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NIA0004
Unsaturated fatty acids diminish the detrimental effects of saturated fatty acids on insulin signalling in human muscle by decreasing de novo ceramide production
Author(s) -
Sabin MA,
Holly JMP,
Hunt LP,
Turner SJ,
Grohmann MJ,
Crowne EC,
Stewart CEH,
Shield JPH
Publication year - 2006
Publication title -
obesity reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.845
H-Index - 162
eISSN - 1467-789X
pISSN - 1467-7881
DOI - 10.1111/j.1467-7881.2006.00280_10.x
Subject(s) - ceramide , medicine , endocrinology , palmitic acid , insulin , intracellular , sphingolipid , fumonisin b1 , chemistry , apoptosis , fatty acid , lipid signaling , biology , biochemistry , enzyme , food science , mycotoxin
Objective: Fatty acids (FAs) are raised in obesity and saturated FAs have adverse effects on insulin signalling. We investigated this further using in vitro differentiated myotubes derived from 6 normal‐weight prepubertal children. Methods: We examined the effect of 24‐hour exposure to 750 μ M palmitate, and/or 2000 μ M oleate on the phosphorylation of the key insulin‐signalling molecule AKT (pAKT) in response to 100ng/mL insulin (by Western immunoblotting). We then determined whether palmitate must be metabolized to have its effect (using bromopalmitate – a non‐metabolizable form of palmitate) and whether a ceramide synthase inhibitor (Fumonisin B1) could block palmitate‐induced effects. Intracellular ceramide levels were then quantified by Thin Layer Chromatography and radiolabelling studies were utilized to assess the effects of oleate on palmitate‐induced ceramide production. Results: Palmitate significantly decreased insulin‐stimulated pAKT (mean (SEM) %change vs. control; −38.7% (11.7); P < 0.001), whilst oleate was without effect (−1.8% (14.0); P = 0.55). Together, oleate reversed the reduction seen with palmitate alone (+35.6% (18.4); P = 0.27). Bromopalmitate did not cause a similar decrease in pAKT (+10.7% (5.6); P = 0.23) and addition of 1 μ M Fumonisin B1 prevented the palmitate‐induced effects. 750 μ M palmitate led to a 2.2 fold increase in intracellular ceramide levels while only minimal increases were seen with bromopalmitate/oleate. Radiolabelling studies demonstrated that the addition of 375 μ M oleate to 375 μ M 14 C‐palmitate led to a significant decrease in de novo 14 C‐ceramide production compared to palmitate alone (101.6 (21.6) vs. 371.5(122.4); P < 0.001). Conclusions: These data suggest that saturated FAs have detrimental effects on insulin signalling in human muscle, by promoting de novo ceramide production, and that unsaturated FAs confer a degree of protection against these effects.