Red Blood Cells from Individuals with Abdominal Obesity or Metabolic Abnormalities Exhibit Less Deformability upon Entering a Constriction

Abstract

Abdominal obesity and metabolic syndrome (MS) are multifactorial conditions associated with increased risk of cardiovascular disease and type II diabetes mellitus. Previous work has demonstrated that the hemorheological profile is altered in patients with abdominal obesity and MS, as evidenced for example by increased whole blood viscosity. To date, however, no studies have examined red blood cell (RBC) deformability of blood from individuals with obesity or metabolic abnormalities under typical physiological flow conditions. In this study, we pumped RBCs through a constriction in a microfluidic device and used high speed video to visualize and track the mechanical behavior of ~8,000 RBCs obtained from either healthy individuals (n = 5) or obese participants with metabolic abnormalities (OMA) (n = 4). We demonstrate that the OMA+ cells stretched on average about 25% less than the healthy controls. Furthermore, we examined the effects of ingesting a high-fat meal on RBC mechanical dynamics, and found that the postprandial period has only a weak effect on the stretching dynamics exhibited by OMA+ cells. The results suggest that chronic rigidification of RBCs plays a key role in the increased blood pressure and increased whole blood viscosity observed in OMA individuals and was independent of an acute response triggered by consumption of a high-fat meal.

Trial registration: ClinicalTrials.gov NCT01803633.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1

(A) Schematic of the microfluidic device. Dilute RBCs are pumped from a region of low shear (a wide channel, at left) to a region of high shear (the constriction, at right). Note that the origin is at the center of the entrance of the constriction as shown on the figure. (B) Representative superimposed series of time-lapse images extracted from high speed video each showing an individual RBC entering a constriction and stretching in response to the increased velocity. The original “raw” image of the RBC is shown in grayscale with the detected cell borders superimposed in blue. (C) High magnification time lapse images of a representative stretching RBC upon entering a constriction for Control (OMA-) and OMA+. Each image is cropped and centered on the RBC to illustrate its behavior. The box size is 10.2 μm x 10.2 μm. The corresponding plots at the right show major axis length, L, over initial major axis length, L0, as a function of the position in the channel.

Fig 2

(A) Box plot of the ratio of the instantaneous length stretched (L) to initial length (L0) as a function of X position in the channel (OMA- = gray boxes, OMA+ = blue boxes). Distributions represent entire population of RBCs examined, from all participants. The top and bottom of the rectangles represent the 25th and 75th quartiles, the thick black bars indicate the median. Bin widths were 5 μm; the boxes for OMA- and OMA+ are staggered within each bin for clarity. Asterisks (*) indicate distributions with p<0.05 compared to the control (OMA-). (B,C) Histograms for the maximum length stretched, Lmax/L0, for (B) OMA- RBCs and (C) OMA+ RBCs, fasting samples only. Note the distribution is shifted to the left (lower Lmax) for OMA+ RBCs. The total number of cells observed: nOMA- = 1156, nOMA+ = 1955.

Fig 3. Effect of participant on observed maximum stretching ratio.

The top and bottom of the lightly shaded rectangles indicate the 25th and 75th quartiles, respectively, the thick black bars indicate the median, the dark square markers indicate the mean, and the whiskers represent the maximum and minimum values observed. Each marker shape corresponds to a particular individual; repeated markers denote trial replicates with blood drawn from that same participant. All samples are fasting samples only. The total number of cells observed: nOMA- = 1156, nOMA+ = 1955. Asterisk (*) indicates p<0.05.

Fig 4. Effect of time elapsed post-prandial on stretching dynamics of OMA+ RBCS.

(A) Box plots of instantaneous stretching ratio as a function of X position in the channel for blood draws taken postprandially in participants with OMA. The top and bottom of the rectangles represent the 25th and 75th quartiles, the thick black bars indicate the median, and the dark square markers indicate the mean. Shown in the second row are histograms for Lmax/L0. The total number of cells observed: n0HR = 1955, n1HR = 1870, n3HR = 1450, and n6HR = 1393

Fig 5. Effect of participant on maximum stretching ratio observed at different times postprandial.

The top and bottom of the lightly shaded rectangles indicate the 25th and 75th quartiles, respectively, the thick black bars indicate the median, the dark square markers indicate the mean, and the whiskers represent the maximum and minimum values observed. Each marker shape corresponds to a particular participant; repeated markers denote trial replicates with blood drawn from that same individual. The total number of cells observed: n0HR = 1955, n1HR = 1870, n3HR = 1450, and n6HR = 1393. Asterisk (*) indicates p<0.05.