Nutritional profile of rodent diets impacts experimental reproducibility in microbiome preclinical research

Optimized breath analysis: customized analytical methods and enhanced workflow for broader detection of VOCs

INTRODUCTION

Breath Volatile organic compounds (VOCs) are promising biomarkers for clinical purposes due to their unique properties. Translation of VOC biomarkers into the clinic depends on identification and validation: a challenge requiring collaboration, well-established protocols, and cross-comparison of data. Previously, we developed a breath collection and analysis method, resulting in 148 breath-borne VOCs identified.

OBJECTIVES

To develop a complementary analytical method for the detection and identification of additional VOCs from breath. To develop and implement upgrades to the methodology for identifying features determined to be "on-breath" by comparing breath samples against paired background samples applying three metrics: standard deviation, paired t-test, and receiver-operating-characteristic (ROC) curve.

METHODS

A thermal desorption (TD)-gas chromatography (GC)-mass spectrometry (MS)-based analytical method utilizing a PEG phase GC column was developed for the detection of biologically relevant VOCs. The multi-step VOC identification methodology was upgraded through several developments: candidate VOC grouping schema, ion abundance correlation based spectral library creation approach, hybrid alkane-FAMES retention indexing, relative retention time matching, along with additional quality checks. In combination, these updates enable highly accurate identification of breath-borne VOCs, both on spectral and retention axes.

RESULTS

A total of 621 features were statistically determined as on-breath by at least one metric (standard deviation, paired t-test, or ROC). A total of 38 on-breath VOCs were able to be confidently identified from comparison to chemical standards.

CONCLUSION

The total confirmed on-breath VOCs is now 186. We present an updated methodology for high-confidence VOC identification, and a new set of VOCs commonly found on-breath.

Nutrient Stability in NASA Spaceflight Experiment Rodent Food Bars

The Nutrient-upgraded Rodent Food Bar (NuRFB) is the standard diet for mice in NASA's Rodent Research Project aboard the International Space Station (ISS). Given the nature of spaceflight and the lengthy production process of the food bars, a shelf-life assessment was conducted to evaluate nutritional stability over time (ranging from 0 to 27 months) and under different storage conditions (refrigerated, ambient, and refrigerated + ambient), where ambient is 22-23 °C. Lipid oxidation markers and fat- and water-soluble vitamins were assessed under various time and temperature conditions using AOAC International methods. Vitamin D levels showed a minor decrease, and riboflavin fluctuated slightly over time, but all vitamin levels remained above National Research Council (NRC) minimum requirements. Food bars stored at 4 °C showed significantly higher thiamine levels than the bars that underwent some degree of ambient temperature storage, but all met the NRC guidelines. Minimal lipid oxidation was observed for up to 18 months, and no mold or yeast growth occurred despite the high moisture content of the bars. This study confirms that NuRFBs maintain stable vitamin and lipid oxidation indices, ensuring adequate nutrition for rodents during spaceflight.

Approaches to nutritional research using organoids; fructose treatment induces epigenetic changes in liver organoids

Nutritional researches have successfully used animal models to gain new insights into nutrient action. However, comprehensive descriptions of their molecular mechanisms of action remain elusive as appropriate in vitro evaluation systems are lacking. Organoid models can mimic physiological structures and reproduce in vivo functions, making them increasingly utilized in biomedical research for a better understand physiological and pathological phenomena. Therefore, organoid modeling can be a powerful approach for to understand the molecular mechanisms of nutrient action. The present study aims to demonstrate the utility of organoids in nutritional research by further investigating the molecular mechanisms responsible for the negative effects of fructose intake using liver organoids. Here, we treated liver organoids with fructose and analyzed their gene expression profiles and DNA methylation levels. Microarray analysis demonstrated that fructose-treated organoids exhibited increased selenoprotein p (Sepp1) gene expression, whereas pyrosequencing assays revealed reduced DNA methylation levels in the Sepp1 region. These results were consistent with observations using hepatic tissues from fructose-fed rats. Conversely, no differences in Sepp1 mRNA and DNA methylation levels were observed in two-dimensional cells. These results suggest that organoids serve as an ideal in vitro model to recapitulate in vivo tissue responses and help to validate the molecular mechanisms of nutrient action compared to conventional cellular models.

Sex- and Age-Specific Differences in Mice Fed a Ketogenic Diet

The ketogenic diet (KD) is a high-fat, low-carbohydrate diet that results in the elevation of serum ketone bodies, known as ketosis. This metabolic consequence has been suggested as a method for treating neurological conditions, improving exercise performance, and facilitating weight loss for overweight individuals. However, since most research primarily uses male populations, little is known about the potential sex differences during the consumption of the KD. In addition, the effects of the KD on aging are relatively unexplored. Therefore, the purpose of this study was to explore sex- and age-specific differences in mice fed the KD. Male and female C57BL/6N mice at either 12 wks or 24 wks of age were randomly assigned to a KD (90% fat, 1% carbohydrate) or chow (13% fat, 60% carbohydrate) group for 6 wks. KD induced weight gain, increased adiposity, induced hyperlipidemia, caused lipid accumulation in the heart and liver, and led to glycogen depletion in the heart, liver, and muscle with varying degrees of changes depending on age and sex. While younger and older male mice on the KD were prone to glucose intolerance, the KD acutely improved rotarod performance in younger females. Overall, this study highlights potential sex and aging differences in the adaptation to the KD.

Alcohol consumption during pregnancy differentially affects the fecal microbiota of dams and offspring

Microbiota imbalances are linked to inflammation and disease, as well as neurodevelopmental conditions where they may contribute to behavioral, physiological, and central nervous system dysfunction. By contrast, the role of the microbiota in Fetal Alcohol Spectrum Disorder (FASD), the group of neurodevelopmental conditions that can occur following prenatal alcohol exposure (PAE), has not received similar attention. Here we utilized a rodent model of alcohol consumption during pregnancy to characterize the impact of alcohol on the microbiota of dam-offspring dyads. Overall, bacterial diversity decreased in alcohol-consuming dams and community composition differed from that of controls in alcohol-consuming dams and their offspring. Bacterial taxa and predicted biochemical pathway composition were also altered with alcohol consumption/exposure; however, there was minimal overlap between the changes in dams and offspring. These findings illuminate the potential importance of the microbiota in the pathophysiology of FASD and support investigation into novel microbiota-based interventions.

Coffee polyphenols ameliorate early-life stress-induced cognitive deficits in male mice

Stress exposure during the sensitive period of early development has been shown to program the brain and increases the risk to develop cognitive deficits later in life. We have shown earlier that early-life stress (ES) leads to cognitive decline at an adult age, associated with changes in adult hippocampal neurogenesis and neuroinflammation. In particular, ES has been shown to affect neurogenesis rate and the survival of newborn cells later in life as well as microglia, modulating their response to immune or metabolic challenges later in life. Both of these processes possibly contribute to the ES-induced cognitive deficits. Emerging evidence by us and others indicates that early nutritional interventions can protect against these ES-induced effects through nutritional programming. Based on human metabolomics studies, we identified various coffee-related metabolites to be part of a protective molecular signature against cognitive decline in humans. Caffeic and chlorogenic acids are coffee-polyphenols and have been described to have potent anti-oxidant and anti-inflammatory actions. Therefore, we here aimed to test whether supplementing caffeic and chlorogenic acids to the early diet could also protect against ES-induced cognitive deficits. We induced ES via the limited nesting and bedding paradigm in mice from postnatal(P) day 2-9. On P2, mice received a diet to which 0.02% chlorogenic acid (5-O-caffeoylquinic acid) + 0.02% caffeic acid (3',4'-dihydroxycinnamic acid) were added, or a control diet up until P42. At 4 months of age, all mice were subjected to a behavioral test battery and their brains were stained for markers for microglia and neurogenesis. We found that coffee polyphenols supplemented early in life protected against ES-induced cognitive deficits, potentially this is mediated by the survival of neurons or microglia, but possibly other mechanisms not studied here are mediating the effects. This study provides additional support for the potential of early nutritional interventions and highlights polyphenols as nutrients that can protect against cognitive decline, in particular for vulnerable populations exposed to ES.

Sex-dependent effects of carbohydrate source and quantity on caspase-1 activity in the mouse central nervous system

BACKGROUND

Mounting evidence links glucose intolerance and diabetes as aspects of metabolic dysregulation that are associated with an increased risk of developing dementia. Inflammation and inflammasome activation have emerged as a potential link between these disparate pathologies. As diet is a key factor in both the development of metabolic disorders and inflammation, we hypothesize that long term changes in dietary factors can influence nervous system function by regulating inflammasome activity and that this phenotype would be sex-dependent, as sex hormones are known to regulate metabolism and immune processes.

METHODS

5-week-old male and female transgenic mice expressing a caspase-1 bioluminescent reporter underwent cranial window surgeries and were fed control (65% complex carbohydrates, 15% fat), high glycemic index (65% carbohydrates from sucrose, 15% fat), or ketogenic (1% complex carbohydrates, 79% fat) diet from 6 to 26 weeks of age. Glucose regulation was assessed with a glucose tolerance test following a 4-h morning fast. Bioluminescence in the brain was quantified using IVIS in vivo imaging. Blood cytokine levels were measured using cytokine bead array. 16S ribosomal RNA gene amplicon sequencing of mouse feces was performed to assess alterations in the gut microbiome. Behavior associated with these dietary changes was also evaluated.

RESULTS

The ketogenic diet caused weight gain and glucose intolerance in both male and female mice. In male mice, the high glycemic diet led to increased caspase-1 biosensor activation over the course of the study, while in females the ketogenic diet drove an increase in biosensor activation compared to their respective controls. These changes correlated with an increase in inflammatory cytokines present in the serum of test mice and the emergence of anxiety-like behavior. The microbiome composition differed significantly between diets; however no significant link between diet, glucose tolerance, or caspase-1 signal was established.

CONCLUSIONS

Our findings suggest that diet composition, specifically the source and quantity of carbohydrates, has sex-specific effects on inflammasome activation in the central nervous system and behavior. This phenotype manifested as increased anxiety in male mice, and future studies are needed to determine if this phenotype is linked to alterations in microbiome composition.

Therapeutic Effects of Anti-Inflammatory and Anti-Oxidant Nutritional Supplementation in Retinal Ischemic Diseases

Appropriate nutrients are essential for cellular function. Dietary components can alter the risk of systemic metabolic diseases, including cardiovascular diseases, cancer, diabetes, and obesity, and can also affect retinal diseases, including age-related macular degeneration, diabetic retinopathy, and glaucoma. Dietary nutrients have been assessed for the prevention or treatment of retinal ischemic diseases and the diseases of aging. In this article, we review clinical and experimental evidence concerning the potential of some nutritional supplements to prevent or treat retinal ischemic diseases and provide further insights into the therapeutic effects of nutritional supplementation on retinopathies. We will review the roles of nutrients in preventing or protecting against retinal ischemic diseases.

Standard rodent diets differentially impact alcohol consumption, preference, and gut microbiome diversity

Alcohol use disorder (AUD) is a complex and widespread disease with limited pharmacotherapies. Preclinical animal models of AUD use a variety of voluntary alcohol consumption procedures to recapitulate different phases of AUD, including binge alcohol consumption and dependence. However, voluntary alcohol consumption in mice is widely variable, making it difficult to reproduce results across labs. Accumulating evidence indicates that different brands of commercially available rodent chow can profoundly influence alcohol intake. In this study, we investigated the effects of three commercially available and widely used rodent diet formulations on alcohol consumption and preference in C57BL/6 J mice using the 24 h intermittent access procedure. The three brands of chow tested were LabDiet 5,001 (LD5001), LabDiet 5,053 (LD5053), and Teklad 2019S (TL2019S) from two companies (Research Diets and Envigo, respectively). Mice fed LD5001 and LD5053 displayed higher levels of alcohol consumption and preference compared to mice fed TL2019S. We also found that alcohol consumption and preference could be rapidly switched by changing the diet 48 h prior to alcohol administration. Sucrose, saccharin, and quinine preferences were not altered, suggesting that the diets did not alter sweet and bitter taste perception. We also found that mice fed LD5001 displayed increased quinine-resistant alcohol intake compared to mice fed TL2019S, suggesting that diets could influence the development of compulsive behaviors such as alcohol consumption. We profiled the gut microbiome of water- and alcohol-drinking mice that were maintained on different diets and found significant differences in bacterial alpha- and beta-diversities, which could impact the gut-brain axis signaling and alcohol consumption.

Grain versus AIN: Common rodent diets differentially affect health outcomes in adult C57BL/6j mice

Semi-synthetic and grain-based diets are common rodent diets for biomedical research. Both diet types are considered nutritionally adequate to support breeding, growth, and long life, yet there are fundamental differences between them that may affect metabolic processes. We have characterized the effects of diet type on breeding outcomes, metabolic phenotype, and microbiota profile in adult mice. Healthy 8-week-old female and male C57BL/6J mice were fed a semi-synthetic or a grain-based diet for 12 weeks and changes in body weight and body composition were monitored. Breeding outcomes were determined. Body fat accumulation of female mice was lower on the semi-synthetic diet than on the grain-based diet. Pregnancy rate and newborn pup survival appeared to be lower in mice exposed to semi-synthetic diet compared to grain-based diet. Both female and male mice showed a profound change in fecal microbiota alpha and beta diversity depending on diet type. Our study shows that type of rodent diet may affect breeding outcomes whilst influencing metabolism and health of female laboratory mice. These factors have the potential to influence other experimental outcomes and the results suggest that semi-synthetic and grain-based diets are not interchangeable in research using rodent models. Careful consideration and increased understanding of the consequences of diet choice would lead to improvements in experimental design and reproducibility of study results.

Differences in enteric neuronal density in the NSE-Noggin mouse model across institutes

The enteric nervous system (ENS) is a large and complex part of the peripheral nervous system, and it is vital for gut homeostasis. To study the ENS, different hyper- and hypo-innervated model systems have been developed. The NSE-Noggin mouse model was described as one of the few models with a higher enteric neuronal density in the colon. However, in our hands NSE-Noggin mice did not present with a hyperganglionic phenotype. NSE-Noggin mice were phenotyped based on fur appearance, genotyped and DNA sequenced to demonstrate transgene and intact NSE-Noggin-IRES-EGFP construct presence, and RNA expression of Noggin was shown to be upregulated. Positive EGFP staining in the plexus of NSE-Noggin mice also confirmed Noggin protein expression. Myenteric plexus preparations of the colon were examined to quantify both the overall density of enteric neurons and the proportions of enteric neurons expressing specific subtype markers. The total number of enteric neurons in the colonic myenteric plexus of transgenic mice did not differ significantly from wild types, nor did the proportion of calbindin, calretinin, or serotonin immunoreactive myenteric neurons. Possible reasons as to why the hyperinnervated phenotype could not be observed in contrast with original studies using this mouse model are discussed, including study design, influence of microbiota, and other environmental variables.

Standard rodent diets differentially impact alcohol consumption and preference and gut microbiome diversity

Alcohol Use Disorder (AUD) is a complex and widespread disease with limited pharmacotherapies. Preclinical animal models of AUD use a variety of voluntary alcohol consumption procedures to recapitulate different phases of AUD including binge alcohol consumption and dependence. However, voluntary alcohol consumption in mice is widely variable rendering it difficult to reproduce results across labs. Accumulating evidence indicates that different brands of commercially available rodent chow can profoundly influence alcohol intake. In this study, we investigated the effects of three commercially available and widely used rodent diet formulations on alcohol consumption and preference in C57BL/6J mice using the 24h intermittent access procedure. The three brands of chow tested were LabDiet 5001 (LD 5001), LabDiet 5053 (LD 5053), and Teklad 2019S (TL2019S) from two companies (Research Diets and Envigo respectively). Mice fed LD5001 displayed the highest levels of alcohol consumption and preference followed by LD5053 and TL2019S. We also found that alcohol consumption and preference could be rapidly switched by changing the diet 48h prior to alcohol administration. Sucrose, saccharin, and quinine preference were not altered suggesting that the diets did not alter taste perception. We also found that mice fed LD5001 displayed increased quinine-resistant alcohol intake compared to mice fed TL2019S, suggesting that diets could influence the development of "compulsive" like alcohol consumption. We profiled the gut microbiome of water and alcohol drinking mice that were maintained on different diets and found significant differences in bacterial alpha and beta diversity, which could impact gut-brain axis signaling and alcohol consumption.

Resistance exercise protects mice from protein-induced fat accretion

Low-protein (LP) diets extend the lifespan of diverse species and are associated with improved metabolic health in both rodents and humans. Paradoxically, many athletes and bodybuilders consume high-protein (HP) diets and protein supplements, yet are both fit and metabolically healthy. Here, we examine this paradox using weight pulling, a validated progressive resistance exercise training regimen, in mice fed either an LP diet or an isocaloric HP diet. We find that despite having lower food consumption than the LP group, HP-fed mice gain significantly more fat mass than LP-fed mice when not exercising, while weight pulling protected HP-fed mice from this excess fat accretion. The HP diet augmented exercise-induced hypertrophy of the forearm flexor complex, and weight pulling ability increased more rapidly in the exercised HP-fed mice. Surprisingly, exercise did not protect from HP-induced changes in glycemic control. Our results confirm that HP diets can augment muscle hypertrophy and accelerate strength gain induced by resistance exercise without negative effects on fat mass, and also demonstrate that LP diets may be advantageous in the sedentary. Our results highlight the need to consider both dietary composition and activity, not simply calories, when taking a precision nutrition approach to health.

High-Soluble-Fiber Diet Attenuates Hypoxia-Induced Vascular Remodeling and the Development of Hypoxic Pulmonary Hypertension

BACKGROUND

Hypoxic pulmonary hypertension is a difficult disease to manage that is characterized by sustained elevation of pulmonary vascular resistance and pulmonary artery pressure due to vasoconstriction, perivascular inflammation, and vascular remodeling. Consumption of soluble-fiber is associated with lower systemic blood pressure, but little is known about its ability to affect the pulmonary circulation.

METHODS

Mice were fed either a low- or high-soluble-fiber diet (0% or 16.9% inulin) and then exposed to hypoxia (FiO2, 0.10) for 21 days to induce pulmonary hypertension. The impact of diet on right ventricular systolic pressure and pulmonary vascular resistance was determined in vivo or in ex vivo isolated lungs, respectively, and correlated with alterations in the composition of the gut microbiome, plasma metabolome, pulmonary inflammatory cell phenotype, and lung proteome.

RESULTS

High-soluble-fiber diet increased the abundance of short-chain fatty acid-producing bacteria, with parallel increases in plasma propionate levels, and reduced the abundance of disease-related bacterial genera such as Staphylococcus, Clostridioides, and Streptococcus in hypoxic mice with parallel decreases in plasma levels of p-cresol sulfate. High-soluble-fiber diet decreased hypoxia-induced elevations of right ventricular systolic pressure and pulmonary vascular resistance. These changes were associated with reduced proportions of interstitial macrophages, dendritic cells, and nonclassical monocytes. Whole-lung proteomics revealed proteins and molecular pathways that may explain the effect of soluble-fiber supplementation.

CONCLUSIONS

This study demonstrates for the first time that a high-soluble-fiber diet attenuates hypoxia-induced pulmonary vascular remodeling and the development of pulmonary hypertension in a mouse model of hypoxic pulmonary hypertension and highlights diet-derived metabolites that may have an immuno-modulatory role in the lung.

The Low-FODMAP Diet, IBS, and BCFAs: Exploring the Positive, Negative, and Less Desirable Aspects-A Literature Review

The literature about the association of branched short-chain fatty acids (BCFAs) and irritable bowel syndrome (IBS) is limited. BCFAs, the bacterial products of the catabolism of branched-chain amino acids, are proposed as markers for colonic protein fermentation. IBS is a gastrointestinal disorder characterized by low-grade inflammation and intestinal dysbiosis. The low-FODMAP diet (LFD) has increasingly been applied as first-line therapy for managing IBS symptoms, although it decreases the production of short-chain fatty acids (SCFA), well known for their anti-inflammatory action. In parallel, high protein consumption increases BCFAs. Protein fermentation alters the colonic microbiome through nitrogenous metabolites production, known for their detrimental effects on the intestinal barrier promoting inflammation. Purpose: This review aims to explore the role of BCFAs on gut inflammation in patients with IBS and the impact of LFD in BCFAs production. Methods: A literature search was carried out using a combination of terms in scientific databases. Results: The included studies have contradictory findings about how BCFAs affect the intestinal health of IBS patients. Conclusions: Although evidence suggests that BCFAs may play a protective role in gut inflammation, other metabolites of protein fermentation are associated with gut inflammation. Further research is needed in order to clarify how diet protein composition and, consequently, the BCFAs are implicated in IBS pathogenesis or in symptoms management with LFD+.

Diet-microbiota interaction in irritable bowel syndrome: looking beyond the low-FODMAP approach

BACKGROUND

Diet is one of the main modulators of the gut microbiota, and dietary patterns are decisive for gut-microbiota-related diseases, including irritable bowel syndrome (IBS). The low-FODMAP diet (LFD) is commonly used to treat IBS, but its long-term effects on microbiota, symptoms and quality of life (QoL) are unclear. Alternative dietary strategies promoting beneficial gut microbiota, combined with reduced symptoms and improved QoL, are therefore of interest.

AIMS

To review current evidence on the diet-microbiota-interaction as a modulator of IBS pathophysiology, and dietary management of IBS, with particular emphasis on strategies targeting the gut microbiota, beyond the LFD.

METHODS

Literature was identified through PubMed-searches with relevant keywords.

RESULTS

Dietary patterns with a low intake of processed foods and a high intake of plants, such as the Mediterranean diet, promote gut microbiota associated with beneficial health outcomes. In contrast, Western diets with a high intake of ultra-processed foods promote a microbiota associated with disease, including IBS. Increasing evidence points towards dietary strategies consistent with the Mediterranean diet being equal to the LFD in alleviating IBS-symptoms and having a less negative impact on QoL. Timing of food intake is suggested as a gut microbiota modulator, but little is known about its effects on IBS.

CONCLUSIONS

Dietary recommendations in IBS should aim to target the gut microbiota by focusing on improved dietary quality, considering the impact on both IBS-symptoms and QoL. Increased intake of whole foods combined with a regular meal pattern and limitation of ultra-processed foods can be beneficial strategies beyond the LFD.

Chowing down: diet considerations in rodent models of metabolic disease

Diet plays a substantial role in the etiology, progression, and treatment of chronic disease and is best considered as a multifaceted set of modifiable input variables with pleiotropic effects on a variety of biological pathways spanning multiple organ systems. This brief review discusses key issues related to the design and conduct of diet interventions in rodent models of metabolic disease and their implications for interpreting experiments. We also make specific recommendations to improve rodent diet studies to help better understand the role of diet on metabolic physiology and thereby improve our understanding of metabolic disease.

Comparison of the Nutritional Status of Swiss Albino Mice Fed on Either a Purified or Cereal-Based Diet for 15 weeks

Background

Laboratory animals are commonly fed on cereal-based diets (CBDs) whose nutrient composition is unknown and may confound the metabolic response to study interventions. Purified diets such as AIN-93M are therefore recommended, as their nutrient composition is known. However, few studies have evaluated their use as adequate control diets. The aim of this study was to compare the nutrition status of Swiss albino mice fed on either CBD or AIN-93M for 15 weeks.

Methods

Twenty Swiss albino mice aged 6-8 weeks and weighing 21.7 g ± 0.6 were fed on either CBD or AIN-93M diet for 15 weeks. Their nutritional status was evaluated using anthropometric and hematological indices, serum glucose, total protein, albumin, and total cholesterol to select an appropriate normal control diet.

Results

The CBD had low-calorie content (2.57 kcal/g) and protein (11 ± 3.8 g/100 g) compared to AIN-93M (3.8 kcal/g and 14 g/100 g, respectively). The BMI of male mice fed on CBD and AIN-93M diets was significantly higher (P=0.0139 and P=0.0325, respectively) compared to that of females fed on similar diets. Animals in the CBD group had lower hemoglobin (15.1-16.9 g/dl) compared to those in the AIN-93M group (18.1-20.8 g/dl). Serum albumin levels were higher in both male (P=0.001) and female (P=3 × 10^-6) mice fed on AIN-93M compared to those fed on CBD. Females in the AIN-93M group had higher cholesterol (P=0.026) than those in the CBD group.

Conclusion

The AIN-93 diet of caloric value 3.85 kcal/g (total protein 14 g, total fat 4 g of soy bean oil, fibre 5 g, and total carbohydrate 42 g per 100 g) can be safely used as a normal control diet in long-term research studies using Swiss albino mice.

Maternal fiber deprivation alters microbiota in offspring, resulting in low-grade inflammation and predisposition to obesity

Diet, especially fiber content, plays an important role in sustaining a healthy gut microbiota, which promotes intestinal and metabolic health. Another major determinant of microbiota composition is the specific microbes that are acquired early in life, especially maternally. Consequently, we hypothesized that alterations in maternal diet during lactation might lastingly impact the microbiota composition and health status of offspring. Accordingly, we observed that feeding lactating dams low-fiber diets resulted in offspring with lasting microbiota dysbiosis, including reduced taxonomic diversity and increased abundance of Proteobacteria species, despite the offspring consuming a fiber-rich diet. Such microbiota dysbiosis was associated with increased encroachment of bacteria into inner mucus layers, low-grade gut inflammation, and a dramatically exacerbated microbiota-dependent increase in adiposity following exposure to an obesogenic diet. Thus, maternal diet is a critical long-lasting determinant of offspring microbiota composition, impacting gut health and proneness to obesity and its associated disorders.

Modulation of microbiome diversity and cytokine expression is influenced in a sex-dependent manner during aging

The microbiome and immune system have a unique interplay, which influences homeostasis within the organism. Both the microbiome and immune system play important roles in health and diseases of the aged including development of cancer, autoimmune disorders, and susceptibility to infection. Various groups have demonstrated divergent changes in the gut microbiota during aging, yet the compounding factor of biological sex within the context of aging remains incompletely understood, and little is known about the effect of housing location in the composition of gut microbiota in the context of both sex and age. To better understand the roles of sex, aging, and location in influencing the gut microbiome, we obtained normal healthy BALB/cByJ mice from a single source and aged male and female mice in two different geographical locations. The 16S rRNA was analyzed from fecal samples of these mice and cytokine levels were measured from serum.16S rRNA microbiome analysis indicated that both age and sex play a role in microbiome composition, whereas location plays a lesser role in the diversity present. Interestingly, microbiome changes occurred with alterations in serum expression of several different cytokines including IL-10 and IL-6, which were also both differentially regulated in context to sex and aging. We found both IL-10 and IL-6 play a role in the constitutive expression of pSTAT-3 in CD5+ B-1 cells, which are known to regulate the microbiome. Additionally, significant correlations were found between cytokine expression and significantly abundant microbes. Based on these results, we conclude aging mice undergo sex-associated alterations in the gut microbiome and have a distinct cytokine profile. Further, there is significant interplay between B-1 cells and the microbiome which is influenced by aging in a sex-dependent manner. Together, these results illustrate the complex interrelationship among sex, aging, immunity, housing location, and the gut microbiome.

A High-Sugar Diet Consumption, Metabolism and Health Impacts with a Focus on the Development of Substance Use Disorder: A Narrative Review

Carbohydrates are important macronutrients in human and rodent diet patterns that play a key role in crucial metabolic pathways and provide the necessary energy for proper body functioning. Sugar homeostasis and intake require complex hormonal and nervous control to proper body energy balance. Added sugar in processed food results in metabolic, cardiovascular, and nervous disorders. Epidemiological reports have shown enhanced consumption of sweet products in children and adults, especially in reproductive age and in pregnant women, which can lead to the susceptibility of offspring's health to diseases in early life or in adulthood and proneness to mental disorders. In this review, we discuss the impacts of high-sugar diet (HSD) or sugar intake during the perinatal and/or postnatal periods on neural and behavioural disturbances as well as on the development of substance use disorder (SUD). Since several emotional behavioural disturbances are recognized as predictors of SUD, we also present how HSD enhances impulsive behaviour, stress, anxiety and depression. Apart from the influence of HSD on these mood disturbances, added sugar can render food addiction. Both food and addictive substances change the sensitivity of the brain rewarding neurotransmission signalling. The results of the collected studies could be important in assessing sugar intake, especially via maternal dietary patterns, from the clinical perspective of SUD prevention or pre-existing emotional disorders. Methodology: This narrative review focuses on the roles of a high-sugar diet (HSD) and added sugar in foods and on the impacts of glucose and fructose on the development of substance use disorder (SUD) and on the behavioural predictors of drugs abuse. The literature was reviewed by two authors independently according to the topic of the review. We searched the PubMed and Scopus databases and Multidisciplinary Digital Publishing Institute open access scientific journals using the following keyword search strategy depending on the theme of the chapter: "high-sugar diet" OR "high-carbohydrate diet" OR "sugar" OR "glucose" OR "fructose" OR "added sugar" AND keywords. We excluded inaccessible or pay-walled articles, abstracts, conference papers, editorials, letters, commentary, and short notes. Reviews, experimental studies, and epidemiological data, published since 1990s, were searched and collected depending on the chapter structure. After the search, all duplicates are thrown out and full texts were read, and findings were rescreened. After the selection process, appropriate papers were included to present in this review.

The development, but not expression, of alcohol front-loading in C57BL/6J mice maintained on LabDiet 5001 is abolished by maintenance on Teklad 2920x rodent diet

BACKGROUND

Excessive alcohol (ethanol) consumption, such as binge drinking, is extremely commonplace and represents a major health concern. Through modeling excessive drinking in rodents, we are beginning to uncover the neurobiological and neurobehavioral causes and consequences of this pattern of ethanol intake. One important factor for modeling binge drinking in mice is that they reliably drink to blood ethanol concentrations (BECs) of 80 mg/dl or higher. Drinking-in-the-dark (DID) is a commonly used mouse model of binge drinking, and we have shown that this method reliably results in robust ethanol front-loading and binge-level BECs in C57BL/6J (B6) mice and other ethanol-preferring mouse strains/lines. However, establishing the DID model in a new vivarium space forced us to consider the use of rodent diet formulations that we had not previously used.

METHODS

The current set of experiments were designed to investigate the role of two standard rodent diet formulations on binge drinking and the development of ethanol front-loading using DID.

RESULTS

We found that BECs in animals maintained on LabDiet 5001 (LD01) were double those found in mice maintained on Teklad 2920x (TL20). Interestingly, this effect was paralleled by differences in the degree of front-loading, such that LD01-fed mice consumed approximately twice as much ethanol in the first 15 min of the 2-h DID sessions as the TL20-fed mice. Surprisingly, however, mice that developed front-loading during maintenance on the LD01 diet continued to display front-loading behavior after being switched to the TL20 diet.

CONCLUSIONS

These data emphasize the importance of choosing and reporting diet formulations when conducting voluntary drinking studies and support the need for further investigation into the mechanisms behind diet-induced differences in binge drinking, particularly front-loading.

Dysbiosis of the gut microbiome impairs mouse skeletal muscle adaptation to exercise

There is emerging evidence of a gut microbiome-skeletal muscle axis. The purpose of this study was to determine if an intact gut microbiome was necessary for skeletal muscle adaptation to exercise. Forty-two 4-month-old female C57BL/6J mice were randomly assigned to untreated (U) or antibiotic-treated (T) non-running controls (CU or CT, respectively) or progressive weighted wheel running (PoWeR, P) untreated (PU) or antibiotic-treated (PT) groups. Antibiotic treatment resulted in disruption of the gut microbiome as indicated by a significant depletion of gut microbiome bacterial species in both CT and PT groups. The training stimulus was the same between PU and PT groups as assessed by weekly (12.35 ± 2.06 vs. 11.09 ± 1.76 km/week, respectively) and total (778.9 ± 130.5 vs. 703.8 ± 112.9 km, respectively) running activity. In response to PoWeR, PT showed less hypertrophy of soleus type 1 and 2a fibres and plantaris type 2b/x fibres compared to PU. The higher satellite cell and myonuclei abundance of PU plantaris muscle after PoWeR was not observed in PT. The fibre-type shift of PU plantaris muscle to a more oxidative type 2a fibre composition following PoWeR was blunted in PT. There was no difference in serum cytokine levels among all groups suggesting disruption of the gut microbiome did not induce systemic inflammation. The results of this study provide the first evidence that an intact gut microbiome is necessary for skeletal muscle adaptation to exercise. KEY POINTS: Dysbiosis of the gut microbiome caused by continuous antibiotic treatment did not affect running activity. Continuous treatment with antibiotics did not result in systemic inflammation as indicated by serum cytokine levels. Gut microbiome dysbiosis was associated with blunted fibre type-specific hypertrophy in the soleus and plantaris muscles in response to progressive weighted wheel running (PoWeR). Gut microbiome dysbiosis was associated with impaired PoWeR-induced fibre-type shift in the plantaris muscle. Gut microbiome dysbiosis was associated with a loss of PoWeR-induced myonuclei accretion in the plantaris muscle.

Estrogen receptor actions in colitis

In recent years, researchers have demonstrated that estrogen and its receptors, aside from their role in regulating several biological functions, contribute to the development and progression/severity of inflammatory bowel diseases (IBDs). IBDs include both ulcerative colitis (UC) and Crohn's disease (CD). Epidemiological data indicate a clear difference in the incidence, severity, and complications of IBDs between sexes. Men present a higher risk of developing colitis than women and a higher risk of developing colorectal cancer, a common complication of this condition. However, fluctuations of estrogen levels have yielded inconsistent data, where oral contraceptives and hormone replacement therapy have been associated with an increased risk of IBDs in premenopausal women but significantly reduce disease activity after menopause. Likewise, improvement of symptoms related to CD has been reported during pregnancy, but not in UC, who often experience worsening symptoms. In the colonic epithelium, estrogen receptor β (ERβ) is the predominant form of the protein expressed, and it helps maintain normal epithelial function and organization. Preclinical data suggest that ER expression and activation via estrogen confers different responses on disease severity depending on the model used to induce colitis, which may reflect what is observed in patients with IBDs. Hence, this review aims to provide an overview of estrogen and its receptors, particularly ERβ, in the pathophysiology of IBDs.

High-Coverage Metabolome Analysis Reveals Significant Diet Effects of Autoclaved and Irradiated Feed on Mouse Fecal and Urine Metabolomics

SCOPE

Using metabolomics to study the relations of nutrition and health requires stringent control of the experimental conditions used in an animal model. This work investigates the diet effects of autoclaved and irradiated feed on mouse urine and fecal metabolomics.

METHODS AND RESULTS

C57BL/6 mice are fed normal-irradiation sterilized diet (n = 9), autoclave sterilized diet (n = 9), and high-irradiation sterilized diet (n = 9) for 4 weeks. Differential chemical isotope labeling liquid chromatography mass spectrometry is used to quantify the metabolome variations of urine and feces collected at five time points. Significant differences are observed in urine or fecal metabolomes of mice fed autoclaved diet versus mice fed high-irradiation diet or fed normal-irradiation diet, while the differences are small between the mice fed normal-irradiation and high-irradiation diet. Correlation studies of metabolite changes of diet- and aging-related biomarkers indicate a large overlap of significantly affected metabolites by the two factors.

CONCLUSIONS

Diet can be a confounding factor that needs to be carefully considered when a metabolomics study is designed and metabolomic results of a mouse model of nutritional or other biological study are interpreted. Using the same sterilized diet for a given metabolomics project is essential to control the diet effect.