On Cabbage and Selenium Binding Protein 1

Mutations in the gene encoding Selenium Binding Protein (SELENBP1) on chromosome 1q21 were found in multiple individuals with extra-oral halitosis. These individuals had increased levels of methanethiol and dimethylsulfide in their breath perceived as unpleasantly cabbage-smelling. It was reported to worsen after drinking beer. 

The mutations responsible include rs1553204817 (OMIM: 604188.0001: c.1039G>T); rs758495626 (c.673G>T (p.Gly225Trp)), rs1357490520 (c.481+1G>A disrupting splice site), and rs1553204840 (c.985C>T)

SELENBP1 was identified as a methanethiol oxidase (MTO), catalyzing the conversion of methanethiol (H3C-SH) to hydrogen sulfide (H2S), hydrogen peroxide (H2O2) and formaldehyde (HCHO). If this enzyme is not properly functional, the body will be releasing more Methanethiol  - a volatile and toxic gas with the characteristic smell of rotten cabbage. We get this compound from food - not only the cancer-fighting cabbage family, including radishes, but also orange juice, pineapple, strawberries, asparagus, wheat bread, gruyere cheese, coffee, roasted filberts and even cooked rice. Water, cherries, apples, whole milk, spinach and citrusy fruits could counteract the odor in some individuals. 

Selenium binding protein1 (SELENBP1) has been also associated with a rare disease hypermethioninemia (sometimes accompanied by learning disabilities and neurological problems), several cancers and schizophrenia (downregulated at its onset and upregulated at later stages); hypertension and ischemic heart conditions. Dysregulation of SELENBP1 is common to Zika virus (ZIKV) and dengue infections, and Guillain-Barré syndrome. It was also found to COVID-19.

REFERENCES

Pol A, Renkema GH, Tangerman A, Winkel EG, Engelke UF, De Brouwer AP, Lloyd KC, Araiza RS, Van Den Heuvel L, Omran H, Olbrich H. Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis. Nature genetics. 2018 Jan;50(1):120-9.

Philipp TM, Will A, Richter H, Winterhalter PR, Pohnert G, Steinbrenner H, Klotz LO. A coupled enzyme assay for detection of selenium-binding protein 1 (SELENBP1) methanethiol oxidase (MTO) activity in mature enterocytes. Redox Biology. 2021 Jul 1;43:101972.

Lin X, Lin Z, Zhao X, Liu Z, Xu C, Yu B, Gao P, Wang Z, Ge J, Shen Y, Li L. Serum SELENBP1 and VCL Are Effective Biomarkers for Clinical and Forensic Diagnosis of Coronary Artery Spasm. International Journal of Molecular Sciences. 2022 Oct 31;23(21):13266.

Chau EJ, Mostaid MS, Cropley V, McGorry P, Pantelis C, Bousman CA, Everall IP. Downregulation of plasma SELENBP1 protein in patients with recent-onset schizophrenia. Progress in Neuro-Psychopharmacology and Biological Psychiatry. 2018 Jul 13;85:1-6.

Zhang X, Hong R, Bei L, Hu Z, Yang X, Song T, Chen L, Meng H, Niu G, Ke C. SELENBP1 inhibits progression of colorectal cancer by suppressing epithelial–mesenchymal transition. Open Medicine. 2022 Jan 1;17(1):1390-404.

Moni MA, Lio’ P. Genetic profiling and comorbidities of zika infection. The Journal of infectious diseases. 2017 Sep 15;216(6):703-12.

de Melo CV, Bhuiyan MA, Gatua WN, Kanyerezi S, Uzairue L, Abechi P, Kumar K, Rahmat J, Giwa A, Mwandira G, Olamilekan AM. Transcriptomic dysregulations associated with SARS-CoV-2 infection in human nasopharyngeal and peripheral blood mononuclear cells. bioRxiv. 2020 Jan 1.

Albert-Puleo M. Physiological effects of cabbage with reference to its potential as a dietary cancer-inhibitor and its use in ancient medicine. Journal of ethnopharmacology. 1983 Dec 1;9(2-3):261-72.

FMO3 and COVID-19

Flavin-containing monooxygenase 3 (FMO3) enzyme is a seemingly insignificant enzyme that normally converts fishy-smelling trimethylamine (TMA) into a neutral trimethylamine-N-oxide (TMAO). The amounts of this highly specialized detoxifying enzyme are highly variable. It depends on the age, sex hormones, infections (estradiol and testosterone, hepatitis virus have been found to reduce FMO3 capacity), obesity traits and diseases such as diabetes. The difference can be up to 20-fold between individuals. Mutations in the FMO3 gene cause low metabolic capacity associated with the disorder trimethylaminuria (TMAU) that attracts little biomedical interest.  This condition, however, might matter more than it seems.

Could there be a link between FMO3 and SARS-CoV-2 infection and vaccination? 

Individuals differ in their susceptibility to viral infections and genes contribute to the risk score. Less than 10% of humans infected with Mycobacterium tuberculosis develop TB, partially because of polymorphism in Tyrosine kinase (TYK2, P1104A) also responsible for severe COVID-19. Early in the pandemic, it was discovered that SARS-CoV-2 infection is dependent on the ACE2 receptor for cell entry and the serine protease TMPRSS2 for spike protein priming. ACE2 expression, indeed, influences COVID-19 risk and a rare variant located close to this gene was found to confer protection against COVID-19, possibly by decreasing ACE2 expression. Interestingly, FMO3 is one of the few genes with expression correlated to ACE2 [Sungnak et al, 2020] along with genes associated with immune functions. 

One of the characteristics of COVID-19 is the appearance of inflammatory processes, which could be leading to increased levels of TMAO. It could contribute to the hypercoagulative state in COVID-19-associated coagulopathy (CAC). SARS-Cov2 was shown to enhance TMAO-induced inflammation.  

Coronavirus disease is associated with increased risk of thrombotic events. According to recent research, low levels of FMO3 protect against thrombosis [Shih et al, 2019] while some FMO3 mutations confer higher risk [Oliveira-Filho et al, 2021]. FMO3 rs1736557 might increase the anti‐platelet efficacy of clopidogrel [Zhu et al, 2021]. Genetic risk can be mediated by gut microbiota [Gabashvili, 2020]. There are also associations with salt tolerance, wound healing, and diseases such as diabetes, renal and cardiovascular conditions increasing risk of severe COVID-19. 

Studying trimethylaminuria-like conditions might help in developing strategies for prevention and therapy of other diseases, including COVID-19.

Our COVID-19 disease and vaccines study [NCT04832932, Gabashvili, 2021] compares side-effects of vaccines and clinical course of infections (including vaccine breakthroughs) in several cohorts including MEBO and TMAU. You can help by enrolling and participating in this online survey in English or Spanish.

REFERENCES

Andreakos E, Abel L, Vinh DC, Kaja E, Drolet BA, Zhang Q, O’Farrelly C, Novelli G, Rodríguez-Gallego C, Haerynck F, Prando C. A global effort to dissect the human genetic basis of resistance to SARS-CoV-2 infection. Nature immunology. 2021 Oct 18:1-6. 

Gabashvili IS. Cutaneous Bacteria in the Gut Microbiome as Biomarkers of Systemic Malodor and People Are Allergic to Me (PATM) Conditions: Insights from a Virtually Conducted Clinical Trial. JMIR Dermatology. 2020 Nov 4;3(1):e10508.  

Gabashvili IS. Community-Based Phenotypic Study of Safety, Tolerability, Reactogenicity and Immunogenicity of Emergency-Use-Authorized Vaccines Against COVID-19 and Viral Shedding Potential of Post-Vaccination Infections: Protocol for an Ambispective study. medRxiv 2021.06.28.21256779; doi: https://doi.org/10.1101/2021.06.28.21256779

Liu W, Wang C, Xia Y, Xia W, Liu G, Ren C, Gu Y, Li X, Lu P. Elevated plasma trimethylamine-N-oxide levels are associated with diabetic retinopathy. Acta Diabetologica. 2021 Feb;58(2):221-9.

Janmohamed A, Dolphin CT, Phillips IR, Shephard EA. Quantification and cellular localization of expression in human skin of genes encoding flavin-containing monooxygenases and cytochromes P450. Biochemical pharmacology. 2001 Sep 15;62(6):777-86.

Oliveira-Filho AF, Medeiros PF, Velloso RN, Lima EC, Aquino IM, Nunes AB. Trimethylaminuria and Vascular Complications. Journal of the Endocrine Society. 2021 Apr;5(Supplement_1):A313-4. 

Zhu KX, Song PY, Li MP, Du YX, Ma QL, Peng LM, Chen XP. Association of FMO3 rs1736557 polymorphism with clopidogrel response in Chinese patients with coronary artery disease. European Journal of Clinical Pharmacology. 2021 Mar;77(3):359-68.

Sungnak W, Huang N, Bécavin C, Berg M, Queen R, Litvinukova M, Talavera-López C, Maatz H, Reichart D, Sampaziotis F, Worlock KB. SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes. Nature medicine. 2020 May;26(5):681-7.

Shih, D.M., Zhu, W., Schugar, R.C., Meng, Y., Jia, X., Miikeda, A., Wang, Z., Zieger, M., Lee, R., Graham, M. and Allayee, H., 2019. Genetic deficiency of Flavin-containing monooxygenase 3 (Fmo3) protects against thrombosis but has only a minor effect on plasma lipid levels—brief report. Arteriosclerosis, thrombosis, and vascular biology, 39(6), pp.1045-1054. 

Odor-prints: individual but genetic connections unclear

Odor is like fingerprints or facial features - it's unique.  Yet no single measurement could be easily applied to recognize an individual.

GC/MS measurements can be used to analyze mixtures of acids, alcohols, aldehydes, hydrocarbons, esters, ketones, and nitrogenous molecules in human odor. Complex algorithms mining patterns help to pinpoint the signatures. But could these signatures be easily derived from genetic makeups?

Recent article published in the Journal of Chemical Ecology looked at the usual suspects -  major histocompatibility locus (MHC) and found that these genes do not determine major patterns. 


Volatile carboxylic acids are the most diverse class of known axillary odorants, and the pattern of these acids is genetically determined. These acids  - like vast majority of human odorous compounds - are produced by human microbiome, in this case by skin bacteria. Odors of 12 families, comprising 3 to 6 siblings,were analyzed with comprehensive two-dimensional gas chromatography (GC x GC) and time-of-flight mass spectrometry (ToF MS). the analysis onfirmed the presence of individual signatures. but failed to find odors specific to HLA genes.

Even though paternally inherited HLA-associated odors were proposed to influence women odor preferences, genetic basis of odors may be more complicated than previously thought.

References

Natsch A, Kuhn F, & Tiercy JM (2010). Lack of Evidence for HLA-Linked Patterns of Odorous Carboxylic Acids Released from Glutamine Conjugates Secreted in the Human Axilla. Journal of chemical ecology PMID: 20623248

Thompson EE, Haller G, Pinto JM, Sun Y, Zelano B, Jacob S, McClintock MK, Nicolae DL, Ober C. (2010) Sequence variations at the human leukocyte antigen-linked olfactory receptor cluster do not influence female preferences for male odors. Hum Immunol. 2010 Jan;71(1):100-3. PMID: 19833159 
 
Jacob S, McClintock MK, Zelano B, Ober C (2002) Paternally inherited HLA alleles are associated with women's choice of male odor. Nature Genet 30: 175-179  PMID: 11799397  PDF