Predicting Chronological Age via the Skin Volatile Profile.

Skin volatile emissions offer a noninvasive insight into metabolic activity within the body as well as the skin microbiome and specific volatile compounds have been shown to correlate with age, albeit only in a few small studies. Building on this, here skin volatiles were collected and analyzed in a healthy participant study (n = 60) using a robust headspace-solid phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS) workflow. Following processing, 18 identified compounds were deemed suitable for this study. These were classified according to gender influences and their correlations with age were investigated. Finally, 6 volatiles (of both endogenous and exogenous origin) were identified as significantly changing in abundance with participant age (p < 0.1). The potential origins of these dysregulations are discussed. Multiple linear regression (MLR) analysis was employed to model age based on these significant volatiles as independent variables, along with gender. Our analysis shows that skin volatiles show a strong predictive ability for age (explained variance of 68%), stronger than other biochemical measures collected in this study (skin surface pH, water content) which are understood to vary with chronological age. Overall, this work provides new insights into the impact of aging on the skin volatile profiles which comprises both endogenously and exogenously derived volatile compounds. It goes toward demonstrating the biological significance of skin volatiles and will help pave the way for more rigorous consideration of the healthy "baseline" skin volatile profile in volatilomics-based health diagnostics development going forward.

Volatilomes of human infection.

The human volatilome comprises a vast mixture of volatile emissions produced by the human body and its microbiomes. Following infection, the human volatilome undergoes significant shifts, and presents a unique medium for non-invasive biomarker discovery. In this review, we examine how the onset of infection impacts the production of volatile metabolites that reflects dysbiosis by pathogenic microbes. We describe key analytical workflows applied across both microbial and clinical volatilomics and emphasize the value in linking microbial studies to clinical investigations to robustly elucidate the metabolic species and pathways leading to the observed volatile signatures. We review the current state of the art across microbial and clinical volatilomics, outlining common objectives and successes of microbial-clinical volatilomic workflows. Finally, we propose key challenges, as well as our perspectives on emerging opportunities for developing clinically useful and targeted workflows that could significantly enhance and expedite current practices in infection diagnosis and monitoring.

Multi-Strain and -Species Investigation of Volatile Metabolites Emitted from Planktonic and Biofilm Candida Cultures.

Candida parapsiliosis is a prevalent neonatal pathogen that attains its virulence through its strain-specific ability to form biofilms. The use of volatilomics, the profiling of volatile metabolites from microbes is a non-invasive, simple way to identify and classify microbes; it has shown great potential for pathogen identification. Although C. parapsiliosis is one of the most common clinical fungal pathogens, its volatilome has never been characterised. In this study, planktonic volatilomes of ten clinical strains of C. parapsilosis were analysed, along with a single strain of Candida albicans. Headspace-solid-phase microextraction coupled with gas chromatography-mass spectrometry were employed to analyse the samples. Species-, strain-, and media- influences on the fungal volatilomes were investigated. Twenty-four unique metabolites from the examined Candida spp. (22 from C. albicans; 18 from C. parapsilosis) were included in this study. Chemical classes detected across the samples included alcohols, fatty acid esters, acetates, thiols, sesquiterpenes, and nitrogen-containing compounds. C. albicans volatilomes were most clearly discriminated from C. parapsilosis based on the detection of unique sesquiterpene compounds. The effect of biofilm formation on the C. parapsilosis volatilomes was investigated for the first time by comparing volatilomes of a biofilm-positive strain and a biofilm-negative strain over time (0-48 h) using a novel sampling approach. Volatilomic shifts in the profiles of alcohols, ketones, acids, and acetates were observed specifically in the biofilm-forming samples and attributed to biofilm maturation. This study highlights species-specificity of Candida volatilomes, and also marks the clinical potential for volatilomics for non-invasively detecting fungal pathogens. Additionally, the range of biofilm-specificity across microbial volatilomes is potentially far-reaching, and therefore characterising these volatilomic changes in pathogenic fungal and bacterial biofilms could lead to novel opportunities for detecting severe infections early.

An Investigation of Stability and Species and Strain-Level Specificity in Bacterial Volatilomes.

Microbial volatilomics is a rapidly growing field of study and has shown great potential for applications in food, farming, and clinical sectors in the future. Due to the varying experimental methods and growth conditions employed in microbial volatilomic studies as well as strain-dependent volatilomic differences, there is limited knowledge regarding the stability of microbial volatilomes. Consequently, cross-study comparisons and validation of results and data can be challenging. In this study, we investigated the stability of the volatilomes of multiple strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli across three frequently used nutrient-rich growth media. Volatilomic stability was assessed based on media-, time- and strain-dependent variation across the examined bacterial volatilomes. Strain-level specificity of the observed volatilomes of E. coli and P. aeruginosa strains was further investigated by comparing the emission of selected compounds at varying stages of cell growth. Headspace solid phase microextraction (HS-SPME) sampling coupled with gas chromatography mass spectrometry (GC-MS) was used to analyze the volatilome of each strain. The whole volatilomes of the examined strains demonstrate a high degree of stability across the three examined growth media. At the compound-level, media dependent differences were observed particularly when comparing the volatilomes obtained in glucose-containing brain heart infusion (BHI) and tryptone soy broth (TSB) growth media with the volatilomes obtained in glucose-free Lysogeny broth (LB) media. These glucose-dependent volatilomic differences were primarily seen in the emission of primary metabolites such as alcohols, ketones, and acids. Strain-level differences in the emission of specific compounds in E. coli and P. aeruginosa samples were also observed across the media. These strain-level volatilomic differences were also observed across varying phases of growth of each strain, therefore confirming that these strains had varying core and accessory volatilomes. Our results demonstrate that, at the species-level, the examined bacteria have a core volatilome that exhibits a high-degree of stability across frequently-used growth media. Media-dependent differences in microbial volatilomes offer valuable insights into identifying the cellular origin of individual metabolites. The observed differences in the core and accessory volatilomes of the examined strains illustrate the complexity of microbial volatilomics as a study while also highlighting the need for more strain-level investigations to ultimately elucidate the whole volatilomic capabilities of microbial species in the future.

Investigation of the relationship between skin-emitted volatile fatty acids and skin surface acidity in healthy participants-a pilot study.

Volatile organic compounds (VOCs) emitted from human skin are of great interest in general in research fields including disease diagnostics and comprise various compound classes including acids, alcohols, ketones and aldehydes. The objective of this research is to investigate the volatile fatty acid (VFA) emission as recovered from healthy participant skin VOC samples and to characterise its association with skin surface acidity. VOC sampling was performed via headspace-solid phase microextraction with analysis via gas chromatography-mass spectrometry. Several VFAs were recovered from participants, grouped based on gender and site (female forehead, female forearm, male forearm). Saturated VFAs (C9, C12, C14, C15, C16) and the unsaturated VFA C16:1 (recovered only from the female forehead) were considered for this study. VFA compositions and abundances are discussed in the context of body site and corresponding gland type and distribution, and their quantitative association with skin acidity investigated. Normalised chromatographic peak areas of the recovered VFAs were found to linearly correlate with hydrogen ion concentration measured at each of the different sites considered and is the first report to our knowledge to demonstrate such an association. Our observations are explained in terms of the free fatty acid content at the skin surface which is well-established as being a major contributor to skin surface acidity. Furthermore, it is interesting to consider that these VFA emissions from skin, governed by equilibrium vapour pressures exhibited at the skin surface, will be dependent on skin pH. It is proposed that these pH-modulated equilibrium vapour pressures of the acids could be resulting in an enhanced VFA emission sensitivity with respect to skin surface pH. To translate our observations made here for future wearable biodiagnostic applications, the measurement of skin surface pH based on the volatile emission was demonstrated using a pH indicator dye in the form of a planar colorimetric sensor, which was incorporated into a wearable platform and worn above the palm surface. As acidic skin surface pH is required for optimal skin barrier function and cutaneous antimicrobial defence, it is envisaged that these colorimetric volatile acid sensors could be deployed in robust wearable formats for monitoring health and disease applications in the future.

Multi-strain volatile profiling of pathogenic and commensal cutaneous bacteria.

The detection of volatile organic compounds (VOC) emitted by pathogenic bacteria has been proposed as a potential non-invasive approach for characterising various infectious diseases as well as wound infections. Studying microbial VOC profiles in vitro allows the mechanisms governing VOC production and the cellular origin of VOCs to be deduced. However, inter-study comparisons of microbial VOC data remains a challenge due to the variation in instrumental and growth parameters across studies. In this work, multiple strains of pathogenic and commensal cutaneous bacteria were analysed using headspace solid phase micro-extraction coupled with gas chromatography-mass spectrometry. A kinetic study was also carried out to assess the relationship between bacterial VOC profiles and the growth phase of cells. Comprehensive bacterial VOC profiles were successfully discriminated at the species-level, while strain-level variation was only observed in specific species and to a small degree. Temporal emission kinetics showed that the emission of particular compound groups were proportional to the respective growth phase for individual S. aureus and P. aeruginosa samples. Standardised experimental workflows are needed to improve comparability across studies and ultimately elevate the field of microbial VOC profiling. Our results build on and support previous literature and demonstrate that comprehensive discriminative results can be achieved using simple experimental and data analysis workflows.

Mitochondrial deficits in human iPSC-derived neurons from patients with 22q11.2 deletion syndrome and schizophrenia.

Schizophrenia (SZ) is a highly heterogeneous disorder in both its symptoms and risk factors. One of the most prevalent genetic risk factors for SZ is the hemizygous microdeletion at chromosome 22q11.2 (22q11DS) that confers a 25-fold increased risk. Six of the genes directly disrupted in 22qDS encode for mitochondrial-localizing proteins. Here, we test the hypothesis that stem cell-derived neurons from subjects with the 22q11DS and SZ have mitochondrial deficits relative to typically developing controls. Human iPSCs from four lines of affected subjects and five lines of controls were differentiated into forebrain-like excitatory neurons. In the patient group, we find significant reductions of ATP levels that appear to be secondary to reduced activity in oxidative phosphorylation complexes I and IV. Protein products of mitochondrial-encoded genes are also reduced. As one of the genes deleted in the 22q11.2 region is MRPL40, a component of the mitochondrial ribosome, we generated a heterozygous mutation of MRPL40 in a healthy control iPSC line. Relative to its isogenic control, this line shows similar deficits in mitochondrial DNA-encoded proteins, ATP level, and complex I and IV activity. These results suggest that in the 22q11DS MRPL40 heterozygosity leads to reduced mitochondria ATP production secondary to altered mitochondrial protein levels. Such defects could have profound effects on neuronal function in vivo.

Early hyperactivity in lateral entorhinal cortex is associated with elevated levels of AßPP metabolites in the Tg2576 mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disorder which is the most common cause of dementia in the elderly today. One of the earliest symptoms of AD is olfactory dysfunction. The present study investigated the effects of amyloid ß precursor protein (AßPP) metabolites, including amyloid-ß (Aß) and AßPP C-terminal fragments (CTF), on olfactory processing in the lateral entorhinal cortex (LEC) using the Tg2576 mouse model of human AßPP over-expression. The entorhinal cortex is an early target of AD related neuropathology, and the LEC plays an important role in fine odor discrimination and memory. Cohorts of transgenic and age-matched wild-type (WT) mice at 3, 6, and 16months of age (MO) were anesthetized and acute, single-unit electrophysiology was performed in the LEC. Results showed that Tg2576 exhibited early LEC hyperactivity at 3 and 6MO compared to WT mice in both local field potential and single-unit spontaneous activity. However, LEC single-unit odor responses and odor receptive fields showed no detectable difference compared to WT at any age. Finally, the very early emergence of olfactory system hyper-excitability corresponded not to detectable Aß deposition in the olfactory system, but rather to high levels of intracellular AßPP-CTF and soluble Aß in the anterior piriform cortex (aPCX), a major afferent input to the LEC, by 3MO. The present results add to the growing evidence of AßPP-related hyper-excitability, and further implicate both soluble Aß and non-Aß AßPP metabolites in its early emergence.

Spared piriform cortical single-unit odor processing and odor discrimination in the Tg2576 mouse model of Alzheimer's disease.

Alzheimer's disease is a neurodegenerative disorder that is the most common cause of dementia in the elderly today. One of the earliest reported signs of Alzheimer's disease is olfactory dysfunction, which may manifest in a variety of ways. The present study sought to address this issue by investigating odor coding in the anterior piriform cortex, the primary cortical region involved in higher order olfactory function, and how it relates to performance on olfactory behavioral tasks. An olfactory habituation task was performed on cohorts of transgenic and age-matched wild-type mice at 3, 6 and 12 months of age. These animals were then anesthetized and acute, single-unit electrophysiology was performed in the anterior piriform cortex. In addition, in a separate group of animals, a longitudinal odor discrimination task was conducted from 3-12 months of age. Results showed that while odor habituation was impaired at all ages, Tg2576 performed comparably to age-matched wild-type mice on the olfactory discrimination task. The behavioral data mirrored intact anterior piriform cortex single-unit odor responses and receptive fields in Tg2576, which were comparable to wild-type at all age groups. The present results suggest that odor processing in the olfactory cortex and basic odor discrimination is especially robust in the face of amyloid ß precursor protein (AßPP) over-expression and advancing amyloid ß (Aß) pathology. Odor identification deficits known to emerge early in Alzheimer's disease progression, therefore, may reflect impairments in linking the odor percept to associated labels in cortical regions upstream of the primary olfactory pathway, rather than in the basic odor processing itself.

Impact of reinforcement of diabetes self-care on poorly controlled diabetes: a randomized controlled trial.

PURPOSE: The purpose of the study was to assess the value of reinforcing diabetes self-management for improving glycemia and self-care among adults with type 2 diabetes who had at least 3 hours of prior diabetes education. METHODS: In this randomized controlled trial, 134 participants (75% white, 51% female, 59 ± 9 years old, 13 ± 8 years with diabetes, A1C = 8.4% ± 1.2%) were randomized to either a group map-based program (intervention) or group education on cholesterol and blood pressure (control). Participants were assessed for A1C levels, diabetes self-care behaviors (3-day pedometer readings, 6-minute walk test, blood glucose checks, frequency of self-care), and psychosocial factors (distress, frustration, quality of life) at baseline, 3, 6, and 12 months post intervention and health literacy at baseline. RESULTS: Groups did not differ on baseline characteristics including A1C levels, health literacy, or self-care; however, the intervention group had more years of education than controls. Intervention arm participants modestly improved A1C levels at 3 months post intervention but did not maintain that improvement at 6 and 12 months while control patients did not improve A1C levels at any time during follow-up. Importantly, frequency of self-reported self-care, diabetes quality of life, diabetes-related distress, and frustration with diabetes self-care improved in both groups over time. CONCLUSIONS: Reinforcing self-care with diabetes education for patients who have not met glycemic targets helps improve A1C and could be considered a necessary component of ongoing diabetes care. The best method to accomplish reinforcement needs to be established.

Do older adults aged 60-75 years benefit from diabetes behavioral interventions?

OBJECTIVE: In this secondary analysis, we examined whether older adults with diabetes (aged 60-75 years) could benefit from self-management interventions compared with younger adults. Seventy-one community-dwelling older adults and 151 younger adults were randomized to attend a structured behavioral group, an attention control group, or one-to-one education. RESEARCH DESIGN AND METHODS: We measured A1C, self-care (3-day pedometer readings, blood glucose checks, and frequency of self-care), and psychosocial factors (quality of life, diabetes distress, frustration with self-care, depression, self-efficacy, and coping styles) at baseline and 3, 6, and 12 months postintervention. RESULTS: Both older (age 67 ± 5 years, A1C 8.7 ± 0.8%, duration 20 ± 12 years, 30% type 1 diabetes, 83% white, 41% female) and younger (age 47 ± 9 years, A1C 9.2 ± 1.2%, 18 ± 12 years with diabetes, 59% type 1 diabetes, 82% white, 55% female) adults had improved A1C equally over time. Importantly, older and younger adults in the group conditions improved more and maintained improvements at 12 months (older structured behavioral group change in A1C -0.72 ± 1.4%, older control group -0.65 ± 0.9%, younger behavioral group -0.55 ± 1.2%, younger control group -0.43 ± 1.7%). Furthermore, frequency of self-care, glucose checks, depressive symptoms, quality of life, distress, frustration with self-care, self-efficacy, and emotional coping improved in older and younger participants at follow-up. CONCLUSIONS: The findings suggest that, compared with younger adults, older adults receive equal glycemic benefit from participating in self-management interventions. Moreover, older adults showed the greatest glycemic improvement in the two group conditions. Clinicians can safely recommend group diabetes interventions to community-dwelling older adults with poor glycemic control.

Assessment of barriers to improve diabetes management in older adults: a randomized controlled study.

OBJECTIVE: To evaluate whether assessment of barriers to self-care and strategies to cope with these barriers in older adults with diabetes is superior to usual care with attention control. The American Diabetes Association guidelines recommend the assessment of age-specific barriers. However, the effect of such strategy on outcomes is unknown. RESEARCH DESIGN AND METHODS: We randomized 100 subjects aged ≥69 years with poorly controlled diabetes (A1C >8%) in two groups. A geriatric diabetes team assessed barriers and developed strategies to help patients cope with barriers for an intervention group. The control group received equal amounts of attention time. The active intervention was performed for the first 6 months, followed by a "no-contact" period. Outcome measures included A1C, Tinetti test, 6-min walk test (6MWT), self-care frequency, and diabetes-related distress. RESULTS: We assessed 100 patients (age 75 ± 5 years, duration 21 ± 13 years, 68% type 2 diabetes, 89% on insulin) over 12 months. After the active period, A1C decreased by -0.45% in the intervention group vs. -0.31% in the control group. At 12 months, A1C decreased further in the intervention group by -0.21% vs. 0% in control group (linear mixed-model, P < 0.03). The intervention group showed additional benefits in scores on measures of self-care (Self-Care Inventory-R), gait and balance (Tinetti), and endurance (6MWT) compared with the control group. Diabetes-related distress improved in both groups. CONCLUSIONS: Only attention between clinic visits lowers diabetes-related distress in older adults. However, communication with an educator cognizant of patients' barriers improves glycemic control and self-care frequency, maintains functionality, and lowers distress in this population.