Effects of various soya protein hydrolysates on lipid profile, blood pressure and renal function in five-sixths nephrectomized rats

Studies have demonstrated that isolated soya protein (ISP) can slow the progression of renal injury, reduce blood pressure and improve the serum lipid profile in experimental animals and human subjects. The mechanisms and components of soya responsible have not been fully established. The present study was designed to evaluate the effects of the hydrophilic supernatant fraction (SF) and the hydrophobic precipitate fraction (PF) isolated from soya protein hydrolysate on renal function, lipid metabolism and blood pressure in five-sixths nephrectomized rats. Experimental animals were subjected to a nephrectomy and allocated to four groups (180 g casein/kg, 180 g ISP/kg, 100 g casein/kg with 80 g SF/kg, and 100 g casein/kg with 80 g PF/kg). The SF group had the most significant decreases in blood pressure and total cholesterol, as well as a significantly retarded progression of the experimentally induced renal disease, compared with the other groups. The PF group exhibited a significantly increased faecal excretion of total steroids. The serum creatinine, level of proteinuria, total cholesterol and LDL-cholesterol concentrations, and blood pressure were significantly reduced, and HDL-cholesterol was significantly increased, in the ISP and PF groups compared with the casein group, but no significant differences were observed between the ISP and PF groups. These results suggest that both soya protein hydrolysate fractions favourably affected chronic renal failure induced by a five-sixths nephrectomy, and the hydrophilic fraction of soya protein hydrolysate had the most pronounced effect on attenuating hypertension and slowing the progression of renal disease.     

Evidence of progressive deterioration of renal function in rats exposed to a maternal low-protein diet in utero

Intrauterine growth retardation associated with maternal undernutrition is proposed to play a significant role in the aetiology of hypertension and CHD. Animal experiments suggest that the kidney, which is extremely vulnerable to the adverse effects of growth-retarding factors, may play an important role in the prenatal programming of hypertension. Maintenance of renal haemodynamic functions following structural impairment in fetal life is proposed to require adaptations which raise systemic blood pressure and promote a more rapid progression to renal failure. Rats were fed on diets containing 180 g casein/kg (control) or 90 g casein/kg (low protein) during pregnancy. The offspring were studied in terms of blood pressure, creatinine clearance, blood urea N, plasma and urinary albumin, renal morphometry and metabolic activity at 4, 12 and 20 weeks of age. Blood pressure was elevated at all ages in the low-protein-exposed offspring, relative to control rats. Rats (4 weeks old) exposed to the low-protein diet had smaller kidneys which were shorter and wider than those of control animals. Creatinine clearance was significantly reduced in 4-week-old rats exposed to the low-protein diet. Renal morphometry and creatinine clearance at older ages were not influenced by prenatal diet. Blood urea N, urinary output and urinary albumin excretion were, however, significantly greater in low-protein-exposed rats than in control rats at 20 weeks of age. These findings are suggestive of a progressive deterioration of renal function in hypertensive rats exposed to mild maternal protein restriction during fetal life. This is consistent with the hypothesis that adaptations to maintain renal haemodynamic functions following impairment of fetal nephrogenesis result in an accelerated progression towards glomerulosclerosis and increased intrarenal pressures mediated by rising vascular resistance.     

Oligo-L-methionine and resistant protein promote cecal butyrate production in rats fed resistant starch and fructooligosaccharide.

We examined the role of resistant protein and peptides in promoting cecal butyrate production in rats fed rapidly fermentable carbohydrates. Rats were fed diets containing raw potato starch (RPS, 200 g/kg diet) or fructooligosaccharide (FOS, 60 g/kg diet) with casein, soy or rice protein (250 g/kg diet) for 13 d. In rats fed RPS with casein, the major cecal organic acid was acetate (441 micromol), but lactate and succinate were also found in considerable amounts (324 micromol). Succinate was the major cecal organic acid (235 micromol) in rats fed FOS with casein. When rice protein was fed with RPS, the contribution of lactate was significantly lower and that of propionate tended to be higher (P < 0.1) than in rats fed casein. In rats fed rice protein with FOS, cecal butyrate and acetate were greater and cecal succinate was lower than in rats fed casein with FOS (P < 0.05). Despite the similar amounts of undigested protein in rice and soy proteins, soy protein did not similarly affect cecal butyrate in rats fed FOS or RPS. In another experiment, rats were fed diets containing high amylose cornstarch (HAS, 200 g/kg diet) with casein, casein + oligo-L-methionine (OM, 3 g/kg diet), soy protein, soy protein + OM (3 g/kg diet) or rice protein (250 g/kg diet) for 10 d. OM (digestibility, 31%) was substituted for the same amount of casein. Rats fed rice protein had greater cecal butyrate than rats fed casein (P < 0.05). OM supplementation to casein or soy protein increased cecal butyrate compared with rats fed casein or soy protein alone (P < 0.05). These data support our hypothesis that resistant protein and peptides promote cecal butyrate production and suggest that the differing potency of rice and soy proteins in promoting cecal butyrate production might be explained in part by the different amino acid composition of resistant protein.     

The effect of high intakes of casein and casein phosphopeptide on calcium absorption in the rat

The effect of the level or source of dietary protein or protein-derived peptides on Ca absorption is not well understood. We determined, therefore, the influence of habitual dietary casein level, meal casein and meal casein phosphopeptide (CPP) on Ca absorption in the rat. True fractional Ca absorption was investigated in male 7-week-old rats, Wistar strain, in three separate studies using a faecal 47Sc: 47Ca ratio method. In studies A and C, rats (n 8 per group) were fed on a purified diet containing 200 g casein/kg for 2 weeks. Rats were then given a 47Ca-labelled meal (10 g) containing (per kg) either 0, 100, 200, or 300 g casein (study A) or 0, 100, 200, 350 or 500 g CPP (study C). In study B, rats (n 24 per group) were fed on a purified diet containing (per kg) either 200, 350 or 500 g casein for 2 weeks. Each group was then further randomized into three groups (n 8 per group) and given a 47Ca-labelled meal (10 g of the same diet) containing (per kg) either 200, 350 or 500 g casein. Ca absorption from a meal was unaffected by increasing meal casein concentration from 0 to 300 g/kg (study A), but was increased with a meal casein content of 500 g/kg (study B). Fractional Ca absorption decreased with increasing usual dietary casein intake in the range 200-500 g/kg (study B), suggesting intestinal adaptation. Ca absorption was unaffected by inclusion of 100 g CPP/kg in a single meal but was significantly (P < 0.001) reduced by 200, 350 and 500 g CPP/kg meal, with no evident dose-relationship. Thus, while Ca absorption was enhanced by high-casein meals, the mechanism remains unclear.     

Effect of dietary protein on hepatic mitochondrial function and cardiac muscle protein turnover in uremic rats

To define the metabolic consequences of diets low in protein in chronic renal failure, young uremic and sham operated rats were fed isoenergetic diets for three weeks varying in protein content from 22% to 8% casein at the expense of carbohydrate. The results indicate that reducing casein content from 22% (control) to either 16%, 12% or 8% in uremic rats did not result in gross differences in renal function or decreases in liver weight, mitochondrial content or respiration. Atrial muscle protein synthesis was increased 26% while degradation was slightly, but not significantly, decreased in uremic and sham-operated rats fed the 8% casein diet compared to control. In both uremic and sham-operated rats fed the 8% casein diet, serum triiodothyronine (T₃) concentrations and hepatic mitochondrial glycerolphosphate (GP) shuttle activity were significantly increased while malate-aspartate shuttle activity was decreased compared to all other diet groups. The increased serum T₃ level and GP shuttle activity produced by feeding the 8% casein diet suggests a diet induced alteration in hepatic mitochondrial intermediary metabolism which may be of benefit in protecting against the potentially serious consequences of lowered thyroid hormone levels in chronic renal insufficiency.     

A soyabean diet does not modify the activity of brown adipose tissue but alters the rate of lipolysis in the retroperitoneal white adipose tissue of male rats recovering from early-life malnutrition

Nutritional recovery with a soyabean diet decreases body and fat weights when compared with a casein diet. We investigated whether the reduced adiposity observed in rats recovering from early-life malnutrition with a soyabean diet results from alterations in lipid metabolism in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Male rats from mothers fed either 17 or 6?% protein during pregnancy and lactation were maintained on 17?% casein (CC and LC groups), 17?% soyabean (CS and LS groups) or 6?% casein (LL group) diets over 60?d. The rats maintained on a soyabean diet had similar relative food intakes, but lower body and retroperitoneal WAT weights and a reduced lipid content in the retroperitoneal WAT. The insulin levels were lower in the recovered rats and were elevated in those fed a soyabean diet. Serum T3 concentration and uncoupling protein 1 content in the BAT were decreased in the recovered rats. The thermogenic capacity of the BAT was not affected by the soyabean diet. The lipogenesis rate in the retroperitoneal WAT was similar in all of the groups except for the LL group, which had exacerbated lipogenesis. The enhancement of the lipolysis rate by isoproterenol was decreased in white adipocytes from the soyabean-recovered rats and was elevated in adipocytes from the soyabean-control rats. Thus, in animals maintained on a soyabean diet, the proportions of fat deposits are determined by the lipolysis rate, which differs depending on the previous nutritional status.     

鱼粉延缓高脂血症大鼠慢性肾衰的发展

目的对比鱼粉和干酪素为蛋白质来源的饮食对自然发生高脂血症(SHC)大鼠慢性肾衰发展的不同影响。方法48只10周龄的SHC大鼠随机分为4组,分别给予含20%、40%鱼蛋白或酪蛋白的饮食饲育至22周龄,每4周检测血压、尿液和血液生化学改变,肾脏于实验结束时用于组织学和免疫组织化学检查。结果与同比例的酪蛋白相比,进食鱼粉为蛋白质来源的SHC大鼠均显示出较少的尿蛋白排泄量、较慢的肾功能下降速率和较轻的肾组织损伤程度。结论与干酪素相比,以鱼粉为蛋白质来源的饮食延缓了SHC大鼠慢性肾衰的发展速度。     

Soy protein affects serum insulin and hepatic SREBP-1 mRNA and reduces fatty liver in rats

The consumption of soy protein was shown to reduce blood lipids in humans and other animal species. Furthermore, it was shown that the ingestion of soy protein maintains normal insulinemia. Thus, the purpose of the present study was to determine whether soy protein affects the synthesis of lipids in the liver through sterol-regulatory element binding protein-1 (SREBP-1) due to modulation of insulin levels. We first conducted a short-term study in which rats were fed a diet containing 18 g/100 g soy protein or casein for 10 d. Rats fed soy protein had significantly lower serum insulin concentrations than rats fed casein, and this response was accompanied by an elevation in hepatic SREBP-1 mRNA that was 53% lower than that in rats fed casein at d 10. The increase in SREBP-1 mRNA occurred 30 min after consumption of the casein mean, and increased steadily for the next 2 h. We then conducted a second study to assess the long-term effect of soy protein consumption for 150 d on hepatic SREBP-1 expression. Long-term consumption of soy protein maintained normal insulin concentrations compared with rats fed casein, which were hyperinsulinemic. Thus, rats fed the soy protein diet had significantly lower expression of SREBP-1 mRNA than rats fed the casein diet. Soy protein intake also reduced the expression of fatty acid synthase (FAS) and malic enzyme, leading to low hepatic lipid depots of triglycerides and cholesterol, whereas rats fed the casein diet developed fatty liver. These data suggest that soy protein regulates SREBP-1 expression by modulating serum insulin concentration, thus preventing the development of fatty liver.     

Dietary effects on pancreatic lesions induced by excess arginine in rats

The effect of nutrition on the incidence of pancreatic damage was studied. Injection of excess arginine was found to cause more massive necrosis of the acinar cells after 24 h in malnourished rats (those given 50 g casein/kg diet) than in well-nourished rats (those given 200 g casein/kg diet). Ultrastructural examination showed that whorl formation of the endoplasmic reticulum, decreases in the number of zymogen granules and formation of vacuoles in the cytoplasm were more marked in rats given 50 g casein/kg diet. Degradation of zymogen granules within vacuoles in the damaged cells was frequently observed in rats given 200 g casein/kg diet. Necrosis of adipose tissue was associated with pancreatic damage more frequently in rats given 200 g casein/kg diet; rats with large amounts of zymogen granules in the acinar cells showed particularly severe necrosis of adipose tissue. Rats given 50 g casein/kg diet did not show necrosis of adipose tissue. These results indicate that in the malnourished state there were more marked arginine lesions of the pancreas in which to study cellular and histologic changes than in the well-nourished state and that the occurrence of necrosis of adipose tissue may be related to a high content of zymogen granules in the acinar cells before pancreatic damage.     

Low-protein diet prevents tissue lipoprotein lipase activity increase in growing rats

The time course of changes in tissue lipolytic activities was studied in young rats during the consumption of a low-protein diet containing 50 g protein/kg (40 g wheat gluten +10 g casein/kg) for 28 d followed by balanced refeeding with 200 g protein/kg (160 g wheat gluten +40 g casein/kg) for 28 d. Lipoprotein lipase (LPL) activities were compared with the values of a control group fed a balanced diet containing 200 g protein/kg for 56 d. At the end of protein malnutrition period, the epididymal fat tissue LPL activity represented 36 %, and that of heart and gastrocnemius was 44 %, of those of the control group. These differences were accompanied by lower serum- and VLDL-triacylglycerols (TAG), respectively 47.6 % and 31 % of the control group values, probably resulting from reduced synthesis of VLDL-apolipoproteins (29 % of control group values), concomitant with liver lipid accumulation (4.8-fold) and little lipid storage in epididymal fat tissue. At day 2 of refeeding, there was no significant difference in liver and epididymal fat tissue LPL activities between experimental and control rats. At the end of the refeeding period, LPL activity of epididymal fat and liver lipolytic activity had increased and became similar to control group values. The consumption of a low-protein diet prevented the increase in extrahepatic LPL activities as observed in the control group. The alterations in LPL activity suggest that a low-protein diet limits lipid storage in adipose tissue due to reduced serum VLDL-TAG availability.     

Effect of refeeding diets containing cottonseed flour with traces of gossypol on rat liver and testis.

The aim of the present work was to show that cottonseed flour introduced into rehabilitation diets is not nutritionally harmful. The cottonseed flour obtained from glandless seeds contains traces of gossypol. As gossypol is known to have pathological hepatic and testicular actions, the effects on hepatic variables and on the histological appearance of liver and testis of diets containing cottonseed flour were compared with those without cottonseed flour. Seventy growing male Wistar rats were divided into two groups. The control group (C) received a balanced diet (200 g casein + 3 g methionine/kg) for 78 d and the experimental group was fed on a low-protein diet (20 g casein + 3 g methionine/kg) for 29 d. After the period of protein deprivation, the depleted rats were divided into four groups and each group was refed with a different diet, for 49 d: a balanced diet (200 g casein + 3 g methionine/kg; rC), maize-soya-bean flour-milk (60:30:5, by wt; MSM), maize-cottonseed flour-milk (60:30:5, by wt; MCM) or rice-cottonseed flour-milk (60:30:5, by wt; RCM). Each diet was supplemented with a vitamin mixture (10 g/kg) and a salt mixture (40 g/kg). In the liver, protein, total lipid, fatty acid composition and nucleic acid contents were determined after 29 d of protein deprivation and after 2, 14, 29, 49 d of refeeding. The refeeding of rats with either diet MSM or RCM promoted a higher growth than that with diet MCM or diet rC. In all groups, a progressive decrease in relative liver weights with age was observed. The highest values were obtained with diets rC and MSM. After 49 d of refeeding, the lowest values for lipid, DNA and protein:RNA and the highest values for RNA and RNA:DNA were obtained with the cottonseed diets (MCM and RCM). Rats fed on the cottonseed-flour diets for a 49 d period after severe protein malnutrition showed no change in size or shape of their hepatocytes compared with those obtained with the control casein diet, and all stages of spermatogenesis occurred normally and spermatozoa were accurately formed. Therefore, our findings show that a low level of gossypol administrated during 49 d, even to an organism weakened by protein malnutrition, does not affect hepatic variables and the histological appearance of liver and testis.     

Relative contribution of cysteine and methionine to glutathione content and thyroid hormone levels in the rat

1. For a period of 24 d rats were given diets containing either casein or pea (Pisum sativum) protein at two different concentrations (180 and 120 g/kg) without or with cysteine or cysteine + methionine supplementation. 2. The effects of these diets on levels of blood and liver reduced glutathione (GSH) and serum thyroid hormones were studied. 3. When compared with the 180 g casein/kg diet, the 120 g casein/kg diet decreased liver GSH and serum thyroid hormone concentrations. These changes were related to dietary cysteine supply since supplementation induced an increase in these variables. 4. When compared with 180 g pea protein/kg diet, the 120 g pea protein/kg diet decreased liver GSH and serum thyroid hormone concentrations. These changes could not be corrected by cysteine or cysteine + methionine supplementation.     

Composition of gain of rats fed low or high protein diets and grown at controlled rates from 80 to 205 grams

Composition of gain was measured in 54 rats fed purified diets that contained either 10 or 20% casein. Rats were weighed three times weekly and their intakes adjusted so that five or six rats within each diet gained maximally or at 2, 3, 4 or 5 g/d. Live weight for each rat was 80 g at the start and 205 g when the experiment ended. Ten additional rats were killed at about 80 g to estimate initial composition. The gain contained less (P less than 0.005) water and protein and more (P less than 0.005) lipid as rate of gain increased. Gain of gastrointestinal tract was increased (P less than 0.005) with increasing rate of gain. Rats that gained faster had shorter (P less than 0.05) tibias. More (P less than 0.005) water and protein and less (P less than 0.005) lipid were in the gain of rats fed the 20% casein diet than of those fed the 10% casein diet. Rats fed the 10% casein diet had longer bodies, and those fed the 20% casein diet had longer tibias. Water and protein gain declined and tibia length was less while liver gain increased with increasing rate of gain, but all rates of change for these measurements were higher for rats fed the 10% casein diet. Dissected epididymal fat pad gain was unaffected by casein level or rate of gain. These results demonstrate that chemical composition of the total gain can be altered when rate of growth is controlled and that the epididymal fat pad is not representative of chemical composition.     

Effects of soya-bean protein and casein on serum cholesterol levels in rats

1. The effect of the soya-bean protein isolate and casein, both given 200 g/kg diet for 3-4 weeks, on serum cholesterol was compared in male rats. 2. Soya-bean protein exerted a hypocholesteramic effect only in a cholesterol-free low-fat (10 g maize oil/kg) diet, when the lowering action appeared independent of the strain of the rat or the feeding pattern. The results obtained with diets containing cholesterol or higher levels of fats or both showed no definite pattern of response. 3. Although the decrease in serum cholesterol appeared greater in alpha-lipoproteins than in beta-lipoproteins, the proportion of the former to total cholesterol remained almost unchanged. The concentration of serum apo A-I was significantly lower in rats given the vegetable protein. 4. Rats given soya-bean protein excreted significantly more neutral sterols. 5. The serum amino acid pattern did not reflect the difference in dietary protein. Addition of cholesterol to the diets modified the serum aminogarm, the decrease in threonine being most marked in both protein groups. 6. This study shows that the hypocholesteraemic action of soya-bean protein is easily modified by the type of diet.     

Effect of proteins from beef, pork, and turkey meat on plasma and liver lipids of rats compared with casein and soy protein

OBJECTIVE: We assessed the effect of dietary proteins isolated from beef, pork, and turkey meat on concentrations of cholesterol and triacylglycerols in plasma, lipoproteins, and liver and the composition of the microsomal membrane (fatty acids, phosphatidylcholine/phosphatidylethanolamine ratio) compared with that of casein and soy protein in rats. METHODS: Five groups of 12 rats each were fed semisynthetic diets for 20 d that contained 200 g/kg of proteins isolated from beef, pork, or turkey meat or, as controls, casein or soy protein. RESULTS: Rats fed beef, pork, or turkey proteins did not differ in cholesterol concentrations of plasma, lipoproteins, and liver and in composition of microsomal membrane from rats fed the casein diet. All groups fed a protein from an animal source had higher very low-density lipoprotein (VLDL) and liver cholesterol concentrations than did rats fed soy protein. However, rats fed pork protein had lower concentrations of triacylglycerols in liver, plasma, and VLDL and lower mRNA concentrations of sterol regulatory element binding protein-1 and glucose-6-phosphate dehydrogenase than did rats fed casein. However, concentrations of plasma and VLDL triacylglycerols in rats fed pork protein were not as low as those observed in rats fed soy protein. CONCLUSION: Proteins isolated from beef, pork, or turkey meat do not differ from casein in their effects on cholesterol metabolism. Pork protein decreases plasma triacylglycerol concentrations compared with casein but not compared with soy protein. The triacylglycerol-lowering effect of pork protein compared with casein is suggested to be caused by decreased hepatic fatty acid synthesis.     

Plasma and muscle carnitine in experimental uremia

The effect of uremia and dietary protein intake on carnitine levels in skeletal muscle and plasma of rats was evaluated. Male Sprague-Dawley rats weighing 160–180 g were made chronically uremic by partial ligation of left renal artery and contralateral nephrectomy. Rats were fed diets containing 8% or 18% casein ad libitum for 8 weeks and sham-operated pair-fed animals were used as controls. At the end of the experiment, all animals were fasted overnight and decapitated. Skeletal muscle and plasma were assayed for free, total acid-soluble and long-chain acylcarnitines. The concentration of total carnitines in skeletal muscle were similar in uremic and control rats fed either 8% or 18% casein diet. However, the muscle long chain acylcarnitines were higher in rats fed the 18% casein diet than those fed the 8% casein diet. Diets (8% or 18% casein) had no effect on the plasma carnitine level, although uremic rats had lower levels than the controls. This study has shown that kidney dysfunction may affect the plasma carnitines level but not the total skeletal muscle carnitines concentration.     

The effects of dietary nitrogen level on the collagen of rat skin

1. Male rats of approximately 120 g body-weight were maintained on a commercial stock diet containing 204 g crude protein (nitrogen x 6.25)/kg, a hydroxyproline-free high-protein (HP) diet containing 200 g casein/kg as the only protein source, or a low-protein (LP) diet containing 40 g casein/kg. After 6 weeks on these diets half of each group was transferred to a non-protein (NP) diet and the experiment was continued for a further 6 weeks. Animals from each group were killed at 4 d, 3 weeks and 6 weeks after the transfer to the NP diet. 2. Throughout the experiment the urinary excretion of N, hydroxyproline and creatinine, and the content and solubility of the skin collagen were determined. 3. When compared with a control group killed at the beginning of the experiment the rats maintained on the LP diet showed an increase of 25% in total N content of the skin but collagen content increased by 100%. Rats transferred from the HP to the NP diet lost both N and collagen from the skin, but those transferred from the LP to the NP diet lost N but increased the collagen content by 42%. 4. Protein deprivation brought about marked changes in the solubility of the skin collagen, suggesting an increase in the rate of maturation of skin collagen.     

Reduced adiposity in bitter melon (Momordica charantia) fed rats is associated with lower tissue triglyceride and higher plasma catecholamines

Slower weight gain and less visceral fat had been observed when rats fed a high-fat diet were supplemented with freeze-dried bitter melon (BM) juice; the metabolic consequences and possible mechanism(s) were further explored in the present study. In a 4-week experiment, rats were fed a low-fat (70 g/kg) or a high-fat (300 g/kg) diet with or without BM (7.5 g/kg or 0.75%). BM-supplemented rats had lower energy efficiency, visceral fat mass, plasma glucose and hepatic triacylglycerol, but higher serum free fatty acids and plasma catecholamines. In the second experiment, 7-week BM supplementation in high-fat diet rats led to a lowering of hepatic triacylglycerol (P<0.05) and steatosis score (P<0.05) similar to those in rats fed a low-fat diet. BM supplementation did not affect serum and hepatic cholesterol. However, plasma epinephrine and serum free fatty acid concentrations were increased (P<0.05). In the third experiment, BM(7.5 and 15 g/kg) and 1.5 % BM lowered triacylglycerol concentration in red gastrocnemius and tibialis anterior (P<0.05) muscle, but a dose-response effect was not observed. These data suggest that chronic BM feeding leads to a general decrease in tissue fat accumulation and that such an effect is mediated in part by enhanced sympathetic activity and lipolysis. BM or its bioactive ingredient(s) could be used as a dietary adjunct in the control of body weight and blood glucose.     

Effects of the long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function in rats

The present paper describes the effects of long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function of rats, and also the effects of inorganic iodine on lipid metabolism. Rats were meal-fed on a diet containing 1% (w/w) of ordinary egg powder (OE diet as control: 35 micrograms I/100 g) or high-iodine egg powder (IE diet: 392 micrograms I/100 g). After the 19-month dietary treatment, rats fed on the IE diet, compared with the controls, showed a higher tissue lipoprotein lipase activity, a lower lipid peroxide level in the brain and a trend toward lower serum triacylglycerol levels and body fat storage without alterations in serum levels of thyroid-related hormones (TSH, T3 and T4). From the results of cold exposure and anti-thyroid drug-treatment conducted on rats fed on the OE and IE diets for 17 months, high-iodine eggs seemed to improve the age-related defects in thermogenic and thyroid hormone responses to cold, and also to result in a resistance to the anti-thyroid drug. The effects of the IE diet on lipid metabolism of rats were partly exhibited by feeding of the OE diet with an equivalent amount of iodine added as KI or KIO3. Thus, it is suggested that iodine ingestion through high-iodine eggs modulates both lipid metabolism and thyroid function in rats.     

Lipid alterations in the liver and serum of rats in histidine-excess and copper deficiency

To obtain further information on lipid metabolism in the histidine-excess and copper-deficiency, rats were fed basal, histidine-excess (the addition of 50 g L-histidine/kg diet) or copper-deficient diets for 0, 7, 21 and 42 d ad libitum. Liver triacylglycerol accumulated and the serum triacylglycerol level decreased after feeding of the histidine-excess diet for 21 or 42 d, but not after feeding of the copper-deficient diet. Serum cholesterol level increased in rats fed the histidine-excess diet for 7, 21 and 42 d, but not in rats fed the copper-deficient diet. Copper content in the liver and serum significantly decreased in rats fed the histidine-excess diet. Copper content in the liver and serum was markedly decreased in rats fed the copper-deficient diet. Liver zinc content was constant, but the serum zinc level decreased in rats fed the histidine-excess diet. Feeding of the copper-deficient diet hardly affected zinc content in the liver and serum. Urinary copper and zinc increased in rats fed the histidine-excess diet, and decreased or showed a decreasing tendency in rats fed the copper-deficient diet. Overall results indicated that feeding the histidine-excess diet caused copper deficiency, whereas hypercholesterolemia was not shown in rats fed the copper-deficient diet although the livers of rats fed the copper-deficient diet contained less copper than those of rats fed the histidine-excess diet. Thus, the responses on liver triacylglycerol and serum cholesterol to copper deficiency induced by the feeding of a histidine-excess diet are different from those to copper deficiency induced by feeding of a copper-deficient diet.