T cell protein tyrosine phosphatase (TCPTP) deficiency in muscle does not alter insulin signalling and glucose homeostasis in mice.

AIMS/HYPOTHESIS: Insulin activates insulin receptor protein tyrosine kinase and downstream phosphatidylinositol-3-kinase (PI3K)/Akt signalling in muscle to promote glucose uptake. The insulin receptor can serve as a substrate for the protein tyrosine phosphatase (PTP) 1B and T cell protein tyrosine phosphatase (TCPTP), which share a striking 74% sequence identity in their catalytic domains. PTP1B is a validated therapeutic target for the alleviation of insulin resistance in type 2 diabetes. PTP1B dephosphorylates the insulin receptor in liver and muscle to regulate glucose homeostasis, whereas TCPTP regulates insulin receptor signalling and gluconeogenesis in the liver. In this study we assessed for the first time the role of TCPTP in the regulation of insulin receptor signalling in muscle. METHODS: We generated muscle-specific TCPTP-deficient (Mck-Cre;Ptpn2(lox/lox)) mice (Mck, also known as Ckm) and assessed the impact on glucose homeostasis and muscle insulin receptor signalling in chow-fed versus high-fat-fed mice. RESULTS: Blood glucose and insulin levels, insulin and glucose tolerance, and insulin-induced muscle insulin receptor activation and downstream PI3K/Akt signalling remained unaltered in chow-fed Mck-Cre;Ptpn2(lox/lox) versus Ptpn2(lox/lox) mice. In addition, body weight, adiposity, energy expenditure, insulin sensitivity and glucose homeostasis were not altered in high-fat-fed Mck-Cre;Ptpn2(lox/lox) versus Ptpn2(lox/lox) mice. CONCLUSIONS/INTERPRETATION: These results indicate that TCPTP deficiency in muscle has no effect on insulin signalling and glucose homeostasis, and does not prevent high-fat diet-induced insulin resistance. Thus, despite their high degree of sequence identity, PTP1B and TCPTP contribute differentially to insulin receptor regulation in muscle. Our results are consistent with the notion that these two highly related PTPs make distinct contributions to insulin receptor regulation in different tissues.

Reduced Socs3 expression in adipose tissue protects female mice against obesity-induced insulin resistance.

AIMS/HYPOTHESIS: Inflammation in obesity increases the levels of the suppressor of cytokine signalling-3 (SOCS3) protein in adipose tissue, but the physiological importance of this protein in regulating whole-body insulin sensitivity in obesity is not known. METHODS: We generated Socs3 floxed (wild-type, WT) and Socs3 aP2 (also known as Fabp4)-Cre null (Socs3 AKO) mice. Mice were maintained on either a regular chow or a high-fat diet (HFD) for 16 weeks during which time body mass, adiposity, glucose homeostasis and insulin sensitivity were assessed. RESULTS: The HFD increased SOCS3 levels in adipose tissue of WT but not Socs3 AKO mice. WT and Socs3 AKO mice had similar body mass and adiposity, assessed using computed tomography (CT) imaging, irrespective of diet or sex. On a control chow diet there were no differences in insulin sensitivity or glucose tolerance. When fed a HFD, female but not male Socs3 AKO mice had improved glucose tolerance as well as lower fasting glucose and insulin levels compared with WT littermates. Hyperinsulinaemic-euglycaemic clamps and positron emission tomography (PET) imaging demonstrated that improved insulin sensitivity was due to elevated adipose tissue glucose uptake. Increased insulin-stimulated glucose uptake in adipose tissue was associated with enhanced levels and activating phosphorylation of insulin receptor substrate-1 (IRS1). CONCLUSIONS/INTERPRETATION: These data demonstrate that inhibiting SOCS3 production in adipose tissue of female mice is effective for improving whole-body insulin sensitivity in obesity.

Partial trisomy 13 in an infant with a mild phenotype: application of fluorescence in situ hybridization in cytogenetic syndromes.

We report on a month-old infant with dysmorphic face and several anomalies known to be associated with trisomy 13. Fluorescence in situ hybridization (FISH) studies performed on metaphase cells allowed us to identify an extra material on the short arm of the chromosome 13 as a duplication of 13q22-qter.

Decay of the IS10 antisense RNA by 3' exoribonucleases: evidence that RNase II stabilizes RNA-OUT against PNPase attack.

RNA-OUT, the 69-nucleotide antisense RNA that regulates Tn10/IS10 transposition folds into a simple stem-loop structure. The unusually high metabolic stability of RNA-OUT is dependent, in part, on the integrity of its stem-domain: mutations that disrupt stem-domain structure (Class II mutations) render RNA-OUT unstable, and restoration of structure restores stability. Indeed, there is a strong correlation between the thermodynamic and metabolic stabilities of RNA-OUT. We show here that stem-domain integrity determines RNA-OUT's resistance to 3' exoribonucleolytic attack: Class II mutations are almost completely suppressed in Escherichia coli cells lacking its principal 3' exoribonucleases, ribonuclease II (RNase II) and polynucleotide phosphorylase (PNPase). RNase II and PNPase are individually able to degrade various RNA-OUT species, albeit with different efficiencies: RNA-OUT secondary structure provides greater resistance to RNase II than to PNPase. Surprisingly, RNA-OUT is threefold more stable in wild-type cells than in cells deficient for RNase II activity, suggesting that RNase II somehow lessens PNPase attack on RNA-OUT. We discuss how this might occur. We also show that wild-type RNA-OUT stability changes only two-fold across the normal range of physiological growth temperatures (30-44 degrees C) in wild-type cells, which has important implications for IS10 biology.

Recombinant bacillus calmette-guerin (BCG) vaccines expressing the Mycobacterium tuberculosis 30-kDa major secretory protein induce greater protective immunity against tuberculosis than conventional BCG vaccines in a highly susceptible animal model.

Tuberculosis (TB) continues to ravage humanity, causing 2 million deaths per year. A vaccine against TB more potent than the current live vaccine, bacillus Calmette-Guérin (BCG), is desperately needed. Using two commercially available strains of BCG as host strains, BCG Connaught and Tice, we have constructed two recombinant BCG vaccines stably expressing and secreting the 30-kDa major secretory protein of Mycobacterium tuberculosis (M. tb.), the primary causative agent of TB. We have tested the efficacy of the two strains in the highly susceptible guinea pig model of pulmonary TB, a model noteworthy for its close resemblance to human TB. Animals immunized with the recombinant BCG vaccines and challenged by aerosol with a highly virulent strain of M. tb. had 0.5 logs fewer M. tb. bacilli in their lungs and 1 log fewer bacilli in their spleens on average than animals immunized with their parental conventional BCG vaccine counterparts. Statistically, these differences were highly significant. Paralleling these results, at necropsy, animals immunized with the recombinant BCG vaccines had fewer and smaller lesions in the lung, spleen, and liver and significantly less lung pathology than animals immunized with the parental BCG vaccines. The recombinant vaccines are the first vaccines against TB more potent than the current commercially available BCG vaccines, which were developed nearly a century ago.