Fuzzy algorithms: Application to adipose tissue quantification on MR images

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Dysfunctional adipose tissue in obesity is now recognized as a major driver of metabolic disorders, inflammation, and cardiovascular disease. The accumulation of visceral adipose tissue (VAT) in particular is strongly linked to inflammatory disease conditions while subcutaneous adipose tissue (SAT) is linked to the metabolic healthy obese phenotype. However, the cellular adaptations underlying dysfunctional VAT and preserved function in SAT in response to obesity remain to be determined. We recently assessed obesity-induced changes to the adipose transcriptome in a mouse model of diet-induced obesity using RNA sequencing and revealed a small subset of genes that were differentially expressed in VAT vs. SAT relative to lean counterparts. Of these genes, me1 stood out based on its roles in cellular metabolism and redox regulation. The expression of me1, confirmed at the protein level using Western immunoblotting, was shown to be upregulated in SAT and downregulated in VAT of obese mice leading to our overarching hypothesis that differential regulation of me1 expression in adipose tissue may drive two indicators of VAT dysfunction, namely i) an increase in reactive oxygen species (ROS) and ii) blunted metabolic efficiency. In the present study, we determined if these indicators linked to me1 are differentially influenced in VAT and SAT of obese mice to establish a rationale for targeting me1 in future studies. First, ROS was directly measured using flow cytometry on single cell populations of digested adipose tissue stained with H2DCFDA as well as in lysed tissue using hydroethidine. Next, the NADP/NADPH ratio, governed in part by me1, was determined in VAT and SAT to assess obesity-induced changes to redox coupling and metabolism. While neither direct measure of ROS revealed significant differences, NADP/NADPH was highest in VAT from obese mice suggesting a decrease in NADP substrate utilization relative to lean controls and SAT from obese mice, which exhibited the lowest ratio. These findings in particular are in line with the expression profile of me1 in VAT vs. SAT of obese mice and suggest differences in metabolic efficiency in distinct adipose tissue challenged by obesity. These data support a rationale for studies catered to determining if increasing me1 expression restores the VAT NADP/NADPH ratio in obesity. National Institute of General Medical Sciences of the National Institutes of Health under award number 2P20GM113125 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Insulin resistance in visceral obesity is substantially driven by adipose tissue inflammation, particularly by macrophages accumulating in obese adipose tissue. In contrast, adipose tissue macrophages express the hemoglobin scavenger receptor (CD163) and heme oxygenase-1 (gene: HMOX1) that together protect from oxidative stress. Our aim was to evaluate the expression of CD163 and HMOX1 in intra-abdominal visceral (omental) and subcutaneous adipose tissue as well as circulating soluble CD163 concentrations in human obesity and its association with adipose tissue inflammation, body fat distribution and insulin resistance. CD163, HMOX1 and CD68 mRNA expression in visceral and subcutaneous adipose tissue, serum concentration of soluble CD163 in morbidly obese patients (body mass index (BMI) >40 kg m(-2)), who underwent laparoscopic surgery for gastric banding (n=20), matched for age and sex to controls (BMI<30 kg m(-2); n=20) was analyzed. CD163 expression was highly upregulated in human adipose tissue and soluble CD163 serum concentration was elevated in obese vs lean subjects. HMOX1 was upregulated in adipose tissue by obesity as well and expressed predominantly in macrophages. Although CD163 expression strictly correlated with macrophage abundance, HMOX1 was additionally upregulated within macrophages. This upregulation was significantly lower in visceral compared with subcutaneous adipose tissue. Strikingly, relative visceral adipose tissue expression of HMOX1 negatively correlated with waist-to-hip ratio and the homeostasis model assessment of insulin resistance (both P=0.024). Visceral obesity is associated with defective upregulation of heme oxygenase-1 in visceral adipose tissue. A lack of this antioxidative and anti-inflammatory enzyme in visceral adipose tissue could contribute to the development of insulin resistance.

Obesity is a major driver of cardiometabolic risk. Abdominal visceral adipose tissue (VAT) and sc adipose tissue (SAT) may confer differential metabolic risk profiles. We investigated the relations of VAT and SAT with cardiometabolic risk factors in the Jackson Heart Study cohort. Participants from the Jackson Heart Study (n=2477; 64% women; mean age, 58 yr) underwent multidetector computed tomography, and the volumetric amounts of VAT and SAT were assessed between 2007 and 2009. Cardiometabolic risk factors were examined by sex in relation to VAT and SAT. Men had a higher mean volume of VAT (873 vs. 793 cm3) and a lower mean volume of SAT (1730 vs. 2659 cm3) than women (P=0.0001). Per 1-sd increment in either VAT or SAT, we observed elevated levels of fasting plasma glucose and triglyceride, lower levels of high-density lipoprotein-cholesterol, and increased odds ratios for hypertension, diabetes, and metabolic syndrome. The effect size of VAT in women was larger than that of SAT [fasting plasma glucose, 5.51±1.0 vs. 3.36±0.9; triglyceride, 0.17±0.01 vs. 0.05±0.01; high-density lipoprotein-cholesterol, -5.36±0.4 vs. -2.85±0.4; and odds ratio for hypertension, 1.62 (1.4-1.9) vs. 1.40 (1.2-1.6); diabetes, 1.82 (1.6-2.1) vs. 1.58 (1.4-1.8); and metabolic syndrome, 3.34 (2.8-4.0) vs. 2.06 (1.8-2.4), respectively; P<0.0001 for difference between VAT and SAT]. Similar patterns were also observed in men. Furthermore, VAT remained associated with most risk factors even after accounting for body mass index (P ranging from 0.006-0.0001). The relationship of VAT to most risk factors was significantly different between women and men. Abdominal VAT and SAT are both associated with adverse cardiometabolic risk factors, but VAT remains more strongly associated with these risk factors. The results from this study suggest that relations with cardiometabolic risk factors are consistent with a pathogenic role of abdominal adiposity in participants of African ancestry.

Adipose Tissue Gene Expression Associations Reveal Hundreds of Candidate Genes for Cardiometabolic Traits

Abdominal adipose tissue consists of visceral and subcutaneous fat deposits, each with unique metabolic and functional properties. Identifying the characteristics that influence different obesity phenotypes can support targeted prevention and intervention strategies. To identify predictive factors associated with visceral and subcutaneous adipose tissue accumulation. This is a cross-sectional study including adults of both sexes aged ≥20 years under outpatient care in a public healthcare service in Northeast Brazil. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were measured via ultrasound. Anthropometric, clinical, sociodemographic, and behavioral variables were incorporated into the predictive model. A total of 347 individuals were included. They were median age of 47.0 years (interquartile range: 39.0 to 56.0). Visceral obesity was found in 79.3% of the sample. Adjusted analysis demonstrated that physical inactivity (OR 2.3; 95% CI 1.1-4.7; p = 0.023) and elevated waist circumference (WC) (OR 6.4; 95% CI 2.6-15.8 p < 0.001) were associated with VAT accumulation. Alcohol consumption increased the likelihood of SAT accumulation by 2.2 times (95% CI 1.3-3.7; p = 0.005), while elevated WC raised this likelihood by 4.5 times (95% CI 2.1-9.8; p < 0.001). The VAT/SAT ratio was significantly higher in older adults (OR 5.5; 95%CI 2.0-14.8; p = 0.001), among individuals of Mixed Race and Black, those with lower educational levels (OR 2.4; 95%CI 1.1-5.2; p = 0.028), and in diabetics (OR 2.4; 95%CI 1.2-4.9; p = 0.017). Distinct factors influence visceral and subcutaneous obesity. Sedentary behavior emerged as an independent predictor of visceral obesity, while alcohol consumption was associated with a subcutaneous obesity pattern. Diabetes and sociodemographic factors (older age, non-White race, and lower education) were predictive of an elevated VAT/SAT ratio.

BackgroundThis study profiles ceramides extracted from visceral and subcutaneous adipose tissue of human subjects by liquid chromatography‐mass spectrometry to determine a correlation with status of diabetes and gender.MethodsSamples of visceral and abdominal wall subcutaneous adipose tissue (n = 36 and n = 31, respectively) were taken during laparoscopic surgery from 36 patients (14 nondiabetic, 22 diabetic and prediabetic) undergoing bariatric surgery with a body mass index (BMI) >35 kg/m2 with ≥1 existing comorbidity or BMI ≥40 kg/m2. Sphingolipids were extracted and analyzed using liquid chromatography‐mass spectrometry.ResultsAfter logarithm 2 conversion, paired analysis of visceral to subcutaneous tissue showed differential accumulation of Cer(d18:1/16:0), Cer(d18:1/18:0), and Cer(d18:1/24:1) in visceral tissue of prediabetic/diabetic female subjects, but not in males. Within‐tissue analysis showed higher mean levels of ceramide species linked to insulin resistance, such as Cer(d18:1/18:0) and Cer(d18:1/16:0), in visceral tissue of prediabetic/diabetic patients compared with nondiabetic subjects and higher content of Cer(d18:1/14:0) in subcutaneous tissue of insulin‐resistant female patients compared with prediabetic/diabetic males. Statistically significant differences in mean levels of ceramide species between insulin‐resistant African American and insulin‐resistant Caucasian patients were not evident in visceral or subcutaneous tissue.ConclusionsAnalysis of ceramides is important for developing a better understanding of biological processes underlying type 2 diabetes, metabolic syndrome, and obesity. Knowledge of the accumulated ceramides/dihydroceramides may reflect on the prelipolytic state that leads the lipotoxic phase of insulin resistance and may shed light on the predisposition to insulin resistance by gender.

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.

Targeted lipidomics and transcriptomics profiling reveal the heterogeneity of visceral and subcutaneous white adipose tissue

We investigated the role of chronic stress burden on adiposity and adiposity-related inflammation with two hypotheses: a) greater chronic stress is associated with higher central adiposity and selective accumulation of visceral adipose tissue (VAT) compared with subcutaneous adipose tissue (SAT), and b) associations between VAT and inflammatory biomarkers are exacerbated when chronic stress is high. Data come from 1809 participants included in a Multi-Ethnic Study of Atherosclerosis ancillary study of body composition and adiposity-related inflammation. Chronic psychosocial stress was measured with a five-item version of the Chronic Stress Burden Scale. First, we tested associations between chronic stress (three-level categorical variable) and VAT, SAT, and VAT/SAT ratio. Second, we tested whether associations between VAT and inflammatory biomarkers varied by level of chronic stress. Participants were approximately 65 years, 50% female, and 40.5% White, 25.6% Hispanic, 21.2% African American, and 12.8% Chinese American. About half of the sample reported little to no stress, and a quarter and a fifth of the sample reported medium and high levels of stress. Higher levels of chronic stress were associated with greater VAT and SAT, but not VAT/SAT ratio. Greater levels of VAT were associated with increased levels of adiposity-related inflammation in a graded pattern. These associations did not vary by stress level. Greater chronic stress burden is associated with both central and subcutaneous adiposity. We found no evidence that the associations between VAT and inflammatory biomarkers are exacerbated by chronic stress. Findings contribute to ongoing literature untangling pathways in which psychosocial stress contributes to adiposity-related inflammation.

Increased Glucose Uptake in Visceral Versus Subcutaneous Adipose Tissue Revealed by PET Imaging

Associations between circulating free fatty acids, visceral adipose tissue accumulation, and insulin sensitivity in postmenopausal women

This Month in Gastroenterology

In postmenopausal women, adipose tissue (AT) levels of estrogens exceed circulating concentrations. Although increased visceral AT after menopause is related to metabolic diseases, little is known about differences in estrogen metabolism between different AT depots. We compared concentrations of and metabolic pathways producing estrone and estradiol in abdominal subcutaneous and visceral AT in postmenopausal women. AT and serum samples were obtained from 37 postmenopausal women undergoing surgery for nonmalignant gynecological reasons. Serum and AT estrone, estradiol, and serum estrone sulfate (E1S) concentrations were quantitated using liquid chromatography-tandem mass spectrometry. Activity of steroid sulfatase and reductive 17β-hydroxysteroid dehydrogenase enzymes was measured using radiolabeled precursors. Messenger RNA (mRNA) expression of estrogen-converting enzymes was analyzed by real-time reverse transcription quantitative polymerase chain reaction. Estrone concentration was higher in visceral than subcutaneous AT (median, 928 vs 706 pmol/kg; P = 0.002) and correlated positively with body mass index (r = 0.46; P = 0.011). Both AT depots hydrolyzed E1S to estrone, and visceral AT estrone and estradiol concentrations correlated positively with serum E1S. Compared with visceral AT, subcutaneous AT produced more estradiol from estrone (median rate of estradiol production, 1.02 vs 0.57 nmol/kg AT/h; P = 0.004). In visceral AT, the conversion of estrone to estradiol increased with waist circumference (r = 0.65; P = 0.022), and estradiol concentration correlated positively with mRNA expression of HSD17B7 (r = 0.76; P = 0.005). Both estrone and estradiol production in visceral AT increased with adiposity, but estradiol was produced more effectively in subcutaneous fat. Both AT depots produced estrone from E1S. Increasing visceral adiposity could increase overall estrogen exposure in postmenopausal women.

Distinct infrastructure of lipid networks in visceral and subcutaneous adipose tissues in overweight humans