Beneficial effects of fish oil on glucose metabolism in spontaneously hypertensive rats.

1. Increased interest in fish oil led us to examine their metabolic effects in spontaneously hypertensive rats, which have been reported to have glucose intolerance. 2. Rats were divided into three groups: (i) a control group fed standard rat laboratory chow; (ii) a lard group fed a high-fat diet containing 20% lard; and (iii) a fish oil group fed a high-fat diet containing 20% fish oil for 14 weeks. 3. Systolic blood pressure and fasting blood glucose were markedly increased in the lard group, whereas in the fish oil group they were only transiently increased at the beginning and decreased to levels seen in the control group. 4. Intraperitoneal glucose tolerance test demonstrated that fish oil reversed the impairment of glucose disposal found in the lard group. However, plasma insulin levels were raised transiently at 30 min in the fish oil group compared with the control group. 5. Insulin secretion from pancreatic islets stimulated with glucose in vitro was also enhanced by fish oil. 6. These results lead us to conclude that fish oil improves glucose tolerance by enhancing insulin secretion from pancreatic beta-cells.