Increased diaphragm expression of GLUT4 in control and streptozotocin-diabetic rats by fish oil-supplemented diets.

Dietary fat intake influences plasma glucose concentration through modifying glucose uptake and utilization by adipose and skeletal muscle tissues. In this paper, we studied the effects of a low-fat diet on diaphragm GLUT4 expression and fatty acid composition in control and streptozotocin-induced diabetic rats. Control as well as diabetic rats were divided into three different dietary groups each. Either 5% olive oil, 5% sunflower oil, or 5% fish oil was the only fat supplied by the diet. Feeding these low-fat diets for 5 wk induced major changes in fatty acid composition, both in control and in diabetic rats. Arachidonic acid was higher in diabetic olive and sunflower oil-fed rats with respect to fish oil-fed, opposite to docosahexaenoic acid which was higher in diabetic fish oil-fed rats with respect to the other two groups. Animals receiving a fish oil diet had the lowest plasma glucose concentration. GLUT4 expression in diaphragm, as indicated by GLUT4 protein and mRNA, is modulated both by diabetes and by diet fatty acid composition. Diabetes induced a decrease in expression in all dietary groups. Plasma glucose levels correlated well with the increased amount of GLUT4 protein and mRNA found in fish oil-fed groups. Results are discussed in terms of the influence that arachidonic and n-3 polyunsaturated fatty acids may exert on the transcriptional and translational control of the GLUT4 gene.

Effects of dietary polyunsaturated fatty acids and nucleotides on tissue fatty acid profiles of rats with carbon tetrachloride-induced liver damage.

The deficiency of polyunsaturated fatty acids (PUFA) that occurs in plasma of patients with liver cirrhosis has been assessed in rats with severe steatosis and mild liver necrosis induced by repeated administration of low doses of carbon tetrachloride (CCl(4)). The contribution of both dietary (n-3) long-chain PUFA and nucleotides to the recovery of the altered fatty acid profiles of tissue lipids of these rats has also been studied. Two groups of rats were used. The first was intraperitoneally injected 0.15 ml of a 10% (v/v) CCl(4)solution in paraffin per 100 g of body weight, three times a week for 9 weeks; the second received paraffin alone. After the treatment, six rats of each group were killed. Afterwards, the remaining controls were fed a semipurified diet (SPD) for 3 weeks, and the remaining rats in the CCl(4)group were divided into three new groups: the first was fed the SP diet; the second was fed the SP diet supplemented with 1% (n-3) polyunsaturated fatty acids (PUFA diet); and the third was fed the SP diet supplemented with 250 mg nucleotides per 100 g diet (NT diet). Fatty acids of plasma, erythrocyte membranes and liver microsomes were analyzed. Decreases in linoleic and arachidonic acids in both total plasma lipids and liver microsomal phospholipids were the main findings due to CCl(4)treatment. The rats that received CCl(4)and the PUFA diet showed the lowest levels of (n-6) PUFA and the highest levels of (n-3) PUFA in liver microsomal phospholipids, as well as a significant increase of (n-3) PUFAs in total plasma lipids. The animals that received the NT diet showed no signs of fatty infiltration and exhibited the highest levels of (n-6) PUFAs in liver microsomal phospholipids. These results show that CCl(4)affects fatty acid metabolism which is accordingly reflected in altered tissue fatty acid profiles, and that balanced diets containing PUFA and nucleotides are important for the recovery of the damaged liver in rats.

Modulation of hepatic and intestinal glutathione S-transferases and other antioxidant enzymes by dietary lipids in streptozotocin diabetic rats.

Antioxidant enzymes in liver and small intestine were investigated using control and streptozotocin diabetic rats fed diets with 5% olive, sunflower or fish oil for five weeks. In liver, Glutathione Peroxidase and Superoxide Dismutase decreased and in intestine Glutathione-S-transferase (GST) increased by diabetes. In isolated jejunum and ileum, this increase in GST activity was due to an increase in GST-alpha and -mu isoenzymes in jejunum and GST-alpha, mu and -pi in ileum. Since GST plays an important role in protecting tissues from oxidative damage, our results highlight the role of the intestine against free radicals in physiological or pathological situations.

Effects of dietary fatty acids on lipid metabolism in streptozotocin-induced diabetic rats.

We measured the activity of liver delta9- and delta6-desaturases and examined plasma and liver microsome phospholipid fatty acid composition in control and diabetic rats fed a basal diet supplemented with 5% (by weight) olive oil (OO), sunflower oil (SO), or fish oil (FO), respectively. Plasma glucose, cholesterol, triacylglyceride, and phospholipid levels were also measured. An increase in plasma and liver microsome oleic acid and a decrease in arachidonic acid were found in diabetes. In the liver, docosahexaenoic acid levels were higher in diabetic versus control rats. Diabetes increased liver delta9-desaturase in OO-fed rats and did not modify delta6-desaturase activity in OO- or SO-fed rats. Both enzymatic activities were decreased in diabetic rats fed the FO diet. As a main conclusion, it appears that diet-induced alterations in membrane composition provide a mechanism for improving the diabetic condition in animals and overcoming the effect of insulin deficiency on desaturase activities. Plasma cholesterol was not modified either by diabetes or by diet. In diabetes, OO-fed rats showed the lowest levels of triglycerides. Plasma phospholipids were significantly higher in OO-fed versus FO-fed rats. These findings suggest that OO contributes to a better control of the hypertriglyceridemia accompanying diabetes as compared with the other two diets in this rat model.

Effect of dietary (n-9), (n-6) and (n-3) fatty acids on membrane lipid composition and morphology of rat erythrocytes.

Studies focused on the intake of different dietary fats have shown changes in membrane lipid composition and, as a result, alterations in membrane physical properties. These changes affect erythrocyte morphology, receptor activity and oxygen transport, among others. Here, we compare the effects of diets exclusively differing in the type of fat (olive oil rich in monounsaturates, sunflower oil rich in n-6 polyunsaturates and fish oil rich in n-3 polyunsaturates) on fatty acid composition of plasma and erythrocyte membranes and erythrocyte morphology under scanning electron microscopy in rats. Monounsaturates are highest in animals fed olive oil diets; as are linoleic and arachidonic acids in sunflower oil-fed animals and n-3 PUFAs in fish oil-fed animals. The lowest levels of arachidonic acid are found in fish oil-fed animals and so are n-3 PUFAs in sunflower oil-fed animals. Our results show that sunflower oil-fed animals present lower discocyte, the major cell shape related to tissue oxygen supply, and higher codocyte percentages than olive oil- and fish oil-fed groups. Echinocyte percentage is higher in fish oil-fed animals with respect to the other two groups. The collective data indicate that olive oil elevates monounsaturates and the number of discocytes, pointing out a possible beneficial aspect of this dietary fat.

Changes in fatty acid composition of plasma, liver microsomes, and erythrocytes in liver cirrhosis induced by oral intake of thioacetamide in rats.

The aim of this study was to evaluate the changes in fatty acid composition of lipids of plasma, erythrocytes, and liver microsomes in rats with liver cirrhosis induced by oral intake of thioacetamide and to determine to what extent the experimental model reproduces the fatty acid tissue alterations reported in human cirrhosis. Two groups of rats were studied. The control group received water ad libitum, and the experimental group received 0.03% w/v thioacetamide in drinking water for 2, 4, and 6 months. At these times, lipids of plasma, erythrocytes, and liver microsomes were extracted, and their fatty acid compositions were determined. Thioacetamide intake led to macronodular and micronodular cirrhosis at 2 months. These alterations progressed at 4 months and eventuated in liver tumors at 6 months. Thioacetamide-treated rats showed a drop in total plasma fatty acids, higher percentages of palmitic acid in all lipid fractions, and lower levels of stearic acid in erythrocyte lipids and liver microsomal phospholipids. Oleic acid increased in plasma cholesteryl esters and phospholipids, as well as in erythrocyte lipids and liver microsomal phospholipids. In plasma lipids and liver microsomal phospholipids, the percentages of arachidonic and docosahexaenoic acids decreased. The latter also decreased in erythrocyte lipids. In addition, liver microsomes showed a higher cholesterol/lipid phosphorus molar ratio. The experimental model of cirrhosis obtained by intake of thioacetamide in drinking water for 4 months reproduces many of the fatty acid tissue alterations that appear in human cirrhosis and may serve to ascertain the biochemical mechanisms involved in these changes.

The n-3 polyunsaturated fatty acid levels in rat tissue lipids increase in response to dietary olive oil relative to sunflower oil.

In the present study, changes in phospholipid compositions of liver microsomes, erythrocyte membranes, platelets, aorta, cardiac muscle and brain of rats fed olive oil were compared with those of rats fed sunflower oil. Four groups of rats starting at weaning were fed for four weeks a basal diet containing 5 or 25% olive oil or sunflower oil. We found that oleic acid was higher and linoleic acid was lower in membrane phospholipids of olive oil fed rats compared to sunflower oil fed rats. Polyunsaturated fatty acids of the n-3 series were markedly elevated in all tissues of rats on the olive oil diets relative to those on the sunflower oil diets. The results are consistent with a lower linoleic/linolenic acid ratio induced by the olive oil diets, suggesting a positive correlation between olive oil ingestion and n-3 polyunsaturated fatty acid levels in cell and tissue lipids. The study suggests that an adequate intake of olive oil may enhance the conversion of n-3 fatty acids.

Malnutrition-related polyunsaturated fatty acid changes in plasma lipid fractions of cirrhotic patients.

Cirrhotic patients have both impaired liver function and nutritional derangement. In fact, the prevalence of protein-energy malnutrition (PEM) is very high in these patients. The aim of the present study was to elucidate whether the nutritional status in cirrhosis could be an additional factor that would affect levels of plasma lipids. Plasma lipid phosphorus, cholesterol, and triglycerides (TG), and fatty acid profiles in plasma and plasma fractions were determined in 50 healthy subjects and 92 patients with liver cirrhosis. The cirrhotic patients were prospectively included in three groups according to the result of nutritional assessment: group 1 (n = 38), acceptable nutritional status (including well-nourished and mildly malnourished patients); group 2 (n = 29), moderate PEM; and group 3 (n = 25), severe PEM. The main findings of this study were that the decrease in plasma cholesterol and linoleic, dihomo-gamma-linolenic, and arachidonic acid levels of cirrhotic patients was related to the degree of PEM. Cholesteryl esters (CE) appeared to be the most sensitive indicator of lipid changes in cirrhosis. We consider that the role of malnutrition in the changes observed for polyunsaturated fatty acid (PUFA) profiles in plasma lipids of cirrhotic patients may be of major importance, since severe malnourished subjects exhibited the lowest levels of those compounds. Dietary supplementation of both essential fatty acids (EFA) and long-chain PUFA in adequate amounts to the cirrhotic patient might be of importance in the management of the disease.

Effect of dietary olive and sunflower oils on the lipid composition of the aorta and platelets and on blood eicosanoids in rats.

The effects on aortic and platelet fatty acid compositions and on blood levels of prostacyclin and thromboxane A2 of low- and high-fat diets containing olive oil or sunflower oil were studied. For 4 weeks, four groups of weanling rats were fed a basal diet containing 5% or 25% olive oil or sunflower oil. Rats fed olive oil diets showed higher levels of 18:1(n-9) and polyunsaturated fatty acids of the n-3 series and lower percentages of 18:0 and 18:2(n-6) in aortic and platelet phosphatidylcholine and phosphatidylethanolamine than those fed the sunflower oil diets. Arachidonic acid increased in platelet phosphatidylethanolamine and aortic phosphatidylcholine of rats fed the diet containing 5% sunflower oil compared with those fed 5% olive oil. Plasma 6-ketoprostaglandin F1 alpha increased in both groups of animals fed olive oil while these rats also showed the lowest levels of serum thromboxane B2 and plasma cholesterol. Olive oil feeding leads to changes in lipid metabolism of the vascular compartment that could be favorable in the prevention of thrombosis and atherosclerosis.

Plasma polyunsaturated fatty acids in liver cirrhosis with or without chronic hepatic encephalopathy: a preliminary study.

Fatty acid levels (from C14:0 to C22:6n3) in plasma lipid fractions were prospectively studied in 11 cirrhotic patients with chronic hepatic encephalopathy and compared with those in 23 cirrhotic patients without chronic hepatic encephalopathy with similar age, sex distribution, and liver and nutritional status, and in 11 age- and sex-matched, healthy subjects. Plasma lipid fractions were separated by thin-layer chromatography and fatty acids were identified by capillary column gas-liquid chromatography. Total n6 polyunsaturated fatty acid plasma levels were lower in cirrhotic patients--with and without chronic hepatic encephalopathy--than in control subjects. In addition, arachidonic acid levels, both in total lipids and fractions, were lower in patients with than in those without chronic encephalopathy. On the other hand, a selective decrease of plasma docosahexaenoic acid (a major component of neuronal membranes) was observed in those patients with chronic encephalopathy as compared with both control and cirrhotic subjects without chronic encephalopathy. These findings may be due to various mechanisms. Differences in long-chain polyunsaturated fatty acid content in fish- and meat-restricted diets partly may account for these findings. However, it could be speculated that polyunsaturated fatty acid biosynthesis may be reduced further in patients with chronic hepatic encephalopathy because of either a decrease in portal essential fatty acid extraction in the postabsorptive phase due to portal-systemic shunting or to the effect of protein-restricted diets. Furthermore, the finding of low plasma docosahexaenoic acid in these patients raises the possibility that this deficiency might be an additional pathogenic factor in chronic hepatic encephalopathy.

Factors related to the plasma fatty acid profile in healthy subjects, with special reference to antioxidant micronutrient status: a multivariate analysis.

The plasma lipid fatty acid (FA) profile was measured in 83 healthy subjects (35 men, 48 women; ages 18-82 y). The association of 19 variables (including serum antioxidant micronutrients) with saturated (SFA), monounsaturated (MUFA), essential (EFA), and polyunsaturated fatty acid (PUFA) status was assessed by stepwise multiple-linear regression. Serum selenium was directly associated with percent EFA and n-6 PUFA (r = 0.38, P = 0.0004 for both) and inversely related to percent SFA in phospholipids (r = -0.38, P = 0.0004). Serum selenium was the only predictor of the unsaturation index of this fraction (r = 0.45, P = 0.0000). Although associations of plasma FA pattern with age, serum cholesterol, bilirubin, vitamin E, and zinc were also disclosed, only for selenium did the antioxidant effect seem to explain this relationship. These results suggest that antioxidant micronutrients should be measured when PUFA metabolism is studied. The relationship between plasma FA and antioxidant micronutrients in disease states needs further research.

Plasma fatty acid profile in advanced cirrhosis: unsaturation deficit of lipid fractions.

Fatty acid (FA) profile of plasma total lipids, phospholipids (PL), cholesteryl esters (CE), and triglycerides (TG) were measured in 101 patients with advanced liver cirrhosis and in 44 age- and sex-matched healthy controls. Plasma levels of lipidic phosphorus, esterified cholesterol, and TG also were measured, and the unsaturation index (UI) was calculated for each fraction. Total plasma concentrations of saturated FA, linoleate, and polyunsaturated FA (PUFA) were lower in cirrhotics than in controls. This profile was also found in plasma levels of PL- and CE-associated FA. No detectable amounts of C20:3n9 were found in cirrhotic patients. Percent FA distribution of lipid fractions showed a lower percentage of linoleate and PUFA and a higher relative amount of saturated and monoenoic FA in cirrhotics than in controls. As a consequence, the UI of PL and CE was diminished in liver cirrhosis. Linoleate and PUFA deficiency was more marked in CE than in PL, as shown by the number of patients with values below the 5th percentile of the control group, suggesting an attempt to maintain the unsaturation of PL as the most important component of cell membranes. Hepatic failure, poor essential FA intake, and malnutrition are some of the possible etiologic factors for PUFA deficiency in cirrhosis. Their relative contribution to plasma FA abnormalities, as well as the clinical and pathophysiological consequences of PUFA deficit in cirrhotic patients, requires further investigation.

Effect of dietary olive oil, corn oil and medium-chain triglycerides on the lipid composition of rat red blood cell membranes.

The effects of dietary olive oil, corn oil and medium-chain triglycerides (MCT) on factors that characterized erythrocyte membrane lipid fluidity were studied. Weanling rats were fed for 3 or 5 wk high fat diets (10%) containing olive oil, corn oil or a mixture of MCT with olive oil or corn oil. Total phospholipids and phosphatidylcholine of erythrocyte ghosts obtained from olive oil-fed animals, as compared to those fed corn oil, showed an increase in long-chain polyunsaturated fatty acids (PUFA) of the (n-6) and (n-3) series and a decrease in saturated fatty acids. The addition of MCT to the olive oil diet induced an increase in palmitic, palmitoleic and delta-5,8,11-eicosatrienoic acids and a decrease in long-chain PUFA of the (n-6) series in erythrocyte membrane phospholipids. Conversely, rats fed a mixture of MCT and corn oil, as compared to those fed exclusively corn oil, showed increase in long-chain PUFA of the (n-6) and (n-3) series, with no changes in saturated fatty acid levels. The cholesterol/phosphorus molar ratio showed only a slight increase with MCT supplementation. Olive oil feeding induced important changes in fatty acid composition of erythrocyte membrane phospholipids as compared to corn oil feeding without modifying the cholesterol/phosphorus ratio and MCT feeding slightly affected red blood cell membrane lipid composition.

Changes in lipid composition of liver microsomes and fatty acyl-CoA desaturase activities induced by medium chain triglyceride feeding.

Changes in fatty acid composition, microsomal delta 9- and delta 6-desaturase activities and liver contents of cholesterol and phospholipids were studied in rats fed medium chain triglyceride-supplemented diets. Weanling rats were divided into four groups and fed for three weeks a basal diet with different 10%-fat supplements: corn oil, medium chain triglyceride-corn oil, olive oil and medium chain triglyceride-olive oil. The highest relative content of saturated fatty acids corresponded to corn oil-fed animals. Both monounsaturated fatty acid content and delta 9-desaturase activity were higher in the animals fed olive oil diets than in corn oil-fed rats. The long chain polyunsaturated fatty acids of the n-3 series were increased in the olive oil and medium chain triglyceride-olive oil-fed groups probably due to the lower linoleic/alpha-linolenic ratios found in these two diets. The cholesterol/phospholipid molar ratio was unaffected by diet and the unsaturation index was only slightly changed in the four groups. Thus, some mechanism may be operative under these conditions to maintain the homeostasis of the membrane.

Differences in the serum amino acid pattern of injured and infected children promoted by two parenteral nutrition solutions.

The effects of two parenteral nutrition (PN) amino acid solutions (FreAmine II and F080) on the serum amino acid levels of 51 children, 27 affected by multiple trauma and 24 by bacterial sepsis, and aged from 1 month to 12 years, were studied. Serum amino acids were determined on day 1 immediately before administrating PN, and on day 5 during PN. Trauma patients on F080 exhibited higher levels of alanine, aspartate, asparagine, leucine, isoleucine, valine, total branched-chain amino acids (BCAA) and total essential amino acids than those on FreAmine II; in contrast septic children showed similar levels of serum amino acids on both PN solutions. BCAA were lower in septics than in trauma patients, probably as a consequence of an increased utilization of these amino acids in sepsis because of the higher organ protein synthesis typical of this situation. The phenylalanine/tyrosine ratio was found elevated both in septic and trauma children, but it decreased after PN in the latter when using an enriched BCAA solution. Utilization of this solution, partly corrects the metabolic disturbances induced by stress, but the metabolical responses induced either by sepsis or trauma are partially different which may have important implications for patient care.

Lipid composition of liver microsomes in rats fed a high monounsaturated fatty acid diet.

The fatty acid and cholesterol contents of tissue membranes are the determinants of membrane stability and functionality. This study was designed to evaluate the influence of a high monounsaturated fatty acid diet on the fatty acid composition of rat liver microsomes and on their cholesterol and lipid phosphorus content. Weanling animals were fed for 5 weeks with high fat diets containing olive oil or corn oil. Saturated fatty acids were increased and oleic acid decreased in microsomal total phospholipids and in the three major phosphoglycerides, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), of rats fed corn oil as compared to the olive oil group. The percentage of linoleic acid was higher in the corn oil group, but only for total phospholipids and PC. Linoleic and alpha-linolenic metabolites were significantly increased in total phospholipids of olive oil-fed animals with respect to those fed corn oil. These changes were responsible for the low unsaturation index found in microsomal phospholipids of the corn oil group. The diet did not affect the microsome cholesterol or the lipid phosphorus content. These results show that, in olive oil-fed rats, the cholesterol content and the degree of unsaturation of liver microsomes was similar to that observed in weanling animals; this probably suggests an adequate maintenance of functionality of membranes in olive oil-fed animals.

Polyunsaturated fatty acid deficiency in liver cirrhosis: its relation to associated protein-energy malnutrition (preliminary report).

Plasma fatty acids (FA) from C14:0 to C22:6 omega 3 were measured in five healthy subjects and in 27 patients with liver cirrhosis. According to the assessment of triceps skinfold, mid-arm muscle circumference, and serum albumin concentration, patients were prospectively included in three groups: group A (n = 7) with acceptable nutritional status (including good nutrition and mild malnutrition), group B (n = 10) with moderate malnutrition, and group C (n = 10) with severe malnutrition. Plasma levels of total FA, saturated FA, linoleic acid, and omega 6 greater than 18C and omega 3 greater than 18 polyunsaturated fatty acids (PUFA) were lower in cirrhotics than in controls. Linoleic:arachidonic ratio was increased and delta 5-desaturation precursors:products ratio did not change, suggesting a reduction in delta 6-desaturase and/or C18-C20 elongase activities. In addition, a stepwise fall in plasma levels of all but saturated FA was found as the nutritional status worsened, suggesting that, in cirrhosis, impairment in PUFA biosynthesis is related to the severity of associated malnutrition. Since PUFA have important biological functions as components of cell membranes and precursors of eicosanoids, the results reported here may open new perspectives in the understanding of the cirrhosis-malnutrition relationship.

Influences of diet and postnatal age on the lipid composition of red blood cell membrane in newborn infants.

The fatty acid and cholesterol contents of tissue membranes are determinants of their stability and functionality. This study was designed to evaluate the influences of diet and postnatal age on the polyunsaturated fatty acid (PUFA) composition of erythrocyte membrane phospholipid fractions and on the red blood cell membrane cholesterol and phosphorus contents in newborn infants during the 1st month of life. A group of infants was fed on human milk and another group on adapted milk formula. Blood samples were obtained at birth, from cord blood, and at 7 and 30 days of age. Long-chain w6 PUFA declined with advancing age in all membrane phosphoglycerides and sphingomyelin (SM) in those infants fed formula. w6 PUFA also decreased in phosphatidylcholine (PC) and phosphatidylserine (PS) in infants fed human milk and were maintained constant in phosphatidylethanolamine (PE) and SM. w3 PUFA were less affected by postnatal age. PE and SM showed significantly higher percentages of w6 and w3 long-chain PUFA in infants fed human milk than in those fed formula. Membrane cholesterol content increased in all infants from birth to 1 month of life but phosphorus levels were unaffected by diet and postnatal age. These results suggest that diets with a low content of long-chain PUFA, such as adapted cow's milk formulas, may induce changes in membrane functionality and that incorporation of PUFA to the diet in amounts similar to those found in human milk should be considered at least in early life.

Changes in the fatty acid composition of plasma and red blood cell membrane during the first hours of life in human neonates.

The objective of this work was to examine the changes in the fatty acid profiles of plasma lipid fractions and red blood cell membrane phospholipids in newborn infants during the first 6-8 h of life. Methyl esters of fatty acids from plasma free fatty acids and phospholipids and from membrane phosphatidylethanolamine, phosphatidylcholine and sphingomyelin for cord blood (n = 20) and venous blood (n = 19) were analyzed by GLC. Important changes were observed in plasma fatty acids. Palmitic and palmitoleic acid increased from birth to 6-8 h of age for both free fatty acids and phospholipids. Palmitic acid also increased in membrane phosphatidylcholine and phosphatidylethanolamine. In the former, stearic acid declined whereas oleic and docosatetraenoic acids increased. Phosphatidylethanolamine and sphingomyelin were less affected than phosphatidylcholine probably because the internal location of the two first fractions in erythrocyte membrane. Polyunsaturated fatty acids dropped slightly during the first hours of life in most lipid fractions. This may be a consequence of the interruption of placental fatty acid supply and the limited capacity of the newborn to desaturate their essential fatty acid tissue stores.

[Free amino acids of various lacteal formulas used in Spain]. / Contenido de aminoácidos libres de algunas fórmulas lácteas utilizadas en España.

A comparative study has been made upon free amino-acids in human milk, cow's milk and some infant formulas commercialized in Spain. The contents of free amino-acids in human milk is significantly increased when compared to those of raw of UHT sterilized cow's milk and to those of infant formulas. The concentrations of alanine are significantly lower in cow's milk and in infant formulas compared to human milk. The same occurs with branched chain amino-acids, glutamic acid, serine, threonine and taurine. On the contrary, the levels of free cysteine are significantly higher in cow's milk and in infant formulas. The concentrations of free amino-acids determined in different infant formulas on sale in Spain are rather similar between each others, being the cuantitative pattern very different from that determined in human milk.