Véronique Turcotte

Depot-specific effects of the PPARγ agonist rosiglitazone on adipose tissue glucose uptake and metabolism

We investigated mechanisms whereby peroxisome proliferator-activated receptor gamma (PPARgamma) agonism redistributes lipid from visceral (VF) toward subcutaneous fat (SF) by studying the impact of PPARgamma activation on VF and SF glucose uptake and metabolism, lipogenesis, and enzymes involved in triacylglycerol (TAG) synthesis. VF (retroperitoneal) and SF (inguinal) of rats treated or not for 7 days with rosiglitazone (15 mg/kg/day) were evaluated in vivo for glucose uptake and lipogenesis and in vitro for glucose metabolism, gene expression, and activities of glycerolphosphate acyltransferase (GPAT), phosphatidate phosphatase-1 (or lipin-1), and diacylglycerol acyltransferase. Rosiglitazone increased SF glucose uptake, GLUT4 mRNA, and insulin-stimulated glucose oxidation, conversion to lactate, glycogen, and the glycerol and fatty acid components of TAG. In VF, only glucose incorporation into TAG-glycerol was stimulated by rosiglitazone and less so than in SF (1.5- vs. 3-fold). mRNA levels of proteins involved in glycolysis, Krebs cycle, glycogen synthesis, and lipogenesis were markedly upregulated by rosiglitazone in SF and again less so in VF. Rosiglitazone activated TAG-glycerol synthesis in vivo (2.8- vs. 1.9-fold) and lipin activity (4.6- vs. 1.5-fold) more strongly in SF than VF, whereas GPAT activity was increased similarly in both depots. The preferential increase in glucose uptake and intracellular metabolism in SF contributes to the PPARgamma-mediated redistribution of TAG from VF to SF, which in turn favors global insulin sensitization.

Costs associated with resource utilization during the palliative phase of care: a Canadian perspective.

Objective: This study aimed to evaluate prospectively the resource utilization and related costs during the palliative phase of care in five regions across Canada. Subjects: A cohort of 248 patients registered in a palliative care program and their main informal caregivers were consecutively recruited. Research Design: A prospective research design with repeated measures was adopted. Interviews were conducted at two-week intervals until the patient s passing or up to a maximum of 6 months. Measures: The survey questions prompted participants to provide information on the types and number of goods and services they used, and who paid for these goods and services. Results: The largest cost component for study participants was inpatient hospital care stays, followed by home care and informal caregiving time. In regard to cost sharing, the public health care system (PHCS), the family, and not-for-profit organizations (NFPO) sustained respectively 71.3%, 26.6%, and 1.6% of the mean total cost per patient. Conclusion: Such results provide a comprehensive picture of costs related to palliative care in Canada, by specifying the cost sharing between the PHCS, the family, and NFPO.

Major involvement of mTOR in the PPARγ-induced stimulation of adipose tissue lipid uptake and fat accretion

Evidence points to a role of the mammalian target of rapamycin (mTOR) signaling pathway as a regulator of adiposity, yet its involvement as a mediator of the positive actions of peroxisome proliferator-activated receptor (PPAR)γ agonism on lipemia, fat accretion, lipid uptake, and its major determinant lipoprotein lipase (LPL) remains to be elucidated. Herein we evaluated the plasma lipid profile, triacylglycerol (TAG) secretion rates, and adipose tissue LPL-dependent lipid uptake, LPL expression/activity, and expression profile of other lipid metabolism genes in rats treated with the PPARγ agonist rosiglitazone (15 mg/kg/day) in combination or not with the mTOR inhibitor rapamycin (2 mg/kg/day) for 15 days. Rosiglitazone stimulated adipose tissue mTOR complex 1 and AMPK and induced TAG-derived lipid uptake (136%), LPL mRNA/activity (2- to 6-fold), and fat accretion in subcutaneous (but not visceral) white adipose tissue (WAT; 50%) and in brown adipose tissue (BAT; 266%). Chronic mTOR inhibition attenuated the upregulation of lipid uptake, LPL expression/activity, and fat accretion induced by PPARγ activation in both subcutaneous WAT and BAT, which resulted in hyperlipidemia. In contrast, rapamycin did not affect most of the other WAT lipogenic genes upregulated by rosiglitazone. Together these findings demonstrate that mTOR is a major regulator of adipose tissue LPL-mediated lipid uptake and a critical mediator of the hypolipidemic and lipogenic actions of PPARγ activation.

The PPARγ agonist rosiglitazone enhances rat brown adipose tissue lipogenesis from glucose without altering glucose uptake

We investigated the mechanisms whereby peroxisome proliferator-activated receptor-gamma (PPARgamma) agonism affects glucose and lipid metabolism in brown adipose tissue (BAT) by studying the impact of PPARgamma activation on BAT glucose uptake and metabolism, lipogenesis, and mRNA levels plus activities of enzymes involved in triacylglycerol (TAG) synthesis. Interscapular BAT of rats treated or not with rosiglitazone (15 mg*kg(-1).day(-1), 7 days) was evaluated in vivo for glucose uptake and lipogenesis and in vitro for glucose metabolism, gene expression, and activities of glycerolphosphate acyltransferase (GPAT), phosphatidate phosphatase-1 (PAP or lipin-1), and diacylglycerol acyltransferase (DGAT). Rosiglitazone increased BAT mass without affecting whole tissue glucose uptake. BAT glycogen content (-80%), its synthesis from glucose (-50%), and mRNA levels of UDP-glucose pyrophosphorylase (-40%), which generates UDP-linked glucose for glycogen synthesis, were all reduced by rosiglitazone. In contrast, BAT TAG-glycerol synthesis in vivo and glucose incorporation into TAG-glycerol in vitro were stimulated by the agonist along with the activities and mRNA levels of glycerol 3-phosphate-generating phosphoenolpyruvate carboxykinase and glycerokinase. Furthermore, rosiglitazone markedly increased the activities of GPAT and DGAT but not those of lipin-1-mediated PAP-1, enzymes involved in the sequential acylation of glycerol 3-phosphate and TAG synthesis. Because an adequate supply of fatty acids is essential for BAT nonshivering thermogenesis, the enhanced ability of BAT to synthesize TAG under PPARgamma activation may constitute an important mechanism by which lipid substrates are stored in preparation for an eventual thermogenic activation.

Quantitative profiling of human renal UDP-glucuronosyltransferases and glucuronidation activity: a comparison of normal and tumoral kidney tissues.

Renal metabolism by UDP-glucuronosyltransferase (UGT) enzymes is central to the clearance of many drugs. However, significant discrepancies about the relative abundance and activity of individual UGT enzymes in the normal kidney prevail among reports, whereas glucuronidation in tumoral kidney has not been examined. In this study, we performed an extensive profiling of glucuronidation metabolism in normal (n = 12) and tumor (n = 14) kidneys using targeted mass spectrometry quantification of human UGTs. We then correlated UGT protein concentrations with mRNA levels assessed by quantitative polymerase chain reaction and with conjugation activity for the major renal UGTs. Beyond the wide interindividual variability in expression levels observed among kidney samples, UGT1A9, UGT2B7, and UGT1A6 are the most abundant renal UGTs in both normal and tumoral tissues based on protein quantification. In normal kidney tissues, only UGT1A9 protein levels correlated with mRNA levels, whereas UGT1A6, UGT1A9, and UGT2B7 quantification correlated significantly with their mRNA levels in tumor kidneys. Data support that posttranscriptional regulation of UGT2B7 and UGT1A6 expression is modulating glucuronidation in the kidney. Importantly, our study reveals a significant decreased glucuronidation capacity of neoplastic kidneys versus normal kidneys that is paralleled by drastically reduced UGT1A9 and UGT2B7 mRNA and protein expression. UGT2B7 activity is the most repressed in tumors relative to normal tissues, with a 96-fold decrease in zidovudine metabolism, whereas propofol and sorafenib glucuronidation is decreased by 7.6- and 5.2-fold, respectively. Findings demonstrate that renal drug metabolism is predominantly mediated by UGT1A9 and UGT2B7 and is greatly reduced in kidney tumors.

Prediagnostic Sex Steroid Hormones in Relation to Male Breast Cancer Risk

PURPOSE Although previous studies have implicated a variety of hormone-related risk factors in the etiology of male breast cancers, no previous studies have examined the effects of endogenous hormones. PATIENTS AND METHODS Within the Male Breast Cancer Pooling Project, an international consortium comprising 21 case-control and cohort investigations, a subset of seven prospective cohort studies were able to contribute prediagnostic serum or plasma samples for hormone quantitation. Using a nested case-control design, multivariable unconditional logistic regression analyses estimated odds ratios and 95% CIs for associations between male breast cancer risk and 11 individual estrogens and androgens, as well as selected ratios of these analytes. RESULTS Data from 101 cases and 217 matched controls were analyzed. After adjustment for age and date of blood draw, race, and body mass index, androgens were found to be largely unrelated to risk, but circulating estradiol levels showed a significant association. Men in the highest quartile had an odds ratio of 2.47 (95% CI, 1.10 to 5.58) compared with those in the lowest quartile (trend P = .06). Assessment of estradiol as a ratio to various individual androgens or sum of androgens showed no further enhancement of risk. These relations were not significantly modified by either age or body mass index, although estradiol was slightly more strongly related to breast cancers occurring among younger (age < 67 years) than older men. CONCLUSION Our results support the notion of an important role for estradiol in the etiology of male breast cancers, similar to female breast cancers.

The trajectory of palliative care costs over the last 5 months of life: a Canadian longitudinal study

Objective: This study aimed to highlight the trajectory of palliative care costs over the last five months of life in five urban centres across Canada. Subjects: The study sample was comprised of 160 terminally ill patients and their main informal caregivers. Research Design: A first interview took place in the patient’s home, and subsequent follow-up interviews were conducted by telephone at two week intervals until the patient’s passing. Measures: Participants were asked to provide information on the goods and services they used related to the patients’ health condition, and on informal caregiving time. Results: The overall costs of care gradually increased from the fifth to the last month of the patients’ life. A large part of this cost increase was attributable to inpatient care. Among outpatient care costs the largest increase was observed for home care. Informal care costs were particularly high over the last 3 months of life. Conclusions: The knowledge gained from this study would be useful to policy makers when developing policies that could help families caring for a terminally ill loved one at home.

A chromatography/tandem mass spectrometry method for the simultaneous profiling of ten endogenous steroids, including progesterone, adrenal precursors, androgens and estrogens, using low serum volume.

Measurement of a large set of sex steroids in clinical epidemiology and laboratory research with reliable methods providing low quantification limits and using a limited volume of blood sample represents a significant challenge. We report a new validated gas chromatography selected reaction monitoring - tandem mass spectrometry assay (GC-MS/MS) for the simultaneous quantification of ten endogenous steroids including progesterone (PROG), dehydroepiandrosterone (DHEA), androstenediol (5-diol), androstenedione (4-dione), testosterone (T), dihydrotestosterone (DHT), androsterone (ADT), 5alpha-androstan-3beta-17beta-diol (3β-diol), estrone (E1) and estradiol (E2). After addition of stable isotope internal standards, the approach involved the combination of liquid-liquid extraction, derivatization and solid-phase extraction for injection into the GC system and multiple reaction monitoring (MRM). The method presents high reproducibility for all analytical parameters in 250 μl serum samples. The lower limit of quantification (LLOQ) were of 100 pg/ml for DHEA, 50 pg/ml for PROG, 5-diol, 4-dione and ADT, 30 pg/ml for T, 10 pg/ml for 3β-diol and DHT, 5 pg/ml for E1, and 1 pg/ml for E2. The applicability of the validated method to determine the concentrations of these 10 steroids was successfully tested on serum from men (n=15), premenopausal (n=10) and postmenopausal women (n=20), and is currently used for larger cancer-related epidemiology studies. One of the most considerable advantages over existing methods is the simultaneous determination of ten steroids in a limited volume of serum that will help conserve important clinical samples from existing biobanks.

Association Between Circulating Levels of Sex Steroid Hormones and Barrett’s Esophagus in Men: A Case–Control Analysis

BACKGROUND & AIMS Esophageal adenocarcinoma is believed to result from the progression of gastroesophageal reflux disease to erosive esophagitis and re-epithelialization of the esophagus with a columnar cell population termed Barretts esophagus (BE). Men develop BE and esophageal adenocarcinoma more frequently than women, yet little is known about the mechanisms of this difference. We assessed whether sex steroid hormones were associated with BE in a male population. METHODS We analyzed data from the Barretts Esophagus Early Detection Case Control Study, based at the Walter Reed National Military Medical Center. Blood samples were collected from 174 men with BE and 213 men without BE (controls, based on endoscopic analysis); 13 sex steroid hormones were measured by mass spectrometry and sex hormone binding globulin was measured by enzyme-linked immunosorbent assay. We also calculated free estradiol, free testosterone, and free dihydrotestosterone (DHT). We used multivariable logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for age, race, smoking status, alcohol consumption, body mass index, heartburn, regurgitation, and gastroesophageal symptom score (excluding heartburn and regurgitation). RESULTS Levels of free testosterone and free DHT were associated positively with BE risk; patients in the highest quartile for these hormones were most likely to have BE (free testosterone: OR, 5.36; 95% CI, 2.21-13.03; P = .0002; free DHT: OR, 4.25; 95% CI, 1.87-9.66; P = .001). Level of estrone sulfate was associated inversely with BE risk (P for trend = .02). No other hormone was associated with BE risk. Relationships were not modified by age or BMI. CONCLUSIONS In an analysis of men, levels of free testosterone and free DHT were significantly associated with BE.

Importance of 5α-reductase gene polymorphisms on circulating and intraprostatic androgens in prostate cancer.

Purpose: Polymorphisms in the genes SRD5A1 and SRD5A2 encoding androgen biosynthetic 5α-reductase enzymes have been associated with an altered risk of biochemical recurrence after radical prostatectomy in localized prostate cancer. Experimental Design: To gain potential insights into SRD5A biologic effects, we examined the relationship between SRD5A prognostic markers and endogenous sex-steroid levels measured by mass spectrometry in plasma samples and corresponding prostatic tissues of patients with prostate cancer. Results: We report that five of the seven SRD5A markers differentially affect sex-steroid profiles of dihydrotestosterone and its metabolites in both the circulation and prostatic tissues of patients with prostate cancer. Remarkably, a 32% increase in intraprostatic testosterone levels was observed in the presence of the high-risk SRD5A rs2208532 polymorphism. Moreover, SRD5A2 markers were associated predominantly with circulating levels of inactive glucuronides. Indeed, the rs12470143 SRD5A2 protective allele was associated with high circulating androstane-3α, 17β-diol-17-glucuronide (3α-diol-17G) levels as opposed to lower levels of both 3α-diol-17G and androsterone-glucuronide observed with the rs2208532 SRD5A2 risk allele. Moreover, SRD5A2 rs676033 and rs523349 (V89L) risk variants, in strong linkage disequilibrium, were associated with higher circulating levels of 3α-diol-3G. The SRD5A2 rs676033 variant further correlated with enhanced intraprostatic exposure to 5α-reduced steroids (dihydrotestosterone and its metabolite 3β-diol). Similarly, the SRD5A1 rs166050C risk variant was associated with greater prostatic exposure to androsterone, whereas no association was noted with circulating steroids. Conclusions: Our data support the association of 5α-reductase germline polymorphisms with the hormonal milieu in patients with prostate cancer. Further studies are needed to evaluate if these variants influence 5α-reductase inhibitor efficacy. Clin Cancer Res; 20(3); 576–84. ©2013 AACR.