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Advanced Science (Weinheim,... Sep 2023Ketone bodies have long been known as a group of lipid-derived alternative energy sources during glucose shortages. Nevertheless, the molecular mechanisms underlying...
Ketone bodies have long been known as a group of lipid-derived alternative energy sources during glucose shortages. Nevertheless, the molecular mechanisms underlying their non-metabolic functions remain largely elusive. This study identified acetoacetate as the precursor for lysine acetoacetylation (Kacac), a previously uncharacterized and evolutionarily conserved histone post-translational modification. This protein modification is comprehensively validated using chemical and biochemical approaches, including HPLC co-elution and MS/MS analysis using synthetic peptides, Western blot, and isotopic labeling. Histone Kacac can be dynamically regulated by acetoacetate concentration, possibly via acetoacetyl-CoA. Biochemical studies show that HBO1, traditionally known as an acetyltransferase, can also serve as an acetoacetyltransferase. In addition, 33 Kacac sites are identified on mammalian histones, depicting the landscape of histone Kacac marks across species and organs. In summary, this study thus discovers a physiologically relevant and enzymatically regulated histone mark that sheds light on the non-metabolic functions of ketone bodies.
Topics: Animals; Histones; Lysine; Acetoacetates; Tandem Mass Spectrometry; Protein Processing, Post-Translational; Mammals
PubMed: 37382194
DOI: 10.1002/advs.202300032 -
Journal of Lipid Research Aug 2023Acetoacetyl-CoA synthetase (AACS) is the key enzyme in the anabolic utilization of ketone bodies (KBs) for denovo lipid synthesis, a process that bypasses citrate and... (Review)
Review
Acetoacetyl-CoA synthetase (AACS) is the key enzyme in the anabolic utilization of ketone bodies (KBs) for denovo lipid synthesis, a process that bypasses citrate and ATP citrate lyase. This review shows that AACS is a highly regulated, cytosolic, and lipogenic enzyme and that many tissues can readily use KBs for denovo lipid synthesis. AACS has a low micromolar K for acetoacetate, and supply of acetoacetate should not limit its activity in the fed state. In many tissues, AACS appears to be regulated in conjunction with the need for cholesterol, but in adipose tissue, it seems tied to fatty acid synthesis. KBs are readily utilized as substrates for lipid synthesis in lipogenic tissues, including liver, adipose tissue, lactating mammary gland, skin, intestinal mucosa, adrenals, and developing brain. In numerous studied cases, KBs served several-fold better than glucose as substrates for lipid synthesis, and when present, KBs suppressed the utilization of glucose for lipid synthesis. Here, it is hypothesized that a physiological role for the utilization of KBs for lipid synthesis is a metabolic process of lipid interconversion. Fatty acids are converted to KBs in liver, and then, the KBs are utilized to synthesize cholesterol and other long-chain fatty acids in liver and nonhepatic tissues. The conversion of fatty acids to cholesterol via the KBs may be a particularly important example of lipid interconversion. Utilizing KBs for lipid synthesis is glucose sparing and probably is important with low carbohydrate diets. Metabolic situations and tissues where this pathway may be important are discussed.
Topics: Female; Humans; Acetoacetates; Lactation; Ketone Bodies; Fatty Acids; Liver; Cholesterol; Glucose
PubMed: 37356666
DOI: 10.1016/j.jlr.2023.100407 -
Diabetes Sep 2023With rising incidence and prevalence of type 2 diabetes, prevention including identification of prospective biomarkers becomes increasingly relevant. Although ketone...
UNLABELLED
With rising incidence and prevalence of type 2 diabetes, prevention including identification of prospective biomarkers becomes increasingly relevant. Although ketone bodies recently received a renewed interest as potential biomarkers, data linking these metabolites to diabetes risk are scarce. Therefore, the present prospective study investigated a potential association between fasting ketone bodies and incident type 2 diabetes in the general population. This study from the PREVEND cohort included 3,307 participants from the general population initially free of diabetes or impaired fasting glucose. Baseline fasting ketone body concentrations were measured by nuclear magnetic resonance spectroscopy. One hundred twenty-six participants (3.8%) developed type 2 diabetes during a median (interquartile range) follow-up of 7.3 (6.3-7.6) years. In Kaplan-Meier analysis, sex-stratified ketone body levels strongly positively associated with incident type 2 diabetes, which was confirmed in Cox regression analyses adjusted for several potential confounders. There was no significant interaction by sex. Both 3-β-hydroxybutyrate and acetoacetate+acetone individually associated with incident type 2 diabetes. In conclusion, fasting plasma ketone body levels are strongly positively associated with incident type 2 diabetes in the general population independent of several other recognized risk factors. These results may have important implications for diabetes prevention including dietary strategies.
ARTICLE HIGHLIGHTS
The identification of biomarkers that predict type 2 diabetes is increasingly relevant for personalized medicine strategies. Data regarding ketone bodies and incident type 2 diabetes are scarce. This study shows that ketone bodies, either combined or as individual subspecies, are strongly associated with incident type 2 diabetes in the general population, independent of potential confounders. These results may have important implications for diabetes prevention including dietary strategies.
Topics: Humans; Diabetes Mellitus, Type 2; Ketone Bodies; Blood Glucose; Prospective Studies; 3-Hydroxybutyric Acid; Fasting; Biomarkers
PubMed: 37352012
DOI: 10.2337/db22-0826 -
MBio Aug 2023Polyphenols are abundant in nature, and their anaerobic biodegradation by gut and soil bacteria is a topic of great interest. The O requirement of phenol oxidases is...
Polyphenols are abundant in nature, and their anaerobic biodegradation by gut and soil bacteria is a topic of great interest. The O requirement of phenol oxidases is thought to explain the microbial inertness of phenolic compounds in anoxic environments, such as peatlands, termed the enzyme latch hypothesis. A caveat of this model is that certain phenols are known to be degraded by strict anaerobic bacteria, although the biochemical basis for this process is incompletely understood. Here, we report the discovery and characterization of a gene cluster in the environmental bacterium for the degradation phloroglucinol (1,3,5-trihydroxybenzene), a key intermediate in the anaerobic degradation of flavonoids and tannins, which constitute the most abundant polyphenols in nature. The gene cluster encodes the key C-C cleavage enzyme dihydrophloroglucinol cyclohydrolase, as well as ()-3-hydroxy-5-oxo-hexanoate dehydrogenase and triacetate acetoacetate-lyase, which enable phloroglucinol to be utilized as a carbon and energy source. Bioinformatics studies revealed the presence of this gene cluster in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on human health and carbon preservation in peat soils and other anaerobic environmental niches. IMPORTANCE This study provides novel insights into the microbiota's anaerobic metabolism of phloroglucinol, a critical intermediate in the degradation of polyphenols in plants. Elucidation of this anaerobic pathway reveals enzymatic mechanisms for the degradation of phloroglucinol into short-chain fatty acids and acetyl-CoA, which are used as a carbon and energy source for bacterium growth. Bioinformatics studies suggested the prevalence of this pathway in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on carbon preservation in peat soils and human gut health.
Topics: Humans; Phloroglucinol; Anaerobiosis; Bacteria; Bacteria, Anaerobic; Phenols; Polyphenols; Soil
PubMed: 37341492
DOI: 10.1128/mbio.01099-23 -
CEN Case Reports Nov 2023Metformin-associated lactic acidosis is a well-known metformin treatment complication; however, the development of euglycemic diabetic ketoacidosis (euDKA) has rarely...
Metformin-associated lactic acidosis is a well-known metformin treatment complication; however, the development of euglycemic diabetic ketoacidosis (euDKA) has rarely been reported. Here we report a case of lactic acidosis and euDKA after metformin overdose. A 57-year-old female patient was transferred to our hospital with severe metabolic acidosis and acute kidney injury. She had type 2 diabetes mellitus and was on oral antidiabetic therapy of vildagliptin metformin hydrochloride daily. On the admission day, she had committed suicide by overdosing 50 tablets of vildagliptin metformin hydrochloride, which was equivalent to 25,000 mg of metformin and 2500 mg of vildagliptin. She had severe lactic acidosis 5 h after overdosing. However, after 34 h of overdosing, serum lactate levels decreased while serum anion gap levels increased. She received single hemodialysis treatment. Serum total ketone bodies, β-hydroxybutyrate acetoacetic acid, and acetone were increased even after hemodialysis treatment. Her blood glucose levels have never exceeded 250 mg/dL since admission. Therefore, we considered that the cause of metabolic acidosis in this patient was not only lactic acidosis but also euDKA. The causes of euDKA in our patient might be hepatic production of ketone bodies due to metformin overdose in addition to type 2 diabetes mellitus, starvation, infection, and stressful physical conditions such as vomiting and diarrhea. We propose that not only lactic acidosis but also ketoacidosis is one of the important pathological conditions in patients with metformin overdose.
Topics: Female; Humans; Middle Aged; Acidosis; Acidosis, Lactic; Diabetes Mellitus, Type 2; Diabetic Ketoacidosis; Ketone Bodies; Metformin; Vildagliptin
PubMed: 36934381
DOI: 10.1007/s13730-023-00783-w -
Journal of Diabetes Science and... May 2024Ketone bodies are an energy substrate produced by the liver and used during states of low carbohydrate availability, such as fasting or prolonged exercise. High ketone... (Review)
Review
Ketone bodies are an energy substrate produced by the liver and used during states of low carbohydrate availability, such as fasting or prolonged exercise. High ketone concentrations can be present with insulin insufficiency and are a key finding in diabetic ketoacidosis (DKA). During states of insulin deficiency, lipolysis increases and a flood of circulating free fatty acids is converted in the liver into ketone bodies-mainly beta-hydroxybutyrate and acetoacetate. During DKA, beta-hydroxybutyrate is the predominant ketone in blood. As DKA resolves, beta-hydroxybutyrate is oxidized to acetoacetate, which is the predominant ketone in the urine. Because of this lag, a urine ketone test might be increasing even as DKA is resolving. Point-of-care tests are available for self-testing of blood ketones and urine ketones through measurement of beta-hydroxybutyrate and acetoacetate and are cleared by the US Food and Drug Administration (FDA). Acetone forms through spontaneous decarboxylation of acetoacetate and can be measured in exhaled breath, but currently no device is FDA-cleared for this purpose. Recently, technology has been announced for measuring beta-hydroxybutyrate in interstitial fluid. Measurement of ketones can be helpful to assess compliance with low carbohydrate diets; assessment of acidosis associated with alcohol use, in conjunction with SGLT2 inhibitors and immune checkpoint inhibitor therapy, both of which can increase the risk of DKA; and to identify DKA due to insulin deficiency. This article reviews the challenges and shortcomings of ketone testing in diabetes treatment and summarizes emerging trends in the measurement of ketones in the blood, urine, breath, and interstitial fluid.
Topics: Humans; Diabetic Ketoacidosis; Ketones; Ketone Bodies; Acetoacetates; 3-Hydroxybutyric Acid; Breath Tests; Point-of-Care Testing
PubMed: 36794812
DOI: 10.1177/19322968231152236