PHOSPHOLIPID MEMBRANE ABNORMALITIES AND REDUCED NIACIN SKIN FLUSH RESPONSE IN SCHIZOPHRENIA Alena Buretić-Tomljanović 1, Jasminka Giacometti 1, Sergej Nadalin 1, Gordana Rubeša 2, Mirjana Vulin 3, Draško Tomljanović 4 1 School of Medicine, University of Rijeka, Rijeka, Croatia 2 Psychiatry Clinic, Clinical Medical Centre, Rijeka, Croatia 3 Psychiatric Hospital Lopača, Rijeka, Croatia 4 Private psychiatric practice, Rijeka, Croatia
DNA RNA Genomics Proteins Proteomics Metabolites Metabolomics Enzymes involved in lipid metabolism and transport Lipids Sugars and other metabolites/toxins Extraction, purification, composition, quantitation LIPIDOMICS Chromatography (GC, HPLC) Mass spectroscopy Nuclear magnetic resonance Adapted from: Adibhatla et al., AAPS J (2006)
Three classes of lipids are main constituents of membrane bilayers: phospholipids, sphingolipids and cholesterol Cell membrane & organellar membranes
The phospholipid molecule Saturated fatty acid - SFA Polyunsaturated fatty acid - PUFA Long-chain PUFAs (18-22 carbon atoms): n-3 & n-6 families
DHA Brain phospholipids are enriched in PUFAs, especially long-chain DHA - 22:6n-3 in the brain, DHA is enriched at the cytofacial site Early embryonal development accumulation of DHA that is implicated in: -growth modulation -synaptogenesis -neurogenesis - dopaminergic and serotonergic neurotransmission Roles of PUFAs in the brain - neurodevelopmental processes (cell migration, cell communication) - eicosanoid precursors (intracellular signaling) - ligands for transcription factors (PPARs, NFκB, SREBP) - interaction with proteins -regulation of inflammatory response - cognitive aging - regulation of brain glucose uptake (n-3, not n-6) - maintenance of balanced oxydative status Early deprivation of DHA: - elevation of dopamine D1 and D2 receptors - impaired glucose utilization and glucose transport in the brain - vulnerability to neuropathological insult
PUFA-depleted neurons are morphologically normal but defective in neurotransmission experimental species: nematode C. elegans strains unable to synthesize PUFAs PUFAs play crucial role in neurotransmitter release the number of synaptic vesicles dramatically decreases in PUFA-depleted neurons Top: serotonergic neurons vizualized with green fluorescent protein in living animals Bottom: electron micrograph showing the number of synaptic vesicles (pseudocoloured in pink) Source: www.physiol.ucl.ac.uk/research/lesa_g/
Monoaminergic neurotransmission is coupled with PLA2 activity and PUFA release from membrane phospholipids Pre-synaptic site PLs cpla2 PLs ipla2 CYP450 AA 20:4n-6 (-) COX-1 COX-2 Other bioactive mediators Eicosanoids Adapted from: Rao et al., Mol Psychiatr, 2006 CYP450 Post-synaptic site DHA 22:6n-3 Other bioactive metabolites COX-2/LOX Neuroprotectins, resolvins
Mechanism of phospholipases A2 action (mediating the fatty acid composition of cellular membranes - cpla2, ipla2) sn-3 fatty acid sn-3 fatty acid sn-2 AA or DHA sn-2 sn-1 PLA2 sn-1 Free AA or DHA phospholipid group phospholipid group Membrane phospholipid Lysophospholipid cpla2 cytosolic, calcium dependent phospholipase A2 ipla2 calcium independent phospholipase A2
Monoaminergic neurotransmission is coupled with PLA2 activity and PUFA release from membrane phospholipids Pre-synaptic site PLs cpla2 PLs ipla2 CYP450 AA COX-1 COX-2 (-) CYP450 DHA COX-2/LOX Other bioactive mediators Eicosanoids Other bioactive metabolites Neuroprotectins, resolvins Post-synaptic site PRO-INFLAMMATORY METABOLITES ANTI-INFLAMMATORY METABOLITES Adapted from: Rao et al., Mol Psychiatr, 2006
Schizophrenic patients have depletion of PUFAs, reduced n-3/n-6 (DHA/AA) and PUFA/SFA ratio in the neuronal and RBC membranes Abnormalities in schizophrenia - elevated activity of AA-metabolizing enzymes (cpla2, COX-2) in serum and brain tissue - disturbance of calcium homeostasis and neurodegeneration - lower membrane fluidity level and unproper ion channels, and receptors function - synthesis of proinflammatory eicosanoids and inflammatory cytokines - increased oxydative stress - disturbed immune functions - disturbed glucose tolerance - risk for cardiovascular disease - features of metabolic syndrome - increased lipid peroxidation Arachidonic acid - AA 20:4n-6
1) Diet influences the fatty acid composition of cellular membranes Essential fatty acids - EFAs 18:2n-6 linoleic acid-la 18:3n-3 α-linolenic acid- ALA Polyunsaturated fatty acids - PUFAs 20:5n-3 eicosapentaenoic acid-epa 22:6n-3 docosahexaenoic acid-dha Western diet n-6/n-3 20:1
n-6 family 18:2n-6 linoleic acid-la 18:3n-6 -GLA 20:3n-6 -DGLA 20:4n-6 arachidonic acid-aa 22:4n-6 24:4n-6 24:5n-6 22:5n-6 EFA (diet) Δ-6-desaturase elongase Δ-5-desaturase elongase elongase Δ-6-desaturase β-oxydation n-3 family 18:3n-3 α-linolenic acid-ala 18:4n-3 20:4n-3 20:5n-3 eicosapentaenoic acid-epa 22:5n-3 24:5n-3 24:6n-3 22:6n-3 docosahexaenoic acid-dha 2) Conversion rate of EFA to PUFA endoplasmic reticulum peroxisomes Depends on the rate-limiting enzyme Δ-6-desaturase (more efficient in females) Δ-5-desaturase controls the synthesis of AA and EPA that compete for sn-2 position of PLs
Up to 80% of schizophrenic patients have reduced niacin skin flush response cpla2 Membrane phospholipids Metabolic pathway including cpla2 and COX-2 does not function properly in vast majority of schizophrenic patients AA COX-2 PGG 2 PGH 2 local vasodilatation due to prostaglandin PGD 2 synthesis PGD 2 flushing and edema vasodilatation Source: www.abpi.org.uk attenuated niacin skin response in schizophrenic patient
Disturbance of lipid homeostasis was found in neuronal membranes but also peripheral tissue i.e. red blood cells of schizophrenic patients Subjects: N Age Gender M F Controls (1) 16 34,6 ± 6,5 6 10 First episode (2) 6 27,6 ± 7,5 6 0 Chronic patients (3) 23 46,2 ± 12,4 10 13 All 45 36,9 ± 12,2 22 23 Method: gas chromatography Statistical analysis: Kruskal-Walis ANOVA, ANCOVA, StatSoft, Inc, version 7.1
35 30 25 20 15 10 5 Fatty acids profile of red blood cell membranes Control First episode Chronic p < 0.01 0 C14:0 C14:1 C16:0 C16:1 C18:0 C18:1 C18:2 C20:0 C18:3 C20:1 C20:2 C20:3 C20:4 C22:0 C20:5 C24:0 C22:4 C22:5 C22:6 Fatty acids %
Fatty acids profile of red blood cell membranes 70 60 Control First episode Chronic p < 0.01 50 40 30 20 10 0 n-6 n-3 SFA MUFA PUFA SFA saturated fatty acids =Σ% (14:0+16:0+18:0+20:0+22:0+24:0); MUFA monounsaturated fatty acids =Σ% (14:1+16:1+18:1+20:1); PUFA polyunsaturated fatty acids =Σ% (PUFAn-3 + PUFAn-6)
Fatty acids ratios and activity of desaturases 3 Control First episode Chronic p < 0.01 2 1 0 PUFA/SFA PUFA/MUFA 20:4/18:2 22:6/20:4 n-3/n-6 D9C16 D9C18 D9C18 stearoyl-coa desaturase index =18:1n-9/18:0
Direction of activity of stearoyl-coa desaturase, delta-6-desaturase and delta-5-desaturase 0.4 0.2 0.0-0.2-0.4-0.6-0.8-1.0-1.2-1.4 D9C18 Control First episode Chronic p < 0.01 D6D D5D D9C18 stearoyl-coa desaturase index =18:1n-9/18:0 D6D delta-6-desaturase =[(18:3n-6+20:3n-6)/18:2n-6]; D5D delta-5-desaturase =20:4n-6/20:3n-6
Double bond index and peroxidizability index in three groups of subjects 160 140 DBI PI p < 0.01 p < 0.01 120 100 80 60 40 20 0 Control First episode Chronic DBI double bond index =Σ % of unsaturated FAs x number of duble bonds of each unsaturated FAs PI peroxidizability index =[(%Monoenoic x 0.025) + (%Dienoic x 1) + (%Trienoic x 2) + (%Tetraenoic x 4) + (%Pentaenoic x 6) + (%Hexaenoic x 8)]
Parameter estimates for group differences (ANCOVA) Dependent Group variable difference β t P 18:0 1 vs 2 0.650 4.276 0.0005 18:1n-9 1 vs 2-0.504-2.944 0.009 18:2n-6 1 vs 2 & 3-0.500-3.473 0.001 22:5n-3 2 vs 3-0.687-4.480 0.002 22:6n-3 1 vs 2 & 3-0.475-3.316 0.002 n-3 1 vs 2 & 3-0.529-3.847 0.0004 n-6 1 vs 2 & 3-0.421-2.839 0.007 SFAs 1 vs 2 & 3 0.487 3.354 0.002 PUFAs 1 vs 2 & 3-0.507-3.600 0.001 PUFAs/SFAs 1 vs 2 & 3-0.566-4.086 0.0002 D9C18 1 vs 2 & 3-0.502-3.619 0.0008 DBI 1 vs 2 & 3-0.520-3.760 0.0005 PI 1 vs 2 & 3-0.413-2.947 0.005 DBI/ACL 1 vs 2 & 3-0.522-2.763 0.0005 Group 1 non-psychiatric controls; Group 2 first-episode patients; Group 3 chronic medicated patients; Categorical predictor variables: group, sex, nicotine usage; Continuous predictor variables: age, body mass index; SFAs saturated fatty acids; PUFAs polyunsaturated fatty acids; D9C18 stearoyl-coa desaturase index; DBI double bond index; PI peroxidizability index; ACL average chain length
CONCLUSIONS 1) Disturbance of lipid homeostasis in RBC membranes is an intrinsic feature of schizophrenia (regardless of illness duration and antipsychotic treatment when compared to nonpsychiatric controls); 2) Decreased DBI, PI, and PUFA/SFA ratio in schizophrenic patients are indicative of oxidative stress; 3) Decreased activity of stearoyl-coa desaturase (D9C18) is indicative of increased energy expenditure and reduced lipogenesis in the liver; 4) Disturbances of lipid homeostasis might represent biochemical markers in the preclinical phase of illness; 5) Beneficial effects in schizophrenia might have drugs affecting fatty acid metabolism and providing recovery of lipid homeostasis in cellular membranes, along with specific medical nutrition therapies. Thank you for your attention!