Simultaneous quantitation of fatty acids, sterols and bile acids in human stool by capillary gas-liquid chromatography

Apparent total tract nutrient digestibility of frozen raw, freeze-dried raw, fresh, and extruded dog foods and their effects on serum metabolites and fecal characteristics, metabolites, and microbiota of healthy adult dogs

Various pet food diet formats are available, but many are poorly studied. The objective of this study was to determine the apparent total tract macronutrient digestibility (ATTD) of frozen raw, freeze-dried raw, fresh, and extruded dog foods and assess their effects on serum metabolites, hematology, and fecal characteristics, metabolites, and microbiota of healthy adult dogs. Ten beagle dogs (4.10 ± 0.74 yr) were used in a replicated 5 × 5 Latin square study to test the following diets: Chicken and Barley Recipe (extruded; Hill's Science Diet [EXT]), Chicken and White Rice Recipe (fresh; Just Food for Dogs [FRSH]), Chicken Formula (frozen raw; Primal [FRZN]), Chicken and Sorghum Hybrid Freeze-dried Formula (freeze-dried raw; Primal [HFD]), and Chicken Dinner Patties (freeze-dried raw; Stella & Chewy's [FD]). The experiment was composed of five 35-d periods, with each ending with fecal and blood collections. Data were analyzed using Mixed Models in SAS 9.4, with P < 0.05 being significant. Treatment was a fixed effect and dog a random effect. Protein ATTD was higher for FRZN and FD than other diets and higher for HFD than FRSH and EXT. Fat ATTD was higher for HFD than FRZN and EXT and lower for EXT than other diets. Fecal output was higher for dogs fed EXT than those fed other diets and higher for dogs fed FRSH than those fed FRZN, HFD, or FD. Fecal pH was lower in dogs fed EXT and FRSH than those fed other diets. Fecal scores were higher (looser) in dogs fed EXT and FRSH than those fed FRZN and FD. Fecal dry matter was higher in dogs fed FD than those fed other diets and higher in those fed FRZN and HFD than those fed EXT and FRSH. In general, fecal short-chain fatty acids were highest in dogs fed EXT, intermediate in dogs fed FRSH and HFD, and lowest in dogs fed FRZN and FD. Fecal isobutyrate and isovalerate were highest in dogs fed HFD, lowest in dogs fed FRSH, and intermediate in dogs fed other diets. Fecal primary bile acids were higher, while secondary bile acids were lower in dogs fed FRSH than in dogs fed other diets. Fecal microbiota were greatly impacted by diet, with alpha diversity, beta diversity, and relative abundances of over 40 bacterial genera being different among treatments. This study shows that dietary format may lead to great differences in nutrient digestibility and fecal characteristics, metabolites, and microbiota. More research is needed to distinguish the effects of ingredient source, processing method, and nutrient composition.

Dysbiosis index and fecal concentrations of sterols, long-chain fatty acids and unconjugated bile acids in dogs with inflammatory protein-losing enteropathy

Introduction

Canine protein-losing enteropathy (PLE) is a syndrome characterized by gastrointestinal loss of proteins. While fecal microbiome and metabolome perturbations have been reported in dogs with chronic enteropathy, they have not been widely studied in dogs with PLE. Therefore, the study aims were to investigate gut microbiome and targeted fecal metabolites in dogs with inflammatory PLE (iPLE) and evaluate whether treatment affects these changes at short-term follow-up.

Methods

Thirty-eight dogs with PLE and histopathological evidence of gastrointestinal inflammation and 47 healthy dogs were enrolled. Fecal samples were collected before endoscopy (T0) and after one month of therapy (T1). Microbiome and metabolome alterations were investigated using qPCR assays (dysbiosis index, DI) and gas chromatography/mass spectrometry (long-chain fatty acids, sterols, unconjugated bile acids), respectively.

Results

Median (min-max) DI of iPLE dogs was 0.4 (-5.9 to 7.7) and was significantly higher (p < 0.0001) than median DI in healthy dogs [-2.0 (-6.0 to 5.3)]. No significant associations were found between DI and selected clinicopathological variables. DI did not significantly differ between T0 and T1. In iPLE dogs, at T0, myristic, palmitic, linoleic, oleic, cis-vaccenic, stearic, arachidonic, gondoic, docosanoic, erucic, and nervonic acids were significantly higher (p < 0.0001) than healthy dogs. In iPLE dogs, oleic acid (p = 0.044), stearic acid (p = 0.013), erucic acid (p = 0.018) and nervonic acid (p = 0.002) were significantly decreased at T1. At T0, cholesterol and lathosterol (p < 0.0001) were significantly higher in iPLE dogs compared to healthy dogs, while total measured phytosterols were significantly lower (p = 0.001). No significant differences in total sterols, total phytosterols and total zoosterols content were found at T1, compared to T0. At T0, total primary bile acids and total secondary bile acids did not significantly differ between healthy control dogs and iPLE dogs. No significant differences in fecal bile acid content were found at T1.

Discussion

Dysbiosis and lipid metabolism perturbations were observed in dogs with iPLE. Different therapeutic protocols lead to an improvement of some but not all metabolome perturbations at short-term follow-up.

An essential host dietary fatty acid promotes TcpH inhibition of TcpP proteolysis promoting virulence gene expression in Vibrio cholerae

Vibrio cholerae is a Gram-negative gastrointestinal pathogen responsible for the diarrheal disease cholera. Expression of key virulence factors, cholera toxin and toxin-coregulated pilus, is regulated directly by ToxT and indirectly by two transmembrane transcription regulators (TTRs), ToxR and TcpP, that promote the expression of toxT. TcpP abundance and activity are controlled by TcpH, a single-pass transmembrane protein, which protects TcpP from a two-step proteolytic process known as regulated intramembrane proteolysis (RIP). The mechanism of TcpH-mediated protection of TcpP represents a major gap in our understanding of V. cholerae pathogenesis. The absence of tcpH leads to unimpeded degradation of TcpP in vitro and a colonization defect in a neonate mouse model of V. cholerae colonization. Here, we show that TcpH protects TcpP from RIP via direct interaction. We also demonstrate that α-linolenic acid, a dietary fatty acid, promotes TcpH-dependent inhibition of RIP via co-association of TcpP and TcpH molecules within detergent-resistant membranes (DRMs) in a mechanism requiring the TcpH transmembrane domain. Taken together, our data support a model where V. cholerae cells use exogenous α-linolenic acid to remodel the phospholipid bilayer in vivo, leading to co-association of TcpP and TcpH within DRMs where RIP of TcpP is inhibited by TcpH, thereby promoting V. cholerae pathogenicity.

IMPORTANCE

Vibrio cholerae continues to pose a significant global burden on health and an alternative therapeutic approach is needed, due to evolving multidrug resistance strains. Transcription of toxT, stimulated by TcpP and ToxR, is essential for V. cholerae pathogenesis. Our results show that TcpP, one of the major regulators of toxT gene expression, is protected from proteolysis by TcpH, via direct interaction. Furthermore, we identified a gut metabolite, α-linolenic acid, that stimulates the co-association of TcpP and TcpH within detergent-resistant membranes (also known as lipid-ordered membrane domains), thereby supporting TcpH-dependent antagonism of TcpP proteolysis. Data presented here extend our knowledge of RIP, virulence gene regulation in V. cholerae, and, to the best of our knowledge, provides the first evidence that lipid-ordered membranes exist within V. cholerae. The model presented here also suggests that TTRs, common among bacteria and archaea, and co-component signal transduction systems present in Enterobacteria, could also be influenced similarly.

Shigella flexneri utilizes intestinal signals to control its virulence

The enteric pathogens have evolved to utilize elements from their surroundings to optimize their infection strategies. A common mechanism to achieve this is to employ intestinal compounds as signals to control the activity of a master regulator of virulence. Shigella flexneri (S. flexneri) is a highly infectious entero-invasive pathogen which requires very few organisms to cause invasion of the colonic mucosa. The invasion program is controlled by the virulence master regulator VirF. Here, we show that the fatty acids commonly found in the colon can be exploited by S. flexneri to repress its virulence, allowing it to energetically finance its proliferation, thus increasing its pathogenicity. Colonic fatty acids such as oleic, palmitoleic and cis-2-hexadecenoic acid were shown to directly bind to VirF and mediate its prompt degradation. These fatty acids also disrupted the ability of VirF to bind to its target DNA, suppressing the transcription of the downstream virulence genes and significantly reducing the invasion of S. flexneri to colonic epithelial cells. Treatment with colonic fatty acids significantly increased the growth rate of the pathogen only under invasion-inducing conditions, showing that the reduction in the burden of virulence promotes a growth advantage. These results demonstrate the process by which S. flexneri can employ intestinal compounds as signals to increase its numbers at its preferred site of invasion, highlighting the mechanism by which the full spectrum of shigellosis is achieved despite a miniscule infectious dose. This highlights an elegant model of environmental adaption by S. flexneri to maximize the pathogenic benefit.

Fecal Concentrations of Long-Chain Fatty Acids, Sterols, and Unconjugated Bile Acids in Cats with Chronic Enteropathy

Chronic enteropathy (CE) in cats encompasses food-responsive enteropathy, chronic inflammatory enteropathy (or inflammatory bowel disease), and low-grade intestinal T-cell lymphoma. While alterations in the gut metabolome have been extensively studied in humans and dogs with gastrointestinal disorders, little is known about the specific metabolic profile of cats with CE. As lipids take part in energy storage, inflammation, and cellular structure, investigating the lipid profile in cats with CE is crucial. This study aimed to measure fecal concentrations of various fatty acids, sterols, and bile acids. Fecal samples from 56 cats with CE and 77 healthy control cats were analyzed using gas chromatography-mass spectrometry, targeting 12 fatty acids, 10 sterols, and 5 unconjugated bile acids. Fecal concentrations of nine targeted fatty acids and animal-derived sterols were significantly increased in cats with CE. However, fecal concentrations of plant-derived sterols were significantly decreased in cats with CE. Additionally, an increased percentage of primary bile acids was observed in a subset of cats with CE. These findings suggest the presence of lipid maldigestion, malabsorption, and inflammation in the gastrointestinal tract of cats with CE. Understanding the lipid alterations in cats with CE can provide insights into the disease mechanisms and potential future therapeutic strategies.

The impact of protein source and grain inclusion on digestibility, fecal metabolites, and fecal microbiome in adult canines

This study was conducted to determine the effect of animal protein inclusion rate and grain-free or grain-inclusive diets on macronutrient digestibility, fecal characteristics, metabolites, and microbiota in mixed-breed hounds and Beagles. Four experimental extruded kibble diets were made with varying amounts of animal protein and carbohydrates: 1) high animal protein, grain-inclusive (HA-GI), 2) low animal protein, grain-free (LA-GF), 3) low animal protein, grain-inclusive (LA-GI), and 4) high animal protein, grain-free (HA-GF). Thirty-two Beagles and 33 mixed-breed hounds were assigned to 1 of the 4 treatment groups in a completely randomized design that lasted 180 d. All diets were similar in chemical composition and well-digested by the animals. In general, for fecal metabolites, mixed-breed hounds had a greater concentration of total short-chain fatty acid (SCFA) and ammonia and lower indole concentration than Beagles (P < 0.05). In mixed-breed hounds, LA-GF had a greater (P < 0.05) total SCFA concentration than HA-GI and LA-GI; however, this was not observed in Beagles. There were greater concentrations of ammonia, phenol, and indole in HA-GI than in LA-GF (P < 0.05). Breed-affected fecal primary bile acid (BA) concentration, as mixed-breed hounds had a greater concentration of cholic acid (CA) than Beagles (P < 0.05). Mixed-breed hounds fed LA-GF resulted in greater CA concentrations than HA-GI and LA-GI (P < 0.05). Dogs who consumed LA-GF had lower fecal secondary BA content than the other groups (P < 0.05). The distribution of the fecal microbiota community differed in LA-GF compared with the other groups, with lower α-diversity. However, dogs fed LA-GF had the largest difference in composition with greater Selenomonadaceae, Veillonellaceae, Lactobacillaceae, Streptococcus, Ligilactobacillus, Megamonas, Collinsella aerofaciens, and Bifidobacterium sp. than the other groups. A significant breed effect was noted on nutrient digestibility, fecal metabolites, and microbiota. A treatment effect was observed in LA-GF as it resulted in greater fecal SCFA, lower protein fermentative end products, greater fecal primary BAs, lower fecal secondary BA concentrations, and shifts in fecal microbiota.

Effects of a milk oligosaccharide biosimilar on fecal characteristics, microbiota, and bile acid, calprotectin, and immunoglobulin concentrations of healthy adult dogs treated with metronidazole

In recent dog and cat experiments, a novel milk oligosaccharide biosimilar (GNU100) positively modulated fecal microbiota and metabolite profiles, suggesting benefits to gastrointestinal health. The objective of this study was to investigate the effects of GNU100 on the fecal characteristics, microbiota, and bile acid (BA) concentrations of healthy adult dogs treated with antibiotics. Twelve healthy adult female dogs (mean age: 3.74 ± 2.4 yr) were used in an 8-wk crossover design study (dogs underwent both treatments). All dogs were fed a control diet during a 2-wk baseline, then randomly allotted to 1 of 2 treatments (diet only or diet + 1% GNU100) for another 6 wk. From weeks 2 to 4, dogs were orally administered metronidazole (20 mg/kg BW) twice daily. Fecal scores were recorded daily and fresh fecal samples were collected at weeks 2, 4, 5, 6, and 8 for measurement of pH, dry matter, microbiota populations, and BA, immunoglobulin A, and calprotectin concentrations. On weeks 0, 4, and 8, blood samples were collected for serum chemistry and hematology analysis. All data were analyzed as repeated measures using the Mixed Models procedure of SAS version 9.4, with significance considered P < 0.05. Metronidazole increased (P < 0.0001) fecal scores (looser stools) and modified (P < 0.05) fecal microbiota and BA profiles. Using qPCR, metronidazole reduced fecal Blautia, Fusobacterium, Turicibacter, Clostridium hiranonis, and Faecalibacterium abundances, and increased fecal Streptococcus and Escherichia coli abundances. DNA sequencing analysis demonstrated that metronidazole reduced microbial alpha diversity and influenced the relative abundance of 20 bacterial genera and families. Metronidazole also increased primary BA and reduced secondary BA concentrations. Most antibiotic-induced changes returned to baseline by week 8. Fecal scores were more stable (P = 0.01) in GNU100-fed dogs than controls after antibiotic administration. GNU100 also influenced fecal microbiota and BA profiles, reducing (P < 0.05) the influence of metronidazole on microbial alpha diversity and returning some fecal microbiota and secondary BA to baseline levels at a quicker (P < 0.05) rate than controls. In conclusion, our results suggest that GNU100 supplementation provides benefits to dogs treated with antibiotics, providing more stable fecal scores, maintaining microbial diversity, and allowing for quicker recovery of microbiota and secondary BA profiles which play an essential role in gut health.

Microbial dysbiosis and fecal metabolomic perturbations in Yorkshire Terriers with chronic enteropathy

Dysbiosis and perturbations of fecal metabolic profiles have been reported in dogs with inflammatory bowel disease. Currently the incidence of dysbiosis and the fecal metabolomic profile in Yorkshire Terriers with chronic enteropathy (YTE) and the effects of treatment are unknown. This prospective observational study analyzed the dysbiosis index (DI) and fecal bile acid, sterol and fatty acid profiles in 14 Yorkshire Terriers with active YTE, 11 dogs in clinical remission, and 26 healthy Yorkshire Terriers. YTE was associated with dysbiosis and a significant increase in fatty acids (docosanoate, p = 0.002; gondoate, p = 0.026; erucate, p < 0.001; nervonate, p < 0.001; linolenate, p < 0.001), and plant sterols (campesterol, p < 0.001; brassicasterol, p = 0.024). The abundances of Fusobacterium (p < 0.001) and Cl. hiranonis (p = 0.018) and the concentrations of the secondary bile acid ursodeoxycholic acid (p = 0.033) and the plant sterol sitostanol (p = 0.003) were significantly decreased compared to healthy dogs. Dysbiosis, abundances of Fusobacterium, Cl. hiranonis and fecal concentrations of bile acids and sterols did not recover after treatment, while fecal fatty acid concentrations decreased in treated dogs. YTE is associated with dysbiosis and changes in bile acid, fatty acid, and sterol metabolism. These changes only recovered partially despite clinical remission. They might be breed-specific and involved in the pathogenesis of YTE.

Long Chain Fatty Acids and Virulence Repression in Intestinal Bacterial Pathogens

When bacterial pathogens enter the gut, they encounter a complex milieu of signaling molecules and metabolites produced by host and microbial cells or derived from external sources such as the diet. This metabolomic landscape varies throughout the gut, thus establishing a biogeographical gradient of signals that may be sensed by pathogens and resident bacteria alike. Enteric bacterial pathogens have evolved elaborate mechanisms to appropriately regulate their virulence programs, which involves sensing and responding to many of these gut metabolites to facilitate successful gut colonization. Long chain fatty acids (LCFAs) represent major constituents of the gut metabolome that can impact bacterial functions. LCFAs serve as important nutrient sources for all cellular organisms and can function as signaling molecules that regulate bacterial metabolism, physiology, and behaviors. Moreover, in several enteric pathogens, including Salmonella enterica, Listeria monocytogenes, Vibrio cholerae, and enterohemorrhagic Escherichia coli, LCFA sensing results in the transcriptional repression of virulence through two general mechanisms. First, some LCFAs function as allosteric inhibitors that decrease the DNA binding affinities of transcriptional activators of virulence genes. Second, some LCFAs also modulate the activation of histidine kinase receptors, which alters downstream intracellular signaling networks to repress virulence. This mini-review will summarize recent studies that have investigated the molecular mechanisms by which different LCFA derivatives modulate the virulence of enteric pathogens, while also highlighting important gaps in the field regarding the roles of LCFAs as determinants of infection and disease.

Weight loss and high-protein, high-fiber diet consumption impact blood metabolite profiles, body composition, voluntary physical activity, fecal microbiota, and fecal metabolites of adult dogs

Canine obesity is associated with reduced lifespan and metabolic dysfunction, but can be managed by dietary intervention. This study aimed to determine the effects of restricted feeding of a high-protein, high-fiber (HPHF) diet and weight loss on body composition, physical activity, blood metabolites, and fecal microbiota and metabolites of overweight dogs. Twelve spayed female dogs (age: 5.5 ± 1.1 yr; body weight [BW]: 14.8 ± 2.0 kg, body condition score [BCS]: 7.9 ± 0.8) were fed a HPHF diet during a 4-wk baseline phase to maintain BW. After baseline (week 0), dogs were first fed 80% of baseline intake and then adjusted to target 1.5% weekly weight loss for 24 wk. Body composition using dual-energy x-ray absorptiometry and blood samples (weeks 0, 6, 12, 18, and 24), voluntary physical activity (weeks 0, 7, 15, and 23), and fresh fecal samples for microbiota and metabolite analysis (weeks 0, 4, 8, 12, 16, 20, and 24) were measured over time. Microbiota data were analyzed using QIIME 2. All data were analyzed statistically over time using SAS 9.4. After 24 wk, dogs lost 31.2% of initial BW and had 1.43 ± 0.73% weight loss per week. BCS decreased (P < 0.0001) by 2.7 units, fat mass decreased (P < 0.0001) by 3.1 kg, and fat percentage decreased (P < 0.0001) by 11.7% with weight loss. Many serum metabolites and hormones were altered, with triglycerides, leptin, insulin, C-reactive protein, and interleukin-6 decreasing (P < 0.05) with weight loss. Relative abundances of fecal Bifidobacterium, Coriobacteriaceae UCG-002, undefined Muribaculaceae, Allobaculum, Eubacterium, Lachnospira, Negativivibacillus, Ruminococcus gauvreauii group, uncultured Erysipelotrichaceae, and Parasutterella increased (P < 0.05), whereas Prevotellaceae Ga6A1 group, Catenibacterium, Erysipelatoclostridium, Fusobacterium, Holdemanella, Lachnoclostridium, Lactobacillus, Megamonas, Peptoclostridium, Ruminococcus gnavus group, and Streptococcus decreased (P < 0.01) with weight loss. Despite the number of significant changes, a state of dysbiosis was not observed in overweight dogs. Fecal ammonia and secondary bile acids decreased, whereas fecal valerate increased with weight loss. Several correlations between gut microbial taxa and biological parameters were observed. Our results suggest that restricted feeding of a HPHF diet and weight loss promotes fat mass loss, minimizes lean mass loss, reduces inflammatory marker and triglyceride concentrations, and modulates fecal microbiota phylogeny and activity in overweight dogs.

Longitudinal assessment of taurine and amino acid concentrations in dogs fed a green lentil diet

A recent association between the inclusion of pulses in canine diets and taurine deficiency has become a prevalent issue in the pet food industry. Although dogs do not currently have a nutritional requirement for taurine, taurine deficiencies that do occur can result in serious health issues, such as dilated cardiomyopathy. The objective of this study was to determine the circulating concentrations of plasma and whole blood taurine, indispensable and dispensable amino acid concentrations in the plasma, and taurine and creatinine concentrations in the urine of adult dogs fed a green lentil diet. Twelve adult, intact, female beagles were randomly assigned to a diet containing 45% green lentils (GLD) or a poultry byproduct meal diet (CON) for 90 d. Fresh urine samples were collected every 30 d and analyzed for taurine and creatinine concentrations. A blood sample was also collected every 30 d and analyzed for amino acids including taurine. Animal procedures were approved by the University of Illinois Institutional Animal Care and Use Committee. All diets were formulated to meet or exceed the nutrient requirements for adult dogs at maintenance. The concentrations of taurine in the plasma and whole blood showed no differences (P > 0.05) between dietary treatments or across time points. Similarly, no differences (P > 0.05) in plasma methionine concentrations were observed between treatments or across time points. A treatment effect (P < 0.05) showed dogs fed GLD had higher total primary fecal bile acid excretion compared with dogs fed CON. The differential abundance of fecal microbial communities showed Firmicutes as the predominant phyla in dogs fed both GLD and CON, with Bacteroidaceae, Erysipelotrichaceae, and Lactobacillaceae as predominant families in dogs fed GLD. The α-diversity of dogs fed GLD (P < 0.05) was lower than in dogs fed CON. These data suggest that the inclusion of 45% green lentil in extruded diets does not lower whole blood and plasma taurine concentrations during a 90-d period and is appropriate for use in a complete and balanced formulation for dogs.

Effects of Dietary Macronutrient Profile on Apparent Total Tract Macronutrient Digestibility and Fecal Microbiota, Fermentative Metabolites, and Bile Acids of Female Dogs after Spay Surgery

Obesity and estrogen reduction are known to impact the gut microbiota and gut microbial-derived metabolites in some species, but limited information is available in dogs. The aim of this study was to determine the effects of dietary macronutrient profile on apparent total tract macronutrient digestibility, fecal microbiota, and fecal metabolites of adult female dogs after spay surgery. Twenty-eight adult intact female beagles (age: 3.02 ± 0.71 yr, BW: 10.28 ± 0.77 kg; BCS: 4.98 ± 0.57) were used. After a 5-wk baseline phase (wk 0), 24 dogs were spayed and randomly allotted to one of three experimental diets (n=8/group): 1) control (CO) containing moderate protein and fiber (COSP), 2) high-protein, high-fiber (HPHF), or 3) high-protein, high-fiber plus omega-3 and medium-chain fatty acids (HPHFO). Four dogs were sham-operated and fed CO (COSH). All dogs were fed to maintain BW for 12 wk after spay, then allowed to consume twice that amount for 12 wk. Fecal samples were collected at wk 0, 12, and 24 for digestibility, microbiota, and metabolite analysis. All data were analyzed using repeated measures and linear Mixed Models procedure of SAS 9.4, with results reported as change from baseline. Apparent organic matter and energy digestibilities had greater decreases in HPHF and HPHFO than COSH and COSP. Increases in fecal acetate, total short-chain fatty acids, and secondary bile acids were greater and decreases in primary bile acids were greater in HPHF and HPHFO. Principal coordinates analysis of weighted UniFrac distances revealed that HPHF and HPHFO clustered together and separately from COSH and COSP at wk 12 and 24, with relative abundances of Faecalibacterium, Romboutsia, and Fusobacterium increasing to a greater extent and Catenibacterium, Bifidobacterium, Prevotella 9, Eubacterium, and Megamonas decreasing to a greater extent in HPHF or HPHFO. Our results suggest that high-protein, high-fiber diets alter nutrient and energy digestibilities, fecal metabolite concentrations, and fecal gut microbiota, but spay surgery had minor effects. Future research is needed to investigate how food intake, nutrient profile, and changes in hormone production influence gut microbiota and metabolites of dogs individually and how this knowledge may be used to manage spayed pets.

Short-chain fatty acids and bile acids in human faeces are associated with the intestinal cholesterol conversion status

BACKGROUND AND PURPOSE

The analysis of human faecal metabolites can provide an insight into metabolic interactions between gut microbiota and the host organism. The creation of metabolic profiles in faeces has received little attention until now, and reference values, especially in the context of dietary and therapeutic interventions, are missing. Exposure to xenobiotics significantly affects the physiology of the microbiome, and microbiota manipulation and short-chain fatty acid administration have been proposed as treatment targets for several diseases. The aim of the present study is to give concomitant concentration ranges of faecal sterol species, bile acids and short-chain fatty acids, based on a large cohort.

EXPERIMENTAL APPROACH

Sterol species, bile acids and short-chain fatty acids in human faeces from 165 study participants were quantified by LC-MS/MS. For standardization, we refer all values to dry weight of faeces. Based on the individual intestinal sterol conversion, we classified participants into low and high converters according to their coprostanol/cholesterol ratio.

KEY RESULTS

Low converters excrete more straight-chain fatty acids and bile acids than high converters; 5th and 95th percentile and median of bile acids and short-chain fatty acids were calculated for both groups.

CONCLUSION AND IMPLICATIONS

We give concentration ranges for 16 faecal metabolites that can serve as reference values. Patient stratification into high or low sterol converter groups is associated with significant differences in faecal metabolites with biological activities. Such stratification should then allow better assessment of faecal metabolites before therapeutic interventions.

LINKED ARTICLES

This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.

California strawberry consumption increased the abundance of gut microorganisms related to lean body weight, health and longevity in healthy subjects

It was our hypothesis that foods high in polyphenols and fiber have prebiotic activity. This human intervention study aimed to determine if daily consumption of freeze-dried California strawberry powder (SBP) leads to changes in the intestinal microbiota, fecal cholesterol and bile acid (BA) microbial metabolites. Fifteen healthy adults consumed a beige diet+26 g of SBP for 4 weeks, followed by 2 weeks of beige diet only. Stool samples were collected at 0, 4, and 6 weeks. Fecal microbiota was analyzed by 16S rRNA sequencing; fecal cholesterol, BA, and microbial metabolites by gas chromatography. Confirming compliance, urine concentration of pelargonidin, urolithin A glucuronide and dimethylellagic acid glucuronide were present after 4 weeks of SBP consumption. Daily SBP altered the abundance of 24 operational taxonomic units (OTUs). Comparing week 4 to baseline the most significant increases were observed for one OTU from Firmicutes\Clostridia\ Christensenellaceae\NA, one OTU from Firmicutes\ Clostridia\Mogibacteriacea\NA, one OTU from Verrucomicrobia\ Verrucomicrobiaceae\Akkermansia\Muciniphila, one OTU from Actinobacteria\ Bifidobacteriaceae\Bifidobacterium\NA, and one OTU from Bacteroidetes\Bacteroidia\ Bacteroidaceae\Bacteroides and decrease of one OTU from Proteobacteria\ Betaproteobacteria\Alcaligenaceae\Sutterella. Comparing week 4 to 6, we observed a reversal of the same OTUs from C Christensenellaceae, V muciniphilia and C Mogibacteriaceae. Fecal short chain fatty acids and most of the fecal markers including cholesterol, coprostanol, primary and secondary BAs were not changed significantly except for lithocholic acid, which was increased significantly at week 6 compared to baseline. In summary, SBP consumption increased the abundance of gut microorganisms related to lean body weight, health and longevity, and increased fecal lithocholic acid at week 6 in healthy study participants.

Effects of metronidazole on the fecal microbiome and metabolome in healthy dogs

Background

Metronidazole has a substantial impact on the gut microbiome. However, the recovery of the microbiome after discontinuation of administration, and the metabolic consequences of such alterations have not been investigated to date.

Objectives

To describe the impact of 14‐day metronidazole administration, alone or in combination with a hydrolyzed protein diet, on fecal microbiome, metabolome, bile acids (BAs), and lactate production, and on serum metabolome in healthy dogs.

Animals

Twenty‐four healthy pet dogs.

Methods

Prospective, nonrandomized controlled study. Dogs fed various commercial diets were divided in 3 groups: control group (no intervention, G1); group receiving hydrolyzed protein diet, followed by metronidazole administration (G2); and group receiving metronidazole only (G3). Microbiome composition was evaluated with sequencing of 16S rRNA genes and quantitative polymerase chain reaction (qPCR)‐based dysbiosis index. Untargeted metabolomics analysis of fecal and serum samples was performed, followed by targeted assays for fecal BAs and lactate.

Results

No changes were observed in G1, or G2 during diet change. Metronidazole significantly changed microbiome composition in G2 and G3, including decreases in richness (P < .001) and in key bacteria such as Fusobacteria (q < 0.001) that did not fully resolve 4 weeks after metronidazole discontinuation. Fecal dysbiosis index was significantly increased (P < .001). Those changes were accompanied by increased fecal total lactate (P < .001), and decreased secondary BAs deoxycholic acid and lithocholic acid (P < .001).

Conclusion and Clinical Importance

Our results indicate a minimum 4‐week effect of metronidazole on fecal microbiome and metabolome, supporting a cautious approach to prescription of metronidazole in dogs.

Altered microbiota, fecal lactate, and fecal bile acids in dogs with gastrointestinal disease

The intestinal microbiota plays an important role in health and disease and produces, through fermentative reactions, several metabolic products, such as lactate, that can affect the host. The microbiota also interacts with and metabolizes compounds produced by the host, such as primary bile acids. Lactate and bile acids (BA) are of particular interest in gastrointestinal diseases because they have been associated with metabolic acidosis and bile acid diarrhea, respectively. The objectives of this study were to validate an enzymatic assay to quantify D-, L-, and total lactate in canine feces, and to characterize fecal lactate and BA concentrations as well as bacterial abundances in healthy dogs and dogs with gastrointestinal diseases. Fecal samples were collected from 34 healthy dogs, 15 dogs with chronic enteropathy (CE), and 36 dogs with exocrine pancreatic insufficiency (EPI). Lactate was quantified with an enzymatic assay, BA with gas chromatography-mass spectrometry, and 11 bacterial groups with qPCR. A fecal lactate reference interval was established from 34 healthy dogs and was 0.7–1.4 mM, 0.3–6.0 mM, and 1.0–7.0 mM for D-, L-, and total lactate, respectively. The assay to measure D-, L-, and total lactate in canine fecal samples was linear, accurate, precise, and reproducible. Significant increases in fecal lactate and decreases in secondary BA concentrations were observed in dogs with CE and dogs with EPI. Dogs with EPI had an increased abundance of Escherichia coli, Lactobacillus, and Bifidobacterium; a decreased abundance of Fusobacterium and Clostridium hiranonis; and a higher Dysbiosis Index when compared to healthy dogs. Further studies are necessary to determine the clinical utility of lactate and BA quantification in canine feces. These metabolites suggest functional alterations of intestinal dysbiosis and may become promising targets for further elucidating the role of the microbiota in health and disease.

Assessment of gut microbiota fecal metabolites by chromatographic targeted approaches

Gut microbiota, the specific microbial community of the gastrointestinal tract, by means of the production of microbial metabolites provides the host with several functions affecting metabolic and immunological homeostasis. Insights into the intricate relationships between gut microbiota and the host require not only the understanding of its structure and function but also the measurement of effector molecules acting along the gut microbiota axis. This article reviews the literature on targeted chromatographic approaches in analysis of gut microbiota specific metabolites in feces as the most accessible biological matrix which can directly probe the connection between intestinal bacteria and the (patho)physiology of the holobiont. Together with a discussion on sample collection and preparation, the chromatographic methods targeted to determination of some classes of microbiota-derived metabolites (e.g., short-chain fatty acids, bile acids, low molecular masses amines and polyamines, vitamins, neurotransmitters and related compounds) are discussed and their main characteristics, summarized in Tables.

Microbiota-Related Changes in Unconjugated Fecal Bile Acids Are Associated With Naturally Occurring, Insulin-Dependent Diabetes Mellitus in Dogs

Diabetes mellitus (DM) in humans has recently been associated with altered intestinal microbiota. The consequences of intestinal dysbiosis, such as increased intestinal permeability and altered microbial metabolites, are suspected to contribute to the host inflammatory state and peripheral insulin resistance. Human diabetics have been shown to have changes in bile acid (BA) metabolism which may be detrimental to glycemic control. The purpose of this study was to examine BA metabolism in dogs with naturally-occurring, insulin-dependent DM and to relate these findings to changes in the intestinal microbiota. A prospective observational study of adult dogs with a clinical diagnosis of DM (n = 10) and healthy controls (HC, n = 10) was performed. The fecal microbiota were analyzed by 16S rRNA gene next-generation (Illumina) sequencing. Concentrations of fecal unconjugated BA (fUBA) were measured using gas chromatography and mass spectrometry. Analysis of bacterial communities showed no significant difference for any of the alpha-diversity measures between DM vs. HC dogs. Principal coordinate analysis based on unweighted Unifrac distance metric failed to show significant clustering between dog groups (ANOSIM_Unweighted: R = 0.084; p = 0.114). However, linear discriminate analysis effects size (LEfSe) detected differentially abundant bacterial taxa (α = 0.01, LDA score >2.0) on various phylogenetic levels. While Enterobacteriaceae was overrepresented in dogs with DM, the proportions of Erysipelotrichia, Mogibacteriaceae, and Anaeroplasmataceae were increased in HC dogs. Dogs with DM had increased concentration of total primary fUBA compared to HC dogs (p = 0.028). The concentrations of cholic acid and the cholic acid percentage of the total fUBA were increased (p = 0.028 and p = 0.035, respectively) in the feces of DM dogs relative to HC dogs. The levels of lithocholic acid (both absolute value and percentage of the total fUBA) were decreased (p = 0.043 and p < 0.01, respectively) in DM dogs vs. HC dogs. Results indicate that dogs with DM have both intestinal dysbiosis and associated fUBA alterations. The pattern of dysbiosis and altered BA composition is similar to that seen in humans with Type 2 DM. The dog represents a novel large animal model for advancing translational medicine research efforts (e.g., investigating pathogenesis and therapeutics) in DM affecting humans.

A comprehensive method to determine sterol species in human faeces by GC-triple quadrupole MS

The human gut microbiome plays a crucial role in both health and disease. Metabolites in human faeces related to microbial activity might therefore be attractive surrogate markers to track changes of microbiota induced by diet or disease. The hyphenation of gas chromatography with triple quadrupole mass spectrometry is a promising approach to increase sensitivity and selectivity as compared to single quad MS instruments. The versatility of gas chromatography-tandem mass spectrometry (GC-MS/MS) can be advantageously exploited in clinical laboratory medicine, e.g. for quantification of sterols in biological material. In this paper, we present the application of GC-MS/MS for determination of sterol components in human faeces. A serious problem of analysis of faeces is preanalytics. Uncontrolled degradation of metabolites during transport and storage of faeces before entering the clinical laboratory might occur. In our experiments we did not observe any increasing or decreasing concentration after storage of native faeces material even at room temperature. Furthermore, we answer the question of how personal metabolic responses with respect to sterols are and address the importance of sampling strategies. From a pilot study it is concluded that differentiation between high and low metabolizers is independent of the type of sampling and constant over several days.

Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy

Background

Mounting evidence from human studies suggests that bile acid dysmetabolism might play a role in various human chronic gastrointestinal diseases. It is unknown whether fecal bile acid dysmetabolism occurs in dogs with chronic inflammatory enteropathy (CE).

Objective

To assess microbial dysbiosis, fecal unconjugated bile acids (fUBA), and disease activity in dogs with steroid‐responsive CE.

Animals

Twenty‐four healthy control dogs and 23 dogs with steroid‐responsive CE.

Methods

In this retrospective study, fUBA were measured and analyzed. Fecal microbiota were assessed using a dysbiosis index. The canine inflammatory bowel disease activity index was used to evaluate remission of clinical signs. This was a multi‐institutional study where dogs with steroid‐responsive CE were evaluated over time.

Results

The dysbiosis index was increased in dogs with CE (median, 2.5; range, −6.2 to 6.5) at baseline compared with healthy dogs (median, −4.5; range, −6.5 to −2.6; P = .002) but did not change in dogs with CE over time. Secondary fUBA were decreased in dogs with CE (median, 29%; range, 1%‐99%) compared with healthy dogs (median, 88%; 4%‐96%; P = .049). The percent of secondary fUBA in dogs with CE increased from baseline values (median, 28%; range, 1%‐99%) after 2‐3 months of treatment (median, 94%; range, 1%‐99%; P = 0.0183).

Conclusions and Clinical Importance

These findings suggest that corticosteroids regulate fecal bile acids in dogs with CE. Additionally, resolution of clinical activity index in dogs with therapeutically managed CE and bile acid dysmetabolism are likely correlated. However, subclinical disease (i.e., microbial dysbiosis) can persist in dogs with steroid‐responsive CE.

Comparative study of the hypocholesterolemic and hypolipidemic activity of alginate and amidated alginate in rats

Alginate is a copolymer of β-d-mannuronate and α-l-guluronate, which are present in the cell wall of brown algae. The hypocholesterolemic and hypolipidemic activities of alginate and its derivative, which is prepared by a reaction with octadecylamine, were compared in rats fed diets containing cholesterol and palm fat at 10 and 50g/kg, respectively. Amidated alginate at 20g/kg significantly decreased serum cholesterol from 2.93 to 2.00μmol/mL, serum triacylglycerols from 1.66 to 0.92μmol/mL, hepatic cholesterol from 17.5 to 5.9μmol/g, and total hepatic lipids from 67.4 to 51.7mg/g. Alginate at 20g/kg significantly reduced hepatic cholesterol to 13.1μmol/g, but did not influence serum cholesterol, triacylglycerols, and total hepatic lipids. Amidated alginate significantly increased the faecal concentrations of neutral sterols from 98.7 to 122.4μmol/g DM, but decreased faecal concentration of bile acids from 19.4 to 14.0μmol/g DM. In samples of intestinal contents, taurine-conjugated bile acids dominated glycine conjugates. The supplementation of diets with cholesterol significantly increased the expression of hepatic cholesterol 7α-hydroxylase, especially in rats that received cholesterol without alginate or amidated alginate. In conclusion, amidated alginate is an effective hypocholesterolemic agent that is more efficient than its parent polysaccharide.

Steroid Biomarkers Revisited - Improved Source Identification of Faecal Remains in Archaeological Soil Material

Steroids are used as faecal markers in environmental and in archaeological studies, because they provide insights into ancient agricultural practices and the former presence of animals. Up to now, steroid analyses could only identify and distinguish between herbivore, pig, and human faecal matter and their residues in soils and sediments. We hypothesized that a finer differentiation between faeces of different livestock animals could be achieved when the analyses of several steroids is combined (Δ⁵-sterols, 5α-stanols, 5β-stanols, epi-5β-stanols, stanones, and bile acids). We therefore reviewed the existing literature on various faecal steroids from livestock and humans and analysed faeces from old livestock breed (cattle, horse, donkey, sheep, goat, goose, and pig) and humans. Additionally, we performed steroid analyses on soil material of four different archaeological periods (sites located in the Lower Rhine Basin, Western Germany, dating to the Linearbandkeramik, Urnfield Period / Bronze Age, Iron Age, Roman Age) with known or supposed faecal inputs. By means of already established and newly applied steroid ratios of the analysed faeces together with results from the literature, all considered livestock faeces, except sheep and cattle, could be distinguished on the basis of their steroid signatures. Most remarkably was the identification of horse faeces (via the ratio: epi-5β-stigmastanol: 5β-stigmastanol + epicoprostanol: coprostanol; together with the presence of chenodeoxycholic acid) and a successful differentiation between goat (with chenodeoxycholic acid) and sheep/cattle faeces (without chenodeoxycholic acid). The steroid analysis of archaeological soil material confirmed the supposed faecal inputs, even if these inputs had occurred several thousand years ago.

Quantitative profiling of bile acids in blood, adipose tissue, intestine, and gall bladder samples using ultra high performance liquid chromatography-tandem mass spectrometry

An ultra high performance liquid chromatography tandem mass spectrometry method (UHPLC-MS/MS) was developed for the determination of 33 target and 28 unknown bile acids (BAs) in biological samples. Sixty-one BAs could be measured in 20 min using only a small amount of sample and with a simple sample preparation. The method proved to be very sensitive (limit of detection 5-350 pg/mL, lower limit of quantitation 0.1-2.6 ng/mL), linear (R(2) > 0.99) and reproducible (typically CV <15 % in biological matrixes). The method was used to analyze human adipose tissue, plasma, and serum (from same subjects) and mouse serum, gall bladder, small intestine, and colon samples (from same animals). Cholic acid, ursodeoxycholic acid, and chenodeoxycholic acid, deoxycholic acid, and their conjugates (mainly glycine, but also taurine conjugates) were the main metabolites in human samples, and cholic acid, glycine cholic acid, and several taurine conjugates in mouse samples. Using the method, 28 unknown BAs could also be detected. UHPLC-MS/MS spectra, accurate mass, and tissue distribution suggested that nine of the unknown bile acids were taurine conjugates, 13 were glycine conjugates, and six were intact BAs, respectively. To our knowledge, this was the first time BAs were detected in adipose tissue. Results showed that 17 targeted BAs were found at ng/g level in human adipose tissue. Our findings give a novel insight of the endogenous role of BAs in adipose tissue and their role as biomarkers (e.g., in metabolic diseases).

Comprehensive gas chromatography-electron ionisation mass spectrometric analysis of fatty acids and sterols using sequential one-pot silylation: quantification and isotopologue analysis

RATIONALE

Fatty acids and sterol lipids play crucial roles in several biological processes and several biological facts underline the interconnection between these lipid classes. Therefore, it is of interest to develop a comprehensive method analysing both classes in the form of their most favourable derivatives suitable for quantification and isotopologue analysis.

METHODS

Lipids were derivatised by a sequential one-pot procedure using N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MtBSTFA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). No clean-up or concentration steps were necessary. The prepared samples were directly available for gas chromatography-electron ionisation mass spectrometric (GC-EI-MS) analysis on a standard column. For quantification, the SIM mode was used and for isotopologue analysis scheduled scan mode was applied.

RESULTS

Development of a sequential one-pot derivatisation for GC-EI-MS allowing comprehensive analysis of fatty acids and sterols as their most favourable derivatives. Validation carried out using human plasma, comparison with certified NIST plasma. LLOQ of usually 3.3 ng/mL achieved. Isotopologue analysis of 2-[(13)C]-acetate incorporation in HL-60 cells proving feasibility of method.

CONCLUSIONS

The presented method successfully combines two consecutive silylation reactions in one pot, enabling the analysis of both fatty acids and sterols in a comprehensive analytical method. The method has great potential for the quantification of lipids as well as the comprehensive study of both biochemical pathways, using [(13)C]-flux analysis.

Evaluation of safety and tolerance of microencapsulated Lactobacillus reuteri NCIMB 30242 in a yogurt formulation: a randomized, placebo-controlled, double-blind study

Probiotic organisms have shown promise in treating diseases. Previously, we have reported on the efficacy of microencapsulated Lactobacillus reuteri NCIMB 30242 in a yogurt formulation at lowering serum cholesterol levels in otherwise healthy hypercholesterolemic adults. This study investigates the safety and toxicology of oral ingestion of microencapsulated L. reuteri NCIMB 30242 in a yogurt formulation. A randomized group of 120 subjects received a dose of 5 × 10(10) CFU microencapsulated L. reuteri NCIMB 30242 in yogurt (n=59) or placebo yogurt (n=61) twice/day for 6 weeks. Clinical chemistry and hematological parameters of safety were analyzed. Fecal samples were collected at these time points for the analysis of deconjugated bile acids. The frequency, duration and intensity of adverse events (AEs) and clinical significance of safety parameters were recorded for both groups. No clinically significant differences between the probiotic yogurt and placebo yogurt treated groups were detected in either the blood clinical chemistry or hematology results and there was no significant increase in fecal deconjugated bile acids (P>0.05) between treated and control groups. The frequency and intensity of AEs was similar in the two groups. These results demonstrate the safe use of this formulation in food.

Real-time estimation of small-area populations with human biomarkers in sewage

A new approach is conceptualized for measuring small-area human populations by using biomarkers in sewage. The basis for the concept (SCIM: Sewage Chemical-Information Mining) is supported by a comprehensive examination and synthesis of data published across several disciplines, including medicine, microbiology, clinical chemistry, and environmental science. Accurate measures of human populations are fundamental to numerous disciplines, including economics, marketing, politics, sociology, public health and safety (e.g., disease management; assessment of natural hazards; disaster prevention and response), quality of life, and the environment. Knowing the size, distribution, and flow of a small-area (local) population facilitates understanding the numerous and complex linkages and interactions between humans and the environment. Examples include material-flow (substance-flow) analysis, determining the magnitude of per capita contribution of pollutant loadings to watersheds, or forecasting future impacts of local populations on the environment or a population's demands on resources. While no definitive approach exists for measuring small-area populations, census-taking is a long-established convention. No approach exists, however, for gauging small-area populations in real-time, as none is able to capture population dynamics, which involve transient changes (e.g., daily influx and efflux) and lasting changes (e.g., births, deaths, change in residence). Accurate measurement of small-area populations in real time has never been possible but is essential for facilitating the design of more sustainable communities. Real-time measurement would provide communities the capability of testing what-if scenarios in design and policy decisions. After evaluation of a range of biomarkers (including the nitrogenous waste product creatinine, which has been long used in clinical chemistry as a parameter to normalize the concentrations of other urinary excretion products to account for urine dilution), the biomarker with the most potential for the SCIM concept for real-time measurement of population was determined to be coprostanol - the major sterol produced by microbial reduction of cholesterol in the colon.

Artichoke extract lowered plasma cholesterol and increased fecal bile acids in Golden Syrian hamsters

A study was conducted in hamsters to determine if artichoke leaf extract (ALE) could lower plasma total and non-HDL cholesterol by increasing fecal excretion of neutral bile acids and sterols. Sixty-four Golden Syrian hamsters (8 week old) were fed control diet or a similar diet containing ALE (4.5 g/kg diet) for 6 weeks. No significant changes for total cholesterol, HDL, non-HDL cholesterol triglycerides or fecal neutral sterols and bile acids were found after 21 days for ALE-fed animals compared with controls. But after 42 days, ALE-fed male hamsters had significantly lower total cholesterol (15%), non-HDL cholesterol (30%) and triglycerides (22%) and female hamsters fed ALE showed reductions of 15% for total cholesterol, 29% for non-HDL cholesterol and 29% for triglycerides compared with controls. Total neutral sterol and bile acids concentrations increased significantly by 50% and 53% in fecal samples of ALE fed males, and 82.4% and 25% in ALE fed females compared with controls. The ALE lowered hamster plasma cholesterol levels by a mechanism involving the greater excretion of fecal bile acids and neutral sterols after feeding for 42 days.

Cholesterol-lowering efficacy of a microencapsulated bile salt hydrolase-active Lactobacillus reuteri NCIMB 30242 yoghurt formulation in hypercholesterolaemic adults

Several studies have reported limited or no reduction in serum cholesterol in response to probiotic formulations. Recently, probiotics have shown promise in treating metabolic disease due to improved strain selection and delivery technologies. The aim of the present study was to evaluate the cholesterol-lowering efficacy of a yoghurt formulation containing microencapsulated bile salt hydrolase (BSH)-active Lactobacillus reuteri NCIMB 30242, taken twice per d over 6 weeks, in hypercholesterolaemic adults. A total of 114 subjects completed this double-blind, placebo-controlled, randomised, parallel-arm, multi-centre study. This interventional study included a 2-week washout, 2-week run-in and 6-week treatment period. Subjects were randomised to consume either yoghurts containing microencapsulated L. reuteri NCIMB 30242 or placebo yoghurts. Over the intervention period, subjects consuming yoghurts containing microencapsulated L. reuteri NCIMB 30242 attained significant reductions in LDL-cholesterol (LDL-C) of 8·92 % (P = 0·016), total cholesterol (TC) of 4·81 % (P = 0·031) and non-HDL-cholesterol (HDL-C) of 6·01 % (P = 0·029) over placebo, and a significant absolute change in apoB-100 of - 0·19 mmol/l (P = 0·049). Serum concentrations of TAG and HDL-C were unchanged over the course of the study. Present results show that consumption of microencapsulated BSH-active L. reuteri NCIMB 30242 yoghurt is efficacious and safe for lowering LDL-C, TC, apoB-100 and non-HDL-C in hypercholesterolaemic subjects. The efficacy of microencapsulated BSH-active L. reuteri NCIMB 30242 yoghurts appears to be superior to traditional probiotic therapy and akin to that of other cholesterol-lowering ingredients.

Fatty acid bile acid conjugate inhibits hepatic stearoyl coenzyme A desaturase and is non-atherogenic

BACKGROUND AND AIMS

Suppression of stearoyl-coenzyme A desaturase (SCD) activity leads to reduction of obesity, fatty liver as well as of insulin resistance. It was, however, recently reported to enhance atherogenesis. The aim of the present study was to investigate whether inhibition of SCD by Aramchol, a fatty acid bile conjugate with known hypocholesterolemic effects, will affect atherogenesis and how.

METHODS

Aramchol was tested in vitro in cultured cells and in vivo in rodents.

RESULTS

Aramchol, at very low concentrations, reduced SCD activity in liver microsomes of mice. Aramchol enhanced cholesterol efflux from macrophages more than twofold. In vivo it increased fecal sterol output and decreased markedly plasma cholesterol levels in mice. In ApoE(-/-), LDRL(-/-) and C57Bl6 mice, the effects of Aramchol on atherogenesis were non-atherogenic.

CONCLUSIONS

Aramchol reduces SCD activity and is non-atherogenic. It may offer a means to obtain the desirable hepatic metabolic effects of SCD inhibition without the deleterious atherogenic effect.

Bile acids: analysis in biological fluids and tissues

The formation of bile acids/bile alcohols is of major importance for the maintenance of cholesterol homeostasis. Besides their functions in lipid absorption, bile acids/bile alcohols are regulatory molecules for a number of metabolic processes. Their effects are structure-dependent, and numerous metabolic conversions result in a complex mixture of biologically active and inactive forms. Advanced methods are required to characterize and quantify individual bile acids in these mixtures. A combination of such analyses with analyses of the proteome will be required for a better understanding of mechanisms of action and nature of endogenous ligands. Mass spectrometry is the basic detection technique for effluents from chromatographic columns. Capillary liquid chromatography-mass spectrometry with electrospray ionization provides the highest sensitivity in metabolome analysis. Classical gas chromatography-mass spectrometry is less sensitive but offers extensive structure-dependent fragmentation increasing the specificity in analyses of isobaric isomers of unconjugated bile acids. Depending on the nature of the bile acid/bile alcohol mixture and the range of concentration of individuals, different sample preparation sequences, from simple extractions to group separations and derivatizations, are applicable. We review the methods currently available for the analysis of bile acids in biological fluids and tissues, with emphasis on the combination of liquid and gas phase chromatography with mass spectrometry.

Effects of nevirapine and efavirenz on HDL cholesterol levels and reverse cholesterol transport in mice

OBJECTIVE

The mechanism by which non-nucleoside reverse transcriptase inhibitors (NNRTIs) increase HDL cholesterol (HDL-C) in HIV+ patients and the benefits of this with respect to cardiovascular risk are not known. Studies were conducted to test the hypothesis that NNRTIs have a beneficial effect on HDL-C and reverse cholesterol transport (RCT).

METHODS

LDLr-/- and hA-I transgenic mice were fed a Western diet containing either nevirapine (20mg/kg per day), efavirenz (10mg/kg per day), or diet alone. hA-I transgenic mice underwent a study to measure RCT (measured by excretion of macrophage [(3)H]-cholesterol into HDL and feces) at 8 weeks.

RESULTS

LDLr-/- and hA-I transgenic mice treated with nevirapine and efavirenz had a significant increase in HDL-C level (up to 23% in hA-I transgenic) at 4 weeks. However, there was no difference in HDL levels beyond 4 weeks of treatment. At 4 weeks, the FPLC profile of hA-I transgenic mice showed an increase in large HDL. hApoA-I transgenic mice treated with efavirenz for 4 weeks had increased expression of human apoA-I in liver and an increased human apoA-I production rate. Incubation of plasma from hA-I transgenic mice treated for 4 weeks with [(3)H]-cholesterol-labeled macrophages revealed increased cholesterol efflux to plasma from mice treated with efavirenz and nevirapine. Following injection of hA-I transgenic mice treated for 8 weeks with [(3)H]-cholesterol-labeled macrophages, RCT was increased in the efavirenz (p=0.01) group and trended towards an increase in the nevirapine (p=0.15) group.

CONCLUSION

Nevirapine and efavirenz transiently increased HDL-C in LDLr-/- and hA-I transgenic mice fed a Western diet that was associated with increased apoA-I production. An increase in RCT in hA-I transgenic mice at 8 weeks despite no difference in HDL levels indicates that these drugs affect additional factors in the RCT pathway that enhance cholesterol efflux from the macrophage and peripheral tissues to plasma and delivery to liver for excretion. These results suggest that treatment with NNRTIs has a beneficial effect on cholesterol efflux and RCT.

Treatment of preestablished diet-induced fatty liver by oral fatty acid-bile acid conjugates in rodents

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in industrialized countries. It has no accepted medical therapy. Fatty acid-bile acid conjugates (FABACs) were proven to prevent diet-induced NAFLD in rodents.

AIM

This study was undertaken to test whether oral FABACs are also effective in reducing liver fat in preestablished diet-induced NAFLD.

METHODS

NAFLD was induced in mice and rats by a high-fat diet and maintained by various proportions thereof. The FABACs used were conjugates of cholic acid with either arachidic or stearic acids.

RESULTS

FABAC therapy reduced liver fat in all four series of experiments. The rapidity of the effect was inversely proportional to the concentration of fat in the maintenance diet. In mice on a 25% maintenance diet FABACs decreased total liver lipids by about 30% in 4 weeks (P<0.03). Diglycerides (P<0.003) and triglycerides (P<0.01) were the main neutral liver lipids that decreased during FABAC therapy. Both FABACs tested reduced liver fat in NAFLD at doses of 25 and 150 mg/kg/day. High-fat diet increased, whereas FABAC therapy decreased plasma 16 : 1/(16 : 0+16 : 1) fatty acid ratio - a marker of stearoyl CoA desaturase activity. In HepG2 cells FABACs decreased de-novo fatty acid synthesis dose dependently.

CONCLUSION

Oral FABAC therapy decreased liver fat in preestablished NAFLD in mice and rats. Inhibition of stearoyl CoA desaturase activity and fatty acid synthesis are mechanisms that may contribute to this decrease. FABACs may be potential therapeutic agents for human NAFLD.

AcrAB multidrug efflux pump regulation in Salmonella enterica serovar Typhimurium by RamA in response to environmental signals

Salmonella enterica serovar Typhimurium has at least nine multidrug efflux pumps. Among these pumps, AcrAB is effective in generating drug resistance and has wide substrate specificity. Here we report that indole, bile, and an Escherichia coli conditioned medium induced the AcrAB pump in Salmonella through a specific regulator, RamA. The RamA-binding sites were located in the upstream regions of acrAB and tolC. RamA was required for indole induction of acrAB. Other regulators of acrAB such as MarA, SoxS, Rob, SdiA, and AcrR did not contribute to acrAB induction by indole in Salmonella. Indole activated ramA transcription, and overproduction of RamA caused increased acrAB expression. In contrast, induction of ramA was not required for induction of acrAB by bile. Cholic acid binds to RamA, and we suggest that bile acts by altering pre-existing RamA. This points to two different AcrAB regulatory modes through RamA. Our results suggest that RamA controls the Salmonella AcrAB-TolC multidrug efflux system through dual regulatory modes in response to environmental signals.