Association between insulin resistance and endothelial dysfunction in renal transplant recipients

Association of FGF19, FGF21 and FGF23 with carbohydrate metabolism parameters and insulin resistance in patients with chronic kidney disease

Insulin resistance (IR) is characterised by increased gluconeogenesis in the liver and the resistance of peripheral receptors to insulin. Several factors, including IR, type 2 diabetes, new-onset diabetes after transplant (NODAT) and secondary parathyroidism, are related to chronic kidney disease (CKD). These factors are associated with higher mortality due to the increased risk of cardiovascular complications. Many factors have been identified as potential markers of IR in CKD. These factors include fibroblast growth factors (FGFs), a subfamily of endocrine polypeptides. In this study, we examined the association of FGF19, FGF21 and FGF23 with selected parameters related to carbohydrate metabolism and insulin resistance in non diabetic patients with predialysis CKD and in non diabetic patients after renal transplantation. The study included 108 non diabetic subjects: 40 patients with predialysis CKD, 45 patients with CKD who had undergone renal transplantation, and 23 healthy subjects (control group). In patients who had undergone renal transplantation, concentrations of FGF23 were increased compared to the control group and patients with predialysis CKD. The highest and lowest FGF19 concentrations were observed in CKD patients and in patients who had undergone kidney transplantation, respectively. This difference was statistically significant. Leptin concentrations were higher in CKD patients compared to the control group and patients who had undergone kidney transplantation. There were no statistically significant differences in adiponectin concentrations, lean body mass or fat tissue mass between the studied groups. HOMA-IR and insulin levels were significantly increased in CKD patients and in patients who had undergone renal transplantation in comparison to the control group. The results of the study suggest the involvement of FGF in carbohydrate metabolism and insulin resistance in patients with predialysis CKD, as well as a correlation with kidney function.

Calcineurin inhibitor effects on glucose metabolism and endothelial function following renal transplantation

BACKGROUND

Calcineurin inhibitors (CNI) are involved in the development of post-transplant diabetes mellitus (PTDM). Changes in insulin secretion and sensitivity contribute to the development of PTDM and are associated with endothelial function.

METHODS

In a pre-defined substudy of a previously published randomized trial in renal transplant recipients we compared the effect of CNI treatment (n = 23) with complete CNI-avoidance (n = 21) on insulin secretion and sensitivity (oral glucose tolerance test) as well as endothelial function (laser Doppler flowmetry), 10 wk and 12 months following transplantation.

RESULTS

Insulin sensitivity differed 10 wk post-transplant and was significantly better after 12 months in patients never treated with CNI drugs [0.091 (0.050) vs. 0.083 (0.036) micromol/kg/min/pmol/L, p = 0.043]. Insulin secretion tended to be higher in CNI treated patients at both time points (p = 0.068). Endothelial function was not significantly different at week 10 [540 (205) vs. 227 (565) arbitary units x minutes, p = 0.35] or month 12 [510 (620) vs. 243 (242), p = 0.33].

CONCLUSIONS

Findings in the present study indicate that long-term CNI treatment negatively affects glucose metabolism and this may contribute to the increased risk for premature cardiovascular disease in CNI treated renal transplant recipients. Further studies to elucidate this hypothesis are, however, needed.

Vascular calcification is associated with impaired microcirculatory function in chronic haemodialysis patients

Although vascular calcification (VC) in dialysis patients is associated with increased cardiovascular events, the pathophysiology is still largely obscure. Microcirculatory dysfunction may contribute to demand myocardial ischaemia. We have studied cutaneous microcirculatory function in haemodialysis (HD) patients with and without large-vessel VC. 37 non-diabetic subjects (20 HD and 17 healthy controls) were studied. VC was assessed using CT scanning of a standardised segment of superficial femoral artery (11 VC+, 9 VC-). Laser Doppler imaging was undertaken using a Periscan PIM II(R) at rest and under vasodilator challenge. Baseline perfusion was not statistically different in VC+ patients than VC- patients or controls (1.03 +/- 0.2, 1.08 +/- 0.2, 0.93 +/- 0.3 PU respectively). Overall, the maximum vasodilatory response to both ACh (p < 0.001) and SNP (p = 0.004) was lower in the HD than the control group. In addition, the HD patients took longer to reach a maximum vasodilatation than the controls (p = 0.008 for ACh, n.s. for SNP). Further, the maximum vasodilatory response in the VC+ patients was lower and patients took longer to reach maximum vasodilatation than the VC- group. We have demonstrated, for the first time, impaired and dysregulated microcirculatory function in patients with VC. This may be important in understanding the pathophysiology of the complications and cardiovascular consequences of VC.

Endothelial dysfunction and fetuin A levels before and after kidney transplantation

BACKGROUND

Endothelial dysfunction (ED) has a major role in the cardiovascular outcome of patients with chronic kidney disease (CKD). The aim of this study was to investigate the relation between fetuin A levels and ED in kidney transplant recipients.

METHODS

Forty-two living donor kidney transplant recipients, 21 (11 male) on cyclosporine A and 21 (10 male) on tacrolimus-based regimes, were studied. Forty-two (21 male) healthy subjects were enrolled as controls. Fetuin A, highly sensitive C-reactive protein (hsCRP) levels, brachial artery endothelium-dependent vasodilatation (FMD), nitroglycerine mediated dilatation (NMD), and carotid intima-media thickness (CIMT) were measured before transplantation and on the 30th and 90th days posttransplant.

RESULTS

Pretransplantation serum fetuin A concentrations and FMD values of patients were significantly lower than those of the controls (P<0.001 for both). These were significantly increased in the 30th and 90th days posttransplantation There was a significant positive correlation between Fetuin A and FMD levels both before and after kidney transplantation (r=0.534, r=0.576; respectively, P<0.001 for both). Carotid intima-media thickness and hsCRP levels decreased after transplantation (P<0.001 for all). According to the regression analysis, fetuin A, intact parathyroid hormone, and hsCRP levels were the independent determinants of FMD.

CONCLUSION

The results of the present study suggest that low serum fetuin A levels in CKD may contribute to impaired endothelial functions in CKD. Future studies should clarify the role of fetuin A levels in cardiovascular outcomes of CKD.