The discrete geodesic flow on Nagao lattice quotient of the space of bi-infinite geodesics in regular trees can be viewed as the right diagonal action on the double quotient of PGL2Fq((t-1)) by ...PGL2Fqt and PGL2(Fqt-1). We investigate the measure-theoretic entropy of the discrete geodesic flow with respect to invariant probability measures.
Sirtuin 3 (SIRT3) deacetylates and regulates many mitochondrial proteins to maintain health, but its functions are depressed in aging and obesity. The best-studied sirtuin, SIRT1, counteracts aging- ...and obesity-related diseases by deacetylating many proteins, but whether SIRT1 has a role in deacetylating and altering the function of SIRT3 is unknown. Here we show that SIRT3 is reversibly acetylated in the mitochondria and unexpectedly is a target of SIRT1 deacetylation. SIRT3 is hyperacetylated in aged and obese mice, in which SIRT1 activity is low, and SIRT3 acetylation at Lys57 inhibits its deacetylase activity and promotes protein degradation. Adenovirus-mediated expression of SIRT3 or an acetylation-defective SIRT3-K57R mutant in diet-induced obese mice decreased acetylation of mitochondrial long-chain acyl-CoA dehydrogenase, a known SIRT3 deacetylation target; improved fatty acid β-oxidation; and ameliorated liver steatosis and glucose intolerance. These SIRT3-mediated beneficial effects were not observed with an acetylation-mimic SIRT3-K57Q mutant. Our findings reveal an unexpected mechanism for SIRT3 regulation via SIRT1-mediated deacetylation. Improving mitochondrial SIRT3 functions by inhibiting SIRT3 acetylation may offer a new therapeutic approach for obesity- and aging-related diseases associated with mitochondrial dysfunction.
Abstract
Fluid flux through Earth’s surface and its interior causes geochemical cycling of elements in the Earth. Quantification of such process needs accurate knowledge about the composition and ...properties of the fluids. Knowledge about the fluids in Earth’s interior is scarce due to limitations in both experimental methods and thermodynamic modeling in high/ultrahigh pressure–temperature conditions. In this study, we present halogen (Cl, F) measurements in apatite grains from the mafic (metagabbro), and felsic (two-pyroxene granulite, charnockite, hornblende-biotite gneiss) rocks preserved in the Nilgiri Block, southern India. Previous experiments show that it is difficult to incorporate Cl in apatite compared to F at high pressure and temperature conditions. Based on regional trends in Cl and F content in apatite (with highest Cl content 2.95 wt%), we suggest the presence of acidic C–O–H fluids in the lower crust (~20–40 km deep) during the high-grade metamorphism of these rocks. These fluids are capable of causing extreme chemical alterations of minerals, especially refractory ones. They also have significant potential for mass transfer, causing extensive geochemical variations on a regional scale and altering the chemical and isotope records of rocks formed in the early Earth. Our findings have important relevance in understanding speciation triggered by acidic fluids in the lower crust, as well as the role of fluids in deep Earth processes.
Display omitted
•Discovery of a suprasubduction zone ophiolite suite with near-complete stratigraphy.•Geochemical features suggest mantle source and MORB-IAT setting.•Age peaks at 2486 Ma and 1832 Ma ...correspond to emplacement and metamorphism.•Markedly positive ɛHf(t) values suggest Neoarchean depleted mantle (juvenile) source.•Evaluation of Archean–Paleoproterozoic subduction system in the NCC.
The North China Craton (NCC) offers a window to Archean–Paleoproterozoic crustal evolution. Following the amalgamation of microblocks during Neoarchean, the NCC witnessed another protracted Wilson cycle in the Paleoproterozoic with subduction-accretion-collision process. Here we report a newly identified suprasubduction zone ophiolite suite from the Miyun complex in the NCC where a rare and near-complete ophiolite succession is preserved including serpentinite, lherzolite, olivine clinopyroxenite, websterite, gabbro, dolerite, diorite, monzonite, metabasalts and trondhjemite, in association with Banded Iron Formation (BIF). The geochemical features of the suite are consistent with those of suprasubduction ophiolite complexes, with the mafic and intermediate members displaying Island Arc Tholeiite (IAT) and Mid-Ocean Ridge Basalt (MORB) affinity. Zircon grains from lherzolite define three groups of 207Pb/206Pb weighted mean ages at 2500 ± 12 Ma marking the formation age, and 2237 ± 47 Ma, and 1843 ± 30 Ma representing subsequent thermal events. The majority of zircon grains in olivine clinopyroxenite, gabbro, and quartz monzonite yield 207Pb/206Pb weighted mean ages of 2510 ± 19 Ma, 2495 ± 10 Ma, and 2486 ± 21 Ma respectively. Those from the trondhjemite show weighted mean age of 2476 ± 9.4 Ma. The compiled age data from all the rock types in the Miyun suite show two distinct age peaks at ca. 2486 Ma and 1832 Ma, corresponding to the timing of magma differentiation and subsequent metamorphism. The zircon Lu-Hf isotope data display distinct positive ɛHf(t) values in the range 0.35–7.05, suggesting magma derived from Neoarchean to Paleoproterozoic depleted mantle (juvenile) source. The zircon TDM ages show a peak at 2670 Ma, confirming Neoarchean components. The timing of magma formation in the Miyun ophiolite is broadly identical to those of the other rare Neoarchean – early Paleoproterozoic ophiolite suites described from the NCC including those from Yishui and Zunhua. Furthermore, evidence from the recently reported Alaskan-type intrusions and arc root mafic-ultramafic complexes around Miyun complex with ages in the range of 2.4–2.0 Ga suggest continued subduction-related magmatic processes, with final collision in latest Paleoproterozoic at around 1.84 Ga. We propose that following the assembly of ancient microblocks along multiple zones of ocean closure marked by major greenstone belts of 2.6–2.5 Ga, and high-grade metamorphism along the margins of the microblocks during Archean–Paleoproterozoic transition, the NCC went through another major Wilson cycle from early to late Paleoproterozoic involving prolonged subduction, accretion and collision of larger crustal blocks and intervening arc complexes, leading to final cratonization.
Obesity and elevated circulating cholesterol are risk factors for breast cancer recurrence, while the use of statins, cholesterol biosynthesis inhibitors widely used for treating ...hypercholesterolemia, is associated with improved disease-free survival. Here, we show that cholesterol mediates the metastatic effects of a high-fat diet via its oxysterol metabolite, 27-hydroxycholesterol. Ablation or inhibition of CYP27A1, the enzyme responsible for the rate-limiting step in 27-hydroxycholesterol biosynthesis, significantly reduces metastasis in relevant animal models of cancer. The robust effects of 27-hydroxycholesterol on metastasis requires myeloid immune cell function, and it was found that this oxysterol increases the number of polymorphonuclear-neutrophils and γδ-T cells at distal metastatic sites. The pro-metastatic actions of 27-hydroxycholesterol requires both polymorphonuclear-neutrophils and γδ-T cells, and 27-hydroxycholesterol treatment results in a decreased number of cytotoxic CD8
T lymphocytes. Therefore, through its actions on γδ-T cells and polymorphonuclear-neutrophils, 27-hydroxycholesterol functions as a biochemical mediator of the metastatic effects of hypercholesterolemia.High cholesterol is a risk factor for breast cancer recurrence. Here the authors show that cholesterol promotes breast cancer metastasis via its metabolite 27-hydroxycholesterol (27HC) that acts on immune myeloid cells residing at the distal metastatic sites, thus promoting an immune suppressive environment.
Southern peninsular India preserves records of Late Neoarchean−Early Paleoproterozoic continental building and cratonization. A transect from the Paleoarchean Dharwar Craton to the Neoarchean arc ...magmatic complex in the Nilgiri Block across the intervening Moyar Suture Zone reveals an arc-accretionary complex composed of banded iron formation (BIF), amphibolite, metatuff, garnet-kyanite schist, metagabbro, pyroxenite and charnockite. Here we investigate the petrology, geochronology and petrogenesis of the pyroxenite and garnet-clinopyroxenite. The pyroxenite is mainly composed of orthopyroxene and clinopyroxene with local domains/pockets enriched in a clinopyroxene-garnet assemblage. Thermobarometric calculations and phase equilibria modeling suggest that the orthopyroxene- and clinopyroxene-rich domains formed at 900–1000°C, 1−1.2GPa whereas the garnet- and clinopyroxene-rich domains record higher pressure of about 1.8−2GPa at similar temperature conditions (900−1000°C). Zircon U–Pb SHRIMP dating show weighted mean 207Pb–206Pb age of 2532±22Ma, with metamorphic overgrowth at 2520±27Ma and 2478±27Ma. We propose a tectonic model involving decoupling and break-off of the oceanic plate along the southern flanks of the Dharwar Craton, which initiated oceanic plate subduction. Slab melting eventually built the Nilgiri volcanic arc on top of the over-riding plate along the flanks of the Dharwar Craton. Our study supports an active plate tectonic regime at the end of the Archean Era, aiding in the growth of paleo-continents and their assembly into stable cratons.
Display omitted
•Late Neoarchean convergent margin magmatism and earliest Paleoproterozoic metamorphism•Evidence for high pressure and ultrahigh-temperature metamorphism•Subduction and arc−continent collision during the Neoarchean-Paleoproterozoic transition
The Cretaceous tectonomagmatism of the Korean Peninsula was examined based on geochemical and geochronological data of the Cretaceous plutonic rocks, along with distribution of volcano-sedimentary ...nonmarine N- to NE-trending fault bounded sedimentary basins. We conducted sensitive high-resolution ion microprobe (SHRIMP) zircon U–Pb ages and whole-rock geochemical compositions of 21 Cretaceous plutonic rocks, together with previously published data, from the central to southern Korean Peninsula. Four age groups of plutonic rocks were identified: Group I (ca. 119–106Ma) in the northern to central area, Group II (ca. 99–87Ma) in the central southern area, Group III (ca. 85–82Ma) in the central to southern area, and Group IV (ca. 76–67Ma) in the southernmost area. These results indicate a sporadic trenchward-younging trend of the Cretaceous magmatism in the Korean Peninsula. The Group I, II, and III rocks are dominated by high-K calc-alkaline I-type rocks with rift-related A-type granitoids. In contrast, the Group IV rocks are high-K calc-alkaline I-type plutonic rocks with no A-type rocks. The geochemical signatures of the entire groups indicated LREEs (light rare earth elements) enrichments and negative Nb, Ta, and Ti anomalies, indicating normal arc magmatism. A new tectonic model of the Cretaceous Korean Peninsula was proposed based on temporal and spatial distribution of the Cretaceous plutons represented by four age groups; 1) magmatic quiescence throughout the Korean Peninsula from ca. 160 to 120Ma, 2) intrusions of the I- and A-type granitoids in the northern and central Korean Peninsula (Group I plutonic rocks from ca. 120 to 100Ma) resulted from the partial melting of the lower continental crust due to the rollback of the Izanagi plate expressed as the conversion from flat-lying subduction to normal subduction. The Gyeongsang nonmarine sedimentary rift basin in the Korean Peninsula and adakite magmatism preserved in the present-day Japanese Islands supported the slab rollback followed by steepening of the Izanagi plate with an injection of upwelling of the hot asthenosphere into the mantle wedge. 3) Alternating shallow (from ~100 to 85Ma) to steep (from ~85 to 65Ma) subduction resulted in the migration of the normal arc magmatism in the southern Korean Peninsula, expressed as the intruded I- and A-type (Group III) and I-type granitoids (Group IV), respectively. The tectonomagmatism of the Korean Peninsula showed the unique style of evolution, different from those of South China and Japanese Islands.
Display omitted
•Cretaceous plutonism of the Korean Peninsula was geochemically and geochronologically analyzed.•Four age groups of the Cretaceous plutonism were identified through temporal and spatial distributions of the plutonic rocks.•Conversion of flat to normal subduction and subsequent steepening and shallowing slab resulted in the Cretaceous plutonism.
The global ‘type area’ charnockites and those in the surrounding localities within Madras block of the Southern Granulite Terrane in India dominantly comprise felsic to intermediate, coarse to medium ...grained, orthopyroxene-bearing anhydrous granulite facies rocks with sporadic garnet. In several localities, the charnockitic suite contains mafic magmatic enclaves of gabbroic to dioritic composition showing calcic and peraluminous composition. The charnockite suite shows compositional range from monzonite through granodiorite to granite, and are calcic and calc-alkalic, peraluminous, including both magnesian and ferroan types. Their major and trace element variations are consistent with progressive magmatic differentiation. The charnockites show high Ba-Sr content with a trend from normal arc-related rocks to adakites. The geochemical features of the charnockites and mafic enclaves are consistent with subduction-related arc setting, and slab-derived magmas interacting with mantle wedge peridotite. The P-T conditions as estimated through mineral phase equilibria modelling and pseudosection computations of representative charnockite and mafic enclave samples show a range of ca. 7 to 9 kbar and 870 to 960 °C, suggesting high- to ultra-high temperature granulite facies conditions during the peak metamorphism.
The zircon grains from the charnockites show magmatic features with oscillatory or banded zoning, and in many cases display core-rim structure indicating dissolution and metamorphic overgrowth. The magmatic grains/domains show typical steep LREE to HREE pattern, whereas the metamorphic domains show relatively flat HREE. Magmatic zircon U-Pb data indicate crystallization ages of ca. 2.53 Ga to 2.57 Ga. The identical age from magmatic zircon grains in the mafic enclaves suggests bimodal magmatism with underplated mafic magmas intruding into the felsic magma chamber. The U-Pb data from metamorphic zircon and monazite indicate that all the rocks were metamorphosed coevally at ca. 2.47 Ga to 2.49 Ga, soon after their emplacement. The close timing between magmatism and metamorphism of ca. 40 Myr also suggests the formation of the magmatic suite along an active convergent margin, followed by collisional metamorphism during the termination of subduction and ocean closure. The Lu-Hf analyses of magmatic domains in zircon show mostly positive ɛHf(t) values up to +8.7, with only a few spots showing slightly negative values up to −0.8. Zircon grains in the mafic enclaves also show mostly positive ɛHf(t) values up to +4.3. The U-Pb-Hf data are consistent with juvenile arc building during late Neoarchean, with no significant older components. Together with the Hf model ages, the data indicate that the magmas were derived from depleted mantle components of Meso- to Neoarchean age, which would suggest an active subduction regime that continued until the ocean closure during end Neoarchean-earliest Paleoproterozoic. The granulite blocks surrounding the southern margin of the Dharwar craton including the Madras block are interpreted as multiple arcs that coalesced and accreted onto the craton during the Neoarchean-Paleoproterozoic transition. These blocks, which are dominated by charnockites and ranging in age from Mesoarchean to late Neoarchean, and their equivalents in other cratonic fragments over the globe, can be correlated to the ‘expanded Ur’, in building the oldest supercontinent on Earth.
Display omitted
•Type area charnockites incorporate mafic magmatic enclaves.•Charnockites show high Ba-Sr and adakitic features, and transition from normal arc to adakite.•U-Pb data indicate arc magmatism at 2.53 to 2.57 Ga and metamorphism at 2.47 to 2.49 Ga.•Zircon Lu-Hf data indicate juvenile arc building during late Neoarchean.•Multiple arc assembly and their accretion associated with oldest supercontinent ‘Ur’.
Sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages and whole-rock chemical compositions are reported here from charnockite, anorthosite and metagranite (orthogneisses) from the ...Jirishan complex in the southwestern part of the Yeongnam massif, Korea. The charnockite and the Kfs-megacryst metagranite yielded zircon U–Pb ages of ca. 1871–1863Ma. In contrast, the Neoproterozoic porphyritic metagranite and anorthosite yielded zircon U–Pb ages of ca. 908–904Ma. The geochemical signatures of both Paleoproterozoic and Neoproterozoic rocks display enrichment in LREEs and negative Nb, Ta and Ti anomalies. The geochronological and geochemical data suggest that the Proterozoic Jirishan complex preserves the imprints of arc-related magmatism at different periods associated with the formation of the Paleoproterozoic Columbia and the Neoproterozoic Rodinia supercontinents. The ca. 1871–1863Ma ages from the charnockites and metagranites from the Jirishan complex are coeval with similar events in the North China Craton, which also represent arc magmatism in a convergent margin setting related to the amalgamation of the Columbia supercontinent. In contrast, the Neoproterozoic porphyritic metagranite and anorthosite, together with the Neoproterozoic metagranites reported from the western Gyeonggi massif, provide a temporal link to the Neoproterozoic tonalite–granodiorite plutons recently identified in and around the South China Craton. They represent orogenic-type magmas that can be attributed to the amalgamation of the Rodinia supercontinent. However, the foliated granites in the central to southwestern Yeongnam massif are related to an arc setting associated with the Permo–Triassic Paleo-Pacific subduction.
Display omitted
•Preservations of both Paleoproterozoic and Neoproterozoic arc magmatisms in Korea•Tectonic subdivision of the Proterozoic Korean Peninsula based on SHRIMP ages•Imprints of the Columbia and Rodinia supercontinents in the Yeongnam massif
Dismembered mafic and serpentinized ultramafic bodies within the Hongseong suture zone of the Gyeonggi massif, southwestern Korean Peninsula are tectonically correlated with those from the Chinese ...Qinling–Dabie–Sulu collisional belt. We report sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages, detailed mineral compositions and whole rock geochemical data from the mafic rocks including eclogite and garnetite from the Hongseong suture zone. The zircon U–Pb data show multiple protolith ages corresponding to Neoproterozoic (ca. 815–770Ma), Paleozoic (ca. 310Ma) and Middle Triassic (ca. 240Ma). The peak high-pressure and retrograde regional intermediate-pressure metamorphic events of Middle Triassic (ca. 240–230Ma) are also recorded in zircons from the mafic rocks in the Hongseong suture zone. The ages and P–T estimates presented in this study match well with those of the peak ultra-high-pressure metamorphism in the Sulu area of China. Our results from the Hongseong suture zone provide important insights into the geodynamic history of the NE Asian region, with evidence for both Neoproterozoic subduction and a Paleozoic to Triassic subduction/accretion event.
Display omitted
► Multi-generations of dismembered ultramafic–mafic bodies have been recorded in the HSZ. ► Early tectonic events occurred during a Neoproterozoic subduction. ► Subsequent events occurred during a prolonged Paleozoic–Triassic subduction/accretion. ► Mid-Triassic retrograded P–T path ranged from eclogite to epidote-amphibolite facies.
PDF
