Mitochondrial genomics identifies major haplogroups in Aboriginal Australians

We classified diversity in eight new complete mitochondrial genome sequences and 41 partial sequences from living Aboriginal Australians into five haplogroups. Haplogroup AuB belongs to global lineage M, and AuA, AuC, AuD, and AuE to N. Within N, we recognize subdivisions, assigning AuA to haplogroup S, AuD to haplogroup O, AuC to P4, and AuE to P8. On available evidence, (S)AuA and (M)AuB are widespread in Australia. (P4)AuC is found in the Riverine region of western New South Wales, and was identified by others in northern Australia. (O)AuD and (P8)AuE were clearly identified only from central Australia. Our eight Australian full mt genome sequences, combined with 20 others (Ingman and Gyllensten 2003 Genome Res. 13:1600-1606) and compared with full mt genome sequences from regions to the north that include Papua New Guinea, Malaya, and Andaman and Nicobar Islands, show that ancestral connections between regions are deep and limited to clustering at the level of the N and M macrohaplogroups. The Australian-specific distribution of the five haplogroups identified indicates genetic isolation over a long period. Ancestral connections within Australia are deeper than those reflected by known linguistic or culturally based affinities. Applying a coalescence analysis to a gene tree for the coding regions of the eight genomic sequences, we made estimates of time depth that support a continuity of presence for the descendants of a founding population already established by 40,000 years ago.     

Inhibition of human pancreatic and biliary output but not intestinal motility by physiological intraileal lipid loads

Lipid perfusion into the distal ileal lumen at supraphysiological loads inhibits pancreatic exocrine secretion and gastrointestinal motility in humans. In the present study, we sought to determine the effects of physiological postprandial intraileal lipid concentrations on endogenously stimulated pancreaticobiliary secretion, intestinal motility, and release of regulatory mediators. Eight healthy volunteers were intubated with an oroileal multilumen tube for continuous duodenal perfusion of essential amino acids (450 mumol/min), ileal perfusion of graded doses of lipids (0, 50 and 100 mg/min, each dose for 90-120 min), aspiration of duodenal and ileal chyme, and intestinal manometry. Venous blood samples were obtained for measurement of GLP-1 and PYY. Ileal lipid perfusion dose dependently decreased endogenously stimulated trypsin [262 +/- 59 vs. 154 +/- 42 vs. 92 +/- 20 U/min (P < 0.05)] and bile acid output [18.6 +/- 1.9 vs. 8.4 +/- 2.8 vs. 3.0 +/- 1.0 micromol/min (P < 0.05)]. Duodenal motor activity was not inhibited by either lipid dose. Trypsin and bile acid output correlated inversely with the release of GLP-1 and PYY (absolute value of R > 0.84; P < 0.05), whereas the motility index did not. Physiological postprandial ileal lipid concentrations dose dependently inhibited human digestive pancreatic protease and bile acid output, but not intestinal motor activity. Thus physiological postprandial ileal nutrient exposure may be of importance for the termination of digestive secretory responses. Ileocolonic release of GLP-1 and PYY appears to participate in mediating these effects.     

Liebe bei Tupajas. Warum sind die Weibchen bei der Partnerwahl so wählerisch?

Treeshrews (Tupaia belangeri) usually live in pairs in the wild. Putting a male and a female together, however, leads only in about 25% to a harmonious pair characterized from the outset by amicable behaviour, improved health in both partners and successful reproduction. In most pairings the females reject the males, as evident from occasional fights and persistent stress reactions in both individuals. The individually different female choice is based on olfactory signals, which convey information on the major histocompatibility complex of the males.     

Serum Bile Acids Are Higher in Humans With Prior Gastric Bypass: Potential Contribution to Improved Glucose and Lipid Metabolism

The multifactorial mechanisms promoting weight loss and improved metabolism following Roux‐en‐Y gastric bypass (GB) surgery remain incompletely understood. Recent rodent studies suggest that bile acids can mediate energy homeostasis by activating the G‐protein coupled receptor TGR5 and the type 2 thyroid hormone deiodinase. Altered gastrointestinal anatomy following GB could affect enterohepatic recirculation of bile acids. We assessed whether circulating bile acid concentrations differ in patients who previously underwent GB, which might then contribute to improved metabolic homeostasis. We performed cross‐sectional analysis of fasting serum bile acid composition and both fasting and post‐meal metabolic variables, in three subject groups: (i) post‐GB surgery (n = 9), (ii) without GB matched to preoperative BMI of the index cohort (n = 5), and (iii) without GB matched to current BMI of the index cohort (n = 10). Total serum bile acid concentrations were higher in GB (8.90 ± 4.84 µmol/l) than in both overweight (3.59 ± 1.95, P = 0.005, Ov) and severely obese (3.86 ± 1.51, P = 0.045, MOb). Bile acid subfractions taurochenodeoxycholic, taurodeoxycholic, glycocholic, glycochenodeoxycholic, and glycodeoxycholic acids were all significantly higher in GB compared to Ov (P < 0.05). Total bile acids were inversely correlated with 2‐h post‐meal glucose (r = ?0.59, P < 0.003) and fasting triglycerides (r = ?0.40, P = 0.05), and positively correlated with adiponectin (r = ?0.48, P < 0.02) and peak glucagon‐like peptide‐1 (GLP‐1) (r = 0.58, P < 0.003). Total bile acids strongly correlated inversely with thyrotropic hormone (TSH) (r = ?0.57, P = 0.004). Together, our data suggest that altered bile acid levels and composition may contribute to improved glucose and lipid metabolism in patients who have had GB.     

Fatness-Associated FTO Gene Variant Increases Mortality Independent of Fatness – in Cohorts of Danish Men

Background

The A-allele of the single nucleotide polymorphism (SNP), rs9939609, in the FTO gene is associated with increased fatness. We hypothesized that the SNP is associated with morbidity and mortality through the effect on fatness.

Methodology/Principal Findings

In a population of 362,200 Danish young men, examined for military service between 1943 and 1977, all obese (BMI≥31.0 kg/m²) and a random 1% sample of the others were identified. In 1992–94, at an average age of 46 years, 752 of the obese and 876 of the others were re-examined, including measurements of weight, fat mass, height, and waist circumference, and DNA sampling. Hospitalization and death occurring during the following median 13.5 years were ascertained by linkage to national registers. Cox regression analyses were performed using a dominant effect model (TT vs. TA or AA). In total 205 men died. Mortality was 42% lower (p = 0.001) with the TT genotype than in A-allele carriers. This phenomenon was observed in both the obese and the randomly sampled cohort when analysed separately. Adjustment for fatness covariates attenuated the association only slightly. Exploratory analyses of cause-specific mortality and morbidity prior to death suggested a general protective effect of the TT genotype, whereas there were only weak associations with disease incidence, except for diseases of the nervous system.

Conclusion

Independent of fatness, the A-allele of the FTO SNP appears to increase mortality of a magnitude similar to smoking, but without a particular underlying disease pattern barring an increase in the risk of diseases of the nervous system.     

Modifying the conserved C‐terminal tyrosine of the peptide hormone PYY3‐36 to improve Y2 receptor selectivity

The Y2 selective PYY derived peptide PYY3‐36 was recently shown to play a role in appetite regulation. Novel PYY3‐36 analogs with high selectivity for the Y2 receptor could be potential drug candidates for the treatment of obesity. The C‐terminal pentapeptide segment of PYY3‐36 is believed to bind to the Y receptors. Tyr‐36 is highly conserved across species and only few successful modifications of Tyr‐36 have been documented. PYY3‐36 analogs were prepared using solid‐phase peptide chemistry and tested for binding to the Y1, Y2 and Y4 receptor subtypes by radioligand displacement assay. The Y2 receptor agonists with the best affinity and selectivity were further investigated for activity towards the Y1 and Y2 receptor subtypes. Unexpectedly, modifications of Tyr‐36 were well‐tolerated, and the analogs of PYY3‐36 in which the Tyr‐36 hydroxyl group was substituted with a halogen or an amino group were particularly well tolerated and yielded an improved selectivity and approximately equipotent affinity to the Y2 receptor. These modifications could be used to design new potential drug candidates for the treatment of obesity. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.     

Girdling Affects Ectomycorrhizal Fungal (EMF) Diversity and Reveals Functional Differences in EMF Community Composition in a Beech Forest

The relationships between plant carbon resources, soil carbon and nitrogen content, and ectomycorrhizal fungal (EMF) diversity in a monospecific, old-growth beech (Fagus sylvatica) forest were investigated by manipulating carbon flux by girdling. We hypothesized that disruption of the carbon supply would not affect diversity and EMF species numbers if EM fungi can be supplied by plant internal carbohydrate resources or would result in selective disappearance of EMF taxa because of differences in carbon demand of different fungi. Tree carbohydrate status, root demography, EMF colonization, and EMF taxon abundance were measured repeatedly during 1 year after girdling. Girdling did not affect root colonization but decreased EMF species richness of an estimated 79 to 90 taxa to about 40 taxa. Cenococcum geophilum, Lactarius blennius, and Tomentella lapida were dominant, colonizing about 70% of the root tips, and remained unaffected by girdling. Mainly cryptic EMF species disappeared. Therefore, the Shannon-Wiener index (H′) decreased but evenness was unaffected. H′ was positively correlated with glucose, fructose, and starch concentrations of fine roots and also with the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC/DON), suggesting that both H′ and DOC/DON were governed by changes in belowground carbon allocation. Our results suggest that beech maintains numerous rare EMF species by recent photosynthate. These EM fungi may constitute biological insurance for adaptation to changing environmental conditions. The preservation of taxa previously not known to colonize beech may, thus, form an important reservoir for future forest development.In temperate and boreal forest ecosystems, most tree species form ectomycorrhizal fungal (EMF) associations. EM fungi ensheathe the root tip, forming characteristic mantlelike structures (1). The presence and lengths of hyphae emanating from the mantle are characteristic of different EMF species and establish different soil exploration types (2). It has been assumed that EMF communities are adapted specifically to mobilize sparse soil nutrient resources in boreal and temperate forests (11, 50). Current estimates indicate that about 80% of all nitrogen and phosphorus present in plants has been taken up via mycorrhizas (30, 41, 63).Unlike free-living soil microbes, EM fungi have direct access to reduced carbon from their host plants. More than 50 years ago, Melin and Nilsson (46) showed that ¹⁴C applied to leaves was recovered within one day in EM fungi, suggesting a strong dependence of fungal metabolism on host photosynthesis. Subsequent isotopic studies corroborated tight connections between current photosynthate and EM fungi (28, 42). EMF hyphae constitute the main path of plant-derived carbon into the soil (24, 29). Furthermore, EMF hyphae contribute substantially to soil respiration (25% from hyphae and 15% from roots) (27). As hyphal respiration decreases strongly in response to girdling of trees, a tight metabolic link between extramatrical mycelia and host photosynthetic activity must exist (5, 9, 32). In addition, fruiting body formation of EMF species was strongly dependent on host photosynthetic capacity (32, 40). In contrast, the significance of the current assimilate supply for EMF colonization of root tips and for community composition is not yet well understood. Since trees contain substantial stores of carbohydrates in the roots and stem (7), it may be expected that EM fungi can be maintained if this carbon resource is available. For example, defoliation experiments with conifers, which restricted but did not eliminate current photosynthate transfer to roots, showed no effects on root EMF colonization. Massive defoliation that negatively affected aboveground biomass production suppressed morphotypes with thick mantles compared to those with thin mantles, suggesting a shift to less-carbon-demanding EMF species (14, 40, 44, 54, 56). Earlier studies also reported decreased EMF colonization of root tips (21, 52).In a common garden experiment with young beech trees, strong shading over several years, which severely limited plant growth, suppressed EMF colonization and resulted in low EMF diversity (20). EMF community composition was affected strongly by shading and slightly by short-term girdling, suggesting that EMF taxa are sensitive to changes in plant internal carbohydrate resources (20). However, the overall EMF diversity was low, probably because the young trees were grown in nutrient-rich compost soil (20). The significance of photoassimilates for EMF abundance, diversity, and community composition, therefore, remains to be shown for adult forest trees, which usually have high EMF diversity and low nitrogen availability (10, 26, 53, 61).The aim of this work was to test the hypothesis that EMF abundance and diversity are independent of the current photoassimilate supply and can be maintained by internal resources. To investigate this concept, old-growth beech trees (Fagus sylvatica L.) were girdled to suppress carbon allocation to roots. Since disruption of the current assimilate flux affects the carbohydrate source strength, we hypothesized that changes in EMF taxon composition would occur if EMF species had different carbon demands. Tree carbohydrate status, root demography, EMF colonization, and EMF taxon abundance were measured repeatedly during 1 year after girdling. Since girdling also affects carbon release into and probably nutrient uptake from soil, the influence of possible feedback by changes in the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC/DON) in the soil on EMF diversity was also assessed.     

Water fluxes within beech stands in complex terrain

We investigated the water balances of two beech stands (Fagus sylvatica L.) on opposite slopes (NE, SW) of a narrow valley near Tuttlingen in the southern Swabian Jura, a low mountain range in Southwest Germany. Our analysis combines results from continuous measurements of forest meteorological variables significant to the forest water balance, stand transpiration (ST) estimates from sap flow measurements, and model simulations of microclimate and water fluxes. Two different forest hydrological models (DNDC and BROOK90) were tested for their suitability to represent the particular sites. The investigation covers the years 2001–2007. Central aims were (1) to evaluate meteorological simulations of variables below the forest canopy, (2) to evaluate ST, (3) to quantify annual water fluxes for both beech stands using the evaluated hydrological models, and (4) to analyse the model simulations with regard to assumptions inherent in the respective model. Overall, both models were very well able to reproduce the observed dynamics of the soil water content in the uppermost 30 cm. However, the degree of fit depended on the year and season. The comparison of experimentally determined ST within the beech stand on the NE-slope during the growing season of 2007 with simulated transpiration did not yield a reliable statistical relationship. The simulation of water fluxes for the beech stand on the NE- and SW-slopes showed similar results for vegetation-related fluxes with both models, but different with respect to runoff and percolation flows. Overall, the higher evaporation demand on the warmer SW-slope did not lead to a significantly increased drought stress for the vegetation but was reflected mainly in decreased water loss from the system. This finding is discussed with regard to potential climate change and its impact on beech growth.