Effects of n-6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: A randomized controlled trial

Department of Public Health, Uppsala University, Uppsala, Sweden.
American Journal of Clinical Nutrition (Impact Factor: 6.77). 04/2012; 95(5):1003-12. DOI: 10.3945/ajcn.111.030114
Source: PubMed

ABSTRACT Replacing SFAs with vegetable PUFAs has cardiometabolic benefits, but the effects on liver fat are unknown. Increased dietary n-6 PUFAs have, however, also been proposed to promote inflammation-a yet unproven theory.
We investigated the effects of PUFAs on liver fat, systemic inflammation, and metabolic disorders.
We randomly assigned 67 abdominally obese subjects (15% had type 2 diabetes) to a 10-wk isocaloric diet high in vegetable n-6 PUFA (PUFA diet) or SFA mainly from butter (SFA diet), without altering the macronutrient intake. Liver fat was assessed by MRI and magnetic resonance proton (1H) spectroscopy (MRS). Proprotein convertase subtilisin/kexin type-9 (PCSK9, a hepatic LDL-receptor regulator), inflammation, and adipose tissue expression of inflammatory and lipogenic genes were determined.
A total of 61 subjects completed the study. Body weight modestly increased but was not different between groups. Liver fat was lower during the PUFA diet than during the SFA diet [between-group difference in relative change from baseline; 16% (MRI; P < 0.001), 34% (MRS; P = 0.02)]. PCSK9 (P = 0.001), TNF receptor-2 (P < 0.01), and IL-1 receptor antagonist (P = 0.02) concentrations were lower during the PUFA diet, whereas insulin (P = 0.06) tended to be higher during the SFA diet. In compliant subjects (defined as change in serum linoleic acid), insulin, total/HDL-cholesterol ratio, LDL cholesterol, and triglycerides were lower during the PUFA diet than during the SFA diet (P < 0.05). Adipose tissue gene expression was unchanged.
Compared with SFA intake, n-6 PUFAs reduce liver fat and modestly improve metabolic status, without weight loss. A high n-6 PUFA intake does not cause any signs of inflammation or oxidative stress. Downregulation of PCSK9 could be a novel mechanism behind the cholesterol-lowering effects of PUFAs. This trial was registered at as NCT01038102.

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Available from: Ulf Risérus, Sep 27, 2015
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    • "Indeed, a direct association was found between CRP and TNF-R2. One could speculate that apart from a role of dietary fiber as indicated above, a reduction in saturated fat and increase in polyunsaturated fat might lower certain systemic inflammation markers [24], possibly by influencing inflammatory gene expression An increased intake of fish might also inhibit inflammatory process, although the evidence is inconsistent [28]. "
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    • "The small sample size and short study duration with limited statistical interpretation may reduce the strength of findings. In addition, Bjermo et al. (2012) reported that n-6 PUFA decreased plasma IL-1RA and TNF-R2 concentrations compared with a SFA-enriched diet after a 10-week iso-caloric dietary intervention in 61 abdominally obese individuals [75]. n-6 PUFA (from sunflower oil) was exchanged at 10% en with SFA derived predominantly from butter. "
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