Effect of IL-6 on the insulin sensitivity in patients with type 2 diabetes.

Elevated interleukin-6 (IL-6) levels are associated with type 2 diabetes, but its role in glucose metabolism is controversial. We investigated the effect of IL-6 on insulin-stimulated glucose metabolism in type 2 diabetes patients and hypothesized that an acute, moderate IL-6 elevation would increase the insulin-mediated glucose uptake. Men with type 2 diabetes not treated with insulin [n = 9, age 54.9 ± 9.7 (mean ± SD) yr, body mass index 34.8 ± 6.1 kg/m(2), HbA1c 7.0 ± 1.0%] received continuous intravenous infusion with either recombinant human IL-6 (rhIL-6) or placebo. After 1 h with placebo or rhIL-6, a 3-h hyperinsulinemic-isoglycemic clamp was initiated. Whole body glucose metabolism was measured using stable isotope-labeled tracers. Signal transducer and activator of transcription 3 (STAT3) phosphorylation and suppressor of cytokine signaling 3 (SOCS3) expression were measured in muscle biopsies. Whole body energy expenditure was measured using indirect calorimetry. In response to the infusion of rhIL-6, circulating levels of IL-6 (P < 0.001), neutrophils (P < 0.001), and cortisol (P < 0.001) increased while lymphocytes decreased (P < 0.01). However, IL-6 infusion did not change glucose infusion rate, rate of appearance, or rate of disappearance during the clamp. While IL-6 enhanced phosphorylation of STAT3 in skeletal muscle (P = 0.041), the expression of SOCS3 remained unchanged. Whole body oxygen uptake (P < 0.01) and expired carbon dioxide (P < 0.01) increased during rhIL-6 infusion. In summary, although IL-6 induced local and systemic responses, the insulin-stimulated glucose uptake was not affected. While different contributing factors may be involved, our results are in contrast to our hypothesis and previous findings in young, healthy men.

Plasma follistatin is elevated in patients with type 2 diabetes: relationship to hyperglycemia, hyperinsulinemia, and systemic low-grade inflammation.

BACKGROUND: Plasma follistatin is elevated in patients with low-grade inflammation and insulin resistance as observed with polycystic ovary syndrome. In the present study, we evaluated plasma follistatin in patients with type 2 diabetes characterised by low-grade inflammation and assessed the acute effects of hyperglycemia, hyperinsulinemia and LPS on plasma follistatin. METHODS: Baseline plasma follistatin and inflammatory biomarkers were measured in a cross-sectional study that involved 95 patients with type 2 diabetes and 103 matched controls. To determine the acute effect of hyperglycemia and hyperinsulinemia on follistatin, hyperglycemic and hyperinsulinemic-euglycemic clamps were performed in five healthy males. Furthermore, 15 patients with type 2 diabetes and 22 healthy controls were challenged with low-dose LPS to determine the effect on follistatin. RESULTS: Patients with type 2 diabetes have higher HOMA2-IR values mean [95% CI] 1.64 [1.40-1.93] versus mean 0.86 [0.75-0.99], p < 0.001 and inflammatory markers compared with controls. Baseline plasma follistatin is elevated in patients with type 2 diabetes compared with controls mean 1564 [1456-1680] versus mean 1328 [1225-1440] ng/L, p = 0.003 and correlates with fasting glucose levels (r = 0.44, p < 0.0001), 2 h glucose (r = 0.48, p < 0.0001), HbA1c (r = 0.41, p < 0.0001), triacylglycerol (r = 0.28, p = 0.008) and total cholesterol (r = 0.33, p = 0.004) in patients but not in controls. No correlation exists between plasma follistatin and inflammatory biomarkers in either of the groups. Neither hyperglycemia, hyperinsulinemia nor LPS increase plasma follistatin. CONCLUSIONS: Plasma follistatin is moderately elevated in patients with type 2 diabetes. Our findings suggest that this is not likely caused by hyperglycemia, hyperinsulinemia or systemic low-grade inflammation.

Soluble CD163: a biomarker linking macrophages and insulin resistance.

AIMS/HYPOTHESIS: Soluble CD163 (sCD163) was recently identified as a strong risk marker for developing type 2 diabetes. We hypothesised that sCD163 independently associates with insulin resistance. METHODS: This cross-sectional study includes 234 participants: 96 with type 2 diabetes, 34 with impaired glucose tolerance (IGT) and 104 with normal glucose tolerance (NGT), matched for sex and BMI. Glucose-lowering medication was paused for 1 week before plasma samples were obtained for determination of sCD163 and other inflammatory and metabolic variables. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-IR). RESULTS: Concentrations of sCD163 were 1.95 mg/l (0.63-6.97) in individuals with type 2 diabetes, 1.64 mg/l (0.58-4.19) in those with IGT, and 1.48 mg/l (0.48-4.11) (median [range]) in those with NGT (p < 0.0001). In univariate analyses, sCD163 correlated significantly with HOMA-IR (R = 0.44), insulin (R = 0.41), glucose (R = 0.30), triacylglycerol (R = 0.29) and HDL-cholesterol (R = -0.34) (all p < 0.0001). All but glucose remained significant when adjusting for age, sex, BMI and glycaemic group. In univariate regression analyses, HOMA-IR was associated with sCD163, C-reactive protein (CRP), TNF-α and IL-6 (all p ≤ 0.0001). An increase of 50% in sCD163 resulted in an estimated increase in HOMA-IR of 36% (95% CI 26, 48; p < 0.0001). In multiple linear regression analyses, sCD163 (p = 0.001) and CRP (p = 0.01) remained independent predictors of HOMA-IR, whereas TNF-α and IL-6 did not. CONCLUSIONS/INTERPRETATION: Macrophage-specific sCD163 was strongly associated with insulin resistance independently of TNF-α and other predictors. Moreover, sCD163 was associated with well-known variables of the metabolic syndrome.

RBP-to-retinol ratio, but not total RBP, is elevated in patients with type 2 diabetes.

AIM: It was recently reported that serum retinol-binding protein (RBP), also known as retinol-binding protein 4 (RBP4), was positively associated with systemic insulin resistance. We hypothesized that an imbalance between RBP and retinol might be the underlying cause for this association. METHODS: We studied the ratio between RBP and retinol in 233 humans divided into groups depending on normal glucose tolerance (NGT), impaired glucose tolerance (IGT), type 2 diabetes (T2DM) and presence or absence of obesity. RESULTS: Plasma RBP and retinol levels were lower in patients with T2DM than in individuals with NGT (p < 0.05 and p < 0.0001 respectively). In contrast, RBP-to-retinol ratio was higher in individuals with T2DM (p < 0.0001) and IGT (p < 0.05). Following multivariate adjustment, RBP and retinol correlated positively with low-density lipoprotein (LDL) and triglycerides (p < 0.0001, except retinol and LDL: p < 0.001). RBP-to-retinol ratio correlated positively with glucose 2 h after an oral glucose tolerance test (p < 0.0001) and with C-reactive protein (p < 0.001). Retinol, RBP and adipose tissue RBP messenger RNA (mRNA) levels shared an inverse relationship with plasma interleukin-6, and adipose tissue RBP mRNA levels correlated positively with plasma tumour necrosis factor-alpha (TNF-alpha) and skeletal muscle TNF-alpha mRNA levels. CONCLUSIONS: Our results suggest that the excess of RBP relative to retinol, assessed as the RBP-to-retinol ratio, is more indicative of T2DM than RBP itself. Hence, the previously reported insulin resistance in mice induced by overexpression or injection of RBP could be because of higher levels of RBP relative to retinol rather than higher total levels of RBP. Moreover, TNF-alpha may have a role in RBP-mediated adipose to muscle crosstalk.

Hepatic uptake of glutamine and other amino acids during infection and inflammation.

Catabolic illness such as sepsis and injury induce profound changes in host amino acid metabolism, including increased hepatic amino acid uptake. Because many amino acid-dependent pathways such as gluconeogenesis and acute-phase protein synthesis are activated in the liver during severe infection, this review will focus on the control of hepatic plasma membrane amino acid transport by specific inflammatory mediators. We specifically review the role of cytokines, eicosanoids, and glucorticoids in this response. Collectively, these signaling molecules act in a concerted manner to exert local control of hepatic function including the stimulation of amino acid transport. In particular, we review the role of glutamine and its transport in the liver, as it occupies a unique role in interorgan ammonia metabolism during critical illness.

Amino acid metabolism and the vascular endothelium: regulation and disease implications.

Amino acid metabolism by the vascular endothelium is a complex process that often begins with the carrier-mediated uptake of circulating amino acids into the endothelial cytoplasm. Amino acids are essential for maintaining intact endothelial functions, which include cell proliferation, regulation of blood flow and vascular tone, coagulation and fibrinolysis, and metabolism of a variety of macromolecules. The disturbances in endothelial amino acid transport and metabolism that occur during infection and inflammation are due, in part, to changes in substrate availability and to the local and/or systemic elaboration of specific mediators. An improved understanding of endothelial amino acid metabolism will not only provide new knowledge regarding disease mechanisms and regulation, but may also lead to new treatment strategies that may include the clinical use of specific nutritional formulas.

Use of cryoprecipitate coagulum in extracting renal calculi.

Human cryoprecipitated plasma can form an extractable coagulum which will effectively remove renal calculi in selected cases. We successfully used this blood product and a simplified injection technique in 30 patients undergoing surgery for upper tract calculi. Coagulum pyelolithotomy was performed in 24 cases with removal of all stones in 23 (96 per cent). In 6 patients incomplete stone removal by conventional operative methods was successfully completed by using the coagulum as an adjunctive procedure. In 10 of the 30 cases (33 per cent) radiographically "silent" calculi were recovered within the cryoprecipitate clot. The advantages of cryoprecipitate over previously reported blood products, certain technical simplifications, and the appropriate clinical indications for the coagulum procedure are discussed.

Adult renal myoepithelial hamartoma.

A renal myoepithelial hamartoma presented as a lucent filling defect with gross hematuria in an adult female. Preoperative studies caused conflicting impressions. The predominance of smooth muscle and incorporated tubuloepithelial elements characterize the tumor as a hamartoma of myoepithelial type. Pertinent review of the literature confirms the rarity of this lesion in adults.

Preferential loss of large neocortical neurons during HIV infection: a study of the size distribution of neocortical neurons in the human brain.

The infection with human immunodeficiency virus (HIV) is associated with a global and severe loss of neocortical neurons. However, there is limited knowledge concerning whether all neurons are equally susceptible to damage during HIV infection. Other studies have reported low vulnerability of small interneurons and high vulnerability of large motor neurons. Thus, it is natural to suggest that HIV infection, which causes damage to neurons in several ways, may predominantly affect large neurons in the neocortex. In this study we have used three unbiased stereological probes: Cavalieri's principle, the optical dissector and the rotator method, to obtain both total neocortical neuron number and their size distribution in formalin-fixed brains from six male acquired immunodeficiency syndrome (AIDS) patients and six male controls. The material is a selection of a large material choosing the youngest. The number of neurons in neocortex was reduced by 25% from 24.4 x 10(9) in controls to 18.3 x 10(9) in the AIDS patients; the reduction is similar to that of 27% found in the large material. In the normal size distribution of the neocortical neurons most neurons were smaller than 5000 micron3 and no sampled neurons were larger than 28,000 micron3. In addition, the absolute size distribution of neocortical neurons showed a significant decrease of the largest group of neurons by 50% (2p = 0.01) in the AIDS group, while there was no significant difference between controls and AIDS patients in the number of small neurons. The pattern of reduction in the number of large neocortical neurons was found in frontal, temporal, parietal as well as in occipital regions. This suggests that large neurons are more sensitive than small neurons to the destruction caused by the HIV infection.

Plasma levels of interleukin-6 and C-reactive protein are associated with physical inactivity independent of obesity.

It is recognized that the path from physical inactivity and obesity to lifestyle-related diseases involves low-grade inflammation, indicated by elevated plasma levels of inflammatory markers. Interestingly, contracting skeletal muscle is a major source of circulating interleukin-6 (IL-6) in response to acute exercise, but with a markedly lower response in trained subjects. As C-reactive protein (CRP) is induced by IL-6, we hypothesized that basal levels of IL-6 and CRP reflect the degree of regular physical activity when compared with other markers of inflammation associated with lifestyle-related morbidity. Fasting plasma/serum levels of IL-6, IL-18, CRP, tumur necrosis factor-alpha (TNF-alpha), soluble TNF receptor II (sTNF-RII), and adiponectin were measured in healthy non-diabetic men and women (n=84). The amount of leisure-time physical activity (LTPA) was assessed by interview. Obesity was associated with elevated insulin, C-peptide, triglycerides, low-density lipoprotein, IL-6, CRP, and adiponectin (all P<0.05). Importantly, physical inactivity was associated with elevated C-peptide (P=0.036), IL-6 (P=0.014), and CRP (P=0.007) independent of obesity, age, gender, and smoking. Furthermore, the LTPA score was inversely associated with IL-6 (P=0.017) and CRP (P=0.005), but with neither of the other markers. The results indicate that low levels of IL-6 and CRP - not IL-18, TNF-alpha, sTNF-RII, or adiponectin - reflect regular physical activity.

Brain-derived neurotrophic factor (BDNF) and type 2 diabetes.

AIMS/HYPOTHESIS: Decreased levels of brain-derived neurotrophic factor (BDNF) have been implicated in the pathogenesis of Alzheimer's disease and depression. These disorders are associated with type 2 diabetes, and animal models suggest that BDNF plays a role in insulin resistance. We therefore explored whether BDNF plays a role in human glucose metabolism. SUBJECTS AND METHODS: We included (Study 1) 233 humans divided into four groups depending on presence or absence of type 2 diabetes and presence or absence of obesity; and (Study 2) seven healthy volunteers who underwent both a hyperglycaemic and a hyperinsulinaemic-euglycaemic clamp. RESULTS: Plasma levels of BDNF in Study 1 were decreased in humans with type 2 diabetes independently of obesity. Plasma BDNF was inversely associated with fasting plasma glucose, but not with insulin. No association was found between the BDNF G196A (Val66Met) polymorphism and diabetes or obesity. In Study 2 an output of BDNF from the human brain was detected at basal conditions. This output was inhibited when blood glucose levels were elevated. In contrast, when plasma insulin was increased while maintaining normal blood glucose, the cerebral output of BDNF was not inhibited, indicating that high levels of glucose, but not insulin, inhibit the output of BDNF from the human brain. CONCLUSIONS/INTERPRETATION: Low levels of BDNF accompany impaired glucose metabolism. Decreased BDNF may be a pathogenetic factor involved not only in dementia and depression, but also in type 2 diabetes, potentially explaining the clustering of these conditions in epidemiological studies.

Associations between insulin resistance and TNF-alpha in plasma, skeletal muscle and adipose tissue in humans with and without type 2 diabetes.

AIMS/HYPOTHESIS: Clear evidence exists that TNF-alpha inhibits insulin signalling and thereby glucose uptake in myocytes and adipocytes. However, conflicting results exist with regard to the role of TNF-alpha in type 2 diabetes. METHODS: We obtained blood and biopsy samples from skeletal muscle and subcutaneous adipose tissue in patients with type 2 diabetes (n = 96) and healthy controls matched for age, sex and BMI (n = 103). RESULTS: Patients with type 2 diabetes had higher plasma levels of fasting insulin (p < 0.0001) and glucose (p < 0.0001) compared with controls, but there was no difference between groups with regard to fat mass. Plasma levels of TNF-alpha (p = 0.0009) and soluble TNF receptor 2 (sTNFR2; p = 0.002) were elevated in diabetic patients. Insulin sensitivity was correlated with quartiles of plasma TNF-alpha after adjustment for age, sex, obesity, WHR, neutrophils, IL-6 and maximum O(2) uptake (VO2/kg) in the diabetes group (p < 0.05). The TNF mRNA content of adipose or muscle tissue did not differ between the groups, whereas muscle TNF-alpha protein content, evaluated by western blotting, was higher in type 2 diabetic patients. Immunohistochemistry revealed more TNF-alpha protein in type 2 than in type 1 muscle fibres. CONCLUSIONS/INTERPRETATION: After adjustment for multiple confounders, plasma TNF-alpha is associated with insulin resistance. This supports the idea that TNF-alpha plays a significant role in the pathogenesis of chronic insulin resistance in humans. However, findings on the TNF-alpha protein levels in plasma and skeletal muscle indicate that measurement of TNF mRNA content in adipose or muscle tissue provides no information with regard to the degree of insulin resistance.

Recombinant human interleukin-6 infusion during low-intensity exercise does not enhance whole body lipolysis or fat oxidation in humans.

The present study examined the role of the cytokine IL-6 in the regulation of fatty acid metabolism during exercise in humans. Six well-trained males completed three trials of 120 min of cycle ergometry at 70% peak O(2) consumption (Vo(2 peak); MOD) and 40% Vo(2 peak) with (LOW + IL-6) and without (LOW) infusion of recombinant human (rh)IL-6. The dose of rhIL-6 during LOW + IL-6 elicited IL-6 concentration similar to those during MOD but without altering the circulating hormonal milieu seen in MOD. Palmitate rate of appearance (R(a)), rate of disappearance (R(d)), and oxidation were measured by means of a constant infusion of [U-(13)C]palmitate (0.015 micromol.kg(-1).min(-1), prime NaHCO(3), 1 micromol/kg). Palmitate R(a), R(d), and oxidation were not affected by rhIL-6 infusion, remaining similar to LOW at all times. Palmitate R(a) and oxidation were significantly greater in the MOD trial (P < 0.05) compared with the LOW + IL-6 and LOW trials. Our data show that a low dose of rhIL-6, administered during low-intensity exercise without altering the hormonal milieu, does not alter fatty acid metabolism. These data suggest that the increase in fatty acid utilization seen during exercise at moderate compared with low intensity is not mediated via alterations in plasma IL-6.

Interleukin-6 infusion during human endotoxaemia inhibits in vitro release of the urokinase receptor from peripheral blood mononuclear cells.

Leucocyte expression of the urokinase receptor [urokinase-type plasminogen activator receptor (uPAR)] is regulated by inflammatory mediators. This study investigated the in vivo effect of endotoxin, interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha on uPAR-release in vivo and in vitro in humans. Healthy subjects received intravenous endotoxin injection [high-dose, 2 ng/kg (n=8) and low-dose, 0.06 ng/kg (n=7)], coadministration of 0.06 ng/kg endotoxin and 3 h recombinant human (rh)IL-6 infusion (n=7) or 3 h infusion of rhIL-6 (n=6), rhTNF-alpha (n=6) or NaCl (n=5). Soluble uPAR (suPAR) was measured by enzyme-linked immunosorbent assay in plasma and supernatants from unstimulated and phytohaemagglutinin and lipopolysaccharide-stimulated peripheral blood mononuclear cell (PBMC) cultures incubated for 24 h. The spontaneous and stimulated uPAR-release from PBMC cultures was enhanced 5 h after low-dose endotoxin (both P <0.05), but coadministration of rhIL-6 during low-dose endotoxaemia abolished this enhanced uPAR release. High-dose endotoxin increased plasma suPAR levels (P <0.001) whereas low-dose endotoxin, rhIL-6 or TNF-alpha did not influence uPAR release in vivo to such degree that a systemic effect on the plasma suPAR level was detectable. Even subclinical doses of endotoxin in vivo enhance the capacity of PBMC to release uPAR after incubation in vitro. The inhibitory effect of IL-6 on endotoxin-mediated uPAR-release in vitro suggests that IL-6 has anti-inflammatory effects on endotoxin-mediated inflammation.

Laparoscopic approach to small bowel obstruction.

Historically, laparotomy and open adhesiolysis have been the treatment of choice for patients requiring surgery with small bowel obstruction (SBO), although laparotomy itself is an independent risk factor for bowel obstruction. Laparoscopy is known to create fewer intra-abdominal adhesions than open laparotomy. The observation that many patients with SBO have isolated adhesive bands has led to the use of laparoscopy as primary treatment of SBO by some authors. Although the laparoscopic approach to SBO has been described, the outcomes and indications are not well established. We will review the available literature regarding the laparoscopic approach to SBO. Additionally, we will describe the technique and make recommendations regarding which patients may be best suited for a trial of laparoscopy for adhesiolysis.

Cryoprecipitate: its use and effects in canine coagulum pyelolithotomy.

A fibrin clot forming an extractable cast or "coagulum" of the pyelocalyceal system was developed and characterized using a blood product not previously described--single donor type specific cryoprecipitate. The physical properties of the cryoprecipitate coagulum were investigated and compared with other described formulations. Simulated coagulum pyelolithotomy was performed in vivo in 11 canine kidneys with no adverse effect upon creatinine clearance or anatomic integrity. The advantages of the cryoprecipitate are detailed and a new, simplified operative technique is described.

Laparoscopic appendectomy: indications and controversies.

The introduction of laparoscopic appendectomy has been more controversial than that of laparoscopic cholecystectomy. Randomized trials have been performed, as well as meta-analysis, with equivocal results regarding effectiveness. The further expansion of the technique for interval appendectomy and in cases of complicated appendicitis has introduced new controversies and success stories. We hope to review the current application of laparoscopic appendectomy in adults based on the available literature and discuss some current controversies.

A sarcoma-derived protein regulates hepatocyte metabolism via autocrine production of tumor necrosis factor-alpha.

OBJECTIVE: The effects of conditioned media from the methylcholanthrene (MCA) fibrosarcoma on hepatocyte albumin production and amino acid transport were studied. The authors characterized a factor responsible for the observed effects and investigated the role of tumor necrosis factor-alpha (TNF-alpha) in these events. SUMMARY BACKGROUND DATA: Cancer cachexia is mediated in part by TNF-alpha. However, few tumors secrete TNF-alpha, implicating host production of this cytokine in response to as yet uncharacterized tumor-derived factors. Autocrine production of TNF-alpha recently has been described as a potent mechanism for orchestrating hepatic metabolism. METHODS: Conditioned media from the MCA fibrosarcoma was incubated with isolated primary rat hepatocytes. Albumin production and TNF-alpha production by hepatocytes was measured by enzyme-linked immunosorbent assay and amino acid transport assayed by tritium (3H)-labeled amino acid uptake. Dialysis membranes ranging from 3 kD to 100 kD were used to determine the size of the factor/factors responsible for the observed effects. RESULTS: Conditioned media from the MCA fibrosarcoma contained no TNF-alpha, whereas treatment of primary rat hepatocytes with the conditioned media resulted in a 53-fold increase in TNF-alpha production by hepatocytes compared with control. Treatment of hepatocytes with MCA fibrosarcoma-conditioned media resulted in decreases in hepatic albumin production of 46%, 61%, and 42% over 3 days of treatment, and these effects were reversible by the addition of antibody to TNF-alpha. Treatment of hepatocytes with MCA fibrosarcoma conditioned media resulted in increases in hepatocyte amino acid transport via inductions of System N (1.87 fold) and System A (1.93 fold). These effects were partially abrogated by the addition of antibody to TNF-alpha. Dialysis experiments determined the molecular weight of the factor or factors responsible for the observed effects to be greater than 100 kD. The effects of the MCA fibrosarcoma conditioned media were abolished by both trypsin treatment and heat inactivation, indicating the protein nature of the factor being studied. CONCLUSIONS: A tumor-derived protein has been isolated from the MCA fibrosarcoma. The protein inhibits hepatocyte albumin production and increases amino acid transport in vitro via the autocrine production of TNF-alpha.

Cystourethrography: the effect of reservoir height upon intravesical pressure.

The effect of infusion height upon intravesical pressure during cystography was studied in three dogs and three patients. Results indicate that during bladder filling the intravesical pressure is independent of the reservoir height.