Alicia Elbert

HDL-associated enzymes and proteins in hemodialysis patients.

OBJECTIVES To evaluate HDL-associated proteins and enzymes and their relation with lipoprotein profile and inflammatory markers in chronic renal patients on hemodialysis. DESIGN AND METHODS We studied 53 patients under hemodialysis and 32 healthy subjects as controls. We compared plasma lipids, Apoprotein-AI and hs-CRP, as a marker of chronic inflammation. We evaluated proteins and enzymes associated to HDL, involved in several points of lipoprotein metabolism: CETP, paraoxonase and LpPLA2 activities. Hepatic lipase was measured in postheparin plasma. RESULTS Patients showed higher triglycerides and lower LDL-, HDL- and total-cholesterol than controls (p<0.05). Also, in comparison with controls, Apoprotein-AI, paraoxonase and hepatic lipase were lower, while CETP was higher (p<0.03). LpPLA2 did not show changes between groups. CONCLUSION Beyond plasma lipid-lipoprotein profile, other factors could contribute to induce a pro-oxidative and pro-inflammatory status. The protective role of HDL does not only depend on its concentration, but also on its functionality.

Endothelial Lipase Activity Predicts High-Density Lipoprotein Catabolism in Hemodialysis: Novel Phospholipase Assay in Postheparin Human Plasma

Objective—A novel phospholipase assay was used to measure for the first time the behavior of endothelial and hepatic phospholipase activities in postheparin human plasma of hemodialyzed patients and its relationship with atherogenic and antiatherogenic lipoprotein levels. Methods and Results—Endothelial and hepatic phospholipase activity was assessed in a total SN1-specific phospholipase assay, using (1-decanoylthio-1-deoxy-2-decanoyl-sn-glycero-3-phosphoryl) ethylene glycol as the substrate. Hemodialyzed patients presented lower values of total and hepatic phospholipase activity than controls: 4.4 (1.9–9.0) versus 7.5 (3.6–18.0) and 2.6 (0.7–6.2) versus 6.6 (1.3–15.2) &mgr;mol of fatty acid released per milliliter of postheparin plasma per hour, respectively (P<0.001); however, endothelial lipase (EL) phospholipase activity was increased in patients: 1.7 (0.8–3.0) versus 1.1 (0.1–2.7) &mgr;mol of fatty acid released per milliliter of postheparin plasma per hour (P=0.008). EL was negatively associated with high-density lipoprotein (HDL)-cholesterol (r=–0.427; P=0.001), and apolipoprotein A-I levels, total phospholipase, and hepatic lipase activity were directly associated with low-density lipoprotein-cholesterol and apolipoprotein B. The association of EL and HDL-cholesterol remained significant when adjusting for waist circumference (&bgr;=–0.26; P=0.05), and the effect of hepatic lipase on low-density lipoprotein-cholesterol continued after adjusting for age (&bgr;=0.46; P= 0.001). Conclusion—Our results support the hypothesis that EL is the predominant enzyme responsible for lipolytic catabolism of HDLs in hemodialyzed patients and resolve the apparent paradox observed between low hepatic lipase activity and decreased HDL-cholesterol levels observed in these patients. In addition, the ability to assess total hepatic lipase and EL phospholipase activity in plasma will increase our knowledge of the mechanisms involved in controlling HDL levels and cardiovascular risk in hemodialyzed patients, as well as other populations with low levels of HDL-cholesterol.

Detection of structural alterations in LDL isolated from type 2 diabetic patients: application of the fructosamine assay to evaluate the extent of LDL glycation

Modifications in LDL such as glycation contribute to the accelerated development of macrovascular alterations in diabetic patients [1], but to date there is no recommended method to determine the extent of plasma LDL glycation. The fructosamine assay originally described by Johnson et al. [2] to evaluate medium term glycemic control in diabetic patients, was previously applied to measurements of glycated protein in LDL fractions isolated from in vitro glycated plasma obtained from non-diabetic subjects [3]. However, fructosamine values in LDL from diabetic patients are as yet unknown. Therefore, we re-adapted and evaluated the fructosamine assay for the determination of glycated LDL in type 2 diabetic patients. Besides, we characterized LDLs by means of their chemical composition and estimated the predominance of small dense LDL through the total proteins/cholesterol ratio in the LDL fraction [4]. Twenty-three type 2 diabetic patients of either sex, whose ages ranged from 47 to 82 years, were studied. Mean (9S.D.) levels of HbA1c were 8.592.5%, serum fructosamine 370990 mmol/l and glycemia in the fasting state 213956 mg/dl. Mean (9S.D.) levels of plasma triglycerides (TG) and total, HDLand LDLcholesterol were 173976, 227942, 49913 and 1419 36 mg/dl, respectively. Throughout, there was no clinical or laboratory evidence of impaired liver or kidney function. The control group comprised 19 subjects of either sex, ages ranging from 22 to 87 years, whose mean (9S.D.) levels of HbA1c were 4.990.5%, serum fructosamine 230910 mmol/l and glycemia in the fasting state 8697 mg/dl. Mean (9S.D.) levels of plasma triglycerides and total, HDLand LDLcholesterol were 85938, 197944, 59916 and 118943 mg/dl, respectively. LDL was isolated from fasting plasma supplemented with EDTA 1 g/l, by sequential ultracentrifugation within the 1.019–1.063 g/ml density range. The proposed assay was evaluated as below. An LDL aliquot obtained from controls was used to make up a pool to check the correlation between the degree of in vitro glycation and the measurement of fructosamine in the LDL fraction isolated, as well as to determine assay recovery and reproducibility. For this purpose, an aliquot of the pool was incubated with 100 mmol/l glucose during 1–7 days. Another aliquot was incubated at 37°C with glucose concentrations ranging from 13 to 100 mmol/l during 4 days, a period roughly equal to LDL mean life in plasma. Fructosamine was determined in LDL fractions using Nitro Blue Tetrazolium (NBT) reagent and serum con* Corresponding author. Fax: +54-1-823-7351; e-mail: ssanguinetti@dbc.ffyb.uba.ar.

Alteraciones glucémicas en los pacientes con enfermedad renal crónica

In Argentina, there have been no studies aimed at establishing the prevalence of dysglycaemia (impaired fasting glucose [IFG], impaired glucose tolerance [IGT] and diabetes mellitus [DM]) in patients with chronic kidney disease (CKD). Our group decided to conduct an observational study to evaluate the frequency with oral glucose tolerance test (OGTT) in CKD patients with no previous data for dysglycaemia in their medical records. OGTT was performed in 254 patients (60.62% male) with stage 3, 4 and 5 CKD under conservative treatment, haemodialysis or transplantation. Results for DM were found in 10 patients according to fasting glucose alone (3.94%; 95% CI: 1.35-6.53%), 11 patients with exclusively the second hour criterion (4.33%; 95% CI: 1.63-7.03%), 15 with both criteria (5.91%; 95% CI: 2.81-9.00%) and 36 patients with at least one criteria (14.17%; 95% CI: 9.69-18.66%). In a multivariate analysis, DM was associated with waist circumference (OR=1.033 per cm; 95% CI, 1.005 to 1.062; P=.019) and with conservative treatment vs. replacement therapy (OR=0.41; 95% CI: 0.19-0.92; P=.028). IGT was evident in 24.6% and 20.3 on conservative vs. replacement therapy, with no statistically significant difference. IFG (ADA criteria) was 19.75 vs. 9.24% in conservative vs. replacement therapy, with a statistically significant difference. OGTT is suggested for all CKD patients since it is able to detect the full range of unknown dysglycaemias, which avoids underdiagnoses and favours performing treatments to prevent progression in DM risk groups (IFG and/or IGT). It also aids in the selection of the most appropriate medication for transplantation or treatment initiation in new cases of undiagnosed DM to decrease morbidity and mortality.