Nadia J. T. Roumans

Wound administration of M2-polarized macrophages does not improve murine cutaneous healing responses.

Macrophages play a crucial role in all stages of cutaneous wound healing responses and dysregulation of macrophage function can result in derailed wound repair. The phenotype of macrophages is influenced by the wound microenvironment and evolves during healing from a more pro-inflammatory (M1) profile in early stages, to a less inflammatory pro-healing (M2) phenotype in later stages of repair. The aim of the current study was to investigate the potential of exogenous administration of M2 macrophages to promote wound healing in an experimental mouse model of cutaneous injury. Bone marrow derived macrophages were stimulated in-vitro with IL-4 or IL-10 to obtain two different subsets of M2-polarized cells, M2a or M2c respectively. Polarized macrophages were injected into full-thickness excisional skin wounds of either C57BL/6 or diabetic db/db mice. Control groups were injected with non-polarized (M0) macrophages or saline. Our data indicate that despite M2 macrophages exhibit an anti-inflammatory phenotype in-vitro, they do not improve wound closure in wild type mice while they delay healing in diabetic mice. Examination of wounds on day 15 post-injury indicated delayed re-epithelialization and persistence of neutrophils in M2 macrophage treated diabetic wounds. Therefore, topical application of ex-vivo generated M2 macrophages is not beneficial and contraindicated for cell therapy of skin wounds.

The effect of rate of weight loss on long‐term weight regain in adults with overweight and obesity

To investigate the effect of rate of weight loss, with similar total weight loss, on weight regain in individuals with overweight and obesity.

Calorie restriction-induced changes in the secretome of human adipocytes, comparison with resveratrol-induced secretome effects

Obesity is characterized by dysfunctional white adipose tissue (WAT) that ultimately may lead to metabolic diseases. Calorie restriction (CR) reduces the risk for age and obesity-associated complications. The impact of CR on obesity has been examined with human intervention studies, which showed alterations in circulating adipokines. However, a direct effect of CR on the human adipocyte secretome remains elusive. Therefore, the effect of a 96h low glucose CR on the secretion profile of in vitro cultured mature human SGBS adipocytes was investigated by using proteomics technology. Low-glucose CR decreased the adipocyte triglyceride contents and resulted in an altered secretion profile. Changes in the secretome indicated an improved inflammatory phenotype. In addition, several adipocyte-secreted proteins related to insulin resistance showed a reversed expression after low-glucose CR. Furthermore, 6 novel CR-regulated adipocyte-secreted proteins were identified. Since resveratrol (RSV) mimics CR we compared results from this study with data from our previous RSV study on the SGBS adipocyte secretome. The CR and RSV adipocyte secretomes partly differed from each other, although both treatment strategies lead to secretome changes indicating a less inflammatory phenotype. Furthermore, both treatments induced SIRT1 expression and resulted in a reversed expression of detrimental adipokines associated with metabolic complications.

The cilium: a cellular antenna with an influence on obesity risk

Primary cilia are organelles that are present on many different cell types, either transiently or permanently. They play a crucial role in receiving signals from the environment and passing these signals to other parts of the cell. In that way, they are involved in diverse processes such as adipocyte differentiation and olfactory sensation. Mutations in genes coding for ciliary proteins often have pleiotropic effects and lead to clinical conditions, ciliopathies, with multiple symptoms. In this study, we reviewed observations from ciliopathies with obesity as one of the symptoms. It shows that variation in cilia-related genes is itself not a major cause of obesity in the population but may be a part of the multifactorial aetiology of this complex condition. Both common polymorphisms and rare deleterious variants may contribute to the obesity risk. Genotype-phenotype relationships have been noticed. Among the ciliary genes, obesity differs with regard to severity and age of onset, which may relate to the influence of each gene on the balance between pro- and anti-adipogenic processes. Analysis of the function and location of the proteins encoded by these ciliary genes suggests that obesity is more linked to activities at the basal area of the cilium, including initiation of the intraflagellar transport, but less to the intraflagellar transport itself. Regarding the role of cilia, three possible mechanistic processes underlying obesity are described: adipogenesis, neuronal food intake regulation and food odour perception.

Adipose tissue gene expression is differentially regulated with different rates of weight loss in overweight and obese humans

Background/Objectives:Moderate weight loss (WL) can ameliorate adverse health effects associated with obesity, reflected by an improved adipose tissue (AT) gene expression profile. However, the effect of rate of WL on the AT transcriptome is unknown. We investigated the global AT gene expression profile before and after two different rates of WL that resulted in similar total WL, and after a subsequent weight stabilization period.Subjects/Methods:In this randomized controlled trial, 25 male and 28 female individuals (body mass index (BMI): 28–35 kg m−2) followed either a low-calorie diet (LCD; 1250 kcal day−1) for 12 weeks or a very-low-calorie diet (VLCD; 500 kcal day−1) for 5 weeks (WL period) and a subsequent weight stable (WS) period of 4 weeks. The WL period and WS period together is termed dietary intervention (DI) period. Abdominal subcutaneous AT biopsies were collected for microarray analysis and gene expression changes were calculated for all three periods in the LCD group, VLCD group and between diets (ΔVLCD−ΔLCD).Results:WL was similar between groups during the WL period (LCD: −8.1±0.5 kg, VLCD: −8.9±0.4 kg, difference P=0.25). Overall, more genes were significantly regulated and changes in gene expression appeared more pronounced in the VLCD group compared with the LCD group. Gene sets related to mitochondrial function, adipogenesis and immunity/inflammation were more strongly upregulated on a VLCD compared with a LCD during the DI period (positive ΔVLCD−ΔLCD). Neuronal and olfactory-related gene sets were decreased during the WL period and DI period in the VLCD group.Conclusions:The rate of WL (LCD vs VLCD), with similar total WL, strongly regulates AT gene expression. Increased mitochondrial function, angiogenesis and adipogenesis on a VLCD compared with a LCD reflect potential beneficial diet-induced changes in AT, whereas differential neuronal and olfactory regulation suggest functions of these genes beyond the current paradigm.

Diet-induced weight loss decreases adipose tissue oxygen tension with parallel changes in adipose tissue phenotype and insulin sensitivity in overweight humans

BACKGROUND/OBJECTIVES:Although adipose tissue (AT) hypoxia is present in rodent models of obesity, evidence for this in humans is limited. Here, we investigated the effects of diet-induced weight loss (WL) on abdominal subcutaneous AT oxygen tension (pO2), AT blood flow (ATBF), AT capillary density, AT morphology and transcriptome, systemic inflammatory markers and insulin sensitivity in humans.SUBJECTS/METHODS:Fifteen overweight and obese individuals underwent a dietary intervention (DI), consisting of a 5-week very-low-calorie diet (VLCD, 500 kcal day−1; WL), and a subsequent 4-week weight stable diet (WS). Body composition, AT pO2 (optochemical monitoring), ATBF (133Xe washout), and whole-body insulin sensitivity were determined, and AT biopsies were collected at baseline, end of WL (week 5) and end of WS (week 9).RESULTS:Body weight, body fat percentage and adipocyte size decreased significantly during the DI period. The DI markedly decreased AT pO2 and improved insulin sensitivity, but did not alter ATBF. Finally, the DI increased AT gene expression of pathways related to mitochondrial biogenesis and non-mitochondrial oxygen consumption.CONCLUSIONS:VLCD-induced WL markedly decreases abdominal subcutaneous AT pO2, which is paralleled by a reduction in adipocyte size, increased AT gene expression of mitochondrial biogenesis markers and non-mitochondrial oxygen consumption pathways, and improved whole-body insulin sensitivity in humans.

Weight loss-induced stress in subcutaneous adipose tissue is related to weight regain

Initial successful weight loss is often followed by weight regain after the dietary intervention. Compared with lean people, cellular stress in adipose tissue is increased in obese subjects. However, the relation between cellular stress and the risk for weight regain after weight loss is unclear. Therefore, we determined the expression levels of stress proteins during weight loss and weight maintenance in relation to weight regain. In vivo findings were compared with results from in vitro cultured human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes. In total, eighteen healthy subjects underwent an 8-week diet programme with a 10-month follow-up. Participants were categorised as weight maintainers or weight regainers (WR) depending on their weight changes during the intervention. Abdominal subcutaneous adipose tissue biopsies were obtained before and after the diet and after the follow-up. In vitro differentiated SGBS adipocytes were starved for 96 h with low (0·55 mm) glucose. Levels of stress proteins were determined by Western blotting. WR showed increased expressions of β-actin, calnexin, heat shock protein (HSP) 27, HSP60 and HSP70. Changes of β-actin, HSP27 and HSP70 are linked to HSP60, a proposed key factor in weight regain after weight loss. SGBS adipocytes showed increased levels of β-actin and HSP60 after 96 h of glucose restriction. The increased level of cellular stress proteins in the adipose tissue of WR probably resides in the adipocytes as shown by in vitro experiments. Cellular stress accumulated in adipose tissue during weight loss may be a risk factor for weight regain.

A role for leukocyte integrins and extracellular matrix remodeling of adipose tissue in the risk of weight regain after weight loss

Background: Weight loss (WL) is often followed by weight regain after an energy-restricted dietary intervention (DI). When people are following a diet, the volume of an adipocyte decreases by loss of triglycerides, which creates stress between the cell contents and the surrounding extracellular matrix (ECM). Previously, we observed that genetic variations in ECM genes are associated with an increased risk of weight regain.Objective: We investigated the relation between the expression of ECM genes during WL and a period of weight stabilization (WS) and the risk of weight regain.Design: In this randomized controlled trial, 61 healthy overweight or obese participants followed either a 5-wk very-low-calorie diet (VLCD; 500 kcal/d) or a 12-wk low-calorie diet (1250 kcal/d) (WL period) with a subsequent 4-wk WS period and a 9-mo follow-up. The WL and WS periods combined were considered the DI. Abdominal subcutaneous adipose tissue biopsy samples were collected for microarray analysis. Gene expression changes for a broad set of ECM-related genes were correlated with the weight-regain percentage (WR%).Results: A total of 26 of the 277 genes were significantly correlated with WR% during WL, WS, or the DI periods. Most correlations were observed in the VLCD group during the WS period. Four genes code for leukocyte-specific receptors. These and other genes belong to a group of 26 genes, among which the expression changes were highly correlated (r ≥ 0.7, P ≤ 0.001). This group could be divided into 3 subclusters linking to 2 biological processes-leukocyte integrin gene activity and ECM remodeling-and a link to insulin sensitivity was also apparent.Conclusions: Our present findings indicate the importance of adipose tissue leukocytes for the risk of weight regain. ECM modification also seems to be involved, and we observed a link to insulin sensitivity. This trial was registered at clinicaltrials.gov as NCT01559415.

Adipose tissue meal‐derived fatty acid uptake before and after diet‐induced weight loss in adults with overweight and obesity

This study investigated whether diet‐induced weight loss alters indices of in vivo postprandial fat uptake in adipose tissue (AT) and whether these changes are associated with weight regain in adults with overweight and obesity.

Weight loss-induced cellular stress in subcutaneous adipose tissue and the risk for weight regain in overweight and obese adults

Background/objective:Weight loss is often followed by weight regain after the dietary intervention (DI). Cellular stress is increased in adipose tissue of obese individuals. However, the relation between cellular stress and weight regain is unclear. Previously, we observed increased adipose tissue cellular stress of participants regaining weight compared with participants maintaining weight loss. In the current study, we further investigated the relation between weight regain and changes in the expression of stress-related genes and stress protein levels to determine possible predictors of weight regain.Participants/methods:In this randomized controlled trial, sixty-one healthy overweight/obese participants followed a DI of either a 5-week very-low-calorie diet (500 kcal per day) or a 12-week low-calorie diet (1250 kcal per day; WL period) with a subsequent 4-week weight stable diet (WS period), and a 9-month follow-up. The WL and WS period taken together was named the DI. Abdominal subcutaneous adipose tissue biopsies were collected in 53 participants for microarray and liquid chromatography-mass spectrometry analysis. RNA and protein levels for a broad set of stress-related genes were correlated to the weight regain percentage.Results:Different gene sets correlated to weight regain percentage during WS and DI. Bioinformatics clustering suggests that during the WS phase-defined genes for actin filament dynamics, glucose handling and nutrient sensing are related to weight regain. HIF-1 (hypoxia-inducible factor-1) is indicated as an important regulator. With regard to DI, clustering of correlated genes indicate that LGALS1, ENO1 and ATF2 are important nodes for conferring risk for weight regain.Conclusions:Our present findings indicate that the risk for weight regain is related to expression changes of distinct sets of stress-related genes during the first 4 weeks after returning to energy balance, and during the DI. Further research is required to investigate the mechanistic significance of these findings and find targets for preventing weight regain.