de novo synthesis of Fats from Carbohydrates

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One of the interesting questions about macronutrient balance is: how

much saturated fat is created from carbohydrates in the diet?

Here is an article that gives us a good idea:

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=507644

J Clin Invest. 1996 November 1; 98(9): 2008–2017.

Contributions of de novo synthesis of fatty acids to total

VLDL-triglyceride secretion during prolonged

hyperglycemia/hyperinsulinemia in normal man.

A Aarsland, D Chinkes, and R R Wolfe

Metabolism Unit, Shriners Burns Institute and University of Texas

Medical Branch, Galveston 77550, USA.

Triglycerides (TG) are synthesized in the liver principally from two

sources of fatty acids (FA): FA synthesized de novo in the liver and

preformed FA. We have measured the rate of secretion of de novo

synthesized FA and total secretion of FA bound to VLDL-TG in healthy

men (n = 5) in the basal state, and after 1 (day 1) and 4 d (day 4) of

a hypercaloric carbohydrate diet (approximately 2.5 times energy

expenditure) that generated a moderate endogenous hyperinsulinemia

(plasma insulin approximately 60 microU/ml). Prolonged carbohydrate

hyperalimentation/hyperinsulinemia increased plasma VLDL-TG

approximately 10-fold in part due to a 3.4-fold increase in total

VLDL-TG secretion rate (basal state = 72+/-23, day 4 = 242+/-78

micromol TG/kg/d). Although the secretion of de novo synthesized FA

increased throughout the study (basal state = 1.1+/-0.4, day 1 =

15.9+/-7.9, day 4 = 50.0+/-18.8 micromol TG/ kg/d), the 2.7-fold

increase in secretion rate of preformed FA (basal state = 70+/-23, day

4 = 191+/-57 micromol TG/kg/d) quantitatively contributed the most to

total VLDL-TG secretion rate. Decreased catabolism of VLDL-TG also

contributed to the hypertriglyceridemia as reflected by an

approximately fourfold decrease in both fractional turnover rate

(basal state = 9.2+/-3.8, day 1 = 2.1+/-0.2, day 4 = 2.1+/-0.3

pools/d) and rate of clearance (basal state = 0.35+/-0.08, day 1 =

0.11+/-0.01, day 4 = 0.09+/-0.01 liter/kg/d) of VLDL-TG. Thus, the

primary difference between 1 and 4 d of hyperinsulinemia in

conjunction with carbohydrate hyperalimentation is the increase in

hepatic secretion of preformed FA into VLDL-TG.

Tony