Protein and lipid refeeding changes protein metabolism and colonic but not small intestinal morphology in protein-depleted rats

Dietary protein restriction during pregnancy and/or early weaning reduces the number of goblet cells in the small and large intestines of female mice pups

Background

It remains unclear whether goblet cell numbers in offspring are altered by maternal nutritional status and/or early weaning. Herein, using a murine model, we clarified whether a low-protein (LP) diet during pregnancy and/or early weaning changes villus structures, goblet cell numbers, mucin intensity, and mucin mRNA expression in the mucosal layer throughout the intestines in mice offspring.

Methods

We examined villus-crypt structures and goblet cell numbers using hematoxylin-eosin staining. By performing alcian blue-PAS staining and RT-qPCR, we investigated mucin intensity in the mucosal layer and mRNA expressions of Muc2 and Muc4, respectively, in 17 (early weaning)-, 21 (normal weaning)- and 28-day old mice born from LP diet-fed mothers or those born from control diet-fed mothers during pregnancy.

Results

Dietary protein restriction reduced goblet cell numbers in throughout the intestine, particularly in the duodenum and jejunum, and mucin intensity in the mucosal layer at the border of the jejunum and colon. The LP diet increased villus height and decreased villus thickness throughout the small intestine and crypt depth and width in the cecum and colon.

Conclusions

Dietary protein restriction during pregnancy and/or early weaning decreased the number of goblet cells, mucin intensity in the mucosal layer, and the Muc2 and Muc4 mRNA expressions in the small and large intestines, and affected the villus and crypt structures in the small and large intestines in female offspring mice during and after weaning.

General significance

Dietary abnormalities in fetal and weaning periods affects intestinal function.

Re-feeding rapidly restores protection againstHeligmosomoides bakeri(Nematoda) in protein-deficient mice

This study determined whether the timing of re-feeding of protein-deficient mice restored functional protection against the gastrointestinal nematode,Heligmosomoides bakeri. Balb/c mice were fed a 3% protein-deficient (PD) diet and then transferred to 24% protein-sufficient (PS) diet either on the day of primary infection, 10 days after the primary infection, on the day of challenge infection, or 7 days after the challenge infection. Control mice were fed either the PD or PS diet. Onset of challenge, but not primary, infection caused short-term body weight loss, anorexia and reduced feed efficiency. Weight gain was delayed in mice when re-feeding commenced on the day of challenge infection; alkaline phosphatase (ALP) was also elevated in these mice on day 28 post-challenge. In contrast, other re-feeding groups attained similar body weights to PS mice within 4 days and had similar ALP at day 28. Serum leptin was higher in PD than PS mice and positively associated with food intake. As expected, worm survival was prolonged in mice fed the PD diet. However, egg production and worm burdens were similar in all re-feeding groups to the PS mice, indicating that protein re-feeding during either the primary or challenge infection rapidly restored normal parasite clearance.

Effects of protein malnutrition on IL-6-mediated signaling in the liver and the systemic acute-phase response in rats

This study examines the effects of malnutrition on IL-6 signaling pathways of rats fed 2% vs. 20% casein diets for 14 days. Effects of malnutrition on the abundance and IL-6-stimulated phosphorylation of signaling proteins in the JAK-STAT and MAP kinase pathways were examined in the liver. Changes of the acute-phase response as reflected by serum α1-acid glycoprotein (AG), TNF-α (TNF), and IL-1β (IL-1) were compared in the two dietary groups at 0, 4, 8, 16, and 24 h after IL-6 administration. Under basal conditions, the abundance of the IL-6 receptor, gp130, JAK1, STAT1, and STAT3 proteins and levels of phosphorylation of ERK1/2 and p38 were significantly increased in the liver in the 2% casein group compared with the 20% casein group. With IL-6 stimulation, the increased phosphorylation per unit of protein of these signaling proteins was not different in the liver between the two groups. Before IL-6 stimulation, serum levels of TNF, IL-1, IL-6, and AG were significantly higher in the 2% casein group than in the 20% casein group. After bolus injection of IL-6, changes in IL-1 and AG were similar in the two dietary groups, although a slight decline in AG level was noted after 8 h of IL-6 administration in the 2% protein group. These data demonstrate that protein malnutrition produces changes in inflammation-related proteins characteristic of a low-grade systemic inflammatory response and, thus, can serve as an inflammatory stimulus. The capacity for response to IL-6 is preserved, suggesting adaptive preservation of acute-phase responsiveness during malnutrition.

Recuperação da desnutrição em ratos mediante rações adicionadas ou não de suplemento alimentar e de vitaminas e minerais durante o período de crescimento

OBJETIVOS: O propósito deste estudo foi analisar experimentalmente a eficiência da suplementação alimentar da dieta do Município de Quissamã, RJ, em recuperar a desnutrição durante o período de crescimento. MÉTODOS: Foram utilizados 42 Rattus norvegicus, desmamados ao 26º dia e induzidos à desnutrição por 21 dias (ração hipoprotéica 2%, ad libitum). Os animais foram distribuídos em sete grupos, alimentados com suas respectivas dietas, todas isoprotéicas (10%) e isoenergéticas (350Kcal/100g). Foi registrado o peso dos animais e, após o sacrifício, foram coletados e pesados fígado, rins, baço e intestino. RESULTADOS: O ganho ponderal médio no 28º dia do controle suplemento alimentar (75,33g) foi significativamente inferior aos demais grupos, e o do controle suplemento alimentar e vitaminas+minerais foi o mais elevado (213,17). Quase todos os grupos diferenciaram-se estatisticamente no peso médio de fígado, rins e baço; os órgãos do controle suplemento alimentar apresentaram o menor peso (respectivamente 3,34g; 0,97g; 0,24g) sendo significativamente inferior aos demais grupos. O controle suplemento alimentar e vitaminas+minerais apresentou o maior peso médio do fígado (13,85g). O Controle vitaminas+minerais apresentou o maior peso médio dos rins (1,88g) e do baço (0,87g). O número de placas de Peyer/animal variou de nove a treze, sem diferenças entre os grupos; o tamanho das placas de Peyer do controle suplemento alimentar (2,6mm) foi significativamente inferior aos demais grupos. O Quissamã suplemento alimentar apresentou as maiores placas de Peyer (4,4mm). O controle suplemento alimentar apresentou sempre valores inferiores para todos os parâmetros estudados comparativamente, já que não foram adicionados à sua ração vitaminas e minerais. CONCLUSÃO: A dieta de Quissamã, RJ experimentalmente alcança as necessidades mínimas para promover a recuperação da desnutrição, sendo desnecessária a adição de vitaminas e minerais e/ou suplemento alimentar.

Effects of dietary protein and tumor necrosis factor on components of the insulin-like growth factor-I pathway in the colon and small intestine in protein-depleted rats

Intestinal cell growth is markedly affected by nutrient intake and the presence of cytokines. Since insulin-like growth factor-I (IGF-I) is an important hormone regulator of intestinal proliferation, this study examined the effects of dietary protein content and tumor necrosis factor (TNF) on mRNA levels of IGF-I, IGF-I receptor, IGF binding protein-3 (IGFBP-3), and IGFBP-4 and on the histology of the colon, jejunum, and ileum in protein-malnourished rats. After 2 weeks of feeding a 2% casein diet, rats continued on the 2% casein diet or were refed with a 20% casein diet and received daily intraperitoneal injections of either TNF (50 microg/kg) or saline for 4 days. The abundance of mRNA in the intestine was determined by RNA dot-blot analysis, and morphology measurements were performed by light microscopy. Simultaneous refeeding with the 20% casein diet and administration of TNF led to a modest increase in IGF-I and IGFBP-4 mRNA abundance in the colon. However, in the jejunum and ileum, refeeding had no effect but TNF caused a decrease in IGF-I and IGFBP-3 mRNA levels in malnourished rats. Refeeding with the 20% casein diet resulted in relatively modest histologic changes, which were greater in the colon versus the small intestine. The decreased magnitude of histologic changes in the order of the colon, ileum, and jejunum may reflect a response to a gradient of amino acid availability from intraluminal nutrients. These data demonstrate that TNF has distinct effects on colon and small intestine mRNA, but these mild changes had only a slight impact in the colon and did not translate into identifiable histologic changes in the small intestine. Combined protein restriction and TNF administration had only a modest effect on intestinal mRNA levels and mucosal histology.

Tissue-specific effects of chronic dietary protein restriction and gastrostomy on the insulin-like growth factor-I pathway in the liver and colon of adult rats

Dietary protein restriction decreases plasma concentrations of insulin-like growth factor-I (IGF-I) and reduces IGF-I mRNA levels in the liver. In addition to the actions of systemic IGF-I, locally produced IGF-I is thought to mediate autocrine and paracrine growth effects in the colon. The objectives of the present study were to investigate the IGF-I pathway in the colon and liver of adult rats under conditions of dietary protein restriction, surgical stress, and dietary protein repletion. Two groups of rats were placed on either a 20% or 2% casein diet for 19 days. Two additional groups of rats underwent gastrostomy after a 2% casein diet for 2 weeks, and then were either kept on the 2% casein diet or changed to a 20% casein diet until day 19. Dietary protein restriction reduced plasma concentrations of IGF-I and IGF-binding proteins (IGFBPs) and hepatic IGF-I mRNA content, while increasing colonic IGF-I receptor mRNA. Gastrostomy in protein-depleted animals had no effect on hepatic IGF-I mRNA, but led to a marked increase in colonic IGF-I mRNA levels. Dietary protein repletion resulted in a decrease in colonic IGF-I receptor mRNA. The distinct effects of dietary protein depletion and operative stress on the IGF pathway in the colon as compared with the liver may serve to maintain the level of IGF-I signaling in the colon by autocrine or paracrine mechanisms under these conditions.