5a-Carba-β-D-glucopyranose derivatives as novel sodium-dependent glucose cotransporter 2 (SGLT2) inhibitors for the treatment of type 2 diabetes

5a-Carba-β-D-glucopyranose derivatives were synthesized and identified as novel SGLT2-selective inhibitors. These inhibitors exhibited potent SGLT2 inhibition with high selectivity over SGLT1. Among the tested compounds, 6f indicated the most potent hSGLT2 inhibition and the highest selectivity over hSGLT1. Moreover, the pharmacokinetics data also showed that 6h, which had the same aglycon structure as sergliflozin-active (3-active), had a threefold longer half-life time (T(1/2)) than sergliflozin (3) with a high distribution volume in db/db mice. Subsequently, 6h lowered blood glucose levels as much as 3 and showed longer hypoglycemic action than 3 in db/db mice.     

Defective maintenance of intracellular Ca^2＋ homeostasis is linked to increasedmuscle fatigability in the MG29 null mice

Mitsugumin 29 (MG29) is a transmembrane protein that is normally found in the triad junction of skeletal muscle. Our previous studies have shown that targeted deletion of rag29 from the skeletal muscle resulted in abnormality of the triad junction structure, and also increased susceptibility to muscle fatigue. To elucidate the basis of these effects, we investigated the properties of Ca^2 uptake and -release in toxin-skinned Extensor Digitorium Longus (EDL) muscle fibers from control and rag29 knockout mice. Compared with the control muscle, submaximal Ca^2 uptake into the sarcoplasmic reticulum (SR) was slower and the storage of Ca^2 inside the SR was less in the mutant muscle, due to increased leakage process of Ca^2 movement across the SR. The leakage pathway is associated with the increased sensitivity of Ca^2 /caffeine -induced Ca^2 release to myoplasmic Ca^2 . Therefore, the increased fatigability of mutant EDL muscles can result from a combination of a slowing of Ca^2 uptake, modification of Ca^2 -induced Ca^2 release (CICR), and a reduction in total SR Ca^2 content.     

TSC1/2 signaling complex is essential for peripheral naïve CD8+ T cell survival and homeostasis in mice

The PI3K-Akt-mTOR pathway plays crucial roles in regulating both innate and adaptive immunity. However, the role of TSC1, a critical negative regulator of mTOR, in peripheral T cell homeostasis remains elusive. With T cell-specific Tsc1 conditional knockout (Tsc1 KO) mice, we found that peripheral na?ve CD8(+) T cells but not CD4(+) T cells were severely reduced. Tsc1 KO na?ve CD8(+) T cells showed profound survival defect in an adoptive transfer model and in culture with either stimulation of IL-7 or IL-15, despite comparable CD122 and CD127 expression between control and KO CD8(+) T cells. IL-7 stimulated phosphorylation of Akt(S473) was diminished in Tsc1 KO na?ve CD8(+)T cells due to hyperactive mTOR-mediated feedback suppression on PI3K-AKT signaling. Furthermore, impaired Foxo1/Foxo3a phosphorylation and increased pro-apoptotic Bim expression in Tsc1 KO na?ve CD8(+)T cells were observed upon stimulation of IL-7. Collectively, our study suggests that TSC1 plays an essential role in regulating peripheral na?ve CD8(+) T cell homeostasis, possible via an mTOR-Akt-FoxO-Bim signaling pathway.     

Normalization of cholesterol homeostasis by 2-hydroxypropyl-β-cyclodextrin in neurons and glia from Niemann-Pick C1 (NPC1)-deficient mice

Niemann-Pick C (NPC) disease is an inherited, progressive neurodegenerative disorder caused by mutations in the NPC1 or NPC2 gene that result in an accumulation of unesterified cholesterol in late endosomes/lysosomes (LE/L) and impaired export of cholesterol from LE/L to the endoplasmic reticulum (ER). Recent studies demonstrate that administration of cyclodextrin (CD) to Npc1(-/-) mice eliminates cholesterol sequestration in LE/L of many tissues, including the brain, delays neurodegeneration, and increases lifespan of the mice. We have now investigated cholesterol homeostasis in NPC1-deficient cells of the brain in response to CD. Primary cultures of neurons and glial cells from Npc1(-/-) mice were incubated for 24 h with 0.1 to 10 mm CD after which survival and cholesterol homeostasis were monitored. Although 10 mm CD was profoundly neurotoxic, and altered astrocyte morphology, 0.1 and 1 mm CD were not toxic but effectively mobilized stored cholesterol from the LE/L as indicated by filipin staining. However, 0.1 and 1 mm CD altered cholesterol homeostasis in opposite directions. The data suggest that 0.1 mm CD releases cholesterol trapped in LE/L of neurons and astrocytes and increases cholesterol availability at the ER, whereas 1 mm CD primarily extracts cholesterol from the plasma membrane and reduces ER cholesterol. These studies in Npc1(-/-) neurons and astrocytes establish a dose of CD (0.1 mm) that would likely be beneficial in NPC disease. The findings are timely because treatment of NPC disease patients with CD is currently being initiated.     

Retinoic acid homeostasis regulates meiotic entry in developing anuran gonads and in Bidder’s organ through Raldh2 and Cyp26b1 proteins

The vitamin A (retinol) and its metabolites such as retinoic acid (RA) affect vertebrate gametogenesis. The level of RA in cells relies on the balance between its synthesis and degradation. The sex-dependent equilibrium is reached in different ways in various species. It is known that RA induces meiosis in developing gonads in mouse, chicken and urodel amphibians, but its role in anuran amphibians has not been studied. Here we show in six anuran species (Xenopus laevis, Bombina bombina, Hyla arborea, Bufo viridis, Rana arvalis and Rana temporaria) that cultured undifferentiated gonads were insensitive to RA treatment, but the RA induced ectopic meiosis in cultured larval testes. In larval testes of all studied species, the exogenous RA induced leptotene phase of I meiotic prophase in gonia, but only in H. arborea and B. viridis gonia progressed to zygotene phase. In the cultured developing ovaries, exogenous RA led to increase in the number of oocytes as compared to the control. Inhibition of either RA synthesis or RA-receptors prevented meiotic entry in larval gonads of all species. Exogenous RA rescued this inhibitory effect demonstrating that the balance in RA homeostasis plays a key role in meiotic entry in anuran gonads. The localization of two enzymes, Raldh2 and Cyp26b1, which antagonistically control RA levels and whose abundance suggests the sites of RA synthesis and degradation respectively, showed two distinct expression patterns specific for (i) X. laevis, H. arborea, R. arvalis, R. temporaria and (ii) B. bombina, B. viridis. Thus, RA, in correlation with specific expression patterns of Raldh2 and Cyp26b, induces meiosis during gonad development in anurans. In addition, in B. viridis, RA signalling seems important for development of the Bidder’s organ containing oocytes both in males and females.     

Inflammation and skin cholesterol in LDLr−/−, apoA-I−/− mice: link between cholesterol homeostasis and self-tolerance?

Diet-fed low density lipoprotein receptor-deficient/apolipoprotein A-I-deficient (LDLr-/-, apoA-I-/-) mice accumulate a 10-fold greater mass of cholesterol in their skin despite a 1.5- to 2-fold lower plasma cholesterol concentration compared with diet-fed LDLr-/- mice. The accumulation of cholesterol predominantly in the skin has been shown to occur in a growing number of other hypercholesterolemic double knockout mouse models sharing deficits in genes regulating cellular cholesterol homeostasis. Exploring the relationship between cholesterol balance and inflammation, we have examined the time course of cholesterol accumulation in a number of extrahepatic tissues and correlated with the onset of inflammation in diet-fed LDLr-/-, apoA-I-/- mice. After 4 weeks of diet, LDLr-/-, apoA-I-/- mice showed a significant increase in skin cholesterol mass compared with LDLr-/- mice. In addition, after 4 weeks on the diet, cholesterol accumulation in the skin was also found to be associated with macrophage infiltration and accompanied by increases in tumor necrosis factor-alpha, cyclooxygenase-2, and langerin mRNA, which were not seen in the liver. Overall, these data suggest that as early as 4 weeks after starting the diet, the accumulation of skin cholesterol and the onset of inflammation occur concurrently. In summary, the use of hypercholesterolemic LDLr-/-, apoA-I-/- mice may provide a useful tool to investigate the role that apoA-I plays in maintaining cholesterol homeostasis and its relationship to inflammation.     

X-inactivation analysis of embryonic lethality in Ocrl wt/−;Inpp5b −/− mice

Mutations in the human OCRL gene, which encodes a phosphatidylinositol(4,5)bisphosphate 5-phosphatase, result in the X-linked oculocerebrorenal syndrome of Lowe. Mice with a targeted disruption of Ocrl have no phenotypic abnormalities. Targeted disruption of its closest paralog, Inpp5b, causes male infertility in the 129S6 background. Mice with disruptions of both genes are lost in utero prior to 9.5-10.5 dpc, indicating that there is a functional overlap between the two paralogs early in development. We analyzed the pattern of X-inactivation in four tissues of distinct embryonic origin from Ocrl ^wt/?;Inpp5b ^?/? females to explore the timing and tissue distribution of the functional overlap. X-inactivation was strongly skewed against the disrupted Ocrl ^? allele being on the active X chromosome in all four tissues tested, indicating that there is early selection against cell lineages lacking both Ocrl and Inpp5b. Extraembryonic tissue was also involved in the lethality because there were never any live-born Ocrl ^wt/?;Inpp5b ^?/? females when the functional Ocrl ^wt allele was on the paternal X chromosome, which is preferentially inactivated in trophoblast-derived extraembryonic tissues. Live-born Ocrl ^wt/?;Inpp5b ^?/? females were found when the functional Ocrl ^wt allele was maternal, although in fewer numbers than expected. The importance of the extraembryonic tissues in the early embryonic lethality of embryos lacking both Ocrl and Inpp5b is reinforced by the successful isolation of a viable 40,XX Ocrl ^?/?;Inpp5b ^?/? embryonic stem cell from the inner cell mass of a 3.5-dpc blastocyst prior to implantation. These results indicate a functional overlap of Ocrl and Inpp5b in most cell lineages, especially in extraembryonic tissues.     

Activation of peroxisome proliferator-activated receptor-γ by rosiglitazone improves lipid homeostasis at the adipose tissue-liver axis in ethanol-fed mice

The development of alcohol-induced fatty liver is associated with a reduction of white adipose tissue (WAT). Peroxisome proliferator-activated receptor (PPAR)-γ prominently distributes in the WAT and plays a crucial role in maintaining adiposity. The present study investigated the effects of PPAR-γ activation by rosiglitazone on lipid homeostasis at the adipose tissue-liver axis. Adult C57BL/6 male mice were pair fed liquid diet containing ethanol or isocaloric maltose dextrin for 8 wk with or without rosiglitazone supplementation to ethanol-fed mice for the last 3 wk. Ethanol exposure downregulated adipose PPAR-γ gene and reduced the WAT mass in association with induction of inflammation, which was attenuated by rosiglitazone. Ethanol exposure stimulated lipolysis but reduced fatty acid uptake capacity in association with dysregulation of lipid metabolism genes. Rosiglitazone normalized adipose gene expression and corrected ethanol-induced lipid dyshomeostasis. Ethanol exposure induced steatosis and upregulated inflammatory genes in the liver, which were attenuated by rosiglitazone. Hepatic peroxisomal fatty acid β-oxidation was suppressed by ethanol in associated with inhibition of acyl-coenzyme A oxidase 1. Rosiglitazone elevated plasma adiponectin level and normalized peroxisomal fatty acid β-oxidation rate. However, rosiglitazone did not affect ethanol-reduced very low-density lipoprotein secretion from the liver. These results demonstrated that activation of PPAR-γ by rosiglitazone reverses ethanol-induced adipose dysfunction and lipid dyshomeostasis at the WAT-liver axis, thereby abrogating alcoholic fatty liver.     

Proteasomes in the brain of β2-microglobulin knockout mice

MHC class I molecules play an important role in synaptic plasticity of the mammalian nervous system. Proteolytic complexes (proteasomes) produce oligopeptides that are presented on cell surfaces in complexes with MHC class I molecules and regulate many cellular processes beside this. The goal of the present work was to study peculiarities in functioning of proteasomes and associated signaling pathways along with evaluation of NeuN and gFAP expression in different sections of the brain in mice with knockout of β2-microglobulin, a constituent of MHC class I molecules. It was found that the frontal cortex and the brainstem, structures with different ratio of NeuN and gFAP expression, are characterized by opposite changes in the proteasome pool under constant total proteasome levels in B2m-knockout mice in comparison with those in control animals. ChTL-activity as well as expression of LMP7 immune subunit and PA28 regulator of proteasomes was elevated in the cortex of B2m-knockout mice, while these indicators were decreased in the brainstem. The concentrations of the signaling molecules nNOS and HSP70 in B2m-knockout mice were increased in the cortex, while being decreased in the brainstem, and this indicates the possibility of control of expression of the LMP7 subunit and the regulator PA28 by these molecules. Changes in the proteasome pool observed in striatum of B2m-knockout mice are similar to those observed in the brainstem. At the same time, the cerebellum is characterized by a specific pattern of proteasome functioning in comparison with that in all other brain structures. In cerebellum the expression of immune subunits LMP7 and LMP2 and the regulator PA28 was increased, while expression of regulator PA700 was decreased. Deficiency of NeuN and gFAP was revealed in most brain compartments of B2m-knockout mice. Thus, increased expression of the above-mentioned immune subunits and the proteasome regulator PA28 in the cortex and cerebellum may compensate disturbances revealed in the brain structures and the absence of MHC class I molecules. Apparently, this promotes production of peptides necessary for cell-to-cell interactions and maintains nervous system plasticity in B2m-knockout mice.     

Phospholamban ablation in hearts expressing the high affinity SERCA2b isoform normalizes global Ca²⁺ homeostasis but not Ca²⁺-dependent hypertrophic signaling

Cardiomyocytes from failing hearts exhibit reduced levels of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA) and/or increased activity of the endogenous SERCA inhibitor phospholamban. The resulting reduction in the Ca(2+) affinity of SERCA impairs SR Ca(2+) cycling in this condition. We have previously investigated the physiological impact of increasing the Ca(2+) affinity of SERCA by substituting SERCA2a with the higher affinity SERCA2b pump. When phospholamban was also ablated, these double knockouts (DKO) exhibited a dramatic reduction in total SERCA levels, severe hypertrophy, and diastolic dysfunction. We presently examined the role of cardiomyocyte Ca(2+) homeostasis in both functional and structural remodeling in these hearts. Despite the low SERCA levels in DKO, we observed near-normal Ca(2+) homeostasis with rapid Ca(2+) reuptake even at high Ca(2+) loads and stimulation frequencies. Well-preserved global Ca(2+) homeostasis in DKO was paradoxically associated with marked activation of the Ca(2+)-dependent nuclear factor of activated T-cell-calcineurin pathway known to trigger hypertrophy. No activation of the MAP kinase signaling pathway was detected. These findings suggest that local changes in Ca(2+) homeostasis may play an important signaling role in DKO, perhaps due to reduced microdomain Ca(2+) buffering by SERCA2b. Furthermore, alterations in global Ca(2+) homeostasis can also not explain impaired in vivo diastolic function in DKO. Taken together, our results suggest that normalizing global cardiomyocyte Ca(2+) homeostasis does not necessarily protect against hypertrophy and heart failure development and that excessively increasing SERCA Ca(2+) affinity may be detrimental.     

Sodium–glucose cotransporter 2 inhibitors and inflammation in chronic kidney disease: Possible molecular pathways

Clinical trials with sodium–glucose cotransporter 2 (SGLT2) inhibitors (empagliflozin, dapagliflozin, and canagliflozin) have shown a decrease in the progression of chronic kidney disease (CKD). SGLT2 inhibitors represent a new category of oral antidiabetic agents that can also reduce systolic and diastolic blood pressure, as well as serum uric acid, and improve the glomerular filtration rate. Apart from affecting renal hemodynamics and glycotoxicity, evidence suggests that SGLT2 inhibitors may be renoprotective due to their effects on inflammation in renal tissues. Inflammatory responses play a prominent role in the pathophysiology of CKD as several structural and functional disorders of renal failure are strongly related to the overproduction of proinflammatory mediators. The present review discusses the anti-inflammatory properties of SGLT2 inhibitors. The different molecular pathways through which SGLT2 inhibitors may affect inflammation in the kidneys are also commented upon.     

Dietary phosphatidylcholine supplementation reduces atherosclerosis in Ldlr−/− male mice2

Choline is an essential nutrient required for various biological processes. Eggs, dairy, and meat are rich in phosphatidylcholine (PC), whereas cereal and legumes are rich in free choline. Excess dietary choline leads to increase plasma trimethylamine N-oxide (TMAO). Epidemiological studies suggest that plasma TMAO is a biomarker for atherosclerosis and it has been suggested that a lower intake of eggs and meat would reduce choline consumption and thus reduce atherosclerosis development. To investigate whether the form of dietary choline influences atherosclerosis development in Ldlr^−/−, we randomly fed Ldlr^−/−male mice (aged 8 – 10 wk) one of the three 40% (calories) high fat diets (with 0.5% w/w of cholesterol): Control (0.1% w/w free-choline, CON), choline-supplemented (0.4% free-choline, CS), or PC-supplemented (0.1% free-choline and 0.3% choline from PC, PCS). After 12-wk of dietary intervention, the animals were euthanized and tissues and blood collected. Aortic atherosclerotic plaque area, plasma choline, lipid metabolites, and spleen and peripheral blood cell phenotypes were quantified. Surprisingly, the PCS group had significantly lower atherosclerotic lesions while having 2-fold higher plasma TMAO levels compared with both CON and CS groups (P<0.05). In the fasting state, we found that PCS decreased plasma very low-density lipoprotein-cholesterol (VLDL-C) and apolipoprotein B48 (APOB48), and increased plasma high-density lipoprotein-cholesterol (HDL-C). However, very low-density lipoprotein (VLDL) secretion was not affected by dietary treatment. We observed lower levels of circulating pro-atherogenic chemokines in the PCS group. Our study suggests that increased dietary PC intake does not induce a pro-atherogenic phenotype.     

11-Phenoxyundecyl phosphate as a 2-acetamido-2-deoxy-α-d-glucopyranosyl phosphate acceptor in O-antigen repeating unit assembly of Salmonella arizonae O:59

A synthesis of 11-phenoxyundecyl phosphate and its biochemical transformation (using GlcNAc-P transferase from Salmonella arizonae O:59 membranes catalysing transfer of GlcNc-phosphate from UDP-GlcNAc on lipid-phosphate) into P¹-11-phenoxyundecyl, P²-2-acetamido-2-deoxy-α-d-glucopyranosyl diphosphate are described.     

Major urinary metabolites of 6-keto-prostaglandin F2α in mice

Western diets are enriched in omega-6 vs. omega-3 fatty acids, and a shift in this balance toward omega-3 fatty acids may have health benefits. There is limited information about the catabolism of 3-series prostaglandins (PG) formed from eicosapentaenoic acid (EPA), a fish oil omega-3 fatty acid that becomes elevated in tissues following fish oil consumption. Quantification of appropriate urinary 3-series PG metabolites could be used for noninvasive measurement of omega-3 fatty acid tone. Here we describe the preparation of tritium- and deuterium-labeled 6-keto-PGF_2α and their use in identifying urinary metabolites in mice using LC-MS/MS. The major 6-keto-PGF_2α urinary metabolites included dinor-6-keto-PGF_2α (∼10%) and dinor-13,14-dihydro-6,15-diketo-PGF_1α (∼10%). These metabolites can arise only from the enzymatic conversion of EPA to the 3-series PGH endoperoxide by cyclooxygenases, then PGI₃ by prostacyclin synthase and, finally, nonenzymatic hydrolysis to 6-keto-PGF_2α. The 6-keto-PGF derivatives are not formed by free radical mechanisms that generate isoprostanes, and thus, these metabolites provide an unbiased marker for utilization of EPA by cyclooxygenases.     

Aberrant expression of IFN-γ in Th2 cells from Th2 LCR-deficient mice

The Th2 locus control region (LCR) has been shown to be a crucial cis-acting element for Th2 cytokine expression and Th2 cell differentiation. To study the role of Th2 LCR in ifng locus regulation, we examined the expression of IFN-γ in Th2 cells from Th2 LCR-deficient mice. We found IFN-γ to be aberrantly up-regulated. In addition, histone 3(H3)-acetylation and histone 3 lysine 4 (H3-K4)-methylation greatly increased at the ifng locus of the Th2 cells. GATA-3 and STAT6 bound to the ifng promoter in Th2 cells from the wild type but not from the Th2 LCR-deficient mice, and they directly repressed ifng expression in transient reporter assay. Moreover, ectopic expression of GATA-3 and STAT6-VT repressed the aberrant expression of the ifng gene and restored repressive chromatin state at the ifng locus in Th2 cells from Th2 LCR-deficient mice. These results suggest that expression of the ifng gene and chromatin remodeling of the ifng locus are under the control of a Th2 LCR-mediated Th2 differentiation program.     

A urine-concentrating defect in 11β-hydroxysteroid dehydrogenase type 2 null mice

In aldosterone target tissues, 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) is coexpressed with mineralocorticoid receptors (MR) and protects the receptor from activation by glucocorticoids. Null mutations in the encoding gene, HSD11B2, cause apparent mineralocorticoid excess, in which hypertension is thought to reflect volume expansion secondary to sodium retention. Hsd11b2(-/-) mice are indeed hypertensive, but impaired natriuretic capacity is associated with significant volume contraction, suggestive of a urine concentrating defect. Water turnover and the urine concentrating response to a 24-h water deprivation challenge were therefore assessed in Hsd11b2(-/-) mice and controls. Hsd11b2(-/-) mice have a severe and progressive polyuric/polydipsic phenotype. In younger mice (～2 mo of age), polyuria was associated with decreased abundance of aqp2 and aqp3 mRNA. The expression of other genes involved in water transport (aqp4, slc14a2, and slc12a2) was not changed. The kidney was structurally normal, and the concentrating response to water deprivation was intact. In older Hsd11b2(-/-) mice (>6 mo), polyuria was associated with a severe atrophy of the renal medulla and downregulation of aqp2, aqp3, aqp4, slc14a2, and slc12a2. The concentrating response to water deprivation was impaired, and the natriuretic effect of the loop diuretic bumetanide was lost. In older Hsd11b2(-/-) mice, the V2 receptor agonist desmopressin did not restore full urine concentrating capacity. We find that Hsd11b2(-/-) mice develop nephrogenic diabetes insipidus. Gross changes to renal structure are observed, but these were probably secondary to sustained polyuria, rather than of developmental origin.