Co-methylated genes in different adipose depots of pig are associated with metabolic, inflammatory and immune processes

It is well established that the metabolic risk factors of obesity and its comorbidities are more attributed to adipose tissue distribution rather than total adipose mass. Since emerging evidence suggests that epigenetic regulation plays an important role in the aetiology of obesity, we conducted a genome-wide methylation analysis on eight different adipose depots of three pig breeds living within comparable environments but displaying distinct fat level using methylated DNA immunoprecipitation sequencing. We aimed to investigate the systematic association between anatomical location-specific DNA methylation status of different adipose depots and obesity-related phenotypes. We show here that compared to subcutaneous adipose tissues which primarily modulate metabolic indicators, visceral adipose tissues and intermuscular adipose tissue, which are the metabolic risk factors of obesity, are primarily associated with impaired inflammatory and immune responses. This study presents epigenetic evidence for functionally relevant methylation differences between different adipose depots.     

Chronic phosphodiesterase type 5 inhibition has beneficial effects on subcutaneous adipose tissue plasticity in type 2 diabetic mice

Different adipose tissue (AT) depots are associated with multiple metabolic risks. Phosphodiesterase type 5 (PDE5) is involved in adipocyte physiology and PDE5 inhibition may affect adipogenesis and ameliorate white AT quality. The aim of this study is to investigate the distribution of AT and the composition of the stroma‐vascular fraction (SVF) of subcutaneous AT (SAT) in type 2 diabetic mice after prolonged treatment with a PDE5 inhibitor, Sildenafil. 18 db/db mice were treated with Sildenafil or vehicle for 12 weeks. AT distribution was monitored and SAT was processed for isolation of SVF by flow cytometry. Sildenafil induced an overall reduction in AT, mainly in visceral AT (VAT), compared with SAT. In Sildenafil‐treated mice, the mean change in body weight from baseline positively correlated with VAT, but not with SAT. Characterization of SVF of SAT showed an increase in the frequency of M2 macrophages and endothelial cells in treated mice. Sildenafil improved the maintenance of SAT homeostasis and distribution.     

Differential modulation of white adipose tissue endocannabinoid levels by n-3 fatty acids in obese mice and type 2 diabetic patients

n-3 polyunsaturated fatty acids (n-3 PUFA) might regulate metabolism by lowering endocannabinoid levels. We examined time-dependent changes in adipose tissue levels of endocannabinoids as well as in parameters of glucose homeostasis induced by n-3 PUFA in dietary-obese mice, and compared these results with the effect of n-3 PUFA intervention in type 2 diabetic (T2DM) subjects. Male C57BL/6J mice were fed for 8, 16 or 24?weeks a high-fat diet alone (cHF) or supplemented with n-3 PUFA (cHF?+?F). Overweight/obese, T2DM patients on metformin therapy were given for 24?weeks corn oil (Placebo; 5?g/day) or n-3 PUFA concentrate as above (Omega-3; 5?g/day). Endocannabinoids were measured by liquid chromatography-tandem mass-spectrometry. Compared to cHF-fed controls, the cHF?+?F mice consistently reduced 2-arachidonoylglycerol (up to ~2-fold at week 24) and anandamide (~2-fold) in adipose tissue, while the levels of endocannabinoid-related anti-inflammatory molecules N-eicosapentaenoyl ethanolamine (EPEA) and N-docosahexaenoyl ethanolamine (DHEA) increased more than ~10-fold and ~8-fold, respectively. At week 24, the cHF?+?F mice improved glucose tolerance and fasting blood glucose, the latter being positively correlated with adipose 2-arachidonoylglycerol levels only in obese cHF-fed controls, like fasting insulin and HOMA-IR. In the patients, n-3 PUFA failed to reduce 2-arachidonoylglycerol and anandamide levels in adipose tissue and serum, but they increased both adipose tissue and serum levels of EPEA and DHEA. In conclusion, the inability of n-3 PUFA to reduce adipose tissue and serum levels of classical endocannabinoids might contribute to a lack of beneficial effects of these lipids on glucose homeostasis in T2DM patients.     

DNA modification in rat lungs following intratracheal or subcutaneous administration of 4-nitroquinoline-1-oxide, benzo[a]pyrene or 2-aminoanthracene

Benzo[a]pyrene (BP)-, 2-aminoanthracene (2AA)- and 4-nitroquinoline-1-oxide (4NQO)-mediated DNA modification were investigated in rat lungs by using alkaline sucrose gradient sedimentation. The exposure-route, the physicochemical nature of the administered compound and the number of treatments were all important in determining the extent of DNA modification. 4NQO produced qualitatively similar modification whether instilled intratracheally (i.t.) as a suspension or injected subcutaneously (s.c.) in a soluble form. BP and 2AA produced no DNA alteration when injected s.c; they did, however, modify DNA sedimentation when instilled as a suspension, but not until 24 h after treatment. Furthermore, BP caused no DNA modification at any sampling time when instilled in a lipid solvent. In contrast to the DNA modification observed at 24 h after a single i.t. treatment with a BP suspension, no such alteration was detected 12 or 24 h after the last of 5 similar daily treatments. These results are discussed with respect to mechanisms of differential transport, clearance and metabolism of administered carcinogens.     

Major Gene Influence on the Propensity to Store Fat in Trunk Versus Extremity Depots: Evidence From the Québec Family Study

Regional fat distribution is related to higher risks of cardiovascular morbidity and mortality, independent of general obesity. In particular, a centralized pattern of fat deposition, characterized by greater abdominal stores relative to extremity stores, is associated with a higher propensity to metabolic complications. Motivated by these considerations, we have initiated a systematic investigation of several measures of regional fat distribution aimed at the identification of possible major gene effects. Two measures approximate the size of subcutaneous fat stores: the sum of six skinfold thicknesses (SF6 = abdominal + suprailiac + subscapular + calf + triceps-+ biceps), and the sum of three trunk skinfold thicknesses (TSF3 = abdominal + suprailiac + subscapular). Both of these phenotypes are highly correlated with total fat mass, 0. 83 and 0.78 for SF6 and TSF3, respectively. The trunk to extremity ratio [TER = TSF3 / (calf + triceps + biceps)] is perhaps the most important of these phenotypes insofar as it is an index of centralized obesity; it is modestly correlated with fat mass (r = 0.18). Each of these phenotypes was adjusted for total fat mass by regression prior to analysis so that we could examine genetic effects on these measures of regional fat distribution without the confounding influence of the determinants of fat mass itself. Segregation analysis of SF6 and TSF3 controlled for total fat mass suggests the presence of a major effect underlying the observed phenotypic distribution; however, tests on the transmission probabilities did not substantiate the segregation of a Mendelian gene. Despite the sexual dimorphism in the expression of the TER, the distribution of age-, generation-, sex-, and fat mass-adjusted TER was not significantly heterogeneous comparing males to females. Consistent evidence of a recessive major gene determinant was obtained, accounting for 37% of the phenotypic variance with the frequency of the gene leading to high values of the TER being 0.35. This finding suggests that further studies to investigate the role of specific candidate genes are warranted.     

Subcutaneous infection of mice with Paracoccidioides brasiliensis induces a peculiar pattern of inflammatory and immune responses

It is well established that resistance or susceptibility to Paracoccidioidis brasiliensis infection in mice is under strict host's genetic control. Mice from A/Sn strain inoculated by the ip route are resistant to fungal infection while infection induced in mice from B10.A strain results in a fatal disease. The early cellular events of infection in both strains are characterized by a marked neutrophilic infiltration that is more prominent in B10.A mice. A peculiar characteristic of the Paracoccidioides brasiliensis-mouse model is that the subcutaneous (sc) inoculations of the fungus either in resistant (A/Sn) or susceptible (B10.A) mice is self-curing and turns mice from the B10.A strain able to express typical DTH reaction to fungal antigens, as observed in A/Sn mice. Here we report the investigation on the early events of the inflammatory response induced by the inoculation of live fungus into the hind footpad of A/Sn (resistant) and B10.A (susceptible) mice. The influence of neutrophils on the inflammatory response and antibody titers or DTH response to gp43, the major fungal antigen, was also evaluated. Results showed a different course of the inflammatory response induced by fungal inoculation in A/Sn and B10.A mice. Neutrophil depletion before infection differently influenced the kinetics of the inflammatory process in both mice strains but did not modifythe fungal load in the lesions. In neutrophil depleted mice from both strains, a decrease in DTH response and an increase in total antibody titers to gp43 were observed. The significant increase in the fungal load in lesions seen in nude mice indicates that the self-limited infection evoked by fungal inoculation into the subcutaneous tissue is a T-cell dependent phenomenon. The implications of these observations in the pathogenesis of paracoccidioidomycosis are discussed.This revised version was published online in October 2005 with corrections to the Cover Date.     

Reconstitution of a metastatic-resistant tumor microenvironment with cancer-associated fibroblasts enables metastasis

The tumor microenvironment is critical for metastasis to occur. Subcutaneous xenografts of tumors in immunodeficient mice are usually encapsulated and rarely metastasize as opposed to orthotopic tumors which metastasize if the original tumor was metastatic. In the present report, we were able to reconstitute a metastatic tumor microenvironment by subcutaneously co-transplanting a human cervical cancer cell line and human cervical cancer-associated fibroblasts (CAFs), in athymic mice, which resulted in lymph node metastasis in 40% of the animals. In contrast, no metastasis occurred from the cervical cancer without CAFs. These results suggest that CAFs can overcome an anti-metastatic tumor environment and are a potential target to prevent metastasis.