American Journal of Clinical Nutrition, Vol. 87, No. 4, 1067,
April 2008
© 2008 American Society for Nutrition
Reply to T Okada et al
Sonsoles Morcillo,
Gemma Rojo-Martínez and
Federico Soriguer
Servicio de Endocrinología y Nutrición
Hospital Universitario Carlos Haya
CIBER de Diabetes y Metabolismo (CB07/08/0019)
CIBER de Obesidad (CB06/03/1022)
Málaga 29009
Spain
E-mail: sonsoles.morcillo.exts{at}juntadeandalucia.es
Dear Sir:
First, we thank Okada et al for their interest in our article. In a study of 32 obese children (1), they found that the content of arachidonic acid (AA) in fasting plasma and the delta-6 desaturase (D6D) activity estimated by the (18:3+20:3)/18:2 ratio were significantly lower in Thr54Thr carriers than in Ala54Thr or Ala54Ala carriers. This finding is interesting, because it provides information about the role played by the various fatty acid desaturases in the risks of obesity and the metabolic syndrome (2-4). However, clinical and epidemiologic studies on fatty acid desaturase activity cannot be evaluated without also considering diet and the metabolic status of the study subjects (2). In our study, we (5) examined the fatty acid composition of the plasma phospholipids and used an analysis of variance model to evaluate the association between the fatty acid composition and the Ala54Thr polymorphism of the FABP2 gene. The main variable was FABP2 polymorphism (Ala54Ala, Ala54Thr, or Thr54Thr), and the independent variables were sex, obesity [body mass index (BMI; in kg/m2) > 30], the presence of a carbohydrate metabolism disorder (eg, impaired fasting glucose, impaired glucose tolerance, or type 2 diabetes), and the type of dietary cooking oil (olive or sunflower), with age as a covariable. The variance in saturated fatty acids and n–3 fatty acids in the plasma phospholipids was explained by age (P = 0.02 and P < 0.0001, respectively), whereas the variance in the n–6 fatty acids was explained by the type of dietary fatty acids (P = 0.001). The Ala54Thr polymorphism contributed significantly to the explanation for the variance in the monounsaturated fatty acids of the plasma phospholipids (P = 0.02) and the delta-9-desaturase activity (measured by the 16:0/16:1 ratio) (P = 0.01) after adjustment for age, sex, the presence of obesity, the type of oil consumed, and the presence of any carbohydrate metabolism disorder (Table 1
). The D6D activity, however, measured by the AA/18:2 ratio, was explained by the type of dietary fatty acid (P = 0.02) and age (P = 0.02), but not by Ala54Thr polymorphism. The study was undertaken within the context of an epidemiologic study representative of a culturally homogeneous ethnic population for whom 20% of dietary calories come from the consumption of monounsaturated fatty acids (6), and with the cases and the controls coming from the same population, thereby avoiding the possibility of selection bias. The results highlight the difficulty of speaking about fatty acid desaturase activity independently of information about the type of dietary fatty acid and about the metabolic status.
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TABLE 1. Plasma phospholipid fatty acid composition (%) according to the Ala54Thr polymorphism of the FABP2 gene1
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ACKNOWLEDGMENTS
None of the authors had a personal or financial conflict of interest.
REFERENCES
- Okada T, Sato NF, Kuromori Y. Thr-encoding allele homozygosity at codon 54 of FABP2 gene may be associated with impaired delta-6 desaturase activity and reduced plasma arachidonic acid in obese children. J Atheroscler Thromb 2006;13:192–6.[Medline]
- Soriguer F, Rojo-Martínez G, de Fonseca FR, García-Escobar E, García Fuentes E. Obesity and the metabolic syndrome in Mediterranean countries: a hypothesis related to olive oil. Mol Nutr Food Res 2007;51:1260–7.[Medline]
- Warensjö E, Ohrvall M, Vessby B. Fatty acid composition and estimated desaturase activities are associated with obesity and lifestyle variables in men and women. Nutr Metab Cardiovasc Dis 2006;16:128–36.[Medline]
- Flowers MT, Miyazaki M, Liu X, Ntambi JM. Probing the role of stearoyl-CoA desaturase-1 in hepatic insulin resistance. J Clin Invest 2006 Jun;116:1478–81.[Medline]
- Morcillo S, Rojo-Martínez G, Cardona F, et al. Effect of the interaction between the fatty acid–binding protein 2 gene Ala54Thr polymorphism and dietary fatty acids on peripheral insulin sensitivity: a cross-sectional study. Am J Clin Nutr 2007;86:1232–7.[Abstract/Free Full Text]
- Soriguer F, Morcillo S, Cardona F, et al. Pro12Ala polymorphism of the PPARG2 gene is associated with type 2 diabetes mellitus and peripheral insulin sensitivity in a population with a high intake of oleic acid. J Nutr 2006;136:2325–30.[Abstract/Free Full Text]
