Re: The Skinny on Fats FA oxidation/ synthesis

[Guest guest]

Since our enlightenment by Tony and now you, I have delved into Lehninger's "Principles of biochemistry".

Pg 594/595 show what happens to palmitic acid. "Since fatty acids are not stored as such but only as triacylglycerols, the concentration of glycerol phosphate, a required precursor in the synthesis of triacylglycerols, can control fatty acid synthesis." {A feedback control mechanism. Possibly the one that fails and makes us fat.}

Pg 594, Palmitic and stearic serve as precursors of the two most common monosaturated fatty acids of animal tissues namely, palmitoleic acid (16 carbons) and oleic (18 carbons) acid....."

Pg 597, Regulated by Hormones

"In normal human adults and in animals triacylglyerol biosynthesis and oxidation occur simultaneously in a steady state, so the amount of body fat stays relatively constant over long periods, although there may be minor short-term changes as the caloric intake fluctuates. However, if carbohydrate, fat, or protein is consumed in excess above normal energy needs, the excess calories are stored in the form of triacylglycerols."

"The rate of triacylglycerol biosynthesis is profoundly altered by the action of several hormones. Insulin, eg, promotes...."

pg 518, The first stage of oxidation yields Acetyl-CoA and ATP. Palmitic yields myristic. That can be further reduced in two carbon stages until all the energy is released (seven passes thru the fatty acid oxidation cycle).

It appears the body can make any FA except 18:2 and 18:3. As if we had to guess, regulated by hormones.

Still looking why 18:2 would alter the synthesis or oxidation, but I'm sure it does something in me.

Regards.

----- Original Message -----

From: Francesca Skelton

support group

Sent: Wednesday, March 02, 2005 7:39 AM

Subject: [ ] The Skinny on Fats

By L. Wolke One of the most bizarre phenomena in the world of publishing is theextraordinary success of books purportedly written for dummies and idiots.Readers apparently aren't the least bit insulted by being so labeled. I have been thinking that maybe I should try the dummy-and-idiot techniquein my writing, despite the fact that I am privileged to have the most astutereaders any writer could wish for.But there is one topic that has been crying out for such treatment, becausethe public has not been able to grasp it in any other way.I mean the topic of fats, where mass mystification still reigns.So I hereby offer a sugar coated, deliberately oversimplified explanation"for dummies."May the gods of chemistry and pedagogy forgive me.Shape Matters Like people, different molecules have different shapes. What distinguishesone biochemical molecule from another is mostly its shape. Chemicalreactions occur when the molecules collide. Then they either stick togetherlike jigsaw pieces or break into new shapes.And there you have it: the shortest chemistry course in history. I'm goingto explain all those fatty words in terms of the molecules' differentshapes, because that's what makes them behave differently in our bodies. FAT A fat is a particular type of chemical compound. Its molecules areshaped like a short flagpole with three long, starched streamers or pennantsflying from it. The shapes of fat molecules -- and hence their properties --differ from one another because the streamers themselves are differentshapes. The flagpoles don't count.What we popularly refer to as "a fat" in our diets, such as butter orvegetable oil, is actually a mixture of many kinds of fats. FATTY ACID Those three streamers flying from the flagpole are fatty acids(FAs): long chains of carbon atoms with a couple of oxygen atoms at one end,tying them to the pole. Our bodies' metabolism breaks off the FA streamers,which are absorbed. Their exact shapes are what determine theirhealthfulness.Common FAs include oleic acid, the primary FA in olive oil, and stearicacid, found in animal fats. SATURATED FATTY ACID A saturated FA is one whose molecules are relativelystraight. Saturated FAs are unhealthful because they raise the amounts ofLDL ("bad") cholesterol in our bloodstreams. They are found mostly in animalfats.Butyric acid is a saturated FA found in milk fat (butter). UNSATURATED FATTY ACID An unsaturated FA is one whose molecules containone or more sharp bends or kinks. If an unsaturated FA contains only onekink, it is said to be monounsaturated; if more than one, polyunsaturated.Unsaturated FAs are found mostly in vegetable oils. They do not raisecholesterol levels. Monounsaturated FAs are even considered healthful.Olive oil's oleic acid is a monounsaturated FA. OMEGA-3 and OMEGA-6 FATTY ACIDS These are polyunsaturated FAs that havekinks in their chains at either the third or the sixth carbon atom from theend. Examples are alpha-linolenic acid, an omega-3 FA and linoleic acid, anomega-6 FA.Omega-3 and omega-6 FAs are "essential" FAs because our bodies can'tproduce them. We have to get them from our foods, such as fish oils, walnutoil, flaxseed oil and canola oil. Omega-3 FAs actually reduce our risk ofcoronary disease. HYDROGENATION is a high- temperature, high-pressure process that changeskinky, unsaturated FAs into straight-chain saturated FAs, by forcing a pairof hydrogen atoms into each kink as a splint would support a broken bone.The straightened-out FA molecules can now pack together more compactly,like a bundle of twigs that have had all their crooked twiglets trimmed off.Fats containing these compacted FAs therefore become harder and less fluid.If your soybean- or sunflower-oil margarine hadn't been hydrogenated, youwould be pouring it, rather than spreading it, on your toast. Manufacturersuse hydrogenated oils in virtually every cake, cookie or cracker in yoursupermarket to make it smooth, rather than oily.Partial hydrogenation straightens out only some of the kinks in theunsaturated FA molecules. The rest are left in their bent, unsaturatedshapes. Complete hydrogenation straightens out all the kinks in the FAmolecules, making the fats completely saturated, and that's not good. TRANS FATTY ACID A trans FA is an unsaturated FA that has been subjectedto hydrogenation, but was able to evade the hydrogen atoms and remaindefiantly kinky and unsaturated. However -- and this is the crucialdistinction -- in the fiery cauldron of hydrogenation, its kink has beentwisted into an angle different from that of a normal unsaturated FA.Chemists call this shape of FA a "trans" fatty acid.Trans FAs are rarely found in nature; they are unnatural. When we eat atrans FA, our metabolism is baffled by its alien kinkiness and doesn't knowwhat to do with it. So it vents its frustration not only by raising our LDL("bad") cholesterol level, as saturated FAs do, but also by lowering our HDL("good") cholesterol level. That double whammy is just about the worst thinga fat can do to us.Complete hydrogenation, by the way, as distinguished from partialhydrogenation, does not form trans FAs, because when all of the kinks in anunsaturated FA are straightened out -- no escapees -- there are nounsaturated kinks left, either natural or trans. Not that the resultingsaturated fats aren't harmful, but at least they are not as harmful as transFAs. Trans fatty acids are commonly but erroneously referred to as "trans fats,"but they are not the entire fat molecules. They are merely the fatty-acidparts. The Food and Drug Administration has declared that the only acceptableamount of trans FAs in our diets is zero. Manufacturers don't "add transfats" to foods, as I have seen stated. What they do is use partiallyhydrogenated fats for their desirable properties, and trans FAs are aninevitable result. When you see "partially hydrogenated" on a food label,you can bet that trans FA villains are in there. But if the product containsless than half a gram of trans FAs per serving, the FDA permits the label tosay "No trans fats."On the labels of manufactured foods, the amounts of trans FAs havecustomarily been incorporated into the total amounts of unsaturated FAs. Butbeginning on Jan. 1, 2006, the FDA will require the amounts of trans FAs tobe stated separately. Manufacturers are engaged in a frantic scramble toachieve the benefits of partial hydrogenation without generating theconcomitant trans FAs.As they begin to succeed, we will see more and more food labels flauntingthe words "no trans fats," just as they have flaunted the words "lowcalorie," "low fat," "low sodium" and "low carb."I wonder how long it will be before we see labels reading "contains nothingat all"? L. Wolke is professor emeritus of chemistry at the University ofPittsburgh. He can be reached at wolke@....

[Guest guest]

FYI

2005 American Heart Association, Inc.

Volume 45(3) March 2005 pp 368-373

Dietary Linolenic Acid Is Associated With a Lower Prevalence of Hypertension in the NHLBI Family Heart Study

Abstract—

Dietary linolenic acid has been shown to be associated with coronary artery disease. However, limited data are available on its effects on blood pressure. We used data from 4594 white participants (aged 25 to 93 years) in the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study to evaluate whether dietary linolenic acid was associated with prevalent hypertension and resting blood pressure. We used generalized estimating equations to determine the prevalence odds ratios (ORs) of hypertension and adjusted means of systolic and diastolic blood pressure across quartiles of linolenic acid. Mean dietary linolenic acid intake was 0.81±0.35 g per day for men and 0.69±0.29 g per day for women. From the lowest to the highest quartile of linolenic acid, multivariable adjusted ORs (95% confidence interval [CI]) for hypertension were 1.0 (reference), 0.73 (0.56 to 0.95), 0.71 (0.53 to 0.95), and 0.67 (0.47 to 0.96), respectively (P for trend 0.04), controlling for age, sex, energy intake, body mass index, risk group, study site, education, smoking, alcohol intake, exercise, and history of coronary artery disease and diabetes mellitus. Dietary linolenic acid was related inversely to resting systolic (P for trend 0.03) but not diastolic blood pressure (P for trend 0.43). Linoleic acid, an omega-6 fatty acid, was not associated with prevalent hypertension or blood pressure. These data suggest that dietary linolenic acid is associated with a lower prevalence of hypertension and lower systolic blood pressure in white subjects.

regards.

[Guest guest]

Hi JW:

Great stuff! Is there a way to determine how much palmitic gets

converted to myristic? And does it remain myristic, or get converted

promptly to something else?

Rodney.

--- In , " jwwright " <jwwright@e...>

wrote:

> Since our enlightenment by Tony and now you, I have delved into

Lehninger's " Principles of biochemistry " . ........................

>

> Pg 594, Palmitic and stearic serve as precursors of the two most

common monosaturated fatty acids of animal tissues namely,

palmitoleic acid (16 carbons) and oleic (18 carbons)

acid..... " .....................

> pg 518, The first stage of oxidation yields Acetyl-CoA and ATP.

Palmitic yields myristic. That can be further reduced in two carbon

stages until all the energy is released (seven passes thru the fatty

acid oxidation cycle. ....................