LIPID METABOLISM

16/6/52 นศพ.

Metabolism (Catabolism and Anabolism), Regulation and Importance of fatty acids (FÂ) and lipidsFÂ -Saturated FÂ

-Unsaturated FÂ-Monounsaturated FÂ -Polyunsaturated FÂ-Eicosanoids

Lipids Storage lipids ; Fat, oilsMembrane lipids

PhospholipidsGlycolipidsCholesterol

Precursor & derived lipidsSterolsPolyprenoid compounds

FA

FA

FATG

FA

MGGLYCEROL

FA

DG

CHOLESTEROL – FA = CH. ESTERR – COOH carboxylic acid

R – C - acyl = FA -O

FA

FA

PPA

FA

FA

P-XPL

FA

P-XLYSO-PL

PA = phosphatidic acid

PL = phospholipid

= phosphatidyl - x

( x = choline ; lecithin )

LYSO - PL = lysophosphatidyl - x

MG = monoacylglycerol

CTP = cytidine triphosphate

CDP = cytidine diphosphate

FA

small intestine

dietary lipids and proteins

gall bladder

pancreas

secretin (in blood)

gut endocrine

cells (enlarged)

cholecystokinin (in blood)

stomach

gastric motility

bicarbonate

pancreatic enz.

bile

+

+

+

+

-

duodenum

Hormones actiongastrin

Intestinal motility

LCTG

MG

FA

G

CH.ECH

FA

PLLPL

FA

MG

FA

G

CH

FA

LPL

FA

TG

CH.E

PL

apoprotein

chylomicron

MCTG MCTG

FFA G

Int. lipase

portal vein

target tissue

lymphatic

TG , CHE , PL , PROT.

FCH

+ albDIGESTION AND

ABSORPTION OF LIPIDS

pan.lipase

CHYLOMICRON

dietary lipids

gall bladder

pancreaspancreatic

juice

bile

defective cells

liversmall intestine

Intestinal mucosal

cells

Excess lipid in feces (steatorrhea)

Ca++ + FA Ca SOAP

Possible causes of steatorrhea :

Feces : bacteria ¼ - ½ total

large intestine

bile pigment

stercobilin

( สี feces )

steatorrhea

Orlistat (xenecal, tetrahydrolipstatin)

- Inhibit gastric and pancreatic lipases- Obesity, non-alcoholic steatohepatitis (NASH)

treatment

ENZYMES DIGEST LIPIDS : LIPASE

FA

FA

FATG

FA + 2FA

MG

+ 3FA

GLYCEROL

;

1 2

PANCREATIC (CO-LIPASE) : LC-FA

2.1 gastric : SC - FA2.2 lipoprotein (extrahepatic tiss.)

TG in chylomicron , VLDL activated by heparin , apo –C-II

2.3 hormone sensitive lipase in adipocyte :stim. : Gg , Epi , T4 , etc.

inh. : Pgs , Is

2.4 Int. lipase MCTG

1

2

FATTY ACIDS :

1. CHAIN : RCOOH

short chain (SC) medium chain (MC) long chain (LC) very long chain (VLC)

(<4) (6 – 12) ( 12 - 20 ) (>20)

2. ODD CHAIN : WAX ( C25 – C35 ) , EVEN

3. SAT. VS. UNSAT. :

SAT. : palmitic acid ( C16 : 0 )

stearic acid ( C18 : 0 )

CH3 CH2 CH2 CH2 CH2 CH2 CH2 COOH

ω αβγ

UNSAT. : oleic acid ( C18 : 1▲9 )

palmitoleic acid ( C16 : 1▲9 )

LINOLEIC LINOLENIC ARACHIDONIC

18 : 2▲9,1218 : 3▲9,12,15

20 : 4▲5,8,11,14

FATTY ACID OXIDATION :

supply energy : 40 % normal ; 90 + % - fast

3 ways : β- (major) ; α - & ω - (minor)

STEPS :

activation : 2ATP (cyto -)

GTP (FAs in mito -)

transfer ( cyto mito ) - carnitine

β- oxidation ( mito )

1. DHase : FAD+ 2. hydratase : + H2O

3. DHase : NAD+ 4. thiolase : 2C

end products : Ac. CoA ; propionyl CoA

Krebs succinyl CoA

palmitic ac. (C16 ) + 23 O2 16 CO2 + 16 H2O + EC16H32O2

FATTY ACID ACTIVATION AND TRANSPORT

RCOOH + CoA + ATP RCSCoA + AMP +PPiO

Acyl CoA synthetase (thiokinase)

SC-FA and MCFA can cross the inner membrane of mitochondria without the aid of carnitine or CAT system

translocase

Acyl CoA ligase

cytosolouter inner

mito-memb. matrix

PPi+

AMP

ATP

RCOOH

RCSCoA

CoASH

carnitine

RCO-C

RCSCoA

CoASH

RCOOH

GDP + Pi

GTP

O

I II

Acyl CoA-synthetase or thiokinase

CAT I : carnitine acyl transferase I is inhibited by malonyl CoA

CAT II : carnitine acyl transferase II

ACTIVATION TRANSLOCATION

Synthesized from lysine and methionine in liver and kidney but not in skeletal and heart muscles (MCFAs are plentiful in human milk)

Deficiency cause cardiomyopathy and muscle weakness- liver disease- strictly vegetarian diets

BETA – OXIDATION (not found in nerve and red cells)

FA R – CH2 – CH2 – CH2 – C - OHO

R – CH2 – CH2 – CH2 – CO ~S CoA

R – CH2 – CH = CH – CO ~S CoA

R – CH2 – CH - CH – CO ~S CoA

OH H

R – CH2 – C - CH2 – CO ~S CoA

O

R – CH2CO ~S CoA + CH3 CO ~S CoA

GTP , CoA

GDP , PiAMP , PPi

CoA , ATP

FADH2

FAD

-hydrataseH2O

NADH + H+

CoA SH

THIOKINASE

Acyl CoA- DHase

▲2- TRANS -ENOYL CoA

L – 3 – OH – acyl CoA

-DHase

3 – KETO – acyl CoATHIOLASE

(β-)

1

2

3

4

5

2

END PRODUCTS OF β - OXIDATION OF FA

EVEN – CARBON FA :

CH3 – CH2 – CH2 – CH2 – CH2 - CH2 – CH2 – C ~S CoA

Oβ 123

n คร้ัง ; CH3 CO.SCoA = n + 1

ODD – CARBON FA :

CH3 – CH2 – CH2 – CH2 – CH2 - CH2– C ~S CoA

O12

1. PROPIONYL CoA + n ACETYL CoA

SUCCINYL CoA

“KREBS”

“TCA”OAA

GLUC.

CO2 + H2O + E

FATE OF PROPIONYL CoA :

CH2 CH3

C ~ S CoA

O

HC CH3

O

C ~ S CoA

COOH

CARBOXYLASE( B7 )

( BIOTIN )

CO2 ATP ADP , Pi

PROPIONYL CoA D – Mt – MALONYL CoA

CHH3C

O

C ~ S CoA

COOH

L – Mt – MALONYL CoA

MUTASE

( B12 )CH2

CH2

CO ~ S CoA

COOH

SUCCINYL CoA

B12 DEF : PROPIONIC ; Mt – MALONIC ACIDACIDEMIA & ACIDURIA

( PERNICIOUS ANEMIA )

RACEMASE

Acyl CoA dehydrogenase1. short-chain acyl CoA dehydrogenase

- oxidised 4 and 6 carbon2. medium-chain acyl CoA dehydrogenase

- oxidised 4- 14 carbon3. long-chain acyl CoA dehydrogenase

- oxidised 12-18 carbon

Medium-chain acyl CoA dehydrogenase deficiency- deficiency of ketone bodies but high in

dicarboxylic acid- fasting hypoglycemia

sudden infant death syndrome- avoid excessive fasting

hyhoglycin from unripened akee fruit inhibits acyl CoA DH

hypoglycemia

Vomiting, convulsion, coma, death(Jamaican vomiting sickness)

BETA - OXIDATION

C16S CoA

1234567 β O

PALMITIC ACID Ac. CoA ( n+1 ); n = BETA - OXIDATION

OLEIC ACID : C18 : 1▲9 CIS-

O

S CoA

123918CIS

S CoA + 3 Ac. CoA

312▲3 - CIS -

OO

S CoA212▲2 - TRANS -

6Ac. CoA

ISOMERASE

SAT.

UNSAT. double bond at an odd-numbered carbon

UNSAT. double bond at an even-numbered carbon

CoA

POLYUNSAT.

Acyl CoA DH

cis

β-oxidation of very long chain fatty acid - Peroxisome

- Membrane transport is unknown

- Peroxisomal oxidation differs from β-oxidation inthe initial dehydrogenase reaction

- FADH2 of acyl dehydrogenase in peroxisome transfers electron to O2 to yield H2O2

- Catalase is needed to convert H2O2 into H2O and O2

- Subsequent steps are identical with β-oxidation

H2O + 1/2O2

catalase

Acyl-CoA DH

hydratase

DH

β-ketothiolase

Zellweger syndrome (cerebrohepatorenal syndrome)

- in the family of leukodystrophies

- result from the defect in the import of enzymes intoperoxisome

- characterized by liver, kidney, brain and muscle abnormalities

- Death by age six to twelve

Symptoms-Enlarged liver

- Lack of muscle tone, an inability to move, suck and/or swallow

- Glaucoma (ตอหิน)

- Mental retardation, seizure

- albuminuria

พลังงานจากการสลายกรดไขมัน

กรดไขมันแตละชนดิ ใหพลังงานไมเทากัน ขึ้นอยูกับจํานวนคารบอน และ unsaturation

ตัวอยาง

1. การสลายกรด palmitic ; ( กรดไขมันอิ่มตัวมีคารบอน 16 ตัว ) ได 106 ATP

C 16 : 0

palmitoyl CoACH3 – CH2 – CH2 – CH2 – CH2 - CH2 – CH2 – C ~S CoA

8 acetyl CoA

16 CO2

Activation

β - oxidation x 7

TCA cycle x 8

AMP

(FADH2 + NADH) x 7 = 4 ATP x 7

(3NADH + FADH2) x 8 = 10 ATP x 8

+ GTP

- 2 ATP

28 ATP

80 ATP

Net = 106 ATP

2. การสลายกรด stearic ; ( กรดไขมันอ่ิมตัวมีคารบอน 18 ตัว ) ได 120 ATP C 18 : 0

Activation

β - oxidation x 8TCA cycle x 9

18 CO2

AMP - 2 ATP

4 ATP x 8 32 ATP10 ATP x 9 90 ATP

Net = 120 ATP

3. กรดไขมันไมอ่ิมตวั จะเปนไปตามปกติจนกวาจะถึงพันธะคู

ของกรดไขมัน ซ่ึงเปนแบบ cis จะตองมีเอนไซมอ่ืนชวยเปล่ียนใหเปนแบบ

trans เพื่อใหเอนไซมตัวท่ี 2 ของ β - oxidation ทํางานได เน่ืองจากมี

พันธะคูแลว จึงไมได FADH2 (1.5 ATP) ทําใหไดพลังงานนอยลง 1.5 ATP ตอ 1พนัธะคู

^

α - OXIDATION OF FATTY ACIDS :

- MICROSOME, PEROXISOME, MITO. (HEART , LIVER , OTHERS)

- BRANCHED , α-OH – FA ( CEREBROSIDE in brain)

CH3 CH2 CH2 COOH CH3 CH2 COOH + CO2

COOH ( PHYTANIC ACID )

PHYTOL ( CHLOROPHYLL IN GREEN VEGETABLE )

O

COOH

OHCOOH

OOH + CO2

O

αHydroxylase , Vc(monooxygenase) , 4H-biopterin

O2

H2O

H2

H2

REFSUM’S DISEASE (phytanic acid storage disease)-hydroxylase deficiency -slowly progressive peripheral neuropathy with weakness and muscle wasting, combined with blindness-avoid green vegetables

OxidasePristanic acid

Isobutyryl CoA 3 Acetyl CoA 3 Propionyl CoA

α-OH – FA

ω - OXIDATION OF FATTY ACID :

- LIVER MICROSOME

- MEDIUM , LONG CHAIN FA.

- OXYGENASE SYSTEM :

ANIMAL : CYT. P 450 , NADPH2

BACT : RUBRIDOXIN : HC , DETERGENT

COOHH3Cω

α

H2C

OH

HCO

HOCO

COOH

COOH

COOH

O2

β -

FA OXIDATION : β - α - ω -

1. SITE mito microsome

2. ORGAN general general, brain L , other

3. P’ way major minor

4. FA even , odd Br , OH - MC , LCsat , unsat

5. ENZYME multi oxygenase( hydroxylase )

6. PRODUCTS : Ac. CoA FA ( - 1C ) ω -Propionyl CoA + CO2 DI - COOH

7. NEXT O : TCA β - β -^( KREBS )

LIPOLYSIS

-liver

-mitochondrial matrix

-significant amount of HMG-CoA synthase

-HMG CoA synthase is a rate-limiting enzyme

-stimulated by fasting, dietary fat, insulin deficiency

KETOGENESIS

KETOLYSIS

EXTRAHEPATIC TISSUES

-brain, heart, kidney, skeletal tissue

-mitochondrial matrix

-significant amount of β-ketoacyl-CoA transferase

(thiophorase)

KETOGENESIS AND KETOLYSIS

Myocardial ischaemia

reduced O2

anaerobic glycolysis

lactate increase

cell acidosis

β−oxidation

acetyl CoA increase

ketone bodies increase

cell acidosis

trimetazidine inhibits β-ketothiolase in β-oxidation

inhibits fatty acid oxidationincreases carbohydrate oxidation

reduces lactate production

higher cell pH

reduces angina pectoris (chest pain)

FA SYNTHESIS : cyto , ACP palmitic acid

Acetyl CoA + 7 malonyl CoA + 14 NADPH2

Palmitic Acid (C16) + 8 CoA + 14 NADP+ + 7 CO2 + 6 H2O

-liver, lactating mammary gland-cytosol

A. Production of cytosolic acetyl CoA

B. Carboxylation of acetyl CoA to form malonyl CoA

CONTROL OF FATTY ACID SYNTHESIS

NADH, Citrate activates acetyl CoA carboxylase

Long chain fatty acyl CoA inhibits acetylCoA carboxylase

C. Major sources of NADPH required for fatty acid synthesis

1. Pentose phosphate pathway (major)

2. NAD(P)+ - dependent malate dehydrogenase (malic enzyme) (minor)

D. Fatty acid synthesis

Palmitoyl thioesterase (TE) Liberation of palmitate product

TE

TE

FATTY ACID SYNTHESIS

transferase

transacetylasesynthase

FATTY ACID SYNTHESIS

TE

1. MITO : SAT. ; Ac. CoA

2. MICROSOME : SAT. , UNSAT. ; Mal. CoA

R CH2 COSCoA + 2 NADPH2 + ACETYL CoA ( MITO )

R (CH2)3 COSCoA + 2 NADP+ + CoA

FA ELONGATION :

FA DESATURATION : SAT. FA UNSAT. FA

- MICROSOME ; ER of liver , adipose tissue

- MONOXYGENASE SYSTEM : NADPH2 , O2

CH3 – (CH2)7 – CH2 – CH2 – (CH2)7 –COOH + NADPH2 , O2

CH3 – (CH2)7 – CH = CH – (CH2)7 –COOH + NADP+ + 2H2O

DESATURATION OF FATTY ACID

non-heme iron

FATTY ACID SYNTHESIS IN PLANT AND ANIMAL

(in mammals)

essential fatty acid deficiency- dermatitis- poor wound healing

EPA and DHAsupport neuraland visual development

Linoleic, C 18:2 9, 12 α - Linolenic, C 18:3 9, 12, 15

(C 18:2n-6) (C 18:3n-3)

γ- Linolenic, C 18:3 6, 9, 12 C 18:4 6, 9, 12, 15

6 - desaturase

(C 18:3n-6) (C 18:4n-3)elongase

Dinorno - y - linolenic, C 20:3 8, 11, 14 C 20:4 8, 11, 14, 17

(C 20:3n-6) (C 20:4n-3)

Arachidonic, C 20:4 5, 8, 11, 14 Eicosapentaenoic, C 20:5 5, 8, 11, 14, 17

5 - desaturase

(C 22:4n-6) (C 20:5n-3)

elongase

C 22:4 7, 10, 13, 16 C 22:5 7, 10, 13, 16, 19

(C 20:4n-6) (C 22:5n-3)

(C 22:5n-6) (C 22:6n-3)C 22:5 4, 7 10, 13, 16 C 22:6 4, 7, 10, 13, 16, 19

4 -desaturase

-2H

C2

C2

-2H

-2H

EPA

DHA

FISH OIL

Docosahexaenoic

C2+2C3

(Ac.CoA) C2 C2 - C (MALONYL CoA)

ATP + CO2

CO22NADPH2

C2 - C2

2NADPH2

CO2

C2 - C2 - C2

3

2

1

2CO2

CH3- CH2 - CH2 - CH2 - CH2 COOH C6 : 0

C6 : 1 3 CH3 CH2 - CH = CH - CH2 COOH + C2

C8 : 1 5 CH3 CH2 - CH = CH - CH2 CH2 CH2 COOH

3 2 1

5 4 3 2 1

DESATURATION : -H2 , NADPH2STEARIC ; CH3 : -(CH2)7 - CH2 - CH2 - (CH2) 7 COOH (C18 : 0)

OLEIC ; CH3 : -(CH2)7 - CH = CH - (CH2)7 COOH (C18 : 1 9)9 PLANT -2H ANIMAL, คน

LINOLEIC(ω-6) C18 : 2 9, 12 C18:2 6 , 9 (ω-9)

(ω-3) -2HLINOLENIC C18 : 3

9, 12, 15 C18 : 3 3, 6, 9

6 5 4 3 2 1

SUMMARY OF FA SYNTHESIS + ELONGATION

Triacylglycerol synthesis

Glycerol phosphate production

1. Liver and adipose tissuesynthesized from dihydroxyacetone phosphate (DHAP) by glycerol phosphate dehydrogenase

2. Liversynthesized from glycerol by glycerol kinase

SYNTHESIS OF GLYCEROL 3 - PO4

LIVER ONLYLIVER AND ADIPOCYTE

INSULIN

3. Conversion of free fatty acid to its activated form

- Attached to CoA by fatty acyl CoA synthetasebefore participating in TG synthesis

4. Fate of TG

- TG is stored in adipose tissue and serves as depot fat - TG in liver is exported in the form of lipoprotein particles called VLDL and secreted into the blood to the peripheral tissue

adipocyte (visceral fat)

adipocytokines (adipokines)- plasminogen activator inhibitor-1 (PAI-1)- tumor necrosis factor-α (TNF- α)

: thrombosis and insulin resistance- adiponectin

: insulin-sensitizing, anti-atherogenic effect

- interleukin-6 (IL-6)- monocyte chemotactic protein-1(MCP-1)

: inflammation: กระตุน NADPH oxidase

reactive oxygen species (ROS)

T2DM, CAD, cancer

• NEFA ยับยั้ง glycosis ในกลามเนื้อ และกระตุน

gluconeogenesis ท่ีตับ ทําใหเกดิ hyperglycemia

Insulin resistance

T2DM

Fatty liverก. steatosis โดยเฉพาะในตับ ทําใหเกดิ insulin

resistance ยังไมมีอาการของตับ

risk factor 1. DM2. protein mulnutrition3. hypertension4. obesity5. anoxia6. alcohol7. cell toxin

Alcohol and FA synthesis

Ethanol + NAD+

Acetaldehyde + NADH

Acetyl CoA+ NADH

Alcohol DH

Aldehyde DH

ข. non-alcoholic steatohepatitis (NASH)มีอาการตับอักเสบเรื้อรังเกิดจาก TNF-α ทีไ่มไดเกิดจาก

hepatitis B, C, alcohol หรือรับประทานยา

Cholesterol synthesis

- cholesterol is the least soluble membrane lipid

- only important membrane steroid in animals

- most of it are in the form of “free” (unesterified)cholesterol in cellular membrane

- brain contains large amounts of cholesterol

- brain is considered as unhealthy kind of food

- also used for synthesized steroid hormones and bile salts

Steroid hormones

– Progestins (Progesterone)

– Glucocorticoids (Cortisol)

– Mineralocorticoids ( Aldosterone)

– Androgens (Testosterone)

– Estrogens (Estradiol)

CHOLESTEROL SYNTHESIS- occur in liver and intestine- cytosol, ER

CHOLESTEROLSYNTHESIS

Regulation of cholesterol synthesis- HMG CoA reductase is allosteric enzyme

- feedback-inhibited by free cholesterol- insulin stimulates HMG CoA reductase

HMG CoA REDUCTASE INHIBITORS

- liver- intestine

EXOGENOUSDIET

CHOLESTEROLสมองไขแดงตับเนยหอยนางรม

ไขมันสัตวกะทิ

CHOLESTEROL

ENDOGENOUS

SYNTHESIS PERIPHERALLIVER C2 TISSUEINTESTINE

LDL-RECEPTOR

SAT. FA

HORMONES:STEROIDSEXCELL MEMB.

CATABOLISM

BILE ACIDS

EXCRETION

COPROSTEROL

FECES

HMG CoA REDUCTASE INHIBITORS

RESIN

CHOLESTEROL METABOLISM

Plant sterols

-inhibit cholesterol absorption

-found in cereal and vegetables (most)fruit (less)

CBH MET. IN LIVER

LIPID MET. IN LIVER

DIABETES MELLITUS

1.IDDM: INSULIN DEPENDENT

2.NIDDM: INSULIN INDEPENDENT

LIPID METABOLISM IN DIABETES

MELLITUS

KETOLYSIS( Is dependent,indirect )

CHOLESTEROL