Synthetic Diet Research Articles

Purified fibers in chemically defined synthetic diets destabilize the gut microbiome of an omnivorous insect model.

The macronutrient composition of a host's diet shapes its gut microbial community, with dietary fiber in particular escaping host digestion to serve as a potent carbon source for gut microbiota. Despite widespread recognition of fiber's importance to microbiome health, nutritional research often fails to differentiate hyper-processed fibers from cell-matrix derived intrinsic fibers, limiting our understanding of how individual polysaccharides influence the gut community. We use the American cockroach (Periplaneta americana) as a model system to dissect the response of complex gut microbial communities to diet modifications that are impossible to test in traditional host models. Here, we designed synthetic diets from lab-grade, purified ingredients to identify how the cockroach microbiome responds to six different carbohydrates (chitin, methylcellulose, microcrystalline cellulose, pectin, starch, xylan) in otherwise balanced diets. We show via 16S rRNA gene profiling that these synthetic diets reduce bacterial diversity and alter the phylogenetic composition of cockroach gut microbiota in a fiber-dependent manner, regardless of the vitamin and protein content of the diet. Comparisons with cockroaches fed whole-food diets reveal that synthetic diets induce blooms in common cockroach-associated taxa and subsequently fragment previously stable microbial correlation networks. Our research leverages an unconventional microbiome model system and customizable lab-grade artificial diets to shed light on how purified polysaccharides, as opposed to nutritionally complex intrinsic fibers, exert substantial influence over a normally stable gut community.

Context-dependent impact of the dietary non-essential amino acid tyrosine on Drosophila physiology and longevity.

Dietary protein intake modulates growth, reproduction, and longevity by stimulating amino acid (AA)-sensing pathways. Essential AAs are often considered as limiting nutrients during protein scarcity, and the role of dietary non-essential AAs (NEAAs) is less explored. Although tyrosine has been reported to be crucial for sensing protein restriction in Drosophila larvae, its effect on adult physiology and longevity remains unclear. Here, using a synthetic diet, we perform a systematic investigation of the effect of single NEAA deprivation on nutrient-sensing pathways, reproductive ability, starvation resistance, feeding behavior, and life span in adult female flies. Specifically, dietary tyrosine deprivation decreases internal tyrosine levels and fecundity, influences AA-sensing machineries, and extends life span. These nutritional responses are not observed under higher total AA intake or in infertile female flies, suggesting a context-dependent influence of dietary tyrosine. Our findings highlight the unique role of tyrosine as a potentially limiting nutrient, underscoring its value for dietary interventions aimed at enhancing health span.

Larval diet impacts black soldier fly (Diptera: Stratiomyidae) thermal tolerance and preference.

Thermal tolerance and preference are key parameters impacting agricultural production systems. In this study, the impact of larval diet on black soldier fly thermal tolerance and preference across life-stages and sexes was examined. Larvae were fed either a low-protein high-carbohydrate synthetic diet (i.e., P7C35), a high-protein low-carbohydrate synthetic diet (i.e., P35C7), or the Gainesville diet (i.e., C) as a control and reference. Our results demonstrate that the impacts of larval diet on black soldier fly thermal tolerance and preference could be stage and sex specific. The mean heat knockdown temperatures (HKT) ranged between 46.6 and 47.9 °C. Synthetic diets resulted in greater HKT and the difference decreased form larvae (e.g., ∼1 °C) to adults (e.g., ∼0.2 °C). The mean chill-coma recovery time (CCRT) ranged between 8.3 and 21.6 min. Not much differences were detected between diets, but CCRT became longer from larvae to adults. The mean thermal preference ranged between 13.6 and 29.5 °C. Larvae fed synthetic diets preferred much lower temperatures than the control diet. A bimodal distribution was observed for adults regardless of sex. Differences on body mass, lipid, and protein contents were detected among diets; however, more research should be done before any conclusions can be linked to their thermal traits. These findings highlight the importance of considering the ingredients and nutritional makeup of larval diets when optimizing temperature management protocols for mass production of black soldier flies. Conversely, specific diets can be developed to promote survival under extreme rearing temperatures.

Fitness effects of synthetic and natural diet preservatives on the edible insect Bombyx mori

Silkworm pupae as widely consumed insect products are good biosources of protein and micronutrients. Silkworm rearing throughout the year can be achieved by feeding them an artificial diet instead of native plants, facilitating extensive pupa production. However, artificial diets are prone to spoilage caused by bacterial contamination. Here, we evaluated the antiseptic effect of ethylparaben (EP, chemical preservative) and medium-chain fatty acids (MCFA, natural preservative) in a silkworm artificial diet. Results showed that both preservatives effectively inhibited pathogenic bacterial growth. Furthermore, the addition of EP or MCFA did not negatively impact the production capacity of silkworms and the homeostasis of gut microbiota. However, the expression of genes involved in detoxification such as Ugt2, and immune response such as Cecropin B, were upregulated after EP consumption. Therefore, natural preservative MCFA emerges as a suitable option from a safety perspective. These findings highlight future directions for improving insect artificial diet formulation.

Impact of aging and ergothioneine pre-treatment on naphthalene toxicity in lung

Aging increases susceptibility to lung disease, but the topic is understudied, especially in relation to environmental exposures with the bulk of rodent studies using young adults. This study aims to define the pulmonary toxicity of naphthalene (NA) and the impacts of a dietary antioxidant, ergothioneine (ET), in the liver and lungs of middle-aged mice. NA causes a well-characterized pattern of conducting airway epithelial injury in the lung in young adult mice, but NA’s toxicity has not been characterized in middle-aged mice, aged 1–1.5 years. ET is a dietary antioxidant that is synthesized by bacteria and fungi. The ET transporter (ETT), SLC22A4, is upregulated in tissues that experience high levels of oxidative stress. In this study, middle-aged male and female C57BL/6 J mice, maintained on an ET-free synthetic diet from conception, were gavaged with 70 mg/kg of ET for five consecutive days. On day 8, the mice were exposed to a single intraperitoneal NA dose of 50, 100, 150, or 200 mg/kg. At 24 hours post NA injection samples were collected and analyzed for ET concentration and reduced (GSH) and oxidized glutathione (GSSG) concentrations. Histopathology, morphometry, and gene expression were examined. Histopathology of mice exposed to 100 mg/kg of NA suggests reduction in toxicity in the terminal airways of both male (p ≤ 0.001) and female (p ≤ 0.05) middle-aged mice by the ET pretreatment. Our findings in this study are the first to document the toxicity of NA in middle-aged mice and show some efficacy of ET in reducing NA toxicity.

Sex-dependent benefit of B vitamins on cardiac function and lipid metabolism in a murine model of heart failure with reduced ejection fraction

Background: Heart failure (HF) is a global health problem requiring more effective therapeutic alternatives. While HF involves disturbances in cardiac metabolism associated with lipidomic remodeling, there is a lack of approaches to specifically target cardiac metabolism. Recently, it has been shown in murine models of HF, that the use of nicotinamide riboside (vitamin B3) alone or the combination of B9 and B12 vitamins, before the development of HF, improved cardiac metabolism and function. Our hypothesis is that the combination of B3, B9 and B12 vitamins, used when HF is declared, will improve lipid metabolism, cardiac function and survival. The aim of this study is to evaluate the curative benefit of a synthetic diet enriched with the combination of these three vitamins (VitB) in a murine model of HF with reduced ejection fraction (EF). Method: Pressure overload was induced by constriction of the transverse aorta (TAC) in male and female mice. After 4 weeks, TAC mice reaching a pressure gradient of 60 mmHg, an increased left ventricle mass >30% and a reduced EF >10%, were randomized to a VitB-enriched diet or not. Results: In females, VitB improved survival and cardiac hypertrophy (-24%, p<0.05) as well as EF (+22%, p<0.01). We also observed a reduction of cardiac fibrosis emphasized by a significant decrease expression of collagen 1a and 3 (-30% and -19% respectively) and hydroxyproline concentration (-32%, p<0.01). No benefit was observed in males in terms of survival, cardiac function and fibrosis. Untargeted mass spectrometry (MS)-based lipidomics on plasmas at 8 weeks of treatment showed a decrease in several individual triglycerides (TG from 43 to 48 %; p<0.05) in TAC females that were normalized by VitB. In contrast, in TAC males, most of the annotated TGs were increased (from ̴35 to 210%; p<0.05), a profile exacerbated upon VitB treatment. MSMS identification of TG side chains revealed a differential profile in terms of fatty acid composition according to sex and treatment. In VitB females, longer and polyunsaturated TGs (53 to 60C; 5 to 12 double bonds) were significantly increased (1.6- to 2.1-fold) while, in VitB males, the increased TGs (1.2- to 5.2-fold) were shorter (24C to 48C) and saturated (no double bonds). Conclusion: Our study pointed out a sexual dimorphism in the response to VitB treatment in HF in favor of females and implying a lipidomic remodeling promoting cardioprotective polyunsaturated TGs. European Research Area Network on Cardiovascular Diseases, Canadian Institutes of Health Research, Fonds de recherche du Québec - Santé. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A recipe for change: Analyzing the climate and ecosystem impacts of the Brazilian diet shift

Diet shift is an opportunity to mitigate the impacts of food systems, which are responsible for about a third of greenhouse gas (GHG) emissions globally and exert various environmental pressures on ecosystems. This study evaluates the mitigation potential of both global and local environmental impacts through dietary changes within the Brazilian context. Furthermore, the study aims to identify the potential benefits and trade-offs that may arise from these dietary transitions, thus providing a comprehensive analysis of the overall environmental implications. To this end, a life cycle assessment (LCA) was performed to evaluate the environmental impacts of a conventional diet in Brazil and seven alternatives, namely adjusted-EAT-Lancet, pescatarian, vegetarian, entomophagic (insect-based food), mycoprotein (microbial-based food), and synthetic (cell-based food) diets. Results indicate a substantial mitigation potential for GHG emissions (4-9 kg CO2e/cap/day) (39 % to 86 %) and land use (4-9 m2/cap/day) (38 % to 82 %) through a diet shift from a conventional diet to any of the seven alternative diets. However, certain trade-offs exist. A diet shift demonstrates no mitigation potential of soil acidification, and opportunities to reduce water eutrophication (0.02-0.2 g Pe/cap/day) (2 % to 24 %) and water consumption (0.2-0.5 m3/cap/day) (7 % to 14 %) were only found by completely substituting animal products for insect-based food, microbial-based food, and cell-based food. This study highlights the considerable potential of dietary changes to mitigate global environmental impacts associated with food systems. By revealing opportunities and challenges, this study supports science-based decision-making and guides efforts toward sustainable and environmentally friendly food consumption patterns.

Evaluation of the use of commercial-type and synthetic diets to test a nucleotide-rich yeast-derived product as a growth promotor for first feeding rainbow trout fry raised at 10 or 16 °C

A nucleotide-rich yeast-derived product (Maxi-Gen™; CBS Bio Platforms, Inc., Calgary AB, Canada), was fed to rainbow trout fry housed at 10 or 16 °C to determine its effect on weight gain and feed intake. Rainbow trout fry housed in 40 16 L tanks (25 fish/tank) were fed commercial-type or synthetic diets with or without the nucleotide-rich yeast product added (0% or 0.5% inclusion) until they reached 60 days of age (5 tanks/4 diets/2 temperatures). Fish housed at 16 °C consumed significantly more feed and gained significantly more weight than fish housed at 10 °C. Trout fed the commercial-type diet gained significantly more weight than those fed the synthetic diet without the nucleotide-rich yeast product added. There was no significant difference in weight gain or feed intake among fish fed either commercial-type diet and the fish fed the synthetic diets with the nucleotide-rich yeast product added, although fish fed the commercial-type diets had significantly better feed conversion efficiencies than those fed the synthetic diets. The nucleotide-rich yeast product could be used in low fish meal, low fish oil first feeding diets, as the aquaculture industry decreases fish meal and oil use in aquafeeds in response to their increasing cost and decreasing availability.

A defined diet for pre-adult Drosophila melanogaster

Drosophila melanogaster is unique among animal models because it has a fully defined synthetic diet available to study nutrient-gene interactions. However, use of this diet is limited to adult studies due to impaired larval development and survival. Here, we provide an adjusted formula that reduces the developmental period, restores fat levels, enhances body mass, and fully rescues survivorship without compromise to adult lifespan. To demonstrate an application of this formula, we explored pre-adult diet compositions of therapeutic potential in a model of an inherited metabolic disorder affecting the metabolism of branched-chain amino acids. We reveal rapid, specific, and predictable nutrient effects on the disease state consistent with observations from mouse and patient studies. Together, our diet provides a powerful means with which to examine the interplay between diet and metabolism across all life stages in an animal model.

Abstract 6608: Therapeutic enzyme depletion of L-serine for the treatment of serine auxotrophic tumors

Abstract The non-essential amino acid L-serine (serine) plays an important role in cancer cell growth due to its diverse biosynthetic functions. In many cancer cells, serine can be taken up from the circulation or can be synthesized through the serine synthesis pathway (SSP). We have recently discovered that luminal breast tumors are auxotrophic for serine due to lineage-specific silencing of the SSP gene PSAT1, rendering luminal breast cancer cells sensitive to serine deprivation both in vitro and in vivo. At present the only way to reduce serine availability for tumors in vivo is through dietary serine starvation, which in mice reduces circulating serine levels by ~50% and has been shown to inhibit the growth of numerous mouse models of cancer. Importantly, dietary serine is achieved in mice using a synthetic protein-free diet that may be difficult for humans to sustain. Nevertheless, dietary serine starvation is currently being explored in a clinical trial for pancreatic cancer. To circumvent some of the challenges associated with dietary serine starvation, we have developed a therapeutic serine degrading enzyme that we are exploring as a potential treatment for serine auxotrophic tumors. Our enzyme, eSDH, is based on the human serine dehydratase enzyme that facilitates the pyridoxal phosphate-dependent irreversible deamination of serine to pyruvate and ammonia. Relative to wild-type serine dehydratase, eSDH has significantly improved stability in serum as well increased activity towards serine. Injection of eSDH into mice is well-tolerated and leads to long-term, near-complete (>95%) reduction in circulating serine levels without the need for dietary changes. Importantly, eSDH treatment inhibits the growth of serine auxotrophic cancer cells in vitro and in vivo. We are currently assessing the efficacy of eSDH treatment in advanced models of luminal/ER+ breast cancer and when utilized in combination with endocrine therapy and other standard-of-care treatments for luminal/ER+ cancer patients. In addition to the degradation of serine, eSDH also depletes circulating L-threonine (threonine), which could contribute to the in vivo activity of eSDH. However, we have recently developed new eSDH variants that are highly selective for serine over threonine and show enhanced specificity for serine auxotrophic cancer cells. In conclusion, we have developed a prototypical therapeutic serine degrading enzyme that may provide an opportunity to clinically achieve more complete serine starvation in patients without the need for restrictive dietary changes. Citation Format: Vipin Rawat, Huiping Zhao, Ladan Mashouri, Prarthana Prasanth, Kelly Conger, Sarita Bhetawal, Alessandra Araujo, Everett Stone, Jonathan Coloff. Therapeutic enzyme depletion of L-serine for the treatment of serine auxotrophic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6608.

Evaluating the Use of Crude and Synthetic Gossypol as Reproduction Bio-control Agents in Coptodon zillii and Oreochromis niloticus

Select this text, right click and click Merge Formatting (B) from the paste options. Two hundred (200) Coptodon zillii and Oreochromis niloticus (10g ±0.13) were subjected to an investigation to uncover the efficiency of crude and synthetic gossypol as reproduction bio-control agents. The treatment groups were five (5) altogether with twenty (20) fish per treatment (male and female 1:1). Each treatment was replicated twice and subjected to the same condition. The fish were fed with five isoproteic experimental diets of 37.5% crude protein for 90 days. In the diets, cottonseed meal (CSM) and synthetic gossypol (GSP) were used to replace soyabean meal (SBM) at 0%, 25%, 50%, 75% and 100% respectively. Histological sections of testes in O. niloticus and C. zillii showed a decline in spermatozoa with increasing inclusion of crude CSM and synthetic gossypol. Diets four and five which has the highest inclusion of both crude and synthetic gossypol (327g CSM/Kg diet, 436g CSM/Kg diet) exhibited spent and empty seminiferous lumina. Ovarian section in C. zillii and O. niloticus showed distortion with increasing inclusion rates of crude CSM and synthetic gossypol; to the point that most of the eggs were still in their early phases of embryonic formation after 90 days trial with prominent vitellogenic stages for 0% 0g (CSM/kg diet) and 25% (109 CSM/kg diet); atretic oocytes for 75% (327g CSM/Kg diet) and 100% (436g CSM/Kg diet). Milt and egg production of both O. niloticus and C. zillii all declined as the dietary inclusion of crude and synthetic gossypol increased. Overall results showed that dietary crude and synthetic gossypol destroyed the spermatocytes and oocytes; lumina was devoid of spermatozoa, subsequent reproduction was inhibited; the eggs were unable to finish their cytological cycles which would have led to fertilization. There were fewer offspring in crude gossypol-based diet treatments and there was no reproduction at all in all the synthetic gossypol-based diet treatments.

A Synthetic Formula Amino Acid Diet Leads to Microbiome Dysbiosis, Reduced Colon Length, Inflammation, and Altered Locomotor Activity in C57BL/6J Mice.

The effects of synthetic, free-amino acid diets, similar to those prescribed as supplements for (phenylketonuria) PKU patients, on gut microbiota and overall health are not well understood. In the current, multidisciplinary study, we examined the effects of a synthetically-derived, low-fiber, amino acid diet on behavior, cognition, gut microbiome composition, and inflammatory markers. A cohort of 20 male C57BL/6J mice were randomly assigned to either a standard or synthetic diet (n = 10) at post-natal day 21 and maintained for 13 weeks. Sequencing of the 16S rRNA gene from fecal samples revealed decreased bacterial diversity, increased abundance of bacteria associated with disease, such as Prevotella, and a downward shift in gut microbiota associated with fermentation pathways in the synthetic diet group. Furthermore, there were decreased levels of short chain fatty acids and shortening of the colon in mice consuming the synthetic diet. Finally, we measured TNF-α, IL-6, and IL-10 in serum, the hippocampus, and colon, and found that the synthetic diet significantly increased IL-6 production in the hippocampus. These results demonstrate the importance of a multidisciplinary approach to future diet and microbiome studies, as diet not only impacts the gut microbiome composition but potentially systemic health as well.

The physiological consequences of a very large natural meal in a voracious marine fish, the staghorn sculpin (Leptocottus armatus).

Little information exists on physiological consequences when wild fish eat natural food. Staghorn sculpins at 10-13°C voluntarily consumed 15.8% of their body mass in anchovies. Gastric clearance was slow with >60% of the meal retained in the stomach at 48 h, and was not complete until 84 h. At 14-24 h post-feeding, pH was depressed by 3 units and Cl- concentration was elevated 2-fold in gastric chyme, reflecting HCl secretion, while in all sections of the intestine, pH declined by 1 pH unit but Cl- concentration remained unchanged. PCO2and total ammonia concentration were greatly elevated throughout the tract, whereas PNH3and HCO3- concentration were depressed. Intestinal HCO3- secretion rates, measured in gut sacs in vitro, were also lower in fed fish. Whole-animal O2 consumption rate was elevated approximately 2-fold for 72 h post-feeding, reflecting 'specific dynamic action', whereas ammonia and urea-N excretion rates were elevated about 5-fold. Arterial blood exhibited a modest 'alkaline tide' for about 48 h, but there was negligible excretion of metabolic base to the external seawater. PaCO2and PaO2remained unchanged. Plasma total amino acid concentration and total lipid concentration were elevated about 1.5-fold for at least 48 h, whereas small increases in plasma total ammonia concentration, PNH3and urea-N concentration were quickly attenuated. Plasma glucose concentration remained unchanged. We conclude that despite the very large meal, slow processing with high efficiency minimizes internal physiological disturbances. This differs greatly from the picture provided by previous studies on aquacultured species using synthetic diets and/or force-feeding. Questions remain about the role of the gastro-intestinal microbiome in nitrogen and acid-base metabolism.

Hypolypidemic Activity of L-Rhamnopyranosyl-6-O-Methyl-D-Galacturonan, a Polysaccharide Isolated from Birch Leaves (Betula pendula L.).

In male Syrian hamsters fed a synthetic high-fat diet enriched with cholesterol (0.3%), administration of a polysaccharide from birch leaves L-rhamnopyranosyl-6-O-methyl-D-galacturonan (3 g/100 g of diet) resulted in a decrease in total cholesterol levels, mainly due to the LDL fraction, triglycerides, and bile acids in blood serum; the content of triglycerides and cholesterol in the liver also decreased, while excretion of bile acids with feces increased. Thus, the lipid-lowering effect of L-rhamnopyranosyl-6-O-methyl-D-galacturonan is related to its ability to bind bile acids in the intestine and interrupt their enterohepatic circulation.

The influence of different dietary patterns on changes in the intestinal microbiota and human body weight

The human gut microbiome responds dynamically to changes in diet, contributing to the diversity of the human diet. The composition of the diet can also influence the metabolic products that are ultimately present in the intestinal lumen and plasma. Observations in humans on vegan, omnivorous, or synthetic enteral diets deficient in fiber have demonstrated dramatic imbalances in the gut microbiome, accompanied by changes in carbohydrate and amino acid-derived bacterial metabolites. It has been established that diet plays a dominant role in the formation of interindividual variations in host-associated microbial communities. Given the impact of the microbial community on human health and its multiple mechanisms of action, establishing the impact of different dietary approaches and models is critical.

Hypolipidemic activity of the polysaccharide L-rhamnopyranosyl-6-O-methyl-galacturonan in combined administration with HMG-CoA reductase and cholesterol absorption inhibitors

Introduction . Dyslipidemia treatment in many cases requires carefully selected combination of lipid-lowering drugs including bile acid sequestrants. A promising compound is L-rhamnopyranosyl-6- O -methyl-galacturonan (L-RAG), a polysaccharide obtained from the birch leaves ( Betula pendula L.). Aim . To evaluate the lipid-lowering activity of L-RAG administered in combination with the HMG-CoA reductase inhibitor rosuvastatin or the cholesterol absorption inhibitor ezetimibe. Materials and methods . Hyperlipidemia in hamsters was reproduced by synthetic diet supplemented with 0.3 % cholesterol and 11 % coconut oil (HFCD). At the end of the experiment the levels of triacylglycerols (TAG), bile acids, total cholesterol (TC), cholesterol of low-density lipoproteins (LDL-C) and high-density lipoproteins (HDL-C) were determined in the blood serum using Chronolab Systems S. L. enzymatic kits (Spain), and atherogenic index (AI) was calculated. Results and discussion . L-RAG demonstrates a lipid-lowering effect in a model of diet-induced hyperlipidemia in hamsters. The decrease in the TC level was mainly caused by a decrease in the content of cholesterol in the atherogenic LDL fraction, which led to a decrease in AI. The use of rosuvastatin and ezetimibe in combination with L-RAG leads to a better lipid-lowering effect. The additive effect of the polysaccharide is mainly due to a decrease in the level of bile acids in the blood serum, which indicates its ability to absorb them in the intestinal lumen and interrupt enterohepatic circulation, acting like bile acid sequestrants. Conclusion . It was shown that administration of L-RAG together with ezetimibe or rosuvastatin led to a better decrease in the TC, TAG, LDL-C levels than with polysaccharide monotherapy or comparison drugs alone. The obtained data substantiate the prospects of using L-RAG in the complex therapy of hyperlipidemia.

Honey bee symbiont buffers larvae against nutritional stress and supplements lysine.

Honey bees have suffered dramatic losses in recent years, largely due to multiple stressors underpinned by poor nutrition [1]. Nutritional stress especially harms larvae, who mature into workers unable to meet the needs of their colony [2]. In this study, we characterize the metabolic capabilities of a honey bee larvae-associated bacterium, Bombella apis (formerly Parasaccharibacter apium), and its effects on the nutritional resilience of larvae. We found that B. apis is the only bacterium associated with larvae that can withstand the antimicrobial larval diet. Further, we found that B. apis can synthesize all essential amino acids and significantly alters the amino acid content of synthetic larval diet, largely by supplying the essential amino acid lysine. Analyses of gene gain/loss across the phylogeny suggest that four amino acid transporters were gained in recent B. apis ancestors. In addition, the transporter LysE is conserved across all sequenced strains of B. apis. Finally, we tested the impact of B. apis on developing honey bee larvae subjected to nutritional stress and found that larvae supplemented with B. apis are bolstered against mass reduction despite limited nutrition. Together, these data suggest a novel role of B. apis as a nutritional mutualist of honey bee larvae.

Abstract 3523: A Black Raspberry dietary intervention to modify the gut microbiome and improve the response to immune checkpoint inhibitors

Abstract Lung cancer kills more people annually worldwide than any other cancer. Outcomes have improved with the use of immune checkpoint inhibitor (ICI) treatment, however, only about 20% of tumors respond. Emerging data demonstrate that responses to ICI may depend on the host microbiome. The challenge is to identify strategies to manipulate the gut microbiome to improve response to ICIs. Here we explore a targeted dietary intervention to modify the microbiome and determine the response to ICIs. Studies in a preclinical murine model showed that freeze-dried black raspberry powder (AIN-76A synthetic diet containing 5% lyophilized black raspberry powder) increased the abundance of Akkermansia muciniphila, which has been associated with improved response to ICIs in melanoma. Next, we conducted a human intervention trial called the BEWELL Study (Black raspberry nEctar Working to prEvent Lung cancer NCT04267874). This placebo-controlled, randomized, cross-over trial examined the impact of 2x 80 mL black raspberry (BRB) nectar drink boxes per day for 4 weeks. There were 96 participants recruited and classified as being at high risk of developing lung cancer (eligibility criteria: >30 pack-year smoking history and 55-77 years old) in an attempt to match the phenotype of typical lung cancer patients but allowing us to clearly assess the impact of the intervention on the microbiome. Pre- and post-dietary intervention gut microbiome, blood, and urine samples were collected. Black raspberry dietary supplementation was not associated with a significant change in A. muciniphila (logistic regression with negative binomial Wald test p-value 0.056), however, changes in other taxa were observed. Finally, stool from participants in the BEWELL study was gavaged into C57BL/6J mice to create human microbiome avatar models. Mouse colon cancer cells (mc38) were injected subcutaneously and treated with anti-PD1 Ab (5mg/kg mouse; clone RMP1-14) or isotype control (clone 2A3). Preliminary experiments using avatar mice with post-BRB human microbiomes showed smaller tumors relative to mice receiving stool from that same individual pre-BRB dietary intervention, relative to isotype control (t-test, p-value 0.05). These results suggest that black raspberry nectar may modify the human gut microbiome in a way that promotes an improved response to immunotherapy. Citation Format: Amna Bibi, Aaditya Pallerla, Nyelia Williams, Caroline Wheeler, Rebecca Hoyd, Shankar Suman, Joseph Amann, Mounika Goruganthu, Tamio Okimoto, Yangyang Liu, Marisa Bittoni, Ni Shi, Shiqi Zhang, Alvin Anand, Kristen Heitman, Maxine Mendelson, Elizabeth M. Grainger, Madison Grogan, Carolyn J. Presley, Fred K. Tabung, Lang Li, Yael Vodovotz, Jiangjiang Zhu, David P. Carbone, Tong Chen, Steven K. Clinton, Daniel Spakowicz. A Black Raspberry dietary intervention to modify the gut microbiome and improve the response to immune checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3523.

Impact of Oil Sources on In Vitro Fermentation, Microbes, Greenhouse Gas, and Fatty Acid Profile in the Rumen

This study estimated the effects of oil sources on fermentation characteristics, greenhouse gas, microbial diversity, and biohydrogenation of fatty acids in the rumen. In vitro ruminal incubation was performed with 7 mg of oil source, 15 mL rumen buffer, and 150 mg of synthetic diet at 39 °C for 0, 3, 6, 12, and 24 h. Oil sources consisted of corn oil (CO; linoleic acid (C18:2n-6)), linseed oil (LSO; linolenic acid (C18:3n-3)), or Ca-salts (protected C18:2n-6). The ruminal gas was collected for CH4 and CO2 analysis. Incubated rumen buffer was sub-sampled for the analysis of microbial quantification, fermentation characteristics, and fatty acid profiles. The results showed that Ca-salt increased acetate (p = 0.013), while CO increased propionate (p = 0.007). Fibrobacter succinogenes, Ruminococcus flavefaciens, and R. albus increased (p < 0.05) with Ca-salt after 12 h of incubation, while Streptococcus bovis increased (p < 0.05) by LSO. The CO and Ca-salt resulted in the highest C18:2n-6 (p = 0.002), while LSO resulted in the highest C18:3n-3 (p = 0.001). The Ca-salt had the lowest C18:0 (p = 0.002), but the highest C18:1cis-9 (p = 0.004). In conclusion, Ca-salt supplementation resisted biohydrogenation to some extent, decreased methanogenic archaea and protozoa, and exerted less toxic effects on fibrolytic bacteria.

Sexual Dimorphism in Response to Vitamins B3, B9 and B12, Used in Combination, in a Mice Model of Heart Failure Induced by Pressure Overload

IntroductionHeart failure (HF) is still a major cause of mortality worldwide. HF pathogenesis involves disturbances in cardiac energy metabolism. Studies have shown that preventive treatment with a diet supplemented with vitamins B3 or B9/B12 in experimental models of HF, exhibits beneficial effects on cardiac and mitochondrial functions and improves survival. Therefore, the overall objective of our pilot study is to evaluate the curative benefit of a synthetic diet enriched with vitamins B3 (nicotinamide riboside), B9 and B12 (BVit) in a mouse model of HF based on the hypothesis that this enriched diet is beneficial for cardiac function via an improvement of cardiac metabolism.MethodPressure overload was induced by transverse aortic constriction (TAC) in 8‐week‐old male and female C57Bl6/N mice. Four weeks post‐TAC and according to their cardiac function evaluated by echocardiography, mice were randomised to a BVit‐enriched diet or not and compared to SHAM animals. The criteria of selection for randomisation were as follows: 10% decrease in ejection fraction (EF), 30% increase in left ventricular (LV) mass and an average pressure gradient of 60mmHg. Mice survival was evaluated and cardiac function was assessed by echocardiography every 4 weeks. Blood samples were taken at 8 weeks of treatment in fasted mice (5 hours) for non‐targeted lipidomics mass spectrometry‐based analysis.ResultsOur pilot study show that survival is not improved in males while mortality is reduced in females from 12 weeks of treatment. In males, the reduced EF in the TAC group is not improved by BVit treatment and myocardial hypertrophy, as illustrated by the left ventricular mass (+20% in TAC), is exacerbated with BVit treatment. In contrast, in females, both EF and cardiac hypertrophy were improved (+20% and ‐13% respectively) after 12 weeks of BVit treatment. To better understand the sexual dimorphism in the response of BVit, non‐targeted lipidomics was used on plasma from mice following 8 weeks of treatment. In TAC‐females, compared to their SHAM controls, a decrease in triglycerides (TG) and an increase in choline phospholipids were observed while the lipid profile was normalized with BVit treatment. In TAC‐males vs SHAM, however, TGs were significantly increased and the treatment with BVit exacerbated the lipidomic profile both in terms of TGs and additional lipid species (identification in progress).ConclusionOur pilot study suggests a sexual dimorphism in the response to BVit treatment in experimental HF. Indeed, the benefit of BVit treatment is only shown in females with a delay in the mortality rate associated with improved cardiac function and normalisation of lipid disturbances. To explore and understand the mechanisms underlying this sexual dimorphism, the lipid profile hypothesis appears as a relevant avenue to explore in the future.