The serum- and glucocorticoid-regulated kinase (sgk1) is induced by mineralocorticoids and, in turn, upregulates heterologously expressed renal epithelial Na+ channel (ENaC) activity in Xenopus oocytes. Accordingly, Sgk1 is considered to mediate the mineralocorticoid stimulation of renal ENaC activity and antinatriuresis. Here we show that at standard NaCl intake, renal water and electrolyte excretion is indistinguishable in sgk1-knockout (sgk1–/–) mice and wild-type (sgk1+/+) mice. In contrast, dietary NaCl restriction reveals an impaired ability of sgk1–/– mice to adequately decrease Na+ excretion despite increases in plasma aldosterone levels and proximal-tubular Na+ and fluid reabsorption, as well as decreases in blood pressure and glomerular filtration rate

Cachexia is a devastating muscle-wasting syndrome that occurs in patients who have chronic diseases. It is most commonly observed in individuals with advanced cancer, presenting in 80% of these patients, and it is one of the primary causes of morbidity and mortality associated with cancer. Additionally, although many people with cachexia show hypermetabolism, the causative role of metabolism in muscle atrophy has been unclear. To understand the molecular basis of cachexia-associated muscle atrophy, it is necessary to develop accurate models of the condition. By using transcriptomics and cytokine profiling of human muscle stem cell-based models and human cancer-induced cachexia models in mice, we found that cachectic cancer cells secreted many inflammatory factors that rapidly led to high levels of fatty acid metabolism and to the activation of a p38 stress-response signature in skeletal muscles, before manifestation of cachectic muscle atrophy occurred. Metabolomics profiling revealed that factors secreted by cachectic cancer cells rapidly induce excessive fatty acid oxidation in human myotubes, which leads to oxidative stress, p38 activation and impaired muscle growth. Pharmacological blockade of fatty acid oxidation not only rescued human myotubes, but also improved muscle mass and body weight in cancer cachexia models in vivo. Therefore, fatty acid-induced oxidative stress could be targeted to prevent cancer-induced cachexia.

Previous studies showed increased extracellular nucleotides during renal ischemia-reperfusion. While nucleotides represent the main source for extracellular adenosine and adenosine signaling contributes to renal protection from ischemia, we hypothesized a role for ecto-nucleoside-triphosphate-diphosphohydrolases (E-NTPDases) in renal protection. We used a model of murine ischemia-reperfusion and in situ ischemic preconditioning (IP) via a hanging weight system for atraumatic renal artery occlusion. Initial studies with a nonspecific inhibitor of E-NTPDases (POM-1) revealed inhibition of renal protection by IP. We next pursued transcriptional responses of E-NTPDases (E-NTPDase1-3, and 8) to renal IP, and found a robust and selective induction of E-NTPDase1/CD39 transcript and protein. Moreover, based on clearance studies, plasma electrolytes, and renal tubular histology, IP protection was abolished in gene-targeted mice for cd39 whereas increased renal adenosine content with IP was attenuated. Furthermore, administration of apyrase reconstituted renal protection by IP in cd39-/- mice. Finally, apyrase treatment of wild-type mice resulted in increased renal adenosine concentrations and a similar degree of renal protection from ischemia as IP treatment. Taken together, these data identify CD39-dependent nucleotide phosphohydrolysis in renal protection. Moreover, the present studies suggest apyrase treatment as a novel pharmacological approach to renal diseases precipitated by limited oxygen availability.

Abstract. Serum-and glucocorticoid-regulated kinase 1 (Sgk1) contributes to Na ϩ reabsorption in the aldosterone-sensitive distal nephron. Sgk1-knockout (sgk1Ϫ/Ϫ) and littermate wildtype mice (sgk1ϩ/ϩ) were used to test the importance of Sgk1 in renal elimination of K ϩ .

The mineralocorticoids aldosterone and deoxycorticosterone acetate (DOCA) stimulate renal tubular salt reabsorption, increase salt appetite, induce extracellular volume expansion, and elevate blood pressure. Cardiac effects of mineralocorticoids include stimulation of matrix protein deposition leading to cardiac fibrosis, which is at least partially due to the direct action of the hormones on cardiac cells. The signaling mechanisms mediating mineralocorticoid-induced cardiac fibrosis have so far remained elusive. Mineralocorticoids have been shown to upregulate the serum- and glucocorticoid-inducible kinase 1 (SGK1), which participates in the effects of mineralocorticoids on renal tubular Na+ reabsorption and salt appetite. To explore the involvement of SGK1 in the pathogenesis of mineralocorticoid-induced cardiac fibrosis, SGK1 knockout mice (sgk1-/-) and wild-type littermates (sgk1+/+) were implanted a 21-day-release 50-mg DOCA pellet and supplied with 1% NaCl in drinking water for 18 days. This DOCA/high-salt treatment increased blood pressure in both genotypes but led to significant cardiac fibrosis only in sgk1+/+ but not in sgk1-/- mice. According to real-time polymerase chain reaction and Western blotting, DOCA/high-salt treatment enhanced transcript levels and protein expression of cardiac connective tissue growth factor (CTGF) only in sgk1+/+ but not in sgk1-/- mice. Furthermore, DOCA (10 microM) upregulated CTGF expression and enhanced CTGF promoter activity in lung fibroblasts isolated from sgk1+/+ but not from sgk1-/- mice, an effect involving spironolactone-sensitive mineralocorticoid receptors and activation of nuclear factor-kappaB (NFkappaB). Our results suggest that SGK1 plays a decisive role in mineralocorticoid-induced CTGF expression and cardiac fibrosis.

Background/Aims: Dairy cows with ketosis are characterized by oxidative stress and hepatic damage. The aim of this study was to investigate hepatic oxidative stress and the apoptotic status of ketotic cows, as well as the underlying apoptosis pathway. Methods: The blood aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (GGT) activities and the haptoglobin (HP), serum amyloid A (SAA) and serum apoptotic cytokeratin 18 neo-epitope M30 (CK18 M30) concentrations were determined by commercially available kits and ELISA kits, respectively. Liver histology, TUNEL and Oil red O staining were performed in liver tissue samples. TG contents were measured using an enzymatic kit; Caspase 3 assays were carried out using the Caspase 3 activity assay kit; oxidation and antioxidant markers were measured using biochemical kits; apoptosis pathway were determined by qRT-PCR and western blot. Results: Ketotic cows displayed hepatic fat accumulation. The hepatic malondialdehyde (MDA) content was significantly increased, but the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were markedly decreased in ketotic cows compared with control cows, indicating that ketotic cows displayed severe oxidative stress. Significantly higher serum levels of the hepatic damage markers AST, ALT, GGT and GLDH were observed in ketotic cows than in control cows. The blood concentration of the apoptotic marker CK18 M30 and the number of TUNEL-positive cells in the liver of ketotic cows were 1.19- and 2.61-fold, respectively, higher than the values observed in control cows. Besides, Caspase 3 activity was significantly increased in the liver of ketosis cows. Importantly, the levels of phosphorylated c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK) were significantly increased but the level of phosphorylated extracellular signal-regulated kinase1/2 (ERK1/2) was markedly decreased, which further promoted tumor protein 53 (p53) expression and inhibited nuclear factor E2-related factor 2 (Nrf2) expression. The apoptosis-related molecules p21, MDM2, Caspase 3, Caspase 9 and Bax were expressed at significantly higher levels in ketotic cows than in healthy cows, whereas the anti-apoptosis molecule Bcl-2 was expressed at significantly lower levels. Conclusions: Based on these results, ketotic cows display severe hepatic oxidative stress. The hepatic MAPK-p53-Nrf2 apoptotic pathway is over induced and partially mediated apoptotic damage in the liver.

. SGK1 as a determinant of kidney function and salt intake in response to mineralocorticoid excess.

Mineralocorticoid regulation of the renal epithelial Na + channel (ENaC) is of paramount importance for the maintenance of extracellular fluid volume and blood pressure (1). Targeted disruption of αENaC (2, 3), βENaC (4), γENaC (5), or the mineralocorticoid receptor (6) in mice is either not compatible with survival or leads to severe salt wasting. Similarly, loss-of-function mutations of ENaC subunits (7, 8) or the mineralocorticoid receptor (9) in humans cause pseudohypoaldosteronism type 1, characterized by salt wasting and hypotension, despite elevated levels of aldosterone. Conversely, gain-of-function mutations of ENaC (Liddle syndrome) (10) or of the mineralocorticoid receptor (11) lead to severe hypertension. Low dietary Na + intake (12, 13) or exogenous application of aldosterone (14) increases the apical abundance of ENaC in the renal collecting system, the renal target for mineralocorticoid action (15). Recently, compelling evidence has been gathered pointing to an important role for the serum-and glucocorticoid-regulated kinase (Sgk1) in the regulation of ENaC by mineralocorticoids (16). The sgk1 gene was originally cloned as a glucocorticoid-sensitive (17, 18) or a cell volume-regulated (19) gene and was subsequently shown to be strongly upregulated by mineralocorticoids (20-23). In kidney, Sgk1 is highly expressed in the collecting system (14, 20, 24), where aldosteroneinduced apical translocation of ENaC is preceded by an upregulation of Sgk1 in ENaC-positive epithelial cells (14). In Xenopus oocytes expressing the α, β, and γ subunits of ENaC, coexpression of Sgk1 results in a marked upregulation of Na + channel activity (20, 21, 23-26), presumably by increasing ENaC abundance in the cell membrane (14, 23, 26). Although highly suggestive, these observations do not allow one to estimate the contribution of Sgk1 to renal Na + reabsorption and extracellular fluid homeostasis. To address the functional significance of Sgk1 expression in vivo, we generated sgk1-deficient mice. We show that Sgk1 indeed participates in, but does not fully account for, the mineralocorticoid regulation of distal-tubular Na + reabsorption. Methods Generation of sgk1-/mice. Genomic fragments of sgk1 were isolated from a λ phage genomic library (AB-1) prepared from 129/Sv(ev) embryonic stem (ES) cells.