[Circadian changes in remnant-like particle-cholesterol (RLP-C), and its diagnostic value for postprandial increase in remnant lipoprotein in diabetes mellitus].

To investigate whether remnant-like particle-cholesterol (RLP-C) increases in the postprandial state, and if so, whether such response can be used for detecting postprandial increase in remnant lipoprotein, we measured RLP-C levels at two points (before breakfast, and after lunch), or seven points (before and after each meal, and midnight) in 36 diabetic patients. delta RLP-C was calculated by subtracting RLP-C level before breakfast from that at each point. delta RLP-C after lunch was defined as delta RLP-CL and maximum delta RLP-C as delta RLP-Cmax. Daily profiles of RLP-C (n = 22) showed that RLP-C increased during the daytime in 6 patients (27.3%; responders), but not in the others (nonresponders). In the histogram of delta RLP-Cmax, we could easily distinguish responders (delta RLP-Cmax = 6 approximately 12 mg/dl) from nonresponders (< 4 mg/dl). By using delta RLP-CL of 4 mg/dl as the cut-off value, we could also separate two groups without overlap. With this cut-off value, 11 out of 36 patients (30.6%) were diagnosed as responders. High performance liquid chromatography (HPLC) analysis with cholesterol-monitoring revealed that VLDL-sized RLP increased markedly after lunch in responders. In conclusion, RLP-C increases in some diabetic patients, and delta RLP-CL is useful for detecting postprandial increase in remnant lipoprotein.