nine patients with type 2 diabetes and eight healthy control subjects gave informed consent to the approved protocol .
patients with poor metabolic control were intentionally chosen . lipid profile and inflammatory proteins ( fibrinogen , von clauss method ;
haptoglobin and immunoglobin g , immunonephelometric method ; and c - reactive protein , latex agglutination technique ) were determined for each participant .
six patients were on oral antidiabetic and aspirin medications , three were on insulin , five were on cholesterol - lowering therapy , and four were treated for hypertension .
those on insulin had a history of coronary artery disease , and two of them had suffered from myocardial infarction .
mean  sd age of patients was 58.3  8.8 years ( range 4170 ) .
healthy subjects were age matched ( 51.1  8.7 years [ range 4164 ] ) , did not take regular medications , and had no history of cardiovascular disease .
a couette instrument made of two concentric cylinders and installed in an incubator at 37c generated homogeneous shear rates via a rotating outer cylinder .
the 32-mhz polyvinylidine flouride ultrasound transducer ( visualsonics , toronto , canada ) had a 6 db bandwidth of 1545 mhz .
avb2-ta - c - crima ; avtech , ottawa , canada ) . received radio frequency ( rf ) echoes ( model no .
au-3a-0120 ; miteq , hauppauge , ny ) were amplified by 54 db , filtered between 10 and 50 mhz ( model no .
5900 pr ; panametrics , waltham , ma ) , and digitized at 250 mhz ( model no .
the protocol consisted of imposing a 500 s shear rate for 120 s to disrupt aggregates .
then , aggregation kinetics were recorded for 380 s at randomly applied reduced shear rates of 0 , 1 , 2 , 10 , 50 , 100 , and 200 s. one hundred rf echoes were acquired every 2 s. for each blood sample , the protocol was repeated three times for averaging .
rf signals were adjusted to compensate for blood attenuation at each shear rate and integrated backscatter coefficient ( ibsc ) was determined as previously described ( 6 ) .
nine patients with type 2 diabetes and eight healthy control subjects gave informed consent to the approved protocol .
patients with poor metabolic control were intentionally chosen . lipid profile and inflammatory proteins ( fibrinogen , von clauss method ;
haptoglobin and immunoglobin g , immunonephelometric method ; and c - reactive protein , latex agglutination technique ) were determined for each participant .
six patients were on oral antidiabetic and aspirin medications , three were on insulin , five were on cholesterol - lowering therapy , and four were treated for hypertension .
those on insulin had a history of coronary artery disease , and two of them had suffered from myocardial infarction .
mean  sd age of patients was 58.3  8.8 years ( range 4170 ) .
healthy subjects were age matched ( 51.1  8.7 years [ range 4164 ] ) , did not take regular medications , and had no history of cardiovascular disease .
a couette instrument made of two concentric cylinders and installed in an incubator at 37c generated homogeneous shear rates via a rotating outer cylinder .
the 32-mhz polyvinylidine flouride ultrasound transducer ( visualsonics , toronto , canada ) had a 6 db bandwidth of 1545 mhz .
avb2-ta - c - crima ; avtech , ottawa , canada ) . received radio frequency ( rf ) echoes ( model no .
au-3a-0120 ; miteq , hauppauge , ny ) were amplified by 54 db , filtered between 10 and 50 mhz ( model no .
5900 pr ; panametrics , waltham , ma ) , and digitized at 250 mhz ( model no .
the protocol consisted of imposing a 500 s shear rate for 120 s to disrupt aggregates .
then , aggregation kinetics were recorded for 380 s at randomly applied reduced shear rates of 0 , 1 , 2 , 10 , 50 , 100 , and 200 s. one hundred rf echoes were acquired every 2 s. for each blood sample , the protocol was repeated three times for averaging .
rf signals were adjusted to compensate for blood attenuation at each shear rate and integrated backscatter coefficient ( ibsc ) was determined as previously described ( 6 ) .
bmi , blood pressure , triglycerides , total cholesterol , hdl and ldl cholesterol , fibrinogen , and c - reactive protein were not different between groups ( p > 0.05 ; unpaired t tests ) , whereas immunoglobin g ( 8.4  1.0 vs. 11.3  1.8 g / l , p < 0.001 ) , haptoglobin ( 1.0  0.4 vs. 1.6  0.5 g / l , p < 0.05 ) , and a1c ( 5.5  0.8 vs. 8.8  2.1% , p < 0.01 ) were significantly higher in diabetic patients than in control subjects .
couette flow protocol resulted in disaggregation of rbc and minimum ibsc at 500 s , formation of aggregates and rapid increase in ibsc depending on reduced applied shear ( fig . 2 of ref . 7 ) , and development of stable aggregate sizes and plateaus of ibsc after a few seconds for most shears to minutes at 0 s. figure 1a
summarizes mean raising slopes of ibsc between 2 and 8 s after shear rate reductions . in control subjects , maximum slope at 2 s was not different from that at 1 and 10 s ( p > 0.89 ) , whereas in diabetic patients , maximum slope of ibsc occurring at 2 s was similar to that at 1 s ( p = 1.0 ) .
except for that at 200 s ( p = 0.11 ) , kinetic slopes were always faster in diabetic patients , which is indicative of higher rates of neighboring rbc clustering .
ibsc at plateaus averaged between 180 and 380 s after shear rate reductions as presented in fig .
maximum ibsc at 2 s was similar to those at 0 and 1 s ( p > 0.95 ) .
similarly , ibscs at 1 and 2 s were similar in diabetic patients ( p > 0.95 ) .
ibscs were statistically higher in diabetic patients between 2 and 100 s , which reflects stronger adhesions and bigger steady - state aggregate sizes in diabetes .
statistically significant differences in fig . 1 were noted for shears between 2 and 100 s , which correspond to normal flow at center streams and pathological flow stasis in recirculation zones of large systemic veins and arteries .
accordingly , ea in diabetes can be related to lower - limb artery ischemic events , microangiopathy in foot extremities , and retinopathy .
inflammation is involved in pathogenesis of type 2 diabetes and rbc aggregation , which agrees with our results ( legend of fig .
1 ) . subacute inflammatory state promoting rbc aggregation is also associated with obesity ( 8) and metabolic syndrome ( 9 ) .
thus , reducing inflammation ( and indirectly aggregation ) with statins and a1c with antidiabetic medication and/or diet are indicated because both have known benefits to cardiovascular consequences of diabetes .
we reported measurements from a laboratory instrument , but a short - term objective is sizing rbc aggregates in vivo with ultrasound ( 10 ) . at 32 mhz ,
the proposed noninvasive method should be investigated further because it may have potential benefit for diagnosis and follow - up of diabetic foot complications and for monitoring therapy .
 objective  to measure with ultrasound the increased erythrocyte aggregation ( ea ) kinetics and adhesion energy between erythrocytes in patients with type 2 diabetes and poor metabolic control.research design and methods  
 blood samples were analyzed in a couette rheometer at 32 mhz following shear rate reductions from 500 s1 to residual shears of 0 ( stasis ) , 1 , 2 , 10 , 50 , 100 , and 200 s1 . 
 the increase in ea was determined with the integrated backscatter coefficient as a function of time and shear rate.resultsthe time required to form aggregates was shorter in diabetic patients at shear rates below 200 s1 ( p < 0.01 ) . 
 erythrocytes formed larger aggregates in diabetic patients than in control subjects ( p < 0.05 at 2 to 100 s1).conclusions  ultrasound can potentially noninvasively demonstrate , in vivo and in situ , the impact of local abnormal ea on arteriovenous flow disorders in diabetes . 
RESEARCH DESIGN AND METHODS
Populations
Couette experiments
RESULTS
CONCLUSIONS