LIPID METABOLISM

Metabolism (Catabolism and

Anabolism), Regulation and

Importance of fatty acids (FÂ)

and lipids and clinical applications

FÂ -Saturated FÂ

-Unsaturated FÂ -Monounsaturated FÂ

-Polyunsaturated FÂ

-Eicosanoids

Lipids

Storage lipids ; Fat, oils

Membrane lipids Phospholipids

Glycolipids

Cholesterol

Precursor & derived lipids Sterols

Polyprenoid 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

+

+

+

+

-

secretes

secretes

secretes

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

pancreas

pancreatic juice

bile

defective cells

liver

small 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&LC-FA (30% in adults and 50% in infants) 2.2 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

2.5 lingual lipase

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 CHAIN

3. SAT. VS.VS. UNSAT. :

SAT. : palmitic acid ( C16 : 0 )

stearic acid ( C18 : 0 )

CH3 CH2 CH2 CH2 CH2 CH2 CH2 COOH

UNSAT. : oleic acid ( C18 : 1▲9 )

palmitoleic acid ( C16 : 1▲9 )

LINOLEIC LINOLENIC ARACHIDONIC

18 : 2▲9,12 18 : 3▲9,12,15

20 : 4▲5,8,11,14

FATTY ACID OXIDATION :

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

3 ways : - (major) ; - & - (minor)

STEPS :

activation : 2ATP (cyto -)

GTP (FAs in mito -, severe starvation)

transfer ( cyto mito ) - carnitine

- 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

Activation: cytosol

Translocation: matrix

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 and is stimulated by long chain fatty acyl 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)BETA – OXIDATION (not found in nerve and red cells)

FA R – CH2 – CH2 – CH2 – C - OH

O

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

(-)

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

O 123

n ครั้��ง ; 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 ACID

ACIDEMIA & ACIDURIA

( PERNICIOUS ANEMIA )

RACEMASE

Acyl CoA dehydrogenase 1. short-chain acyl CoA dehydrogenase - oxidised 4 and 6 carbon 2. medium-chain acyl CoA dehydrogenase - oxidised 4- 14 carbon 3. long-chain acyl CoA dehydrogenase - oxidised 12-18 carbon

Medium-chain acyl CoA dehydrogenase deficiency - deficiency of ketone bodies but high in dicarboxylic acid (use ω-oxidation instead) - 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 - OXIDATIONBETA - OXIDATION

C16S CoA

1234567 O

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

OLEIC ACID : C18 : 1▲9 CIS-

O

S CoA

123918

CIS

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

5

POLYUNSAT.

Acyl CoA DH

cis

-oxidation of very long chain fatty acid

- Peroxisome

- Membrane transport is unknown

- Peroxisomal oxidation differs from β-oxidation in the 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 into peroxisome and cause defects in peroxisomal β-oxidation leading to accumulation of very long chain fatty acid in plasma and tissue body

- 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 (ต้�อหิ�น)

- Mental retardation, seizure

- albuminuria

พลั�งงานจากการั้สีลัายกรั้ดไขมั�นพลั�งงานจากการั้สีลัายกรั้ดไขมั�น กรั้ดไขมั�นแต่�ลัะชน�ด ให้�พลั�งงานไมั�เท่�าก�น ข��นอย �ก�บจ"านวน

คารั้$บอน แลัะ unsaturationต่�วอย�าง1. การั้สีลัายกรั้ด palmitic ; ( กรั้ดไขมั�นอ�%มัต่�วมั�คารั้$บอน 16 ต่�ว

) ได� 106 ATP C 16 : 0

palmitoyl CoA

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

8 acetyl CoA

16 CO2

Activation

- oxidation x 7

TCA cycle x 8

AMP

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

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

- 2 ATP

28 ATP

80 ATP

Net = 106 ATP

2. การั้สีลัายกรั้ด stearic ; ( กรั้ดไขมั�นอ�%มัต่�วมั�คารั้$บอน 18 ต่�ว ) ได� 120 ATP

C 18 : 0

Activation

- oxidation x 8

TCA cycle x 9

18 CO2

AMP - 2 ATP

4 ATP x 8 32 ATP

10 ATP x 9 90 ATP

Net = 120 ATP

3. กรั้ดไขมั�นไมั�อ�%มัต่�ว จะเป็(นไป็ต่ามัป็กต่�จนกว�าจะถึ�งพ�นธะค � ของกรั้ดไขมั�น ซึ่�%งเป็(นแบบ cis จะต่�องมั�

เอนไซึ่มั$อ,%นช�วยเป็ลั�%ยนให้�เป็(นแบบ trans เพ,%อให้� เอนไซึ่มั$ต่�วท่�% 2 ของ - oxidation ท่"างานได�

เน,%องจากมั�พ�นธะค �แลั�ว จ�งไมั�ได� FADH2 (1.5 ATP) ท่"าให้�ได� พลั�งงานน�อยลัง 1.5 ATP ต่�อ 1 พ�นธะค �

^

- OXIDATION OF FATTY ACIDS :

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

- BRANCHED CHAIN FA , -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

Hydroxylase , Vc

(dioxygenase) , 4H-biopterin

O2

H2O

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

dehydrogenase

Pristanic acid

Isobutyryl CoA 3 Acetyl CoA 3 Propionyl CoA

-OH – FA

Lyase + oxidation

+ O2

CO2

- OXIDATION OF FATTY ACID :

- LIVER MICROSOME

- MEDIUM , LONG CHAIN FA.

- OXYGENASE SYSTEM :

ANIMAL : CYT. P 450 , NADPH2

BACT : RUBRIDOXIN : HC , DETERGENT

COOHH3C

H2C

OH

HC

O

HOCO

COOH

COOH

COOH

O2

-

FA OXIDATION : - - -

1. SITE mito microsome

2. ORGAN general general, brain L , others

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 ) -

Propionyl CoA + CO2 DI - COOH

7. NEXT O : TCA - -^ ( KREBS )

LIPOLYSIS

summary

-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 -

ketoacyl-CoA transferase

(thiophorase)*

- stimulated by fasting, dietary

fat, insulin deficiency

*

KETOGENESIS AND KETOLYSIS

Myocardial ischaemia

reduced O2

anaerobic glycolysis

lactate increase

cell acidosis

-oxidation

acetyl CoA increase

ketone bodies increase

cell acidosis

trimetazidine inhibits -ketothiolase in -oxidation

inhibits fatty acid oxidationincreases carbohydrate oxidation

reduces lactate production

higher cell pH

reduces angina pectoris (chest pain)

FA SYNTHESIS : cytosol , 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, adipose tissue

Note: ACP = acyl carrier protein

A. Production of cytosolic acetyl CoA

fat

B. Carboxylation of acetyl CoA to form malonyl CoA

CONTROL OF FATTY ACID SYNTHESIS

NADH, Citrate activates acetyl CoA carboxylaseLong chain fatty acyl CoA inhibits acetyl CoA 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. FA ; Ac. CoA

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

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

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

FA ELONGATION :

elongase

3. PEROXISOME : VERY LONG CHAIN FA : Ac. CoA

Peroxisome are required for normal brain development and function and formation of myelin, the whitest substance that coats the nerve fiber and are also required for normal eye, liver, kidney and bone functions. Defects called Zellweger syndrome.

β-trans-Enoyl-CoA reductase

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

desaturase

desaturase

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

Eicosanoidssynthesis

(ω6-series)

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

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

- 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 22:5n-3)

elongase

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

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

Fish oil benefit (ω3-series) - supports brain and retina development - slow or prevent progression of osteoarthritisby inhibition : proteoglycan (aggrecan) degrading enzyme(aggrecanase) : expression of inflammation- inducible cytokines - IL-1α - TNF-α - cyclooxygenase-2 (COX-2) not COX-1

Function of COX

- constitutive COX-1 : cytoprotective stomach : renal function : platelet homeostasis : vascular tone of endothelium

- inducible COX-2

: เกี่ยวข้�องกี่�บกี่ารอ�กี่เสบ ทำ�าใหิ�ปวด บวม ร�อน

Note: COX เป็(นเอนไซึ่มั$ท่�%เป็ลั�%ยน arachidonic acid ให้�เป็(น PGs ชน�ดต่�างๆ มั�ต่�วย�บย��งค,อ aspirin and NSAIDs

C2+2C3

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

ATP + CO2

CO2

2NADPH2

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 , NADPH2 , O2

STEARIC ; 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) -2H

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

6 5 4 3 2 1

SUMMARY OF FA SYNTHESIS + ELONGATION

Triacylglycerol (fat) 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 through apo B-100 in the form of lipoprotein particles called VLDL and secreted into the blood to the peripheral tissue

Tg, triglyceride; CE, cholesterol ester; FC, free cholesterol; Pl, phospholipid

Apo C-II

C Apo C-III

VLDL

adipocyte (visceral fat)

adipocytokines (adipokines)

- plasminogen activator inhibitor-1 (PAI-1)- tumor necrosis factor-α (TNF- α) : induce inflammation

: thrombosis and insulin resistance

- adiponectin: insulin-sensitizing, anti-atherogenic effect

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

: inflammation

: กี่ระต้��น NADPH oxidase

reactive oxygen species (ROS)

T2DM, CAD, liver cancer

Obesity

Elevated levels of fatty acids

- increase oxidative stress via NADPH oxidase activation

- decrease antioxidant enzymes

• NEFA (nonesterified fatty acid or free fatty acid) ย�บย��ง glycolysis ในกี่ล้�ามเน��อ แล้ะกี่ระต้��น gluconeogenesis ทำต้�บ ทำ�าใหิ�เกี่�ด hyperglycemia

Insulin resistance

T2DM

Fatty liverก. steatosis โดยเฉพาะในต้�บ ทำ�าใหิ�เกี่�ด insulin

resistance ย�งไม%มอากี่ารข้องต้�บrisk factors

1. DM

2. protein mulnutrition

3. hypertension

4. obesity

5. anoxia

6. alcohol

7. cell toxin

Alcohol and FA synthesis

Ethanol + NAD+

Acetaldehyde + NADH

Acetyl CoA+ NADH

Alcohol DH

Aldehyde DH, NAD+

ข. non-alcoholic steatohepatitis (NASH)มอากี่ารต้�บอ�กี่เสบเร��อร�งเกี่�ดจากี่ TNF-α ทำไม%ได�

เกี่�ดจากี่เชื้��อ hepatitis B, C, alcohol หิร�อร�บประทำานยา

Treatment - reduce weight by diet control - follow healthy diet - increase physical activity - avoid alcohol - avoid unnecessary medications - metformin and orlistat may be used - take antioxidants

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

*

- liver- intestine

HMG CoA REDUCTASE INHIBITORS

Plant sterols

- inhibit cholesterol absorption

- found in cereals and vegetables (most), fruit (less)

EXOGENOUS DIET

CHOLESTEROL

สีมัองไข�แดงต่�บเนยห้อยนางรั้มั

ไขมั�นสี�ต่ว$กะท่�

CHOLESTEROL

ENDOGENOUS

SYNTHESIS PERIPHERALLIVER C2 TISSUEINTESTINE

LDL-

RECEPTOR

SAT. FA

HORMONES:

STEROID

SEX

CELL MEMB.

CATABOLISM

BILE ACIDS

EXCRETION

COPROSTEROL

FECES

HMG CoA REDUCTASE INHIBITORS

RESIN

CHOLESTEROL METABOLISM

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