Microstructural features of lyophilized adipose - A new concept to estimate the metabolic symptoms for obese patients.

The aim of this study was to investigate the distribution of different morphological features in different layers of lyophilized adipose tissue. In this work the scanning electron microscopy (SEM) was adopted for investigation of lyophilized adipose tissue taken from obese patients. The adipose tissue was taken from subcutaneous (SAT), preperitoneal (PAT) and visceral (VAT) layers of adipose tissue. The obtained results of the main microstructural features provided information about morphological features of subcutaneous, preperitoneal and visceral layers in obese people. The obtained SEM results possibly could be used for the estimation of metabolic symptoms and prediction different diseases. The SEM method was never used before to investigate morphology of SAT, PAT and VAT layers of lyophilized human adipose tissue.

Inter-tissue expression patterns of the key metabolic biomarker PGC-1α in severely obese individuals: Implication in obesity-induced disease.

OBJECTIVE: PGC-1α is already known as a significant regulator of mitochondrial biogenesis, oxidative phosphorylation and fatty acid metabolism. Our study focuses on the role of PGC1α in morbid obesity, in five different tissues, collected from 50 severely obese patients during planned bariatric surgery. METHODS: The investigated tissues included subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), skeletal muscle (SM), extramyocellular adipose tissue (EMAT) and liver. PGC1α expression was investigated with immunohistochemistry and evaluated with microscopy. RESULTS: Our findings highlighted significant positive inter-tissue correlations regarding PGC-1α expression between several tissue pairs (VAT-SAT, VAT-SM, VAT-EMAT, SAT-SM, SAT-EMAT, SM-EMAT). Moreover, we found significant negative correlations between PGC1α expression in VAT with CD68 expression in skeletal muscle and EMAT, implying a possible protective role of PGC1α against obesity-induced inflammation. CONCLUSION: Unmasking the inter-tissue communication networks regarding PGC-1α expression in morbid obesity, will give more insight into its significant role in obesity-induced diseases. PGC1α could potentially represent a future preventive and therapeutic target against obesity-induced disease, probably through enhancing mitochondrial biogenesis and metabolism.

PTRF acts as an adipokine contributing to adipocyte dysfunctionality and ectopic lipid deposition

Adipose tissue (AT) expands under obesogenic conditions. Yet, when the growth exceeds a certain limit, AT becomes dysfunctional and surplus lipids start depositing ectopically. Polymerase I and transcription release factor (PTRF) has been proposed as a mechanism leading to a dysfunctional AT by decreasing the adipogenic potential of human adipocyte precursors. However, whether or not PTRF can be secreted by the adipocytes into the bloodstream is not yet known. For this work, PTRF presence was investigated in plasma. We also produced a recombinant PTRF (rPTRF) and examined its impact on the functional interactions between the adipocyte and the hepatocyte in vitro. We demonstrated that PTRF can be found in human plasma, and is at least in part, carried by exosomes. In vitro treatment with rPTRF increased the hypertrophy and senescence of 3T3-L1 adipocytes. In turn, those rPTRF-treated adipocytes increased lipid accumulation in hepatocytes. Lastly, we found a positive correlation between circulating PTRF and the concentration of PTRF in the visceral fat depot. All these findings point toward the presence of an enlarged and dysfunctional visceral adipose tissue which secretes PTRF. This circulating PTRF behaves as an adipokine and may partially contribute to the well-known detrimental effects of visceral fat accumulation

PTRF acts as an adipokine contributing to adipocyte dysfunctionality and ectopic lipid deposition.

Adipose tissue (AT) expands under obesogenic conditions. Yet, when the growth exceeds a certain limit, AT becomes dysfunctional and surplus lipids start depositing ectopically. Polymerase I and transcription release factor (PTRF) has been proposed as a mechanism leading to a dysfunctional AT by decreasing the adipogenic potential of human adipocyte precursors. However, whether or not PTRF can be secreted by the adipocytes into the bloodstream is not yet known. For this work, PTRF presence was investigated in plasma. We also produced a recombinant PTRF (rPTRF) and examined its impact on the functional interactions between the adipocyte and the hepatocyte in vitro. We demonstrated that PTRF can be found in human plasma, and is at least in part, carried by exosomes. In vitro treatment with rPTRF increased the hypertrophy and senescence of 3T3-L1 adipocytes. In turn, those rPTRF-treated adipocytes increased lipid accumulation in hepatocytes. Lastly, we found a positive correlation between circulating PTRF and the concentration of PTRF in the visceral fat depot. All these findings point toward the presence of an enlarged and dysfunctional visceral adipose tissue which secretes PTRF. This circulating PTRF behaves as an adipokine and may partially contribute to the well-known detrimental effects of visceral fat accumulation.

Circulating Soluble IL-6 Receptor Concentration and Visceral Adipocyte Size Are Related to Insulin Resistance in Taiwanese Adults with Morbid Obesity.

BACKGROUND: Morbid obesity is related to chronic inflammation and many metabolic complications. Interleukin (IL)-6 plays a pivotal pathophysiological role in obesity, and IL-6 trans-signaling through the soluble IL-6 receptor (sIL-6R) has a major proinflammatory effect. The aim of this study was to investigate the association between sIL-6R, adipocyte size, and insulin resistance in morbidly obese individuals. METHODS: We measured concentrations of sIL-6R, high-sensitivity C-reactive protein, and lipid parameters and estimated homeostasis model assessment of insulin resistance (HOMA-IR) before the patients underwent bariatric surgery. Mesenteric adipose tissue was collected during surgery, and adipocyte size and concentrations of membrane-bound IL-6 receptor (mIL-6R) were evaluated. In total, 35 adults (20 men and 15 women) were recruited. RESULTS: The subjects with high HOMA-IR (≥2.4) had higher fasting glucose/insulin, triglycerides, sIL-6R, and adipocyte size and lower high-density lipoprotein cholesterol and mIL-6R than those with low HOMA-IR (<2.4). Adipocyte size positively correlated with sIL-6R (r = 0.559, P = 0.001) and HOMA-IR (r = 0.773, P ≤ 0.001) independent of age, gender, body mass index (BMI), waist, and use of diabetic drugs. In addition, every 1 ng/mL increase in sIL-6R concentration corresponded to a 10.2% decrease in the likelihood of maintaining lower insulin resistance. Furthermore, an sIL-6R level of 77.45 ng/mL was a reasonable cutoff level to propose lower insulin resistance in morbidly obese subjects. CONCLUSIONS: Circulating sIL-6R is more closely associated with insulin resistance status than waist-to-hip ratio or BMI in morbidly obese Taiwanese adults. sIL-6R may be a useful biomarker to assess insulin resistance among morbidly obese subjects.

Multiphoton Microscopy for Visualizing Lipids in Tissue.

Visualizing the appearance of fat droplets and adipocytes in tissue can be realized using a label-free imaging method known as coherent anti-Stokes Raman spectroscopy (CARS). CARS is a nonlinear optical technique that allows label-free imaging of a material with contrast based on the same vibrational signatures of molecules found in Raman spectroscopy. CARS can be combined with other single and multiphoton imaging modes such as second harmonic generation and two-photon fluorescence to image a broad variety of biological structures.Here we describe the construction of a multiphoton microscope that will enable the study of both fluorescently labeled and unlabeled tissue. This has been used to monitor the contribution of Wt1 expressing cells towards the visceral fat depots during gestation.

Constitutive adipocyte mTORC1 activation enhances mitochondrial activity and reduces visceral adiposity in mice.

Mechanistic target of rapamycin complex 1 (mTORC1) loss of function reduces adiposity whereas partial mTORC1 inhibition enhances fat deposition. Herein we evaluated how constitutive mTORC1 activation in adipocytes modulates adiposity in vivo. Mice with constitutive mTORC1 activation in adipocytes induced by tuberous sclerosis complex (Tsc)1 deletion and littermate controls were evaluated for body mass, energy expenditure, glucose and fatty acid metabolism, mitochondrial function, mRNA and protein contents. Adipocyte-specific Tsc1 deletion reduced visceral, but not subcutaneous, fat mass, as well as adipocyte number and diameter, phenotypes that were associated with increased lipolysis, UCP-1 content (browning) and mRNA levels of pro-browning transcriptional factors C/EBPß and ERRα. Adipocyte Tsc1 deletion enhanced mitochondrial oxidative activity, fatty acid oxidation and the expression of PGC-1α and PPARα in both visceral and subcutaneous fat. In brown adipocytes, however, Tsc1 deletion did not affect UCP-1 content and basal respiration. Adipocyte Tsc1 deletion also reduced visceral adiposity and enhanced glucose tolerance, liver and muscle insulin signaling and adiponectin secretion in mice fed with purified low- or high-fat diet. In conclusion, adipocyte-specific Tsc1 deletion enhances mitochondrial activity, induces browning and reduces visceral adiposity in mice.

Mitochondrial respiration in subcutaneous and visceral adipose tissue from patients with morbid obesity.

Adipose tissue exerts important endocrine and metabolic functions in health and disease. Yet the bioenergetics of this tissue is not characterized in humans and possible regional differences are not elucidated. Using high resolution respirometry, mitochondrial respiration was quantified in human abdominal subcutaneous and intra-abdominal visceral (omentum majus) adipose tissue from biopsies obtained in 20 obese patients undergoing bariatric surgery. Mitochondrial DNA (mtDNA) and genomic DNA (gDNA) were determined by the PCR technique for estimation of mitochondrial density. Adipose tissue samples were permeabilized and respirometric measurements were performed in duplicate at 37 degrees C. Substrates (glutamate (G) + malate (M) + octanoyl carnitine (O) + succinate (S)) were added sequentially to provide electrons to complex I + II. ADP ((D)) for state 3 respiration was added after GM. Uncoupled respiration was measured after addition of FCCP. Visceral fat contained more mitochondria per milligram of tissue than subcutaneous fat, but the cells were smaller. Robust, stable oxygen fluxes were found in both tissues, and coupled state 3 (GMOS(D)) and uncoupled respiration were significantly (P < 0.05) higher in visceral (0.95 +/- 0.05 and 1.15 +/- 0.06 pmol O(2) s(1) mg(1), respectively) compared with subcutaneous (0.76 +/- 0.04 and 0.98 +/- 0.05 pmol O(2) s(1) mg(1), respectively) adipose tissue. Expressed per mtDNA, visceral adipose tissue had significantly (P < 0.05) lower mitochondrial respiration. Substrate control ratios were higher and uncoupling control ratio lower (P < 0.05) in visceral compared with subcutaneous adipose tissue. We conclude that visceral fat is bioenergetically more active and more sensitive to mitochondrial substrate supply than subcutaneous fat. Oxidative phosphorylation has a higher relative activity in visceral compared with subcutaneous adipose tissue.

Changes in visceral adipose tissue mitochondrial content with type 2 diabetes and daily voluntary wheel running in OLETF rats.

Using the hyperphagic, obese, Otsuka Long-Evans Tokushima Fatty (OLETF) rat, we sought to determine if progression to type 2 diabetes alters visceral white adipose tissue (WAT) mitochondrial content and if these changes are modified through prevention of type 2 diabetes with daily exercise. At 4 weeks of age, OLETF rats began voluntary wheel running (OLETF-EX) while additional OLETF rats (OLETF-SED) and Long-Evans Tokushima Otsuka (LETO-SED) rats served as obese and lean sedentary controls, respectively, for 13, 20 and 40 weeks of age (n = 6-8 for each group at each age). OLETF-SED animals displayed insulin resistance at 13 and 20 weeks and type 2 diabetes by 40 weeks. OLETF-SED animals gained significantly (P < 0.001) more weight and omental fat mass compared with OLETF-EX and LETO-SED. Markers of WAT mitochondrial protein content (cytochrome c, COXIV-subunit I, and citrate synthase activity) significantly increased (P < 0.05) from 13 to 40 weeks in the LETO-SED, but were significantly attenuated in the OLETF-SED rats. Daily exercise normalized WAT cytochrome c and COXIV-subunit I protein content in the OLETF-EX to the healthy LETO-SED animals. In conclusion, increases in omental WAT mitochondrial content between 20 and 40 weeks of age in LETO control animals are attenuated in the hyperphagic, obese OLETF rat. These alterations occurred in conjunction with the progression from insulin resistance to type 2 diabetes and were prevented with daily exercise. Reduced ability to increase WAT mitochondrial content does not appear to be a primary cause of insulin resistance, but may play a key role in the worsening of the disease condition.

Comparison of anthropometric, area- and volume-based assessment of abdominal subcutaneous and visceral adipose tissue volumes using multi-detector computed tomography.

PURPOSE: Cross-sectional imaging may enable accurate localization and quantification of subcutaneous and visceral adipose tissue. The reproducibility of multi-detector computed tomography (MDCT)-based volumetric quantification of abdominal adipose tissue and the ability to depict age- and gender-related characteristics of adipose tissue deposition have not been reported. METHODS: We evaluated a random subset of 100 Caucasian subjects (age range: 37-83 years; 49% women) of the Framingham Heart Study offspring cohort who underwent MDCT scanning. Two readers measured subcutaneous and visceral adipose tissue volumes (SAV and VAV; cm(3)) and areas (SAA and VAA; cm(2)) as well as abdominal sagital diameter (SD) and waist circumference (WC). RESULTS: Inter-reader reproducibility was excellent (relative difference: -0.34+/-0.52% for SAV and 0.59+/-0.93% for VAV, intra-class correlation (ICC)=0.99 each). The mean SAA/VAA ratio was significantly different from the mean SAV/VAV ratio (2.0+/-1.2 vs 1.7+/-0.9; P<0.001). The ratio of SAV/VAV was only weakly inversely associated with SD (ICC=-0.32, P=0.01) and not significantly associated with WC (ICC=-0.14, P=0.14) or body mass index (ICC=-0.17, P=0.09). The mean SAV/VAV ratio was significantly different between participants <60 vs >60 years (1.9+/-1.0 vs 1.5+/-0.7; P<0.001) and between men and women (1.2+/-0.5 vs 2.2+/-0.9; P<0.001). CONCLUSION: This study demonstrates that MDCT-based volumetric quantification of abdominal adipose tissue is highly reproducible. In addition, our results suggest that volumetric measurements can depict age- and gender-related differences of visceral and subcutaneous abdominal adipose tissue deposition. Further research is warranted to assess whether volumetric measurements may substantially improve the predictive value of obesity measures for insulin resistance, type 2 diabetes mellitus and other diseases.