Fibrosis in Human Adipose Tissue: Composition, Distribution, and Link With Lipid Metabolism and Fat Mass Loss

OBJECTIVE

Fibrosis is a newly appreciated hallmark of the pathological alteration of human white adipose tissue (WAT). We investigated the composition of subcutaneous (scWAT) and omental WAT (oWAT) fibrosis in obesity and its relationship with metabolic alterations and surgery-induced weight loss.

RESEARCH DESIGN AND METHODS

Surgical biopsies for scWAT and oWAT were obtained in 65 obese (BMI 48.2 ± 0.8 kg/m²) and 9 lean subjects (BMI 22.8 ± 0.7 kg/m²). Obese subjects who were candidates for bariatric surgery were clinically characterized before, 3, 6, and 12 months after surgery, including fat mass evaluation by dual energy X-ray absorptiometry. WAT fibrosis was quantified and characterized using quantitative PCR, microscopic observation, and immunohistochemistry.

RESULTS

Fibrosis amount, distribution and collagen types (I, III, and VI) present distinct characteristics in lean and obese subjects and with WAT depots localization (subcutaneous or omental). Obese subjects had more total fibrosis in oWAT and had more pericellular fibrosis around adipocytes than lean subjects in both depots. Macrophages and mastocytes were highly represented in fibrotic bundles in oWAT, whereas scWAT was more frequently characterized by hypocellular fibrosis. The oWAT fibrosis negatively correlated with omental adipocyte diameters (R = −0.30, P = 0.02), and with triglyceride levels (R = −0.42, P < 0.01), and positively with apoA1 (R = 0.25, P = 0.05). Importantly, scWAT fibrosis correlated negatively with fat mass loss measured at the three time points after surgery.

CONCLUSIONS

Our data suggest differential clinical consequences of fibrosis in human WAT. In oWAT, fibrosis could contribute to limit adipocyte hypertrophy and is associated with a better lipid profile, whereas scWAT fibrosis may hamper fat mass loss induced by surgery.White adipose tissue (WAT) is the main energy repository in the body. It stores and mobilizes, according to body demand, fatty acids that have been implicated in the development of insulin resistance. In turns, the phenotype and the biology of WAT cellular components are altered by two major processes: adipose cell hypertrophy and immune cells accumulation. Inflammation, reticulum endoplasmic stress, and hypoxia are part of the biologic alterations that attract and retain inflammatory cells in WAT (1). Both adipocytes and nonadipose cells of the stromal vascular fraction of WAT have been implicated in the secretion of inflammatory molecules and in the development of insulin resistance (2,3). WAT extracellular matrix (ECM) remodeling, which plays a pivotal role in adipogenesis (4) and tissue architecture (5), is crucial to accommodate obesity-induced cellular alterations (6). However, the persistence of an inflammation stimulus in WAT may be responsible for an excessive synthesis of ECM components and subsequent interstitial deposition of fibrotic material. Fibrosis, attributed to excessive deposition of ECM proteins, is a ubiquitous tissue response to an unresolved chronic inflammation (7). We recently highlighted this phenomenon in obese WAT (8), showing increased expression of genes encoding extracellular matrix components and demonstrating the presence of fibrosis (8,9). In a small number of subjects, we scored histologic WAT fibrous tissue using a picrosirius red staining and observed an increased abundance of ECM in obese versus lean WAT (8). Moreover, we demonstrated that human adipocyte precursors secrete ECM components when challenged by macrophage secretions (10), emphasizing the prominence of macrophage-preadipocyte interactions in WAT fibrosis development or maintenance. Other inflammatory cells accumulate in obese WAT, including T-lymphocytes and mast cells (11), and might also participate in the orchestration of fibrosis deposition.The nature and consequences of ECM modification in WAT have been investigated in mice. In db/db obese mice, various types of collagens are overexpressed in epididymal WAT (12). The predominantly expressed collagen mRNAs in epididymal WAT encode types I, IV, and VI. In mice deleted for the col6a1 gene, the lack of collagen VI associates with increased adipocyte size, both in response to a high-fat diet and on the obese ob/ob genetic background (11). A similar phenotype of adipose cell hypertrophy has been reported in mice deleted for secreted acidic cysteine-rich glycoprotein (SPARC), a matricellular glycoprotein implicated in the synthesis of ECM components (13). A mirror phenotype results from gene invalidation of the collagenase MT1-matrix metalloproteinase (MT1-MMP), which leads to the formation of a rigid network of collagen fibrils and reduced lipid accumulation in the adipocytes (14). These observations suggest that increased ECM deposition in WAT may contribute to restrain adipocyte expansion in obesity.In humans, the nature of WAT fibrosis and its clinical relevance are poorly documented and have been addressed mostly by gene expression evaluation. Subcutaneous white adipose tissue (scWAT) collagen VI expression is increased in Asian Indian subjects compared with Caucasians, in relation to their higher level of susceptibility to insulin resistance (12). Pasarica et al. (15) showed that the expression of collagen VI in human WAT is upregulated after 8 weeks of overfeeding, concomitant with increased inflammatory gene expression. These two studies suggest that increased collagen VI deposition could be a hallmark of WAT deregulation in obesity.Here, we aimed to characterize more precisely fibrotic depots in lean and obese subjects and the pathologic relevance of fibrosis in scWAT and omental white adipose tissue (oWAT). First, we analyzed qualitatively and quantitatively fibrosis in scWAT and oWAT of obese and lean subjects. Second, we characterized cells structurally linked with fibrotic depots. Third, we determined if there is a link between the altered metabolic parameters of obese and fibrosis quantified in WAT depots. And fourth, we examined the consequence of fibrosis accumulation in the outcome of body fat loss in the model of gastric bypass.     

CD133(+) human umbilical cord blood stem cells enhance angiogenesis in experimental chronic hepatic fibrosis

The in vivo angiogenic potential of transplanted human umbilical cord blood (UCB) CD133(+) stem cells in experimental chronic hepatic fibrosis induced by murine schistosomiasis was studied. Enriched cord blood-derived CD133(+) cells were cultured in primary medium for 3 weeks. Twenty-two weeks post-Schistosomiasis infection in mice, after reaching the chronic hepatic fibrotic stage, transplantation of stem cells was performed and mice were sacrificed 3 weeks later. Histopathology and electron microscopy showed an increase in newly formed blood vessels and a decrease in the fibrosis known for this stage of the disease. By immunohistochemical analysis the newly formed blood vessels showed positive expression of the human-specific angiogenic markers CD31, CD34 and von Willebrand factor. Few hepatocyte-like polygonal cells showed positive expression of human vascular endothelial growth factor and inducible nitric oxide synthase. The transplanted CD133(+) human stem cells primarily enhanced hepatic angiogenesis and neovascularization and contributed to repair in a paracrine manner by creating a permissive environment that enabled proliferation and survival of damaged cells rather than by direct differentiation to hepatocytes. A dual advantage of CD133(+) cell therapy in hepatic disease is suggested based on its capability of hematopoietic and endothelial differentiation.     

Novel mutations of the nucleophosmin (NPM-1) gene in Egyptian patients with acute myeloid leukemia: A pilot study

Mutations of the nucleophosmin (NPM-1) gene have been reported in 50-60% of acute myeloid leukemia (AML) patients with normal karyotype. This work was designed to study the prevalence and nature of NPM1 gene mutations in a group of Egyptian patients with AML to get an idea about the profile of NPM1 gene mutations in our society. In 45 previously untreated patients with de novo AML, peripheral blood and/or bone marrow samples from all patients were subjected to microscopic morphologic examination, cytochemical analysis, immunophenotyping and karyotyping. Patients with normal cytogenetic results were selected for molecular analysis of NPM1 exon 12 by PCR amplification followed by DNA sequencing of the amplified product. Twenty-one patients (46.7%) had abnormal karyotype: six cases with t(15;17), five cases with t(8;21), five cases had trisomy 8, two cases carrying inv(3) and three cases had monosomy 7. The remaining 24 patients (53.3%) had normal karyotype. These patients were then subjected to molecular analysis. Out of these 24 patients with normal karyotype, mutant NPM-1 was detected in 11 patients (45.8%) by DNA sequencing; 2 cases showed type A mutation, 2 cases were harboring [ins 1015-1019 (CACG)], with point mutation [1006C>G], while the remaining 7 cases showed heterozygous deletion of nt A [del 1178 (A)]. Conclusion: Two novel NPM1 gene mutations were detected among our study population of AML patients identified as: the insertion CACG associated with point mutation, deletion of one base, or associated with point mutation. NPM1 gene mutations may become a new tool for monitoring minimal residual disease in AML with normal karyotype. Whether these previously unreported NPM-1 mutations will confer the same better outcome as previously reported mutations is currently unknown and warrants a larger study. Conclusion: Two novel NPM1 gene mutations were detected among our study population of AML patients identified as: the insertion CACG associated with point mutation, deletion of one base, or associated with point mutation. NPM1 gene mutations may become a new tool for monitoring minimal residual disease in AML with normal karyotype. Whether these previously unreported NPM-1 mutations will confer the same better outcome as previously reported mutations is currently unknown and warrants a larger study.     

Can the partial deletion in the Y chromosome of male mice affect the reproductive efficiency of their daughters?

The tunica albuginea (TA) of the penis is claimed to share in erectile mechanism by compressing the emissary veins passing through it. Apparently this claim is theoretical as no experimental studies could be traced in literature proving this concept. We investigated the hypothesis that TA acts as a cover to corpora cavernosa (CC) and spongiosa (CS) and does not have an active role in erectile mechanism. Penises of 9 dogs were degloved and TA was divided at upper, middle and lower 1/3 of the penis. The intracorporal and glans penis (GP) pressures were measured in the TA-covered and non-covered parts of CC and CS in the flaccid and erectile phases. Sham operation, without performing the TA incisions, was done in 7 control animals.

In the test animals, intracorporal pressure (ICP) in the non-TA covered corpora and in GP recorded in flaccid phase a mean of 12.2 ± 0.8 cmH₂O for CC and 11.3 ± 0.7 cmH₂O for the CS and GP, and in the erectile phase 98.4 ± 8.6 and 76.2 ± 9.3 cmH₂O, respectively. There was no significant difference between covered and non-covered corpora or between test and control animals. In conclusion, the TA seems to act as a cover to the corporal tissue. Its absence did not change ICP.     

Prediction of Preterm and Low Birth Weight Delivery by Maternal Periodontal Parameters: Receiver Operating Characteristic (ROC) Curve Analysis

In this study we used receiver-operating characteristic (ROC) analysis to comparatively evaluate maternal periodontal parameters to predict preterm (PB) delivery and low birth weight (LBW) delivery among Jordanian women. A total of 277 pregnant women (20 weeks of gestation or less) had periodontal examination at baseline and followed up until delivery. Gestational age and birth weight were retrieved from their medical records. ROC curve analyses were used to examine the overall discriminatory power of the studied periodontal parameters to predict PB, LBW, and PB or LBW. For the three outcome variables, the area under curve (AUC) ranged from 0.84 to 0.87 for average clinical attachment level (CAL), 0.78–0.86 for percent of sites with CAL ≥ 5 mm, 0.63–0.74 for percent of sites with CAL ≥ 6 mm, and 0.71–0.82 for number of missing teeth indicating that they had high discriminating power to predict adverse pregnancy outcomes. All other parameters had AUC less than 0.60 and thus had low discriminating power. Average CAL performed the best in predicting the studied adverse pregnancy outcomes because it has the highest AUC. The severity and extent of periodontal disease as measured by CAL can be used to predict the occurrence of adverse pregnancy outcomes.     

Hepatic fibrosis and serum alpha-fetoprotein (AFP) as predictors of response to HCV treatment and factors associated with serum AFP normalisation after treatment

Background and study aimElevated levels of alpha-fetoprotein (AFP) can be seen in patients with chronic hepatitis C (CHC) and liver cirrhosis without hepatocellular carcinoma and were negatively associated with treatment response. However, factors associated with its changes are not identified. We aimed in this study to verify a cut-off value for AFP as a predictor of response to standard of care (SOC) antiviral therapy in Egyptian chronic hepatitis C virus (HCV)-infected patients and identify factors associated with its changes post treatment.Patients and methodsA total of 175 chronic non-cirrhotic HCV-infected patients were evaluated for baseline serum AFP and liver biopsy were classified according to Ishak scoring system of hepatic fibrosis. All patients were scheduled to receive SOC antiviral therapy for 48 weeks and had been followed up to week 72. Reassessment of AFP and repeated liver biopsy at week 72 were feasible only in 79 patients.ResultsHigh baseline AFP levels were observed in non-respondents (non-sustained virological respondents (non-SVRs)) (P < 0.01); the AFP level decreased in all patients post treatment (P = 0.01), especially in the SVRs (P < 0.01). In multivariate analysis, hepatic fibrosis was a predictor of response to treatment (P = 0.02), while body mass index (BMI) (25–30 kg m^?2), hepatic activity (A2), hepatic fibrosis stage (F2–F4) and fibrosis improvement were predictors of AFP difference (P = 0.007, 0.01, 0.012, <0.001, 0.030, and 0.018), respectively. The diagnostic performance to predict the HCV treatment response was best by adding both AFP and hepatic fibrosis stage factors; the best cut-off value for AFP was 3.57 ng dl^?1 with 50% sensitivity and 68% specificity with area under the curve (AUC) of 0.55 and for hepatic fibrosis stage was 3, with a sensitivity of 88%, a specificity of 30% with an AUC of 0.58.ConclusionIn chronic HCV-infected patients, serum AFP below 3.57 ng dl^?1 and hepatic fibrosis ?stage 3 are expected to have good response to treatment; BMI (25–30 kg m^?1), A2, fibrosis >2 and fibrosis improvement predict AFP change post treatment.