Characterization of impaired beta and alpha cell function in response to an oral glucose challenge in cystic fibrosis: a cross-sectional study.

Aims: The purpose of the study was to further elucidate the pathophysiology of cystic fibrosis (CF)-related diabetes (CFRD) and potential drivers of hypoglycaemia. Hence, we aimed to describe and compare beta cell function (insulin and proinsulin) and alpha cell function (glucagon) in relation to glucose tolerance in adults with CF and to study whether hypoglycaemia following oral glucose challenge may represent an early sign of islet cell impairment. Methods: Adults with CF (≥18 years) were included in a cross-sectional study using an extended (-10, -1, 10, 20, 30, 45, 60, 90, 120, 150, and 180 min) or a standard (-1, 30, 60, and 120 min) oral glucose tolerance test (OGTT). Participants were classified according to glucose tolerance status and hypoglycaemia was defined as 3-hour glucose <3.9 mmol/L in those with normal glucose tolerance (NGT) and early glucose intolerance (EGI). Results: Among 93 participants, 67 underwent an extended OGTT. In addition to worsening in insulin secretion, the progression to CFRD was associated with signs of beta cell stress, as the fasting proinsulin-to-insulin ratio incrementally increased (p-value for trend=0.013). The maximum proinsulin level (pmol/L) was positively associated with the nadir glucagon, as nadir glucagon increased 6.2% (95% confidence interval: 1.4-11.3%) for each unit increase in proinsulin. Those with hypoglycaemia had higher 60-min glucose, 120-min C-peptide, and 180-min glucagon levels (27.8% [11.3-46.7%], 42.9% [5.9-92.85%], and 80.3% [14.9-182.9%], respectively) and unaltered proinsulin-to-insulin ratio compared to those without hypoglycaemia. Conclusions: The maximum proinsulin concentration was positively associated with nadir glucagon during the OGTT, suggesting that beta cell stress is associated with abnormal alpha cell function in adults with CF. In addition, hypoglycaemia seemed to be explained by a temporal mismatch between glucose and insulin levels rather than by an impaired glucagon response.

Effect of aerobic exercise training on the fat fraction of the liver in persons with chronic hepatitis B and hepatic steatosis: Trial protocol for a randomized controlled intervention trial- The FitLiver study.

BACKGROUND: The global prevalence of chronic hepatitis B is more than 300 million people, and in Denmark, 17,000 people are estimated to have chronic hepatitis B. Untreated, chronic hepatitis B can lead to the development of liver cirrhosis and liver cancer. There is no curable therapy. In persons with obesity and chronic hepatitis B infection, the development of hepatic steatosis imposes a double burden on the liver, leading to an increased risk of cirrhosis and liver cancer. In patients without chronic hepatitis B, exercise interventions have shown beneficial effects on hepatic steatosis through improvements in fat fraction of the liver, insulin resistance, fatty acid metabolism, and glucose metabolism, as well as activation of liver-induced regulatory protein secretion (hepatokines) after the exercise intervention. OBJECTIVE: To investigate in persons with chronic hepatitis B and hepatic steatosis: Primary: Whether exercise will decrease the fat fraction of the liver. Secondary: If exercise will affect hepatokine secretion and if it will improve lipid- and glucose metabolism, liver status, markers of inflammation, body composition, and blood pressure. METHODS: A randomized, controlled, clinical intervention trial consisting of 12 weeks of aerobic exercise training or no intervention. Thirty persons with chronic hepatitis B and hepatic steatosis will be randomized 1:1. Before and after the intervention, participants will undergo an MRI scan of the liver, blood sampling, oral glucose tolerance test, fibroscan, VO2max test, DXA scan, blood pressure measurements, and optional liver biopsy. Lastly, a hormone infusion test with somatostatin and glucagon to increase the glucagon/insulin ratio for stimulating secretion of circulating hepatokines will be performed. The training program includes three weekly training sessions of 40 min/session over 12 weeks. DISCUSSION: This trial, investigating high-intensity interval training in persons with chronic hepatitis B and hepatic steatosis, is the first exercise intervention trial performed on this group of patients. If exercise reduces hepatic steatosis and induces other beneficial effects of clinical markers in this group of patients, there might be an indication to recommend exercise as part of treatment. Furthermore, the investigation of the effect of exercise on hepatokine secretion will provide more knowledge on the effects of exercise on the liver. TRIAL REGISTRATION: Danish Capital Regions committee on health research ethics reference: H-21034236 (version 1.4 date: 19-07-2022) and ClinicalTrials.gov: NCT05265026.

Human visceral and subcutaneous adipose stem and progenitor cells retain depot-specific adipogenic properties during obesity.

Abdominal obesity associates with cardiometabolic disease and an accumulation of lipids in the visceral adipose depot, whereas lipid accumulation in the subcutaneous depot is more benign. We aimed to further investigate whether the adipogenic properties where cell-intrinsic, or dependent on a depot-specific or obesity-produced microenvironment. We obtained visceral and subcutaneous biopsies from non-obese women (n = 14) or women living with morbid obesity (n = 14) and isolated adipose stem and progenitor cells (ASPCs) from the stromal vascular fraction of non-obese (n = 13) and obese (n = 13). Following in vitro differentiation into mature adipocytes, we observed a contrasting pattern with a lower gene expression of adipogenic markers and a higher gene expression of immunogenic markers in the visceral compared to the subcutaneous adipocytes. We identified the immunogenic factor BST2 as a marker for visceral ASPCs. The effect of obesity and insulin resistance on adipogenic and immunogenic markers in the in vitro differentiated cells was minor. In contrast, differentiation with exogenous Tumor necrosis factor resulted in increased immunogenic signatures, including increased expression of BST2, and decreased adipogenic signatures in cells from both depots. Our data, from 26 women, underscore the intrinsic differences between human visceral and subcutaneous adipose stem and progenitor cells, suggest that dysregulation of adipocytes in obesity mainly occurs at a post-progenitor stage, and highlight an inflammatory microenvironment as a major constraint of human adipogenesis.

Biomarkers for iron metabolism among patients hospitalized with community-acquired pneumonia caused by infection with SARS-CoV-2, bacteria, and influenza.

Ferritin, the central iron storage protein, has attracted attention as a biomarker of severe COVID-19. Few studies have investigated regulators of iron metabolism in the context of COVID-19. The aim was to evaluate biomarkers for iron metabolism in the acute phase response to community-acquired pneumonia (CAP) caused by SARS-CoV-2 compared with CAP caused by bacteria or influenza virus in hospitalized patients. A cross-sectional study of 164 patients from the Surviving Pneumonia Cohort recruited between January 8, 2019 and May 26, 2020. Blood samples were collected at admission and analyzed for levels of C-reactive protein (CRP), ferritin, soluble transferrin receptor, erythroferrone, and hepcidin. Median (IQR) hepcidin was higher in SARS-CoV-2 with 143.8 (100.7-180.7) ng/mL compared with bacterial and influenza infection with 78.8 (40.1-125.4) and 53.5 (25.2-125.8) ng/mL, respectively. The median ferritin level was more than 2-fold higher in patients with SARS-CoV-2 compared with the other etiologies (p < 0.001). Patients with SARS-CoV-2 had lower levels of erythroferrone and CRP compared with those infected with bacteria. Higher levels of hepcidin and lower levels of erythroferrone despite lower CRP levels among patients with SARS-CoV-2 compared with those infected with bacteria indicate alterations in iron metabolism in patients with SARS-CoV-2 infection.

Levels and correlates of physical activity and capacity among HIV-infected compared to HIV-uninfected individuals.

INTRODUCTION: In the HIV-infected individuals, physical activity improves physical strength, quality of life and reduces the risk of developing non-communicable diseases. In Sub-Saharan Africa, HIV-infected patients report being less active compared to HIV-uninfected individuals. We assessed the levels and correlates of objectively measured physical activity and capacity among HIV-infected antiretroviral therapy (ART)-naive individuals compared to HIV-uninfected individuals in Mwanza, Tanzania. METHOD: We conducted a cross-sectional study among newly diagnosed HIV-infected ART-naive individuals and HIV-uninfected individuals frequency-matched for age and sex. Socio-demographic data, anthropometrics, CD4 counts, haemoglobin level, and C-reactive protein (CRP) were collected. Physical activity energy expenditure (PAEE) was assessed as measure of physical activity whereas sleeping heart rate (SHR) and grip strength were assessed as measures of physical capacity. Multivariable linear regression was used to assess the correlates associated with physical activity and capacity. RESULTS: A total of 272 HIV-infected and 119 HIV-uninfected individuals, mean age 39 years and 60% women participated in the study. Compared to HIV-uninfected individuals, HIV-infected had poorer physical activity and capacity: lower PAEE (-7.3 kj/kg/day, 95% CI: -11.2, -3.3), elevated SHR (7.7 beats/min, 95%CI: 10.1, 5.3) and reduced grip strength (-4.7 kg, 95%CI: -6.8, -2.8). In HIV-infected individuals, low body mass index, moderate-severe anaemia, low CD4 counts and high CRP were associated with lower physical activity and capacity. In HIV-uninfected individuals, abdominal obesity and moderate anaemia were associated with lower physical activity and capacity. CONCLUSION: HIV-infected participants had lower levels of physical activity and capacity than HIV-uninfected participants. Correlates of physical activity and capacity differed by HIV status. Management of HIV and related conditions needs to be provided effectively in health care facilities. Interventions promoting physical activity in these populations will be of importance to improve their health and reduce the risk of non-communicable diseases.

Body composition, physical capacity, and immuno-metabolic profile in community-acquired pneumonia caused by COVID-19, influenza, and bacteria: a prospective cohort study.

BACKGROUND: Different pathogens can cause community-acquired pneumonia (CAP); however, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19) has re-emphasized the vital role of respiratory viruses as a cause of CAP. The aim was to explore differences in metabolic profile, body composition, physical capacity, and inflammation between patients hospitalized with CAP caused by different etiology. METHODS: A prospective study of Danish patients hospitalized with CAP caused by SARS-CoV-2, influenza, or bacteria. Fat (FM) and fat-free mass (FFM) were assessed with bioelectrical impedance analysis. Physical activity and capacity were assessed using questionnaires and handgrip strength. Plasma (p)-glucose, p-lipids, hemoglobin A1c (HbA1c), p-adiponectin, and cytokines were measured. RESULTS: Among 164 patients with CAP, etiology did not affect admission levels of glucose, HbA1c, adiponectin, or lipids. Overall, 15.2% had known diabetes, 6.1% had undiagnosed diabetes, 51.3% had pre-diabetes, 81% had hyperglycemia, and 60% had low HDL-cholesterol, with no difference between groups. Body mass index, FM, and FFM were similar between groups, with 73% of the patients being characterized with abdominal obesity, although waist circumference was lower in patients with COVID-19. Physical capacity was similar between groups. More than 80% had low handgrip strength and low physical activity levels. Compared to patients with influenza, patients with COVID-19 had increased levels of interferon (IFN)-γ (mean difference (MD) 4.14; 95% CI 1.36-12.58; p = 0.008), interleukin (IL)-4 (MD 1.82; 95% CI 1.12-2.97; p = 0.012), IL-5 (MD 2.22; 95% CI 1.09-4.52; p = 0.024), and IL-6 (MD 2.41; 95% CI 1.02-5.68; p = 0.044) and increased IFN-γ (MD 6.10; 95% CI 2.53-14.71; p < 0.001) and IL-10 (MD 2.68; 95% CI 1.53-4.69; p < 0.001) compared to patients with bacterial CAP, but no difference in IL-1ß, tumor necrosis factor-α, IL-8, IL-18, IL-12p70, C-reactive protein, and adiponectin. CONCLUSION: Despite higher inflammatory response in patients with COVID-19, metabolic profile, body composition, and physical capacity were similar to patients with influenza and bacterial CAP.

Risk factors for impaired renal function in HIV-infected and HIV-uninfected adults: cross-sectional study in North-Western Tanzania.

BACKGROUND: Although the burden of impaired renal function is rising in sub-Saharan Africa (SSA), little is known about correlates of impaired renal function in the region. We determined factors associated with estimated glomerular filtration rate (eGFR) and impaired renal function in HIV-infected and HIV-uninfected adults. METHODS: We undertook cross-sectional analysis of data from 1947 adults at enrolment for a cohort study on diabetes and associated complications in HIV patients in Mwanza, north-western Tanzania. A structured questionnaire was used to collect data on sociodemography, smoking, alcohol, physical activity, antiretroviral therapy (ART) and anthropometry. We measured blood pressure, tested blood samples for creatinine, glucose and HIV, and performed Kato Katz for Schistosoma mansoni. Correlates of eGFR (mL/min/1.73 m2) and impaired renal function (eGFR< 60 mL/min/1.73 m2) were determined using linear regression and logistic regression, respectively. RESULTS: 655 (34%) participants were HIV-uninfected, 956 (49%) were ART-naive HIV-infected and 336 (17%) were HIV-infected adults on ART. The mean age was 41 years (SD12) and majority (59%) were females. Overall, the mean eGFR was 113.6 mL/min/1.73 m2 but 111.2 mL/min/1.73 m2 in HIV-uninfected, 109.7 mL/min/1.73 m2 in ART-naive HIV-infected and 129.5 mL/min/1.73 m2 in HIV-infected ART-experienced adults, and respective prevalence of impaired renal function was 7.0, 5.7, 8.1 and 6.3%. Correlates of lower eGFR were increasing age, higher socioeconomic status, unhealthy alcohol drinking, higher body mass index and diabetes mellitus. Anaemia was associated with 1.9 (95% Confidence Interval (CI):1.2, 2.7, p = 0.001) higher odds of impaired renal function compared to no anaemia and this effect was modified by HIV status (p value 0.02 for interaction). CONCLUSION: Impaired renal function is prevalent in this middle-aged study population. Interventions for prevention of impaired renal function are needed in the study population with special focus in HIV-infected adults and those with high socioeconomic status. Interventions targeting modifiable risk factors such as alcohol and weight reduction are warranted.

Associations Between Glucose Tolerance, Insulin Secretion, Muscle and Fat Mass in Cystic Fibrosis.

BACKGROUND: A frequent comorbidity in cystic fibrosis (CF) is CF related diabetes (CFRD) caused by a gradual decline in insulin secretion. The reduction in the anabolic hormone, insulin, might explain the weight loss that precedes onset of CFRD. We investigated the association between muscle and fat mass in relation to glucose tolerance and insulin function. METHODS: In a cross-sectional study with CF patients (⩾18 years), we conducted an oral glucose tolerance test and dual energy X-ray absorptiometry scan (DXA). Based on plasma glucose, glucose tolerance was defined as normal (NGT): 1-hour <11.1 mmol/L and 2-hour <7.8 mmol/L, impaired (IGT): 2-hour ⩾7.8 and <11.1 mmol/L or CFRD: 2-hour ⩾11.1 mmol/L. Insulin resistance (HOMA-IR) was derived from fasting levels of plasma glucose and plasma insulin, and fat-free and fat mass index (kg/m2) from DXA. Associations were evaluated using linear regression models adjusted for age, sex, and pancreas insufficiency. RESULTS: Among 79 CF patients with exocrine pancreas insufficiency, impairment of glucose tolerance corresponded to reduced insulin secretion. In the IGT group the fat-free mass index (FFMI) was 1.2 kg/m2 (95% CI: [-2.3, -0.03] kg/m2, P = .044) lower compared to the NGT group. FFMI increased insignificantly by 0.4 kg/m2 (95% CI: [-0.6, 1.5] kg/m2, P = .422) among the insulin-treated CFRD group compared to IGT. Fat mass index (FMI) was not different between groups but tended to decrease with glucose tolerance impairment. For each 100 pmol/L increase in fasting insulin FFMI increased by 1.77 kg/m2 (95% CI: [0.21, 3.33] kg/m2/pmol/L/100) and FMI increased by 6.15 kg/m2 (95% CI: [3.87, 8.44] kg/m2/pmol/L/100). In multivariate analyses, HOMA-IR was positively associated with FFMI (ß = 0.5 kg/m2/HOMA-IR, 95% CI: [0.08, 0.92] kg/m2/HOMA-IR, P = .021) and FMI (ß = 1.5 kg/m2/HOMA-IR, 95% CI: [0.87, 2.15] kg/m2/HOMA-IR, P < .001). CONCLUSIONS: Muscle mass was significantly lower among participants with impaired glucose tolerance (IGT), while muscle mass was normalized among those treated with insulin.

Human immune cell mobilization during exercise: effect of IL-6 receptor blockade.

NEW FINDINGS: What is the central question of this study? Does blockade of the IL-6 receptor by tocilizumab inhibit immune cell mobilization to the blood stream in humans during an acute bout of exercise? What is the main finding and its importance? Blockade of IL-6 receptor signalling by tocilizumab attenuates mobilization of NK cells and dendritic cells to the blood stream during exercise. This implies an inhibitory effect of tocilizumab on the innate immune response to physical stress, which could be considered in clinical settings. ABSTRACT: Immune cells are recruited from their storage organs and the endothelial walls to the blood stream in response to physiological stress. This is essential for the recognition and clearing of infected, transformed or damaged cells. One of the most potent stimuli to recruit immune cells to the circulation is exercise. Accordingly, exercise has proven beneficial in disease settings, such as cancer and diabetes. Interleukin-6 (IL-6) is released from contracting skeletal muscle in response to exercise, and rodent studies have established a link between exercise-induced IL-6 and recruitment of natural killer (NK) cells. Whether exercise-induced IL-6 is involved in regulating NK cell mobilization in humans is unclear. This study explored the effect of IL-6 receptor blockade on immune cell mobilization during an acute bout of exercise in humans. In a randomized, placebo-controlled clinical study, abdominally obese humans receiving placebo infusions or tocilizumab infusions performed an acute bout of exercise before and after the intervention. Immune cell recruitment was measured by flow cytometry. IL-6 receptor blockade attenuated the increase of NK cells by 53% (mean difference -0.49 (95% CI: -0.89 to -0.08) × 109 cells L-1 , P < 0.001) and dendritic cells by 66% (mean difference -0.14 (95% CI: -0.28 to 0.010) × 109 cells L-1 , P < 0.001) induced by an acute bout of exercises. No changes were observed for T cells, monocytes and neutrophils. Treatments which interact with the exercise-mediated immune surveillance provide relevant clinical information in pursuing the 'exercise as medicine' concept.

Heterogeneity in the perirenal region of humans suggests presence of dormant brown adipose tissue that contains brown fat precursor cells.

OBJECTIVE: Increasing the amounts of functionally competent brown adipose tissue (BAT) in adult humans has the potential to restore dysfunctional metabolism and counteract obesity. In this study, we aimed to characterize the human perirenal fat depot, and we hypothesized that there would be regional, within-depot differences in the adipose signature depending on local sympathetic activity. METHODS: We characterized fat specimens from four different perirenal regions of adult kidney donors, through a combination of qPCR mapping, immunohistochemical staining, RNA-sequencing, and pre-adipocyte isolation. Candidate gene signatures, separated by adipocyte morphology, were recapitulated in a murine model of unilocular brown fat induced by thermoneutrality and high fat diet. RESULTS: We identified widespread amounts of dormant brown adipose tissue throughout the perirenal depot, which was contrasted by multilocular BAT, primarily found near the adrenal gland. Dormant BAT was characterized by a unilocular morphology and a distinct gene expression profile, which partly overlapped with that of subcutaneous white adipose tissue (WAT). Brown fat precursor cells, which differentiated into functional brown adipocytes were present in the entire perirenal fat depot, regardless of state. We identified SPARC as a candidate adipokine contributing to a dormant BAT state, and CLSTN3 as a novel marker for multilocular BAT. CONCLUSIONS: We propose that perirenal adipose tissue in adult humans consists mainly of dormant BAT and provide a data set for future research on factors which can reactivate dormant BAT into active BAT, a potential strategy for combatting obesity and metabolic disease.

Markers of bone turnover are reduced in patients with CF related diabetes; the role of glucose.

BACKGROUND: Cystic fibrosis(CF) related diabetes(CFRD) and osteoporosis are prevalent in adult patients with CF. We aimed to evaluate if CFRD and markers of glucose metabolism and inflammation are associated with bone turnover in CF. METHODS: Cross sectional study at the adult section at the Copenhagen CF Center from January-October 2017. Fasting blood samples, including bone turnover markers(BTMs) and cytokines, Dual-x-ray absorptiometry scan and oral glucose tolerance test were performed. Lung-transplanted participants and patients in antiosteoporotic treatment were excluded from analyses. RESULTS: 102 patients were included of whom 19 had a prior CFRD diagnosis. CFRD patients had lower procollagen type 1 N-terminal propeptide(P1NP) and C-Terminal cross-linked Telopeptide(CTX) levels compared to CF patients without diabetes (median[IQR]) 49.5 µg/l [29.6,57.1] vs 56.9 µg/l [38.2,74.3], p = .03 and 0.2 µg/l [0.1,0.3] vs 0.4 µg/l [0.3,0.6], p < .01, respectively. Fasting plasma glucose(FPG) was negatively associated with the bone formation markers P1NP and osteocalcin and bone resorption marker CTX. In multivariate linear regression FPG remained a significant predictor of P1NP -1.07 [-1.09;-0.01] and CTX -1.13 [-1.21;-1.06]. Bone mineral density Z-score was not different between patients with and without CFRD but FPG was negatively associated with hip and femoral neck Z-score. There was no consistent association between inflammatory cytokines and BTMs. CONCLUSIONS: Bone turnover markers are reduced in CF patients with CFRD and negatively associated with glucose levels. Extra attention towards frequent hyperglycemia in CF patients should be taken when evaluating decreased BMD. Glycemia may be a future target for improving outcome in CFBD.

Exercise-Induced Changes in Visceral Adipose Tissue Mass Are Regulated by IL-6 Signaling: A Randomized Controlled Trial.

Visceral adipose tissue is harmful to metabolic health. Exercise training reduces visceral adipose tissue mass, but the underlying mechanisms are not known. Interleukin-6 (IL-6) stimulates lipolysis and is released from skeletal muscle during exercise. We hypothesized that exercise-induced reductions in visceral adipose tissue mass are mediated by IL-6. In this randomized placebo-controlled trial, we assigned abdominally obese adults to tocilizumab (IL-6 receptor antibody) or placebo during a 12-week intervention with either bicycle exercise or no exercise. While exercise reduced visceral adipose tissue mass, this effect of exercise was abolished in the presence of IL-6 blockade. Changes in body weight and total adipose tissue mass showed similar tendencies, whereas lean body mass did not differ between groups. Also, IL-6 blockade increased cholesterol levels, an effect not reversed by exercise. Thus, IL-6 is required for exercise to reduce visceral adipose tissue mass and emphasizes a potentially important metabolic consequence of IL-6 blockade.

The role of exercise combined with tocilizumab in visceral and epicardial adipose tissue and gastric emptying rate in abdominally obese participants: protocol for a randomised controlled trial.

BACKGROUND: Exercise reduces the amount of visceral adipose tissue (VAT) and the risk of cardiometabolic diseases. The underlying mechanisms responsible for these exercise-induced adaptations are unclear, but they may involve lipolytic actions of interleukin-6 (IL-6). Contracting skeletal muscles secrete IL-6, leading to increased circulating IL-6 levels in response to exercise. The aim of this study is to investigate whether IL-6 is involved in mediating the effects of exercise on visceral and epicardial adipose tissue volume and glycaemic control. METHODS/DESIGN: Seventy-five physically inactive males and females aged > 18 years with a waist-to-height ratio > 0.5 and/or waist circumference ≥ 88 cm (females) or ≥ 102 cm (males) are being recruited to participate in a 12-week intervention study. Participants are randomly allocated to one of five groups (1:1:1:1:1). Two groups consist of supervised endurance exercise training combined with the IL-6 blocker tocilizumab (ET) or saline used as placebo (EP), two groups consist of no exercise combined with tocilizumab (NT) or placebo (NP), and one group consists of resistance exercise and placebo (RP). Although the study is an exploratory trial, the primary outcome is change in VAT volume from before to after intervention, with secondary outcomes being changes in (1) epicardial adipose tissue, (2) pericardial adipose tissue and (3) gastric emptying. Depots of adipose tissue are quantitated by magnetic resonance imaging Gastric emptying and glucose metabolism are assessed using mixed-meal tolerance tests. DISCUSSION: Understanding the role of IL-6 in mediating the effects of exercise on visceral and epicardial adipose tissue and glycaemic control may lead to novel therapeutic approaches in the prevention of cardiometabolic diseases. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02901496 . Registered on 1 August 2016 and posted retrospectively on 15 September 2016.

Cardiorespiratory fitness and the metabolic syndrome: Roles of inflammation and abdominal obesity.

OBJECTIVE: Individuals with metabolic syndrome have increased risk of type 2 diabetes and cardiovascular disease. We aimed to test the hypothesis that a high level of cardiorespiratory fitness (CR-fitness), counteracts accumulation of visceral fat, decreases inflammation and lowers risk factors of the metabolic syndrome. METHOD: The study sample included 1,293 Danes (age 49-52 years) who from 2009 to 2011 participated in the Copenhagen Aging and Midlife Biobank, including a questionnaire, physical tests, and blood samples. Multiple linear regression models were performed with CR-fitness as exposure and plasma levels of cytokines and high sensitive C-reactive protein as outcomes and measures of abdominal obesity were added to test if they explained the potential association. Similarly, multiple linear regression models were performed with CR-fitness as exposure and factors of the metabolic syndrome as outcomes and the potential explanation by inflammatory biomarkers were tested. All models were adjusted for the effect of age, sex, smoking, alcohol consumption, socio-economic status, and acute inflammatory events within the preceding two weeks. RESULTS: CR-fitness was inversely associated with high sensitive C-reactive protein, Interleukin (IL)-6, and IL-18, and directly associated with the anti-inflammatory cytokine IL-10, but not associated with tumor necrosis factor alpha, interferon gamma or IL-1ß. Abdominal obesity could partly explain the significant associations. Moreover, CR-fitness was inversely associated with an overall metabolic syndrome score, as well as triglycerides, glycated haemoglobin A1c, systolic blood pressure, diastolic blood pressure and directly associated with high-density lipoprotein. Single inflammatory biomarkers and a combined inflammatory score partly explained these associations. CONCLUSION: Data suggest that CR-fitness has anti-inflammatory effects that are partly explained by a reduction in abdominal obesity and a decrease in the metabolic syndrome risk profile. The overall inflammatory load was mainly driven by high sensitive C-reactive protein and IL-6.

The effect of 8 days of strict bed rest on the incretin effect in healthy volunteers.

Bed rest and physical inactivity are the consequences of hospital admission for many patients. Physical inactivity induces changes in glucose metabolism, but its effect on the incretin effect, which is reduced in, e.g., Type 2 diabetes, is unknown. To investigate how 8 days of strict bed rest affects the incretin effect, 10 healthy nonobese male volunteers underwent 8 days of strict bed rest. Before and after the intervention, all volunteers underwent an oral glucose tolerance test (OGTT) followed by an intravenous glucose infusion (IVGI) on the following day to mimic the blood glucose profile from the OGTT. Blood glucose, serum insulin, serum C-peptide, plasma incretin hormones [glucagon-like peptide (GLP-1) and glucose-dependent insulinotropic peptide (GIP)], and serum glucagon were measured serially during both the OGTT and the IVGI. The incretin effect is calculated as the relative difference between the area under the curve for the insulin response during the OGTT and that of the corresponding IVGI, respectively. Concentrations of glucose, insulin, C-peptide, and GIP measured during the OGTT were higher after the bed rest intervention (all P < 0.05), whereas there was no difference in the levels of GLP-1 and Glucagon. Bed rest led to a mean loss of 2.4 kg of fat-free mass, and induced insulin resistance evaluated by the Matsuda index, but did not affect the incretin effect (P = 0.6). In conclusion, 8 days of bed rest induces insulin resistance, but we did not see evidence of an associated change in the incretin effect.

The incretin effect in critically ill patients: a case-control study.

INTRODUCTION: Patients admitted to the intensive care unit often develop hyperglycaemia, but the underlying mechanisms have not been fully described. The incretin effect is reduced in patients with type 2 diabetes. Type 2 diabetes and critical illness have phenotypical similarities, such as hyperglycaemia, insulin resistance and systemic inflammation. Previous studies have shown beneficial effects of exogenous glucagon-like peptide (GLP)-1 on glycaemia in critically ill patients, a phenomenon also seen in patients with type 2 diabetes. In this study, we hypothesised that the incretin effect, which is mediated by the incretin hormones GLP-1 and glucose-dependent insulinotropic peptide (GIP), is impaired in critically ill patients. METHODS: The incretin effect (i.e., the relative difference between the insulin response to oral and intravenous glucose administration) was investigated in a cross-sectional case-control study. Eight critically ill patients without diabetes admitted to a mixed intensive care unit and eight healthy control subjects without diabetes, matched at group level by age, sex and body mass index, were included in the study. All subjects underwent an oral glucose tolerance test (OGTT) followed by an intravenous glucose infusion (IVGI) on the next day to mimic the blood glucose profile from the OGTT. Blood glucose, serum insulin, serum C-peptide and plasma levels of GLP-1, GIP, glucagon and proinflammatory cytokines were measured intermittently. The incretin effect was calculated as the increase in insulin secretion during oral versus intravenous glucose administration in six patients. The groups were compared using either Student's t test or a mixed model of repeated measurements. RESULTS: Blood glucose levels were matched between the OGTT and the IVGI in both groups. Compared with control subjects, proinflammatory cytokines, tumour necrosis factor α and interleukin 6, were higher in patients than in control subjects. The endogenous response of GIP and glucagon, but not GLP-1, to the OGTT was greater in patients. The insulin response to the OGTT did not differ between groups, whereas the insulin response to the IVGI was higher in patients. Consequently, the calculated incretin effect was lower in patients (23 vs. 57%, p=0.003). CONCLUSIONS: In critically ill patients, the incretin effect was reduced. This resembles previous findings in patients with type 2 diabetes. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01347801 . Registered on 2 May 2011.

Tumour necrosis factor-alpha infusion produced insulin resistance but no change in the incretin effect in healthy volunteers.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is associated with peripheral insulin resistance, impaired incretin effect, and increased plasma levels of tumour necrosis factor-alpha (TNF-α). Although TNF-α infusion at a dose that induces systemic inflammation in healthy volunteers has been demonstrated to induce peripheral insulin resistance, the influence of this cytokine on the incretin effect is unknown. METHODS: We investigated whether systemic inflammation induced by TNF-α infusion in healthy volunteers alters the incretin hormone response to oral and intravenous glucose loads in a crossover study design with ten healthy male volunteers (mean age 24 years, mean body mass index 23.7 kg/m(2) ). The study consisted of four study days: days 1 and 2, 6-h infusion of saline; days 3 and 4, 6-h infusion of TNF-α; days 1 and 3, 4-h oral glucose tolerance test; and days 2 and 4, 4-h corresponding intravenous isoglycaemic glucose tolerance test. Glucose tolerance tests were initiated after 2 h of saline/TNF-α infusion. Plasma concentrations of TNF-α, interleukin 6, glucose, incretin hormones, and cortisol, and serum concentrations of C-peptide and insulin were measured throughout the study days. Insulin sensitivity was estimated by the Matsuda index and homeostasis model assessment of insulin resistance (HOMA-IR). Prehepatic insulin secretion rates were calculated. RESULTS: TNF-α infusion induced symptoms of systemic inflammation; increased plasma levels of cortisol, TNF-α, and interleukin 6; and increased the HOMA-IR. The secretion of incretin hormones as well as the incretin effect remained unchanged. CONCLUSION: In healthy young male volunteers, acute systemic inflammation induced by infusion of TNF-α is associated with insulin resistance with no change in the incretin effect.

GLUT4 and glycogen synthase are key players in bed rest-induced insulin resistance.

To elucidate the molecular mechanisms behind physical inactivity-induced insulin resistance in skeletal muscle, 12 young, healthy male subjects completed 7 days of bed rest with vastus lateralis muscle biopsies obtained before and after. In six of the subjects, muscle biopsies were taken from both legs before and after a 3-h hyperinsulinemic euglycemic clamp performed 3 h after a 45-min, one-legged exercise. Blood samples were obtained from one femoral artery and both femoral veins before and during the clamp. Glucose infusion rate and leg glucose extraction during the clamp were lower after than before bed rest. This bed rest-induced insulin resistance occurred together with reduced muscle GLUT4, hexokinase II, protein kinase B/Akt1, and Akt2 protein level, and a tendency for reduced 3-hydroxyacyl-CoA dehydrogenase activity. The ability of insulin to phosphorylate Akt and activate glycogen synthase (GS) was reduced with normal GS site 3 but abnormal GS site 2+2a phosphorylation after bed rest. Exercise enhanced insulin-stimulated leg glucose extraction both before and after bed rest, which was accompanied by higher GS activity in the prior-exercised leg than the rested leg. The present findings demonstrate that physical inactivity-induced insulin resistance in muscle is associated with lower content/activity of key proteins in glucose transport/phosphorylation and storage.

A 2-wk reduction of ambulatory activity attenuates peripheral insulin sensitivity.

US adults take between approximately 2,000 and approximately 12,000 steps per day, a wide range of ambulatory activity that at the low range could increase risk for developing chronic metabolic diseases. Dramatic reductions in physical activity induce insulin resistance; however, it is uncertain if and how low ambulatory activity would influence peripheral insulin sensitivity. We aimed to explore if healthy, nonexercising subjects who went from a normal to a low level of ambulatory activity for 2 wk would display metabolic alterations including reduced peripheral insulin sensitivity. To do this, ten healthy young men decreased their daily activity level from a mean of 10,501+/-808 to 1,344+/-33 steps/day for 2 wk. Hyperinsulinemic-euglycemic clamps with stable isotopes and muscle biopsies, maximal oxygen consumption (VO2 max) tests, and blood samples were performed pre- and postintervention. A reduced number of daily steps induced a significant reduction of 17% in the glucose infusion rate (GIR) during the clamp. This reduction was due to a decline in peripheral insulin sensitivity with no effect on hepatic endogenous glucose production. The insulin-stimulated ratio of pAktthr308/total Akt decreased after step reduction, with a post hoc analysis revealing the most pronounced effect after 4 h of insulin infusion. In addition, the 2-wk period induced a 7% decline in VO2 max (ml/min; cardiovascular fitness). Lean mass of legs, but not arms and trunk, decreased concurrently. Taken together, one possible biological cause for the public health problem of Type 2 diabetes has been identified. Reduced ambulatory activity for 2 wk in healthy, nonexercising young men significantly reduced peripheral insulin sensitivity, cardiovascular fitness, and lean leg mass.