Plasma lipoprotein and platelet function after heparin injection: studies in normal fasted and postprandial and in type V hyperlipoproteinemic subjects

Severe hypertriglyceridaemia and pancreatitis in a patient with lipoprotein lipase deficiency based on mutations in lipoprotein lipase (LPL) and apolipoprotein A5 (APOA5) genes

A 44-year-old woman was admitted with pancreatitis caused by hypertriglyceridaemia (fasting triglycerides 28 mmol/L). She used oral contraceptives and ezetimibe 10 mg. She was overweight (body mass index 29.7 kg/m²). Diabetes mellitus was ruled out, as were nephrotic syndrome, alcohol abuse, hypothyroidism and dysbetalipoproteinaemia. Genetic analysis revealed mutations in two genes involved in triglyceride metabolism (apolipoprotein A5 and lipoprotein lipase [LPL]). The LPL activity was 45% compared with pooled healthy controls. The post-heparin triglyceride reduction was 6%, compared with a normal reduction of >20%. The patient was initially treated with gemfibrozil, but this was discontinued due to side effects. Dietary triglyceride restriction and discontinuation of the oral contraceptives lowered the plasma triglycerides within 2 weeks to 3.4 mmol/L. Hypertriglyceridaemia is a risk factor for pancreatitis and cardiovascular disease, and has a broad differential diagnosis including genetic causes. Patients can achieve near-normal triglyceride values with a low-fat diet only.

Platelet function in the postprandial period

Background

Postprandial hyperlipidemia and hyperglycemia have been related to cardiovascular events. Among different underlying mechanisms platelet activation seems to be responsible too. No comparable data between various tests in normo- vs. hyperlipidemics before and at different time intervals are available after a fat meal. We aimed to compare 9 of them within the same patients at several time points in postprandial hyperlipidemia.

Results

For some tests baseline values between the groups were significantly different (TXB₂, platelet sensitivity, sedimentation and WU-test). However, hyperlipidemia revealed a variable influence on the tests examined. Some of the available tests apparently sensitive to show platelet activation reflect the increase in triglycerides (TG), such as the sedimentation index. ADP-induced platelet aggregatory activity in count adjusted washed isolated platelet samples during postprandial hyperlipidemia indicates mildly enhanced platelet activity, but does not seem to induce significant changes in aggregation. In patients with severe hypertriglyceridemia (> 400 mg/dl fasting) changes in platelet function are more pronounced due to delayed decay and may last up to 16 hours paralleling TG reaching the prevalue. The overwhelming majority of platelet function tests do not significantly respond to postprandial hyperlipidemia. The correlation between the tests applied is poor. For standardization purpose, platelet aggregation tests, aimed to examine proaggregatory capacity in atherosclerosis, should only be performed at the same time of the day after a fasting period > 6 hours. The great variation in preanalytical work-up on comparison of various tests, large number of platelet tests available and their respective potential value are discussed.

Conclusions

At present, the suspicion that platelet function is significantly activated in the postprandial period cannot be supported by any of the tests used. The information provided is valuable to know for which test and group of patients a fasting period of which duration is recommendable.

Potential organ or tumor imaging agents. 32. A triglyceride ester of p-iodophenyl pentadecanoic acid as a potential hepatic imaging agent

A triglyceride analog, glycerol-2-palmitoyl-1,3-di-15-(p-iodophenyl)pentadecanoate (DPPG) was synthesized and radiolabeled for evaluation as a potential functional liver scintigraphic agent. Uptake of DPPG was compared in normal, diabetic, tumor-bearing and heparin pretreated rats, revealing differences in uptake and clearance of radioactivity, correlating with hepatic lipase activity of these groups. Similar results were observed by gamma-camera scintigraphy. Comparing the uptake of DPPG with that of its fatty acid component, 15-(p-iodophenyl)pentadecanoic acid (IPPA), revealed that the peak uptake of IPPA in the liver was about half that of DPPG. Based upon these findings, DPPG warrants further study as a hepatic radiodiagnostic agent.