Browsing by Author "Malin, Steven K."

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    Glucose-stimulated oxidative stress in mononuclear cells is related to pancreatic β-cell dysfunction in polycystic ovary syndrome
    (The Endocrine Society, 2014-01) Malin, Steven K.; Kirwan, John P.; Sia, Chang Ling; González, Frank; Department of Obstetrics and Gynecology, IU School of Medicine
    CONTEXT: Oxidative stress induced by reactive oxygen species (ROS) is involved in the development of pancreatic β-cell dysfunction. OBJECTIVE: We determined the relationship between mononuclear cell (MNC)-derived ROS generation and p47phox protein content in response to glucose ingestion and β-cell function in women with polycystic ovary syndrome (PCOS). DESIGN: This was a cross-sectional study. SETTING: This study was conducted at an academic medical center. PARTICIPANTS: Twenty-nine normoglycemic women with PCOS (13 lean, 16 obese) and 25 ovulatory controls (16 lean, 9 obese) underwent a 3-h 75-g oral glucose tolerance test (OGTT). MAIN OUTCOME VARIABLES: Pancreatic β-cell function was calculated as glucose-stimulated insulin secretion (insulin/glucose area under the curve0-30 min; GSIS)×Matsuda index-derived insulin sensitivity (ISOGTT). ROS generation was measured by chemiluminescence, and p47phox protein was quantified by Western blotting in MNC isolated from blood samples obtained at 0 and 2 hours of the OGTT. RESULTS: Compared with controls, women with PCOS exhibited a higher percent change from baseline in ROS generation and p47phox protein in conjunction with greater GSIS and a tendency toward lower β-cell function. Lean women with PCOS exhibited a greater percent change from baseline in ROS generation and p47phox protein yet had similar GSIS responses compared with lean controls despite having lower ISOGTT. For the combined groups, β-cell function was inversely related to ROS generation and p47phox protein. GSIS was directly related to body mass index, central obesity, and circulating androgens. CONCLUSION: In normoglycemic women, obesity plays a role in exaggerating GSIS. However, MNC-derived oxidative stress is independent of obesity and may contribute to the decline in β-cell function in women with PCOS.
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    Pancreatic β-cell dysfunction in polycystic ovary syndrome: role of hyperglycemia-induced nuclear factor-κB activation and systemic inflammation
    (American Physiological Society, 2015-05) Malin, Steven K.; Kirwan, John P.; Sia, Chang Ling; Gonzalez, Frank; Department of Obstetrics and Gynecology, IU School of Medicine
    In polycystic ovary syndrome (PCOS), oxidative stress is implicated in the development of β-cell dysfunction. However, the role of mononuclear cell (MNC)-derived inflammation in this process is unclear. We determined the relationship between β-cell function and MNC-derived nuclear factor-κB (NF-κB) activation and tumor necrosis factor-α (TNF-α) secretion in response to a 2-h 75-g oral glucose tolerance test (OGTT) in normoglycemic women with PCOS (15 lean, 15 obese) and controls (16 lean, 14 obese). First- and second-phase β-cell function was calculated as glucose-stimulated insulin secretion (insulin/glucose area under the curve for 0-30 and 60-120 min, respectively) × insulin sensitivity (Matsuda Index derived from the OGTT). Glucose-stimulated NF-κB activation and TNF-α secretion from MNC, and fasting plasma thiobarbituric acid-reactive substances (TBARS) and high-sensitivity C-reactive protein (hs-CRP) were also assessed. In obese women with PCOS, first- and second-phase β-cell function was lower compared with lean and obese controls. Compared with lean controls, women with PCOS had greater change from baseline in NF-κB activation and TNF-α secretion, and higher plasma TBARS. β-Cell function was inversely related to NF-κB activation (1st and 2nd) and TNF-α secretion (1st), and plasma TBARS and hs-CRP (1st and 2nd). First- and second-phase β-cell function also remained independently linked to NF-κB activation after adjustment for body fat percentage and TBARS. In conclusion, β-cell dysfunction in PCOS is linked to hyperglycemia-induced NF-κB activation from MNC and systemic inflammation. These data suggest that in PCOS, inflammation may play a role in impairing insulin secretion before the development of overt hyperglycemia.