Yap regulates skeletal muscle fatty acid oxidation and adiposity in metabolic disease.

Obesity is a major risk factor underlying the development of metabolic disease and a growing public health concern globally. Strategies to promote skeletal muscle metabolism can be effective to limit the progression of metabolic disease. Here, we demonstrate that the levels of the Hippo pathway transcriptional co-activator YAP are decreased in muscle biopsies from obese, insulin-resistant humans and mice. Targeted disruption of Yap in adult skeletal muscle resulted in incomplete oxidation of fatty acids and lipotoxicity. Integrated 'omics analysis from isolated adult muscle nuclei revealed that Yap regulates a transcriptional profile associated with metabolic substrate utilisation. In line with these findings, increasing Yap abundance in the striated muscle of obese (db/db) mice enhanced energy expenditure and attenuated adiposity. Our results demonstrate a vital role for Yap as a mediator of skeletal muscle metabolism. Strategies to enhance Yap activity in skeletal muscle warrant consideration as part of comprehensive approaches to treat metabolic disease.

Regulation of angiotensinogen by angiotensin II in mouse primary astrocyte cultures.

Astrocytes are the major source of angiotensinogen in the brain and play an important role in the brain renin-angiotensin system. Regulating brain angiotensinogen production alters blood pressure and fluid and electrolyte homeostasis. In turn, several physiological and pathological manipulations alter expression of angiotensinogen in brain. Surprisingly, little is known about the factors that regulate astrocytic expression of angiotensinogen. There is evidence that angiotensinogen production in both hepatocytes and cardiac myocytes can be positively regulated via the angiotensin type 1 receptor, but this effect has not yet been studied in astrocytes. Therefore, the aim of this project was to establish whether angiotensin II modulates angiotensinogen production in brain astrocytes. Primary astrocyte cultures, prepared from neonatal C57Bl6 mice, expressed angiotensinogen measured by immunocytochemistry and real-time PCR. Using a variety of approaches we were unable to identify angiotensin receptors on cultured astrocytes. Exposure of cultured astrocytes to angiotensin II also did not affect angiotensinogen expression. When astrocyte cultures were transduced with the angiotensin type 1A receptor, using adenoviral vectors, angiotensin II induced a robust down-regulation (91.4% ± 1.8%, p < 0.01, n = 4) of angiotensinogen gene expression. We conclude that receptors for angiotensin II are present in extremely low levels in astrocytes, and that this concurs with available data in vivo. The signaling pathways activated by the angiotensin type 1A receptor are negatively coupled to angiotensinogen expression and represent a powerful pathway for decreasing expression of this protein, potentially via signaling pathways coupled to Gα(q/11) .

The extracellular matrix affects axonal regeneration in peripheral neuropathies.

OBJECTIVE: Recent evidence in animal models suggests that components of the extracellular matrix (ECM) play a primary role in peripheral nerve degeneration and regeneration. METHODS: We investigated the expression of several ECM molecules in human sural nerves by immunohistochemistry, Western blot, and reverse transcriptase PCR analysis. To unravel the possible role of these molecules in nerve regeneration, we compared results obtained from nerves with abundant signs of regeneration with those with complete absence of axonal regeneration. The role of some ECM components on neurite extension was further tested in dorsal root ganglion cultures. RESULTS: We observed that the ECM composition significantly differs in regenerating compared with nonregenerating nerves, independently from their etiologic background. Fibronectin was abundantly expressed in regenerating nerves, whereas vitronectin and fibrin(ogen) prevailed in nonregenerating nerves. Whereas fibronectin is secreted by endoneurial cells, in vivo and vitro studies showed that the source of vitronectin and fibrin(ogen) is the bloodstream. CONCLUSIONS: These data indicate that nerve regeneration is impaired in the presence of breaches in the blood-nerve barrier or impaired extracellular matrix (ECM) degradation that leads to accumulation of plasma vitronectin and fibrin(ogen). The transformation into mature, fibronectin-enriched ECM is necessary for efficient nerve regeneration in humans.

Estrogen receptor alpha and APOEepsilon4 polymorphisms interact to increase risk for sporadic AD in Italian females.

Alzheimer's disease (AD) is a progressive neurodegenerative disease that affects both sexes, with a higher prevalence in women. Declining estrogen levels after menopause may render estrogen target neurons in the brain more susceptible to age or disease-related processes such as AD. To investigate the role of two single nucleotide polymorphisms in the first intron of the ER-alpha gene, denominated PvuII and XbaI, and their interaction with the known AD susceptibility gene APOE, we examined 131 patients with sporadic AD and 109 healthy control subjects. In multinomial logistic regression analysis, a significantly increased risk of sporadic AD because of interaction between the ER-alpha p allele and APOE epsilon4 allele was observed in women, taking subjects who had neither the p allele nor epsilon4 as reference [odds ratio (OR) 7.24; 95% CI, 2.22-23.60]. For women carrying the ER-alpha x allele together with APOE epsilon4, the risk of sporadic AD was similarly elevated (OR 8.33; 95% CI, 1.73-40.06). The data suggest that the p and x alleles of polymorphic ER-alpha gene interact synergistically with the APOE epsilon4 allele to increase the risk of AD in women but not in men in this Italian cohort.

Characterization of the effect of ganstigmine (CHF2819) on amyloid precursor protein metabolism in SH-SY5Y neuroblastoma cells.

We have investigated the effect of ganstigmine (CHF2819), a novel geneserine derived acetylcholinesterase (AChE) inhibitor, on the expression and metabolism of the amyloid precursor protein (APP) in neuroblastoma cell line SH-SY5Y. The rationale was based on the suggestion that cholinergic activity may also be involved in the regulation of APP metabolism. We studied the acute effect on APP metabolism following the secretion of sAPPalpha in the conditioned medium of cells. Following short term treatment (2h), ganstigmine promoted a slight increase in the release of sAPPalpha, the maximal effect approaching on average 1.5 fold baseline value. The data obtained in the long term experiments demonstrate that continuous inhibition of AchE obtained with 100 nM ganstigmine following an exposure of 24 hours did not influence APP isoforms expression. However, the compound appeared to increase the constitutive release of sAPPalpha, with a mechanism that is derived from an indirect cholinergic stimulation.