Dietary cystine is important to maintain plasma mercaptalbumin levels in rats fed low-protein diets.

The oxidized/reduced state of plasma albumin in rats is influenced by the quantity of dietary protein. However, the effects of the protein quality on the oxidized/reduced state of plasma albumin are not clear. We hypothesized that the quality of dietary protein might modulate the oxidized/reduced state of plasma albumin. The aim of the present study was to examine whether the amino acid composition of dietary protein modulates the oxidized/reduced state of plasma albumin in rats. Male Sprague-Dawley rats were fed low-protein diets containing 5% casein (CA), 5% egg white (EW), or 6% wheat gluten (WG) for 2 weeks. The plasma albumin concentration gradually decreased in rats fed each diet; however, there was no significant difference among the groups. In rats fed the 5% CA diet, the percentage of mercaptalbumin within the total plasma albumin was significantly lower than in those fed the EW or WG diet. Compared with EW or WG, CA contains lower amounts of glycine and cystine. In rats fed a 5% CA diet supplemented with cystine, the percentage of mercaptalbumin was significantly higher than that in rats fed a 5% CA diet supplemented with glycine. The expression of hepatic eukaryotic initiation factor 4E-binding protein 1 was significantly lower in rats fed the cystine-supplemented diet than in those fed the glycine-supplemented diet. These results suggest that dietary protein with a high cystine content maintains plasma mercaptalbumin levels in rats fed low-protein diets.

Egg Yolk Protein Delays Recovery while Ovalbumin Is Useful in Recovery from Iron Deficiency Anemia.

Protein is a main nutrient involved in overall iron metabolism in vivo. In order to assess the prevention of iron deficiency anemia (IDA) by diet, it is necessary to confirm the influence of dietary protein, which coexists with iron, on iron bioavailability. We investigated the usefulness of the egg structural protein in recovery from IDA. Thirty-one female Sprague-Dawley rats were divided into a control group (n = 6) fed a casein diet (4.0 mg Fe/100 g) for 42 days and an IDA model group (n = 25) created by feeding a low-iron casein diet (LI, 0.4 mg Fe/100 g) for 21 days and these IDA rats were fed normal iron diet with different proteins from eggs for another 21 days. The IDA rats were further divided into four subgroups depending on the proteins fed during the last 21 days, which were those with an egg white diet (LI-W, 4.0 mg Fe/100 g, n = 6), those with an ovalbumin diet (LI-A, 4.0 mg Fe/100 g, n = 7), those with an egg yolk-supplemented diet (LI-Y, 4.0 mg Fe/100 g, n = 6), and the rest with a casein diet (LI-C, 4.0 mg Fe/100 g, n = 6). In the LI-Y group, recovery of the hematocrit, hemoglobin, transferrin saturation level and the hepatic iron content were delayed compared to the other groups (p < 0.01, 0.01, 0.01, and 0.05, respectively), resulting in no recovery from IDA at the end of the experimental period. There were no significant differences in blood parameters in the LI-W and LI-A groups compared to the control group. The hepatic iron content of the LI-W and LI-A groups was higher than that of the LI-C group (p < 0.05). We found that egg white protein was useful for recovery from IDA and one of the efficacious components was ovalbumin, while egg yolk protein delayed recovery of IDA. This study demonstrates, therefore, that bioavailability of dietary iron varies depending on the source of dietary protein.

Supplementation with branched-chain amino acids attenuates hepatic apoptosis in rats with chronic liver disease.

Branched-chain amino acids (BCAA) can function as pharmacologic nutrients for patients with decompensated cirrhosis. However, the effects of BCAA at the early stage of chronic liver disease are not clear. We hypothesized that early BCAA supplementation would attenuate the progression of chronic liver disease. The present study examined the effects of BCAA supplementation on the progression of chronic liver disease in rats caused by injected carbon tetrachloride (CCl4). Sprague-Dawley rats were fed with a casein diet (control group) or the same diet supplemented with BCAA (BCAA group) for 11 weeks, and all rats were repeatedly injected with CCl4. Food intake did not significantly differ between control and BCAA groups during the experimental period. Plasma alanine aminotransferase activities gradually increased during the experimental period in both groups but peaked later in the BCAA group. Liver fibrosis was more evident in the control group. Levels of connective tissue growth factor messenger RNA were significantly lower in the livers of rats in the BCAA group than in the control group. Terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick end labeling assays found considerably more hepatic apoptosis in the control group. Liver cytosolic cytochrome c levels and expression of the proapoptotic Bax protein in the mitochondrial fraction were significantly lower in the BCAA group than in the control group. These results suggest that supplementation with BCAA delays the progression of chronic liver disease caused by CCl4 in rats by attenuating hepatic apoptosis.

Acidic xylooligosaccharide preserves hepatic iron storage level in adult female rats fed a low-iron diet.

Iron deficiency anemia (IDA) is one of the most serious forms of malnutrition. This experiment was conducted to investigate whether acidic xylooligosaccharide (U-XOS), expected to have a high iron bioavailability, was useful in the prevention of iron deficiency. Experiment 1: Nineteen female Sprague-Dawley rats (20 wk old) were fed three different diets for 28 d; a U-XOS-supplemented low-iron diet (LI-X, n=7), a low-iron diet (LI, n=6), and a control diet (C, n=6). On day 28, the LI-X and LI groups showed iron deficiency without anemia. A significant difference in the total and unsaturated iron binding capacity, and serum transferrin saturation level was shown in the LI-X and LI groups, compared with the C group. However, the decrease of hepatic iron content of the LI-X group was suppressed compared with the LI group. Experiment 2: Eleven male Sprague-Dawley rats (7 wk old) were fed a U-XOS-supplemented diet (X, n=5) or a control diet (C, n=6) for 7 d. No significant difference in body weight gain or food intake was demonstrated between the two groups; the apparent iron absorption rate of the X group increased clearly compared with that of the C group. These results suggested that a U-XOS diet could preserve storage of hepatic iron in adult female rats fed a low-iron diet and could prevent IDA by promotion of dietary iron absorption, inhibition of iron excretion, and/or improvement of iron bioavailability.

Oral administration of acidic xylooligosaccharides prevents the development of atopic dermatitis-like skin lesions in NC/Nga mice.

We examined whether two types of xylooligosaccharides (neutral or acidic xylooligosaccharides) derived from hardwood kraft pulp ameliorate the development of atopic dermatitis (AD)-like skin lesions induced by repeated application of picryl chloride (PiCl) in NC/Nga mice. Oral administration of acidic xylooligosaccharides at a daily dose of 100 mg/kg significantly prevented the development of AD-like skin lesions. Serum histamine level was significantly suppressed, but serum total IgE level was not significantly suppressed. Moreover, the secretion of inflammatory cytokine IL-12 from splenic lymphocytes was significantly suppressed. On the other hand, neutral xylooligosaccharides showed no significant preventive effect on the development of AD-like symptoms. These results suggest that oral administration of acidic xylooligosaccharides may be effective in preventing the development of AD-like skin disease and one of the mechanisms is the suppressive effect on IL-12.

Dietary polyunsaturated fatty acids slow the progression of diabetic nephropathy in streptozotocin-induced diabetic rats.

Diabetic nephropathy is associated with lipid deposits in the kidney. We hypothesized that a diet containing polyunsaturated fatty acids (PUFAs) could ameliorate pathogenesis of diabetic kidney diseases associated with lipid depositions in the kidneys. We examined if the pathogenesis and progression of diabetic nephropathy are affected by the type of dietary fat using streptozotocin (45 mg/kg body weight, intravenous)-induced diabetic rats (5-week-old male Sprague-Dawley rats). Streptozotocin-induced diabetic rats were fed a lard diet containing saturated fatty acids or a rapeseed oil diet containing PUFAs (DML and DMR, respectively) for 11 days. Similarly, streptozotocin-nontreated rats were fed a lard diet or a rapeseed oil diet (NL and NR, respectively) for 11 days. Hyperglycemia was induced in DML and DMR, compared with NL and NR groups. The levels of plasma ketone, total cholesterol, and triglyceride (TG) were significantly increased in the DML group. Moreover, albuminuria and renal TG content were enhanced in the DML group. The renal TG content correlated positively with urinary albumin excretion (P < .001). Oil-Red O staining of kidney sections indicated a marked accumulation of neutral lipids in both glomerular and tubular cells in the DML group. In addition, a renal sterol regulatory element-binding protein-1 mature protein increment was induced in the DML group. Conversely, sterol regulatory element-binding protein-1 expression in the kidney was maintained at normal levels in the DMR group. These results suggest that dietary PUFAs may slow the progression of diabetic nephropathy associated with lipid depositions in the kidney.