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Shaikh Articles > N-3 polyunsaturated fatty acid, lipid microclusters, and Vit E > Flashcards

N-3 polyunsaturated fatty acid, lipid microclusters, and Vit E Flashcards

1
Q

lipid rafts

A

cholesterol-dependent signaling or sphingolipid-cholesterol-enriched microdomains that compartmentalize signalling proteins

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2
Q

cholesterol-dependent signaling or sphingolipid-cholesterol-enriched microdomains that compartmentalize signalling proteins

A

lipid rafts

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3
Q

lipid rafts are generally nanoscale, but can form micron scale domains upon ?

A

receptor ligation

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4
Q

N-3 PUFA directly binding G-protein coupled receptor (GPR) 120 results in ?

A

anti-inflammatory effects in macrophages important in regulating insulin signaling in obesity

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5
Q

N-3 PUFA acyl chains, upon enzymatic release from the membrane, regulate eicosanoid production and can serve as precursors for the synthesis of lipid mediators known as ?, ? and ?

A

resolvins, protectins, and maresins

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6
Q

downstream of the plasma membrane, n-3 PUFAs exert their effects by targeting ? to modify gene expression

A

transcription factors

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7
Q

presence of multiple double bonds in n-3 PUFA acyl chains gives a high/low degree of conformational freedom

A

high

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8
Q

Our understanding of DHAs structure comes from ? and ?

A

2H NMR (experimental) and MD simulations (computational)

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9
Q

In NMR studies, DHA is typically esterified to PC or PE in the ? position while palmitic or stearing acid occupies the ? position

A

DHA occupies sn-2. palmitic or stearing acid occupies the sn-1 position

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10
Q

the fundamental property that distinguishes n-3 PUFA from less unsaturated fatty acids

A

tremendously high disorder

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11
Q

origin of disorder in n-3 PUFAs

A

low energy barrier about C-C single bonds in the repeating units that link C=C double bonds

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12
Q

indicative of low microviscosity, order parameters measured by solid state 2H NMR throughout almost all of the DHA chain in the sn-2 position are large/small

A

small. S_CD ~ 0.01

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13
Q

order within the stearic acid chain at the sn-1 position is increased/decreased by the presence of DHA in sn-2 position

A

decreased order (~10%)

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14
Q

reduction in stearic acid order as a result of DHA is more significant in the upper/lower half

A

lower half

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15
Q

rapid isomerization of DHA chain. explores entire conformational space in ?

A

~ 10 nanoseconds

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16
Q

DHA MD simulations reveal bent configurations where ____

A

terminal methyl group approaches hydrophobic-philic and redistribution of the lower portion of DHA chains toward the interface

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17
Q

DHA acyl chains generally increase/decrease microviscosity (to different degrees in different cell types)

A

decrease

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18
Q

DHA effects on physical properties of bilayers

A

reduced membrane thickness, increased compressibility, permeability, fusion and flip-flop

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19
Q

DHA has high/low affinity for cholesterol

A

low affinity

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20
Q

rapid interconversion between torsional states undergone by PUFAs pushes the rigid steroid moiety away was shown by ?

A

low solubility and binding coefficients for cholesterol in polyunsaturated membranes

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21
Q

PUFA induced reduction in cholesterol affinity is more significant in PE or PC? why?

A

PE. tighter packing associated with smaller headgroup brings sterol and PUFA closer together

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22
Q

sphingolipid had high/low affinity for cholesterol. why?

A

high affinity. saturated and adopt largely linear conformation

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23
Q

in the extreme case of bilayers comprised of phospholipids with a PUFA chain at both sn-1 and sn-2 positions, sterol can be forced into an unusual position where?

A

deep within the interior of the bilayer

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24
Q

DHA remodels lipid raft-like domains that are nano-sized in a manner that is dependent upon the ____ headgroup. How was this observed?

A

phospholipid. observed using solid state 2H NMR, DSC, and detergent extraction experiments

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25
Q

Majority of PDPE was found to segregate into domains high/low in SM and cholesterol

A

low

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26
Q

introduction of cholesterol increased/decreased the order of PDPE more significantly than that seen with POPE. How was this observed?

A

increased. From 2H NMR spectra for analogs of PE perdeuterated in the sn-1 chain at 40 C

27
Q

More than 3x as much PDPE (70%) as POPE (22%) was isolated in detergent soluble (nonraft) fractions while almost all of the cholesterol and SM (>90%) were isolated in detergent resistant (raft) fractions. How was this observed?

A

detergent extraction experiments

28
Q

PDPC was shown to directly infiltrate into SM and cholesterol rich domains. This was observed using?

A

2H NMR (williams 2012)

29
Q

what is the significance of the formation of inverted hexagonal (Hii) phase that becomes accentuated with increasing levels of acyl chain saturation

A

??? (Dekker, Kessel, Klomp 1983)

30
Q

XX% of EPA containing PC was found in raft-like domains compared to 70% for DHA containing PC. Conclusion?

A

40% of EPA PC. DHA PC is more likely to incorporate into lipid rafts and disrupt organization

31
Q

DRMs and DSMs are isolated from ____ and used to represent native rafts and nonrafts

A

sucrose gradient fractions of cells subjected to low levels of detergent at cold temperature

32
Q

the most common approach to studying n-3 PUFAs and lipid rafts with DRM and DSM fractions is to either _____ or _____

A

either treat imortal cells with EPA or DHA or provide animals diets rich in EPA or DHA

33
Q

Most prevalent change resulting from n-3 PUFA uptake? consequence?

A

arachidonic acid levels decrease. AA itself is a disordered PUFA and its loss could make membrane more packed. Also numerous lipid mediators are derived from AA.

34
Q

Effect of n-3 PUFA uptake on cholesterol

A

cholesterol is displaced between DRM and DSM fractions. However, no clear consensus on direction of movement

35
Q

In response to DHA treatment, cholesterol levels increase in ____ fractions and decrease in ____ fractions

A

DEPENDS! sometimes cholesterol moves between DRMs and DSMs in either direction, sometimes can selectively lower with no increase in the other

36
Q

clustering of GM1 molecules is diminished in cell culture treated with DHA/EPA

A

DHA

37
Q

what is cholera toxin subunit b used for in GM1 molecules

A

artificial means of inducing lipid rafts on a micron scale

38
Q

translational studies with splenic B220+ B cells show that dietary administration of _____ to animals diminished GM1 clustering in a dose dependent manner

A

n-3 PUFAs

39
Q

polarization microscopy experiments revelaed that n-3 PUFAs enhanced/diminished membrane packing in B and T lymphocytes

A

enhanced

40
Q

fat-1 transgenic mice have high/low levels of endogenous n-3 PUFAs. why?

A

high levels due to a desaturase that converts n-6 to n-3

41
Q

it was shown that lipid raft accumulation in the immunological synapse was high/low for fat-1 mice compared to control mice

A

accumulation high for fat-1 mice

42
Q

consequence of accumulation in the immunological synapse

A

suppressed helper CD4+ Th1 cell activation (potential health benefits in murine models)

43
Q

work in B cells and EL4 lymphomas showed that crosslinking of GM1 microdomains with cholera toxin subunit b had this effect on membrane packing?

A

enhanced membrane packing with dietary n-3 PUFAs compared to cells not cross-linked with cholera toxin

44
Q

EPA and DHA ethyl esters (modeling prescription supplements) differentially enhanced membrane packing upon formation of lipid microdomains induced by ?

A

lowering the temperature of cells to 4 C

45
Q

n-3 PUFAs MAY be redistributing cholesterol in a manner that increases/decreases formation of lipid rafts

A

increases

46
Q

it is possible/not possible that the effects of n-3 PUFAs are independent of cholesterol

A

possible

47
Q

disrupting lipid raft microdomains in B and T lymphocytes can displace key proteins and suppress function. This has potential health benefits for these types of diseases?

A

inflammatory diseases including rheumatoid arthritis, renal transplant, or metabolic diseases

48
Q

In B cells, MHC II molecules are displaced from raft-enriched regions of the immunological synapse by n-3 PUFAs. This was observed using ?

A

confocal and acceptor photobleaching FRET studies. Similar observation for MHC I molecules.

49
Q

In CD4+ T cells, protein kinase C and phospholipase C gamma-1 were displaced from raft-like membranes by n-3 PUFAs. This was observed using ?

A

biochemical DRM/DSM fractionations and confocal imaging

50
Q

n-3 PUFAs generally have a preference for incorporation into ?

A

PE’s rather than PC’s

51
Q

what might happen when n-3 PUFAs incorporate into PC’s

A

PC’s are abundant in lipid rafts. this may force cholesterol out of the lipid rafts and into non-raft regions making them more raft like

52
Q

what might happen when n-3 PUFAs incorporate into PE’s

A

rafts are generally not enriched in PE’s. n-3 PUFA acyl chains may force cholesterol to move into rafts and make them more packed

53
Q

n-3 PUFAs phase seperate from liquid-ordered lipid raft -like domains when incorporated into ?

A

incorporated into PE’s

54
Q

n-3 PUFAs incorporate directly into liquid liquid-ordered rafts when esterified to ?

A

esterified to PC’s

55
Q

aside from phospholipids, what else might n-3 PUFAs esterify to ?

A

SM (shown in murine) or cholesterol (shown in cholesterol esters. low membrane solubility)

56
Q

the major lipid soluble antioxidant

A

Vitamin E (alpha tocopherol)

57
Q

advantage of n-3 PUFA-vitamin E clusters?

A

could explain how low levels of Vit E can protect relatively large amounts of n-3 PUFA from oxidation

58
Q

chromanol group of Vit E generally resides here?

A

near the hydrophobic-philic interface of bilayers

59
Q

DMPC location in bilayer

A

in center at the water interface independent of headgroup or acyl chains

60
Q

emerging evidence for sphingolipid enriched cholesterol-free domains comes from ?

A

high res mass spectrometry

61
Q

emerging evidence for sphingolipid enriched cholesterol-free domains comes from ?. What was observed?

A

high res mass spectrometry in cell culture. labelled sphingolipids form micron size domains that are not disrupted by cholesterol depletion. However, they were effectd by disruption of the cytoskeleton.

62
Q

helper t-cells isolated from fat-1 transgenic mice or from mice fed DHA displayed a 50% reduction in phosphatidylinositol 4,5-bisphosphate which contributed toward?

A

diminished actin remodeling and thereby T cell activation

63
Q

___ and ___ delay opening of the mitochondrial permeability transition pore in the rat myocardium.

A

EPA and DHA

Shaikh Articles (5 decks)

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