Increased Adipose Tissue Indices of Androgen Catabolism and Aromatization in Women With Metabolic Dysfunction.

CONTEXT: Body fat distribution is a risk factor for obesity-associated comorbidities, and adipose tissue dysfunction plays a role in this association. In humans, there is a sex difference in body fat distribution, and steroid hormones are known to regulate several cellular processes within adipose tissue. OBJECTIVE: Our aim was to investigate if intra-adipose steroid concentration and expression or activity of steroidogenic enzymes were associated with features of adipose tissue dysfunction in individuals with severe obesity. METHODS: Samples from 40 bariatric candidates (31 women, 9 men) were included in the study. Visceral (VAT) and subcutaneous adipose tissue (SAT) were collected during surgery. Adipose tissue morphology was measured by a combination of histological staining and semi-automated quantification. Following extraction, intra-adipose and plasma steroid concentrations were determined by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Aromatase activity was estimated using product over substrate ratio, while AKR1C2 activity was measured directly by fluorogenic probe. Gene expression was measured by quantitative PCR. RESULTS: VAT aromatase activity was positively associated with VAT adipocyte hypertrophy (P valueadj < 0.01) and negatively with plasma high-density lipoprotein (HDL)-cholesterol (P valueadj < 0.01), while SAT aromatase activity predicted dyslipidemia in women even after adjustment for waist circumference, age, and hormonal contraceptive use. We additionally compared women with high and low visceral adiposity index (VAI) and found that VAT excess is characterized by adipose tissue dysfunction, increased androgen catabolism mirrored by increased AKR1C2 activity, and higher aromatase expression and activity indices. CONCLUSION: In women, increased androgen catabolism or aromatization is associated with visceral adiposity and adipose tissue dysfunction.

Associations between markers of mammary adipose tissue dysfunction and breast cancer prognostic factors.

BACKGROUND: Obesity fosters worse clinical outcomes in both premenopausal and postmenopausal women with breast cancer. Emerging evidence suggests that an android body fat distribution in particular is deleterious for breast cancer prognosis. The extent of adipose tissue dysfunction, especially how it relates to breast cancer prognostic factors and anthropometric measurements, has not been fully investigated. OBJECTIVE: Our objective was to examine if markers of adipose tissue dysfunction, such as hypertrophy and macrophage accumulation, are relevant for the pathophysiology of breast cancer and its associated prognostic factors in a well-characterised cohort of women with breast cancer who did not receive treatment before surgery. METHODS: A consecutive series of 164 women with breast cancer provided breast adipose tissue sample. Multivariate generalised linear models were used to test associations of anthropometric indices and prognostic factors with markers of adipose tissue dysfunction. RESULTS: We found associations of breast adipocyte size and macrophage infiltration (number of CD68+ cells/100 adipocytes) with adiposity, particularly a strong association between breast adipocyte size and central obesity, independent of total adiposity, age and menopausal status (ßadj = 0.87; p = 0.0001). We also identified relationships of adipocyte hypertrophy and macrophage infiltration with prognostic factors, such as cancer stage and tumour grade (p < 0.05). RNA expression of pro-inflammatory cytokines (IL6, TNF) and leptin was also increased as a function of adipocyte size and CD86+/CD11c+ macrophage number/100 adipocytes (p < 0.05). CONCLUSIONS: Our findings support the model of dysfunctional adipose tissue in obesity-associated breast cancer.

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.

Focus on dedifferentiated adipocytes: characteristics, mechanisms, and possible applications.

It is largely believed that after undergoing differentiation, adipocytes can no longer divide. Yet, using ceiling culture, it was demonstrated in vitro that some adipocytes are able to regain proliferative abilities by becoming fibroblast-like cells called dedifferentiated adipocytes. Mature adipocytes are abundant, can be easily isolated, and represent a homogenous cell population. Because of these advantageous characteristics, dedifferentiated adipocytes are clinically attractive in tissue engineering as a potential treatment resource for conditions such as type 2 diabetes, cardiac and kidney diseases, as well as autoimmune diseases. The aim of this review article is to summarize current knowledge on adipocyte dedifferentiation by accurately describing dedifferentiated adipocyte characteristics such as morphological appearance, gene expression, antigen signature, pluripotency, and functionality. Current hypotheses possibly explaining the biological mechanisms and cellular reprogramming of the dedifferentiation process are summarized. Dedifferentiated adipocytes show a stem cell-like antigen profile and genome signature which add to their proliferative capacities and their ability to re-differentiate into diverse cell lineages. The dedifferentiation process likely involves liposecretion, that is, the rapid secretion of the cell's lipid droplet. Dedifferentiated adipocytes may allow development of new uses in tissue engineering.

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

IL-1ß 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-1ß, 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-1ß 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-1ß. Preadipocyte differentiation experiments were also performed. IL-1ß 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-1ß blunted PGF2α and PGE2 release, but did not alter IL-1ß effects on adipose tissue function markers. IL-1ß down-regulated adipocyte differentiation whereas NS-398 alone increased this process. However, NS-398 did not prevent IL-1ß inhibition of adipogenesis. We conclude that IL-1ß induces a pro-inflammatory response in human adipose tissues, particularly in visceral fat, and acts independently of concomitant PG release. IL-1ß 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 ß-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.