Nutritional significance of dietary cystine for maintaining the hepatic albumin mRNA level in rats fed on a soybean diet

Comparison of the Nutritional Status of Swiss Albino Mice Fed on Either a Purified or Cereal-Based Diet for 15 weeks

Background

Laboratory animals are commonly fed on cereal-based diets (CBDs) whose nutrient composition is unknown and may confound the metabolic response to study interventions. Purified diets such as AIN-93M are therefore recommended, as their nutrient composition is known. However, few studies have evaluated their use as adequate control diets. The aim of this study was to compare the nutrition status of Swiss albino mice fed on either CBD or AIN-93M for 15 weeks.

Methods

Twenty Swiss albino mice aged 6-8 weeks and weighing 21.7 g ± 0.6 were fed on either CBD or AIN-93M diet for 15 weeks. Their nutritional status was evaluated using anthropometric and hematological indices, serum glucose, total protein, albumin, and total cholesterol to select an appropriate normal control diet.

Results

The CBD had low-calorie content (2.57 kcal/g) and protein (11 ± 3.8 g/100 g) compared to AIN-93M (3.8 kcal/g and 14 g/100 g, respectively). The BMI of male mice fed on CBD and AIN-93M diets was significantly higher (P=0.0139 and P=0.0325, respectively) compared to that of females fed on similar diets. Animals in the CBD group had lower hemoglobin (15.1-16.9 g/dl) compared to those in the AIN-93M group (18.1-20.8 g/dl). Serum albumin levels were higher in both male (P=0.001) and female (P=3 × 10^-6) mice fed on AIN-93M compared to those fed on CBD. Females in the AIN-93M group had higher cholesterol (P=0.026) than those in the CBD group.

Conclusion

The AIN-93 diet of caloric value 3.85 kcal/g (total protein 14 g, total fat 4 g of soy bean oil, fibre 5 g, and total carbohydrate 42 g per 100 g) can be safely used as a normal control diet in long-term research studies using Swiss albino mice.

Cystine supplementation sustains plasma mercaptalbumin levels in rats fed low-protein diets more effectively than methionine

We recently reported that dietary cystine maintained plasma mercaptalbumin levels in rats fed low-protein diets. The present study aimed to compare the influence of low-protein diets supplemented with cystine and methionine, which is another sulfur amino acid, on plasma mercaptalbumin levels in rats. Male Sprague-Dawley rats were fed a 20% soy protein isolate diet (control group), 5% soy protein isolate diet (low-protein group) or 5% soy protein isolate diet supplemented with either methionine (low-protein + Met group) or cystine (low-protein + Cyss group) for 1 week. The percentage of mercaptalbumin within total plasma albumin of the low-protein + Met group was significantly lower than that of the control and low-protein + Cyss groups. No significant differences in the mRNA levels of tumor necrosis factor-α, interleukin-6, interleukin-1β, and cyclooxygenase 2 in blood cells were observed between the low-protein + Met and low-protein + Cyss groups. Treatment with buthionine-(S,R)-sulfoximine, an inhibitor of glutathione synthesis, did not influence the percentage of mercaptalbumin within total plasma albumin in rats fed the low-protein diet supplemented with cystine. These results suggest that supplementation with cystine may be more effective than that with methionine to maintain plasma mercaptalbumin levels in rats with protein malnutrition. Cystine might regulate plasma mercaptalbumin levels via the glutathione-independent pathway.

LMNA-mutated Rabbits: A Model of Premature Aging Syndrome with Muscular Dystrophy and Dilated Cardiomyopathy

Premature aging syndromes are rare genetic disorders mimicking clinical and molecular features of aging. Products of the LMNA gene, primarily lamin A and C, are major components of the nuclear lamina. A recently identified group of premature aging syndromes was related to mutations of the LMNA gene. Although LMNA disorders have been identified in premature aging syndromes, affect specifically the skeletal muscles, cardiac muscles, and lipodystrophy, understanding the pathogenic mechanisms still need to be elucidated. Here, to establish a rabbit knockout (KO) model of premature aging syndromes, we performed precise LMNA targeting in rabbits via co-injection of Cas9/sgRNA mRNA into zygotes. The LMNA-KO rabbits exhibited reduced locomotion activity with abnormal stiff walking posture and a shortened stature, all of them died within 22 days. In addition, cardiomyopathy, muscular dystrophy, bone and joint abnormalities, as well as lipodystrophy were observed in LMNA-KO rabbits. In conclusion, the novel rabbit LMNA-KO model, displayed typical features of histopathological defects that are observed in premature aging syndromes, and may be utilized as a valuable resource for understanding the pathophysiological mechanisms of premature aging syndromes and elucidating mysteries of the normal process of aging in humans.

Comparison of the effects of dietary protein on the sexual organ development of male mice and rats kept under constant darkness

The purpose of this study was to determine whether the effects of dietary protein on sexual organ development were different in mice and rats kept under constant darkness. Four-week-old mice (ICR strain) and rats (F344 strain) were kept under constant darkness (D) or normal lighting (N; 12-h light/dark cycle) for 4 wk. The dietary protein level was 9% casein with the addition of 0.135% cystine (9PC) or without it (9P); other components of the diet were based on the AIN-93G diet. The testes and epididymides weights (g/100 g BW) of the rats given the 9P diet in the D-group were lower than those of the rats given the 9P diet in the N-group. In the mice, lighting conditions and diet did not affect testes or epididymides weights. Body weight and food intake in the rats were affected by diet, and these values were lower in the 9P diet group; however, body weight and food intake in the mice was not affected by diet. The serum albumin concentration in the rats was lower in the 9P diet group, while that of the mice was lower in the 9PC diet group. In the rats kept under constant darkness, a diet lacking in cystine accelerated the suppression of sexual organ development and decreased serum albumin concentration, but this diet had no such effects on the mice. The finding that the effects of dietary protein were different in mice and rats suggests that protein requirements of mice are different from those of rats.