Diabetes-associated alterations in the cecal microbiome and metabolome are independent of diet or environment in the UC Davis Type 2 Diabetes Mellitus Rat model

Analysis of immunohistomorphological changes in the colonic mucosa in a high-saturated fat and high-cholesterol fed streptozotocin/nicotinamide diabetic rat model

The mucosal surface of gastrointestinal tract is lined with epithelial cells that establish an effective barrier between the lumen and internal environment through intercellular junctions, preventing the passage of potentially harmful substances. The "intestinal barrier function" consist of a defensive system that prevent the passage of antigens, toxins, and microbial products, while maintains the correct development of the epithelial barrier, the immune system and the acquisition of tolerance toward dietary antigens and intestinal microbiota. Intestinal morphology changes subsequent to nutritional variations, stress, aging or diseases, which can also affect the composition of the microbiota, altering the homeostasis of the intestine. A growing body of evidence suggests that alterations in intestinal barrier function favor the development of exaggerated immune responses, leading to metabolic endotoxemia, which seems to be the origin of many chronic metabolic diseases such as type 2 diabetes mellitus (T2DM). Although the mechanisms are still unknown, the interaction between dietary patterns, gut microbiota, intestinal mucosa, and metabolic inflammation seems to be a key factor for the development of T2DM, among other diseases. This chapter details the different techniques that allow evaluating the morphological and molecular alterations that lead of the intestinal barrier dysfunction in a T2DM experimental model. To induce both diabetic metabolic disturbances and gut barrier disruption, Wistar rats were fed a high-saturated fat and high-cholesterol diet and received a single dose of streptozotocin/nicotinamide. This animal model may contribute to clarify the understanding of the role of intestinal barrier dysfunction on the late-stage T2DM etiology.

Colonic epithelial hypoxia remains constant during the progression of diabetes in male UC Davis type 2 diabetes mellitus rats

INTRODUCTION

Colonocyte oxidation of bacterial-derived butyrate has been reported to maintain synergistic obligate anaerobe populations by reducing colonocyte oxygen levels; however, it is not known whether this process is disrupted during the progression of type 2 diabetes. Our aim was to determine whether diabetes influences colonocyte oxygen levels in the University of California Davis type 2 diabetes mellitus (UCD-T2DM) rat model.

RESEARCH DESIGN AND METHODS

Age-matched male UCD-T2DM rats (174±4 days) prior to the onset of diabetes (PD, n=15), within 1 month post-onset (RD, n=12), and 3 months post-onset (D3M, n=12) were included in this study. Rats were administered an intraperitoneal injection of pimonidazole (60 mg/kg body weight) 1 hour prior to euthanasia and tissue collection to estimate colonic oxygen levels. Colon tissue was fixed in 10% formalin, embedded in paraffin, and processed for immunohistochemical detection of pimonidazole. The colonic microbiome was assessed by 16S gene rRNA amplicon sequencing and content of short-chain fatty acids was measured by liquid chromatography-mass spectrometry.

RESULTS

HbA1c % increased linearly across the PD (5.9±0.1), RD (7.6±0.4), and D3M (11.5±0.6) groups, confirming the progression of diabetes in this cohort. D3M rats had a 2.5% increase in known facultative anaerobes, Escherichia-Shigella, and Streptococcus (false discovery rate <0.05) genera in colon contents. The intensity of pimonidazole staining of colonic epithelia did not differ across groups (p=0.37). Colon content concentrations of acetate and propionate also did not differ across UCD-T2DM groups; however, colonic butyric acid levels were higher in D3M rats relative to PD rats (p<0.01).

CONCLUSIONS

The advancement of diabetes in UCD-T2DM rats was associated with an increase in facultative anaerobes; however, this was not explained by changes in colonocyte oxygen levels. The mechanisms underlying shifts in gut microbe populations associated with the progression of diabetes in the UCD-T2DM rat model remain to be identified.

Conserved signatures of the canine faecal microbiome are associated with metronidazole treatment and recovery

Antibiotic resistance is recognised as one of the biggest global threats to human and animal health. Understanding the influence of antibiotics on the canine microbiome is important to know the potential mid-to-long term effects on dysbiosis and mitigate side-effects such as antibiotic-associated diarrhoea. In this study, metronidazole was prescribed to 22 dogs for suspected giardiasis after exhibiting gastrointestinal symptoms such as diarrhoea and/or vomiting. Faecal samples were collected before, during seven days of treatment, and six months post-cessation. Faecal microbiota was assessed with 16S rRNA sequencing. Shannon diversity was reduced for up to three days after the treatment ended, and an altered community persisted for four to six weeks. All dogs recovered to a similar microbiome composition as pre-treatment. Immediately after receiving metronidazole, an increase in the relative abundance of the genera Lactobacillus, Bifidobacterium, and Enterococcus was observed. This may be due to antibiotic resistance commonly exhibited by these organisms. One-to-two weeks post-cessation, several other genera that were sensitive to the antibiotic recovered in abundances, with taxa belonging to the Erysipelotrichaceae family particularly driving composition change. Many of the bacteria initially reduced were associated with carbohydrate fermentation. This suggests scope exists to explore interventions to augment gastrointestinal health and support the re-establishment of the microbiome.

Electroacupuncture at ST36 modulates the intestinal microecology and may help repair the intestinal barrier in the rat model of severe acute pancreatitis

Severe acute pancreatitis (SAP) onset and development are closely associated with intestinal barrier injury. Evidence from clinical practice and research has shown that electroacupuncture (EA) at the Zusanli (ST36) acupoint can improve intestinal barrier function and abdominal symptoms in patients with SAP; however, the specific mechanisms of action remain unclear. This study aimed to observe the changes in the intestinal microbiota and metabolites in SAP rats and to explore the effect of EA at ST36 on intestinal barrier injury in SAP rats. 16S rRNA gene sequencing combined with microbial diversity analysis, short-chain fatty acids (SCFAs)-targeted metabolomics, immunohistochemistry, immunofluorescence, western blotting, and other techniques were used to explore the mechanism of EA at bilateral ST36 acupoints on SAP-related intestinal barrier injury. Our results showed that EA at ST36 could repair intestinal barrier injury by modulating intestinal microecology, thereby reducing intestinal inflammation, restoring intestinal function, and ultimately alleviating the prognosis of SAP. Our study provides new insights into the mechanisms and treatment of intestinal barrier injury in patients with SAP from the perspectives of microbiota and SCFAs regulation.

Microbial taxonomic and functional shifts in adolescents with type 1 diabetes are associated with clinical and dietary factors

BACKGROUND

Evidence indicates a link between the pathogenesis of type 1 diabetes (T1D) and the gut microbiome. However, the regulation of microbial metabolic pathways and the associations of bacterial species with dietary factors in T1D are largely unknown. We investigated whether microbial metagenomic signatures in adolescents with T1D are associated with clinical/dietary factors.

METHODS

Adolescents with T1D (case) and healthy adolescents (control) were recruited, and microbiome profiling in participants' stool samples was performed using shotgun metagenomic sequencing. The bioBakery3 pipeline (Kneaddata, Metaphlan 4 and HUMAnN) was used to assign taxonomy and functional annotations. Clinical (HbA1c) and dietary information (3-day food record) were collected for conducting association analysis using Spearman's correlation.

FINDINGS

Adolescents with T1D exhibited modest changes in taxonomic composition of gut microbiome. Nineteen microbial metabolic pathways were altered in T1D, including downregulation of biosynthesis of vitamins (B2/flavin, B7/biotin and B9/folate), enzyme cofactors (NAD+ and s-adenosyl methionine) and amino acids (aspartate, asparagine and lysine) with an upregulation in the fermentation pathways. Furthermore, bacterial species associated with dietary and clinical factors differed between healthy adolescents and adolescents with T1D. Supervised models modeling identified taxa predictive of T1D status, and the top features included Coprococcus and Streptococcus.

INTERPRETATION

Our study provides new insight into the alteration of microbial and metabolic signatures in adolescents with T1D, suggesting that microbial biosynthesis of vitamins, enzyme cofactors and amino acids may be potentially altered in T1D.

FUNDING

Research grants from NIH/NCCIH: R01AT010247 and USDA/NIFA: 2019-67017-29253; and Larry & Gail Miller Family Foundation Assistantship.

Gut microbiota diversity in middle-aged and elderly patients with end-stage diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD), but the mechanism between DKD and ESRD remains unclear. Some experts have put forward the "microbial-centered ESRD development theory", believing that the bacterial load caused by gut microecological imbalance and uremia toxin transfer are the core pathogenic links. The purpose of this study was to analyze the genomic characteristics of gut microbiota in patients with ESRD, specifically DKD or non-diabetic kidney disease (NDKD).

METHODS

In this cross-sectional study, patients with ESRD were recruited in a community, including 22 DKD patients and 22 NDKD patients matched using gender and age. Fecal samples of patients were collected for 16S rDNA sequencing and gut microbiota analysis. The distribution structure, diversity, and abundance of microflora in DKD patients were analyzed by constructing species evolutionary trees and analyzing alpha diversity, beta diversity, and linear discriminant analysis effect size (LEfSe).

RESULTS

The results of our study showed that there were statistically significant differences in the richness and species of gut microbiota at the total level between DKD patients and NDKD patients. The analysis of genus level between the two groups showed significant differences in 16 bacterial genera. Among them, Oscillibacter, Bilophila, UBA1819, Ruminococcaceae UCG-004, Anaerotruncus, Ruminococcaceae, and Ruminococcaceae NK4A214 bacteria in DKD patients were higher than those in NDKD patients.

CONCLUSIONS

16S rDNA sequencing technology was used in this study to analyze the characteristics of intestinal flora in ESRD patients with or without diabetes. We found that there was a significant difference in the intestinal flora of ESRD patients caused by DKD and NDKD, suggesting that these may be potential causative bacteria for the development of ERSD in DKD patients.

Cardiac NF-κB Acetylation Increases While Nrf2-Related Gene Expression and Mitochondrial Activity Are Impaired during the Progression of Diabetes in UCD-T2DM Rats

The onset of type II diabetes increases the heart’s susceptibility to oxidative damage because of the associated inflammation and diminished antioxidant response. Transcription factor NF-κB initiates inflammation while Nrf2 controls antioxidant defense. Current evidence suggests crosstalk between these transcription factors that may become dysregulated during type II diabetes mellitus (T2DM) manifestation. The objective of this study was to examine the dynamic changes that occur in both transcription factors and target genes during the progression of T2DM in the heart. Novel UC Davis T2DM (UCD-T2DM) rats at the following states were utilized: (1) lean, control Sprague-Dawley (SD; n = 7), (2) insulin-resistant pre-diabetic UCD-T2DM (Pre; n = 9), (3) 2-week recently diabetic UCD-T2DM (2Wk; n = 9), (4) 3-month diabetic UCD-T2DM (3Mo; n = 14), and (5) 6-month diabetic UCD-T2DM (6Mo; n = 9). NF-κB acetylation increased 2-fold in 3Mo and 6Mo diabetic animals compared to SD and Pre animals. Nox4 protein increased 4-fold by 6Mo compared to SD. Nrf2 translocation increased 82% in Pre compared to SD but fell 47% in 6Mo animals. GCLM protein fell 35% in 6Mo animals compared to Pre. Hmox1 mRNA decreased 45% in 6Mo animals compared to SD. These data suggest that during the progression of T2DM, NF-κB related genes increase while Nrf2 genes are suppressed or unchanged, perpetuating inflammation and a lesser ability to handle an oxidant burden altering the heart’s redox state. Collectively, these changes likely contribute to the diabetes-associated cardiovascular complications.

Zucker Diabetic Sprague Dawley rat (ZDSD): type 2 diabetes translational research model

New Findings

What is the topic of this review?

The Zucker Diabetic‐Sprague Dawley (ZDSD) rat is in the early adoption phase of use by researchers in the fields of diabetes, including prediabetes, obesity and metabolic syndrome. It is essential that physiology researchers choose preclinical models that model human type 2 diabetes appropriately and are aware of the limitations on experimental design.

What advances does it highlight?

Our review of the scientific literature finds that although sex, age and diets contribute to variability, the ZDSD phenotype and disease progression model the characteristics of humans who have prediabetes and diabetes, including co‐morbidities.

Abstract

Type 2 diabetes (T2D) is a prevalent disease and a significant concern for global population health. For persons with T2D, clinical treatments target not only the characteristics of hyperglycaemia and insulin resistance, but also co‐morbidities, such as obesity, cardiovascular and renal disease, neuropathies and skeletal bone conditions. The Zucker Diabetic‐Sprague Dawley (ZDSD) rat is a rodent model developed for experimental studies of T2D. We reviewed the scientific literature to highlight the characteristics of T2D development and the associated phenotypes, such as metabolic syndrome, cardiovascular complications and bone and skeletal pathologies in ZDSD rats. We found that ZDSD phenotype characteristics are independent of leptin receptor signalling. The ZDSD rat develops prediabetes, then progresses to overt diabetes that is accelerated by introduction of a timed high‐fat diet. In male ZDSD rats, glycated haemoglobin (HbA1c) increases at a constant rate from 7 to >30 weeks of age. Diabetic ZDSD rats are moderately hypertensive compared with other rat strains. Diabetes in ZDSD rats leads to endothelial dysfunction in specific vasculatures, impaired wound healing, decreased systolic and diastolic cardiac function, neuropathy and nephropathy. Changes to bone composition and the skeleton increase the risk of bone fractures. Zucker Diabetic‐Sprague Dawley rats have not yet achieved widespread use by researchers. We highlight sex‐related differences in the ZDSD phenotype and gaps in knowledge for future studies. Overall, scientific data support the premise that the phenotype and disease progression in ZDSD rats models the characteristics in humans. We conclude that ZDSD rats are an advantageous model to advance understanding and discovery of treatments for T2D through preclinical research.

Progression of diabetes is associated with changes in the ileal transcriptome and ileal-colon morphology in the UC Davis Type 2 Diabetes Mellitus rat

Deterioration in glucose homeostasis has been associated with intestinal dysbiosis, but it is not known how metabolic dysregulation alters the gastrointestinal environment. We investigated how the progression of diabetes alters ileal and colonic epithelial mucosal structure, microbial abundance, and transcript expression in the University of California Davis Type 2 Diabetes Mellitus (UCD-T2DM) rat model. Male UCD-T2DM rats (age ~170 days) were included if <1-month (n = 6, D1M) or 3-month (n = 6, D3M) post-onset of diabetes. Younger nondiabetic UCD-T2DM rats were included as a nondiabetic comparison (n = 6, ND, age ~70 days). Ileum villi height/crypt depths and colon crypt depths were assessed by histology. Microbial abundance of colon content was measured with 16S rRNA sequencing. Ileum and colon transcriptional abundances were analyzed using RNA sequencing. Ileum villi height and crypt depth were greater in D3M rats compared to ND. Colon crypt depth was greatest in D3M rats compared to both ND and D1M rats. Colon abundances of Akkermansia and Muribaculaceae were lower in D3M rats relative to D1M, while Oscillospirales, Phascolarctobacterium, and an unidentified genus of Lachnospiraceae were higher. Only two transcripts were altered by diabetes advancement within the colon; however, 2039 ileal transcripts were altered. Only colonic abundances of Sptlc3, Enpp7, Slc7a15, and Kctd14 had more than twofold changes between D1M and D3M rats. The advancement of diabetes in the UCD-T2DM rat results in a trophic effect on the mucosal epithelia and was associated with regulation of gastrointestinal tract RNA expression, which appears more pronounced in the ileum relative to the colon.

Microbial community structure and composition is associated with host species and sex in Sigmodon cotton rats

BACKGROUND

The cotton rat (genus Sigmodon) is an essential small animal model for the study of human infectious disease and viral therapeutic development. However, the impact of the host microbiome on infection outcomes has not been explored in this model, partly due to the lack of a comprehensive characterization of microbial communities across different cotton rat species. Understanding the dynamics of their microbiome could significantly help to better understand its role when modeling viral infections in this animal model.

RESULTS

We examined the bacterial communities of the gut and three external sites (skin, ear, and nose) of two inbred species of cotton rats commonly used in research (S. hispidus and S. fulviventer) by using 16S rRNA gene sequencing, constituting the first comprehensive characterization of the cotton rat microbiome. We showed that S. fulviventer maintained higher alpha diversity and richness than S. hispidus at external sites (skin, ear, nose), but there were no differentially abundant genera. However, S. fulviventer and S. hispidus had distinct fecal microbiomes composed of several significantly differentially abundant genera. Whole metagenomic shotgun sequencing of fecal samples identified species-level differences between S. hispidus and S. fulviventer, as well as different metabolic pathway functions as a result of differential host microbiome contributions. Furthermore, the microbiome composition of the external sites showed significant sex-based differences while fecal communities were not largely different.

CONCLUSIONS

Our study shows that host genetic background potentially exerts homeostatic pressures, resulting in distinct microbiomes for two different inbred cotton rat species. Because of the numerous studies that have uncovered strong relationships between host microbiome, viral infection outcomes, and immune responses, our findings represent a strong contribution for understanding the impact of different microbial communities on viral pathogenesis. Furthermore, we provide novel cotton rat microbiome data as a springboard to uncover the full therapeutic potential of the microbiome against viral infections.

Gut Microbiota of Chinese Obese Children and Adolescents With and Without Insulin Resistance

OBJECTIVE

The intestinal flora of gut microbiota in obese Chinese children and adolescents with and without insulin resistance (IR) was analyzed, as well as associations between the gut microbiota and two serum cytokines related to glucose metabolism, adropin and angiopoietin-like 4 (ANGPTL4).

METHODS

Clinical data, fecal bacterial composition, glucose-related hormones, and serum adipokines (adropin and ANGPTL4) were analyzed in 65 Chinese children with exogenous obesity. The composition of the gut microbiota was determined by 16S rRNA-based metagenomics and IR was calculated using the homeostasis model assessment (HOMA).

RESULTS

The 65 obese subjects were divided into two groups: insulin sensitive (IS) (n=40, 57.5% males) or IR (n=25, 60% males). Principal coordinates analysis revealed that the gut microbiota samples from the IS group clustered together and separated partly from the IR group (p=0.008). By Mann-Whitney U-test, at a phylum level, a reduction of Firmicutes and an increase of Bacteroidetes in the IR subjects was observed. LEfSe analysis revealed that IS subject, when compared to their IR counterparts, harbored members of the order Coriobacteriales, Turicibacterales, Pasteurellales and family Turicibacteraceae, that were significantly more abundant. In contrast, the IR subjects had members of family Peptococcaceae that were significantly more prevalent than the IS subjects (all p<0.05). Spearman's correlation analysis revealed that serum ANGPTL4 was positively associated with genus Bacteroides, Butyricimonas, and Alistipes, and adropin was positively associated with genus Anaerostipes and Alistipes, and negatively associated with genus Blautia (all p<0.05).

CONCLUSION

In obese children, the gut microbiome in IR subjects was significantly discordant from the IS subjects, and the abundance of some metabolism-related bacteria correlated with the serum concentrations of adropin and ANGPTL4. These observations infer that the gut microbiota may be involved in the regulation of glucose metabolism in obesity.

Measuring the microbiome: Best practices for developing and benchmarking microbiomics methods

Microbiomes are integral components of diverse ecosystems, and increasingly recognized for their roles in the health of humans, animals, plants, and other hosts. Given their complexity (both in composition and function), the effective study of microbiomes (microbiomics) relies on the development, optimization, and validation of computational methods for analyzing microbial datasets, such as from marker-gene (e.g., 16S rRNA gene) and metagenome data. This review describes best practices for benchmarking and implementing computational methods (and software) for studying microbiomes, with particular focus on unique characteristics of microbiomes and microbiomics data that should be taken into account when designing and testing microbiomics methods.

Xenometabolite signatures in the UC Davis type 2 diabetes mellitus rat model revealed using a metabolomics platform enriched with microbe-derived metabolites

The gut microbiome has the potential to create or modify xenometabolites (i.e., nonhost-derived metabolites) through de novo synthesis or modification of exogenous and endogenous compounds. While there are isolated examples of xenometabolites influencing host health and disease, wide-scale characterization of these metabolites remains limited. We developed a metabolomics platform ("XenoScan") using liquid chromatography-mass spectrometry to characterize a range of known and suspected xenometabolites and their derivatives. This assay currently applies authentic standards for 190 molecules, enriched for metabolites of microbial origin. As a proof-of-principle, we characterized the cecal content xenometabolomics profile in adult male lean Sprague-Dawley (LSD) and University of California, Davis type 2 diabetes mellitus (UCD-T2DM) rats at different stages of diabetes. These results were correlated to specific bacterial species generated via shotgun metagenomic sequencing. UCD-T2DM rats had a unique xenometabolite profile compared with LSD rats, regardless of diabetes status, suggesting that at least some of the variation is associated with host genetics. Furthermore, modeling approaches revealed that several xenometabolites discriminated UCD-T2DM rats at early stages of diabetes versus those at 3 mo postdiabetes onset. Several xenometabolite hubs correlated with specific bacterial species in both LSD and UCD-T2DM rats. For example, indole-3-propionic acid negatively correlated with species within the Oscillibacter genus in UCD-T2DM rats considered to be prediabetic or recently diagnosed diabetic, in contrast to gluconic acid and trimethylamine, which were positively correlated with Oscillibacter species. The application of a xenometabolite-enriched metabolomics assay in relevant milieus will enable rapid identification of a wide variety of gut-derived metabolites, their derivatives, and their potential biochemical origins of xenometabolites in relationship to host gastrointestinal microbial ecology.NEW & NOTEWORTHY We debut a liquid chromatography-mass spectrometry (LC/MS) platform called the XenoScan, which is a metabolomics platform for xenometabolites (nonself-originating metabolites). This assay has 190 in-house standards with the majority enriched for microbe-derived metabolites. As a proof-of-principle, we used the XenoScan to discriminate genetic differences from cecal samples associated with different rat lineages, in addition to characterizing diabetes progression in rat model of type 2 diabetes. Complementing microbial sequencing data with xenometabolites uncovered novel microbial metabolism in targeted organisms.

Single-Anastomosis Duodenal Jejunal Bypass Improve Glucose Metabolism by Regulating Gut Microbiota and Short-Chain Fatty Acids in Goto-Kakisaki Rats

In recent years, bariatric surgery has emerged as a promising treatment for type 2 diabetes. Bariatric surgery is known to cause alterations in the relative abundance and composition of gut microbiota, which may lead to alterations in the levels of Short-Chain Fatty Acids (SCFAs) that are produced during fermentation by gut microbes. However, little is known about the mechanism of improved glucose metabolism mediated by gut microbiota following bariatric surgery. The aim of our study was to explore whether changes in gut microbiota and in fecal SCFA could be detected following single-anastomosis duodenal jejunal bypass (DJB-sa) surgery, a type of bariatric surgery, and whether these alterations might be related to the improvement of glucose metabolism. To this end, we performed DJB-sa or SHAM surgery on Goto-Kakisaki (GK) rats. We then compared the glucose metabolism as well as changes in gut microbiota and SCFAs levels between both groups. Our results showed that DJB-sa surgery was associated with a significant decrease in fasting blood glucose (FBG), intraperitoneal glucose tolerance test (IPGTT), and fasting serum insulin (FSI). And, DJB-sa led to a change in the composition of gut microbiota including an increase in the relative abundance of SCFA-producing bacteria (Bifidobacterium and Subdoligranulum). Moreover, the levels of six SCFAs in feces, as well as the intestinal expression of SCFA receptors including G-protein-coupled receptor 41 (GPR41), G-protein-coupled receptor 43 (GPR43), and G-protein-coupled receptor 109A (GPR109A), and the expression of Glucagon-like peptide-1 (GLP-1) displayed a significant increase following DJB-sa compared with the Sham group. Thus, the gut microbiota may contribute to the improvement of glucose metabolism in type 2 diabetes following DJB-sa. In conclusion, our study shows that DJB-sa improves glucose metabolism by modulating gut microbiota and by increasing short-chain fatty acid production.

Exercise plasma metabolomics and xenometabolomics in obese, sedentary, insulin-resistant women: impact of a fitness and weight loss intervention

Insulin resistance has wide-ranging effects on metabolism, but there are knowledge gaps regarding the tissue origins of systemic metabolite patterns and how patterns are altered by fitness and metabolic health. To address these questions, plasma metabolite patterns were determined every 5 min during exercise (30 min, ∼45% of V̇o_2peak, ∼63 W) and recovery in overnight-fasted sedentary, obese, insulin-resistant women under controlled conditions of diet and physical activity. We hypothesized that improved fitness and insulin sensitivity following a ∼14-wk training and weight loss intervention would lead to fixed workload plasma metabolomics signatures reflective of metabolic health and muscle metabolism. Pattern analysis over the first 15 min of exercise, regardless of pre- versus postintervention status, highlighted anticipated increases in fatty acid tissue uptake and oxidation (e.g., reduced long-chain fatty acids), diminution of nonoxidative fates of glucose [e.g., lowered sorbitol-pathway metabolites and glycerol-3-galactoside (possible glycerolipid synthesis metabolite)], and enhanced tissue amino acid use (e.g., drops in amino acids; modest increase in urea). A novel observation was that exercise significantly increased several xenometabolites ("non-self" molecules, from microbes or foods), including benzoic acid-salicylic acid-salicylaldehyde, hexadecanol-octadecanol-dodecanol, and chlorogenic acid. In addition, many nonannotated metabolites changed with exercise. Although exercise itself strongly impacted the global metabolome, there were surprisingly few intervention-associated differences despite marked improvements in insulin sensitivity, fitness, and adiposity. These results and previously reported plasma acylcarnitine profiles support the principle that most metabolic changes during submaximal aerobic exercise are closely tethered to absolute ATP turnover rate (workload), regardless of fitness or metabolic health status.