Liver fat and SHBG affect insulin resistance in midlife women: The Study of Women's Health Across the Nation (SWAN)

Objective:

The liver is an insulin‐responsive organ that contributes significantly to both whole body insulin sensitivity and availability of sex steroids through the production of sex hormone binding globulin (SHBG). Our objective was to explore whether lower SHBG was associated with ectopic liver fat and mediated its effect on insulin resistance in The Study of Women's Health Across the Nation (SWAN).

Design and Methods:

A subset of midlife African American and Caucasian women from SWAN (n = 208; 50.9 ± 0.18 yrs; 71% Caucasian) had computed tomography scans to quantify visceral, subcutaneous and liver fat. Blood samples were collected and assayed for hormonal and metabolic markers.

Results:

The cohort, while overweight, was generally healthy, and both liver fat and SHBG were unaffected by menopausal stage or race. Both higher liver fat and lower SHBG levels were significantly associated with higher insulin concentrations after adjustment for adiposity (r = ?0.25, P < 0.001 and r = ?0.18, P = 0.01). SHBG and liver fat had additive effects on insulin concentrations such that women with the lowest SHBG and the highest fat levels had the highest values (interaction P = 0.09). The association between SHBG and insulin was more apparent among women with fattier livers. SHBG and liver fat appear to have independent effects on insulin levels as adjustment for each other did not diminish the strength of either association (P = 0.023 and 0.001 respectively).

Conclusion:

These results confirmed the strong independent associations between increased liver fat and decreased SHBG with increased metabolic risk in midlife women. Further these data underscore the need for additional research into the role of liver fat in modifying SHBG's influence on insulin levels.

     

Passiflora plastome sequencing reveals widespread genomic rearrangements

Although past studies have included Passiflora among angiosperm lineages with highly rearranged plastid genomes (plastomes), knowledge about plastome organization in the genus is limited. So far only one draft and one complete plastome have been published. Expanded sampling of Passiflora plastomes is needed to understand the extent of the genomic rearrangement in the genus, which is also unusual in having biparental plastid inheritance and plastome‐genome incompatibility. We sequenced 15 Passiflora plastomes using either Illumina paired‐end or shotgun cloning and Sanger sequencing approaches. Assembled plastomes were annotated using Dual Organellar GenoMe Annotator (DOGMA) and tRNAscan‐SE. The Populus trichocarpa plastome was used as a reference to estimate genomic rearrangements in Passiflora by performing whole genome alignment in progressiveMauve. The phylogenetic distribution of rearrangements was plotted on the maximum likelihood tree generated from 64 plastid encoded protein genes. Inverted repeat (IR) expansion/contraction and loss of the two largest hypothetical open reading frames, ycf1 and ycf2, account for most plastome size variation, which ranges from 139 262 base pairs (bp) in P. biflora to 161 494 bp in P. pittieri. Passiflora plastomes have experienced numerous inversions, gene and intron losses along with multiple independent IR expansions and contractions resulting in a distinct organization in each of the three subgenera examined. Each Passiflora subgenus has a unique plastome structure in terms of gene content, order and size. The phylogenetic distribution of rearrangements shows that Passiflora has experienced widespread genomic changes, suggesting that such events may not be reliable phylogenetic markers.     

Isoprostanes, prostaglandins and tocopherols in pre-eclampsia, normal pregnancy and non-pregnancy

This study is designed to evaluate whether oxidative stress and inflammation are involved in severe pre-eclampsia compared to normal pregnancy and non-pregnancy. We have measured plasma and urinary levels of 8-iso-PGF2alpha, a major isoprostane as an indicator of oxidative stress; plasma and urinary 15-keto-dihydro-PGF2alpha, a major metabolite of cyclooxygenase-catalysed PGF2alpha as an indicator of inflammatory response, and plasma -alpha-and -gamma-tocopherol in 18 pre-eclamptic, 19 normal pregnancy and 20 non-pregnant women. Pregnant women had significantly higher levels of 8-iso-PGF2alpha and PGF2alpha metabolite as compared to the non-pregnancy. Levels of 8-iso-PGF2alpha in the pre-eclamptic women did not differ from the normal pregnancy but PGF2alpha metabolite levels were significantly higher in normal pregnancy. On the other hand, gamma-tocopherol levels were significantly lower in pre-eclampsia than normal pregnancy. In contrast, the concentration of alpha-tocopherol was very similar between the groups. alpha-and gamma-tocopherol levels were significantly lower in pregnancy compared to non-pregnancy. Although no direct evidence of oxidative stress and inflammatory response was observed in severe pre-eclampsia, a reduction of gamma-tocopherol suggests the possible precedence of oxidative stress in this condition. Higher levels of isoprostanes and prostaglandin metabolite in late pregnancy suggest the importance of both free radicals and cyclooxygenase-catalysed oxidation products in normal biological processes of pregnancy.     

Biochemical and crystallographic studies of the Met144Ala, Asp92Asn and His254Phe mutants of the nitrite reductase from Alcaligenes xylosoxidans provide insight into the enzyme mechanism

Dissimilatory nitrite reductase catalyses the reduction of nitrite (NO(2)(-)) to nitric oxide (NO). Copper-containing nitrite reductases contain both type 1 and type 2 Cu sites. Electron transfer from redox partners is presumed to be mediated via the type 1 Cu site and used at the catalytic type 2 Cu centre along with the substrate nitrite. At the type 2 Cu site, Asp92 has been identified as a key residue in substrate utilisation, since it hydrogen bonds to the water molecule at the nitrite binding site. We have also suggested that protons enter the catalytic site via Asp92, through a water network that is mediated by His254. The role of these residues has been investigated in the blue copper nitrite reductase from Alcaligenes xylosoxidans (NCIMB 11015) by a combination of point mutation, enzymatic activity measurement and structure determination.In addition, it has been suggested that the enzyme operates via an ordered mechanism where an electron is transferred to the type 2 Cu site largely when the second substrate nitrite is bound and that this is controlled via the lowering of the redox potential of the type 2 site when it is loaded with nitrite. Thus, a small perturbation of the type 1 Cu site should result in a significant effect on the activity of the enzyme. For this reason a mutation of Met144, which is the weakest ligand of the type 1 Cu, is investigated. The structures of H254F, D92N and M144A have been determined to 1.85 A, 1.9 A and 2.2 A resolution, respectively. The D92N and H254F mutants have negligible or no activity, while the M144A mutant has 30 % activity of the native enzyme. Structural and spectroscopic data show that the loss of activity in H254F is due to the catalytic site being occupied by Zn while the loss/reduction of activity in D92N/M144A are due to structural reasons. The D92N mutation results in the loss of the Asp92 hydrogen bond to the Cu-ligated water. Therefore, the ligand is no longer able to perform proton abstraction. Even though the loss of activity in H254F is due to lack of catalytic Cu, the mutation does cause the disruption of the water network, confirming its key role in proton channel. The structure of the H254F mutant is the first case where full occupancy Zn at the type 2 Cu site is observed, but despite the previously noted similarity of this site to the carbonic anhydrase catalytic site, no carbonic anhydrase activity is observed. The H254F and D92N mutant structures provide, for the first time, observation of surface Zn sites which may act as a Zn sink and prevent binding of Zn at the catalytic Cu site in the native enzyme.     

The N-terminal extension of rusticyanin is not responsible for its acid stability

The N-terminal extension of rusticyanin is a unique structural feature of this protein in the cupredoxin family and has been speculated to be responsible for the extreme acid stability of the protein. We have removed the 35 residues from the N-terminus and show that the resulting -35 mutant is insoluble in aqueous media above pH 5.0 and exists primarily in a hexameric form at lower pHs. Synchrotron radiation circular dichroism (SRCD) and solution X-ray scattering data indicate that much of the beta-sheet structure is retained in acidic solution and indeed there is a small but significant increase in the beta-sheet contribution. We suggest this to be a result of beta-sheet formation between the monomer interfaces. The mutant does not bind copper. These results provide evidence that the unique N-terminus of rusticyanin is not responsible for the acid stability of the hydrophobic beta-barrel core of the protein.     

Trichothecenes and zearalenone production by fusarium species isolated from Argentinean black beans

Isolates of Fusarium species obtained from freshly harvested bean grains for human consumption collected from different Argentinean regions, were investigated for their ability to biosynthesise trichothecenes and zearalenone either on rice grains or beans. Low incidence of toxigenic fungi was observed. These mycotoxigenic species produced several toxins when grown on rice but none or little amount when cultured on beans. The results of this report suggest that contamination of Argentinean beans with Fusarium mycotoxins will not be common and therefore people would be at low mycotoxicosis risk through consumption of beans.     

The Impact of the Carer Support Needs Assessment Tool (CSNAT) in Community Palliative Care Using a Stepped Wedge Cluster Trial

Family caregiving towards the end-of-life entails considerable emotional, social, financial and physical costs for caregivers. Evidence suggests that good support can improve caregiver psychological outcomes. The primary aim of this study was to investigate the impact of using the carer support needs assessment tool (CSNAT), as an intervention to identify and address support needs in end of life home care, on family caregiver outcomes. A stepped wedge design was used to trial the CSNAT intervention in three bases of Silver Chain Hospice Care in Western Australia, 2012-14. The intervention consisted of at least two visits from nurses (2-3 weeks apart) to identify, review and address caregivers’ needs. The outcome measures for the intervention and control groups were caregiver strain and distress as measured by the Family Appraisal of Caregiving Questionnaire (FACQ-PC), caregiver mental and physical health as measured by SF-12v2, and caregiver workload as measured by extent of caregiver assistance with activities of daily living, at baseline and follow up. Total recruitment was 620. There was 45% attrition for each group between baseline and follow-up mainly due to patient deaths resulting in 322 caregivers completing the study (233 in the intervention group and 89 in the control group). At follow-up, the intervention group showed significant reduction in caregiver strain relative to controls, p=0.018, d=0.348 (95% CI 0.25 to 0.41). Priority support needs identified by caregivers included knowing what to expect in the future, having time for yourself in the day and dealing with your feelings and worries. Despite the challenges at the clinician, organisational and trial levels, the CSNAT intervention led to an improvement in caregiver strain. Effective implementation of an evidence-informed and caregiver-led tool represents a necessary step towards helping palliative care providers better assess and address caregiver needs, ensuring adequate family caregiver support and reduction in caregiver strain.     

Changes in cellular levels of inositol polyphosphates during apoptosis

Accumulations of higher inositol polyphosphates, diphosphoinositol polyphosphates or pyrophosphates, have been implicated to mediate cellular apoptosis. Whether cellular levels of lower inositol phosphates (lower than inositol hexakisphosphates) change during apoptosis is not known, although these inositol phosphates are known to play crucial roles in a number of cellular signaling processes including calcium mobilization. Therefore, in this study, we have examined changes in cellular levels of inositol phosphates following metabolic labeling of these compounds by [³H]myo-inositol and induction of apoptosis. The levels of inositol mono- and bis-phosphates were increased, whereas the levels of inositol tris- and tetrakis-phosphates decreased significantly with an increasing rate of apoptosis induced by etoposide in a dose-dependent manner. NaF treatment, which increased the rate of apoptosis in a time- and dose-dependent manner, also increased the levels of inositol mono- and bis-phosphates and drastically reduced the levels of inositol tris- and tetrakis-phosphates. Prior treatment with antimycin A, a strategy used to reverse the NaF-induced accumulations of higher InsPs, partially reduced the effects of NaF on apoptosis as well as the levels of lower InsPs. Taken together, our results suggest that cellular levels of lower InsPs are altered during apoptosis.     

Maintaining nitric oxide-induced airway relaxation with superoxide dismutase

BACKGROUND: We have previously shown that the protective effect of inhaled nitric oxide (iNO) against methacholine-induced bronchoconstriction is negated in airways subjected to hyperosmotic stress. In this study, hypothesizing that the impaired efficiency of iNO was caused by release of reactive oxygen radicals, we examined the effect of the radical scavenging enzyme superoxide dismutase (SOD). METHODS: Hemodynamic and respiratory measurements were performed on anesthetized rabbits after (1) inhalation of methacholine (MCh), (2) iNO (80ppm), followed by MCh, (3) inhalation of hypertonic saline (HS), followed by iNO and MCh and (4) pre-treatment with inhalation of SOD, followed by HS, iNO and MCh. We analyzed plasma for a marker of oxidative stress, 8-iso-prostaglandin (PG)F(2alpha) and for a marker of activation of COX-mediated inflammatory cascades, PGF(2alpha) metabolite. RESULTS: Pre-treatment with SOD restored the bronchoprotective response to iNO in hyperosmotic airways. No direct effect was seen by SOD treatment on levels of 8-iso-PGF(2alpha), but this marker of oxidative stress correlated positively with increased bronchoconstriction. Hyperosmotic challenge elevated levels of PGF(2alpha) metabolite, and pre-treatment with SOD protected against this activation of the inflammatory cascade. CONCLUSION: SOD pre-treatment restores the relaxant effects of iNO in hyperosmotically challenged airways by attenuating oxidative stress and activation of COX-mediated inflammatory cascades.