Roles of Major Facilitator Superfamily Transporters in Phosphate Response in Drosophila

The major facilitator superfamily (MFS) transporter Pho84 and the type III transporter Pho89 are responsible for metabolic effects of inorganic phosphate in yeast. While the Pho89 ortholog Pit1 was also shown to be involved in phosphate-activated MAPK in mammalian cells, it is currently unknown, whether orthologs of Pho84 have a role in phosphate-sensing in metazoan species. We show here that the activation of MAPK by phosphate observed in mammals is conserved in Drosophila cells, and used this assay to characterize the roles of putative phosphate transporters. Surprisingly, while we found that RNAi-mediated knockdown of the fly Pho89 ortholog dPit had little effect on the activation of MAPK in Drosophila S2R+ cells by phosphate, two Pho84/SLC17A1–9 MFS orthologs (MFS10 and MFS13) specifically inhibited this response. Further, using a Xenopus oocyte assay, we show that MSF13 mediates uptake of [³³P]-orthophosphate in a sodium-dependent fashion. Consistent with a role in phosphate physiology, MSF13 is expressed highest in the Drosophila crop, midgut, Malpighian tubule, and hindgut. Altogether, our findings provide the first evidence that Pho84 orthologs mediate cellular effects of phosphate in metazoan cells. Finally, while phosphate is essential for Drosophila larval development, loss of MFS13 activity is compatible with viability indicating redundancy at the levels of the transporters.National Institutes of Health (U.S.) (NIDDK 5K08DK078361)Harvard Catalys

Genetic Determinants of Phosphate Response in Drosophila

Phosphate is required for many important cellular processes and having too little phosphate or too much can cause disease and reduce life span in humans. However, the mechanisms underlying homeostatic control of extracellular phosphate levels and cellular effects of phosphate are poorly understood. Here, we establish Drosophila melanogaster as a model system for the study of phosphate effects. We found that Drosophila larval development depends on the availability of phosphate in the medium. Conversely, life span is reduced when adult flies are cultured on high phosphate medium or when hemolymph phosphate is increased in flies with impaired Malpighian tubules. In addition, RNAi-mediated inhibition of MAPK-signaling by knockdown of Ras85D, phl/D-Raf or Dsor1/MEK affects larval development, adult life span and hemolymph phosphate, suggesting that some in vivo effects involve activation of this signaling pathway by phosphate. To identify novel genetic determinants of phosphate responses, we used Drosophila hemocyte-like cultured cells (S2R+) to perform a genome-wide RNAi screen using MAPK activation as the readout. We identified a number of candidate genes potentially important for the cellular response to phosphate. Evaluation of 51 genes in live flies revealed some that affect larval development, adult life span and hemolymph phosphate levels

Effects of Zinc and Selenium Supplementation on Thyroid Function in Overweight and Obese Hypothyroid Female Patients: A Randomized Double-Blind Controlled Trial

Objective: Zinc (Zn) and selenium (Se) are essential trace elements involved in thyroid hormone metabolism. This study was conducted to investigate the effects of Zn and Se supplementation on thyroid function of overweight or obese female hypothyroid patients in a double-blind, randomized controlled trial. Methods: Sixty-eight female hypothyroid patients were randomly allocated to one of the 4 supplementation groups receiving Zn + Se (ZS; 30 mg Zn as zinc-gluconate and 200 μg Se as high-selenium yeast), Zn + placebo (ZP), Se + placebo (SP), or placebo + placebo (PP) for 12 weeks. Serum Zn, Se, free and total triiodothyronine (FT3 and FT4), free and total thyroxine (FT4 and TT4), thyroid-stimulating hormone (TSH), and anthropometric parameters were measured. Dietary intake was recorded using 24-hour food recall. Physical activity questionnaire was completed. Results: No significant alterations were found in serum Zn or Se concentrations. Mean serum FT3 increased significantly in the ZS and ZP groups (p < 0.05) but this effect was significant in the ZP group compared to those in SP or PP groups (p < 0.05). Mean serum FT4 increased and TSH decreased significantly (p < 0.05) in the ZS group. TT3 and TT4 decreased significantly in the SP group (p < 0.05). Mean FT3:FT4 ratio was augmented significantly in the ZP group (p < 0.05). No significant treatment effects were found for TT3, FT4, TT4, or TSH between groups. Conclusion: This study showed some evidence of an effect of Zn alone or in combination with Se on thyroid function of overweight or obese female hypothyroid patients. © 2015, © American College of Nutrition

Visfatin/NAMPT/PBCEF and Cytokine Concentration in Multiple Sclerosis Patients Compared to Healthy Subjects

The aim of the study is to measure IL-1 β, TNF-α, hs-CRP levels and Nampt/visfatin/PBCEF concentrations in patients with multiple sclerosis and to compare them with those of healthy control subjects. In a case-control study a total number of 192 people were recruited. Ninety-six of them were suffering from multiple sclerosis, age 34.80±8.75 years (mean±SD), who were referred form the Iranian Multiple Sclerosis Society. They included relapsing remitting (82 subjects) and both primary and secondary progressive (14 subjects) types of MS. The diagnosis was made according to the diagnostic criteria by a neurology consultant. Ninety-six healthy individuals were recruited from the Iranian Multicenter Osteoporosis Study (IMOS) as the control group. Following an overnight fasting, peripheral blood was taken from all subjects and centrifuged in order to separate serum for measurement of serum visfatin, Interleukin-1beta (IL-1β), TNF-α, and hs-CRP concentrations. Fat tissue mass was measured using DXA. Levels of visfatin, TNF-α and hs-CRP were significantly higher in MS patients. Besides, significant correlation was found between visfatin levels and those of TNF-α, IL-1β, hs-CRP in MS patients. Regarding the control group, significant correlation was found between visfatin levels and levels of TNF-α. However, we did not find any significant correlation between fat tissue mass and visfatin, TNF-α, IL-1β or hs-CRP levels in the MS group. However, there was a significant correlation between fat tissue mass and TNF-α level in the study population. Our findings demonstrated that proinflammatory factor levels were, although not significantly, higher in RRMS patients compared to PPMS and SPMS patients. The results suggest that levels of visfatin and pro-inflammatory cytokines are higher in MS patients compared to healthy subjects. Their higher levels may be, in part, attributable to the MS phenotypes independent of fat mass in patients. We believe that these results may shed some light on a potentially novel source of visfatin as well as explaining its regulating role in the inflammation process

Comparison of the Bone Turn-over Markers in Patients with Multiple Sclerosis and Healthy Control Subjects

One of the major concerns for patients with multiple sclerosis (MS) is developing osteoporosis, especially when corticosteroid treatment is used. The aim of the present study is to compare the bone turnover markers in patients with multiple sclerosis and healthy control subjects. A total of 176 subjects were enrolled in this case-control. Ninety-one MS patients with mean age of 35.26 ± 8.76 yrs were randomly selected from the Committee on Multiple Sclerosis Registry. The control group was composed of 85 healthy subjects who were recruited from the Iranian Multicenter Osteoporosis Study (IMOS). Fasting serum levels of parathyroid hormone (PTH), 25 (OH) D3, osteocalcin and cross laps were measured in two groups. Hip and spine BMD were measured using DXA. Our findings showed significant differences in hip BMD and its T-score and Z-score values between MS patients and the control group. Osteoporosis prevalence at hip area of the MS patients was almost 5 times higher than the control group [OR=4.66, (95% CI 0.97 to 22.27), RR=4.29, (95% CI 0.95 to l9.32), p value=0.03]. No significant difference was found in BMD L2-L4, BMD T-score and BMD Z-score of lumbar area between two groups. The PTH and cross laps serum concentrations in MS patients were significantly higher than the control group. We did not find significant difference in serum osteocalcin level between the two groups. We concluded that in our study the serum levels of bone resorbtion markers in MS patients were significantly higher than the healthy control group. This may explain, at least in part, the elevated susceptibility of MS patients for developing osteoporosis