ABSTRACT
Aim of the study is to define the diagnostic accuracy of selected urinary protein biomarkers in the non-invasive detection of primary and recurrent urothelial carcinoma of the urinary bladder. The urinary levels of calprotectin, CD147, APOA4 and protein deglycase DJ-1 were examined in 255 individuals, including 60 controls with non-malignant urological disease, 61 patients with a history of urinary bladder cancer with negative cytology and negative cystoscopy and 134 patients with urinary bladder cancer. Urinary concentrations of biomarkers were determined by Enzyme-Linked Immunosorbent Assay (ELISA). During the follow-up of patients with non-muscle invasive bladder cancer (NMIBC), a group of 44 patients with cancer recurrence was compared to the group of 61 patients with a history of NMIBC but with no evidence of disease. Urinary concentrations of the evaluated markers did not reveal any significant difference between these groups. During the primary diagnosis, a group of 90 patients with primary bladder cancer and 60 subjects with benign disease were compared. Urinary levels of CD147 were not significantly higher in patients with tumors. The greatest diagnostic accuracy was observed in APOA4 (sensitivity 55.6, specificity 83.3, AUC 0.75), and lesser in calprotectin (sensitivity 39.4, specificity 87.7, AUC 0.66) and in DJ-1 (sensitivity 61.1, specificity 66.7, AUC 0.64), respectively. Apolipoprotein A4 may be used potentially as a supplemental urinary marker in the diagnosis of primary bladder cancer.
Subject(s)
Apolipoproteins A/urine , Basigin/urine , Leukocyte L1 Antigen Complex/urine , Protein Deglycase DJ-1/urine , Urinary Bladder Neoplasms/diagnosis , Biomarkers, Tumor/urine , Humans , Neoplasm Recurrence, Local , Sensitivity and Specificity , Urinary Bladder Neoplasms/urineABSTRACT
BACKGROUND: Trace amounts of lipids are present in the urine of patients with glomerular disease, raising the possibility that the excess lipids reabsorbed by tubule cells may be toxic to these cells. In the present study, we assessed the prognostic value of micro-cholesterol (mCHO) levels in patients with chronic glomerular disease. METHODS: The urinary mCHO levels of healthy subjects and patients with chronic kidney disease were measured by the enzymatic cholesterol cycling (ECC) method with a minimum detection level of 0.10 x 10(-3) mmol/L. First, the urinary mCHO levels of healthy subjects and 320 patients with various glomerular diseases with proteinuria >1000 mg/gCr were measured. Second, correlations of urinary mCHO levels with those of various other molecules, including albumin, IgG, IgM, transferrin, phospholipid, alpha1-microglobulin (alpha1MG), Apo A1, Apo A2, and Apo B, and urinary fatty body counts, were determined. Third, urinary mCHO, total protein (TP), albumin, and N-acetyl-beta-D-glucosaminidase (NAG) levels were measured longitudinally over 12 months (20.5 +/- 5.8 months) in 68 nondiabetic patients with impaired renal function [serum creatinine (Cr) > or = 1.5 mg/dL]. Correlations of the concentrations of urinary parameters in the initial 3-month period with the slopes of the reciprocal of creatinine versus time for the entire follow-up period were assessed by the ROC method and multiple regression analysis. RESULTS: Urinary mCHO levels of the healthy subjects were 0.06 to 0.72 mg/gCr for males and 0.16 to 2.34 mg/gCr for females. Urinary mCHO levels in subjects with minimal change nephrotic syndrome were significantly lower than those in the patients with other glomerular diseases with massive proteinuria. Urinary mCHO levels correlated significantly with Apo A1 and Apo A2 levels, but not with urinary Apo B levels, in the latter subjects. The correlation coefficient of urinary fatty body counts (a marker of lipoprotein loading tubulopathy) with mCHO was higher than those with TP, albumin, IgG, IgM, and alpha1MG. The urinary mCHO elevation was significantly greater in patients who had a nonselective index of proteinuria than in those with a highly or moderately selective index. In nondiabetic patients with impaired renal function, the urinary mCHO level had a higher predictive value for rapid decline of renal function than TP, albumin, or NAG. CONCLUSION: The urinary cholesterol level corresponds to the magnitude of urinary HDL excretion, and correlates with the degree of lipoprotein loading tubulopathy. Measurement of urinary mCHO by the ECC method is a simple and useful tool for predicting progression of chronic glomerular disease.
Subject(s)
Cholesterol/urine , Kidney Failure, Chronic/diagnosis , Kidney Failure, Chronic/urine , Acetylglucosaminidase/urine , Albuminuria/diagnosis , Albuminuria/urine , Apolipoproteins A/urine , Apolipoproteins B/urine , Creatinine/blood , Female , Follow-Up Studies , Humans , Male , Predictive Value of Tests , Prognosis , ROC CurveABSTRACT
Hypercholesterolemia is frequently associated with elevated Lp(a) levels, an independent risk factor for coronary, cerebrovascular, and peripheral vascular disease. A portion of apolipoprotein(a) [apo(a)] circulates as a series of fragments derived from the N-terminal region of apo(a). The relationship of elevated lipoprotein(a) [Lp(a)] levels to those of circulating apo(a) fragments in polygenic hypercholesterolemia is indeterminate. Therefore, plasma Lp(a) and plasma and urinary apo(a) fragment levels were measured by ELISA in 82 patients with polygenic type IIa hypercholesterolemia (low density lipoprotein cholesterol >/=4.13 mmol/L and triglycerides <2.24 mmol/L) and in 90 normolipidemic subjects. Lp(a) levels were significantly elevated in patients compared with control subjects (0.35+/-0.4 and 0.24+/-0.31 mg/mL, respectively; median 0.13 and 0.11 mg/mL, respectively; P=0.039), although apo(a) isoform distribution did not differ. Patients displayed significantly higher plasma and urinary apo(a) fragment levels than did control subjects (respective values were as follows: 4.97+/-5.51 and 2.15+/-2.57 [median 2.85 and 1.17] microg/mL in plasma, P<0.0001; 75+/-86 and 40+/-57 [median 38 and 17] ng/mg urinary creatinine in urine, P<0.0001). The ratio of plasma apo(a) fragments to Lp(a) levels was also significantly higher in patients than in control subjects (1.93+/-1.5% and 1.75+/-2.36%, respectively; P<0.0001). We conclude that increased plasma Lp(a) levels in polygenic hypercholesterolemia are associated with elevated circulating levels of apo(a) fragments but that this increase is not due to decreased renal clearance of apo(a) fragments. Furthermore, we identified a new pattern of apo(a) fragmentation characterized by the predominance of a fragment band whose size was related to that of the parent apo(a) isoform and that was superimposed on the series of fragments described previously by Mooser et al (J Clin Invest. 1996; 98:2414-2424). This new pattern was associated with small apo(a) isoforms and did not discriminate between hypercholesterolemic and normal subjects. However, this new apo(a) fragment pattern may constitute a novel marker for cardiovascular risk.
Subject(s)
Apolipoproteins A/chemistry , Hypercholesterolemia/metabolism , Adolescent , Adult , Aged , Apolipoproteins A/blood , Apolipoproteins A/urine , Female , Humans , Lipids/blood , Lipoprotein(a)/blood , Male , Middle Aged , Protein IsoformsABSTRACT
BACKGROUND: Lipoprotein(a) [Lp(a)] is an atherothrombotic plasma lipoprotein with unknown function. Little is known about the catabolism of this lipoprotein, in particular the steps related to apolipoprotein(a) [apo(a)] fragmentation and excretion by the kidney. MATERIAL AND METHODS: High plasma levels (up to 9 mg dL(-1)) of the N-terminal fragment of apo(a) were expressed in mice by adenovirus mediated gene transfer. Plasma of such N-apo(a) mice was injected into acceptor mice and the fragmentation and urinary secretion of N-apo(a) were followed by immunochemical techniques. RESULTS: Mice transduced with N-Ad expressed apo(a)-fragments with 3-11 kringle-IV (KIV) repeats. Injection of N-apo(a)-plasma from donor mice into acceptor mice resulted in fragmentation of N-apo(a)s with 3-11 KIVs yielding smaller peptides down to 2 KIVs. Secretion of N-apo(a)-fragments with 2 to maximally 6 KIVs into urine occurred as early as 2 min after injection. Immunohistochemical studies of kidney suggested filtration as a mechanism of apo(a)-fragment excretion. When N-apo(a) was incubated in vitro with various tissues from perfused mice, skeletal muscle and kidney followed by liver and spleen contributed to fragmentation. Tissues from unperfused organs, or the addition of normal mouse plasma, caused marked reduction in N-apo(a) fragmentation. EDTA, and not aprotinin or leupeptin, prevented apo(a) cleavage. CONCLUSION: Here we provide evidence that apo(a) is cleaved by metalloproteinases located on skeletal muscle, kidney and other organs. Small apo(a)-fragments up to a size of 6 KIVs are excreted into urine, yet a major portion of apo(a) fragments is removed from circulation extrarenally.
Subject(s)
Apolipoproteins A/physiology , Apolipoproteins A/urine , Kidney/physiology , Liver/physiology , Peptide Fragments/physiology , Peptide Fragments/urine , Adenoviridae/genetics , Animals , Apolipoproteins A/biosynthesis , Apolipoproteins A/genetics , DNA, Recombinant/genetics , Endopeptidases/metabolism , Genetic Vectors , Humans , Kidney/enzymology , Kidney/metabolism , Kidney Glomerulus/metabolism , Kidney Glomerulus/physiology , Kinetics , Liver/enzymology , Liver/metabolism , Mice , Peptide Fragments/biosynthesis , Peptide Fragments/genetics , Transduction, GeneticABSTRACT
Lipoprotein(a) (Lp(a)) is an independent risk factor for atherosclerotic disease. However, information concerning the site of Lp(a) catabolism and breakdown is scarce. Several studies have shown that, in renal insufficiency, plasma Lp(a) levels are elevated, and that after normalisation of kidney function they return to normal. We have recently shown that fragments of apo(a) are found in the urine of healthy individuals. Despite this evidence that apo (a) is excreted into the urine, the mode of excretion of apo(a) remains unclear. Since it has been reported that intravenous infusion of somatostatin can reduce glomerular filtration rate (GFR) and renal plasma flow (RPF), we analysed urinary apo(a) excretion in ten healthy volunteers receiving somatostatin infusions. The infusion of somatostatin led to reversible changes in GFR and RPF. Apo(a) excretion was constant in all 10 individuals over the entire time course when normalised for creatinine. There was a highly significant correlation between plasma Lp(a) levels and urinary apo(a) values. Changes in renal plasma flow and glomerular filtration rate did not alter urinary apo(a) excretion. We conclude that a constant amount of apo(a) is excreted into urine, depending on plasma Lp(a) levels, and that urinary apo(a) excretion is not altered by changes in GFR and RPF in healthy males.
Subject(s)
Apolipoproteins A/urine , Glomerular Filtration Rate , Renal Plasma Flow , Adult , Age Factors , Analysis of Variance , Humans , Infusions, Intravenous , Lipoprotein(a)/blood , Lipoprotein(a)/metabolism , Male , Sex Factors , Somatostatin/administration & dosageABSTRACT
Fragments of apolipoprotein(a) [apo(a)], the distinctive glycoprotein of lipoprotein(a) [Lp(a)], are present in human plasma and urine and have been implicated in the development of atherosclerosis. The mechanism responsible for the generation of apo(a) fragments in vivo is poorly understood. In this study, we examined the plasma levels of Lp(a) and apo(a) fragments [or free apo(a)] and urinary apo(a) in 15 subjects who underwent cardiac surgery necessitating cardiopulmonary bypass. We also measured the plasma concentration and activity of polymorphonuclear elastase, an Lp(a)-cleaving enzyme in vitro, and plasma levels of C-reactive protein. Despite a marked activation of polymorphonuclear cells and a pronounced inflammatory response, as documented by an 8-fold and a 35-fold increase in plasma levels of polymorphonuclear elastase and C-reactive protein, respectively, the proportion of plasma free apo(a) to Lp(a) and urinary excretion of apo(a) remained unchanged over a 7-day period after surgery, and polymorphonuclear elastase activity remained undetectable in plasma. No fragmentation of apo(a) was observed ex vivo in plasma samples collected before and after surgery. These data indicate that in this model, apo(a) is not fragmented in plasma and are consistent with the hypothesis that apo(a) fragments result from a constitutively active tissue mechanism that is not modified by cardiac surgery with cardiopulmonary bypass.
Subject(s)
Apolipoproteins A/blood , Cardiopulmonary Bypass , Heparin/pharmacology , Lipoprotein(a)/blood , Aged , Apolipoproteins A/urine , Cardiopulmonary Bypass/adverse effects , Female , Heparin/administration & dosage , Humans , Injections, Intravenous , Male , Middle AgedABSTRACT
High levels of plasma lipoprotein(a) [Lp(a)] represent an independent risk factor for cardiovascular morbidity; however, Lp(a) has not yet been identified as a risk factor for type 1 diabetic patients. Results from the limited number of available studies on plasma Lp(a) levels in relation to renal function in type 1 diabetes mellitus are inconclusive. We hypothesized that only type 1 diabetes mellitus patients with impaired renal function show increased plasma Lp(a) levels, due to decreased urinary apolipoprotein(a) [apo(a)] excretion. We therefore measured urinary apo(a) levels in 52 type 1 diabetes mellitus patients and 52 matched controls, and related the urinary apo(a) concentration to the plasma Lp(a) level, kidney function, and metabolic control. Our findings indicate that patients with incipient diabetic nephropathy as evidenced by microalbuminuria (20 to 200 microg/min) exhibit significantly higher plasma Lp(a) levels (median, 15.6 mg/dL) in comparison to normoalbuminuric patients (median, 10.3 mg/dL) and healthy controls (median, 12.0 mg/dL). Urinary apo(a) normalized to creatinine excretion was significantly elevated in both normoalbuminuric (median, 22.3 microg/dL) and microalbuminuric type 1 diabetic patients (median, 29.1 microg/dL) compared with healthy subjects (median, 16.0 microg/dL) and correlated significantly with Lp(a) plasma levels in both patient and control groups (P < .003). No correlation existed between the Lp(a) plasma level or urinary apo(a) concentration and metabolic control in type 1 diabetes mellitus patients. From these studies, we conclude that urinary apo(a) excretion is significantly increased in type 1 diabetic patients and correlates with plasma Lp(a) levels, and only type 1 diabetic patients with microalbuminuria have higher plasma levels of Lp(a) compared with patients with normoalbuminuria and healthy controls.
Subject(s)
Apolipoproteins A/urine , Diabetes Mellitus, Type 1/urine , Adult , Albuminuria/blood , Albuminuria/urine , Apolipoproteins A/blood , Diabetes Mellitus, Type 1/blood , Diabetic Nephropathies/blood , Diabetic Nephropathies/urine , Female , Humans , Lipids/blood , Lipids/urine , Lipoprotein(a)/blood , Lipoprotein(a)/urine , Male , Peptide Fragments/blood , Peptide Fragments/urineABSTRACT
BACKGROUND: Plasma lipoprotein (a) [Lp(a)] levels are elevated in patients with kidney disease and are strongly associated with premature cardiovascular disease and stroke. METHODS: As the kidney is suggested to play an important role in apolipoprotein (a) [apo(a)] catabolism and as apo(a) fragments appear in urine, we determined plasma Lp(a) levels and urinary apo(a) excretion in relation to kidney function in a large cohort of renal patients. A total of 368 renal patients with normal or different degrees of impaired renal function and 163 healthy control subjects matched for age and sex were investigated. Plasma Lp(a) and urinary apo(a) were analysed immunochemically. RESULTS: Renal patients were found to have significantly elevated total cholesterol and low-density lipoprotein (LDL)-C values but lower high-density lipoprotein (HDL)-C values than control subjects. Plasma Lp(a) values were significantly higher only in patients with creatinine clearance < 70 mL min-1. There was a significant correlation between urinary apo(a) and plasma Lp(a) in patients and control subjects. Urinary apo(a) excretion was significantly lower in patients than in control subjects and showed no correlation with urinary protein excretion. CONCLUSION: Although it is unlikely that impaired renal excretion of apo(a) fragments largely contributes to increased plasma Lp(a) levels in patients suffering from impaired kidney function, these data suggest that urinary apo(a) excretion is significantly decreased in renal patients and that this might contribute to increased plasma Lp(a) levels in this patient group.
Subject(s)
Apolipoproteins A/urine , Kidney Diseases/urine , Aged , Female , Humans , Kidney Diseases/blood , Lipoprotein(a)/blood , Male , Middle Aged , Statistics, NonparametricSubject(s)
Apolipoproteins A/urine , Kidney Diseases/blood , Kidney Diseases/urine , Lipoprotein(a)/blood , HumansABSTRACT
Increased plasma lipoprotein (a) (Lp(a)) levels are associated with premature cardiovascular diseases and stroke. Since Lp(a) immune reactivity is found in urine we compared urinary apolipoprotein (a) (apo(a)) with plasma Lp(a) levels in 116 patients suffering from angiographically proven coronary artery diseases with that of 109 controls. Urinary apo(a) investigated by immuno blotting, revealed a distinct apo(a) fragmentation pattern with molecular weights between 50 and 160 kDa. Apolipoprotein B however was not secreted into urine. Lp(a) and apo(a) were measured by a fluorescence immuno assay. Within single individuals, urinary apo(a) levels correlated significantly with creatinine (Rho, 0.98; P < 0.0005). Medians and 25/75 percentiles of urinary apo(a) in coronary artery disease (CAD) patients were 5.70, 3.25 and 10.35 microg/dl and in controls 2.64, 1.43 and 3.50 microg/dl respectively. At cut-off levels of 30 mg/dl for plasma Lp(a) and 10 microg/dl of urinary apo(a) respectively, both paramenters showed comparable sensitivities (33.8% vs. 26.7%), yet the specificity (76.1% vs. 91.7%) and the positive predictive value (60.0% vs.76.4%) of urinary apo(a) were much higher. In receiver-operating characteristic plots, urinary apo(a) was much more sensitive at high specificities i.e. greater than 60% as compared to Lp(a). Urinary secretion of apo(a) fragments normalized to creatinine is stable in a given individual and significantly associated with coronary artery disease.
Subject(s)
Apolipoproteins A/urine , Coronary Disease/urine , Apolipoproteins A/blood , Blotting, Western , Coronary Angiography , Coronary Disease/blood , Coronary Disease/diagnostic imaging , Creatinine/blood , Creatinine/urine , Electrophoresis, Polyacrylamide Gel , Female , Humans , Immunoassay , Lipoprotein(a)/blood , Lipoprotein(a)/urine , Male , Middle Aged , Predictive Value of Tests , Risk FactorsABSTRACT
Increased plasma Lp(a) is an established risk factor for atherosclerosis. We recently described the presence of apo(a) fragments in urine and the significant correlation between urinary apo(a) concentrations and plasma Lp(a). Here we investigated urinary apo(a) in patients suffering from familial hypercholesterolaemia (FH), treated with LDL apheresis. Before treatment, plasma Lp(a) levels and urinary apo(a) normalized to creatinine were > 2-fold increased in FH patients (P < 0.0001) as compared to controls. LDL-apheresis led to a reduction of plasma Lp(a) by 75% and a concomitant immediate reduction of urinary apo(a) by 45%. We conclude that a steady state condition for urinary apo(a) is rapidly achieved via LDL-apheresis.
Subject(s)
Apolipoproteins A/urine , Blood Component Removal , Hypercholesterolemia/therapy , Lipoprotein(a)/urine , Adult , Apolipoproteins A/blood , Cholesterol/blood , Cholesterol, HDL/blood , Cholesterol, LDL/blood , Humans , Hypercholesterolemia/metabolism , Lipoproteins, LDL/blood , Male , Middle Aged , Triglycerides/bloodABSTRACT
Lp(a), one of the most atherogenic lipoproteins, is believed to contribute significantly to vascular diseases in non-insulin-dependent diabetic (NIDDM) patients. Contradictive data have been published on these patients concerning plasma concentrations of Lp(a) and their relation to renal function. Since apo(a) fragments appear in urine, we measured urinary apo(a) in 134 NIDDM patients and 100 matched controls and related urinary apo(a) concentrations to plasma Lp(a) levels and kidney function. Plasma Lp(a) values were found to be significantly higher in NIDDM patients. NIDDM patients also secreted significantly more apo(a) into their urine as compared to control subjects. There was no correlation between creatinine clearance or albumin excretion and urinary apo(a) concentrations. Patients with macroalbuminuria exhibited a twofold higher apparent fractional excretion of apo(a) in comparison to patients with normal renal function. Urinary apo(a) values in both patients and control subjects were highly correlated to plasma Lp(a), yet no correlation was found with HbA1c or serum lipoproteins. It is concluded that urinary apo(a) excretion is correlated to plasma Lp(a) levels but not to creatinine clearance in patients suffering from NIDDM.
Subject(s)
Apolipoproteins A/urine , Diabetes Mellitus, Type 2/urine , Peptide Fragments/urine , Aged , Blotting, Western , Creatinine/urine , Diabetic Nephropathies/blood , Diabetic Nephropathies/urine , Female , Glycated Hemoglobin/metabolism , Humans , Lipoprotein(a)/blood , Lipoproteins/blood , Male , Middle AgedABSTRACT
BACKGROUND: Increased plasma Lipoprotein (a) (Lp(a)) levels are strongly associated with premature cardiovascular disease and stroke. The kidney is purported to play an important role in apo(a) catabolism. Therefore we investigated plasma Lp(a) levels in relation to kidney function and urinary apo(a) excretion. METHODS: One hundred and sixteen kidney transplant patients with normal or impaired renal function and 109 age- and sex-matched healthy controls were investigated. Plasma Lp(a) and urinary apo(a) levels were determined immunochemically and all other parameters were determined by routine laboratory methods. RESULTS: Transplant recipients were found to have significantly elevated total cholesterol and LDL-C values, but equal HDL-C values compared to controls. Plasma Lp(a) values were higher and urinary apo(a) excretion was lower in transplant recipients compared to controls, independent of renal function. When the patient group was subdivided into 'normal' and 'impaired creatinine clearance', only the latter group secreted less apo(a) than normal controls. CONCLUSION: These data suggest that urinary apo(a) excretion is reduced in transplant recipients with impaired excretory graft function, which may contribute to the elevation of plasma Lp(a) levels in these patients.
Subject(s)
Apolipoproteins A/urine , Kidney Transplantation , Aged , Female , Humans , Lipoprotein(a)/blood , Male , Middle Aged , Postoperative Period , Reference ValuesABSTRACT
The biosynthesis and assembly of lipoprotein(a) [Lp(a)], a marker for atherosclerotic disease, appears to be well understood. However, information is lacking concerning the mode and site of Lp(a) catabolism. Apo(a) is reported to be excreted into the urine. To study the effect of this pathway on the overall catabolism of Lp(a), urinary apo(a) was characterized by immunoblotting. More than 10 distinct apo(a) bands with molecular masses between 30 and 160 kD were observed. Apo(a) fragments were not complexed to apoB. In more than 30 individuals the size of apo(a) bands was comparable irrespective of their apo(a) phenotype, although marked differences in the relative intensities of the bands were observed. Eight batches of 24-hour urine collections collected from one proband at 2-week intervals exhibited a significant correlation between creatinine and apo(a) concentrations as measured by DELFIA (r = .93; P < .01). In 193 healthy volunteers a highly significant correlation was found between urinary apo(a) concentrations normalized to creatinine levels and plasma Lp(a) values (p = 0.659; P < .0001). Of the total plasma apo(a), 0.073%, i.e., 121 micrograms apo(a), was excreted in the form of apo(a) fragments in 24-hour urine samples from 12 healthy volunteers. We conclude that the catabolism of Lp(a) via excretion of apo(a) fragments accounts for < 1% of the daily Lp(a) catabolism.
Subject(s)
Apolipoproteins A/urine , Lipoprotein(a)/metabolism , Adult , Aged , Apolipoproteins A/blood , Creatinine/blood , Female , Humans , Kidney/metabolism , Kringles , Male , Middle Aged , Reference ValuesABSTRACT
Apolipoprotein (apo) A-IV is an intestinally derived apolipoprotein that plays a potentially important role in lipoprotein metabolism and reverse cholesterol transport. However, the factors that regulate its plasma concentrations are not well understood. Plasma apoA-IV levels have been previously shown to correlate with fasting triglyceride (TG) levels in humans with TG levels less than 300 mg/dl (Lagrost et al. 1989. J. Lipid Res. 30: 701-710). In this study, we established that apoA-IV levels were significantly elevated (mean 29.3 mg/dl) in a group of 15 hypertriglyceridemic patients (TG > 300 mg/dl) compared with normolipidemic controls (mean 13.4 mg/dl). In order to investigate the relationship between hypertriglyceridemia and apoA-IV metabolism, we then studied the in vivo kinetics of apoA-IV in two healthy hypertriglyceridemic patients (mean TG = 1297 mg/dl) compared with normolipidemic control subjects. Combined studies using endogenous stable isotope labeling (with a primed constant infusion of deuterated L-leucine) and exogenous radiolabeling (with 125I) of apoA-IV were performed. Both stable isotope and radiotracer studies demonstrated substantially decreased apoA-IV fractional catabolic rates (FCR) in the hypertriglyceridemic patients (1.24 +/- 0.13 day-1) compared with controls (2.33 +/- 0.08 day-1). The apoA-IV production rate was not significantly different between the two groups. Gel filtration chromatography of plasma indicated an increased proportion of apoA-IV in the triglyceride-rich lipoproteins (TRL) of the hypertriglyceridemic patients compared with controls and delayed catabolism of this TRL-associated apoA-IV. The rate of apoA-IV catabolism from the lipid deficient fraction was not different between the hypertriglyceridemic patients and controls. In summary, plasma levels of apoA-IV are significantly elevated in hypertriglyceridemic patients due to delayed catabolism of apoA-IV as demonstrated by both endogenous stable isotope labeling and exogenous radiotracer techniques.
Subject(s)
Apolipoproteins A/metabolism , Hypertriglyceridemia/blood , Isotope Labeling , Apolipoproteins A/urine , Chromatography, Gel , Humans , Iodine Radioisotopes , Kinetics , Triglycerides/bloodABSTRACT
Using experimental nephrotic rats, we investigated the potential feedback regulation of apolipoproteins (apos) at their hepatic and intestinal synthetic sites. Nephrotic syndrome (NS) was induced in rats by puromycin aminonucleoside (PAN) with a single intraperitoneal injection (120 mg/kg). In nephrotic rats, we observed a 60% reduction in serum apo A-IV levels despite a 3.4-fold increase in jejunum and a 1.5-fold increase in ileum apo A-IV mRNA levels, although hepatic apo A-IV levels were unchanged compared with those in pair-fed control rats. A strikingly positive correlation was observed between daily urinary excretion of apo A-IV and its mRNA levels in jejunum (r = .856, P < .01; n = 10) and ileum (r = .710, P < .05; n = 10). On the other hand, nephrotic rats had an 8.2-fold increase in serum apo A-I level associated with a 4.6-fold increase in hepatic and a small but significant increase in jejunum apo A-I mRNA levels. Compared with the fractional catabolic loss of albumin or apo A-IV, that of apo A-I was small and suggests a diminished level of glomerular filtration, leading to a further elevation in serum apo A-I level. Barring nonspecific effects of PAN, these data suggest that reduction of serum apo A-IV level due to urinary loss may directly upregulate mRNA levels in the small intestine. Alternatively, it may be the result of an effective filtration of a serum component unassociated with lipoproteins that normally and site-specifically reduces apo A-I and apo A-IV mRNA transcription.
Subject(s)
Apolipoproteins A/genetics , Intestines/chemistry , Nephrotic Syndrome/metabolism , RNA, Messenger/analysis , Albumins/metabolism , Albuminuria/metabolism , Animals , Apolipoprotein A-I/analysis , Apolipoprotein A-I/genetics , Apolipoprotein A-I/urine , Apolipoproteins A/analysis , Apolipoproteins A/urine , Blotting, Northern , Glomerular Filtration Rate , Ileum/chemistry , Ileum/metabolism , Injections, Intraperitoneal , Intestinal Mucosa/metabolism , Jejunum/chemistry , Jejunum/metabolism , Male , Metabolic Clearance Rate , Nephrotic Syndrome/chemically induced , Nephrotic Syndrome/urine , Puromycin Aminonucleoside/adverse effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Rats, Wistar , Transcription, GeneticABSTRACT
The kinetics of apolipoprotein A-IV associated with high density lipoproteins (HDL) of plasma from fasting human subjects was followed for 15 days in five healthy normolipidemic volunteers. Purified apoA-IV and apoA-I were radioiodinated, respectively, with 125I and 131I, incubated in vitro with normal HDL, isolated at density 1.250 g/ml, and finally reinjected intravenously as HDL-125I-labeled apoA-IV and HDL-131I-labeled apoA-I. Blood samples were withdrawn at regular intervals for 15 days, and 24-h urine samples were collected. More than 93% (93.5 +/- 0.9%) of apoA-IV was recovered in apoA-I-containing lipoprotein particles after affinity chromatography on an anti-apoA-I column and 69.7 +/- 4.8% was bound to apoA-II in apoA-I:A-II particles separated on an anti-apoA-II column. 125I-labeled apoA-IV showed a much faster decay than 131I-labeled apoA-I for the first 5 days and thereafter the curves became parallel. Urinary/plasma ratios (U/P) for the 125I-labeled parallel. Urinary/plasma ratios (U/P) for the 125I-labeled apoA-IV were much higher than those for 131I-labeled apoA-I for the first days, but the U/P curves became parallel for the last 7 days, suggesting heterogeneity of apoA-IV metabolism. A heterogeneous multicompartmental model was constructed to describe the metabolism of lipoprotein particles containing apoA-IV and apoA-I and to calculate the kinetic parameters, fitting simultaneously all plasma and urine data for both tracers.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Apolipoproteins A/blood , Lipoproteins, HDL/blood , Adult , Apolipoprotein A-I , Apolipoproteins A/urine , Female , Humans , Iodine Radioisotopes , Male , Models, BiologicalABSTRACT
Extracorporeal shock wave lithotripsy (ESWL) causes proteinuria. In our study we investigated the protein fractions and the electrolyte composition of the urine in patients who had been treated with ESWL. The aim was to obtain information on the degree and the localisation of the glomerular, tubular or vascular destruction caused by ESWL in humans. A total of 34 patients with stones had been treated with ESWL. As parameters we used: urine output, creatinine clearance, total protein, albumin, immunoglobulin G, N-acetyl-beta-D-glucosaminidase (beta-NAG), alpha-1-microglobulin, the fractional excretion of Na+ and apolipoprotein-A-1. After ESWL treatment proteinuria and albuminuria are found. Our parameters show no deterioration of the glomerula or the tubulus. The increase in apolipoprotein-A-1, a postglomerular parameter, however, is interpreted as a manifestation of vascular destruction after ESWL; this is normally temporary, leaving no permanent damage.
Subject(s)
Albuminuria/etiology , Kidney Calculi/therapy , Kidney Function Tests , Lithotripsy/adverse effects , Proteinuria/etiology , Acetylglucosaminidase/urine , Albuminuria/enzymology , Alpha-Globulins/urine , Apolipoprotein A-I , Apolipoproteins A/urine , Creatinine/urine , Female , Humans , Immunoglobulin G/urine , Kidney Calculi/enzymology , Male , Middle Aged , Proteinuria/enzymology , Risk Factors , Sodium/urine , Urodynamics/physiologyABSTRACT
The effect of prazosin treatment on blood pressure, plasma HDL-cholesterol concentration, and apoprotein-AI/HDL (apoAI/HDL) kinetics was studied in 11 patients with mild hypertension. Blood pressure (mean +/- SEM) fell from 143 +/- 1/96 +/- 1 to 134 +/- 1/86 +/- 1 mm Hg after 4 to 5 months of prazosin treatment (P less than .001), associated with an increase in plasma HDL-cholesterol concentration from 38 +/- 2 to 46 +/- 2 mg/dL (P less than .001). Both the fractional catabolic rate (FCR) and total synthetic rate of apoAI/HDL, which were higher than previous reported values for normal individuals, decreased from 0.36 +/- 0.02 to 0.30 +/- 0.02 L/day and 17.4 +/- 1.1 to 13.8 +/- 1.1 mg/kg/min, respectively. These changes were statistically significant, and the post-treatment values for both variables were now within the normal range. When the decay curve was further analyzed by nonlinear curve fitting, it was shown that the return to normal of the FCR of apoAI/HDL in patients treated with prazosin was accounted for by the decrease of the decay constants of the second [p(2)] and third [p(3)] components of the 125I-AI/HDL disappearance curve. In conclusion, abnormalities in HDL concentration and HDL kinetics exist in patients with very mild hypertension. These defects were significantly improved with prazosin treatment, and this may render the compound of particular clinical benefit in the treatment of patients with mild hypertension.