Analbuminaemia: a natural model of metabolic compensatory systems
Descrição do Produto
J. Inher. Metab. Dis. 10 (1987) 317-329
Lihat lebih banyak...
Analbuminaemia: a Natural Model of Metabolic Compensatory Systems G. BALDO-ENZI ~, M. R. BAIOCCHI1, G. VIGNA 1, C. ANDRIAN 1, C. MOSCONI2 a n d R. FELLIN1 1Department of Internal Medicine, University of Padua; 2Institute of Pharmacology and Pharmacognosy, University of Milan
Summary: Important clinical signs are usually not present in analbuminaemia, a congenital condition inherited as an autosomal recessive trait, but several biochemical alterations in proteins, cholesterol, phospholipids and plasma beta lipoproteins have been observed. We studied two sibs, R.U. and R.R., with this disease and observed a striking increase in the variables mentioned above as well as a high L D L fraction with concomitant increase in apo B; increases in HDL3 and apo A-I and A-II levels were also observed. The lipoproteins, however, were not altered in morphology but showed a slight increase in lipid/protein ratio. Post-heparin lipolytic activity was normal in the male patient and reduced in the female while L C A T enzyme activity instead was increased in both. Fatty acids bound to phospholipids and serum cholesterol were mostly monounsaturated. Free fatty acid concentration was normal and they appeared mostly bound to the L D L and HDL3 fractions, which are increased in this disease and appear to replace albumin in one of its main carrier functions. Analbuminaemia (McKusick 20530), better known as idiopathic hypoalbuminaemia, and first described by Bennhold et al., 1954, is a rare congenital disease inherited as an autosomal recessive trait, and characterized by an absence or extremely low levels of albumin (Irumberry et al., 1971; Gitlin and Gitlin, 1975; Boman, 1976; Goul6 et al., 1976). Studies conducted in a recently identified strain of analbuminaemic rats by Nagase et al., (1979) demonstrated a genetic alteration, which involves posttranscriptional m R N A processing (Esumi et al., 1982, 1983); a similar defect has been advanced for the human disease (Avery et al., 1983). Despite the low albumin levels, very few symptoms are present (slight oedema, fatigue and low blood pressure), and this may be explained in part by a compensating increase in other proteins, which would keep the oncotic pressure at nearly normal values (Russi and Weigand, 1983). In this disease setting, alterations in lipid metabolism are very important and consist of a increase in total cholesterol, MS received 21.8.86 Accepted 6.5.87 317 Journal of Inherited Metabolic Disease. ISSN0141-8955. Copyright© SSIEM and MTP Press Limited, Queen Square, Lancaster, UK. Printed in The Netherlands.
B a l d o - E n z i et al.
phospholipids, and apoproteins A-I, A-II and B (Keller, 1972; Weinstock et al., 1979; Baldo et al., 1983; Weigand et al., 1983). The objective of this study was to evaluate lipid and apoprotein composition and distribution, lipoprotein structure, enzymes involved in lipid metabolism, and the protein and hormonal profile in two previously partially described sibs with analbuminaemia (Fabiani and Pauluzzi, 1971; Baldo et al., 1983), in order to improve understanding of the metabolic alterations caused by the absence of albumin.
CLINICAL Patients: The two patients with analbuminaemia are children of first-degree cousins: R.U., a 55-year-old man, and R.R., his 48-year-old sister. At 16 years of age, R.U. had experienced an important, prolonged peripheral paralysis of the right facial nerve, and had permanent signs of paresis but otherwise was well. The patient is overweight with fat located mostly at the hips, thighs and buttocks; moreover he presents bilateral corneal arcus, slightly enlarged liver with normal spleen, no swellings, and a reclining blood pressure of 110/65 mmHg. His sister, R.R., is premenopausal and has occasionally experienced slight pretibial oedema. The patient is obese at the hips, buttocks and thighs. Arterial femoral pulses are reduced on both sides, and she presents bilateral corneal arcus as well as mild hepatosplenomegaly. Blood pressure in a reclined position is 120/ 80 mmHg. Routine laboratory investigation showed a very high ESR, high haematocrit, and macrocytosis in both patients. Controls: The control group consisted on 20 healthy subjects (10 males and 10 females) matched for sex and age.
MATERIAL AND METHODS
Following a 12-14h fast, 60 mL of venous blood were drawn; 10 mL were placed in a test tube containing 0.1mL EDTA (1.4%, w/v), centrifuged at 3500rpm for 10min at 4°C, and the plasma thus obtained was promptly stored at -20°C for determination of free fatty acids, proteins, total lipoprotein lipase activity, and lecithin-cholesterol acyltransferase (LCAT) enzyme activity (Stokke and Norum, 1971). After the base-line specimen was obtained 60 U/kg of Na heparin (Liquemin 5000 Roche, Baden, FRG) were injected, and after 10rain another blood sample was collected in EDTA-eontaining test tubes, centrifuged at 4°C, stored at -20°C, and then used to determine post-heparin lipase activity, PHLA (Huttunen et al., 1976). Total H D L and HDL3 cholesterol was determined after selective precipitation of lipoproteins with polyanionic compounds (Gidez et al., 1982). HDLz cholesterol was obtained by substraction (HDLT-C minus HDL3-C ). To separate the phospholipid fractions, serum was extracted with a chloroform: methanol (1 : 1, v/v) mixture and then with chloroform. Following thin layer chromatography J. Inher. Metab. Dis. 10 (1987)
A nalb u m i n a e m i a
on silica gel plates (60 F 254, Merck), the spots were removed and phospholipid phosphorus was assayed according to Bartlett (1959). The VLDL, LDL, HDLz and HDL3 fractions were separated by sequential preparative ultracentrifugation, according to Havel et al., (1955), and their purity was evaluated by agarose (0.8%, w/v) gel electrophoresis (Seidel, 1979). The density of solutions was adjusted using a density meter DMA 46 (Paar, Graz, Austria). The H D L 2 fractions were tested by simple immunodiffusion in 1.1% (w/v) agar gel against anti-B and anti-Lp(a) antisera. Total and free cholesterol (Allain et al., 1974), triglycerides (Wahlefeld, 1974), phospholipids (Zilversmit and Davis, 1950) and FFA (Duncombe, 1964) levels were evaluated in both serum and lipoprotein fractions. Apoprotein B levels in whole serum, and in the VLDL and LDL fractions were determined immunoelectrophoretically, according to Laurell (1960) with monospecific antibody obtained in our laboratory. Apoprotein A-I levels in serum and in the HDL2, H D L 3 and >1.21 g/mL density fractions were assayed by radial immunodiffusion (Mancini et al., 1965) with antibody obtained in our laboratory; apo A-II in serum and in the above fractions was determined by radial immunodiffusion using a commercial kit (Daichi, Tokyo, Japan). Apoproteins in the several fractions were evaluated by isoelectricfocusing in polyacrylamide gel and LKB ampholine (pH 46) (Catapano et al., 1978), and by analytical electrophoresis with 3.75% (w/v) sodium dodecylsulphate (Kane et aI., 1980). Proteins in the lipoprotein fractions were determined according to Lowry et al., (1951), while plasma proteins were assayed for the most part by nephelometric kinetic method with a Beckman analyzer; albumin, pre-albumin, haemopexin, C 1 inhibitor, fibrinogen, ferritin, afetoprotein, antithrombin III and globulin binding thyroxine (TBG) were determined by radial immunodiffusion. All plasma hormones, tryptophan and globulin binding sex steroids (SHBG) were assayed radioimmunologically. For the study of fatty acids, total lipids were extracted from serum by stepwise addition of 1 volume of water, 4 volumes methanol, and 8 volumes chloroform to i ml of sample. Total phospholipids, and cholesterol esters were separated by thin layer chromatography, and analysed by gas chromatography on SP-2330 columns (Supelco, Bellefonte, Pennsylvania). Electron microscopy specimens were prepared by negative staining with uranyl acetate (1.1% w/v). RESULTS
Both patients showed a decrease in calcium concentration (7.6 and 7 mg/dL in R.U. and R.R. respectively), and an increase in lactic dehydrogenase and alkaline phosphatase enzyme activities; all other routine variables were within normal limits. Plasma protein levels are summarized in Table 1. Total proteins were decreased, albumin levels were below the sensitivity of the radial immunodiffusion technique, and all other proteins, in particular transport proteins, were increased. Fibrinogen was very high, and total and free tryptophan were reduced in both patients who also showed an increase in testosterone, FSH, LH and thyroxine and a reduction in 17~-oestradiol (Table 2). J. Inher. Metab. Dis. 10 (1987)
Table 1 Plasma protein and tryptophan levels in two analbuminaemie patients (R.U. and R.R.) (mgdL -1)
Total proteins (gdL 1) Albumin (g dL -1) chAntitrypsin Haptoglobin Transferrin Ceruloplasmin ch Acid glycoprotein c~2 Macroglobulin IgG IgA IgM C; Fraction C~ Fraction Properdin's B Factor C~ Inhibitor Retinol binding protein Thyroxine binding globulin Pre-albumin Haemopexin c~ Fetoprotein Sex hormone binding globulin (nM L -1) Fibrinogen Antithrombin III Tryptophan total free
N o r m a l range
5.5 -365 248 598 66.4 170 244 1150 147 234 240 55.3 80.5 48.6 11.4 4.9 61 182 1.79 64 1160 37.2
5.7 -386 200 581 79.5 106 418 1480 107 314 242 61.4 72.0 46.2 9.2 5.9 50 192 0.55 201 1057 37.2
6.0-8.0 3.5-5.0 200-400 50-220 200-400 20-45 60-120 220-380 800-1800 60-400 50-250 80-150 15-45 17-42 15-35 3-6 1-4.2 10-40 50-115