Date Published: January 26, 2017
Publisher: Public Library of Science
Author(s): Zayed D. Alsharari, Ulf Risérus, Karin Leander, Per Sjögren, Axel C. Carlsson, Max Vikström, Federica Laguzzi, Bruna Gigante, Tommy Cederholm, Ulf De Faire, Mai-Lis Hellénius, Matti Marklund, Alberico Catapano.
Abdominal obesity is a key contributor of metabolic disease. Recent trials suggest that dietary fat quality affects abdominal fat content, where palmitic acid and linoleic acid influence abdominal obesity differently, while effects of n-3 polyunsaturated fatty acids are less studied. Also, fatty acid desaturation may be altered in abdominal obesity. We aimed to investigate cross-sectional associations of serum fatty acids and desaturases with abdominal obesity prevalence in a population-based cohort study. Serum cholesteryl ester fatty acids composition was measured by gas chromatography in 60-year old men (n = 1883) and women (n = 2015). Cross-sectional associations of fatty acids with abdominal obesity prevalence and anthropometric measures (e.g., sagittal abdominal diameter) were evaluated in multivariable-adjusted logistic and linear regression models, respectively. Similar models were employed to investigate relations between desaturase activities (estimated by fatty acid ratios) and abdominal obesity. In logistic regression analyses, palmitic acid, stearoyl-CoA-desaturase and Δ6-desaturase indices were associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals) for highest versus lowest quartiles were 1.45 (1.19–1.76), 4.06 (3.27–5.05), and 3.07 (2.51–3.75), respectively. Linoleic acid, α-linolenic acid, docohexaenoic acid, and Δ5-desaturase were inversely associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals): 0.39 (0.32–0.48), 0.74 (0.61–0.89), 0.76 (0.62–0.93), and 0.40 (0.33–0.49), respectively. Eicosapentaenoic acid was not associated with abdominal obesity. Similar results were obtained from linear regression models evaluating associations with different anthropometric measures. Sex-specific and linear associations were mainly observed for n3-polyunsaturated fatty acids, while associations of the other exposures were generally non-linear and similar across sexes. In accordance with findings from short-term trials, abdominal obesity was more common among individuals with relatively high proportions of palmitic acid, whilst the contrary was true for linoleic acid. Further trials should examine the potential role of linoleic acid and its main dietary source, vegetable oils, in abdominal obesity prevention.
Abdominal obesity (AO) is a strong predictor of cardiometabolic disease  and some cancer types[2, 3]. In particular, visceral obesity is a potential driver of insulin resistance and metabolic disorders. The prevalence of AO is increasing [5, 6] and although genetic factors are influential, AO is largely determined by lifestyle . Thus, lifestyle factors including diet might be key modifiable risk factors of AO[8, 9]. High intake of dietary fats has long been considered to promote AO, while recent studies suggest that the fatty acid (FA) compositing may be more important for modulating fat deposition and fat distribution [9, 10]. Diets high in saturated fatty acids (SFA) may promote the development of AO and metabolic syndrome [9–11], whereas high intake of polyunsaturated fatty acids (PUFA) may counteract body fat accumulation [9, 10]. In particular, linoleic acid (LA, 18:2n-6) and palmitic acid (PA, 16:0) have been reported to be associated with the degree of fat accumulation in both visceral and subcutaneous adipose tissue . Apart from the potential role of dietary FA in AO, enzymes metabolizing FA may influence body fat storage, body weight, waist circumference, and obesity . Stearoyl-CoA desaturase (SCD), Δ5-desaturase (D5D), and Δ6-desaturase (D6D) are together with elongases the main enzymes responsible for endogenous synthesis of monounsaturated FA and PUFA . While SCD synthesizes monounsaturated FA from SFA, D5D and D6D catalyze the synthesis of long-chain PUFA, e.g., eicosapentaenoic acid (EPA) and docohexaenoic acid (DHA), from the two essential fatty acids, LA and α-linolenic acid (ALA).
The present study represents the largest cross-sectional study to date investigating the relationships between serum FA as biomarkers of dietary fat quality and AO in men and women. In line with current dietary guidelines, the results suggest that higher intake of PUFA, n-6 in particular, is associated with lower AO. A higher proportion of PA in serum was associated with higher prevalence of AO, whilst the contrary was found for serum LA. Associations between n-3 PUFA and AO were in general weaker and partly sex-specific.
Serum proportions of fatty acids, partly reflecting dietary fat intake, were associated with abdominal obesity in this large-scale population-based study and the associations were to some extent sex-specific. The most abundant serum fatty acid, linoleic acid, was strongly and inversely associated with abdominal obesity in both men and women. Contrary, a high serum proportion of palmitic acid, a major saturated fatty acid, was linked to higher odds of abdominal obesity and greater levels of all anthropometric measures. Docohexaenoic acid and α-linoleic acid were inversely associated with AO, in a partly sex-specific manner. Overall, these findings support those of recent interventional and experimental studies suggesting that a higher relative intake of polyunsaturated fatty acids (especially linoleic acid) from vegetable oils, associates with decreased abdominal adiposity. These findings are therefore coherent with current dietary guidelines regarding partial replacement of saturated fats with polyunsaturated fatty acids, especially in the light of the high and increasing prevalence of abdominal obesity and related diseases (e.g., diabetes and cardiovascular disease). In accordance with previous studies, fatty acid desaturase activities were altered in people with abdominal obesity.