White matter microstructure associated with the range of attentional and impulsive performance in school-aged children

Introduction

Inhibition capabilities have been shown to be a strong predictor of social and educational life outcomes (Mischel & Ebbesen, 1970; Shoda et al., 1990). Inhibition capabilities have an enormous impact on attention and impulsivity (Bari & Robbins, 2013). These two executive functions are associated with numerous psychiatric disorders but are not well understood in terms of white matter (WM) connectivity (Puiu et al., 2018). Novel techniques and statistical approaches in neuroimaging bring us closer to a biologically sustained model.

Objectives

This research aims to: 1) identify WM connections associated with attention/impulsivity performance and 2) characterize the differences in WM microstructure associated with the variation of the performance.

Methods

157 children (GESTE cohort, 8-12 years, 27 Dx ADHD, 2 Dx ASD) with b=1500mm²/s, 2mm isotropic dMRI acquisitions were included. Tractography was performed with TractoFlow pipeline (Theaud et al., 2020). Dimensionality reduction of diffusion metrics yielded two components : microstructural complexity (DTI Metrics, AFD & NuFo) and axonal density (AFD_fixel) (Chamberland et al., 2019). Attention/impulsivity were evaluated with the CPT3. Multivariate linear regression was performed in python.

Results

Lower microstructural complexity was associated with poorer attentional performance on regions of the parietal lobe to the occipital gyrus (P-O, p=0.044, R²=0.14, Figure 1.) and the Broadman’s area 8 to area 6 (SF8-SF6, p=0.002, R²=0.12, Figure 1.). Lower axonal density was associated with a less impulsive pattern on SF8-SF6 (p=0.001, R²=0.13, Figure 1.). Results remained significant when removing children with an ADHD or ASD diagnosis.

Conclusions

We identified underlying difference in WM microstructure that may be associated with the variation in attention/impulsivity performance in school-aged children.

Disclosure

No significant relationships.

A271 ETIOLOGICAL CHARACTERIZATION OF DRUG-INDUCED ACUTE PANCREATITIS

Background

Drugs are considered a relatively rare and understudied cause of acute pancreatitis (AP). The lack of convincing and conclusive data on drug-induced AP (DIAP) complicates the diagnosis as well as the identification of the causative drug.

Aims

We hypothesized that documenting the causes of DIAP in the Saguenay-Lac-Saint-Jean (SLSJ) will add new evidence to the current literature and will provide a comprehensive picture of this health condition in the region. The aim of this study is to document causes of DIAP cases that occurred in the SLSJ population.

Methods

We have conducted a retrospective and descriptive population-based study of DIAP cases that occurred between 2006 and 2014 in the six hospitals deserving the SLSJ entire population. Cases were selected from the Quebec Ministry of Health hospitalizations registry (MED-ECHO) administrative public database. Medical chart review was performed in attempt to characterize DIAP hospitalizations and to identify the imputable drugs.

Results

During the studied period, 75 cases (30.7% male, 69.3% female) were included totalling 90 hospitalizations for DIAP. Among them, 51 causative drugs were identified and were distributed in 17 different drug classes. Recurrent DIAP were documented in 13 cases and among them, 6 cases have experimented positive rechallenge. Six drugs (5-fluorouracil, atorvastatin, bortezomib, nilotinib, rosuvastatin and triamcinolone) were associated with the highest degree of evidence. The most common causative drugs of DIAP hospitalization were azathioprine (n = 7), followed by atorvastatin (n =6), hydrochlorothiazide (n = 5), rosuvastatin (n = 4) and codeine (n = 4).

Conclusions

This study has added new evidences about potentially pancreatitis-associated drugs in literature. This is the first study to report definite 5-fluorouracil and triamcinolone-induced AP. An updated version of the evidence-based literature review is needed to support the clinicians in the identification of the causative drugs.

Funding Agencies

None

Thyroid-Stimulating Hormone-Stimulated Human Adipocytes Express Thymic Stromal Lymphopoietin

When recombinant human (rh) thyroid-stimulating hormone (TSH) is administered to thyroid cancer survivors, an acute extra-thyroidal effect raises pro-inflammatory cytokines and activates platelets. Thymic stromal lymphopoietin (TSLP) is a cytokine recently implicated in platelet activation. Our aim was to measure platelet microparticle levels after rhTSH stimulation in vivo, and to investigate TSLP expression in TSH-stimulated human adipocytes in culture. Blood samples for total and platelet microparticle analysis were obtained from thyroid cancer survivors before (day 1) and after rhTSH administration (day 5). Adipocytes, differentiated from stromal preadipocytes isolated from adipose tissue from surgical patients, were stimulated with TSH. TSLP mRNA expression, protein expression, and protein release into the adipocyte medium were measured. The level of platelet microparticles in thyroid cancer patients rose 5-fold after rhTSH stimulation. TSH upregulated TSLP mRNA expression in adipocytes in culture through a pathway that was inhibited by 66% by H89, a protein kinase A inhibitor. TSLP protein expression rose in response to TSH, and TSH-stimulated TSLP release into the medium was completely blocked by dexamethasone. In conclusion, TSLP is a novel TSH-responsive adipokine. Future studies will be needed to address the potential role of adipocyte-derived TSLP and whether it is linked to TSH-dependent platelet activation.

The anti-adipogenic effect of peripheral blood mononuclear cells is absent with PCSK9 loss-of-function variants

OBJECTIVE

To determine the effect of (1) an oral fat load and (2) pro-protein convertase subtilisin/kexin type (PCSK) 9 loss-of-function (LOF) variant status on the ability of peripheral blood mononuclear cells (PBMC) to inhibit human adipogenesis.

METHODS

PBMC from subjects with one or more PCSK9 LOF variants versus non-variant controls were compared in the fasting state and after an oral fat load.

RESULTS

Fasting triglyceride (TG) levels were lower in the LOF variant versus non-variant group but rose to the same level after the oral fat load. Conditioned medium from PBMC was obtained in fasting (PBMC-CM-F) and 4-h postprandial (PBMC-CM-PP) states. PBMC-CM-PP from non-variant controls inhibited adipogenesis of human preadipocytes more than did PBMC-CM-F. In contrast, PBMC-CM-F or -PP from PCSK9 LOF variant subjects had no effect on adipogenesis. After the oral fat load, PBMC from PCSK9 LOF variant subjects showed significant increases in mRNA levels of interleukin-1β, tumor necrosis factor-α, sterol regulatory element binding protein-1c, CD36, and monocyte chemoattractant protein-1 (MCP-1), only MCP-1 mRNA levels increased in PBMC from non-variant controls.

CONCLUSIONS

The absence of anti-adipogenic action of PBMC from PCSK9 LOF variant subjects points to a novel role for PCSK9 in PBMC-adipose cell interactions.

Thyroid-stimulating hormone acutely increases monocyte gene expression in vivo

OBJECTIVES

Thyroid-stimulating hormone (TSH) acts in an extra-thyroidal fashion and induces a pro-inflammatory, pro-coagulant state. Blood monocytes can be activated by vascular stress, but it is not known if this occurs upon TSH administration. Our aim was to determine if recombinant human (rh) TSH, administered acutely to patients being screened for thyroid cancer recurrence, alters blood monocyte gene expression.

DESIGN AND SETTING

Patients (14 women, 1 man) had a mean (±SD) age of 48±10 years, a body mass index of 26±6 kg/m2, a history of total thyroidectomy and radioablation for thyroid cancer, and were on L-thyroxine therapy at a university teaching hospital. They received 2 intramuscular doses of rhTSH (0.9 mg), administered on days 1 and 2. Blood samples were obtained at baseline on day1, and on days 3 and 5.

RESULTS

Monocyte MCP-1 mRNA (mean±SE) increased significantly by 1.7±0.3 fold on day 5 following rhTSH stimulation (p=0.03, n=15). IL-1β and CD36 mRNA expression also increased on day 5 (1.9±0.4 fold, p=0.07, n=14) and 2.5±0.4 fold, p=0.1, n=10), respectively, although did not quite reach statistical significance. Significant correlations were detected between the BMI of patients and their TSH-stimulated monocyte mRNA responses at day 5 for CD11a, (r=0.66, n=14, p=0.01); CD14 (r=0.638, n=13, p=0.019), and CD16, r=0.84, n=13, p=0.0003).

CONCLUSION

TSH administration increases pro-atherogenic monocyte gene expression.

Effects of intramuscular administration of folic acid and vitamin B12 on granulosa cells gene expression in postpartum dairy cows

The fertility of dairy cows is challenged during early lactation, and better nutritional strategies need to be developed to address this issue. Combined supplementation of folic acid and vitamin B12 improve energy metabolism in the dairy cow during early lactation. Therefore, the present study was undertaken to explore the effects of this supplement on gene expression in granulosa cells from the dominant follicle during the postpartum period. Multiparous Holstein cows received weekly intramuscular injection of 320 mg of folic acid and 10 mg of vitamin B12 (treated group) beginning 24 (standard deviation=4) d before calving until 56 d after calving, whereas the control group received saline. The urea plasma concentration was significantly decreased during the precalving period, and the concentration of both folate and vitamin B12 were increased in treated animals. Milk production and dry matter intake were not significantly different between the 2 groups. Plasma concentrations of folates and vitamin B12 were increased in treated animals. Daily dry matter intake was not significantly different between the 2 groups before [13.5 kg; standard error (SE)=0.5] and after (23.6 kg; SE=0.9) calving. Average energy-corrected milk tended to be greater in vitamin-treated cows, 39.7 (SE=1.4) and 38.1 (SE=1.3) kg/d for treated and control cows, respectively. After calving, average plasma concentration of β-hydroxybutyrate tended to be lower in cows injected with the vitamin supplement, 0.47 (SE=0.04) versus 0.55 (SE=0.03) for treated and control cows, respectively. The ovarian follicle ≥12 mm in diameter was collected by ovum pick-up after estrus synchronization. Recovered follicular fluid volumes were greater in the vitamin-treated group. A microarray platform was used to investigate the effect of treatment on gene expression of granulosa cells. Lower expression of genes involved in the cell cycle and higher expression of genes associated with granulosa cell differentiation before ovulation were observed. Selected candidate genes were analyzed by reverse transcription quantitative PCR. Although the effects of intramuscular injections of folic acid and vitamin B12 on lactational performance and metabolic status of animals were limited, ingenuity pathway analysis of gene expression in granulosa cells suggests a stimulation of cell differentiation in vitamin-treated cows, which may be the result of an increase in LH secretion.

Interacting Effects of TSH and Insulin on Human Differentiated Adipocytes

Subclinical hypothyroidism, characterized by an isolated rise in TSH serum levels with normal thyroid function, is a pro-inflammatory state associated with insulin resistance. Adipocytes express TSH receptors, but it is not known if TSH can directly inhibit insulin signaling. Using primary human differentiated adipocytes, we examined the effects of TSH on insulin-stimulated Akt phosphorylation, and whether conventional PKC (cPKC) were involved. The effect of insulin on TSH-stimulated lipolysis was also investigated. TSH inhibited insulin-stimulated Akt phosphorylation in adipocytes by 54%. TSH activated cPKC, and Gö6976, a PKCα and -β1 inhibitor, prevented the inhibitory effect of TSH on the insulin response. Insulin reduced the ability of TSH to activate cPKC and to stimulate lipolysis.Our data reveal novel interactions between TSH and insulin. TSH inhibits insulin-stimulated Akt signaling in a cPKC-dependent fashion, whereas insulin blocks TSH-stimulated cPKC activity and lipolysis. TSH and insulin act on differentiated human adipocytes to modulate their respective intracellular signals.

TSH signaling pathways that regulate MCP-1 in human differentiated adipocytes

OBJECTIVE

Adipose tissue is an extra-thyroidal thyroid-stimulating hormone (TSH) target. Increases in lipolysis and in expression and release of interleukin-6 (IL-6) occur in TSH-stimulated adipocytes, and levels of circulating free fatty acids and IL-6 rise following TSH administration to patients with previous thyroidectomy and radioablation for thyroid cancer. Our first objective was to compare how TSH stimulates protein kinase A (PKA) and inhibitor of κB (IκB) kinase (IKK)-β. Our second objective was to investigate whether TSH induces other cytokines besides IL-6.

METHODS

TSH stimulation of either CHO cells expressing human TSH receptor or human abdominal subcutaneous differentiated adipocytes.

RESULTS

Signaling studies showed TSH increased NADPH oxidase activity, and either diphenyleneiodonium (oxidase inhibitor) or N-acetyl cysteine (scavenger of reactive oxygen species) reduced IKKβ phosphorylation. Phosphorylation of protein kinase C-δ, an upstream regulator of NADPH oxidase, was increased by TSH, and rottlerin (PKCδ inhibitor) reduced TSH-stimulated IKKβ phosphorylation. TSH upregulated monocyte chemoattractant protein-1 (MCP-1) mRNA expression and the release of MCP-1 protein in human abdominal differentiated adipocytes. H89 (PKA inhibitor) and sc-514 (IKKβ inhibitor) each blocked TSH-stimulated MCP-1 mRNA expression and protein release, suggesting PKA and IKKβ participate in this pathway.

CONCLUSIONS

These data provide new information about TSH signaling in human differentiated adipocytes, and add to the evidence that TSH is a pro-inflammatory stimulus of adipocytes.

Migrant women's utilization of prenatal care: a systematic review

Our objectives were to determine whether migrant women in Western industrialized countries have higher odds of inadequate prenatal care (PNC) compared to receiving-country women and to summarize factors that are associated with inadequate PNC among migrant women in these countries. We conducted searches of electronic databases (MEDLINE, EMBASE, and PsycINFO), reference lists, known experts, and an existing database of the Reproductive Outcomes And Migration international research collaboration for articles published between January, 1995 and April, 2010. Title and abstract review and quality appraisal were conducted independently by 2 reviewers using established criteria, with consensus achieved through discussion. In this systematic review of 29 studies, the majority of studies demonstrated that migrant women were more likely to receive inadequate PNC than receiving-country women, with most reporting moderate to large effect sizes. Rates of inadequate PNC among migrant women varied widely by country of birth. Only three studies explored predictors of inadequate PNC among migrant women. These studies found that inadequate PNC among migrant women was associated with being less than 20 years of age, multiparous, single, having poor or fair language proficiency, education less than 5 years, an unplanned pregnancy, and not having health insurance. We concluded that migrant women as a whole were more likely to have inadequate PNC and the magnitude of this risk differed by country of origin. Few studies addressed predictors of PNC utilization in migrant women and this limits our ability to provide effective PNC in this population.

Serum fetuin-A levels following recombinant human thyroid-stimulating hormone stimulation

Purpose: Fetuin-A is a hepatokine that is linked to lipid metabolism, obesity, insulin resistance, type 2 diabetes and cardiovascular disease. Elevated thyroid-stimulating hormone (TSH) levels are associated with metabolic and cardiovascular disturbances. Our aim was to determine if TSH can regulate fetuin-A levels. Methods: Fetuin-A serum levels were examined in 26 subjects (19 women; previous thyroidectomy and radioactive iodine ablation) undergoing recombinant human TSH (rhTSH) stimulation to screen for thyroid cancer recurrence. Their age was 49±10 years, and body mass index (BMI) was 28±6 (both expressed as mean±SD). The patients received two doses of rhTSH (0.9 mg), administered 24 hours apart on days 1 and 2, without discontinuation of ongoing L-thyroxine therapy. Morning blood samples were obtained on days 1 (prior to the first dose of rhTSH), 3 and 5. Results: The baseline value of fetuin-A (mean±SD) for all participants was 527±186 mg/L. Values of fetuin-A did not change in response to rhTSH administration. The lack of response was not dependent on gender, age, baseline free thyroxine level or BMI. Conclusion: Fetuin-A has been implicated in metabolic and inflammatory conditions, but there have been no reports on whether fetuin-A is influenced by TSH. Within the context of rhTSH administration for surveillance of thyroid cancer recurrence, there was no effect on serum levels of fetuin-A.

Macrophage-induced adipose tissue dysfunction and the preadipocyte: should I stay (and differentiate) or should I go?

Adipose tissue can be regarded as a multidepot organ responsible for metabolic homeostasis by managing sophisticated energy transactions as well as by producing bioactive molecules that regulate insulin sensitivity and immune and vascular responses. Chronic nutrient excess expands adipose tissue, and concomitant variations in its cellular and matrix remodeling can affect the extent of the metabolic dysfunction that is associated with obesity. Preadipocytes, also termed adipose progenitor cells, play a pivotal role in determining whether a dysfunctional hypertrophic state arises as opposed to a hyperplastic process in which mature adipocytes remain relatively responsive. Obesity is associated with infiltration of macrophages, and these immune cells have been shown to communicate with preadipocytes to influence how they differentiate, survive, and proliferate. Understanding macrophage-preadipocyte interactions and their effect on adipose remodeling mechanisms may identify potential therapeutic molecular targets to improve adipose tissue function, even in the face of obesity.

PKC activation is required for TSH-mediated lipolysis via perilipin activation

Adipocytes express TSH receptors, and TSH can stimulate cAMP-dependent protein kinase, perilipin phosphorylation, and lipolysis in human and mouse 3T3-L1 adipocytes. TSH activates PKC in thyrocytes. Since PKC has been implicated in lipolysis in adipocytes, we examined whether the family of conventional isoforms of PKC (cPKC) is a target of TSH in adipocytes, and whether cPKC is required for TSH-stimulated lipolysis. Differentiated 3T3-L1 and subcutaneous abdominal human adipocytes in culture were treated with TSH in the presence or absence of either PKC inhibitor Gö6976 (inhibits PKCα, βI) or Gö6983 (inhibits PKCα, βI, βII, γ, δ). Activation of cPKC was assessed by phospho-(ser) PKC substrate antibody immunoblot analysis. Perilipin phosphorylation was measured by SDS-PAGE electromobility shift followed by anti-perilipin immunoblot analysis. Lipolysis was quantified by the amount of nonesterified fatty acids (NEFAs) released into the medium. TSH strongly and significantly activated cPKC in differentiated human and 3T3-L1 adipocytes from undetectable levels in control conditions. This cPKC stimulation in human adipocytes by TSH was reduced significantly by 40% or 48% in the presence of PKC inhibitor Gö6983 or Gö6976, respectively. Gö6976 inhibited TSH-stimulated human adipocyte perilipin phosphorylation and NEFA release by 80% and 50%, respectively. We conclude that cPKC is activated by TSH in human differentiated adipocytes. Based on the effects of cPKC inhibition, cPKC activation is required for TSH-stimulated perilipin phosphorylation and lipolysis in human differentiated adipocytes.

The activation state of macrophages alters their ability to suppress preadipocyte apoptosis

Adipose tissue contains macrophages whose state of activation is regulated as obesity develops. Macrophage-secreted factors influence critical processes involved in adipose tissue homeostasis, including preadipocyte proliferation and differentiation into adipocytes. Macrophage-conditioned medium (MacCM) from J774A.1 macrophages protects 3T3-L1 preadipocytes from apoptosis through platelet-derived growth factor (PDGF) signaling. Here, we investigated the effect of macrophage activation on MacCM-dependent preadipocyte survival. MacCM was prepared following activation of either J774A.1 macrophages with lipopolysaccharide (LPS) or human primary monocyte-derived macrophages (MD-macrophages) with LPS or interleukin 4 (IL4). 3T3-L1 and human primary preadipocytes were induced to undergo apoptosis in MacCM, and apoptosis was quantified by cell enumeration or Hoechst nuclear staining. Preadipocyte PDGF signaling was assessed by immunoblot analysis of phosphorylated PDGF receptor, Akt, and ERK1/2. Pro-inflammatory activation of J774A.1 macrophages with LPS inhibited the pro-survival activity of MacCM on 3T3-L1 preadipocytes, despite intact PDGF signaling. Upregulation of macrophage tumor necrosis factor a (TNFα) expression occurred in response to LPS, and TNFα was demonstrated to be responsible for the inability of LPS-J774A.1-MacCM to inhibit preadipocyte apoptosis. Furthermore, MacCM from human MD-macrophages (MD-MacCM) inhibited apoptosis of primary human preadipocytes. MD-MacCM from LPS-treated macrophages, but not IL4-treated anti-inflammatory macrophages, was unable to protect human preadipocytes from cell death. In both murine cell lines and human primary cells, pro-inflammatory activation of macrophages inhibits their pro-survival activity, favoring preadipocyte death. These findings may be relevant to preadipocyte fate and adipose tissue remodeling in obesity.

Effect of collagen I and aortic carboxypeptidase-like protein on 3T3-L1 adipocyte differentiation

Aortic carboxypeptidase-like protein (ACLP) is a secreted protein expressed in preadipocytes and down-regulated during adipogenesis. Results from previous studies on the influence of ACLP overexpression on adipogenesis vary from no effect to complete inhibition. We hypothesized that ACLP may modulate adipogenesis in the presence of collagen I, a protein to which it binds. We compared control (pLXSN) 3T3-L1 preadipocytes with 3T3-L1 preadipocytes stably overexpressing ACLP (pLXSN-ACLP) that were grown in standard vs collagen I-coated dishes. Aortic carboxypeptidase-like protein overexpression, via retroviral transduction, resulted in a 3.2-fold increase in ACLP cellular levels and a 2.1-fold increase in ACLP levels released into medium. Aortic carboxypeptidase-like protein overexpression did not inhibit differentiation in standard dishes. In collagen I-coated dishes compared with standard dishes, control preadipocytes, when induced to differentiate, exhibited the same increase in triacylglycerol accumulation, but showed a significantly higher induction of fatty acid synthase (1.6-fold more), peroxisome proliferator-activated receptor γ (1.4-fold more), and CCAAT/enhancer-binding protein α (1.4-fold more). Aortic carboxypeptidase-like protein overexpression significantly reduced this enhanced induction of fatty acid synthase, peroxisome proliferator-activated receptor γ, and CCAAT/enhancer-binding protein α by 65%, 59%, and 66%, respectively, but had no effect on the accumulation of triacylglycerol during differentiation. Finally, studies on proadipogenic insulin signaling in ACLP-overexpressing preadipocytes demonstrated that insulin-stimulated Akt phosphorylation was significantly decreased by 27% in cells cultured in collagen I-coated dishes vs standard dishes. Our data suggest that ACLP inhibits certain aspects of 3T3-L1 adipogenesis in a collagen I-rich environment.

Macrophage-induced preadipocyte survival depends on signaling through Akt, ERK1/2, and reactive oxygen species

Obesity is associated with adipose tissue remodeling, characterized by macrophage accumulation, adipocyte hypertrophy, and apoptosis. We previously reported that macrophage-conditioned medium (MacCM) protects preadipocytes from apoptosis, due to serum withdrawal, in a platelet-derived growth factor (PDGF)-dependent manner. We have now investigated the role of intracellular signaling pathways, activated in response to MacCM versus PDGF, in promoting preadipocyte survival. Exposure of 3T3-L1 preadipocytes to J774A.1-MacCM or PDGF strongly stimulated Akt and ERK1/2 phosphorylation from initially undetectable levels. Inhibition of the upstream regulators of Akt or ERK1/2, i.e. phosphoinositide 3-kinase (PI3K; using wortmannin or LY294002) or MEK1/2 (using UO126 or PD98509), abrogated the respective phosphorylation responses, and significantly impaired pro-survival activity. J774A.1-MacCM increased reactive oxygen species (ROS) levels by 3.4-fold, and diphenyleneiodonium (DPI) or N-acetyl cysteine (NAC) significantly inhibited pro-survival signaling and preadipocyte survival in response to J774A.1-MacCM. Serum withdrawal itself also increased ROS levels (2.1-fold), and the associated cell death was attenuated by DPI or NAC. In summary, J774A.1-MacCM-dependent 3T3-L1 preadipocyte survival requires the Akt and ERK1/2 signaling pathways. Furthermore, ROS generation by J774A.1-MacCM is required for Akt and ERK1/2 signaling to promote 3T3-L1 preadipocyte survival. These data suggest potential mechanisms by which macrophages may alter preadipocyte fate.

The anti-adipogenic effect of macrophage-conditioned medium requires the IKKβ/NF-κB pathway

Macrophage-secreted factors inhibit adipogenesis, but the underlying mechanism is not well understood. Our objective was to determine if anti-adipogenic signaling pathways in human preadipocytes are activated by macrophage-conditioned medium (MacCM). Human abdominal subcutaneous stromal preadipocytes were treated with adipogenic inducers in either standard medium or medium conditioned by human THP-1 macrophages. THP-1-MacCM increased inhibitor of κB kinase β (IKKβ) phosphorylation, inhibitor of NF-κB α (IκBα) degradation, and NF-κB activity in human preadipocytes in a time-dependent manner. Concomitant treatment of human abdominal subcutaneous preadipocytes with sc-514, a selective inhibitor of IKKβ, prevented the inhibitory effect of THP-1-MacCM on lipid accumulation and expression of adipogenic markers. Our data indicate that activation of the preadipocyte IKKβ/NF-κB pathway is required for the anti-adipogenic effect of THP-1-MacCM on human adipogenesis.

Insulin sensitization of human preadipocytes through glucocorticoid hormone induction of forkhead transcription factors

Glucocorticoids are synthesized locally in adipose tissue and contribute to metabolic disease through the facilitation of adipose tissue expansion. Here we report that exposure of human primary preadipocytes to glucocorticoids increases their sensitivity to insulin and enhances their subsequent response to stimuli that promote differentiation. This effect was observed in primary human preadipocytes but not in immortalized 3T3-L1 murine preadipocytes or in fully differentiated primary human adipocytes. Stimulation of insulin signaling was mediated through induction of insulin receptor (IR), IR substrate protein 1 (IRS1), IRS2, and the p85 regulatory subunit of phosphoinositide-3-3-kinase, which led to enhanced insulin-mediated activation of Akt. Although induction of IRS2 was direct, induction of IR and IRS1 by glucocorticoids occurred subsequent to primary induction of the forkhead family transcription factors FoxO1A and FoxO3A. These results reveal a new role for glucocorticoids in preparing preadipocytes for differentiation.

IKKbeta and the anti-adipogenic effect of platelet-derived growth factor in human abdominal subcutaneous preadipocytes

To clarify how anti-adipogenic factors act on preadipocytes to inhibit their differentiation, we compared preadipocyte signaling responses generated by platelet-derived growth factor (PDGF; anti-adipogenic) versus insulin (pro-adipogenic). PDGF, but not insulin, stimulated the phosphorylation of inhibitor of kappaB kinase beta (IKKbeta) in a time-dependent manner. This PDGF-dependent phosphorylation event was inhibited by 60% (P<0.05) when the cells were pretreated with wortmannin, indicating a requirement for the phosphatidylinositol (PI) 3-kinase/AKT pathway. IKKbeta phosphorylation by PDGF was neither accompanied by IkappaBalpha degradation nor NF-kappaB activation. PDGF inhibited human adipocyte differentiation, assessed by triacylglycerol accumulation (75% reduction; P<0.01) and by fatty acid synthase protein expression (60% reduction; P<0.05); these responses were no longer apparent in the presence of sc-514, a selective inhibitor of IKKbeta. Our data describe a novel PDGF response in human preadipocytes that involves the pro-inflammatory kinase IKKbeta and demonstrate that it is required for the inhibition of adipogenesis.

Somali women and their pregnancy outcomes postmigration: data from six receiving countries

Objective

This study aimed to investigate pregnancy outcomes in Somali-born women compared with those women born in each of the six receiving countries: Australia, Belgium, Canada, Finland, Norway and Sweden.

Design

Meta-analyses of routinely collected data on confinements and births.

Setting

National or regional perinatal datasets spanning 3–6 years between 1997 and 2004 from six countries.

Sample

A total of 10 431 Somali-born women and 2 168 891 receiving country-born women.

Methods

Meta-analyses to compare outcomes for Somali-born and receiving country-born women across the six countries.

Main outcome measures

Events of labour (induction, epidural use and proportion of women using no analgesia), mode of birth (spontaneous vaginal birth, operative vaginal birth and caesarean section) and infant outcomes (preterm birth, birthweight, Apgar at 5 minutes, stillbirths and neonatal deaths).

Results

Compared with receiving country-born women, Somali-born women were less likely to give birth preterm (pooled OR 0.72, 95% CI 0.64–0.81) or to have infants of low birthweight (pooled OR 0.89, 95% CI 0.82–0.98), but there was an excess of caesarean sections, particularly in first births (pooled OR 1.41, 95% CI 1.25–1.59) and an excess of stillbirths (pooled OR 1.86, 95% CI 1.38–2.51).

Conclusions

This analysis has identified a number of disparities in outcomes between Somali-born women and their receiving country counterparts. The disparities are not readily explained and they raise concerns about the provision of maternity care for Somali women postmigration. Review of maternity care practices followed by implementation and careful evaluation of strategies to improve both care and outcomes for Somali women is needed.

A French prospective observational study of the treatment of chronic hepatitis C in drug abusers

The objective of this prospective, multicenter, observational study was to evaluate healthcare for hepatitis C virus (HCV)-infected drug abusers in France and to determine predictors of successful therapeutic intervention. A total of 170 drug users were recruited from 40 French centers. Three centers recruited 66 participants (38.8%), and one to eight patients each were enrolled from 37 other centers (n=104). A sustained viral response (SVR) was seen in 65 (38.2%) patients. SVR rates were significantly higher in compliant than in non-compliant patients (43.5% versus 23.9%; P=0.019), in patients from high- rather than low-recruiting centers (54.5% versus 27.9%; P<0.001) and in patients receiving Buprenorphine rather than methadone (48.1% versus 21.8%; P=0.001). In patients, who completed both the treatment and follow-up (n=94), SVR rate was 57.4%. Buprenorphine substitution therapy and genotypes 2 or 3 HCV infection were associated with significantly higher rates of SVR (P<0.01, for both comparisons). In conclusion, successful care of hepatitis requires an active treatment policy of every center toward drug addicts. Additional studies are needed to explore the difference in SVR with methadone versus Buprenorphine therapy.

Thyroid-stimulating hormone induces interleukin-6 release from human adipocytes through activation of the nuclear factor-kappaB pathway

Our objective was to identify the signaling pathway activated by TSH that induces IL-6 secretion from human abdominal sc differentiated adipocytes. Human abdominal sc preadipocytes in culture were differentiated into adipocytes. IL-6 release stimulated by TSH was inhibited by 35% (P < 0.05) with SN50, an inhibitor of nuclear factor-kappaB (NF-kappaB) nuclear translocation, and 60% (P < 0.01) with sc-514, an inhibitor of inhibitory-kappaB (IkappaB) kinase (IKK)-beta. Phosphorylation of IKKbeta increased upon TSH treatment (10.3-fold, P < 0.01), and IkappaBalpha levels were reduced by 78% (P < 0.01). TSH activated NF-kappaB (23-fold, P < 0.001), a process that was inhibited (60%, P < 0.01) by SN50. Inhibition of protein kinase A by H89 did not affect TSH-stimulated IKKbeta phosphorylation or IkappaBalpha degradation. TSH-mediated NF-kappaB activation and IL-6 induction also specifically occurred in Chinese hamster ovarian cells expressing the human TSH receptor, resulting in a 5.9-fold (P < 0.001) increase in IKKbeta phosphorylation and a 9.5-fold increase in IL-6 mRNA expression. Our data demonstrate that the IKKbeta/NF-kappaB pathway is a novel TSH target that is required for TSH-induced IL-6 release from human adipocytes.

The Adipocyte as a novel TSH target

Thyroid stimulating hormone (TSH; also known as thyrotropin), binds cognate receptors on the surface of thyrocytes to regulate proliferation and thyroid hormone synthesis. This unidimensional view of TSH is being transformed as new evidence indicates that TSH acts on adipose tissue. Adipocyte inflammatory responses that predispose to cardiovascular disease may occur in thyroid disorders associated with elevated TSH levels.

Discoidin domain receptor 2 impairs insulin-stimulated insulin receptor substrate-1 tyrosine phosphorylation and glucose uptake in 3T3-L1 adipocytes

Differentiation of preadipocytes into functional adipocytes depends on early proliferative events (mitotic clonal expansion) and extracellular matrix interactions. We report that discoidin domain receptor (DDR) 2, a novel adhesion receptor, is expressed in 3T3-L1 preadipocytes and is downregulated during the early phase of adipogenesis. DDR2 overexpression (DDR2-L1 preadipocytes) reduced subconfluent proliferation by 56% (p<0.001) and insulin-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS)-1 by 34% (p<0.05). The mitotic clonal expansion phase of differentiating confluent DDR2-L1 preadipocytes was impaired by approximately 25% (p<0.05). Although induction of peroxisome proliferator-activated receptor gamma, fatty acid synthase, and adiponectin was not altered, the resulting adipocytes were 55% larger (p<0.05), and contained 66% more triacylglycerol (p<0.01). The induction of CCAAT/enhancer binding protein alpha was reduced by 37% (p<0.05), correlating with a similar reduction in insulin-stimulated IRS-1 tyrosine phosphorylation and glucose transport in DDR2-L1 adipocytes (decreases of 22% and 27%, respectively; p<0.05 for both). Our data show that DDR2 is expressed in adipose cells and that its overexpression leads to insulin resistance.

Regulation of PDGF-stimulated SHIP2 tyrosine phosphorylation and association with Shc in 3T3-L1 preadipocytes

In 3T3-L1 and human preadipocytes, insulin results in the isolated rise in phosphatidylinositol (PI)-3,4,5-P3, whereas PDGF produces PI(3,4)P2 in addition to PI(3,4,5)P3. SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) converts PI(3,4,5)P3 into PI(3,4)P2. PDGF, but not insulin, stimulates SHIP2 tyrosine phosphorylation and its association with Shc in human and 3T3-L1 preadipocytes. We now demonstrate that SHIP2 tyrosine phosphorylation and association with Shc in PDGF-treated 3T3-L1 preadipocytes was reduced by bisindolylmaleimide I (BisI), an inhibitor of conventional/novel protein kinase C (PKC). However, the production of PI(3,4)P2 and PI(3,4,5)P3 by PDGF was unaffected by BisI. Activation of PKC by 12-O-tetradecanoylphorbol-13-acetate (TPA) was not sufficient to induce SHIP2 tyrosine phosphorylation. Furthermore, we identified threonine 958 (T958) as a novel PDGF-responsive SHIP2 phosphorylation site. Mutation of T958 to alanine reduced PDGF-stimulated SHIP2 tyrosine phosphorylation and association with Shc, but did not alter its anti-proliferative effect on preadipocytes. This study demonstrates that SHIP2 tyrosine phosphorylation and Shc association can be regulated by serine/threonine signaling pathways, either indirectly (via PKC), or directly (via T958). Interestingly, the anti-proliferative effect of SHIP2 T958A, as well as another SHIP2 mutant (Y986F, Y987F) that also displays defective tyrosine phosphorylation and Shc association, does not depend on these molecular events.

Macrophage-conditioned medium inhibits the differentiation of 3T3-L1 and human abdominal preadipocytes

AIMS/HYPOTHESIS

In obesity, a limited adipogenic capacity may promote adipocyte hypertrophy and increase the risk of insulin resistance and type 2 diabetes. Recent data indicate that macrophages reside within adipose tissue in obese rodents and humans. We hypothesised that secreted macrophage factors may inhibit adipogenesis.

MATERIALS AND METHODS

Conditioned media from cultured murine J774 or human THP-1 macrophages were collected, and added to either murine 3T3-L1 preadipocytes or human abdominal stromal preadipocytes from subcutaneous or omental fat depots.

RESULTS

Macrophage-conditioned medium (MacCM) strongly inhibited 3T3-L1 adipogenesis. Dose-response studies with J774-MacCM revealed that 80 and 100% of J774-MacCM completely suppressed triacylglycerol accumulation as well as the induction of fatty acid synthase, peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha, and adiponectin. Similar inhibitory effects on 3T3-L1 preadipocytes were observed with THP-1-MacCM. Differentiation of human abdominal subcutaneous stromal preadipocytes was moderately reduced (subcutaneous>omental) by J744-MacCM. In contrast, the differentiation of both subcutaneous and omental stromal preadipocytes was completely inhibited by THP-1-MacCM, as determined on the basis of morphology and triacylglycerol accumulation, as well as fatty acid synthase and adiponectin protein expression.

CONCLUSIONS/INTERPRETATION

Secreted macrophage products inhibit the differentiation of 3T3-L1 preadipocytes as well as human abdominal stromal preadipocytes.

Interleukin-6 release from human abdominal adipose cells is regulated by thyroid-stimulating hormone: effect of adipocyte differentiation and anatomic depot

Adipose cells are extrathyroidal targets of thyroid-stimulating hormone (TSH). TSH stimulates interleukin-6 (IL-6) release from adipocytes. We examined TSH responsiveness as a function of stage of differentiation or adipose tissue depot in cultured adipose cells and determined the effect of TSH on extrathyroidal IL-6 production in vivo. Stromal preadipocytes, isolated from human abdominal subcutaneous or omental adipose tissue, and their differentiated counterparts were studied. IL-6 protein concentration in the medium was measured after TSH stimulation. Basal IL-6 release was greater for preadipocytes than differentiated adipocytes, whether derived from subcutaneous or omental fat depots. A depot-dependent effect (omental > subcutaneous) on basal IL-6 release was observed for preadipocytes (1.6-fold, P < 0.05); a similar trend for differentiated adipocytes was not significant (6.2-fold, P > 0.05). IL-6 responsiveness to TSH was observed upon differentiation, but only for subcutaneous adipocytes (1.9-fold over basal, P < 0.001). To determine if TSH could stimulate IL-6 release from extrathyroidal tissues in vivo, we measured serum IL-6 levels from five thyroidectomized patients who received recombinant human (rh) TSH and found that levels increased by threefold on days 3 and 4 (P < 0.05) after its administration. Our data demonstrate that stage of differentiation and fat depot origin affect basal and TSH-stimulated IL-6 release from adipose cells in culture. Furthermore, rhTSH elevates serum IL-6 response in thyroidectomized patients, indicating an extrathyroidal site of TSH action.

Anti-adipogenic effect of PDGF is reversed by PKC inhibition

Healthy adipose tissue function depends on adipogenesis. The capacity to form new adipocytes prevents the emergence of insulin-resistant hypertrophied adipocytes, as well as the deleterious lipid deposition in muscle, liver, and pancreas. It is therefore important to understand how adipogenesis is modulated. Platelet-derived growth factor (PDGF) is anti-adipogenic, but the stage of differentiation that it targets, and the signaling pathways that it triggers, are not defined. We have studied the inhibitory effect of PDGF on murine 3T3-L1 preadipocyte and human preadipocyte differentiation. There was a significant attenuation in the protein expression of the adipogenic transcription factors, PPARgamma and C/EBPalpha, as well as in the levels of later differentiation markers, including adiponectin, aP2, and fatty acid synthase. PDGF treatment resulted in the persistence of PDGF receptor and PKCalpha expression, in contrast to the expected downregulation of both proteins that occurs during differentiation. Inactivation of conventional PKC isoforms, by bisindolylmaleimide I or PKC pseudosubstrate M20-28, partially reversed the inhibition of 3T3-L1 and human preadipocyte differentiation by PDGF, as assessed by fatty acid synthase expression and morphological appearance.

Aortic carboxypeptidase-like protein is regulated by transforming growth factor β in 3T3-L1 preadipocytes

Adipogenesis is characterized by early remodeling of the extracellular matrix, allowing preadipocytes to adopt a more spherical shape and optimize lipid accumulation as they mature. Aortic carboxypeptidase-like protein (ACLP), found in collagen-rich tissues including adipose tissue, is expressed in 3T3-L1 and 3T3-F442A preadipocytes, and is downregulated during adipogenesis. We now report that ACLP is found in medium conditioned by 3T3-L1 preadipocytes. Transforming growth factor (TGF) beta, a known modulator of fibrillar matrix protein production, increased ACLP expression by 2.4+/-0.4-fold (mean+/-SE; n=3) in 3T3-L1 preadipocytes, through a mechanism that requires p42/44 MAPK activity. Addition of TGFbeta to differentiation medium, which inhibits adipogenesis, raised ACLP levels in 3T3-L1 cells. However, sustained expression of ACLP in stable clones of 3T3-L1 or 3T3-F442A preadipocytes did not interfere with adipogenesis.

Phosphoinositide 3-kinase is required for human adipocyte differentiation in culture

OBJECTIVE

Phosphoinositide 3-kinase (PI3K) is required for murine adipocyte differentiation. However, a recent report concluded that PI3K was not involved in the differentiation of human preadipocytes into adipocytes. We have re-examined the role of PI3K in human preadipocyte differentiation, enrolling more patients and using more adipogenic indices.

METHODS

Human preadipocytes, isolated from nine patients, were induced to differentiate in the presence or absence of 100 nM wortmannin. After 12-15 days, triacylglycerol accumulation and the expression of adipogenic markers (fatty acid synthase and adiponectin) were measured.

RESULTS

A significant inhibition in triacylglycerol accumulation and in the induction of fatty acid synthase protein expression was observed, but there was no effect on adiponectin protein expression.

CONCLUSION

Inhibition of PI3K reduces the differentiation of human preadipocytes into adipocytes, suggesting a role for this enzyme in the human adipogenic process.

Activation of the mammalian target of rapamycin pathway acutely inhibits insulin signaling to Akt and glucose transport in 3T3-L1 and human adipocytes

The mammalian target of rapamycin (mTOR) pathway has recently emerged as a chronic modulator of insulin-mediated glucose metabolism. In this study, we evaluated the involvement of this pathway in the acute regulation of insulin action in both 3T3-L1 and human adipocytes. Insulin rapidly (t(1/2) = 5 min) stimulated the mTOR pathway, as reflected by a 10-fold stimulation of 70-kDa ribosomal S6 kinase 1 (S6K1) activity in 3T3-L1 adipocytes. Inhibition of mTOR/S6K1 by rapamycin increased insulin-stimulated glucose transport by as much as 45% in 3T3-L1 adipocytes. Activation of mTOR/S6K1 by insulin was associated with a rapamycin-sensitive increase in Ser636/639 phosphorylation of insulin receptor substrate (IRS)-1 but, surprisingly, did not result in impaired IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. However, insulin-induced activation of Akt was increased by rapamycin. Insulin also activated S6K1 and increased phosphorylation of IRS-1 on Ser636/639 in human adipocytes. As in murine cells, rapamycin treatment of human adipocytes inhibited S6K1, blunted Ser636/639 phosphorylation of IRS-1, leading to increased Akt activation and glucose uptake by insulin. Further studies in 3T3-L1 adipocytes revealed that rapamycin prevented the relocalization of IRS-1 from the low-density membranes to the cytosol in response to insulin. Furthermore, inhibition of mTOR markedly potentiated the ability of insulin to increase PI 3,4,5-triphosphate levels concomitantly with an increased phosphorylation of Akt at the plasma membrane, low-density membranes, and cytosol. However, neither GLUT4 nor GLUT1 translocation induced by insulin were increased by rapamycin treatment. Taken together, these results indicate that the mTOR pathway is an important modulator of the signals involved in the acute regulation of insulin-stimulated glucose transport in 3T3-L1 and human adipocytes.

Adipogenic and antiapoptotic protein levels in human adipose stromal cells after weight loss

OBJECTIVE

Obesity is a major risk factor for type 2 diabetes and cardiovascular disease. However, current strategies to achieve sustained weight loss are often unsuccessful. Fat reaccumulation might be favored by enhanced adipose cell differentiation or survival in the postreduced state.

RESEARCH METHODS AND PROCEDURES

We measured adipogenic and apoptotic protein expression in subcutaneous abdominal adipose stromal-vascular cells from 10 obese patients (7 women and 3 men) that were obtained before and after a 16% weight loss in a medically supervised weight loss program.

RESULTS

After weight loss, protein expression was 2.4-fold higher (p < 0.005) for p42 C/CAAT enhancer binding protein alpha, but there was no change for peroxisome proliferator-activated receptor gamma1; both of these are adipogenic regulators. For neuronal apoptosis inhibitory protein, a protein associated with adipose cell apoptotic resistance, there was a rise of 1.7-fold (p < 0.02).

DISCUSSION

Alterations in C/CAAT enhancer binding protein alpha and neuronal apoptosis inhibitory protein expression occurred in human adipose stromal-vascular cells after weight loss in a pilot study of 10 patients. It will be important for future studies to directly examine whether the adipogenic and antiapoptotic capacity of these cells is changed after weight loss.

Inhibition of insulin signaling and adipogenesis by rapamycin: effect on phosphorylation of p70 S6 kinase vs eIF4E-BP1

OBJECTIVE

Insulin-responsive adipogenic signaling molecules include insulin receptor substrates (IRS)-1 and -2, phosphoinositide 3-kinase (PI3K), and protein kinase B (PKB; also known as Akt). Mammalian target of rapamycin (mTOR) is a PKB substrate, and regulates p70 S6 kinase (p70 S6K). Since p70 S6K is an insulin-responsive kinase downstream of PI3K and PKB, its potential role in adipogenic insulin signaling was investigated.

DESIGN

We measured the effect of rapamycin, a specific inhibitor of mTOR, on insulin-induced 3T3-L1 adipogenesis and on insulin-stimulated p70 S6K activation.

RESULTS

Rapamycin partially reduced differentiation, measured by Oil Red O staining, triacylglycerol accumulation (by up to 46%), and peroxisome proliferator-activated receptor gamma protein expression (by 50%). In contrast, rapamycin completely inhibited insulin-stimulated p70 S6K activation, assessed by phosphorylation of p70 S6K and its substrate, S6. Expression of a constitutively activated form of p70 S6K did not promote 3T3-L1 adipogenesis. The considerable residual differentiation in the presence of rapamycin, despite the complete blockade of p70 S6K activation, prompted us to measure the phosphorylation of another rapamycin-sensitive protein, eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). Insulin-stimulated 4E-BP1 phosphorylation in 3T3-L1 preadipocytes was only partially affected by rapamycin, consistent with the differentiation data. Phosphorylation of eIF4E itself, an expected consequence of 4E-BP1 phosphorylation, was also only partially inhibited.

CONCLUSION

Our data suggest that adipogenic mTOR signaling occurs via the 4E-BP1/eIF4E pathway, rather than through p70 S6K.

Apoptosis of human abdominal preadipocytes before and after differentiation into adipocytes in culture

Differentiation of murine 3T3-L1 preadipocytes into adipocytes is associated with the acquisition of apoptotic resistance accompanied by the upregulation of cell survival genes. We have now examined the effect of adipogenesis on apoptotic susceptibility of human abdominal preadipocytes in primary culture. To induce apoptosis, human preadipocytes, or their differentiated counterparts, were serum-deprived for 24 or 48 hours. When indicated, ceramide was also used as an apoptotic trigger. Cell death was assessed by enumeration of adherent viable cells, and its apoptotic nature was verified by Hoechst staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). After 48 hours of serum withdrawal, cell death was 26% +/- 4% in preadipocytes and was increased to 41% +/- 4% in differentiated adipocytes (mean +/- SE; n = 7 patients; P <.002). Under serum-free conditions for 24 hours, ceramide-induced cell death was 40% +/- 6% in preadipocytes and increased to 68% +/- 8% in adipocytes (mean +/- SE; P <.01; n = 8 patients). Neuronal apoptosis inhibitor protein (NAIP), an antiapoptotic protein cell survival that increases upon 3T3-L1 adipogenesis, was reduced in human preadipocytes undergoing differentiation (n = 6 patients). Preadipocytes derived from omental versus subcutaneous abdominal fat were more susceptible to apoptosis induced by serum deprivation, 16% +/- 4% versus 31% +/- 3% cell death, respectively (mean +/- SE; P <.02; n = 7 patients). Although the murine 3T3-L1 preadipocyte cell line is a useful model that approximates primary preadipocyte cell biology, our data derived from human preadipocyte studies suggest important differences with respect to the regulation of apoptosis.

Down-regulation of aortic carboxypeptidase-like protein during the early phase of 3T3-L1 adipogenesis

Aortic carboxypeptidase-like protein (ACLP) is a 175-kDa protein that is expressed in vascular smooth muscle cells and contains a signal peptide sequence, a lysine- and proline-rich repeating motif, a discoidin-like domain with 35% identity to discoidin I, and a carboxypeptidase-like domain that is 39% identical with carboxypeptidase E. It is secreted into the extracellular matrix and may play a role in abdominal wall development and dermal wound healing. ACLP is also expressed in adipose tissue, but at lower levels. In this study we demonstrate that ACLP protein and mRNA are severely down-regulated in the early phase of 3T3-L1 preadipocyte differentiation induced by insulin, dexamethasone, and isobutylmethylxanthine. Neither dexamethasone, isobutylmethylxanthine, nor insulin treatment alone reduced the level of ACLP protein, suggesting that ACLP down-regulation is a differentiation-associated event. ACLP down-regulation coincided with the onset of the postconfluent mitotic clonal expansion phase of adipogenesis. In contrast, subconfluent 3T3-L1 cell proliferation did not alter ACLP expression, suggesting a specific linkage between ACLP and differentiation-induced clonal expansion. Stable overexpression of ACLP had no effect on preadipocyte differentiation assessed by triacylglycerol accumulation and peroxisome proliferator-activated receptor-gamma levels. The role of ACLP and its marked reduction during adipogenesis merit further study.

Orbital fibroblast heterogeneity may determine the clinical presentation of thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy, a process in which the orbital tissues become inflamed and are remodeled, occurs with a variable presentation. In some patients, eye muscle enlargement predominates. In others, the connective/adipose tissue enlargement appears the more significant problem. Orbital fibroblasts exhibit heterogeneous phenotypes in culture. Here we report that fibroblasts derived from the connective/adipose tissue depot are distinct from those investing the extraocular muscles. Connective tissue fibroblasts represent a bimodal population of cells with regard to the surface display of the glycoprotein, Thy-1. Perimysial fibroblasts in contrast express Thy-1 uniformly. In that regard, they resemble those from the skin. When subjected to a newly defined set of culture conditions, adipocyte differentiation occurs in up to 43% of the cells. All adipocytes examined failed to display Thy-1. Fibroblasts derived from perimysium and dermis uniformly do not differentiate into adipocytes when incubated under identical culture conditions. Both Thy-1(+) and Thy-1(-) connective tissue fibroblasts express the adipogenic trigger, peroxisome proliferator activator gamma, suggesting that differences in the potential for differentiation may reside with phenotypic attributes downstream from this receptor/adipogenic transcription factor. These observations enhance our understanding of orbital adipogenesis and define previously unrecognized differences between fibroblasts from the extraocular muscle and connective tissue.

Rapamycin-sensitive phase of 3T3-L1 preadipocyte differentiation after clonal expansion

Inhibition of insulin-induced 3T3-L1 preadipocyte differentiation by rapamycin has been attributed to a blockade of the early critical clonal expansion phase of the adipogenic program. Rapamycin binds to, and inhibits, mTOR (mammalian target of rapamycin), leading to diminution of p70 S6 kinase activity and eukaryotic initiation factor 4E binding protein 1 (eIF4E-BP1) function. Our objective was to determine if rapamycin-sensitive pathways exist subsequent to the clonal expansion phase. We determined that the mitotic clonal expansion was complete by day 4 of the differentiation protocol, based on the response to Ara-C (cytosine beta-D-arabinofuranoside), which only inhibits differentiation when administered during this phase. Treatment of differentiating 3T3-L1 cells with rapamycin, starting on day 4, exerted potent negative effects on glycerol phosphate dehydrogenase activity, and triacylglycerol accumulation, as well as on the protein expression of adipogenic transcription factors, C/EBPalpha and PPARgamma. Insulin-stimulated p70 S6 kinase activity, and its inhibition by rapamycin, were comparable in preadipocytes at day 0 vs. day 4 post-differentiation. We conclude that a component of the adipogenic program, operating after the completion of clonal expansion, is inhibited by rapamycin, suggesting an ongoing need for mTOR function in this process.

Intergenerational correlation of effective family size in early Québec (Canada)

The use of a comprehensive demographic database of the early French Canadian population (1608-1800) reveals an almost null impact of parents' fertility on children's fertility (r approximately 0.01-0.05), which contradicts the commonly held view that family size has a tendency to run in families. However, in this population, there is a clear transmission from one generation to the next of the effective family size within a given geographical area (EFS, defined as the number of children that settle per settled individual). Three types of correlations between EFS of parents and children are presented in order to account for the impact of socio-demographic differentials. Individuals who belong to a large sibship and who settled in a given subdivision tend to encourage the settlement of a high number of their own children in the same subdivision (r approximately 0.1-0.3). An additional correlation was introduced to see if geographically-based differentials of EFS can account for the differential of founders' regional genetic contribution. The analysis shows that EFS correlation has a definite impact on the concentration of a population's gene pool (it increases it by approximately 20%-45%), and partly accounts for the differences between subdivisions in this regard.

Phosphatidylinositol-3,4,5-trisphosphate is required for insulin-like growth factor 1-mediated survival of 3T3-L1 preadipocytes

Adipocyte number, a determinant of adipose tissue mass, reflects the balance between the rates of proliferation/differentiation vs. apoptosis of preadipocytes. The percentage of 3T3-L1 preadipocytes undergoing cell death following serum deprivation was reduced by 10 nM insulin-like growth factor (IGF)-1 (from 50.0 +/- 0.7% for control starved cells to 27.5 +/- 3.1%). TUNEL staining confirmed the apoptotic nature of the cell death. The protective effect of IGF-1 was blocked by phosphoinositide 3-kinase (PI3K) inhibitors, wortmannin, and LY294002, but was unaffected by rapamycin, PD98059, or SB203580, which inhibit mammalian target of rapamycin (mTOR), ERK kinase (MEK1), and p38 MAPK respectively. Exogenous PI(3,4,5)P3 (10 microM), the principal product of IGF-1-stimulated PI3K in 3T3-L1 preadipocytes, had a modest survival effect on its own, reducing cell death from 47.9 +/- 3.4% to 35.6 +/- 3.5%. When added to the combination of IGF-1 and LY294002, PI(3,4,5)P3 reversed most of the inhibitory effect of LY294002 on IGF-1-dependent cell survival, protein kinase B/Akt phosphorylation, and caspase-3 activity. Taken together, these results implicate PI(3,4,5)P3 as a necessary signal for the anti-apoptotic action of IGF-1 on 3T3-L1 preadipocytes.

Fragmentation of the Québec population genetic pool (Canada): evidence from the genetic contribution of founders per region in the 17th and 18th centuries

The 6 million French-Canadians of Québec derive from a relatively small number of founders. Consequently, some hereditary diseases, which may or may not present a worldwide distribution, have been detected in high frequency in this population. Several studies, however, indicate a nonuniform distribution of these diseases through the population, suggesting that the French-Canadian founder effect has been geographically stratified. Here we explore this stratification by using a demographic database, the Population Register of Early Québec, that contains almost all birth, marriage, and death certificates (>712,000) recorded in parish registers between 1608-1800. In this database, every genealogical link has been traced back to the founders of the population, so that we can compute the genetic contribution of founder per region, and then account for the early events that have shaped the distribution of diseases. Ten regions, comprising varying numbers of parishes, have been selected. We first describe each region in terms of homogeneity and concentration of its gene pool. For this purpose, a new concept is introduced, the founders' uniform contribution number (FUN), i.e., the number of founders a population would have if all its founders had an equal contribution. Second, we estimate genetic similarity between regions on the basis of differential genetic contribution. To classify the regions, we use principal component and cluster analysis. Our results show a tripartite clustering of the population, and invite us to reconsider the results obtained from biomolecular and clinical studies, which show a bipartite clustering.

Ritonavir increases the level of active ADD-1/SREBP-1 protein during adipogenesis

OBJECTIVE

A novel lipodystrophy syndrome characterized by truncal adiposity, peripheral fat atrophy, type 2 diabetes mellitus, and dyslipidemia occurs in HIV-infected individuals, and may be aggravated by HIV-1 protease inhibitors. The increase in truncal fat could be due to enhanced preadipocyte differentiation. Using the 3T3-L1 preadipocyte model, we reported that ritonavir enhances adipocyte differentiation in culture. The goal of this study was to characterize the molecular mechanism of ritonavir on preadipocyte differentiation.

DESIGNS AND METHODS

Time course studies of 3T3-L1 preadipocytes placed in standard differentiation medium (insulin, dexamethasone, and isobutylmethylxanthine) were performed. Glycerol phosphate dehydrogenase (GPDH) was assayed enzymatically, and triacylglycerol (TG) mass was quantified. The adipogenic transcription factors adipocyte determination and differentiation-dependent factor 1 (ADD-1)/sterol regulatory element binding protein 1 (SREBP-1), CCAAT/enhancer-binding protein-alpha (CEBPalpha), and peroxisome proliferator activated receptor-gamma (PPARgamma), were measured by Western analysis.

RESULTS

Ritonavir (10 microg/ml) enhanced 3T3-L1 preadipocyte differentiation (30% increase in TG mass; 50% increase in GPDH activity), and transiently raised levels of the 68 kDa active mature form of ADD-1/SREBP-1 during adipogenesis by threefold, compared with standard differentiation. In contrast, ritonavir attenuated the differentiation-induced increase in CEBPalpha and PPARgamma.

CONCLUSIONS

Our data suggest that ritonavir enhances 3T3-L1 adipogenesis by increasing the level of active mature ADD-1/SREBP-1. This effect may be due to reduced proteolysis of ADD-1/SREBP-1, as ritonavir inhibits an N-acetyl-leucyl-leucyl-norleucinal (ALLN)-sensitive proteosomal degradation pathway in lymphocytes, and ALLN itself inhibits the breakdown of mature ADD-1/SREBP-1. As mature ADD-1/SREBP-1 regulates several lipogenic enzymes, higher levels may explain the effect of ritonavir on TG accumulation and GPDH activity. Studying ADD-1/SREBP-1 may lead to better understanding and prevention of the lipodystrophy syndrome.