Changes in plasma metabolites and glucose homeostasis during omega-3 polyunsaturated fatty acid supplementation in women with polycystic ovary syndrome.

Key Findings

Polyunsaturated fatty acids (PUFA) are powerful modulators of lipid and glucose metabolism with n-3 and n-6 having different and usually opposing actions. Previous research from this group assessed the effects fish, flaxseed and soybean oils on glucose homeostasis in polycystic ovary syndrome (PCOS), which affects young women. Most are insulin resistant and have metabolic syndrome. One third of patients have glucose intolerance; and one out of five develops type 2 diabetes before the age of 40 years. In this study, insulin resistance and secretion were determined using oral and frequently sampled intravenous glucose tolerance tests (OGTT and FS-IGT, respectively). Unexpectedly, fish and soybean oils caused similar changes in glucose homeostasis. The authors speculate that these oils improved impairments of branched chain amino acid (BCAA) and aromatic AA metabolism characteristic in insulin resistance and obesity. The findings suggest that the n-3 PUFA act differently in altering glucose homeostasis indirectly. However, the small sample size and wide range of BMI of the study subjects reduced the power for detection of several of the changes in glucose homeostasis parameters.

ABSTRACT

BACKGROUND: Both fish (FO) and flaxseed oils (FLX) are n-3 polyunsaturated fatty acids (PUFA). Fish oil contains long chain while FLX contains essential n-3 PUFA. We demonstrated that FO altered insulin secretion and resistance in polycystic ovary syndrome (PCOS) women but FLX did not. Surprisingly, the effects of FO were similar to those of the n-6 PUFA-rich soybean oil (SBO). Since increased branched chain (BCAA) and aromatic amino acids (AA) affect insulin secretion and resistance, we investigated whether FO, FLX and /or SBO affect plasma metabolites, especially AA. METHODS AND FINDINGS: In this six-week, randomized, 3-parallel arm, double-blinded study, 54 women received 3.5 g/day FO, FLX or SBO. In 51 completers (17 from each arm), fasting plasma metabolites were measured at the beginning and at the end. As compared to FLX, FO and SBO increased insulin response and resistance as well as several BCAA and aromatic AA. Pathway analysis indicated that FO exerted the largest biochemical impact, affecting AA degradation and biosynthesis, amine, polyamine degradation and alanine, glycine, l-carnitine biosynthesis and TCA cycle, while FLX had minimal impact affecting only alanine biosynthesis and l-cysteine degradation. CONCLUSION: Effects of FO and SBO on plasma AA were similar and differed significantly from those of the FLX. The primary target of dietary PUFA is not known. Dietary PUFA may influence insulin secretion and resistance directly and alter plasma AA indirectly. Alternatively, as a novel concept, dietary PUFA may directly affect AA metabolism and the changes in insulin secretion and resistance may be secondary.