Parenteral nutrition dysregulates bile salt homeostasis in a rat model of parenteral nutrition-associated liver disease

Lactobacillus johnsonii Attenuates Liver Steatosis and Bile Acid Dysregulation in Parenteral Nutrition-Fed Rats

Parenteral nutrition (PN), a vital therapy for patients with intestinal failure, can lead to the development of parenteral nutrition-associated liver disease (PNALD). In this study, we aimed to investigate the role of Lactobacillus johnsonii (L. johnsonii) in a rat model of PNALD. Total parenteral nutrition (TPN)-fed rats were used to assess the role of L. johnsonii in liver steatosis, bile acid metabolism, gut microbiota, and hepatocyte apoptosis. We observed a depletion of L. johnsonii that was negatively correlated with the accumulation of glycochenodeoxycholic acid (GCDCA), a known apoptosis inducer, in rats subjected to TPN. L. johnsonii attenuated TPN-induced liver steatosis by inhibiting fatty acid synthesis and promoting fatty acid oxidation. TPN resulted in a decrease in bile acid synthesis and biliary bile secretion, which were partially restored by L. johnsonii treatment. The gut microbial profile revealed depletion of pathogenic bacteria in L. johnsonii-treated rats. L. johnsonii treatment reduced both hepatic GCDCA levels and hepatocyte apoptosis compared with the TPN group. In vitro, L. johnsonii treatment inhibited GCDCA-induced hepatocyte apoptosis via its bile salt hydrolase (BSH) activity. Our findings suggest that L. johnsonii protects against liver steatosis, bile acid dysregulation, and hepatocyte apoptosis in TPN-fed rats.

Alterations of gut microbiota and serum bile acids are associated with parenteral nutrition-associated liver disease

BACKGROUND

Parenteral nutrition-associated liver disease (PNALD) is a major complication of long-term parenteral nutrition (PN). The pathogenesis of PNALD remains unclear. We investigated the changes in taxonomic and functional composition of gut microbiota and serum bile acid levels in a rat model of PNALD.

METHODS

Male 4-week-old Sprague Dawley rats received either total parenteral nutrition or standard chow with 0.9% saline for 7 days. The taxonomic composition of cecal microbiota and its functional composition associated with bile acid metabolism were measured.

RESULTS

There were differences in taxonomic composition between the two groups. The abundance of the secondary bile acid biosynthesis pathway was higher in the TPN group (p < 0.05) with an increase in the percentage of bacteria expressing 7-alpha-hydroxysteroid dehydrogenase (p < 0.05). The abundance of enzymes associated with bile salt hydrolase was also higher (p < 0.05) in the TPN group. The TPN group showed a distinct bile acid profile characterized by a higher ratio of secondary bile acids to primary bile acids.

CONCLUSIONS

The alteration of bile acid-associated microbiota may lead to increased secondary bile acid production in a rat model of PNALD.

Diarrhea and elevation of plasma markers of cholestasis are common and often occur concomitantly in critically ill patients

PURPOSE

We aimed to describe epidemiology of diarrhea and cholestasis in critically ill patients and explore associations between these two conditions.

MATERIAL AND METHODS

We performed a retrospective study including all consecutive patients who stayed in the ICU for at least 3 days and in whom plasma measurements of liver enzymes/cholestasis parameters were performed. Diarrhea was defined as 3 or more loose or liquid stools per day and cholestasis as increase of alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (GGT) 1.5 times above the upper limit of normality.

RESULTS

Diarrhea was observed in 26.1% and cholestasis in 27.9% of study patients, about one third of the cases in both diarrhea and cholestasis occurred beyond the first week of patient's ICU stay. Cholestasis occurred in 45.6% of patients with diarrhea vs 28.0% of patients without diarrhea (p < 0.001). In 94 patients (13.1%) both diarrhea and cholestasis occurred, cholestasis was more commonly (2/3 of cases) documented before manifestation of diarrhea.

CONCLUSIONS

Cholestasis is more common in patients with diarrhea and vice versa. Diarrhea and cholestasis both occur in approximately one quarter of ICU patients, with significant proportion manifesting beyond the first week in the ICU.

Translational Advances in Pediatric Nutrition and Gastroenterology: New Insights from Pig Models

Pigs are increasingly important animals for modeling human pediatric nutrition and gastroenterology and complementing mechanistic studies in rodents. The comparative advantages in size and physiology of the neonatal pig have led to new translational and clinically relevant models of important diseases of the gastrointestinal tract and liver in premature infants. Studies in pigs have established the essential roles of prematurity, microbial colonization, and enteral nutrition in the pathogenesis of necrotizing enterocolitis. Studies in neonatal pigs have demonstrated the intestinal trophic effects of akey gut hormone, glucagon-like peptide 2 (GLP-2), and its role in the intestinal adaptation process and efficacy in the treatment of short bowel syndrome. Further, pigs have been instrumental in elucidating the physiology of parenteral nutrition-associated liver disease and the means by which phytosterols, fibroblast growth factor 19, and a new generation of lipid emulsions may modify disease. The premature pig will continue to be a valuable model in the development of optimal infant diets (donor human milk, colostrum), specific milk bioactives (arginine, growth factors), gut microbiota modifiers (pre-, pro-, and antibiotics), pharmaceutical drugs (GLP-2 analogs, FXR agonists), and novel diagnostic tools (near-infrared spectroscopy) to prevent and treat these pediatric diseases.

Novel Strategies to Prevent Total Parenteral Nutrition-Induced Gut and Liver Inflammation, and Adverse Metabolic Outcomes

Total parenteral nutrition (TPN) is a life-saving therapy administered to millions of patients. However, it is associated with significant adverse effects, namely liver injury, risk of infections, and metabolic derangements. In this review, the underlying causes of TPN-associated adverse effects, specifically gut atrophy, dysbiosis of the intestinal microbiome, leakage of the epithelial barrier with bacterial invasion, and inflammation are first described. The role of the bile acid receptors farnesoid X receptor and Takeda G protein-coupled receptor, of pleiotropic hormones, and growth factors is highlighted, and the mechanisms of insulin resistance, namely the lack of insulinotropic and insulinomimetic signaling of gut-originating incretins as well as the potentially toxicity of phytosterols and pro-inflammatory fatty acids mainly released from soybean oil-based lipid emulsions, are discussed. Finally, novel approaches in the design of next generation lipid delivery systems are proposed. Propositions include modifying the physicochemical properties of lipid emulsions, the use of lipid emulsions generated from sustainable oils with favorable ratios of anti-inflammatory n-3 to pro-inflammatory n-6 fatty acids, beneficial adjuncts to TPN, and concomitant pharmacotherapies to mitigate TPN-associated adverse effects.

Exogenous Secretin Improves Parenteral Nutrition-associated Liver Disease in Rats

OBJECTIVES

Intestinal failure-associated liver disease (IFALD) is a feared and life-threatening complication in neonates with intestinal failure (IF) receiving long-term total parenteral nutrition (TPN). This study aims to investigate the effect of exogenous secretin on liver pathology and hepatic function in a rat model of PN-associated liver disease (PNALD).

METHODS

Male Sprague-Dawley rats underwent right jugular venous catheterization to receive 14-day continuous TPN therapy. All rats were allocated into 3 groups: the Control group (n = 8) did not have surgery or TPN and was fed standard rat chow ad libitum; the TPN group (n = 8) underwent catheter insertion and TPN treatment; and the TPN/S group (n = 8) also underwent catheter insertion, TPN treatment, and exogenous secretin treatment (2.5 nmol · kg · day) daily. Fourteen days after initial surgery, we collected the animals' liver and blood samples for further test.

RESULTS

The TPN/S group had diminished direct bilirubin (TPN, 2.1 ± 0.7 μmol/L; TPN/S, 1.5 ± 0.2 μmol/L) and liver total bile acid levels (TPN, 144.5 ± 21.2 μmol/L; TPN/S, 123.4 ± 10.4 μmol/L) and improved histological outcomes compared with those in the TPN group. Exogenous secretin also enhanced the canalicular transporter (BSEP, 0.5-fold, P = 0.011) and inhibited the basolateral transporter (OSTA, -0.48-fold, P = 0.002; OSTB, -0.6-fold, P = 0.013) of liver bile acid.

CONCLUSIONS

In this animal model of PNALD, secretin may improve cholestasis by enhancing canalicular transport, inhibiting the basolateral export of liver bile acid, and eventually decreasing the total bile acid level in the liver. Exogenous secretin treatment may potentially prevent and treat IFALD in IF patients relying on long-term TPN therapy.

The Role of Parenteral Lipids in the Development of Hepatic Dysfunction and Hepatic Steatosis in a Mouse Model of Total Parenteral Nutrition

Parenteral nutrition-associated liver disease, a common and life-threating complication among people who require long-term parenteral nutrition, has been associated with abnormal liver function, cholestasis, steatosis and fibrosis. Intravenous soybean lipids may be associated with the development of liver disease. We therefore examined whether different doses of parenteral lipids would affect the development of liver disease, and further investigated the possible pathogenesis of it. C57BL/6J mice with a central catheter placed in the right jugular vein were divided into three groups. The control group received normal mouse chow with intravenous normal saline; The lipids group received parenteral nutrition solution (0.14 g lipids per day); the H-lipids group received parenteral nutrition solution with twice the amount of lipids (0.3 g lipids per day). Changes in body weight, serum biochemical parameters, liver histology and farnesoid X receptor gene expression in the liver were assessed. The values of serum direct bilirubin, total bilirubin and cholesterol were markedly increased in the H-lipids group at day 7. The predominant histologic finding in the H-lipids group was steatosis, and the steatosis score in the H-lipids group was much higher than in the other two groups at either day 5 or day 7. Hepatic expression of farnesoid X receptor mRNA decreased after 7 d of parenteral nutrition. High doses of parenteral lipids are more likely to develop liver disease in a mouse model of parenteral nutrition. Farnesoid X receptor may play a key role in the development of parenteral nutrition-associated liver disease.

No Gut No Gain! Enteral Bile Acid Treatment Preserves Gut Growth but Not Parenteral Nutrition-Associated Liver Injury in a Novel Extensive Short Bowel Animal Model

BACKGROUND

Parenteral nutrition (PN) provides nutrition intravenously; however, this life-saving therapy is associated with significant liver disease. Recent evidence indicates improvement in PN-associated injury in animals with intact gut treated with enteral bile acid (BA), chenodeoxycholic acid (CDCA), and a gut farnesoid X receptor (FXR) agonist, which drives the gut-liver cross talk (GLCT). We hypothesized that similar improvement could be translated in animals with short bowel syndrome (SBS).

METHODS

Using piglets, we developed a novel 90% gut-resected SBS model. Fifteen SBS piglets receiving PN were given CDCA or control (vehicle control) for 2 weeks. Tissue and serum were analyzed posteuthanasia.

RESULTS

CDCA increased gut FXR (quantitative polymerase chain reaction; P = .008), but not downstream FXR targets. No difference in gut fibroblast growth factor 19 (FGF19; P = .28) or hepatic FXR (P = .75), FGF19 (P = .86), FGFR4 (P = .53), or Cholesterol 7 α-hydroxylase (P = .61) was noted. PN resulted in cholestasis; however, no improvement was noted with CDCA. Hepatic fibrosis or immunostaining for Ki67, CD3, or Cytokeratin 7 was not different with CDCA. PN resulted in gut atrophy. CDCA preserved (P = .04 vs control) gut mass and villous/crypt ratio. The median (interquartile range) for gut mass for control was 0.28 (0.17-0.34) and for CDCA was 0.33 (0.26-0.46).

CONCLUSIONS

We note that, unlike in animals with intact gut, in an SBS animal model there is inadequate CDCA-induced activation of gut-derived signaling to cause liver improvement. Thus, it appears that activation of GLCT is critically dependent on the presence of adequate gut. This is clinically relevant because it suggests that BA therapy may not be as effective for patients with SBS.

Metabolic programming of the epigenome: host and gut microbial metabolite interactions with host chromatin

The mammalian gut microbiota has been linked to host developmental, immunologic, and metabolic outcomes. This collection of trillions of microbes inhabits the gut and produces a myriad of metabolites, which are measurable in host circulation and contribute to the pathogenesis of human diseases. The link between endogenous metabolite availability and chromatin regulation is a well-established and active area of investigation; however, whether microbial metabolites can elicit similar effects is less understood. In this review, we focus on seminal and recent research that establishes chromatin regulatory roles for both endogenous and microbial metabolites. We also highlight key physiologic and disease settings where microbial metabolite-host chromatin interactions have been established and/or may be pertinent.

p38α MAPK antagonizing JNK to control the hepatic fat accumulation in pediatric patients onset intestinal failure

The p38α mitogen-activated protein kinase (MAPK) has been related to gluconeogenesis and lipid metabolism. However, the roles and related mechanisms of p38α MAPK in intestinal failure (IF)-associated liver steatosis remained poor understood. Here, our experimental evidence suggested that p38α MAPK significantly suppressed the fat accumulation in livers of IF patients mainly through two mechanisms. On the one hand, p38α MAPK increased hepatic bile acid (BA) synthesis by upregulating the expression of the rate-limiting enzyme cholesterol 7-α-hydroxylase (CYP7A1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), which in turn activated the transcription of the CYP7A1. On the other hand, p38α MAPK promoted fatty acid (FA) β-oxidation via upregulating peroxisome proliferator-activated receptor alpha (PPARα) and its transcriptional target genes carnitine palmitoyltransferase 1A (CPT1A) and peroxisomal acyl-coenzyme aoxidase 1 (ACOX1). Dual luciferase assays indicated that p38α MAPK increased the transcription of PPARα, PGC-1α and CYP7A1 by upregulating their promoters’ activities. In addition, in vitro and in vivo assays indicated p38α MAPK negatively regulates the hepatic steatosis by controlling JNK activation. In conculsion, our findings demonstrate that hepatic p38α MAPK functions as a negative regulator of liver steatosis in maintaining BA synthesis and FAO by antagonizing the c-Jun N-terminal kinase (JNK).