Effect of industrially produced trans fat on markers of systemic inflammation: evidence from a randomized trial in women.

Consumption of industrially produced trans fatty acids (IP-TFA) has been positively associated with systemic markers of low-grade inflammation and endothelial dysfunction in cross-sectional studies, but results from intervention studies are inconclusive. Therefore, we conducted a 16 week double-blind parallel intervention study with the objective to examine the effect of IP-TFA intake on biomarkers of inflammation, oxidative stress, and endothelial dysfunction. Fifty-two healthy overweight postmenopausal women (49 completers) were randomly assigned to receive either partially hydrogenated soybean oil (15.7 g/day IP-TFA) or control oil without IP-TFA. After 16 weeks, IP-TFA intake increased baseline-adjusted serum tumor necrosis factor (TNF) α by 12% [95% confidence interval (CI): 5-20; P = 0.002] more in the IP-TFA group compared with controls. Plasma soluble TNF receptors 1 and 2 were also increased by IP-TFA [155 pg/ml (CI: 63-247); P < 0.001 and 480 pg/ml (CI: 72-887); P = 0.02, respectively]. Serum C-reactive protein, interleukin (IL) 6 and adiponectin and subcutaneous abdominal adipose tissue mRNA expression of IL6, IL8, TNFα, and adiponectin as well as ceramide content were not affected by IP-TFA, nor was urinary 8-iso-prostaglandin-F(2α). In conclusion, this dietary trial indicates that the mechanisms linking dietary IP-TFA to cardiovascular disease may involve activation of the TNFα system.

Effect of trans-fatty acid intake on insulin sensitivity and intramuscular lipids--a randomized trial in overweight postmenopausal women.

Intake of industrially produced trans-fatty acids (TFA) has been linked to increased risk of type 2 diabetes mellitus in observational studies. We investigated the causality of this association by examining if a high intake of TFA impairs measures of glucose homeostasis and induces intramuscular lipid deposition in abdominally obese women. In a double-blind, parallel dietary intervention study, 52 healthy but overweight postmenopausal women were randomized to receive either partially hydrogenated soybean oil (15 g/d TFA) or a control oil (mainly oleic and palmitic acid) for 16 weeks. Three markers of glucose homeostasis and 4 markers of lipolysis were derived from glucose, insulin, C-peptide, nonesterified fatty acid, and glycerol concentrations during a 3-hour frequent sampling oral glucose tolerance test. Intramuscular lipids were assessed by magnetic resonance spectroscopy. Forty-nine women completed the study. Insulin sensitivity (assessed by ISI(composite)), ß-cell function (the disposition index), and the metabolic clearance rate of insulin were not significantly affected by the dietary intervention. Neither was the ability of insulin to suppress plasma nonesterified fatty acid and glycerol during oral glucose ingestion nor the intramuscular lipid deposition. In conclusion, high TFA intake did not affect glucose metabolism over 16 weeks in postmenopausal overweight women. A study population with a stronger predisposition to insulin resistance and/or a longer duration of exposure may be required for insulin sensitivity to be affected by intake of industrial TFA.