ipid Esters of fatty acids and alcohols (e.g. glycerol, cholesterol, sfingosin) Sometimes, they also contain other chemical groups - e.g. Phosphate, choline, inositol (phospholipids), monosaccharide (glycolipids) In wider sense lipid involve generally small hydrophobic or amphiphilic molecule with hydrocarbon chain (which involves free cholesterol, free fatty acids, icosanoids, retinoids) Molecule of phosphatidylcholin CH2 I 0 1 0 = P-0 I 0 1 CH2-CH-CH2 II 0 0 1 I C=0 C=0 I I CH2 CH2 II CH2 CHa-NTCHzJj ] choline phosphate glycerol Physiological functions of lipids Energy storage - 1 gram of triacylglycerol can produce 39 kJ, double compared to saccharides and proteins Structural - amphiphilic lipids (especially phospholipids, cholesterol) makes most of cellular membranes and intracellular membrane compartments, myelin in nervous system (esp. sphingolipids, cholesterol) ^^^^^^ signal --MpidsajicUJa e i r derivates are responsible for^^ endocrine (steroids), paracrine (icosanoids) and intracellular signalization (phosphatidylinositol phosphates) Other - role in embryogenesis, vision (retinoids), antioxidants (vitamins A, E) ^ Transport of blood lipids Lipids are not soluble in water Part is transformed into soluble metabolites Free fatty acids (FFA) are bound to albumin in blood Most lipids in circulation form compounds of lipoprotein particles Lipoproteins Specific particles present in blood plasma They consist of lipid and protein compounds Plwsph<;lipiiifi Cholcsicnol Coro mm Liming iriiicylglyccruls iind diolcstcryl Apolipopj^tüiriü Lipid compound Phospholipids Cholesterol Triacylglyceroles (TAG) Protein compound Apolipoproteins (Apo) A-M Lipoprotein classes ■ A particle is formed out of amphiphilic coat (apolipoproteins, phospholipids, cholesterol) and hydrophobic core (cholesteryl esters, triacylglycerols) ■ In increasing diameter, surface increases with the power of two, volume with the power of three ■ That means, the greater the diameter, the bigger is the core compared to the coat ■ With the diameter, the ratio of TAG to proteins increases and the density decreases ■ Acording to increasing density (and decreasing diameter), lipoproteins can be divided into 5 basic classes- chylomicrons, VLDL, IDL, LDL and HDL Apolipoproteins Are situated on the surface of A ,. . A , Apohpoprotein A-l lipoproteins ^^^^^^^^^^^^ Everything what is done with B^^N^v^^^^l lipoprotein particles is dependent on k/^0rI^^^^^| Apos (i.e.binding specific receptors, L^Bt^C^^^H induction/inhibition of enzymes and ^■^vtSE'* iH transport proteins) lEiS'^-fmt^M They are distinguished by letters A-M Some apolipoproteins (A, C and E) can^^^^^^^ESjjBBPt be exchanged between different ^^^^^^H^^>CT particles ^^^^^^^^^■■i ApoA and ApoC are in fact groups of proteins with similar structure, distinguished by Roman numbers. They, together with ApoE, form a structural family. ApoB occurs in two forms, ApoB-48 and ApoB-100, which are products of the same gene (by mRNA editing, stop-codon can be made, which leads into mRNA translation into shorter ApoB-48). Metabolism of lipoproteins ■ Different lipoprotein classes can exchange both apolipoproteins and lipid compound IBS En " " !; ■ Depending on the compositioi^^— of protein compound, lipoprotein ensures a specific mn ■ lipid transport between tissues. ■ Lipoprotein metabolism can be divided into three main pathways: ■H • Exogennous pathway 89b • Endogenous pathway • Reverse transport----- Lipid transport between tissues ■fro Ethr bloodstream £h|^riilcrDii Ftnmpart CUR f*LupLoi Lipoproteins - exogenous pathway ■ Chylomicrons (CMs) are big particles formed in the small intenstine They contain all mam types of apolipoproteins (A, B, C, E), ApoB-48 is a specific apolipoprotein Through lipoprotein lipase (LPL) on capilary endothelium, induced by ApoC-ll and inhibited by ApoC-lll, CMs get rid of TAG, newly formed FFA get out of capillaries into tissues. Most apolipoproteins are, together with TAG, transfered to HDL Thus, chylomicrone remnants are formed. Through their ApoE, they bind to LDL or LRP receptors in the liver, where they are internalized Lipoproteins - endogenous pathway VLDL are similar to chylomicrons, but they are smaller and contain ApoB-100 instead of ApoB-48 In peripheral capillaries, they undergo similar modification as chylomicrons. Their remants are called IDL Through LPL and hepatic lipase (on the endothelium of hepatic capillaries), they get rid of the rest of lipids (with the exception of cholesterol) and of ApoE As a result, LDL particles are formed. They contain only one apolipoprotein, ApoB-100, and dominating lipid compound is cholesterol and its esters ApoB-100 binds only to LDL receptor, which is frequent both in liver and peripheral tissues. The process leads to the transport of cholesterol into periphery Clearance of LDL is relatively slow. In a consequence, they are prone to oxidation and other modifications LDL-receptor is degraded with the help of chaperon PCSK-9 TG : tri acyl glycerol s Chi : chol e sterol and cholesterol esters Pl_ : phospholipids FA : free fatty acids A : apo - A - I , apo - A - II and apo - A - IV B - 43 : apo - B - 48 C - II : apo - C - II E : apo - E CRR : chylomicron remnant receptor LDL - R : LDL receptor Copyright 1 99G , S. Ma rc he si n i Lipoproteins - reverse transport ■ HDL are formed as nascent particles in the liver (and intestine), protein compound -ApoA-l - is dominant ■ Using ABCA-I transporter, ApoA-l is capable of reverse transport of cholesterol out of peripheral tissues (by other mechanisms, also ApoA-ll a ApoE). ■ Apolipoproteins (except of Apo-B), TAG (in exchange for cholesterol esters - CETP) and phospholipids are transferred from other lipoproteins ■ Larger, lipid-enriched forms of HDL are formed, using LCAT, cholesterol is esterified. ■ Thanks to binding of ApoA-l to SR-BI receptor in liver (and steroidogenic issues), HDL „unloads" cholesterol and gets back into .circulation. TAG and phospholipides are degraded by hepatic lipase ^^^^^^^^^^^^^h^^^^b^^^^^^^^^^^^ If modified HDL contains ApoE, it can be internalized by binding its receptors ApoA-l and ApoA-ll bind to their receptor in kidney andean be excreted, they can return into circulation by binding protein cubilin Gut and Liver Liver Atherogenic and antiatherogenic lipoproteins Antiatherogenic ■ HDL (especially nascent) - do not contain apoB Neutral ■ Chylomicrons and VLDL (they are potentially atherogenic, bu too large to pass through the endothelial layer - big and contain apoB Atherogenic V VW ■ Small and contain apoB ■ LDJ^ in subendothelial space and other tissues (gingiva) they undergo oxidative modification, oxLDL are not recognized by LDL-R, but by macrophage scavenger receptors. Formation of oxLDL is easier, when the diet is rich for oxidated lipids. Subgroup of „small dense LDL" is especially atherogenic ■ Chylomicron remnants and IDL-they bind scavenger receptoxs^ithout modifications ■ Other atherogenic modifications ■ glycation, glucooxidation, carbamylation (urea), aggregation ■ Lipoprotein (a) Aterogenic lipoprotein penetration They must be sufficiently small (i.e. not chylomicrons and nascent VLDL) Endothelium: transcellular transport (vesicles) and paracellular transport (Jeaky junctions") Scavenger receptors SR-B participate in transcellular transport (on the other hand, the binding to LDL-receptor supports lipoprotein internalization - role of previous atherogenic modifications)^ Retention in subendothelial space Vesicular transport through the endothelium goes both ways "^^^^^^^H^ ■ i.e. lipoproteins are rapidly removed from the subendothelial space „^ Binding to subendothelial glycosaminoglycans -> retention— -> retention i Further modification (oxidation /glycation aggregation...) -> binding to macrophage scavenger receptors ("toxic lipoproteins") i Activation -> differentiation into foam cell: Foam cells Macrophage-derived ■ Both Ml and M2 type ■ Ml retain higher inflammatory activity VSMC-derived ^^^^T ^^Btt^l ■ Cytokine-derived differentiation - inflammation (TNF-a, IL-ip) + oxLDL ■ Expression of scavenger receptors, MMPs Ratio is approximately 1:1, there are functional differences between both population (unknown significance) Arterioscler Thromb Vase Biol PMID: 33792344 Foam cells and atherosclerosis Production of matrix metalloproteinases (MMPs) and proinflammatory cytokines Necrosis -> lipid core formation -> mechanical destabilization ^^^^^^^^ Secretion or osteogennic phenotypes of VSMC - attempt to stabilize the plaque by a fibrous cap Vascular lumen Si Macrophage foam cell cell ■ Eariy lipoprotein retention ■ Lowering plasma apoB LPs and decreasing risk factors will readily promote removal of atherogenic components and prevent maladaptive responses and future disease PRE-TEENS 1 Pre "iesional susceptible area of the arterial watl with diffuse intimal thickening (DIT) ' Lowering plasma apoB LPs and decreasing risk factors will prevent future vascular disease Diffuse intmnal thickening (DIT) apoB-LPs in plasma Endothelium VSMCs in media Atherothrombotic vascular disease Fibrous Mast ^tr. Expanded intima, rich in retentive ^ proteoglycans , Plaque necrosis with cholesterol crystals Ü C • Early responses to LP retention, e.g., monocyte entry - Lowering plasma apoB LPs _l and decreasing risk factors will m readily promote removal of athero-m genie components and prevent Z further responses and future W disease * Future strategies to prevent LP retention are likely to be most feasible up to this stage v<5 Tcell Dying Ivty ■TWENTIES AND BEYOND ■ Advanced responses to LP retention, including maladaptive inflammation, death, and plaque necrosis ■ LP retention continues to accelerates - Lowering plasma apoB LPs and reducing risk factors can promote removal of atherogenic components and promote regression, but reversal is more difficult and prolonged, and vascular disease may still develop ■ Continued responses to LP retention, e.g^ M foam cell formation and SMC migration • LP retention starts to accelerate . Lowering plasma apoB LPs and other risk factors can still promote removal of atherogenic components, promote regression, and prevent further responses and future disease Lipoprotein (a) Small particle containing ApoB-100 and Apo(a) Its elevated concentration is usually inherited (different genetic substrate) It is one of most frequent causes of infarctions in young age (<20 years) Its physiological function is unclear, Apo(a) is similar to plasminogene and tPA and binds fibrin. Probably, it is used in a repair of damaged vessel wall. Lp(a) and cardiovascular events Possible unmet need for secondary prevention in individuals with high lipoprotein(a) Risk of major adverse cardiovascular event (MACE) Pí runt lufjiiLT rrik 114% Upo|:ro1nir,!ai ■■:-u-:i: i iliüNLJ: si 00 (as i4) 50-99 (105-213) 10-49 < 13-104) 2-1 S 8 10 Time gii study (years) 2,527 mgfdL: ö 50 100 150 nmol/L:ie 105 214 333 Lipopfotdnfa) 432 individuals wilh cardiovascular disease at baseline identified among 58,527 individuals from the general population Madsen CM, Arterioscler Thromb Vase, Biol, 2020, PMID: 31578080 Lp(a)today Both European and American Guidelines recommend the measurement of Lp(a) at least once per a lifetime ■ Small intraindividual, but large interindividua variability ^^^-^X The risk is independent on traditional risk factors (SCORE) and CAC On the other way, it is not clear what to do with the information (specific treatment of high Lp(a) is still uticTer development) ^ Dyslipidemias Disorders of lipid metabolism They are not necessarily linked to obesity (but often they are) Typically iHotal cholesterol, I^LDL-cholesterol, nI,HDL-cholesterol and 1sTAG Sometimes, only some components are present (isolated hypertriacylglycerolemia, isolated hypercholesterolemia) Hyper-TAG is in 90% connected with nI/HDL-C (phospholipid and TAG transfer to HDL leads to rapid degradation). Isolated nI/HDL-C (hypoalfalipoproteinemia) is rare ^^^^ LDL concentration is sometimes not measured directly, but is estimated using Friewald formula: LDL-C = total chol. - HDL-C - (TAG/2,2) ^^^Ě0 Clinical manifestation of severe hyperchlesterolemia Cholesterol and cardiovascular risk (SCORE) ■ 15% and over lOyearrbfcof rauf CVDki popLditkms et Consequences of elevated TAG Cardiovascular risk sharply increases up to approx. 4 mmol/l, but does not substantially change further (contrary to overall mortality) ^™ Copenhagen City Heart study and Copenhagen Oeneral Population study Myocardial infarction N-96,394 (Events=3,287) Median follow-up 6 years Ischemic (=coronary) heart disease N-93,4I0 (Events^?, 183) Median follow-up 6 years In high levels of TAG the TAG-rich lipoprotein particles increases in size, but not in number ■ Large lipoproteins do not pass into vascular intima, but may obstruct the microcirculation - see further Other complications of hyperTAGemia Acute pancreatitis ■ During pancreatitis development in hyperTAGemia, cytotoxic damage of acinar cells by unesterified FFA takes place Lipemia retinalis, retinal vein thrombosis Xantelasmas— Target values of blood lipids Czech atherosclerosis society recommendations, 2007 Patients Without complications Risk factors (e.g. DM2, DM1 with mikroalbuminuria) Presence of atherosclerosis \ Lipid mm o 1/1 mmol/1 mmol/1 Cholesterol <5,0 <4,5 <4,0 LDL-C <3,0 <2,5 <2,0 HDL-C >1,0 (men), >1,2 (women) TAG <1,7 Highly above the optimal values, but realistically achieva Primary and secondary dyslipidemias Primary ■ More frequent ■ Usually multifactorial, polygenic heritability, usually as a component of ^metabolic syndrome" (syndrom X, ^Beimnn nyiTrlTSm) ■ Rare monogenic forms - usually mutations of apolipoproteins or their receptors Secondary ■ They are a consequence of other disease E.g. diabetic dyslipidemia, nephrotic syndrome They also may be a component of metabolic syndrome (the boundary between primary and secondary dyslipidemia is not shaj|^^PP Better reaction to dietary intervention Primary dyslipidemia classification i Simple phenotypic ■ hypercholesterolemia, hypertriacylglycerolemia, mixed ■ clinical practice, ICD ■ useful in monogennic dyslipidemia -> diagnostics, pharmacogenetics, gene therapy ^^^^^ ■ in polygennic dyslipidemia, the risk factor may not match the phenotype i Biochemical (Frederickson) ^^^^ ■ according to the dominating faction ■ complicated Frederickson classification of primary dyslipidemia ■ Type I - ^ chylomicrons ■ Type Ma - 1s LDL ■ Type lib - ^ LDL and VLDL ■ Type III - ^ chylomicron remnants and IDL ■ Type IV - ^ VLDL ■ Type V -1^ VLDL and chylomicrons Familial hyperlipoproteinemia type I Very rare (1/1000000), endemic in Quebec Hypertriacylglycerolemia with high concentration of circulating chylomicrons Defect of LPL (LPLD) or deficiency of ApoC-ll TAG up to 50mmol/l, manifestation in the childhood, often through acute pancreatitis or retinal thrombosis ^00^ In serious cases, there is a necessity of plasma transfusion ^ ^^^^^m Familial hypercholesterolemia (FH) Frequent, prevalence 1:500 It is caused by defects of LDL-receptor, more rarely ApoB-100 (different sites of genes) Phenotype Ma, TAG are not very much elevated (lipoproteins rich by TAG contain also ApoE, so they can use alternative ways of degradation, while LDL clearance is dependent on ApoB-100 and LDL receptor) More serious homozygous, less serious heterozygous form FH - complications ■ In heterozygotes Ml in 3rd -5th decade, in homozygotes before 20 years of age Polygenic hypercholesterolemia (Ha) Combination of disadvantageous", cholesterol-raising common polymorfisms in genes for ApoB, ApoE, PCSK9, LCAT, CETP and other proteins together with environmental factors Out of environmental factors, namely high caloric intake, high amounts of saturated fat^and \ cholesterol in diet, little physical activity^^ Role of fetal programing and early postnat^^k development -^"^^ Clinically, there is also higher susceptibility for gallstones formation ^ _^^^P^ Combined hyperlipidemia (Mb) It is usually caused by ApoB overproduction in the liver, often elevated ApoC-l 11 . ApoB/ApoA-l ratio is one of the most important risk factors for heart and brain atherosclerosis Variable fenotype, usually together with insulin resistance Monogenic forms are usually caused by variants of the genes for ApoC-ll, Apo-C-lll or CETP More frequent polygenic form is usually part of the metabolic syndrome, heritability cca 20-30% (which is quite low -„acquired combined hyperlipidemia"), enviromental risk factors are basically the same as inoolygem^^^pP hypercholesterolemia Familial hyperlipoproteinemia type III (familiar dysbetalipoproteinemia, FDBL) ■ ApoE occurs in 3 functionally different isoforms, E2, E3, E4, which are coded by three common alleles e2, e3 a e4 (in most European populations, their frequency is "5-10%, 70-80%, 10-20%) ■ Izoform E2 binds badly to LDL-receptor, however ApoE2-containing lipoproteins can be degraded by alternative pathways ■ In cca 5% of e2/e2 homozygotes, the degradation is impaired as a result of their independent genetic defect and/or metabolic disease (e.g. DM2) ApoE and FDBL This leads into the disease known as familial dysbetalipoproteinemia (FDBL, FH III) FDBL can be caused also by rare mutations of ApoE, in these cases, it is inherited in dominant fashion with high penetrancy Both TAG (more) and cholesterol (less) is present, clinically xanthomas and precocious atherosclerosis Most s2/s2 homozygotes are normo- to hypolipidemic, in its heterozygous form, the allele is protective against the onset of atherosclerosis and its development ^^^^^CV Allele s4 mildly increases the risk (and it markedly increases the risk of late-onset neurodegenerative diseases; because of its preferential binding to large lipoproteins it is insufficient for transferring lipids into neurons during their repair. The transport of lipids in the nervous system uses small, HDL-like Polygennic hypertriacylglycerolemia i Common, phenotype IV i Genetically heterogeneous disease i Polygennic, causes include LPL deficiency, overproduction of VLDL, deficiency of ApoA-V (inhibits chylomicron and VLDL production) ^^s^ \ i It often occurs together with diabetes and obesity, but it has probably different genetic background - howeveFTH^ manifestation of hyperTAGemia is much more serious in a coincidence with diabetes i The onset is usually provoked by alcoholic or nutritional excess Clinically often manifestated by serious fo rms of pan creatiti: Familial hyperlipoproteinemia type V ■ Basically intermediate type between 1 and 4 ■ As well as in all hyperTAGemias, there is a susceptibility to acute pancreatitis (esp. in TAG>10 mmol/l). Sometimes, chronic pancreatitis can occur Secondary dyslipidemia 1s cholesterol ■ mixed 1s TAG cholestasis kidney disease hypothyreosis obesity (TAG predominance) diabetes mellitus alcohol Diabetic hypertriacylglycerolemia Lack of insulin and insulin resistance leads into enhanced lipolysis in adipocytes and FFA formation In the liver, FFA can be used for TAG synthesis. TAG become part of VLD^^^^B^^^^H \ Moreover, insulin directly stimulates the production of LPL (and maybe also hepatic lipase). Activity of these enzymes is then lower in DM and that helps I^VLDL (secondarily also >1/HDL) --- Non-esterified FFA also induce cytolysis of pancreatic P-cells ^^^B^E Kidney diseases and dyslipidemia Nephrotic syndrome ■ Loss of LPL activators (4/ ratio ApoC-ll / ApoC- - Ill) 1^TAG ■ 4/HDL-cholesterol / total cholesterol ■ LCAT loss -> impaired transport of cholesterol ipttfHDL ■ ?|k P(M-9 hepatic expression -> 4ADL-R -> decreased clearance of LDL (mediated possibly by increased TNF-a from damaged podocytes) CKD ■ ^Apo-CIII ■ replacement of ApoA-l in HDL for serum amyloid A ■ I^PCSK-9 -» 1^ small dense LDL ■ CHRI often follows diabetes - see above Strategies of the treatment Lifestyle adjustment, physical activity (HDL) Lowering of caloric intake, low-lipid (in ^cholesterol) and low-saccharide (in ^TAG) diet - more efficient in secondary dyslipidemia Pharmacotherapy (clinical efficiency in arrange of years!) \ ■ statins (they inhibit cholesterol synthesis) ^^^^^^^ ■ resins, ezetimib (they lower intestinal absorption of lipids) ■ PCSK- inhibitors (they prevent internalization of hepatic LDL-R) ■ fibrates, niacin (they lower VLDL synthesis) ■ eikosapentaenic acid (activates LPL) ^^^^^ ■ gene therapy - e.g. antisense oligonucleotides In serious case^aphaeresis, transfusion of blood plasma, exceptionaflyliver transplantation ^ Most expensive cure of history Alipogene tiparvorec (Glybera) Adenoviral vector with a gene for LPL Indication: familial hyperlipoproteinemia type I (LPLD) EMA approval in r. 2012 after approx. 10 years of testing -historically first gene therapy \ Controversial expressions of EMA commitees (weak evidence aboiJt^elinical efficiency with low power of a test in a rare disease) 60 i.m. injections per a therapy - total price 1 mil. USD First doses came to market in 2015 Several tens of patients during a period of testing, 1 following the approval (2015-2017) 2017 the request for prolojjgattfrrfof EMA registration was withdrawn by a company Thank you for your attention