title: Fish oil supplemented for 9 months does not improve glycaemic control or insulin sensitivity in subjects with impaired glucose regulation: a parallel randomised controlled trial.
abstract: The effects of fish oil (FO) supplementation on glycaemic control are unclear, and positive effects may occur only when the phospholipid content of tissue membranes exceeds 14% as n-3 PUFA. Subjects (n 36, thirty-three completed) were paired based on metabolic parameters and allocated into a parallel double-blind randomised trial with one of each pair offered daily either 6 g of FO (3·9 g n-3 PUFA) or 6 g of maize oil (MO) for 9 months. Hyperinsulinaemic-euglycaemic-euaminoacidaemic (HIEGEAA) clamps (with [6,6 2H2 glucose]) were performed at the start and end of the intervention. Endogenous glucose production (EGP) and whole-body protein turnover (WBPT) were each measured after an overnight fast. The primary outcome involved the effect of oil type on insulin sensitivity related to glycaemic control. The secondary outcome involved the effect of oil type on WBPT. Subjects on FO (n 16) had increased erythrocyte n-3 PUFA concentrations >14%, whereas subjects on MO (n 17) had unaltered n-3 PUFA concentrations at 9%. Type of oil had no effect on fasting EGP, insulin sensitivity or total glucose disposal during the HIEGEAA clamp. In contrast, under insulin-stimulated conditions, total protein disposal (P=0·007) and endogenous WBPT (P=0·001) were both increased with FO. In an associated pilot study (n 4, three completed), although n-3 PUFA in erythrocyte membranes increased to >14% with the FO supplement, the enrichment in muscle membranes remained lower (8%; P<0·001). In conclusion, long-term supplementation with FO, at amounts near the safety limits set by regulatory authorities in Europe and the USA, did not alter glycaemic control but did have an impact on WBPT.
authors.affiliation: 1The Rowett Institute of Nutrition and Health,University of Aberdeen,Aberdeen AB21 9SB,UK.
authors.forename: Louise F
authors.initials: LF
authors.lastname: Clark
authors.affiliation: 1The Rowett Institute of Nutrition and Health,University of Aberdeen,Aberdeen AB21 9SB,UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Thivierge
authors.affiliation: 1The Rowett Institute of Nutrition and Health,University of Aberdeen,Aberdeen AB21 9SB,UK.
authors.forename: Claire A
authors.initials: CA
authors.lastname: Kidd
authors.affiliation: 2Aberdeen Diabetes Centre,Aberdeen Royal Infirmary,Aberdeen AB25 2ZP,UK.
authors.forename: Susan C
authors.initials: SC
authors.lastname: McGeoch
authors.affiliation: 2Aberdeen Diabetes Centre,Aberdeen Royal Infirmary,Aberdeen AB25 2ZP,UK.
authors.forename: Prakash
authors.initials: P
authors.lastname: Abraham
authors.affiliation: 2Aberdeen Diabetes Centre,Aberdeen Royal Infirmary,Aberdeen AB25 2ZP,UK.
authors.forename: Donald W M
authors.initials: DW
authors.lastname: Pearson
authors.affiliation: 3Biomathematics and Statistics Scotland,Aberdeen AB21 9SB,UK.
authors.forename: Graham W
authors.initials: GW
authors.lastname: Horgan
authors.affiliation: 3Biomathematics and Statistics Scotland,Aberdeen AB21 9SB,UK.
authors.forename: Grietje
authors.initials: G
authors.lastname: Holtrop
authors.affiliation: 1The Rowett Institute of Nutrition and Health,University of Aberdeen,Aberdeen AB21 9SB,UK.
authors.forename: Frank
authors.initials: F
authors.lastname: Thies
authors.affiliation: 1The Rowett Institute of Nutrition and Health,University of Aberdeen,Aberdeen AB21 9SB,UK.
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Lobley
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D004042:Dietary Fats, Unsaturated / Q000097:blood / Q000494:pharmacology*; D019587:Dietary Supplements; D004311:Double-Blind Method; D004912:Erythrocytes; D005215:Fasting; D015525:Fatty Acids, Omega-3 / Q000097:blood / Q000494:pharmacology; D005260:Female; D005395:Fish Oils / Q000494:pharmacology*; D005943:Gluconeogenesis / Q000187:drug effects; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D011506:Proteins / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D005395:Fish Oils; D007328:Insulin; D011506:Proteins
keywords: BCAA branched-chain amino acids; EGP endogenous glucose production; FO fish oil; Fish oil; Glycaemic control; HIEGEAA hyperinsulinaemic–euglycaemic–euaminoacidaemic; Insulin sensitivity; MO maize oil; MOP 4-methyl-2-oxo pentanoic acid; Protein metabolism; n-3 PUFA membrane enrichment