Donatella Spotti

Lack of Feedback Inhibition of Insulin Secretion in Denervated Human Pancreas

In this study, pancreas transplantation is used as a clinical model of pancreas denervation in humans. To assess the role of innervation on the feedback autoinhibition of insulin secretion, we studied four groups of subjects--group 1: 16 patients with combined pancreas and kidney transplantation (plasma glucose = 5.1 mM, HbA1c = 6.4%, creatinine = 86 mM); group 2: 8 patients with chronic uveitis on the same immunosuppressive therapy as transplanted patients (12 mg/day prednisone, 5 mg.kg-1.day-1 CsA); group 3: 4 uremic, nondiabetic patients in chronic hemodialysis; group 4: 7 normal, nondiabetic control subjects. The following means were used to study the groups: 1) a two-step hyperinsulinemic euglycemic clamp (insulin infusion rate = 1 mU and 5 mU.kg-1.min-1); and 2) a 0.3 mU.kg-1.min-1 hypoglycemic clamp (steady-state plasma glucose = 3.1 mM). Basal plasma-free IRI (84 +/- 6, 42 +/- 12, 72 +/- 12, and 30 +/- 6 pM in groups 1, 2, 3, and 4, respectively), basal C-peptide (0.79 +/- 0.05, 0.66 +/- 0.05, 3.04 +/- 0.20, and 0.59 +/- 0.06 nM in groups 1, 2, 3, and 4, respectively), and glucagon (105 +/- 13, 69 +/- 4, 171 +/- 10, and 71 +/- 5 pg/ml in groups 1, 2, 3, and 4, respectively) were increased in groups 1 and 3 with respect to groups 2 and 4 (P < 0.01). During euglycemic hyperinsulinemia, plasma C-peptide decreased by 45, 20, and 44% in groups 2, 3, and 4, respectively, but showed no significant change from the basal in patients with transplanted pancreases.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphisms at the regulatory regions of the CASR gene influence stone risk in primary hyperparathyroidism

BACKGROUND AND OBJECTIVE Single nucleotide polymorphisms (SNPs) of the calcium-sensing receptor (CASR) gene at the regulatory region were associated with idiopathic calcium nephrolithiasis. To confirm their association with nephrolithiasis, we tested patients with primary hyperparathyroidism (PHPT). DESIGN A genotype-phenotype association study. METHODS In all, 332 PHPT patients and 453 healthy controls were genotyped for the rs7652589 (G>A) and rs1501899 (G>A) SNPs sited in the noncoding regulatory region of the CASR gene. Allele, haplotype, and diplotype distribution were compared between PHPT patients and controls, and in stone forming and stone-free PHPT patients. RESULTS The allele frequency at rs7652589 and rs1501899 SNPs was similar in PHPT patients and controls. The A minor alleles at these two SNPs were more frequent in stone forming (n=157) than in stone-free (n=175) PHPT patients (rs7652589: 36.9 vs 27.1%, P=0.007; rs1501899: 37.1 vs 26.4%, P=0.003). Accordingly, homozygous or heterozygous PHPT patients for the AA haplotype (n=174, AA/AA or AA/GG diplotype) had an increased stone risk (odds ratio 1.83, 95% confidence interval 1.2-2.9, P=0.008). Furthermore, these PHPT patients had higher serum concentrations of ionized calcium and parathyroid hormone (1.50 ± 0.015 mmol/l and 183 ± 12.2 pg/ml) than patients with the GG/GG diplotype (n=145, 1.47 ± 0.011 mmol/l (P=0.04) and 150 ± 11.4 pg/ml (P=0.049)). Using a logistic regression model, the increase in stone risk in PHPT patients was predicted by AA/AA or AA/GG diplotype, the highest tertile of serum ionized calcium values and the lowest tertile of age. CONCLUSIONS Polymorphisms located in the regulatory region of the CASR gene may increase susceptibility of the PHPT patients to kidney stone production.

1983 to 1992: Report on Regular Dialysis and Transplantation in Lombardy

This 1993 report of the Lombardy Regional Dialysis and Transplant Registry refers to all the data collected between January 1, 1983, and December, 31, 1992, by means of individual patient questionnaires sent to all of Lombardys 44 renal units (100% replies). The number of patients recorded by the Registry as being alive progressively increased; by the end of 1992, the number was 6,014 (655 patients per million population): 4,770 patients were on dialysis treatment (515 patients per million population, 79.3%) and 1,244 patients (140 patients per million population, 20.7%) had received a kidney graft. The acceptance rate for dialysis increased from 64 per million population in 1983 to 102 per million population in 1992; the increase in the transplant rate was much lower (from 18.7 to 21.3 per million population). The percentage of primary nephropathies in the new patients accepted for dialysis treatment were 22.0% glomerulonephritis, 13.8% interstitial nephritis, 15.2% vascular diseases, 10.1% cystic kidney, and 10.6% diabetes. The use of acetate hemodialysis declined over the 10-year period from 72.4% to 17.5%; that of bicarbonate hemodialysis increased from 8.8% to 50.1% and that of hemodiafiltration increased from 0.2% to 11.1%. The prevalence of hospital hemodialysis was stable, ranging from 55.4% to 52.2%; home hemodialysis decreased from 15.7% to 5.3%, continuous ambulatory peritoneal dialysis increased from 13.3% to 19.6%, and limited care increased from 13.7% to 22.4%. The crude death rate increased from 7.5% in 1983 to 10.5% in 1992. The survival rate (Kaplan-Meier) of all patients on dialysis was 78.8% at 2 years, 62.2% at 4 years, and 40% at 8 years; for transplanted patients, the survival and graft survival rate at 2 years was, respectively, 95% and 86%. The relative death risk of the patients on peritoneal dialysis with respect to those on hemodialysis was 1.419, as estimated by the Cox proportional hazard regression model. The main causes of deaths of patients on dialysis treatment during the year 1992 were cardiovascular diseases (47.0%) and cachexia (19.5%); in transplanted patients, they were cardiovascular diseases (36.6%) and infections (34%). Registries are not only important for planning health care but are also very useful instruments for clinical research.

Free-Insulin Profiles After Intraperitoneal, Intramuscular, and Subcutaneous Insulin Administration

The aim of our study was to compare the time course of plasma free-insulin appearance after injection of equal amounts of insulin into the peritoneal cavity above and below the transverse mesocolon, intramuscularly, and subcutaneously. Seven nondiabetic subjects undergoing cholecystectomy received in random sequence 0.2 IU/kg of insulin into the peritoneal cavity above or below the transverse mesocolon. Concentrations of plasma free insulin were compared with those obtained from seven other nondiabetic subjects after repeated injections of equal amounts of insulin intramuscularly and subcutaneously. Intraperitoneal insulin above the transverse mesocolon yielded a faster rise of free insulin, peaking at 15 min, whereas intraperitoneal insulin below the transverse mesocolon produced a somewhat slower rise, peaking at 30 min. The area under the curves between 0 and 15 min was greater after the injection above than below the transverse mesocolon (P < .05). Intramuscular and subcutaneous insulin injections resulted in a slower rise of plasma free insulin, peaking at 60 and 90 min, respectively. We conclude that the pattern of insulin appearance in the plasma resembles more closely physiologic events after intraperitoneal than after subcutaneous or intramuscular insulin administration.

Decreased transcriptional activity of calcium-sensing receptor gene promoter 1 is associated with calcium nephrolithiasis

BACKGROUND CaSR gene is a candidate for calcium nephrolithiasis. Single-nucleotide polymorphisms (SNPs) encompassing its regulatory region were associated with calcium nephrolithiasis. AIMS We tested SNPs in the CaSR gene regulatory region associated with calcium nephrolithiasis and their effects in kidney. SUBJECTS AND METHODS One hundred sixty-seven idiopathic calcium stone formers and 214 healthy controls were genotyped for four CaSR gene SNPs identified by bioinformatics analysis as modifying transcription factor binding sites. Strontium excretion after an oral load was tested in 55 stone formers. Transcriptional activity induced by variant alleles at CaSR gene promoters was compared by luciferase reporter gene assay in HEK-293 and HKC-8 cells. CaSR and claudin-14 mRNA levels were measured by real-time PCR in 107 normal kidney medulla samples and compared in patients with different CaSR genotype. RESULTS Only rs6776158 (A>G), located in the promoter 1, was associated with nephrolithiasis. Its minor G allele was more frequent in stone formers than controls (37.8% vs 26.4%, P = .001). A reduced strontium excretion was observed in GG homozygous stone formers. Luciferase fluorescent activity was lower in cells transfected with the promoter 1 including G allele at rs6776158 than cells transfected with the A allele. CaSR mRNA levels were lower in kidney medulla samples from homozygous carriers for the G allele at rs6776158 than carriers for the A allele. Claudin-14 mRNA levels were also lower in GG homozygous subjects. CONCLUSIONS Minor allele at rs6776158 may predispose to calcium stones by decreasing transcriptional activity of the CaSR gene promoter 1 and CaSR expression in kidney tubules.

Combined pancreas and kidney transplantation normalizes protein metabolism in insulin-dependent diabetic-uremic patients

In order to assess the combined and separate effects of pancreas and kidney transplant on whole-body protein metabolism, 9 insulin-dependent diabetic-uremic patients (IDDUP), 14 patients after combined kidney-pancreas transplantation (KP-Tx), and 6 insulin-dependent diabetic patients with isolated kidney transplant (K-Tx), were studied in the basal postabsorptive state and during euglycemic hyperinsulinemia (study 1). [1-14C]Leucine infusion and indirect calorimetry were utilized to assess leucine metabolism. The subjects were studied again with a combined infusion of insulin and amino acids, given to mimic postprandial amino acid levels (study 2). In the basal state, IDDUP demonstrated with respect to normal subjects (CON): (a) higher free-insulin concentration (17.8 +/- 2.8 vs. 6.8 +/- 1.1 microU/ml, P < 0.01) (107 +/- 17 vs. 41 +/- 7 pM); (b) reduced plasma leucine (92 +/- 9 vs. 124 +/- 2 microM, P < 0.05), branched chain amino acids (BCAA) (297 +/- 34 vs. 416 +/- 10 microM, P < 0.05), endogenous leucine flux (ELF) (28.7 +/- 0.8 vs. 39.5 +/- 0.7 mumol.m-2.min-1, P < 0.01) and nonoxidative leucine disposal (NOLD) (20.7 +/- 0.2 vs. 32.0 +/- 0.7 mumol.m-2. min-1, P < 0.01); (c) similar leucine oxidation (LO) (8.0 +/- 0.1 vs. 7.5 +/- 0.1 mumol.m-2.min-1; P = NS). Both KP-Tx and K-Tx patients showed a complete normalization of plasma leucine (116 +/- 5 and 107 +/- 9 microM), ELF (38.1 +/- 0.1 and 38.5 +/- 0.9 mumol.m-2.min-1), and NOLD (28.3 +/- 0.6 and 31.0 +/- 1.3 mumol.m-2.min-1) (P = NS vs, CON). During hyperinsulinemia (study 1), IDDUP showed a defective decrease of leucine (42% vs. 53%; P < 0.05), BCAA (38% vs. 47%, P < 0.05), ELF (28% vs. 33%, P < 0.05), and LO (0% vs. 32%, P < 0.05) with respect to CON. Isolated kidney transplant reverted the defective inhibition of ELF (34%, P = NS vs. CON) of IDDUP, but not the inhibition of LO (18%, P < 0.05 vs. CON) by insulin. Combined kidney and pancreas transplanation normalized all kinetic parameters of insulin-mediated protein turnover. During combined hyperinsulinemia and hyperaminoacidemia (study 2), IDDUP showed a defective stimulation of NOLD (27.9 +/- 0.7 vs. 36.1 +/- 0.8 mumol.m-2.min-1, P < 0.01 compared to CON), which was normalized by transplantation (44.3 +/- 0.8 mumol.m-2.min-1).

A best practice position statement on the role of the nephrologist in the prevention and follow-up of preeclampsia: the Italian study group on kidney and pregnancy

Preeclampsia (PE) is a protean syndrome causing a transitory kidney disease, characterised by hypertension and proteinuria, ultimately reversible after delivery. Its prevalence is variously estimated, from 3 to 5% to 10% if all the related disorders, including also pregnancy-induced hypertension (PIH) and HELLP syndrome (haemolysis, increase in liver enzyme, low platelets) are included. Both nephrologists and obstetricians are involved in the management of the disease, according to different protocols, and the clinical management, as well as the role for each specialty, differs worldwide. The increased awareness of the role of chronic kidney disease in pregnancy, complicating up to 3% of pregnancies, and the knowledge that PE is associated with an increased risk for development of CKD later in life have recently increased the interest and redesigned the role of the nephrologists in this context. However, while the heterogeneous definitions of PE, its recent reclassification, an emerging role for biochemical biomarkers, the growing body of epidemiological data and the new potential therapeutic interventions lead to counsel long-term follow-up, the lack of resources for chronic patients and the increasing costs of care limit the potential for preventive actions, and suggest tailoring specific interventional strategies. The aim of the present position statement of the Kidney and Pregnancy Study Group of the Italian Society of Nephrology is to review the literature and to try to identify theoretical and pragmatic bases for an agreed management of PE in the nephrological setting, with particular attention to the prevention of the syndrome (recurrent PE, presence of baseline CKD) and to the organization of the postpartum follow-up.

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

OBJECTIVE Platelet hyperfunction is a typical feature of the prothrombotic state that frequently complicates the natural history of diabetes. In uremia, a bleeding diathesis is present, which principally involves the primary phase of hemostasis. Thus, in patients with uremia of diabetic origin, the infrequent coexistence of two opposite alterations of hemostasis takes place. In patients with uremia, an increased incidence of cardiovascular events and related mortality is observed. This phenomenon is greatly amplified in uremia of diabetic origin. Calcium homeostasis is a critical aspect of platelet function, which has recently become available in human diseases. The aim of this study was to evaluate calcium homeostasis in platelets from patients with uremia of diabetic and nondiabetic origin. RESEARCH DESIGN AND METHODS We evaluated, by means of Fura 2, the intracellular concentration of ionized calcium ([Ca2+]i) in platelets from 18 patients with uremia of diabetic origin, 12 patients with uremia of nondiabetic origin and 16 healthy control subjects [Ca2+]i was evaluated in resting conditions and after stimulation with 0.05, 0.1, 0.5 U/ml thrombin. RESULTS Platelets from uremic patients with diabetes had higher resting [Ca2+]i than both control subjects (P = 0.01) and uremic patients without diabetes (P = 0.001). Similarly, after stimulation with thrombin, the absolute increase of [Ca2+]i was higher (P < 0.05) in platelets from uremic patients with diabetes compared with both control subjects and uremic patients without diabetes. The relative increase of [Ca2+]i was higher (P < 0.05) than normal in platelets from uremic patients after weak or intermediate strength thrombin. No correlation were present between [Ca2+]i values and other clinical and laboratory variables potentially associated with platelet hyperfunction. CONCLUSIONS Diabetes and uremia in combination further deteriorate the abnormal platelet calcium homeostasis observed in uremia.

Dietary style and acid load in an Italian population of calcium kidney stone formers

BACKGROUND AND AIMS Animal protein intake may cause an acid load that predisposes individuals to stones by influencing calcium and citrate excretion. These associations were not confirmed in recent studies. Therefore the present study was aimed to compare acid load of diet in stone formers and controls. METHODS AND RESULTS Participants to the study were 157 consecutive calcium stone formers and 144 controls. Diet was analyzed in these subjects using a software that evaluated nutrient intake from a three-day food intake diary. This software also estimated the potential renal acid load (PRAL, mEq/day). Twenty-four-hour urine excretion of ions and citrate was measured in stone formers. Stone former diet had lower intake of glucose, fructose, potassium and fiber and higher PRAL in comparison with controls. The multinomial logistic regression analysis showed that stone risk decreased in association with the middle and the highest tertiles of fiber intake and increased in association with the highest tertile of PRAL. The linear multiple regression analysis showed that calcium excretion was associated with the sodium excretion and that citrate excretion was associated with the PRAL and animal protein intake in stone formers. CONCLUSION Our findings suggest that stone formers may undergo a greater dietary acid load sustained by a low vegetable intake and base provision. Dietary acid load does not appear as the main determinant of calcium excretion, but may promote stone risk by decreasing citrate excretion. Sodium intake may predispose to stones by stimulating calcium excretion.

Intestinal Calcium Absorption among Hypercalciuric Patients with or without Calcium Kidney Stones

BACKGROUND AND OBJECTIVES Idiopathic hypercalciuria is a frequent defect in calcium kidney stone formers that is associated with high intestinal calcium absorption and osteopenia. Characteristics distinguishing hypercalciuric stone formers from hypercalciuric patients without kidney stone history (HNSFs) are unknown and were explored in our study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We compared 172 hypercalciuric stone formers with 36 HNSFs retrospectively selected from patients referred to outpatient clinics of the San Raffaele Hospital in Milan from 1998 to 2003. Calcium metabolism and lumbar bone mineral density were analyzed in these patients. A strontium oral load test was performed: strontium was measured in 240-minute urine and serum 30, 60, and 240 minutes after strontium ingestion; serum strontium concentration-time curve and renal strontium clearance were evaluated to estimate absorption and excretion of divalent cations. RESULTS Serum strontium concentration-time curve (P<0.001) and strontium clearance (4.9±1.3 versus 3.5±2.7 ml/min; P<0.001) were higher in hypercalciuric stone formers than HNSFs, respectively. The serum strontium-time curve was also higher in hypercalciuric stone formers with low bone mineral density (n=42) than in hypercalciuric stone formers with normal bone mineral density (n=130; P=0.03) and HNSFs with low (n=22; P=0.01) or normal bone mineral density (n=14; P=0.02). Strontium clearance was greater in hypercalciuric stone formers with normal bone mineral density (5.3±3.4 ml/min) than in hypercalciuric stone formers and HNSFs with low bone mineral density (3.6±2.5 and 3.1±2.5 ml/min, respectively; P=0.03). Multivariate regression analyses displayed that strontium absorption at 30 minutes was positively associated calcium excretion (P=0.03) and negatively associated with lumbar bone mineral density z score (P=0.001) in hypercalciuric stone formers; furthermore, hypercalciuric patients in the highest quartile of strontium absorption had increased stone production risk (odds ratio, 5.06; 95% confidence interval, 1.2 to 20.9; P=0.03). CONCLUSIONS High calcium absorption in duodenum and jejunum may expose hypercalciuric patients to the risk of stones because of increased postprandial calcium concentrations in urine and tubular fluid. High calcium absorption may identify patients at risk of bone loss among stone formers.