Hiroyuki Koshiyama

Publications (135) View all

• Article: Improvement of Insulin Resistance Following Transsphenoidal Surgery in Patients with Acromegaly: Correlation with Serum IGF-1 Levels.

  K Mori, Y Iwasaki, Y Kawasaki-Ogita, S Honjo, Y Hamamoto, H Tatsuoka, K Fujimoto, H Ikeda, Y Wada, Y Takahashi, J Takahashi, H Koshiyama
  [show abstract] [hide abstract]
  ABSTRACT: Aim: The aim of this study was to determine the correlation between the growth hormone (GH)-insulin-like growth factor-1 (IGF-1) axis and glucose intolerance in acromegaly during the early postoperative period. Subjects and Methods: The study included 20 patients with acromegaly caused by GH-secreting pituitary adenoma who received transsphenoidal surgery in our hospital. Glucose tolerance was evaluated with oral glucose tolerance tests (OGTTs) performed pre- and early postoperative periods (9 [7-18] days after surgery). Homeostasis model assessment of insulin resistance (HOMA-R) and insulinogenic index (IGI) were calculated, and correlation analyses were performed between these values and the GH- IGF-1 axis. Patients were divided according to postoperative changes of the axis, and glucose tolerance was compared between the groups. Results: In preoperative OGTTs, nine patients had impaired glucose tolerance and two had diabetes mellitus patterns. Postoperatively, significant reduction was observed both in fasting plasma glucose levels (p < 0.01) and in HOMA-R (p < 0.01), whereas IGI showed no significant change. HOMA-R was significantly correlated with serum IGF-1 levels both before (r = 0.83, p < 0.01) and after (r = 0.57, p < 0.01) surgery, although it was not correlated with serum GH levels. Patients who achieved more than 50% postoperative reduction in serum IGF-1 levels showed significant improvement in OGTTs results (p < 0.05). Conclusions: In patients with acromegaly, serum IGF-1 levels, but not GH levels, were significantly correlated with insulin resistance. Early postoperative improvement of glucose tolerance is observed in patients who achieved postoperative reduction in serum IGF-1 levels.
  Journal of endocrinological investigation 05/2013; · 1.57 Impact Factor
• Article: Species-Specific Actions of Incretin: From the Evolutionary Perspective

  Kawasaki Yukiko, Hamamoto Yoshiyuki, Koshiyama Hiroyuki
  Japanese Clinical Medicine. 01/2010;
• Article: Seasonal variations of urinary albumin creatinine ratio in Japanese subjects with Type 2 diabetes and early nephropathy.

  Y Wada, Y Hamamoto, H Ikeda, S Honjo, Y Kawasaki, K Mori, H Koshiyama
  [show abstract] [hide abstract]
  ABSTRACT: It has been recognized that blood pressure shows a seasonal variation, but it remains unknown whether diabetic nephropathy shows a seasonal variation. In the present study, we investigated the change in urinary albumin/creatinine ratio in relation to the season in Japanese patients with Type 2 diabetes. A total of 430 subjects (275 male, 155 female) with Type 2 diabetes and early nephropathy (defined by UACR 30-300 mg/g creatinine) were included. One year was divided into four seasons and each season was defined as winter (December-February), spring (March-May), summer (June-August), and fall (September-November), and systolic and diastolic blood pressure, serum creatinine levels, and the urinary albumin/creatinine ratio were examined. The estimated glomerular filtration rate was also calculated and evaluated. The mean age (± SE) was 64.8 ± 0.8 years. The mean systolic blood pressure was significantly higher in winter than in summer (136 ± 0.68 vs. 133 ± 0.68 mmHg, P < 0.001). The urinary albumin/creatinine ratio showed a significantly higher value in winter than in summer (72.8 ± 4.4 vs. 54.6 ± 3.4 mg/g creatinine, P < 0.001). The curve of seasonal variation of this ratio showed a similar change to that of systolic blood pressure. No significant seasonal variation was observed in estimated glomerular filtration rate and diastolic blood pressure. Our results suggest that there is a hitherto unknown seasonal variation in the urinary albumin/creatinine ratio, and that it may be necessary to consider this seasonal change, especially when performing an intervention study of nephropathy.
  Diabetic Medicine 10/2011; 29(4):506-8. · 2.90 Impact Factor
• Article: Diabetes Mellitus as Dysfunction of Interactions Among all Organs: “Ominous Orchestra of Organs”

  Koshiyama Hiroyuki, Ogawa Yoshihiro, Tanaka Kiyoshi, Tanaka Issei
  [show abstract] [hide abstract]
  ABSTRACT: Epidemiological evidence has established a link among hyperlipidemia, visceral obesity, osteoporosis, and cardiovascular diseases. We have recently proposed a hypothesis that the associations of those disorders are based on interactions of the three organs, i.e. the bone, adipose, and vascular tissues, possibly through multiple actions of several humoral factors and/or transcription factors. We call this unified hypothesis ‘osteo-lipo-vascular interactions’, which may be explained by the common origin of the cells in each organ, such as mesenchymal stem cells or macrophages. Several groups proposed similar hypotheses. On the other hand, there have been accumulating evidences which indicate that there exist hitherto unknown various interactions between many organs, such as hypothalamus-liver, fat-liver, liver-muscle, intestine-pancreas, kidney-heart and so on. Therefore, it seems insufficient to consider only the interactions among several organs, and the standpoint of considering interactions among all organs may be warranted, especially in order to understand the pathogenesis of metabolic syndrome, insulin resistance and type 2 diabetes. We here propose a hypothesis that the abnormal interactions of all organs (“Ominous Orchestra of Organs”) underlies the pathogenesis of type 2 diabetes. It is to be elucidated which of the “players” or the “conductor” may be mainly responsible for disharmony of the orchestra.
  Clinical Medicine : Endocrinology and Diabetes. 01/2008;
• Article: Which should we ADOPT: sulphonylureas or glitazones?

  H Koshiyama, N Inagaki, Y Seino
  Diabetic Medicine 08/2007; 24(7):804. · 2.90 Impact Factor