ABSTRACT
We investigated the metabolic effects of omega-6 (safflower oil) and omega-3 (fish oil) fatty acid-enriched diets (65% carbohydrate, 20% fat) in two patients with a syndrome of diabetes mellitus, lipodystrophy, acanthosis nigricans, chylomicronemia, and abdominal pain. 3H-glycerol was used to evaluate triglyceride-rich lipoprotein-triglyceride (TRLP-TG) metabolism, and changes in glucose and insulin dynamics were also studied. On the omega-6 diet, both subjects demonstrated four- to five-times normal rates of TRLP-TG production and glycerol biosynthesis, and striking decrements in the fractional catabolic rate (FCR) for TRLP-TG and TRLP-particles. Both subjects had elevations in nonesterified fatty acid (NEFA) concentrations. In one patient, the omega-3 diet markedly decreased serum triglycerides and newly synthesized triglyceride glycerol production, in association with a fall in NEFA. In both subjects, plasma glycerol reutilization for triglyceride synthesis, normal on the omega-6 diet, was abolished on the omega-3 regimen. Plasma postheparin lipolytic activity was normal on both diets. On the omega-3 diet, xanthomas and hepatomegaly decreased and, in the patient who had no reduction in serum triglycerides, pancreatitis attacks virtually ceased. Mean 24-hour serum glucose levels were higher, and both basal and peak C-peptide responses to a carbohydrate meal were blunted on the omega-3 diet. One patient became ketonuric. We conclude the cause of hypertriglyceridemia in these patients was due to increased lipid synthesis and hypothesize that this is secondary to high plasma concentrations of NEFA. In addition, an omega-3 diet in these subjects inhibited insulin secretion and worsened glucose tolerance.
