Unique bone microanatomy reveals ancestry of subterranean specializations in mammals.

Acquiring a subterranean lifestyle entails a substantial shift for many aspects of terrestrial vertebrates' biology. Although this lifestyle is associated with multiple instances of convergent evolution, the relative success of some subterranean lineages largely remains unexplained. Here, we focus on the mammalian transitions to life underground, quantifying bone microanatomy through high-resolution X-ray tomography. The true moles stand out in this dataset. Examination of this family's bone histology reveals that the highly fossorial moles acquired a unique phenotype involving large amounts of compacted coarse cancellous bone. This phenotype exceeds the adaptive optimum seemingly shared by several other subterranean mammals and can be traced back to some of the first known members of the family. This remarkable microanatomy was acquired early in the history of the group and evolved faster than the gross morphology innovations of true moles' forelimb. This echoes the pattern described for other lifestyle transitions, such as the acquisition of bone mass specializations in secondarily aquatic tetrapods. Highly plastic traits-such as those pertaining to bone structure-are hence involved in the early stages of different types of lifestyle transitions.

Hyena paleogenomes reveal a complex evolutionary history of cross-continental gene flow between spotted and cave hyena.

The genus Crocuta (African spotted and Eurasian cave hyenas) includes several closely related extinct and extant lineages. The relationships among these lineages, however, are contentious. Through the generation of population-level paleogenomes from late Pleistocene Eurasian cave hyena and genomes from modern African spotted hyena, we reveal the cross-continental evolutionary relationships between these enigmatic hyena lineages. We find a deep divergence (~2.5 Ma) between African and Eurasian Crocuta populations, suggesting that ancestral Crocuta left Africa around the same time as early Homo. Moreover, we find discordance between nuclear and mitochondrial phylogenies and evidence for bidirectional gene flow between African and Eurasian Crocuta after the lineages split, which may have complicated prior taxonomic classifications. Last, we find a number of introgressed loci that attained high frequencies within the recipient lineage, suggesting some level of adaptive advantage from admixture.

Oligocene stratigraphy across the Eocene and Miocene boundaries in the Valley of Lakes (Mongolia).

Cenozoic sediments of the Taatsiin Gol and TaatsiinTsagaan Nuur area are rich in fossils that provide unique evidence of mammal evolution in Mongolia. The strata are intercalated with basalt flows. 40Ar/39Ar data of the basalts frame the time of sediment deposition and mammal evolution and enable a composite age chronology for the studied area. We investigated 20 geological sections and 6 fossil localities of Oligocene and early Miocene deposits from this region. Seventy fossil beds yielded more than 19,000 mammal fossils. This huge collection encompasses 175 mammal species: 50% Rodentia, 13% Eulipotyphla and Didelphomorphia, and 12% Lagomorpha. The remaining 25% of species are distributed among herbivorous and carnivorous large mammals. The representation of lower vertebrates and gastropods is comparatively poor. Several hundred SEM images illustrate the diversity of Marsupialia, Eulipotyphla, and Rodentia dentition and give insight into small mammal evolution in Mongolia during the Oligocene and early Miocene. This dataset, the radiometric ages of basalt I (∼31.5 Ma) and basalt II (∼27 Ma), and the magnetostratigraphic data provide ages of mammal assemblages and time ranges of the Mongolian biozones: letter zone A ranges from ∼33 to ∼31.5 Ma, letter zone B from ∼31.5 to ∼28 Ma, letter zone C from ∼28 to 25.6 Ma, letter zone C1 from 25.6 to 24 Ma, letter zone C1-D from 24 to ∼23 Ma, and letter zone D from ∼23 to ∼21 Ma.

Oligocene and early Miocene mammal biostratigraphy of the Valley of Lakes in Mongolia.

The Taatsiin Gol Basin in Mongolia is a key area for understanding the evolution and dispersal of Central Asian mammal faunas during the Oligocene and early Miocene. After two decades of intense fieldwork, the area is extraordinarily well sampled and taxonomically well studied, yielding a large dataset of 19,042 specimens from 60 samples. The specimens represent 176 species-level and 99 genus-level taxa comprising 135 small mammal species and 47 large mammals. A detailed lithostratigraphy and new magnetostratigraphic and radiometric datings provide an excellent frame for these biotic data. Therefore, we test and evaluate the informal biozonation scheme that has been traditionally used for biostratigraphic correlations within the basin. Based on the analysis of the huge dataset, a formalised biostratigraphic scheme is proposed. It comprises the Cricetops dormitor Taxon Range Zone (Rupelian), subdivided into the Allosminthus khandae Taxon Range Subzone and the Huangomys frequens Abundance Subzone, the Amphechinus taatsiingolensis Abundance Zone (early Chattian), the Amphechinus major Taxon Range Zone (late Chattian), subdivided into the Yindirtemys deflexus Abundance Subzone and the Upper Amphechinus major T. R. Z., and the Tachyoryctoides kokonorensis Taxon Range Zone (Aquitanian). In statistical analyses, samples attributed to these biozones form distinct clusters, indicating that each biozone was also characterised by a distinct faunal type.

[Osteoporosis and cardiovascular disease--two sides of the same coin?]. / Osteoporose und koronare Herzkrankheit--zwei Seiten der gleichen Münze?

BACKGROUND: Osteoporosis and cardiovascular disease have numerous epidemiologic changes, health economic consequences, and molecular mechanisms in common, which are highlighted in this short review. EPIDEMIOLOGY AND CLINICAL STUDIES: The incidence of osteoporosis and cardiovascular disease is increasing in western societies, and genetic background, nutrition and psychologic factors play important roles in the pathogenesis of both diseases. The presence of a decreased bone mass or osteoporotic vertebral fractures are associated with an increased cardiovascular mortality. Calcaneal bone loss of 1 SD (standard deviation) as measured by osteodensitometry is associated with a 1.31 times increased risk for the occurrence of stroke. MOLECULAR MECHANISMS: The observed increase in interleukin-6 and tumor necrosis factor serum concentrations during the menopause contributes to osteoporotic bone loss and is associated with arteriosclerosis. Furthermore, the presence of hydroxyapatite in arteriosclerotic plaques supports the notion of common pathogenetic mechanisms for both, osteoporosis and arteriosclerosis. Osteopontin, bone GLA protein and bone morphogenetic protein-2, which have first been isolated from the organic bone matrix, are also present in arteriosclerotic plaques. 1,25-dihydroxycholecalciferol potently stimulates bone matrix mineralization and is also a negative regulator of the renin-angiotensin system; therefore vitamin D(3) deficiency in addition to bone metabolism also affects blood pressure. Osteoporosis and arteriosclerosis develop in mice lacking the osteoprotegerin gene and also in klotho gene knockout mice. CONCLUSION: Diagnosis of osteopenia, osteoporosis and osteoporotic vertebral or hip fractures indicates the presence of an increased cardiovascular risk which needs to be addressed by the physician who cares for patients with osteoporosis. The experimental finding of an osteoanabolic effect of statins supports the possibility of common pathogenetic disturbances which may be responsible for the simultaneous and frequent manifestation of osteoporosis and arteriosclerosis in elderly patients.

Metformin modulates insulin post-receptor signaling transduction in chronically insulin-treated Hep G2 cells.

AIM: To study the effect of chronic insulin treatment on insulin post-receptor signaling transduction and whether the effects of metformin are transmitted throughout the cascade of insulin signaling intermediates in a human hepatoma cell line (Hep G2). METHODS: Hep G2 cells were incubated in serum free media containing either insulin 100 nmol/L or insulin 100 nmol/L plus different concentrations (0.01-10 mmol/L) of metformin for 16 h and then were stimulated with insulin 100 nmol/L for 1 min. RESULTS: Chronic treatment of insulin 100 nmol/L induced a significant reduction in the phosphorylation and protein expression of IR?, IRS1 and IRS2, which therefore resulted in a downregulation of association of PI3K with IRS. Therapeutic concentrations (0.01-0.1 mmol/L) of metformin prevented the changes induced by chronic insulin treatment in these post-receptor components of insulin signaling pathway. Tyrosine phosphorylation of IR?, IRS1, and IRS2 was increased by 2.7 fold (P < 0.01), 6.8 fold (P < 0.01), and 2.3 fold (P <0.01) of chronically insulin-treated cells alone, respectively, after metformin 0.1 mmol/L was added. The association of p85 with IRS1 and IRS2 was also increased from 34 % to 86 % (P <0.01) and from 30 % to 92 % (P <0.01), respectively. In contrast, metformin in pharmacological concentration (1-10 mmol/L) further inhibited tyrosine phosphorylation of IR?, IRS1, IRS2 and the interaction of PI3K with IRS. The association of IRS1 with p85 was further decreased by 58 % (P >0.05) and of IRS2 by 30 % (P <0.05). CONCLUSION: Chronic insulin exposure of Hep G2 cells induces the downregulation of insulin signal transduction via PI3K pathway. The effect of metformin on insulin signaling transduction represent a primary mechanism of metformin action in insulin resistant state.

[Effect of metformin on gene expression of phosphoenolpyruvate carboxykinase].

OBJECTIVE: To investigate the effect and mechanism of antihyperglycemic agent metformin on the gene expression of phosphoenolpyruvate carboxykinase (PEPCK)-a key enzyme within the regulation of gluconeogenesis in hepatocytes and to determine whether the effects of metformin on hepatocytes are transmitted throughout the known insulin signaling pathways. METHODS: Confluent H4IIE rat heptoma cells were cultured with metformin 0.1 mmol/L for 16 h and then stimulated with various agents: insulin, cyclic adenosine monophosphate (cAMP), dexamethasone, signaling transduction inhibitor wortmannin and UO126. The gene expression of PEPCK was examined by Northern blot analysis. RESULTS: Metformin significantly decreased basal PEPCK mRNA levels by 75% (P < 0.01). Incubation with metformin alone had no significant effect on cAMP/dexamethasone stimulated PEPCK gene expression. In contrast, insulin 0.1 nmol/L significantly inhibited cAMP/dexamethasone stimulated PEPCK gene expression by 67% (P < 0.01), when insulin 0.1 nmol/L was present together with metformin, cAMP/dexamethasone induced PEPCK gene expression was decreased by 94% (P < 0.01). Both insulin signaling pathway inhibitors, phosphatidyl-inositol-3-kinase (PI3K) inhibitor wortmannin and mitogen-activated protein kinase (MAPK) inhibitor UO126, had no significant effect on inhibited PEPCK mRNA expression by metformin, but wortmannin blocked significantly inhibitory regulation of insulin on PEPCK gene expression (P < 0.01). CONCLUSION: Metformin can inhibit the PEPCK gene expression via either an insulin-independent or interaction with insulin manner. The inhibitory effects of insulin on PEPCK gene expression are mediated through PI3K pathway, not MAPK pathway.

Activation of tubular epithelial cells in diabetic nephropathy.

Previous studies have shown that renal function in type 2 diabetes correlates better with tubular changes than with glomerular pathology. Since advanced glycation end products (AGEs; AGE-albumin) and in particular carboxymethyllysine (CML) are known to play a central role in diabetic nephropathy, we studied the activation of nuclear factor kappaB (NF-kappaB) in tubular epithelial cells in vivo and in vitro by AGE-albumin and CML. Urine samples from healthy control subjects (n = 50) and type 2 diabetic patients (n = 100) were collected and tested for excretion of CML and the presence of proximal tubular epithelial cells (pTECs). CML excretion was significantly higher in diabetic patients than in healthy control subjects (P < 0.0001) and correlated with the degree of albuminuria (r = 0.7, P < 0.0001), while there was no correlation between CML excretion and HbA(1c) (r = 0.03, P = 0.76). Urine sediments from 20 of 100 patients contained pTECs, evidenced by cytokeratin 18 positivity, while healthy control subjects (n = 50) showed none (P < 0.0001). Activated NF-kappaB could be detected in the nuclear region of excreted pTECs in 8 of 20 patients with pTECs in the urine sediment (40%). Five of eight NF-kappaBp65 antigen-positive cells stained positive for interleukin-6 (IL-6) antigen (62%), while only one of the NF-kappaB-negative cells showed IL-6 positivity. pTECs in the urine sediment correlated positively with albuminuria (r = 0.57, P < 0.0001) and CML excretion (r = 0.55, P < 0.0001). Immunohistochemistry in diabetic rat kidneys and a human diabetic kidney confirmed strong expression of NF-kappaB in tubular cells. To further prove an AGE/CML-induced NF-kappaB activation in pTECs, NF-kappaB activation was studied in cultured human pTECs by electrophoretic mobility shift assays (EMSAs) and Western blot. Stimulation of NF-kappaB binding activity was dose dependent and was one-half maximal at 250 nmol/l AGE-albumin or CML and time dependent at a maximum of activation after 4 days. Functional relevance of the observed NF-kappaB activation was demonstrated in pTECs transfected with a NF-kappaB-driven luciferase reporter plasmid and was associated with an increased release of IL-6 into the supernatant. The AGE- and CML-dependent activation of NF-kappaBp65 and NF-kappaB-dependent IL-6 expression could be inhibited using the soluble form of the receptor for AGEs (RAGE) (soluble RAGE [sRAGE]), RAGE-specific antibody, or the antioxidant thioctic acid. In addition transcriptional activity and IL-6 release from transfected cells could be inhibited by overexpression of the NF-kappaB-specific inhibitor kappaBalpha. The findings that excreted pTECs demonstrate activated NF-kappaB and IL-6 antigen and that AGE-albumin and CML lead to a perpetuated activation of NF-kappaB in vitro infer that a perpetuated increase in proinflammtory gene products, such as IL-6, plays a role in damaging the renal tubule.

[Do markers of bone metabolism reflect the presence of a high- or low-turnover state of bone metabolism?]. / Korrelieren biochemische Knochenstoffwechselmarker mit einer histologisch gesicherten High- bzw. Low-Turnover-Osteoporose?

BACKGROUND: A pathophysiological concept of osteoporosis therapy - antiresorptive treatment of high-turnover osteoporosis (e. g. bisphosphonates, raloxifen) and osteoanabolic treatment of low-turnover osteoporosis (e. g. parathyroid hormone) - is clinically and economically reasonable to enable physicians to decide who will benefit most from which drug. Biochemical bone markers in serum and urine are frequently used for the diagnosis of high- or low-turnover osteoporosis. We investigated whether bone marker levels reflect the histologically diagnosed high- or low-turnover state of osteoporosis. MATERIALS AND METHODS: 175 bone biopsies of male and female osteoporotic patients (WHO criteria) were histologically classified in high- and low-turnover osteoporosis and associated with bone marker levels in serum and urine. Patients with any osteotropic therapy and with fractures were excluded. RESULTS: There were no significant differences between patients with high- and low-turnover osteoporosis with regards to osteocalcin, DPD crosslinks, alkaline phosphatase, 25-OH vitamin D(3), parathyroid hormone and bone mass (spine and hip). CONCLUSIONS: Single measurements of biochemical bone markers in serum and urine do not allow a valid differentiation between histologically diagnosed high- and low-turnover states of osteoporosis. The therapeutic concept of treating with osteoanabolic drugs requires valid diagnostic criteria for the differentiation between high- and low-turnover state of bone metabolism which can be provided by a bone biopsy but not by single measurements of bone markers.

Inhibition of phosphoenolpyruvate carboxykinase gene expression by metformin in cultured hepatocytes.

OBJECTIVE: To investigate the effect and mechanism of the antihyperglycemic agent metformin on the expression of phosphoenolpyruvate carboxykinase (PEPCK) gene in hepatocytes and to determine whether the effects of metformin in hepatocytes are transmitted throughout the known insulin signaling pathways. METHODS: Confluent H4IIE rat heptoma cells were cultured for 16 h with 0.1 mmol/L metformin either in absence or presence of 0.1 nmol/L insulin, and then stimulated with various agents. The expression of PEPCK gene was examined by Northern blot analysis. RESULTS: Therapeutic concentrations of metformin significantly inhibited basal PEPCK mRNA expression and also decreased cAMP and dexamethasone induced PEPCK gene expression through interaction with insulin. In the presence of insulin signaling pathway inhibitors wortmannin and UO126, metformin reduced PEPCK mRNA levels, but wortmannin blocked inhibitory regulation of insulin on PEPCK gene expression. CONCLUSION: Metformin inhibits PEPCK gene expression via either an insulin-independent or an interacting-with-insulin manner. The results suggest that a possible mechanism by which metformin reduces gluconeogenesis could be associated with the inhibition of PEPCK gene expression.

Chronic hyperinsulinism induced down-regulation of insulin post-receptor signaling transduction in Hep G2 cells.

To study the regulatory effect of acute and chronic insulin treatment on insulin post-receptor signaling transduction pathway in a human hepatoma cell line (Hep G2), Hep G2 cells were incubated in the presence or absence of insulin with different concentrations in serum free media for 16 h and then stimulated with 100 nmol/L insulin for 1 min. Protein levels of insulin receptor beta-subunit (IR beta), insulin receptor substrate-1 (IRS-1) and p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) were determined in total cell lysates by Western-immunoblot. Phosphorylated proteins IR beta, IRS-1 and interaction of PI 3-kinase with IRS-1 were determined by immunoprecipitation. Results showed that 1-min insulin stimulation rapidly induced tyrosine phosphorylation of IR beta and IRS-1, which in turn, resulting in association of PI 3-kinase with IRS-1. 1-100 nmol/L chronic insulin treatment induced a dose-dependent decrease in the protein level of IR beta and a slight decrease in the protein level of IRS-1. There was a more marked reduction in the phosphorylation of IR beta, IRS-1, reaching a nadir of 22% (P < 0.01) and 15% (P < 0.01) of control levels, respectively, after 16 h treatment with 100 nmol/L insulin. The association between IRS-1 and PI 3-kinase was decreased by 66% (P < 0.01). There was no significant change in PI 3-kinase protein levels. These data suggest that chronic insulin treatment can induce alterations of IR beta, IRS-1 and PI 3-kinase three early steps in insulin action, which contributes significantly to insulin resistance, and may account for desensitization of insulin action.

Açöes do 17B-estradiol sobre a secreçäo de calcitonina "in vitro" / Action of 17B-estradiol on calcitonin secretion \"in vitro\"

Em doses farmacológicas a Calcitonina (CT) é tida como um hormônio poupador de cálcio (Ca) e protetor da massa óssea. Devido a isto, tem sido utilizada como alternativa terapêutica das osteoporose pós-menopáusica, doença de grande prevalência entre as mulheres. O papel da CT no desenvolvimento desta forma de osteoporose, entretanto, apesar do grande número de trabalhos respeito, ainda permanece controverso na literatura, assim como a existência de um efeito direto dos estrógenos sobre a secreçao e síntese de CT. Nossa proposta foi avaliar a açao do 17B-estradiol (E2) sobre a secreçao basal e estimulada de CT "in-vitro". Para isso utilizamos uma linhagem de células de carcinoma medular de tireóide humano (TT), na qual já havia sido descrita a presença de receptores estrogênicos. Estudamos o efeito de diferentes concentraçoes de E2 (1 e 100nM) sobre a secreçao basal de CT após períodos de incubaçao que variaram de 6 horas a 6 dias, além do efeito sobre a estimulaçao das células com TPA+Forskolina após 6 dias de pré-incubaçao com E2. A incubaçao das células TT com E2 nao resultou em nenhum incremento na secreçao basal ou estimulada de CT em comparaçao aos grupos controles, em nenhum dos períodos de tempo estudados. O efeito observado, ao contrário, foi de inibiçao transitória da secreçao de CT, de forma dose-dependente (80,5 porcento e 59,1 porcento do controle para 1 a 100 nM respectivamente), cujo nadir apresentou-se após 24h de incubaçao, retornando aos níveis dos grupos controles após 72h. Somado a isto, E2 levou a um efeito estimulatório dose-dependente sonre o conteúdo celular protéico, mas sem qualquer efeito sobre a incorporaçao de timidina triciada, indicando induzir a uma hipertrofia ao invés de uma hiperplasia das células TT. Os dados obtidos demonstraram ausência de qualquer efeito estimulatório direto do E2 sobre a secreçao basal ou estimulada de CT, revelando adicionalmente em efeito de inibiçao transitória na secreçao de CT. (Arq Bras Endocrinol Metab 1994; 38/1:23-28).

Down-regulation of different post-receptor signal transduction pathways by chronic insulin stimulation / 中华内分泌代谢杂志

Objective To study the effect of chronic insulin stimulation on different signal transduction pathways of insulin post-receptor in a human hepatoma cells line (HepG2). Methods HepG2 cells were incubated in serum-free media in either presence or absence of various concentrations of insulin (0-100 nmol/L) for 16 h before the cells were stimulated with 100 nmol/L insulin for 1 min. Protein levels of insulin receptor ?-subunit (IR?), insulin receptor substrate (IRS)-1, IRS-2, P85 subunit of phosphatidylinositol 3-kinase (PI3K), mitogen activated protein kinase (MAPK) and phosphorylated proteins of MAPK were determined in total cell lysates by Western-immunoblot, and determination of phosphorylated proteins IR?, IRS-1, IRS-2 and interaction of PI3K with IRS-1/-2 were performed by immunoprecipitation. Results Insulin stimulation for 1 min rapidly induced tyrosine phosphorylation of IR?, IRS-1 and IRS-2 and phosphorylation of MAPK, which in turn, resulted in binding of P85 with IRS-1/-2 and activation of MAPK. After 100 nmol/L insulin treatment for 16 h, there was a more marked reduction in the phosphorylations of IR?,IRS1andIRS2inHepG2 cells, reaching 22.2% (P