TABLE 2.
Summary of lipids that change in AD.
| Lipids | Changes observed in AD |
| Fatty acids | |
| Omega-3 fatty acids (#DHA, EPA, DPA, ALA) | DHA decreased in brains, circulation, and CSF of AD individuals (Fonteh et al., 2014, 2020; de Wilde et al., 2017; Snowden et al., 2017; Hosseini et al., 2020). EPA decreased in brain and circulation of AD individuals (Hosseini et al., 2020). DPA increased in livers of AD (Dyall, 2015). ALA increased in plasma and peripheral tissues (Cherubini et al., 2007). |
| Omega-6 fatty acids (#AA, LA) | AA increased in brains, erythrocytes, and CSF of AD individuals (Thomas et al., 2016; Goozee et al., 2017; Fonteh et al., 2020). LA decreased in AD brain and plasma (Snowden et al., 2017; Cunnane et al., 2012). |
| Saturated fatty acids (#PA, SA, C15:0) | Increased in the CSF and brains of AD individuals (Fonteh et al., 2014). Odd chain saturated fatty acids derived from microbiome or measures of dairy consumption decreased in CSF of AD (Fonteh et al., 2014; Nasaruddin et al., 2016). |
| Eicosanoids | Pro-inflammatory eicosanoid pathways are upregulated in AD individuals, while anti-inflammatory eicosanoids are decreased (Biringer, 2019). Prostaglandin and thromboxane B2 increased in AD brains (Iwamoto et al., 1989). Pro-resolvin mediators, such as lipoxins, are reduced in AD brains (Wang et al., 2015b). |
| Endocannabinoids | Decreased levels of endocannabinoids and receptors in AD brains (Bedse et al., 2015). |
| Glycerolipids | |
| Triglycerides | Total TG lipid levels decreased in the serum of individuals with probable AD (Lepara et al., 2009). Polyunsaturated TG decreased in AD brains (Bernath et al., 2019). |
| Glycerophospholipids | |
| Phosphatidylcholine (PC) Phosphatidylethanolamine (PE) Phosphatidylserine (PS) | Total PC lipids decreased in AD brains (Wood, 2012). PC species decreased in CSF of AD individuals #PC32:0, PC34p:0/34e:1, PC34:1, PC34:0, PC36:1, PC38a:5 (PC-EPA), PC36:0/38p:6, 38a:6 (PC-DHA) (Fonteh et al., 2013). PC species decreased in plasma of AD individuals. PC36:5 (PC-EPA), PC38:6 (PC-DHA), PC40:6 (PC-DHA) (Whiley et al., 2014). PC species increased in the prefrontal cortex of AD individuals. PC38:6 (PC-DHA), PC40:6 (PC-DHA) (Igarashi et al., 2011). Total PE lipids decreased in the hippocampus of AD individuals (Prasad et al., 1998). PE species decreased in the hippocampus of AD individuals. PE-SA, PE-OA, PE-AA, PE-DHA (Guan et al., 1999). A decrease in PE plasmalogen in AD (Farooqui and Horrocks, 1998). Total PS lipids decreased in the occipital lobe and inferior parietal lobule of AD brains (Farooqui and Horrocks, 1998). |
| Sphingolipids | |
| Sphingomyelin (SM) Ceramides (CM) Sulfatides Gangliosides | Total SM lipids lower in CSF of AD individuals (Fonteh et al., 2015). SM species decreased in the CSF of AD individuals #SM18/14:0, SM18/16:0, SM18/16:1, SM18/17:0 SM species (SM18/18:0, SM18/18:1) increased in the CSF of prodromal AD individuals (Kosicek et al., 2012). Total CM lipids increased in AD brains (Filippov et al., 2012). CM species increased in AD brains and plasma CM16:0 (PA), CM18:0 (SA), CM20:0, CM24:0, CM24:1 (Kim et al., 2017). Total sulfatide levels significantly lower in AD brains in both gray and white matter. The compositional distribution of sulfatide subtypes is unaltered (Han et al., 2002). Ganglioside lipid levels reduced in the temporal lobe of AD brains (Molander-Melin et al., 2005). |
| Sterols | |
| Cholesterol Oxysterols Hormones | Cholesterol decreased, and oxysterol/cholesterol precursors increased in MCI and sporadic AD brains (Hascalovici et al., 2009). Total oxidized cholesterol increased in AD brains (Heverin et al., 2004). Oxidized cholesterol species decreased in AD brains, 24S-hydroxycholesterol (Heverin et al., 2004). Oxidized cholesterol species increased in AD brains, 27-hydroxycholesterol (Heverin et al., 2004). Lower estrogen increases the risk of AD (Ratnakumar et al., 2019; Uddin et al., 2020). Increased basal cortisol levels in the plasma of demented individuals (Csernansky et al., 2006). Association of cortisol with Aβ deposition (Toledo et al., 2012) and with hypometabolism (Wirth et al., 2019). |
#DHA, Docosahexaenoic acid (C22:6, n-3); EPA, Eicosapentaenoic acid (C20:5, n-3); DPA, Docosapentaenoic acid (C22:5, n-3); ALA, Alpha-linolenic acid (C18:3, n-3); AA, Arachidonic acid (C20:4, n-6); LA, Linoleic acid (C18:2, n-6); PA, Palmitic acid (C16:0); SA, Stearic acid (C18:0); OA, Oleic Acid (C18:1, n-9); PC, phosphatidylcholine; PCxxa:#, PC specie with xx carbon number and acyl-linked fatty acid at the sn-1 position containing # (number) double bonds; PCxxp:#, PC specie with xx carbon number and alk-1-enyl (plasmalogen)-linked fatty acid at the sn-1 position containing # (number) double bonds PCxxe:# PC specie with xx carbon number and alkyl (ether)-linked fatty acid at the sn-1 position containing # (number) double bond; PE, phosphatidylethanolamine; PS, phosphatidylserine; SM, sphingomyelin; CM, ceramide; TG, triglyceride.