Acetone as biomarker for ketosis buildup capability--a study in healthy individuals under combined high fat and starvation diets

An inexpensive UV-LED photoacoustic based real-time sensor-system detecting exhaled trace-acetone

In this research we present a low-cost system for breath acetone analysis based on UV-LED photoacoustic spectroscopy. We considered the end-tidal phase of exhalation, which represents the systemic concentrations of volatile organic compounds (VOCs) - providing clinically relevant information about the human health. This is achieved via the development of a CO2-triggered breath sampling system, which collected alveolar breath over several minutes in sterile and inert containers. A real-time mass spectrometer is coupled to serve as a reference device for calibration measurements and subsequent breath analysis. The new sensor system provided a 3σ detection limit of 8.3 ppbV and an NNEA of 1.4E-9 Wcm-1Hz-0.5. In terms of the performed breath analysis measurements, 12 out of 13 fell within the error margin of the photoacoustic measurement system, demonstrating the reliability of the measurements in the field.

Image Sensing of Gaseous Acetone Using Secondary Alcohol Dehydrogenase-Immobilized Mesh for Exhaled Air

Human-borne acetone is a potent marker of lipid metabolism. Here, an enzyme immobilization method for secondary alcohol dehydrogenase (S-ADH), which is suitable for highly sensitive and selective biosensing of acetone, was developed, and then its applicability was demonstrated for spatiotemporal imaging of concentration distribution. After various investigations, S-ADH-immobilized meshes could be prepared with less than 5% variation by cross-linking S-ADH with glutaraldehyde on a cotton mesh at 40 °C for 15 min. Furthermore, high activity was obtained by adjusting the concentration of the coenzyme nicotinamide adenine dinucleotide (NADH) solution added to the S-ADH-immobilized mesh to 500 μM and the solvent to a potassium phosphate buffer solution at pH 6.5. The gas imaging system using the S-ADH-immobilized mesh was able to image the decrease in NADH fluorescence (ex 340 nm, fl 490 nm) caused by the catalytic reaction of S-ADH and the acetone distribution in the concentration range of 0.1-10 ppm-v, including the breath concentration of healthy people at rest. The exhaled breath of two healthy subjects at 6 h of fasting was quantified as 377 and 673 ppb-v, which were consistent with the values quantified by gas chromatography-mass spectrometry.

A Novel Acetone Sensor for Body Fluids

Ketones are well-known biomarkers of fat oxidation produced in the liver as a result of lipolysis. These biomarkers include acetoacetic acid and β-hydroxybutyric acid in the blood/urine and acetone in our breath and skin. Monitoring ketone production in the body is essential for people who use caloric intake deficit to reduce body weight or use ketogenic diets for wellness or therapeutic treatments. Current methods to monitor ketones include urine dipsticks, capillary blood monitors, and breath analyzers. However, these existing methods have certain disadvantages that preclude them from being used more widely. In this work, we introduce a novel acetone sensor device that can detect acetone levels in breath and overcome the drawbacks of existing sensing approaches. The critical element of the device is a robust sensor with the capability to measure acetone using a complementary metal oxide semiconductor (CMOS) chip and convenient data analysis from a red, green, and blue deconvolution imaging approach. The acetone sensor device demonstrated sensitivity of detection in the micromolar-concentration range, selectivity for detection of acetone in breath, and a lifetime stability of at least one month. The sensor device utility was probed with real tests on breath samples using an established blood ketone reference method.

Low level detection of acetone vapor by improvised design of high "Q" tunable frequency Helmholtz photoacoustic cell using UV, mid- IR and THz sources

The paper reports the designing and fabrication aspects of a high "Q = 492.3" Helmholtz photoacoustic (PA) cell employed for the trace level detection of acetone, a biomarker by using 266 nm- UV, Mid-IR (5.4-10.6 micron) and 0.11 Terahertz (THz) sources. The designed Helmholtz PA cell is made of Aluminum and possesses a natural frequency tunable between 1.4 to 4.4 kHz range using a movable piston arrangement of the microphone sensor. Numerous types of disorders, including diabetes, asthma, lung cancer, etc., can be diagnosed using the acetone concentration obtained through breath analysis. The comparative study is related to the response of different types of excitation mechanisms contributed by electronics, vibrational and rotational modes of acetone. The low-level detection (LoD) limit for acetone is of the order of 5.06 & 7.92 ppbV, and 15.3 pptV, respectively, in UV, Mid-IR, and THz region. This study contributes to the development of a highly sensitive, non-invasive acetone detection and quantification modality.

Feeding the gut microbiome: impact on multiple sclerosis

Multiple sclerosis (MS) is a multifactorial neurological disease characterized by chronic inflammation and immune-driven demyelination of the central nervous system (CNS). The rising number of MS cases in the last decade could be partially attributed to environmental changes, among which the alteration of the gut microbiome driven by novel dietary habits is now of particular interest. The intent of this review is to describe how diet can impact the development and course of MS by feeding the gut microbiome. We discuss the role of nutrition and the gut microbiota in MS disease, describing preclinical studies on experimental autoimmune encephalomyelitis (EAE) and clinical studies on dietary interventions in MS, with particular attention to gut metabolites-immune system interactions. Possible tools that target the gut microbiome in MS, such as the use of probiotics, prebiotics and postbiotics, are analyzed as well. Finally, we discuss the open questions and the prospects of these microbiome-targeted therapies for people with MS and for future research.

A sub-ppbv-level Acetone and Ethanol Quantum Cascade Laser Based Photoacoustic Sensor - Characterization and Multi-Component Spectra Recording in Synthetic Breath

Trace gas analysis in breath is challenging due to the vast number of different components. We present a highly sensitive quantum cascade laser based photoacoustic setup for breath analysis. Scanning the range between 8263 and 8270 nm with a spectral resolution of 48 pm, we are able to quantify acetone and ethanol within a typical breath matrix containing water and CO₂. We photoacoustically acquired spectra within this region of mid-infra-red light and prove that those spectra do not suffer from non-spectral interferences. The purely additive behavior of a breath sample spectrum was verified by comparing it with the independently acquired single component spectra using Pearson and Spearman correlation coefficients. A previously presented simulation approach is improved and an error attribution study is presented. With a 3σ detection limit of 6.5 ppbv in terms of ethanol and 250 pptv regarding acetone, our system is among the best performing presented so far.

Inter-Day Variation in the Fasting Plasma Lipopolysaccharide Concentration in the Morning Is Associated with Inter-Day Variation in Appetite in Japanese Males: A Short-Term Cohort Study

Injection of lipopolysaccharide (LPS), a product of gut bacteria, into the blood increases blood triglycerides and cortisol, an appetite-stimulating hormone. Meanwhile, small amounts of LPS derived from gut bacteria are thought to enter the bloodstream from the gut in daily basis. This study aimed to investigate the effect of LPS influx on appetite or lipid metabolism in humans in everyday life. We measured the fasting plasma LPS concentration before breakfast and the corresponding days’ appetite and fat-burning markers for 10 days in four Japanese males (28–31 years) and analyzed the correlation of their inter-day variation. The LPS concentration was negatively correlated with fullness, and positively correlated with the carbohydrate intake. Against our hypothesis, the LPS concentration was positively correlated with the fasting breath acetone concentration, a fat-burning marker. There was a positive correlation between the LPS concentration and fasting body mass index (BMI), but the inter-day variation in BMI was slight. The results suggest that the LPS influx in everyday life is at least associated with appetite in the day.

Non-Invasive Disease Specific Biomarker Detection Using Infrared Spectroscopy: A Review

Many life-threatening diseases remain obscure in their early disease stages. Symptoms appear only at the advanced stage when the survival rate is poor. A non-invasive diagnostic tool may be able to identify disease even at the asymptotic stage and save lives. Volatile metabolites-based diagnostics hold a lot of promise to fulfil this demand. Many experimental techniques are being developed to establish a reliable non-invasive diagnostic tool; however, none of them are yet able to fulfil clinicians' demands. Infrared spectroscopy-based gaseous biofluid analysis demonstrated promising results to fulfil clinicians' expectations. The recent development of the standard operating procedure (SOP), sample measurement, and data analysis techniques for infrared spectroscopy are summarized in this review article. It has also outlined the applicability of infrared spectroscopy to identify the specific biomarkers for diseases such as diabetes, acute gastritis caused by bacterial infection, cerebral palsy, and prostate cancer.

Dietary energy restriction in neurological diseases: what's new?

Energy-restricted diet is a specific dietary regimen, including the continuous energy-restricted diet and the intermittent energy-restricted diet. It has been proven effective not only to reduce weight and extend the lifespan in animal models, but also to regulate the development and progression of various neurological diseases such as epilepsy, cerebrovascular diseases (stroke), neurodegenerative disorders (Alzheimer's disease and Parkinson's disease) and autoimmune diseases (multiple sclerosis). However, the mechanism in this field is still not clear and a systematic neurological summary is still missing. In this review, we first give a brief summary of the definition and mainstream strategies of energy restrictions. We then review evidence about the effects of energy-restricted diet from both animal models and human trials, and update the current understanding of mechanisms underlying the biological role of energy-restricted diet in the fight against neurological diseases. Our review thus contributes to the modification of dietary regimen and the search for special diet mimics.

A bibliometric analysis of the global trends and hotspots for the ketogenic diet based on CiteSpace

The ketogenic diet (KD) is a potential nutritional therapy that is frequently utilized in various conditions. More and more studies are being done on KD in recent years. However, as far as we know, few studies have made an effort to offer a thorough synthesis and assessment of this topic. This paper aims to do a rigorous and thorough evaluation of the knowledge structure, development trend, and research hotspot of scientific outputs connected to KD. The bibliographic records connected to KD from January 1, 2001 to April 22, 2022 were collected using the core collection database of Web of Science. The complex data input, that consisted of the amount of publications, journals, authors, institutions, countries, keywords and cited references, was generated and analyzed visually using CiteSpace. A total of 2676 literatures on the KD were published between 2001 and 2022. The most KD-related publications were found in Epilepsia and Epilepsia Research. The authors with the most KD-related papers are Kossoff EH and Rho J. The United States is the country with the most publications, and Johns Hopkins University, Johns Hopkins University Hospital, and Johns Hopkins Medical Institutions are the institutions with the most articles. The high frequency keywords are "KD," "ketone body," "children," "efficacy," "weight loss," "low carbohydrate diet," "metabolism," "epilepsy," "beta hydroxybutyrate," and "modified atkins diet." The 2018 study by Kossoff EH on epilepsia and the 2017 study by Puchalska P on ketone body metabolism earned 127 and 114 citations, respectively. The results of this bibliometric analysis provide information on the state and trends in KD and may be used by researchers to pinpoint hot issues and discover new areas of study.

Breath Analysis for the In Vivo Detection of Diabetic Ketoacidosis

Human breath analysis of volatile organic compounds has gained significant attention recently because of its rapid and noninvasive potential to detect various metabolic diseases. The detection of ketones in the breath and blood is key to diagnosing and managing diabetic ketoacidosis (DKA) in patients with type 1 diabetes. It may also be of increasing importance to detect euglycemic ketoacidosis in patients with type 1 or type 2 diabetes or heart failure, treated with sodium-glucose transporter-2 inhibitors (SGLT2-i). The present research evaluates the efficiency of colorimetry for detecting acetone and ethanol in exhaled human breath with the response time, pH effect, temperature effect, concentration effect, and selectivity of dyes. Using the proposed multidye system, we obtained a detection limit of 0.0217 ppm for acetone and 0.029 ppm for ethanol in the detection range of 0.05-50 ppm. A smartphone-assisted unit consisting of a portable colorimetric device was used to detect relative red/green/blue values within 60 s of the interface for practical and real-time application. The developed method could be used for rapid, low-cost detection of ketones in patients with type 1 diabetes and DKA and patients with type 1 or type 2 diabetes or heart failure treated with SGLT2-I and euglycemic ketoacidosis.

Activation of G protein-coupled receptors by ketone bodies: Clinical implication of the ketogenic diet in metabolic disorders

Ketogenesis takes place in hepatocyte mitochondria where acetyl-CoA derived from fatty acid catabolism is converted to ketone bodies (KB), namely β-hydroxybutyrate (β-OHB), acetoacetate and acetone. KB represent important alternative energy sources under metabolic stress conditions. Ketogenic diets (KDs) are low-carbohydrate, fat-rich eating strategies which have been widely proposed as valid nutritional interventions in several metabolic disorders due to its substantial efficacy in weight loss achievement. Carbohydrate restriction during KD forces the use of FFA, which are subsequently transformed into KB in hepatocytes to provide energy, leading to a significant increase in ketone levels known as "nutritional ketosis". The recent discovery of KB as ligands of G protein-coupled receptors (GPCR) - cellular transducers implicated in a wide range of body functions - has aroused a great interest in understanding whether some of the clinical effects associated to KD consumption might be mediated by the ketone/GPCR axis. Specifically, anti-inflammatory effects associated to KD regimen are presumably due to GPR109A-mediated inhibition of NLRP3 inflammasome by β-OHB, whilst lipid profile amelioration by KDs could be ascribed to the actions of acetoacetate via GPR43 and of β-OHB via GPR109A on lipolysis. Thus, this review will focus on the effects of KD-induced nutritional ketosis potentially mediated by specific GPCRs in metabolic and endocrinological disorders. To discriminate the effects of ketone bodies per se, independently of weight loss, only studies comparing ketogenic vs isocaloric non-ketogenic diets will be considered as well as short-term tolerability and safety of KDs.

Ketogenic Diets and their Therapeutic Potential on Breast Cancer: A Systemic Review

Breast cancer remains a major cause of morbidity and mortality in women, and there is still a lack of complementary approaches to significantly improve the efficacy of standard therapies. For many kinds of cancers, the usual standard care is the combination of surgery, radiation, and chemotherapy. However, this standard therapy is not effective alone. Therefore, new approaches that increase therapeutic effectiveness are urgently needed. The ketogenic diet is a novel therapeutic approach for certain types of cancers, as indicated by several preclinical and clinical evidences. The ketogenic diet, which consists of a high-fat, low-carbohydrate diet with adequate protein, appears to sensitize most cancers to standard therapy by utilizing the reprogrammed metabolism of cancer cells, making it a promising candidate for adjuvant cancer treatment. The majority of preclinical and clinical studies argue that the use of a ketogenic diet in combination with standard therapies is based on its potential to improve the antitumor effects of conventional chemotherapy, its overall good safety and tolerability, and quality of life improvement. According to new evidence, a ketogenic diet lowers the level of glucose and insulin in the blood, which are necessary for tumor growth. Thus, the ketogenic diet has emerged as a potential treatment option for a variety of cancers, including breast cancer. Besides, implementation of a Ketogenic diet in the clinic could improve progression-free and overall survival for patients with breast cancer. This review summarizes the composition and metabolism of ketogenic diets and their potential mechanisms in breast carcinogenesis in addition to their therapeutic potential on breast cancer.

Theory helps experiment to reveal VOCs in human breath

Volatile organic compounds (VOCs) present in human breath not only provide information about the internal chemistry of the body but can also be specific to diseases. Therefore, detection and analysis of specific VOCs can be used for medical diagnostics. However, up until today in spite of several existing VOC-based detection techniques and significant efforts, breath analysis is not a diagnostic method available for clinicians. Infrared absorption spectroscopy is a promising technique to fill this gap, with tens of identified VOCs in breath. Currently, a lack of digital spectral databases and several masking effects make difficult reliable molecular identification of observed absorption features. We demonstrate that calculations of rotational bands of vibrational spectra could serve as a basic method for molecular identification of spectral features observed in experiment. Results of comparison of several known VOCs spectra with the predictions of the theoretical model are presented.

Towards a standard operating procedure for revealing hidden volatile organic compounds in breath: the Fourier-transform IR spectroscopy case

Human breath contains a large amount of small volatile organic compounds (VOCs) and could therefore be used as a carrier of metabolic information for medical diagnostics. Still, in spite of several promising techniques that have been applied during the last decades to study breath content, there is a lack of breath-based diagnostic tools available for physicians. Among several promising techniques, infrared (IR) spectroscopy has already proved its potential for reliable detection of VOCs in the breath. However, due to the large dynamic range of molecular concentrations and overlapping absorption spectra of different VOCs, many low-absorption molecules stay hidden in spectroscopic measurements. To overcome this obstacle, we propose the Matryoshka method for removing masking effects and revealing the buried spectral structures in any bio-fluid in the gas phase. By exploiting both physical and digital removal steps, we demonstrate how the method reveals methane, acetone, aldehyde, and methyl butyrate in a real breath.

Effect of short-term ketogenic diet on end-tidal carbon dioxide

BACKGROUND & AIMS

Previous studies have shown that end-tidal carbon dioxide (EtCO₂) is lower with the presence of supraphysiological ketones as in the case of chronic ketogenic diet (KD) and diabetic ketoacidosis (DKA). This study aimed to determine changes in EtCO₂ upon short term KD.

METHODS

Healthy subjects were screened not to have conditions that exerts abnormal EtCO₂ nor contraindicated for KD. Subjects underwent seven days of KD while the EtCO2 and blood ketone (beta-hydroxybutyrate; β-OHB) parameters were sampled at day zero (t0) and seven (t7) of ketosis respectively. Statistically, the t-test and Pearson's coefficient were conducted to determine the changes and correlation of both parameters.

RESULTS

12 subjects completed the study. The mean score ± standard deviation (SD) for EtCO₂ were 35.08 ± 3.53 and 35.67 ± 3.31 mm Hg for t0 and t7 respectively. The mean score ±SD for β-OHB were 0.07 ± 0.08 and 0.87 ± 0.84 mmol/L for t0 and t7 respectively. There was no significant difference of EtCO₂ between the period of study (p > 0.05) but the β-OHB increased during t7 (p < 0.05). There was also no correlation between the parameters.

CONCLUSIONS

These findings suggest that EtCO₂ may not be utilized to determine short term nutritional ketosis.

Ketotherapy as an epigenetic modifier in cancer

Epigenetic alterations in cancer play a variety of roles. Aberrant DNA methylation, as one of the epigenetic mechanisms, has been widely studied in both tumor and liquid biopsies and provide a useful bench mark for treatment response in cancer. Recently, several studies have reported an association between the type of diet and epigenetic modifications. Whereby there is a growing interest in finding the "anti-cancer diet formula", if such a thing exists. In this sense, ketogenic diets (KD) have reported potentially beneficial effects, which were able to prevent malignancies and decrease tumor growth. Some studies have even shown increased survival in cancer patients, reduced side effects of cytotoxic treatments, and intensified efficacy of cancer therapies. Although the biological mechanisms of KD are not well understood, it has been reported that KD may affect DNA methylation by modulating the expression of crucial genes involved in tumor survival and proliferation. However, there are many considerations to take into account to use ketotherapy in cancer, such as epigenetic mark, type of cancer, immunological and metabolic state or microbiota profile. In this review, we argue about ketotherapy as a potential strategy to consider as coadjuvant of cancer therapy. We will focus on mainly epigenetic mechanisms and dietary approach that could be included in the current clinical practice guidelines.

Keto microbiota: A powerful contributor to host disease recovery

Gut microbiota (GM) is a key contributor to host metabolism and physiology. Data generated on comparing diseased and healthy subjects have reported changes in the GM profile between both health states, suggesting certain bacterial composition could be involved in pathogenesis. Moreover, studies reported that reshaping of GM could contribute actively to disease recovery. Interestingly, ketogenic diets (KD) have emerged recently as new economic dietotherapeutic strategy to combat a myriad of diseases (refractory epilepsy, obesity, cancer, neurodegenerative diseases…). KD, understood in a broad sense, refers to whatever dietetic approximation, which causes physiological ketosis. Therefore, high fat-low carbs diets, fasting periods or caloric restriction constitute different strategies to produce an increase of main ketones bodies, acetoacetate and β-hydroxybutyrate, in blood. Involved biological mechanisms in ketotherapeutic effects are still to be unravelled. However, it has been pointed out that GM remodelling by KD, from now on "keto microbiota", may play a crucial role in patient response to KD treatment. In fact, germ-free animals were resistant to ketotherapeutic effects; reinforcing keto microbiota may be a powerful contributor to host disease recovery. In this review, we will comment the influence of gut microbiota on host, as well as, therapeutic potential of ketogenic diets and keto microbiota to restore health status. Current progress and limitations will be argued too. In spite of few studies have defined applicability and mechanisms of KD, in the light of results, keto microbiota might be a new useful therapeutic agent.

In Situ Observation of Metal to Metal Oxide Progression: A Study of Charge Transfer Phenomenon at Ru-CuO Interfaces

Surface charge and charge transfer between nanoclusters and oxide supports are of paramount importance to catalysis, surface plasmonics, and optical energy harvesting areas. At present, high-energy X-rays and theoretical investigation are always required to determine the chemical state changes in the nanoclusters and the oxide supports, as well as the underlying transfer charge between them. This work presents the idea of using chrono-conductometric measurements to determine the chemical states of the Ru nanoclusters on CuO supports. Both icosahedral and single-crystal hexagonal close-packed Ru nanoclusters were deposited through gas-phase synthesis. To study the charge transfer phenomenon at the interface, a bias was applied to cupric oxide nanowires with metallic nanocluster decoration. In situ conductometric measurements were performed to observe the evolution of Ru into RuO_x under heating conditions. Structural elucidation techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, and Kelvin probe force microscopy were employed to study the corresponding progression of structure, chemical ordering, and surface potential, respectively, as Ru(0) was oxidized to RuO_x on the supporting oxide surface. Experimental and theoretical investigation of charge transfer between the nanocluster and oxide support highlighted the importance of metallic character and structure of the nanoclusters on the interfacial charge transfer, thus allowing the investigation of surface charge behavior on oxide-supported catalysts, in situ, during catalytic operation via conductometric measurements.

Starvation Ketoacidosis due to the Ketogenic Diet and Prolonged Fasting - A Possibly Dangerous Diet Trend

Patient: Male, 60

Final Diagnosis: Starvation ketoacidosis

Symptoms: Nausea • syncope • vomiting

Medication: —

Clinical Procedure: —

Specialty: Metabolic Disorders and Diabetics

Ketogenic diet in endocrine disorders: Current perspectives

Ketogenic diet (KD) is a high-fat, adequate-protein, and low-carbohydrate diet that leads to nutritional ketosis, long known for antiepileptic effects and has been used therapeutically to treat refractory epilepsy. This review attempts to summarize the evidence and clinical application of KD in diabetes, obesity, and other endocrine disorders. KD is usually animal protein based. An empiric vegetarian Indian variant of KD has been provided keeping in mind the Indian food habits. KD has beneficial effects on cardiac ischemic preconditioning, improves oxygenation in patients with respiratory failure, improves glycemic control in diabetics, is associated with significant weight loss, and has a beneficial impact on polycystic ovarian syndrome. Multivitamin supplementations are recommended with KD. Recently, ketones are being proposed as super-metabolic fuel; and KD is currently regarded as apt dietary therapy for "diabesity."

Fluorometric gas-imaging system (sniff-cam), using the extinction of NADH with an ADH reverse reaction, for acetaldehyde in the gas phase

A gas-imaging system (sniff-cam) that allows fluorometric visualization of a two-dimensional (2-D) distribution of gaseous acetaldehyde (AcH) was developed. It employed a reverse reaction of a nicotinamide adenine dinucleotide (NADH) dependent enzyme that led to consumption of NADH in that reaction. The system was constructed with a highly sensitive camera, an ultraviolet light emitting diode array sheet, two band pass filters and an alcohol dehydrogenase (ADH)-immobilized mesh that was used for AcH detection. The reverse reaction of the ADH catalyzed the reduction of AcH to ethanol and the oxidation of NADH to NAD⁺, which occurred when gaseous AcH was applied to the ADH immobilized mesh that was wetted with a slightly acidic NADH solution. As NADH has an autofluorescence property [emission (λ_em) at 490 nm; excitation (λ_ex) at 340 nm], the presence of gaseous AcH was visualized by a decrease of fluorescence of the NADH at the ADH immobilized mesh. After constructing the gaseous AcH imaging system, optimizations of pH, and concentration of the NADH solution were performed. As a result of the optimizations (500 μM of NADH in 0.1 M of Tris hydrochloride (Tris-HCl) buffer at pH 6.5), the AcH sniff-cam showed a wide dynamic range (0.1-10 ppm) for gaseous AcH with a high correlation coefficient (R = 0.999). Furthermore, a fluorescence gradient with a rounded shape centered in a gas outlet was observed. These results demonstrated that the AcH sniff-cam utilizing the fluorescence decrease of NADH could be used to quantitatively evaluate the 2-D distribution of gaseous AcH.

Impact of Nutrition on Cardiovascular Function

The metabolic sources of energy for myocardial contractility include mainly free fatty acids (FFA) for 95%, and in lesser amounts for 5% from glucose and minimal contributions from other substrates such lactate, ketones, and amino acids. However, myocardial efficiency is influenced by metabolic condition, overload, and ischemia. During cardiac stress, cardiomyocytes increase glucose oxidation and reduce FFA oxidation. In patients with ischemic coronary disease and heart failure, the low oxygen availability limits myocardial reliance on FFA and glucose utilization must increase. Although glucose uptake is fundamental to cardiomyocyte function, an excessive intracellular glucose level is detrimental. Insulin plays a fundamental role in maintaining myocardial efficiency and in reducing glycemia and inflammation; this is particularly evident in obese and type-2 diabetic patients. An excess of F availability increase fat deposition within cardiomyocytes and reduces glucose oxidation. In patients with high body mass index, a restricted diet or starvation have positive effects on cardiac metabolism and function while, in patients with low body mass index, restrictive diets, or starvation have a deleterious effect. Thus, weight loss in obese patients has positive impacts on ventricular mass and function, whereas, in underweight heart failure patients, such weight reduction adds to the risk of heart damage, predisposing to cachexia. Nutrition plays an essential role in the evolution of cardiovascular disease and should be taken into account. An energy-restricted diet improves myocardial efficiency but can represent a potential risk of heart damage, particularly in patients affected by cardiovascular disease. Micronutrient integration has a marginal effect on cardiovascular efficiency.

Prospects and Challenges of Volatile Organic Compound Sensors in Human Healthcare

The chemical signatures of volatile organic compounds (VOCs) in humans can be utilized for point-of-care (POC) diagnosis. Apart from toxic exposure studies, VOCs generated in humans can provide insights into one's healthy and diseased metabolic states, acting as a biomarker for identifying numerous diseases noninvasively. VOC sensors and the technology of e-nose have received significant attention for continuous and selective monitoring of various physiological and pathophysiological conditions of an individual. Noninvasive detection of VOCs is achieved from biomatrices of breath, sweat and saliva. Among these, detection from sweat and saliva can be continuous in real-time. The sensing approaches include optical, chemiresistive and electrochemical techniques. This article provides an overview of such techniques. These, however, have limitations of reliability, precision, selectivity, and stability in continuous monitoring. Such limitations are due to lack of sensor stability and complexity of samples in a multivariate environment, which can lead to false readings. To overcome selectivity barriers, sensor arrays enabling multimodal sensing, have been used with pattern recognition techniques. Stability and precision issues have been addressed through advancements in nanotechnology. The use of various forms of nanomaterial not only enhance sensing performance, but also plays a major role in detection on a miniaturized scale. The rapid growth in medical Internet of Things (IoT) and artificial intelligence paves a pathway for improvements in human theranostics.

Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis?

Background

The ketogenic diet (KD) is a very low-carbohydrate, high-fat and adequate-protein diet with no calorie limit that induces a metabolic condition called “physiological ketosis”. It was first introduced to treat epilepsy in the 1920s and has become quite popular recently as weight-loss and performance-enhancing diet. Its therapeutic use in a range of diseases is under investigation. During KD interventions people are supposed to monitor compliance with the dietary regimen by daily urine testing for ketosis. However, there are no studies investigating the best time for testing.

Findings

Twelve healthy subjects (37 ± 11 years; BMI = 23.0 ± 2.5 kg/m²) were instructed to, during the sixth week of a KD and with stable ketosis, measure their urine (8×) and blood (18×) ketone concentration at regular intervals during a 24-h period. According to their 1-day food record, the subjects consumed on average a diet with 74.3 ± 4.0 %, 19.5 ± 3.5 %, and 6.2 ± 2.0 % of total energy intake from fat, protein and carbohydrate, respectively. The lowest blood ß-hydroxybutyrate (BHB) (0.33 ± 0.17 mmol/l) and urine acetoacetate (AA) (0.46 ± 0.54 mmol/l) concentrations were measured at 10:00, respectively. The highest BHB (0.70 ± 0.62 mmol/l) and AA concentrations were noted at 03:00, respectively. Via urine testing the highest levels of ketosis were found at 22:00 and 03:00 and the highest detection rates (>90 %) for ketosis were at 07:00, 22:00 and 03:00, respectively.

Conclusions

These results indicate that ketonuria in subjects with stable ketosis is highest and can be most reliably detected in the early morning and post-dinner urine. Recommendations can be given regarding precise time of the day for measuring ketone bodies in urine in future studies with KDs.