al, 2007), and we previously showed that different concentrations of n-6 and n-3 LC-PUFAs in the diet modify the brain levels of APP in WT mice (Herrera et al, 2018). Therefore, we analyzed the impact of both dietary composition and gonadal status on brain amyloid accumulation in APP/PS1 animals.…”

“…Homogenates were then mixed for 3 h at room temperature and stored at −20 • C. Cerebral C 20:1 n-9 0.18 ± 0.00 0.12 ± 0.00 1.09 ± 0.07 C 20:4 n-6 (ARA) 0.00 ± 0.00 0.00 ± 0.00 0.20 ± 0.00 C 20:4 n-3 0.00 ± 0.00 0.00 ± 0.00 0.24 ± 0.01 C 20:5 n-3 (EPA) 0.00 ± 0.00 0.00 ± 0.00 2.29 ± 0.02 C 22:0 0.18 ± 0.01 0.10 ± 0.01 0.13 ± 0.02 C 22:1 n-11 0.05 ± 0.02 0.10 ± 0.06 0.74 ± 0.04 C 22: 5 n-6 (DPA) 0.00 ± 0.00 0.00 ± 0.00 0.11 ± 0.01 cortex tissue for Western blotting was homogenized in three volumes of ice-cold lysis buffer containing 20 mM HEPES, 100 mM NaCl, 100 mM NaF, 1 mM Na 3 VO 4 , 5 mM EDTA, 1% Triton X-100, 1 µM Okadaic acid (Calbiochem) and a protease inhibitor cocktail (Roche Diagnostic). The homogenates were processed as described previously (Herrera et al, 2018) and all samples were probed in 3-4 Western blots. For lipid analysis, the tissues were homogenized at a concentration of 5 mg/ml in phosphate-buffered saline (PBS) with 0.01% 3,5-Di-tert-4butylhydroxytoluene (BHT) as an antioxidant, and they were processed as described below.…”

“…Cerebral cortex protein lysates (20 µg) were resolved by SDS-PAGE, using 8 or 12% polyacrylamide gels, depending on the molecular weight of the studied proteins, and transferred onto nitrocellulose (Whatman) or PVDF (Millipore) membranes, that were subsequently blocked by incubation in 10% non-fat milk for 1 h at room temperature and incubated overnight at 4 • C with the appropriate primary antibodies (Table 3) in the conditions described previously (Herrera et al, 2018). Antibody binding was detected with Supersignal (Thermo Fisher Scientific) using β-actin as the internal loading control.…”