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Increased interest in using omega-3 fatty acids led us to examine their metabolic effects in six men with type II (non-insulin-dependent) diabetes mellitus. After 1 month of a diet supplemented with these fatty acids, the patients' fasting glucose rose from 13.1 +/- 1.3 to 15.3 +/- 1.3 mmol/L (P = 0.03) and glucose area during a mixed meal profile rose by 22% (P = 0.04). Basal hepatic glucose output rose from 97 +/- 9 to 122 +/- 8 mg/m2 . min (P = 0.004) but glucose disposal rates measured by euglycemic glucose clamp were unchanged. Fasting insulin levels were similar; peak insulin levels stimulated by meals or intravenous glucagon fell by 30% and 39%, respectively. Plasma and erythrocyte content of omega-3 fatty acid rose significantly. After omega-3 fatty acid withdrawal, fasting glucose returned to baseline. Omega-3 fatty acid treatment in type II diabetes leads to rapid but reversible metabolic deterioration, with elevated basal hepatic glucose output and impaired insulin secretion but unchanged glucose disposal rates. Caution should be used when recommending omega-3 fatty acids in type II diabetic persons.

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Subjects with overt non-insulin-dependent diabetes mellitus (NIDDM) were studied in comparison to obese nondiabetic control subjects and patients with subclinical diabetes. Pancreatic insulin secretion rates were measured by deconvolution of peripheral C-peptide over a 24-h period while subjects consumed an isocaloric mixed diet. Subjects were then placed on caloric restriction for at least 6 weeks, during which time body weight fell by at least 10%. Refeeding with solid mixed meals was then resumed for at least 2 weeks until isocaloric intake was attained, and then the meal profiles were repeated. Before weight loss, insulin, C-peptide, and insulin secretion rates were significantly higher in subjects with subclinical diabetes than in the other two groups. Proinsulin concentrations were significantly greater in the two diabetic groups than in control subjects, but, when expressed as a percentage of the total insulin immunoreactivity, the differences were significant only in the group with overt diabetes. Weight loss because of hypocaloric feeding resulted in a significant increase in the rate of clearance of endogenously secreted insulin but did not affect the clearance of C-peptide. In obese subjects and those with subclinical diabetes, weight loss was associated with a reduction in insulin secretion rates, presumably as a result of improvements in insulin sensitivity. In patients with overt diabetes and hyperglycemia, weight loss improved beta-cell responsiveness to glucose and was associated with an increase in insulin clearance and a reduction in proinsulin immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)