Abstract
Recent studies have highlighted the role of palmitoleic acid [16:1n-7 (cis-9-hexadecenoic acid)] as a lipid hormone that coordinates cross-talk between liver and adipose tissue and exerts anti-inflammatory protective effects on hepatic steatosis and insulin signaling in murine models of metabolic disease. More recently, a 16:1n-7 isomer, cis-7-hexadecenoic acid (16:1n-9), that also possesses marked anti-inflammatory effects, has been described in human circulating monocytes and monocyte-derived macrophages. By using gas chromatographic/mass spectrometric analyses of dimethyl disulfide derivatives of fatty acyl methyl esters, we describe in this study the presence of a third 16:1 isomer, sapienic acid [16:1n-10 (6-cis-hexadecenoic acid)], in phagocytic cells. Cellular levels of 16:1n-10 appear to depend not only on the cellular content of linoleic acid, but also on the expression level of fatty acid desaturase 2, thus revealing a complex regulation both at the enzyme level, via fatty acid substrate competition, and directly at the gene level. However, unlike 16:1n-7 and 16:1n-9, 16:1n-10 levels are not regulated by the activation state of the cell. Moreover, while 16:1n-7 and 16:1n-9 manifest strong anti-inflammatory activity when added to the cells at low concentrations (10 μM), notably higher concentrations of 16:1n-10 are required to observe a comparable effect. Collectively, these results suggest the presence in phagocytic cells of an unexpected variety of 16:1 isomers, which can be distinguished on the basis of their biological activity and cellular regulation.
Highlights
Recent studies have highlighted the role of palmitoleic acid [16:1n-7] as a lipid hormone that coordinates cross-talk between liver and adipose tissue and exerts anti-inflammatory protective effects on hepatic steatosis and insulin signaling in murine models of metabolic disease
Aside from, or in addition to, these biophysical effects, there appears to be something else to 16:1n-7 that makes it unique in terms of biological activity, leading to the concept of this fatty acid serving as a lipid hormone or “lipokine” that coordinates metabolic responses between tissues [1, 2]
We have previously shown that human monocytes and macrophages contain significant amounts of 16:1n-9, an unusual isomer of 16:1n-7 [14]
Summary
Recent studies have highlighted the role of palmitoleic acid [16:1n-7 (cis-9-hexadecenoic acid)] as a lipid hormone that coordinates cross-talk between liver and adipose tissue and exerts anti-inflammatory protective effects on hepatic steatosis and insulin signaling in murine models of metabolic disease. Recent studies have revealed that in animal models of metabolic disease, the adipose tissue releases the monounsaturated fatty acid, palmitoleic acid [16:1n-7 (cis-9hexadecenoic acid)], which suppresses hepatic steatosis and improves insulin sensitivity in the whole body [1, 2]. This fatty acid has taken the spotlight as a promising antiinflammatory lipid that may help to ameliorate metabolic disorders [1, 2]. A recent study has found a positive correlation between circulating 16:1n-7 levels and markers of inflammation in young healthy Canadians [13]
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