Diabetes-related quality of life is enhanced by glycaemic improvement in older people.

AIMS: To investigate the validity and reliability of the Audit of Diabetes-Dependent Quality of Life instrument in older Italians with diabetes and to test the association of diabetes-related quality of life with glycaemic control over time. METHODS: A total of 558 outpatients with Type 2 diabetes from the Diabetic Unit of the Italian National Research Centre on Aging Hospital in Ancona were enrolled to complete questionnaires (Audit of Diabetes-Dependent Quality of Life-19 and the Short-Form-12), and to undergo clinical and biochemical testing at baseline and at 12 months of follow-up. The overall impact of diabetes using the average weighted impact score from the Audit of Diabetes-Dependent Quality of Life questionnaire was calculated. Participants were categorized according to this score as having either less or more negative diabetes-related quality of life. RESULTS: Participants had a mean ± SD age of 67.7 ± 9.2 years and 51.8% were male. Factor analysis and Cronbach's coefficient of internal consistency (Cronbach's α = 0.931) confirmed that the 19 domain-specific Audit of Diabetes-Dependent Quality of Life items could be combined into a single scale in this Italian population. The impact score correlated with the physical (r = 0.275; P < 0.001) and mental components (r = 0.291; P < 0.001) of the Short-Form-12 questionnaire. Significant differences were found according to diabetic complications in specific Audit of Diabetes-Dependent Quality of Life items and impact scores. Insulin use had a greater association with a more negative quality of life compared with other antidiabetic agents. A multivariate linear regression model with restricted linear spline application showed that the relationship between HbA1c and impact score was not linear and that the change in the impact score was associated with improved glycaemic control in those with a less negative diabetes-related quality of life at 12 months. CONCLUSIONS: The Audit of Diabetes-Dependent Quality of Life-19 is a valid tool for measuring the impact of diabetes on quality of life in older Italians. Perception of diabetes-related quality of life is associated with glycaemic control over time.

Muscle activation patterns related to diabetic neuropathy in elderly subjects: A Functional Reach Test study.

BACKGROUND: This study was designed to assess, in healthy elderly, non-neuropathic and neuropathic diabetic subjects, the activation patterns of the main muscles involved in the Functional Reach Test, a well-recognized method to identify elderly subjects at risk of balance impairments. METHODS: Surface electromyographic analysis of Sternocleidomastoideus, Rectus Abdominis, Erectores Spinae at L4 level, Rectus Femoris, Hamstrings, Tibialis Anterior and Soleus was performed in 10 healthy, 10 diabetic non-neuropathic and 10 diabetic neuropathic subjects. FINDINGS: Results showed that in every group the first motor is Tibialis Anterior, that is recruited before the start of the test. An earlier activation of Tibialis Anterior (P<0.05) was detected in diabetic neuropathic (ON at -24% of the test period), compared with healthy (-11%) and diabetic non-neuropathic (-13%) groups. A significant earlier activation of Sternocleidomastoideus and Rectus Abdominis was found in diabetic neuropathic group, only with respect to healthy subjects. No significant difference was found in Rectus Femoris, Soleus, Hamstrings an Erectores Spinae onset among the three groups. INTERPRETATION: Results suggest a trend of diabetic neuropathic patients in earlier anticipation of the activation of the anterior body-muscles. In particular, the earlier onset of Tibialis Anterior is likely to be performed to adjust the movement timing and to compensate for the delay in the recruitment of the motor units. This anticipation might be involved in the altered postural control with increased balance impairment detected in diabetic neuropathic patients, and thereby it might also be proposed as an index of neuropathy, evidenced in a simple and non-invasive manner.

The surface electromyographic evaluation of the Functional Reach in elderly subjects.

This study proposes a comprehensive assessment of myoelectric activity of the main muscles involved in the Functional Reach (FR) test, in 24 elderly subjects. A specific protocol for the surface electromyography (sEMG) signal acquisition during FR-test was developed. Results show that anterior muscles activate following a caudo-cranial order. Tibialis Anterior (TA) is the first to be activated (-18.0±16.3% of the FR-period), together with Rectus Femoris (-10.4±17.9%). Then, Rectus Abdominis (19.7±24.7%) and Sternocleidomastoideus (19.9±15.6%) activate after the FR-start. Hamstrings, Soleus, and L4-level Erectores Spinae (posterior muscles) activate after the FR-start in this order (11.4±16.8%, 17.7±16.6%, and 35.2±29.0%, respectively) and remain active until the movement end. The analysis of the kinematic strategies adopted by subjects revealed an association between TA-activation patterns and two kinematic strategies (hip/mixed strategy), quantified by an increase (p<0.05) of TA-activity duration in subjects adopting the hip strategy (89.9±34.5) vs. subjects adopting the mixed strategy (27.0±16.8). This suggests that TA sEMG activity could be able to discriminate among kinematic strategies, providing different information on balance control. Thus, the present analysis represents the first attempt to quantify the sEMG activity during FR-test in elderly subjects, providing an early contribution in building a reference frame for balance assessment in clinical context.

Modifications in platelet membrane transport functions in insulin-dependent diabetes mellitus and in gestational diabetes.

The pathogenesis of plasma membrane alterations present in diabetes mellitus is unclear. To add new insights to the question, platelet membrane properties were evaluated in 16 women presenting impaired glucose tolerance at the 28-29th week of gestation (GDM) and in 8 women with insulin-dependent diabetes mellitus (IDDM). 15 healthy pregnant women (HPW) and 21 healthy non-pregnant (HNPW) women were the control group for GDM and IDDM, respectively. Pregnancy (HPW vs. HNPW) provoked an increase in Ca(2+)-ATPase activity and a decrease in membrane fluidity; in contrast, Na+/K(+)-ATPase, intracellular free Ca2+ concentrations, membrane cholesterol and phospholipid content did not vary. Both GDM and IDDM showed lower Na+/K(+)-ATPase activity and higher Ca2+ concentration, compared to HPW and HNPW, respectively, whereas Ca(2+)-ATPase activity was higher only in IDDM; furthermore, membrane fluidity was lower in GDM and higher in IDDM. Finally, GDM showed higher membrane cholesterol content. Both GDM and IDDM showed a very good metabolic control so that variations reported cannot be due to hyperglycemia; it is tempting to suggest that membrane variations are present before the clinical metabolic alteration. Furthermore, both GDM and IDDM were on insulin therapy, therefore: (i) insulin may be the pathogenetic factor of higher intracellular free Ca2+ concentrations and lower Na+/K(+)-ATPase activity since they both varied accordingly in GDM and IDDM, but not of (ii) changes in Ca(2+)-ATPase, membrane fluidity and cholesterol content which did not vary accordingly in GDM and IDDM.

Altered platelet membrane dynamic properties in type 1 diabetes.

A modified platelet response to aggregating stimuli is supposed to play a role in the pathogenesis of diabetic macroangiopathy. We studied the fluidity and microheterogeneity of the external surface of the platelet membrane and the activities of the plasma membrane Na+-K+-ATPase and Ca2+-ATPase in 21 men with type 1 diabetes and in 20 control subjects before and after in vitro thrombin addition. In the resting state, platelets from type 1 diabetic patients showed an increased fluidity and microheterogeneity of the platelet membrane, a higher Ca2+-ATPase activity, and a reduced Na+-K+-ATPase activity in comparison with platelets from healthy subjects. The fatty acid composition was also modified, with increased C 16:1 and decreased C 18:0 content. Control cells incubated with thrombin showed a modification of the membrane parameters opposite to the response observed in type 1 cells after the stimulation. The incubation of control platelets in the resting state with high concentrations of glucose modified the fluidity of the plasma membrane Na+-K+-ATPase and Ca2+-ATPase activities in an opposite way in comparison with the alterations observed in type 1 platelets. This study suggests that in type 1 diabetic patients, the platelet membrane responds to activation with a molecular remodeling different from the response of healthy subjects. The abnormal organization of the membrane might contribute to the altered platelet functions in type 1 diabetic patients, but acute exposure to high glucose levels does not seem able to modify the platelet membrane in the way observed in type 1 diabetes.

Altered cellular Ca2+ and Na+ transport in diabetes mellitus.

Platelet intracellular Ca2+ concentration ([Ca2+]i) and its response to stimuli (ADP and thrombin) were studied in 15 insulin-dependent and 22 non-insulin-dependent diabetes mellitus patients with the fluorescent probe Fura 2. The activity of Ca2(+)-ATPase and Na(+)-K(+)-ATPase, membrane fluidity, and cholesterol and phospholipid content were also determined in platelet membranes. Compared with control subjects, diabetic patients showed 1) increased platelet [Ca2+]i in the resting state, 2) higher Ca2+ levels after stimulation with thrombin and ADP, due entirely to increased resting concentrations, 3) reduced activity of Na(+)-K(+)-ATPase, 4) increased activity of Ca2(+)-ATPase, 5) higher fluidity of the platelet membrane, and 6) increased membrane concentration of total phospholipids. Na(+)-K(+)-ATPase activity was inversely related to platelet [Ca2+]i in each group studied, whereas Ca2(+)-ATPase activity was positively correlated with intracellular Ca2+ levels. The data obtained in diabetic subjects suggest an abnormality in Ca2+ and Na+ transport across the platelet membrane that might be responsible for the reported platelet hyperreactivity to stimuli in diabetes.

Modifications induced by LDL from type 1 diabetic patients on endothelial cells obtained from human umbilical vein.

The aim of the present work was to analyze the effect of LDL obtained from type 1 diabetic patients in good metabolic control on human umbilical vein endothelial cells (HUVECs) after a short incubation period to detect possible atherogenic modifications of endothelial properties. Cultured HUVECs were incubated for 3 h with culture medium alone (control HUVEC), with native LDL from 12 healthy men (control LDL), or with native LDL from 12 type 1 diabetic men (type 1 LDL) (100 pg/ml). After the incubation, the following parameters were evaluated: nitric oxide synthase (NOS) activity, cytoplasmic Ca2+ levels, Na+-K+-ATPase activity, plasma membrane fluidity determined by means of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), and plasma membrane conjugated diene (CD) content. The same experiments were repeated after bradykinin stimulation or in the presence of the antioxidant butylated hydroxytoluene (BHT), and nitric oxide (NO) production in intact HUVECs was also evaluated. HUVECs incubated with control LDL in comparison with control HUVECs showed a decreased fluidity of the membrane surface evaluated by TMA-DPH and a higher CD content. These alterations were prevented by the presence of BHT. HUVECs incubated with type 1 LDL in comparison with both control HUVECs and cells incubated with control LDL showed 1) increased NOS and Na+-K+-ATPase activity, cytoplasmic Ca2+ levels, and CD content, and 2) decreased fluidity of the membrane surface evaluated by TMA-DPH. These modifications were blunted--but not abolished--by the presence of BHT. After bradykinin stimulation either in the absence or in the presence of BHT, both cytoplasmic Ca2+ levels and NO production were increased in control HUVECs and in HUVECs incubated with control LDL, while a reduced response was observed in HUVECs incubated with type 1 LDL. The alterations observed in the endothelial function after the cell-LDL interaction might play a central role in the atherogenic process in diabetes.

Reduced Na(+)-K(+)-ATPase activity and plasma lysophosphatidylcholine concentrations in diabetic patients.

A fraction from normal human plasma inhibiting Na(+)-K(+)-ATPase has been recently identified as lysophosphatidylcholine (LPC). The aim of this study was to investigate the existence of a relationship between the activity of the cellular membrane Na(+)-K(+)-ATPase and plasma LPC in human diabetes. We studied 10 patients with insulin-dependent-diabetes mellitus (IDDM), 14 patients with non-insulin-dependent diabetes mellitus (NIDDM), and 10 sex- and age-matched control subjects. Plasma LPC concentrations were increased in both IDDM and NIDDM patients compared with control subjects. Na(+)-K(+)-ATPase activity was reduced in both groups of patients in erythrocyte and platelet membranes. There was a significant correlation between the concentrations of plasma LPC and Na(+)-K(+)-ATPase activity in both erythrocyte and platelet membranes (P < 0.01). To investigate the effect of LPC on the enzyme, Na(+)-K(+)-ATPase activity was determined in erythrocyte membranes obtained from six healthy subjects after in vitro incubation with increasing concentrations of LPC (1-10 microM). Enzymatic activity was significantly reduced by in vitro LPC at a concentration of 2.5 microM, with a further decrease at 5 microM. These data suggest that the decrease in Na(+)-K(+)-ATPase activity in diabetes might be due to increased LPC concentrations.

Assessment of the activation patterns of the muscles involved in the FR test in diabetic neuropathic patients.

This study was designed to assess, in elderly neuropathic diabetic (DN) patients, the activation patterns of the main muscles involved in the Functional Reach (FR) Test, a well-recognized method to identify elderly subjects at risk of recurrent falls. Surface electromyographic (sEMG) analysis of Sternocleidomastoideus (Scm), Rectus Abdominis (RAbd), Erectores Spinae at L4 level (L4), Rectus Femoris (RF), Hamstrings (Ham), Tibialis Anterior (TA) and Soleus (Sol) was performed to this aim. Results in DN patients are compared with a control group (CH) of healthy age-matched subjects. In DN patients, TA is identified as the first muscle to be recruited (ON at -34% of the FR-period) before the movement start, in order to initiate the body forward displacement. RF is the first muscle to be recruited after TA and, togheter with RAbd, showed a progressive earlier onset from CH group. Sol and Ham (ON after the FR-start), followed by L4, act mainly as tonic muscles, opposing the movement and preventing falls. Compared to the CH group, the DN subjects show an anticipatory recruitment (-34%±6%) of TA, showing a statistically significant difference (p<;0.05) in comparison to CH group, together with the Scm activation. Results suggest a trend of DN patients in anticipating the activation of the anterior muscles of the body. This is likely due to an attempt to compensate the neuropathy-related proprioception dysfunction and to adjust the movement timing. In conclusion, the present study shows that sEMG is a suitable tool to deepen the interpretation of the FR-test execution and proposes the earlier start of TA as a possible element to identify the presence of neuropathy in diabetic subjects.

Abnormal membrane fluidity and acetylcholinesterase activity in erythrocytes from insulin-dependent diabetic patients.

An alteration in the enzymatic properties of the erythrocyte membrane acetylcholinesterase (AchE) and Na+,K+-ATPase has been described in experimental diabetes mellitus. We studied erythrocyte membrane fluidity and AchE and Na+,K+-ATPase activities in 15 insulin-dependent diabetic patients and 11 normal subjects. Fluidity was assessed by fluorescence polarization, using 1,6-diphenyl-1,3,5-hexatriene as a probe, and AchE and Na+,K+-ATPase activities were measured enzymatically. We found a significant increase in the enzymatic activity of AchE and a change in its enzymatic properties in diabetic patients compared with those in normal subjects. AchE activity correlated inversely with membrane fluorescence polarization, which was decreased in the diabetic patients, indicating an increase in membrane fluidity. Na+,K+-ATPase activity was reduced in the diabetic patients and correlated positively with the fluorescence polarization values. We hypothesize that the abnormal dynamic properties of the erythrocyte membrane may play a major role in determining the described change in enzymatic activity.

Protective effect of paraoxonase activity in high-density lipoproteins against erythrocyte membranes peroxidation: a comparison between healthy subjects and type 1 diabetic patients.

High-density lipoproteins (HDL) plays a key role in the protection against oxidative damage of lipoprotein and biological membranes. The aim of the present study was to investigate the relationship between the antioxidant role of HDL and the HDL-paraoxonase (PON) activity in healthy subjects and in type 1 diabetic patients. Moreover, the ability of HDL of controls and diabetic patients to protect and/or repair biological membranes from oxidative damage was studied. HDL were isolated from 31 type 1 diabetic patients and 31 sex- and age-matched healthy subjects and immediately used to evaluate lipid hydroperoxides and HDL-PON activity. Erythrocyte membranes obtained from healthy subjects were oxidized with 2,2-azo-bis(2-aminidinopropane)dihydrochloride and then incubated in the presence of HDL isolated from healthy or type 1 diabetic subjects, with measurements of membrane lipid hydroperoxides before and after the incubation. HDL from type 1 diabetic patients showed higher levels of lipid hydroperoxides and a lower activity of HDL-PON than healthy subjects. Moreover, HDL of type 1 diabetic patients protected less efficiently erythrocyte membranes against oxidative damage compared with HDL from healthy subjects. A negative correlation was found between HDL-PON activity and the levels of hydroperoxides of HDL, confirming the relationship between PON and lipid peroxidation and suggesting that subjects with low PON activity are more exposed to oxidative damage than subjects with high PON activity. The ability of HDL to protect erythrocyte membranes was positively correlated with HDL-PON activity and negatively correlated with the levels of lipid hydroperoxides of HDL of healthy subjects. These results confirm a linkage between PON activity and lipid peroxidation of lipoproteins and suggest that the ability of HDL to protect erythrocyte membranes might be related to the PON activity. It might be hypothesized that the decrease of PON activity in diabetic patients and the lower HDL protective action against membrane peroxidation could contribute to acceleration of arteriosclerosis in type 1 diabetes mellitus.

Glycated low density lipoproteins modify platelet properties: a compositional and functional study.

The interaction between low density lipoproteins (LDL) and platelets might play a central role in the development of atherosclerosis in diabetes. The aim of the present study was to investigate whether the glycation of LDL is associated with modifications of their physico-chemical and functional properties and to study the action of glycated LDL (glycLDL) on platelets. LDL and platelets were isolated from 15 healthy subjects. The content of thiobarbituric acid-reactive substances and the generalized polarization of the fluorescent probe Laurdan were determined in LDL glycated in vitro. Platelets were incubated with native LDL, GlycLDL, and minimally oxidized LDL, and the following parameters were evaluated: platelet aggregation, nitric oxide production, intracellular Ca(2+) concentrations, Na(+)/K(+)-adenosine triphosphatase (Na(+)/K(+)-ATPase), and Ca(2+)-ATPase activities. GlycLDL showed increased thiobarbituric acid-reactive substance levels, a red shift of the Laurdan emission maximum, and a decrease in generalized polarization, indicating a higher polarity and a reduced molecular order compared with native LDL. GlycLDL caused a significant increase in platelet nitric oxide production, intracellular Ca(2+) concentration, and aggregating response to ADP; an inhibition of the platelet membrane Na(+)/K(+)-ATPase activity; and a stimulation of Ca(2+)-ATPase activity. Minimally oxidized LDL did not cause statistically significant changes in the parameters studied. The present work demonstrates that glycation induces compositional and structural changes in LDL and suggests that an altered interaction between glycLDL and platelets might play a role in the vascular complications of diabetes.

Modifications induced by plasma from insulin-dependent diabetic patients and by lysophosphatidylcholine on human Na+,K(+)-adenosine triphosphatase.

To investigate the molecular mechanisms of the inhibition of Na+,K(+)-adenosine triphosphatase (Na+,K(+)-ATPase) in diabetes mellitus, we incubated Na+,K(+)-ATPase purified from human placenta of six healthy nondiabetic women with plasma from six insulin-dependent diabetic (IDDM) men and six healthy controls and with different concentrations of lysophosphatidylcholine (LPC). We determined the enzyme activity, anthroyl ouabain-binding capacity, dissociation constant (Kd), and average lifetime values (tau) by the static and dynamic fluorescence of anthroyl ouabain. The lipid annulus of the enzyme was studied by static and dynamic fluorescence of 1-(4-trimethylamino-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Moreover, we studied the lipid microenvironment surrounding the Na+,K(+)-ATPase purified from the placentas of six healthy women and six insulin-dependent diabetic women, determining the percent composition of phospholipids of the lipid annulus. The addition of total and protein-free IDDM plasma to normal Na+,K(+)-ATPase significantly inhibited the enzymatic activity even at the lowest concentration studied (1: 100), whereas the ouabain-binding capacity, Kd, and tau were not affected by IDDM plasma. The fluorescence polarization and lifetime values of TMA-DPH were significantly decreased by diabetic plasma. The incubation of Na+,K(+)-ATPase with LPC caused an inhibition of the enzymatic activity without modifications of the anthroyl ouabain-binding capacity and dissociation constant. The fluorescence polarization and lifetime values of TMA-DPH were significantly decreased by 5 mumol/L LPC. The study of the phospholipids surrounding Na+,K(+)-ATPase demonstrated a significant increase in the percent LPC content in IDDM patients compared with controls together with a concomitant decrease in phosphatidylcholine. These observations indicate that the inhibition caused by diabetic plasma on Na+,K(+)-ATPase is not dependent on a modification of the ouabain-binding site and that it seems to mimic the effect of LPC addition. A link between modification of the lipid moiety of the enzyme and Na+,K(+)-ATPase inhibition might be hypothesized.

Influence of low density lipoprotein from insulin-dependent diabetic patients on platelet functions.

In the present work we studied in vitro the action of low density lipoproteins (LDL) isolated from normolipemic insulin-dependent diabetic (IDDM) patients on transmembrane cation transport, nitric oxide synthase (NOS) activity, and aggregating response to stimuli of platelets from healthy subjects to elucidate whether the modified interaction between circulating lipoproteins and cells might be one of the pathogenetic mechanisms of the increased platelet activation in IDDM. LDL were obtained by discontinuous gradient ultracentrifugation from 15 IDDM out-patients and 15 sex- and age-matched healthy subjects and used for incubation experiments with control platelets. Lipid composition and hydroperoxide concentrations were studied in LDL. Platelet aggregation responses to ADP, NOS activity, cytosolic Ca2+ concentrations, and platelet membrane Na+/K+-adenosine triphosphatase (Na+/K+-ATPase) and Ca2+-ATPase activities were measured after incubation. IDDM LDL showed an increased lysophosphatidylcholine content compared with that of control LDL. IDDM LDL significantly increased the platelet aggregating response to ADP, cytosolic Ca2+ concentrations, and plasma membrane Ca2+-ATPase activity and significantly reduced NOS activity and platelet membrane Na+/K+-ATPase activity compared with those of platelets incubated in buffer or cells incubated with control LDL. The effects exerted by IDDM LDL on platelet suspensions from healthy subjects mimic the alterations observed in platelets from diabetic subjects in basal conditions. Both the decreased activity of NOS and the higher cytoplasmic concentrations of Ca2+ might cause increased platelet activation, as observed in IDDM. In conclusion, the present study suggests a new mechanism with a potential role in the early development of atherosclerosis in diabetic patients, i.e. an altered interaction between circulating lipoproteins and platelets.

Reduced susceptibility to peroxidation of erythrocyte plasma membranes from centenarians.

The plasma membrane composition affects intracellular processes and the cellular susceptibility to free radical attack, which has been associated with the impairment of cellular functions occurring during senescence. The study of the modifications of the plasma membrane in centenarians might elucidate the biological mechanisms at the basis of longevity and successful aging. The work was performed in 190 subjects, divided into five groups according to the age range: (1) 21-40 years (n=25); (2) 41-60 years (n=30); (3) 61-80 years (n=30); (4) 81-99 years (n=50); and (5) centenarians (> or = 100 years) (n=55). The following determinations were performed on erythrocyte membranes: (i) the lipid peroxide level (Lp) evaluated as malondialdehyde content; (ii) susceptibility to in vitro oxidation evaluated as difference in the content of thiobarbituric acid-reactive substances before and after phenylhydrazine addition; (iii) unsaturated/saturated fatty acid ratio and individual polyunsaturated fatty acid composition measured by gas chromatography; and (iv) fluidity studied by means of the anisotropy of the probe 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Erythrocyte membranes from centenarians showed: (i) decreased basal lipid peroxide levels and reduced susceptibility to peroxidation in comparison with elderly subjects; (ii) increased unsaturated/saturated fatty acid ratio in comparison with every other age group; (iii) higher levels of eicosapentaenoic and docosahexaenoic acid and reduced content of linoleic and arachidonic acid in comparison with elderly subjects; and (iv) decreased anisotropy of TMA-DPH, i.e. higher fluidity compared with all the other age groups. In conclusion, the present work demonstrates that erythrocyte membranes from centenarians show some distinct features in comparison with elderly subjects that might act in a protective way against injuries.

Sialic acid, diabetes, and aging: a study on the erythrocyte membrane.

Sialic acid (SA) content and Na+/K+-ATPase activity of red blood cell (RBC) membranes were studied in 26 normoalbuminuric patients with insulin-dependent diabetes mellitus (IDDM), 25 normoalbuminuric patients with non-insulin-dependent diabetes mellitus (NIDDM), and 40 healthy nondiabetic subjects with a negative family history for diabetes. A decrease in RBC membrane SA content and Na+/K+-ATPase activity was observed in older control subjects compared with younger controls. A significant correlation between age, Na+/K+-ATPase activity, and SA content was also found. No difference was observed in RBC membrane SA content between IDDM and NIDDM subjects, but Na+/K+-ATPase activity was significantly lower in IDDM patients. SA content was increased in NIDDM subjects compared with healthy subjects of similar age, whereas Na+/K+-ATPase activity was significantly lower in both IDDM and NIDDM subjects compared with controls. In NIDDM, Na+/K+-ATPase activity was significantly correlated with age, whereas both Na+/K+-ATPase activity and SA content were significantly correlated in IDDM and NIDDM patients. Hemoglobin A1c, (HbA1c) levels did not show any significant correlation either with Na+/K+-ATPase or with SA content in diabetic patients. The modified SA content and Na+/K+-ATPase activity in elderly subjects described in the present study indicate a similar behavior of the erythrocyte membrane during both RBC senescence and aging of subjects.

A study on human umbilical cord endothelial cells: functional modifications induced by plasma from insulin-dependent diabetes mellitus patients.

The aim of the present study was to evaluate the action of plasma from insulin-dependent diabetic (IDDM) pregnant women on nitric oxide synthase (NOS) activity in cultured human umbilical vein endothelial cells (HUVECs). We also studied the effect of the plasma on cytosolic calcium and on Na+/K+-adenosine triphosphatase (ATPase) activity. Dynamic fluorescence studies of membrane fluidity were contemporarily performed to detect a direct effect of plasma on the endothelial cell membrane. We observed a significant increase in NOS activity, intracellular calcium, and Na+/K+-ATPase activity in cultured HUVECs exposed to IDDM plasma. Our dynamic fluorescence study showed a different microenvironmental organization of the cellular membrane after incubation with plasma from IDDM pregnant women, with a marked decrease in microheterogeneity as evaluated in terms of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) lifetime distribution width. The present investigation suggests that plasma from IDDM pregnant women can cause a generalized disturbance in the function of endothelial cells cultured from healthy subjects. Such a modification might play a central role in the pathogenesis of the vascular complications of the disease.

Sialic acid content in erythrocyte membranes from pregnant women affected by gestational diabetes.

Sialic acid (SA) content, membrane fluidity, and Na(+)/K(+)-adenosine triphosphatase (ATPase) activity were determined in erythrocyte membrane from 10 nonpregnant women (HNPW), 16 pregnant women affected by gestational diabetes mellitus (GDM), and 25 healthy pregnant women (HPW). In GDM patients the membrane erythrocyte SA content was significantly increased compared with HNPW and membrane fluidity was significantly increased in comparison with HPW. Erythrocyte membrane Na(+)/K(+)-ATPase activity was significantly reduced in GDM patients compared both to HNPW and to HPW subjects. A significant inverse correlation was found between 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) anisotropy and erythrocyte membrane SA content in HNPW and in HPW, while this significant correlation was not observed in GDM. The present results indicate that in comparison with normal pregnancy GDM is characterized by deep alterations of the erythrocyte plasma membrane physicochemical properties (increased fluidity) and functional activities (reduced Na(+)/K(+)-ATPase activity). These modifications might be at the basis of the altered blood viscosity and placental perfusion observed under such conditions. Moreover, these results show that in physiological pregnancy and in the nonpregnant state, the erythrocyte surface membrane fluidity is inversely correlated with SA content, while in GDM there is an unbalance of this relation, which might be associated with the microcirculatory abnormality present in this disease.

Increased susceptibility to lipid oxidation of low-density lipoproteins and erythrocyte membranes from diabetic patients.

The aim of the present study was to determine if low-density lipoproteins (LDLs) and red blood cell (RBC) membranes from diabetic patients present an increased susceptibility to lipoperoxidation, which might be related to the increased incidence of atherosclerosis in diabetes. LDLs and RBC membranes were isolated from 11 insulin-dependent (IDDM) and 18 non-insulin-dependent diabetic (NIDDM) patients and exposed to a peroxidative stress by incubation with phenylhydrazine. The susceptibility to peroxidation was determined by measuring the production of thiobarbituric acid-reactive substances (TBARS) after the incubation. The following parameters were also evaluated: plasma glucose, triglycerides (TG), phospholipids (PL), total and high-density lipoprotein (HDL) cholesterol, apolipoprotein (apo) A-I, apo B, hemoglobin A1c (HbA1c), LDL PL and cholesterol, LDL fatty acid composition, and RBC membrane PL and cholesterol. Although they were apparently normolipidemic, diabetic patients showed an increased susceptibility to peroxidation in LDLs and erythrocyte membranes as compared with control subjects. The amount of arachidonic acid in LDLs and the PL concentration of RBC membranes from diabetic patients were significantly higher than in normal subjects. The increased lipoperoxidability of both RBC membranes and LDLs might play a central role in the pathogenesis of the vascular complications of diabetes mellitus.