The erythrocyte membrane in kwashiorkor

The effect of malnutrition on insulin binding to rat erythrocytes

Insulin binding to erythrocyte receptors was compared in malnourished and control rats. Percentage specific insulin binding to malnourished rat erythrocytes was significantly lower than to control erythrocytes (P less than 0.001). The low insulin binding in the malnourished rat erythrocytes was accompanied by low insulin receptor affinity (P = 0.035).

Fatty acid composition of erythrocyte membrane lipid obtained from children suffering from kwashiorkor and marasmus

The fatty acid composition of erythrocyte membrane (EM) lipids obtained from normal, kwashiorkor, and marasmic children was analyzed by gas chromatography. The proportion of palmitic acid (16:0) was lower and of oleic acid (18:1) higher in the kwashiorkor group than in the control group. The marasmic group showed lower proportions of eicosatrienoic acid (20:3) and arachidonic acid (20:4) and a higher proportion of oleic acid (18:1) than the control group. A significant difference was found between the marasmic and kwashiorkor groups with respect to arachidonic acid (20:4), which showed a lower proportion in the former group than the latter. The ratio of arachidonic acid to linoleic acid (20:4/18:2) was markedly lower in the marasmic group than the control group, suggesting a possible impairment in the conversion of linoleic acid to arachidonic acid in marasmic children. The ratio of unsaturated fatty acids to saturated fatty acids was markedly elevated in the kwashiorkor group over that of control group, indicating increased fluidity of EM in kwashiorkor. It is suggested that the altered membrane fatty acid composition reflects deranged lipid metabolism and affects the physical and physiological properties of EM and could contribute to changes in the activities of several red blood cell membrane-bound enzymes reported earlier in kwashiorkor children.

Comparative action of calpain on erythrocyte Ca2(+)-pumping ATPase in sickle cell anaemia, essential hypertension and kwashiorkor

Calpain, a calcium-dependent, neutral cysteine-protease was purified from the erythrocyte cytosol of subjects having essential hypertension (HTN), sickle cell anaemia, (SCA), or kwashiorkor (KWA). Identical electrophoretic mobility on SDS-polyacrylamide gradient gel, sensitivity to micromolar amounts of Ca2+, absolute requirement for a reducing environment and a high susceptibility to inhibition by leupeptin and thiol-group modifying reagents confirm that calpain preparations from these erythrocytes are equivalent to calpain I. Whereas the extent of calpain activation of erythrocyte membrane Ca2(+)-pumping ATPase of normal subjects was almost equal to that due to calmodulin, calpain activation of the HTN and SCA pump was greater than activation by calmodulin. Like in normal membranes, exogenous calmodulin protected the Ca2(+)-pumping ATPase of these erythrocytes against calpainization; the degree of protection by calmodulin is least in SCA and HTN. Electrophoretic separation of erythrocyte membranes and the purified Ca2(+)-pumping ATPase of HTN, SCA and KWA subjects does not indicate the presence of fragments resulting from the proteolytic action of calpain.

Erythrocyte membrane (Ca2+ + Mg2+)-ATPase in human protein-energy malnutrition

Calmodulin-free ghost membranes were prepared from erythrocytes of kwashiorkor children and from healthy children in the same age bracket. In the absence of calmodulin, the specific activity of Mg2+-dependent Ca2+-pumping ATPase (Ca2+ + Mg2+-ATPase) of kwashiorkor membranes was more than 40 percent lower than the specific activity of the normal enzymes, whose maximum velocity was increased by at least four-fold by the modulator protein. In contrast, the maximum velocity of the enzymes of kwashiorkor membranes was enhanced by calmodulin by about 1 1/2 times the basal activity of the normal enzymes and by 2 times the basal activity of the kwashiorkor enzymes. The affinity of the pump for ATP was lower in the membranes of kwashiorkor children (Km for ATP = 30.6 +/- 2.8 microM ATP) in comparison to normal membranes (Km for ATP = 21.7 +/- 2.0 microM ATP). Similarly, calmodulin-affinity of the enzymes, was lower in kwashiorkor membranes than in the normal membranes irrespective of source of calmodulin. Calmodulin from haemolysates of kwashiorkor red cells activated the enzymes of normal and kwashiorkor membranes to the same degree as calmodulin partially purified from the haemolysate of healthy children. A determination of the dependence of the activity of the pump on calcium in the absence and presence of calmodulin reveals that the affinity of the kwashiorkor enzymes for Ca2+ is at least 70 percent lower than that of enzymes of normal membranes. Altogether, these findings suggest that the Ca2+-pumping ATPase of kwashiorkor membranes is less functional than the enzymes of healthy erythrocytes.

Detergent induced lysis of erythrocytes in kwashiorkor

The effect of the non-ionic detergent Nonidet P40 on lysis of erythrocytes in children suffering from kwashiorkor was studied. The concentration of the detergent causing 50% haemolysis was significantly reduced in these patients. Detergent haemolysis was more sensitive than osmotic fragility (which was reduced). The abnormality was only slight in marasmic children.

Fatty acid composition of plasma lipids in Nigerian children with protein-energy malnutrition

The fatty acid (FA) composition of the main plasma lipids was analysed in eight well-nourished, generally healthy Nigerian children aged 14.1 +/- 7.2 months and in 17 malnourished children (8 marasmus, 9 kwashiorkor) aged 14.6 +/- 3.8 months within the first 2 days of admission at the Dept. of Child Health, University of Benin. In comparison to the control group, the malnourished children showed a marked decrease of polyunsaturated FA with low linoleic acid, mainly in sterol esters (STE), and severely reduced linoleic acid metabolites, including arachidonic acid, in all lipid fractions. omega-3-FA were not altered except for a reduction of docosapentaenoic and docosahexaenoic acids in phospholipids. Clearly increased values were found for saturated FA in STE and for the non-essential monoenoic FA in all lipid classes. This pattern indicates the presence of essential fatty acid deficiency in the malnourished children. There was no significant difference between marasmus and kwashiorkor. Eight malnourished children were followed up in the early phase of recovery during hospital treatment 14.0 +/- 3.1 days after obtaining the first sample. Linoleic acid had increased again in STE, but its metabolites were as low or even lower than before. An impaired activity of delta-6-desaturase, the rate limiting enzyme of linoleic acid metabolism, in suggested by elevated substrate-product-ratios of this enzyme in untreated children with protein energy malnutrition and in the early phase of recovery, which may be due to low insulin levels, protein and zinc deficiency. The trientetraen ratio (20:3 omega 9/20:4 omega 6) thus is not a reliable indicator of essential FA status in protein-energy malnutrition.

Red blood cells amino-acid pattern in protein energy malnutrition and the effect of oral dosing with single amino acids

R.B.C.'s amino acid pattern was investigated in control and PEM subjects. The effect of oral dosing with cysteine, tryptophan and lysine on total amino acid nitrogen level of R.B.C.s was also studied. Results revealed that in moderate and severe kwashiorkor the total essential and non-essential R.B.C.'s amino acids were decreased. In 2nd grade marasmus the total R.B.C.'s amino acids in general showed lower values than normal. After oral administration of the tested amino acids, the transport index calculated as the level of maximum value of the total R.B.C.'s amino acids reached to the fasting level was lower in malnourished cases relative to controls except in 2nd grade marasmic cases given tryptophan or lysine. This criteria was considered to indicate lower rate of amino acid transport to R.B.C.s due to lower concentration in plasma or shift of transport mechanism from active transport to exchange diffusion.

The erythrocyte membrane disturbances in protein-energy malnutrition: nature and mechanisms

In protein-energy malnutrition (PEM), as observed in Kivu, the RBC have an increased ratio of surface area to volume which is demonstrated by the presence of target cells on light microscopy and cup cells with scanning electron microscopy. The osmotic fragility is decreased. These abnormalities can be attributed to the accumulation of cholesterol and phosphatidylcholine (PC) in the RBC membrane. The molar ratio of cholesterol to phospholipids is moderately increased. Several findings suggest that the cholesterol and PC build-up results from disturbed exchanges in these lipids between the RBC and the plasma lipoproteins. Firstly, the osmotic fragility of a patient's RBC gradually becomes normal when the cells are transfused into a healthy recipient. Secondly, the cholesterol flux between the RBC and the plasma LDL seems to be low. Thirdly, the increase in RBC PC cannot be explained by a diminished fatty acids transport between the deep RBC PC pool and the RBC phosphatidylethanolamine (PE) pool. Finally complex disturbances of the plasma lipoproteins are obvious. It is improbable that the cholesterol and PC build-up accounts for the premature RBC destruction which has been described in Kivu PEM. However, the observation of an increased fatty acid turnover in RBC PC and PE, as well as other data previously obtained in Kivu PEM, lead to the conclusion that membrane peroxidation may be a major cause of the shortened erythrocyte life-span in this syndrome.