Expression of human growth hormone (hGH) in lymphocytes was examined by reverse transcription polymerase chain reaction (RT-PCR) in five normal subjects. Transcripts of hGH-N gene, but not hGH-V gene, were detected. Sequence analysis revealed four kinds of transcripts: 22kDa GH, 20kDa GH and two other forms of variant GH. The 20kDa GH transcript was generated by alternative splicing within exon 3, resulting in a 45bp deletion. One of the variant GH transcripts was also generated by alternative splicing within exon 3, but at a different site, resulting in a 73bp deletion. Because of a frameshift, this variant GH transcript may encode a 6.6kDa protein (truncated GH) that structurally differs from that of 22kDa GH after residue 31. In the other variant GH mRNA, exons 3 and 4 were completely skipped. The proportions of expression of 22kDa GH, 20kDa GH and the truncated GH were 60.9+/-13.6 (+/-S.D.)%, 32.7+/-14.1% and 6.4+/-1.1% (n=5), respectively, by comparative RT-PCR.We conclude that human lymphocytes, like the pituitary gland, express hGH-N gene transcripts of mainly 22kDa GH, but also 20kDa GH and minor variant forms of GH.
N Hattori, K Kitagawa and C Inagaki
A Katsuki, Y Sumida, EC Gabazza, S Murashima, H Urakawa, K Morioka, N Kitagawa, T Tanaka, R Araki-Sasaki, Y Hori, K Nakatani, Y Yano and Y Adachi
OBJECTIVE: To investigate the effect of acute hyperinsulinemia on the plasma levels of adrenomedullin (AM) in patients with type 2 diabetes mellitus. DESIGN: We measured the plasma levels of AM in 18 patients with type 2 diabetes mellitus and in 19 normal subjects before and during a euglycemic hyperinsulinemic clamp study (the goal was for blood sugar levels of 5.24 mmol/l and insulin levels of 1200 pmol/l). Both plasma AM and serum insulin were measured by immunoradiometric assays. RESULTS: Before the glucose clamp study there was no significant difference in the plasma levels of AM between patients with type 2 diabetes mellitus and normal subjects. During the glucose clamp study, the serum levels of insulin significantly increased (from 33.0+/-3.6 to 1344.6+/-67.8 pmol/ml, P<0.001), as did the plasma levels of AM (from 12.8+/-0.7 to 14.2+/-0.9 fmol/ml, P<0.03) only in patients with type 2 diabetes mellitus. There was a significant correlation between the change in circulating levels of insulin and AM (r=0.755, P<0.01). CONCLUSIONS: Acute hyperinsulinemia induced a significant increase in the plasma levels of AM in patients with type 2 diabetes mellitus. Increased insulin may regulate circulating levels of AM in patients with type 2 diabetes mellitus.
T Tanaka, K Nakatani, K Morioka, H Urakawa, N Maruyama, N Kitagawa, A Katsuki, R Araki-Sasaki, Y Hori, EC Gabazza, Y Yano, H Wada, T Nobori, Y Sumida and Y Adachi
OBJECTIVE: It is well known that nitric oxide synthase (NOS) is expressed and that it modulates glucose transport in skeletal muscles. Recent studies have shown that adipose tIssues also express inducible and endothelial nitric oxide synthase (eNOS). In the present study, we investigated whether nitric oxide (NO) induces glucose uptake in adipocytes, and the signaling pathway involved in the NO-stimulated glucose uptake in 3T3-L1 adipocytes. METHODS: First, we determined the expression of eNOS in 3T3-L1 adipocytes, and then these cells were treated with the NO donor sodium nitroprusside (SNP) and/or insulin, and glucose uptake and phosphorylation of insulin receptor substrate (IRS)-1 and Akt were evaluated. Moreover, we examined the effects of a NO scavenger, a guanylate cyclase inhibitor or dexamethasone on SNP-stimulated glucose uptake and GLUT4 translocation. RESULTS: SNP at a concentration of 50 mmol/l increased 2-deoxyglucose uptake (1.8-fold) without phosphorylation of IRS-1 and Akt. Treatment with the NO scavenger or guanylate cyclase inhibitor decreased SNP-stimulated glucose uptake to the basal level. Dexamethasone reduced both insulin- and SNP-stimulated glucose uptake with impairment of GLUT4 translocation. CONCLUSION: NO is capable of stimulating glucose transport through GLUT4 translocation in 3T3-L1 adipocytes, via a mechanism different from the insulin signaling pathway.