Dietary restriction of single essential amino acids reduces plasma insulin-like growth factor-I (IGF-I) but does not affect plasma IGF-binding protein-1 in rats

The effects of dietary restriction of a single essential amino acid (EAA) on insulin-like growth factor-I (IGF-I) and IGF-binding protein (IGFBP)-1 were investigated in rats. Rats were fed experimental diets containing amino acid (AA) mixtures in which the concentrations of all EAA were at levels recommended by the National Research Council (control), in which a single EAA was restricted to 20% of that of the control diets (Leu(-), Lys(-), Met(-) or Thr(-)), or in which the diet was devoid of amino acids (AA(-)). To eliminate the effect of differences in energy intake, rats were fed the mean amount of food as consumed by the AA(-) group on the previous day. Growth was significantly retarded in rats fed diets restricted in just one EAA compared with that of rats fed the control diet, and further growth retardation was observed in rats fed the AA(-) diet. On the other hand, the plasma IGF-I concentrations in the groups with a single EAA restriction or in the AA(-) group were 66% (P: < 0. 05) and 50% (P: < 0.05) of that of the control group, respectively. The effect of any single EAA restriction was not significantly different from that of total AA deprivation. The plasma IGFBP-1 concentration in the control group did not differ from that of rats fed diets with the single EAA restrictions except for methionine restriction, but it was approximately 6-fold greater in the AA(-) group. Differences in plasma IGFBP-1 concentration under these conditions could be explained by differences in hepatic IGFBP-1 mRNA contents. Based on these results, we conclude that restriction of single EAA does not affect IGFBP-1 synthesis in vivo, although the deprivation of a single EAA has been reported to increase IGFBP-1 production in hepatocyte cultures. Our results also indicated that a single EAA restriction decreased IGF-I production but did not affect IGFBP-1 production. The present study suggests that not only plasma IGF-I, but also IGFBP-1, affects the magnitude of growth retardation in vivo.     

Amino acid content in seaweeds from the Magellan Straits (Chile)

Total proteins, amino acid (AA) profile and AA score (AAS) were determined in 73 red, green and brown seaweeds collected in the sub-Antarctic ecoregion of Magallanes. Significant differences were found between the genera and seaweed colour for protein contents, essential AA (EAA), non-essential AA (NEAA) and ratio EAA/NEAA. A serving of brown seaweed would contribute to a lower protein intake than a portion of red or green seaweed. However, AAS and the EAA index (EAAI) showed that brown seaweeds had a better protein quality than red and green seaweeds. Sulfur AA were the limiting AA in red and green seaweeds while leucine was the limiting AA in brown seaweed. A high concentration of lysine was found, which is often the limiting amino acid in animal feeds. Seaweeds might be important sources of proteins with high level of EAA, however the protein and AA content varies depending on the seaweed colour and genus.     

Arginine-deficient diets alter plasma and tissue amino acids in young and aged rats.

Blood and urine metabolites were measured in two experiments for young (2-mo-old) and aged (20-mo-old) male Sprague-Dawley rats fed arginine-devoid diets made isonitrogenous to a control 1.12% arginine diet by adding alanine or glycine. Diet, fed for 7 or 13 d, had little effect on urinary or plasma ammonia and urea. Urinary orotate excretion was more than 40-fold higher in rats fed the arginine-deficient diets (P less than 0.01) in both experiments. Source of nonessential N (alanine or glycine) in the arginine-deficient diets did not alter orotic acid excretion or plasma or urine ammonia or urea. Changes in plasma arginine, alanine and glycine concentrations reflected the levels of these amino acids in the diet. Tissue ornithine levels reflected dietary arginine level, but tissue citrulline was unaffected by dietary arginine. Glutamate and glutamine were greater in the plasma and liver of rats fed arginine-deficient diets. Plasma concentrations of glutamate and glutamine were positively correlated with urinary orotic acid excretion (P less than 0.05) and ornithine and arginine were negatively correlated with orotic acid excretion (P less than 0.01). Increased tissue glutamine may be related to the greater orotate excretion in rats fed arginine-devoid diets. The metabolic responses to dietary arginine deficiency were similar in young and aged rats. In general, concentrations of amino acids in plasma, liver and spleen were higher in aged rats.     

Portal net appearance of amino acids in growing pigs fed a barley-based diet with inclusion of three different forage meals

The net absorption of amino acids (AA) in young pigs fed a barley-based control diet (C) and diets where barley was replaced by 200 g/kg fresh weight of dried lucerne (Medicago sativa; L20), white clover (Trifolium repens; W20) or perennial ryegrass (Lolium perenne; PR20) meal was studied. Castrated male pigs were fitted with permanent catheters in the hepatic portal vein and mesenteric artery, and the hepatic portal net absorption of AA was estimated from the porto-arterial plasma concentration differences and the hepatic portal-vein blood flow. In general, the essential AA (EAA) concentrations in the hepatic portal vein reached peak levels 90 min after feeding and thereafter exhibited a transient decline. Maximum porto-arterial differences were reached between 1 and 3 h postprandially for most of the AA. The cumulative net absorption of non-essential AA (NEAA) and EAA did not differ significantly between the barley-based diet and diets W20 and PR20. Due to a lower intake of AA on diet L20, the cumulative net absorption of NEAA and EAA was significantly (P < 0.05) lower than diet C. With the exceptions of the EAA arginine, cystine and valine, and the NEAA glutamic acid + glutamine and glycine, there were no significant differences in the absorption coefficients for the EAA and NEAA between the diets. In addition, the pattern of the total EAA in the mixture absorbed postprandially did not differ significantly between the diets. The present study gives support to the contention that the replacement of barley AA with forage meal AA in a barley-based diet for growing pigs should be expected to result in minor differences in the net portal flux of AA.     

Isoleucine and leucine independently regulate mTOR signaling and protein synthesis in MAC-T cells and bovine mammary tissue slices

Understanding the regulatory effects of individual amino acids (AA) on milk protein synthesis rates is important for improving protein and AA requirement models for lactation. The objective of this study was to examine the effects of individual essential AA (EAA) on cellular signaling and fractional protein synthesis rates (FSR) in bovine mammary cells. Omission of L-arginine, L-isoleucine, L-leucine, or all EAA reduced (P < 0.05) mammalian target of rapamycin (mTOR; Ser2448) and ribosomal protein S6 (rpS6; Ser235/236) phosphorylation in MAC-T cells. Phosphorylation of mTOR and rpS6 kinase 1 (S6K1; Thr389) decreased (P < 0.05) in the absence of L-isoleucine, L-leucine, or all EAA in lactogenic mammary tissue slices. Omission of L-tryptophan also reduced S6K1 phosphorylation (P = 0.01). Supplementation of L-leucine to media depleted of EAA increased mTOR and rpS6 and decreased eukaryotic elongation factor 2 (Thr56) phosphorylation (P < 0.05) in MAC-T cells. Supplementation of L-isoleucine increased mTOR, S6K1, and rpS6 phosphorylation (P < 0.05). No single EAA considerably affected eukaryotic initiation factor 2-α (eIF2α; Ser51) phosphorylation, but phosphorylation was reduced in response to provision of all EAA (P < 0.04). FSR declined when L-isoleucine (P = 0.01), L-leucine (P = 0.01), L-methionine (P = 0.02), or L-threonine (P = 0.07) was depleted in media and was positively correlated (R = 0.64, P < 0.01) with phosphorylation of mTOR and negatively correlated (R = -0.42, P = 0.01) with phosphorylation of eIF2α. Such regulation of protein synthesis will result in variable efficiency of transfer of absorbed EAA to milk protein and is incompatible with the assumption that a single nutrient limits protein synthesis that is encoded in current diet formulation strategies.     

Evaluation of the bioavailability and metabolism in the rat of punicalagin,an antioxidant polyphenol from pomegranate juice

BACKGROUND & AIMS: Punicalagin is an antioxidant ellagitannin of pomegranate juice. This compound is responsible for the high antioxidant activity of this juice. Nothing is known about the bioavailability and metabolism of punicalagin or other food ellagitannins. The present work aims to evaluate the bioavailability and metabolism of punicalagin in the rat as an animal model. DESIGN: Two groups of rats were studied. One fed with standard rat diet (n = 5) and another with the same diet plus 6 % punicalagin (n = 5). Samples of urine and faeces were taken during 37 days and plasma every week. The different metabolites were analysed by HPLC-MS-MS. RESULTS: The daily intake of punicalagin ranged from 0.6 to 1.2 g. Values around 3-6 % the ingested punicalagin were excreted as identified metabolites in faeces and urine. In faeces, punicalagin is transformed to hydrolysis products and partly metabolites by the rat microflora to 6H-dibenzo[b,d]pyran-6-one derivatives. In plasma, punicalagin was detected at concentrations around 30 microg/mL, and glucuronides of methyl ether derivatives of ellagic acid were also detected. 6H-Dibenzo[b,d]pyran-6-one derivatives were also detected especially during the last few weeks of the experiment. In urine, the main metabolites observed were the 6H-dibenzo[b,d]pyran-6-one derivatives, as aglycones or glucuronides. CONCLUSION: As only 3-6 % of the ingested punicalagin was detected as such or as metabolites in urine and faeces, the majority of this ellagitannin has to be converted to undetectable metabolites (i. e. CO(2)) or accumulated in non-analysed tissues, however with only traces of punicalagin metabolites being detected in liver or kidney. This is the first report on the absorption of an ellagitannin and its presence in plasma. In addition, the transformation of ellagic acid derivatives to 6H-dibenzo[b,d]pyran-6-one derivatives in the rat is also confirmed.     

A controlled study of supplementation with essential amino acids and α-keto acids in the conservative management of patients with chronic renal failure

Oral therapy with essential amino acids (EAA) or α-keto acids (α-KA) has been recommended in patients with renal failure, but quality and quantity of optimal protein intake are still controversial. This study compares sequentially the effect of supplementation with EAA, and with α-KA versus placebo in 15 ambulatory patients with chronic renal failure (average creatinine clearance 10.8 ml/min), maintained on a protein diet of 0.57 g/kg body weight (40 g for a 70-kg patient). The actual dietary intake averaged 0.55 g protein/kg and 27 kcal/kg according to repeated 7-day dietary recordings. After a 6-week baseline period on this diet, all patients received additionally 0.112 g EAA/kg for 6 weeks followed by a double-blind cross-over study of 0.105 g α-KA/kg versus placebo supplementation for 6 weeks each. Fasting blood samples for multiple parameters, including 15 indicators for protein deficiency, as well as anthropometric and clinical data were evaluated every 3 weeks. Laboratory data revealed no indications of protein deficiency. Therapy with α-KA diminished serum phosphate concentration (p<0.05), however no other significant beneficial effects could be demonstrated during supplementation with either EAA or α-KA. Therefore, such supplementation to a 0.55-g/kg-protein diet appears superfluous in stable ambulatory patients with renal insufficiency.     

Vitamin C and the anti-obesity effect of fenfluramine

Increasing doses of fenfluramine were given to female guinea-pigs on a scorbutogenic diet with or without Ascorbic Acid (AA) supplementation. AA alone increased weight and appetite, hepatic and plasma AA. AA deficiency reduced weight after an initial rise. 10 mg/kg fenfluramine in association with the diet produced a gain in weight. Larger doses caused weight loss and reduced appetite. These effects were prevented by AA supplementation. Fenfluramine reduced hepatic and plasma AA significantly in comparison with the animals receiving the diet alone, or the diet with AA supplementation in the absence of fenfluramine administration. It is concluded that AA release plays an important role in the anti-obesity and anorectic actions of fenfluramine.     

In vivo evidence for a vitamin B-6 requirement in carnitine synthesis

The purpose of this study was to determine whether there is a requirement for vitamin B-6 (B6) in carnitine synthesis. Rats were fed a B6-deficient (-B6) (0.04 mg pyridoxine [PN]/kg) diet (ad libitum or meal-fed) or a control (+B6) (5.7 mg PN/kg) diet (ad libitum or pair-fed). These diets were fed for 6 wk, then some of the rats were repleted with the +B6 diet for 2 wk. Total acid-soluble carnitine (TCN) and free carnitine (FCN) levels were compared in the plasma, liver, skeletal muscle, heart muscle and urine and rats fed +B6 or -B6 diets. In -B6 rats vs. +B6 rats, TCN levels were significantly lower (P less than 0.05) in the plasma, skeletal muscle, heart muscle and urine, but not in the liver. However, if rats were fasted for 3 d, liver TCN concentration of -B6 rats was significantly lower than that of +B6 rats. After B6-deficient rats were repleted with the +B6 diet, the TCN level in the plasma, liver, skeletal muscle, heart muscle and urine returned to the levels of control rats. Thus, the decrease in TCN and FCN levels with a B6-deficient diet and the increase of these levels after B6 repletion provides evidence for the B6 requirement in the biosynthesis of carnitine.     

Effect of vitamin A deficiency on nitrogen balance and hepatic urea cycle enzymes and intermediates in rats

After 12 wk of feeding a 4-d nitrogen balance was carried out in 8 vitamin A--deficient and 8 pair-fed control rats to understand the effect of vitamin A deficiency on protein metabolism. Urea nitrogen (UN) was lower and amino nitrogen (AN) was higher in plasma of deficient animals than in pair-fed controls. No significant alteration in the nitrogen retention or in the general pattern of other nitrogen metabolites in plasma and urine was observed in vitamin A--deficient rats as compared to controls. However, there was a significant increase in the excretion of urinary ammonium nitrogen (Am-N) in relation to creatinine (CR). Activities of hepatic carbamoylphosphate synthase-I (CPS-I) and ornithine transcarbamoylase (OTC) were significantly lower in vitamin A--deficient animals than in control rats at the end of 13 wk of feeding. While the liver levels of ornithine and polyamines were significantly greater, that of glutamine was lower in vitamin A--deficient rats than in pair-fed controls. The results suggest that vitamin A deficiency leads to a reduced efficiency of urea synthesis pathway, thus accounting for the increased Am-N excretion seen in vitamin A deficiency.     

Hepatic PKA inhibition accelerates the lipid accumulation in liver

Zinc deficiency can change the concentrations of minerals and trace elements in the body. However, previous studies still had many limitations. To reveal the effects of zinc deficiency on homeostasis of 16 minerals and trace elements. Forty-five rats were divided randomly into three groups: normal zinc diet (30 mg/kg), low zinc diet (10 mg/kg), and pair-fed diet(30 mg/kg). The concentrations of 16 minerals and trace elements in serum, feces, urine, and liver were measured by inductively coupled plasma mass spectrometry. The excretion of 16 elements in urine and feces were calculated and compared. Zinc-deficient rats exhibited significant changes in up to 12 minerals and trace elements. The low zinc diet induced decreased excretion of zinc and concentrations of zinc in serum, feces, urine, and liver. Zinc deficiency increased feces concentrations of Mg, Cu, Se, K, Ag, Fe and Mn; decreased the concentrations of Mg, Cu, Se, K in liver and urine, and a diminished amount of Ag was observed in serum. Decreased urinary concentrations of Zn Ca, Mg, Cu, Se, K, Na, As and Cr, suggested that zinc-deficient rats increased the 9 elements’ renal reabsorption. Decreased concentrations of Ca in liver, urine, and feces, decreased excretion in urine and feces and increased serum total Ca suggested that zinc deficiency increased the redistribution of Ca in serum or other tissues. Zinc deficiency increased excretion of Cu, Se, Fe; and decreased the excretion of other 8 elements except for Ag. Zinc deficiency changed the excretion, reabsorption and redistribution of 12 minerals and trace elements in rats. Our findings are the first to show that zinc deficiency alters the concentrations of Ag, Cr, and As.     

Rapid fall in plasma threonine followed by increased intermeal interval in response to first ingestion of a threonine-devoid diet in rats

In most animals, ingestion of a diet lacking an essential amino acid (EAA) gives rise to anorexia within a few hours. The first signal in this feeding response may be the fall in plasma levels of the limiting EAA. In the present study, we measured plasma amino acid levels and food intake after the first exposure to either a threonine-devoid (THR-DEV) or corrected (COR) diet in 16 rats bearing a chronic jugular catheter for blood sampling. Food intake was reduced 165 min (p<0.05) after presentation of the THR-DEV diet. Analysis of the feeding pattern showed that intake was reduced via a four-fold lengthening of the second inter-meal interval. Plasma threonine levels started to fall between 30 and 60 min after onset of the meal (p<0.05). These results, observed in the same rats, lend further support for an early modification of the plasma amino acid pattern in relation to the decrease in feeding of a diet that is EAA deficient.     

Essential amino acids regulate both initiation and elongation of mRNA translation independent of insulin in MAC-T cells and bovine mammary tissue slices

Current nutrient requirement models assume fixed efficiencies of absorbed amino acid (AA) conversion to milk protein. Regulation of mammary protein synthesis (PS) potentially violates this assumption by changing the relationship between AA supply and milk protein output. The objective of this study was to investigate the effects of essential AA (EAA) and insulin on cellular signaling and PS rates in bovine mammary cells. MAC-T cells were subjected to 0 or 100% of normal EAA concentrations in DMEM/F12 and 0 or 100 μg insulin/L in a 2 × 2 factorial arrangement of treatments. Lactogenic bovine mammary tissue slices (MTS) were subjected to the same treatments, except low-EAA was 5% of normal DMEM/F12 concentrations. In MAC-T cells, EAA increased phosphorylation of mammalian target of rapamycin (mTOR; Ser2448), ribosomal protein S6 kinase 1 (S6K1; Thr389), eIF4E binding protein 1 (4EBP1; Thr37/46), and insulin receptor substrate 1 (IRS1; Ser1101), and reduced phosphorylation of eukaryotic elongation factor 2 (eEF2; Thr56) and eukaryotic initiation factor (eIF) 2-α (Ser51). In the presence of insulin, phosphorylation of Akt (Ser473), mTOR, S6K1, 4EBP1, and IRS1 increased in MAC-T cells. In MTS, EAA had similar effects on phosphorylation of signaling proteins and increased mammary PS rates. Insulin did not affect MTS signaling, perhaps due to inadequate levels. Effects of EAA and insulin were independent and additive for mTOR signaling in MAC-T cells. EAA did not inhibit insulin stimulation of Akt phosphorylation. PS rates were strongly associated with phosphorylation of 4EBP1 and eEF2 in MTS. EAA availability affected translation initiation and elongation control points to more strongly regulate PS than insulin.     

Effect of dietary protein on zearalenone metabolism and toxicity in the rat

Three experiments were conducted to determine the effect of dietary protein on zearalenone metabolism and toxicity in the rat. Young female rats were fed a semipurified diet containing 7.5, 15 or 45% protein, ad libitum. 1) After 14 days of feeding the activities of 3α-hydroxysteroid dehydrogenase (3α-HSD) and UDP-glucuronyl transferase (UDP-G), the zearalenone metabolizing enzymes, were determined. Dietary protein did not effect 3α-HSD activity, however UDP-G activity increased significantly in low-protein animals. 2) Animals, after 14 days of feeding, were dosed with 1 mg zearalenone/kg body weight, zearalenone and its metabolites were measured in urine and feces. Dietary protein enhanced urinary excretion of zearalenone and its metabolites, animals on the high-protein diet excreted 49% of the dose in the urine while rats on the standard- and low-protein diets excreted 23% of the dose in the urine. 3) Rats were fed the same diets, but 0–400 ppm zearalenone was added for 3 weeks and feed intake, growth and organ weights were measured. The high-protein diet ameloriated the symptoms of zearalenone toxicity. These results indicate that dietary protein affects zearalenone metabolism and toxicity.     

Procyanidins are not bioavailable in rats fed a single meal containing a grapeseed extract or the procyanidin dimer B3

Flavanols are the most abundant flavonoids in the human diet where they exist as monomers, oligomers and polymers. In the present study, catechin, the procyanidin dimer B3 and a grape-seed extract containing catechin, epicatechin and a mixture of procyanidins were fed to rats in a single meal. After the meals, catechin and epicatechin were present in conjugated forms in both plasma and urine. In contrast, no procyanidins or conjugates were detected in the plasma or urine of any rats. Procyanidins were not cleaved into bioavailable monomers and had no significant effects on the plasma levels or urinary excretion of the monomers when supplied together in the grapeseed extract. We conclude that the nutritional effects of dietary procyanidins are unlikely to be due to procyanidins themselves or monomeric metabolites with the intact flavonoid-ring structure, as they do not exist at detectable concentrations in vivo. Future research should focus on other procyanidin metabolites such as phenolic acids and on the effects of the unabsorbed oligomers and polymers on the human gastrointestinal tract.     

Post-prandial plasma aminograms in the assessment of protein quality for young children: maize and grain amaranth, alone and combined

Post-prandial (p.p.) changes in plasma free amino acid (AA) concentrations of children consuming a single source of protein at critical levels are determined by its digestibility and total essential AA/total AA ratios; the molar proportion of the limiting EAA (EAA/TEAA), if any, will fall significantly in plasma as it is utilized more completely than others. Grain amaranths (Am), reputedly rich in lysine (Lys) and tryptophan (Trp), but moderately deficient in leucine (Leu), should be ideal complements to Lys and Trp-poor, Leu-rich maize (M). Most animal studies confirm this. In children, 20, 30 and even 50 per cent replacement of M proteins with toasted Am proteins had failed to show any gains over M or Am alone: heat losses of Lys were suspected. Plasma obtained during the above studies, before and 3 h and 4 h after the first meal of the last day of consuming Am alone, three M-toasted Am mixtures, or M alone, were analysed for free AAs. Toasted, popped or flaked Am consumption caused significant p.p. falls in molar proportions of Leu from 99 to 85, 88 to 82, and 92 to 75, and of threonine (Thr) from 118 to 108 (popped) and 109 to 97 (flaked) mmol/mol TEAA, suggesting that these were first- and second-limiting EAAs. Post-prandial fall in Lys proportion was questionably significant. The M diet produced highly significant 3-h Leu elevation from 132 to 187, Lys fall from 167 to 135, and Trp fall from 62 to 46 mmol/mol TEAA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary Essential Amino Acid Restriction Promotes Hyperdipsia via Hepatic FGF21

Prior studies have reported that dietary protein dilution (DPD) or amino acid dilution promotes heightened water intake (i.e., hyperdipsia) however, the exact dietary requirements and the mechanism responsible for this effect are still unknown. Here, we show that dietary amino acid (AA) restriction is sufficient and required to drive hyperdipsia during DPD. Our studies demonstrate that particularly dietary essential AA (EAA) restriction, but not non-EAA, is responsible for the hyperdipsic effect of total dietary AA restriction (DAR). Additionally, by using diets with varying amounts of individual EAA under constant total AA supply, we demonstrate that restriction of threonine (Thr) or tryptophan (Trp) is mandatory and sufficient for the effects of DAR on hyperdipsia and that liver-derived fibroblast growth factor 21 (FGF21) is required for this hyperdipsic effect. Strikingly, artificially introducing Thr de novo biosynthesis in hepatocytes reversed hyperdipsia during DAR. In summary, our results show that the DPD effects on hyperdipsia are induced by the deprivation of Thr and Trp, and in turn, via liver/hepatocyte-derived FGF21.     

Uricogenic potential of selected cooked foods in rats.

Samples of beefsteak, beef liver, haddock, and mushrooms were cooked by two methods: boiling and broiling. Growth and purine metabolism in rats fed diets containing 20% protein (N × 6.25) were studied for a period of 26 days. The cooked meats and fish were used as the sole source of dietary protein, while cooked mushrooms provided 5% protein in mushroom-casein diets. Body weight, and food and water intakes were recorded weekly while total urine was collected during the last 6 days of the feeding period. Levels of purine metabolites (uric acid and allantoin) in blood and urine were determined by enzymatic methods and reverse-phase HPLC techniques. Dietary treatments had no significant effects on weight gain and food consumption. Compared with animals fed the casein control diet, rats fed the broiled liver, broiled haddock, and boiled mushroom diets had significantly (p less than 0.05) higher concentrations of serum allantoin, suggesting that uricogenicity of these foods was influenced by the method of cooking. The renal excretion of purine metabolites was significantly correlated with purine intake, the renal excretion of allantoin and uric acid being the highest in rats fed the liver diets.     

The effect of protein and energy deficiency on skin glycosaminoglycan levels in the rat

1. The effects of protein-deficient and energy-deficient diets on the concentrations of skin glycosaminoglycans (GAGs) and collagen were studied in young rats. 2. In Expt 1, comparisons were made between animals fed on a control (C) diet (protein:energy (P:E) 0.210), a low-protein (LP) diet (P:E 0.032) and a very-low protein (VLP) diet (P:E 0.005) ad lib. Skin GAGs and collagen concentrations were determined at intervals as the animals became malnourished and when some of those fed on the VLP diet started showing signs of oedema. Concurrently, plasma albumin concentrations were determined to assess the extent of hypoalbuminaemia. With prolonged severe protein deficiency all GAGs species were reduced below normal levels. Collagen concentration decreased with prolonged protein deficiency. Protein-deficient rats developed hypoalbuminaemia. 3. In Expt 2, comparisons were made between animals fed on the C, LP and VLP diets ad lib. and others given the C diet in restricted amounts sufficient to maintain body-weights identical to those fed on LP or VLP diets ad lib. Energy-deficient rats, wasting at rates similar to protein-deficient ones, had higher skin GAGs concentrations than those in protein-deficient or control animals. With prolonged malnutrition, collagen concentrations were similar in protein- and energy-deficient animals and lower than those observed in control animals. Plasma albumin concentrations in energy-deficient animals were above starting values, except in severely energy-deficient animals at the end of the experiment. Protein-deficient animals developed hypoalbuminaemia. 4. In conclusion, the present study has shown that the main difference between prolonged severe protein deficiency and energy deficiency in the rat is that skin hyaluronic acid concentration is higher than normal in energy deficiency but below normal levels in prolonged severe protein deficiency. Initially skin collagen concentrations are higher than normal in both protein- and energy-deficient animals. However, with prolonged malnutrition the concentrations are reduced.     

Uricogenic potential of selected cooked foods in rats

Samples of beefsteak, beef liver, haddock, and mushrooms were cooked by two methods: boiling and broiling. Growth and purine metabolism in rats fed diets containing 20% protein (N x 6.25) were studied for a period of 26 days. The cooked meats and fish were used as the sole source of dietary protein, while cooked mushrooms provided 5% protein in mushroom-casein diets. Body weight, and food and water intakes were recorded weekly while total urine was collected during the last 6 days of the feeding period. Levels of purine metabolites (uric acid and allantoin) in blood and urine were determined by enzymatic methods and reverse-phase HPLC techniques. Dietary treatments had no significant effects on weight gain and food consumption. Compared with animals fed the casein control diet, rats fed the broiled liver, broiled haddock, and boiled mushroom diets had significantly (p less than 0.05) higher concentrations of serum allantoin, suggesting that uricogenicity of these foods was influenced by the method of cooking. The renal excretion of purine metabolites was significantly correlated with purine intake, the renal excretion of allantoin and uric acid being the highest in rats fed the liver diets.