[Is obesity a barrier to kidney transplantation?]. / L'obésité est-elle un frein à la transplantation rénale ?

INTRODUCTION: Kidney transplantation is the most suitable of ESRD care. The proportion of obese people is increasing in the general population and patients with kidney impairment. It is important to assess the impact of obesity on surgical complications of kidney transplantation. The aim of this retrospective study was to signify the correlation between obesity and the occurrence of postoperative urological complications during the first year. METHODS: We conducted a retrospective study from March 1999 to December 2009. We conducted a chart review of patients undergoing kidney transplantation. The kidneys were taken from cadaveric donors. Data collected included age, weight, height, preoperative BMI; causal nephropathy, smoking, hypertension, diabetes, anticoagulation therapy. Intraoperative data included operative time (DO), cold ischemia. Urological complications were recorded during the first year after the kidney transplantation (vascular anastomotic strictures, ureterovesical stenosis, lymphorrheas, pyelonephritis, hematoma, wound infection). Statistical analysis consisted of a t-test for independent samples and univariate and multivariate logistic regression for the occurrence of complications. RESULTS: Four hundred and twenty-two patients were transplanted in total. We excluded 20 patients. BMI and duration of surgery patients with complications were significantly different from those of patients with no complications (P=0.016 and P=0.039, respectively). Obese (n=48) had more diabetes (12.5% versus 3.7%, P=0.014), were more often smoking (35.4% versus 22%, P=0.012), had a longer DO (203.64minutes versus 182.46minutes, P=0.006), and complications (62.5% versus 50.28%, P=0.03) than patients with a BMI <30 (n=354). After adjusting for age, smoking, DO, diabetes and BMI showed that only BMI was an independent predictor of the occurrence of postoperative complications with P=0.048 and RR=1.058 [CI: 1 to 1.119]. However, there was no more transplantectomy obese (P=0.911). CONCLUSION: Our study showed that there is a significant risk of surgical complications after kidney transplantation in obese patients. But ultimately, this does not affect graft survival because there are no more transplantectomies or return to dialysis. LEVEL OF EVIDENCE: 5.

[The impact of obesity on renal function at one year after kidney transplantation: single-center experience]. / Impact de l'obésité sur la fonction rénale à 1 an chez les transplantés rénaux: expérience mono centrique.

INTRODUCTION: Kidney transplantation is the treatment of choice for ESRD. Several studies have investigated the factors that may affect kidney function at 1 year. The factors mentioned are anemia, hypercholesterolemia, immunosuppressors, etc. We studied the independent predictors of serum creatinine>100µmol/L at 1 year. MATERIALS AND METHODS: We conducted a retrospective study from March 1999 to December 2009. We conducted a chart review of 402 kidney transplant patients. The kidneys were removed from cadaveric donors. Data collected included age, weight, height, preoperative BMI, the causal nephropathy, smoking, hypertension, diabetes, anticoagulation. Intraoperative data included operative time, and cold ischemia. Statistical analysis consisted of a t-test for independent samples comparing the group with a creatinine≤100µmol/L vs>100 group, and univariate and multivariate Cox regression for a serum creatinine>100µmol/L at 1 year and test of correlation between BMI and serum creatinine at 1 year postoperatively. RESULTS: We found a significant difference in BMI and cold ischemia with P=0.008 and P=0.002, respectively. In contrast there was no difference in age, operative time and blood loss, P=0.758, P=0.941 and P=0.963, respectively. Multivariate Cox regression showed that donor age P=0.004 (HR: 1.016 and CI: 1.005-1.027), a recipient age P=0.023 (HR: 0.986 and CI: 0.974-0.998) and BMI P=0.001 (HR: 1.019 and CI: 1.010-1.028) were independent predictors of serum creatinine>100µmol/L at 1 year. The Pearson correlation coefficient r=0.154 (P=0.004) showed a significant correlation between BMI and serum creatinine. CONCLUSION: Our study showed that donor age, recipient age and BMI were independent predictors of renal function>100µmol/L at 1 year. Our results highlight the difficulty of the management of obesity in renal transplant patients. LEVEL OF EVIDENCE: 5.

Genetic mapping of the human C5a receptor. Identification of transmembrane amino acids critical for receptor function.

Many hormones and sensory stimuli signal through a superfamily of seven transmembrane-spanning receptors to activate heterotrimeric G proteins. How the seven transmembrane segments of the receptors (a molecular architecture of bundled alpha-helices conserved from yeast to man) work as "on/off" switches remains unknown. Previously, we used random saturation mutagenesis coupled with a genetic selection in yeast to determine the relative importance of amino acids in four of the seven transmembrane segments of the human C5a receptor (Baranski, T. J., Herzmark, P., Lichtarge, O., Gerber, B. O., Trueheart, J., Meng, E. C., Iiri, T., Sheikh, S. P., and Bourne, H. R. (1999) J. Biol. Chem. 274, 15757-15765). In this study, we evaluate helices I, II, and IV, thereby furnishing a complete mutational map of the seven transmembrane helices of the human C5a receptor. Our analysis identified 19 amino acid positions resistant to non-conservative substitutions. When combined with the 25 essential residues previously identified in helices III and V-VII, they delineate two distinct components of the receptor switch: a ligand-binding surface at or near the extracellular surface of the helix bundle and a core cluster in the cytoplasmic half of the bundle. In addition, we found critical amino acids in the first and second helices that are predicted to face the lipid membrane. These residues form an extended surface that might mediate interactions with lipids and other membrane proteins or function as an oligomerization domain with other receptors.