Regulation of 11beta-hydroxysteroid dehydrogenase type 1 and glucose-stimulated insulin secretion in pancreatic islets of Langerhans

BACKGROUND: In rodents, the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts inactive 11-dehydrocorticosterone (DHC) into active corticosterone. The mRNA and activity of 11beta-HSD1 have been shown to be present in batch-incubated pancreatic islets from the ob/ob mouse. In other tissues, 11beta-HSD1 expression has been demonstrated to be regulated by glucocorticoids. In the present study, the influence of DHC on 11beta-HSD1 levels and glucose-induced changes in insulin secretion were studied in pancreatic islets isolated from the ob/ob mouse. METHODS: Western blotting with antiserum for 11beta-HSD1 verified the presence of 11beta-HSD1 in islets from obese ob/ob and normal C57BL/6J mice. Insulin secretion was determined by perifusing islets and assaying the perifusate with ELISA. RESULTS: Islets from the ob/ob mouse contained almost twofold more 11beta-HSD1 protein than islets from the C57BL/6J mouse. When islets from ob/ob mice were cultured with 50 nM DHC, the 11beta-HSD1 levels doubled compared with islets cultured in the absence of DHC. Selective inhibition of 11beta-HSD1 attenuated DHC-induced increase in 11beta-HSD1 levels, as did an antagonist of the glucocorticoid receptor. In individually perifused ob/ob mouse islets, early and late phases of glucose-stimulated insulin secretion (GSIS) were dose-dependently inhibited by 5, 50 and 500 nM DHC. Whereas inclusion of 11beta-HSD1 inhibitors restored, addition of the glucocorticoid receptor antagonist attenuated the DHC-mediated inhibition of GSIS. CONCLUSIONS: Levels of 11beta-HSD1 in islets from ob/ob mice are positively regulated by DHC and could be lowered by a selective 11beta-HSD1 inhibitor and a glucocorticoid receptor antagonist. Increased levels of 11beta-HSD1 were associated with impaired GSIS.     

Increase in IL-6, TNF-α, and MMP-9, but not sICAM-1, concentrations depends on exercise duration

It has been suggested that exercise intensity is of importance in the regulation of increase in pro-inflammatory molecules, but there is still a debate about the effect of duration on these molecules. Therefore, the effect of exercise duration on the serum concentrations of interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), soluble form of intercellular adhesion molecule-1 (sICAM-1), and matrix metalloproteinase-9 (MMP-9) was studied in 22 half-marathon (HM) and 18 marathon (M) male amateur runners who completed their exercise task in 1.8 ± 0.2 (mean ± standard deviation) and 3.6 ± 0.4 h, respectively (thus, average speed was 11.7 ± 1.5 and 11.9 ± 1.8 km h^?1, respectively). Blood was sampled 2 days before, 15 min after, and 28 h after the race. IL-6, TNF-α, and MMP-9 always increased immediately after exercise, but the increase was larger (P < 0.05) in M versus HM (?IL-6: 31 ± 24 vs. 5 ± 4 pg ml^?1; ?TNF-α: 1.7 ± 1.9 vs. 0.5 ± 0.8 pg ml^?1; MMP-9: 288 ± 216 vs. 145 ± 128 ng ml^?1, respectively). sICAM-1 also increased with exercise, but similarly in M and HM (20 ± 40 vs. 23 ± 32 ng ml^?1, respectively). Only sICAM-1 remained elevated 28 h post-exercise in both HM and M, while IL-6, TNF-α, and MMP-9 returned to pre-exercise levels. Competitive HM and M races induce significant increases in IL-6, TNF-α, sICAM-1, and MMP-9 concentrations. As HM and M runners performed the competition with similar absolute intensity, the difference in response between the groups suggests that exercise duration is of importance in the regulation of IL-6, TNF-α, and MMP-9, but not sICAM-1 concentrations in response to prolonged running.     

Discovery of novel melanocortin4 receptor selective MSH analogues

1. We synthesized a novel series of cyclic melanocyte stimulating hormone (MSH) analogues and tested their binding properties on cells transiently expressing the human melanocortin₁ (MC₁), MC₃, MC₄ and MC₅ receptors.
2. We discovered that compounds with 26 membered rings of [Cys⁴,D-Nal⁷,Cys¹¹]α-MSH(4–11) displayed specific MC₄ receptor selectivity. The preference order of the different MC receptor subtypes for the novel [Cys⁴D-Nal⁷Cys¹¹]α-MSH(4–11) analogues are distinct from all other known MSH analogues, particularly as they bind the MC₄ receptor with high and the MC₁ receptor with low relative affinities.
3. HS964 and HS014 have 12 and 17 fold MC₄/MC₃ receptor selectivity, respectively, which is much higher than for the previously described cyclic lactam and [Cys⁴,Cys¹⁰]α-MSH analogues SHU9119 and HS9510.
4. HS964 is the first substance showing higher affinity for the MC₅ receptor than the MC₁ receptor.
5. HS014, which was the most potent and selective MC₄ receptor ligand (K_i 3.2 nM, which is ∼300 fold higher affinity than for α-MSH), was also demonstrated to antagonize α-MSH stimulation of cyclic AMP in MC₄ receptor transfected cells.
6. We found that a compound with a 29 membered ring of [Cys³,Nle¹⁰,D-Nal⁷,Cys¹¹]α-MSH(3–11) (HS010) had the highest affinity for the MC₃ receptor.
7. This is the first study to describe ligands that are truly MC₄ selective and a ligand having a high affinity for the MC₃ receptor. The novel compounds may be of use in clarifying the physiological roles of the MC₃, MC₄ and MC₅ receptors.