Deranged platelet calcium homeostasis in diabetic patients with end-stage renal failure. A possible link to increased cardiovascular mortality?

Dapagliflozin acutely improves kidney function in type 2 diabetes mellitus. The PRECARE study

Dapagliflozin has been demonstrated to improve glycemic control, blood pressure, and body weight in type 2 diabetes mellitus (T2D); indeed, it can also reduce the risk of progression to renal failure, of hospitalization for heart failure and of cardiovascular death. We aim to investigate the acute effect of Dapagliflozin on kidney function in the common clinical practice in T2D. This is a study including 1402 patients with T2D recruited from 11 centers in Lombardia, Italy, who were evaluated at baseline and after 6 months of treatment with Dapagliflozin 10 mg per day. The primary outcome of the study was the change in HbA1c, while the secondary outcomes were modification of weight, BMI, systolic and diastolic pressure, creatinine, eGFR and albuminuria status. After 24 weeks of treatment with Dapagliflozin, a reduction in Hb1Ac was observed (-0.6 ± 1.8%) as well as in BMI (-1.5 ± 5.2 kg/m²). Statistically significant changes were also found for systolic and diastolic blood pressure, cholesterol and triglycerides. Interestingly, a statistically significant acute improvement of kidney function was evident. Our analyses confirm the beneficial effects of dapagliflozin after 6 months of therapy, with improvements of glycemic and lipid profiles, blood pressure, BMI. Finally, an acute positive effect on albuminuria and KIDGO classes was observed during a 6 months treatment with dapagliflozin in patients with T2D.

Continuous glucose monitoring in patients with type 2 diabetes on hemodialysis

Diabetic kidney disease is the leading cause of end-stage kidney disease in high-income countries. The strict control of glycemic oscillations is the principal therapeutic target, but this could be hard to achieve in uremic patients due to their unpredictable insulin sensitivity. Currently, the evaluation of the glycemic profile relies on serum markers (glycated hemoglobin HbA1c, glycated albumin, and fructosamine), capillary glucose blood control (self-monitoring of blood glucose), and interstitial glucose control (continue glucose monitoring). We conducted a systematic review of published articles on continue glucose monitoring in hemodialysis patients with type 2 diabetes, which included 12 major articles. Four studies found significant fluctuations in glucose levels during hemodialysis sessions. All studies reported a higher mean amplitude of glucose variations on the hemodialysis day. Three studies agreed that continue glucose monitoring is better than glycated hemoglobin in detecting these abnormalities. Moreover, continue glucose monitoring was more accurate and perceived as easier to use by patients and their caregivers. In patients with type 2 diabetes on hemodialysis, glucose levels show different variation patterns than the patients on hemodialysis without diabetes. Considering manageability, accuracy, and cost-effectiveness, continue glucose monitoring could be the ideal diagnostic tool for the patient with diabetes on hemodialysis.

Vitamin D, sub-inflammation and insulin resistance. A window on a potential role for the interaction between bone and glucose metabolism

Vitamin D is a key hormone involved in the regulation of calcium/phosphorous balance and recently it has been implicated in the pathogenesis of sub-inflammation, insulin resistance and obesity. The two main forms of vitamin D are cholecalciferol (Vitamin D3) and ergocalciferol (Vitamin D2): the active form (1,25-dihydroxyvitamin D) is the result of two hydroxylations that take place in liver, kidney, pancreas and immune cells. Vitamin D increases the production of some anti-inflammatory cytokines and reduces the release of some pro-inflammatory cytokines. Low levels of Vitamin D are also associated with an up-regulation of TLRs expression and a pro-inflammatory state. Regardless of the effect on inflammation, Vitamin D seems to directly increase insulin sensitivity and secretion, through different mechanisms. Considering the importance of low grade chronic inflammation in metabolic syndrome, obesity and diabetes, many authors hypothesized the involvement of this nutrient/hormone in the pathogenesis of these diseases. Vitamin D status could alter the balance between pro and anti-inflammatory cytokines and thus affect insulin action, lipid metabolism and adipose tissue function and structure. Numerous studies have shown that Vitamin D concentrations are inversely associated with pro-inflammatory markers, insulin resistance, glucose intolerance and obesity. Interestingly, some longitudinal trials suggested also an inverse association between vitamin D status and incident type 2 diabetes mellitus. However, vitamin D supplementation in humans showed controversial effects: with some studies demonstrating improvements in insulin sensitivity, glucose and lipid metabolism while others showing no beneficial effect on glycemic control and on inflammation. In conclusion, although the evidences of a significant role of Vitamin D on inflammation, insulin resistance and insulin secretion in the pathogenesis of obesity, metabolic syndrome and type 2 diabetes, its potential function in treatment and prevention of type 2 diabetes mellitus is unclear. Encouraging results have emerged from Vitamin D supplementation trials on patients at risk of developing diabetes and further studies are needed to fully explore and understand its clinical applications.

Near normalization of metabolic and functional features of the central nervous system in type 1 diabetic patients with end-stage renal disease after kidney-pancreas transplantation

OBJECTIVE

The pathogenesis of brain disorders in type 1 diabetes (T1D) is multifactorial and involves the adverse effects of chronic hyperglycemia and of recurrent hypoglycemia. Kidney-pancreas (KP), but not kidney alone (KD), transplantation is associated with sustained normoglycemia, improvement in quality of life, and reduction of morbidity/mortality in diabetic patients with end-stage renal disease (ESRD).

RESEARCH DESIGN AND METHODS

The aim of our study was to evaluate with magnetic resonance imaging and nuclear magnetic resonance spectroscopy ((1)H MRS) the cerebral morphology and metabolism of 15 ESRD plus T1D patients, 23 patients with ESRD plus T1D after KD (n = 9) and KP (n = 14) transplantation, and 8 age-matched control subjects.

RESULTS

Magnetic resonance imaging showed a higher prevalence of cerebrovascular disease in ESRD plus T1D patients (53% [95% CI 36-69]) compared with healthy subjects (25% [3-6], P = 0.04). Brain (1)H MRS showed lower levels of N-acetyl aspartate (NAA)-to-choline ratio in ESRD plus T1D, KD, and KP patients compared with control subjects (control subjects vs. all, P < 0.05) and of NAA-to-creatine ratio in ESRD plus T1D compared with KP and control subjects (ESRD plus T1D vs. control and KP subjects, P ≤ 0.01). The evaluation of the most common scores of psychological and neuropsychological function showed a generally better intellectual profile in control and KP subjects compared with ESRD plus T1D and KD patients.

CONCLUSIONS

Diabetes and ESRD are associated with a precocious form of brain impairment, chronic cerebrovascular disease, and cognitive decline. In KP-transplanted patients, most of these features appeared to be near normalized after a 5-year follow-up period of sustained normoglycemia.

Circulatory syndrome: an evolution of the metabolic syndrome concept!

The metabolic syndrome has been a useful, though controversial construct in clinical practice as well as a valuable model in order to understand the interactions of diverse cardiovascular risk factors. However the increasing importance of the circulatory system in particular the endothelium, in both connecting and controlling organ function has underlined the limitations of the metabolic syndrome definition. The proposed "Circulatory Syndrome" is an attempt to refine the metabolic syndrome concept by the addition of recently documented markers of cardiovascular disease including renal impairment, microalbuminuria, arterial stiffness, ventricular dysfunction and anaemia to more classic factors including hypertension, dyslipidemia and abnormal glucose metabolism; all of which easily measured in clinical practice. These markers interact with each other as well as with other factors such as aging, obesity, physical inactivity, diet and smoking. The final common pathways of inflammation, oxidative stress and hypercoagulability thereby lead to endothelial damage and eventually cardiovascular disease. Nevertheless, the Circulatory (MARC) Syndrome, like its predecessor the metabolic syndrome, is only a small step toward an understanding of these complex and as yet poorly understood markers of disease.

Platelet PMCA- and SERCA-type Ca2+ -ATPase expression in diabetes: a novel signature of abnormal megakaryocytopoiesis

BACKGROUND

Previous studies have shown platelet Ca(2+) abnormalities in diabetes mellitus and some reports suggest abnormal platelet production. Platelet Ca(2+) homeostasis is controlled by a multi-Ca(2+)-ATPase system that includes two plasma membrane Ca(2+)-ATPase (PMCA) and seven sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) isoforms. In addition, we recently found that the expression of PMCA4b and SERCA3 isoforms may serve as new markers of abnormal megakaryocytopoiesis [Nurden P et al. Impaired megakaryocytopoiesis in type 2B von Willebrand disease with severe thrombocytopenia. Blood 2006; 108: 2587-95].

AIM

To analyze the expression of major platelet Ca(2+)-ATPases in 27 patients with type 1 or type 2 diabetes (T1D or T2D) compared with normal donors.

METHODS

Investigation of protein and mRNA expressions of PMCA1b and PMCA4b, and SERCA2b, SERCA3a and SERCA3b, using specific Western blotting and reverse transcriptase-polymerase chain reaction, respectively.

RESULTS

Remarkably, all patients with T1D were found to present a higher expression of PMCA4b protein (212% +/- 28%; n = 10) and PMCA4b mRNA (155% +/- 16%; n = 17), coupled with a higher expression of SERCA3b mRNA (165% +/- 9%) in some cases. Patients with T2D (n = 10) were also studied for protein expression and were found to present similar major upregulation of the expression of PMCA4b protein (180% +/- 28%; n = 10). Lastly, five of 10 patients with T1D were studied for PMCA4b expression after insulin treatment, with four of five recovering normal expression (96% +/- 15%; n = 5).

CONCLUSIONS

Compared with the expression of PMCA4b upon platelet maturation, platelets from diabetic patients exhibit similarities with immature megakaryocytes. Thus, this study reinforces the idea that abnormal megakaryocytopoiesis can provide additional insights into diabetes and could represent a novel therapeutic target for antithrombotic drugs.

Morphological and functional differences in haemostatic axis between kidney transplanted and end-stage renal disease patients

End-stage renal disease (ESRD) is characterized by several atherothrombotic abnormalities, and kidney transplant seems to improve most of them. However, because it is not clear which mechanism is responsible for such improvement, our purpose was to clarify that point.We conducted a cross sectional study involving 30 ESRD patients, 30 ESRD kidney-transplanted patients (Ktx) and 30 healthy controls (C) to evaluate platelet morphology and function, atherothrombotic profile, endothelial abnormalities and cytokine levels involved in the insulin resistance/endothelial dysfunction. (i) Platelet morphology: The ESRD group showed platelet size similar to the other two groups (ESRD=3518x10(3)+/-549x10(3) nm2, C=3075x10(3)+/-197x10(3) nm2, Ktx=2862x10(3)+/-205x10(3) nm2) with similar platelet granules and number. (ii) Platelet surface glycoprotein: The CD41 and P-Selectin were similar between groups. (iii) Platelet intracellular calcium: Resting intracellular calcium was statistically higher in ESRD compared to the C group (ESRD=182.1+/-34.5, Ktx=126.7+/-14.1, C=72.0+/-11.0 nM, P<0.01). (iv) Hypercoagulability markers and natural anticoagulants: The Ktx and ESRD groups showed higher levels of hypercoagulability markers compared to the C group. A reduction in antithrombin activity was evident in ESRD compared to the Ktx group (P=0.03). (v) Endothelial morphology: The ESRD group showed a thickened vessel basal membrane compared to the Ktx and C groups with more endothelial sufference. (vi) Insulin resistance and pro-inflammatory cytokine profile: The ESRD showed a higher homeostasis model assessment provided equations for estimating insulin resistance (HOMA-IR) compared to the Ktx and C groups (ESRD=2.6+/-0.3, Ktx=1.8+/-0.2, C=1.1+/-0.1, P=0.005) and increased soluble tumor neurosis factor alpha (sTNFalpha) (P<0.05) and soluble vascular cell adhesion molecule (sVCAM) levels (P<0.01). Positive correlations were evident among HOMA-IR and sTNFalpha (P<0.001) and sVCAM (P=0.01), respectively. In a small subgroup of ESRD who underwent Ktx (five pts), our findings were confirmed at 1 year of follow-up, suggesting an improvement of almost haemostatic abnormalities. Kidney transplant is associated with a better atherothrombotic profile in ESRD, platelet intracellular calcium and cytokines seem to be most influenced by the transplant, while most morphological abnormalities are retained.

Pathobiology and cell interactions of platelets in diabetes

Diabetes is a well-recognised risk factor for atherosclerotic cardiovascular disease and in fact most diabetic patients die from vascular complications. The Diabetes Control and Complications Trial (DCCT) and the U.K. Prospective Diabetes Study (UKPDS) indicate a consistent relationship between hyperglycaemia and the incidence of chronic vascular complications in patients with diabetes. Platelets are essential for haemostasis, and abnormalities of platelet function may cause vascular disease in diabetes. Diabetic patients have hyperreactive platelets with exaggerated adhesion, aggregation and thrombin generation. In summary, the entire coagulation cascade is dysfunctional in diabetes. This review provides a comprehensive overview of the physiological role of platelets in maintaining haemostasis and of the pathophysiological processes that contribute to platelet dysfunction in diabetes and associated cardiovascular diseases, with special emphasis on proteomic approaches and leukocyte-platelet cross-talk.

Normalization of multiple hemostatic abnormalities in uremic type 1 diabetic patients after kidney-pancreas transplantation

To evaluate the effects of kidney-pancreas transplantation on hemostatic abnormalities in uremic type 1 diabetic patients, we conducted a cross-sectional study involving 12 type 1 diabetic patients, 30 uremic type 1 diabetic patients, 27 uremic type 1 diabetic patients who had a kidney-pancreas transplant, 12 uremic type 1 diabetic patients who had a kidney-alone transplant, and 13 healthy control subjects. We evaluated platelet and clotting system. Platelets in the group of uremic type 1 diabetic patients were significantly larger than platelets in the other groups. Resting calcium levels were significantly higher in the uremic type 1 diabetic patients and uremic type 1 diabetic patients who had a kidney-alone transplant than in the type 1 diabetic patients who had a kidney-pancreas transplant and control subjects. CD41 expression was significantly reduced in platelets from the uremic type 1 diabetic patients compared with the other groups. Levels of hypercoagulability markers in the type 1 diabetic patients who had a kidney-pancreas transplant and, to a lesser extent, the uremic type 1 diabetic patients who had a kidney-alone transplant but not the uremic type 1 diabetic patients were similar to those of the control subjects. A reduction in natural anticoagulants was evident in the uremic type 1 diabetic patients, whereas near-normal values were observed in the type 1 diabetic patients who had a kidney-pancreas transplant and uremic type 1 diabetic patients who had a kidney-alone transplant. Hemostatic abnormalities were not observed in type 1 diabetic patients who had a kidney-pancreas transplant. This finding might explain the lower cardiovascular death rate observed in type 1 diabetic patients who had a kidney-pancreas transplant compared with uremic type 1 diabetic patients who had a kidney-alone transplant or uremic type 1 diabetic patients.

Long-term beneficial effect of islet transplantation on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients

OBJECTIVE

Our aim was to evaluate the long-term effects of transplanted islets on diabetic macro-/microangiopathy in type 1 diabetic kidney-transplanted patients.

RESEARCH DESIGN AND METHODS

A total of 34 type 1 diabetic kidney-transplanted patients underwent islet transplantation and were divided into two groups: successful islet-kidney transplantation (SI-K; 21 patients, fasting C-peptide serum concentration >0.5 ng/ml for >1 year) and unsuccessful islet-kidney transplantation (UI-K; 13 patients, fasting C-peptide serum concentration <0.5 ng/ml). Patients cumulative survival, cardiovascular death rate, and atherosclerosis progression were compared in the two groups. Skin biopsies, endothelial dependent dilation (EDD), nitric oxide (NO) levels, and atherothrombotic risk factors [von Willebrand factor (vWF) and D-dimer fragment (DDF)] were studied cross-sectionally.

RESULTS

The SI-K group showed a significant better patient survival rate (SI-K 100, 100, and 90% vs. UI-K 84, 74, and 51% at 1, 4, and 7 years, respectively, P = 0.04), lower cardiovascular death rate (SI-K 1/21 vs. UI-K 4/13, chi(2) = 3.9, P = 0.04), and lower intima-media thickness progression than the UI-K group (SI-K group: delta1-3 years -13 +/- 30 micro m vs. UI-K group: delta1-3 years 245 +/- 20 micro m, P = 0.03) with decreased signs of endothelial injuring at skin biopsy. Furthermore, the SI-K group showed a higher EDD than the UI-K group (EDD: SI-K 7.8 +/- 4.5% vs. UI-K 0.5 +/- 2.7%, P = 0.02), higher basal NO (SI-K 42.9 +/- 6.5 vs. UI-K 20.2 +/- 6.8 micro mol/l, P = 0.02), and lower levels of vWF (SI-K 138.6 +/- 15.3 vs. UI-K 180.6 +/- 7.0%, P = 0.02) and DDF (SI-K 0.61 +/- 0.22 vs. UI-K 3.07 +/- 0.68 micro g/ml, P < 0.01). C-peptide-to-creatinine ratio correlated positively with EDD and NO and negatively with vWF and DDF.

CONCLUSIONS

Successful islet transplantation improves survival, cardiovascular, and endothelial function in type 1 diabetic kidney-transplanted patients.

Modulators of intraplatelet calcium concentration affect the binding of thrombospondin to blood platelets in healthy donors and patients with type 2 diabetes mellitus

Thrombospondin (TSP), which is secreted from alpha-granules of activated platelets, binds to its surface receptor (CD36) in the presence of Ca2+.

OBJECTIVES

We monitored how the modulation of intraplatelet Ca2+ affects TSP binding to CD36 on platelets from healthy donors and patients with type 2 diabetes mellitus. We also aimed to verify whether the impaired Ca2+ mobilisation in diabetes influences TSP binding upon the pharmacological modulation of calcium transport.

METHODS

Whole blood cytometry was used to monitor TSP release/binding and CD36 presentation in platelets from 28 type 2 patients and 33 healthy donors.

RESULTS

No significant changes in TSP and CD36 levels were revealed between the groups in circulating platelets and TRAP-, collagen- or thrombin-activated platelets. In healthy donors, 1 microM thapsigargin (TG) elevated the TRAP-activated TSP binding (by up to 50%, p<0.001), 5 mM EGTA reversed the effect (by up to 85%, p<0.001), and overcame the effect of TG when used together. Less profoundly expressed effects occurred in the NIDDM group. In both groups TG increased the presentation of CD36 in TRAP-stimulated platelets (p<0.05), whereas EGTA lowered the TRAP-stimulated increase in CD36 (p<0.001). The inhibition of CD36 by EGTA was stronger in healthy volunteers (41% vs. 32%, respectively, p<0.05), whereas the activation by TG was higher in the NIDDM group (11% vs. 27%, p<0.05). When acting together the suppressive effects of EGTA on TG-dependent Ca2+ mobilisation were much attenuated in diabetic subjects (p<0.05).

CONCLUSION

Both the release of TSP and CD36 presentation are under the influence of agents modulating intracellular Ca2+. Diabetic platelets seem more vulnerable to the releasers of cytosolic [Ca2+] and more resistant to the blockers of cytosolic [Ca2+] mobilisation.

Improved glycemic control and platelet function abnormalities in diabetic patients with microvascular disease

Patients with diabetes mellitus have a variety of platelet and coagulation system dysfunctions. At least theoretically, these can contribute to microvascular complications. Intensive glycemic control has been demonstrated to decrease microvascular complications in type 1 diabetics. We studied 16 patients with type 1 diabetes mellitus (11 men and five women; mean age, 39 years) with albuminuria greater than 0.1 g/d and/or proteinuria greater than 0.3 g/d and a creatinine clearance rate higher than 30 mL/min. They received a regimen including three to four injections of insulin per day with or without a weekly infusion of intravenous insulin, and were evaluated for 6 months. We compared the plasma level of von Willebrand factor, platelet aggregation responses to adenosine diphosphate (ADP), epinephrine, and collagen, and platelet adhesion at the beginning of the study and at follow-up intervals. Glycemic control improved significantly. There were no significant differences in the platelet aggregation responses to ADP (1.59 +/- 0.34 v 1.88 +/- 0.23 mmol/L, P = .3; normal, 4.6 +/- 0.2), epinephrine (0.50 +/- 0.20 v 1.11 +/- 0.31 mmol/L, P = .06; normal, 7.6 +/- 1.5), or collagen (92.4 +/- 6.61 v 82.60 +/- 3.78 seconds, P = .6; normal, 79.1 +/- 3.1) or in platelet adhesion (126.31 +/- 16.95 v 195.08 +/- 30.2 platelets, P = .34; normal, 68.6 +/- 1.4). Baseline von Willebrand factor increased, but not significantly (166.38% +/- 10.6% v 142.72% +/- 14.73%, P = .21; normal, 102.0% +/- 6.0%). In type 1 diabetic patients with established microvascular complications of nephropathy, a statistically significant improvement in glycemic control did not improve the in vitro platelet function abnormalities. Improved glycemic control delays the progression of microvascular disease through mechanisms not measured by tests of platelet function.

Platelet membrane lipid fluidity and intraplatelet calcium mobilization in type 2 diabetes mellitus

The aim of the present study was to relate the impairments in calcium mobilization and/or release to the altered membrane dynamics in platelets from patients with type 2 diabetes mellitus. Higher expression of P-selectin (1.4-fold, NS) and the reduction in GPIb alpha expression (by 27.8+/-16.7%, p < 0.0002), as well as the increased fractions of platelet microparticles (p < 0.03), reflected more intensified platelet release reaction in diabetic platelets. Overall, diabetic platelets appeared more vulnerable to stimuli facilitating calcium mobilization (by 41%, p < 0.01) and less susceptible to preventive effects of the agents hampering calcium release from intraplatelet storage pools (by 38%, p < 0.01). Both the increased calcium mobilization from intraplatelet storage pools and higher levels of intracellular free calcium in the presence of procaine in diabetic platelets correlated with the reduced platelet membrane lipid fluidity (resp. pR < 0.03 and pR < 0.015). We conclude that the biophysical state of platelet membrane components in diabetes mellitus is the crucial determinant of platelet hyperfunction and probably contributes to the intensified calcium mobilization in diabetic platelets. The depressed preventive effects of procaine on platelet release reaction and calcium mobilization in diabetic platelets may result from the primary dislocations and/or distortions of membrane components caused by the diabetic state.