11 beta-hydroxysteroid dehydrogenase type 1 regulates glucocorticoid-induced insulin resistance in skeletal muscle

OBJECTIVE: Glucocorticoid excess is characterized by increased adiposity, skeletal myopathy, and insulin resistance, but the precise molecular mechanisms are unknown. Within skeletal muscle, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts cortisone (11-dehydrocorticosterone in rodents) to active cortisol (corticosterone in rodents). We aimed to determine the mechanisms underpinning glucocorticoid-induced insulin resistance in skeletal muscle and indentify how 11beta-HSD1 inhibitors improve insulin sensitivity. \ud RESEARCH DESIGN AND METHODS: Rodent and human cell cultures, whole-tissue explants, and animal models were used to determine the impact of glucocorticoids and selective 11beta-HSD1 inhibition upon insulin signaling and action. \ud RESULTS: Dexamethasone decreased insulin-stimulated glucose uptake, decreased IRS1 mRNA and protein expression, and increased inactivating pSer$^{307}$ insulin receptor substrate (IRS)-1. 11beta-HSD1 activity and expression were observed in human and rodent myotubes and muscle explants. Activity was predominantly oxo-reductase, generating active glucocorticoid. A1 (selective 11beta-HSD1 inhibitor) abolished enzyme activity and blocked the increase in pSer$^{307}$ IRS1 and reduction in total IRS1 protein after treatment with 11DHC but not corticosterone. In C57Bl6/J mice, the selective 11beta-HSD1 inhibitor, A2, decreased fasting blood glucose levels and improved insulin sensitivity. In KK mice treated with A2, skeletal muscle pSer$^{307}$ IRS1 decreased and pThr$^{308}$ Akt/PKB increased. In addition, A2 decreased both lipogenic and lipolytic gene expression.\ud CONCLUSIONS: Prereceptor facilitation of glucocorticoid action via 11beta-HSD1 increases pSer$^{307}$ IRS1 and may be crucial in mediating insulin resistance in skeletal muscle. Selective 11beta-HSD1 inhibition decreases pSer$^{307}$ IRS1, increases pThr$^{308}$ Akt/PKB, and decreases lipogenic and lipolytic gene expression that may represent an important mechanism underpinning their insulin-sensitizing action

11 beta-hydroxysteroid dehydrogenase type 1 regulates glucocorticoid-induced insulin resistance in skeletal muscle

OBJECTIVE: Glucocorticoid excess is characterized by increased adiposity, skeletal myopathy, and insulin resistance, but the precise molecular mechanisms are unknown. Within skeletal muscle, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts cortisone (11-dehydrocorticosterone in rodents) to active cortisol (corticosterone in rodents). We aimed to determine the mechanisms underpinning glucocorticoid-induced insulin resistance in skeletal muscle and indentify how 11beta-HSD1 inhibitors improve insulin sensitivity. \ud RESEARCH DESIGN AND METHODS: Rodent and human cell cultures, whole-tissue explants, and animal models were used to determine the impact of glucocorticoids and selective 11beta-HSD1 inhibition upon insulin signaling and action. \ud RESULTS: Dexamethasone decreased insulin-stimulated glucose uptake, decreased IRS1 mRNA and protein expression, and increased inactivating pSer$^{307}$ insulin receptor substrate (IRS)-1. 11beta-HSD1 activity and expression were observed in human and rodent myotubes and muscle explants. Activity was predominantly oxo-reductase, generating active glucocorticoid. A1 (selective 11beta-HSD1 inhibitor) abolished enzyme activity and blocked the increase in pSer$^{307}$ IRS1 and reduction in total IRS1 protein after treatment with 11DHC but not corticosterone. In C57Bl6/J mice, the selective 11beta-HSD1 inhibitor, A2, decreased fasting blood glucose levels and improved insulin sensitivity. In KK mice treated with A2, skeletal muscle pSer$^{307}$ IRS1 decreased and pThr$^{308}$ Akt/PKB increased. In addition, A2 decreased both lipogenic and lipolytic gene expression.\ud CONCLUSIONS: Prereceptor facilitation of glucocorticoid action via 11beta-HSD1 increases pSer$^{307}$ IRS1 and may be crucial in mediating insulin resistance in skeletal muscle. Selective 11beta-HSD1 inhibition decreases pSer$^{307}$ IRS1, increases pThr$^{308}$ Akt/PKB, and decreases lipogenic and lipolytic gene expression that may represent an important mechanism underpinning their insulin-sensitizing action

Potassium Channel Antagonists 4-Aminopyridine and the T-Butyl Carbamate Derivative of 4-Aminopyridine Improve Hind Limb Function in Chronically Non-Ambulatory Dogs; A Blinded, Placebo-Controlled Trial

<div><p>4-Aminopyridine (4-AP) blocks voltage gated potassium channels, restoring conduction to demyelinated axons and improving function in demyelinating conditions, but its use is associated with adverse effects and benefit in spinal cord injury is limited. Derivatives of 4-AP have been developed to improve clinical efficacy while reducing toxicity. We compared the therapeutic effects of orally administered 4-AP and its t-butyl carbamate derivative (t-butyl) with placebo in dogs that had suffered an acute spinal cord injury that left them chronically paralyzed. Nineteen dogs were entered into the trial, conducted in two-week treatment blocks starting with placebo, followed by random assignment to 4-AP or t-butyl, a washout and then the opposite medication followed by placebo. Investigators and owners were blinded to treatment group. Primary outcome measures included open field gait score (OFS), and treadmill based stepping score and regularity index, with additional secondary measures also considered. Thirteen of 19 dogs completed the protocol. Two were euthanized due to unrelated heath problems, two developed side effects and two were unable to complete for unrelated reasons. Dogs showed significant improvement in supported stepping score (from 17.39 to 37.24% with 4-AP; 16.85 to 29.18% with t-butyl p<0.0001) and OFS (from 3.63 to 4.73 with 4-AP; 3.78 to 4.45 with t-butyl, p = 0.005). Response was individually variable and most dramatic in three dogs that were able to walk without support with treatment. No significant difference was found between 4-AP and t-butyl. No adverse effects were reported with t-butyl but gastrointestinal upset and seizures were observed in two dogs with 4-AP. In conclusion, both 4-AP and t-butyl significantly improved supported stepping ability in dogs with chronic spinal cord injury with no adverse effects noted with t-butyl. Drug response varied widely between individuals, highlighting the need to understand the factors that influence canine and human patients' response to therapy.</p></div

Results of the primary outcome measurements of gait.

<p>Mean supported stepping score (a), regulatory index (b) and OFS (c) during weeks 1–2, 5–6 and 9–10 did not change significantly (see p values for <i>ß</i>^k₁ provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116139#pone-0116139-t004" target="_blank">Table 4</a>), showing that there is no significant treatment effect carried over from the treatment periods. Mean supported stepping score (d), regulatory index (e) and OFS (f) for 4-AP and t-butyl treatment periods compared to the preceding 2 week period. Stepping score and OFS show significant improvement with treatment (***) (see p values for <i>ß</i>^k₀ provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116139#pone-0116139-t004" target="_blank">Table 4</a>); Data represents mean ± SD, CTR: the 2-week control period immediately preceding treatment.</p

Patient signalment.

<p>Wt: weight; MC: male castrated; FS: female spayed; M: male; IVDD:intervertebral disc disease (type I); T-SCI: traumatic spinal cord injury; m:months;</p><p>*: at the time of enrollmen.</p><p>Patient signalment.</p

Outcome data.

<p>Control weeks: 2 weeks period immediately preceding treatment with either 4-AP or t-butyl; OFS: open field score (0–13); SS: stepping score; RI: regularity index; DNI: decreased (−1), no change (0), improved (+1); HL: hind limb; <i>ß</i>^k₀: treatment effect of 4-AP or t-butyl relative to control; <i>ß</i>^k₁: relative treatment effects of 4-AP and t-butyl. Positive values of <i>ß</i>^k₁ reflect outperformance by 4-AP, and negative values reflect t-butyl. The scores denoted with * were not changed by treatment, therefore <i>ß</i>^k₀ and <i>ß</i>^k₁ values could not be calculated.</p><p>Outcome data.</p

Outcome measures.

<p>Outcome measures.</p

Study design and patient treatment allocation.

<p>A: Diagram of the study design. B: Treatment assignments for each subject by week. Boxes indicated by an asterisk (*) represent sub-therapeutic dosing with t-butyl. These and the preceding two-week treatment periods were removed from statistical analysis. Symbols indicate dogs that did not complete the trial; Δ: owners unable to continue; ‡: euthanasia; ¶: discontinuation due to adverse effects. Dog 13 received just 2 doses of 4-AP prior to development of seizures. Dog 19 received 10 doses of 4-AP prior to developing gastrointestinal signs.</p

Ordinal testing scales.

<p>Ordinal testing scales.</p