Red blood cell lipid alterations in type II diabetes mellitus

Altered red blood cell deformability-A novel hypothesis for retinal microangiopathy in diabetic retinopathy

PURPOSE

Impaired red blood cell (RBC) deformability impedes tissue perfusion. This study aims to investigate RBC biomechanics in type 2 diabetes mellitus (DM) patients with different grades of diabetic retinopathy (DR) and to correlate RBC deformability with hematological and serum biochemical markers.

METHODS

This cross-sectional study included 86 type 2 DM patients (31 with no DR, 31 with non-proliferative DR [NPDR] and 24 with proliferative DR [PDR]) and 32 control subjects. RBC deformability was measured by a microfluidic cross-slot channel (elongation index, EI). Venous blood samples were taken for assessment of hematological and serum biochemical markers.

RESULTS

RBC deformability showed significant reduction in diabetic patients, being lowest in the PDR group, followed by NPDR and DM with no DR groups, and highest in control group (P = .018). RBC deformability was not affected by age or gender but showed significant associations with certain hematological and serum biochemical markers. In the regression analysis controlling for DM status, urea concentration and reticulocyte count were shown to be negatively associated with EI.

CONCLUSION

Impaired RBC deformability measured by a microfluidic cross-slot channel in DM patients with different grades of DR underscores the contribution of RBC rheological properties to the pathogenesis and progression of DM related microangiopathy.

Identification of megakaryocytes as a target of advanced glycation end products in diabetic complications in bone marrow

AIMS

To define the possible effect of diabetic conditions on megakaryocytes, the long-know precursors of platelets and lately characterized modulator of hematopoietic stem quiescence-activation transition.

METHODS

Megakaryoblastic MEG-01 cell culture and TPO/SCF/IL-3-induced differentiation of human umbilical blood mononuclear cells toward megakaryocytes were used to test effects of glycated bovine serum albumin (BSA-AGEs). The ob/ob mice and streptozotocin-treated mice were used as models of hyperglycemia. MTT was used to measure cell proliferation, FACS for surface marker and cell cycle, and RT-qPCR for the expression of interested genes. Megakaryocytes at different stages in marrow smear were checked under microscope.

RESULTS

When added in MEG-01 cultures at 200 μg/ml, BSA-AGEs increased proliferation of cells and enhanced mRNA expression of RAGE, VEGFα and PF4 in the cells. None of cell cycle distribution, PMA-induced platelet-like particles production, expression of GATA1/NF-E2/PU-1/IL-6/OPG/PDGF in MEG-01 cells nor TPO/SCF/IL-3 induced umbilical cord blood cells differentiation into megakaryocyte was affected by BSA-AGEs. In the ob/ob diabetic mice, MKs percentages in marrow cells and platelets in peripheral blood were significantly increased compared with control mice. In streptozotocin-induced diabetic mice, however, MKs percentage in marrow cells was decreased though peripheral platelet counts were not altered. Gene expression assay showed that the change in MKs in these two diabetic conditions might be explained by the alteration of GATA1 and NF-E2 expression, respectively.

CONCLUSIONS

Diabetic condition in animals might exert its influence on hematopoiesis via megakaryocytes-the newly identified modulator of hematopoietic stem cells in bone marrow.

Myocyte membrane and microdomain modifications in diabetes: determinants of ischemic tolerance and cardioprotection

Cardiovascular disease, predominantly ischemic heart disease (IHD), is the leading cause of death in diabetes mellitus (DM). In addition to eliciting cardiomyopathy, DM induces a ‘wicked triumvirate’: (i) increasing the risk and incidence of IHD and myocardial ischemia; (ii) decreasing myocardial tolerance to ischemia–reperfusion (I–R) injury; and (iii) inhibiting or eliminating responses to cardioprotective stimuli. Changes in ischemic tolerance and cardioprotective signaling may contribute to substantially higher mortality and morbidity following ischemic insult in DM patients. Among the diverse mechanisms implicated in diabetic impairment of ischemic tolerance and cardioprotection, changes in sarcolemmal makeup may play an overarching role and are considered in detail in the current review. Observations predominantly in animal models reveal DM-dependent changes in membrane lipid composition (cholesterol and triglyceride accumulation, fatty acid saturation vs. reduced desaturation, phospholipid remodeling) that contribute to modulation of caveolar domains, gap junctions and T-tubules. These modifications influence sarcolemmal biophysical properties, receptor and phospholipid signaling, ion channel and transporter functions, contributing to contractile and electrophysiological dysfunction, cardiomyopathy, ischemic intolerance and suppression of protective signaling. A better understanding of these sarcolemmal abnormalities in types I and II DM (T1DM, T2DM) can inform approaches to limiting cardiomyopathy, associated IHD and their consequences. Key knowledge gaps include details of sarcolemmal changes in models of T2DM, temporal patterns of lipid, microdomain and T-tubule changes during disease development, and the precise impacts of these diverse sarcolemmal modifications. Importantly, exercise, dietary, pharmacological and gene approaches have potential for improving sarcolemmal makeup, and thus myocyte function and stress-resistance in this ubiquitous metabolic disorder.

Erythrocytes as Potential Link between Diabetes and Alzheimer's Disease

Many studies support the existence of an association between type 2 diabetes (T2DM) and Alzheimer's disease (AD). In AD, in addition to brain, a number of peripheral tissues and cells are affected, including red blood cell (RBC) and because there are currently no reliable diagnostic biomarkers of AD in the blood, a gradually increasing attention has been given to the study of RBC's alterations. Recently it has been evidenced in diabetes, RBC alterations superimposable to the ones occurring in AD RBC. Furthermore, growing evidence suggests that oxidative stress plays a pivotal role in the development of RBC's alterations and vice versa. Once again this represents a further evidence of a shared pathway between AD and T2DM. The present review summarizes the two disorders, highlighting the role of RBC in the postulated common biochemical links, and suggests RBC as a possible target for clinical trials.

[Erythrocyte lipid composition at different stages of type 1 diabetes in children]

Complete profiles of phospholipid and ceramide molecular species from erythrocyte lipid extracts of children without carbohydrate metabolism disorders, and children with type 1 diabetes were compared by means of high performance liquid chromatography/mass spectrometry. For the first time a statistically significant increase (p<0.05) of lysophosphatidylcholine content in two groups of diabetic children with different duration of the disease (less than one year and more than one year) was found. Statistically significant changes in other lipid classes were not observed. The dependence of the content of phosphatidylcholine and phosphatidylethanolamine molecular species containing arachidonic acid residue (20:4) on the duration of the disease was found. The observed shift in lipid metabolism suggests of phospholipase A2 and chronic inflammatory process at different stages of diabetes mellitus, in cells (erythrocytes), which aer not involved in the immune response.

Determination of RBC membrane and serum lipid composition in Trinidadian type II diabetics with and without nephropathy

AIM

The rheological properties of erythrocytes are impaired in diabetes mellitus, especially because of changes in their membrane lipid composition.The aim of this study was to determine and examine the relationship between red blood cell (RBC) membrane and serum lipid composition in type II diabetes subjects with and without nephropathy.

METHODS

Trinidadian subjects aged 18-65 years were recruited for the study regardless of gender and ethnicity. Fasting blood samples were collected from 60 subjects of whom 20 were healthy individuals, 20 had type II diabetes without complications, and 20 were type II diabetics with nephropathy. Weight, height, waist/hip ratio, and blood pressure were recorded. All the blood samples were analysed to determine the serum lipid concentration, membrane lipid composition and plasma glucose concentration.

RESULTS

The body mass index and the systolic blood pressure of the diabetics (28.17 +/- 4.98 kg/m2, 153.21 +/- 22.10 mmHg) and those with nephropathy (25.87 +/- 4.68, 158.60 +/- 22.49 mmHg) were higher when compared with controls (24.67 +/- 5.18, 119.15 +/- 13.03 mmHg). The diabetic (175.89 +/- 102.73 microg/mgprotein) and diabetic nephropathy (358.80 +/- 262.66) subjects showed significantly higher levels of RBC membrane cholesterol compared with controls (132.27 +/- 66.47). The membrane phospholipids, protein and Na+/K+ATPase concentrations were altered in diabetics and diabetic nephropathy patients when compared with controls. The trends of increased serum cholesterol and decreased high-density lipoprotein in diabetics and diabetic nephropathy patients were noted as compared with controls but they are not significant as expected. The low-density lipoprotein cholesterol was significantly higher in diabetics when compared with diabetic nephropathy and control subjects.

CONCLUSIONS

Our data suggest that there is a relationship between RBC membrane and serum lipid composition in subjects with type II diabetes with and without nephropathy. This relationship shows that diet and lifestyle plays a significant role in the alterations of the lipids both in serum and RBC membrane. The membrane and serum lipid composition may be used as possible indicators for type II diabetic patients with and without nephropathy to control their diet in the beginning stages to prevent them from further complications.

Unfavorable effect of type 1 and type 2 diabetes on maternal and fetal essential fatty acid status: a potential marker of fetal insulin resistance

BACKGROUND

Pregestational maternal diabetes increases obesity and diabetes risks in the offspring. Both conditions are characterized by insulin resistance, and diabetes is associated with low membrane arachidonic (AA) and docosahexaenoic (DHA) acids.

OBJECTIVE

We investigated whether type 1 and type 2 diabetes in pregnancy compromise maternal and fetal membrane essential fatty acids (FAs).

DESIGN

We studied 39 nondiabetic (control subjects), 32 type 1 diabetic, and 17 type 2 diabetic pregnant women and the infants they delivered. Maternal and cord blood samples were obtained at midgestation and at delivery, respectively. Plasma triacylglycerols and choline phosphoglycerides and red blood cell (RBC) choline and ethanolamine phosphoglyceride FAs were assessed.

RESULTS

The difference in maternal plasma triacylglycerol FAs between groups was not significant. However, the type 1 diabetes group had lower plasma choline phosphoglyceride DHA (3.7 +/- 0.9%; P < 0.01) than did the control group (5.2 +/- 1.6%). Likewise, RBC DHA was lower in the type 1 [choline: 3.4 +/- 1.5% (P < 0.01); ethanolamine: 5.9 +/- 2.5% (P < 0.05)] and type 2 [choline: 3.5 +/- 1.6% (P < 0.05)] diabetes groups than in the control group (choline: 5.5 +/- 2.2%; ethanolamine: 7.5 +/- 2.5%). Cord AA and DHA were lower in the plasma (type 1: P < 0.01) and RBC (type 2: P < 0.05) choline phosphoglycerides of the diabetics than of the control subjects, and cord RBC ethanolamine phosphoglycerides were lower in DHA (P < 0.05) in both diabetes groups than in the control group.

CONCLUSIONS

Diabetes (either type) compromises maternal RBC DHA and cord plasma and RBC AA and DHA. The association of these 2 FAs with insulin sensitivity may mean that the current finding explains the higher incidence of insulin resistance and diabetes in the offspring of diabetic women.

Absence of correlation between glycated hemoglobin and lipid composition of erythrocyte membrane in type 2 diabetic patients

Correlation of glycated hemoglobin (HbA(1c)) level with degrees of certain peroxidative changes in erythrocyte membrane lipids in diabetic patients have been reported. In the present study, peroxidation of erythrocyte lipids was assessed by changes in tocopherols (Toc), phospholipids (PL), and malondialdehyde (MDA). Membrane cholesterol, Toc, and PL were determined from the same lipid extract. Toc and cholesterol were measured simultaneously by high-performance liquid chromatography (HPLC), and each PL class was determined by a single HPLC elution with ultraviolet light (UV) detection. The detection of PL with UV depends primarily on double bonds in fatty acids and shows a decrease in fatty acids by peroxidation. Changes in Toc and each PL were calculated on the basis of cholesterol and SM, respectively, since cholesterol and sphingomyelin (SM) in the cell membrane are not prone to peroxidation. MDA was measured by an HPLC method with fluorescence detection. These methods for assessment for peroxidation of membrane lipids in intact erythrocytes were validated by experiments with 2, 2-azobis(2-amidinopropane)dihydrochloride (AAPH) and tert-butylhydroperoxide (tBHP); nevertheless, significant differences in the levels of Toc, each PL class, and MDA between a high-HbA(1c) group and a low-HbA(1c) group were not detected.

Critique of a biologic mechanism linking calcium antagonists to increased risk for cardiovascular events in diabetes

Calcium antagonists represent a chemically and pharmacologically diverse group of agents that function by modulating the transmembrane influx of Ca2+ into contractile cells. These compounds, widely used for the treatment of hypertension and angina, bind in a highly specific and reversible fashion to voltage-sensitive Ca2+ channels in vascular smooth muscle cells. A recent study raised concerns about the safety of certain calcium antagonists for treatment of hypertension in diabetic patients. The safety issue has not been resolved and is the subject of other articles in this supplement. However, a biologic mechanism has been proposed to rationalize the potentially deleterious effects of calcium antagonists in this group of patients. This mechanism is based on an assumption that the biochemical composition of cellular membranes in patients with diabetes is fundamentally different, leading to an abnormal increase in the membrane concentration of calcium antagonists and, hence, adverse pharmacologic effects. In support of this model, original research on the lipid composition of membranes from patients with diabetes was cited, along with our own published findings, showing that accumulation of calcium antagonists in membranes is influenced by the molar ratio of cholesterol to phospholipid (C:P). A careful review of these and other related scientific reports, however, yields no evidence for reproducible changes in the membrane C:P molar ratio of diabetic patients that would lead to adverse pharmacologic effects of calcium antagonists.

In vitro modulation of rat adipocyte ghost membrane fluidity by cholesterol oxysterols

The effects of cholesterol and cholesterol-derived oxysterols (cholestanone, cholestenone, coprostanone and epicoprostanol) on adipocyte ghost membrane fluidity were studied using a fluorescence depolarization method. The fluorescence anisotropy of the treated membranes was determined using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Cholestanone and cholesterol decreased membrane fluidity at both the concentrations tested (10 & 50 microM) while the rest of the sterols did not exert any significant effect on membrane fluidity. In the presence of epinephrine, cholestanone partitioned more towards the lipid core but cholesterol partitioning was not affected. The fusion activation energies (delta E) obtained for membranes preincubated with cholestanone (8.6 kcal/mol) and cholesterol (8.2 kcal/mol) were not significantly different from that of untreated membranes (8.3 kcal/mol). Membranes preincubated with cholestanone and cholesterol did not exhibit any change in lipid phase throughout the temperature range (10-45 degrees C) tested. The sterols were found to inhibit fisetin-induced phospholipid methylation in isolated rat adipocytes in the rank order of cholesterol > epicoprostanol > cholestanone = cholestenone = coprostanone, while basal methylation was unaffected. When adipocytes were preincubated with the sterols before the addition of fisetin, cholestanone and cholestenone showed 74% and 66% inhibition of maximal methylation respectively. These results indicated that cholesterol oxysterols interact differently with rat adipocyte membranes, with cholestanone interacting more with phospholipids located at the inner lipid bilayer (e.g. phosphatidylethanolamine) while cholesterol interacts more with phosphatidylcholine located at the outer lipid bilayer. This differential interaction may cause selective changes in membrane fluidity at different depths of the bilayer and thus may modulate the activities of membrane-bound proteins such as enzymes and receptors.

Alterations in erythrocyte membrane lipid composition and fluidity in primary lipoprotein lipase deficiency

Lipid composition of plasma lipoproteins and erythrocyte ghost membranes has been studied in 16 healthy normolipidaemic subjects and in 16 patients affected by primary lipoprotein lipase deficiency, resulting in severe chylomicronaemia and in cholesterol-depleted low-density lipoproteins and high-density lipoproteins. A significant decrease in membrane cholesterol/phospholipid ratio was observed in lipoprotein lipase deficient patients compared to controls (3.27 +/- 0.33 vs. 3.95 +/- 0.50, mean +/- S.D.; P less than 0.0001). There was also an increase in the erythrocyte membrane phosphatidylcholine/sphingomyelin ratio in lipoprotein lipase deficient patients compared to controls (1.53 +/- 0.10 vs. 1.05 +/- 0.13; P less than 0.0001) due to a concurrent increase in phosphatidylcholine and decrease in sphingomyelin relative concentrations in these patients. Erythrocyte ghost membrane fluidity was determined by fluorescence anisotropy and found to be higher in membranes from lipoprotein lipase deficient patients. This increase in membrane fluidity can be attributed in part to changes in membrane cholesterol and phospholipid concentrations in response to abnormal plasma lipoprotein composition.

The effect of glycemic control and duration of diabetes on cholesterol and phospholipid classes in erythrocytes of type I diabetes

Abnormalities in the lipid composition of erythrocytes can alter blood rheology and viscosity. These alterations have been implicated in the pathogenesis of microvascular disease in diabetic patients. The present study was undertaken to examine whether or not long-term glycemic control or duration of diabetes has any role in the altered membrane cholesterol and phospholipid composition of erythrocytes in type I diabetes. Long-term glycemic control was assessed by measuring glycosylated hemoglobin (GHb) from diabetic patients and age-matched normal volunteers. There was no significant correlation between GHb or duration of diabetes with total cholesterol, phospholipid, and cholesterol to phospholipid molar ratios in erythrocytes of these patients. Among phospholipid classes, GHb showed a significantly negative relationship with sphingomyelin (SM) (r = .55, P less than .01) levels, but was not related to phosphatidylcholine (PC) and phosphatidylethanolamine (PE) levels of erythrocytes. Duration of diabetes had no effect on SM, PC, or PE levels of erythrocytes.

Elevated lipid peroxidation levels in red blood cells of streptozotocin-treated diabetic rats

This study was performed to determine whether or not hyperglycemia in diabetes results in elevated levels of lipid peroxidation products in red blood cells (RBC). Diabetes was induced in rats by treatment with streptozotocin. The level of lipid peroxidation products was examined in fresh RBC by measuring their thiobarbituric acid (TBA) reactivity after 2 and 4 months of induction of diabetes. Hyperglycemia was assessed by measuring the level of glycosylated hemoglobin and blood glucose. Results show that lipid peroxidation levels were significantly higher (50% to 84%) in RBC of diabetic rats than in controls. The increase in the level of lipid peroxidation was blocked in diabetic rats in which hyperglycemia was controlled by insulin treatment. Among phospholipid classes, relative percentage of sphingomyelin (SM) was significantly reduced in RBC at both 2 and 4 months of diabetes; whereas phosphatidylethanolamine (PE) levels were higher in RBC at 4 months of diabetes only. The level of phosphatidylcholine (PC) did not differ significantly between RBC of control and diabetic rats. This study suggests a significantly altered lipid composition and an accumulation of lipid peroxidation products in RBC of streptozotocin-treated diabetic rats.