Genetic Association of Interleukin-1β (−511C/T) and Its Receptor Antagonist (86-bpVNTR) Gene Polymorphism With Susceptibility to Bacteremia in Kidney Transplant Recipients

BackgroundBacteremia remains a significant cause of morbidity and mortality after kidney transplantation. The present study was conducted to determine the influence of the polymorphisms of interleukin-1 β (IL-1 β) and IL-1 receptor antagonist gene (IL-1RN) on the susceptibility to bacteremia within the first year after kidney transplantation.MethodsTwenty-one bacteremic and 60 noninfected kidney transplant recipients, underwent extraction genomic DNA, from peripheral blood leukocytes. The region containing the AvaI polymorphic site at position ?511 of 1L-I β gene was amplified by a polymerase chain reaction (PCR) and subsequently digested with AvaI restriction enzyme. The polymorphic regions within intron 2 of IL-1RN, containing variable numbers of a tandem repeat of 86 base pairs, were amplified by PCR.ResultsWe observed greater frequency of the IL-1 β ?511CC genotype and IL-1 β ?511C allele among bacteremic versus noninfected recipients (P = .023 and P = .015, respectively). In contrast, the current study failed to show significant difference, either in genotypic or allelic frequency, for the IL-1RN polymorphisms regarding the incidence of bacteremia (P = .508 and P = .507, respectively). After adjustment we observed recipient IL-1 β ?511CC genotype (odds ratio [OR] = 4.400, 95% confidence interval [CI] = 1.517–12.759, P = .006) and recipient IL-1 β?511C allele (OR = 2.444, 95% Cl = 1.172–5.100, P = .015) to predict independently the risk for bacteremia within the first year after kidney transplantation.ConclusionThe present work provided evidence that recipient IL-1 β ?511CC genotype or IL-1 β ?511C allele was associated with susceptibility to bacteremia within the first year after kidney transplantation. These results suggested that genotyping data may afford a more accurate prediction of bacteremia and the design of strategies to protect the most vulnerable patients.     

Transforming Growth Factor-β1 Gene Polymorphism in Renal Transplant Recipients

Background. Cytokine transforming growth factor (TGF) is involved in regulation of tissue repair after injury. More recently, TGF–β1 codon 10 gene polymorphism has been shown to be associated with circulating TGF-β levels. We tested whether TGF-β1 genotype polymorphism was predictive of renal allograft function decline. Patients and Methods. The study population consisted of 129 consecutive cadaveric or living related renal transplant recipients at our center between 1985 and 2001. The recipient TGF-β1 genotype polymorphism was determined from peripheral blood leucocytes DNA. The primary endpoint was rate of glomerular filtration rate decline between the first year and the third year of transplant. Results. Baseline glomerular filtration rate as estimated by MDRD study equation at 1 year measured 50 ± 17 mL/min/1.73 m². At the end of the 3-year follow-up period, 52 patients (40%) experienced biopsy-confirmed acute rejections. Frequency and severity of allograft rejection did not differ with TGF-β genotypes. However, the decline in glomerular filtration rate was significantly greater in Leu/Leu (TT) than Leu/Pro (CT) recipients, 6.3 ± 16.9 mL/min/1.73 m² versus 0.1±10.2 mL/min/1.73 m², p = 0.04. Conclusion. Our results demonstrate that recipient TGF-β1 codon 10 Leu/Leu homozygosity is a potential risk factor of kidney allograft function decline.     

Study of Transforming Growth Factor-β1 Gene,mRNA, and Protein in Japanese Renal Transplant Recipients

Background

Transforming growth factor (TGF)-β1 may contribute to chronic allograft nephropathy and graft loss; however, the exact molecular mechanism remains unclear. Therefore, we assess the relationship between TGF-β1 gene polymorphisms, expression, and development of allograft nephropathy.

Methods

We studied 135 renal transplant recipients at our hospital. TGF-β1 gene polymorphisms (codons 10 and 25) were determined from peripheral blood leukocyte DNA. Plasma TGF-β1 mRNA was measured by real-time polymerase chain reaction and TGF-β1 protein levels were assessed by enzyme-linked immunosorbent assay. The relationship between TGF-β1 genotyping, expression, and rejection and results of renal biopsy were evaluated.

Results

The genotype frequency of transplant recipients was 49.6%, 30.4%, and 20.0% for C/T, C/C and T/T at codon 10, 100% for G/G at codon 25, respectively. According to the criteria of Banff ‘97 classification, 24 cases were classified as acute rejection and whose genotypes were 16, 3, and 5 cases for C/T, C/C and T/T at codon 10. Plasma mRNA expression was elevated in 14 cases and decreased in 8 cases after acute rejection. We measured 267 specimens of TGF-β1 protein and there was no relation between amount of TGF-β1 protein and mRNA.

Conclusion

Our results suggest that the relationship between plasma TGF-β1 expression and the development of allograft nephropathy remains uncertain. Frequency of allograft rejection differ with TGF-β1 codon 10 genotypes and the high-risk genotype was different from the reports of other countries.     

Interleukin 1 Receptor Antagonist and Tumor Necrosis Factor-α Gene Polymorphism in Patients with End-Stage Renal Failure

Urea and creatinine are not generally considered to be important uremic toxins despite evidence from dialysis experiments to the contrary, and despite striking elevations of these nitrogenous waste products in uremia. In order to study this problem in acute uremia, we used a new dietary method for prolonging the survival of bilaterally nephrectomized rats. Urea or creatinine were injected on three successive days starting one day after the inception of uremia. Urea or creatinine injections shortened the survival time of acutely uremic rats, and increased the involution of thymus and spleen. The extra urea, but not creatinine, increased the serum osmolality. These data indicate that urea and creatinine are toxic in the acutely uremic rat. Hypertonicity of the serum may contribute to the toxicity of urea. Additional mechanisms of toxicity and additional toxins are not excluded.     

Interleukin-6 and Tumor Necrosis Factor-α Levels following Hepatic Cryotherapy: Association with Volume and Duration of Freezing

Although morbidity following cryotherapy is usually minor, a syndrome of multiorgan failure and disseminated intravascular coagulation (DIC) has been described and referred to as the cryoshock phenomenon. We hypothesized that mediators similar to those in septic shock may be involved in this syndrome. In this study we aimed to assess the plasma concentrations of the cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) following hepatic cryotherapy and to relate them to the duration and volume of freezing and to hepatocellular injury. Between April and December 1997 blood samples were taken preoperatively and at different times postoperatively from patients undergoing hepatic artery catheter-insertion (HAC) (n= 15), cryotherapy (n= 5), liver resection (n= 9), liver resection and edge cryotherapy (n= 7), or liver resection and cryotherapy of additional lesions (n= 9). They were analyzed for serum aspartate transaminase (AST) and plasma TNF-α and IL-6 levels. There was a significant association (Pearson correlation) of serum AST levels 1 hour postoperatively with plasma TNF-α and IL-6 levels at the end of the procedure. In patients undergoing cryotherapy or resection with cryotherapy of additional lesions (n= 14), the volume and duration of hepatic freezing were significantly associated with postoperative serum AST and plasma TNF-α and IL-6 levels at various postoperative times. Hepatic cryotherapy is followed by cytokine release, with postoperative plasma TNF-α and IL-6 levels associated with the degree of hepatic cryotrauma. These mediators may be involved in the occurrence of cryoshock following large-volume hepatic freezing.     

Role of Serum (1,3)-Β-D-Glucan to Screen for Pneumocystis Pneumonia in Kidney Transplant Recipients

BackgroundPneumocystis pneumonia is a common opportunistic infection in kidney transplant recipients caused by the ascomycetous fungi Pneumocystis jirovecii. Its clinical presentation of a progressive nonproductive cough, shortness of breath, and fever is nonspecific and often delays diagnosis and appropriate treatment. Moreover, the plain radiograph may show a spectrum of findings from normal to bilateral diffuse infiltrates. Detection of serum (1,3)-β-D-glucan along with consistent clinical findings can be used as early screening tools to diagnose and initiate treatment for Pneumocystis pneumonia pending confirmation by bronchoscopy.MethodsThis case series describes 6 kidney transplant recipients who were diagnosed as having Pneumocystis pneumonia. The baseline demographic variables, presenting symptoms, radiographic findings, laboratory findings including lactate dehydrogenase and serum (1,3)-β-D-glucan levels, bronchoscopy findings, and its timing in relation to a positive serum (1,3)-β-D-glucan test, and response to treatment were collected.ResultsAll 6 patients who completed the first 3 months of prophylaxis against Pneumocystis pneumonia with sulfamethoxazole-trimethoprim were diagnosed as having Pneumocystis pneumonia between 2 to 24 years post transplant. They initiated treatment early based on a positive serum (1,3)-β-D-glucan and negative Histoplasma antigen and serum galactomannan test with a presumptive diagnosis of Pneumocystis pneumonia, which was later confirmed with a positive polymerase chain reaction on bronchoalveolar lavage fluid.ConclusionsPneumocystis pneumonia is a common opportunistic fungal infection in immunosuppressed kidney transplant recipients, and use of serum (1,3)-β-D-glucan can be used as an initial screening test for its early diagnosis and treatment.     

Treatment of Anemia With Erythropoietin-Stimulating Agents in Kidney Transplant Recipients and Chronic Kidney Disease—Another Drawback of Immunosuppression?

Anemia is more prevalent in allograft recipients compared with glomerular filtration rate (GFR) matched patients with chronic kidney diseases. There is a paucity of data concerning the correction of anemia in the posttransplant period with erythropoietin-stimulating agents (ESA). The aim of this study was to compare the iron status, kidney function, inflammatory state, use of drugs affecting erythropoiesis (immunosuppressants ACEi/ARB) and correction of anemia using ESA in a chronic kidney disease (CKD) population versus kidney transplant recipients. We included 67 patients treated with ESA including 17 after kidney transplantation. CKD Patients with native kidneys were significantly older than allograft recipients (mean age 69 versus 51 years; P < .001, and despite similar serum creatinine and iron parameters showed an estimated lower GFR (19 mL/min versus 23 mL/min; P < .05). Median time of ESA therapy was similar among patients with native kidney CKD versus kidney recipients, but they achieved a significantly higher hemoglobin (11.04 versus 10.36 g/dL; P < .05). There was no difference between patients administered or not a mammalian target of rapamycin antagonist. None of the patients with native kidney CKD received immunosuppressive therapy, but they were prescribed ACEi more often than kidney recipients. The higher degree of anemia in kidney allograft recipient is the most probably attributed to the use of immunosuppressive drugs, despite their better kidney function and comparable iron status. This study suggested that higher doses of ESA should be employed to anemia in kidney transplant recipients.     

Tumor Necrosis Factor-α, Interleukin-1β and Nitric Oxide: Induction of Liver Megamitochondria in Prehepatic Portal Hypertensive Rats

Abstact It has been shown that portal hypertension in the rat causes microvesicular hepatocytic fatty infiltration. Formation of megamitochondria (MG) is one of the most prominent alterations in steatosis. Because nitric oxide (NO), tumor necrosis factor-α (TNFα), and interleukin-1β (IL-1β) impair mitochondrial function, these mediators have been studied in prehepatic portal hypertensive rats to verify their coexistence with MG and therefore with steatosis. Male Wistar rats were divided into two groups: a control group (n = 7) and a group with partial portal vein hgation (n = 19) at 6 weeks of evolution. TNFα and IL-1β were quantified in liver by enzyme-linked immunosorbent assay, and NO was measured in the portal vein, suprahepatic inferior vena cava, and infrahepatic inferior vena cava by the Griess reaction. In portal hypertensive rats, the-serum concentration of NO of hepatic origin increases (132.10 ± 34.72 vs. 52.44 ± 11.32 nmol/ml; p < 0.001), as do TNF-α (2.02 ± 0.20 vs. 1.12 ± 0.43 μmol/mg protein) and IL-1β (18.95 ± 2.59 vs. 5.48 ± 1.70 μmol/mg protein) (p = 0.005) in the liver. The most frequent hepatic histologic findings are the presence of MG (p < 0.001), steatosis, and hyperplasia. An increase in hepatic release of NO, TNFα and IL-Iβ with MG formation is produced in rats with portal hypertension. Therefore these proinflammatory mediators and this morphologic mitochondrial alteration could both be involved in the etiopathogenesis of steatosis.     

The Effects of C-Reactive Protein, Interleukin-6, and Tumor Necrosis Factor-α in Rat Allograft Adventitial Inflammation and Allograft Arteriosclerosis

This study was designed to investigate the role of C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) during allograft adventitial inflammation and arteriosclerosis. Lewis rats were used as donors and Wistar rats as recipients for the experimental groups, while both donors and recipients were Wistar rats in the control groups. The 36 experimental and 16 control allografts were divided into four groups (nine in each experimental and four in each control group): group A animals were euthanized at 1 week posttransplantation; groups B, C, and D animals were euthanized at 2, 3, and 4 weeks posttransplantation, respectively. The method of enzyme-linked immunosorbent assay (ELISA) was used to test serum levels of CRP, IL-6, and TNF-α. Immunohistological and pathological studies were performed to evaluate allograft adventitial inflammation, arteriosclerosis, and expression of proliferating cell nuclear antigen (PCNA). Allografts collected from group D demonstrated abundant infiltration of smooth muscle cells and collagenous fibers with inflammatory cells in the adventitia. ELISA demonstrated a higher levels of CRP, IL-6, and TNF-α in experimental than control groups. Additionally, PCNA increased over time in the adventitia. Our results suggested that the expressions of CRP, IL-6, and TNF-α play important roles during the development of allograft adventitial inflammation and arteriosclerosis.     

Effects of Substrate Stiffness on Morphology and MMP-1 Gene Expression in Tenocytes Stimulated With Interleukin-1β

Tendon cells, tenocytes, are constantly subjected to mechanical stress in vivo, which maintains a level of cellular tension. When a tendon is subjected to overloading, local rupture of collagen fibers are induced, which deprives tenocytes of mechanical stress, lowers their cellular tension level and upregulates their catabolism. In addition, leukocytes are attracted to the rupture sites and produce interleukin-1β (IL-1β), and this exogenous IL-1β also stimulates tenocyte catabolism. We tested a hypothesis that catabolic tenocytes with low cellular tension at the rupture sites excessively respond to the exogenous IL-1β and further upregulate matrix metalloproteinase 1 (MMP-1) gene expression. Tenocytes from rabbit Achilles tendon were cultured on the following substrates: glass or polydimethylsiloxane micropillar substrates with a height of 2, 4, or 8 µm. Following a 3-day IL-1β stimulation at a concentration of 0, 1, 10, or 100 pM, the effects of IL-1β stimulation on cell morphology and MMP-1 gene expression was analysed with fluorescent microscopy and fluorescence in situ hybridization, respectively. In addition, the effects of IL-1β stimulation on cell membrane fluidity were examined. It was demonstrated that the cells on 8-µm-height micropillars exhibited a greater response than those on rigid substrates with flat (glass) and topologically the same surface (2-µm-height micropillars) to IL-1β when supplied at the same concentration. Besides this, membrane fluidity was lower in the cells on micropillars. Therefore, it appears that cellular attachment to softer substrates lowers the cellular actin cortex tension, reducing the membrane fluidity and possibly elevating the sensitivity of IL-1 receptors to ligand binding. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:150–159, 2020     

Is There Any Association Between Triglyceride–Glucose Index and Graft Function in Kidney Transplant Recipients?

BackgroundAlthough previous studies have illustrated the relationship between chronic kidney disease, coronary artery disease, erectile dysfunction, and the triglyceride–glucose index (TyGi), the relationship between this index and postoperative graft function in patients undergoing renal transplantation has yet to be investigated. In the present study, we aimed to reveal the association between the TyGi and renal graft outcomes in patients who underwent renal transplantation.MethodsWe retrospectively collected data on living and cadaveric kidney donor recipients between May 2019 and April 2022. The recipients’ age, sex, body mass index, preoperative fasting glucose and triglyceride levels, TyGi, estimated glomerular filtration rate (eGFR), and serum creatinine measurement data were recorded. The patients were divided into 2 groups according to their GFR values (group 1: GFR <60 mL/min/1.73 m²; group 2: GFR ≥60 mL/min/1.73 m²). Follow-up serum creatinine–eGFR levels and TyGi measurements were compared between the recipients in group 1 and group 2.ResultsThe mean TyGi measurements of the recipients were 8.79 ± 0.64 in group 1 and 8.83 ± 0.72 in group 2. There was no statistically significant difference in terms of the TyGi measurements between the 2 groups (P >. 05). No statistically significant correlation was found between the recipients’ creatinine, eGFR, and TyGi at 1st, 6th, and 12th postoperative months (P > .05).ConclusionsWe believe that the relationship between the TyGi and renal graft function can be more clearly understood in prospective studies that include a higher number of patients and a longer follow-up period.     

Zonulin,Iron Status,and Anemia in Kidney Transplant Recipients: Are They Related?

Background

In patients after kidney transplantation, anemia is relatively common and is associated with impaired kidney function, subclinical inflammatory state, and immunosuppressive treatment. Zonulin-prehaptoglobin-2, a newly discovered protein, is necessary for integrity of intracellular tight junctions in the gut. Taking into consideration iron metabolism, including its absorption in the gut, we designed a cross-sectional study to look for the possible interactions among zonulin, iron status, and anemia in kidney transplant recipients.

Methods

The study was performed on 72 stable kidney transplant recipients and 22 healthy volunteers. Zonulin, iron status, and inflammatory markers were assessed with the use of commercially available kits.

Results

Zonulin was significantly lower in kidney allograft recipients than in healthy volunteers (P < .001). Zonulin correlated with systolic blood pressure (r = −0.33; P < .05), thyroid-binding globulin (r = 0.24; P < .05), hematocrit (r = 0.28; P < .005), hemoglobin (r = 0.32; P < .01), total protein (r = −0.33; P < .01), erythrocyte count (r = 0.26; P < .05), and fasting glucose (r = −0.25; P < .05). Zonulin was not affected by sex, type of immunosuppressive therapy, presence of diabetes, coronary artery disease, heart failure, hypertension, or cause of end-stage renal disease. Zonulin was not related to any of the iron parameters studied. In multiple regression analysis, predictors of zonulin were total protein and thyroglobulin-binding protein, explaining 46% of variation.

Conclusions

Zonulin, with its poorly defined function, does not seem to play a role in the anemia in kidney allograft recipients; however, it seems to be related to the absorption process in the gut.     

Absence of Severe Systemic Toxicity After Leakage-Controlled Isolated Limb Perfusion With Tumor Necrosis Factor-α and Melphalan

Background: Severe systemic toxicity and hemodynamic changes after isolated limb perfusion (ILP) with tumor necrosis factor- (TNF-) and melphalan, with or without interferon-, have been reported in several series. We studied whether these side effects could be precluded by preventing leakage from the isolated circuit into the systemic circulation.Methods: Clinical and pharmacokinetic data for 20 consecutive patients with recurrent melanoma of the limbs who were treated by ILP with TNF- (3–4 mg) and melphalan, with or without interferon-, were studied. Leakage rates and TNF- levels were determined during and after ILP and were correlated with systemic toxicity and hemodynamic changes.Results: Only two patients experienced leaks (2% and 13%) during ILP. For 18 patients without leakage, the mean peak systemic TNF- level was 2.8 ng/ml at 10 minutes after ILP. After leakage, the peak systemic TNF- levels were 31.9 and 88.3 ng/ml at 5 minutes. Toxicity was mild and consisted mainly of fever (n = 17) and nausea/vomiting (n = 19) during the first day after ILP. Some patients developed tachycardia (n = 6), hypotension (n = 3; responding immediately to fluid challenge), a decrease in the WBC count (n = 3; grade I) or thrombocyte count (n = 11; grade I/II, no hemorrhage or therapeutic intervention), or hepatotoxicity [cytolysis (n = 15; 14 grade I/II and 1 grade IV) or hyperbilirubinemia (n = 7; grade I/II, all resolving spontaneously)]. Patients with tachycardia or hepatotoxicity exhibited significantly higher TNF- levels after ILP, compared with other patients.Conclusions: Systemic toxicity after ILP with TNF- is minimal and does not differ from that after ILP with melphalan alone when leakage is adequately controlled.     

Hypoxia-Inducible Factor-1α Expression in Kidney Transplant Biopsy Specimens After Reperfusion Is Associated With Early Recovery of Graft Function After Cadaveric Kidney Transplantation

Background

Ischemia/reperfusion injury during kidney transplantation (KTx) delays allograft recovery. Hypoxia-inducible factor-1α (HIF-1α) is the key regulator of the protective response to ischemia/reperfusion injury. We evaluated the impact of the HIF-1α signaling pathway on allograft recovery during cadaveric KTx.

Inverse Association of N-terminal Pro‒B-type Natriuretic Peptide Level With Metabolic Syndrome in Kidney Transplant Patients

Background

Low levels of natriuretic peptide may activate the renin-angiotensin-aldosterone system, which may contribute to the development of obesity. Therefore, in study we aim to evaluate the relationship between metabolic syndrome (MetS) and serum N-terminal pro?B-type natriuretic peptide (NT-proBNP) concentration in kidney transplant recipients.

Clinical Significance of C3d Assay in Kidney Transplant Recipients With Donor-Specific Anti–Human Leukocyte Antigen Antibodies

BackgroundAntibody-mediated rejection (AMR) is a major cause of allograft loss in kidney transplant. Although donor-specific anti–human leukocyte antigen antibody (DSA) is a key cause of AMR, not all patients with DSA are diagnosed as having AMR and show poor allograft outcomes. This study aimed to evaluate clinical significance of C3d-binding activity in patients with DSA identified by single-antigen bead (SAB) assay.MethodsA total of 168 recipients screened for DSA from 2015 to 2018 were enrolled. Among them, 52 patients had DSA confirmed by SAB assay. Sera were tested using the C3d assay on Luminex platform. AMR was defined by kidney allograft biopsy results using Banff 2015 criteria.ResultsOf 52 patients, C3d-binding DSAs were detected in 22 patients (42.3%). Indication allograft biopsy was performed in 35 patients, with 31 (88.6%) diagnosed as having AMR. Patients with C3d-binding DSA had more class II SAB-DSA (73.3% vs 100%, P = .015) and showed significantly higher mean (SD) fluorescence intensity of class II SAB-DSA than the C3d-binding DSA(?) group (9606.7 [6096.6] vs 1921.0 [1483.8], P < .001). There was a positive correlation in the highest mean fluorescence intensity between class II SAB-DSA and class II C3d-binding DSA (r = 0.70, P < .001). Patients with C3d-binding DSA showed worse death-censored graft survival than those with non-C3d-binding DSA (P = .023).ConclusionsThis study showed that presence of C3d-binding DSA was significantly associated with allograft loss in SAB-DSA–positive patients. Further trials are warranted.     

Impaired Preadipocyte Differentiation in Human Abdominal Obesity: Role of Wnt, Tumor Necrosis Factor-��, and Inflammation

OBJECTIVE

We examined preadipocyte differentiation in obese and nonobese individuals and the effect of cytokines and wingless-type MMTV (mouse mammary tumor virus) integration site family, member 3A (Wnt3a) protein on preadipocyte differentiation and phenotype.

RESEARCH DESIGN AND METHODS

Abdominal subcutaneous adipose tissue biopsies were obtained from a total of 51 donors with varying BMI. After isolation of the adipose and stromalvascular cells, inflammatory cells (CD14- and CD45-positive cells) were removed by immune magnetic separation. CD133-positive cells, containing early progenitor cells, were also isolated and quantified. The CD14- and CD45-negative preadipocytes were cultured with tumor necrosis factor (TNF)-α, interleukin (IL)-6, resistin, or Wnt3a with or without a differentiation cocktail.

RESULTS

The number of preadipocytes able to differentiate to adipose cells was negatively correlated with both BMI and adipocyte cell size of the donors, whereas the number of CD133-positive cells was positively correlated with BMI, suggesting an impaired differentiation of preadipocytes in obesity. Cultured preadipocytes, like freshly isolated mature adipocytes, from obese individuals had an increased expression of mitogen-activated protein 4 kinase 4 (MAP4K4), which is known to inhibit peroxisome proliferator–activated receptor-γ induction. TNF-α, but not IL-6 or resistin, increased Wnt10b, completely inhibited the normal differentiation of the preadipocytes, and instead induced a proinflammatory and macrophage-like phenotype of the cells.

CONCLUSIONS

The apparent number of preadipocytes in the abdominal subcutaneous tissue that can undergo differentiation is reduced in obesity with enlarged fat cells, possibly because of increased MAP4K4 levels. TNF-α promoted a macrophage-like phenotype of the preadipocytes, including several macrophage markers. These results document the plasticity of human preadipocytes and the inverse relationship between lipid storage and proinflammatory capacity.In adult humans, the increased adipose tissue mass in obesity mainly leads to an expansion of the size of the prevailing adipose cells (1,2). However, there is also a continuous turnover of the adipose cells, and thus recruitment of new adipocytes (2–4).The development of insulin resistance and its complications are predominantly seen in conjunction with abdominal adipose tissue distribution and associated cell enlargement (hypertrophic or abdominal/upper-body obesity) rather than peripheral obesity, which is usually associated with a recruitment of new preadipocytes and thus small adipose cells (hyperplastic or peripheral/lower-body obesity) (5–7).An important consequence of adipose cell enlargement is the development of local inflammation in the adipose tissue with infiltration of monocytes/macrophages (8,9). The reason for this is currently unclear but may be attributable to adipose cell death, where macrophages can be seen as scavengers of remaining debris and lipids (10).In addition, adipose cell enlargement leads to increased secretion of cytokines and chemokines, which in turn attract monocytes/macrophages into the tissue (11–14). Both mechanisms may well be operative, and, in addition, local activation of the macrophages in the adipose tissue plays a key role (15), but the tissue factors involved are currently unknown.Obesity-associated inflammation leads to highly dysregulated adipose tissue with an altered pattern of secreted adipokines and increased lipolysis (rev. in (14,16). Secretion of cytokines like tumor necrosis factor (TNF)-α in the adipose tissue impairs the differentiation of preadipocytes, reduces adiponectin secretion, and promotes a proinflammatory state, which in turn further promotes the local secretion of cytokines and chemokines (17,18). In addition, both interleukin (IL)-6 and TNF-α induce insulin resistance in the adipose cells at the level of insulin signaling and action because of reduced expression of insulin receptor substrate-1 and GLUT4 (17,19).Obesity, both in animal models and in humans, is associated with an increase in different markers of inflammatory cells, such as CD68, macrophage inflammatory protein (MIP)-1α, EMR (epidermal growth factor–like module containing mucin-like hormone receptor), and ADAM-8 (a disintegrin and metalloproteinase domain-8) in the adipose tissue (rev. in (14,18,20). In fact, using such markers, Weisberg et al. (8) reported that up to 50% of the cells in the adipose tissue were positive for CD68 and thus could be classified as macrophages. They also reported that the CD68-positive cells were the major producers of the different cytokines studied (8).Although there is no doubt that macrophages are present in the adipose tissue in obesity, it is highly unlikely that they could account for up to 50% of the cells. This raises the question of whether other cells present in the adipose tissue can also become positive for macrophage markers and under what conditions. However, several studies with human preadipocytes cultured in vitro have been unable to find these cells positive for CD68 or other macrophage markers (21). Nevertheless, both gene arrays and the report that 3T3-L1 cells injected into the peritoneal cavity of mice assumed a macrophage-like phenotype (22,23) support the close link between preadipocytes and macrophages.Here, we asked whether human undifferentiated preadipocytes cultured in vitro could assume a macrophage-like phenotype if they were activated by proinflammatory molecules (TNF, IL-6, or resistin). During the course of the experiments, we also we found that the number of preadipocytes in subcutaneous abdominal adipose tissue that differentiated to adipose cells was negatively correlated with BMI as well as mean adipose cell size of the donors. A potential mechanism for this may be increased mitogen-activated protein 4 kinase 4 (MAP4K4) expression in preadipocytes from obese individuals because MAP4K4 inhibits peroxisome proliferator–activated receptor (PPAR)-γ activation as well as adipogenesis (24,25).