Response of rumen microbiota,and metabolic profiles of rumen fluid,liver and serum of goats to high-grain diets

Feeding ruminants a high-grain (HG) diet is a widely used strategy to improve milk yield and cost efficiency. However, it may cause certain metabolic disorders. At present, information about the effects of HG diets on the systemic metabolic profile of goats and the correlation of such diets with rumen bacteria is limited. In the present study, goats were randomly divided into two groups: one was fed the hay diet (hay; n = 5), while the other was fed HG diets (HG; n = 5). On day 50, samples of rumen contents, peripheral blood serum and liver tissues were collected to determine the metabolic profiles in the rumen fluid, liver and serum and the microbial composition in rumen. The results revealed that HG diets reduced (P < 0.05) the community richness and diversity of rumen microbiota, with an increase in the Chao 1 and Shannon index and a decrease in the Simpson index. HG diets also altered the composition of rumen microbiota, with 30 genera affected (P < 0.05). Data on the metabolome showed that the metabolites in the rumen fluid, liver and serum were affected (variable importance projection > 1, P <0.05) by dietary treatment, with 47, 10 and 27 metabolites identified as differentially metabolites. Pathway analysis showed that the common metabolites in the shared key pathway (aminoacyl-transfer RNA biosynthesis) in the rumen fluid, liver and serum were glycine, lysine and valine. These findings suggested that HG diets changed the composition of the rumen microbiota and metabolites in the rumen fluid, liver and serum, mainly involved in amino acid metabolism. Our findings provide new insights into the understanding of diet-related systemic metabolism and the effects of HG diets on the overall health of goats.     

Establishment of Quantitative Severity Evaluation Model for Spinal Cord Injury by Metabolomic Fingerprinting

Spinal cord injury (SCI) is a devastating event with a limited hope for recovery and represents an enormous public health issue. It is crucial to understand the disturbances in the metabolic network after SCI to identify injury mechanisms and opportunities for treatment intervention. Through plasma 1H-nuclear magnetic resonance (NMR) screening, we identified 15 metabolites that made up an “Eigen-metabolome” capable of distinguishing rats with severe SCI from healthy control rats. Forty enzymes regulated these 15 metabolites in the metabolic network. We also found that 16 metabolites regulated by 130 enzymes in the metabolic network impacted neurobehavioral recovery. Using the Eigen-metabolome, we established a linear discrimination model to cluster rats with severe and mild SCI and control rats into separate groups and identify the interactive relationships between metabolic biomarkers in the global metabolic network. We identified 10 clusters in the global metabolic network and defined them as distinct metabolic disturbance domains of SCI. Metabolic paths such as retinal, glycerophospholipid, arachidonic acid metabolism; NAD–NADPH conversion process, tyrosine metabolism, and cadaverine and putrescine metabolism were included. In summary, we presented a novel interdisciplinary method that integrates metabolomics and global metabolic network analysis to visualize metabolic network disturbances after SCI. Our study demonstrated the systems biological study paradigm that integration of 1H-NMR, metabolomics, and global metabolic network analysis is useful to visualize complex metabolic disturbances after severe SCI. Furthermore, our findings may provide a new quantitative injury severity evaluation model for clinical use.     

Conditions for C NMR detection of 2-hydroxyglutarate in tissue extracts from isocitrate dehydrogenase-mutated gliomas

¹³C NMR (nuclear magnetic resonance) spectroscopy of extracts from patient tumor samples provides rich information about metabolism. However, in isocitrate dehydrogenase (IDH)-mutant gliomas, ¹³C labeling is obscured in oncometabolite 2-hydroxyglutaric acid (2HG) by glutamate and glutamine, prompting development of a simple method to resolve the metabolites. J-coupled multiplets in 2HG were similar to glutamate and glutamine and could be clearly resolved at pH 6. A cryogenically cooled ¹³C probe, but not J-resolved heteronuclear single quantum coherence spectroscopy, significantly improved detection of 2HG. These methods enable the monitoring of ¹³C–¹³C spin–spin couplings in 2HG expressing IDH-mutant gliomas.     

Diet-induced metabolic disturbances as modulators of brain homeostasis

A number of metabolic disturbances occur in response to the consumption of a high fat western diet. Such metabolic disturbances can include the progressive development of hyperglycemia, hyperinsulemia, obesity, metabolic syndrome, and diabetes. Cumulatively, diet-induced disturbances in metabolism are known to promote increased morbidity and negatively impact life expectancy through a variety of mechanisms. While the impact of metabolic disturbances on the hepatic, endocrine, and cardiovascular systems is well established there remains a noticeable void in understanding the basis by which the central nervous system (CNS) becomes altered in response to diet-induced metabolic dysfunction. In particular, it remains to be fully elucidated which established features of diet-induced pathogenesis (observed in non-CNS tissues) are recapitulated in the brain, and identification as to whether the observed changes in the brain are a direct or indirect effect of peripheral metabolic disturbances. This review will focus on each of these key issues and identify some critical experimental questions which remain to be elucidated experimentally, as well as provide an outline of our current understanding for how diet-induced alterations in metabolism may impact the brain during aging and age-related diseases of the nervous system.     

Oligodendrocyte-derived transcellular signaling regulates axonal energy metabolism

The unique morphology and functionality of central nervous system (CNS) neurons necessitate specialized mechanisms to maintain energy metabolism throughout long axons and extensive terminals. Oligodendrocytes (OLs) enwrap CNS axons with myelin sheaths in a multilamellar fashion. Apart from their well-established function in action potential propagation, OLs also provide intercellular metabolic support to axons by transferring energy metabolites and delivering exosomes consisting of proteins, lipids, and RNAs. OL-derived metabolic support is crucial for the maintenance of axonal integrity; its dysfunction has emerged as an important player in neurological disorders that are associated with axonal energy deficits and degeneration. In this review, we discuss recent advances in how these transcellular signaling pathways maintain axonal energy metabolism in health and neurological disorders.     

Isocitrate dehydrogenase variants in cancer — Cellular consequences and therapeutic opportunities

Abnormal metabolism is common in cancer cells and often correlates with mutations in genes encoding for enzymes involved in small-molecule metabolism. Isocitrate dehydrogenase 1 (IDH1) is the most frequently mutated metabolic gene in cancer. Cancer-associated substitutions in IDH1 and IDH2 impair wild-type production of 2-oxoglutarate and reduced nicotinamide adenine dinucleotide phosphate (NADPH) from isocitrate and oxidised nicotinamide adenine dinucleotide phosphate (NADP⁺ ), and substantially promote the IDH variant catalysed conversion of 2-oxoglutarate to d-2-hydroxyglutarate (d-2HG). Elevated d-2HG is a biomarker for some cancers, and inhibition of IDH1 and IDH2 variants is being pursued as a medicinal chemistry target. We provide an overview of the types of cancer-associated IDH variants, discuss some of the proposed consequences of altered metabolism as a result of elevated d-2HG, summarise therapeutic efforts targeting IDH variants and identify areas for future research.     

Metabolic Footprint Analysis Uncovers Strain Specific Overflow Metabolism and D-Isoleucine Production of Staphylococcus Aureus COL and HG001

During infection processes, Staphylococcus aureus is able to survive within the host and to invade tissues and cells. For studying the interaction between the pathogenic bacterium and the host cell, the bacterial growth behaviour and its metabolic adaptation to the host cell environment provides first basic information. In the present study, we therefore cultivated S. aureus COL and HG001 in the eukaryotic cell culture medium RPMI 1640 and analyzed the extracellular metabolic uptake and secretion patterns of both commonly used laboratory strains. Extracellular accumulation of D-isoleucine was detected starting during exponential growth of COL and HG001 in RPMI medium. This non-canonical D-amino acid is known to play a regulatory role in adaptation processes. Moreover, individual uptake of glucose, accumulation of acetate, further overflow metabolites, and intermediates of the branched-chain amino acid metabolism constitute unique metabolic footprints. Altogether these time-resolved footprint analyses give first metabolic insights into staphylococcal growth behaviour in a culture medium used for infection related studies.     

Global metabolic profiling to model biological processes of aging in twins

Aging is intimately linked to system‐wide metabolic changes that can be captured in blood. Understanding biological processes of aging in humans could help maintain a healthy aging trajectory and promote longevity. We performed untargeted plasma metabolomics quantifying 770 metabolites on a cross‐sectional cohort of 268 healthy individuals including 125 twin pairs covering human lifespan (from 6 months to 82 years). Unsupervised clustering of metabolic profiles revealed 6 main aging trajectories throughout life that were associated with key metabolic pathways such as progestin steroids, xanthine metabolism, and long‐chain fatty acids. A random forest (RF) model was successful to predict age in adult subjects (≥16 years) using 52 metabolites (R² = .97). Another RF model selected 54 metabolites to classify pediatric and adult participants (out‐of‐bag error = 8.58%). These RF models in combination with correlation network analysis were used to explore biological processes of healthy aging. The models highlighted established metabolites, like steroids, amino acids, and free fatty acids as well as novel metabolites and pathways. Finally, we show that metabolic profiles of twins become more dissimilar with age which provides insights into nongenetic age‐related variability in metabolic profiles in response to environmental exposure.     

Therapeutic effects of higenamine combined with [6]-gingerol on chronic heart failure induced by doxorubicin via ameliorating mitochondrial function

Higenamine (HG) is a natural benzylisoquinoline alkaloid isolated from Aconitum with positive inotropic and chronotropic effects. This study aimed to investigate the possible cardioprotective effects of HG combined with [6]-gingerol (HG/[6]-GR) against DOX-induced chronic heart failure (CHF) by comprehensive approaches. DOX-induced cardiotoxicity model in rats and H9c2 cells was established. Therapeutic effects of HG/[6]-GR on haemodynamics, serum indices and histopathology of cardiac tissue were analysed. Cell mitochondrial energy phenotype and cell mitochondrial fuel flex were measured by a Seahorse XFp analyser. Moreover, UHPLC-Q-TOF/MS was performed to explore the potential metabolites affecting the therapeutic effects and pathological process of CHF. To further investigate the potential mechanism of HG/[6]-GR, mRNA and protein expression levels of RAAS and LKB1/AMPK/Sirt1-related pathways were detected. The present data demonstrated that the therapeutic effects of HG/[6]-GR combination on CHF were presented in ameliorating heart function, down-regulation serum indices and alleviating histological damage of heart tissue. Besides, HG/[6]-GR has an effect on increasing cell viability of H9c2 cells, ameliorating DOX-induced mitochondrial dysfunction and elevating mitochondrial OCR and ECAR value. Metabolomics analyses showed that the therapeutic effect of HG/[6]-GR combination is mainly associated with the regulation of fatty acid metabolites and energy metabolism pathways. Furthermore, HG/[6]-GR has an effect on down-regulating RAAS pathway-related molecules and up-regulating LKB1/AMPKα/Sirt1-related pathway. The present work demonstrates that HG/[6]-GR prevented DOX-induced cardiotoxicity via the cardiotonic effect and promoting myocardial energy metabolism through the LKB1/AMPKα/Sirt1 signalling pathway, which promotes mitochondrial energy metabolism and protects against CHF.     

Monitoring the specific activities of dopamine and its metabolites in striatum and olfactory tubercle after intravenous administration of l-[3H]tyrosine: Complex relations,indicating more than two compartments

It is still a matter of debate whether in dopaminergic nerve endings dopamine (DA) is present in different functional and/or metabolic compartments. To investigate this, DA metabolism was studied in vivo by measuring the specific activity of DA and its metabolites after intravenous administration of l-[3,5-³H]tyrosine (200 μCi/rat) to freely moving animals. The incorporation of ³H into DA and metabolites was determined in striatum and olfactory tubercle at 5, 10, 20, 40, 60 and 80 min after [³H]tyrosine administration. In both structures the level of [³H]tyrosine initially declined monoexponentially, but deviated from that pattern later on. The curves representing the formation in time of [³H]DA and [³H]metabolites were very similar in both structures, although as a whole, the levels in the olfactory tubercle were higher. The relative patterns of the specific activities of DA and those of its metabolites, a possible clue to DA compartmentation, neither indicated a clearcut metabolic one-compartment, nor a two-compartment system. The flow of radioactivity through DA metabolism could in fact only be explained by assuming more complex metabolic relations.     

Metabolomic dynamics of the arsenic-transformed bronchial epithelial cells and the derived cancer stem-like cells

Accumulating evidence indicates a carcinogenic role of environmental arsenic exposure, but mechanisms on how arsenic fosters malignant transformation of the normal cells are not fully established. By applying untargeted global metabolomics approach, we now show that arsenic is highly capable of perturbing the intracellular metabolic programs of the human bronchial epithelial cells, some of which are prominent hallmarks of cancer cell metabolism. To understand the spatiotemporal patterns of arsenic regulation on multiple metabolic pathways, we treated the cells with environmentally relevant concentration of arsenic, 0.25 μM, consecutively for 6 weeks to 24 weeks, and found that arsenic prompted heme metabolism, glycolysis, sphingolipid metabolism, phospholipid catabolism, protein degradation, and cholesterol breakdown constitutively, but inhibited metabolism of uracil-containing pyrimidine, carnitine, serotonin, polyamines, and fatty acid β-oxidation. A strong inhibition of all metabolites in mitochondrial tricarboxylic acid (TCA) cycle was noted in the cells treated with As³⁺ for 6 to 13 weeks. However, the metabolites in the earlier, but not the later steps of TCA cycle, including citrate, aconitate and isocitrate, were induced at 16 weeks through 24 weeks of arsenic treatment. This comprehensive metabolomics analysis provides new insights into metabolic perturbation by arsenic and may lead to more precise indications of arsenic in molecular carcinogenesis.     

The effects of N-dodecane pretreatment on the metabolism and distribution of benzo(A) pyrene in the isolated perfused rabbit lung

B(a)P is an ubiquitous potent carcinogen that has been associated with the increased incidence of human bronchiogenic carcinoma in occupational and urban populations. An isolated perfused rabbit lung preparation (IPL) was used to study the influence of pretreatment with a cocarcinogen, n-dodecane, on the metabolism of benzo (a)-pyrene (B(a)P). ¹⁴C-B(a)P was administered intratracheally to the IPL following biweekly inhalation exposure of the rabbits to n-dodecane. Results from n-dodecane pretreatment group were compared to those from the no-pretreatment group and an intratracheally administered B(a)P pretreatment group (B(a)P IT). Metabolites were isolated from serial blood samples up to 3 hours after administration of the ¹⁴C-B(a)P to the IPL. Patterns of B(a)P metabolites were determined using thin layer and high performance liquid chromatography, and liquid scintillation counting. The rates of appearance of B(a)P metabolites in the blood and the B(a)P metabolic pattern for n-dodecane groups were compared to B(a)P IT and no-pretreatment groups. The rates of appearance of metabolites in the blood (ng/hr/g of lung) were similar for B(a)P IT and n-dodecane pretreatment groups, but were five and four times greater, respectively, when compared to rates of appearance of metabolites for the no-pretreatment group. The B(a)P metabolic pattern of n-dodecane pretreatment showed an increase in the dihydrodiol and nonextractable formation and a decrease in the monohydroxy and diones compared to the no-pretreatment group. The metabolite pattern for B(a)P IT pretreatment group was similar to the metabolite pattern for the n-dodecane pretreatment group. The significance of the findings is that a known cocarcinogen, n-dodecane, appears to be as good an enzyme inducer as B(a)P in stimulating metabolism of B(a)P in lung. Therefore, man's risk in developing cancer may not be solely a result of exposure to a carcinogen, but may be dependent upon other constituents in his environment.     

Exposure to 12C particles alters the normal dynamics of brain monoamine metabolism and behaviour in rats

Planning of the deep-space exploration missions raises a number of questions on the radiation protection of astronauts. One of the medical concerns is associated with exposure of a crew to highly energetic particles of galactic cosmic rays. Among many other health disorders, irradiation with these particles has a substantial impact on the central nervous system (CNS). Although radiation damage to CNS has been addressed extensively during the last years, the mechanisms underlying observed impairments remain mostly unknown. The present study reveals neurochemical and behavioural alterations induced in rats by 1 Gy of 500 MeV/u ¹²C particles with a relatively moderate linear energy transfer (10.6 keV/μm). It is found that exposure to carbon ions leads to significant modification of the normal monoamine metabolism dynamics as well as the locomotor, exploratory, and anxiety-like behaviours during a two-month period. The obtained results indicate an abnormal redistribution of monoamines and their metabolites in different brain regions after exposure. The most pronounced impairments are detected in the prefrontal cortex, nucleus accumbens, and hypothalamus that illustrate the sensitivity of these brain regions to densely ionizing radiations. It is also shown that exposure to ¹²C particles enhances the anxiety in animals and accelerates the age-related reduction in their exploratory capability. The observed monoamine metabolism pattern may indicate the presence of certain compensatory mechanisms being induced in response to irradiation and capable of partial restoration of monoaminergic systems’ functions. Overall, these findings support a possibility of CNS damage by space-born particles of a relatively moderate linear energy transfer.     

Metabolic signatures of esophageal cancer: NMR-based metabolomics and UHPLC-based focused metabolomics of blood serum

Focused metabolic profiling is a powerful tool for the determination of biomarkers. Here, a more global proton nuclear magnetic resonance (¹H NMR)-based metabolomic approach coupled with a relative simple ultra high performance liquid chromatography (UHPLC)-based focused metabolomic approach was developed and compared to characterize the systemic metabolic disturbances underlying esophageal cancer (EC) and identify possible early biomarkers for clinical prognosis. Serum metabolic profiling of patients with EC (n = 25) and healthy controls (n = 25) was performed by using both ¹H NMR and UHPLC, and metabolite identification was achieved by multivariate statistical analysis. Using orthogonal projection to least squares discriminant analysis (OPLS-DA), we could distinguish EC patients from healthy controls. The predictive power of the model derived from the UHPLC-based focused metabolomics performed better in both sensitivity and specificity than the results from the NMR-based metabolomics, suggesting that the focused metabolomic technique may be of advantage in the future for the determination of biomarkers. Moreover, focused metabolic profiling is highly simple, accurate and specific, and should prove equally valuable in metabolomic research applications. A total of nineteen significantly altered metabolites were identified as the potential disease associated biomarkers. Significant changes in lipid metabolism, amino acid metabolism, glycolysis, ketogenesis, tricarboxylic acid (TCA) cycle and energy metabolism were observed in EC patients compared with the healthy controls. These results demonstrated that metabolic profiling of serum could be useful as a screening tool for early EC diagnosis and prognosis, and might enhance our understanding of the mechanisms involved in the tumor progression.     

Protective Effects of 28-O-Caffeoyl Betulin (B-CA) on the Cerebral Cortex of Ischemic Rats Revealed by a NMR-Based Metabolomics Analysis

28-O-caffeoyl betulin (B-CA) has been demonstrated to reduce the cerebral infarct volume caused by transient middle cerebral artery occlusion (MCAO) injury. B-CA is a novel derivative of naturally occurring caffeoyl triterpene with little information associated with its pharmacological target(s). To date no data is available regarding the effect of B-CA on brain metabolism. In the present study, a ¹H-NMR-based metabolomics approach was applied to investigate the therapeutic effects of B-CA on brain metabolism following MCAO in rats. Global metabolic profiles of the cortex in acute period (9 h after focal ischemia onset) after MCAO were compared between the groups (sham; MCAO?+?vehicle; MCAO?+?B-CA). MCAO induced several changes in the ipsilateral cortex of ischemic rats, which consequently led to the neuronal damage featured with the downregulation of NAA, including energy metabolism dysfunctions, oxidative stress, and neurotransmitter metabolism. Treatment with B-CA showed statistically significant rescue effects on the ischemic cortex of MCAO rats. Specifically, treatment with B-CA ameliorated the energy metabolism dysfunctions (back-regulating the levels of succinate, lactate, BCAAs, and carnitine), oxidative stress (upregulating the level of glutathione), and neurotransmitter metabolism disturbances (back-regulating the levels of γ-aminobutyric acid and acetylcholine) associated with the progression of ischemic stroke. With the administration of B-CA, the levels of three phospholipid related metabolites (O-phosphocholine, O-phosphoethanolamine, sn-glycero-3-phosphocholine) and NAA improved significantly. Overall, our findings suggest that treatment with B-CA may provide neuroprotection by augmenting the metabolic changes observed in the cortex following MCAO in rats.

     

NMR spectroscopy based metabolic profiling of urine and serum for investigation of physiological perturbations during radiation sickness

Radiation accidents are rare events that induce radiation syndrome, a complex pathology which is difficult to treat. In medical management of radiation victims, life threatening damage to different physiological systems should be taken into consideration. The present study was proposed to identify metabolic and physiological perturbations in biofluids of mice during different phases of radiation sickness using ¹H nuclear magnetic resonance (¹H NMR) spectroscopy and pattern recognition (PR) technique. The ¹H NMR spectra of the biofluids collected from mice irradiated with 5 Gray (Gy) at different time points during radiation sickness were analysed visually and by principal components analysis. Urine and serum spectral profile clearly showed altered metabolic profiles during different phases of radiation sickness. Increased concentration of urine metabolites viz. citrate, α ketoglutarate, succinate, hippurate, and trimethylamine during prodromal and clinical manifestation phase of radiation sickness shows altered gut microflora and energy metabolism. On the other hand, serum nuclear magnetic resonance (NMR) spectra reflected changes associated with lipid, energy and membrane metabolism during radiation sickness. The metabonomic time trajectory based on PR analysis of ¹H NMR spectra of urine illustrates clear separation of irradiated mice group at different time points from pre dose. The difference in NMR spectral profiles depicts the pathophysiological changes and metabolic disturbances observed during different phases of radiation sickness, that in turn, demonstrate involvement of multiple organ dysfunction. This could further be useful in development of multiparametric approach for better evaluation of radiation damage as well as for medical management during radiation sickness.     

Metabonomics reveals plasma metabolic changes and inflammatory marker in polycystic ovary syndrome patients

Polycystic ovary syndrome (PCOS) is a common, clinically heterogeneous endocrine disorder affecting women of reproductive age, associated with endocrinopathy and metabolic abnormalities. Although some metabolic parameters have been investigated, very little information has been reported on the changes of small metabolites in biofluids. The aim of this study was to establish the metabolic profile of PCOS and compare it with that of controls. In this cross-sectional study of 34 women with PCOS and 36 controls, contents of small metabolites and lipids in plasma samples were measured using nuclear magnetic resonance (NMR)-based techniques and analyzed using multivariate statistical methods. Significant decrease (P < 0.05) in the levels of amino acids (leucine, isoleucine, methionine, glutamine, and arginine), citrate, choline, and glycerophosphocholine/phosphocholine (GPC/PC), and increase (P < 0.05) in the levels of lactate, dimethylamine (DMA), creatine, and N-acetyl glycoproteins were observed in PCOS patients compared with the controls. Subgroups of patients with obesity, metabolic syndrome, or hyperandrogenism exhibited greater metabolic deviations than their corresponding subgroups without these factors. PCOS patients have perturbations in amino acid metabolism, the tricarboxylic acid (TCA) cycle, and gut microflora, as well as mild disturbances in glucose and lipid metabolism. The elevated level of N-acetyl glycoproteins demonstrates the existence of low-grade chronic inflammation in PCOS patients.     

Identification of candidate biomarkers of brain damage in a mouse model of closed head injury: a metabolomic pilot study

We aim to identify candidate brain biomarkers for, and to elucidate the pathophysiology of closed traumatic brain injury (TBI). Nuclear magnetic resonance (NMR) based metabolomic analysis was performed on the whole brain of mice undergoing TBI using a validated technique. There were 10 TBI mice compared to 8 sham operated controls. A total of 45 metabolites were evaluated. There was a statistically significant alteration in concentrations of 29 metabolites in TBI brains as compared to controls (FDR <0.05). Profound disturbances of several metabolic pathways (FDR <1E-07), including pathways associated with purine, alanine, aspartate and glutamine and glutathione metabolism were observed. Also, a significant elevation in glutamate (the main excitatory neurotransmitter) and depression of GABA (the main inhibitory neurotransmitter) was observed. Four metabolites, ADP, AMP, NAD+, and IMP were the most important indicators of TBI, relative to normal controls. All were elevated in the TBI mice. A combination of these 4 biomarkers produced a perfect predictor of TBI status, AUC (95 % CI) = 1.0 (1.0, 1.0). We also detected significant disturbances in mitochondrial function, energy metabolism, neurotransmitter metabolism and other important biochemical pathways in TBI mouse brains. Further studies to assess the utility of metabolomics to detect and classify the severity of and assess the prognosis of TBI is warranted.     

Differential metabolism of benzo[alpha]pyrene in vitro by human placental tissues exposed to active maternal cigarette smoke

OBJECTIVES: Generation of different metabolites and DNA-adduct(s) of metabolites of benzo[alpha]pyrene (B[alpha]P) in vitro by placental tissues (microsomes) of mothers who actively smoked cigarettes (tobacco) and those who did not smoke were analyzed to determine the variability in metabolism of the B[alpha]P substrate among individual placental samples. METHODS: Overall B[alpha]P metabolism was assayed by alkaline aqueous extraction of metabolites, and reactive metabolites by DNA adducts of B[alpha]P-metabolites produced by salmon sperm DNA added to the incubation mixtures of the substrate and microsomes of exposed- and unexposed-placentas to maternal cigarette smoke. Array of B[alpha]P-metabolites produced by the same incubations were identified by high pressure liquid chromatography of the aqueous extracts. RESULTS: Subsets of smoke-exposed placentas assessed by cluster analysis had augmented metabolic activity, others did not respond to smoke exposure. CYP1A1 expression in trophoblast cells analyzed by immunohistochemistry did not correlate with smoke exposure. The DNA-adducts generated was variable, regardless of verbally reported levels of maternal exposure. The amounts of different B[alpha]P-metabolites produced by individual samples matched for similar levels of exposure during pregnancy by self-reported smoking (1 pack/day) were also not comparable. Metabolism of B[alpha]P into different metabolites, and production of toxic DNA adducts from metabolites in vitro by human placenta were variable and unrelated to the extent of smoke exposure. CONCLUSIONS: The metabolic characteristic of human placenta for xenobiotic exposure substrates is based on the expression and function of diverse enzymes, and such metabolism exhibited inter-individual variation for toxic metabolite production or detoxification of the substrates in response to maternal smoke exposure.