Delayed β-cell response and glucose intolerance in young women with Turner syndrome

<p>Abstract</p> <p>Background</p> <p>To investigate glucose homeostasis in detail in Turner syndrome (TS), where impaired glucose tolerance (IGT) and type 2 diabetes are frequent.</p> <p>Methods</p> <p>Cross sectional study of women with Turner syndrome (TS)(n = 13) and age and body mass index matched controls (C) (n = 13), evaluated by glucose tolerance (oral and intravenous glucose tolerance test (OGTT and IVGTT)), insulin sensitivity (hyperinsulinemic, euglycemic clamp), beta-cell function (hyperglycaemic clamp, arginine and GLP-1 stimulation) and insulin pulsatility.</p> <p>Results</p> <p>Fasting glucose and insulin levels were similar. Higher glucose responses was seen in TS during OGTT and IVGTT, persisting after correction for body weight or muscle mass, while insulin responses were similar in TS and C, despite the higher glucose level in TS, leading to an insufficient increase in insulin response during dynamic testing. Insulin sensitivity was comparable in the two groups (TS vs. control: 8.6 ± 1.8 vs. 8.9 ± 1.8 mg/kg*30 min; p = 0.6), and the insulin responses to dynamic β-cell function tests were similar. Insulin secretion patterns examined by deconvolution analysis, approximate entropy, spectral analysis and autocorrelation analysis were similar. In addition we found low IGF-I, higher levels of cortisol and norepinephrine and an increased waist-hip ratio in TS.</p> <p>Conclusions</p> <p>Young normal weight TS women show significant glucose intolerance in spite of normal insulin secretion during hyperglycaemic clamping and normal insulin sensitivity. We recommend regularly testing for diabetes in TS.</p> <p>Trial Registration</p> <p>Registered with <url>http://clinicaltrials.com</url>, ID nr: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00419107">NCT00419107</a></p

Catalytic activity and stability of laccase entrapped in sol-gel silica with additives

This study investigated the effects of different additives and precursors on the catalytic activity of laccase entrapped in sol-gel silica. It was found that the laccase catalytic activity and stability of sol-gel laccase could be enhanced if the entrapment was performed in the presence of additives such as PVA, PEG and APTS. The use of TEOS as a precursor showed slightly higher laccase catalytic activity compared to TMOS. The PVA as an additive showed a better catalytic activity enhancement compared to the PEG and APTMS with the optimum PVA concentration of 0.03 mg/mL. The optimal temperatures of sol-gel laccase without and with additives were found to be at 40 and 27°C, respectively. After 70 days of storage at 27°C, the catalytic activity of the immobilized sol-gel laccase with additives maintained its catalytic activity compared to only 30% of its original catalytic activity for the sol-gel laccase without additives

Effects of prolonged fasting and sustained lipolysis on insulin secretion and insulin sensitivity in normal subjects

Normal β-cells adjust their function to compensate for any decrease in insulin sensitivity. Our aim was to explore whether a prolonged fast would allow a study of the effects of changes in circulating free fatty acid (FFA) levels on insulin secretion and insulin sensitivity and whether any potential effects could be reversed by the antilipolytic agent acipimox. Fourteen (8 female, 6 male) healthy young adults (aged 22.8–26.9 yr) without a family history of diabetes and a body mass index of 22.6 ± 3.2 kg/m2 were studied on three occasions in random order. Growth hormone and FFA levels were regularly measured overnight (2200-0759), and subjects underwent an intravenous glucose tolerance test in the morning (0800-1100) on each visit. Treatment A was an overnight fast, treatment B was a 24-h fast with regular administrations of a placebo, and treatment C was a 24-h fast with regular ingestions of 250 mg of acipimox. The 24-h fast increased overnight FFA levels (as measured by the area under the curve) 2.8-fold [51.3 (45.6–56.9) vs. 18.4 (14.4–22.5) *104 μmol/l*min, P < 0.0001], and it led to decreases in insulin sensitivity [5.7 (3.6–8.9) vs. 2.6 (1.3–4.7) *10−4 min−1 per mU/l, P < 0.0001] and the acute insulin response [16.3 (10.9–21.6) vs. 12.7 (8.7–16.6) *102 pmol/l*min, P = 0.02], and therefore a reduction in the disposition index [93.1 (64.8–121.4) vs. 35.5 (21.6–49.4) *102 pmol/mU, P < 0.0001]. Administration of acipimox during the 24-h fast lowered FFA levels by an average of 20% (range: −62 to +49%; P = 0.03), resulting in a mean increase in the disposition index of 31% (P = 0.03). In conclusion, the 24-h fast was accompanied by substantial increases in fasting FFA levels and induced reductions in the acute glucose-simulated insulin response and insulin sensitivity. The use of acipimox during the prolonged fast increased the disposition index, suggesting a partial reversal of the effects of fasting on the acute insulin response and insulin sensitivity