Effect of Docosahexaenoic Acid (DHA) at the Enteric Level in a Synucleinopathy Mouse Model

Sex and Age Differences in a Progressive Synucleinopathy Mouse Model

The mutation and overexpression of the alpha-synuclein protein (αSyn), described as synucleinopathy, is associated with Parkinson's disease (PD)-like pathologies. A higher prevalence of PD is documented for men versus women, suggesting female hormones' implication in slowing PD progression. The nigrostriatal dopamine (DA) neurons in rodent males are more vulnerable to toxins than those in females. The effect of biological sex on synucleinopathy remains poorly described and was investigated using mice knocked out for murine αSyn (SNCA-/-) and also overexpressing human αSyn (SNCA-OVX) compared to wildtype (WT) mice. All the mice showed decreased locomotor activity with age, and more abruptly in the male than in the female SNCA-OVX mice; anxiety-like behavior increased with age. The SNCA-OVX mice had an age-dependent accumulation of αSyn. Older age was associated with the loss of nigral DA neurons and decreased striatal DA contents. The astrogliosis, microgliosis, and cytokine concentrations increased with aging. More abrupt nigrostriatal DA decreases and increased microgliosis were observed in the male SNCA-OVX mice. Human αSyn overexpression and murine αSyn knockout resulted in behavioral dysfunctions, while only human αSyn overexpression was toxic to DA neurons. At 18 months, neuroprotection was lost in the female SNCA-OVX mice, with a likely loss of estrus cycles. In conclusion, sex-dependent αSyn toxicity was observed, affecting the male mice more significantly.

Dietary intake of α-ketoglutarate ameliorates α-synuclein pathology in mouse models of Parkinson's disease

Parkinson's disease (PD) is a progressive movement disorder characterized by dopaminergic (DA) neuron degeneration and the existence of Lewy bodies formed by misfolded α-synuclein. Emerging evidence supports the benefits of dietary interventions in PD due to their safety and practicality. Previously, dietary intake of α-ketoglutarate (AKG) was proved to extend the lifespan of various species and protect mice from frailty. However, the mechanism of dietary AKG's effects in PD remains undetermined. In the present study, we report that an AKG-based diet significantly ameliorated α-synuclein pathology, and rescued DA neuron degeneration and impaired DA synapses in adeno-associated virus (AAV)-loaded human α-synuclein mice and transgenic A53T α-synuclein (A53T α-Syn) mice. Moreover, AKG diet increased nigral docosahexaenoic acid (DHA) levels and DHA supplementation reproduced the anti-α-synuclein effects in the PD mouse model. Our study reveals that AKG and DHA induced microglia to phagocytose and degrade α-synuclein via promoting C1q and suppressed pro-inflammatory reactions. Furthermore, results indicate that modulating gut polyunsaturated fatty acid metabolism and microbiota Lachnospiraceae_NK4A136_group in the gut-brain axis may underlie AKG's benefits in treating α-synucleinopathy in mice. Together, our findings propose that dietary intake of AKG is a feasible and promising therapeutic approach for PD.

Impact of Sex on Neuroimmune contributions to Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. Inflammation has been observed in both the idiopathic and familial forms of PD. Importantly, PD is reported more often in men than in women, men having at least 1.5- fold higher risk to develop PD than women. This review summarizes the impact of biological sex and sex hormones on the neuroimmune contributions to PD and its investigation in animal models of PD. Innate and peripheral immune systems participate in the brain neuroinflammation of PD patients and is reproduced in neurotoxin, genetic and alpha-synuclein based models of PD. Microglia and astrocytes are the main cells of the innate immune system in the central nervous system and are the first to react to restore homeostasis in the brain. Analysis of serum immunoprofiles in female and male control and PD patients show that a great proportion of these markers differ between male and female. The relationship between CSF inflammatory markers and PD clinical characteristics or PD biomarkers shows sex differences. Conversely, in animal models of PD, sex differences in inflammation are well documented and the beneficial effects of endogenous and exogenous estrogenic modulation in inflammation have been reported. Targeting neuroinflammation in PD is an emerging therapeutic option but gonadal drugs have not yet been investigated in this respect, thus offering new opportunities for sex specific treatments.

Esterification of Docosahexaenoic Acid Enhances Its Transport to the Brain and Its Potential Therapeutic Use in Brain Diseases

Docosahexaenoic acid-containing lysophosphatidylcholine (DHA-LysoPC) is presented as the main transporter of DHA from blood plasma to the brain. This is related to the major facilitator superfamily domain-containing protein 2A (Mfsd2a) symporter expression in the blood-brain barrier that recognizes the various lyso-phospholipids that have choline in their polar head. In order to stabilize the DHA moiety at the sn-2 position of LysoPC, the sn-1 position was esterified by the shortest acetyl chain, creating the structural phospholipid 1-acetyl,2-docosahexaenoyl-glycerophosphocholine (AceDoPC). This small structure modification allows the maintaining of the preferential brain uptake of DHA over non-esterified DHA. Additional properties were found for AceDoPC, such as antioxidant properties, especially due to the aspirin-like acetyl moiety, as well as the capacity to generate acetylcholine in response to the phospholipase D cleavage of the polar head. Esterification of DHA within DHA-LysoPC or AceDoPC could elicit more potent neuroprotective effects against neurological diseases.