Nutrient sensing: LEAP2 concentration in response to fasting, glucose, lactate, and ß-hydroxybutyrate in healthy young males.

BACKGROUND: The appetite-suppressing potential of liver-expressed antimicrobial peptide 2 (LEAP2), and its antagonistic effects on the hunger-inducing hormone ghrelin have attracted scientific interest. It is unclear how LEAP2 is influenced by fasting and how it responds to specific nutrients. OBJECTIVES: The purpose of this investigation was to assess whether LEAP2 concentration 1) decreases after fasting, 2) increases postprandially, and 3) is regulated by nutrient sensing in the splanchnic bed. METHODS: Plasma LEAP2 concentration was measured in blood samples from 5 clinical cross-over trials, following 1) 36 h of fasting (n = 8), 2) 10 h of fasting (n = 37, baseline data pooled from 4 of the clinical trials), 3) Oral and intravenous glucose administration (n = 11), 4) Oral and intravenous Na-lactate administration (n = 10), and 5) Oral and intravenous Na-ß-hydroxybutyrate (BHB) administration (n = 8). All 5 trials included healthy males. RESULTS: Compared with a 10-h fasting period, the median LEAP2 concentration was 38% lower following 36 h of fasting (P < 0.001). Oral administration of glucose elevated, whereas intravenous glucose administration lowered LEAP2 concentration (intervention x time, P = 0.001), resulting in a mean difference of 9 ng/mL (95% confidence interval [CI]: 1, 17) after 120 min. Oral lactate increased, and intravenous lactate decreased LEAP2 (intervention x time, P = 0.007), with a mean difference between interventions of 10 ng/mL (95% CI: 6, 15) after 120 min. In contrast, oral and intravenous administration of BHB reduced the LEAP2 concentration (main effect of time, P < 0.001). CONCLUSIONS: Our investigations show that LEAP2 concentration was lower after a 36-h fast than an overnight fast and that oral delivery of glucose and lactate elevated LEAP2 concentration compared with intravenous administration, whereas LEAP2 concentrations decreased with both oral and intravenous BHB. This indicates that the LEAP2 concentration is sensitive to intestinal exposure to specific substrates, highlighting the need for future studies exploring the relationship between nutrients and LEAP2. This trial was registered at clinicaltrials.gov as NCT01840098, NCT03204877, NCT04299815, NCT03935841, and NCT01705782.

Insulin Signaling Is Preserved in Skeletal Muscle During Early Diabetic Ketoacidosis.

BACKGROUND AND AIMS: During diabetic ketoacidosis (DKA), muscle tissue develops a profound insulin resistance that complicates reversal of this potentially lethal condition. We have investigated mediators of insulin action in human skeletal muscle during total insulin withdrawal in patients with type 1 diabetes, under the hypothesis that initial phases of DKA are associated with impaired postreceptor signaling. MATERIALS AND METHODS: Muscle biopsies were obtained during a randomized, controlled, crossover trial involving 9 patients with type 1 diabetes. The subjects were investigated during a high-dose insulin clamp preceded by either: (1) insulin-controlled euglycemia (control) or (2) total insulin withdrawal for 14 hours. Insulin action in skeletal muscle and whole-body substrate metabolism were investigated using western blot analysis and indirect calorimetry respectively. RESULTS: During insulin withdrawal, insulin-stimulated dephosphorylation of glycogen synthase decreased by ∼30% (P < .05) compared with the control situation. This was associated with a decrease in glucose oxidation by ∼30% (P < .05). Despite alterations in glucose metabolism, insulin transduction to glucose transport and protein synthesis (Akt, AS160, mammalian target of rapamycin, and eukaryotic translation initiation factor 4E binding protein) was intact, and glucose transporter (GLUT4) and mitochondrial proteins (succinate dehydrogenase complex, subunit A and prohibitin 1) protein expression were unaffected by the intervention. CONCLUSION: DKA impairs insulin-stimulated activation of glycogen synthase, whereas insulin signal transduction to glucose transport and protein synthesis remains intact. Reversal of insulin resistance during treatment of DKA should target postreceptor mediators of glucose uptake. CLINICAL TRIAL REGISTRATION NUMBER: NCT02077348.

Oral 3-hydroxybuturate ingestion acutely lowers circulating testosterone concentrations in healthy young males.

Ketone bodies, such as 3-hydroxybutyrate (3-OHB), have been frequently used by endurance athletes, such as cyclists, to enhance performance and recovery and are recognized for their health benefits and therapeutic effects for decades. Testosterone is a potent regulator of red blood cell production. Evidence suggests that ketone bodies can increase the production of erythropoietin, which stimulates red blood cell production. Therefore, we investigated whether an acute increase in 3-OHB levels affects testosterone levels in healthy young men. We studied six healthy, young male participants who fasted overnight and were tested twice: (i) after drinking 37.5 g of Na-D/L-3-OHB dissolved in 500 mL of distilled water (KET), and (ii) after drinking 500 mL of placebo saline water (0.9% NaCl) (CTR). During the KET trial, 3-OHB levels increased to approximately 2.5 mM. Testosterone levels decreased significantly by 20% during KET compared to 3% during CTR. A simultaneous increase in luteinizing hormone was observed in KET. We observed no changes in other adrenal androgens, such as androstenedione and 11-keto androgens. In conclusion, an acute increase in 3-OHB levels decreases testosterone levels. Concomitantly, an increase in luteinizing hormone was observed. This suggests that 3-OHB may counteract some of the beneficial effects of endurance training. Further studies, involving larger sample sizes and performance outcomes, are required to fully understand this phenomenon.

Investigating effects of sodium beta-hydroxybutyrate on metabolism in placebo-controlled, bilaterally infused human leg with focus on skeletal muscle protein dynamics.

Systemic administration of beta-hydroxybutyrate (BHB) decreases whole-body protein oxidation and muscle protein breakdown in humans. We aimed to determine any direct effect of BHB on skeletal muscle protein turnover when administered locally in the femoral artery. Paired design with each subject being investigated on one single occasion with one leg being infused with BHB and the opposing leg acting as a control. We studied 10 healthy male volunteers once with bilateral femoral vein and artery catheters. One artery was perfused with saline (Placebo) and one with sodium-BHB. Labelled phenylalanine and palmitate were used to assess local leg fluxes. Femoral vein concentrations of BHB were significantly higher in the intervention leg (3.4 (3.2, 3.6) mM) compared with the placebo-controlled leg (1.9 (1.8, 2.1) mM) with a peak difference of 1.4 (1.1, 1.7) mM, p < 0.0005. Net loss of phenylalanine for BHB vs Placebo -6.7(-10.8, -2.7) nmol/min vs -8.7(-13.8, -3.7) nmol/min, p = 0.52. Palmitate flux and arterio-venous difference of glucose did not differ between legs. Under these experimental conditions, we failed to observe the direct effects of BHB on skeletal muscle protein turnover. This may relate to a combination of high concentrations of BHB (close to 2 mM) imposed systemically by spillover leading to high BHB concentrations in the saline-infused leg and a lack of major differences in concentration gradients between the two sides-implying that observations were made on the upper part of the dose-response curve for BHB and the relatively small number of subjects studied.

Hypokalemic Paresis in a 26-Year-Old Man After Recreational Cannabis Use.

BACKGROUND Hypokalemia (serum potassium level below 3.5 mmol/L) is present in approximately 11% of patients admitted to emergency departments. Hypokalemia can be a manifestation of many underlying causes and if untreated can be fatal. A careful approach to work-up and management is required in hypokalemic patients. CASE REPORT Here we report a 26-year-old previously healthy male patient who was admitted to the Emergency Department with rapidly progressing paresis of the lower and upper extremities. Initial laboratory results revealed severe hypokalemia of 2.1 mmol/l, which aggravated to 1.6 mmol/l before receiving treatment with intravenous potassium chloride supplementation. In addition, the patient developed rhabdomyolysis secondary to prolonged paralysis and immobilization induced by hypokalemia. Following this treatment, the patient's symptoms eased rapidly, and his potassium concentration was normalized. The patient admitted to smoking cannabis the day before admission. In this case report, we systematically elaborate and exclude the causes of hypokalemia in this otherwise healthy young adult, including medication, gastrointestinal symptoms, licorice consumption, and genetical testing. Cannabis has been associated with hypokalemia, proposedly through activation of the cannabinoid receptor 1 (CB1)-mediated activation of G protein-coupled inwardly rectifying potassium (GIRK) channels. CONCLUSIONS This case report emphasizes that hypokalemia can cause paralysis and cannabis should be included in the diagnostic mindset.

A macrophage-hepatocyte glucocorticoid receptor axis coordinates fasting ketogenesis.

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.

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.

Impact of Acutely Increased Endogenous- and Exogenous Ketone Bodies on FGF21 Levels in Humans.

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).

A Human Randomized Controlled Trial Comparing Metabolic Responses to Single and Repeated Hypoglycemia in Type 1 Diabetes.

AIMS: Hypoglycemia hinders optimal glycemic management in type 1 diabetes (T1D). Long diabetes duration and hypoglycemia impair hormonal counter-regulatory responses to hypoglycemia. Our study was designed to test whether (1) the metabolic responses and insulin sensitivity are impaired, and (2) whether they are affected by short-lived antecedent hypoglycemia in participants with T1D. MATERIALS AND METHODS: In a randomized, crossover, 2x2 factorial design, 9 male participants with T1D and 9 comparable control participants underwent 30 minutes of hypoglycemia (p-glucose < 2.9 mmol/L) followed by a euglycemic clamp on 2 separate interventions: with and without 30 minutes of hypoglycemia the day before the study day. RESULTS: During both interventions insulin sensitivity was consistently lower, while counter-regulatory hormones were reduced, with 75% lower glucagon and 50% lower epinephrine during hypoglycemia in participants with T1D, who also displayed 40% lower lactate and 5- to 10-fold increased ketone body concentrations following hypoglycemia, whereas palmitate and glucose turnover, forearm glucose uptake, and substrate oxidation did not differ between the groups. In participants with T1D, adipose tissue phosphatase and tensin homolog (PTEN) content, hormone-sensitive lipase (HSL) phosphorylation, and muscle glucose transporter type 4 (GLUT4) content were decreased compared with controls. And antecedent hypoglycemic episodes lasting 30 minutes did not affect counter-regulation or insulin sensitivity. CONCLUSIONS: Participants with T1D displayed insulin resistance and impaired hormonal counter-regulation during hypoglycemia, whereas glucose and fatty acid fluxes were intact and ketogenic responses were amplified. We observed subtle alterations of intracellular signaling and no effect of short-lived antecedent hypoglycemia on subsequent counter-regulation. This plausibly reflects the presence of insulin resistance and implies that T1D is a condition with defective hormonal but preserved metabolic responsiveness to short-lived hypoglycemia.

Oral D/L-3-Hydroxybutyrate Stimulates Cholecystokinin and Insulin Secretion and Slows Gastric Emptying in Healthy Males.

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.

Effects of protein intake prior to carbohydrate-restricted endurance exercise: a randomized crossover trial.

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.

Effects of ß-hydroxybutyrate on cognition in patients with type 2 diabetes.

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 ß-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 (ß-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, ß-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 < 0.001) corresponding to a 17% increase in performance during ketone infusion compared to placebo. There was no change for global cognitive performance or any other cognitive measure after adjusting for multiple comparisons. Blood concentrations of ß-hydroxybutyrate and glycaemic status did not associate with test performance; however, insulin resistance measured by HOMA was related to improved working memory performance during ketone infusion (ß = 4%; 95% CI: 1.1, 7.7; 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.

Licorice induced pseudohyperaldosteronism, severe hypertension, and long QT.

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 <3 mmol/L and present ECG changes should be treated with potassium intravenously. 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.

[Acute renal failure in a healthy 19-year-old woman after intake of 7 g of paracetamol].

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.

Soluble CD163 correlates with lipid metabolic adaptations in type 1 diabetes patients during ketoacidosis.

INTRODUCTION: 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 patients during mild DKA. MATERIALS AND METHODS: We investigated nine patients with type 1 diabetes twice during: (i) euglycemic control conditions and a bolus of saline; and (ii) hyperglycemic ketotic conditions induced by lipopolysaccharide 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 after lipopolysaccharide exposure (P < 0.001). Concentrations of sCD163 were positively correlated with plasma concentrations of free fatty acids, palmitate rate of appearance and lipid oxidation rates, and negatively correlated to the expression of G0/G1 switch 2 gene messenger ribonucleic acid content in adipose tissue (P < 0.01 for all). Furthermore, sCD163 levels correlated positively with plasma peak concentrations of cortisol, glucagon, tumor necrosis factor-α, interleukin-6 and interleukin-10 (P < 0.01 for all). Data on lipolysis and inflammation have previously been published. CONCLUSIONS: Macrophage activation assessed by sCD163 might play an important role in DKA, as it correlates strongly with important components of lipid metabolism including free fatty acids, palmitate, lipid oxidation, G0/G1 switch 2 gene and pro-inflammatory cytokines during initial steps of DKA. These results are novel and add important knowledge to the field of DKA.

Substrate metabolism, hormone and cytokine levels and adipose tissue signalling in individuals with type 1 diabetes after insulin withdrawal and subsequent insulin therapy to model the initiating steps of ketoacidosis.

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.

A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects.

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.

Regional cerebral effects of ketone body infusion with 3-hydroxybutyrate in humans: Reduced glucose uptake, unchanged oxygen consumption and increased blood flow by positron emission tomography. A randomized, controlled trial.

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.

Macrophage activation marker sCD163 correlates with accelerated lipolysis following LPS exposure: a human-randomised clinical trial.

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 < 0.001), and sCD163 concentrations correlated positively with the plasma concentration of free fatty acids, Rapalmitate, lipid oxidation rates and phosphorylation of the hormone-sensitive lipase at serine 660 in adipose tissue (P < 0.05, all). Furthermore, sCD163 concentrations correlated positively with plasma concentrations of cortisol, glucagon, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 (P < 0.05, all). 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.