Living with trimethylaminuria and body and breath malodour: personal perspectives.

BACKGROUND: Many people suffer from body and breath malodour syndromes. One of these is trimethylaminuria, a condition characterized by excretion in breath and bodily fluids of trimethylamine, a volatile and odorous chemical that has the smell of rotting fish. Trimethylaminuria can be primary, due to mutations in the gene encoding flavin-containing monooxygenase 3, or secondary, due to various causes. To gain a better understanding of problems faced by United Kingdom residents affected by body and breath malodour conditions, we conducted a survey. METHODS: Two anonymous online surveys, one for adults and one for parents/guardians of affected children, were conducted using the Opinio platform. Participants were invited via a trimethylaminuria advisory website. Questions were a mix of dropdown, checkbox and open-ended responses. Forty-four adults and three parents/guardians participated. The dropdown and checkbox responses were analysed using the Opinio platform. RESULTS: All participants reported symptoms of body/breath odour. However, not all answered every question. Twenty-three respondents experienced difficulties in being offered a diagnostic test for trimethylaminuria. Problems encountered included lack of awareness of the disorder by medical professionals and reluctance to recognise symptoms. Of those tested, 52% were diagnosed with trimethylaminuria. The main problems associated with living with body/breath malodours were bullying, harassment and ostracism in either the workplace (90%) or in social settings (88%). All respondents thought their condition had disadvantaged them in their daily lives. Open-ended responses included loss of confidence, stress, exclusion, isolation, loneliness, depression and suicidal thoughts. Respondents thought their lives could be improved by greater awareness and understanding of malodour conditions by medical professionals, employers and the general public, and appreciation that the malodour was due to a medical condition and not their fault. CONCLUSIONS: Breath and body malodour conditions can cause immense hardship and distress, both mentally and socially, having devastating effects on quality of life. It would be advantageous to establish a standardised pathway from primary care to a specialist unit with access to a robust and reliable test and diagnostic criteria. There is a need to recognise malodour disorders as a disability, giving affected individuals the same rights as those with currently recognised disabilities.

Recognizing sinonasal cancer in primary care: a matched case-control study using electronic records.

BACKGROUND: Cancers of the nasopharynx, nasal cavity, and accessory sinuses ("sinonasal") are rare in England, with around 750 patients diagnosed annually. There are no specific National Institute for Health and Care Excellence (NICE) referral guidelines for these cancers and no primary care research published. OBJECTIVE: To identify and quantify clinical features of sinonasal cancer in UK primary care patients. METHODS: This matched case-control study used UK Clinical Practice Research Datalink (CPRD) data. Patients were aged ≥40 years with a diagnosis of sinonasal cancer between January 1, 2000 and December 31, 2009 and had consulted their GP in the year before diagnosis. Clinical features of sinonasal cancer were analysed using conditional logistic regression. Positive predictive values (PPVs) for single and combined features were calculated. RESULTS: In total, 155 cases and 697 controls were studied. Nine symptoms and one abnormal investigation were significantly associated with the cancer: nasal mass; odds ratio, 95 (95% confidence interval 7.0, 1315, P = 0.001); head and neck lumps, 68 (12, 387, P < 0.001); epistaxis, 17 (3.9, 70, P < 0.001); rhinorrhoea, 14 (4.6, 44, P < 0.001); visual disturbance, 12 (2.2, 67, P = 0.004); sinusitis, 7.3 (2.2, 25, P = 0.001); sore throat, 6.0 (2.0, 18, P = 0.001); otalgia, 5.4 (1.6, 18, P = 0.007); headache, 3.6 (1.4, 9.5, P = 0.01); raised white cell count, 8.5 (2.8, 27, P < 0.001). Combined PPVs for epistaxis/rhinorrhoea, epistaxis/sinusitis, and rhinorrhoea/sinusitis were 0.62%. CONCLUSION: This is the first primary care study identifying epistaxis, sinusitis, and rhinorrhoea as part of the clinical prodrome of sinonasal cancer. Although no PPVs meet the 3% NICE referral threshold, these results may help clinicians identify who warrants safety-netting and possible specialist referral, potentially reducing the number of advanced-stage diagnoses of sinonasal cancer.

Sinonasal cancer occurs in the back of the nose or in the sinuses. It is rare in the United Kingdom, with most cases being diagnosed at an advanced stage. Delayed presentation and non-specific symptoms often lead to diagnosis at a later stage, with consequently poorer survival outcomes. Currently, there is no research describing the symptoms presented by these patients to their general practitioner (GP), nor referral guidelines for primary healthcare professionals. The aim of this study was to detect the symptoms of patients aged ≥40 years, diagnosed with sinonasal cancer in primary care. Three symptoms in the year before their diagnosis were linked with sinonasal cancer: nosebleeds, runny nose, and sinusitis. These symptoms may help GPs to identify possible sinonasal cancer patients earlier, though each symptom was low-risk on its own.

Quantifying the impact of pre-existing conditions on the stage of oesophagogastric cancer at diagnosis: a primary care cohort study using electronic medical records.

BACKGROUND: Pre-existing conditions interfere with cancer diagnosis by offering diagnostic alternatives, competing for clinical attention or through patient surveillance. OBJECTIVE: To investigate associations between oesophagogastric cancer stage and pre-existing conditions. METHODS: Retrospective cohort study using Clinical Practice Research Datalink (CPRD) data, with English cancer registry linkage. Participants aged ≥40 years had consulted primary care in the year before their incident diagnosis of oesophagogastric cancer in 01/01/2010-31/12/2015. CPRD records pre-diagnosis were searched for codes denoting clinical features of oesophagogastric cancer and for pre-existing conditions, including those providing plausible diagnostic alternatives for those features. Logistic regression analysed associations between stage and multimorbidity (≥2 conditions; reference category: no multimorbidity) and having 'diagnostic alternative(s)', controlling for age, sex, deprivation and cancer site. RESULTS: Of 2444 participants provided, 695 (28%) were excluded for missing stage, leaving 1749 for analysis (1265/1749, 72.3% had advanced-stage disease). Multimorbidity was associated with stage [odds ratio 0.63, 95% confidence interval (CI) 0.47-0.85, P = 0.002], with moderate evidence of an interaction term with sex (1.76, 1.08-2.86, P = 0.024). There was no association between alternative explanations and stage (odds ratio 1.18, 95% CI 0.87-1.60, P = 0.278). CONCLUSIONS: In men, multimorbidity is associated with a reduced chance of advanced-stage oesophagogastric cancer, to levels seen collectively for women.

Diagnosing cancer is complicated by existing medical conditions. Diagnosis may be delayed if conditions explain cancer symptoms, or dominate appointments. Diagnosis may be quicker if conditions increase doctor­patient contact. We studied the association between existing illness and stage (early or advanced) of diagnosis with cancer of the stomach or gullet. We studied the primary-care records of patients aged ≥40 years, diagnosed in 01/01/2010­31/12/2015, and got stage from English cancer registry data. We searched the primary-care records for cancer symptoms (e.g. difficulty swallowing), and for 27 conditions that were common or explained cancer symptoms (e.g. difficulty swallowing following a stroke). We analysed cancer stage, looking at age, sex, multimorbidity (two or more conditions) and explanations for symptoms. We studied 1749 patients, of whom 1265 (72.3%) had advanced-stage cancer. The chance of advanced stage was similar in women with (71%, 95% CI 66­75%) or without (69%, 62­76%) multimorbidity. It was lower for men with (70%, 67­74%) than without (79%, 75­83%) multimorbidity. Stage of cancer was not affected by having explanations for cancer symptoms. In summary, for men, multimorbidity is associated with a reduced chance of advanced-stage cancer of the stomach or gullet to levels seen collectively for women.

Flavin-Containing Monooxygenase 1 Catalyzes the Production of Taurine from Hypotaurine.

Taurine is one of the most abundant amino acids in mammalian tissues. It is obtained from the diet and by de novo synthesis from cysteic acid or hypotaurine. Despite the discovery in 1954 that the oxygenation of hypotaurine produces taurine, the identification of an enzyme catalyzing this reaction has remained elusive. In large part, this is due to the incorrect assignment, in 1962, of the enzyme as an NAD-dependent hypotaurine dehydrogenase. For more than 55 years, the literature has continued to refer to this enzyme as such. Here we show, both in vivo and in vitro, that the enzyme that oxygenates hypotaurine to produce taurine is flavin-containing monooxygenase (FMO) 1. Metabolite analysis of the urine of Fmo1-null mice by 1H NMR spectroscopy revealed a buildup of hypotaurine and a deficit of taurine in comparison with the concentrations of these compounds in the urine of wild-type mice. In vitro assays confirmed that human FMO1 catalyzes the conversion of hypotaurine to taurine, utilizing either NADPH or NADH as cofactor. FMO1 has a wide substrate range and is best known as a xenobiotic- or drug-metabolizing enzyme. The identification that the endogenous molecule hypotaurine is a substrate for the FMO1-catalyzed production of taurine resolves a long-standing mystery. This finding should help establish the role FMO1 plays in a range of biologic processes in which taurine or its deficiency is implicated, including conjugation of bile acids, neurotransmitter, antioxidant and anti-inflammatory functions, and the pathogenesis of obesity and skeletal muscle disorders. SIGNIFICANCE STATEMENT: The identity of the enzyme that catalyzes the biosynthesis of taurine from hypotaurine has remained elusive. Here we show, both in vivo and in vitro, that flavin-containing monooxygenase 1 catalyzes the oxygenation of hypotaurine to produce taurine.

Flavin-containing monooxygenase 3 (FMO3): genetic variants and their consequences for drug metabolism and disease.

The review focuses on genetic variants of human flavin-containing monooxygenase 3 (FMO3) and their impact on enzyme activity, drug metabolism and disease.The majority of FMO-mediated metabolism in adult human liver is catalyzed by FMO3. Some drugs are metabolized in human liver predominantly by FMO3, but most drug substrates of FMO3 are metabolized also by other enzymes, particularly cytochromes P-450, and the FMO3-catalyzed reaction is not the major route of metabolism.Rare variants that severely affect production or activity of FMO3 cause the disorder trimethylaminuria and impair metabolism of drug substrates of FMO3. More common variants, particularly p.[(Glu158Lys);(Glu308Gly)], can moderately affect activity of FMO3 in vitro and reduce metabolism of drug substrates in vivo, in some cases increasing drug efficacy or toxicity.Common variants of FMO3 have been associated with a number of disorders, but additional studies are needed to confirm or refute such associations.Elevated plasma concentrations of trimethylamine N-oxide, a product of an FMO3-catalyzed reaction, have been implicated in certain diseases, particularly cardiovascular disease. However, the evidence is often contradictory and additional work is required to establish whether trimethylamine N-oxide is a cause, effect or biomarker of the disease.Genetic variants of other FMOs are also briefly discussed.

Effect of Flavin-Containing Monooxygenase Genotype, Mouse Strain, and Gender on Trimethylamine N-oxide Production, Plasma Cholesterol Concentration, and an Index of Atherosclerosis.

The objectives of the study were to determine the contribution, in mice, of members of the flavin-containing monooxygenase (FMO) family to the production of trimethylamine (TMA) N-oxide (TMAO), a potential proatherogenic molecule, and whether under normal dietary conditions differences in TMAO production were associated with changes in plasma cholesterol concentration or with an index of atherosclerosis (Als). Concentrations of urinary TMA and TMAO and plasma cholesterol were measured in 10-week-old male and female C57BL/6J and CD-1 mice and in mouse lines deficient in various Fmo genes (Fmo1-/- , 2-/- , 4-/- , and Fmo5-/- ). In female mice most TMA N-oxygenation was catalyzed by FMO3, but in both genders 11%-12% of TMA was converted to TMAO by FMO1. Gender-, Fmo genotype-, and strain-related differences in TMAO production were accompanied by opposite effects on plasma cholesterol concentration. Plasma cholesterol was negatively, but weakly, correlated with TMAO production and urinary TMAO concentration. Fmo genotype had no effect on Als. There was no correlation between Als and either TMAO production or urinary TMAO concentration. Our results indicate that under normal dietary conditions TMAO does not increase plasma cholesterol or act as a proatherogenic molecule.

Identification of Flavin-Containing Monooxygenase 5 (FMO5) as a Regulator of Glucose Homeostasis and a Potential Sensor of Gut Bacteria.

We have previously identified flavin-containing monooxygenase 5 (FMO5) as a regulator of metabolic aging. The aim of the present study was to investigate the role of FMO5 in glucose homeostasis and the impact of diet and gut flora on the phenotype of mice in which the Fmo5 gene has been disrupted (Fmo5-/- mice). In comparison with wild-type (WT) counterparts, Fmo5-/- mice are resistant to age-related changes in glucose homeostasis and maintain the higher glucose tolerance and insulin sensitivity characteristic of young animals. When fed a high-fat diet, they are protected against weight gain and reduction of insulin sensitivity. The phenotype of Fmo5-/- mice is independent of diet and the gut microbiome and is determined solely by the host genotype. Fmo5-/- mice have metabolic characteristics similar to those of germ-free mice, indicating that FMO5 plays a role in sensing or responding to gut bacteria. In WT mice, FMO5 is present in the mucosal epithelium of the gastrointestinal tract where it is induced in response to a high-fat diet. In comparison with WT mice, Fmo5-/- mice have fewer colonic goblet cells, and they differ in the production of the colonic hormone resistin-like molecule ßFmo5-/- mice have lower concentrations of tumor necrosis factor α in plasma and of complement component 3 in epididymal white adipose tissue, indicative of improved inflammatory tone. Our results implicate FMO5 as a regulator of body weight and of glucose disposal and insulin sensitivity and, thus, identify FMO5 as a potential novel therapeutic target for obesity and insulin resistance.

Trimethylamine and Trimethylamine N-Oxide, a Flavin-Containing Monooxygenase 3 (FMO3)-Mediated Host-Microbiome Metabolic Axis Implicated in Health and Disease.

Flavin-containing monooxygenase 3 (FMO3) is known primarily as an enzyme involved in the metabolism of therapeutic drugs. On a daily basis, however, we are exposed to one of the most abundant substrates of the enzyme trimethylamine (TMA), which is released from various dietary components by the action of gut bacteria. FMO3 converts the odorous TMA to nonodorous TMA N-oxide (TMAO), which is excreted in urine. Impaired FMO3 activity gives rise to the inherited disorder primary trimethylaminuria (TMAU). Affected individuals cannot produce TMAO and, consequently, excrete large amounts of TMA. A dysbiosis in gut bacteria can give rise to secondary TMAU. Recently, there has been much interest in FMO3 and its catalytic product, TMAO, because TMAO has been implicated in various conditions affecting health, including cardiovascular disease, reverse cholesterol transport, and glucose and lipid homeostasis. In this review, we consider the dietary components that can give rise to TMA, the gut bacteria involved in the production of TMA from dietary precursors, the metabolic reactions by which bacteria produce and use TMA, and the enzymes that catalyze the reactions. Also included is information on bacteria that produce TMA in the oral cavity and vagina, two key microbiome niches that can influence health. Finally, we discuss the importance of the TMA/TMAO microbiome-host axis in health and disease, considering factors that affect bacterial production and host metabolism of TMA, the involvement of TMAO and FMO3 in disease, and the implications of the host-microbiome axis for management of TMAU.

Relationships between flavin-containing mono-oxygenase 3 (FMO3) genotype and trimethylaminuria phenotype in a Japanese population.

AIM: The aim of this study was to investigate relationships between flavin-containing mono-oxygenase 3 (FMO3) genotype and phenotype (conversion of odorous trimethylamine into non-odorous trimethylamine N-oxide) in a large Japanese cohort suffering from trimethylaminuria. METHODS: Urinary excretion of trimethylamine and trimethylamine N-oxide was determined for 102 volunteers with self-reporting symptoms of trimethylaminuria. For each we determined the sequence of the entire coding region, plus 1.3 kb of flanking intronic and 2.5 kb of the upstream region of the FMO3 gene. The affect of upstream variants on transcription was determined with a reporter gene assay. RESULTS: Seventy-eight subjects were diagnosed as suffering from trimethylaminuria, based on urinary excretion of <90% of total TMA as TMA N-oxide. Of these, 13 were classified as severe, 56 as moderate and nine as mild cases, excreting <43%, 48-70% and 73-83% of trimethylamine as trimethylamine N-oxide, respectively. Twenty-seven mutations were identified in FMO3, 15 in the coding region, of which eight abolish or severely impair FMO3 activity (Pro70Leu, Cys197fsX, Thr201Lys, Arg205Cys, Met260Val, Trp388Ter, Gln470Ter and Arg500Ter), and 12 in the upstream region. The mutations segregate into 19 haplotypes, including four different combinations of upstream mutations, each of which reduces transcriptional activity in comparison with the ancestral upstream sequence of FMO3. CONCLUSIONS: Comparisons of genotype and phenotype reveal that severe trimethylaminuria is caused by loss of function mutations in FMO3. For moderate and mild cases the situation is more complex, with most resulting from factors other than FMO3 genotype. Our results have implications for the diagnosis and management of the disorder.

Metabolomic and transcriptomic analyses of Fmo5-/- mice reveal roles for flavin-containing monooxygenase 5 (FMO5) in NRF2-mediated oxidative stress response, unfolded protein response, lipid homeostasis, and carbohydrate and one-carbon metabolism.

Flavin-containing monooxygenase 5 (FMO5) is a member of the FMO family of proteins, best known for their roles in the detoxification of foreign chemicals and, more recently, in endogenous metabolism. We have previously shown that Fmo5-/- mice display an age-related lean phenotype, with much reduced weight gain from 20 weeks of age. The phenotype is characterized by decreased fat deposition, lower plasma concentrations of glucose, insulin and cholesterol, higher glucose tolerance and insulin sensitivity, and resistance to diet-induced obesity. In the present study we report the use of metabolomic and transcriptomic analyses of livers of Fmo5-/- and wild-type mice to identify factors underlying the lean phenotype of Fmo5-/- mice and gain insights into the function of FMO5. Metabolomics was performed by the Metabolon platform, utilising ultrahigh performance liquid chromatography-tandem mass spectroscopy. Transcriptomics was performed by RNA-Seq and results analysed by DESeq2. Disruption of the Fmo5 gene has wide-ranging effects on the abundance of metabolites and expression of genes in the liver. Metabolites whose concentration differed between Fmo5-/- and wild-type mice include several saturated and monounsaturated fatty acids, complex lipids, amino acids, one-carbon intermediates and ADP-ribose. Among the genes most significantly and/or highly differentially expressed are Apoa4, Cd36, Fitm1, Hspa5, Hyou1, Ide, Me1 and Mme. The results reveal that FMO5 is involved in upregulating the NRF2-mediated oxidative stress response, the unfolded protein response and response to hypoxia and cellular stress, indicating a role for the enzyme in adaptation to oxidative and metabolic stress. FMO5 also plays a role in stimulating a wide range of metabolic pathways and processes, particularly ones involved in lipid homeostasis, the uptake and metabolism of glucose, the generation of cytosolic NADPH, and in one-carbon metabolism. The results predict that FMO5 acts by stimulating the NRF2, XBP1, PPARA and PPARG regulatory pathways, while inhibiting STAT1 and IRF7 pathways.

Diagnoses after newly recorded abdominal pain in primary care: observational cohort study.

BACKGROUND: Non-acute abdominal pain in primary care is diagnostically challenging. AIM: To quantify the 1-year cumulative incidence of 35 non-malignant diagnoses and nine cancers in adults after newly recorded abdominal pain in primary care. DESIGN AND SETTING: Observational cohort study of 125 793 Clinical Practice Research Datalink GOLD records. METHOD: Participants, aged ≥40 years, had newly recorded abdominal pain between 1 January 2009 and 31 December 2013. Age- and sex-stratified 1-year cumulative incidence by diagnosis is reported. RESULTS: Most (>70%) participants had no pre-specified diagnoses after newly recorded abdominal pain. Non-malignant diagnoses were most common: upper gastrointestinal problems (gastro-oesophageal reflux disease, hiatus hernia, gastritis, oesophagitis, and gastric/duodenal ulcer) in males and urinary tract infection in females. The incidence of upper gastrointestinal problems plateaued at age ≥60 years (aged 40-59 years: males 4.9%, 95% confidence interval [CI] = 4.6 to 5.1, females 4.0%, 95% CI = 3.8 to 4.2; aged 60-69 years: males 5.8%, 95% CI = 5.4 to 6.2, females 5.4%, 95% CI = 5.1 to 5.8). Urinary tract infection incidence increased with age (aged 40-59 years: females 5.1%, 95% CI = 4.8 to 5.3, males 1.1%, 95% CI = 1.0 to 1.2; aged ≥70 years: females 8.0%, 95% CI = 7.6 to 8.4, males 3.3%, 95% CI = 3.0 to 3.6%). Diverticular disease incidence rose with age, plateauing at 4.2% (95% CI = 3.9 to 4.6) in males aged ≥60 years, increasing to 6.1% (95% CI = 5.8 to 6.4) in females aged ≥70 years. Irritable bowel syndrome incidence was higher in females (aged 40-59 years: 2.9%, 95% CI = 2.7 to 3.1) than males (aged 40-59 years: 2.1%, 95% CI = 1.9 to 2.3), decreasing with age to 1.3% (95% CI = 1.2 to 1.5) in females and 0.6% (95% CI = 0.5 to 0.8) in males aged ≥70 years. CONCLUSION: Although abdominal pain commonly remains unexplained, non-malignant diagnosis are more likely than cancer.

Intra-abdominal cancer risk with abdominal pain: a prospective cohort primary care study.

BACKGROUND: Quantifying cancer risk in primary care patients with abdominal pain informs diagnostic strategies. AIM: To quantify oesophagogastric, colorectal, liver, pancreatic, ovarian, uterine, kidney, and bladder cancer risks associated with newly reported abdominal pain with or without other symptoms, signs, or abnormal blood tests (that is, features) indicative of possible cancer. DESIGN AND SETTING: This was an observational prospective cohort study using Clinical Practice Research Datalink records with English cancer registry linkage. METHOD: The authors studied 125 793 patients aged ≥40 years with newly reported abdominal pain in primary care between 1 January 2009 and 31 December 2013. The 1-year cumulative incidence of cancer, and the composite 1-year cumulative incidence of cancers with shared additional features, stratified by age and sex are reported. RESULTS: With abdominal pain, overall risk was greater in men and increased with age, reaching 3.4% (95% confidence interval [CI] = 3.0 to 3.7, predominantly colorectal cancer 1.9%, 95% CI = 1.6 to 2.1) in men ≥70 years, compared with their expected incidence of 0.88% (95% CI = 0.87 to 0.89). Additional features increased cancer risk; for example, for men, colorectal or pancreatic cancer risk with abdominal pain plus diarrhoea at 60-69 years of age was 3.1% (95% CI = 1.9 to 4.9) predominantly colorectal cancer (2.2%, 95% CI = 1.2 to 3.8). CONCLUSION: Abdominal pain increases intra-abdominal cancer risk nearly fourfold in men aged ≥70 years, exceeding the 3% threshold warranting investigation. This threshold is surpassed for the >60 years age group only with additional features. These results will help direct appropriate referral and testing strategies for patients based on their demographic profile and reporting features. The authors suggest non-invasive strategies first, such as faecal immunochemical testing, with safety-netting in a shared decision-making framework.

Treatment of wild-type mice with 2,3-butanediol, a urinary biomarker of Fmo5 -/- mice, decreases plasma cholesterol and epididymal fat deposition.

We previously showed that Fmo5 -/- mice exhibit a lean phenotype and slower metabolic ageing. Their characteristics include lower plasma glucose and cholesterol, greater glucose tolerance and insulin sensitivity, and a reduction in age-related weight gain and whole-body fat deposition. In this paper, nuclear magnetic resonance (NMR) spectroscopy-based metabolite analyses of the urine of Fmo5 -/- and wild-type mice identified two isomers of 2,3-butanediol as discriminating urinary biomarkers of Fmo5 -/- mice. Antibiotic-treatment of Fmo5 -/- mice increased plasma cholesterol concentration and substantially reduced urinary excretion of 2,3-butanediol isomers, indicating that the gut microbiome contributed to the lower plasma cholesterol of Fmo5 -/- mice, and that 2,3-butanediol is microbially derived. Short- and long-term treatment of wild-type mice with a 2,3-butanediol isomer mix decreased plasma cholesterol and epididymal fat deposition but had no effect on plasma concentrations of glucose or insulin, or on body weight. In the case of long-term treatment, the effects were maintained after withdrawal of 2,3-butanediol. Short-, but not long-term treatment, also decreased plasma concentrations of triglycerides and non-esterified fatty acids. Fecal transplant from Fmo5 -/- to wild-type mice had no effect on plasma cholesterol, and 2,3-butanediol was not detected in the urine of recipient mice, suggesting that the microbiota of the large intestine was not the source of 2,3-butanediol. However, 2,3-butanediol was detected in the stomach of Fmo5 -/- mice, which was enriched for Lactobacillus genera, known to produce 2,3-butanediol. Our results indicate a microbial contribution to the phenotypic characteristic of Fmo5 -/- mice of decreased plasma cholesterol and identify 2,3-butanediol as a potential agent for lowering plasma cholesterol.

Microcytosis as a risk marker of cancer in primary care: a cohort study using electronic patient records.

BACKGROUND: Microcytosis (smaller than normal red blood cells) has previously been identified as a possible early risk marker for some cancers. However, the role of microcytosis across all cancers has not been fully investigated. AIM: To examine cancer incidence in a cohort of patients with microcytosis, with and without accompanying anaemia. DESIGN AND SETTING: Cohort study of patients aged ≥40 years using UK primary care electronic patient records. METHOD: The 1-year cancer incidence was compared between cohorts of patients with a mean red cell volume of <85 femtolitres (fL) (low) or 85-101 fL (normal). Further analyses examined sex, age group, cancer site, and haemoglobin values. RESULTS: Of 12 289 patients with microcytosis, 497 had a new cancer diagnosis within 1 year (4.0%, 95% confidence interval [CI] = 3.7 to 4.4), compared with 1465 of 73 150 without microcytosis (2.0%, CI = 1.9 to 2.1). In males, 298 out of 4800 with microcytosis were diagnosed with cancer (6.2%, CI = 5.5 to 6.9), compared with 940 out of 34 653 without (2.7%, CI = 2.5 to 2.9). In females with microcytosis, 199 out of 7489 were diagnosed with cancer (2.7%, CI = 2.3 to 3.1), compared with 525 out of 38 497 without (1.4%, CI = 1.3 to 1.5). In patients with microcytosis but normal haemoglobin, 86 out of 2637 males (3.3%, CI = 2.6 to 4.0) and 101 out of 5055 females (2.0%, CI = 1.6 to 2.4) were diagnosed with cancer. CONCLUSION: Microcytosis is a predictor of underlying cancer even if haemoglobin is normal. Although a benign explanation is more likely, clinicians in primary care should consider simple testing for cancer on encountering unexplained microcytosis, particularly in males.

Flavin-containing monooxygenases: mutations, disease and drug response.

Flavin-containing monooxygenases (FMOs) metabolize numerous foreign chemicals, including drugs, pesticides and dietary components and, thus, mediate interactions between humans and their chemical environment. We describe the mechanism of action of FMOs and insights gained from the structure of yeast FMO. We then concentrate on the three FMOs (FMOs 1, 2 and 3) that are most important for metabolism of foreign chemicals in humans, focusing on the role of the FMOs and their genetic variants in disease and drug response. Loss-of-function mutations of FMO3 cause the disorder trimethylaminuria. More common variants that decrease enzyme activity are associated with increased drug efficacy. Most humans are homozygous for a nonsense mutation that inactivates FMO2. But a substantial proportion of sub-Saharan Africans express functional FMO2 and, thus, are predicted to respond differently to drugs and other foreign chemicals.

Human flavin-containing monooxygenase 2.1 catalyzes oxygenation of the antitubercular drugs thiacetazone and ethionamide.

The second-line antitubercular drugs thiacetazone (TAZ) and ethionamide (ETA) are bioactivated by the mycobacterial enzyme EtaA. We report here that human flavin-containing monooxygenase 2.1 (FMO2.1), which is expressed predominantly in the lung, catalyzes oxygenation of TAZ. The metabolites generated, the sulfenic acid, sulfinic acid, and carbodiimide derivatives, are the same as those produced by EtaA and human FMO1 and FMO3. Two of the metabolites, the sulfenic acid and carbodiimide, are known to be harmful to mammalian cells. FMO2.1 also catalyzes oxygenation of ETA, producing the S-oxide. We have developed a novel spectrophotometric assay for TAZ oxygenation. The assay was used to determine kinetic parameters for TAZ oxygenation catalyzed by human FMO1, FMO2.1, and FMO3 and by EtaA. Although the K(M) values for the four enzyme-catalyzed reactions are similar, k(cat) and, consequently, k(cat)/K(M) (the specificity constant) for FMO2.1-catalyzed TAZ oxygenation are much higher than those of FMO1, FMO3, or EtaA. This indicates that FMO2.1 is more effective in catalyzing TAZ oxygenation than are the other three enzymes and thus is likely to contribute substantially to the metabolism of TAZ, decreasing the availability of the prodrug to mycobacteria and producing toxic metabolites. Because of a genetic polymorphism, Europeans and Asians lack FMO2.1. However, in sub-Saharan Africa, a region in which tuberculosis is a major health problem, a substantial proportion of individuals express FMO2.1. Thus, our results may explain some of the observed interindividual differences in response to TAZ and ETA and have implications for the treatment of tuberculosis in sub-Saharan Africa.

Recognising laryngeal cancer in primary care: a large case-control study using electronic records.

BACKGROUND: Over 1700 people are diagnosed with laryngeal cancer annually in England. Current National Institute for Health and Care Excellence (NICE) guidelines on referral for suspected laryngeal cancer were based on clinical consensus, in the absence of primary care studies. AIM: To identify and quantify the primary care features of laryngeal cancer. DESIGN AND SETTING: Matched case-control study of patients aged ≥40 years using data from the UK's Clinical Practice Research Datalink. METHOD: Clinical features of laryngeal cancer with which patients had presented to their GP in the year before diagnosis were identified and their association with cancer was assessed using conditional logistic regression. Positive predictive values (PPVs) for each clinical feature were calculated for the consulting population aged >60 years. RESULTS: In total, 806 patients diagnosed with laryngeal cancer between 2000 and 2009 were studied, together with 3559 age-, sex-, and practice-matched controls. Ten features were significantly associated with laryngeal cancer: hoarseness odds ratio [OR] 904 (95% confidence interval [CI] = 277 to 2945); sore throat, first attendance OR 6.2 (95% CI = 3.7 to 10); sore throat, re-attendance OR 7.7 (95% CI = 2.6 to 23); dysphagia OR 6.5 (95% CI = 2.7 to 16); otalgia OR 5.0 (95% CI = 1.9 to 13); dyspnoea, re-attendance OR 4.7 (95% CI = 1.9 to 12); mouth symptoms OR 4.7 (95% CI = 1.8 to 12); recurrent chest infection OR 4.5 (95% CI = 2.4 to 8.5); insomnia OR 2.7 (95% CI = 1.3 to 5.6); and raised inflammatory markers OR 2.5 (95% CI = 1.5 to 4.1). All P-values were <0.01. Hoarseness had the highest individual PPV of 2.7%. Symptom combinations currently not included in NICE guidance were sore throat plus either dysphagia, dyspnoea, or otalgia, for which PPVs were >5%. CONCLUSION: These results expand current NICE guidance by identifying new symptom combinations that are associated with laryngeal cancer; they may help GPs to select more appropriate patients for referral.

Alternative promoters and repetitive DNA elements define the species-dependent tissue-specific expression of the FMO1 genes of human and mouse.

In humans, expression of the FMO1 (flavin-containing mono-oxygenase 1) gene is silenced postnatally in liver, but not kidney. In adult mouse, however, the gene is active in both tissues. We investigated the basis of this species-dependent tissue-specific transcription of FMO1. Our results indicate the use of three alternative promoters. Transcription of the gene in fetal human and adult mouse liver is exclusively from the P0 promoter, whereas in extra-hepatic tissues of both species, P1 and P2 are active. Reporter gene assays showed that the proximal P0 promoters of human (hFMO1) and mouse (mFmo1) genes are equally effective. However, sequences upstream (-2955 to -506) of the proximal P0 of mFmo1 increased reporter gene activity 3-fold, whereas hFMO1 upstream sequences (-3027 to -541) decreased reporter gene activity by 75%. Replacement of the upstream sequence of human P0 with the upstream sequence of mouse P0 increased activity of the human proximal P0 8-fold. Species-specific repetitive elements are present immediately upstream of the proximal P0 promoters. The human gene contains five LINE (long-interspersed nuclear element)-1-like elements, whereas the mouse gene contains a poly A region, an 80-bp direct repeat, an LTR (long terminal repeat), a SINE (short-interspersed nuclear element) and a poly T tract. The rat and rabbit FMO1 genes, which are expressed in adult liver, lack some (rat) or all (rabbit) of the elements upstream of mouse P0. Thus silencing of FMO1 in adult human liver is due apparently to the presence upstream of the proximal P0 of L1 (LINE-1) elements rather than the absence of retrotransposons similar to those found in the mouse gene.

Selection of men for investigation of possible testicular cancer in primary care: a large case-control study using electronic patient records.

BACKGROUND: Testicular cancer incidence has risen over the last two decades and is expected to continue to rise. There are no primary care studies on the clinical features of testicular cancer, with recent National Institute for Health and Care Excellence (NICE) guidance based solely upon clinical consensus. AIM: To identify clinical features of testicular cancer and to quantify their risk in primary care patients, with the aim of improving the selection of patients for investigation. DESIGN AND SETTING: A matched case-control study in males aged ≥17 years, using Clinical Practice Research Datalink records. METHOD: Putative clinical features of testicular cancer were identified and analysed using conditional logistic regression. Positive predictive values (PPVs) were calculated for those aged <50 years. RESULTS: In all, 1398 cases were available, diagnosed between 2000 and 2012, with 4956 age-, sex-, and practice-matched controls. Nine features were independently associated with testicular cancer, the top three being testicular swelling (odds ratio [OR] 280, 95% confidence interval [CI] = 110 to 690), testicular lump (OR 270, 95% CI = 100 to 740), and scrotal swelling (OR 170, 95% CI = 35 to 800). The highest PPV for 17-49-year-olds was testicular lump, at 2.5% (95% CI = 1.1 to 5.6). Combining testicular lump with testicular swelling or testicular pain produced PPVs of 17% and 10%, respectively. CONCLUSION: Testicular enlargement carries a risk of cancer of 2.5% - close to the current 3% threshold in UK referral guidance. Contrary to traditional teaching, painful testicular enlargement may signify cancer. Some initial hydrocele diagnoses appear to be wrong, with missed cancers, suggesting an ultrasound may be useful when a hydrocele diagnosis is uncertain. These results support the existing NICE guidelines, and help to characterise when an ultrasound should be considered in symptomatic men.