Single-cell systems analysis: decision geometry in outliers.

MOTIVATION: Anti-cancer therapeutics of the highest calibre currently focus on combinatorial targeting of specific oncoproteins and tumour suppressors. Clinical relapse depends upon intratumoral heterogeneity which serves as substrate variation during evolution of resistance to therapeutic regimens. RESULTS: The present review advocates single-cell systems biology as the optimal level of analysis for remediation of clinical relapse. Graph theory approaches to understanding decision-making in single cells may be abstracted one level further, to the geometry of decision-making in outlier cells, in order to define evolution-resistant cancer biomarkers. Systems biologists currently working with omics data are invited to consider phase portrait analysis as a mediator between graph theory and deep learning approaches. Perhaps counter-intuitively, the tangible clinical needs of cancer patients may depend upon the adoption of higher level mathematical abstractions of cancer biology. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

11ß-Hydroxysteroid dehydrogenase blockade prevents age-induced skin structure and function defects.

Glucocorticoid (GC) excess adversely affects skin integrity, inducing thinning and impaired wound healing. Aged skin, particularly that which has been photo-exposed, shares a similar phenotype. Previously, we demonstrated age-induced expression of the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) in cultured human dermal fibroblasts (HDFs). Here, we determined 11ß-HSD1 levels in human skin biopsies from young and older volunteers and examined the aged 11ß-HSD1 KO mouse skin phenotype. 11ß-HSD1 activity was elevated in aged human and mouse skin and in PE compared with donor-matched photo-protected human biopsies. Age-induced dermal atrophy with deranged collagen structural organization was prevented in 11ß-HSD1 KO mice, which also exhibited increased collagen density. We found that treatment of HDFs with physiological concentrations of cortisol inhibited rate-limiting steps in collagen biosynthesis and processing. Furthermore, topical 11ß-HSD1 inhibitor treatment accelerated healing of full-thickness mouse dorsal wounds, with improved healing also observed in aged 11ß-HSD1 KO mice. These findings suggest that elevated 11ß-HSD1 activity in aging skin leads to increased local GC generation, which may account for adverse changes occurring in the elderly, and 11ß-HSD1 inhibitors may be useful in the treatment of age-associated impairments in dermal integrity and wound healing.

Regulation of lipid metabolism by glucocorticoids and 11ß-HSD1 in skeletal muscle.

The prevalences of insulin resistance and type 2 diabetes mellitus are rising dramatically, and, as a consequence, there is an urgent need to understand the pathogenesis underpinning these conditions to develop new and more efficacious treatments. We have tested the hypothesis that glucocorticoid (GC)-mediated changes in insulin sensitivity may be associated with changes in lipid flux. Furthermore, prereceptor modulation of GC availability by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) may represent a critical regulatory step. Dexamethasone (DEX) decreased lipogenesis in both murine C2C12 and human LHC-NM2 myotubes. Inactivating p-Ser-79/218 of acetyl-CoA carboxylase 1/2 and activating p-Thr-172 of AMP-activated protein kinase were both increased after DEX treatment in C2C12 myotubes. In contrast, DEX increased ß-oxidation. Selective 11ß-HSD1 inhibition blocked the 11-dehydrocorticosterone (11DHC)-mediated decrease in lipogenic gene expression and increase in lipolytic gene expression. Lipogenic gene expression was decreased, whereas lipolytic and ß-oxidative gene expression increased in corticosterone (CORT)- and 11DHC-treated wild-type mice and CORT (but not 11DHC)-treated 11ß-HSD1(-/-) mice. Furthermore, CORT- and 11DHC-treated wild-type mice and CORT (but not 11DHC)-treated 11ß-HSD1(-/-) mice had increased p-Ser-79/218 acetyl-CoA carboxylase 1/2, p-Thr-172 AMP-activated protein kinase and intramyocellular diacylglyceride content. In summary, we have shown that GCs have potent actions on intramyocellular lipid homeostasis by decreasing lipid storage, increasing lipid mobilization and utilization, and increasing diacylglyceride content. It is plausible that dysregulated intramyocellular lipid metabolism may underpin GC-induced insulin resistance of skeletal muscle.

Biomarkers of hypothalamic-pituitary-adrenal axis activity in mice lacking 11ß-HSD1 and H6PDH.

Glucocorticoid concentrations are a balance between production under the negative feedback control and diurnal rhythm of the hypothalamic-pituitary-adrenal (HPA) axis and peripheral metabolism, for example by the enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), which catalyses the reduction of inactive cortisone (11-dehydrocorticosterone (11-DHC) in mice) to cortisol (corticosterone in mice). Reductase activity is conferred upon 11ß-HSD1 by hexose-6-phosphate dehydrogenase (H6PDH). 11ß-HSD1 is implicated in the development of obesity, and selective 11ß-HSD1 inhibitors are currently under development. We sought to address the concern regarding potential up-regulation of the HPA axis associated with inhibition of 11ß-HSD1. We assessed biomarkers for allele combinations of 11ß-HSD1 and H6PDH derived from double heterozygous mouse crosses. H6PDH knock out (KO) adrenals were 69% larger than WT while 11ß-HSD1 KO and double KO (DKO) adrenals were ~30% larger than WT - indicative of increased HPA axis drive in KO animals. ACTH-stimulated circulating corticosterone concentrations were 2.2-fold higher in H6PDH KO animals and ~1.5-fold higher in 11ß-HSD1 KO and DKO animals compared with WT, proportional to the observed adrenal hypertrophy. KO of H6PDH resulted in a substantial increase in urinary DHC metabolites in males (65%) and females (61%). KO of 11ß-HSD1 alone or in combination with H6PDH led to significant increases (36 and 42% respectively) in urinary DHC metabolites in females only. Intermediate 11ß-HSD1/H6PDH heterozygotes maintained a normal HPA axis. Urinary steroid metabolite profile by gas chromatography/mass spectrometry as a biomarker assay may be beneficial in assaying HPA axis status clinically in cases of congenital and acquired 11ß-HSD1/H6PDH deficiency.