From a total of 22 hypertriglyceridemic subjects tested, 14 subjects were selected on the basis of normal postheparin plasma lipoprotein lipase (LPL) levels and the presence of LPL inhibitory activity in their fasting plasma. The inhibitory activity was detected in both the lipoprotein fraction (d < 1.25 g/ml) and the lipo~protein-deficient fraction (d > 1.25 g/ml).Correlational analyses of LPL inhibitory activity and apolipoprotein levels present in the lipoprotein fraction (d < 1.25 g/ml)indicated that only apolipoprotein C-III (ApoC-III) was significantly correlated (r = 0.602, P < 0.05) with the inhibition activity of the lipoprotein fraction. Furthermore, it was found that LPL-inhibitory activities of the plasma lipoprotein fraction and lipoprotein-deficient fraction were also correlated (r = 0.745, P < 0.005), though the activity in the lipoprotein-deficient plasma was not related to the ApoC-III or apolipoprotein E levels. Additional correlational analyses indicated that the LPL levels in the postheparin plasma of these subjects were inversely related to the levels of plasma apolipoproteins C-II, C-III, and E. To explain some of these observations, we directly examined the in vitro effect of ApoC-III on LPL activity. The addition of ApoC-III-2 resulted in a decreased rate of lipolysis of human' very low density lipoproteins by LPL. Kinetic analyses indicated that ApoC-III-2 was a noncompetitive inhibitor of LPL suggesting a direct interaction of the inhibitor with LPL. Results of these studies suggest that ApoCIII may represent a physiologic modulator of LPL activity levels and that the incidence of LPL inhibitory activity in the plasma of hypertriglyceridemic subjects is more common than previously recognized.

Diabetes mellitus secondary to pancreatic diseases (especially chronic pancreatitis) seems more common than generally believed with a prevalence of 9.2% among the subjects studied here. Because the awareness of this diabetes type is poor, misclassification is quite frequent. A common problem seems to be the differentiation between type 2 and type 3. Yet, the right classification of diabetes mellitus is important, because there are special therapeutic options and problems in patients with diabetes secondary to pancreatic diseases.

Exocrine pancreatic insufficiency is frequently associated with diabetes, with high prevalence in both insulin-dependent or insulin-independent patients. Exocrine pancreatic failure has often been perceived as a complication of diabetes. In contrast, recent clinical observations lead to the notion that nonendocrine pancreatic disease is a critical factor for development rather than a sequel to diabetes. The incidence of diabetes caused by exocrine pancreatic disease appears to be underestimated and may comprise 8% or more of the general diabetic patient population. Nonendocrine pancreas disease can cause diabetes by multiple mechanisms. Genetic defects have been characterized, resulting in a syndrome of both exocrine and endocrine failure. Regulation of β-cell mass and physiological incretin secretion are directly dependent on normal exocrine function. Algorithms for diagnosis and therapy of diabetes should therefore address both endocrine and exocrine pancreatic function.

Pancreatin therapy can be used safely in patients with diabetes mellitus and exocrine dysfunction. Parameters of glucose metabolism were not improved by enzyme replacement therapy.

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