RESUMO
Phosphatidylinositol 3-phosphate (PI(3)P) is the predominant phosphoinositide species in early endosomes and autophagosomes, in which PI(3)P dictates traffic of these organelles. Phosphoinositide levels are tightly regulated by lipid-kinases and -phosphatases; however, a phosphatase that converts PI(3)P back to phosphatidylinositol in the endosomal and autophagosomal compartments is not fully understood. We investigated the subcellular distribution and functions of myotubularin-related protein-4 (MTMR4), which is distinct among other MTMRs in that it possesses a PI(3)P-binding FYVE domain, in lung alveolar epithelium-derived A549 cells. MTMR4 was localized mainly in late endosomes and autophagosomes. MTMR4 knockdown markedly suppressed the motility, fusion, and fission of PI(3)P-enriched structures, resulting in decreases in late endosomes, autophagosomes, and lysosomes, and enlargement of PI(3)P-enriched early and late endosomes. In amino acid- and serum-starved cells, MTMR4 knockdown decreased both autophagosomes and autolysosomes and markedly increased PI(3)P-containing autophagosomes and late endosomes, suggesting that the fusion with lysosomes of autophagosomes and late endosomes might be impaired. Notably, MTMR4 knockdown inhibited the nuclear translocation of starvation stress responsive transcription factor-EB (TFEB) with reduced expression of lysosome-related genes in starved cells. These findings indicate that MTMR4 is essential for the integrity of endocytic and autophagic pathways.
RESUMO
OBJECTIVE: Preconception micronutrient interventions may be a promising approach to reduce anemia and iron deficiency during pregnancy, but currently we have limited data to inform policies. We evaluated whether providing additional pre-pregnancy weekly iron-folic acid (IFA) or multiple micronutrient (MM) supplements compared to only folic acid (FA) improves iron status and anemia during pregnancy and early postpartum. METHODS: We conducted a double blind randomized controlled trial in which 5011 Vietnamese women were provided with weekly supplements containing either only 2800 µg FA (control group), IFA (60 mg Fe and 2800 µg FA) or MM (15 micronutrients with similar amounts of IFA). All women who became pregnant (n = 1813) in each of the 3 groups received daily IFA (60 mg Fe and 400 µg FA) through delivery. Hematological indicators were assessed at baseline (pre-pregnancy), during pregnancy, 3 months post-partum, and in cord blood. Adjusted generalized linear models were applied to examine the impact of preconception supplementation on anemia and iron stores, using both intention to treat and per protocol analyses (women consumed supplements ≥ 26 weeks before conception). RESULTS: At baseline, 20% of women were anemic, but only 14% had low iron stores (ferritin <30 µg/L) and 3% had iron deficiency (ferritin <12 µg/L). The groups were balanced for baseline characteristics. Anemia prevalence increased during pregnancy and post-partum but was similar among intervention groups. In intention to treat analyses, prenatal ferritin was significantly higher among women receiving MM (geometric mean (µg/L) [95% CI]: 93.6 [89.3-98.2]) and IFA (91.9 [87.6-96.3]) compared to control (85.3 [81.5-89.2]). In per protocol analyses, women receiving MM or IFA had higher ferritin 3 months postpartum (MM 118.2 [109.3-127.8]), IFA 117.8 [108.7-127.7] vs control 101.5 [94.0-109.7]) and gave birth to infants with greater iron stores (MM 184.3 [176.1-192.9]), IFA 189.9 [181.6-198.3] vs control 175.1 [167.9-182.6]). CONCLUSION: Preconception supplementation with MM or IFA resulted in modest increases in maternal and infant iron stores but did not impact anemia. Further research is needed to characterize the etiology of anemia in this population and identify effective interventions for reducing prenatal anemia. TRIAL REGISTRATION: ClinicalTrials.Gov NCT01665378.
