Dysfonctionnement systémique de la différenciation ostéoblastique des cellules souches adipeuses des patients atteints de myélome multiple

International audienceMultiple myeloma is characterized by bone lesions linked to increased osteoclast and decreased osteoblast activities. In particular, the osteoblast differentiation of bone marrow-derived stem cells (MSC) is impaired. Among the potential therapeutic tools for counteracting bone lesions, adipose-derived stem cells (ASC) could represent an appealing source for regenerative medicine due to their similar characteristics with MSC. Our study is among the first giving detailed insights into the osteoblastogenic capacities of ASC isolated by fat aspiration from myeloma patients (MM-ASC) compared to healthy subjects (HD-ASC). We showed that MM-ASC and HD-ASC exhibited comparable morphology, proliferative capacity, and immunophenotype. Unexpectedly, although normal in adipocyte differentiation, MM-ASC present a defective osteoblast differentiation, as indicated by less calcium deposition, decreased alkaline phosphatase activity, and downregulation of RUNX2 and osteocalcin. Furthermore, these ASC-derived osteoblasts displayed enhanced senescence, as shown by an increased β-galactosidase activity and cell cycle inhibitors expression (p16 INK4A , p21 WAF1/CIP1 .), associated with a markedly increased expression of DKK1, a major inhibitor of osteoblastogenesis in multiple myeloma. Interestingly, inhibition of DKK1 attenuated senescence and rescued osteoblast differentiation, highlighting its key role. Our findings show, for the first time, Cells 2019, 8, 441 2 of 16 that multiple myeloma is a systemic disease and suggest that ASC from patients would be unsuitable for tissue engineering designed to treat myeloma-associated bone disease.Le myélome multiple est caractérisé par des lésions osseuses liées à une augmentation de l'activité ostéoclastique et à une diminution de l'activité ostéoblastique. En particulier, la différenciation ostéoblastique des cellules souches issues de la moelle osseuse (CSM) est altérée. Parmi les outils thérapeutiques potentiels pour contrer les lésions osseuses, les cellules souches dérivées de l'adipeux (CSA) pourraient représenter une source intéressante pour la médecine régénérative en raison de leurs caractéristiques similaires à celles des cellules MSC. Notre étude est l'une des premières à donner un aperçu détaillé des capacités ostéoblastogènes de l'ASC isolée par aspiration graisseuse chez les patients atteints de myélome (MM-ASC) par rapport aux sujets sains (HD-ASC). Nous avons montré que le MM-ASC et le HD-ASC présentaient une morphologie, une capacité proliférative et un immunophénotype comparables. De façon inattendue, bien que normal dans la différenciation adipocytaire, le MM-ASC présente une différenciation ostéoblastique défectueuse, comme l'indiquent la diminution des dépôts de calcium, la diminution de l'activité des phosphatases alcalines et la régulation négative de RUNX2 et de l'ostéocalcine. De plus, ces ostéoblastes dérivés de l'ASC présentaient une sénescence accrue, comme en témoigne l'augmentation de l'activité de la β-galactosidase et de l'expression des inhibiteurs du cycle cellulaire (p16 INK4A, p21 WAF1/CIP1 .), associée à une expression nettement accrue du DKK1, un inhibiteur majeur de l'ostéoblastogenèse dans les myélomes multiples. Il est intéressant de noter que l'inhibition du DKK1 a atténué la sénescence et sauvé la différenciation des ostéoblastes, soulignant son rôle clé. Nos résultats montrent, pour la première fois, que le myélome multiple est une maladie systémique et suggèrent que les cellules 2019, 8, 441 2 sur 16 ne conviennent pas au génie tissulaire conçu pour traiter les maladies osseuses associées au myélome

Familial Glucocorticoid Receptor Haploinsufficiency by Non-Sense Mediated mRNA Decay, Adrenal Hyperplasia and Apparent Mineralocorticoid Excess

Primary glucocorticoid resistance (OMIM 138040) is a rare hereditary disease that causes a generalized partial insensitivity to glucocorticoid action, due to genetic alterations of the glucocorticoid receptor (GR). Investigation of adrenal incidentalomas led to the discovery of a family (eight affected individuals spanning three generations), prone to cortisol resistance, bilateral adrenal hyperplasia, arterial hypertension and hypokalemia. This phenotype exacerbated over time, cosegregates with the first heterozygous nonsense mutation p.R469[R,X] reported to date for the GR, replacing an arginine (CGA) by a stop (TGA) at amino-acid 469 in the second zinc finger of the DNA-binding domain of the receptor. In vitro, this mutation leads to a truncated 50-kDa GR lacking hormone and DNA binding capacity, devoid of hormone-dependent nuclear translocation and transactivation properties. In the proband's fibroblasts, we provided evidence for the lack of expression of the defective allele in vivo. The absence of detectable mutated GR mRNA was accompanied by a 50% reduction in wild type GR transcript and protein. This reduced GR expression leads to a significantly below-normal induction of glucocorticoid-induced target genes, FKBP5 in fibroblasts. We demonstrated that the molecular mechanisms of glucocorticoid signaling dysfunction involved GR haploinsufficiency due to the selective degradation of the mutated GR transcript through a nonsense-mediated mRNA Decay that was experimentally validated on emetine-treated propositus' fibroblasts. GR haploinsufficiency leads to hypertension due to illicit occupation of renal mineralocorticoid receptor by elevated cortisol rather than to increased mineralocorticoid production reported in primary glucocorticoid resistance. Indeed, apparent mineralocorticoid excess was demonstrated by a decrease in urinary tetrahydrocortisone-tetrahydrocortisol ratio in affected patients, revealing reduced glucocorticoid degradation by renal activity of the 11β-hydroxysteroid dehydrogenase type 2, a GR regulated gene. We propose thus that GR haploinsufficiency compromises glucocorticoid sensitivity and may represent a novel genetic cause of subclinical hypercortisolism, incidentally revealed bilateral adrenal hyperplasia and mineralocorticoid-independent hypertension

Prolactin Receptor Signaling Is Essential for Perinatal Brown Adipocyte Function: A Role for Insulin-like Growth Factor-2

BACKGROUND: The lactogenic hormones prolactin (PRL) and placental lactogens (PL) play central roles in reproduction and mammary development. Their actions are mediated via binding to PRL receptor (PRLR), highly expressed in brown adipose tissue (BAT), yet their impact on adipocyte function and metabolism remains unclear. METHODOLOGY/PRINCIPAL FINDINGS: PRLR knockout (KO) newborn mice were phenotypically characterized in terms of thermoregulation and their BAT differentiation assayed for gene expression studies. Derived brown preadipocyte cell lines were established to evaluate the molecular mechanisms involved in PRL signaling on BAT function. Here, we report that newborn mice lacking PRLR have hypotrophic BAT depots that express low levels of adipocyte nuclear receptor PPARgamma2, its coactivator PGC-1alpha, uncoupling protein 1 (UCP1) and the beta3 adrenoceptor, reducing mouse viability during cold challenge. Immortalized PRLR KO preadipocytes fail to undergo differentiation into mature adipocytes, a defect reversed by reintroduction of PRLR. That the effects of the lactogens in BAT are at least partly mediated by Insulin-like Growth Factor-2 (IGF-2) is supported by: i) a striking reduction in BAT IGF-2 expression in PRLR KO mice and in PRLR-deficient preadipocytes; ii) induction of cellular IGF-2 expression by PRL through JAK2/STAT5 pathway activation; and iii) reversal of defective differentiation in PRLR KO cells by exogenous IGF-2. CONCLUSIONS: Our findings demonstrate that the lactogens act in concert with IGF-2 to control brown adipocyte differentiation and growth. Given the prominent role of brown adipose tissue during the perinatal period, our results identified prolactin receptor signaling as a major player and a potential therapeutic target in protecting newborn mammals against hypothermia

When therapeutic drugs lead to diabetes.

peer reviewedDrug-induced diabetes mellitus is a growing problem in clinical practice. New, potent medications contribute to this problem in a population already at high risk of developing glucose disturbances because of poor lifestyle habits and high prevalence of being overweight/obese. The present review focuses on four important pharmacological classes: glucocorticoids; antipsychotics, especially second generation; antiretroviral therapies, which revolutionised the management of individuals with HIV; and immune checkpoint inhibitors, recently used for the immunotherapy of cancer. For each class, the prevalence of drug-induced diabetes will be evaluated, the most common clinical presentations will be described, the underlying mechanisms leading to hyperglycaemia will be briefly analysed, and some recommendations for appropriate monitoring and management will be proposed

Preface to special issue on “Liver Metabolic Diseases and Hepatocellular Carcinoma: New Hormonal and Clinical Insights”

International audienceAbstract The Wnt/β-catenin pathway plays a pivotal role in liver structural and metabolic homeostasis. Wnt activity is tightly regulated by the acyltransferase Porcupine through the addition of palmitoleate. Interestingly palmitoleate can be endogenously produced by the stearoyl-CoA desaturase 1 (SCD1), a lipogenic enzyme transcriptionally regulated by insulin. This study aimed to determine whether nutritional conditions, and insulin, regulate Wnt pathway activity in liver. An adenoviral TRE-Luciferase reporter was used as a readout of Wnt/β-catenin pathway activity, in vivo in mouse liver and in vitro in primary hepatocytes. Refeeding enhanced TRE-Luciferase activity and expression of Wnt target genes in mice liver, revealing a nutritional regulation of the Wnt/β-catenin pathway. This effect was inhibited in liver specific insulin receptor KO (iLIRKO) mice and upon wortmannin or rapamycin treatment. Overexpression or inhibition of SCD1 expression regulated Wnt/β-catenin activity in primary hepatocytes. Similarly, palmitoleate added exogenously or produced by SCD1-mediated desaturation of palmitate, induced Wnt signaling activity. Interestingly, this effect was abolished in the absence of Porcupine, suggesting that both SCD1 and Porcupine are key mediators of insulin-induced Wnt/β-catenin activity in hepatocytes. Altogether, our findings suggest that insulin and lipogenesis act as potential novel physiological inducers of hepatic Wnt/β-catenin pathway

When therapeutic drugs lead to diabetes

International audienceDrug-induced diabetes mellitus is a growing problem in clinical practice. New, potent medications contribute to this problem in a population already at high risk of developing glucose disturbances because of poor lifestyle habits and high prevalence of being overweight/obese. The present review focuses on four important pharmacological classes: glucocorticoids; antipsychotics, especially second generation; antiretroviral therapies, which revolutionised the management of individuals with HIV; and immune checkpoint inhibitors, recently used for the immunotherapy of cancer. For each class, the prevalence of drug-induced diabetes will be evaluated, the most common clinical presentations will be described, the underlying mechanisms leading to hyperglycaemia will be briefly analysed, and some recommendations for appropriate monitoring and management will be proposed

Molecular Cloning of a Major mRNA Species in Murine 3T3 Adipocyte Lineage

International audienceIn an effort to identify novel mRNAs modulated during the course of adipose conversion, we have used a simplified differential display technique and have isolated a cDNA encoding an amine oxidase tremendously expressed in the adipocyte, the semicarbazide-sensitive amine oxidase (SSAO). The predicted amino acid sequence (765 amino acids) is likely to be the homologue of the human placental amine oxidase and of the partially known sequence of the rat adipocyte membrane amine oxidase. SSAO mRNAs are present in several tissues, but strikingly, the highest levels of gene expression are found in adipose tissue and aorta. Enzyme transcript levels are barely detectable in preadipocytes but are induced several hundred-fold during the adipocyte differentiation of 3T3-L1 or 3T3-F442A cells and of rat precursor primary cultures. These changes in transcript levels parallel a sharp increase in SSAO enzyme activity. The biochemical properties of the SSAO present in 3T3-L1 or 3T3-F442A adipocytes closely resemble the features of the SSAO activity previously described in white and brown adipose tissues. Interestingly, SSAO mRNA levels and enzyme activity drop in response to effectors of the cAMP pathway and to the cytokine tumor necrosis factor-alpha, indicating that two major signaling molecules of adipose tissue development and metabolism can control SSAO function. Moreover, the expression of SSAO transcripts and activity are clearly down-regulated in white adipose tissue from obese Zücker rats. Because of its known stimulatory effect on glucose transport, its biochemical properties and its pattern of expression and regulation, SSAO could play an important role in the regulation of adipocyte homeostasis