Effects of n-3 fatty acids in subjects with type 2 diabetes: reduction of insulin sensitivity and time-dependent alteration from carbohydrate to fat oxidation.
BACKGROUND
Effects of fish oil supplements on metabolic variables are insufficiently clarified in type 2 diabetes.


OBJECTIVE
We aimed to investigate short-term (1 wk) and longer-term (9 wk) effects of n-3 fatty acids.


METHODS
Twenty-six subjects with type 2 diabetes without hypertriacylglycerolemia participated in a double-blind controlled study. Median intake in the intervention group was 17.6 mL fish oil/d (1.8 g 20:5n-3, 3.0 g 22:6n-3, and 5.9 g total n-3 fatty acids). The control group received 17.8 mL corn oil/d (8.5 g 18:2n-6).


RESULTS
Plasma phospholipid 20:5n-3 and 22:6n-3 increased, whereas 18:2n-6 decreased, in the fish oil group compared with the corn oil group after 1 wk. The two n-3 fatty acids also increased in adipose tissue biopsy samples taken after 9 wk in the fish oil group. Glucose concentrations (home-monitored) were approximately 1 mmol/L higher in the fish oil group than in the corn oil group at the end of the intervention (P = 0.035). Glucose utilization measured by using an isoglycemic clamp was lowered in the fish oil group compared with that in the corn oil group at the end of the intervention (P = 0.049), whereas glucagon-stimulated C-peptide tended to increase (P = 0.078). The fish oil group utilized less fat for oxidation after 1 wk, with a change to more fat and less carbohydrate oxidation after 9 wk (P = 0.040), than did the corn oil group.


CONCLUSIONS
A high intake of fish oil moderately increases blood glucose and decreases insulin sensitivity in persons with type 2 diabetes without hypertriacylglycerolemia and alters carbohydrate and fat utilization in a time-dependent manner.
Mostad
Ingrid L
IL
Department of Cancer Research and Molecular Medicine, Faculty of Medicine, St Olavs Hospital, Trondheim, Norway. ingrid.l.mostad@ntnu.no
Bjerve
Kristian S
KS
Bjorgaas
Marit R
MR
Lydersen
Stian
S
Grill
Valdemar
V
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000187:drug effects / Q000502:physiology*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism*; D004042:Dietary Fats, Unsaturated / Q000378:metabolism*; D019587:Dietary Supplements; D004311:Double-Blind Method; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage*; D005260:Female; D005395:Fish Oils; D015309:Glucose Clamp Technique; D006487:Hemostasis / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010743:Phospholipids / Q000097:blood; D013997:Time Factors
D001786:Blood Glucose; D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D005395:Fish Oils; D007328:Insulin; D010743:Phospholipids