Magnetic Resonance Imaging Assessment of Abdominal Ectopic Fat Deposition in Correlation With Cardiometabolic Risk Factors.

Purpose: Ectopic fat accumulation and abdominal fat distribution may have different cardiometabolic risk profiles. This study aimed to assess the associations between various magnetic resonance imaging (MRI)-acquired fat depots and cardiometabolic risk factors. Methods: A total of 320 subjects with median age of 59 years, 148 men and 172 women, were enrolled in the study. Visceral adipose tissue (VAT) area and fat fraction (FF), subcutaneous adipose tissue (SAT) area and FF at the L1-L2 levels, preperitoneal adipose tissue (pPAT) area and FF, hepatic FF, pancreatic FF, and intramuscular FF were assessed by MRI FF maps. The associations of various MRI-acquired fat depots with blood pressure, glucose, and lipid were examined using sex-stratified linear regression. Logistic regression stratified by sex was used to analyze the association of various MRI-acquired fat depots with the risk of hypertension, T2DM, and dyslipidemia. Results: The intraclass correlation coefficient (ICC) values were >0.9, which suggested good interobserver and intraobserver agreement. VAT area, V/S, hepatic fat, pancreatic fat, and pPAT rather than SAT area were significantly associated with multiple cardiometabolic risk factors (all p < 0.05). However, the patterns of these correlations varied by sex and specific risk factors. Also, VAT and SAT FF were only significantly associated with multiple cardiometabolic risk factors in women (all p < 0.05). Conclusions: VAT, hepatic fat, pancreatic fat, and pPAT were associated with cardiovascular metabolic risk factors independent of BMI. The patterns of these correlations were related to gender. These findings further the understanding of the association between ectopic fat deposition and cardiometabolic risk factors and help to better understand the obesity heterogeneity.

Donor metabolic characteristics drive effects of faecal microbiota transplantation on recipient insulin sensitivity, energy expenditure and intestinal transit time.

OBJECTIVE: Bariatric surgery improves glucose metabolism. Recent data suggest that faecal microbiota transplantation (FMT) using faeces from postbariatric surgery diet-induced obese mice in germ-free mice improves glucose metabolism and intestinal homeostasis. We here investigated whether allogenic FMT using faeces from post-Roux-en-Y gastric bypass donors (RYGB-D) compared with using faeces from metabolic syndrome donors (METS-D) has short-term effects on glucose metabolism, intestinal transit time and adipose tissue inflammation in treatment-naïve, obese, insulin-resistant male subjects. DESIGN: Subjects with metabolic syndrome (n=22) received allogenic FMT either from RYGB-D or METS-D. Hepatic and peripheral insulin sensitivity as well as lipolysis were measured at baseline and 2 weeks after FMT by hyperinsulinaemic euglycaemic stable isotope (2H2-glucose and 2H5-glycerol) clamp. Secondary outcome parameters were changes in resting energy expenditure, intestinal transit time, faecal short-chain fatty acids (SCFA) and bile acids, and inflammatory markers in subcutaneous adipose tissue related to intestinal microbiota composition. Faecal SCFA, bile acids, glycaemic control and inflammatory parameters were also evaluated at 8 weeks. RESULTS: We observed a significant decrease in insulin sensitivity 2 weeks after allogenic METS-D FMT (median rate of glucose disappearance: from 40.6 to 34.0 µmol/kg/min; p<0.01). Moreover, a trend (p=0.052) towards faster intestinal transit time following RYGB-D FMT was seen. Finally, we observed changes in faecal bile acids (increased lithocholic, deoxycholic and (iso)lithocholic acid after METS-D FMT), inflammatory markers (decreased adipose tissue chemokine ligand 2 (CCL2) gene expression and plasma CCL2 after RYGB-D FMT) and changes in several intestinal microbiota taxa. CONCLUSION: Allogenic FMT using METS-D decreases insulin sensitivity in metabolic syndrome recipients when compared with using post-RYGB-D. Further research is needed to delineate the role of donor characteristics in FMT efficacy in human insulin-resistant subjects. TRIAL REGISTRATION NUMBER: NTR4327.

Assessment of anthropometric indices other than BMI to evaluate arterial stiffness.

Based on the obesity paradox, people with a normal body mass index (BMI) may have a higher risk of mortality than those with a BMI that falls within the obese range. Despite the availability of other anthropometric measures, obesity is commonly evaluated based on BMI. A body shape index (ABSI) and body roundness index (BRI) have recently been proposed as new anthropometric measures that are calculated with height, weight, and waist circumference. This study investigated the associations between the traditional and new body composition indices and arterial stiffness using the brachial-ankle pulse wave velocity (baPWV). Overall, 3512 individuals (1228 men and 2284 women) were enrolled and were divided into two groups according to BMI. Multiple regression analysis was performed to assess the relationship between baPWV and body composition. baPWV was significantly associated with ABSI (ß = 0.087, p = 0.002), visceral adipose tissue (VAT; ß = 0.081, p = 0.002), and the visceral/subcutaneous adipose tissue (VAT/SAT) ratio (ß = 0.108, p < 0.001) in non-obese men. In non-obese women, baPWV was significantly associated with several variables but not the VAT/SAT ratio. Similarly, baPWV was significantly associated with BMI (ß = 0.103, p = 0.038), BRI (ß = 0.104, p = 0.036), VAT (ß = 0.167, p = 0.001), and the VAT/SAT ratio (ß = 0.106, p = 0.028) in obese women. ABSI can be used with high accuracy to evaluate fat distribution in non-obese men to predict arterial stiffness. However, the BRI should be used in addition to BMI to assess the body composition of women more accurately. ABSI and the BRI can be used to identify predictors of vascular remodeling or organic vascular dysfunction.

Asthma alleviates obesity in males through regulating metabolism and energy expenditure.

Many epidemiological studies suggested a correlation between obesity and asthma. However, little is known about the molecular details explaining this correlation. Here, we show that asthma decreased body weight of asthmatic male mice fed with high fat diet via increasing energy expenditure and insulin sensitivity. The increase of energy expenditure was mainly due to upregulation of pAMPK and Sirt1. The activation of AMPK/Sirt1/PGC1α signaling promoted the expression of the thermogenic genes like ucp1, PRDM16, cidea, Elovl3, PPARα, which occurred in brown adipocyte tissue and subcutaneous white adipose tissue. Besides, by activating IL33/ILC2/AAMac pathway in subcutaneous white adipose tissue, asthma promoted subcutaneous white adipose tissue into beige fat. In addition, insulin sensitivity was improved in the asthmatic male mice by decreasing the expression of G6Pase in the liver, which was recapitulated in HepG2. In human, we found that Body Mass Index (BMI) and waist circumference were significantly lower in males suffering asthma compared with the control in the National Health and Nutrition Examination Survey (NHANES) cohort. These data together suggest asthma in males decreases obesity by improving the metabolism function of brown and subcutaneous adipose tissue, and decreasing insulin resistant in the liver.

The Absence of Laminin α4 in Male Mice Results in Enhanced Energy Expenditure and Increased Beige Subcutaneous Adipose Tissue.

Laminin α4 (LAMA4) is located in the extracellular basement membrane that surrounds each individual adipocyte. Here we show that LAMA4 null (Lama4-/-) mice exhibit significantly higher energy expenditure (EE) relative to wild-type (WT) mice at room temperature and when exposed to a cold challenge, despite similar levels of food intake and locomotor activity. The Lama4-/- mice are resistant to age- and diet-induced obesity. Expression of uncoupling protein 1 is higher in subcutaneous white adipose tissue of Lama4-/- mice relative to WT animals on either a chow diet or a high-fat diet. In contrast, uncoupling protein 1 expression was not increased in brown adipose tissue. Lama4-/- mice exhibit significantly improved insulin sensitivity compared with WT mice, suggesting improved metabolic function. Overall, these data provide critical evidence for a role of the basement membrane in EE, weight gain, and systemic insulin sensitivity.

Longitudinal changes in visceral and subcutaneous adipose tissue and metabolic syndrome: Results from the Multicultural Community Health Assessment Trial (M-CHAT).

AIM: Few studies have examined whether longitudinal changes in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), independent of each other, are associated with the risk of developing metabolic syndrome (MetS). The objective of this study was to examine the longitudinal effects of VAT and SAT on MetS and metabolic risk factors in a multi-ethnic sample of Canadians followed for 5-years. MATERIALS AND METHODS: In total, 598 adults of the Multicultural Community Health Assessment Trial (M-CHAT) were included in this study. Assessments of body composition using computed tomography (CT) and metabolic risk factors were conducted at baseline, 3-, and 5-years. Mixed-effects logistic regression was used to model the longitudinal effects of VAT and SAT on MetS and metabolic risk factors. RESULTS: There were significant between-person (cross-sectional) effects such that for every 10cm2 higher VAT, the odds of MetS, high-risk fasting glucose levels and high-risk HDL-C levels significantly increased by 16% (95% CI: 9-24%), 11% (3-20%), and 7% (0-14%) respectively. Significant within-person (longitudinal) effects were also found such that for every 10cm2 increase in VAT the odds of MetS and high-risk triglyceride levels significantly increased by 23% (9-39%) and 30% (14-48%), respectively. Cross-sectional or longitudinal changes in SAT were not associated with MetS or metabolic risk factors. CONCLUSIONS: This study found a direct relationship between longitudinal change in VAT and MetS risk independent of changes in SAT. Clinical practice should focus on the reduction of VAT to improve cardiovascular health outcomes.

Central Obesity and Liver Iron Content: A Noninvasive Assessment in General Population by Magnetic Resonance Imaging.

BACKGROUND/AIM: Existing evidence points to an altered status of iron metabolism in obesity. We aimed to investigate whether central obesity is independently associated with estimated liver iron content (liver T2* value) in general population that used the noninvasive assessment method by MRI. METHODS: The study was carried out on 200 subjects randomly selected from the Golestan Cohort Study who underwent abdominal MRI. Quantitative T2* maps of entire cross-sectional area of liver were calculated using a semi-automated software for estimating the levels of iron content. Segmentation and calculation of visceral (VFA) and subcutaneous fat area (SFA) were also performed. RESULTS: There was no significant difference in mean liver T2* values between obese (body mass index, BMI >30 kg/m2) and non-obese (BMI ≤30 kg/m2) subjects. After controlling for other covariates, no statistically significant association was detected between liver T2* values and VFA, SFA and VFA/SFA ratio. The drop in the relative signal intensity as an indicator of steatosis and serum ferritin predicted liver T2* values that almost had the same strength (standardized ß of -0.41 and -0.41, respectively). CONCLUSIONS: Central obesity indices are not correlated with estimated liver iron content by MRI. Hepatic steatosis and serum ferritin seem to be the best predictors of hepatic T2* value. Since central obesity indices were not direct predictors of hepatic T2* value after the adjustment for confounding factors, it is possible that lipid accumulation in the liver locally, but not systematically, influences hepatic iron metabolism.

Diffuse optical spectroscopic imaging of subcutaneous adipose tissue metabolic changes during weight loss.

BACKGROUND: Changes in subcutaneous adipose tissue (AT) structure and metabolism have been shown to correlate with the development of obesity and related metabolic disorders. Measurements of AT physiology could provide new insight into metabolic disease progression and response to therapy. An emerging functional imaging technology, diffuse optical spectroscopic imaging (DOSI), was used to obtain quantitative measures of near infrared (NIR) AT optical and physiological properties. METHODS: Ten overweight or obese adults were assessed during 3 months on calorie-restricted diets. DOSI-derived tissue concentrations of hemoglobin, water and lipid and the wavelength-dependent scattering amplitude (A) and slope (b) obtained from 30 abdominal locations and three time points (T0, T6, T12) were calculated and analyzed using linear mixed-effects models and were also used to form 3D surface images. RESULTS: Subjects lost a mean of 11.7±3.4% of starting weight, while significant changes in A (+0.23±0.04 mm(-1), adj. P<0.001),b (-0.17±0.04, adj. P<0.001), tissue water fraction (+7.2±1.1%, adj. P<0.001) and deoxyhemoglobin (1.1±0.3 µM, adj. P<0.001) were observed using mixed-effect model analysis. DISCUSSION: Optical scattering signals reveal alterations in tissue structure that possibly correlate with reductions in adipose cell volume, while water and hemoglobin dynamics suggest improved AT perfusion and oxygen extraction. These results suggest that DOSI measurements of NIR optical and physiological properties could be used to enhance understanding of the role of AT in metabolic disorders and provide new strategies for diagnostic monitoring of obesity and weight loss.

Sensitive and rapid assessment of amyloid by oligothiophene fluorescence in subcutaneous fat tissue.

Systemic amyloidosis (SA) is often diagnosed late. Combining clinical and biochemical biomarkers is necessary for raising suspicion of disease. Fine needle aspiration (FNA) of subcutaneous fat enables SA detection by Congo red staining. The luminescent conjugated probe heptameric formic thiophene acetic acid (h-FTAA) is a sensitive alternative to Congo red-staining of tissue samples. Our objective was to compare h-FTAA fluorescence with the Congo red stain for amyloid detection in FNA-obtained fat tissue. Herein, we studied samples from 57 patients with established SA (19 with AA, 20 with AL, and 18 with ATTR) and 17 age-matched controls (34-75 years). Positivity for h-FTAA was graded according to a Congo red-based grading scale ranging from 0 to 4+. Amyloid grading by both methods correlated strongly (r = 0.87). Here h-FTAA was positive in 53 of 54 Congo red-positive cases (sensitivity 98%) and h-FTAA was negative in 7 of 17 Congo red-negative controls (specificity 41%), but was also positive for 3 Congo red-negative SA cases. We conclude that h-FTAA fluorescence is more sensitive than Congo red staining in this small exploratory study of fat tissue samples, implicating potential sensitivity for prodromal amyloidosis, but is less specific for clinical amyloidosis defined by Congo red positivity. Given its simplicity h-FTAA staining may therefore be the most appropriate method for rapid screening of fat tissue samples but should presently treat grade 1+ as only suggestive, whereas 2+ or higher as positive for amyloidosis. Parallel assessment of h-FTAA and Congo red staining appears highly promising for clinical applications.

Continuous versus short-term infusion of cefuroxime: assessment of concept based on plasma, subcutaneous tissue, and bone pharmacokinetics in an animal model.

The relatively short half-lives of most ß-lactams suggest that continuous infusion of these time-dependent antimicrobials may be favorable compared to short-term infusion. Nevertheless, only limited solid-tissue pharmacokinetic data are available to support this theory. In this study, we randomly assigned 12 pigs to receive cefuroxime as either a short-term or continuous infusion. Measurements of cefuroxime were obtained every 30 min in plasma, subcutaneous tissue, and bone. For the measurements in solid tissues, microdialysis was applied. A two-compartment population model was fitted separately to the drug concentration data for the different tissues using a nonlinear mixed-effects regression model. Estimates of the pharmacokinetic parameters and time with concentrations above the MIC were derived using Monte Carlo simulations. Except for subcutaneous tissue in the short-term infusion group, the tissue penetration was incomplete for all tissues. For short-term infusion, the tissue penetration ratios were 0.97 (95% confidence interval [CI], 0.67 to 1.39), 0.61 (95% CI, 0.51 to 0.73), and 0.45 (95% CI, 0.36 to 0.56) for subcutaneous tissue, cancellous bone, and cortical bone, respectively. For continuous infusion, they were 0.53 (95% CI, 0.33 to 0.84), 0.38 (95% CI, 0.23 to 0.57), and 0.27 (95% CI, 0.13 to 0.48) for the same tissues, respectively. The absolute areas under the concentration-time curve were also lower in the continuous infusion group. Nevertheless, a significantly longer time with concentrations above the MIC was found for continuous infusion up until MICs of 4, 2, 2, and 0.5 µg/ml for plasma and the same three tissues mentioned above, respectively. For drugs with a short half-life, like cefuroxime, continuous infusion seems to be favorable compared to short-term infusion; however, incomplete tissue penetration and high MIC strains may jeopardize the continuous infusion approach.

The association between chemerin and homeostasis assessment of insulin resistance at baseline and after weight reduction via lifestyle modifications in young obese adults.

BACKGROUND: Chemerin is a recently discovered adipocytokine, associated with adiposity and insulin sensitivity. The current study investigated the effects of lifestyle intervention on circulating chemerin level and its association with insulin resistance and adiponectin in human. METHODS: Forty male and 20 female obese adults (mean age: 29.7±5.7 y, mean BMI: 29.3±4.5 kg/m(2)) completed an 8-week lifestyle intervention program, which consisted of a home-based diet and exercise program. Anthropometric measurements and biomarkers were assessed at the baseline and at the end of the study. RESULTS: Eight weeks of lifestyle intervention reduced body weight, visceral fat and subcutaneous fat by 3.8%, 15.3% and 11.5%, respectively. The lifestyle intervention further reduced fasting insulin (10.9±6.6 vs. 7.6±5.3 µU/ml, p<0.001) and homeostasis assessment of insulin resistance (HOMA-IR) (2.3±1.5 vs. 1.6±1.2, p<0.001), chemerin (103.3±20.7 vs. 96.5±19.5 ng/ml, p<0.001) and hs-CRP levels (1.3±1.8 vs. 0.2±0.2 mg/dl, p<0.001) while it increased fasting pentraxin (PTX) 3 (0.6±0.7 vs. 0.7±0.4 ng/ml, p=0.049) level. The Δ chemerin levels correlated with Δ insulin (r=0.349, p=0.024) and HOMA-IR (r=0.333, p=0.36) even after adjusting for age and gender. CONCLUSION: The lifestyle intervention reduced circulating chemerin levels independent of visceral fat mass and adiponectin. Chemerin levels are associated with insulin resistance at the baseline and after the lifestyle intervention.

Assessment of different techniques for subcutaneous glucose monitoring in Type 1 diabetic patients during 'real-life' glucose excursions.

AIMS: To compare the accuracy of two marketed subcutaneous glucose monitoring devices (Guardian RT, GRT; GlucoDay S, GDS) and standard microdialysis (CMA60; MD) in Type 1 diabetic patients. METHODS: Seven male Type diabetic patients were investigated over a period of 26 h simulating real-life meal glucose excursions. Catheters of the three systems were inserted into subcutaneous adipose tissue of the abdominal region. For MD, interstitial fluid was sampled at 30- to 60-min intervals for offline glucose determination. Reference samples were taken at 15- to 60-min intervals. All three systems were prospectively calibrated to reference. Median differences, median absolute relative differences (MARD), median absolute differences (MAD), Bland-Altman plot and Clark Error Grid were used to determine accuracy. RESULTS: Bland-Altman analysis indicated a mean glucose difference (2 standard deviations) between reference and interstitial glucose of -10.5 (41.8) % for GRT, 20.2 (55.9) % for GDS and 6.5 (35.2) % for MD, respectively. Overall MAD (interquartile range) was 1.07 (0.39; 2.04) mmol/l for GRT, 1.59 (0.54; 3.08) mmol/l for GDS and 0.76 (0.26; 1.58) mmol/l for MD. Overall MARD was 15.0 (5.6; 23.4) % (GRT), 19.7 (6.1; 37.6) % (GDS) and 8.7 (4.1; 18.3) % (MD), respectively. Total sensor failure occurred in two subjects using GRT and one subject using GDS. CONCLUSIONS: The three investigated technologies had comparable performance. Whereas GRT underestimated actual blood glucose, GDS and MD overestimated blood glucose. Considerable deviations during daily life meal glucose excursions from reference glucose were observed for all three investigated technologies. Present technologies may require further improvement until individual data can lead to direct and automated generation of therapeutic advice in diabetes management.

SAR versus S(inc): What is the appropriate RF exposure metric in the range 1-10 GHz? Part I: Using planar body models.

This is the first of two articles addressing the most appropriate crossover frequency at which incident power flux density (S(inc)) replaces the spatial peak value of the specific energy absorption rate (SAR) averaged over 1 or 10 g (i.e., peak 1 or 10 g SAR) as the basic restriction for protecting against radiofrequency (RF) heating effects in the 1-10 GHz range. Our general approach has been to compare the degree of correlation between these basic restrictions and the peak induced tissue temperature rise (DeltaT) for a representative range of population/exposure scenarios. In this article we particularly address the effect of human population diversity in the thickness of body tissue layers at eight different sites of the body. We used a Monte Carlo approach to specify 32000 models (400 models for each of 8 body sites for 10 frequencies) which were representative of tissue thicknesses for age (18-74 years) and sex at the eight body sites. Histogram distributions of S(inc) and peak 1 and 10 g SAR corresponding to a peak 1 degrees C temperature rise were obtained from RF and thermal analyses of 1D multiplanar models exposed to a normally incident plane wave ranging from 1 to 10 GHz in thermo-neutral environmental conditions. Examination of the distribution spread of the histograms indicated that peak SAR was a better predictor of peak tissue temperature rise across the entire 1-10 GHz frequency range than S(inc), as indicated by the smaller spread in its histogram distributions, and that peak 10 g SAR was a slightly better predictor than peak 1 g SAR. However, this result must be weighed against partly conflicting indications from complex body modeling in the second article of this series, which incorporates near-field effects and the influence of complex body geometries.

Circulating white blood cell count and measures of adipose tissue inflammation predict higher 24-h energy expenditure.

OBJECTIVE: Energy expenditure (EE) and measures of inflammation increase with adiposity, and this obesity-induced chronic and subclinical inflammation was extensively reported to be a cause of insulin resistance. However, whether subclinical inflammation has a role in increasing EE, which may be at the cost of developing insulin resistance, is not clear. METHODS: We investigated the association between circulating white blood cell count (WBC) in a population of Native Americans (n=243) with measurement of EE in a respiratory chamber, and in a subset of the same population (n=34), with gene expression measures of inflammation in subcutaneous abdominal adipose tissue (SAAT). All subjects were healthy on oral glucose tolerance test. Statistically, nonnormally distributed variables were logarithmically transformed before analyses to approximate normal distributions. RESULTS: WBC was associated with 24-h EE adjusted for age, sex, fat-free mass, and fat mass (r=0.13, P=0.04). In SAAT, tumor necrosis factor-alpha (TNF-alpha), shown as log10-transformed TNF-alpha (r=0.36, P=0.05), and plasminogen activator inhibitor-1 (PAI-1), shown as log10-transformed PAI-1 (lPAI-1; r=0.41, P=0.02), expressions were also positively correlated with adjusted 24-h EE. lPAI-1 was also correlated with adjusted sleep EE (r=0.34, P=0.07). CONCLUSIONS: In conclusion, circulating markers of inflammation (WBC) and markers of inflammation within adipose tissue (TNF-alpha and PAI-1) are positively associated with EE, indicating a role of chronic subclinical inflammation in the regulation of metabolic rate.

Costs of pair-bonding and paternal care in male prairie voles (Microtus ochrogaster).

The direct costs of paternal care are relatively well documented in primates, however little research has explored these effects in monogamous rodents. The present study examines the long-term effects that pairing and parenting have on male prairie voles. We hypothesized that there would be a significant weight loss over the course of pairing and parenting, presumably from the energetic demands that accompany these changes in social condition. In a longitudinal study, we followed ten male prairie voles through being housed with their brother; paired with a female; and caring for three consecutive litters. We found a significant drop in bodyweight across time, with maximum weight loss near the weaning of the first litter. At that same time, feeding increased, leading to possible recovery in weight; however, leptin levels dropped precipitously across time and did not recover. Corticosterone did not change significantly across time points, and overall activity levels also did not vary significantly over the course of the study. In addition, newly paired males showed a significant increase in preference for a 2% sucrose solution during a three-hour test, indicating a metabolic need for more calories. A cross-sectional study confirmed leptin and corticosterone findings, and showed significant loss of subcutaneous (inguinal) fat in males that had cared for a litter of pups, when compared to males housed with their brothers or newly paired males. These results suggest that cohabitation with a female, and caring for pups, all have costs for male prairie voles.

In vivo quantification of subcutaneous and visceral adiposity by micro-computed tomography in a small animal model.

Accurate and precise techniques that identify the quantity and distribution of adipose tissue in vivo are critical for investigations of adipose development, obesity, or diabetes. Here, we tested whether in vivo micro-computed tomography (microCT) can be used to provide information on the distribution of total, subcutaneous and visceral fat volume in the mouse. Ninety C57BL/6J mice (weight range: 15.7-46.5 g) were microCT scanned in vivo at 5 months of age and subsequently sacrificed. Whole body fat volume (base of skull to distal tibia) derived from in vivo microCT was significantly (p<0.001) correlated with the ex vivo tissue weight of discrete perigonadal (R(2)=0.94), and subcutaneous (R(2)=0.91) fat pads. Restricting the analysis of tissue composition to the abdominal mid-section between L1 and L5 lumbar vertebrae did not alter the correlations between total adiposity and explanted fat pad weight. Segmentation allowed for the precise discrimination between visceral and subcutaneous fat as well as the quantification of adipose tissue within specific anatomical regions. Both the correlations between visceral fat pad weight and microCT determined visceral fat volume (R(2)=0.95, p<0.001) as well as subcutaneous fat pad weight and microCT determined subcutaneous fat volume (R(2)=0.91, p<0.001) were excellent. Data from these studies establish in vivo microCT as a non-invasive, quantitative tool that can provide an in vivo surrogate measure of total, visceral, and subcutaneous adiposity during longitudinal studies. Compared to current imaging techniques with similar capabilities, such as microMRI or the combination of DEXA with NMR, it may also be more cost-effective and offer higher spatial resolutions.

The effects of the surgical removal of subcutaneous adipose tissue on energy expenditure and adipocytokine concentrations in obese women.

OBJECTIVE: To analyze the effects of the surgical removal of subcutaneous adipose tissue by ultrasound-assisted megalipoplasty (UAM) on energy expenditure and adipocytokine concentrations in obese women. METHODS: Fifteen premenopausal obese women with BMI 37.5+/-6.3 kg/m(2) (range: 30.7-53.6 kg/m(2)) underwent UAM. Body composition (by DEXA), resting metabolic rate (REE) by indirect calorimetry, insulin resistance (by the HOMA method), leptin, C-reactive protein, interleukin-6, resistin and adiponectin were measured before and 1, 3, 28 and 180 days after the procedure. RESULTS: UAM significantly reduced fat mass at day 3, without further changes in the following days. REE increased at day 3 after UAM, returned to baseline levels at day 28 and significantly declined at day 180. Leptin levels transiently increased after UAM and then declined according to fat mass reduction. C-reactive protein, interleukin-6 and resistin levels acutely increased after UAM and then returned to the baseline levels. Adiponectin levels acutely declined after the procedure and then stabilized to a plasma level slightly lower than at baseline. Insulin resistance deteriorated in the acute post-operative phase and then improved. CONCLUSION: The surgical removal of subcutaneous fat was associated to an acute inflammatory reaction with high REE and insulin-resistance. Later on, the metabolic effects of fat mass removal appeared, with a reduction of leptin levels and REE and an improvement of insulin resistance.

Tyramine in the assessment of regional adrenergic function.

Regional adrenergic function is difficult to assess in humans. Tyramine given through a microdialysis probe may be a useful tool in this regard. However, tyramine data is hard to interpret given the drug's complex mode of action. We characterized the response to tyramine, isoproterenol, and dopamine in adipose tissue with microdialysis probes in normal subjects. We measured glycerol concentrations to follow changes in lipolysis and monitored tissue perfusion with ethanol dilution. During perfusion with tyramine, dialysate glycerol concentration increased dose-dependently from 83+/-8 microM at baseline to 181+/-18 microM at 3.5 mM tyramine (p<0.001) followed by a fall down to 121+/-9 microM at 35 mM tyramine (p<0.001). Propranolol almost completely blocked this response. A similar lipolytic response was not observed in isolated human adipocytes. Dopamine <35 microM did not replicate the tyramine-induced lipolysis; however, dopamine >35 microM potently inhibited lipolysis. We conclude that tyramine-induced lipolysis is explained by a pre-synaptic mechanism. Tyramine applied through a microdialysis probe in concentrations up to 3.5 mM can be used to assess pre- and post-synaptic mechanisms regulating lipid mobilization.