Conference summary and future directions.
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Biomedical subjects
Publications and source records attributed to J Dyerberg.
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The section for preventive cardiology within the Danish Society for Cardiology has established a lipid group with representatives from The Danish Society for Clinical Chemistry, The Danish Society for Internal Medicine, The Danish Society for Cardiology, The Danish Society of Hypertension, The Danish College of General Practitioners, and The Danish Paediatric Society. The lipid group has elaborated recommendations for clinical chemical departments regarding lipid and lipoprotein analyses. The group suggests that doctors ordering lipid and lipoprotein analyses are offered the following: S-Cholesterol (total), substance conc., (fPt)S-Triglycerides, substance conc., S-HDL-cholesterol, substance conc., and (fPt)S-LDL-cholesterol, substance conc. (calculated). It is recommended that the biological variation be minimized by sampling in a sitting position after a 15 minutes' rest and by basing the clinical decision on a minimum of 2-3 determinations with an interval of about one month. The analytical variations should be reduced to below 3% (calculated as the variation coefficient), and it is recommended that laboratories participate in external quality control systems at least four times annually by reporting at least two human reference materials with different concentrations. As the use of reference intervals dependent on age and sex, based on random samplings of the background population, are less informative, it is recommended to refer to cutoff values for the clinical decision. The following cutoff values are recommended: S-Cholesterol (total), substance conc.: 6 mmol/l, (fPt)S-Triglycerides, substance conc.; 2.5 mmol/l, S-HDL-cholesterol, substance conc.: 0.9 mmol/l (fPt)-LDL-cholesterol, substance conc. (calculated): 4.5 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)
Twenty-five fish oil products commercially available in Denmark were examined for their content of n-3 fatty acids. The magnitude of n-3 fatty acid intake was calculated when the dosage recommended by the manufacturers was adhered to. Where the majority of the products were concerned, the intake was much less than the approximately 2 g daily which produces demonstrable effect. Where isolated preparations are concerned, the intake is so limited that this has probably no value. The content of oxidation products in the preparations was also investigated. Compared with the quantity of oxidation products from other sources, the content in the preparations examined is of minor significance.
We have studied the dose-response effects of dietary supplementation with n-3 polyunsaturated fatty acids (n-3 PUFA's) on lipids and haemostasis. Ten healthy males were each given 1.3 g, 4 g or 9 g of n-3 PUFA's daily for 6-week periods. Bleeding time, HDL-cholesterol and plasminogen activator inhibitor increased with the dose of n-3 PUFA. Plasma fibrinogen and triglyceride levels were reduced in a dose-dependent fashion. After ingestion of 1.3 g of n-3 PUFA's plasma fibrinogen decreased from 9 to 7 mumol/l and HDL-cholesterol increased from 1.2 to 1.3 mmol/l. The bleeding time was prolonged from 5 to 6.5 min while triglyceride levels decreased from 1.2 to 0.9 mmol/l after ingestion of 4 g of n-3 PUFA's. Dietary supplementation with the highest daily dose (9 g) reduced plasma levels of triglycerides, fibrinogen and von Willebrand factor, while bleeding time, plasminogen activator antigen, plasminogen activator inhibitor and the ratio of HDL-cholesterol to total cholesterol increased.
We have studied the effect of dietary supplementation with 4 g of n-3 polyunsaturated fatty acids (n-3 PUFA) daily for 6 wk on plasma lipids, haemostasis and monocyte chemotaxis in 10 patients with untreated hypertension. Total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides did not change, but the ratio of total to HDL-cholesterol was significantly reduced after the fish oil supplement. Platelet function was unaltered by intake of n-3. Plasma fibrinogen and fibronectin decreased after supplementation with n-3 PUFA, while the effects on fibrinolysis were equivocal. Monocyte chemotaxis was reduced by the supplement. These data lend support to a role for an increased intake of n-3 PUFA in the management of patients with hypertension.
In 10 patients admitted to hospital with diabetic ketoacidosis plasma prostanoids 6-keto-PGF alpha, thromboxane B2 and PGE2 were studied before treatment and following recovery. During ketoacidosis the median plasma 6-keto-PGF1 alpha and PGE2 were significantly increased compared to those of a normal reference group: 5.2 pg/ml and 3.9 pg/ml versus 1.7 pg/ml and 0.4 pg/ml (p less than 0.01 and p less than 0.05). In response to therapy both prostanoids decreased significantly towards a normal level, 6-keto-PGF1 alpha: 0.5 pg/ml p less than 0.01 and PGE2: 0.08 p less than 0.05 respectively. The changes in plasma 6-keto-PGF1 alpha were negatively correlated to changes in pH, rho: -0.7788 p = 0.0135, whereas the changes in PGE2 were positively correlated to serum creatinine at admittance, rho: 0.6976, p = 0.0368 and to the amount of intravenous fluid and insulin used during treatment, rho: 0.7500 p = 0.0126 and rho: 0.8424, p = 0.0023 respectively. Plasma thromboxane B2 concentrations were not elevated and did not change after treatment of the ketoacidosis.
The prognostic value of plasma prekallikrein activity, prothrombin time, and serum albumin with regard to survival in chronic liver insufficiency was evaluated in 21 consecutive patients. Twenty patients had liver cirrhosis, and one patient had malignant liver disease (hepatocellular carcinoma). Eight patients died between 4 and 43 days after the time of blood sampling. These patients had a prekallikrein value less than 0.42. There were no overlapping prekallikrein values between patients who died and patients who survived (overlap index 0; p less than 0.001). Overlap index for prothrombin time was 0.35 (p less than 0.02), and for serum albumin 0.34 (p less than 0.02). In conclusion, plasma prekallikrein seems to indicate whether death is imminent in patients with liver insufficiency due to cirrhosis. Longitudinal studies of prekallikrein activity in different subgroups of patients with chronic and acute liver disease are recommended.
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Plasma lipids and haemostasis were investigated in 17 patients with hyperlipidaemia before and after 6 weeks supplementation with 6 g n-3 fatty acids. Nine of the patients had type IIa and 8 had type IV hyperlipidaemia. No effect on plasma cholesterol, LDL- or HDL-cholesterol were seen, but plasma triglycerides decreased after n-3 supplementation. Apolipoprotein B increased and apolipoprotein A1 decreased after the oil supplement. The bleeding time was prolonged, but platelet aggregation was unaltered by n-3 fatty acids. Protein C activity increased in type IIa and decreased in type IV after the supplement. Fibrinolysis was markedly depressed while von Willebrand factor antigen was reduced after intake of n-3 fatty acids.
Protein C was determined in 42 patients with terminal uremia and 20 healthy controls in three different ways 1) anticoagulant activity 2) amidolytic activity 3) antigen level. Protein C anticoagulant activity was markedly decreased in uremia, but was partly normalized during hemodialysis treatment, whereas the amidolytic activity and antigen level of protein C were normal and without changes during dialysis. The activities and antigen levels of factor II and X were normal before and after hemodialysis. In anticoagulated patients we found a good correlation between prothrombin levels and protein C levels determined with three different assays. We did not find any evidence for a defect carboxylation of protein C as the cause for the defective protein C in uremia. The BaCl2 precipitation in the Protein C anticoagulant assay was incomplete both in uremia and in controls but without differences between the two groups. In vitro addition of urea and creatinine did not decrease protein C activity. The cause of the defective protein C in uremia is still not known but it might contribute to thromboembolic complications.
Polyunsaturated fatty acids of the n-3 type (n-3 PUFAs) may offer some protection against ischaemic heart disease (IHD). Part of the evidence has been derived from our investigations on Greenland Eskimos. Through six expeditions to Greenland, we have studied Eskimos living on their traditional sea diet. We found favourable changes in lipids and lipoproteins, together with a reduced platelet reactivity in the Eskimos - findings of importance for their low incidence of IHD. In this survey we intend to review studies on the effects of an increased intake of n-3 PUFAs, focusing on lipids and platelets. We conclude that beneficial changes in general have been obtained. However, individual patients and patient groups likely to profit from supplementation with n-3 PUFAs need to be further defined. The optimum dose needs to be established, and the effect and safety to be documented by highly needed long term studies.
Epidemiological evidence suggests a reduced rate of chronic inflammatory diseases and ischaemic heart disease in populations with a high consumption of fish. This has been ascribed to the high content in sea food of polyunsaturated fatty acids (PUFAs), belonging to the n - 3 family. We have studied neutrophil and monocyte chemotaxis in 12 healthy males before and after 6 weeks supplementation with cod liver oil, corresponding to 5.3 g n - 3 PUFAs daily. Neutrophil and monocyte chemotaxis were investigated using the under agarose technique with N-formyl-methionyl-leucyl-phenylalanine (N-FMLP) and autologous serum as chemoattractants. Neutrophil chemotaxis towards both chemoattractants and monocyte chemotaxis towards N-FMLP were significantly reduced after supplementation with cod liver oil.
Protein C activity, both coagulant and amidolytic, as well as antigen level were studied during the perioperative period in 40 renal transplants recipients and 21 healthy controls. At transplantations the protein C coagulant activity was significantly lower in the patients than in the normal controls, and further decreased in the patients during the first week after transplantation, whereas the amidolytic activity of protein C was normal and the protein C antigen level was elevated. In the patients with established kidney function, protein C coagulant activity was higher than in patients with impaired graft function. Furthermore, it seems that the protein C coagulant activity was closely related to changes in graft function in the 11 patients with graft rejection episodes. The low protein C coagulant activity following renal transplantation could be a contributing factor to thromboembolic complications.
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The low incidence of myocardial infarction in Greenland Eskimos may be due to their intake of marine food with a high content of n-3 polyunsaturated fatty acids (PUFAs). In Eskimos the platelet count is lowered, the platelet aggregation is inhibited, the bleeding time is prolonged and the ratio between proaggregatory thromboxanes and anti-aggregatory prostacyclins is decreased, when compared to age- and sex-matched Danes. In this review, studies evaluating the effect of a fish diet or fish-oil supplementation on human platelet function are summarized. Most studies have demonstrated that supplementation with n-3 PUFAs can cause inhibition of platelet behaviour. The optimal dose of n-3 PUFAs and the patient groups most likely to profit from supplementation need to be defined. The safety and the clinical effect of the supplementation should be investigated in long-term studies.