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Fasting metabolism and immunity are tightly linked; however, it is largely unknown how immune cells contribute to metabolic homeostasis during fasting in healthy subjects. Here, we combined cell-type-resolved genomics and computational approaches to map crosstalk between hepatocytes and liver macrophages during fasting. We identified the glucocorticoid receptor (GR) as a key driver of fasting-induced reprogramming of the macrophage secretome including fasting-suppressed cytokines and showed that lack of macrophage GR impaired induction of ketogenesis during fasting as well as endotoxemia. Mechanistically, macrophage GR suppressed the expression of tumor necrosis factor (TNF) and promoted nuclear translocation of hepatocyte GR to activate a fat oxidation/ketogenesis-related gene program, cooperatively induced by GR and peroxisome proliferator-activated receptor alpha (PPARα) in hepatocytes. Together, our results demonstrate how resident liver macrophages directly influence ketogenesis in hepatocytes, thereby also outlining a strategy by which the immune system can set the metabolic tone during inflammatory disease and infection.

Background D-3-hydroxybutyrate (D-3-OHB) is a ketone body that serves as an alternative nutritional fuel but also as an important signaling metabolite. Oral ketone supplements containing D/L-3-OHB are becoming a popular approach to achieve ketosis. Aim To explore the gut-derived effects of ketone supplements. Methods Eight healthy lean male volunteers were investigated on 2 separate occasions: An acetaminophen test was performed to evaluate gastric emptying and blood samples were obtained consecutively throughout the study period. Results We show that oral consumption of D/L-3-OHB stimulates cholecystokinin release (P = 0.02), elevates insulin (P = 0.03) and C-peptide (P < 0.001) concentrations, and slows gastric emptying (P = 0.01) compared with matched intravenous D/L-3-OHB administration. Measures of appetite and plasma concentrations of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) were unaffected by interventions. Conclusion Our findings show that D/L-3-OHB exert incretin effects and indicate luminal sensing in the gut endothelium. This adds to our understanding of ketones as signaling metabolites and displays the important difference between physiological ketosis and oral ketone supplements.

PURPOSE: Fibroblast growth factor (FGF) 21 is a circulating hormone with metabolic regulatory importance. In mice, FGF21 increases in response to a ketogenic diet and fasting. In humans, a similar increase is only observed after prolonged starvation. We aim to study the acute effects of ketone bodies on circulating FGF21 levels in humans.METHODS: Participants from three randomized, placebo-controlled crossover studies, with increased endogenous or exogenous ketone bodies, were included. Study 1: patients with type 1 diabetes (T1D) (n = 9) were investigated after a) insulin deprivation and lipopolysaccharide (LPS) injection and b) insulin-controlled euglycemia. Study 2: patients with T1D (n = 9) were investigated after a) total insulin deprivation for 9 hours and b) insulin-controlled euglycemia. Study 3: Healthy adults (n = 9) were examined during a) 3-hydroxybutyrate (OHB) infusion and b) saline infusion. Plasma FGF21 was measured with immunoassay in serial samples.RESULTS: Circulating OHB levels were significantly increased to 1.3, 1.5, and 5.5 mmol/l in the three studies, but no correlations with FGF21 levels were found. Also, no correlations between FGF21, insulin, or glucagon were found. Insulin deprivation and LPS injection resulted in increased plasma FGF21 levels at t = 120 min (p = .005) which normalized at t = 240 min.CONCLUSION: We found no correlation between circulating FGF21 levels and levels of ketone bodies. This suggests that it is not ketosis per se which controls FGF21 production, but instead a rather more complex regulatory mechanism.TRIAL REGISTRATION: clinicaltrials.gov ID number: Study 1: NCT02157155 (5/6-2014), study 2: NCT02077348 (4/3-2014), and study 3: NCT02357550 (6/2-2015).

Objective Cognitive impairment in type 2 diabetes is associated with cerebral glucose hypometabolism. Providing a glucose substitute such as ketone bodies might restore metabolic balance in glucose-compromised neurones and improve cognitive performance. We aimed to investigate if β-hydroxybutyrate (ketone body) infusion acutely affects cognitive performance, measured by a neuropsychological test battery, in patients with type 2 diabetes. Design Randomised, placebo-controlled, double-blind cross-over trial. Methods Eighteen patients with type 2 diabetes received i.v. ketone body (β-hydroxybutyrate) and placebo (saline) infusion in a randomised order on two separate occasions. On both days of examination, blood glucose was clamped at 7.5 mmol/L and a neuropsychological test battery was used to assess global cognitive performance (primary outcome) and specialized cognitive measures of verbal memory, working memory, executive function, psychomotor speed, and sustained attention. Results During neurocognitive testing, β-hydroxybutyrate concentrations were 2.4 vs 0.1 mmol/L. Working memory assessed by Wechsler Adult Intelligence Scale letter-number-sequencing significantly improved by 1.6 points (95% CI: 0.7, 2.4; non-adjusted P P = 0.012). Conclusions Ketone infusion specifically improved working memory performance in patients with type 2 diabetes in the absence of changes in global cognition.

Aims: To test whether oral administration of D/L-3-hydroxybutyrate as a sodium salt inhibits lipolysis and intracellular lipid signalling, in particular, hormone-sensitive lipase, and whether D/L-3-hydroxybutyrate alters endogenous glucose production. Methods: We studied six young men in a randomized, controlled, crossover study after ingestion of Na-D/L-3-hydroxybutyrate (hyperketotic condition) or saline (placebo control). We quantified lipolysis and endogenous glucose production using [9,10-3H]-palmitate and [3-3H]glucose tracers, and adipose tissue biopsies were collected to investigate key lipolytic enzymes. Results: After ingestion, D/L-3-hydroxybutyrate increased by more than 2.5 mmol/l, free fatty acid concentrations decreased by >70%, and palmitate rate of appearance was halved. Protein kinase A phosphorylation of perilipin was reduced and hormone-sensitive lipase 660 phosphorylation in adipose tissue biopsies was 70–80% decreased in the hyperketotic condition and unchanged in the control. Compared to the control, endogenous glucose production was reduced by close to 20% (P

BACKGROUND: Deliberately training with reduced carbohydrate availability, a paradigm coined training low, has shown to promote adaptations associated with improved aerobic capacity. In this context researchers have proposed that protein may be ingested prior to training as a means to enhance the protein balance during exercise without spoiling the effect of the low carbohydrate availability. Accordingly, this is being practiced by world class athletes. However, the effect of protein intake on muscle protein metabolism during training low has not been studied. This study aimed to examine if protein intake prior to exercise with reduced carbohydrate stores benefits muscle protein metabolism in exercising and non-exercising muscles.METHODS: Nine well-trained subjects completed two trials in random order both of which included a high-intensity interval ergometer bike ride (day 1), a morning (day 2) steady state ride (90 min at 65% VO2peak, 90ss), and a 4-h recovery period. An experimental beverage was consumed before 90ss and contained either 0.5 g whey protein hydrolysate [WPH]/ kg lean body mass or flavored water [PLA]. A stable isotope infusion (L-[ring-13C6]-phenylalanine) combined with arterial-venous blood sampling, and plasma flow rate measurements were used to determine forearm protein turnover. Myofibrillar protein synthesis was determined from stable isotope incorporation into the vastus lateralis.RESULTS: Forearm protein net balance was not different from zero during 90ss exercise (nmol/100 ml/min, PLA: 0.5 ± 2.6; WPH: 1.8, ± 3.3) but negative during the 4 h recovery (nmol/100 ml/min, PLA: - 9.7 ± 4.6; WPH: - 8.7 ± 6.5); no interaction (P = 0.5) or main effect of beverage (P = 0.11) was observed. Vastus lateralis myofibrillar protein synthesis rates were increased during 90ss exercise (+ 0.02 ± 0.02%/h) and recovery (+ 0.02 ± 0.02%/h); no interaction (P = 0.3) or main effect of beverage (P = 0.3) was observed.CONCLUSION: We conclude that protein ingestion prior to endurance exercise in the energy- and carbohydrate-restricted state does not increase myofibrillar protein synthesis or improve net protein balance in the exercising and non-exercising muscles, respectively, during and in the hours after exercise compared to ingestion of a non-caloric control.TRIAL REGISTRATION: clinicaltrials.gov, NCT01320449. Registered 10 May 2017 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03147001.

Summary Excessive intake of licorice may cause pseudohyperaldosteronism which, in turn, may lead to hypertension and hypokalemia. Severe hypokalemia may lead to electrocardiogram (ECG) changes including long QT interval potentially progressing into malignant arrhythmias. Here we present a 43-year-old woman admitted to the hospital with chest pain and a stinging sensation in the upper extremities. Her peak blood pressure was 177/98 mmHg and the blood test revealed low plasma potassium of 1.9 mmol/L. The ECG revealed flattened T-waves and long QT interval. Prior to admission, the patient had increased licorice ingestion to a total of some 70 g daily. The licorice intake was stopped and potassium was administrated orally and intravenously. Plasma potassium normalized and the ECG changes remitted. To our knowledge a few other cases of licorice-induced pseudohyperaldosteronism and long QT interval have previously been reported. This underlines the importance of quantifying licorice intake in younger people with unexplained high blood pressure and low potassium. Learning points: Even small amounts of licorice daily may increase the risk of developing hypertension; therefore, licorice should be asked for specifically. Even though licorice intake is very easy to cover in the patient’s history, it is often missed. Excessive licorice intake may course severe hypokalemia causing long QT interval in the ECG recording, potentially progressing into arrhythmias and even cardiac arrest/sudden death. Hypokalemia Licorice-induced hypertension may be associated with syndrome of apparent mineralocorticoid excess (SAME). Plasma renin and aldosterone are both low at diagnosis and normalize when licorice is stopped.

CONTEXT: 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 minutes.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.

Hypoglycemia is the leading limiting factor in glycemic management of insulin-treated diabetes. Skeletal muscle is the predominant site of insulin-mediated glucose disposal. Our study used a crossover design to test to what extent insulin-induced hypoglycemia affects glucose uptake in skeletal muscle and whether hypoglycemia counterregulation modulates insulin and catecholamine signaling and glycogen synthase activity in skeletal muscle. Nine healthy volunteers were examined on three randomized study days: 1) hyperinsulinemic hypoglycemia (bolus insulin), 2) hyperinsulinemic euglycemia (bolus insulin and glucose infusion), and 3) saline control with skeletal muscle biopsies taken just before, 30 min after, and 75 min after insulin/saline injection. During hypoglycemia, glucose levels reached a nadir of ∼2.0 mmol/L, and epinephrine rose to ∼900 pg/mL. Hypoglycemia impaired insulin-stimulated glucose disposal and glucose clearance in skeletal muscle, whereas insulin signaling in glucose transport was unaffected by hypoglycemia. Insulin-stimulated glycogen synthase activity was completely ablated during hyperinsulinemic hypoglycemia, and catecholamine signaling via cAMP-dependent protein kinase and phosphorylation of inhibiting sites on glycogen synthase all increased.

Context: Insulin resistance and metabolic inflexibility are features of obesity and are amplified by fasting. Growth hormone (GH) secretion increases during fasting and GH causes insulin resistance. Objective: To study the metabolic effects of GH blockade during fasting in obese subjects. Subjects and Methods: Nine obese males were studied thrice in a randomized design: (1) after an overnight fast (control), (2) after 72 hour fasting (fasting), and (3) after 72 hour fasting with GH blockade (pegvisomant) [fasting plus GH antagonist (GHA)]. Each study day consisted of a 4-hour basal period followed by a 2-hour hyperinsulinemic, euglycemic clamp combined with indirect calorimetry, assessment of glucose and palmitate turnover, and muscle and fat biopsies. Results: GH levels increased with fasting (P < 0.01), and the fasting-induced reduction of serum insulin-like growth factor I was enhanced by GHA (P < 0.05). Fasting increased lipolysis and lipid oxidation independent of GHA, but fasting plus GHA caused a more pronounced suppression of lipid intermediates in response to hyperinsulinemic, euglycemic clamp. Fasting-induced insulin resistance was abrogated by GHA (P, 0.01) primarily due to reduced endogenous glucose production (P = 0.003). Fasting plus GHA also caused elevated glycerol levels and reduced levels of counterregulatory hormones. Fasting significantly reduced the expression of antilipolytic signals in adipose tissue independent of GHA. Conclusions: Suppression of GH activity during fasting in obese subjects reverses insulin resistance and amplifies insulin-stimulated suppression of lipid intermediates, indicating that GH is an important regulator of substrate metabolism, insulin sensitivity, and metabolic flexibility also in obese subjects.

In this case report, a 19-year-old woman was admitted with delayed acute renal failure due to a paracetamol intake of 7 g. No liver damage was present, and the renal function recovered spontaneously after a few weeks. Paracetamol is the most common cause of medical induced overdose or death. It is well known, that poisoning from paracetamol may cause liver damage, but the risk of renal toxicity is known to a lesser extent. Acute renal failure due to paracetamol overdose may easily be missed due to the delayed manifestation.

BACKGROUND: Diabetic ketoacidosis (DKA) is associated with inflammation and increased lipolysis. The macrophage activation marker soluble CD163 (sCD163) is associated with obesity, non-alcoholic fatty liver disease, and type-2 diabetes. We aimed to investigate whether sCD163 correlates with, key elements of lipolysis in type-1 diabetes (DM1) patients during mild diabetic ketoacidosis.METHODS: We investigated nine patients with DM1 twice during: (i) euglycaemic control conditions (CTR) and a bolus of saline and (ii) hyperglycaemic ketotic conditions (KET) induced by lipopolysaccharide (LPS) administration combined with insulin deprivation. Blood samples, indirect calorimetry, palmitate tracer, and adipose tissue biopsies were used to investigate lipid metabolism.RESULTS: We observed a significant increase in plasma sCD163 levels following LPS exposure (pCONCLUSION: Macrophage activation assessed by sCD163 may play an important role in DKA, as it correlates strongly with important components of lipid metabolism including FFA, palmitate, lipid oxidation, G0S2, and proinflammatory cytokines during initial steps of DKA. These results are novel and add important knowledge to the field of DKA. This article is protected by copyright. All rights reserved.

Sodium–glucose cotransporter 2 (SGLT2) inhibition was originally developed as a facile way of lowering blood glucose through increased renal elimination. However, clinical trials have demonstrated that SGLT2 inhibition not only improves glycemic control but also increases circulating ketone bodies and hematocrit (1,2). Recently, SGLT2 inhibitor–driven modest hyperketonemia has attracted much focus as a possible explanation of the improved cardiac outcome in patients treated with SGLT2 inhibitors (3), whereas the increased hematocrit has mostly been ascribed to hemoconcentration due to increased osmotic diuresis. In this Observation, we present data indicating that hyperketonemia directly stimulates circulating erythropoietin concentrations and is associated with increased bone marrow activity assessed by 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). Seventeen healthy subjects undergoing either cardiac (study A) or brain (study B) PET/CT as part of protocols involving experimental hyperketonemia were investigated. Study A (4) consisted of 8 subjects (3 women) aged mean 60 (range 50–68) years with BMI mean 26 (range 22–35) kg/m2, and study B (5) of 9 subjects (4 women) aged 62 (56–69) years with BMI 24 (21–27) kg/m2. Both studies were randomized, single-blinded crossover trials in which participants were infused with either 7.5% Na-3-β-hydroxybutyrate (3-OHB) (infusion rate 0.18 g/kg/h [study A] and 0.22 g/kg/h [study B]) or saline (0.9%). In study A, bone marrow palmitate and glucose uptake …

The aims of this study were to determine the role of lipolysis in hypoglycaemia and define the underlying intracellular mechanisms. Nine healthy volunteers were randomised to treatment order of three different treatments (crossover design). Treatments were: (1) saline control; (2) hyperinsulinaemic hypoglycaemia (HH; i.v. bolus of 0.1 U/kg insulin); and (3) hyperinsulinaemic euglycaemia (HE; i.v. bolus of 0.1 U/kg insulin and 20% glucose). Inclusion criteria were that volunteers were healthy, aged >18 years, had a BMI between 19 and 26 kg/m2, and provided both written and oral informed consent. Exclusion criteria were the presence of a known chronic disease (including diabetes mellitus, epilepsy, ischaemic heart disease and cardiac arrhythmias) and regular use of prescription medication. The data was collected at the medical research facilities at Aarhus University Hospital, Denmark. The primary outcome was palmitic acid flux. Participants were blinded to intervention order, but caregivers were not. Adrenaline (epinephrine) and glucagon concentrations were higher during HH than during both HE and control treatments. NEFA levels and lipid oxidation rates (determined by indirect calorimetry) returned to control levels after 105 min. Palmitate flux was increased to control levels during HH (p = NS) and was more than twofold higher than during HE (overall mean difference between HH vs HE, 114 [95% CI 64, 165 μmol/min]; p

AIMS/HYPOTHESIS: Lack of insulin and infection/inflammation are the two most common causes of diabetic ketoacidosis (DKA). We used insulin withdrawal followed by insulin administration as a clinical model to define effects on substrate metabolism and to test whether increased levels of counter-regulatory hormones and cytokines and altered adipose tissue signalling participate in the early phases of DKA.METHODS: Nine individuals with type 1 diabetes, without complications, were randomly studied twice, in a crossover design, for 5 h followed by 2.5 h high-dose insulin clamp: (1) insulin-controlled euglycaemia (control) and (2) after 14 h of insulin withdrawal in a university hospital setting.RESULTS: Insulin withdrawal increased levels of glucose (6.1 ± 0.5 vs 18.6 ± 0.5 mmol/l), NEFA, 3-OHB (127 ± 18 vs 1837 ± 298 μmol/l), glucagon, cortisol and growth hormone and decreased HCO3- and pH, without affecting catecholamine or cytokine levels. Whole-body energy expenditure, endogenous glucose production (1.55 ± 0.13 vs 2.70 ± 0.31 mg kg-1 min-1), glucose turnover, non-oxidative glucose disposal, lipid oxidation, palmitate flux (73 [range 39-104] vs 239 [151-474] μmol/min), protein oxidation and phenylalanine flux all increased, whereas glucose oxidation decreased. In adipose tissue, Ser473 phosphorylation of Akt and mRNA levels of G0S2 decreased, whereas CGI-58 (also known as ABHD5) mRNA increased. Protein levels of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase phosphorylations were unaltered. Insulin therapy decreased plasma glucose concentrations dramatically after insulin withdrawal, without any detectable effect on net forearm glucose uptake.CONCLUSIONS/INTERPRETATION: Release of counter-regulatory hormones and overall increased catabolism, including lipolysis, are prominent features of preacidotic ketosis induced by insulin withdrawal, and dampening of Akt insulin signalling and transcriptional modulation of ATGL activity are involved. The lack of any increase in net forearm glucose uptake during insulin therapy after insulin withdrawal indicates muscle insulin resistance.TRIAL REGISTRATION: ClinicalTrials.gov NCT02077348 FUNDING: This study was supported by Aarhus University and the KETO Study Group/Danish Agency for Science Technology and Innovation.

Ketone bodies are neuroprotective in neurological disorders such as epilepsy. We randomly studied nine healthy human subjects twice-with and without continuous infusion of 3-hydroxybutyrate-to define potential underlying mechanisms, assessed regionally (parietal, occipital, temporal, cortical grey, and frontal) by PET scan. During 3-hydroxybutyrate infusions concentrations increased to 5.5±0.4 mmol/l and cerebral glucose utilisation decreased 14%, oxygen consumption remained unchanged, and cerebral blood flow increased 30%. We conclude that acute 3-hydroxybutyrate infusion reduces cerebral glucose uptake and increases cerebral blood flow in all measured brain regions, without detectable effects on cerebral oxygen uptake though oxygen extraction decreased. Increased oxygen supply concomitant with unchanged oxygen utilisation may contribute to the neuroprotective effects of ketone bodies.

Background Macrophage activation determined by levels of soluble sCD163 is associated with obesity, insulin resistance, diabetes mellitus type 2 (DM2) and non-alcoholic fatty liver disease (NAFLD). This suggests that macrophage activation is involved in the pathogenesis of conditions is characterised by adaptions in the lipid metabolism. Since sCD163 is shed to serum by inflammatory signals including lipopolysaccharides (LPS, endotoxin), we investigated sCD163 and correlations with lipid metabolism following LPS exposure. Methods Eight healthy male subjects were investigated on two separate occasions: (i) following an LPS exposure and (ii) following saline exposure. Each study day consisted of a four-hour non-insulin-stimulated period followed by a two-hour hyperinsulinemic euglycemic clamp period. A 3H-palmitate tracer was used to calculate the rate of appearance (Rapalmitate). Blood samples were consecutively obtained throughout each study day. Abdominal subcutaneous adipose tissue was obtained for western blotting. Results We observed a significant two-fold increase in plasma sCD163 levels following LPS exposure (P palmitate, lipid oxidation rates and phosphorylation of the hormone-sensitive lipase at serine 660 in adipose tissue (P P Conclusion We observed a strong correlation between sCD163 and stimulation of lipolysis and fat oxidation following LPS exposure. These findings support preexisting theory that inflammation and macrophage activation play a significant role in lipid metabolic adaptions under conditions such as obesity, DM2 and NAFLD.

Background: Animal studies suggest a positive role for nicotinamide riboside (NR) on insulin sensitivity and hepatic steatosis in models of obesity and type 2 diabetes. NR, an NAD+ precursor, is a member of the vitamin B-3 family now available as an over-the-counter supplement. Although data from preclinical trials appear consistent, potential effects and safety need to be evaluated in human clinical trials.Objective: The aim of this study was to test the safety of dietary NR supplementation over a 12-wk period and potential to improve insulin sensitivity and other metabolic parameters in obese, insulin-resistant men.Design: In an investigator-initiated randomized, placebo-controlled, double-blinded, and parallel-group designed clinical trial, forty healthy, sedentary men with a body mass index (BMI) > 30 kg/m2, age-range 40-70 y were randomly assigned to 12 wk of NR (1000 mg twice daily) or placebo. We determined the effects of NR supplementation on insulin sensitivity by a hyperinsulinemic euglycemic clamp and substrate metabolism by indirect calorimetry and labeled substrates of tritiated glucose and palmitate. Body composition and fat mass distribution were determined by whole-body dual-energy X-ray absorptiometry (DXA) and MRI scans, and measurements of intrahepatic lipid content were obtained by MR spectroscopy.Results: Insulin sensitivity, endogenous glucose production, and glucose disposal and oxidation were not improved by NR supplementation. Similarly, NR supplementation had no effect on resting energy expenditure, lipolysis, oxidation of lipids, or body composition. No serious adverse events due to NR supplementation were observed and safety blood tests were normal.Conclusion: 12 wk of NR supplementation in doses of 2000 mg/d appears safe, but does not improve insulin sensitivity and whole-body glucose metabolism in obese, insulin-resistant men. This trial was registered at clinicaltrials.gov as NCT02303483.

Background High levels of ketone bodies are associated with improved survival as observed with regular exercise, caloric restriction, and—most recently—treatment with sodium–glucose linked transporter 2 inhibitor antidiabetic drugs. In heart failure, indices of ketone body metabolism are upregulated, which may improve energy efficiency and increase blood flow in skeletal muscle and the kidneys. Nevertheless, it is uncertain how ketone bodies affect myocardial glucose uptake and blood flow in humans. Our study was therefore designed to test whether ketone body administration in humans reduces myocardial glucose uptake ( MGU ) and increases myocardial blood flow. Methods and Results Eight healthy subjects, median aged 60 were randomly studied twice: (1) During 390 minutes infusion of Na‐3‐hydroxybutyrate ( KETONE ) or (2) during 390 minutes infusion of saline ( SALINE ), together with a concomitant low‐dose hyperinsulinemic–euglycemic clamp to inhibit endogenous ketogenesis. Myocardial blood flow was measured by 15 O‐H 2 O positron emission tomography/computed tomography, myocardial fatty acid metabolism by 11 C‐palmitate positron emission tomography/computed tomography and MGU by 18 F‐fluorodeoxyglucose positron emission tomography/computed tomography. Similar euglycemia, hyperinsulinemia, and suppressed free fatty acids levels were recorded on both study days; Na‐3‐hydroxybutyrate infusion increased circulating Na‐3‐hydroxybutyrate levels from zero to 3.8±0.5 mmol/L. MGU was halved by hyperketonemia ( MGU [nmol/g per minute]: 304±97 [ SALINE ] versus 156±62 [ KETONE ], P Conclusions Ketone bodies displace MGU and increase myocardial blood flow in healthy humans; these novel observations suggest that ketone bodies are important cardiac fuels and vasodilators, which may have therapeutic potentials.

AIMS/HYPOTHESIS: Diabetic ketoacidosis (DKA) is often caused by concomitant systemic inflammation and lack of insulin. Here we used an experimental human model to test whether and how metabolic responses to insulin are impaired in the early phases of DKA with a specific focus on skeletal muscle metabolism.METHODS: Nine individuals with type 1 diabetes from a previously published cohort were investigated twice at Aarhus University Hospital using a 120 min infusion of insulin (3.0/1.5 mU kg(-1) min(-1)) after an overnight fast under: (1) euglycaemic conditions (CTR) or (2) hyperglycaemic ketotic conditions (KET) induced by an i.v. bolus of lipopolysaccharide and 85% reduction in insulin dosage. The primary outcome was insulin resistance in skeletal muscle. Participants were randomly assigned to one of the two arms at the time of screening using www.randomizer.org . The study was not blinded.RESULTS: All nine volunteers completed the 2 days and are included in the analysis. Circulating concentrations of glucose and 3-hydroxybutyrate increased during KET (mean ± SEM 17.7 ± 0.6 mmol/l and 1.6 ± 0.2 mmol/l, respectively), then decreased after insulin treatment (6.6 ± 0.7 mmol/l and 0.1 ± 0.07 mmol/l, respectively). Prior to insulin infusion (KET vs CTR) isotopically determined endogenous glucose production rates were 17 ± 1.7 μmol kg(-1) min(-1) vs 8 ± 1.3 μmol kg(-1) min(-1) (p = 0.003), whole body phenylalanine fluxes were 2.9 ± 0.5 μmol kg(-1) min(-1) vs 3.1 ± 0.4 μmol kg(-1) min(-1) (p = 0.77) and urea excretion rates were 16.9 ± 2.4 g/day vs 7.3 ± 1.7 g/day (p = 0.01). Insulin failed to stimulate forearm glucose uptake and glucose oxidation in KET compared with CTR (p < 0.05). Glycogen synthase phosphorylation was impaired in skeletal muscle.CONCLUSIONS/INTERPRETATION: In KET, hyperglycaemia is primarily driven by increased endogenous glucose production. Insulin stimulation during early phases of DKA is associated with reduced glucose disposal in skeletal muscle, impaired glycogen synthase function and lower glucose oxidation. This underscores the presence of muscle insulin resistance in the pathogenesis of DKA. Trial registration www.clinicaltrials.gov (ID number: NCT02157155). Funding This work was funded by the Danish Council for Strategic Research (grant no. 0603-00479B).

Diabetic ketoacidosis (DKA), a hallmark of type 1 diabetes, is the result of uncontrolled production of ketone bodies (3-hydroxybuturate and acetoacetic acid), leading to a lowering of blood pH (1). Ketogenesis in the liver is triggered by low levels of insulin and high levels of glucagon. In addition, other stress hormones (epinephrine, growth hormone, and cortisol), together with lack of insulin, accelerate lipolysis in peripheral tissues and lead to increased amounts of free fatty acids (FFAs) in the blood. FFAs are the most important precursor for ketone body formation. This process takes place in the mitochondiria (1). In general, ketoacidosis presents in patients with type 1 diabetes and is characterized by a high anion gap metabolic acidosis, which is usually compensated by hyperventilation and pulmonary loss of carbon dioxide. Below we report six unusual presentations of ketoacidosis. A 42-year-old man with known alcohol abuse and type 1 diabetes resulting from pancreatitis was brought to the hospital with vomiting, coughing, and general weakness. Before hospitalization, he had not taken any alkaline medicine or diuretics. His status at arrival and his blood test results are shown in Table 1. He had high 3-hydroxybutyrate (3-OHB), low potassium, and an anion gap >12 mEq/L. His condition was furthermore complicated by pneumonia. He was moved to the intensive care unit (ICU), where treatment with antibiotics, insulin, glucose, and potassium was initiated, and he recovered. …

Most often, diabetic ketoacidosis (DKA) in adults results from insufficient insulin administration and acute infection. DKA is assumed to release proinflammatory cytokines and stress hormones that stimulate lipolysis and ketogenesis. We tested whether this perception of DKA can be reproduced in an experimental human model by using combined insulin deficiency and acute inflammation and tested which intracellular mediators of lipolysis are affected in adipose tissue. Nine subjects with type 1 diabetes were studied twice: 1) insulin-controlled euglycemia and 2) insulin deprivation and endotoxin administration (KET). During KET, serum tumor necrosis factor-α, cortisol, glucagon, and growth hormone levels increased, and free fatty acids and 3-hydroxybutyrate concentrations and the rate of lipolysis rose markedly. Serum bicarbonate and pH decreased. Adipose tissue mRNA contents of comparative gene identification-58 (CGI-58) increased and G0/G1 switch 2 gene (G0S2) mRNA decreased robustly. Neither protein levels of adipose triglyceride lipase (ATGL) nor phosphorylations of hormone-sensitive lipase were altered. The clinical picture of incipient DKA in adults can be reproduced by combined insulin deficiency and endotoxin-induced acute inflammation. The precipitating steps involve the release of proinflammatory cytokines and stress hormones, increased lipolysis, and decreased G0S2 and increased CGI-58 mRNA contents in adipose tissue, compatible with latent ATGL stimulation.

The a-oxoaldehyde methylglyoxal is a ubiquitousand highly reactive metabolite known to be involvedin aging- and diabetes-related diseases. If notdetoxified by the endogenous glyoxalase system,it exerts its detrimental effects primarily by reactingwith biopolymers such as DNA and proteins. Wenow demonstrate that during ketosis, another meta-bolic route is operative via direct non-enzymaticaldol reaction between methylglyoxal and the ke-tone body acetoacetate, leading to 3-hydroxyhex-ane-2,5-dione. This novel metabolite is present ata concentration of 10%–20% of the methylglyoxallevel in the blood of insulin-starved patients. By em-ploying a metabolite-alkyne-tagging strategy it isclarified that 3-hydroxyhexane-2,5-dione is furthermetabolized to non-glycating species in humanblood. The discovery represents a new directionwithin non-enzymatic metabolism and within theuse of alkyne-tagging for metabolism studies andit revitalizes acetoacetate as a competent endoge-nous carbon nucleophile.