ODP001 AKR1C2 Activity in Abdominal Adipose Tissue of Women with or without Excess Visceral Adiposity

Background

Adipose tissue is known to play an active role in androgen turnover, as illustrated by the presence of enzymes of the aldo-keto reductase 1C family such as AKR1C2 and AKR1C3, respectively coding for 3α-hydroxysteroid dehydrogenase type 3 and 17β-hydroxysteroid dehydrogenase type 5. Our group demonstrated that these enzymes are mainly expressed in mature adipocytes and that in women, trunk fat percentage is positively associated with adipose tissue mRNA abundance of both AKR1C2 and AKR1C3. In this context, our aim was to assess whether abdominal adipose tissue activity of AKR1C2 relates to excess visceral adiposity index (VAI) in women.

Methods

AKR1C2 activity was measured in visceral (VAT) and subcutaneous adipose tissue (SAT) of 31 women (age: 39 ± 7; BMI: 51 ± 6) undergoing bariatric surgery. Adipose tissue homogenate activity was measured by fluorimetry in a 12-hour kinetic experiment using the chemical compound cumberone, a competitive substrate in the inactivation of 5a-dihydrotestosterone to 3α-androstanediol by AKR1C2. Visceral adipose tissue excess was quantified using the previously published VAI equation and using the age-specific cut-offs for women, who were categorized into either high VAI or low VAI. Other markers of adipose tissue dysfunction included diacylglycerol acyltransferase 2 (DGAT2) and glutathione peroxidase 3 (GPX3) mRNA abundance, adipocyte size and pericellular fibrosis.

Results

Our technique allowed us to detect significant AKR1C2 activity in SAT (13.5±5.7 fluorescence units (FU)/min) and VAT (8.3±4.8 FU/min). Using the VAI equation, we identified 18 women with high VAI and 13 with low VAI. Women with high VAI were characterized by significantly higher VAT AKR1C2 activity when compared to women with low VAI (9.5 ± 4.4 vs. 6.4± 3.6 FU/min, p<0. 05). AKR1C2 mRNA abundance in either VAT or SAT was not significantly different as a function of VAI. Women with high VAI also had larger VAT adipocyte diameter and lower mRNA abundance of GPX3 in both adipose tissue depots compared to women with low VAI (p<0. 05 for all). No differences were seen in DGAT2 mRNA abundance, pericellular fibrosis or SAT adipocyte diameter as a function of VAI.

Conclusion

In women with severe obesity, excess visceral adiposity as indicated by a high VAI, is associated with higher AKR1C2 activity in VAT only. Similarly, adipose tissues of women with high VAI displayed features of adipose tissue dysfunction such as increased VAT adipocyte diameter and decreased GPX3expression in comparison to women with low VAI. Taken together our results confirm the link between adipose AKR1C2 and excess visceral adiposity.

Presentation: No date and time listed

Adipocyte Size, Adipose Tissue Fibrosis, Macrophage Infiltration and Disease Risk Are Different in Younger and Older Individuals with Childhood and Adulthood Onset Obesity

Objectives

The timing of obesity onset and age have been shown to affect the risk of obesity-related comorbidities, although the impact of each of these factors on markers of adipose tissue function remains unclear. The aim of this study is to determine whether differences in regional adipose tissue characteristics vary with age and age of obesity onset, and whether these differences are associated with the markers of cardiometabolic health.

Methods

Adipose tissue samples were from 80 female bariatric surgery candidates who were classified by age of obesity onset and age into 4 groups: 1) younger adults (<40 y) with childhood-onset obesity (< 18 y) (Childhood-Young); 2) younger adults with adulthood-onset obesity (>18 y) (Adulthood-Young); 3) older adults (>55 y) with childhood-onset obesity (Childhood-Old); and 4) older adults with adulthood-onset obesity (Adulthood-Old). Adipocyte diameter, adipose tissue fibrosis and macrophage infiltration were determined in subcutaneous (SAT) and visceral adipose tissue (VAT). Clinical parameters were obtained from participants’ medical records.

Results

Visceral adipocyte size in the Childhood-Young group was the smallest of all the groups. Age affected visceral infiltration of M1-like cells in both older groups, whereas onset, specifically childhood-onset, was related to visceral infiltration of M2-like cells in the Childhood-Old group. Fibrosis accumulation in SAT and VAT varied with age and onset, particularly in the Childhood-Old group having the lowest fibrosis levels. Markers of cardiometabolic health (fasting glucose, glycated hemoglobin, total, HDL- and LDL-cholesterol and triglyceride concentrations) were positively and well associated with adipose tissue characteristics of the Childhood-Old group but not of the Adulthood-Young group.

Conclusions

Older adults with childhood onset obesity, who had the greatest duration of obesity exposure, were particularly vulnerable to the cardiometabolic effects associated with perturbations in adipose tissue characteristics. These results, suggest that age and age of obesity onset may have independent and cumulative effects on obesity pathology.

Funding Sources

Sylvia Santosa holds a Canada Research Chair – Tier 2 in Clinical Nutrition. This research is also supported by a Discovery Grant from The Natural Science and Engineering Research Council of Canada.

Single-cell analysis of human adipose tissue identifies depot and disease specific cell types

The complex relationship between metabolic disease risk and body fat distribution in humans involves cellular characteristics which are specific to body fat compartments. Here we show depot-specific differences in the stromal vascual fraction of visceral and subcutaneous adipose tissue by performing single-cell RNA sequencing of tissue specimen from obese individuals. We characterize multiple immune cells, endothelial cells, fibroblasts, adipose and hematopoietic stem cell progenitors. Subpopulations of adipose-resident immune cells are metabolically active and associated with metabolic disease status and those include a population of potential dysfunctional CD8+ T cells expressing metallothioneins. We identify multiple types of adipocyte progenitors that are common across depots, including a subtype enriched in individuals with type 2 diabetes. Depot-specific analysis reveals a class of adipocyte progenitors unique to visceral adipose tissue, which shares common features with beige preadipocytes. Our human single-cell transcriptome atlas across fat depots provides a resource to dissect functional genomics of metabolic disease.

Interleukin-1β and prostaglandin-synthesizing enzymes as modulators of human omental and subcutaneous adipose tissue function

IL-1β stimulates expression of prostaglandin (PG)-synthesizing enzymes cyclooxygenase (COX)-2 and aldo-keto reductase (AKR)1B1 in human preadipocytes. We aimed to examine the impact of IL-1β, COX-2 and AKR1B1 on markers of human visceral and subcutaneous adipose tissue function, and to assess whether PG synthesis by these enzymes mediates IL-1β effects. Omental and subcutaneous fat samples were obtained from bariatric surgery patients. PG release and expression of inflammatory and adipogenic markers were assessed in explants treated with COX-2 inhibitor NS-398 or AKR1B1 inhibitor Statil, with or without IL-1β. Preadipocyte differentiation experiments were also performed. IL-1β decreased expression of PPARγ in both fat depots compared to control and increased expression of NF-κB1, IL-6, CCL-5, ICAM-1 and VEGFA, especially in visceral fat for IL-6, CCL-5 and VEGFA. Adding Statil or NS-398 to IL-1β blunted PGF_2α and PGE₂ release, but did not alter IL-1β effects on adipose tissue function markers. IL-1β down-regulated adipocyte differentiation whereas NS-398 alone increased this process. However, NS-398 did not prevent IL-1β inhibition of adipogenesis. We conclude that IL-1β induces a pro-inflammatory response in human adipose tissues, particularly in visceral fat, and acts independently of concomitant PG release. IL-1β and COX-2 appear to be critical determinants of adipose tissue pathophysiologic remodeling in obesity.

Characterization and visualization of the liposecretion process taking place during ceiling culture of human mature adipocytes

OBJECTIVE

To investigate and further characterize the process of mature adipocyte dedifferentiation. Our hypothesis was that dedifferentiation does not involve mitosis but rather a phenomenon of liposecretion.

METHODS

Mature adipocytes were isolated by collagenase digestion of human adipose tissue samples. Ceiling cultures were established using our six-well plate model. Cells were treated with cytosine β-d-arabinofuranoside (AraC) or vincristine (VCR), two agents blocking cell division, and were compared with vehicle. Liposecretion events were visualized by time-lapse microscopy, with and without AraC in adipocytes transducted with a baculovirus. Microscopic analyses were performed after labeling phosphorylated histone 3 and cyclin B1 in ceiling cultures.

RESULTS

Treatment with AraC almost entirely prevented the formation of fibroblasts up to 12 days of ceiling culture. Similar results were obtained with VCR. The antimitotic effectiveness of the treatment was confirmed in fibroblast cultures from the adipose tissue stromal-vascular fraction by proliferation assays and colony-forming unit experiments. Using time-lapse microscopy, we visualized liposecretion events in which a large lipid droplet was rapidly secreted from isolated mature adipocytes. The same phenomenon was observed with AraC. This was observed in conjunction with histone 3 phosphorylation and cyclin B1 segregation to the nucleus.

CONCLUSION

Our results support the notion that dedifferentiation involves rapid secretion of the lipid droplet by the adipocytes with concomitant generation of fibroblast-like cells that subsequently proliferate to generate the dedifferentiated adipocyte population during ceiling culture. The presence of mitotic markers suggests that this process involves cell cycle progression, although cell division does not occur.