Role of vagal innervation in diurnal rhythm of intestinal peptide transporter 1 (PEPT1)

Later eating rhythm measured in children at 7 years of age in the ALSPAC cohort

Later eating rhythm (LER) refers to later timing, greater energy intake (EI), and higher frequency of eating occasions (meal/snack) in the evening. The significance of LER in child health is becoming increasingly recognised. However, the lack of consensus regarding definitions of LER make it challenging to fully comprehend its role. This data note describes LER variables derived in the Avon Longitudinal Study of Parents and Children (ALSPAC), an ongoing birth cohort which enrolled 14,541 pregnant women living in Avon, UK, with an expected date of delivery between April 1991 - December 1992. When children were 7 years, parents completed a structured 3-day food diary, recording all foods/drinks consumed over 3 days (preferably 1 weekend day and 2 weekdays). Data was available for 7,285 children (50.1% response rate). A subsample of 4,869 children had exact time of eating occasions added to the existing database, which only included broad indications of eating timing based on 2-7 hour long meal slots. 13 LER variables were derived for the entire week and weekdays/weekend days separately. These comprise: 1) eating around individual bedtime (number days); 2) eating around average bedtime (number days); 3) time of evening main meal (hrs:mins); 4) time of last eating occasion (hrs:mins); 5) EI in the evening (percentage of total daily energy intake, %TDEI); 6) EI within 2hrs before bedtime (%TDEI); 7) EI for evening main meal (%TDEI); 8) EI for evening snacks (%TDEI); 9) Night eating1 (NE1): eating over 30% of total daily energy intake after 18:00 (number days); 10) NE2: eating over 25% of total daily energy intake within 2hrs before bedtime (number days); 11) eating frequency after 17:00 (number of eating occasions); 12) regularity of dinner (number of days); 13) frequency of evening snacks (number days). We describe the derivation, prevalence and inter-corelations between LER variables.

Unraveling the role of the circadian clock genes in cervical squamous cell carcinoma and endocervical adenocarcinoma: A prognostic indicator for prognostic, immunotherapy response, and chemotherapy sensitivity

Background: Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) account for a significant proportion of gynecological malignancies and represent a major global health concern. Globally, CESC is ranked as the fourth most common cancer among women. Conventional treatment of this disease has a less favorable prognosis for most patients. However, the discovery of early molecular biomarkers is therefore important for the diagnosis of CESC, as well as for slowing down their progression process. Methods: To identify differentially expressed genes strongly associated with prognosis, univariate Cox proportional hazard analysis and least absolute shrinkage and selection operator (LASSO) regression analysis were used. Using multiple Cox proportional hazard regression, a multifactorial model for prognostic risk assessment was then created. Results: The expression of biological clock-related genes, which varied considerably among distinct subtypes and were associated with significantly diverse prognoses, was used to categorize CESC patients. These findings demonstrate how the nomogram developed based on the 7-CRGs signature may assist physicians in creating more precise, accurate, and successful treatment plans that can aid CESC patients at 1, 3, and 5 years. Conclusions: By using machine learning techniques, we thoroughly investigated the impact of CRGs on the prognosis of CESC patients in this study. By creating a unique nomogram, we were able to accurately predict patient prognosis. At the same time, we showed new perspectives on the development of CESC and its treatment by analyzing the associations of the prognostic model with immunity, enrichment pathways, chemotherapy sensitivity, and so on. This research provides a new direction for clinical treatment.

The Circadian Clock as a Potential Biomarker and Therapeutic Target in Gastrointestinal Cancers

The circadian clock consists of a hierarchical multi-oscillator network of intracellular and intercellular mechanisms throughout the body that contributes to anticipating metabolic activity and maintaining system homeostasis in response to environmental cues and intrinsic stimuli. Over the past few years, genetic variations of core clock genes have been associated with cancer risk in several epidemiological studies. A growing number of epidemiological research studies have demonstrated a direct correlation between the disturbance of circadian rhythms and the growth of tumors, indicating that shift workers are more susceptible to malignancies of the colon, prostate, ovarian, breast, lung, and liver. One of the most related cancers with circadian rhythm is Gastrointestinal (GI) cancer, which is a leading cause of cancer-related mortality nowadays. The aim of this review was to demonstrate the effect of the clock gene network on the growth of GI cancer, providing molecular targets for GI cancer treatment, possible prognostic biomarkers, and guidance for treatment choices.

The association between later eating rhythm and adiposity in children and adolescents: a systematic review and meta-analysis

CONTEXT

Childhood adiposity, an important predictor of adult chronic disease, has been rising dramatically. Later eating rhythm, termed night eating, is increasing in adults but rarely studied in younger ages.

OBJECTIVE

The objective of this study was to review the association between later eating rhythm and adiposity in children and adolescents. The aspects of later eating being considered included: energy intake (for evening main meal, evening snack, whole evening period, and around bedtime); timing (any food eaten at later timing); and meal frequency in the evening/night (evening main meal skipping, evening snack consumption).

DATA SOURCES

Five databases (the Cochrane Library, CINAHL, Embase, MEDLINE (via OVID), and Web of Science) were searched for eligible articles published prior to and including August 2020.

DATA EXTRACTION

Data extraction and quality assessment were conducted by 2 reviewers independently.

DATA ANALYSIS

Forty-seven studies were included, all of which were observational. Meta-analysis showed positive associations between both higher energy intake around bedtime (odds ratio [OR] 1.19, 95% CI 1.06, 1.33) and evening main meal skipping (OR 1.30, 95% CI 1.14, 1.48), and adiposity. There was evidence to suggest that consuming evening snacks reduced adiposity, but it was very weak (OR 0.80, 95% CI 0.62, 1.05). No association was seen between eating later and adiposity (OR 1.04, 95% CI 0.68, 1.61). In the narrative analysis, approximately half of the studies suggested that there was no association between later eating rhythm and adiposity, either as a whole or within exposure subsets.

CONCLUSION

The magnitude of the relationship between later eating rhythm and adiposity is very small, and may vary depending on which aspects of later eating rhythm are under consideration; however, the evidence for this conclusion is of very low certainty . Further research with a more consistent definition of "later timing", and longitudinal studies in different populations, may lead to different conclusions.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42019134187.

Nutrient timing and metabolic regulation symposium review from "Novel dietary approaches to appetite regulation, health and performance (2021)"

Daily (circadian) rhythms coordinate our physiology and behaviour with regular environmental changes. Molecular clocks in peripheral tissues (e.g. liver, skeletal muscle and adipose) give rise to rhythms in macronutrient metabolism, appetite regulation and the components of energy balance such that our bodies can align the periodic delivery of nutrients with ongoing metabolic requirements. The timing of meals both in absolute terms (i.e. relative to clock time) and in relative terms (i.e. relative to other daily events) is therefore relevant to metabolism and health. Experimental manipulation of feeding–fasting cycles can advance understanding of the effect of absolute and relative timing of meals on metabolism and health. Such studies have extended the overnight fast by regular breakfast omission and revealed that morning fasting can alter the metabolic response to subsequent meals later in the day, whilst also eliciting compensatory behavioural responses (i.e. reduced physical activity). Similarly, restricting energy intake via alternate‐day fasting also has the potential to elicit a compensatory reduction in physical activity, and so can undermine weight‐loss efforts (i.e. to preserve body fat stores). Interrupting the usual overnight fast (and therefore also the usual sleep cycle) by nocturnal feeding has also been examined and further research is needed to understand the importance of this period for either nutritional intervention or nutritional withdrawal. In summary, it is important for dietary guidelines for human health to consider nutrient timing (i.e. when we eat) alongside the conventional focus on nutrient quantity and nutrient quality (i.e. how much we eat and what we eat).

The impact of later eating rhythm on childhood adiposity: protocol for a systematic review

BACKGROUND

Childhood adiposity has increased dramatically in the last few decades and is an important predictor of adulthood chronic disease. Later eating rhythm, termed night eating (NE), is increasingly prevalent in adults; however, the prevalence of NE in children and relationship between NE and adiposity in children still remains uncertain. The aim of this work is to review the association between adiposity in children and adolescents and NE, in terms of calorie intake, timing and meal frequency in the evening/night.

METHODS

The Cochrane library, CINAHL, Embase, MEDLINE (via OVID) and Web of Science databases will be searched from inception to November 2019 for randomised controlled trials (RCTs) and observational studies (cohort, cross-sectional and case-control studies) which investigate the association between later vs. earlier timing of food intake at night or relatively more vs. less energy intake in any eating occasions or time period after 4 pm on adiposity in children and adolescents (4-18 years). The outcomes will be body mass index (BMI)/BMI standard deviation score (BMI-SDS or BMI Z-score), waist circumference (WC), fat mass index (FMI)/percentage of body fat (%BF) or waist to hip ratio (WHR). No language restriction will be applied. Screening for eligibility from the title and abstracts and data extraction from the full texts will be carried out by two reviewers independently. References listed in the included studies will be hand-searched for any additional articles. The quality of included RCT studies will be assessed using Revised Cochrane Risk of Bias tool (RoB 2), and of observational studies using Newcastle Ottawa scale. A qualitative synthesis of the results will be presented, and meta-analysis will be conducted, where appropriate.

DISCUSSION

The planned systematic review will investigate the association between later eating rhythm and adiposity in children and adolescents. Understanding the best meal size, timing of energy intake and meal frequency across the evening time for maintaining healthy weight in children is important in order to give parents the best advice to help prevent adulthood obesity and associated chronic diseases in their children.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019134187.

H. pylori infection induced BMAL1 expression and rhythm disorder aggravate gastric inflammation

BACKGROUND

Rhythm abnormalities are crucial for diverse diseases. However, their role in disease progression induced by Helicobacter pylori (H. pylori) remains elusive.

METHODS

H. pylori infection was used in in vivo and in vitro experiments to examine its effect on rhythmic genes. The GEO database was used to screen H. pylori affecting rhythm genes, and the effect of rhythm genes on inflammatory factors. Chromatin immunoprecipitation and dual luciferase assays were used to further find out the regulation between molecules. Animal models were used to confirm the relationship between rhythm genes and H. pylori-induced inflammation.

FINDINGS

BMAL1 disorders aggravate inflammation induced by H. pylori. Specifically, H. pylori induce BMAL1 expression in vitro and in vivo through transcriptional activation of LIN28A, breaking the circadian rhythm. Mechanistically, LIN28A binds to the promoter region of BMAL1 and directly activates its transcription under H. pylori infection. BMAL1 in turn functions as a transcription factor and enhances the expression of proinflammatory cytokine TNF-α, thereby promoting inflammation. Of note, BMAL1 dysfunction in the rhythm disorder animal model aggravates inflammatory response induced by H. pylori infection in vivo.

INTERPRETATION

These findings in this study imply the pathogenic relationship between BMAL1 and H. pylori. BMAL1 may serve as a potential diagnostic marker and therapeutic target for the early diagnosis and treatment of diseases related to H. pylori infection. FUND: National Natural Science Foundation of China.

An individual 12-h shift of the light-dark cycle alters the pancreatic and duodenal circadian rhythm and digestive function

In mammals, behavioral and physiological rhythms are controlled by circadian clocks which are entrained by environmental light and food signals. However, how the environmental cues affect digestive tract's circadian clock remains poorly understood. Therefore, in order to elucidate the effect of light cue on the resetting of the peripheral clocks, we investigated the expressions of clock genes (Bmal1, Cry1, Rev-erbα, Per1, and Per2) and digestive function genes (Cck, Cck-1r, Sct, Sctr, and Ctrb1) in the pancreas and duodenum of rats after the light-dark (LD) cycle reversal for 7 days. We found that both the clock genes and digestive function genes exhibited a clear and similar daily rhythmicity in the pancreas and duodenum of rats. After reversal of the LD cycle for 7 days, the expressions of clock genes in pancreas, including Bmal1, Cry1, and Rev-erbα were affected; whereas the expression of Per1 gene failed to fit the cosine wave. However, in the duodenum the shifted genes were Bmal1, Rev-erbα, and Per2; in parallel, the Per1 gene expression also lost its circadian rhythm by reversal of the LD cycle. Therefore, the acrophases of the clock genes were shifted in a tissue- and gene-specific manner. Furthermore, the profiles of the digestive function genes, including Sctr and Ctrb1, were also affected by changes in LD cycle. These observations suggest that the mechanisms underlying the pancreatic and duodenal clocks are distinct, and there may be a potential linkage between the circadian clock system and the digestive system.

Di- and tripeptide transport in vertebrates: the contribution of teleost fish models

Solute Carrier 15 (SLC15) family, alias H⁺-coupled oligopeptide cotransporter family, is a group of membrane transporters known for their role in the cellular uptake of di- and tripeptides (di/tripeptides) and peptide-like molecules. Of its members, SLC15A1 (PEPT1) chiefly mediates intestinal absorption of luminal di/tripeptides from dietary protein digestion, while SLC15A2 (PEPT2) mainly allows renal tubular reabsorption of di/tripeptides from ultrafiltration, SLC15A3 (PHT2) and SLC15A4 (PHT1) possibly interact with di/tripeptides and histidine in certain immune cells, and SLC15A5 has unknown function. Our understanding of this family in vertebrates has steadily increased, also due to the surge of genomic-to-functional information from 'non-conventional' animal models, livestock, poultry, and aquaculture fish species. Here, we review the literature on the SLC15 transporters in teleost fish with emphasis on SLC15A1 (PEPT1), one of the solute carriers better studied amongst teleost fish because of its relevance in animal nutrition. We report on the operativity of the transporter, the molecular diversity, and multiplicity of structural-functional solutions of the teleost fish orthologs with respect to higher vertebrates, its relevance at the intersection of the alimentary and osmoregulative functions of the gut, its response under various physiological states and dietary solicitations, and its possible involvement in examples of total body plasticity, such as growth and compensatory growth. By a comparative approach, we also review the few studies in teleost fish on SLC15A2 (PEPT2), SLC15A4 (PHT1), and SLC15A3 (PHT2). By representing the contribution of teleost fish to the knowledge of the physiology of di/tripeptide transport and transporters, we aim to fill the gap between higher and lower vertebrates.

Loss of circadian rhythm of circulating insulin concentration induced by high-fat diet intake is associated with disrupted rhythmic expression of circadian clock genes in the liver

OBJECTIVE

Peripheral clock genes show a circadian rhythm is correlated with the timing of feeding in peripheral tissues. It was reported that these clock genes are strongly regulated by insulin action and that a high-fat diet (HFD) intake in C57BL/6J mice for 21days induced insulin secretion during the dark phase and reduced the circadian rhythm of clock genes. In this study, we examined the circadian expression patterns of these clock genes in insulin-resistant animal models with excess secretion of insulin during the day.

MATERIALS/METHODS

We examined whether insulin resistance induced by a HFD intake for 80days altered blood parameters (glucose and insulin concentrations) and expression of mRNA and proteins encoded by clock and functional genes in the liver using male ICR mice.

RESULTS

Serum insulin concentrations were continuously higher during the day in mice fed a HFD than control mice. Expression of lipogenesis-related genes (Fas and Accβ) and the transcription factor Chrebp peaked at zeitgeber time (ZT)24 in the liver of control mice. A HFD intake reduced the expression of these genes at ZT24 and disrupted the circadian rhythm. Expression of Bmal1 and Clock, transcription factors that compose the core feedback loop, showed circadian variation and were synchronously associated with Fas gene expression in control mice, but not in those fed a HFD.

CONCLUSIONS

These results indicate that the disruption of the circadian rhythm of insulin secretion by HFD intake is closely associated with the disappearance of circadian expression of lipogenic and clock genes in the liver of mice.

Deregulated expression of circadian clock genes in gastric cancer

BACKGROUND

Gastric cancer (GC), an aggressive malignant tumor of the alimentary tract, is a leading cause of cancer-related death. Circadian rhythm exhibits a 24-hour variation in physiological processes and behavior, such as hormone levels, metabolism, gene expression, sleep and wakefulness, and appetite. Disruption of circadian rhythm has been associated with various cancers, including chronic myeloid leukemia, head and neck squamous cell carcinoma, hepatocellular carcinoma, endometrial carcinoma, and breast cancer. However, the expression of circadian clock genes in GC remains unexplored.

METHODS

In this study, the expression profiles of eight circadian clock genes (PER1, PER2, PER3, CRY1, CRY2, CKIϵ, CLOCK, and BMAL1) of cancerous and noncancerous tissues from 29 GC patients were investigated using real-time quantitative reverse-transcriptase polymerase chain reaction and validated through immunohistochemical analysis.

RESULTS

We found that PER2 was significantly up-regulated in cancer tissues (p < 0.005). Up-regulated CRY1 expression was significantly correlated with more advanced stages (stage III and IV) (p < 0.05).

CONCLUSIONS

Our results suggest deregulated expressions of circadian clock genes exist in GC and circadian rhythm disturbance may be associated with the development of GC.

Plasticity of gastro-intestinal vagal afferent endings

Vagal afferents are a vital link between the peripheral tissue and central nervous system (CNS). There is an abundance of vagal afferents present within the proximal gastrointestinal tract which are responsible for monitoring and controlling gastrointestinal function. Whilst essential for maintaining homeostasis there is a vast amount of literature emerging which describes remarkable plasticity of vagal afferents in response to endogenous as well as exogenous stimuli. This plasticity for the most part is vital in maintaining healthy processes; however, there are increased reports of vagal plasticity being disrupted in pathological states, such as obesity. Many of the disruptions, observed in obesity, have the potential to reduce vagal afferent satiety signalling which could ultimately perpetuate the obese state. Understanding how plasticity occurs within vagal afferents will open a whole new understanding of gut function as well as identify new treatment options for obesity.

Circadian regulation of epithelial functions in the intestine

Many physiological functions exhibit a diurnal rhythmicity that is influenced by biological clocks and feeding rhythms. In this review, we discuss the growing evidence showing the important role of circadian rhythms in regulating intestinal mucosa. First, we introduce the molecular timing system and the interrelationship between the master biological clock in the suprachiasmatic nuclei of the brain and the peripheral intestinal clock and provide evidence that the intestinal clock is entrained with the external environment. Second, we review the circadian rhythmicity of enterocyte proliferation and the largely unknown regulatory mechanisms behind these rhythms. Finally, we focus on the circadian clock control of food processing that functions by regulating the expression of digestive enzymes and intestinal nutrient and salt transporters. The concepts to be discussed highlight the ability of the intestinal epithelium to utilize self-sustained clock signals together with signals associated with changes in the cellular environment and to use endogenous temporal control of the gastrointestinal functions to meet varying physiological and pathophysiological demands. The fact that internal de-synchronizations within the body, such as those that occur in shift workers or with changes in food intake behaviour, are often associated with malfunctions of the gastrointestinal tract indicates that more information about the connections between the circadian clock and intestinal mucosa/transporting enterocytes could provide clues for future therapies.

Peptide absorption after massive proximal small bowel resection: mechanisms of ileal adaptation

BACKGROUND

Protein absorption occurs as di- and tri-peptides via H(+)/peptide co-transporter-1 (PepT1).

AIM

The aim of this study is to identify mechanisms of ileal adaptation after massive proximal enterectomy.

HYPOTHESIS

Ileal adaptation in uptake of peptides is mediated through upregulation of PepT1 gene expression.

STUDY DESIGN

Rats underwent 70% jejunoileal resection. Total mucosal cellular levels of messenger RNA (mRNA) and protein and transporter-mediated uptake per centimeter of the di-peptide glycyl-sarcosine (Gly-Sar) were compared in remnant ileum 1 and 4 weeks postoperatively to control and to 1-week sham laparotomy rats. Histomorphology, food consumption, and weights of rats were monitored.

RESULTS

After 70% resection, although mRNA per cell for PepT1 decreased at 1 week (p = 0.002), expression of mRNA at 4 weeks and protein at 1 and 4 weeks in remnant ileum were unchanged (p > 0.1). Ileal Gly-Sar uptake (V (max)-nanomoles per centimeter per minute, i.e., number of transporters per centimeter) increased at 1 and 4 weeks compared to control and 1-week sham (p < 0.05 each); K (m) (i.e., transporter function) was unchanged. Villous heights (millimeters) in remnant ileum increased at 1- and 4-week time points over controls (0.45 and 0.57 vs 0.21, resp; p < 0.001).

CONCLUSIONS

Ileal adaptation to proximal resection for peptide absorption occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of PepT1 mRNA or protein per enterocyte.

Neural regulation of intestinal nutrient absorption

The nervous system and the gastrointestinal (GI) tract share several common features including reciprocal interconnections and several neurotransmitters and peptides known as gut peptides, neuropeptides or hormones. The processes of digestion, secretion of digestive enzymes and then absorption are regulated by the neuro-endocrine system. Luminal glucose enhances its own absorption through a neuronal reflex that involves capsaicin sensitive primary afferent (CSPA) fibres. Absorbed glucose stimulates insulin release that activates hepatoenteric neural pathways leading to an increase in the expression of glucose transporters. Adrenergic innervation increases glucose absorption through α1 and β receptors and decreases absorption through activation of α2 receptors. The vagus nerve plays an important role in the regulation of diurnal variation in transporter expression and in anticipation to food intake. Vagal CSPAs exert tonic inhibitory effects on amino acid absorption. It also plays an important role in the mediation of the inhibitory effect of intestinal amino acids on their own absorption at the level of proximal or distal segment. However, chronic extrinsic denervation leads to a decrease in intestinal amino acid absorption. Conversely, adrenergic agonists as well as activation of CSPA fibres enhance peptides uptake through the peptide transporter PEPT1. Finally, intestinal innervation plays a minimal role in the absorption of fat digestion products. Intestinal absorption of nutrients is a basic vital mechanism that depends essentially on the function of intestinal mucosa. However, intrinsic and extrinsic neural mechanisms that rely on several redundant loops are involved in immediate and long-term control of the outcome of intestinal function.

Differentiating passive from transporter-mediated uptake by PepT1: a comparison and evaluation of four methods

BACKGROUND

To quantify transmembrane transport of dipeptides by PepT1, passive uptake (non-PepT1 mediated) must be subtracted from total (measured) uptake. Three methods have been described to estimate passive uptake: perform experiments at cold temperatures, inhibit target dipeptide uptake with a greater concentration of a second dipeptide, or use modified Michaelis-Menten kinetics. We hypothesized that performing uptake experiments at pH 8.0 would estimate passive uptake accurately, because PepT1 requires a proton gradient. Our aim was to determine the most accurate method to estimate passive uptake.

METHODS

Caco-2 cells were incubated with various concentrations of glycyl-sarcosine (gly-sar) at pH 6.0 and at 37°C to measure total uptake. Passive uptake was estimated: (1) by incubating Caco-2 cells with varying concentrations of gly-sar at 4°C, (2) in the presence of 50 mM glycyl-leucine, (3) in solution at pH 8.0, or (4) using modified Michaelis-Menten kinetics. PepT1-mediated uptake was calculated by subtracting passive uptake from total uptake. K(m), V(max), and % gly-sar transported by PepT1 were calculated and compared.

RESULTS

K(m), V(max), and % gly-sar transported by PepT1 varied from 0.7 to 2.4 mM, 8.4 to 21.0 nmol/mg protein/10 min, and 69% to 87%, respectively. Uptakes calculated with cold, 50 mM gly-leu and using modified Michaelis-Menten kinetics were similar but differed significantly from uptake at pH 8.0 (P < 0.001).

CONCLUSIONS

Estimating passive uptake at pH 8.0 does not appear to be accurate. Measuring uptake at cold temperatures or in the presence of a greater concentration of a second dipeptide, and confirming results with modified Michaelis-Menten kinetics is recommended.

Intestinal adaptation for oligopeptide absorption via PepT1 after massive (70%) mid-small bowel resection

INTRODUCTION

Proteins are absorbed primarily as short peptides via peptide transporter 1 (PepT1).

HYPOTHESIS

Intestinal adaptation for peptide absorption after massive mid-small intestinal resection occurs by increased expression of PepT1 in the remnant small intestine and colon.

METHODS

Peptide uptake was measured in duodenum, jejunum, ileum, and colon using glycyl-sarcosine 1 week (n = 9) and 4 weeks (n = 11) after 70% mid-small bowel resection and in corresponding segments from unoperated rats (n = 12) and after transection and reanastomosis of jejunum and ileum (n = 8). Expression of PepT1 (mRNA, protein) and villus height were measured.

RESULTS

Intestinal transection/reanastomosis did not alter gene expression. Compared to non-operated controls, 70% mid-small bowel resection increased jejunal peptide uptake (p < 0.05) associated with increased villus height (1.13 vs 1.77 and 1.50 mm, respectively, p < 0.01). In ileum although villus height increased at 1 and 4 weeks (1.03 vs 1.21 and 1.35 mm, respectively; p < 0.01), peptide uptake was not altered. PepT1 mRNA and protein were decreased at 1 week, and PepT1 protein continued low at 4 weeks. Gene expression, peptide uptake, and histomorphology were unchanged in the colon.

CONCLUSIONS

Jejunal adaptation for peptide absorption occurs by hyperplasia. Distal ileum and colon do not have a substantive role in adaptation for peptide absorption.