Cardiovascular Effects of Treatment With the Ketone Body 3-Hydroxybutyrate in Chronic Heart Failure Patients

Supplemental Digital Content is available in the text.

Background:

Myocardial utilization of 3-hydroxybutyrate (3-OHB) is increased in patients with heart failure and reduced ejection fraction (HFrEF). However, the cardiovascular effects of increased circulating plasma-3-OHB levels in these patients are unknown. Consequently, the authors’ aim was to modulate circulating 3-OHB levels in HFrEF patients and evaluate: (1) changes in cardiac output (CO); (2) a potential dose-response relationship between 3-OHB levels and CO; (3) the impact on myocardial external energy efficiency (MEE) and oxygen consumption (MVO₂); and (4) whether the cardiovascular response differed between HFrEF patients and age-matched volunteers.

Methods:

Study 1: 16 chronic HFrEF patients (left ventricular ejection fraction: 37±3%) were randomized in a crossover design to 3-hour of 3-OHB or placebo infusion. Patients were monitored invasively with a Swan-Ganz catheter and with echocardiography. Study 2: In a dose-response study, 8 HFrEF patients were examined at increasing 3-OHB infusion rates. Study 3 to 4: 10 HFrEF patients and 10 age-matched volunteers were randomized in a crossover design to 3-hour 3-OHB or placebo infusion. MEE and MVO₂ were evaluated using 11C-acetate positron emission tomography.

Results:

3-OHB infusion increased circulating levels of plasma 3-OHB from 0.4±0.3 to 3.3±0.4 mM (P<0.001). CO rose by 2.0±0.2 L/min (P<0.001) because of an increase in stroke volume of 20±2 mL (P<0.001) and heart rate of 7±2 beats per minute (bpm) (P<0.001). Left ventricular ejection fraction increased 8±1% (P<0.001) numerically. There was a dose-response relationship with a significant CO increase of 0.3 L/min already at plasma-3-OHB levels of 0.7 mM (P<0.001). 3-OHB increased MVO₂ without altering MEE. The response to 3-OHB infusion in terms of MEE and CO did not differ between HFrEF patents and age-matched volunteers.

Conclusions:

3-OHB has beneficial hemodynamic effects in HFrEF patients without impairing MEE. These beneficial effects are detectable in the physiological concentration range of circulating 3-OHB levels. The hemodynamic effects of 3-OHB were observed in both HFrEF patients and age-matched volunteers. 3-OHB may potentially constitute a novel treatment principle in HFrEF patients.

Ketone Body Infusion With 3-Hydroxybutyrate Reduces Myocardial Glucose Uptake and Increases Blood Flow in Humans: A Positron Emission Tomography Study

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 ¹⁵O-H₂O positron emission tomography/computed tomography, myocardial fatty acid metabolism by ¹¹C-palmitate positron emission tomography/computed tomography and MGU by ¹⁸F-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<0.01), whereas no effects were observed on palmitate uptake oxidation or esterification. Hyperketonemia increased heart rate by ≈25% and myocardial blood flow by 75%.

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.

Clinical Use of Coronary CTA-Derived FFR for Decision-Making in Stable CAD

OBJECTIVES

The goal of this study was to assess the real-world clinical utility of fractional flow reserve (FFR) derived from coronary computed tomography angiography (FFR_CT) for decision-making in patients with stable coronary artery disease (CAD).

BACKGROUND

FFR_CT has shown promising results in identifying lesion-specific ischemia. The real-world feasibility and influence on the diagnostic work-up of FFR_CT testing in patients suspected of having CAD are unknown.

METHODS

We reviewed the complete diagnostic work-up of nonemergent patients referred for coronary computed tomography angiography over a 12-month period at Aarhus University Hospital, Denmark, including all patients with new-onset chest pain with no known CAD and with intermediate-range coronary lesions (lumen reduction, 30% to 70%) referred for FFR_CT. The study evaluated the consequences on downstream diagnostic testing, the agreement between FFR_CT and invasively measured FFR or instantaneous wave-free ratio (iFR), and the short-term clinical outcome after FFR_CT testing.

RESULTS

Among 1,248 patients referred for computed tomography angiography, 189 patients (mean age 59 years; 59% male) were referred for FFR_CT, with a conclusive FFR_CT result obtained in 185 (98%). FFR_CT was ≤0.80 in 31% of patients and 10% of vessels. After FFR_CT testing, invasive angiography was performed in 29%, with FFR measured in 19% and iFR in 1% of patients (with a tendency toward declining FFR-iFR guidance during the study period). FFR_CT ≤0.80 correctly classified 73% (27 of 37) of patients and 70% (37 of 53) of vessels using FFR ≤0.80 or iFR ≤0.90 as the reference standard. In patients with FFR_CT >0.80 being deferred from invasive coronary angiography, no adverse cardiac events occurred during a median follow-up period of 12 (range 6 to 18 months) months.

CONCLUSIONS

FFR_CT testing is feasible in real-world symptomatic patients with intermediate-range stenosis determined by coronary computed tomography angiography. Implementation of FFR_CT for clinical decision-making may influence the downstream diagnostic workflow of patients. Patients with an FFR_CT value >0.80 being deferred from invasive coronary angiography have a favorable short-term prognosis.

In Vivo Imaging of Human 11C-Metformin in Peripheral Organs: Dosimetry, Biodistribution, and Kinetic Analyses

Metformin is the most widely prescribed oral antiglycemic drug, with few adverse effects. However, surprisingly little is known about its human biodistribution and target tissue metabolism. In animal experiments, we have shown that metformin can be labeled by ¹¹C and that ¹¹C-metformin PET can be used to measure renal function. Here, we extend these preclinical findings by a first-in-human ¹¹C-metformin PET dosimetry, biodistribution, and tissue kinetics study.

METHODS

Nine subjects (3 women and 6 men) participated in 2 studies: in the first study, human radiation dosimetry and biodistribution of ¹¹C-metformin were estimated in 4 subjects (2 women and 2 men) by whole-body PET. In the second study, ¹¹C-metformin tissue kinetics were measured in response to both intravenous and oral radiotracer administration. A dynamic PET scan with a field of view covering target tissues of metformin (liver, kidneys, intestines, and skeletal muscle) was obtained for 90 (intravenous) and 120 (oral) min.

RESULTS

Radiation dosimetry was acceptable, with effective doses of 9.5 μSv/MBq (intravenous administration) and 18.1 μSv/MBq (oral administration). Whole-body PET revealed that ¹¹C-metformin was primarily taken up by the kidneys, urinary bladder, and liver but also to a lesser extent in salivary glands, skeletal muscle, and intestines. Reversible 2-tissue-compartment kinetics was observed in the liver, and volume of distribution was calculated to be 2.45 mL/mL (arterial input) or 2.66 mL/mL (portal and arterial input). In the kidneys, compartmental models did not adequately fit the experimental data, and volume of distribution was therefore estimated by a linear approach to be 6.83 mL/mL. Skeletal muscle and intestinal tissue kinetics were best described by 2-tissue-compartment kinetics and showed only discrete tracer uptake. Liver ¹¹C-metformin uptake was pronounced after oral administration of the tracer, with tissue-to-blood ratio double what was observed after intravenous administration. Only slow accumulation of ¹¹C-metformin was observed in muscle. There was no elimination of ¹¹C-metformin through the bile both during the intravenous and during the oral part of the study.

CONCLUSION

¹¹C-metformin is suitable for imaging metformin uptake in target tissues and may prove a valuable tool to assess the impact of metformin treatment in patients with varying metformin transport capacity.

A dual tracer (68)Ga-DOTANOC PET/CT and (18)F-FDG PET/CT pilot study for detection of cardiac sarcoidosis

Background

Cardiac sarcoidosis (CS) is a potentially fatal condition lacking a single test with acceptable diagnostic accuracy. ¹⁸F-FDG PET/CT has emerged as a promising imaging modality, but is challenged by physiological myocardial glucose uptake. An alternative tracer, ⁶⁸Ga-DOTANOC, binds to somatostatin receptors on inflammatory cells in sarcoid granulomas. We therefore aimed to conduct a proof-of-concept study using ⁶⁸Ga-DOTANOC to diagnose CS. In addition, we compared diagnostic accuracy and inter-observer variability of ⁶⁸Ga-DOTANOC vs. ¹⁸F-FDG PET/CT.

Methods

Nineteen patients (seven female) with suspected CS were prospectively recruited and dual tracer scanned within 7 days. PET images were reviewed by four expert readers for signs of CS and compared to the reference standard (Japanese ministry of Health and Welfare CS criteria).

Results

CS was diagnosed in 3/19 patients. By consensus, 11/19 ¹⁸F-FDG scans and 0/19 ⁶⁸Ga-DOTANOC scans were rated as inconclusive. The sensitivity of ¹⁸F-FDG PET for diagnosing CS was 33 %, specificity was 88 %, PPV was 33 %, NPV was 88 %, and diagnostic accuracy was 79 %. For ⁶⁸Ga-DOTANOC, accuracy was 100 %. Inter-observer agreement was poor for ¹⁸F-FDG PET (Fleiss’ combined kappa 0.27, NS) and significantly better for ⁶⁸Ga-DOTANOC (Fleiss’ combined kappa 0.46, p = 0.001).

Conclusions

Despite prolonged pre-scan fasting, a large proportion of ¹⁸F-FDG PET/CT images were rated as inconclusive, resulting in low agreement among reviewers and correspondingly poor diagnostic accuracy. By contrast, ⁶⁸Ga-DOTANOC PET/CT had excellent diagnostic accuracy with the caveat that inter-observer variability was still significant. Nevertheless, ⁶⁸Ga-DOTANOC PET/CT looks very promising as an alternative CS PET tracer.

Trial registration

Current Controlled Trials NCT01729169.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-016-0207-6) contains supplementary material, which is available to authorized users.

Ghrelin receptor agonist (TZP-101) accelerates gastric emptying in adults with diabetes and symptomatic gastroparesis

BACKGROUND

TZP-101 is a synthetic, selective ghrelin agonist in development for gastroparesis.

AIM

To assess safety and effects of TZP-101 in diabetes patients with symptomatic gastroparesis.

METHODS

Adults with type 1 or type 2 diabetes mellitus received placebo and TZP-101 (80, 160, 320 or 600 microg/kg) infusions in a cross-over manner following a radiolabelled meal. Blood glucose levels were stabilized using a hyperinsulinemic-euglycemic clamp. Primary endpoints were gastric half emptying and latency times. Secondary measures included assessment of gastroparesis symptoms and endocrine responses.

RESULTS

Ten patients with type 1 (n = 7) or 2 (n = 3) diabetes, moderate-to-severe gastroparesis symptoms and > or =29% retention 4 h after a radiolabelled solid meal were enrolled. TZP-101 produced significant reductions in solid meal half-emptying (20%, P = 0.043) and latency (34%, P = 0.037) times vs. placebo. Reductions in overall postmeal symptom intensity (24%) and postprandial fullness (37%) following TZP-101 infusion were not statistically significant. Most adverse events were mild and self-limiting and there were no identifiable differences in numbers or types of adverse events between TZP-101 and placebo.

CONCLUSIONS

This proof-of-concept study demonstrates that the ghrelin agonist TZP-101 is well-tolerated in diabetes patients with moderate-to-severe chronic gastroparesis and shows statistically significant improvements in gastric emptying.

Safety and efficacy of ghrelin agonist TZP-101 in relieving symptoms in patients with diabetic gastroparesis: a randomized, placebo-controlled study

BACKGROUND

Gastroparesis, a chronic disorder of abnormal gastric motility, is common in patients with diabetes mellitus. A synthetic, selective ghrelin receptor agonist, TZP-101, is in clinical development for treatment of gastroparesis. This double-blind, randomized, placebo-controlled study evaluated the safety and efficacy of multiple TZP-101 doses in patients with moderate to severe symptomatic diabetic gastroparesis.

METHODS

Patients were admitted to the hospital and adaptively randomized to receive a single 30-min intravenous infusion of 20, 40, 80, 160, 320, or 600 μg kg(-1) TZP-101, (n = 57) or placebo, (n = 19) for four consecutive days. Symptoms were evaluated daily with the patient-rated Gastroparesis Cardinal Symptom Index (GCSI) and Gastroparesis Symptom Assessment (GSA). Clinicians rated gastroparesis symptoms on treatment day 4.

KEY RESULTS

  The 80 μg kg(-1) dose was identified as the most effective dose. On day 4, there was statistically significant improvement compared with placebo in the severity of GCSI Loss of Appetite and Vomiting scores for that dose group (P = 0.034 and P = 0.006). In addition, at the 80 μg kg(-1) dose, the proportion of patients with at least 50% improvement in vomiting score was significantly different (P = 0.019) compared with placebo. Meal-related GSA scores for Postprandial fullness were significantly improved in the 80 μg kg(-1) TZP-101 group compared with placebo (P = 0.012). Clinicians rated the 80 μg kg(-1) group better improved than placebo for overall symptom assessment (P = 0.047). Safety profiles were similar in the placebo and TZP-101 groups and all doses were well-tolerated.

CONCLUSIONS & INFERENCES

TZP-101 appears to be safe, well-tolerated, and effective at acutely addressing several gastroparesis symptoms.

Limitations and Pitfalls of FDG-PET/CT in Infection and Inflammation

White blood cells activated by either a pathogen or as part of a systemic inflammatory disease are characterized by high energy consumption and are therefore taking up the glucose analogue PET tracer FDG avidly. It is therefore not surprising that a steadily growing body of research and clinical reports now supports the use of FDG PET/CT to diagnose a wide range of patients with non-oncological diseases. However, using FDG PET/CT in patients with infectious or inflammatory diseases has some limitations and potential pitfalls that are not necessarily as pronounced in oncology FDG PET/CT. Some of these limitations are of a general nature and related to the laborious acquisition of PET images in patients that are often acutely ill, whereas others are more disease-specific and related to the particular metabolism in some of the organs most commonly affected by infections or inflammatory disease. Both inflammatory and infectious diseases are characterized by a more diffuse and less pathognomonic pattern of FDG uptake than oncology FDG PET/CT and the affected organs also typically have some physiological FDG uptake. In addition, patients referred to PET/CT with suspected infection or inflammation are rarely treatment naïve and may have received varying doses of antibiotics, corticosteroids or other immune-modulating drugs at the time of their examination. Combined, this results in a higher rate of false positive FDG findings and also in some cases a lower sensitivity to detect active disease. In this review, we therefore discuss the limitations and pitfalls of FDG PET/CT to diagnose infections and inflammation taking these issues into consideration. Our review encompasses the most commonly encountered inflammatory and infectious diseases in head and neck, in the cardiovascular system, in the abdominal organs and in the musculoskeletal system. Finally, new developments in the field of PET/CT that may help overcome some of these limitations are briefly highlighted.

Growth hormone-induced insulin resistance is associated with increased intramyocellular triglyceride content but unaltered VLDL-triglyceride kinetics

The ability of growth hormone (GH) to stimulate lipolysis and cause insulin resistance in skeletal muscle may be causally linked, but the mechanisms remain obscure. We investigated the impact of GH on the turnover of FFA and VLDL-TG, intramuscular triglyceride content (IMTG), and insulin sensitivity (euglycemic clamp) in nine healthy men in a randomized double-blind placebo-controlled crossover study after 8 days treatment with (A) Placebo+Placebo, (B) GH (2 mg daily)+Placebo, and (C) GH (2 mg daily)+Acipimox (250 mgx3 daily). In the basal state, GH (B) increased FFA levels (P<0.05), palmitate turnover (P<0.05), and lipid oxidation (P=0.05), but VLDL-TG kinetics were unaffected. Administration of acipimox (C) suppressed basal lipolysis but did not influence VLDL-TG kinetics. In the basal state, IMTG content increased after GH (B; P=0.03). Insulin resistance was induced by GH irrespective of concomitant acipimox (P<0.001). The turnover of FFA and VLDL-TG was suppressed by hyperinsulinemia during placebo and GH, whereas coadministration of acipimox induced a rebound increase FFA turnover and VLDL-TG clearance. We conclude that these results show that GH-induced insulin resistance is associated with increased IMTG and unaltered VLDL-TG kinetics; we hypothesize that fat oxidation in muscle tissue is an important primary effect of GH and that circulating FFA rather than VLDL-TG constitute the major source for this process; and the role of IMTG in the development of GH-induced insulin resistance merits future research.

FDG-PET/CT in the management of lymphomas: current status and future directions

FDG-PET/CT is the current state-of-the-art imaging in lymphoma and plays a central role in treatment decisions. At diagnosis, accurate staging is crucial for appropriate therapy selection: FDG-PET/CT can identify areas of lymphoma missed by CT alone and avoid under-treatment of patients with advanced disease stage who would have been misclassified as having limited stage disease by CT. Particularly in Hodgkin lymphoma, positive interim FDG-PET/CT scans are adversely prognostic for clinical outcomes and can inform PET-adapted treatment strategies, but such data are less consistent in diffuse large B-cell lymphoma. The use of quantitative FDG-PET/CT metrics using metabolic tumour volume, possibly in combination with other biomarkers, may better define prognostic subgroups and thus facilitate better treatment selection. After chemotherapy, FDG-PET/CT response is predictive of outcome and may identify a subgroup who benefit from consolidative radiotherapy. Novel therapies, in particular immunotherapies, exhibit different response patterns than conventional chemotherapy, which has led to modified response criteria that take into account the risk of transient pseudo-progression. In relapsed lymphoma, FDG-PET/CT after second-line therapy and prior to high-dose therapy is also strongly associated with outcome and may be used to guide intensity of salvage therapy in relapsed Hodgkin lymphoma. Currently, FDG-PET/CT has no role in the routine follow-up after complete metabolic response to therapy, but it remains a powerful tool for excluding relapse if patients develop clinical features suggestive of disease relapse. In conclusion, FDG-PET/CT plays major roles in the various phases of management of lymphoma and constitutes a step towards the pursuit of personalized treatment.

Human skeletal muscle CD90+ fibro-adipogenic progenitors are associated with muscle degeneration in type 2 diabetic patients

Type 2 diabetes mellitus (T2DM) is associated with impaired skeletal muscle function and degeneration of the skeletal muscles. However, the mechanisms underlying the degeneration are not well described in human skeletal muscle. Here we show that skeletal muscle of T2DM patients exhibit degenerative remodeling of the extracellular matrix that is associated with a selective increase of a subpopulation of fibro-adipogenic progenitors (FAPs) marked by expression of THY1 (CD90)-the FAP^CD90+. We identify platelet-derived growth factor (PDGF) as a key FAP regulator, as it promotes proliferation and collagen production at the expense of adipogenesis. FAPs^CD90+ display a PDGF-mimetic phenotype, with high proliferative activity, clonogenicity, and production of extracellular matrix. FAP^CD90+ proliferation was reduced by in vitro treatment with metformin. Furthermore, metformin treatment reduced FAP content in T2DM patients. These data identify a PDGF-driven conversion of a subpopulation of FAPs as a key event in the fibrosis development in T2DM muscle.

Genetic Polymorphisms in Organic Cation Transporter 1 Attenuates Hepatic Metformin Exposure in Humans

Metformin has been used successfully to treat type 2 diabetes for decades. However, the efficacy of the drug varies considerably from patient to patient and this may in part be due to its pharmacokinetic properties. The aim of this study was to examine if common polymorphisms in SLC22A1, encoding the transporter protein OCT1, affect the hepatic distribution of metformin in humans. We performed noninvasive ¹¹ C-metformin positron emission tomography (PET)/computed tomography (CT) to determine hepatic exposure in 12 subjects genotyped for variants in SLC22A1. Hepatic distribution of metformin was significantly reduced after oral intake in carriers of M420del and R61C variants in SLC22A1 without being associated with changes in circulating levels of metformin. Our data show that genetic polymorphisms in transporter proteins cause variation in hepatic exposure to metformin, and it demonstrates the application of novel imaging techniques to investigate pharmacogenetic properties in humans.

[11C]-Labeled Metformin Distribution in the Liver and Small Intestine Using Dynamic Positron Emission Tomography in Mice Demonstrates Tissue-Specific Transporter Dependency

Metformin is the most commonly prescribed oral antidiabetic drug, with well-documented beneficial preventive effects on diabetic complications. Despite being in clinical use for almost 60 years, the underlying mechanisms for metformin action remain elusive. Organic cation transporters (OCT), including multidrug and toxin extrusion proteins (MATE), are essential for transport of metformin across membranes, but tissue-specific activity of these transporters in vivo is incompletely understood. Here, we use dynamic positron emission tomography with [(11)C]-labeled metformin ([(11)C]-metformin) in mice to investigate the role of OCT and MATE in a well-established target tissue, the liver, and a putative target of metformin, the small intestine. Ablation of OCT1 and OCT2 significantly reduced the distribution of metformin in the liver and small intestine. In contrast, inhibition of MATE1 with pyrimethamine caused accumulation of metformin in the liver but did not affect distribution in the small intestine. The demonstration of OCT-mediated transport into the small intestine provides evidence of direct effects of metformin in this tissue. OCT and MATE have important but separate roles in uptake and elimination of metformin in the liver, but this is not due to changes in biliary secretion. [(11)C]-Metformin holds great potential as a tool to determine the pharmacokinetic properties of metformin in clinical studies.

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.

Growth hormone signaling in vivo in human muscle and adipose tissue: impact of insulin, substrate background, and growth hormone receptor blockade

CONTEXT

GH induces insulin resistance in muscle and fat, and in vitro data indicate that this may involve cross-talk between the signaling pathways of the two hormones.

OBJECTIVE

Our objective was to investigate GH and insulin signaling in vivo in human muscle and fat tissue in response to GH, GH receptor blockade, and insulin stimulation.

DESIGN

We conducted two randomized crossover studies.

PARTICIPANTS

Sixteen healthy males participated.

INTERVENTION

GH was administered as a bolus (n = 8) and constant infusion (n = 8). The bolus study included three arms: 1) control (saline), 2) GH (0.5 mg iv), and 3) GH blockade (pegvisomant 30 mg sc), each combined with a hyperinsulinemic glucose clamp. The infusion study included two arms: 1) GH infusion (45 ng/.kg.min, 5.5 h) and 2) saline infusion (5.5 h) combined with a hyperinsulinemic glucose clamp during the final 2.5 h.

MAIN OUTCOME MEASURES

Muscle and fat biopsies were subjected to Western blotting for expression of Stat5/p-Stat5, Akt/p-Akt, and ERK1/2/p-ERK1/2 and to real-time RT-PCR for expression of SOCS1-3 and IGF-I mRNA.

RESULTS

GH significantly reduced insulin sensitivity. The GH bolus as well as GH infusion induced phosphorylation of Stat5 in muscle and fat, and SOCS3 and IGF-I mRNA expression increased after GH infusion. Hyperinsulinemia induced Akt phosphorylation in both tissues, irrespective of GH status. In muscle, ERK1/2 phosphorylation was increased by insulin, but insulin per se did not induce phosphorylation of Stat5.

CONCLUSIONS

GH exposure associated with insulin resistance acutely translates into GH receptor signaling in human muscle and fat without evidence of cross-talk with insulin signaling pathways. The molecular mechanisms subserving GH-induced insulin resistance in humans remain unclarified.

Dose-response effects of free fatty acids on glucose and lipid metabolism during somatostatin blockade of growth hormone and insulin in humans

CONTEXT

GH and other stress hormones stimulate lipolysis, which may result in free fatty acid (FFA)-mediated insulin resistance. However, there are also indications that FFAs in the very low physiological range have the same effect.

OBJECTIVE

The objective of the study was to address systematically the dose-response relations between FFAs and insulin sensitivity.

DESIGN

We therefore examined eight healthy men for 8 h (6 h basal and 2 h glucose clamp) on four occasions.

INTERVENTION

Intralipid was infused at varying rates (0, 3, 6, 12 microl.kg(-1).min(-1)); lipolysis was blocked by acipimox; and endogenous GH, insulin, and glucagon secretion was blocked by somatostatin and subsequently replaced at fixed rates.

RESULTS

This resulted in four different FFA levels between 50 and 2000 micromol/liter, with comparable levels of insulin and counterregulatory hormones. Both in the basal state and during insulin stimulation, we saw progressively decreased glucose disposal, nonoxidative glucose disposal, and forearm muscle glucose uptake at FFA levels above 500 micromol/liter. Apart from forearm glucose uptake, the very same parameters were decreased at low FFA levels (approximately 50 micromol/liter). FFA rate of disposal was linearly related to the level of FFAs, whereas lipid oxidation reached a maximum at FFA levels approximately 1000 micromol/liter.

CONCLUSION

In the presence of comparable levels of all major metabolic hormones, insulin sensitivity peaks at physiological levels of FFAs with a gradual decrease at elevated as well as suppressed FFA concentrations. These data constitute comprehensive dose-response curves for FFAs in the full physiological range from close to zero to above 2000 micromol/liter.

Bile acid malabsorption investigated by selenium-75-homocholic acid taurine ((75)SeHCAT) scans: causes and treatment responses to cholestyramine in 298 patients with chronic watery diarrhoea

BACKGROUND

The liver produces and secretes bile acids into the small intestine. In the small intestine, most of the bile acids are absorbed in the distal ileum with portal vein transportation back to the liver and resecretion (enterohepatic recycling). Increased spillover of bile acids from the small intestine into the colon (bile acid malabsorption) may affect the secretion of colonic water and electrolytes and result in watery diarrhoea. The aim of this study was to investigate the frequency of bile acid malabsorption and treatment responses to cholestyramine with (75)SeHCAT scanning among patients suffering from chronic watery diarrhoea.

METHODS

This was a retrospective study that included all patients who received a (75)SeHCAT scan over a five-year period (2004-2009).

RESULTS

In total, 298 patients (198 females, 100 men) with a median age of 42 years (range 16-82 years) were investigated. Bile acid malabsorption ((75)SeHCAT retention<15% after seven days) was identified in 201 patients (68%, 95% confidence interval (CI): 62%-73%). Bile acid malabsorption due to ileal dysfunction (Type I) was found in 77 patients, idiopathic bile acid malabsorption (Type II) was found in 68 patients and 56 patients with other conditions had bile acid malabsorption (Type III). Of the 150 patients who were able to take cholestyramine continuously, 108 patients (71%, CI: 63%-78%) reported a positive effect on their bowel habits.

CONCLUSIONS

Bile acid malabsorption is a frequent problem in patients with chronic watery diarrhoea. Treatment with bile acid binders was effective regardless of type and severity.

Metformin increases endogenous glucose production in non-diabetic individuals and individuals with recent-onset type 2 diabetes

AIMS/HYPOTHESIS

Metformin is the endorsed first-line glucose-lowering drug for treating patients with type 2 diabetes but despite more than 50 years of use, no consensus has been reached on its mechanisms of action. In this study, we investigated the glucose-lowering effects of metformin in individuals with type 2 diabetes and non-diabetic individuals.

METHODS

We performed a randomised, placebo-controlled trial in 24 individuals with recent-onset type 2 diabetes (diabetes duration 50 [48] months) who had good glycaemic control (HbA_1c 48 mmol/mmol [6.5%]). The studies were conducted at Aarhus University Hospital between 2013 and 2016. Participants were randomised to receive either metformin (2000 mg/day, n = 12, MET group) or placebo (n = 12, PLA group) for 90 days, using block randomisation set up by an unblinded pharmacist. Two participants withdrew from the study prior to completion and were replaced with two new participants receiving the same treatment. In addition, we recruited a group of non-diabetic individuals with similar age and BMI (n = 12, CONT group), who were all treated with 2000 mg metformin daily. Before and after treatment all individuals underwent studies of whole-body glucose metabolism by non-steady-state [3-³H]glucose kinetics, hyperinsulinaemic-euglycaemic clamping, indirect calorimetry, metabolomics, dual x-ray absorptiometry and muscle biopsies. The primary study endpoint was the effect of metformin treatment on lipid kinetics as well as glucose rate of disappearance (R_d) and endogenous glucose production (EGP).

RESULTS

One participant from the CONT group withdrew due to intolerable gastrointestinal side-effects and was excluded from analysis. As expected, metformin treatment lowered fasting plasma glucose (FPG) in the MET group (~1.5 mmol/l, p < 0.01), whereas no effect was observed in the PLA and CONT groups. Body weight and composition did not change in any of the groups. In both of the metformin-treated groups (MET and CONT), basal glucose R_d, EGP and glucagon levels increased by ~30% (p < 0.05) whereas this was not the case in the PLA group.

CONCLUSIONS/INTERPRETATION

Ninety days of metformin treatment resulted in similar increases in EGP and glucose R_d in individuals with recent-onset type 2 diabetes and in non-diabetic control individuals. These results challenge the existing paradigm that metformin primarily acts in the liver by inhibiting EGP, at least in individuals with type 2 diabetes of short duration and who have discretely affected glycaemic status. Whether metformin increases basal glucose R_d by facilitating glucose uptake in other tissues such as the intestines remains to be further clarified.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01729156 FUNDING: This study was supported by grants from The Danish Council for Independent Research | Medical Sciences, Aase Danielsen Fund, the Novo Nordisk Foundation, the Danish Diabetes Association and the Danish Diabetes Academy supported by the Novo Nordisk Foundation.

Basal and insulin mediated VLDL-triglyceride kinetics in type 2 diabetic men

OBJECTIVE

Increased very-low-density lipoprotein triglycerides (VLDL-TG) concentration is a central feature of diabetic dyslipidemia. The objective was to compare basal and insulin mediated VLDL-TG kinetics, oxidation, and adipose tissue storage in type 2 diabetic and healthy (nondiabetic) men.

RESEARCH DESIGN AND METHODS

Eleven type 2 diabetic and 11 healthy men, matched for BMI and age, were included. Ex vivo-labeled VLDL-TG tracers, blood and breath samples, fat biopsies, indirect calorimetry, and body composition measures were applied to determine VLDL-TG kinetics, VLDL-TG fatty acids (FA) oxidation, and storage in regional adipose tissue before and during a hyperinsulinemic euglycaemic clamp.

RESULTS

VLDL-TG secretion was significantly greater in diabetic compared with healthy men (basal: 86.9 [31.0] vs. 61.9 [30.0] μmol/min, P = 0.03; clamp: 60.0 [26.2] vs. 34.2 [17.9] μmol · min⁻¹, P = 0.01). The insulin mediated suppression of VLDL-TG secretion was significant in both groups. VLDL-TG clearance was lower in diabetic men (basal: 84.6 [32.7] vs. 115.4 [44.3] ml · min⁻¹, P = 0.08; clamp: 76.3 [30.6] vs. 119.0 [50.2] ml · min⁻¹, P = 0.03). During hyperinsulinemia fractional VLDL-TG FA oxidation was comparable, but in percentage of energy expenditure (EE), significantly higher in diabetic men. Basal VLDL-TG storage was similar, but significantly greater in abdominal compared with leg fat.

CONCLUSIONS

Increased VLDL-TG in type 2 diabetic men is caused by greater VLDL-TG secretion and less so by lower VLDL-TG clearance. The ability of hyperinsulinemia to suppress VLDL-TG secretion appears preserved. During hyperinsulinemia VLDL-TG FA oxidation is significantly increased in proportion of EE in type 2 diabetic men. Greater basal abdominal VLDL-TG storage may help explain the accumulation of upper-body fat in insulin-resistant individuals.

Effects of exercise on VLDL-triglyceride oxidation and turnover

Lipids are important substrates for oxidation at rest and during exercise. Aerobic exercise mediates a delayed onset decrease in total and VLDL-triglyceride (TG) plasma concentration. However, the acute effects of exercise on VLDL-TG oxidation and turnover remain unclear. Here, we studied the acute effects of 90 min of moderate-intensity exercise in healthy women and men. VLDL-TG kinetics were assessed using a primed constant infusion of ex vivo labeled [1-(14)C]triolein VLDL-TG. Fractional VLDL-TG-derived fatty acid oxidation was measured from (14)CO(2) specific activity in expired air. VLDL-TG concentration was unaltered during exercise and early recovery, whereas non-VLDL-TG concentration decreased significantly.VLDL-TG secretion rate decreased significantly during exercise and remained suppressed during recovery. Total VLDL-TG oxidation rate was unaffected by exercise. However, the contribution of VLDL-TG oxidation to total energy expenditure fell from 14 ± 9% at rest to 3 ± 4% during exercise. We conclude that VLDL-TG fatty acids are quantitatively important oxidative substrates under basal postabsorptive conditions but remain unaffected during 90-min moderate-intensity exercise and, thus, become relatively less important during exercise. Lower VLDL secretion rate during exercise may contribute to the decrease in TG concentrations during and after exercise.

SGLT2 Inhibition Does Not Affect Myocardial Fatty Acid Oxidation or Uptake, but Reduces Myocardial Glucose Uptake and Blood Flow in Individuals With Type 2 Diabetes: A Randomized Double-Blind, Placebo-Controlled Crossover Trial

Sodium-glucose cotransporter 2 (SGLT2) inhibition reduces cardiovascular morbidity and mortality in individuals with type 2 diabetes. Beneficial effects have been attributed to increased ketogenesis, reduced cardiac fatty acid oxidation, and diminished cardiac oxygen consumption. We therefore studied whether SGLT2 inhibition altered cardiac oxidative substrate consumption, efficiency, and perfusion. Thirteen individuals with type 2 diabetes were studied after 4 weeks' treatment with empagliflozin and placebo in a randomized, double-blind, placebo-controlled crossover study. Myocardial palmitate and glucose uptake were measured with ¹¹C-palmitate and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT). Oxygen consumption and myocardial external efficiency (MEE) were measured with ¹¹C-acetate PET/CT. Resting and adenosine stress myocardial blood flow (MBF) and myocardial flow reserve (MFR) were measured using ¹⁵O-H₂O PET/CT. Empagliflozin did not affect myocardial free fatty acids (FFAs) uptake but reduced myocardial glucose uptake by 57% (P < 0.001). Empagliflozin did not change myocardial oxygen consumption or MEE. Empagliflozin reduced resting MBF by 13% (P < 0.01), but did not significantly affect stress MBF or MFR. In conclusion, SGLT2 inhibition did not affect myocardial FFA uptake, but channeled myocardial substrate utilization from glucose toward other sources and reduced resting MBF. However, the observed metabolic and hemodynamic changes were modest and most likely contribute only partially to the cardioprotective effect of SGLT2 inhibition.

Free fatty acids decrease circulating ghrelin concentrations in humans

OBJECTIVE

Concentrations of the orexigenic peptide ghrelin is affected by a number of hormones, which also affect circulating levels of free fatty acids (FFAs). The present study was therefore designed to determine the direct effect of FFAs on circulating ghrelin.

DESIGN

Eight lean, healthy men were examined for 8 h on four occasions using variable infusion rates (0, 3, 6 and 12 microl/kg per min) of intralipid to create different plasma FFA concentrations. Constant levels of insulin and GH were obtained by administration of acipimox (250 mg) and somatostatin (300 microg/h). At the end of each study day a hyperinsulinaemic-euglycaemic clamp was performed.

RESULTS

Four distinct levels of FFAs were obtained at the end of the lipid infusion period (FFA(LIPID): 0.03 +/- 0.00 vs: 0.49 +/- 0.04, 0.92 +/- 0.08 and 2.09 +/- 0.38 mmol/l; ANOVA P < 0.0001) and during hyperinsulinaemia (FFA(LIPID+INSULIN): 0.02 +/- 0.00 vs: 0.34 +/- 0.03, 0.68 +/- 0.09 and 1.78 +/- 0.32 mmol/l; ANOVA P < 0.0001). Whereas, somatostatin infusion alone reduced ghrelin concentration by approximately 67%, concomitant administration of increasing amounts of intralipid reduced circulating ghrelin by a further 14, 19 and 19% respectively (change in ghrelin: 0.52 +/- 0.05 vs: 0.62 +/- 0.06, 0.72 +/- 0.09 and 0.71 +/- 0.05 microg/l; ANOVA P = 0.04). No further reduction in ghrelin concentration was observed during hyperinsulinaemia.

CONCLUSION

FFA exposure between 0 and 1 mmol/l significantly suppresses ghrelin levels independent of ambient GH and insulin levels.

Metformin targets brown adipose tissue in vivo and reduces oxygen consumption in vitro

AIMS

To test the hypothesis that brown adipose tissue (BAT) is a metformin target tissue by investigating in vivo uptake of [¹¹ C]-metformin tracer in mice and studying in vitro effects of metformin on cultured human brown adipocytes.

MATERIALS AND METHODS

Tissue-specific uptake of metformin was assessed in mice by PET/CT imaging after injection of [¹¹ C]-metformin. Human brown adipose tissue was obtained from elective neck surgery and metformin transporter expression levels in human and murine BAT were determined by qPCR. Oxygen consumption in metformin-treated human brown adipocyte cell models was assessed by Seahorse XF technology.

RESULTS

Injected [¹¹ C]-metformin showed avid uptake in the murine interscapular BAT depot. Metformin exposure in BAT was similar to hepatic exposure. Non-specific inhibition of the organic cation transporter (OCT) protein by cimetidine administration eliminated BAT exposure to metformin, demonstrating OCT-mediated uptake. Gene expression profiles of OCTs in BAT revealed ample OCT3 expression in both human and mouse BAT. Incubation of a human brown adipocyte cell models with metformin reduced cellular oxygen consumption in a dose-dependent manner.

CONCLUSION

These results support BAT as a putative metformin target.

Increased global arterial and subcutaneous adipose tissue inflammation in patients with moderate-to-severe psoriasis

BACKGROUND

Psoriasis is associated with cardiovascular disease; it has been proposed that increased cardiovascular risk is caused by low-grade systemic inflammation involving organs and tissues other than the skin and joints.

OBJECTIVES

To investigate signs of vascular inflammation in untreated patients with moderate-to-severe psoriasis assessed by ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography. A secondary objective was to assess signs of subcutaneous adipose tissue inflammation.

METHODS

This was an observational, controlled clinical study including patients with psoriasis (n = 12, mean ± SD age 61·4 ± 4·1 years, 83% men, mean ± SD Psoriasis Area Severity Index score 14·5 ± 4·3) and matched controls (n = 23, mean ± SD age 60·4 ± 4·5 years, 87% men). Vascular inflammation was measured using aortic maximal standardized uptake values (SUV_max ) and the target-to-background ratio (TBR_max ) of the whole vessel and aortic segments. Subcutaneous adipose tissue inflammation was assessed and compared with regard to SUV_max and TBR_max .

RESULTS

Arterial inflammation was increased in patients with psoriasis vs. controls (mean ± SD whole vessel TBR_max 2·46 ± 0·31 vs. 2·09 ± 0·36; P = 0·005). In patients with psoriasis, higher FDG uptake values were observed for all aortic segments except the ascending aorta. Subcutaneous adipose tissue FDG uptake was increased in patients with psoriasis vs. controls (mean ± SD TBR_max 0·49 ± 0·18 vs. 0·31 ± 0·12; P = 0·002). Associations remained significant after adjusting for body mass index and age.

CONCLUSIONS

Global arterial inflammation and subcutaneous inflammation were significantly increased in patients with moderate-to-severe psoriasis compared with controls.