A Functional Tyr1306Cys Variant in LARG Is Associated With Increased Insulin Action in Vivo
Article Figures & Tables
Figures
- FIG. 1.
Activation of the SRE, via serum response factors, in NIH3T3 cells by LARG plasmids. Plasmids pCGN-expressing LARG(Tyr1306) (Tyr at 1306) and LARG(Cys1306) (Cys at 1306) proteins were cotransfected into NIH3T3 cells with a luciferase reporter plasmid containing a SRE (SRE.L-luciferase) using LipofectAMINE Plus according to the manufacturer’s protocol. Transfections were carried out in duplicate in six-well plates, and the data shown are the mean (±SE) of six experiments. Increase in luciferase activity was quantified relative to the control (pCGN without LARG) vector–induced level of the SRE-luciferase reporter system.
- FIG. 2.
Decreased activity of LARG caused by the Tyr1306Cys substitution is associated with higher skeletal muscle insulin sensitivity in Pima Indians. Rho proteins cycle between an inactive GDP-bound and an active GTP-bound state that is under the regulation of GEFs and GTPase-activating proteins (GAPs). Decreased LARG activity subsequently affects Rho-linked pathways. IRS, insulin receptor substrate; PI3/Akt, phosphatidylinositol 3-kinase/serine-threonine kinase Akt; ROK, Rho kinase.
Tables
- TABLE 1
Main characteristics of genetic variants detected in the LARG and its 5′ region
Variant Position within the gene (nucleotide) Alleles Minor allele frequency GenBank position DbSNP (BUILD 124) LARG-SNP1 5′ UTR (−8029) T/C C = 0.33 98864 (AP001150.4) — LARG-SNP2 5′ UTR (−5854) T/C C = 0.33 101039 (AP001150.4) rs11217821 LARG-SNP3 5′ UTR (−5659) G/A A = 0.42 101234 (AP001150.4) — LARG-SNP4 5′ UTR (−4695) T/C C = 0.12 102198 (AP001150.4) — LARG-SNP5 5′ UTR (−4394) A/G G = 0.33 102499 (AP001150.4) — LARG-SNP6 5′ UTR (−4325) G/A A = 0.33 102568 (AP001150.4) rs12806740 LARG-SNP7 5′ UTR (−2343) TA (repeat) TA (del) = 0.39 104498 (AP001150.4) — LARG-SNP8 5′ UTR (−317) G (ins/del) G (del) = 0.28 105576 (AP001150.4) rs3840762 LARG-SNP9 5′ UTR (−548) A/G G = 0.33 106345 (AP001150.4) rs7126413 LARG-SNP10 Intron 2 (−88) T/C C = 0.28 66021 (AP000681.3) rs6589812 LARG-SNP11 Intron 12 (199) A/G G = 0.28 129684 (AC016034.2) rs10892578 LARG-SNP12 Intron 12 (−987) C/T T = 0.12 131245 (AC016034.2) rs538661 LARG-SNP13 Intron 14 (−67) G/A A = 0.28 134140 (AC016034.2) rs723937 LARG-SNP14 Intron 20 (7) A/C C = 0.28 140461 (AC016034.2) rs2305008 LARG-SNP15 Intron 22 (−1549) G/A A = 0.39 147675 (AC016034.2) rs476636 LARG-SNP16 Intron 29 (23) A/G G = 0.39 159437 (AC016034.2) rs2305011 LARG-SNP17 Intron 34 (−43) GTTGT (ins/del) GTTGT (ins) = 0.28 9563 (AP000681.3) — LARG-SNP18 Exon 38(Tyr1306Cys) A/G (TAT/TGT)* G = 0.42 3924 (NM_015313) — LARG-SNP19 Intron 40 (14) A/G G = 0.12 71241 (AP000681.3) rs503473 LARG-SNP20 3’UTR (6287) T (ins/del) T (del) = 0.28 6287 (NM_015313) rs3832734 LARG-SNP21 3’UTR (6699) TT (ins/del) TT (del) = 0.28 6699 (NM_015313) — - *
* Underlined letters indicate the position of ATG substitution within codon 1306.
- *
- TABLE 2
LARG variants grouped by LD (r2 = 1) among 20 Pima Indians
Group 1 Group 2 Group 3 Group 4 Group 5 LARG-SNP8 LARG-SNP1 LARG-SNP7 LARG-SNP4 LARG-SNP3 LARG-SNP10 LARG-SNP2 LARG-SNP15 LARG-SNP12 LARG-SNP18 LARG-SNP11 LARG-SNP6 LARG-SNP16 LARG-SNP19 LARG-SNP13 LARG-SNP5 LARG-SNP14 LARG-SNP9 LARG-SNP17 LARG-SNP20 LARG-SNP21 -
Representative SNPs for additional genotyping are in bold.
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- TABLE 3
LD between representative SNPs from the five LD groups
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D′ given in upper shaded boxes and r2 given in lower boxes, calculated from genotypic data from 1,346 subjects.
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- TABLE 4
Association of LARG SNPs with diabetes-related phenotypes
Genotype LARG-SNP6 LARG-SNP11 LARG-SNP12 LARG-SNP15 LARG-SNP18 AA (n = 148) AG (n = 137) GG (n = 37) P AA (n = 165) AG (n = 133) GG (n = 24) P CC (n = 253) TT + CT (n = 69) P AA (n = 126) AG (n = 144) GG (n = 52) P Tyr/Tyr (n = 100) Tyr/Cys (n = 171) Cys/Cys (n = 51) P Male/females (n) 89/59 84/53 18/19 0.37 100/65 82/51 9/15 0.08 144/109 43/26 0.42 79/47 78/66 31/21 0.36 63/37 97/74 29/22 0.57 Percent body fat 32 ± 1 32 ± 1 33 ± 1 0.85 32 ± 1 32 ± 1 33 ± 2 0.57 32 ± 1 32 ± 1 0.46 32 ± 1 32 ± 1 32 ± 1 0.38 32 ± 1 32 ± 1 33 ± 1 0.49 2-h plasma glucose (mg/dl) 121 ± 3 126 ± 3 131 ± 5 0.19 121 ± 2 126 ± 2 138 ± 6 0.07 125 ± 2 124 ± 4 0.98 120 ± 3 128 ± 3 127 ± 4 0.15 128 ± 3 124 ± 2 120 ± 5 0.22 (log)2-h plasma insulin 2.2 ± 0.1 2.2 ± 0.1 2.2 ± 0.1 0.60 2.1 ± 0.1 2.2 ± 0.1 2.3 ± 0.1 0.16 2.2 ± 0.1 2.2 ± 0.1 0.43 2.2 ± 0.1 2.2 ± 0.1 2.2 ± 0.1 0.43 2.2 ± 0.1 2.2 ± 0.1 2.1 ± 0.1 0.40 (log)glucose disposal for low-dose insulin clamp (mg · kg EMBS−1 · min−1) 0.41 ± 0.01 0.39 ± 0.01 0.38 ± 0.02 0.22 0.41 ± 0.01 0.40 ± 0.01 0.36 ± 0.02 0.07 0.40 ± 0.01 0.39 ± 0.01 0.42 0.41 ± 0.01 0.39 ± 0.01 0.38 ± 0.01 0.08 0.37 ± 0.01 0.41 ± 0.01 0.43 ± 0.02 0.0001 Glucose disposal for high-dose insulin clamp (mg · kg EMBS−1 · min−1) 9.1 ± 0.2 8.7 ± 0.2 8.0 ± 0.3 0.03 9.0 ± 0.2 8.7 ± 0.2 7.6 ± 0.4 0.02 8.8 ± 0.1 8.5 ± 0.3 0.16 9.2 ± 0.2 8.6 ± 0.2 8.3 ± 0.3 0.008 8.3 ± 0.2 8.8 ± 0.2 9.5 ± 0.3 0.004 -
Data are means ± SE. P values were calculated after adjusting for age, sex, nuclear family membership for the variable percent body fat and for age, sex, percent body fat, and nuclear family membership for the variables 2-h plasma glucose (2 h after ingestion of 75 g glucose for oral glucose tolerance test), 2-h plasma insulin, and log10 glucose disposal for the physiologic and maximally stimulating insulin clamps. Due to the low frequency of the rare alleles for LARG-SNP12 variants, for statistical analysis, the homozygotes for each rare allele were combined with the heterozygotes; therefore, only a dominant effect on risk has been tested for the rare allele. EMBS, estimated metabolic body size.
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