Chromium supplementation in non-obese non-diabetic subjects is associated with a decline in insulin sensitivity

The use of chromium supplements is widespread for the prevention and treatment of diabetes mellitus but there are conflicting reports on efficacy, possibly reflecting discrepant effects across different populations. In the present studies, we test the hypothesis that chromium supplementation raises serum chromium levels and correspondingly improves insulin sensitivity. A double blind placebo-controlled randomized trial was conducted on 31 non-obese, normoglycemic subjects. After baseline studies, the subjects were randomized to placebo or chromium picolinate 500 μg twice a day. The primary endpoint was change in insulin sensitivity as measured by euglycemic hyperinsulinemic clamp. Pre-specified secondary endpoints included fasting lipids, blood pressure, weight, body composition measured by DXA scan. After 16 weeks of chromium picolinate therapy there was no significant change in insulin sensitivity between groups (p=0.83). There was, however, a strong association between serum chromium and change in insulin resistance (β = -0.83, p=0.01), where subjects with the highest serum chromium had a worsening of insulin sensitivity. This effect could not be explained by changes in physiological parameters such as body weight, truncal fat and serum lipids with chromium therapy. Chromium therapy did not improve insulin sensitivity in non-obese normoglycemic individuals. Further, subjects who have high serum chromium levels paradoxically had a decline in insulin sensitivity. Caution therefore should be exercised in recommending the use of this supplement. The study was registered on the NIH registry (clinicaltrials.gov) and the identifier is NCT00846248     

Genetic variants on chromosome 1q41 influence ocular axial length and high myopia

As one of the leading causes of visual impairment and blindness, myopia poses a significant public health burden in Asia. The primary determinant of myopia is an elongated ocular axial length (AL). Here we report a meta-analysis of three genome-wide association studies on AL conducted in 1,860 Chinese adults, 929 Chinese children, and 2,155 Malay adults. We identified a genetic locus on chromosome 1q41 harboring the zinc-finger 11B pseudogene ZC3H11B showing genome-wide significant association with AL variation (rs4373767, β = −0.16 mm per minor allele, P_meta = 2.69×10⁻¹⁰). The minor C allele of rs4373767 was also observed to significantly associate with decreased susceptibility to high myopia (per-allele odds ratio (OR) = 0.75, 95% CI: 0.68–0.84, P_meta = 4.38×10⁻⁷) in 1,118 highly myopic cases and 5,433 controls. ZC3H11B and two neighboring genes SLC30A10 and LYPLAL1 were expressed in the human neural retina, retinal pigment epithelium, and sclera. In an experimental myopia mouse model, we observed significant alterations to gene and protein expression in the retina and sclera of the unilateral induced myopic eyes for the murine genes ZC3H11A, SLC30A10, and LYPLAL1. This supports the likely role of genetic variants at chromosome 1q41 in influencing AL variation and high myopia.     

Aortic Response to Balloon Injury in Obese Zucker Rats

The small diameter of the carotid artery is not compatible with the evaluation of clinically available endovascular devices in the carotid balloon-injury (BI) model. We developed an endovascular BI model in the rat descending aorta, whose size is compatible with available endovascular instruments. We also tested the hypothesis that neointima formation is enhanced in the aorta of obese Zucker rats (OZR) compared with lean Zucker rats (LZR). Left external carotid arteriotomies and BI of the thoracic and abdominal aorta were performed by using a balloon catheter. Aortograms and aortic pathology were examined at 2, 4, and 10 wk after BI. At 10 wk after BI, the abdominal aorta in OZR had narrowed 8.3% ± 1.1% relative to baseline compared with an expansion of 2.4% ± 2.2% in LZR. Simultaneously, the thoracic aorta had expanded 9.5% ± 4.3% in LZR compared with stenosis of 2.8% ± 1.6% in OZR. Calculation of the intimal:medial thickness ratio revealed significantly increased neointimal formation in the OZR descending aorta compared with that in LNR. In conclusion, this minimally invasive BI model involving the rat descending aorta is compatible with available endovascular instruments. The descending aorta of OZR demonstrates enhanced neointimal formation and constrictive vascular remodeling after BI.Abbreviations: BI, balloon injury; LZR, lean Zucker rats; OZR, obese Zucker ratsMany endovascular interventions, either cardiovascular or neuro­vascular, involve balloon-angioplasty or stenting of stenosed or vasospastic arteries. Balloon injury (BI) to the arterial wall is well known to induce restenosis, with a typical decrease in lumen diameter as a result of intimal hyperplasia and vessel wall remodeling.^{4,5,6,15,17,18} Restenosis occurs more frequently in patients with additional cardiovascular risk factors including diabetes, dyslipidemia, obesity, and hypertension.^4,8,23 Zucker rats frequently are used as animal models of obesity, dyslipidemia, and type 2 diabetes.^16,20,24The rat common carotid artery BI model is widely applied to study molecular mechanisms and the role of smooth muscle cells in arterial disease and healing.¹⁷ Data on injury in other arteries and models are not extensive.⁵ From a clinical perspective, the rat carotid artery is too small to test available endovascular devices. Other sites that have been used in rat models include the infrarenal aorta and the common iliac artery.^{4,5,11,13,15,25} The aortic model requires an open laparotomy, whereas the common iliac artery is another small-caliber vessel. The goal of the present study was to create a minimally invasive BI model in the rat descending aorta that would be compatible with many endovascular instruments and implantable devices, such as stents, that are used currently in clinical practice.¹⁵     

Zinc maintains prophase I arrest in mouse oocytes through regulation of the MOS-MAPK pathway

Meiosis in mammalian females is marked by two arrest points, at prophase I and metaphase II, which must be tightly regulated in order to produce a haploid gamete at the time of fertilization. The transition metal zinc has emerged as a necessary and dynamic regulator of the establishment, maintenance, and exit from metaphase II arrest, but the roles of zinc during prophase I arrest are largely unknown. In this study, we investigate the mechanisms of zinc regulation during the first meiotic arrest. Disrupting zinc availability in the prophase I arrested oocyte by treatment with the heavy metal chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN) causes meiotic resumption even in the presence of pharmacological inhibitors of meiosis. We further show that the MOS-MAPK pathway mediates zinc-dependent prophase I arrest, as the pathway prematurely activates during TPEN-induced meiotic resumption. Conversely, inhibition of the MOS-MAPK pathway maintains prophase I arrest. While prolonged zinc insufficiency ultimately results in telophase I arrest, early and transient exposure of oocytes to TPEN is sufficient to induce meiotic resumption and bypass the telophase I block, allowing the formation of developmentally competent eggs upon parthenogenetic activation. These results establish zinc as a crucial regulator of meiosis throughout the entirety of oocyte maturation, including the maintenance of and release from the first and second meiotic arrest points.     

Kalirin/Trio Rho guanine nucleotide exchange factors regulate a novel step in secretory granule maturation

The molecular mechanisms involved in the maturation of secretory granules, organelles that store hormones and neuropeptides, are poorly understood. As granule content proteins are processed, the composition of granule membranes changes, yielding constitutive-like secretion of immature content proteins and producing secretagogue-responsive mature granules. Constitutive-like secretion was not previously recognized as a process subject to regulation. We show that Kalirin and Trio, homologous Rho guanine nucleotide exchange factors (GEFs), which interact with a secretory granule resident protein, modulate cargo secretion from immature granules. Some of the Kalirin and Trio isoforms expressed in neuroendocrine cells colocalize with immature granules. Overexpression of their N-terminal GEF domain (GEF1) enhances secretion from immature granules, depleting cells of secretory cargo in the absence of secretagogue. This response requires GEF1 activity and is mimicked by Kalirin/Trio substrates Rac1 and RhoG. Accordingly, selective pharmacological inhibition of endogenous GEF1 activity decreases secretagogue-independent release of hormone precursors, accumulating product peptide in mature secretory granules. Kalirin/Trio modulation of cargo secretion from immature granules provides secretory cells with an extra layer of control over the sets of peptides released. Control of this step enhances the range of physiological responses that can be elicited, whereas lack of control could have pathological consequences.     

Mitochondrial DNA analysis shows a Near Eastern Neolithic origin for domestic cattle and no indication of domestication of European aurochs

The extinct aurochs (Bos primigenius primigenius) was a large type of cattle that ranged over almost the whole Eurasian continent. The aurochs is the wild progenitor of modern cattle, but it is unclear whether European aurochs contributed to this process. To provide new insights into the demographic history of aurochs and domestic cattle, we have generated high-confidence mitochondrial DNA sequences from 59 archaeological skeletal finds, which were attributed to wild European cattle populations based on their chronological date and/or morphology. All pre-Neolithic aurochs belonged to the previously designated P haplogroup, indicating that this represents the Late Glacial Central European signature. We also report one new and highly divergent haplotype in a Neolithic aurochs sample from Germany, which points to greater variability during the Pleistocene. Furthermore, the Neolithic and Bronze Age samples that were classified with confidence as European aurochs using morphological criteria all carry P haplotype mitochondrial DNA, suggesting continuity of Late Glacial and Early Holocene aurochs populations in Europe. Bayesian analysis indicates that recent population growth gives a significantly better fit to our data than a constant-sized population, an observation consistent with a postglacial expansion scenario, possibly from a single European refugial population. Previous work has shown that most ancient and modern European domestic cattle carry haplotypes previously designated T. This, in combination with our new finding of a T haplotype in a very Early Neolithic site in Syria, lends persuasive support to a scenario whereby gracile Near Eastern domestic populations, carrying predominantly T haplotypes, replaced P haplotype-carrying robust autochthonous aurochs populations in Europe, from the Early Neolithic onward. During the period of coexistence, it appears that domestic cattle were kept separate from wild aurochs and introgression was extremely rare.     

Construction of a sequence-tagged high-density genetic map of papaya for comparative structural and evolutionary genomics in brassicales

A high-density genetic map of papaya (Carica papaya L.) was constructed using microsatellite markers derived from BAC end sequences and whole-genome shot gun sequences. Fifty-four F(2) plants derived from varieties AU9 and SunUp were used for linkage mapping. A total of 707 markers, including 706 microsatellite loci and the morphological marker fruit flesh color, were mapped into nine major and three minor linkage groups. The resulting map spanned 1069.9 cM with an average distance of 1.5 cM between adjacent markers. This sequence-based microsatellite map resolved the very large linkage group 2 (LG 2) of the previous high-density map using amplified fragment length polymorphism markers. The nine major LGs of our map represent papaya's haploid nine chromosomes with LG 1 of the sex chromosome being the largest. This map validates the suppression of recombination at the male-specific region of the Y chromosome (MSY) mapped on LG 1 and at potential centromeric regions of other LGs. Segregation distortion was detected in a large region on LG 1 surrounding the MSY region due to the abortion of the YY genotype and in a region of LG6 due to an unknown cause. This high-density sequence-tagged genetic map is being used to integrate genetic and physical maps and to assign genome sequence scaffolds to papaya chromosomes. It provides a framework for comparative structural and evolutional genomic research in the order Brassicales.     

Purification, kinetic properties and physicochemical characterization of a novel acid phosphatase (AP) from germinating peanut (Arachis hypogaea) seed

Acid phosphatase activity was detected in peanut (Arachis hypogaea) cotyledons during germination. Four (4) to six (6) days of germination was the meantime corresponding to maximum hydrolytic activity of this enzyme. The understanding of the role of acid phosphatase activity during germination led to purify this enzyme by successive chromatography separations on DEAE-Sepharose CL-6B, Sephacryl S-100 HR and Phenyl-Sepharose HP to apparent homogeneity from germinated peanut cotyledon five days old. This enzyme designated peanut cotyledon acid phosphatase (AP) had native molecular weight of 24 kDa by gel permeation. SDS-PAGE of the purified acid phosphatase resolved a single protein band that migrated to approximately 21.5 kDa. Thus, this acid phosphatase likely functions as a monomer. The enzyme had optimum pH (5.0) and temperature (55 degrees C), and appeared to be stable in the presence of anionic, cationic and non-ionic detergents. Substrate specificity indicated that the purified acid phosphatase hydrolyzed a broad range of phosphorylated substrates. However, natural substrates such as ADP and ATP were the compounds with highest rate of hydrolysis for the enzyme. Moreover, the purified acid phosphatase exhibited phytase activity. These results showed that this enzyme played a peculiar role during germination, notably in reducing the rate of phytic acid, an antinutritional substance contained in peanut seed.