Analysis of rapid oscillations of glucose and free fatty acids in plasma

The authors analyzed rapid oscillations of blood sugar (GL) and free fatty acid levels (FFA) in serum of healthy subjects. They investigated a series of blood samples taken under conditions of absolute rest from the cubital vein at 15-s intervals for a period of 6 min. In addition to common statistical parameters, they calculated the course of autocorrelation and cross-correlation functions and periodograms. The magnitude of oscillations is significantly higher than the error of the biochemical methods. In some sequences periodicities were detected which were statistically significant in 23.8% of GL and in 38.1% of FFA. 24-point series of GL collected in parallel from both arms correlate in 36.3% positively, in 27.3% negatively, and in 36.4% they do not correlate. Series of FFA and GL collected simultaneously from one site correlate mutaually in almost all instances either positively or negatively, frequently with a time shift. The oscillations may be due to (a) feedback regulations of the levels of the two metabolites, (b) permanent mutual interaction between the FFA and glucose level and (c) an uneven concentration of the two metabolites in different parts of the circulation. The above factors may combine, and the list of possible factors may not be complete.