Baseline levels of circulating galectin-1 associated with radiographic hand but not radiographic knee osteoarthritis at a two-year follow-up.

Objective: We tested the potential of circulating galectin-1, interleukin (IL)-1 beta, IL-6, and tumour necrosis factor alpha (TNF alpha) levels at baseline in individuals with knee pain as biomarkers for development of radiographic knee and/or hand osteoarthritis (OA). Design: This study comprised 212 individuals with knee pain from the Halland osteoarthritis cohort (HALLOA). Clinical characteristics and serum/plasma levels of galectin-1, IL-1 beta, IL-6, and TNF alpha were measured at baseline, and knee and hand radiographs were obtained at a two-year follow-up. The predictive value of circulating inflammatory markers and clinical variables at baseline was assessed using multinominal logistic regression for those who developed radiographic OA in knees only (n â€‹= â€‹25), in hands only (n â€‹= â€‹40), and in both knees and hands (n â€‹= â€‹43); the group who did not develop OA (n â€‹= â€‹104) was used as reference. Correlations were assessed using Spearman's correlation coefficients. Results: As expected, age was identified as a risk factor for having radiographic knee and/or hand OA at the two-year follow-up. Baseline circulating galectin-1 levels did not associate with developing radiographic knee OA but associated with developing radiographic hand OA (odds ratio (OR) for a 20% increased risk: 1.14, 95% confidence interval (CI) 1.01-1.29) and both radiographic knee and hand OA (OR for a 20% increased risk: 1.18, 95% CI 1.05-1.30). However, baseline IL-1 beta, IL-6, and TNF alpha did not associate with developing radiographic knee and/or hand OA. Conclusion: Non-age adjusted circulating galectin-1 is superior to IL-6, IL-1 beta, and TNF alpha in predicting radiographic hand but not knee OA.

Macrophage gene expression in adipose tissue is associated with insulin sensitivity and serum lipid levels independent of obesity.

OBJECTIVE: Obesity is linked to both increased metabolic disturbances and increased adipose tissue macrophage infiltration. However, whether macrophage infiltration directly influences human metabolism is unclear. The aim of this study was to investigate if there are obesity-independent links between adipose tissue macrophages and metabolic disturbances. DESIGN AND METHODS: Expression of macrophage markers in adipose tissue was analyzed by DNA microarrays in the SOS Sib Pair study and in patients with type 2 diabetes and a BMI-matched healthy control group. RESULTS: The expression of macrophage markers in adipose tissue was increased in obesity and associated with several metabolic and anthropometric measurements. After adjustment for BMI, the expression remained associated with insulin sensitivity, serum levels of insulin, C-peptide, high density lipoprotein cholesterol (HDL-cholesterol) and triglycerides. In addition, the expression of most macrophage markers was significantly increased in patients with type 2 diabetes compared to the control group. CONCLUSION: Our study shows that infiltration of macrophages in human adipose tissue, estimated by the expression of macrophage markers, is increased in subjects with obesity and diabetes and associated with insulin sensitivity and serum lipid levels independent of BMI. This indicates that adipose tissue macrophages may contribute to the development of insulin resistance and dyslipidemia.

Impaired delivery of insulin to adipose tissue and skeletal muscle in obese women with postprandial hyperglycemia.

CONTEXT: An impaired transfer of insulin from the circulation to the interstitial fluid has been suggested to contribute to insulin resistance. OBJECTIVE: The objective of the study was to address whether the delivery of insulin from the circulation to adipose tissue and skeletal muscle is impaired in obese women with postprandial hyperglycemia compared with lean healthy controls. DESIGN, SETTING, AND PARTICIPANTS: Seven obese nondiabetic women with postprandial hyperglycemia and nine lean healthy women were recruited. The interstitial insulin concentration in adipose tissue and muscle tissue was measured by the microdialysis technique during an oral glucose tolerance test (75 g). In parallel, arterial insulin levels were measured. We used ¹³³Xe clearance and plethysmography to monitor blood flow. Subcutaneous needle biopsies were taken to obtain fat cell size. RESULTS: After oral glucose ingestion, mean arterial insulin levels were higher in obese women than in the lean group. However, interstitial insulin levels in sc adipose tissue and forearm muscle were similar in both groups. Accordingly, the proportion of circulating insulin being transported across the vascular endothelium to the interstitial fluid in adipose tissue and in muscle tissue was significantly lower in the obese compared with the lean group. CONCLUSIONS: Obese subjects with postprandial hyperglycemia need higher circulating insulin levels than lean controls to attain similar interstitial insulin levels in adipose tissue and skeletal muscle, indicating an impaired transfer of insulin across the endothelium.

Glucose tolerance, insulin sensitivity and insulin release in European non-diabetic carriers of a polymorphism upstream of CDKN2A and CDKN2B.

AIMS/HYPOTHESIS: The aim of this study was to investigate the association of the rs10811661 polymorphism near the CDKN2B/CDKN2A genes with glucose tolerance, insulin sensitivity and insulin release in three samples of white people with European ancestry. METHODS: Sample 1 comprised 845 non-diabetic offspring of type 2 diabetes patients recruited in five European centres participating in the EUGENE2 study. Samples 2 and 3 comprised, respectively, 864 and 524 Italian non-diabetic participants. All individuals underwent an OGTT. Screening for the rs10811661 polymorphism was performed using a TaqMan allelic discrimination assay. RESULTS: The rs10811661 polymorphism did not show a significant association with age, BMI and insulin sensitivity. Participants carrying the TT genotype showed a significant reduction in insulin release, measured by an OGTT-derived index, compared with carriers of the C allele, in the three samples. When these results were pooled with those of three published studies, and meta-analysed with a random-effects model, the T allele was significantly associated with reduced insulin secretion (-35.09 [95% CI 14.68-55.52], p = 0.0008 for CC+CT vs TT; and -29.45 [95% CI 9.51-49.38], p = 0.0038, for the additive model). In addition, in our three samples, participants carrying the TT genotype exhibited an increased risk for impaired glucose tolerance (IGT) compared with carriers of the C allele (OR 1.55 [95% CI 1.20-1.95] for the meta-analysis of the three samples). CONCLUSIONS/INTERPRETATION: Our data, together with the meta-analysis of previously published studies, show that the rs10811661 polymorphism is associated with impaired insulin release and IGT, suggesting that this variant may contribute to type 2 diabetes by affecting beta cell function.

Insulin sensitivity, insulin release and glucagon-like peptide-1 levels in persons with impaired fasting glucose and/or impaired glucose tolerance in the EUGENE2 study.

AIMS/HYPOTHESIS: We examined the phenotype of individuals with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) with regard to insulin release and insulin resistance. METHODS: Non-diabetic offspring (n=874; mean age 40+/-10.4 years; BMI 26.6+/-4.9 kg/m(2)) of type 2 diabetic patients from five different European Centres (Denmark, Finland, Germany, Italy and Sweden) were examined with regard to insulin sensitivity (euglycaemic clamps), insulin release (IVGTT) and glucose tolerance (OGTT). The levels of glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) were measured during the OGTT in 278 individuals. RESULTS: Normal glucose tolerance was found in 634 participants, while 110 had isolated IFG, 86 had isolated IGT and 44 had both IFG and IGT, i.e. about 28% had a form of reduced glucose tolerance. Participants with isolated IFG had lower glucose-corrected first-phase (0-10 min) and higher second-phase insulin release (10-60 min) during the IVGTT, while insulin sensitivity was reduced in all groups with abnormal glucose tolerance. Similarly, GLP-1 but not GIP levels were reduced in individuals with abnormal glucose tolerance. CONCLUSIONS/INTERPRETATION: The primary mechanism leading to hyperglycaemia in participants with isolated IFG is likely to be impaired basal and first-phase insulin secretion, whereas in isolated IGT the primary mechanism leading to postglucose load hyperglycaemia is insulin resistance. Reduced GLP-1 levels were seen in all groups with abnormal glucose tolerance and were unrelated to the insulin release pattern during an IVGTT.

Insulin differentially modulates the peripheral endocannabinoid system in human subcutaneous abdominal adipose tissue from lean and obese individuals.

Human obesity has been associated with a dysregulation of the peripheral and adipose tissue (AT) endocannabinoid system (ES). The aim of this study was to elucidate the acute in vivo effects of insulin on gene expression of the cannabinoid type 1 (CB-1) and type 2 (CB-2) receptors, as well as of the fatty acid amide hydrolase (FAAH) in the sc abdominal adipose tissue (SCAAT). Nine lean (L) and 9 obese (OB), but otherwise healthy males were studied in the fasting state and during a euglycemic hyperinsulinemic clamp (40 mU/m2 * min(-1)). SCAAT biopsies were obtained at baseline and after 270 min of i.v. maintained hyperinsulinemia. The basal SCAAT gene expression pattern revealed an upregulation of the FAAH in the OB (p=0.03 vs L), whereas similar CB-1 and CB-2 mRNA levels were seen. Following hyperinsulinemia, the FAAH mRNA levels significantly increased approximately 2-fold in the L (p=0.01 vs baseline) but not in the OB. In contrast, insulin failed to significantly change both the adipose CB-1 and CB-2 gene expression. Finally, the FAAH gene expression positively correlated with the fasting serum insulin concentration (r 0.66; p=0.01), whereas an inverse association with the whole-body glucose disposal (r -0.58; p<0.05) was seen. Taken together, these first time observations demonstrate that the ES-related genes in the SCAAT differentially respond to hyperinsulinemia in lean/insulin-sensitive and in obese/insulin-resistant individuals. We suggest that insulin may play a key role in the obesity-linked dysregulation of the adipose ES at the gene level.

Increased lactate release per fat cell in normoglycemic first-degree relatives of individuals with type 2 diabetes.

The aim of this study was to examine subcutaneous lactate production in the relatives of individuals with type 2 diabetes. Therefore, we recruited seven healthy first-degree relatives of type 2 diabetic patients and seven pairwise, matched, healthy control subjects without any heredity for diabetes. All subjects were studied with a euglycemic insulin clamp at approximately 600 pmol/l, abdominal subcutaneous microdialysis, and (133)Xe clearance. Furthermore, a subcutaneous needle biopsy was performed to determine fat cell size. In the fasting state, interstitial lactate was 40% higher in relatives than in control subjects (P = 0.043), but net lactate production was similar in both groups. However, during the insulin clamp, interstitial lactate (2.50 +/- 0.29 vs. 1.98 +/- 0.26 mmol/l, P = 0.018), interstitial-arterial lactate concentration difference (1.08 +/- 0.30 vs. 0.53 +/- 0.24 mmol/l, P = 0.028), and net lactate release per fat cell (10.9 +/- 3.7 vs. 2.8 +/- 1.3 fmol. cell(-1). min(-1), P = 0.018) were increased in the relatives. We conclude that first-degree relatives of type 2 diabetic patients may have an enhanced net lactate release per fat cell in abdominal subcutaneous tissue. This could suggest a pathological regulation in adipose tissue that is of importance for the metabolic defects known in type 2 diabetic relatives.

Nicotine infusion acutely impairs insulin sensitivity in type 2 diabetic patients but not in healthy subjects.

OBJECTIVES: The aim of this study was to examine if an acute nicotine infusion alters insulin sensitivity to a similar degree in type 2 diabetic patients as in healthy control subjects. DESIGN: . Double-blind, cross-over, placebo-controlled, randomized experimental study. Nicotine 0.3 microg kg-1 min(-1) or NaCl was infused (2 h) during a euglycaemic hyperinsulinaemic clamp (4 h) to assess insulin sensitivity. SETTING: University research laboratory. SUBJECTS: Six male and female type 2 diabetic patients [DM2; age 54 +/- 10 (mean +/- SD) years; body mass index (BMI) 25.6 +/- 2.9 kg m(-2)] treated with diet or one oral hypoglycaemic agent and six age- and BMI-matched control subjects (Ctr). MAIN OUTCOME MEASURE: Insulin sensitivity (rate of glucose infusion per kg fat free body mass and minute), nicotine and free fatty acid (FFA) levels, pulse rate and blood pressure. RESULTS: The infusions produced similar nicotine levels in both groups. In the absence of nicotine, DM2 were more insulin resistant than Ctr (6.7 +/- 0.4 vs. 10.9 +/- 0.3 mg kg-1 LBM min(-1), respectively; P < 0.0001). This insulin resistance was further aggravated by the nicotine infusion in DM2 but not in Ctr (4.6 +/- 0.3 vs. 10.9 +/- 0.3 mg kg(-1) LBM min(-1); P < 0.0001). Only minor differences were seen in FFA levels, pulse rates and blood pressure. CONCLUSIONS: At this low infusion rate, nicotine aggravated the insulin resistance in DM2 but not in Ctr. This finding may be because of the (dysmetabolic) diabetic state per se or to an increased sensitivity to environmental factors associated with a genetic predisposition for type 2 diabetes. These results show that diabetic subjects are particularly susceptible to the detrimental effects of nicotine.

Validation of the internal reference technique for microdialysis measurements of interstitial histamine in the rat.

The internal reference technique (IRT) was compared with the no net flux method (NFM) as a microdialysis calibration technique for sampling of interstitial histamine in the rat. Microdialysis catheters (polyacrylonitrile, 50 kD cut off) were inserted in liver, muscle, subcutaneous tissue and in an induced adenocarcinoma. Estimated relative recovery with IRT ranged from 23+/-2% in liver to 30+/-3% in subcutaneous tissue with and without tumor (p<0.05). By using the NFM-technique we found similar recovery as compared to the IRT in all tissues studied. Interstitial histamine was up to 3-fold higher than the mean plasma histamine concentration (54+/-2 nmol/l). Subcutaneous tissue (177+/-39 nmol/l) and subcutaneous tumor (165+/-29 nmol/l) exhibited high histamine while liver (65+/-14 nmol/l) and liver tumor (75+/-7 nmol/l) had low interstitial histamine concentrations. In conclusion, the IRT was validated against the NFM as a rapid method for histamine measurements in situ in the rat.

Peroxovanadate and insulin action in adipocytes from NIDDM patients. Evidence against a primary defect in tyrosine phosphorylation.

We studied the effects of insulin and the stable peroxovanadate compound potassium bisperoxopicolinatooxovanadate (bpV(pic)), a potent inhibitor of phosphotyrosine phosphatases, on lipolysis and glucose uptake in subcutaneous adipocytes from 10 male patients with non-insulin-dependent diabetes mellitus (NIDDM) and 10 matched non-diabetic control subjects. Lipolysis stimulated by isoprenaline or the cAMP analogue, 8-bromo-cyclic AMP (8-br-cAMP), was reduced by approximately 40% in NIDDM compared to control subjects. In both groups bpV(pic) exerted an antilipolytic effect that was similar to insulin (approximately 50 % inhibition). 14C-U-glucose uptake was dose-dependently increased by bpV(pic) treatment, but this effect and also that of insulin were impaired in NIDDM compared to control (bpV(pic) 1.6-fold vs 2.4-fold and insulin 2.2-fold vs 3.4-fold). Furthermore, low concentrations of bpV(pic) did not affect insulin-stimulated glucose uptake, although tyrosine phosphorylation of the insulin receptor beta-subunit was clearly increased by bpV(pic). In conclusion, 1) beta-adrenergic stimulation of lipolysis in vitro is attenuated in NIDDM adipocytes due to post-receptor mechanisms. 2) Both insulin and bpV(pic) decrease lipolysis and enhance glucose uptake in control as well as NIDDM adipocytes. The effect on glucose uptake, but not that on lipolysis, is impaired in NIDDM cells. 3) Peroxovanadate does not improve sensitivity and responsiveness to insulin in NIDDM adipocytes, showing that insulin-resistant glucose uptake in NIDDM is not overcome by phosphotyrosine-phosphatase inhibition and, thus, probably is not caused by impaired tyrosine phosphorylation events alone.

Microdialysis methodology for the measurement of dermal interstitial fluid in humans.

In this study we aimed to validate the microdialysis technique for metabolic measurements in the dermal interstitial fluid. The abdominal and forearm skin was used for microdialysis in 15 healthy normal weight volunteers. The depth of the microdialysis catheter was assessed by ultrasound measurement. Structural impairment and blood flow were judged from biopsies and from laser Doppler measurements taken adjacent to the catheters. Dermal interstitial lactate and pyruvate concentrations were measured, under steady state fasting conditions, after equilibrium calibration of each catheter in situ. The dermal interstitial glucose concentration was estimated by means of the retrodialysis calibration method, which has previously not been evaluated for skin microdialysis. The mean catheter depth (+/- standard deviation) was 0.8 +/- 0.3 mm. Small areas of localized bleeding, but no inflammatory reaction, was found surrounding the catheters. The perfusion in the microdialysis region was slightly increased (15-25%). The lactate/pyruvate ratio (12 +/- 0.7) showed non-ischaemic values. The dermal interstitial lactate concentration was significantly higher (1171 +/- 228 mumol/l) than the plasma lactate (781 +/- 180 mumol/l), indicating an ongoing nonoxidative glucose metabolism. Retrodialysis calibration correctly estimated the dermal glucose level to be similar to that in plasma, which may indicate the usefulness of this calibration method for microdialysis studies of endogenous substrates in the dermal interstitial fluid.

Comparison of two methods to assess the tissue/blood partition coefficient for xenon in subcutaneous adipose tissue in man.

A new method to calculate the tissue/blood partition coefficient (lambda) for xenon in studies on the subcutaneous adipose tissue blood flow was compared with a previously reported method based on local skinfold thickness (lambda LST). The former method included needle biopsies from the abdominal and femoral subcutaneous adipose tissue, and the mean fat cell diameter was measured (lambda ECT). The extracellular tissue fraction in subcutaneous tissue was then estimated from a diagram. The tissue lipid content was approximated to equal the relative intracellular volume and Ostwald's solubility coefficients for 133Xe, based on the distribution of xenon in lipid, albumin and 0.9% saline were applied. Estimated lambda-values based on needle biopsies from the abdominal site were: 8.6 +/- 0.1 versus 9.9 +/- 0.4 ml g-1 (mean +/- SE) (P < 0.05) and from the femoral site: 9.1 +/- 0.1 versus 9.6 +/- 0.2 in lean (n = 10) and obese subjects (n = 10), respectively. The corresponding lambda-values obtained from skinfold measurements were: 6.2 +/- 0.5 versus 11.0 +/- 0.4 (P < 0.001) and 6.9 +/- 0.3 versus 11.4 +/- 0.4 (P < 0.001) in lean and obese subjects, respectively. Pooled lambda LST-values correlated positively with estimated adipose tissue blood flow (ATBF) (r: 0.34, P < 0.05, n = 40) whereas no such correlation was found for lambda ECT-values. In conclusion, a new method is presented which may allow an accurate determination of, and which may lead to reliable data on, subcutaneous ATBF in both lean and obese subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement by microdialysis of the insulin concentration in subcutaneous interstitial fluid. Importance of the endothelial barrier for insulin.

To evaluate the interstitial insulin and inulin concentrations, 20-min microdialysis samples from the abdominal subcutaneous tissue were obtained by using two 45-mm polypropylene dialyzing tubes (o.d. approximately 0.5 mm, pore size 0.2 micron) during a euglycemic hyperinsulinemic (120 mU.m-2 x min-1) clamp (n = 9) or during a constant inulin infusion (n = 5). After in situ calibration of the microdialysis catheters during steady-state conditions, interstitial and plasma insulin concentrations were estimated to 654 +/- 102 and 1176 +/- 66 pM, respectively, i.e., a 44% difference (P < 0.001). A doubling of the insulin infusion rate (240 mU.m-2 x m-1), leading to supraphysiological plasma insulin levels, raised the interstitial insulin concentrations markedly slower (approximately 20 min) than in plasma. Moreover, at steady state the concentration difference in the two compartments prevailed even during the high insulin infusion rate (55% difference, P < 0.01). In contrast, the interstitial inulin levels were similar to the plasma concentrations in subjects given a constant inulin infusion. Thus, the data suggest the presence of an endothelial barrier for insulin in the subcutaneous tissue. This barrier, in combination with tissue clearance of insulin, leads to lower insulin levels and altered kinetics with a slower rise in the interstitial fluid compared with plasma.

Microdialysis of intercellular adenosine concentration in subcutaneous tissue in humans.

To determine the intercellular adenosine concentration the periumbilical subcutaneous interstitial fluid was investigated in five healthy subjects with two single dialysis fiber catheters perfused with isotonic saline at a rate of 2.5 mul/min. A newly developed in situ calibration technique (29) allows an estimation of the adenosine concentration in the perfusate equilibrating with the surrounding medium, i.e., the concentration in the interstitial fluid. The mean interstitial adenosine concentration was 128 +/- 26 nM (range 25-300 nM). The effect of these adenosine concentrations on adipose tissue metabolism was investigated in isolated human fat cells. The influence of 5 and 10 nM 2-chloroadenosine, which is equipotent to 150 and 300 nM adenosine, on the dose-response curve for the lipolytic effect of norepinephrine and the stimulatory effect of insulin on glucose transport was studied. 2-Chloroadenosine at 10 nM decreased basal lipolysis 53 +/- 8% and shifted the dose-response curve for norepinephrine approximately twofold to the right. At 5 nM, 2-chloroadenosine only slightly shifted the dose-response curve, whereas basal lipolysis was not significantly reduced. 2-Chloroadenosine at either concentration had no significant effect on basal or insulin-stimulated glucose transport. In conclusion, endogenous adenosine can reach concentrations in human subcutaneous tissue sufficient for an important modulating effect on lipolysis in vivo.