MO640LASER DOPPLER FLOWMETRY IN STUDYING OF MICROVASCULAR DISORDERS IN PATIENTS WITH DIABETIC NEPHROPATHY

Background and Aims According to various research, vascular complications of type 2 diabetes mellitus are the main reason for patients' mortality. The most specific one, observed in patients with diabetes only, is diabetic microangiopathy, especially diabetic nephropathy. This complication accounts for more than 20% of cases of chronic kidney disease. So, the development of non-invasive methods for the diagnosis of vascular complications of type 2 diabetes mellitus is critically important. There is a perspective method for this problem - Laser Doppler flowmetry (LDF). It is currently used in the diagnosis of diabetic microangiopathy, but the limiting factor is the lack of a unified algorithmic approach to the data interpretation. This work aimed to analyze changes in the amplitude indicators of the low-frequency part of the LDF signal spectrum in patients with chronic kidney disease and type 2 diabetes and to identify their correlations with the glomerular filtration rate. Method The study included 42 patients (20 men and 22 women) with type 2 diabetes mellitus chronic kidney disease (stage C3-C4). The age of patients was 58-77 years (66 years on average). The duration of diabetes was more than 5 years (on average 7 years). All patients had diabetic nephropathy with a decrease in glomerular filtration rate, chronic kidney disease stage C3-C4. Laser Doppler flowmetry was done using the "LAZMA MC-1" system ("Lazma", Russia). Each patient had a 10-minute LDF registration. The sensor was placed on the skin of the rear of the foot. After recording the LDF curve, the special software has calculated amplitudes of endothelial, myogenic, neurogenic, respiratory, and pulse flux motions. Then we assessed the amplitude contribution of every frequency range to the total power of the local flux motion region. The next step was a correlation analysis with the estimated glomerular filtration rate. For statistical analysis, we used the GraphPad Prism 8 (GraphPad Software, USA). Results All examined patients had amplitude peaks in the neurogenic, myogenic, respiratory, and pulse ranges. There were no significant correlations between the glomerular filtration rate and the amplitudes of myogenic and neurogenic flux motions (p>0.05) (Fig. 1). However, there was a significant positive correlation between the contribution of myogenic flux motions to the low-frequency range and glomerular filtration rate (p<0.01), and a negative one – for the contribution of neurogenic flux motions (p<0.01) (Fig. 2). In six observations there was a tendency to a decrease in the contribution of endothelial flux motions as the glomerular filtration rate decreased. Conclusion The results of this study showed that laser Doppler flowmetry has the potential to diagnosis the nature of the dysfunction of individual microcirculation modulation mechanisms. In patients with chronic kidney disease of the C3-C4 stage decreasing the glomerular filtration rate correlated with decreasing the contribution of myogenic flux motions and increasing the contribution of neurogenic flux motions to the total power of the low-frequency part of the LDF signal amplitude-frequency spectrum. These changes can be explained within the framework of the existing understanding of the pathogenesis of diabetic microangiopathy, namely, damage to the smooth muscle layer of the wall of arterioles and venules with damage to myocyte pacemakers and changes of basal vascular tone pattern. It causes an increase in the role of neurogenic modulation of the micro-vascular bloodstream. These data can be an additional argument in favor of the further development of improving laser Doppler flowmetry using for the tasks of early (preclinical) non-invasive diagnosis of microvascular disorders in patients with type 2 diabetes mellitus, as well as for monitoring the effectiveness of the therapy. The reported study was funded by RFBR, project number 19-315-90080.