| 1. |
- Persson, Anders I., 1973, et al.
(författare)
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Expression of delta opioid receptor mRNA and protein in the rat cerebral cortex and cerebellum is decreased by growth hormone.
- 2003
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Ingår i: Journal of neuroscience research. - : Wiley. - 0360-4012 .- 1097-4547. ; 71:4, s. 496-503
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Tidskriftsartikel (refereegranskat)abstract
- Hormones released from the pituitary have been shown to regulate the expression of different proteins in the central nervous system. We wanted to examine whether peripheral administration of bovine growth hormone (bGH) regulates the expression of delta-opioid receptor (DOR) in the cerebral cortex and cerebellum. Expression of the DOR protein was quantified using Western blot densitometry. DOR mRNA was quantified with a solution hybridization RNase protection assay. Hypophysectomized (Hx) and untreated normal female rats were included in the study. All Hx rats were hormonally treated with cortisol (400 microg/kg/day) and L-thyroxine (10 microg/kg/day) for 19 days. Hypophysectomy resulted in a threefold increase in cerebral cortex and a twofold increase in cerebellum of the DOR protein compared with normal rats. One subgroup of Hx rats received bGH (1 mg/kg body weight) as a daily subcutaneous injection for 19 days. This treatment normalized the levels of DOR protein in the cerebral cortex and cerebellum. Immunohistochemical experiments showed that GH decreased DOR expression especially in layers II-VI in cerebral cortex and in stratum moleculare in cerebellum. Quantification of DOR mRNA by solution hybridization RNase protection assay corresponded to the DOR protein measurements. We conclude that the expression of DORs in cerebral cortex and cerebellum is regulated by GH.
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| 2. |
- Frick, Anna, 1982, et al.
(författare)
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X-ray structure of human aquaporin 2 and its implications for nephrogenic diabetes insipidus and trafficking.
- 2014
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:17, s. 6305-10
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Tidskriftsartikel (refereegranskat)abstract
- Human aquaporin 2 (AQP2) is a water channel found in the kidney collecting duct, where it plays a key role in concentrating urine. Water reabsorption is regulated by AQP2 trafficking between intracellular storage vesicles and the apical membrane. This process is tightly controlled by the pituitary hormone arginine vasopressin and defective trafficking results in nephrogenic diabetes insipidus (NDI). Here we present the X-ray structure of human AQP2 at 2.75 Å resolution. The C terminus of AQP2 displays multiple conformations with the C-terminal α-helix of one protomer interacting with the cytoplasmic surface of a symmetry-related AQP2 molecule, suggesting potential protein-protein interactions involved in cellular sorting of AQP2. Two Cd(2+)-ion binding sites are observed within the AQP2 tetramer, inducing a rearrangement of loop D, which facilitates this interaction. The locations of several NDI-causing mutations can be observed in the AQP2 structure, primarily situated within transmembrane domains and the majority of which cause misfolding and ER retention. These observations provide a framework for understanding why mutations in AQP2 cause NDI as well as structural insights into AQP2 interactions that may govern its trafficking.
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| 3. |
- Frick, Fredrik, 1973, et al.
(författare)
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Different effects of IGF-I on insulin-stimulated glucose uptake in adipose tissue and skeletal muscle.
- 2000
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Ingår i: American journal of physiology. Endocrinology and metabolism. - 0193-1849. ; 278:4
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Tidskriftsartikel (refereegranskat)abstract
- The effect of insulin-like growth factor I (IGF-I) on insulin-stimulated glucose uptake was studied in adipose and muscle tissues of hypophysectomized female rats. IGF-I was given as a subcutaneous infusion via osmotic minipumps for 6 or 20 days. All hypophysectomized rats received L-thyroxine and cortisol replacement therapy. IGF-I treatment increased body weight gain but had no effect on serum glucose or free fatty acid levels. Serum insulin and C-peptide concentrations decreased. Basal and insulin-stimulated glucose incorporation into lipids was reduced in adipose tissue segments and isolated adipocytes from the IGF-I-treated rats. In contrast, insulin treatment of hypophysectomized rats for 7 days increased basal and insulin-stimulated glucose incorporation into lipids in isolated adipocytes. Pretreatment of isolated adipocytes in vitro with IGF-I increased basal and insulin-stimulated glucose incorporation into lipids. These results indicate that the effect of IGF-I on lipogenesis in adipose tissue is not direct but via decreased serum insulin levels, which reduce the capacity of adipocytes to metabolize glucose. Isoproterenol-stimulated lipolysis, but not basal lipolysis, was enhanced in adipocytes from IGF-I-treated animals. In the soleus muscle, the glycogen content and insulin-stimulated glucose incorporation into glycogen were increased in IGF-I-treated rats. In summary, IGF-I has opposite effects on glucose uptake in adipose tissue and skeletal muscle, findings which at least partly explain previous reports of reduced body fat mass, increased body cell mass, and increased insulin responsiveness after IGF-I treatment.
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| 4. |
- Frick, Fredrik, 1973
(författare)
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GH, IGF-1 and insulin in the regulation of lipid and lipoprotein metabolism
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that growth hormone (GH) has profound effects on lipid and lipoprotein metabolism. Insulin-like growth factor-I (IGF-I) is believed to mediate some of the effects of GH via endocrine and paracrine mechanisms. Moreover, both GH and IGF-I are known to influence insulin secretion. The aim of the present study was to investigate the importance of IGF-I and insulin, respectively, for the effects of GH on lipid and lipoprotein metabolism. Hypophysectomised female rats were treated with GH, IGF-I, insulin or GH plus insulin for 7 days. Various aspects of lipid and lipoprotein metabolism were studied in adipose tissue (AT), skeletal muscle, heart and liver from these animals. GH treatment increased lipoprotein lipase (LPL) activity in heart and skeletal muscle. In adipose tissue (AT), IGF-I treatment markedly reduced, and insulin increased, LPL activity. IGF-I treatment of Hx rats decreased both basal and insulin-stimulated glucose incorporation in AT, an effect that could be ascribed to decreased plasma insulin levels in IGF-I treated rats. In contrast, IGF-I treatment increased insulin-stimulated glucose incorporation into glycogen in skeletal muscle, indicating that IGF-I directly stimulates glucose uptake and metabolism in skeletal muscle. GH increased the hepatic triglyceride content and secretion rate, an effect that was blunted by combined insulin treatment, suggesting that insulin does not mediate these effects of GH. GH treatment increased the gene expression of two genes important in hepatic fatty acid synthesis, fatty acid synthase (FAS) and stearoyl CoA desaturase (SCD). The effects of GH on editing of apoB mRNA, SCD mRNA, and probably FAS mRNA, could partly be mediated by increased insulin levels. In order to study the effects of prolonged high levels of GH on lipid and lipoprotein metabolism, bGH transgenic mice were studied. In the bGH transgenic mice serum cholesterol levels were higher and serum triglyceride levels were lower. Moreover, transgenic mice showed a marked reduction in cholesterol and triglyceride content of the VLDL fraction and increased cholesterol content of the LDL and HDL fractions. The hepatic triglyceride secretion rate was reduced. LPL activity was increased in heart and adipose tissue. The difference in serum triglycerides between bGH transgenic females and gender controls was abolished after fat feeding. In conclusion, most of the effects of GH on lipid and lipoprotein metabolism are not mediated by IGF-I or insulin. IGF-I seems to have direct effects in skeletal muscle. In adipose tissue, IGF-I has indirect effects via changed insulin secretion.
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| 5. |
- Frick, Fredrik, 1973, et al.
(författare)
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Hepatic and adipose tissue depot-specific changes in lipid metabolism in Late-onset Obese (LOB) rats.
- 2008
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Ingår i: Lipids. - : Wiley. - 0024-4201 .- 1558-9307. ; 43:4, s. 313-24
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Tidskriftsartikel (refereegranskat)abstract
- Transgenic Late-onset OBesity (LOB) rats slowly develop a male-specific, autosomal dominant, obesity phenotype with a specific increase in peri-renal white adipose tissue (WAT) depot and preserved insulin sensitivity (Bains et al. in Endocrinology 145:2666-2679, 2004). To better understand the remarkable phenotype of these rats, the lipid metabolism was investigated in male LOB and non-transgenic (NT) littermates. Total plasma cholesterol (C) levels were normal but total plasma triacylglycerol (TAG) (2.8-fold) and hepatic TAG content (25%) was elevated in LOB males. Plasma VLDL-C and VLDL-TAG levels were higher while plasma apoB levels were 60% lower in LOB males. Increased hepatic TAG secretion explained the increased VLDL levels in LOB males. The hepatic gene expression of FAS, SCD-1, mitochondrial (mt)GPAT, and DGAT2 was up-regulated in both old obese and young non-obese LOB rats. Lipoprotein lipase (LPL) activity in heart and epididymal white adipose tissue (WAT) was unchanged, while LPL activity was increased in peri-renal WAT (30%) and decreased in soleus muscle (40%). Moreover, FAS, SCD-1 and DGAT2 gene expression was increased in peri-renal, but not in epididymal WAT. Basal lipolysis was reduced or unchanged and beta-adrenergic stimulated lipolysis was reduced in WAT from both old obese and young non-obese LOB rats. To summarize, the obese phenotype of LOB male rats is associated with increased hepatic TAG production and secretion, a shift in LPL activity from skeletal muscle to WAT, reduced lipolytic response in WAT depots and a specific increase in expression of genes responsible for fatty acid and TAG synthesis in the peri-renal depot.
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| 6. |
- Olsson, Bob, 1969, et al.
(författare)
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Bovine growth hormone transgenic mice are resistant to diet-induced obesity but develop hyperphagia, dyslipidemia, and diabetes on a high-fat diet
- 2005
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 146:2, s. 920-30
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Tidskriftsartikel (refereegranskat)abstract
- It is known that bovine GH (bGH) transgenic mice have increased body mass, insulin resistance, and altered lipoprotein metabolism when fed a normal diet (ND). In this study, the effects of 8 wk of high-fat diet (HFD) were investigated in 6-month-old male bGH mice. Although littermate controls had unchanged energy intake, energy intake was higher in the bGH mice on a HFD than on a low-fat diet. Nevertheless, the bGH mice were resistant to diet-induced weight gain, and only in the bGH mice did the HFD result in increased energy expenditure. Glucose oxidation was higher in the bGH mice compared with littermate controls on both a HFD and ND. In addition, the bGH mice had 0.5 C higher body temperature throughout the day and increased hepatic uncoupling protein 2 expression; changes that were unaffected by the HFD. On a HFD, the effect of bGH overexpression on serum triglycerides and apolipoprotein B was opposite to that on a ND, resulting in higher serum concentrations of triglycerides and apolipoprotein B compared with littermate controls. Increased serum triglycerides were explained by decreased triglyceride clearance. The HFD led to diabetes only in the bGH mice. In conclusion, bGH transgenic mice were resistant to diet-induced obesity despite hyperphagia, possibly due to increased energy expenditure. On a HFD, bGH mice became dyslipidemic and diabetic and thereby more accurately reflect the metabolic situation in acromegalic patients.
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| 7. |
- Oscarsson, Jan, 1960, et al.
(författare)
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GH but not IGF-I or insulin increases lipoprotein lipase activity in muscle tissues of hypophysectomised rats.
- 1999
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Ingår i: The Journal of endocrinology. - 0022-0795. ; 160:2, s. 247-55
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Tidskriftsartikel (refereegranskat)abstract
- Changes in GH secretion are associated with changes in serum lipoproteins, utilisation of fuels and body composition. Since lipoprotein lipase (LPL) is a key enzyme in the regulation of lipid and lipoprotein metabolism, changes in LPL activity may contribute to these effects of GH. The present study was undertaken to investigate the role of GH and the GH-dependent growth factor, IGF-I, in the regulation of LPL in heart, skeletal muscle and adipose tissue. Female rats were hypophysectomised at 50 days of age. One week later, hormonal therapy was commenced. All hypophysectomised rats received l-thyroxine and cortisol. Adipose tissue, the heart, soleus and gastrocnemius muscles were excised after 1 week of hormonal therapy. The effect of insulin injections on adipose tissue and heart LPL activity was also studied. In separate experiments, LPL activity in post-heparin plasma was measured. Hypophysectomy had no effect on adipose tissue LPL activity, whereas activity was reduced in heart, soleus and gastrocnemius muscle tissues. GH treatment had no significant effect on LPL activity in adipose tissue or soleus muscle, but increased the LPL activity in heart and gastrocnemius muscle. GH treatment increased post-heparin plasma LPL activity. Recombinant human IGF-I treatment (1.25 mg/kg per day) markedly reduced LPL activity in adipose tissue, but had no effect in muscle tissues. The effect of IGF-I treatment on adipose tissue LPL was not reflected by a decrease in post-heparin plasma LPL activity. Daily injections of insulin for 7 days increased LPL activity in adipose tissue but had no effect on heart LPL activity. In adipose tissue, LPL mRNA levels tended to decrease as a result of IGF-I treatment. In the muscle tissues, no significant effects of hypophysectomy, GH or IGF-I treatment on LPL mRNA levels were observed.%It is concluded that GH increases heart and skeletal muscle tissue LPL activity, which probably contributes to an increased post-heparin plasma LPL activity. The effect of GH on muscle LPL activity is probably not mediated by IGF-I or insulin. Insulin and IGF-I have opposite effects on LPL activity in adipose tissue.
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