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Journal articleChambers ES, Viardot A, Psichas A, et al., 2015,
Effects of targeted delivery of propionate to the human colon on appetite regulation, body weight maintenance and adiposity in overweight adults
, Gut, Vol: 64, Pages: 1744-1754, ISSN: 0017-5749Objective The colonic microbiota ferment dietary fibres, producing short chain fatty acids. Recent evidence suggests that the short chain fatty acid propionate may play an important role in appetite regulation. We hypothesised that colonic delivery of propionate would increase peptide YY (PYY) and glucagon like peptide-1 (GLP-1) secretion in humans, and reduce energy intake and weight gain in overweight adults.Design To investigate whether propionate promotes PYY and GLP-1 secretion, a primary cultured human colonic cell model was developed. To deliver propionate specifically to the colon, we developed a novel inulin-propionate ester. An acute randomised, controlled cross-over study was used to assess the effects of this inulin-propionate ester on energy intake and plasma PYY and GLP-1 concentrations. The long-term effects of inulin-propionate ester on weight gain were subsequently assessed in a randomised, controlled 24-week study involving 60 overweight adults.Results Propionate significantly stimulated the release of PYY and GLP-1 from human colonic cells. Acute ingestion of 10 g inulin-propionate ester significantly increased postprandial plasma PYY and GLP-1 and reduced energy intake. Over 24 weeks, 10 g/day inulin-propionate ester supplementation significantly reduced weight gain, intra-abdominal adipose tissue distribution, intrahepatocellular lipid content and prevented the deterioration in insulin sensitivity observed in the inulin-control group.Conclusions These data demonstrate for the first time that increasing colonic propionate prevents weight gain in overweight adult humans.
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Journal articleZhao L, Oliver E, Maratou K, et al., 2015,
The zinc transporter, ZIP12, regulates the pulmonary vascular response to chronic hypoxia
, Nature, Vol: 524, Pages: 356-360, ISSN: 0028-0836The typical response of the adult mammalian pulmonary circulation to a low oxygen environment is vasoconstriction and structural remodelling of pulmonary arterioles, leading to chronic elevation of pulmonary artery pressure (pulmonary hypertension) and right ventricular hypertrophy. Some mammals, however, exhibit genetic resistance to hypoxia-induced pulmonary hypertension1, 2, 3. We used a congenic breeding program and comparative genomics to exploit this variation in the rat and identified the gene Slc39a12 as a major regulator of hypoxia-induced pulmonary vascular remodelling. Slc39a12 encodes the zinc transporter ZIP12. Here we report that ZIP12 expression is increased in many cell types, including endothelial, smooth muscle and interstitial cells, in the remodelled pulmonary arterioles of rats, cows and humans susceptible to hypoxia-induced pulmonary hypertension. We show that ZIP12 expression in pulmonary vascular smooth muscle cells is hypoxia dependent and that targeted inhibition of ZIP12 inhibits the rise in intracellular labile zinc in hypoxia-exposed pulmonary vascular smooth muscle cells and their proliferation in culture. We demonstrate that genetic disruption of ZIP12 expression attenuates the development of pulmonary hypertension in rats housed in a hypoxic atmosphere. This new and unexpected insight into the fundamental role of a zinc transporter in mammalian pulmonary vascular homeostasis suggests a new drug target for the pharmacological management of pulmonary hypertension.
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Journal articleHerranz N, Gallage S, Mellone M, et al., 2015,
mTOR regulates MAPKAPK2 translation to control the senescence-associated secretory phenotype
, Nature Cell Biology, Vol: 17, Pages: 1205-1217, ISSN: 1476-4679Senescent cells secrete a combination of factors collectively known as the senescence-associated secretory phenotype (SASP). The SASP reinforces senescence and activates an immune surveillance response, but it can also show pro-tumorigenic properties and contribute to age-related pathologies. In a drug screen to find new SASP regulators, we uncovered the mTOR inhibitor rapamycin as a potent SASP suppressor. Here we report a mechanism by which mTOR controls the SASP by differentially regulating the translation of the MK2 (also known as MAPKAPK2) kinase through 4EBP1. In turn, MAPKAPK2 phosphorylates the RNA-binding protein ZFP36L1 during senescence, inhibiting its ability to degrade the transcripts of numerous SASP components. Consequently, mTOR inhibition or constitutive activation of ZFP36L1 impairs the non-cell-autonomous effects of senescent cells in both tumour-suppressive and tumour-promoting contexts. Altogether, our results place regulation of the SASP as a key mechanism by which mTOR could influence cancer, age-related diseases and immune responses.
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Journal articleJoshi PK, Esko T, Mattsson H, et al., 2015,
Directional dominance on stature and cognition in diverse human populations
, Nature, Vol: 523, Pages: 459-462, ISSN: 0028-0836Homozygosity has long been associated with rare, often devastating, Mendelian disorders1, and Darwin was one of the first to recognize that inbreeding reduces evolutionary fitness2. However, the effect of the more distant parental relatedness that is common in modern human populations is less well understood. Genomic data now allow us to investigate the effects of homozygosity on traits of public health importance by observing contiguous homozygous segments (runs of homozygosity), which are inferred to be homozygous along their complete length. Given the low levels of genome-wide homozygosity prevalent in most human populations, information is required on very large numbers of people to provide sufficient power3, 4. Here we use runs of homozygosity to study 16 health-related quantitative traits in 354,224 individuals from 102 cohorts, and find statistically significant associations between summed runs of homozygosity and four complex traits: height, forced expiratory lung volume in one second, general cognitive ability and educational attainment (P < 1 × 10−300, 2.1 × 10−6, 2.5 × 10−10 and 1.8 × 10−10, respectively). In each case, increased homozygosity was associated with decreased trait value, equivalent to the offspring of first cousins being 1.2 cm shorter and having 10 months’ less education. Similar effect sizes were found across four continental groups and populations with different degrees of genome-wide homozygosity, providing evidence that homozygosity, rather than confounding, directly contributes to phenotypic variance. Contrary to earlier reports in substantially smaller samples5, 6, no evidence was seen of an influence of genome-wide homozygosity on blood pressure and low density lipoprotein cholesterol, or ten other cardio-metabolic traits. Since directional dominance is predicted for traits under directional evolutionary selection7, this study provides evidence that increased stature and cognit
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Journal articleDuca FA, Cote CD, Rasmussen BA, et al., 2015,
Metformin activates a duodenal Ampk-dependent pathway to lower hepatic glucose production in rats
, Nature Medicine, Vol: 21, Pages: 506-511, ISSN: 1078-8956Metformin is a first-line therapeutic option for the treatment of type 2 diabetes, even though its underlying mechanisms of action are relatively unclear1,2,3,4,5,6. Metformin lowers blood glucose levels by inhibiting hepatic glucose production (HGP), an effect originally postulated to be due to a hepatic AMP-activated protein kinase (AMPK)-dependent mechanism5,6. However, studies have questioned the contribution of hepatic AMPK to the effects of metformin on lowering hyperglycemia1,3,4, and a gut–brain–liver axis that mediates intestinal nutrient- and hormone-induced lowering of HGP has been identified7. Thus, it is possible that metformin affects HGP through this inter-organ crosstalk. Here we show that intraduodenal infusion of metformin for 50 min activated duodenal mucosal Ampk and lowered HGP in a rat 3 d high fat diet (HFD)-induced model of insulin resistance. Inhibition of duodenal Ampk negated the HGP-lowering effect of intraduodenal metformin, and both duodenal glucagon-like peptide-1 receptor (Glp-1r)–protein kinase A (Pka) signaling and a neuronal-mediated gut–brain–liver pathway were required for metformin to lower HGP. Preabsorptive metformin also lowered HGP in rat models of 28 d HFD–induced obesity and insulin resistance and nicotinamide (NA)–streptozotocin (STZ)–HFD-induced type 2 diabetes. In an unclamped setting, inhibition of duodenal Ampk reduced the glucose-lowering effects of a bolus metformin treatment in rat models of diabetes. These findings show that, in rat models of both obesity and diabetes, metformin activates a previously unappreciated duodenal Ampk–dependent pathway to lower HGP and plasma glucose levels.
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Journal articleCebola I, Rodríguez-Seguí SA, Cho CH-H, et al., 2015,
TEAD and YAP regulate the enhancer network of human embryonic pancreatic progenitors
, Nature Cell Biology, Vol: 17, Pages: 615-626, ISSN: 1465-7392 -
Journal articleSmith MA, Katsouri L, Irvine EE, et al., 2015,
Ribosomal S6K1 in POMC and AgRP neurons regulates glucose homeostasis but not feeding behavior in mice
, Cell Reports, Vol: 11, Pages: 335-343, ISSN: 2211-1247 -
Journal articleMarquard J, Otter S, Welters A, et al., 2015,
Characterization of pancreatic NMDA receptors as possible drug targets for diabetes treatment
, Nature Medicine, Vol: 21, Pages: 363-372, ISSN: 1078-8956In the nervous system, NMDA receptors (NMDARs) participate in neurotransmission and modulate the viability of neurons. In contrast, little is known about the role of NMDARs in pancreatic islets and the insulin-secreting beta cells whose functional impairment contributes to diabetes mellitus. Here we found that inhibition of NMDARs in mouse and human islets enhanced their glucose-stimulated insulin secretion (GSIS) and survival of islet cells. Further, NMDAR inhibition prolonged the amount of time that glucose-stimulated beta cells spent in a depolarized state with high cytosolic Ca2+ concentrations. We also noticed that, in vivo, the NMDAR antagonist dextromethorphan (DXM) enhanced glucose tolerance in mice, and that in vitro dextrorphan, the main metabolite of DXM, amplified the stimulatory effect of exendin-4 on GSIS. In a mouse model of type 2 diabetes mellitus (T2DM), long-term treatment with DXM improved islet insulin content, islet cell mass and blood glucose control. Further, in a small clinical trial we found that individuals with T2DM treated with DXM showed enhanced serum insulin concentrations and glucose tolerance. Our data highlight the possibility that antagonists of NMDARs may provide a useful adjunct treatment for diabetes.
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Journal articleShungin D, Winkler TW, Croteau-Chonka DC, et al., 2015,
New genetic loci link adipose and insulin biology to body fat distribution
, NATURE, Vol: 518, Pages: 187-U378, ISSN: 0028-0836- Author Web Link
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Journal articleLocke AE, Kahali B, Berndt SI, et al., 2015,
Genetic studies of body mass index yield new insights for obesity biology
, Nature, Vol: 518, Pages: 197-206, ISSN: 0028-0836
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