Can intestinal absorption of dietary protein be improved through early exposure to plant-based diet?

Abstract

Nutritional Programming (NP) has been studied as a means of mitigating the negative effects of dietary plant protein (PP), but the optimal timing and mechanism behind NP are still unknown. The objectives of this study were: 1) To determine whether zebrafish (Danio rerio) can be programmed to soybean meal (SBM) through early feeding and broodstock exposure to improve SBM utilization; 2) To determine if NP in zebrafish affects expression of genes associated with intestinal nutrient uptake; 3) To determine if early stage NP and/or broodstock affects gene expression associated with intestinal inflammation or any morphological changes in the intestinal tract that might improve dietary SBM utilization. Two broodstocks were used to form the six experimental groups. One broodstock group received fishmeal (FM) diet (FMBS), while the other was fed ("programmed with") SBM diet (PPBS). The first ((+) Control) and the second group ((-) Control) received FM and SBM diet for the entire study, respectively, and were progeny of FMBS. The last four groups consisted of a non-programmed (FMBS-X-PP and PPBS-X-PP) and a programmed group (FMBS-NP-PP and PPBS-NP-PP) from each of the broodstocks. The programming occurred through feeding with SBM diet during 13-23 dph. The non-control groups underwent a PP-Challenge, receiving SBM diet during 36-60 dph. During the PP-Challenge, both PPBS groups experienced significantly lower weight gains than the (+) Control group. NP in early life stages significantly increased the expression of PepT1 in PPBS-NP-PP, compared to PPBS-X-PP. NP also tended to increase the expression of fabp2 in the programmed vs. non-programmed groups of both broodstocks. The highest distal villus length-to-width ratio was observed in the dual-programmed group, suggesting an increase in surface area for nutrient absorption within the intestine. The results of this study suggest that NP during early life stages may increase intestinal absorption of nutrients from PP-based feeds.

Nutritional Programming with Dietary Soybean Meal and Its Effect on Gut Microbiota in Zebrafish (Danio rerio)

“…Kwasek et al 7 later followed that notion in zebrafish and investigated the effect of NP on the expression of appetite-stimulating hormones and found that during the PP challenge period, an upregulation and/or downregulation was observed for ghrelin, cholecystokinin, and neuropeptide Y in the intestine and/or brain. Moreover, both Kwasek et al 7 and Molinari et al 8 reported improved morphological adaptation of the intestine in zebrafish reflected by higher villus length to width ratio in programmed versus nonprogrammed groups possibly allowing for more efficient dietary SBM breakdown and nutrient absorption. Furthermore, Molinari et al 8 found that the expression of Pept1, an intestinal peptide transporter used as an indicator of nutritional status in fish, 38,39 at 60 dph was higher in zebrafish that were previously exposed to dietary SBM during their juvenile stage (13-23 dph).…”

“…Moreover, both Kwasek et al 7 and Molinari et al 8 reported improved morphological adaptation of the intestine in zebrafish reflected by higher villus length to width ratio in programmed versus nonprogrammed groups possibly allowing for more efficient dietary SBM breakdown and nutrient absorption. Furthermore, Molinari et al 8 found that the expression of Pept1, an intestinal peptide transporter used as an indicator of nutritional status in fish, 38,39 at 60 dph was higher in zebrafish that were previously exposed to dietary SBM during their juvenile stage (13-23 dph). The limited studies available therefore suggest that the mechanism behind NP might be associated with endocrine and morphological adaptation of the digestive system that leads to enhanced digestion and absorption capacity ultimately reflected by improved growth performance.…”

“…The dietary formulations of the experimental diets followed formulations from our previous studies investigating the effects of dietary SBM on zebrafish, which have been recently published. 7,8 Two different types of diets were made: a diet formulated to contain SBM as a main protein source (PP diet and SBM diet), and a diet based on FM as a main protein source (FM diet). The levels of dietary protein in the two feed formulations were assumed to be sufficient to meet the requirements of all essential amino acids and therefore maximum weight gain 20 (Table 1).…”

“…37 However, in order for NP to work effectively, the programming stage must occur at the right timing in the early development of fish. 7 Since the early exposure to PP appears to affect gut responses on both molecular and histological level, 7,8 it seems that fish must reach a certain physiological stage, particularly with respect to their digestive tract development, to be able to positively respond to the imposed nutritional trigger (such as SBM) to better adapt to it at a later age. 7 The mechanism behind NP is still not fully resolved, although the few studies available indicate that the improved dietary SBM utilization likely results from the adaptation of the intestinal tract to dietary PP.…”

“…6 NP with PP shows great promise to increase utilization of lower-quality PP sources. 1,5,[7][8][9] Studies have challenged rainbow trout (Oncorhynchus mykiss) with vegetable oil-based diets and reported that the fish later presented higher feed intake, growth, and feed utilization compared to nonprogrammed individuals. 1,10 Previous research has also provided insight that early NP of rainbow trout alevins might lead to similar alpha diversity measures of gut microbes between programmed versus nonprogrammed individuals.…”