| 1. |
- Andrew, R, et al.
(författare)
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The contribution of visceral adipose tissue to splanchnic cortisol production in healthy humans
- 2005
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 54:5, s. 1364-1370
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Tidskriftsartikel (refereegranskat)abstract
- Cortisol is regenerated from cortisone by 11β-hydroxysteroid dehydrogenase type 1 (11HSD1), amplifying glucocorticoid action in adipose tissue and liver. 11HSD1 inhibitors are being developed for type 2 diabetes and may be most effective in obesity, where adipose 11HSD1 is increased. However, the magnitude of regeneration of cortisol in different tissues in humans is unknown, hindering understanding of the pathophysiological and therapeutic importance of 11HSD1. In eight healthy men, we infused 9,11,12,12-2H4-cortisol and measured tracer enrichment in the hepatic vein as an indicator of total splanchnic cortisol generation. Oral cortisone (25 mg) was then given to measure first-pass hepatic cortisol generation. In steady state, splanchnic cortisol production was 45 ± 11 nmol/min when arterialized plasma cortisone concentration was 92 ± 7 nmol/l. Extrapolation from hepatic cortisol generation after oral corti-sone suggested that, at steady state, the liver contributes 15.2 nmol/min and extrahepatic splanchnic tissue contributes 29.8 nmol/min to the total splanchnic cortisol production. We conclude that tissues draining into the portal vein, including visceral adipose tissue, contribute substantially to the regeneration of cortisol. Thus, in addition to free fatty acids and adipokines, the portal vein delivers cortisol to the liver, and inhibition of 11HSD1 in visceral adipose tissue may indeed be valuable in ameliorating insulin resistance in obesity.
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| 2. |
- Cotter, MA, et al.
(författare)
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Effects of proinsulin C-peptide in experimental diabetic neuropathy: vascular actions and modulation by nitric oxide synthase inhibition
- 2003
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 52:7, s. 1812-1817
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Tidskriftsartikel (refereegranskat)abstract
- Proinsulin C-peptide treatment can partially prevent nerve dysfunction in type 1 diabetic rats and patients. This could be due to a direct action on nerve fibers or via vascular mechanisms as C-peptide stimulates the nitric oxide (NO) system and NO-mediated vasodilation could potentially account for any beneficial C-peptide effects. To assess this further, we examined neurovascular function in streptozotocin-induced diabetic rats. After 6 weeks of diabetes, rats were treated for 2 weeks with C-peptide to restore circulating levels to those of nondiabetic controls. Additional diabetic groups were given C-peptide with NO synthase inhibitor NG-nitro-l-arginine (l-NNA) co-treatment or scrambled C-peptide. Diabetes caused 20 and 16% reductions in sciatic motor and saphenous sensory nerve conduction velocity, which were 62 and 78% corrected, respectively, by C-peptide. l-NNA abolished C-peptide effects on nerve conduction. Sciatic blood flow and vascular conductance were 52 and 41%, respectively, reduced by diabetes (P < 0.001). C-peptide partially (57–66%) corrected these defects, an effect markedly attenuated by l-NNA co-treatment. Scrambled C-peptide was without effect on nerve conduction or perfusion. Thus, C-peptide replacement improves nerve function in experimental diabetes, and the data are compatible with the notion that this is mediated by a NO-sensitive vascular mechanism.
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| 3. |
- Ekberg, K, et al.
(författare)
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Amelioration of sensory nerve dysfunction by C-Peptide in patients with type 1 diabetes
- 2003
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 52:2, s. 536-541
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Tidskriftsartikel (refereegranskat)abstract
- Studies have demonstrated that proinsulin C-peptide stimulates the activities of Na+,K+-ATPase and endothelial nitric oxide synthase, both of which are enzyme systems of importance for nerve function and known to be deficient in type 1 diabetes. The aim of this randomized double-blind placebo-controlled study was to investigate whether C-peptide replacement improves nerve function in patients with type 1 diabetes. Forty-nine patients without symptoms of peripheral neuropathy were randomized to either 3 months of treatment with C-peptide (600 nmol/24 h, four doses s.c.) or placebo. Forty-six patients (15 women and 31 men, aged 29 years, diabetes duration 10 years, and HbA1c 7.0%) completed the study. Neurological and neurophysiological measurements were performed before and after 6 and 12 weeks of treatment. At baseline the patients showed reduced nerve conduction velocities in the sural nerve (sensory nerve conduction velocity [SCV]: 50.9 ± 0.70 vs. 54.2 ± 1.2 m/s, P < 0.05) and peroneal nerve (motor nerve conduction velocity: 45.7 ± 0.55 vs. 53.5 ± 1.1 m/s, P < 0.001) compared with age-, height-, and sex-matched control subjects. In the C-peptide treated group there was a significant improvement in SCV amounting to 2.7 ± 0.85 m/s (P < 0.05 compared with placebo) after 3 months of treatment, representing 80% correction of the initial reduction in SCV. The change in SCV was accompanied by an improvement in vibration perception in the patients receiving C-peptide (P < 0.05 compared with placebo), whereas no significant change was detectable in cold or heat perception. In conclusion, C-peptide administered for 3 months as replacement therapy to patients with early signs of diabetic neuropathy ameliorates nerve dysfunction.
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| 4. |
- Ekberg, K, et al.
(författare)
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Contributions by kidney and liver to glucose production in the postabsorptive state and after 60 h of fasting
- 1999
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 48:2, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- Contributions of renal glucose production to whole-body glucose turnover were determined in healthy individuals by using the arteriovenous balance technique across the kidneys and the splanchnic area combined with intravenous infusion of [U-13C6]glucose, [3-(3)H]glucose, or [6-(3)H]glucose. In the postabsorptive state, the rate of glucose appearance was 11.5 +/- 0.6 micromol x kg(-1) x min(-1). Hepatic glucose production, calculated as the sum of net glucose output (9.8 +/- 0.8 micromol x kg(-1) x min(-1)) and splanchnic glucose uptake (2.2 +/- 0.3 micromol x kg(-1) x min(-1)) accounted for the entire rate of glucose appearance. There was no net exchange of glucose across the kidney and no significant renal extraction of labeled glucose. The renal contribution to total glucose production calculated from the arterial, hepatic, and renal venous 13C-enrichments (glucose M+6) was 5 +/- 2%. In the 60-h fasted state, the rate of glucose appearance was 8.2 +/- 0.3 micromol x kg(-1) x min(-1). Hepatic glucose production, estimated as net splanchnic output (5.8 +/- 0.7 micromol x kg(-1) x min(-1)) plus splanchnic uptake (0.6 +/- 0.3 micromol x kg(-1) x min(-1)) accounted for 79% of the rate of glucose appearance. There was a significant net renal output of glucose (0.9 +/- 0.3 micromol x kg(-1) x min(-1)), but no significant extraction of labeled glucose across the kidney. The renal contribution to whole-body glucose turnover calculated from the 13C-enrichments was 24 +/- 3%. We concluded that 1) glucose production by the human kidney in the postabsorptive state, in contrast to recent reports, makes at most only a minor contribution (approximately 5%) to blood glucose homeostasis, but that 2) after 60-h of fasting, renal glucose production may account for 20-25% of whole-body glucose turnover.
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| 5. |
- Hansen, A, et al.
(författare)
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C-peptide exerts beneficial effects on myocardial blood flow and function in patients with type 1 diabetes
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 51:10, s. 3077-3082
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Tidskriftsartikel (refereegranskat)abstract
- Myocardial dysfunction, perfusion abnormalities, and the extent to which these abnormalities may be reversed by C-peptide administration was assessed in type 1 diabetic patients. Eight patients were studied before and during a 0.84-mg/kg dipyridamole administration using a randomized double-blind crossover protocol with infusion of C-peptide (6 pmol · kg−1 · min−1) or saline during 60 min on two different days. Myocardial function was measured as peak myocardial velocity during systole (Vs) and early diastole (Vd) by pulsed tissue Doppler imaging. Myocardial contrast echocardiography was used for assessment of myocardial blood volume (SImax) and myocardial blood flow index (MBFI) calculated from the relation between trigger interval and signal intensity. Eight age-matched healthy volunteers served as control subjects. In the basal state, Vd (13.8 ± 0.6 vs. 15.6 ± 0.5 cm/s, P < 0.04) and SImax (6.6 ± 0.6 vs. 8.2 ± 0.6 a.u. P < 0.04) were reduced in patients compared with control subjects. Dipyridamole administration significantly increased indexes of myocardial function and blood flow to a similar extent in patients and control subjects. During C-peptide administration, Vs and Vd increased by 12% (P = 0.03), SImax increased from 6.6 ± 0.6 to 8.1 ± 0.7 a.u. (P < 0.02), and MBFI increased from 3.3 ± 0.4 to 5.3 ± 0.9 (P < 0.05). The results demonstrate that type 1 diabetic patients have impaired myocardial function and perfusion in the basal state that can be improved by short-term replacement of C-peptide.
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| 6. |
- Kamiya, H, et al.
(författare)
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C-Peptide reverses nociceptive neuropathy in type 1 diabetes
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:12, s. 3581-3587
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Tidskriftsartikel (refereegranskat)abstract
- We examined the therapeutic effects of C-peptide on established nociceptive neuropathy in type 1 diabetic BB/Wor rats. Nociceptive nerve function, unmyelinated sural nerve fiber and dorsal root ganglion (DRG) cell morphometry, nociceptive peptide content, and the expression of neurotrophic factors and their receptors were investigated. C-peptide was administered either as a continuous subcutaneous replacement dose via osmopumps or a replacement dose given once daily by subcutaneous injection. Diabetic rats were treated from 4 to 7 months of diabetes and were compared with control and untreated diabetic rats of 4- and 7-month duration. Osmopump delivery but not subcutaneous injection improved hyperalgesia and restored the diabetes-induced reduction of unmyelinated fiber number (P < 0.01) and mean axonal size (P < 0.05) in the sural nerve. High-affinity nerve growth factor (NGF) receptor (NGFR-TrkA) expression in DRGs was significantly reduced at 4 months (P < 0.01). Insulin receptor and IGF-I receptor (IGF-IR) expressions in DRGs and NGF content in sciatic nerve were significantly decreased in 7-month diabetic rats (P < 0.01, 0.05, and 0.005, respectively). Osmopump delivery prevented the decline of NGFR-TrkA, insulin receptor (P < 0.05), and IGF-IR (P < 0.005) expressions in DRGs and improved NGF content (P < 0.05) in sciatic nerve. However, subcutaneous injection had only marginal effects on morphometric and molecular changes in diabetic rats. We conclude that C-peptide exerts beneficial therapeutic effects on diabetic nociceptive neuropathy and that optimal effects require maintenance of physiological C-peptide concentrations for a major proportion of the day.
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