Min Jung Kwak

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (7)16.47 Total impact

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    ABSTRACT: The objective of this study was to characterize the effect of inhalable growth hormone (GH) delivered by an insufflator to the lungs of hypophysectomized Sprague Dawley rats. In the first cohort, the safety and efficacy of the insufflated GH were evaluated. Three experimental groups (n = 7 per group) were treated with GH for 15 d: One group received sc injection of GH daily at 200 microg/kg (SC200). Two other groups received GH by insufflation daily: 200 microg/kg (INS 200) and 600 microg/kg (INS 600). In the second set of experiments, GH was administered in three routes [SC200, INS200, intravenous (IV200)] (n=10) for 5 d, and escape latency and N-methyl D-aspartate (NMDA) receptor expression were evaluated. In the first cohort, INS200 showed similar bioactivity as SC200 in growth promotion, tibial growth, as well as escape latency on the 12th day of treatment. Insufflated GH was well tolerated without significant inflammatory responses. In the second cohort, expression of the NMDA receptor 1 and 2B in hippocampus measured after 3 or 6 d of daily treatments were significantly higher in INS200 as compared to IV200, consistent with the improvement of the escape latency. In summary, the inhalable form of GH delivered by intratracheal insufflation was safe, and its bioactivity was comparable to sc injection both in promotion of growth and acquisition of learning ability. If applied properly to human, inhalable GH would be effective for growth promotion and possibly for several disorders caused by underexpression of NMDA receptors.
    Endocrinology 09/2010; 151(9):4418-27. · 4.72 Impact Factor
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    ABSTRACT: Context: Prader-Willi syndrome (PWS), a genetic disorder characterized by obesity in early childhood, is reported to have elevated levels of adiponectin. The effects of adiponectin are mediated by adiponectin receptors (ADIPORs) that include ADIPOR1 and ADIPOR2. There is evidence that several cytokines, including adiponectin, TNF-alpha, and IL-6, are involved in insulin sensitivity. Objective and Methods: We measured the relative expression of adiponectin, ADIPORs, several proinflammatory cytokines including TNF-alpha, and IL-6 expression in peripheral blood mononuclear cells (PBMCs) of children with PWS and obese comparators using real-time PCR. Their correlation with homeostasis model assessment insulin resistance index (HOMA-IR) was analyzed. Patients: Thirty children with PWS (median age 7.1 yr, 18 males, 12 females) that were being treated with GH and 32 obese children not receiving GH treatment (median age 9.1 yr, 15 males, 17 females) for comparison were enrolled. Results: The PWS children had increased expression of ADIPOR2 (P = 0.02) and decreased expression of IL-6 (P = 0.03) compared with the comparison group. Moreover, there was a significant positive correlation between the ADIPORs and TNF-alpha (ADIPOR1 vs. TNF-alpha: r = 0.66, P < 0.001 in PWS, r = 0.80, P < 0.001 in comparison group; ADIPOR2 vs. TNF-alpha: r = 0.69, P < 0.001 in comparison group). The ADIPORs in the comparison group showed significant negative correlation with HOMA-IR (ADIPOR1 vs. HOMA-IR; rho = -0.41, P = 0.02, ADIPOR2 vs. HOMA-IR; rho = -0.46, P < 0.01). Conclusion: The results of this study showed that inflammatory cytokine expression was closely associated with the expression of the ADIPORs in the PBMCs of both the children with PWS and the comparison group. Moreover, ADIPOR2 expression was highly expressed in the PBMCs of the children with PWS. A further study on the mechanism of increased expression of ADIPOR2 and its correlation with the expression of TNF-alpha in the PBMCs using the non-GH-treated PWS and obese control will be warranted because this study compared GH-treated PWS with an obese comparator group.
    The Journal of clinical endocrinology and metabolism 03/2010; 95(3):1371-7. · 6.50 Impact Factor
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    ABSTRACT: Adiponectin, an adipose tissue-derived hormone, has been negatively related to obstructive sleep apnea syndrome. Besides sleep apnea, children with Prader-Willi syndrome (PWS) may have excessive daytime sleepiness and rapid eye movement (REM) sleep abnormality. The aim of this study is to determine whether changes in sleep structures are related to plasma adiponectin levels in PWS. Correlations between adiponectin level and sleep variables were analyzed in 28 children with PWS and 18 controls. Overnight polysomnography was performed. The fasting plasma adiponectin levels were higher in the children with PWS than in the controls (P = 0.0006). In the PWS, Epworth sleepiness scale was significantly higher (P = 0.002); sleep latency (P = 0.003) and REM latency (P = 0.001) were significantly shortened; the apnea-hypopnea index (AHI) was significantly increased (P = 0.0001); and the duration of non-rapid eye movement (NREM) sleep stages 3 and 4 was decreased (P = 0.005). Multiple regression analysis revealed correlations between the adiponectin level and the total sleep time (beta = 0.688, P = 0.009), AHI (beta = 1.274, P = 0.010), REM latency (beta = -0.637, P = 0.021) and the percentage of NREM sleep (beta = -7.648, P = 0.002) in PWS. In children with PWS, higher plasma adiponectin levels were independently associated with several sleep variables, which was not observed in the control group. These results suggest a potential influence of elevated adiponectin level on the sleep structures in PWS.
    Journal of Sleep Research 11/2009; 19(1 Pt 2):248-54. · 3.04 Impact Factor
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    ABSTRACT: This study was designed to examine the effects of recombinant human growth hormone replacement on somatic growth and cognitive function in hypophysectomized (HYPOX) female Sprague-Dawley rats. Rats (5 per group) were randomized by weight to 3 experimental groups: group 1, administered 200 microg/kg of GH once daily for 9 days; group 2, administered 200 microg/kg of GH twice daily; and group 3, administered saline daily. Somatic growth was evaluated by measurement of body weight daily and of the width of the proximal tibial growth plate of the HYPOX rats. Cognitive function was evaluated using the Morris water maze (MWM) test. The results indicated that GH replacement therapy in HYPOX rats promoted an increase in the body weight and the width of the tibial growth plate in a dose-dependent manner. On the third day of the MWM test, the escape latency in the GH-treated groups 1 and 2 was significantly shorter than that in the control rats (P<0.001 and P=0.032, respectively), suggesting that rhGH improved spatial memory acquisition in the MWM test. Therefore it is concluded that rhGH replacement therapy in HYPOX rats stimulates an increase in somatic growth in a dose-dependent manner and also has beneficial effects on cognitive functions.
    Journal of Korean medical science 08/2009; 24(4):729-36. · 0.84 Impact Factor
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    ABSTRACT: Ghrelin is a peptide hormone produced mainly in the stomach, and obestatin is derived by proteolytic cleavage of the ghrelin prepro-hormone. The aim of this study was to determine the postoperative serial changes in these hormones and whether hyperplasia of ghrelin-expressing cells occurs in the remnant stomach. We prospectively analyzed serial serum samples of 45 early gastric cancer patients and remnant stomach samples of 24 patients. The serum obestatin level on day 2 was lower than that on day 0, and it subsequently returned to the level observed on day 0. In contrast, the serum ghrelin level was lower on days 120 and 210 than on day 0. Eventually, the obestatin/ghrelin ratio was significantly high on day 210 (p = 0.0003). Moreover, we did not observe an increase in the number of ghrelin-expressing cells. The number of ghrelin-expressing cells correlated with the serum ghrelin level. The serum level of obestatin and ghrelin exhibits a different time course in patients who have undergone gastrectomy, and there was no ghrelin-expressing cell hyperplasia in the remnant stomach despite the decrease in serum ghrelin.
    Digestive surgery 04/2009; 26(2):143-8. · 1.37 Impact Factor
  • Source
    Korean Journal of Pediatrics 01/2008; 51(7).
  • Journal of the Korean Society of Pediatric Nephrology 01/2007; 11(1).