Regulation of brown fat adipogenesis by protein tyrosine phosphatase 1B

Background

Protein-tyrosine phosphatase 1B (PTP1B) is a physiological regulator of insulin signaling and energy balance, but its role in brown fat adipogenesis requires additional investigation.

Methodology/Principal Findings

To precisely determine the role of PTP1B in adipogenesis, we established preadipocyte cell lines from wild type and PTP1B knockout (KO) mice. In addition, we reconstituted KO cells with wild type, substrate-trapping (D/A) and sumoylation-resistant (K/R) PTP1B mutants, then characterized differentiation and signaling in these cells. KO, D/A- and WT-reconstituted cells fully differentiated into mature adipocytes with KO and D/A cells exhibiting a trend for enhanced differentiation. In contrast, K/R cells exhibited marked attenuation in differentiation and lipid accumulation compared with WT cells. Expression of adipogenic markers PPARγ, C/EBPα, C/EBPδ, and PGC1α mirrored the differentiation pattern. In addition, the differentiation deficit in K/R cells could be reversed completely by the PPARγ activator troglitazone. PTP1B deficiency enhanced insulin receptor (IR) and insulin receptor substrate 1 (IRS1) tyrosyl phosphorylation, while K/R cells exhibited attenuated insulin-induced IR and IRS1 phosphorylation and glucose uptake compared with WT cells. In addition, substrate-trapping studies revealed that IRS1 is a substrate for PTP1B in brown adipocytes. Moreover, KO, D/A and K/R cells exhibited elevated AMPK and ACC phosphorylation compared with WT cells.

Conclusions

These data indicate that PTP1B is a modulator of brown fat adipogenesis and suggest that adipocyte differentiation requires regulated expression of PTP1B.     

Genotype Profile of Leishmania major Strains Isolated from Tunisian Rodent Reservoir Hosts Revealed by Multilocus Microsatellite Typing

Zoonotic cutaneous leishmaniasis (ZCL) caused by Leishmania (L.) major parasites represents a major health problem with a large spectrum of clinical manifestations. Psammomys (P.) obesus and Meriones (M.) shawi represent the most important host reservoirs of these parasites in Tunisia. We already reported that infection prevalence is different between these two rodent species. We aimed in this work to evaluate the importance of genetic diversity in L. major parasites isolated from different proven and suspected reservoirs for ZCL. Using the multilocus microsatellites typing (MLMT), we analyzed the genetic diversity among strains isolated from (i) P. obesus (n = 31), (ii) M. shawi (n = 8) and (iii) Mustela nivalis (n = 1), captured in Sidi Bouzid, an endemic region for ZCL located in the Center of Tunisia. Studied strains present a new homogeneous genotype profile so far as all tested markers and showed no polymorphism regardless of the parasite host-reservoir origin. This lack of genetic diversity among these L. major isolates is the first genetic information on strains isolated from Leishmania reservoirs hosts in Tunisia. This result indicates that rodent hosts are unlikely to exert a selective pressure on parasites and stresses on the similarity of geographic and ecological features in this study area. Overall, these results increase our knowledge among rodent reservoir hosts and L. major parasites interaction.     

Adverse effects of free fatty acid associated with increased oxidative stress in postischemic isolated rat hearts

The potential role of butyrate to modulate cellular metabolism through integrin receptor led to evaluation of its effect on collagen biosynthesis in cultured fibroblasts. Confluent human dermal fibroblasts were treated with 2 mM and 4 mM of sodium butyrate (NaB) for 48 h. It was found that butyrate induced collagen biosynthesis and prolidase activity independently of α₂β₁ integrin signaling. The expressions of both α₂ and β₁integrin subunits as well as integrin-induced activation of focal adhesion kinase (FAK) were not affected in the cells treated with NaB. Since insulin-like growth factor-I (IGF-I) is the most potent stimulator of collagen biosynthesis in fibroblasts, the effect of butyrate on IGF-I receptor (IGF-IR) expression was evaluated. It was found that the exposure of the cells to 4 mM butyrate contributed to a distinct increase in IGF-IR. It was accompanied by a parallel increase in the expression of Sos protein and MAP-kinases (ERK₁, ERK₂). The data suggests that butyrate-dependent stimulation of collagen biosynthesis in cultured human skin fibroblasts undergoes through IGF-IR signaling.     

Effect of NaCl on fatty acids, phenolics and antioxidant activity of Nigella sativa organs

The objective of this study was to investigate the effect of salinity on growth, fatty acid composition, phenol content and antioxidant activity of Nigella sativa organs. Plants were grown hydroponically under NaCl stress (0, 20 40 and 60 mM). The results indicated that salinity affected N. sativa growth. The fatty acid composition of the leaves and the roots was investigated for the first time and major fatty acids were linolenic acid (58.1%) in the leaves and linoleic (43.9%) and palmitic (33.3%) acids and in the roots. Total fatty acid (TFA) content of the leaves decreased at 60 mM NaCl while root TFA increased at 20 and 40 mM NaCl. Moreover, the fatty acid composition was affected by NaCl; in leaves, the double bond index (DBI) decreased accompanied by a decrease of the level of linolenic acid which reached 14% at 60 mM NaCl. However, root DBI degree increased at 40 at 60 mM NaCl provoked mainly by the increase of the amount of linoleic acid by 15 and 8%, respectively, and the decrease of the amount of palmitic acid by 20 and 14%, respectively. Salt stress increased total polyphenol and individual phenolic acid contents in shoots. Moreover, the antiradical activity of the shoots (DPPH) increased at 60 mM NaCl. However, in roots, the total polyphenol content and the antiradical activity decreased sharply with increasing NaCl doses. Data reported here revealed the variation of fatty acids and phenolic compound contents in different organs of N. sativa, and the possible role of theses changes in the plant salt response were discussed.     

Brown Norway Chromosome 1 Congenic Reduces Symptoms of Renal Disease in Fatty Zucker Rats

We previously reported that a congenic rat with Brown Norway (BN) alleles on chromosome 1 reduces renal disease of 15-week old fatty Zucker rats (ZUC). Development of renal disease in fatty BN congenic and fatty ZUC rats from 9 through 28 weeks is now examined. Analysis of urine metabolites by ¹H nuclear magnetic resonance (NMR) spectroscopy revealed a significantly increased urinary loss of glucose, myo-inositol, urea, creatine, and valine in ZUC. Food intake was lower in the BN congenic rats at weeks 9–24, but they weighed significantly more at 28 weeks compared with the ZUC group. Fasting glucose was significantly higher in ZUC than congenic and adiponectin levels were significantly lower in ZUC, but there was no significant genotype effect on Insulin levels. Glucose tolerance tests exhibited no significant differences between ZUC and congenic when values were normalized to basal glucose levels. Quantitative PCR on livers revealed evidence for higher gluconeogenesis in congenics than ZUC at 9 weeks. Plasma urea nitrogen and creatinine were more than 2-fold higher in 28-week ZUC. Twelve urine protein markers of glomerular, proximal and distal tubule disease were assayed at three ages. Several proteins that indicate glomerular and proximal tubular disease increased with age in both congenic and ZUC. Epidermal growth factor (EGF) level, a marker whose levels decrease with distal tubule disease, was significantly higher in congenics. Quantitative histology of 28 week old animals revealed the most significant genotype effect was for tubular dilation and intratubular protein. The congenic donor region is protective of kidney disease, and effects on Type 2 diabetes are likely limited to fasting glucose and adiponectin. The loss of urea together with a small increase of food intake in ZUC support the hypothesis that nitrogen balance is altered in ZUC from an early age.     

Atomic force microscopy and hydrodynamic characterization of the adhesion of <Emphasis Type="Italic">staphylococcus aureus</Emphasis> to hydrophilic and hydrophobic substrata at different pH values

Understanding the mechanism of the bacterial cell adhesion to solid surfaces is of great medical and industrial importance. Bacterial adhesion to inert surfaces, such as a catheter, and other indwelling devices can form biofilm, consequently cause severe morbidity and often fatal infections. Initial bacterial adhesion to the material surfaces is a complicated process that is affected by various physicochemical properties of both bacterial cells and substratum surfaces. The surface properties of the cells were characterized by the sessile drop technique. Moreover, the interfacial free energy of Staphylococcus aureus adhesion to the supporting materials was determined. The results showed that S. aureus examined at different pH levels could be considered hydrophilic. We noted hat the electron-donor character of S. aureus was important at intermediate pH (pH 5, pH 7, and pH 9) and it decreased at both limits acidic and basic conditions. In addition, the adhesion of Staphylococcus aureus ATCC 25923 to the hydrophilic glass and hydrophobic indium tin oxide (ITO)-coated glass surfaces at different pH values (2, 3, 5, 7, 9 and 11) was investigated using atomic force microscopy (AFM) and image analysis was assessed with the Mathlab^® program. The data analysis showed that cells (number of adhering cells to glass and ITO-coated glass surface) adhered strongly at acidic pH and weakly at alkaline pH. Also, S. aureus has the ability to attach to both hydrophobic and hydrophilic surfaces, but the adhesion was higher on hydrophobic surface.