Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes

Emerging Role of Hepatic Ketogenesis in Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver diseases, arise from non-alcoholic fatty liver (NAFL) characterized by excessive fat accumulation as triglycerides. Although NAFL is benign, it could progress to non-alcoholic steatohepatitis (NASH) manifested with inflammation, hepatocyte damage and fibrosis. A subset of NASH patients develops end-stage liver diseases such as cirrhosis and hepatocellular carcinoma. The pathogenesis of NAFLD is highly complex and strongly associated with perturbations in lipid and glucose metabolism. Lipid disposal pathways, in particular, impairment in condensation of acetyl-CoA derived from β-oxidation into ketogenic pathway strongly influence the hepatic lipid loads and glucose metabolism. Current evidence suggests that ketogenesis dispose up to two-thirds of the lipids entering the liver, and its dysregulation significantly contribute to the NAFLD pathogenesis. Moreover, ketone body administration in mice and humans shows a significant improvement in NAFLD. This review focuses on hepatic ketogenesis and its role in NAFLD pathogenesis. We review the possible mechanisms through which impaired hepatic ketogenesis may promote NAFLD progression. Finally, the review sheds light on the therapeutic implications of a ketogenic diet in NAFLD.

The β-Hydroxybutyrate-GPR109A Receptor Regulates Fasting-induced Plasticity in the Mouse Adrenal Medulla

During fasting, increased sympathoadrenal activity leads to epinephrine release and multiple forms of plasticity within the adrenal medulla including an increase in the strength of the preganglionic → chromaffin cell synapse and elevated levels of agouti-related peptide (AgRP), a peptidergic cotransmitter in chromaffin cells. Although these changes contribute to the sympathetic response, how fasting evokes this plasticity is not known. Here we report these effects involve activation of GPR109A (HCAR2). The endogenous agonist of this G protein-coupled receptor is β-hydroxybutyrate, a ketone body whose levels rise during fasting. In wild-type animals, 24-hour fasting increased AgRP-ir in adrenal chromaffin cells but this effect was absent in GPR109A knockout mice. GPR109A agonists increased AgRP-ir in isolated chromaffin cells through a GPR109A- and pertussis toxin-sensitive pathway. Incubation of adrenal slices in nicotinic acid, a GPR109A agonist, mimicked the fasting-induced increase in the strength of the preganglionic → chromaffin cell synapse. Finally, reverse transcription polymerase chain reaction experiments confirmed the mouse adrenal medulla contains GPR109A messenger RNA. These results are consistent with the activation of a GPR109A signaling pathway located within the adrenal gland. Because fasting evokes epinephrine release, which stimulates lipolysis and the production of β-hydroxybutyrate, our results indicate that chromaffin cells are components of an autonomic-adipose-hepatic feedback circuit. Coupling a change in adrenal physiology to a metabolite whose levels rise during fasting is presumably an efficient way to coordinate the homeostatic response to food deprivation.

Method Comparison of β-Hydroxybutyrate Using a Point-of-Care Device and Dry Chemistry Analyzer in Three Sea Turtle Species

The ketone β-hydroxybutyrate (BHB) serves as an energy source when bodily energy stores are low. Concentrations of this blood analyte are often determined by spectrophotometric quantitative assays with a dry chemistry analyzer; however, rapid assessment with point-of-care devices have the potential to improve assessment of animals in the field or in clinical settings. We measured BHB concentrations in whole blood samples from 54 leatherback (Dermochelys coriacea), 27 loggerhead (Caretta caretta), and 14 green (Chelonia mydas) sea turtles in Florida, US with a point-of-care device and validated its use with corresponding plasma samples and dry chemistry analyzer as the gold standard. Concentrations of BHB highly correlated between the two methods for all three species, with loggerheads showing the best agreement and lowest bias. Therefore, the point-of-care device used for this study (Lucidplus β-ketone monitoring system) is probably appropriate for sea turtle BHB measurements.

Ketogenic diets, physical activity and body composition: a review

Obesity remains a serious relevant public health concern throughout the world despite related countermeasures being well understood (i.e. mainly physical activity and an adjusted diet). Among different nutritional approaches, there is a growing interest in ketogenic diets (KD) to manipulate body mass (BM) and to enhance fat mass loss. KD reduce the daily amount of carbohydrate intake drastically. This results in increased fatty acid utilisation, leading to an increase in blood ketone bodies (acetoacetate, 3-β-hydroxybutyrate and acetone) and therefore metabolic ketosis. For many years, nutritional intervention studies have focused on reducing dietary fat with little or conflicting positive results over the long term. Moreover, current nutritional guidelines for athletes propose carbohydrate-based diets to augment muscular adaptations. This review discusses the physiological basis of KD and their effects on BM reduction and body composition improvements in sedentary individuals combined with different types of exercise (resistance training or endurance training) in individuals with obesity and athletes. Ultimately, we discuss the strengths and the weaknesses of these nutritional interventions together with precautionary measures that should be observed in both individuals with obesity and athletic populations. A literature search from 1921 to April 2021 using Medline, Google Scholar, PubMed, Web of Science, Scopus and Sportdiscus Databases was used to identify relevant studies. In summary, based on the current evidence, KD are an efficient method to reduce BM and body fat in both individuals with obesity and athletes. However, these positive impacts are mainly because of the appetite suppressive effects of KD, which can decrease daily energy intake. Therefore, KD do not have any superior benefits to non-KD in BM and body fat loss in individuals with obesity and athletic populations in an isoenergetic situation. In sedentary individuals with obesity, it seems that fat-free mass (FFM) changes appear to be as great, if not greater, than decreases following a low-fat diet. In terms of lean mass, it seems that following a KD can cause FFM loss in resistance-trained individuals. In contrast, the FFM-preserving effects of KD are more efficient in endurance-trained compared with resistance-trained individuals.

Haze Air Pollution Health Impacts of Breath-Borne VOCs

Here, we investigated the use of breath-borne volatile organic compounds (VOCs) for rapid monitoring of air pollution health effects on humans. Forty-seven healthy college students were recruited, and their exhaled breath samples (n = 235) were collected and analyzed for VOCs before, on, and after two separate haze pollution episodes using gas chromatography-ion mobility spectrometry (GC-IMS). Using a paired t-test and machine learning model (Gradient Boosting Machine, GBM), six exhaled VOC species including propanol and isoprene were revealed to differ significantly among pre-, on-, and post-exposure in both haze episodes, while none was found between clean control days. The GBM model was shown capable of differentiating between pre- and on-exposure to haze pollution with a precision of 90-100% for both haze episodes. However, poor performance was detected for the same model between two different clean days. In addition to gender and particular haze occurrence influences, correlation analysis revealed that NH₄⁺, NO₃^-, acetic acid, mesylate, CO, NO₂, PM_2.5, and O₃ played important roles in the changes in breath-borne VOC fingerprints following haze air pollution exposure. This work has demonstrated direct evidence of human health impacts of haze pollution while identifying potential breath-borne VOC biomarkers such as propanol and isoprene for haze air pollution exposure.

Very Low-Calorie Ketogenic Diet: A Potential Application in the Treatment of Hypercortisolism Comorbidities

A very low-calorie ketogenic diet (VLCKD) is characterized by low daily caloric intake (less than 800 kcal/day), low carbohydrate intake (<50 g/day) and normoproteic (1−1.5 g of protein/kg of ideal body weight) contents. It induces a significant weight loss and an improvement in lipid parameters, blood pressure, glycaemic indices and insulin sensitivity in patients with obesity and type 2 diabetes mellitus. Cushing’s syndrome (CS) is characterized by an endogenous or exogenous excess of glucocorticoids and shows many comorbidities including cardiovascular disease, obesity, type 2 diabetes mellitus and lipid disorders. The aim of this speculative review is to provide an overview on nutrition in hypercortisolism and analyse the potential use of a VLCKD for the treatment of CS comorbidities, analysing the molecular mechanisms of ketogenesis.

Liver Metastatic Breast Cancer: Epidemiology, Dietary Interventions, and Related Metabolism

The median overall survival of patients with metastatic breast cancer is only 2-3 years, and for patients with untreated liver metastasis, it is as short as 4-8 months. Improving the survival of women with breast cancer requires more effective anti-cancer strategies, especially for metastatic disease. Nutrients can influence tumor microenvironments, and cancer metabolism can be manipulated via a dietary modification to enhance anti-cancer strategies. Yet, there are no standard evidence-based recommendations for diet therapies before or during cancer treatment, and few studies provide definitive data that certain diets can mediate tumor progression or therapeutic effectiveness in human cancer. This review focuses on metastatic breast cancer, in particular liver metastatic forms, and recent studies on the impact of diets on disease progression and treatment.

Beta-Hydroxybutyrate Suppresses Hepatic Production of the Ghrelin Receptor Antagonist LEAP2

INTRODUCTION

Liver-expressed antimicrobial peptide-2 (LEAP2) is an endogenous ghrelin receptor antagonist, which is upregulated in the fed state and downregulated during fasting. We hypothesized that the ketone body beta-hydroxybutyrate (BHB) is involved in the downregulation of LEAP2 during conditions with high circulating levels of BHB.

METHODS

Hepatic and intestinal Leap2 expression were determined in 3 groups of mice with increasing circulating levels of BHB: prolonged fasting, prolonged ketogenic diet, and oral BHB treatment. LEAP2 levels were measured in lean and obese individuals, in human individuals following endurance exercise, and in mice after BHB treatment. Lastly, we investigated Leap2 expression in isolated murine hepatocytes challenged with BHB.

RESULTS

We confirmed increased circulating LEAP2 levels in individuals with obesity compared to lean individuals. The recovery period after endurance exercise was associated with increased plasma levels of BHB levels and decreased LEAP2 levels in humans. Leap2 expression was selectively decreased in the liver after fasting and after exposure to a ketogenic diet for 3 weeks. Importantly, we found that oral administration of BHB increased circulating levels of BHB in mice and decreased Leap2 expression levels and circulating LEAP2 plasma levels, as did Leap2 expression after direct exposure to BHB in isolated murine hepatocytes.

CONCLUSION

From our data, we suggest that LEAP2 is downregulated during different states of energy deprivation in both humans and rodents. Furthermore, we here provide evidence that the ketone body, BHB, which is highly upregulated during fasting metabolism, directly downregulates LEAP2 levels. This may be relevant in ghrelin receptor-induced hunger signaling during energy deprivation.

The newborn metabolome: associations with gestational diabetes, sex, gestation, birth mode, and birth weight

BACKGROUND

Pathways towards many adult-onset conditions begin early in life, even in utero. Maternal health in pregnancy influences this process, but little is known how it affects neonatal metabolism. We investigated associations between pregnancy and birth factors and cord blood metabolomic profile in a large, population-derived cohort.

METHODS

Metabolites were measured using nuclear magnetic resonance in maternal (28 weeks gestation) and cord serum from 912 mother-child pairs in the Barwon Infant Study pre-birth cohort. Associations between maternal (metabolites, age, BMI, smoking), pregnancy (pre-eclampsia, gestational diabetes (GDM)), and birth characteristics (delivery mode, gestational age, weight, infant sex) with 72 cord blood metabolites were examined by linear regression.

RESULTS

Delivery mode, sex, gestational age, and birth weight were associated with specific metabolite levels in cord blood, including amino acids, fatty acids, and cholesterols. GDM was associated with higher cord blood levels of acetoacetate and 3-hydroxybutyrate.

CONCLUSIONS

Neonatal factors, particularly delivery mode, were associated with many cord blood metabolite differences, including those implicated in later risk of cardiometabolic disease. Associations between GDM and higher offspring ketone levels at birth are consistent with maternal ketosis in diabetic pregnancies. Further work is needed to determine whether these neonatal metabolome differences associate with later health outcomes.

IMPACT

Variations in blood metabolomic profile have been linked to health status in adults and children, but corresponding data in neonates are scarce. We report evidence that pregnancy complications, mode of delivery, and offspring characteristics, including sex, are independently associated with a range of circulating metabolites at birth, including ketone bodies, amino acids, cholesterols, and inflammatory markers. Independent of birth weight, exposure to gestational diabetes is associated with higher cord blood ketone bodies and citrate. These findings suggest that pregnancy complications, mode of delivery, gestational age, and measures of growth influence metabolic pathways prior to birth, potentially impacting later health and development.

Chiral Posttranslational Modification to Lysine ε-Amino Groups

ConspectusThe sophistication of proteomic analysis has revealed that protein lysine residues are posttranslationally modified by a variety of acyl groups. Protein lysine acetylation regulates metabolism, gene expression, and microtubule formation and has been extensively studied; however, the understanding of the biological significance of other acyl posttranslational modifications (PTMs) is still in its infancy. The acylation of lysine residues is mediated either by acyltransferase "writer" enzymes or by nonenzymatic mechanisms and hydrolase enzymes, termed "erasers", that cleave various acyl PTMs to reverse the modified state. We have studied the human lysine deacylase enzymes, comprising the 11 Zn²⁺-dependent histone deacetylases (HDACs) and the 7 NAD⁺-consuming sirtuins (SIRTs), over the past decade. We have thus developed selective inhibitors and molecular probes and have studied the acyl substrate scope of each enzyme using chemically synthesized peptide substrates and photo-cross-linking probes. Recently, we have turned our attention to PTMs containing a stereogenic center, such as ε-N-β-hydroxybutyryllysine (Kbhb) and ε-N-lactyllysine (Kla), that each comprise a pair of mirror image stereoisomers as modifications. Both modifications are found on histones, where they affect gene transcription in response to specific metabolic states, and they are found on cytosolic and mitochondrial enzymes involved in fatty acid oxidation (Kbhb) and glycolysis (Kla), respectively. Thus, chiral modifications to lysine side chains give rise to two distinct diastereomeric products, with separate metabolic origins and potentially different activities exhibited by writer and eraser enzymes. Lysine l-lactylation originates from l-lactate, a major energy carrier produced from pyruvate after glycolysis, and it is highly induced by metabolic states such as the Warburg effect. l-Lactate can possibly be activated by acyl-coenzyme A (CoA) synthetases and transferred to lysine residues by histone acetyltransferases such as p300. d-Lactylation, on the other hand, arises primarily from a nonenzymatic reaction with d-lactylglutathione, an intermediate in the glyoxalase pathway. In addition to their distinct origin, we found that both K(l-la) and K(d-la) modifications are erased by HDACs with different catalytic efficiencies. Also, K(l-bhb) and K(d-bhb) arise from different metabolites but depend on interconnected metabolic pathways, and the two stereoisomers of ε-N-3-hydroxy-3-methylglutaryllysine (Khmg) originate from a single precursor that may then be regulated differently by eraser enzymes. Distinguishing between the individual stereoisomers of PTMs is therefore of crucial importance. In the present Account, we will (1) revisit the long-standing evidence for the distinct production and dynamics of enantiomeric forms of chiral metabolites that serve as ε-N-acyllysine PTMs and (2) highlight the outstanding questions that arise from the recent literature on chiral lysine PTMs resulting from these metabolites.

Chronic Cold Exposure Leads to Daytime Preference in the Circadian Expression of Hepatic Metabolic Genes

Circadian control allows organisms to anticipate and adapt to environmental changes through changes in physiology and behavior. The circadian system timing is entrained by cues, such as light, food, and temperature. An ambient temperature dramatically impacts the sleep-wake cycle and metabolic rhythmicity. As endotherms, mammals rely on tissues such as the liver to provide fuel for thermogenesis to maintain body temperature. The adaptive response of the circadian rhythm of liver metabolism to chronic cold exposure remains largely unexplored. Here, we investigated the circadian rhythm adaptation of hepatic metabolism in response to environmental cold stress using a mouse model of chronic cold exposure. We analyzed metabolites and transcripts of mouse livers at 24 h and found that long-term low-temperature exposure resulted in a synergistic and phase synchronization of transcriptional rhythms of many genes associated with metabolic pathways. Notably, transcription peaked in the early light phase when the body temperature was relatively low. Our results suggest that chronic cold does not alter the rhythmic expression of essential core clock genes in the liver, so the rewiring of clock control gene expression is another mechanism that optimizes the circadian rhythm of liver metabolism to meet the energy requirements of animal thermogenesis.

Exenatide and Dapagliflozin Combination Enhances Sertoli Cell Secretion of Key Metabolites for Spermatogenesis

The incidence of metabolic diseases such as type 2 diabetes mellitus (DM) and obesity has been increasing dramatically. Both diseases are closely linked and new approaches for type 2 DM treatment aim to enable weight loss. A combined therapy of dapagliflozin and exenatide has been used against type 2 DM, influencing allbody glucose dynamics. Spermatogenesis is highly dependent on the metabolic cooperation established between Sertoli cells (SCs) and developing germ cells. To study the effects of dapagliflozin and exenatide on SC metabolism, mouse SCs were treated in the presence of sub-pharmacologic, pharmacologic, and supra-pharmacologic concentrations of dapagliflozin (50, 500, 5000 nM, respectively) and/or exenatide (2.5, 25, 250 pM, respectively). Cytotoxicity of these compounds was evaluated and the glycolytic profile, glycogen content assay, and lipid accumulation of SCs were determined. Dapagliflozin treatment decreased fat cellular deposits, demonstrating its anti-obesity properties at the cellular level. Polytherapy of exenatide plus dapagliflozin increased lactate production by SCs, which has been reported to improve sperm production and quality. Thus, the results herein suggest that the use of these two pharmacological agents can protect male fertility, while improving their glucose homeostasis and inducing weight loss.

Studies on Metabolic Alterations due to Hypobaric Hypoxia in Serum using NMR Spectroscopy

Introduction The main physiological challenge in high altitude environment is hypoxia which affects the aerobic metabolism reducing the energy supply. These changes may further progress towards extreme environment related diseases. Rarely has the high-altitude biology been studied using system sciences and omics high-throughput technologies.Objective In the present study, 1H-NMR-based metabolomics, along with multivariate analysis, were employed in a preclinical rat model to characterize the serum metabolic changes under chronic hypobaric hypoxia (HH) stress.Material & Methods Rats were exposed to simulated hypobaric hypoxia equivalent of 6700 m above the sea level. The serum samples were collected from control and HH-exposure (7, 14, and 21 days) of hypobaric hypoxia.Results & Discussion The 1H-NMR metabolomics of the serum showed alterations in the metabolism of membranes, amino-acids altered cellular bioenergetics and osmoregulation. Multivariate statistical analysis revealed alterations in acetoacetate, choline, glutamine, acetate, betaine, ketone bodies & branched amino acid metabolites.Conclusion Present findings establishes the fingerprint biomarkers for chronic environmental hypoxia which will help in understanding extreme environment related health problems, early detection and developing strategies to clinically address high altitude hypoxia.

The Therapeutic Role of Ketogenic Diet in Neurological Disorders

The ketogenic diet (KD) is a high-fat, low-carbohydrate and adequate-protein diet that has gained popularity in recent years in the context of neurological diseases (NDs). The complexity of the pathogenesis of these diseases means that effective forms of treatment are still lacking. Conventional therapy is often associated with increasing tolerance and/or drug resistance. Consequently, more effective therapeutic strategies are being sought to increase the effectiveness of available forms of therapy and improve the quality of life of patients. For the moment, it seems that KD can provide therapeutic benefits in patients with neurological problems by effectively controlling the balance between pro- and antioxidant processes and pro-excitatory and inhibitory neurotransmitters, and modulating inflammation or changing the composition of the gut microbiome. In this review we evaluated the potential therapeutic efficacy of KD in epilepsy, depression, migraine, Alzheimer’s disease and Parkinson’s disease. In our opinion, KD should be considered as an adjuvant therapeutic option for some neurological diseases.

More than meets the islet: aligning nutrient and paracrine inputs with hormone secretion in health and disease

The pancreatic islet is responsive to an array of endocrine, paracrine, and nutritional inputs that adjust hormone secretion to ensure accurate control of glucose homeostasis. Although the mechanisms governing glucose-coupled insulin secretion have received the most attention, there is emerging evidence for a multitude of physiological signaling pathways and paracrine networks that collectively regulate insulin, glucagon, and somatostatin release. Moreover, the modulation of these pathways in conditions of glucotoxicity or lipotoxicity are areas of both growing interest and controversy. In this review, the contributions of external, intrinsic, and paracrine factors in pancreatic β-, α-, and δ-cell secretion across the full spectrum of physiological (i.e., fasting and fed) and pathophysiological (gluco- and lipotoxicity; diabetes) environments will be critically discussed.

Continuous Ketone Monitoring Consensus Report 2021

This article is the work product of the Continuous Ketone Monitoring Consensus Panel, which was organized by Diabetes Technology Society and met virtually on April 20, 2021. The panel consisted of 20 US-based experts in the use of diabetes technology, representing adult endocrinology, pediatric endocrinology, advanced practice nursing, diabetes care and education, clinical chemistry, and bioengineering. The panelists were from universities, hospitals, freestanding research institutes, government, and private practice. Panelists reviewed the medical literature pertaining to ten topics: (1) physiology of ketone production, (2) measurement of ketones, (3) performance of the first continuous ketone monitor (CKM) reported to be used in human trials, (4) demographics and epidemiology of diabetic ketoacidosis (DKA), (5) atypical hyperketonemia, (6) prevention of DKA, (7) non-DKA states of fasting ketonemia and ketonuria, (8) potential integration of CKMs with pumps and automated insulin delivery systems to prevent DKA, (9) clinical trials of CKMs, and (10) the future of CKMs. The panelists summarized the medical literature for each of the ten topics in this report. They also developed 30 conclusions (amounting to three conclusions for each topic) about CKMs and voted unanimously to adopt the 30 conclusions. This report is intended to support the development of safe and effective continuous ketone monitoring and to apply this technology in ways that will benefit people with diabetes.

Ketogenic Diet and Weight Loss: Is There an Effect on Energy Expenditure?

A dysregulation between energy intake (EI) and energy expenditure (EE), the two components of the energy balance equation, is one of the mechanisms responsible for the development of obesity. Conservation of energy equilibrium is deemed a dynamic process and alterations of one component (energy intake or energy expenditure) lead to biological and/or behavioral compensatory changes in the counterpart. The interplay between energy demand and caloric intake appears designed to guarantee an adequate fuel supply in variable life contexts. In the past decades, researchers focused their attention on finding efficient strategies to fight the obesity pandemic. The ketogenic or “keto” diet (KD) gained substantial consideration as a potential weight-loss strategy, whereby the concentration of blood ketones (acetoacetate, 3-β-hydroxybutyrate, and acetone) increases as a result of increased fatty acid breakdown and the activity of ketogenic enzymes. It has been hypothesized that during the first phase of KDs when glucose utilization is still prevalent, an increase in EE may occur, due to increased hepatic oxygen consumption for gluconeogenesis and for triglyceride-fatty acid recycling. Later, a decrease in 24-h EE may ensue due to the slowing of gluconeogenesis and increase in fatty acid oxidation, with a reduction of the respiratory quotient and possibly the direct action of additional hormonal signals.

Inflammatory Bowel Disease and COVID-19: How Microbiomics and Metabolomics Depict Two Sides of the Same Coin

The integrity of the gastrointestinal tract structure and function is seriously compromised by two pathological conditions sharing, at least in part, several pathogenetic mechanisms: inflammatory bowel diseases (IBD) and coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. IBD and COVID-19 are marked by gut inflammation, intestinal barrier breakdown, resulting in mucosal hyperpermeability, gut bacterial overgrowth, and dysbiosis together with perturbations in microbial and human metabolic pathways originating changes in the blood and fecal metabolome. This review compared the most relevant metabolic and microbial alterations reported from the literature in patients with IBD with those in patients with COVID-19. In both diseases, gut dysbiosis is marked by the prevalence of pro-inflammatory bacterial species and the shortfall of anti-inflammatory species; most studies reported the decrease in Firmicutes, with a specific decrease in obligately anaerobic producers short-chain fatty acids (SCFAs), such as Faecalibacterium prausnitzii. In addition, Escherichia coli overgrowth has been observed in IBD and COVID-19, while Akkermansia muciniphila is depleted in IBD and overexpressed in COVID-19. In patients with COVID-19, gut dysbiosis continues after the clearance of the viral RNA from the upper respiratory tract and the resolution of clinical symptoms. Finally, we presented and discussed the impact of gut dysbiosis, inflammation, oxidative stress, and increased energy demand on metabolic pathways involving key metabolites, such as tryptophan, phenylalanine, histidine, glutamine, succinate, citrate, and lipids.

Evaluation of the point-of-care devices KetoSureTM and StatStrip Express® blood ketone tests using β-hydroxybutyrate spiked samples

Measurement of β-hydroxybutyrate (BHB) in blood is used clinically as a measure of ketosis when diabetic ketoacidosis is expected. With the introduction of point-of-care testing (POCT) for blood-BHB, nonproductive time is reduced to a minimum in a potential critical situation; however, studies have observed inferior quality of POCT-BHB. Recently, the POCT device KetoSure (Roche) has been introduced to the clinic. In this study, we evaluated the imprecision and linearity of KetoSure and compared this to the established StatStrip Express (Nova Biomedical) based on spiked full blood samples. We found comparable imprecision for KetoSure and StatStrip Express. However, linearity was only observed in the lower part of the measuring range for both devices. In a method comparison, higher values of BHB were measured by KetoSure than by an enzymatic endpoint spectrophotometric reference method (mean bias: 21% (95% confidence interval (CI): 4%-37%)). Conversely, StatStrip Express returned lower values of BHB (mean bias: -16% (95% CI: -38%-7%), while the widely applied POCT device FreeStyle Precision Neo (Abbott) returned values equivalent with the reference method (mean bias: 5% (95% CI: -14%-24%). In samples with concentrations of BHB above the measuring range, the POCT devices could be provoked to return falsely low results. In conclusion, the quality of KetoSure is in line with other established POCT devices; however, the KetoSure measures higher concentrations than other POCT devices. As, linearity only was observed in the lower part of the measuring range and as falsely low measures could be provoked, we advise users to interpret results with precaution.

Beneficial cardiovascular and remodeling effects of SGLT2 inhibitors: pathophysiologic mechanisms

INTRODUCTION

The intent of this paper is to review the data regarding the multipotential effects of the sodium-glucose cotransporter 2 (SGLT 2) inhibitors, their cardiovascular protective effects, and their mechanism of action.

AREAS COVERED

The SGLT2 inhibitors exert their beneficial antidiabetic and cardioprotective effects through increased glucose excretion from the kidneys, blood pressure and weight lowering, vasodilation and other potential beneficial effects. They have been used for the treatment of patients with type 2 diabetes mellitus (T2DM) as well as in patients with cardiovascular disease (CVD), coronary artery disease (CAD),and heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF). In order to get a better understanding of their mechanism of action for their multiple cardiovascular protective effects, a Medline search of the English language literature was conducted between 2015 and February 2022 and 46 pertinent papers were selected.

EXPERT OPINION

The analysis of data clearly demonstrated that the use of the SGLT2 inhibitors besides their antidiabetic effects, provide additional protection against CVD, CAD, and HFrEF and HFpEF, and death, but not stroke, in both diabetic and non-diabetic patients. Therefore, they should be preferably used for the treatment of patients with T2DM with preexisting CVD, CAD, and HFrEF and HFpEF.

Long-term and daily use of molecular hydrogen induces reprogramming of liver metabolism in rats by modulating NADP/NADPH redox pathways

Molecular hydrogen (H2) has emerged as a new therapeutic option in several diseases and is widely adopted by healthy people. However, molecular data to support therapeutic functions attributed to the biological activities of H2 remain elusive. Here, using transcriptomic and metabolomic approaches coupled with biochemistry and micro-CT technics, we evaluated the effect of long-term (6 months) and daily use of H2 on liver function. Rats exposed 2 h daily to H2 either by drinking HRW (H2 dissolved in H2O) or by breathing 4% H2 gas showed reduced lipogenesis and enhanced lipolysis in the liver, which was associated with apparent loss of visceral fat and brown adipose tissue together with a reduced level of serum lipids. Both transcripts and metabolites enriched in H2-treated rats revealed alteration of amino acid metabolism pathways and activation of purine nucleotides and carbohydrate biosynthesis pathways. Analysis of the interaction network of genes and metabolites and correlation tests revealed that NADP is the central regulator of H2 induced metabolic alterations in the liver, which was further confirmed by an increase in the level of components of metabolic pathways that require NADP as substrate. Evidence of immune response regulation activity was also observed in response to exposure to H2. This work is the first to provide metabolomic and transcriptomic data to uncover molecular targets for the effect of prolonged molecular hydrogen treatment on liver metabolism.

Evaluating diabetic ketoacidosis via a MOF sensor for fluorescence imaging of phosphate and pH

Herein, a new type of composite metal-organic framework sensor for evaluating diabetic ketoacidosis was designed and prepared using in situ fluorescence imaging of phosphate and pH, which provides a new way to effectively evaluate the diabetic complication-ketoacidosis in the early clinical stage.

Important Functions and Molecular Mechanisms of Mitochondrial Redox Signaling in Pulmonary Hypertension

Mitochondria are important organelles that act as a primary site to produce reactive oxygen species (ROS). Additionally, mitochondria play a pivotal role in the regulation of Ca²⁺ signaling, fatty acid oxidation, and ketone synthesis. Dysfunction of these signaling molecules leads to the development of pulmonary hypertension (PH), atherosclerosis, and other vascular diseases. Features of PH include vasoconstriction and pulmonary artery (PA) remodeling, which can result from abnormal proliferation, apoptosis, and migration of PA smooth muscle cells (PASMCs). These responses are mediated by increased Rieske iron–sulfur protein (RISP)-dependent mitochondrial ROS production and increased mitochondrial Ca²⁺ levels. Mitochondrial ROS and Ca²⁺ can both synergistically activate nuclear factor κB (NF-κB) to trigger inflammatory responses leading to PH, right ventricular failure, and death. Evidence suggests that increased mitochondrial ROS and Ca²⁺ signaling leads to abnormal synthesis of ketones, which play a critical role in the development of PH. In this review, we discuss some of the recent findings on the important interactive role and molecular mechanisms of mitochondrial ROS and Ca²⁺ in the development and progression of PH. We also address the contributions of NF-κB-dependent inflammatory responses and ketone-mediated oxidative stress due to abnormal regulation of mitochondrial ROS and Ca²⁺ signaling in PH.

Quantitative Proteomics Analysis Expands the Roles of Lysine β-Hydroxybutyrylation Pathway in Response to Environmental β-Hydroxybutyrate

Lysine β-hydroxybutyrylation (Kbhb) is a newly identified protein posttranslational modification (PTM) derived from β-hydroxybutyrate (BHB), a product of ketone body metabolism in liver. BHB could serve as an energy source and play a role in the suppression of oxidative stress. The plasma concentration of BHB could increase up to 20 mM during starvation and in pathological conditions. Despite the progress, how the cells derived from extrahepatic tissues respond to elevated environmental BHB remains largely unknown. Given that BHB can significantly drive Kbhb, we characterized the BHB-induced lysine β-hydroxybutyrylome and acetylome by quantitative proteomics. A total of 840 unique Kbhb sites on 429 proteins were identified, with 42 sites on 39 proteins increased by more than 50% in response to BHB. The results showed that the upregulated Kbhb induced by BHB was involved in aminoacyl-tRNA biosynthesis, 2-oxocarboxylic acid metabolism, citrate cycle, glycolysis/gluconeogenesis, and pyruvate metabolism pathways. Moreover, some BHB-induced Kbhb substrates were significantly involved in diseases such as cancer. Taken together, we investigate the dynamics of lysine β-hydroxybutyrylome and acetylome induced by environmental BHB, which reveals the roles of Kbhb in regulating various biological processes and expands the biological functions of BHB.

3-Hydroxybutyrate Ameliorates the Progression of Diabetic Nephropathy

Studies report beneficial effects of 3-hydroxybutyrate (3-OHB) on the treatment of type 2 diabetes and obesity, but the effects of 3-OHB on diabetic nephropathy have not been elucidated. This study was designed to investigate the efficacy and mechanism of 3-OHB against progression of diabetic nephropathy (DN). Mice (db/db) were fed normal chow, high-fat, or ketogenic diets (KD) containing precursors of 3-OHB. Hyperglycemia was determined based on random glucose level (≥250 mg/dL). Fasting blood glucose and body weights were measured once a week. Twenty four-hour urine albumin to creatinine ratio was determined 5 weeks after the differential diet. Energy expenditure was measured 9 weeks after the differential diet. Body weights were significantly lower in the KD group than those in other groups, but no significant differences in fasting blood glucose levels among three groups were observed. Urine albumin to creatinine ratio and serum blood urea nitrogen (BUN) to creatinine ratio in the KD group were significantly lower than in other groups. Histologic and quantitative analysis of mesangial area suggested that KD delayed the progression of DN phenotype in db/db mice. Metabolic cage analysis also revealed that KD increased energy expenditure in db/db mice. In vitro studies with proximal tubular cells revealed that 3-OHB stimulated autophagic flux. 3-OHB increased LC3 I to LC3 II ratio, phosphorylation of AMPK, beclin, p62 degradation, and NRF2 expression. Moreover, we found that 3-OHB attenuated high glucose-induced reactive oxygen species (ROS) levels in proximal tubular cells. In vivo study also confirmed increased LC3 and decreased ROS levels in the kidney of KD mice. In summary, this study shows in both in vivo and in vitro models that 3-OHB delays the progression of DN by augmenting autophagy and inhibiting oxidative stress.

Physiological responses to acute fasting: implications for intermittent fasting programs

Intermittent fasting (IF) is a dietary strategy that involves alternating periods of abstention from calorie consumption with periods of ad libitum food intake. There is significant interest in the body of literature describing longitudinal adaptations to IF. Less attention has been given to the acute physiological responses that occur during the fasting durations that are commonly employed by IF practitioners. Thus, the purpose of this review was to examine the physiological responses - including alterations in substrate metabolism, systemic hormones, and autophagy - that occur throughout an acute fast. Literature searches were performed to locate relevant research describing physiological responses to acute fasting and short-term starvation. A single fast demonstrated the ability to alter glucose and lipid metabolism within the initial 24 hours, but variations in protein metabolism appeared to be minimal within this time frame. The ability of an acute fast to elicit significant increases in autophagy is still unknown. The information summarized in this review can be used to help contextualize existing research and better inform development of future IF interventions.

Identification and validation of small molecule analytes in mouse plasma by liquid chromatography-tandem mass spectrometry: A case study of misidentification of a short-chain fatty acid with a ketone body

Recently, there has been growing interest in short-chain fatty acids (SCFA) and ketone bodies (KB) due to their potential use as biomarkers of health and disease. For instance, these diet-related metabolites can be used to monitor and reduce the risk of immune response, diabetes, or cardiovascular diseases. Given the interest in these metabolites, different targeted metabolomic methods based on UPLC-MS/MS have been developed in recent years to detect and quantify SCFA and KB. In this case study, we discovered that applying an existing validated, targeted UPLC-MS/MS method to mouse plasma, resulted in a fragment ion (194 m/z) being originally misidentified as acetic acid (a SCFA), when its original source was 3-hydroxybutyric acid (a KB). Therefore, we report a modified, optimized LC method that can separate both signals. In addition, the metabolite coverage was expanded in this method to detect up to eight SCFA: acetic, propanoic, butyric, isobutyric, 2-methylbutyric, valeric, isovaleric, and hexanoic acids, two KB: 3-hydroxybutyric, and acetoacetic acids, and one related metabolite: 3-hydroxy-3-methylbutyric acid. The optimization of this method increased the selectivity of the UPLC-MS/MS method towards the misidentified compound. These findings encourage the scientific community to increase efforts in validating the original precursor of small molecule fragments in targeted methods.

Effects of Prolonged Intermittent Fasting Model on Energy Metabolism and Mitochondrial Functions in Neurons

Background:

Calorie restriction (CR) during daily nutrition has been shown to affect the prognosis of many chronic diseases such as metabolic syndrome, diabetes, and aging. As an alternative nutrition model, prolonged intermittent fasting (PF) in humans is defined by the absence of food for more than 12 h. In our previous human studies, CR and PF models were compared and it was concluded that the two models might have differences in signal transduction mechanisms. We have investigated the effects of these models on neurons at the molecular level in this study.

Methods:

Neurons (SH-SY5Y) were incubated with normal medium (N), calorie-restricted medium (CR), fasting medium (PF), and glucose-free medium (G0) for 16 h. Simultaneously, ketone (beta-hydroxybutyrate; bOHB) was added to other experiment flasks containing the same media. Concentrations of lactate, lactate dehydrogenase (LDH), bOHB, and glucose were measured to demonstrate the changes in the energy metabolism together with the mitochondrial functions of cells. Citrate synthase activity and flow cytometric mitochondrial functions were investigated.

Results:

At the end of incubations, lactate and LDH levels were decreased and mitochondrial activity was increased in all ketone-added groups (P < .01) regardless of the glucose concentration in the environment. In the fasting model, these differences were more prominent.

Conclusion:

Our results demonstrated that neurons use ketones regardless of the amount of glucose, and bOHB-treated cells had positive changes in mitochondrial function. We conclude that the presence of bOHB might reverse neuron damage and that exogenous ketone treatment may be beneficial in the treatment of neurological diseases in the future.

Therapeutic ketosis decreases methacholine hyperresponsiveness in mouse models of inherent obese asthma

Obese asthmatics tend to have severe, poorly controlled disease and exhibit methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility. Substantial weight loss in obese asthmatics or in mouse models of the condition decreases methacholine hyperresponsiveness. Ketone bodies are rapidly elevated during weight loss, coinciding with or preceding relief from asthma-related comorbidities. As ketone bodies may exert numerous potentially therapeutic effects, augmenting their systemic concentrations is being targeted for the treatment of several conditions. Circulating ketone body levels can be increased by feeding a ketogenic diet or by providing a ketone ester dietary supplement, which we hypothesized would exert protective effects in mouse models of inherent obese asthma. Weight loss induced by feeding a low-fat diet to mice previously fed a high-fat diet was preceded by increased urine and blood levels of the ketone body β-hydroxybutyrate (BHB). Feeding a ketogenic diet for 3 wk to high-fat diet-fed obese mice or genetically obese db/db mice increased BHB concentrations and decreased methacholine hyperresponsiveness without substantially decreasing body weight. Acute ketone ester administration decreased methacholine responsiveness of normal mice, and dietary ketone ester supplementation of high-fat diet-fed mice decreased methacholine hyperresponsiveness. Ketone ester supplementation also transiently induced an "antiobesogenic" gut microbiome with a decreased Fermicutes/Bacteroidetes ratio. Dietary interventions to increase systemic BHB concentrations could provide symptom relief for obese asthmatics without the need for the substantial weight loss required of patients to elicit benefits to their asthma through bariatric surgery or other diet or lifestyle alterations.

Fatty acid-binding protein 4: a key regulator of ketoacidosis in new-onset type 1 diabetes

AIMS/HYPOTHESIS

Fatty acid-binding protein 4 (FABP4) is an adipokine with a key regulatory role in glucose and lipid metabolism. We prospectively evaluated the role of FABP4 in the pathophysiology of diabetic ketoacidosis (DKA) in new-onset type 1 diabetes.

METHODS

Clinical and laboratory data were prospectively collected from consecutive children presenting with new-onset type 1 diabetes. In addition to blood chemistry and gases, insulin, C-peptide, serum FABP4 and NEFA were collected upon presentation and 48 h after initiation of insulin treatment. In a mouse model of type 1 diabetes, glucose, insulin, β-hydroxybutyrate and weight were compared between FABP4 knockout (Fabp4^-/-) and wild-type (WT) mice.

RESULTS

Included were 33 children (mean age 9.3 ± 3.5 years, 52% male), of whom 14 (42%) presented with DKA. FABP4 levels were higher in the DKA group compared with the non-DKA group (median [IQR] 10.1 [7.9-14.2] ng/ml vs 6.3 [3.9-7] ng/ml, respectively; p = 0.005). The FABP4 level was positively correlated with HbA_1c at presentation and inversely correlated with venous blood pH and bicarbonate levels (p < 0.05 for all). Following initiation of insulin therapy, a marked reduction in FABP4 was observed in all children. An FABP4 level of 7.22 ng/ml had a sensitivity of 86% and a specificity of 78% for the diagnosis of DKA, with an area under the receiver operating characteristic curve of 0.78 (95% CI 0.6, 0.95; p = 0.008). In a streptozotocin-induced diabetes mouse model, Fabp4^-/- mice exhibited marked hypoinsulinaemia and hyperglycaemia similar to WT mice but displayed no significant increase in β-hydroxybutyrate and were protected from ketoacidosis.

CONCLUSIONS/INTERPRETATION

FABP4 is suggested to be a necessary regulator of ketogenesis in insulin-deficient states.

Controversies Around the Measurement of Blood Ketones to Diagnose and Manage Diabetic Ketoacidosis

The measurement of blood ketones in preference to urine ketones has become a well-established tool in the diagnosis and management of diabetic ketoacidosis (DKA). However, there remains considerable disparity between diabetes guidelines regarding if, how, and when this test should be used. While recent guidelines now mainly emphasize blood measurement, several issues nonetheless remain. Many laboratories still measure blood ketones using a semiquantitative test that does not measure the predominant ketone, β-hydroxybutyrate (BOHB), which may hinder patient management. Even when BOHB is measured, the evidence for cutoffs used in DKA diagnosis or exclusion is limited, while its use in gauging severity, treatment progress, and resolution is not fully clear. Lastly, although employing point-of-care meters instead of a laboratory for BOHB measurement brings undoubted benefits, this approach has its own challenges. This article provides a perspective on these topics to complement current recommendations and to suggest how future research may improve its use in the DKA context.

Dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, ameliorates type 2 diabetes via reduced gluconeogenesis

Aims

Pyruvate dehydrogenase (PDH) catalyzes the decarboxylation of pyruvate to acetyl-CoA, which plays a key role in linking cytosolic glycolysis to mitochondria metabolism. PDH is physiologically inactivated by pyruvate dehydrogenase kinases (PDKs). Thus, activation of PDH via inhibiting PDK may lead to metabolic benefits. In the present study, we investigated the antidiabetic effect of PDK inhibition using dichloroacetate (DCA), a PDK inhibitor.

Main methods

We evaluated the effect of single dose of DCA on plasma metabolic parameters in normal rats. Next, we investigated the antidiabetic effect of DCA in diabetic ob/ob mice. In addition, we performed in vitro assays to understand the effect and mechanism of action of DCA on gluconeogenesis in mouse myoblast cell line C2C12 and rat hepatoma cell line FaO.

Key findings

In normal rats, a single dose of DCA decreased the plasma level of pyruvate, the product of glycolysis, and the plasma glucose level only in the fasting state. Meanwhile, a single dose of DCA lowered the plasma glucose level, and a three-week treatment decreased the fructosamine level in diabetic ob/ob mice. In vitro experiments demonstrated concentration-dependent suppression of lactate production in C2C12 myotubes. In addition, DCA suppressed glucose production from pyruvate and lactate in FaO hepatoma cells. Thus, DCA-mediated restricted supply of gluconeogenic substrates from the muscle to liver, and direct suppression of hepatic gluconeogenesis might have contributed to its glucose-lowering effect in the current models.

Significance

PDK inhibitor may be considered as a potential antidiabetic agent harboring inhibitory effect on gluconeogenesis.

The Application of Metabolomics in Recent Colorectal Cancer Studies: A State-of-the-Art Review

Simple Summary

Colorectal Cancer (CRC) is one of the leading causes of cancer-related death in the United States. Current diagnosis techniques are either highly invasive or lack sensitivity, suggesting the need for alternative techniques for biomarker detection. Metabolomics represents one such technique with great promise in identifying CRC biomarkers with high sensitivity and specificity, but thus far is rarely employed in a clinical setting. In order to provide a framework for future clinical usage, we characterized dysregulated metabolites across recent literature, identifying metabolites dysregulated across a variety of biospecimens. We additionally put special focus on the interplay of the gut microbiome and perturbed metabolites in CRC. We were able to identify many metabolites showing consistent dysregulation in CRC, demonstrating the value of metabolomics as a promising diagnostic technique.

Abstract

Colorectal cancer (CRC) is a highly prevalent disease with poor prognostic outcomes if not diagnosed in early stages. Current diagnosis techniques are either highly invasive or lack sufficient sensitivity. Thus, identifying diagnostic biomarkers of CRC with high sensitivity and specificity is desirable. Metabolomics represents an analytical profiling technique with great promise in identifying such biomarkers and typically represents a close tie with the phenotype of a specific disease. We thus conducted a systematic review of studies reported from January 2012 to July 2021 relating to the detection of CRC biomarkers through metabolomics to provide a collection of knowledge for future diagnostic development. We identified thirty-seven metabolomics studies characterizing CRC, many of which provided metabolites/metabolic profile-based diagnostic models with high sensitivity and specificity. These studies demonstrated that a great number of metabolites can be differentially regulated in CRC patients compared to healthy controls, adenomatous polyps, or across stages of CRC. Among these metabolite biomarkers, especially dysregulated were certain amino acids, fatty acids, and lysophosphatidylcholines. Additionally, we discussed the contribution of the gut bacterial population to pathogenesis of CRC through their modulation to fecal metabolite pools and summarized the established links in the literature between certain microbial genera and altered metabolite levels in CRC patients. Taken together, we conclude that metabolomics presents itself as a promising and effective method of CRC biomarker detection.

Acute Ingestion of Ketone Monoesters and Precursors Do Not Enhance Endurance Exercise Performance: A Systematic Review and Meta-Analysis

There has been much consideration over whether exogenous ketone bodies have the capacity to enhance exercise performance through mechanisms such as altered substrate metabolism, accelerated recovery, or neurocognitive improvements. This systematic review aimed to determine the effects of both ketone precursors and monoesters on endurance exercise performance. A systematic search was conducted in PubMed, SPORTDiscus, and CINAHL for randomized controlled trials investigating endurance performance outcomes in response to ingestion of a ketone supplement compared to a nutritive or nonnutritive control in humans. A meta-analysis was performed to determine the standardized mean difference between interventions using a random-effects model. Hedge's g and 95% confidence intervals (CI) were reported. The search yielded 569 articles, of which eight were included in this review (80 participants; 77 men and three women). When comparing endurance performance among all studies, no significant differences were found between ketone and control trials (Hedges g = 0.136; 95% CI [-0.195, 0.467]; p = .419). Subanalyses based on type of endurance tests showed no significant differences in time to exhaustion (Hedge's g = -0.002; 95% CI [-0.312, 0.308]; p = .989) or time trial (Hedge's g = 0.057; 95% CI [-0.282, 0.395]; p = .744) values. Based on these findings, exogenous ketone precursors and monoesters do not exert significant improvements on endurance exercise performance. While all studies reported an increase in blood ketone concentrations after ingestion, ketone monoesters appear to be more effective at raising concentrations than precursors.

Colorimetric and Electrochemical Screening for Early Detection of Diabetes Mellitus and Diabetic Retinopathy-Application of Sensor Arrays and Machine Learning

In this review, a selection of works on the sensing of biomarkers related to diabetes mellitus (DM) and diabetic retinopathy (DR) are presented, with the scope of helping and encouraging researchers to design sensor-array machine-learning (ML)-supported devices for robust, fast, and cost-effective early detection of these devastating diseases. First, we highlight the social relevance of developing systematic screening programs for such diseases and how sensor-arrays and ML approaches could ease their early diagnosis. Then, we present diverse works related to the colorimetric and electrochemical sensing of biomarkers related to DM and DR with non-invasive sampling (e.g., urine, saliva, breath, tears, and sweat samples), with a special mention to some already-existing sensor arrays and ML approaches. We finally highlight the great potential of the latter approaches for the fast and reliable early diagnosis of DM and DR.

Machine Learning in Prediction of Bladder Cancer on Clinical Laboratory Data

Bladder cancer has been increasing globally. Urinary cytology is considered a major screening method for bladder cancer, but it has poor sensitivity. This study aimed to utilize clinical laboratory data and machine learning methods to build predictive models of bladder cancer. A total of 1336 patients with cystitis, bladder cancer, kidney cancer, uterus cancer, and prostate cancer were enrolled in this study. Two-step feature selection combined with WEKA and forward selection was performed. Furthermore, five machine learning models, including decision tree, random forest, support vector machine, extreme gradient boosting (XGBoost), and light gradient boosting machine (GBM) were applied. Features, including calcium, alkaline phosphatase (ALP), albumin, urine ketone, urine occult blood, creatinine, alanine aminotransferase (ALT), and diabetes were selected. The lightGBM model obtained an accuracy of 84.8% to 86.9%, a sensitivity 84% to 87.8%, a specificity of 82.9% to 86.7%, and an area under the curve (AUC) of 0.88 to 0.92 in discriminating bladder cancer from cystitis and other cancers. Our study provides a demonstration of utilizing clinical laboratory data to predict bladder cancer.

Comparisons of biochemical parameters and diabetic ketoacidosis severity in adult patients with type 1 and type 2 diabetes

OBJECTIVE

The aim of this study was to determine the differences in biochemical parameters and diabetic ketoacidosis (DKA) severity in adult patients with type 1 and type 2 diabetes and utilization of serum BHB as a biomarker for DKA resolution was also evaluated.

MATERIALS AND METHODS

This prospective observational study of type 1 or type 2 diabetes mellitus who were diagnosed with DKA between 01 October 2018 and 30 September 2020. The correlations between serum BHB, measured by the Ranbut assay, and pH, bicarbonate, and anion gap were examined.

RESULTS

A total of 99 diabetes patients were diagnosed with DKA (mean age 39.4 years, 63.4% female, 53.6% T2DM). while infection was the most common precipitating factor in T2DM (43.4%), non-compliance with treatment was the most common precipitating factor in T1DM (43.5%). T1DM patients had more severe DKA more hypokalemia during treatment. However, there was no significant difference in mortality between type1 and type2 diabetes. The initial laboratories evaluation of patients did not significant differ between type1 and type2 diabetes. Serum BHB during treatment of DKA was significantly correlated with changes in serum bicarbonate (r = - 0.64), serum anion gap (r = 0.84), and venous pH (r = - 0.6). The serum BHB levels corresponding to HCO₃ levels for DKA severity were 4.5, 5.7, and 5.9 mmol/L in mild, moderate, and severe DKA, respectively. The serum BHB level of < 1 mmol/L had 73.7% sensitivity and 100% specificity to predict DKA resolution. Median time to resolution of DKA was 12 h with an optimized BHB cut-off value of < 1 mmol/L. There were no significant difference in time to resolution of DKA in the patients with type 1 and type 2 diabetes.

CONCLUSIONS

There are no differences in DKA-related biochemical parameters between type 1 and type 2 diabetes patients. The present findings suggest that DKA should be assessed and treated similarly, regardless of its occurrence in type 1 or type 2 diabetes patients.

Type 2 Myocardial Infarction Related to Very Low Carbohydrate Ketogenic Diet

A 38-year-old male with no history of cardiac disease presented with chest pain typical of acute coronary syndrome. He assumed very-low-carbohydrate ketogenic diet (VLC-KD) 4 weeks prior to admission but no other lifestyle change. Workup showed dynamic ST-T changes on electrocardiogram, significantly elevated troponins, ketonuria, and mild rhabdomyolysis. Transthoracic echocardiogram revealed mild inferior wall hypokinesia and cardiac catheterization showed normal coronaries; hence, the diagnosis of type II myocardial infarction (MI) was established. Although the pathogenesis remains unclear, this temporal association between VLC-KD and type 2 MI raised some concerns about VLC-KD’s cardiovascular safety profile.

SGLT2 Inhibitors and Ketone Metabolism in Heart Failure

Sodium-glucose cotransporter-2 (SGLT2) inhibitors have emerged as powerful drugs that can be used to treat heart failure (HF) patients, both with preserved and reduced ejection fraction and in the presence or absence of type 2 diabetes. While the mechanisms underlying the salutary effects of SGLT2 inhibitors have not been fully elucidated, there is clear evidence for a beneficial metabolic effect of these drugs. In this review, we discuss the effects of SGLT2 inhibitors on cardiac energy provision secondary to ketone bodies, pathological ventricular remodeling, and inflammation in patients with HF. While the specific contribution of ketone bodies to the pleiotropic cardiovascular benefits of SGLT2 inhibitors requires further clarification, ketone bodies themselves may also be used as a therapy for HF.

A novel hypothesis linking low-grade ketonaemia to cardio-renal benefits with sodium-glucose cotransporter-2 inhibitors

The cardio-renal benefits of sodium-glucose cotransporter-2 (SGLT2) inhibitors are well established. In 2016, we postulated that these benefits are attributable, in part, to the occurrence of chronic low-grade ketonaemia and a shift in myocardial and renal fuel metabolism away from fat oxidation, which is energy inefficient, towards ketone oxidation, which is more energy efficient. This shift improves myocardial and renal function and can potentially translate into lower rates of progression to heart failure and end-stage kidney disease in patients with and without diabetes. There is now evidence that, in addition to being an efficient fuel substrate, ketones also have antiinflammatory and antioxidative benefits on the heart and the kidney. In addition, ketones have positive effects on mitochondrial biogenesis and function, and on erythropoiesis, and thereby are potentially able to further ameliorate the proinflammatory and hypoxic milieu in those with heart and kidney failure, independent of hyperglycaemia. In the present review, we propose a novel hypothesis to link the pleiotropic effects of low-grade ketonaemia to the cardio-renal benefits seen with SGLT2 inhibitors.

Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future

The ketone bodies acetoacetate (AcAc) and β-hydroxybutyrate (βHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and βHB concentrations, which has been termed 'acute nutritional ketosis' or 'intermittent exogenous ketosis'. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.

Clinicopathologic Appearance of Advanced Ketoacidosis With Basal Vacuolation in Renal Tubules

CONTEXT.—

Basal vacuolization (BV) in renal tubules is a histopathologic hallmark of advanced ketoacidosis that enables us to retrospectively diagnose these cases.

OBJECTIVE.—

To clarify the pathologic background and serologic findings of ketoacidosis with BV, and to reveal the pathologic findings by each pathologic background.

DESIGN.—

We examined 664 serial autopsy cases. A systemic histopathologic examination and measurement of serum β-hydroxybutyrate concentration were performed for the cases with BV. The extent of steatosis and fibrosis in the organs and the degree of coronary artery stenosis were semiquantitatively investigated. Immunohistochemistry for adipophilin was also performed to analyze its usefulness for the pathologic diagnosis.

RESULTS.—

Basal vacuolization was found in 16 cases, all of which showed a pathologic serum β-hydroxybutyrate concentration. The main background of ketoacidosis was considered as alcohol abuse in 6 cases, diabetes in 5, malnutrition in 3, and hypothermia and infection in 1 case each. Severe hepatic fibrosis was observed only in the alcohol-abuser group. Moreover, cardiac steatosis was more severe in patients with possible alcohol abuse than in those with other causes. Immunohistochemistry for adipophilin showed immunoreactivity consistent with BV in 13 of 16 cases. There was no correlation between β-hydroxybutyrate concentration and either the postmortem or storage interval.

CONCLUSIONS.—

Basal vacuolization may be a useful finding for detecting ketoacidosis cases in a postmortem investigation. Serum β-hydroxybutyrate was a stable and reliable compound for the definitive diagnosis of ketoacidosis in such cases. The present study showed that pathologic changes in some organs may vary by each pathologic background of ketoacidosis with BV.

Ketone bodies: from enemy to friend and guardian angel

During starvation, fasting, or a diet containing little digestible carbohydrates, the circulating insulin levels are decreased. This promotes lipolysis, and the breakdown of fat becomes the major source of energy. The hepatic energy metabolism is regulated so that under these circumstances, ketone bodies are generated from β-oxidation of fatty acids and secreted as ancillary fuel, in addition to gluconeogenesis. Increased plasma levels of ketone bodies thus indicate a dietary shortage of carbohydrates. Ketone bodies not only serve as fuel but also promote resistance to oxidative and inflammatory stress, and there is a decrease in anabolic insulin-dependent energy expenditure. It has been suggested that the beneficial non-metabolic actions of ketone bodies on organ functions are mediated by them acting as a ligand to specific cellular targets. We propose here a major role of a different pathway initiated by the induction of oxidative stress in the mitochondria during increased ketolysis. Oxidative stress induced by ketone body metabolism is beneficial in the long term because it initiates an adaptive (hormetic) response characterized by the activation of the master regulators of cell-protective mechanism, nuclear factor erythroid 2-related factor 2 (Nrf2), sirtuins, and AMP-activated kinase. This results in resolving oxidative stress, by the upregulation of anti-oxidative and anti-inflammatory activities, improved mitochondrial function and growth, DNA repair, and autophagy. In the heart, the adaptive response to enhanced ketolysis improves resistance to damage after ischemic insults or to cardiotoxic actions of doxorubicin. Sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors may also exert their cardioprotective action via increasing ketone body levels and ketolysis. We conclude that the increased synthesis and use of ketone bodies as ancillary fuel during periods of deficient food supply and low insulin levels causes oxidative stress in the mitochondria and that the latter initiates a protective (hormetic) response which allows cells to cope with increased oxidative stress and lower energy availability. KEYWORDS: Ketogenic diet, Ketone bodies, Beta hydroxybutyrate, Insulin, Obesity, Type 2 diabetes, Inflammation, Oxidative stress, Cardiovascular disease, SGLT2, Hormesis.

Nonalcoholic fatty liver disease, circulating ketone bodies and all-cause mortality in a general population-based cohort

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is increasingly prevalent, paralleling the obesity epidemic. Ketone bodies are produced in the liver, but it is currently uncertain whether circulating ketone bodies are increased in the context of NAFLD. We investigated the association between NAFLD and circulating ketone bodies and determined the extent to which NAFLD and circulating ketone bodies are associated with all-cause mortality.

METHODS

Plasma ketone bodies were measured by nuclear magnetic resonance spectroscopy in participants of the general population-based PREVEND study. A fatty liver index (FLI) ≥60 was regarded as a proxy of NAFLD. Associations of an elevated FLI and ketone bodies with all-cause mortality were investigated using Cox regression analyses.

RESULTS

The study included 6,297 participants aged 54 ± 12 years, of whom 1,970 (31%) had elevated FLI. Participants with elevated FLI had higher total ketone bodies (194 [153-259] vs 170 [133-243] µmol/L; P < .001) than participants without elevated FLI. During 7.9 [7.8-8.9] years of follow-up, 387 (6%) participants died. An elevated FLI was independently associated with an increased risk of mortality (HR: 1.34 [1.06-1.70]; P = .02). Higher total ketone bodies were also associated with an increased mortality risk (HR per doubling: 1.29 [1.12-1.49]; P < .001). Mediation analysis suggested that the association of elevated FLI with all-cause mortality was in part mediated by ketone bodies (proportion mediated: 10%, P < .001).

CONCLUSION

Circulating ketone bodies were increased in participants with suspected NAFLD. Both suspected NAFLD and higher circulating ketone bodies are associated with an increased risk of all-cause mortality.

3-Hydroxybutyrate administration elevates plasma parathyroid hormone in a pilot human randomized, controlled, cross over trial

CONTENT

Ketone bodies, in particular 3-hydroxybutyrate (3OHB), are known to possess important energetic and signaling capacities. There is a growing block of evidence, that ketogenic dieting (KD), fasting, and sodium glucose transporter 2 inhibitor (SGLT2i) treatment are associated with hyperparathyroidism and negative bone health.

OBJECTIVE

We aimed to study the effect of exogenous 3OHB administration on bone metabolism, specifically the effect on parathyroid hormone (PTH) and calcium/phosphate homeostasis.

DESIGN

A randomized, controlled, cross over study with two arms: i) saline infusion and ii) 3OHB infusion.

SETTING

The study was conducted at Aarhus University Hospital.

PARTICIPANTS

We examined eight healthy human subjects aged 50-70 years.

INTERVENTION

Continuous intravenous DL-3OHB-NaCl infusion or 0.9% NaCl was administered for 390 min.

MAIN OUTCOME MEASURES

The study was designed to test the impact of 3OHB on PTH, calcium-phosphate, C-terminal Telopeptide (CTX), and Procollagen I N-terminal Propeptide (PINP). The study was a post hoc study.

RESULTS

The PTH concentration increased by 25% with a concomitant drop in phosphate of 30% in the 3OHB group. 3OHB infusion increased concentrations of CTX by 5%, without changes in PINP and albumin corrected calcium concentrations.

CONCLUSION

In conclusion, 3OHB administration increases PTH concentration and markers of bone resorption. These findings suggest a possible negative effect on bone health, which needs to be determined in future studies.

Plasma β-Hydroxybutyrate for the Diagnosis of Diabetic Ketoacidosis in the Emergency Department

OBJECTIVE

Diabetic ketoacidosis (DKA) is a common emergency department presentation of both new-onset and established diabetes mellitus (DM). β-Hydroxybutyrate (BOHB) provides a direct measure of the pathophysiologic derangement in DKA as compared with the nonspecific measurements of blood pH and bicarbonate. Our objective was to characterize the relationship between BOHB and DKA.

METHODS

This is a cross-sectional retrospective study of pediatric patients with DM presenting to an urban pediatric emergency department between January 1, 2016, and September 30, 2018. Analyses were performed on each patient's initial, simultaneous BOHB and pH. Diagnostic test characteristics of BOHB were calculated, and logistic regression was performed to investigate the effects of age and other key clinical factors.

RESULTS

Among 594 patients with DM, with median age of 12.3 years (interquartile range, 8.7-15.9 years), 176 (29.6%) presented with DKA. The inclusion of age, transfer status, and new-onset in the statistical model did not improve the prediction of DKA beyond BOHB alone. β-Hydroxybutyrate demonstrated strong discrimination for DKA, with an area under the curve of 0.95 (95% confidence interval, 0.93-0.97). A BOHB value of 5.3 mmol/L predicted DKA with optimal accuracy (90.6% of patients were correctly classified). The sensitivity, specificity, and positive and negative predictive values of this cut point were 76.7% (95% confidence interval, 69.8%-82.7%), 96.4% (94.2%-98.0%), 90.0% (84.0%-94.3%), and 90.8% (87.7%-93.3%), respectively.

CONCLUSIONS

β-Hydroxybutyrate accurately predicts DKA in children and adolescents. More importantly, because plasma BOHB is the ideal biochemical marker of DKA, BOHB may provide a more optimal definition of DKA for management decisions and treatment targets.

Outstanding improvement of the advanced lipoprotein profile in subjects with new-onset type 1 diabetes mellitus after achieving optimal glycemic control

AIMS

The impact of glycemic optimization on lipoprotein subfraction parameters in apparently normolipidemic subjects with new-onset type 1 diabetes mellitus (T1D) was examined.

METHODS

We evaluated the serum lipid and advanced lipoprotein profiles in twenty subjects at onset of T1D and twenty non-diabetic controls by laboratory methods and 1H NMR spectroscopy shortly after diabetes diagnosis (baseline), and after achieving optimal glycemic control (HbA1c ≤ 7.0%).

RESULTS

Advanced lipoprotein analysis revealed a significant reduction from baseline in serum concentrations of triglycerides (TG), cholesterol (C), and apolipoprotein (Apo)B-containing lipoproteins of treated subjects (VLDL-TG: -21%, IDL-TG: -30%, LDL-TG: -34%, LDL-TG: -36%, P < 0.05; VLDL-C: -23%, IDL-C: -44%, LDL-C: -16%; p < 0.05). Decreased VLDL and LDL lipids were mainly attributed to concomitant reductions in the concentration of medium-sized VLDL (-36%) and medium-sized LDL (-31%) and, to a lesser extent, to large-sized LDL (-14%). Notably, proatherogenic IDL characteristics and related surrogates of atherogenicity were resolved upon achievement of optimal glycemic status. Moreover, the concentration of HDL-TG was also reduced (-18%) at follow-up.

CONCLUSIONS

Our data showed that the achievement of optimal glycemic control after T1D onset corrected hidden derangements in ApoB-containing lipoproteins (particularly IDL) and HDL-TG that are related to higher cardiovascular risk in poorly controlled T1D.

Fasting Ketonuria and the Risk of Incident Nonalcoholic Fatty Liver Disease With and Without Liver Fibrosis in Nondiabetic Adults

INTRODUCTION

Dietary carbohydrate restriction or ketogenic diets are known to be beneficial in preventing liver fat accumulation. However, the effect of ketonemia on the risk of nonalcoholic fatty liver disease (NAFLD) in nondiabetic population is largely unknown. We investigated the association between fasting ketonuria and the risk of incident NAFLD in healthy adults.

METHODS

A cohort of 153,076 nondiabetic Koreans with no hepatic steatosis and low probability of fibrosis at baseline was followed for a median of 4.1 years. The outcome was incident hepatic steatosis with or without liver fibrosis, and it was assessed by liver ultrasound and noninvasive fibrosis indices, including fibrosis-4 and the NAFLD fibrosis score (NFS). Parametric proportional hazard models were used to estimate hazard ratios (HRs) for outcome according to ketonuria status.

RESULTS

Within 677,702.1 person-years of follow-up, 31,079 subjects developed hepatic steatosis. Compared with no ketonuria (reference), fasting ketonuria was significantly associated with a decreased risk of incident hepatic steatosis, with multivariable-adjusted HRs (95% confidence interval) of 0.81 (0.78-0.84). The corresponding HRs for incident hepatic steatosis with intermediate-to-high NFS were 0.79 (0.69-0.90). Similar associations were observed replacing NFS with fibrosis-4. In addition, the presence of persistent ketonuria at both baseline and subsequent visit was associated with the greatest decrease in the adjusted HR for incident NAFLD.

DISCUSSION

Ketonuria was associated with a reduced risk of developing incident hepatic steatosis with and without intermediate-to-high probability of advanced fibrosis in a large cohort of nondiabetic healthy individuals. The role of hyperketonemia in the prevention of NAFLD requires further exploration.