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Objective: This study investigated remodeling of cellular metabolism and structures during browning of primary human adipocytes derived from both visceral and subcutaneous adipose tissues. Effects of glucocorticoids on the browning were also assessed. Methods: Differentiated omental and subcutaneous human adipocytes were treated with rosiglitazone, with or without dexamethasone, and expression levels of brite adipocyte markers, lipolysis, and lipid droplet and mitochondrial structures were examined. Results: Both omental and subcutaneous adipocytes acquired brite phenotypes upon peroxisome proliferator‐activated receptor‐γ agonist treatment, and dexamethasone tended to enhance the remodeling. Although rosiglitazone increased lipolysis during treatment, brite adipocytes exhibited lower basal lipolytic rates and enhanced responses to β‐adrenergic agonists or atrial natriuretic peptide. Transcriptome analysis identified induction of both breakdown and biosynthesis of lipids in brite adipocytes. After 60+ days in culture, lipid droplet size increased to ~50 microns, becoming almost unilocular in control adipocytes, and after browning, they acquired paucilocular morphology, clusters of small lipid droplets (1–2 micron) surrounded by mitochondria appearing on the periphery of the central large one. Conclusions: Metabolic and structural remodeling during browning of primary human adipocytes is similar to previous findings in human adipocytes in vivo, supporting their uses for mechanical studies investigating browning with translational relevance. [ABSTRACT FROM AUTHOR]

The article discusses the benefits of time-restricted eating (TRE) on metabolic health. It explains that eating frequently throughout the day can lead to metabolic dysfunction, while consuming food at specific times promotes metabolic flexibility. The authors conducted a cell culture study to investigate the mechanisms behind the metabolic benefits of TRE. They found that glycerol release, which indicates fat mobilization, increased with time since the last meal. However, the study has limitations, such as the use of extreme glucose concentrations and the lack of consideration for key metabolic hormones. The article concludes by emphasizing the challenges and complexity of studying nutritional regulation in vitro. [Extracted from the article]

Objective: The purpose of this study was to investigate the effects of vitamin D on adipokine expression and inflammation in human adipose tissues and adipocytes and evaluate the molecular mechanisms involved.Methods: Omental and abdominal subcutaneous human adipose tissues were treated with 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3 ), and adipokine levels were measured. Vitamin D effects were measured with or without dexamethasone because glucocorticoids are known to affect vitamin D actions. Using RNA interference, we examined whether the vitamin D receptor (VDR) mediated vitamin D actions on adipokine expression and inflammatory signaling pathways in human adipocytes.Results: mRNA levels and secretion of leptin and IL-6 were suppressed by 1,25(OH)2 D3 in omental adipose tissues. Cotreatment with dexamethasone did not affect these inhibitory actions but partially blocked CYP24A1 induction. Similar results were observed in the subcutaneous depot. In addition, 1,25(OH)2 D3 suppressed leptin and IL-6 expression as well as nuclear factor-κB and extracellular signal-regulated kinase-1/2 phosphorylation in human adipocytes. Adipokine expression also was decreased by 25-hydroxyvitamin D3 (25(OH)D3 ), but not vitamin D3 . Knockdown of VDR increased the inflammatory signaling activity in the control condition and blocked the inhibitory effects of 1,25(OH)2 D3 on adipokine and inflammatory signaling pathways.Conclusion: Vitamin D acts through VDR to inhibit inflammatory pathways and adipokine expression in human adipocytes. Increasing vitamin D status may ameliorate obesity-associated metabolic complications by decreasing adipose tissue inflammation. [ABSTRACT FROM AUTHOR]

Objective: Lower body fat is associated with diminishing cardiometabolic risk. Physiological differences between gluteofemoral and abdominal subcutaneous adipocyte functions are known, but the molecular basis for depot differences in adipocyte function is poorly understood. The objective of this study was to identify depot differences in microRNA (miRNA) expression in human abdominal and gluteofemoral subcutaneous adipose tissues and their implication in gene regulation.Methods: Abdominal and gluteofemoral adipose tissue aspirates obtained from 18 participants (9 male and 9 female, age 30 ± 1.5 y, BMI 27.3 ± 1.23 kg/m2 ) were analyzed for miRNA expression profiles by next-generation DNA sequencing. The raw reads were mapped to miRBase 17, and differentially expressed miRNAs were confirmed by qRT-PCR. The hsa-mimic-miR196a was transfected into cultured abdominal preadipocytes isolated from five women with obesity. Target gene expression was evaluated by RT-qPCR.Results: Among the 640 miRNAs detected in adipose tissue, miR196a2, miR196a1, miR196b, and miR204 showed a higher expression in the gluteofemoral depot (fold change = 2.7, 2.3, 1.7, and 2.3, respectively) independent of sex. Bioinformatic analyses and human primary preadipocyte transfection with miR196 suggested that the differentially expressed miRNAs could directly or indirectly modulate homeobox (HOX) gene expression.Conclusions: The miR196 gene family could play an important role in the regulation of HOX gene expression in subcutaneous adipose tissue and in fat distribution variation. [ABSTRACT FROM AUTHOR]

Objective: Growth hormone (GH) administration reduces abdominal, but not lower body, fat mass. To gain insight into the underlying mechanisms, this study examined the expression of the GH receptor (GHR) and some of its targets in abdominal and gluteal adipose tissue.Methods: GHR and GH targets in the lipolytic pathway were assessed (quantitative PCR/Western blotting) in adipose aspirates from premenopausal women [n = 15, age 26.9 ± 6.1 years, body mass index (BMI) 28.0 ± 6.8 kg/m(2) ] and men (n = 28, age 29.2 ± 7.0 years, BMI 26.9 ± 3.7 kg/m(2) ).Results: GHR mRNA expression was lower in the gluteal depot when compared with the abdominal depot (P = 0.01). Abdominal GHR correlated negatively with age and BMI, whereas gluteal GHR was associated with lower waist-to-hip ratio (WHR), that is, pear shape. In both sites, GHR mRNA correlated strongly with genes important for the regulation of lipolysis: adipose tissue triglyceride lipase (ATGL), hormone-sensitive lipase, perilipin, and CIDEA (all P < 0.001), independently of BMI, WHR, age, and sex. GHR protein was lower in the gluteal fat when compared with the abdominal fat (P = 0.03) and correlated with ATGL protein in the gluteal depot (P < 0.001).Conclusions: GHR levels correlate with levels of lipases and lipid droplet-associated proteins crucial for lipolysis. Thus, higher GHR expression in the abdominal depot when compared with the gluteal depot may underlie the in vivo effect of GH to specifically reduce abdominal adipose tissue mass. [ABSTRACT FROM AUTHOR]

Objective To review recent advances in understanding the cellular mechanisms that regulate fat distribution. Methods In this review, new insights into depot and sex differences in the developmental origins and growth of adipose tissues as revealed by studies that use new methods, including lineage tracing, are highlighted. Results Variations in fat distribution during normal growth and in response to alterations in nutritional or hormonal status are driven by intrinsic differences in cells found in each adipose depot. Adipose progenitor cells and preadipocytes in different anatomical adipose tissues derive from cell lineages that determine their capacity for proliferation and differentiation. As a result, rates of hypertrophy and hyperplasia during growth and remodeling vary among depots. The metabolic capacities of adipose cells are also determined by variations in the expression of key transcription factors and non-coding RNAs. These developmental events are influenced by sex chromosomes and hormonal and nutrient signals that determine the adipogenic, metabolic, and functional properties of each depot. Conclusions These new developments in the understanding of fat distribution provide a sound basis for understanding the association of body shape and health in men and women with and without obesity. [ABSTRACT FROM AUTHOR]

Objective Peripheral lower body fat is associated with lower cardiometabolic risk. Physiological differences in gluteal compared with abdominal subcutaneous (sc) adipocyte functions are known but the molecular basis for depot differences in adipocyte function is poorly understood. Our goal is to identify novel gene regulatory pathways that underlie the heterogeneity of human fat distribution. Methods Abdominal and gluteal adipose tissue aspirates obtained from 35 subjects (age = 30 ± 1.6 years; BMI = 27.3 ± 1.3 kg/m2) were analyzed using Illumina microarrays and confirmed by RT-PCR. The HOTAIR gene was stably transfected into primary cultured human abdominal sc preadipocytes using a lentivirus and effects on adipogenic differentiation were analyzed. Results A long noncoding RNA, HOTAIR that was expressed in gluteal but not in Abd sc adipose tissue was identified. This difference was retained throughout in vitro differentiation and was maximal at day 4. Ectopic expression of HOTAIR in abdominal preadipocytes produced an increase in differentiation as reflected by a higher percentage of differentiated cells, and increased expression of key adipogenic genes including PPARγ and LPL. Conclusions HOTAIR is expressed in gluteal adipose and may regulate key processes in adipocyte differentiation. The role of this lncRNA in determining the metabolic properties of gluteal compared with abdominal adipocytes merits further study. [ABSTRACT FROM AUTHOR]

Adipose stromal cells proliferate and differentiate into adipocytes, providing a valuable model system for studies of adipocyte biology. We compared differentiation protocols for human preadipocytes and report on their metabolic phenotypes. By simply prolonging the adipogenic induction period from the first 3 to 7 days, the proportion of cells acquiring adipocyte morphology increased from 30-70% to over 80% in human subcutaneous preadipocytes (passages 5-6). These morphological changes were accompanied by increases in the adipogenic marker expression and improved adipocyte metabolic phenotypes: enhanced responses to β-adrenergically stimulated lipolysis and to insulin-stimulated glucose metabolism into triglyceride (TG). Confirming previous studies, fetal bovine serum (FBS) dose-dependently inhibited adipogenesis. However, in subcutaneous preadipocytes that differentiate well (donor-dependant high capacity and subcultured fewer than two times), the use of 7d-induction protocols in both 3% FBS and serum-free conditions allowed >80% differentiation. Responsiveness to β-adrenergically stimulated lipolysis was lower in 3% FBS. Rates of insulin-stimulated glucose uptake were higher in adipocytes differentiated with 3% FBS, whereas the sensitivity to insulin was almost identical between the two groups. In summary, extending the length of the induction period in adipogenic cocktail improves the degree of differentiation and responses to key metabolic hormones. This protocol permits functional analysis of metabolic phenotypes in valuable primary human adipocyte cultures through multiple passages. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study on the conversion of cortisone and cortisol and the expression of 11β-hydroxysteroid dehydrogenases (HSDs) in human adipose tissues. It states the correlation between HSD1 messenger ribonucleic acid (mRNA) and adipocyte size within both omental (Om) than abdominal subcutaneous (Abd sc). The study notes that depot differences in cortisol inativation and HSD2 expression in visceral adipose tissues are potentially significant in regulating the adipose microenvironment and availability of cortisol.

The article discusses a study which showed that the post-absorptive skeletal muscle (SM)-lipoprotein lipase (LPL) activity is higher in African Americans as compared to non-Hispanic white pre-menopausal women. Results of the study showed that there were no differences in post-absorptive adipose tissue (AT)-LPL activity, free fatty acids and systemic fat oxidation or respiratory quotient between the two groups. Results also suggest that African American women may take up more fatty acids into their muscle.

Mario DiGirolamo, MD, dedicated most of his scientific career to understanding how adipose tissue grows with obesity and how obesity affects adipocyte metabolism. Mario worked diligently and systematically to examine key questions in the nascent field of adipose tissue biology. Mario had broad scientific interests and supported several postdoctoral trainees (including author of this In Memoriam JOH), who studied clinical aspects of obesity. [Extracted from the article]

The article discusses adipocyte sizing methods to assess metabolic risks, and the work of researchers to identify the correlation between both. It highlights the benefits of assessing adipocyte size distribution, which is a cited advantage of high-throughput electronic sizing of osmium-fixed adipocytes. The article mentions scanning electron microscopy, insulin resistance and adipocyte as a key obesity phenotype.

Previous studies involving high extracellular concentrations of various NO donors (20 µM to 2 µM) showed that they strongly inhibited lipolysis in adipose tissue. However, the physiological significance of these findings remains obscure. On the basis of our recent report that dietary supplementation with L-arginine (the physiological nitrogenous precursor of NO) reduced fat mass in Zucker diabetic fatty rats, the present study was conducted to test the hypothesis that the arginine-NO pathway modulates lipolysis in adipose tissues of obese human subjects. Subcutaneous and omental fat tissues (∼100 mg) were obtained from 8 adult women with BMI between 30 and 40 kg/m², minced into small fragments, and incubated at 37 °C for 3 h in 1 ml of Krebs bicarbonate buffer (pH 7.4) containing 5 mM glucose, 4% BSA, and one of the following: 0, 0.5, 1, 5, 10, 25, 50, 100, or 500 µM sodium nitroprusside (SNP; an NO donor); 0, 0.5 or 2 mM L-arginine; or 5 µM 8-bromo cGMP (a mediator of NO effect). At the end of the incubation, the medium was analyzed for glycerol as an indicator of lipolysis. SNP at 0 to 5 µM dose-dependently increased (P < 0.05) lipolysis by up to 50-54% in both subcutaneous and omental fat tissues, whereas SNP at 25 to 500 µM dose-dependently decreased (P < 0.05) lipolysis by up to 90% in the tissues. L-Arginine at 0.5 and 2 mM increased (P < 0.05) lipolysis by ∼ 24% and 50%, respectively, in both fat tissues, whereas 5 µM 8-bromo cGMP stimulated their lipolysis by 47-55%. Our results indicate that physiologic levels of NO increase, while excess levels inhibit, lipolysis in human adipose tissue. The dose-dependent lipolytic effects of NO clarify the discrepancies in the literature regarding a role for NO in fat metabolism. [ABSTRACT FROM AUTHOR]

This study was conducted to test the hypothesis that dietary arginine supplementation can reduce fat mass in diet-induced obesity. Male Sprague-Dawley rats were fed low- or high-fat diets for 15 wks. Thereafter, the resultant lean or obese rats continued their respective diets and received drinking water containing either 1.51% arginine-HCl or 2.55% alanine (isonitrogenous control) for 12 wks. High-fat diet increased the mass of retroperitoneal (RP), epididymal, subcutaneous and mesenteric fat by 49-96% compared to the low-fat diet, and arginine reduced the mass of these fat pads by 20-40% (P<0.01). Arginine treatment decreased adipocyte sizes, plasma glucose, triglyceride and leptin levels, increased basal lipolysis and improved glucose tolerance (P<0.05). Arginine stimulated glucose oxidation in muscles as well as oleic acid oxidation in muscles and RP fat (P<0.05). The mRNA levels for hepatic FAS and SCD-I were reduced but those for AMPK and CPT-I as well as skeletal muscle CPT-I were increased by arginine treatment (P<0.05). Hepatic AMPK protein as well as AMPK and ACC activation were increased 2-, 5- and 2.5-fold, respectively, by arginine (P<0.01). These findings indicate that dietary arginine supplementation regulates expression of key genes/proteins involved the metabolism of energy substrates, thereby reducing excess fat and improving insulin sensitivity in rats. [ABSTRACT FROM AUTHOR]