Exploring reasons for state-level variation in incidence of dialysis-requiring acute kidney injury (AKI-D) in the United States

Background: There is considerable state-level variation in the incidence of dialysis-requiring acute kidney injury (AKI-D). However, little is known about reasons for this geographic variation. Methods: National cross-sectional state-level ecological study based on State Inpatient Databases (SID) and the Behavioral Risk Factor Surveillance System (BRFSS) in 2011. We analyzed 18 states and six chronic health conditions (diabetes mellitus [diabetes], hypertension, chronic kidney disease [CKD], arteriosclerotic heart disease [ASHD], cancer (excluding skin cancer), and chronic obstructive pulmonary disease [COPD]). Associations between each of the chronic health conditions and AKI-D incidence was assessed using Pearson correlation and multiple regression adjusting for mean age, the proportion of males, and the proportion of non-Hispanic whites in each state. Results: The state-level AKI-D incidence ranged from 190 to 1139 per million population. State-level differences in rates of hospitalization with chronic health conditions (mostly \u3c 3-fold difference in range) were larger than the state-level differences in prevalence for each chronic health condition (mostly \u3c 2.5-fold difference in range). A significant correlation was shown between AKI-D incidence and prevalence of diabetes, ASHD, and COPD, as well as between AKI-D incidence and rate of hospitalization with hypertension. In regression models, after adjusting for age, sex, and race, AKI-D incidence was associated with prevalence of and rates of hospitalization with five chronic health conditions - diabetes, hypertension, CKD, ASHD and COPD - and rates of hospitalization with cancer. Conclusions: Results from this ecological analysis suggest that state-level variation in AKI-D incidence may be influenced by state-level variations in prevalence of and rates of hospitalization with several chronic health conditions. For most of the explored chronic conditions, AKI-D correlated stronger with rates of hospitalizations with the health conditions rather than with their prevalences, suggesting that better disease management strategies that prevent hospitalizations may translate into lower incidence of AKI-D

Zebrafish IGF genes: gene duplication, conservation and divergence, and novel roles in midline and notochord development.

Insulin-like growth factors (IGFs) are key regulators of development, growth, and longevity. In most vertebrate species including humans, there is one IGF-1 gene and one IGF-2 gene. Here we report the identification and functional characterization of 4 distinct IGF genes (termed as igf-1a, -1b, -2a, and -2b) in zebrafish. These genes encode 4 structurally distinct and functional IGF peptides. IGF-1a and IGF-2a mRNAs were detected in multiple tissues in adult fish. IGF-1b mRNA was detected only in the gonad and IGF-2b mRNA only in the liver. Functional analysis showed that all 4 IGFs caused similar developmental defects but with different potencies. Many of these embryos had fully or partially duplicated notochords, suggesting that an excess of IGF signaling causes defects in the midline formation and an expansion of the notochord. IGF-2a, the most potent IGF, was analyzed in depth. IGF-2a expression caused defects in the midline formation and expansion of the notochord but it did not alter the anterior neural patterning. These results not only provide new insights into the functional conservation and divergence of the multiple igf genes but also reveal a novel role of IGF signaling in midline formation and notochord development in a vertebrate model

Effect of forced IGF expression in zebrafish embryos.

<p>(A, B) Lateral view of a GFP mRNA injected control embryo (A) and an IGF-2a mRNA injected embryo (B) at the bud stage. Note the delayed mesoderm involution associated with an open blastopore (>75%, n = 328) in the IGF-2a mRNA injected embryos (B). (C, D) Lateral views of a control embryo (C) or an IGF-2a mRNA injected embryo (D) at 2-somite stage. Note the shortened A-P axis and more posterior tissues in (D). (E–H) Dorsal view of a control (E, G) or an IGF-2a mRNA injected embryo (F, H) at the 5-somite (E and F) and 15-somite stages (G and H). All embryos are dorsal views with head up. Arrows indicate the width of the notochord. Black bars in panels E and F show the width of the somite. Scale bar  = 200 µm. (I–L) Morphology of a GFP mRNA injected control embryo (I and K) and an IGF-2a mRNA injected embryo (J and L) at 24 hpf. I and J are lateral views with head to the left and K and L are dorsal views with head to the left. MB, mid brain; OtV, otic vesicle; NC, notochord. Scale bar  = 200 µm. (M) Dose-dependent effects of various IGFs in zebrafish embryos. The results are means of 3–4 independent experiments.</p

Molecular characterization of four zebrafish <i>igf</i> genes and their multiple transcripts.

<p>(A) Structure of the zebrafish <i>igf-1a</i> and <i>-1b</i> genes. Signal peptide and E domain regions are shown in grey boxes and the B–C–A–D domains of the mature peptide are shown in dark boxes with the number of amino acids indicated. 3′ and 5′-UTRs are shown in bold lines with the number of base pairs shown (bp). Introns sequences are shown in dashed lines and are indicated in kb. Two alternative splicing transcripts (T1 and T2) are found in the 3′-UTR of <i>igf-1a</i>. Two alternative splicing transcripts are also found in the 5′-UTR and signal peptide region of <i>igf-1b</i>. (B) Structure of the zebrafish <i>igf-2a</i> and <i>igf-2b</i>. Two alternative splicing transcripts are found in the 5′-UTR and signal peptide region of <i>igf-2a</i>.</p

Effect of IGF-2a expression.

<p><i>otx2</i> expression in the anterior neural plate at the bud stage in a control embryo (panels A and E) and an IGF-2a mRNA injected embryo (panels B and F). <i>pax6a</i> expression in the anterior neural plate at the bud stage in a control embryo (panels C and G) and an IGF-2a mRNA injected embryo (panels D and H). <i>pax2a</i> expression in the midbrain hindbrain boundary at the bud stage in a control embryo (panel I) and an IGF-2a mRNA injected embryo (panel J). <i>krox20</i> expression in the rhombomere 3 and 5 at the bud stage in a control embryo (panel K) and an IGF-2a mRNA injected embryo (panel L). <i>emx1</i> expression in the forebrain at the 15-somite stage in a control embryo (panel M) and an IGF-2a mRNA injected embryo (panel N). <i>otx2</i> expression in the midbrain at the 15-somite stage in a control embryo (panel O) and an IGF-2a mRNA injected embryo (panel P). <i>rx1</i> expression in the optic vesicle at the 15-somite stage in a control embryo (panel Q) and an IGF-2a mRNA injected embryo (panel R). <i>rx2</i> expression in the optic vesicle at the 15-somite stage in a control embryo (panel S) and an IGF-2a mRNA injected embryo (panel T). <i>pax2a</i> expression in the midbrain hindbrain boundary at the 15-somite stage in a control embryo (panel U) and an IGF-2a mRNA injected embryo (panel V). <i>krox20</i> expression in the rhombomere 3 and 5 at the 15-somite stage in a control embryo (panel W) and a 500 pg IGF-2a mRNA injected embryo (panel X). Panels A–D, lateral view, head left; panels E–H, dorsal view, head up; panels I–L and U–X, dorsal view, head left; panels M–T, front view. Black line in panels U, V indicates the gap between the midbrain hindbrain boundary and otic vesicle; black line in panels W, X indicates the gap between rhombomere 3 and 5.</p

Overexpression of IGF-2a results in abnormal notochord development.

<p><i>ntl</i> expression in the notochord at the bud stage in a control embryo (panels A and C) and an IGF-2a mRNA injected embryo (panels B and D). <i>ntl</i> expression in the notochord at the 15-somite stage in a control embryo (panel E) and IGF-2a mRNA injected embryos (panels F and G). Among the IGF-2a mRNA injected embryos, 65% showed the expression pattern shown in panel F and 35% showed that in panel G (n = 17). <i>myoD</i> expression in the somite at the bud stage in a control embryo (panel H) and an IGF-2a mRNA injected embryo (panel I). <i>myoD</i> expression in the somite at the 15-somite stage in a control embryo (panel J) and an IGF-2a mRNA injected embryo (panel K). <i>shh</i> expression in the notochord at the 15-somite stage in a control embryo (panel L) and IGF-2a mRNA injected embryos (panels M and N). Among the IGF-2a mRNA injected embryos, 71% showed expression pattern shown in panel M and 24% showed that in panel N (n = 21). <i>myogenin</i> expression in the somite at the 15-somite stage in a control embryo (panel O) and an IGF-2a mRNA injected embryo (panel P). Panels A, B, E–G, and L–N are dorsal view with head up; panels C and D are vegetal view with dorsal the the right; panels H–K, O, and P are dorsal views with head to the left.</p

Structural and phylogenic analysis of four zebrafish IGFs.

<p>(A) Sequence alignment of mature zebrafish (zf) IGF-1a, IGF-1b, IGF-2a, IGF-2b and mature human (h) IGF-1 and IGF-2. The B–C–A–D domains are labeled. Star indicates conserved cysteine. (B) Phylogenetic analysis of the vertebrate insulin/IGF family members. Amino acid sequences in the B and A domains were analyzed by the neighbor-joining method using the MEGA3 program <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007026#pone.0007026-Kumar1" target="_blank">[64]</a>. Gaps were removed from the alignment. Bootstrap values derived from 1,000 runs are shown. Relaxins are used as an outgroup. Accession numbers for the sequences used are: human (<i>IGF-1</i>, NM_000618; <i>IGF-2</i>, NM_000612; <i>insulin</i>, NM_000207; <i>relaxin</i>, NM_080864), mouse (<i>IGF-1</i>, NM_010512; <i>IGF-2</i>, NM_010514, <i>insulin</i> 1, NM_008386; <i>insulin 2</i>, NM_008387; <i>relaxin</i>, NM_173184), <i>Xenopus</i> (<i>IGF-1</i>, M29857; <i>IGF-2</i>, BC070545), zebrafish (<i>insulin a</i>, NM_131056; <i>insulin b</i>, NM_001039064), common carp (<i>IGF-1</i>, EF536889; <i>IGF-2</i>, AF402958; <i>insulin</i>, X00989), trout (<i>IGF-1</i>, EF432852; <i>IGF-2</i>, EF432854; <i>insulin</i>, M21170), tilapia (<i>IGF-1</i>, AF033796; <i>IGF-2</i>, AF033801; <i>IGF-3</i>, EU272147; <i>insulin</i>, AF038123 ), shark (<i>IGF-1</i>, Z50081; <i>IGF-2</i>, Z50082), hagfish (<i>IGF</i>, M57735; <i>insulin</i>, V00649 ), sea lamprey (<i>IGF</i>, AB081462), Amphioxus insulin-like peptide mRNA (<i>ILP</i>, M55302). Sequence for <i>Tetraodon</i>, fugu and stickleback IGF-1, IGF2 and insulin were obtained by searching the <i>Tetraodon</i> genome (<a href="http://www.genoscope.cns.fr/externe/English/Projets/Projet_C/C.html" target="_blank">http://www.genoscope.cns.fr/externe/English/Projets/Projet_C/C.html</a>), fugu genome (<a href="http://fugu.hgmp.mrc.ac.uk/" target="_blank">http://fugu.hgmp.mrc.ac.uk/</a>), and stickleback genome (<a href="http://www.ensembl.org/Gasterosteus_aculeatus/" target="_blank">http://www.ensembl.org/Gasterosteus_aculeatus/</a>). Sequence of sea lamprey insulin was obtained by searching sea lamprey genome (<a href="http://pre.ensembl.org/Petromyzon_marinus/" target="_blank">http://pre.ensembl.org/Petromyzon_marinus/</a>). (C) Conserved synteny between human (Hs) and zebrafish (Zf) IGF loci. Vertical gray lines indicate a group of genes on the same chromosome, with order ignored to facilitate the comparison of orthologs and paralogs. Horizontal gray lines connect presumed orthologs within chromosome groups as well as paralogs between chromosome groups.</p