Current Metabolomics (v.5, #2)

Meet Our Editorial Board Member by Yumi Zuhanis Has-Yun Hashim (77-77).

Editorial: Metabolomics of VOCs by Raquel Cumeras (78-78).

Background: Metabolomics is leaving a gold era, and volatilomics is finding its niche due to its non-invasiveness. Volatilomics is the totality of Volatile Organic Compounds (VOCs) produced by all living organisms (plants, animals, etc.), the analyses of those volatiles can offer, amongst others, the possibility of rapid diagnoses of patients using non-invasive techniques. However, the lack of a central core database of volatilome is a drawback when identifying the biological output of experimental identified metabolites.
Objective: Give an accurate state-of-the-art insight of volatilomics, by revising the published reviews since 2014, giving an accurate list of studied diseases within volatilomics and finally, a detailed list of available VOC databases.
Methods: Recent progress in the volatile metabolomics development, applications and databases are reviewed
Results: What are VOC's, depending on their context or sector. Volatilome is extensively explained and analyzed the VOC etiology (endogenous/exogenous), with special interest in the human volatilome. The amount of review articles (48) published since 2014 indicates that volatilomic is on its height (or ascending) momentum. Biofluid sources and diseases studied are reviewed. Also, we mention what are the current trends of volatilomics in systems biology and precision medicine. Finally, the steps involved in the data analysis and the available volatilome databases are resumed.
Conclusion: The advances in volatile metabolomics are increasing, and a broad spectrum of human diseases or disorders are being interrogated, so the need of detailed databases list of both healthy and disease metabolites is increasing.

Background: Analysis of volatile metabolites derived from the human breath or biofluids provides noninvasive means of detecting and monitoring diseases that occur throughout the body. Diseases arise from different mechanisms that cause alterations in normal physiological processes. Mechanisms of disease (pathogenesis) result in the production of unique mixtures of abnormal volatile organic compounds (VOCs), referred to as disease biomarker metabolites when associated with specific diseases. Regardless of where disease biomarkers originate in the body, they are picked up by the circulatory system and eventually expelled out through the lungs. Analysis of complex mixtures of disease biomarkers provides effective diagnostic clues for detecting the presence of specific disease processes occurring in the body.
Methods: Recent progress in the development of electronic-nose (e-nose) applications and technologies for clinical examinations and human disease diagnoses are reviewed.
Results: Metabolomics has been useful in identifying biomarkers and mechanisms of disease, but is often time-consuming and not easily applied to disease diagnosis. E-nose devices are relatively new gas-sensing technologies that are small, simple, portable and particularly useful for noninvasive early disease detection. Some major advantages of using e-noses for disease diagnoses are that they provide quicker, more efficient diagnostic results and cause less stress, anxiety, and no pain to patients.
Conclusion: Recent advancements in the use of e-nose devices to detect complex mixtures of disease biomarkers are providing the great potential for these instruments to facilitate and accelerate point-ofcare clinical disease diagnoses.

Exploration and Exploitation of the Yeast Volatilome by Birgitta E. Ebert, Christoph Halbfeld, Lars M. Blank (102-118).
Background: Volatile organic compounds (VOCs) are small molecular mass substances, which exhibit high-vapor pressures, low boiling points, and lipophilic character. VOCs are produced by all organisms including eukaryotic microbes like yeast, whose volatile metabolites are for centuries exploited for examples as flavors in bread, beer, and wine. Notably, while the applications of VOCs are many, the knowledge on their biochemical synthesis is still limited.
Objective: We review here the current information of yeast volatile metabolites and techniques to further explore the VOC landscape made possible by improvements of the analytical possibilities, regarding sampling frequency, identification, and quantification and the development to computationally interpret (high-throughput) data. Especially possibilities for online and even real-time analysis should trigger new experimental approaches that elucidate the biochemistry as well as the regulation of VOC synthesis. Baker's yeast is here the organism of choice as the genetic inventory can be linked to VOC formation and with this in hand improved applications can be envisaged. The physical, chemical or biological properties make many VOCs interesting targets for different industrial sectors while their natural function as semiochemicals or in defense mechanisms can be exploited to engineer synthetic microbial communities or to develop new antibiotics.
Conclusion: VOCs produced by microbes including yeast are a chemical diverse group of compounds with highly different applications. The new analytical techniques briefly summarized here will enable the use of VOCs in even broader applications including human health monitoring and bioprocess control. We envisage a bright future for VOC research and for the resulting applications

Background:It is known that the increasing aging of population is the origin of enormous challenges to healthcare provision and treatment of age-related diseases, "aging" being a promissory research field. One of the emerging focus of aging research is to find suitable ways to increase healthspan, rather than lifespan. In this way, metabolomic analysis seems promising once metabolite analysis is been used in several studies of human populations in order to understand both physiological and pathologic metabolic processes.
Focus: Human metabolome changes along with age and those changes are certainly related to the onset of several age related diseases. It is expectable that the study of aging metabolome could help to understand molecular physiology of aging and age related diseases. In order to extract information from the data obtained by all metabolomics techniques applied in this research field it is crucial to recognize the corresponding metabolites, in particular the biological predictors of aging, that is, molecules that ultimately could be used to predict the aging status of tissues, organs or the entire individual.
Prospect: This review presents an exhaustive list of the main classes of the biological predictors of aging, some of which are potential aging biomarkers. The gathered information can be used to sustain the information obtained by the several metabolomics approaches dedicated to the study of aging. This work also defines and characterizes aging, briefly summarizes the main theories and senescence mechanisms and describes the hallmarks of aging. An overview of Fourier Transform Infrared Spectroscopy technique and its potential to study the metabolome of aging is also presented.

Metabolomic profiling of cyanobacterial UV-protective compounds by Jainendra Pathak, Rajneesh, Haseen Ahmed, Richa, Rajeshwar P Sinha (138-163).
Background: Cyanobacteria are the predominant atmospheric nitrogen fixers of the aquatic as well as terrestrial ecosystems. Harvesting of solar energy for photosynthesis exposes cyanobacteria simultaneously to lethal doses of ultraviolet radiation (UVR) in their natural brightly light habitats. To counteract the damaging effect of UVR, cyanobacteria synthesize novel secondary metabolites such as mycosporine-like amino acids (MAAs) and scytonemin. By the application of the 'omics' techniques cyanobacterial molecular biology is benefitted tremendously. Traditionally, only small sets of metabolites are quantified in targeted metabolome approaches. The development of separation technologies coupled with mass-spectroscopy and nuclear-magneticresonance based identification of low molecular mass molecules allows the profiling of several metabolites of different chemical nature.
Objective: MAAs and scytonemin are highly photostable and act as potent photoprotectant and antioxidant hence can be biotechnologically exploited by the cosmetic industry. Till date, 23 MAAs such as shinorine, mycosporine glycine, palythine, palythinol, asterina-330 and porphyra-334, and 7 different forms of scytonemin such as oxidized and reduced scytonemin, scytonemin-3a-imine and scytonemin A have been reported in various cyanobacteria. Metabolome analysis could be applied to characterize changes in the cyanobacterial primary and secondary metabolites such as MAAs and scytonemin under diverse environmental conditions. Untargeted metabolite profiling has the potential to identify numerous novel metabolites; however, de novo identification of metabolites from spectral features remains a challenge.
Conclusion: This review deals with the structure, biosynthesis and various techniques involved in the metabolomic profiling of cyanobacterial UV protective compounds scytonemin and MAAs.