| 1. |
- Bäck, Karolina, 1981-, et al.
(författare)
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Differential expression of insulin and IGF-I receptors in human tissues
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Insulin and IGF-I are related peptides with similar structure. They both signal via their cognate receptors, the insulin receptor (IR) and the insulin-like growth factor (IGF)-I receptor (IGF-IR). Our aim was to simultaneously measure the amount of insulin and IGF-I receptors in different human tissues and also the IR-A and IR-B isoforms to study tissue specific expression Renal artery intima-media, myometrium, skeletal muscle or liver tissue samples were obtained from patients undergoing surgery. IR, IGF-IR, IR-A and IR-B gene expression was investigated with real-time RT-PCR and expression of IR and IGF-IR protein was examined by Western blot and ELISA. Renal arteries and myometrium expressed the IGF-IR gene to a higher extent than the IR gene, liver expressed more IR than IGF-IR and skeletal muscle expressed almost equal amounts of both receptors. IR-B was the most abundant isoform in all tissues. With Western blot we could detect IR in skeletal muscle, liver and myometrium. With ELISA we found that, normalized to total protein, the highest levels of IGF-IR were found in renal arteries and myometrium and low levels in skeletal muscle and liver. The highest levels of IR were found in liver. In conclusion there is a large variation in the quantity and ratio of insulin receptors and IGF-I receptors expressed in different tissues, the extremes being arterial intima media with predominantly IGF-I receptors and liver with predominantly insulin receptors. This suggests that differential expression of insulin and IGF-I receptors is a key mechanism in regulation of growth and metabolism.
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| 2. |
- Bäck, Karolina, 1981-
(författare)
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Interaction between insulin and IGF-I receptors in insulin sensitive and insulin resistant cells and tissues
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Insulin and insulin-like growth factor I (IGF-I) are two related peptides with similar structure. They mediate their effects by binding to their respective receptor, the insulin receptor (IR) and the IGF-I receptor (IGF-IR) and induce intracellular signalling cascades resulting in metabolic or mitogenic effects. The relative abundance of IR and IGF-IR is of importance for the type of effect that is the outcome of the signal. There are few studies investigating the relative receptor abundance and its effects in human cells and tissues.In this thesis we wanted to study abundance and regulation of insulin and IGF-I receptors in different human cells and tissues and examine the effects of variations in insulin and IGF-I receptor abundance between different cells and tissues.We examined IR and IGF-IR gene and protein expression and the effects of insulin and IGF-I on receptor phosphorylation, DNA synthesis and glucose transport.Our results show that there is a large variation in the distribution of IR and IGF-IR in different human cells and tissues. Renal artery intima-media expressed predominantly IGF-IR while in liver IR was the predominant receptor type.Differentiation of human preadipocytes results in a change in relative expression of IGF-IR to IR. Mature adipocytes express almost 10-fold more IR than IGF-IR while preadipocytes express almost the same amounts of both receptors. Mature tissues, such as liver, skeletal muscle, myometrium and renal artery intima-media, express predominantly IR-B. Preadipocytes express IR-A and the expression of IR-B is induced during differentiation.We could show the presence of insulin/IGF-I hybrid receptors in preadipocytes but not in mature adipocytes. Cultured endothelial cells express mostly IGF-IR and insulin/IGF-I hybrid receptors and these cells respond mainly to IGF-I. Due to the large abundance of IR mature adipocytes are sensitive to insulin but insensitive to IGF-I whereas preadipocytes expressing equal amounts of both receptors respond to both insulin and IGF-I. Insulin and IGF-I are only partial agonists to each other’s receptors in human preadipocytes and adipocytes.The overall results indicate that differential expression of IGF-IR and IR is a key mechanism in regulation of growth and metabolism.
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| 3. |
- Bäck, Karolina, 1981-, et al.
(författare)
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Role of insulin and IGF-I receptors in human cardiac microvascular endothelial cells; metabolic, mitogenic and anti-inflammatory effects
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Diabetes is associated with coronary microcirculatory dysfunction and heart failure as well as changes in insulin and IGF-I levels. Our aim was to study the role of insulin receptors and IGF-I receptors in metabolic, mitogenic and anti-inflammatory responses to insulin and IGF-I in human cardiac microvascular endothelial cells (HMVEC-C) and, for comparison, also human umbilical vein endothelial cells (HUVEC). Insulin receptor (IR) and IGF-I receptor (IGF-IR) gene expression was studied with real-time RT-PCR. Receptor protein expression and phosphorylation was determined with Western blot and ELISA. The metabolic and mitogenic effects were measured as glucose accumulation and thymidine incorporation. An E-selectin ELISA was used to investigate the anti-inflammatory responses. IGF-IR was more abundant than IR both regarding gene expression and protein in HMVEC-C and HUVEC. Immunoprecipitation with anti-IGF-IR antibody and immunoblotting with anti-IR antibody and vice versa, showed insulin/IGF-I hybrid receptors in these cells. IGF-I 10-8 M significantly stimulated phosphorylation of both IGF-IR and IR in HMVEC-C. In HUVEC IGF-I 10-8 M phosphorylated IGF-IR. IGF-I also stimulated DNA synthesis at 10-8 M and glucose accumulation at 10-7 M. TNF-α significantly increased E-selectin expression whereas no effects were found by insulin, IGF-I or high glucose. We conclude that HMVEC-C express more IGF-I receptors than insulin receptors and at physiological concentrations of insulin and IGF-I mainly reacts to IGF-I probably due to the predominance of IGF-I receptors and insulin/IGF-I hybrid receptors. TNF-α has a pronounced pro-inflammatory effect in HMVEC-C which is not counteracted by insulin or IGF-I.
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