Koh Yamashita

The role of hinge domain in heterodimerization and specific DNA recognition by nuclear receptors.

Four structural domains are characteristic of the members of the nuclear receptor superfamily. The hinge (D) domain which is located between the DNA binding (C) domain and the ligand binding (EF) domain, is less conserved among the nuclear receptors. In this study, we investigated the effects of the D domain on receptor function with regard to ligand binding, protein-protein interaction and DNA recognition. We found that EF domain of TR lacked T3 binding activity and additional D domain was required for its ligand binding. Using pull down assays and two-hybrid assays, we also demonstrated that the EF domain of TR did not dimerize with TR or RXR in solution, while the DEF domain was able to homo-and heterodimerize with RXR. In contrast, the RXR EF domain alone was able to heterodimerize with TR. The D domain of TR is required but that of RXR is not necessary for the interaction. We further demonstrated that the D domain was required for receptor specific DNA recognition. The ABC domain of vitamin D receptor (VDR) and TR(DEF) chimeric receptor could not bind to VDR response element (VDRE). Addition of own D domain of VDR to the ABC domain enables the chimeric receptor to bind VDRE and transactivate. The D domain of TR cannot substitute for that of VDR in context of specific DNA recognition. These data suggest that the D domain is important to maintain the integrity of the functional structure of the nuclear receptors.

A kindred with Cockayne syndrome caused by multiple splicing variants of the CSA gene.

Cockayne syndrome (CS) is an autosomal recessive disorder, which is associated with abnormal UV hypersensitivity, growth retardation, and psycho‐neural abnormalities. Recently, CSA protein was found to be associated with CS. We obtained mRNAs from immortal lymphoblasts derived from members of the kindred, and sequenced the CSA gene of all family members after reverse transcription (RT) of the coding region. The intact length of the CSA transcript was found in all family members except the proband with CS. Multiple abnormal splicing variant forms were revealed in all cases. No mutation was found in the sequences of the splice donor and acceptor sites of each exon in the CSA gene. UVA irradiation suppressed cell growth in the proband. There was no significant alteration of UVA sensitivity among the normal control and the family members except for the proband. These data suggest that multiple splicing variant forms of CSA mRNA, in the absence of the full‐length form of the mRNA, are associated with CS.

RS3PE in Association With Dipeptidyl Peptidase-4 Inhibitor: Report of Two Cases

Remitting seronegative symmetrical synovitis with pitting edema (RS3PE), first described by McCarty (1), is characterized by symmetrical pitting edema of the hands and feet; tenderness, swelling, and/or limited motion of the joints; fatigue; and fever (1,2). It commonly occurs in elderly people (1,2). We have recently encountered two cases of RS3PE that developed shortly after the initiation of a dipeptidyl peptidase-4 (DPP4) inhibitor and resolved markedly upon cessation of it. Case 1 was a 74-year-old woman with a 30-year history of type 2 diabetes who presented with edema of the hands, low grade fever, and malaise, which developed 5 weeks after switching from 20 mg gliclazide to 50 mg sitagliptin. Physical examination revealed severe pitting edema …

The Retinoic Acid-responsive Proline-rich Protein Is Identified in Promyeloleukemic HL-60 Cells

To identify new genes that retinoic acid activates, we employed an mRNA differential display technique and screened for genes that are differentially expressed in promyeloleukemic HL-60 cells incubated in the presence of all-trans-retinoic acid (ATRA) compared with the absence of ATRA. We cloned the coding region of a retinoic acid-induced gene from a human thymus library, which was the mRNA encoding the 666-amino acid human homologue of mouse proline-rich protein 76. We have designated it RARP1 (retinoic acid response proline-rich protein 1). Transcription of an ∼2.4-kbp mRNA occurred mainly in organs with immune functions, such as thymus, spleen, and peripheral leukocytes. Cycloheximide blocked the ATRA-induced expression. In megakaryocyte-like human erythroleukemia HEL cells, the amount of RARP1 mRNA was high, but it was low in human T-lymphoblastoid Jurkat cells. A specific antibody against RARP1 recognized a 110-kDa protein, which accumulates after incubation of HL-60 cells with ATRA. In immunohistochemical experiments, strong RARP1 staining was observed in the megakaryocytes of bone marrow and spleen, and heterogeneous stain was seen in thymus. Transcriptional studies showed that RARP1 expression impaired the transactivation through activator protein1 and serum responseelement in all cell lines we checked, whereas it did not affect the transactivation through cAMP-response element in the same cell lines. Further analysis demonstrated that proline-rich regions of RARP1 are the functional regions regulated for suppression of activator protein1 transactivation. These data suggest that ATRA-inducible RARP1 selectively affects signal transduction and may contribute to myeloid and megakaryocytic differentiation.

Characterization of Two Novel Retinoic Acid‐resistant Cell Lines Derived from HL‐60 Cells Following Long‐term Culture with all‐trans‐Retinoic Acid

Either all‐trans‐retinoic acid (RA) or vitamin D3 (VD) induces differentiation of the myeloid leukemia cell line HL‐60. RA is available for the treatment of acute promyeloleukemia, although the development of resistance to the agent is a serious problem for differentiation‐inducing therapy. To approach the mechanisms of resistance to RA, we developed two novel cell lines, HL‐60–R2 and R9, which were subcloned after exposure to increasing concentrations of RA. The growth rate of HL‐60–R2 cells was significantly increased by RA treatment, whereas the growth rate of HL‐60–R9 was not affected. RA induces apoptosis in the parental HL‐60 cells. The number of apoptotic cells, however, was not increased and nitroblue tetrazolium (NBT) reduction was not altered by 1 μM RA in either of the cloned cell lines. Treatment with VD induced monocytic differentiation and increased the expression of CD11b in HL‐60 and HL‐60–R9 cells, but not in HL‐60–R2 cells. Flow cytometric and G‐banding analysis demonstrated that R2 cells were near‐triploid. The sequencing analysis revealed a deletion of three nucleotides in the sequence of the RARα gene in HL‐60–R9 cells, resulting in deletion of codon 286. No mutation was found in HL‐60–R2 cells. Taken together, these data indicate that the resistance to RA is caused by the mutation in RARα of HL‐60–R9, but by other factor(s), which also affect the VD‐response pathways, in HL‐60–R2. The abnormal response to VD may be associated with the abnormal ploidy of the R2 cells.

Metabolic syndrome and age-related dementia: Endocrinological aspects of adaptation to aging

Metabolic syndrome is one of the determinants of lifespan in Japan. In order to prevent the acute vascular events, intervention is recommended. However, management of patients with this syndrome increased the number of patients with cognition decline and depressive state. Endocrinological studies with human and experimental animals showed that there is a negative relationship between progression of metabolic syndrome and occurrence of mental disorders. In this review, we summarize our clinical and experimental data, and discuss on the mechanism of the metabolic syndrome prevention of progression of age-related mental disorder.

Fulminant type 1 diabetes with robust recovery of insulin secretion: A case report

In fulminant type 1 diabetes (FT1D), irreversible destruction of pancreatic beta-cells occurs abruptly, leading to sudden diabetic ketoacidosis (DKA) in the absence of diabetes-related autoantibodies. This is the first case report of FT1D in which beta-cell was rescued with the commencement of insulin therapy during the evolution of FT1D.

Type 2 Diabetes: When Does It Start?

Abstract Objective We aimed to clarify the onset of diabetes. Design Data from 27,392 nondiabetic health examinees were retrospectively analyzed for a mean of 5.3 years. Trajectories of fasting plasma glucose (FPG), body mass index (BMI), and the single point insulin sensitivity (Si) estimator (SPISE), an index of Si, 10 years before diagnosis of prediabetes (PDM; n = 4781) or diabetes (n = 1061) were separately assessed by a mixed effects model. Diabetes and PDM were diagnosed by the American Diabetes Association definition on the basis of FPG and glycosylated hemoglobin A1c values. Results In individuals who developed diabetes, mean FPG and BMI were significantly higher (P < 0.01 each) and SPISE lower than those who did not at −10 years: FPG 101.5 mg/dL vs 94.5 mg/dL, BMI 24.0 kg/m2 vs 22.7 kg/m2, and SPISE 7.32 vs 8.34, P < 0.01 each. These measurements, in subjects who developed prediabetes, were slightly but definitely different from those who did not, already at −10 years: FPG 91.8 mg/dL vs 89.6 mg/dL, BMI 22.6 kg/m2 vs 22.1 kg/m2, and SPISE 8.44 vs 8.82, P < 0.01 each. In both cases, the differences were progressively greater toward year 0, the time of diabetes, or PDM diagnosis. Conclusions FPG was significantly elevated in those who developed diabetes at least 10 years before diagnosis of diabetes, and this was also the case in those who developed PDM. Glucose dysregulation precedes diagnosis of diabetes at least for 20 years.

Postchallenge hyperglycemia in subjects with low body weight: implication for small glucose volume

A hypothesis that postchallenge hyperglycemia in subjects with low body weight (BW) may be due, in part, to small glucose volume (GV) was tested. We studied 11,411 nondiabetic subjects with a mean BW of 63.3 kg; 5,282 of them were followed for a mean of 5.3 yr. In another group of 1,537 nondiabetic subjects, insulin sensitivity, secretion, and a product of the two (index of whole body insulin action) were determined. Corrected 2 h-plasma glucose (2hPGcorr) during a 75-g oral glucose tolerance test in subjects with BW ≤ 59 kg was calculated as 2hPGcorr = δPG2h · ECW/[16.1 (males) or 15.3 (females)] + fasting PG (FPG), where δPG2h is plasma glucose increment in 2 h; ECW is extracellular water (surrogate of GV); FPG is fasting plasma glucose; and 16.1 and 15.3 are ECW of men and women, respectively, with BW = 59 kg. Multivariate analyses for BW with adjustment for age, sex, and percent body fat were undertaken. BW was, across its entire range, positively correlated with FPG (P < 0.01). Whereas BW was correlated with 2hPG and δPG in a skewed J-shape, with inflections at around 60 kg (P for nonlinearity < 0.01 for each). Nonetheless, in those with BW ≤ 59 kg, insulin sensitivity, secretion, and action were unattenuated, and incident diabetes was less compared with heavier counterparts. BW was linearly correlated with 2hPGcorr, i.e., the J-shape correlation was mitigated by the correction. In conclusion, postchallenge hyperglycemia in low BW subjects is in part due to small GV rather than impaired glucose metabolism.

Marked improvement of insulin sensitivity without enhancement of GLP-1 and insulin secretion after Roux-en-Y gastric bypass surgery in a mildly obese patient with diabetes.

Roux-en-Y gastric bypass is an option of treatment for morbidly obese patients with diabetes. However, the value of the operation in mildly obese patients is not established. We report the first prospective systematic endocrine and metabolic analysis in a mildly obese patient who underwent a Roux-en-Y gastric bypass. In a 49-year-old man with BMI 32.6 kg/m(2) having type 2 diabetes, intramucosal gastric cancer was treated by partial gastrectomy with Roux-en-Y gastric bypass. Pre-operatively, he received 53 U/day insulin and the HbA1c value was 63 mmol/mol: meal tolerance test showed diabetic hyperglycemia and low insulin sensitivity with attenuated insulin secretion and normal glucagon-like peptide 1(7-36) secretion. After the operation, hypoglycemic agent was stopped. Body weight reduced from 84.0 to 77.0 kg within 2 weeks and increased thereafter to 79.4 kg at 4 months later, when the degree of hyperglycemia was unchanged as indexed by a HbA1c value of 62 mmol/mol. Upon repeated meal tolerance test, no increase of glucagon-like peptide 1 and insulin secretion, but significantly improved hepatic and peripheral insulin sensitivity were found, compared to the preoperative meal tolerance test. Marked dissociation of endocrine and metabolic effects of Roux-en-Y gastric bypass, that is, absence of increased glucagon-like peptide 1/insulin secretion with improvement of insulin sensitivity, was found in a mildly obese patient with type 2 diabetes.