Impaired Bile Acid Homeostasis in Children with Severe Acute Malnutrition

Gut microbiota and childhood malnutrition: Understanding the link and exploring therapeutic interventions

Childhood malnutrition is a metabolic condition that affects the physical and mental well-being of children and leads to resultant disorders in maturity. The development of childhood malnutrition is influenced by a number of physiological and environmental factors including metabolic stress, infections, diet, genetic variables, and gut microbiota. The imbalanced gut microbiota is one of the main environmental risk factors that significantly influence host physiology and childhood malnutrition progression. In this review, we have evaluated the gut microbiota association with undernutrition and overnutrition in children, and then the quantitative and qualitative significance of gut dysbiosis in order to reveal the impact of gut microbiota modification using probiotics, prebiotics, synbiotics, postbiotics, fecal microbiota transplantation, and engineering biology methods as new therapeutic challenges in the management of disturbed energy homeostasis. Understanding the host-microbiota interaction and the remote regulation of other organs and pathways by gut microbiota can improve the effectiveness of new therapeutic approaches and mitigate the negative consequences of childhood malnutrition.

NAD+ precursors and bile acid sequestration treat preclinical refractory environmental enteric dysfunction

Environmental enteric dysfunction (EED) is a diffuse small bowel disorder associated with poor growth, inadequate responses to oral vaccines, and nutrient malabsorption in millions of children worldwide. We identify loss of the small intestinal Paneth and goblet cells that are critical for innate immunity, reduced villous height, increased bile acids, and dysregulated nicotinamide adenine dinucleotide (NAD+) synthesis signaling as potential mechanisms underlying EED and which also correlated with diminished length-for-age z score. Isocaloric low-protein diet (LPD) consumption in mice recapitulated EED histopathology and transcriptomic changes in a microbiota-independent manner, as well as increases in serum and fecal bile acids. Children with refractory EED harbor single-nucleotide polymorphisms in key enzymes involved in NAD+ synthesis. In mice, deletion of Nampt, the gene encoding the rate-limiting enzyme in the NAD+ salvage pathway, from intestinal epithelium also reduced Paneth cell function, a deficiency that was further aggravated by LPD. Separate supplementation with NAD+ precursors or bile acid sequestrant partially restored LPD-associated Paneth cell defects and, when combined, fully restored all histopathology defects in LPD-fed mice. Therapeutic regimens that increase protein and NAD+ contents while reducing excessive bile acids may benefit children with refractory EED.

Impact of protein deficient diet on the pharmacokinetics of glibenclamide in a model of malnutrition in rats

Purpose

The present investigation deals with the impact of protein energy malnourished condition on the pharmacokinetic profile of glibenclamide. Protein energy malnourished condition leads to malnutrition related diabetes mellitus (MRDM), Fibrocalculus pancreatic diabetes mellitus (FCPD) or Lean body mass diabetes mellitus (LBMDM).

Method

In the present study, malnutrition was developed in female wistar rats using a modified protein deficient diet (0.5%). The experiment was performed on 12 animals, each group containing 6 female wistar rats. The control group animals were fed with standard pellet diet (AIN 93 G diet) while group 2 received the low protein diet (0.5%) for 75 days. Glibenclamide (Gli) suspension (30 mg/kg) was administered orally to these rats on 75 days and kinetic parameters were evaluated by HPLC analysis.The pharmacokinetic interpretation done by pksolver software version 2.0, statistical comparison done by applying student T test.

Results

The results of body weight and hematological parameters indicated a significant decreased in the body weight in protein deficit rats to 124.1 ± 6.2 g compared to 235.5 ± 8.4 g (p < 0.01) control rats; whereas a decrease in the hemoglobin to 5.8 ± 0.6 g/dL, total blood protein level to 6.9 ± 0.6 g/dL and blood albumin levels to 2.7 ± 0.4 g/dL in protein deficit rats compared to 15 ± 0.7 g/dL(p < 0.05), 8.1 ± 0.4 g/dL(p < 0.05), and 4.5 ± 0.2 g/dL(p < 0.05), respectively in control rats. All these findings reflect the malnourished condition and weight loss due to a protein deficit diet in experimental animals. There was an increase in the fasting blood glucose levels up to 150 ± 17.4 mg/dL in the protein deficit diet group as compared to 98.7 ± 14.1 mg/dL(p < 0.05) in control rats reflect the prediabetes state in malnourished animals. The results of the pharmacokinetic study reflect a significant lowering of half-life (T½) of glibenclamide to 96.8 ± 0.8 min. in malnourished rats compared to 166.7 ± 0.74 min. (p < 0.001) in control rats. The maximum concentration (Cmax) of glibenclamide in the malnourished rats was significantly higher 20.74 ± 0.65 μg/mL and also took double time i.e. about 180 min. to reach maximum concentration (Tmax) compared to the control rats values 7.9 ± 0.84 μg/mL (p < 0.001) and 90.0 ± 0.24 min. (p < 0.001) respectively. The area under the plasma concentration-time curve [AUC(0-∞)] in malnourished rats increased 4439.1 ± 40.6 μg/ml*min as compared to 1235.9 ± 55.8 μg/ml*min (p < 0.001) in control rats. There was a lowering in the total body clearance (CL) to 0.4 ± 0.02 L/hr and volume of distribution (Vd) to 1.75 ± 0.07 L of glibenclamide in the protein deficit group compared to 1.4 ± 0.3 L/hr (p < 0.001) and 3.14 ± 0.8 L (p < 0.01), respectively in the control rats.

Conclusion

From this study it concludes that there is an increase in the T½, Cmax, Tmax and AUC(0-∞) of glibenclamide in malnourished rats while the total body clearance and volume of distribution is lowered. Therefore this study proposes to conduct an adequate pharmacokinetic study in malnourished patients to decide whether the standard glibenclamide dose should be adapted according to the nutritional status of the individual.

Physiological activation of human and mouse bitter taste receptors by bile acids

Beside the oral cavity, bitter taste receptors are expressed in several non-gustatory tissues. Whether extra-oral bitter taste receptors function as sensors for endogenous agonists is unknown. To address this question, we devised functional experiments combined with molecular modeling approaches to investigate human and mouse receptors using a variety of bile acids as candidate agonists. We show that five human and six mouse receptors are responsive to an array of bile acids. Moreover, their activation threshold concentrations match published data of bile acid concentrations in human body fluids, suggesting a putative physiological activation of non-gustatory bitter receptors. We conclude that these receptors could serve as sensors for endogenous bile acid levels. These results also indicate that bitter receptor evolution may not be driven solely by foodstuff or xenobiotic stimuli, but also depend on endogenous ligands. The determined bitter receptor activation profiles of bile acids now enable detailed physiological model studies.

Inhibition of mTOR improves malnutrition induced hepatic metabolic dysfunction

Severe malnutrition accounts for half-a-million deaths annually in children under the age of five. Despite improved WHO guidelines, inpatient mortality remains high and is associated with metabolic dysfunction. Previous studies suggest a correlation between hepatic metabolic dysfunction and impaired autophagy. We aimed to determine the role of mTORC1 inhibition in a murine model of malnutrition-induced hepatic dysfunction. Wild type weanling C57/B6 mice were fed a 18 or 1% protein diet for two weeks. A third low-protein group received daily rapamycin injections, an mTORC1 inhibitor. Hepatic metabolic function was assessed by histology, immunofluorescence, gene expression, metabolomics and protein levels. Low protein-fed mice manifested characteristics of severe malnutrition, including weight loss, hypoalbuminemia, hypoglycemia, hepatic steatosis and cholestasis. Low protein-fed mice had fewer mitochondria and showed signs of impaired mitochondrial function. Rapamycin prevented hepatic steatosis, restored ATP levels and fasted plasma glucose levels compared to untreated mice. This correlated with increased content of LC3-II, and decreased content mitochondrial damage marker, PINK1. We demonstrate that hepatic steatosis and disturbed mitochondrial function in a murine model of severe malnutrition can be partially prevented through inhibition of mTORC1. These findings suggest that stimulation of autophagy could be a novel approach to improve metabolic function in severely malnourished children.

The Childhood Acute Illness and Nutrition (CHAIN) network nested case-cohort study protocol: a multi-omics approach to understanding mortality among children in sub-Saharan Africa and South Asia

Introduction: Many acutely ill children in low- and middle-income settings have a high risk of mortality both during and after hospitalisation despite guideline-based care. Understanding the biological mechanisms underpinning mortality may suggest optimal pathways to target for interventions to further reduce mortality. The Childhood Acute Illness and Nutrition (CHAIN) Network ( www.chainnnetwork.org) Nested Case-Cohort Study (CNCC) aims to investigate biological mechanisms leading to inpatient and post-discharge mortality through an integrated multi-omic approach. Methods and analysis; The CNCC comprises a subset of participants from the CHAIN cohort (1278/3101 hospitalised participants, including 350 children who died and 658 survivors, and 270/1140 well community children of similar age and household location) from nine sites in six countries across sub-Saharan Africa and South Asia. Systemic proteome, metabolome, lipidome, lipopolysaccharides, haemoglobin variants, toxins, pathogens, intestinal microbiome and biomarkers of enteropathy will be determined. Computational systems biology analysis will include machine learning and multivariate predictive modelling with stacked generalization approaches accounting for the different characteristics of each biological modality. This systems approach is anticipated to yield mechanistic insights, show interactions and behaviours of the components of biological entities, and help develop interventions to reduce mortality among acutely ill children. Ethics and dissemination. The CHAIN Network cohort and CNCC was approved by institutional review boards of all partner sites. Results will be published in open access, peer reviewed scientific journals and presented to academic and policy stakeholders. Data will be made publicly available, including uploading to recognised omics databases. Trial registration NCT03208725.

The Childhood Acute Illness and Nutrition (CHAIN) network nested case-cohort study protocol: a multi-omics approach to understanding mortality among children in sub-Saharan Africa and South Asia

Introduction: Many acutely ill children in low- and middle-income settings have a high risk of mortality both during and after hospitalisation despite guideline-based care. Understanding the biological mechanisms underpinning mortality may suggest optimal pathways to target for interventions to further reduce mortality. The Childhood Acute Illness and Nutrition (CHAIN) Network ( www.chainnnetwork.org) Nested Case-Cohort Study (CNCC) aims to investigate biological mechanisms leading to inpatient and post-discharge mortality through an integrated multi-omic approach. Methods and analysis; The CNCC comprises a subset of participants from the CHAIN cohort (1278/3101 hospitalised participants, including 350 children who died and 658 survivors, and 270/1140 well community children of similar age and household location) from nine sites in six countries across sub-Saharan Africa and South Asia. Systemic proteome, metabolome, lipidome, lipopolysaccharides, haemoglobin variants, toxins, pathogens, intestinal microbiome and biomarkers of enteropathy will be determined. Computational systems biology analysis will include machine learning and multivariate predictive modelling with stacked generalization approaches accounting for the different characteristics of each biological modality. This systems approach is anticipated to yield mechanistic insights, show interactions and behaviours of the components of biological entities, and help develop interventions to reduce mortality among acutely ill children. Ethics and dissemination. The CHAIN Network cohort and CNCC was approved by institutional review boards of all partner sites. Results will be published in open access, peer reviewed scientific journals and presented to academic and policy stakeholders. Data will be made publicly available, including uploading to recognised omics databases. Trial registration NCT03208725.

Nonalcoholic Fatty Liver Disease and the Gut-Liver Axis: Exploring an Undernutrition Perspective

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition affecting one quarter of the global population. Although primarily linked to obesity and metabolic syndrome, undernutrition and the altered (dysbiotic) gut microbiome influence NAFLD progression. Both undernutrition and NAFLD prevalence are predicted to considerably increase, but how the undernourished gut microbiome contributes to hepatic pathophysiology remains far less studied. Here, we present undernutrition conditions with fatty liver features, including kwashiorkor and micronutrient deficiency. We then review the gut microbiota-liver axis, highlighting key pathways linked to NAFLD progression within both overnutrition and undernutrition. To conclude, we identify challenges and collaborative possibilities of emerging multiomic research addressing the pathology and treatment of undernourished NAFLD.

Bile Acid Profiling Reveals Distinct Signatures in Undernourished Children with Environmental Enteric Dysfunction

BACKGROUND

Intestinal inflammation and malabsorption in environmental enteric dysfunction (EED) are associated with early childhood growth faltering in impoverished settings worldwide.

OBJECTIVES

The goal of this study was to identify candidate biomarkers associated with inflammation, EED histology, and as predictors of later growth outcomes by focusing on the liver-gut axis by investigating the bile acid metabolome.

METHODS

Undernourished rural Pakistani infants (n = 365) with weight-for-height Z score (WHZ) < -2 were followed up to the age of 24 mo and monitored for growth, infections, and EED. Well-nourished local children (n = 51) were controls, based on consistent WHZ > 0 and height-for-age Z score (HAZ) > -1 on 2 consecutive visits at 3 and 6 mo. Serum bile acid (sBA) profiles were measured by tandem MS at the ages of 3-6 and 9 mo and before nutritional intervention. Biopsies and duodenal aspirates were obtained following upper gastrointestinal endoscopy from a subset of children (n = 63) that responded poorly to nutritional intervention. BA composition in paired plasma and duodenal aspirates was compared based on the severity of EED histopathological scores and correlated to clinical and growth outcomes.

RESULTS

Remarkably, >70% of undernourished Pakistani infants displayed elevated sBA concentrations consistent with subclinical cholestasis. Serum glycocholic acid (GCA) correlated with linear growth faltering (HAZ, r = -0.252 and -0.295 at the age of 3-6 and 9 mo, respectively, P <0.001) and biomarkers of inflammation. The proportion of GCA positively correlated with EED severity for both plasma (rs = 0.324 P = 0.02) and duodenal aspirates (rs = 0.307 P = 0.06) in children with refractory wasting that underwent endoscopy, and the proportion of secondary BA was low in both undernourished and EED children.

CONCLUSIONS

Dysregulated bile acid metabolism is associated with growth faltering and EED severity in undernourished children. Restoration of intestinal BA homeostasis may offer a novel therapeutic target for undernutrition in children with EED. This trial was registered at clinicaltrials.gov as NCT03588013.

Metabolomic changes in severe acute malnutrition suggest hepatic oxidative stress: a secondary analysis

Severe acute malnutrition (SAM), due to poor energy and/or protein intake, is associated with poor growth, depressed immune function, and long-term impacts on metabolic function. As the liver is a major metabolic organ and malnutrition poses metabolic stress, we hypothesize that SAM will be associated with alterations in the hepatic metabolome reflective of oxidative stress, gluconeogenesis, and ketogenesis. Thus, the purpose of this secondary analysis was to understand how SAM alters hepatic metabolism using a piglet model. Weanling piglets were feed either a reference (REF) or protein-energy deficient diet (MAL) for 5 weeks. After dietary treatment MAL piglets were severely underweight (weight-for-age Z-score of -3.29, Welch's t test, P = .0007), moderately wasted (weight-for-length Z-score of-2.49, Welch's t test, P = .003), and tended toward higher hepatic triglyceride content (Welch's t test, P = .07). Hematologic and blood biochemical measurements were assessed at baseline and after dietary treatment. The hepatic metabolome was investigated using ¹H-NMR spectroscopy. Hepatic concentrations of betaine, cysteine, and glutathione tended to be lower in MAL (Welch's t test with FDR correction, P < .1), while inosine, lactate, and methionine sulfoxide concentrations were higher in MAL (inosine: P = .0448, lactate: P = .0258, methionine sulfoxide: P = .0337). These changes suggest that SAM is associated with elevated hepatic oxidative stress, increased gluconeogenesis, and alterations in 1-carbon metabolism.

Inflammation-induced cholestasis in cancer cachexia

BACKGROUND

Cancer cachexia is a debilitating metabolic syndrome contributing to cancer death. Organs other than the muscle may contribute to the pathogenesis of cancer cachexia. This work explores new mechanisms underlying hepatic alterations in cancer cachexia.

METHODS

We used transcriptomics to reveal the hepatic gene expression profile in the colon carcinoma 26 cachectic mouse model. We performed bile acid, tissue mRNA, histological, biochemical, and western blot analyses. Two interventional studies were performed using a neutralizing interleukin 6 antibody and a bile acid sequestrant, cholestyramine. Our findings were evaluated in a cohort of 94 colorectal cancer patients with or without cachexia (43/51).

RESULTS

In colon carcinoma 26 cachectic mice, we discovered alterations in five inflammatory pathways as well as in other pathways, including bile acid metabolism, fatty acid metabolism, and xenobiotic metabolism (normalized enrichment scores of -1.97, -2.16, and -1.34, respectively; all Padj < 0.05). The hepatobiliary transport system was deeply impaired in cachectic mice, leading to increased systemic and hepatic bile acid levels (+1512 ± 511.6 pmol/mg, P = 0.01) and increased hepatic inflammatory cytokines and neutrophil recruitment to the liver of cachectic mice (+43.36 ± 16.01 neutrophils per square millimetre, P = 0.001). Adaptive mechanisms were set up to counteract this bile acid accumulation by repressing bile acid synthesis and by enhancing alternative routes of basolateral bile acid efflux. Targeting bile acids using cholestyramine reduced hepatic inflammation, without affecting the hepatobiliary transporters (e.g. tumour necrosis factor α signalling via NFκB and inflammatory response pathways, normalized enrichment scores of -1.44 and -1.36, all Padj < 0.05). Reducing interleukin 6 levels counteracted the change in expression of genes involved in the hepatobiliary transport, bile acid synthesis, and inflammation. Serum bile acid levels were increased in cachectic vs. non-cachectic cancer patients (e.g. total bile acids, +5.409 ± 1.834 μM, P = 0.026) and were strongly correlated to systemic inflammation (taurochenodeoxycholic acid and C-reactive protein: ρ = 0.36, Padj = 0.017).

CONCLUSIONS

We show alterations in bile acid metabolism and hepatobiliary secretion in cancer cachexia. In this context, we demonstrate the contribution of systemic inflammation to the impairment of the hepatobiliary transport system and the role played by bile acids in the hepatic inflammation. This work paves the way to a better understanding of the role of the liver in cancer cachexia.

A saliva-based rapid test to quantify the infectious subclinical malaria parasite reservoir

A large proportion of ongoing malaria parasite transmission is attributed to low-density subclinical infections not readily detected by available rapid diagnostic tests (RDTs) or microscopy. Plasmodium falciparum gametocyte carriage is subclinical, but gametocytemic individuals comprise the parasite reservoir that leads to infection of mosquitoes and local transmission. Effective detection and quantification of these carriers can help advance malaria elimination strategies. However, no point-of-need (PON) RDTs for gametocyte detection exist, much less one that can perform noninvasive sampling of saliva outside a clinical setting. Here, we report on the discovery of 35 parasite markers from which we selected a single candidate for use in a PON RDT. We performed a cross-sectional, multi-omics study of saliva from 364 children with subclinical infection in Cameroon and Zambia and produced a prototype saliva-based PON lateral flow immunoassay test for P. falciparum gametocyte carriers. The test is capable of identifying submicroscopic carriage in both clinical and nonclinical settings and is compatible with archived saliva samples.

Current Understanding of Innate Immune Cell Dysfunction in Childhood Undernutrition

Undernutrition affects millions of children in low- and middle-income countries (LMIC) and underlies almost half of all deaths among children under 5 years old. The growth deficits that characterize childhood undernutrition (stunting and wasting) result from simultaneous underlying defects in multiple physiological processes, and current treatment regimens do not completely normalize these pathways. Most deaths among undernourished children are due to infections, indicating that their anti-pathogen immune responses are impaired. Defects in the body's first-line-of-defense against pathogens, the innate immune system, is a plausible yet understudied pathway that could contribute to this increased infection risk. In this review, we discuss the evidence for innate immune cell dysfunction from cohort studies of childhood undernutrition in LMIC, highlighting knowledge gaps in almost all innate immune cell types. We supplement these gaps with insights from relevant experimental models and make recommendations for how human and animal studies could be improved. A better understanding of innate immune function could inform future tractable immune-targeted interventions for childhood undernutrition to reduce mortality and improve long-term health, growth and development.

Fibroblast Growth Factor 15/19: From Basic Functions to Therapeutic Perspectives

Discovered 20 years ago, fibroblast growth factor (FGF)19, and its mouse ortholog FGF15, were the first members of a new subfamily of FGFs able to act as hormones. During fetal life, FGF15/19 is involved in organogenesis, affecting the development of the ear, eye, heart, and brain. At adulthood, FGF15/19 is mainly produced by the ileum, acting on the liver to repress hepatic bile acid synthesis and promote postprandial nutrient partitioning. In rodents, pharmacologic doses of FGF19 induce the same antiobesity and antidiabetic actions as FGF21, with these metabolic effects being partly mediated by the brain. However, activation of hepatocyte proliferation by FGF19 has long been a challenge to its therapeutic use. Recently, genetic reengineering of the molecule has resolved this issue. Despite a global overlap in expression pattern and function, murine FGF15 and human FGF19 exhibit several differences in terms of regulation, molecular structure, signaling, and biological properties. As most of the knowledge originates from the use of FGF19 in murine models, differences between mice and humans in the biology of FGF15/19 have to be considered for a successful translation from bench to bedside. This review summarizes the basic knowledge concerning FGF15/19 in mice and humans, with a special focus on regulation of production, morphogenic properties, hepatocyte growth, bile acid homeostasis, as well as actions on glucose, lipid, and energy homeostasis. Moreover, implications and therapeutic perspectives concerning FGF19 in human diseases (including obesity, type 2 diabetes, hepatic steatosis, biliary disorders, and cancer) are also discussed.

Severe childhood malnutrition

The main forms of childhood malnutrition occur predominantly in children <5 years of age living in low-income and middle-income countries and include stunting, wasting and kwashiorkor, of which severe wasting and kwashiorkor are commonly referred to as severe acute malnutrition. Here, we use the term 'severe malnutrition' to describe these conditions to better reflect the contributions of chronic poverty, poor living conditions with pervasive deficits in sanitation and hygiene, a high prevalence of infectious diseases and environmental insults, food insecurity, poor maternal and fetal nutritional status and suboptimal nutritional intake in infancy and early childhood. Children with severe malnutrition have an increased risk of serious illness and death, primarily from acute infectious diseases. International growth standards are used for the diagnosis of severe malnutrition and provide therapeutic end points. The early detection of severe wasting and kwashiorkor and outpatient therapy for these conditions using ready-to-use therapeutic foods form the cornerstone of modern therapy, and only a small percentage of children require inpatient care. However, the normalization of physiological and metabolic functions in children with malnutrition is challenging, and children remain at high risk of relapse and death. Further research is urgently needed to improve our understanding of the pathophysiology of severe malnutrition, especially the mechanisms causing kwashiorkor, and to develop new interventions for prevention and treatment.

Nutrient-sensing nuclear receptors PPARα and FXR control liver energy balance

The nuclear receptors PPARα (encoded by NR1C1) and farnesoid X receptor (FXR, encoded by NR1H4) are activated in the liver in the fasted and fed state, respectively. PPARα activation induces fatty acid oxidation, while FXR controls bile acid homeostasis, but both nuclear receptors also regulate numerous other metabolic pathways relevant to liver energy balance. Here we review evidence that they function coordinately to control key nutrient pathways, including fatty acid oxidation and gluconeogenesis in the fasted state and lipogenesis and glycolysis in the fed state. We have also recently reported that these receptors have mutually antagonistic impacts on autophagy, which is induced by PPARα but suppressed by FXR. Secretion of multiple blood proteins is a major drain on liver energy and nutrient resources, and we present preliminary evidence that the liver secretome may be directly suppressed by PPARα, but induced by FXR. Finally, previous studies demonstrated a striking deficiency in bile acid levels in malnourished mice that is consistent with results in malnourished children. We present evidence that hepatic targets of PPARα and FXR are dysregulated in chronic undernutrition. We conclude that PPARα and FXR function coordinately to integrate liver energy balance.

Mechanisms of cross-talk between the diet, the intestinal microbiome, and the undernourished host

Undernutrition remains one of the most pressing global health challenges today, contributing to nearly half of all deaths in children under five years of age. Although insufficient dietary intake and environmental enteric dysfunction are often inciting factors, evidence now suggests that unhealthy gut microbial populations perpetuate the vicious cycle of pathophysiology that results in persistent growth impairment in children. The metagenomics era has facilitated new research identifying an altered microbiome in undernourished hosts and has provided insight into a number of mechanisms by which these alterations may affect growth. This article summarizes a range of observational studies that highlight differences in the composition and function of gut microbiota between undernourished and healthy children; discusses dietary, environmental and host factors that shape this altered microbiome; examines the consequences of these changes on host physiology; and considers opportunities for microbiome-targeting therapies to combat the global challenge of child undernutrition.