Enhanced plant tolerance to iron starvation by functional substitution of chloroplast ferredoxin with a bacterial flavodoxin

Iron limitation affects one-third of the cultivable land on Earth and represents a major concern for agriculture. It causes decline of many photosynthetic components, including the Fe-S protein ferredoxin (Fd), involved in essential oxidoreductive pathways of chloroplasts. In cyanobacteria and some algae, Fd down-regulation under Fe deficit is compensated by induction of an isofunctional electron carrier, flavodoxin (Fld), a flavin mononucleotide-containing protein not found in plants. Transgenic tobacco lines expressing a cyanobacterial Fld in chloroplasts were able to grow in Fe-deficient media that severely compromised survival of WT plants. Fld expression did not improve Fe uptake or mobilization, and stressed transformants elicited a normal deficit response, including induction of ferric-chelate reductase and metal transporters. However, the presence of Fld did prevent decrease of several photosynthetic proteins (but not Fd) and partially protected photosynthesis from inactivation. It also preserved the activation state of enzymes depending on the Fd-thioredoxin pathway, which correlated with higher levels of intermediates of carbohydrate metabolism and the Calvin cycle, as well as increased contents of sucrose, glutamate, and other amino acids. These metabolic routes depend, directly or indirectly, on the provision of reduced Fd. The results indicate that Fld could compensate Fd decline during episodes of Fe deficiency by productively interacting with Fd-dependent pathways of the host, providing fresh genetic resources for the design of plants able to survive in Fe-poor lands.     

Relationship between vascular reactivity and lipids in Mexican-Americans with type 2 diabetes treated with pioglitazone

CONTEXT: Vascular dysfunction and insulin resistance precede atherosclerosis in type 2 diabetes (T2DM). Better knowledge of the interaction between these is of considerable clinical interest. OBJECTIVE: The objective of this study was to examine the association between inflammation, glucose, and lipid metabolism and vascular dysfunction. DESIGN AND SETTING: We conducted a randomized, double-blind, controlled trial of pioglitazone vs. placebo and other therapies aimed at equal glycemic control for 24 wk at an academic tertiary referral clinic. PATIENTS AND INTERVENTIONS: Mexican-American subjects with T2DM and no complications were randomly assigned to pioglitazone 45 mg daily (PIO, n=16) or placebo (CON, n=15) and matched for age, gender, body mass index, diabetes duration, and glycemic control. All subjects completed the study. MAIN OUTCOME MEASURE: We looked for improved vascular reactivity independent of glycemic control but closely related to plasma adiponectin, lipids, and insulin sensitivity. RESULTS: After 24 wk, there was an equal decrease in fasting plasma glucose (approximately 135 mg/dl), glycosylated hemoglobin (approximately 7.0%), and glucose production (approximately 15%). The decrease in free fatty acids (30 vs. 10%) and increase in glucose disposal (40 vs. 25%) were greater in PIO vs. CON (P<0.05). In PIO, plasma high-density lipoprotein rose by 15% (P<0.05), and low-density lipoprotein and high-density lipoprotein particle size rose significantly (P<0.01). Plasma adiponectin doubled in PIO (from 6.1+/-0.8 to 12.7+/-2.1 microg/ml). Forearm blood flow rose equally (approximately 130%) during reactive hyperemia in both groups, although after therapy, the increase was greater (P<0.001) in PIO (153%) than in CON (137%); vasodilation was greater (P=0.01) in PIO (92, 160, and 204%) than in CON with acetylcholine (74, 130, and 144%) and with sodium nitroprusside (PIO=164 and 253% vs. 116 and 230%; P=0.04). The elevation in diameter was also greater in PIO (13 vs. 10%; P<0.05). Vascular responses correlated with plasma free fatty acids, adiponectin, and low-density lipoprotein particle size but not with glycemic control. CONCLUSION: These data indicate that pioglitazone improves vascular reactivity irrespective of glycemic control and suggest a close association with changes in fat cell metabolism.     

Hepatitis E virus: zoonotic implications

The Hepatitis E virus (HEV) is transmitted primarily by the feco-oral route throughout contaminated water and/or food, and is one of the main causes of acute hepatitis worldwide. Hepatitis E shows a high mobility but a low mortality rate, except in pregnant women, where it can be as high as 30%. HEV causes sporadic cases and epidemic outbreaks, mainly in Africa, Asia and Central America. In Europe, there is an increase in the number of reported autochthonous cases no related with travel to endemic areas. In addition, HEV also infects animals, including pigs, and its zoonotic potential has been recently demonstrated. In fact, porcine and human strains of the same area are genetically more closely related to each other than to strains of the same species but a different geographical region, and there are data suggesting that people in close contact with pigs presents a higher prevalence of specific anti-HEV antibodies. All together, these data have drove to an increase interest in determining the incidence of the disease in animals, its possible zoonotic risk, and its implications for human health. In the present article we revised the current knowledge about HEV, with special emphasis in the possible consequences of its zoonotic potential.     

Deflazacort induced stronger immunosuppression than expected

Prednisone (PDN) impairs cognitive functioning and brain structures in humans and animals. Deflazacort (DFZ) is a synthetic glucocorticoid claimed to have lesser side effects than prednisone. The objective of this study was to assess whether chronic administration (90 days) of DFZ produces less neuronal degeneration and glial reactivity than PDN. Male Swiss-Wistar rats were studied. Controls received 0.1 ml distilled water orally. The PDN group received prednisone 5 mg per kg per day orally, and the DFZ group received deflazacort 6 mg per kg per day orally. This model had to be assembled in three different occasions due to excess mortality in the DFZ group. A fourth model was assembled using only the DFZ group and slides of water and PDN-exposed rats from a previous study were used as comparators. The index of degenerated neurons and the number and cytoplasmic transformation of astrocytes and microglia cells were evaluated in the prefrontal cortex, CA1, and CA3 hippocampus. The results show that the overall mortality was 49% in the DFZ group, 4.5% in the PDN group, and none of the controls died. Routine necropsy showed infection in multiple organs. The PDN group had two times higher neuronal degeneration in the prefrontal cortex, almost 11 times in CA1, and four times in CA3 hippocampus when compared with controls and DFZ group. Astrocytes reactivity was increased in the PDN- and DFZ-exposed rats compared with controls. The DFZ group showed an average of four times less microgial cells in the three studied regions when compared with controls and the PDN group. In conclusion, it seems that DFZ at the equivalent licensed dose produced a stronger immunosuppressive effect—systemic and in brain tissue—than PDN, but induced less neuronal damage. The immunesuppressant magnitude of DFZ should be further studied in clinical settings.     

Effect of acute exercise on AMPK signaling in skeletal muscle of subjects with type 2 diabetes: a time-course and dose-response study

Activation of AMP-activated protein kinase (AMPK) by exercise induces several cellular processes in muscle. Exercise activation of AMPK is unaffected in lean (BMI approximately 25 kg/m(2)) subjects with type 2 diabetes. However, most type 2 diabetic subjects are obese (BMI >30 kg/m(2)), and exercise stimulation of AMPK is blunted in obese rodents. We examined whether obese type 2 diabetic subjects have impaired exercise stimulation of AMPK, at different signaling levels, spanning from the upstream kinase, LKB1, to the putative AMPK targets, AS160 and peroxisome proliferator-activated receptor coactivator (PGC)-1alpha, involved in glucose transport regulation and mitochondrial biogenesis, respectively. Twelve type 2 diabetic, eight obese, and eight lean subjects exercised on a cycle ergometer for 40 min. Muscle biopsies were done before, during, and after exercise. Subjects underwent this protocol on two occasions, at low (50% Vo(2max)) and moderate (70% Vo(2max)) intensities, with a 4-6 week interval. Exercise had no effect on LKB1 activity. Exercise had a time- and intensity-dependent effect to increase AMPK activity and AS160 phosphorylation. Obese and type 2 diabetic subjects had attenuated exercise-stimulated AMPK activity and AS160 phosphorylation. Type 2 diabetic subjects had reduced basal PGC-1 gene expression but normal exercise-induced increases in PGC-1 expression. Our findings suggest that obese type 2 diabetic subjects may need to exercise at higher intensity to stimulate the AMPK-AS160 axis to the same level as lean subjects.     

Mitochondrial DNA depletion syndrome due to mutations in the RRM2B gene

Mitochondrial DNA depletion syndrome (MDS) is characterized by a reduction in mtDNA copy number and has been associated with mutations in eight nuclear genes, including enzymes involved in mitochondrial nucleotide metabolism (POLG, TK2, DGUOK, SUCLA2, SUCLG1, PEO1) and MPV17. Recently, mutations in the RRM2B gene, encoding the p53-controlled ribonucleotide reductase subunit, have been described in seven infants from four families, who presented with various combinations of hypotonia, tubulopathy, seizures, respiratory distress, diarrhea, and lactic acidosis. All children died before 4 months of age. We sequenced the RRM2B gene in three unrelated cases with unexplained severe mtDNA depletion. The first patient developed intractable diarrhea, profound weakness, respiratory distress, and died at 3 months. The other two unrelated patients had a much milder phenotype and are still alive at ages 27 and 36 months. All three patients had lactic acidosis and severe depletion of mtDNA in muscle. Muscle histochemistry showed RRF and COX deficiency. Sequencing the RRM2B gene revealed three missense mutations and two single nucleotide deletions in exons 6, 8, and 9, confirming that RRM2B mutations are important causes of MDS and that the clinical phenotype is heterogeneous and not invariably fatal in infancy.     

The induction of Bim expression in human T-cell blasts is dependent on nonapoptotic Fas/CD95 signaling

The BH3-only protein Bim is required for maintaining the homeostasis of the immune system, since Bim regulates the down-modulation of T-cell responses, mainly through cytokine deprivation. Using T-cell blasts from healthy donors and also from patients with autoimmune lymphoproliferative syndromes (ALPSs) due to homozygous loss-of-function mutation of FasL (ALPS-Ic) or heterozygous mutation in the Fas/CD95 death domain (ALPS-Ia), it is shown that the induction of Bim expression during the process of human T-cell blast generation is strictly dependent on FasL/Fas-mediated signaling. The main pathway by which Fas signaling regulates the levels of Bim expression in human T-cell blasts is the death-domain- and caspase-independent generation of discrete levels of H2O2, which results in the net increase of Foxo3a levels. The present results connect the 2 main pathways described until the moment for the control of T-cell responses: death receptor-mediated activation-induced cell death and apoptosis by cytokine deprivation.