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- Karefylakis, Christos, 1982-
(författare)
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Vitamin D and its role in obesity and other associated conditions
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vitamin D has received much attention in recent years due to the re-emergence of vitamin D deficiency as a global health issue along with increasing evidence indicating that 1,25-dihydroxivitamin D, the hormonally active form of vita-min D, not only acts in calcium and bone metabolism but also generates ex-traskeletal biological responses.In this thesis, the role of vitamin D in obesity and other associated condi-tions has been studied.In paper 1, the prevalence of vitamin D deficiency and secondary hyperpara-thyroidism over the long term after Roux-en-Y gastric bypass (RYGB) were evaluated. We found a substantial prevalence of vitamin D deficiency and secondary hyperparathyroidism after RYGB, whereas calcium levels remained within normal range. An expected improvement in vitamin D status after weight loss could have been countered by the malabsorption induced by surgery.In paper 2, the prevalence of anemia and related deficiencies over the long term after RYGB were studied. We found that 27% of the patients had anemia postoperatively, 20% had iron deficiency, 12% had folate deficiency and 2% had vitamin B12 deficiency. Anemia was mainly due to iron deficiency, and its frequency did not seem to progress with time after surgery.In paper 3, the effects of vitamin D supplementation on body composition and cardiorespiratory fitness in overweight men with vitamin D deficiency at baseline were investigated. No statistically significant difference between the placebo and the intervention group regarding changes in percentage body fat, maximum oxygen uptake, BMI and maximum load was found.In paper 4, the prevalence and determinants of 3-epi-25(OH)D3 were exam-ined. 3-epi-25(OH)D3 was detected in 7.7% of the study population and the mean concentration was 8.4 nmol/L. The quantification of 3-epi-25(OH)D3 would not significantly influence the clinical interpretation of vitamin D levels.In conclusion, new knowledge about vitamin D is continuously emerging but there is a discrepancy between cross-sectional studies associating low vitamin D levels to obesity and other related metabolic complications and the lack of effects of vitamin D supplementation in clinical trials. Large RCTs with longer duration in obese subjects with baseline vitamin D deficiency are warranted.
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- Rodanaki, Maria, 1987-, et al.
(författare)
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Adding a protease inhibitor to sampling tubes increases the acylated ghrelin and decreases the desacylated ghrelin levels in girls
- 2021
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Ingår i: Hormone Research in Paediatrics. - : S. Karger. - 1663-2818 .- 1663-2826. ; 94:Suppl. 1, s. 111-112
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Ghrelin is a growth hormone-releasing acylated peptide stimulating the appetite, mainly produced in the stomach, and with an important role in pubertal development (1). Two ghrelin forms have been described, acylated (AG) and desacylated (DAG), but it is debated whether DAG is an active hormone or a degradation product of AG (2). Our aim was to evaluate the effects of adding the protease inhibitor 4-(2-aminoethyl) benzenesufonyl fluoride hydrochloride (AEBSF) to sampling tubes and acidification of plasma on levels of AG and DAG in girls with suspected central precocious puberty (CPP).Methods: 13 girls aged 6.6 to 10.1 years with suspected CPP undergoing a gonadotropin-releasing hormone stimulation test during 2015-2017 at the Departments of Paediatrics, at Örebro or Uppsala University Hospital were included. Blood samples were collected at 0 min in precooled EDTA tubes with or without AEBSF at a final concentration of 2mg/ml. After cold centrifugation, HCl at a final concentration of 50 μmol/l, was added to 50% of the plasma tubes containing AEBSF. The AG and DAG concentrations were measured by ELISA kits. Comparison was performed using one-way ANOVA for repeated measurements.Results: The mean plasma AG levels were significantly higher after the addition of AEBSF only (650.9 +/- 257.1 pg/ml) or AEBSF+HCl (681.2 +/- 299 pg/ml) compared to the concentrations without additives (247.6 +/- 123.4 pg/ml, p<0.01 for both comparisons). There was no significant difference between the AG levels after AEBSF and AEBSF+HCl addition. The plasma levels of DAG were significantly lower after the addition of AEBSF+HCl (69.3 +/- 30.6 pg/ml) and even further lowered after the addition of AEBSF only (56.3+/- 30.9 pg/ml) compared to the concentrations of DAG in tubes without any additives (149.9 +/- 73.7 pg/ml, p < 0.01 for both comparisons).Discussion: Due to the unstable nature of AG, special procedures are required for accurate measurement of its plasma levels in children, including the use of a protease inhibitor like AEBSF. However, DAG was still measurable indicating that it may not only be a degradation product of AG. 1. Kojima M, Kangawa K. Ghrelin: structure and function. Physiol Rev. 2005;85(2):495-522.2. Blatnik M, Soderstrom CI, Dysinger M, Fraser SA. Prandial ghrelin attenuation provides evidence that des-acyl ghrelin may be an artifact of sample handling in human plasma. Bio-analysis. 2012;4(20):2447-55.
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- Rodanaki, Maria, 1987-, et al.
(författare)
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The effect of a GnRH analogue injection on the circulating levels of kisspeptin-1 in girls with suspected central precocious puberty
- 2022
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Ingår i: Hormone Research in Paediatrics. - : S. Karger. - 1663-2818 .- 1663-2826. ; 95:Suppl. 2, s. 341-341
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Kisspeptin stimulates the gonadotropin releasing hormone (GnRH) neurons in hypothalamus initiating puberty. However, it is not known whether GnRH inhibits kisspeptin secretion by negative feedback and whether there are any associations between circulating levels of kisspeptin and other hormones, like ghrelin, important for the onset of puberty.Methods: Thirteen girls with suspected central precocious puberty performed an adjusted GnRH stimulation test twice, placebo-controlled in a randomized order, at Örebro or Uppsala University Hospital, Sweden. Blood was sampled 0, 30, 60, 90, 120 and 150 min after the iv injection of either Relefact LHRH® or saline. The protease inhibitor 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) was added to the sampling tubes to a final concentration of 2 mg/ml. An ELISA kit from LifeSpan BioSciences, Inc. (No LS-F8231) was used for the analyses of Kisspeptin-1 levels. The levels of acylated ghrelin were analyzed with Millipore® Human Ghrelin (Active) ELISA kit (#EZGRA-88K). Serum ultrasensitive estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin and glucose levels were analyzed using the usual clinical methods.Results: The median Kisspeptin-1 level at baseline was 39 pg/ml (min–max: 0.1–221.3 pg/ml). The area-under-the curve for Kisspeptin-1 levels was not significantly lower after the GnRH injection as compared to the placebo injection. We did not find any significant correlations between the levels of kisspeptin-1 and acylated ghrelin, estradiol, LH, FSH, or insulin. However, we could see a positive correlation between kisspeptin-1 and glucose levels at baseline (Spearman’s rank test, rho = 0.63, p=0.021).Discussion: We did not find evidence of a negative feedback mechanism between GnRH and kisspeptin in girls with suspected central precocious puberty since the circulating levels of kisspeptin-1 were unaffected by an intravenous injection of a GnRH analogue. However, paracrine actions in the hypothalamus cannot be ruled out by this study. The positive correlation found between kisspeptin-1 and glucose levels is in accordance with previous findings in both adults and children, suggesting a possible role for kisspeptin signaling in glucose metabolism.
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