Thyroid hormone responsive protein Spot14 enhances catalysis of fatty acid synthase in lactating mammary epithelium

Lipid metabolic reprogramming drives triglyceride storage and variable sensitivity to FASN inhibition in endocrine-resistant breast cancer cells

BACKGROUND

Lipid metabolic reprogramming is increasingly recognized as a hallmark of endocrine resistance in estrogen receptor-positive (ER+) breast cancer. In this study, we investigated alterations in lipid metabolism in ER + breast cancer cell lines with acquired resistance to common endocrine therapies and evaluated the efficacy of a clinically relevant fatty acid synthase (FASN) inhibitor.

METHODS

ER + breast cancer cell lines resistant to Tamoxifen (TamR), Fulvestrant (FulvR), and long-term estrogen withdrawal (EWD) were derived. Global gene expression and lipidomic profiling were performed to compare parental and endocrine resistant cells. Lipid storage was assessed using Oil Red O (ORO) staining. The FASN inhibitor TVB-2640 was tested for its impact on lipid storage and cell growth. 13C2-acetate tracing was used to evaluate FASN activity and the efficacy of TVB-2640.

RESULTS

Endocrine resistant cells showed significant enrichment in lipid metabolism pathways and distinct lipidomic profiles, characterized by elevated triglyceride levels and enhanced cytoplasmic lipid droplets. 13C2-acetate tracing revealed increased FASN activity in endocrine resistant cells, which was effectively reduced by TVB-2640. While TVB-2640 reduced lipid storage in most but not all cell lines, this did not correlate with decreased cell growth. Polyunsaturated fatty acids (PUFAs) containing 6 or more double bonds were elevated in endocrine resistant cells and remained unaffected or increased with TVB-2640.

CONCLUSION

Endocrine resistant breast cancer cells undergo a metabolic shift toward increased triglyceride storage and PUFAs with high degrees of desaturation. While TVB-2640 reduced lipid storage in most conditions, it had limited effects on the growth of endocrine resistant breast cancer cells. Targeting specific lipid metabolic dependencies, particularly pathways that produce PUFAs, represents a potential therapeutic strategy in endocrine resistant breast cancer.

Lipid metabolic reprogramming drives triglyceride storage and variable sensitivity to FASN inhibition in endocrine-resistant breast cancer cells

Background

Lipid metabolic reprogramming is increasingly recognized as a hallmark of endocrine resistance in estrogen receptor-positive (ER+) breast cancer. In this study, we investigated alterations in lipid metabolism in ER+ breast cancer cell lines with acquired resistance to common endocrine therapies and evaluated the efficacy of a clinically relevant fatty acid synthase (FASN) inhibitor.

Methods

ER+ breast cancer cell lines resistant to Tamoxifen (TamR), Fulvestrant (FulvR), and long-term estrogen withdrawal (EWD) were derived. Global gene expression and lipidomic profiling were performed to compare parental and endocrine resistant cells. Lipid storage was assessed using Oil Red O (ORO) staining. The FASN inhibitor TVB-2640 was tested for its impact on lipid storage and cell growth. 13 C 2 -acetate tracing was used to evaluate FASN activity and the efficacy of TVB-2640.

Results

Endocrine resistant cells showed significant enrichment in lipid metabolism pathways and distinct lipidomic profiles, characterized by elevated triglyceride levels and enhanced cytoplasmic lipid droplets. 13 C 2 -acetate tracing revealed increased FASN activity in endocrine resistant cells, which was effectively reduced by TVB-2640. While TVB-2640 reduced lipid storage in most but not all cell lines, this did not correlate with decreased cell growth. Polyunsaturated fatty acids (PUFAs) containing 6 or more double bonds were elevated in endocrine resistant cells and remained unaffected or increased with TVB-2640.

Conclusion

Endocrine resistant breast cancer cells undergo a metabolic shift toward increased triglyceride storage and PUFAs with high degrees of desaturation. While TVB-2640 reduced lipid storage in most conditions, it had limited effects on the growth of endocrine resistant breast cancer cells. Targeting specific lipid metabolic dependencies, particularly pathways that produce PUFAs, represents a potential therapeutic strategy in endocrine resistant breast cancer.

NR2F2 Reactivation in Early-life Adipocyte Stem-like Cells Rescues Adipocyte Mitochondrial Oxidation

In humans, perinatal exposure to an elevated omega-6 (n6) relative to omega-3 (n3) Fatty Acid (FA) ratio is associated with the likelihood of childhood obesity. In mice, we show perinatal exposure to excessive n6-FA programs neonatal Adipocyte Stem-like cells (ASCs) to differentiate into adipocytes with lower mitochondrial nutrient oxidation and a propensity for nutrient storage. Omega-6 FA exposure reduced fatty acid oxidation (FAO) capacity, coinciding with impaired induction of beige adipocyte regulatory factors PPARγ, PGC1α, PRDM16, and UCP1. ASCs from n6-FA exposed pups formed adipocytes with increased lipogenic genes in vitro, consistent with an in vivo accelerated adipocyte hypertrophy, greater triacylglyceride accumulation, and increased % body fat. Conversely, n6-FA exposed pups had impaired whole animal 13C-palmitate oxidation. The metabolic nuclear receptor, NR2F2, was suppressed in ASCs by excess n6-FA intake preceding adipogenesis. ASC deletion of NR2F2, prior to adipogenesis, mimicked the reduced FAO capacity observed in ASCs from n6-FA exposed pups, suggesting that NR2F2 is required in ASCs for robust beige regulator expression and downstream nutrient oxidation in adipocytes. Transiently re-activating NR2F2 with ligand prior to differentiation in ASCs from n6-FA exposed pups, restored their FAO capacity as adipocytes by increasing the PPARγ-PGC1α axis, mitochondrial FA transporter CPT1A, ATP5 family synthases, and NDUF family Complex I proteins. Our findings suggest that excessive n6-FA exposure early in life dampens an NR2F2-mediated induction of beige adipocyte regulators, resulting in metabolic programming that is shifted towards nutrient storage.

Research Progress on the Mechanism of Milk Fat Synthesis in Cows and the Effect of Conjugated Linoleic Acid on Milk Fat Metabolism and Its Underlying Mechanism: A Review

Milk fat synthesis in cows mainly includes the synthesis of short- and medium-chain fatty acids, the uptake, transport, and activation of long-chain fatty acids (LCFAs), the synthesis of triglycerides, and the synthesis of the genes, transcription factors, and signaling pathways involved. Although the various stages of milk fat synthesis have been outlined in previous research, only partial processes have been revealed. CLA consists of an aggregation of positional and geometric isomers of linoleic fatty acid, and the accumulated evidence suggests that the two isomers of the active forms of CLA (cis-9, trans-11 conjugated linoleic acid and trans-10, cis-12 conjugated linoleic acid, abbreviated as c9, t11-CLA and t10, c12-CLA) can reduce the fat content in milk by regulating lipogenesis, fatty acid (FA) uptake, oxidation, and fat synthesis. However, the mechanism through which CLA inhibits milk fat synthesis is unique, with most studies focusing only on the effects of CLA on one of the genes, transcription factors, or signaling pathways involved. In this study, we summarized the structure and function of classic genes and pathways (mTOR, SREBP, AMPK, and PPARG) and new genes or pathways (THRSP, METTL3, ELOVL, and LPIN1) involved in each stage of milk fat synthesis and demonstrated the interactions between genes and pathways. We also examined the effects of other substances (melanin, nicotinic acid, SA, etc.). Furthermore, we evaluated the influence of β-sitosterol, sodium butyrate, Met arginine, and Camellia oleifera Abel on milk fat synthesis to improve the mechanism of milk fat synthesis in cows and provide a mechanistic reference for the use of CLA in inhibiting milk fat biosynthesis.

Hypothyroidism and non-alcoholic fatty liver disease: A coincidence or a causal relationship?

Non-alcoholic fatty liver disease (NAFLD) is a global problem. It may be caused by metabolic and hormonal disorders, including hypothyroidism. However, non-thyroid causes of NAFLD in people with hypothyroidism, including improper eating behavior and low physical activity, should be acknowledged. This study aimed to present the current literature on whether the development of NAFLD is related to hypothyroidism or a typical consequence of an unhealthy lifestyle in people with hypothyroidism. The results of previous studies do not allow for an unequivocal determination of the pathogenetic relationship between hypothyroidism and NAFLD. Important non-thyroid-initiating factors include providing too many calories in relation to requirements, consuming excessive amounts of monosaccharides and saturated fats, being overweight, and maintaining low physical activity levels. The recommended nutritional model for both hypothyroidism and NAFLD may be the Mediterranean diet, which is rich in fruits and vegetables, polyunsaturated fatty acids, and vitamin E.

Total daily energy expenditure has declined over the past three decades due to declining basal expenditure, not reduced activity expenditure

Obesity is caused by a prolonged positive energy balance1,2. Whether reduced energy expenditure stemming from reduced activity levels contributes is debated3,4. Here we show that in both sexes, total energy expenditure (TEE) adjusted for body composition and age declined since the late 1980s, while adjusted activity energy expenditure increased over time. We use the International Atomic Energy Agency Doubly Labelled Water database on energy expenditure of adults in the United States and Europe (n = 4,799) to explore patterns in total (TEE: n = 4,799), basal (BEE: n = 1,432) and physical activity energy expenditure (n = 1,432) over time. In males, adjusted BEE decreased significantly, but in females this did not reach significance. A larger dataset of basal metabolic rate (equivalent to BEE) measurements of 9,912 adults across 163 studies spanning 100 years replicates the decline in BEE in both sexes. We conclude that increasing obesity in the United States/Europe has probably not been fuelled by reduced physical activity leading to lowered TEE. We identify here a decline in adjusted BEE as a previously unrecognized factor.

TRB3 Deletion Has a Limited Effect on Milk Fat Synthesis and Milk Fat Depression in C57BL/6N Mice

BACKGROUND

Regulation of the endoplasmic reticulum (ER) stress pathway is critical to mammary epithelial cell function throughout pregnancy, lactation, and involution. Treatment with trans-10, cis-12 conjugated linoleic acid (t10c12CLA) suppresses mammary lipogenesis and stimulates the ER stress pathway. The ER stress pathway includes tribbles pseudokinase 3 (TRB3), a protein that regulates cellular energy and insulin signaling.

OBJECTIVES

Our objective was to describe the effect of TRB3 deficiency on milk fat synthesis and determine if TRB3 deficiency protects against suppression of mammary lipogenesis.

METHODS

First, mammary Trb3 expression was observed throughout pregnancy and lactation using ancillary microarray data (n = 4/time point). Second, intake, litter growth, and milk clot fatty acid (FA) profile of Trb3 knockout (KO) C57BL/6N mice were compared with wild-type (WT) and heterozygous (HET) mice throughout first (n ≥ 8/group) and second (n ≥ 6/group) lactation. Lastly, the interaction between Trb3 genotype and 2 treatments that suppress mammary lipogenesis, t10c12CLA and high safflower oil (HO) diet, was investigated in a 2 × 2 factorial design (n ≥ 6/group).

RESULTS

Trb3 expression was higher during late pregnancy and lactation. Trb3 KO and HET mice had lower feed intake, dam weight, and litter growth throughout first, but not second, lactation than WT mice. Treatment with t10c12CLA decreased litter growth (28%; P < 0.0001) and feed intake (8%; P < 0.0001) regardless of Trb3 genotype. When fed the HO diet, Trb3 KO mice had 17% higher mammary de novo synthesized FAs (<16 carbons; P int = 0.002) than WT mice. Mammary ER stress and lipogenic genes were mostly unaltered by Trb3 deficiency.

CONCLUSIONS

Overall, TRB3 plays a minor role in regulating mammary lipogenesis, because Trb3 deficiency had only a limited protective effect against diet-induced suppression of lipogenesis.

Elevated serum S14 levels are associated with more severe liver steatosis by ultrasonography

S14 has been identified as a potent stimulator of de novo hepatic lipogenesis (DNL) in rodents. However, it is unclear how S14 is regulated in humans with non-alcoholic fatty liver disease (NAFLD). The aim of this study was to investigate the relationship between serum S14 and liver steatosis in humans with NAFLD. A total of 614 participants were recruited from community. Liver steatosis were evaluated according to the Ultrasonographic Fatty Liver Indicator (US-FLI), which is a semi-quantitative liver ultrasound score. Anthropometric and biochemical indices were collected for further analysis. The risk of liver steatosis severity was estimated by a cumulative logistic regression model. NAFLD was found in 52.2% of the participants. The subjects with NAFLD showed higher levels of waist circumference, body mass index, insulin resistance, aspartate aminotransferase, dyslipidemia, visceral fat, serum S14 and risk of metabolic syndrome (MetS) than those of controls. Compared with the first tertile of serum S14, the odds ratios for the risk of more severe liver steatosis were 1.22 (95% confidence interval [CI]: 0.78–1.92) for those of the second tertile and 2.08 (95% CI: 1.28–3.39) for the third tertile (P for trend < 0.05) after adjusting for confounding factors. Higher serum S14 level was not only found in NAFLD subjects but also was positively correlated with the severity of liver steatosis. S14 may play an important role in the mechanism of DNL for NAFLD in humans.

Drosophila STING protein has a role in lipid metabolism

Stimulator of interferon genes (STING) plays an important role in innate immunity by controlling type I interferon response against invaded pathogens. In this work, we describe a previously unknown role of STING in lipid metabolism in Drosophila. Flies with STING deletion are sensitive to starvation and oxidative stress, have reduced lipid storage, and downregulated expression of lipid metabolism genes. We found that Drosophila STING interacts with lipid synthesizing enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FASN). ACC and FASN also interact with each other, indicating that all three proteins may be components of a large multi-enzyme complex. The deletion of Drosophila STING leads to disturbed ACC localization and decreased FASN enzyme activity. Together, our results demonstrate a previously undescribed role of STING in lipid metabolism in Drosophila.

Phosphatase and tensin homolog (PTEN) suppresses triacylglycerol accumulation and monounsaturated fatty acid synthesis in goat mammary epithelial cells

Phosphatase and tensin homolog (PTEN) is a well-known tumor suppressor in nonruminants and regulates various cellular processes including growth through dephosphorylation of phosphoinositide substrates. Although studies with bovine mammary tissue suggested a role for PTEN during lactation, its potential role in lipid metabolism remains unknown. Objectives of the present study were to determine PTEN abundance in goat mammary tissue at 2 stages of lactation (n = 6 Xinong Saanen dairy goats per stage), and to use gene-silencing and adenoviral transfections in vitro with isolated goat mammary epithelial cells (GMEC) to evaluate the role of PTEN abundance of lipid metabolism-related genes. Abundance of PTEN decreased by 51.5% at peak lactation compared with the dry period. The PTEN was overexpressed in isolated GMEC through adenoviral transfection using an adenovirus system with Ad-GFP (recombinant adenovirus of green fluorescent protein) as control, and silenced via targeted small interfering RNA (siRNA) transfection with a scrambled small interfering RNA as a negative control. Cell culture was performed for 48 h before RNA extraction, triacylglycerol (TAG) analysis, and fatty acid analysis. Overexpression of PTEN downregulated abundance of acetyl-coenzyme A carboxylase α (ACACA), fatty acid synthase (FASN), sterol regulatory element binding transcription factor1 (SREBF1), stearoyl-coenzyme A desaturase 1 (SCD1), diacylglycerol acytransferase 1 (DGAT1), 1-acylglycerol-3-phosphate O-acyltransferase 6 (AGPAT6) coupled with an increase in patatin-like-phospholipase domain containing 2 (PNPLA2), hormone-sensitive lipase (LIPE), and carnitine palmitoyltransferase 1 β (CPT1B). Furthermore, overexpressing PTEN in vitro resulted in a significant decrease in TAG concentration and concentration of C16:1. In contrast, interference of PTEN led to an opposite effect on lipid metabolism in GMEC. These changes suggested a shift from lipogenesis and esterification to lipolysis and fatty acid oxidation. Collectively, PTEN seems to play a role in monounsaturated fatty acids synthesis and lipid accumulation in GMEC.

Neonatal hyperoxia inhibits proliferation and survival of atrial cardiomyocytes by suppressing fatty acid synthesis

Preterm birth increases the risk for pulmonary hypertension and heart failure in adulthood. Oxygen therapy can damage the immature cardiopulmonary system and may be partially responsible for the cardiovascular disease in adults born preterm. We previously showed that exposing newborn mice to hyperoxia causes pulmonary hypertension by 1 year of age that is preceded by a poorly understood loss of pulmonary vein cardiomyocyte proliferation. We now show that hyperoxia also reduces cardiomyocyte proliferation and survival in the left atrium and causes diastolic heart failure by disrupting its filling of the left ventricle. Transcriptomic profiling showed that neonatal hyperoxia permanently suppressed fatty acid synthase (Fasn), stearoyl-CoA desaturase 1 (Scd1), and other fatty acid synthesis genes in the atria of mice, the HL-1 line of mouse atrial cardiomyocytes, and left atrial tissue explanted from human infants. Suppressing Fasn or Scd1 reduced HL-1 cell proliferation and increased cell death, while overexpressing these genes maintained their expansion in hyperoxia, suggesting that oxygen directly inhibits atrial cardiomyocyte proliferation and survival by repressing Fasn and Scd1. Pharmacologic interventions that restore Fasn, Scd1, and other fatty acid synthesis genes in atrial cardiomyocytes may, thus, provide a way of ameliorating the adverse effects of supplemental oxygen on preterm infants.

Progesterone receptor isoform-dependent cross-talk between prolactin and fatty acid synthase in breast cancer

Progesterone receptor (PR) isoforms can drive unique phenotypes in luminal breast cancer (BC). Here, we hypothesized that PR-B and PR-A isoforms differentially modify the cross-talk between prolactin and fatty acid synthase (FASN) in BC. We profiled the responsiveness of the FASN gene promoter to prolactin in T47D_co BC cells constitutively expressing PR-A and PR-B, in the PR-null variant T47D-Y cell line, and in PR-null T47D-Y cells engineered to stably re-express PR-A (T47D-YA) or PR-B (T47D-YB). The capacity of prolactin to up-regulate FASN gene promoter activity in T47D_co cells was lost in T47D-Y and TD47-YA cells. Constitutively up-regulated FASN gene expression in T47-YB cells and its further stimulation by prolactin were both suppressed by the prolactin receptor antagonist hPRL-G129R. The ability of the FASN inhibitor C75 to decrease prolactin secretion was more conspicuous in T47-YB cells. In T47D-Y cells, which secreted notably less prolactin and downregulated prolactin receptor expression relative to T47D_co cells, FASN blockade resulted in an augmented secretion of prolactin and up-regulation of prolactin receptor expression. Our data reveal unforeseen PR-B isoform-specific regulatory actions in the cross-talk between prolactin and FASN signaling in BC. These findings might provide new PR-B/FASN-centered predictive and therapeutic modalities in luminal intrinsic BC subtypes.

Got Milk? Identifying and Characterizing Lactation Defects in Genetically-Engineered Mouse Models

The ability to produce and expel milk is important for the health and survival of all mammals. Nevertheless, our understanding of the molecular events underlying the execution of this process remains incomplete. Whilst impaired mammary gland development and lactational competence remains the subject of focused investigations, defects in these events may also be an unintended consequence of genetic manipulation in rodent models. In this technical report, we outline established and emerging methods to characterize lactation phenotypes in genetically-engineered mouse models. We discuss important considerations of common models, optimized conditions for mating and the importance of litter size and standardization. Methods for quantifying milk production and quality, as well as protocols for wholemount preparation, immunohistochemistry and the preparation of RNA and protein lysates are provided. This review is intended to help guide researchers new to the field of mammary gland biology in the systematic analysis of lactation defects and in the preparation of samples for more focused mechanistic investigations.

Single Cell RNA Sequencing of Human Milk-Derived Cells Reveals Sub-Populations of Mammary Epithelial Cells with Molecular Signatures of Progenitor and Mature States: a Novel, Non-invasive Framework for Investigating Human Lactation Physiology

Cells in human milk are an untapped source, as potential "liquid breast biopsies", of material for investigating lactation physiology in a non-invasive manner. We used single cell RNA sequencing (scRNA-seq) to identify milk-derived mammary epithelial cells (MECs) and their transcriptional signatures in women with diet-controlled gestational diabetes (GDM) with normal lactation. Methodology is described for coordinating milk collections with single cell capture and library preparation via cryopreservation, in addition to scRNA-seq data processing and analyses of MEC transcriptional signatures. We comprehensively characterized 3740 cells from milk samples from two mothers at two weeks postpartum. Most cells (>90%) were luminal MECs (luMECs) expressing lactalbumin alpha and casein beta and positive for keratin 8 and keratin 18. Few cells were keratin 14⁺ basal MECs and a small immune cell population was present (<10%). Analysis of differential gene expression among clusters identified six potentially distinct luMEC subpopulation signatures, suggesting the potential for subtle functional differences among luMECs, and included one cluster that was positive for both progenitor markers and mature milk transcripts. No expression of pluripotency markers POU class 5 homeobox 1 (POU5F1, encoding OCT4) SRY-box transcription factor 2 (SOX2) or nanog homeobox (NANOG), was observed. These observations were supported by flow cytometric analysis of MECs from mature milk samples from three women with diet-controlled GDM (2-8 mo postpartum), indicating a negligible basal/stem cell population (epithelial cell adhesion molecule (EPCAM)^-/integrin subunit alpha 6 (CD49f)⁺, 0.07%) and a small progenitor population (EPCAM⁺/CD49f⁺, 1.1%). We provide a computational framework for others and future studies, as well as report the first milk-derived cells to be analyzed by scRNA-seq. We discuss the clinical potential and current limitations of using milk-derived cells as material for characterizing human mammary physiology.

Placental fatty acid transport across late gestation in a baboon model of intrauterine growth restriction

KEY POINTS

Intrauterine growth restriction (IUGR) is associated with perinatal morbidity and increased risk of lifelong disease, including neurodevelopmental impairment. Fatty acids (FA) are critical for normal brain development, although their transport across the placenta in IUGR pregnancies is poorly understood. The present study used a baboon model of IUGR (maternal nutrient restriction, MNR) to investigate placental expression of FA transport and binding proteins, and to determine gestational age-related changes in maternal and fetal plasma FA concentrations. We found MNR to be associated with increased placental expression of FA binding and transport proteins in late gestation, with fetal plasma FA concentrations that were similar to those of control animals. The present study is the first to report a profile of fetal and maternal plasma FA concentrations in a baboon model of growth restriction with data that suggest adaptation of placental transport to maintain delivery of critically needed FA.

ABSTRACT

Intrauterine growth restriction (IUGR) is associated with specific changes in placental transport of amino acids, folate and ions. However, little is known about placental fatty acid (FA) transport in IUGR. We hypothesized that placental FA transport proteins (FATP) and FA binding proteins (FABP) are up-regulated and fetal plasma FA concentrations are decreased at term in a baboon model of IUGR. Pregnant baboons were fed control or maternal nutrient restricted (MNR) diet (70% of control calories) from gestation day (GD) 30 (term 184 days). Plasma and placental samples were collected at GD120 (control n = 8, MNR n = 9), GD140 (control n = 6, MNR n = 7) and GD170 (control n = 6, MNR n = 6). Placentas were homogenized, and syncytiotrophoblast microvillous plasma membrane (MVM) and basal plasma membranes (BM) were isolated. Protein expression of FABP1, 3, 4 and 5 (homogenate) and FATP2, 4, and 6 (MVM, BM) was determined by Western blotting. FA content in maternal and umbilical vein plasma was measured by gas chromatography-mass spectrometry. Placental FABP1 and FABP5 expression was increased in MNR compared to controls at GD170, as was MVM FATP2 and FATP6 expression at GD140 and FATP2 expression at GD170. BM FATP4 and FATP6 expression was increased in MNR at GD140. Fetal plasma FA concentrations were similar in controls and MNR. These data suggest the adaptation of placental transport when aiming to maintain delivery of critically needed FAs for fetal growth and brain development.

Diiodothyronines regulate metabolic homeostasis in primary human hepatocytes by modulating mTORC1 and mTORC2 activity

Until three decades, ago 3,5-diiodothyronine (3,5-T₂) and 3,3'-diiodothyronine (3,3'-T₂) were considered products of thyroid hormone catabolism without biological activity. Some metabolic effects have been described in rodents, but the physiological relevance in humans and the mechanisms of action are unknown. Aim of this work was to investigate the role and the mechanisms of action of 3,5-T₂ and 3,3'-T₂ in the regulation of metabolic homeostasis in human liver. We used primary human hepatocytes freshly isolated from donors and grown on Matrigel as the golden standard in vitro model to study human hepatic metabolism. Results show that diiodothyronines in the range of plasma physiological concentrations reduced hepatic lipid accumulation, by modulating the activity of the mTORC1/Raptor complex through an AMPK-mediated mechanism, and stimulated the mTORC2/Rictor complex-activated pathway, leading to the down regulation of the expression of key gluconeogenic genes. Hence, we propose that diiodothyronines act as key regulators of hepatic metabolic homeostasis in humans.

Liver X receptor-α activation enhances cholesterol secretion in lactating mammary epithelium

Liver X receptors (LXRs) are ligand-dependent transcription factors activated by cholesterol metabolites. These receptors induce a suite of target genes required for de novo synthesis of triglycerides and cholesterol transport in many tissues. Two different isoforms, LXRα and LXRβ, have been well characterized in liver, adipocytes, macrophages, and intestinal epithelium among others, but their contribution to cholesterol and fatty acid efflux in the lactating mammary epithelium is poorly understood. We hypothesize that LXR regulates lipogenesis during milk fat production in lactation. Global mRNA analysis of mouse mammary epithelial cells (MECs) revealed multiple LXR/RXR targets upregulated sharply early in lactation compared with midpregnancy. LXRα is the primary isoform, and its protein levels increase throughout lactation in MECs. The LXR agonist GW3965 markedly induced several genes involved in cholesterol transport and lipogenesis and enhanced cytoplasmic lipid droplet accumulation in the HC11 MEC cell line. Importantly, in vivo pharmacological activation of LXR increased the milk cholesterol percentage and induced sterol regulatory element-binding protein 1c (Srebp1c) and ATP-binding cassette transporter a7 (Abca7) expression in MECs. Cumulatively, our findings identify LXRα as an important regulator of cholesterol incorporation into the milk through key nodes of de novo lipogenesis, suggesting a potential therapeutic target in women with difficulty initiating lactation.

Quantitative NMR-Based Metabolomics on Tissue Biomarkers and Its Translation into In Vivo Magnetic Resonance Spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy is an established analytical platform for analyzing metabolic profiles of cells, tissues, and body fluids. There are several advantages in introducing an NMR-based study design into metabolomics studies, including a fast and comprehensive detection, characterization, and quantification of dozens of endogenous metabolites in a single NMR spectrum. Quantitative proton ¹H-NMR is the most useful NMR-based platform for metabolomics. The frozen tissues can be analyzed noninvasively using a high-resolution magic angle spinning (HR-MAS) ¹H-NMR spectroscopy; or several extraction techniques can be applied to detect additional metabolites using a conventional liquid-based NMR technique. In this chapter, we report on tissue collection, handling, extraction methods, and ¹H-NMR acquisition protocols developed in the past decades for a precise and quantitative NMR-metabolomics approach. The NMR acquisition protocols (both HR-MAS and conventional ¹H-NMR spectroscopy) and spectral analysis steps are also presented. Since NMR can be applied "in vivo" using horizontal bore MRI scanners, several in vivo sequences for localized ¹H-MRS (magnetic resonance spectroscopy) are presented which can be directly applied for noninvasive detection of brain metabolites.

Milk lipid regulation at the maternal-offspring interface

Milk lipids provide a large proportion of energy, nutrients, essential fatty acids, and signaling molecules for the newborns, the synthesis of which is a tightly controlled process. Dysregulated milk lipid production and composition may be detrimental to the growth, development, health and survival of the newborns. Many genetically modified animal models have contributed to our understanding of milk lipid regulation in the lactating mammary gland. In this review, we discuss recent advances in our knowledge of the mechanisms that control milk lipid biosynthesis and secretion during lactation, and how maternal genetic and dietary defects impact milk lipid composition and consequently offspring traits.

Low Neonatal Plasma n-6/n-3 PUFA Ratios Regulate Offspring Adipogenic Potential and Condition Adult Obesity Resistance

Adipose tissue expansion progresses rapidly during postnatal life, influenced by both prenatal maternal factors and postnatal developmental cues. The ratio of omega-6 (n-6) relative to n-3 polyunsaturated fatty acids (PUFAs) is believed to regulate perinatal adipogenesis, but the cellular mechanisms and long-term effects are not well understood. We lowered the fetal and postnatal n-6/n-3 PUFA ratio exposure in wild-type offspring under standard maternal dietary fat amounts to test the effects of low n-6/n-3 ratios on offspring adipogenesis and adipogenic potential. Relative to wild-type pups receiving high perinatal n-6/n-3 ratios, subcutaneous adipose tissue in 14-day-old wild-type pups receiving low n-6/n-3 ratios had more adipocytes that were smaller in size; decreased Pparγ2, Fabp4, and Plin1; several lipid metabolism mRNAs; coincident hypermethylation of the PPARγ2 proximal promoter; and elevated circulating adiponectin. As adults, offspring that received low perinatal n-6/n-3 ratios were diet-induced obesity (DIO) resistant and had a lower positive energy balance and energy intake, greater lipid fuel preference and non-resting energy expenditure, one-half the body fat, and better glucose clearance. Together, the findings support a model in which low early-life n-6/n-3 ratios remodel adipose morphology to increase circulating adiponectin, resulting in a persistent adult phenotype with improved metabolic flexibility that prevents DIO.

Alterations in placental long chain polyunsaturated fatty acid metabolism in human intrauterine growth restriction

Fatty acids (FA) are critical for fetal brain development and are transferred across the placenta by membrane-bound FA transport proteins (FATP), translocases (FAT/CD36), and cytosolic binding proteins (FABP). The cytosolic protein perilipin-2 aids in neutral lipid storage within lipid droplets. Decreased placental nutrient transport is believed to contribute to intrauterine growth restriction (IUGR); however, IUGR placental lipid transport and metabolism are poorly understood. We hypothesized that protein expression of FATPs, FABPs, and perilipin-2 in human placenta is decreased and placental lipid content and incorporation into lipid classes are reduced in IUGR. Placental tissue of idiopathic IUGR (n=25) and gestational age-matched, appropriately grown for gestational age (AGA) fetuses (n=19) was collected. We determined protein expression of FABP4 and perilipin-2 in placental homogenate and FATPs (2, 4, 6, CD36) in syncytiotrophoblast microvillous plasma membrane (MVM) by Western blot. Lipid droplet area (Oil Red O stain) and cellular FA content (GC/MS) were measured in chorionic villous tissue. MVM expression of FATP6 and CD36 was significantly increased in IUGR. The concentrations of seven n-6 and n-3 species long chain polyunsaturated FAs (LCPUFA) were significantly increased in the triglyceride fraction in IUGR vs AGA placenta. In summary, MVM FATP6 and CD36 protein expression is increased and LCPUFA are preferentially routed toward cellular storage in TG in the IUGR placenta, possibly to protect against oxidative stress associated with cellular FA accumulation. We speculate that these changes may be caused by impaired efflux of FA across the fetal-facing syncytiotrophoblast basal plasma membrane in IUGR placenta.

Elevated Serum Growth Differentiation Factor 15 Levels in Hyperthyroid Patients

Background: Recent studies have shown that growth differentiation factor 15 (GDF15), a member of the transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) superfamily, plays an important role in appetite, type 2 diabetes, and cardiovascular diseases. Since thyroid hormone has pleiotropic effects on whole-body energy metabolism, we aimed to explore the effect of thyroid hormone on circulating GDF15 levels in humans and GDF15 genes expression in C57BL/6 mice. Methods: A total of 134 hyperthyroid patients and 105 healthy subjects were recruited. Of them, 43 hyperthyroid patients received thionamide treatment for 3 months until euthyroidism. Serum GDF15 levels were determined using the enzyme-linked immunosorbent assay (ELISA) method. To determine the source for the increased circulating GDF15, C57BL/6 mice were treated with T3, and GDF15 gene expressions in the liver, skeletal muscle, brown adipose tissue (BAT), inguinal white adipose tissue (iWAT), epididymal white adipose tissue (eWAT) were analyzed by quantitative real-time polymerase chain reaction (PCR). Results: Serum GDF15 levels were significantly elevated in hyperthyroid patients as compared with healthy subjects (326.06 ± 124.13 vs. 169.24 ± 82.96 pg/mL; P < 0.001). After thionamide treatment, GDF15 levels in hyperthyroid patients declined markedly from 293.27 ± 119.49 to 118.10 ± 71.83 pg/mL (P < 0.001). After adjustment for potential confounders, serum GDF15 levels were independently associated with hyperthyroidism. T3 treatment increased GDF15 expression in the brown adipose tissue of C57BL/6 mice. Conclusions: Serum GDF15 levels were elevated in patients with hyperthyroidism and declined after thionamide treatment. Thyroid hormone treatment upregulated GDF15 expression in mice. Therefore, our results present the clinical relevance of GDF15 in humans under the condition of hyperthyroidism.

The Androgen Receptor Supports Tumor Progression After the Loss of Ovarian Function in a Preclinical Model of Obesity and Breast Cancer

The androgen receptor (AR) has context-dependent roles in breast cancer growth and progression. Overall, high tumor AR levels predict a favorable patient outcome, but several studies have established a tumor promotional role for AR, particularly in supporting the growth of estrogen receptor positive (ER-positive) breast cancers after endocrine therapy. Our previous studies have demonstrated that obesity promotes mammary tumor progression after ovariectomy (OVX) in a rat model of postmenopausal breast cancer. Here, we investigated a potential role for AR in obesity-associated post-OVX mammary tumor progression following ovarian estrogen loss. In this model, we found that obese but not lean rats had nuclear localized AR in tumors that progressed 3 weeks after OVX, compared to those that regressed. AR nuclear localization is consistent with activation of AR-dependent transcription. Longer-term studies (8 weeks post-OVX) showed that AR nuclear localization and expression were maintained in tumors that had progressed, but AR expression was nearly lost in tumors that were regressing. The anti-androgen enzalutamide effectively blocked tumor progression in obese rats by promoting tumor necrosis and also prevented the formation of new tumors after OVX. Neither circulating nor mammary adipose tissue levels of the AR ligand testosterone were elevated in obese compared to lean rats; however, IL-6, which we previously reported to be higher in plasma from obese versus lean rats, sensitized breast cancer cells to low levels of testosterone. Our study demonstrates that, in the context of obesity, AR plays a role in driving ER-positive mammary tumor progression in an environment of low estrogen availability, and that circulating factors unique to the obese host, including IL-6, may influence how cancer cells respond to steroid hormones.

Fatty acid and lipid profiles in primary human trophoblast over 90h in culture

Little is known about the mechanisms underlying the preferential transport of long chain polyunsaturated fatty acids (LCPUFA) to the fetus by the syncytiotrophoblast and the role of cytotrophoblasts in placental lipid metabolism and transport. We studied primary human trophoblast (PHT) cells cultured for 90h to determine the fatty acid and lipid composition of cytotrophoblast (18h culture) and syncytiotrophoblast (90h culture) cells. In cultured PHT total lipid fatty acids were significantly (P < 0.05) reduced at 90h compared to 18h in culture including lower levels of palmitic acid (PA, 16:0, -37%), palmitoleic acid (POA, 16:1n-7, -30%), oleic acid (OA, 18:1n-9, -31%), LCPUFA arachidonic acid (AA, 20:4n-6, -28%) and α-linolenic acid (ALA, 18:3n-3, -55%). In major lipid classes, OA and most of the n-3 and n-6 LCPUFA were markedly lower at 90h in TG (-57 to -76%; p < 0.05). In the cellular NEFA, n-6 LCPUFA, dihomo-γ-linolenic acid (DGLA, 20:3n-6) and AA were both reduced by -51% and DHA was -55% lower (p < 0.05) at 90h. In contrast, phospholipid FA content did not change between cytotrophoblasts and syncytiotrophoblast except for OA, which decreased by -62% (p < 0.05). Decreasing PHT TG and NEFA lipid content at 90h in culture is likely due to processes related to differentiation such as alterations in lipase activity that occur as cytotrophoblast cells differentiate. We speculate that syncytiotrophoblast prioritizes PL containing AA and DHA for transfer to the fetus by mobilizing FA from storage lipids.

Metformin Accumulation Correlates with Organic Cation Transporter 2 Protein Expression and Predicts Mammary Tumor Regression In Vivo

Several epidemiologic studies have associated metformin treatment with a reduction in breast cancer incidence in prediabetic and type II diabetic populations. Uncertainty exists regarding which patient populations and/or tumor subtypes will benefit from metformin treatment, and most preclinical in vivo studies have given little attention to the cellular pharmacology of intratumoral metformin uptake. Epidemiologic reports consistently link western-style high fat diets (HFD), which drive overweight and obesity, with increased risk of breast cancer. We used a rat model of HFD-induced overweight and mammary carcinogenesis to define intratumoral factors that confer metformin sensitivity. Mammary tumors were initiated with 1-methyl-1-nitrosourea, and rats were randomized into metformin-treated (2 mg/mL drinking water) or control groups (water only) for 8 weeks. Two-thirds of existing mammary tumors responded to metformin treatment with decreased tumor volumes (P < 0.05), reduced proliferative index (P < 0.01), and activated AMPK (P < 0.05). Highly responsive tumors accumulated 3-fold greater metformin amounts (P < 0.05) that were positively correlated with organic cation transporter-2 (OCT2) protein expression (r = 0.57; P = 0.038). Importantly, intratumoral metformin concentration negatively associated with tumor volume (P = 0.03), and each 10 pmol increase in intratumoral metformin predicted >0.11 cm³ reduction in tumor volume. Metformin treatment also decreased proinflammatory arachidonic acid >1.5-fold in responsive tumors (P = 0.023). Collectively, these preclinical data provide evidence for a direct effect of metformin in vivo and suggest that OCT2 expression may predict metformin uptake and tumor response. Cancer Prev Res; 10(3); 198-207. ©2017 AACR.

Human Milk Fatty Acid Composition: Comparison of Novel Dried Milk Spot Versus Standard Liquid Extraction Methods

Accurate assessment of the long chain polyunsaturated fatty acid (LC-PUFA) content of human milk (HM) provides a powerful means to evaluate the FA nutrient status of breastfed infants. The conventional standard for FA composition analysis of HM is liquid extraction, trans-methylation, and analyte detection resolved by gas chromatography. This standard approach requires fresh or frozen samples, storage in deep freeze, organic solvents, and specialized equipment in processing and analysis. Further, HM collection is often impractical for many studies in the free living environment, particularly for studies in developing countries. In the present study, we compare a novel and more practical approach to sample collection and processing that involves the spotting and drying ~50 μL of HM on a specialized paper stored and transported at ambient temperatures until analysis. Deming regression indicated the two methods aligned very well for all LC-PUFA and the abundant HM FA. Additionally, strong correlations (r > 0.85) were observed for DHA, ARA, EPA, linoleic (LA), and alpha-linolenic acids (ALA), which are of particular interest to the health of the developing infant. Taken together, our data suggest this more practical and inexpensive method of collection, storage, and transport of HM milk samples could dramatically facilitate studies of HM, as well as understanding its lipid composition influences on human health and development.

Genetic Variant in Flavin-Containing Monooxygenase 3 Alters Lipid Metabolism in Laying Hens in a Diet-Specific Manner

Genetic variant T329S in flavin-containing monooxygenase 3 (FMO3) impairs trimethylamine (TMA) metabolism in birds. The TMA metabolism that under complex genetic and dietary regulation, closely linked to cardiovascular disease risk. We determined whether the genetic defects in TMA metabolism may change other metabolic traits in birds, determined whether the genetic effects depend on diets, and to identify genes or gene pathways that underlie the metabolic alteration induced by genetic and diet factors. We used hens genotyped as FMO3 c.984 A>T as well as those with the homozygous normal genotype. For each genotype, hens were provided with either a corn-soybean meal basal diets (SM), which contains lower levels of TMA precursor, or the basal diets supplemented with 21% of rapeseed meal (RM), which contains higher levels of TMA precursor. An integrative analysis of metabolomic and transcriptomic was used to explore the metabolic patterns of FMO3 genetic variant in hens that were fed the two defined diets. In birds that consumed SM diets, the T329S mutation increased levels of plasma TMA and lipids, FMO3 mRNA levels, and the expression of genes involved in long chain polyunsaturated fatty acid biosynthesis. In birds that consumed RM diets, the T329S mutation induced fishy odor syndrome, a repression in LXR pathway and a reciprocal change in lipid metabolism. Variations in TMA and lipid metabolism were linked to the genetic variant in FMO3 in a diet-specific manner, which suggest FMO3 functions in TMA metabolism and lipid homeostasis. LXR pathway and polyunsaturated fatty acid metabolism are two possible mechanisms of FMO3 action in response to dietary TMA precursor.

Early infant adipose deposition is positively associated with the n-6 to n-3 fatty acid ratio in human milk independent of maternal BMI

Background/Objectives

Excessive infant weight gain in the first 6-months of life is a powerful predictor of childhood obesity and related health risks. In mice, omega-6 fatty acids (FA) serve as potent ligands driving adipogenesis during early development. The ratio of omega-6 relative to omega-3 (n-6/n-3) FA in human milk (HM) has increased 3-fold over the last 30 years, but the impact of this shift on infant adipose development remains undetermined. This study investigated how maternal obesity and maternal dietary FA (as reflected in maternal red blood cells (RBC) composition) influenced HM n-6 and n-3 FAs, and whether the HM n-6/n-3 ratio was associated with changes in infant adipose deposition between 2-weeks and 4-months postpartum.

Subjects/Methods

Forty-eight infants from normal-weight (NW), overweight (OW) and obese (OB) mothers were exclusively or predominantly breastfed over the first 4 months of lactation. Mid-feed HM and maternal RBC were collected at either transitional (2-weeks) or established (4-months) lactation, along with infant body composition assessed using air-displacement plethysmography. The FA composition of HM and maternal RBC was measured quantitatively by lipid mass spectrometry.

Results

In transitional and established HM, DHA was lower (P=0.008; 0.005) and the AA/DHA+EPA ratio was higher (P=0.05; 0.02) in the OB relative to the NW group. Maternal prepregnancy BMI and AA/ DHA+EPA ratios in transitional and established HM were moderately correlated (P=0.018; 0.001). Total infant fat mass was increased in the upper AA/DHA+EPA tertile of established HM relative to the lower tertile (P=0.019). The amount of changes in infant fat mass and % body fat were predicted by AA/EPA+DHA ratios in established HM (P=0.038; 0.010).

Conclusions

Perinatal infant exposures to a high AA/EPA+DHA ratio during the first 4-months of life, which is primarily reflective of maternal dietary FA, may significantly contribute to the way infants accumulate adipose.

Constitutive expression of microRNA-150 in mammary epithelium suppresses secretory activation and impairs de novo lipogenesis

Profiling of RNA from mouse mammary epithelial cells (MECs) isolated on pregnancy day (P)14 and lactation day (L)2 revealed that the majority of differentially expressed microRNA declined precipitously between late pregnancy and lactation. The decline in miR-150, which exhibited the greatest fold-decrease, was verified quantitatively and qualitatively. To test the hypothesis that the decline in miR-150 is crucial for lactation, MEC-specific constitutive miR-150 was achieved by crossing ROSA26-lox-STOP-lox-miR-150 mice with WAP-driven Cre recombinase mice. Both biological and foster pups nursed by bitransgenic dams exhibited a dramatic decrease in survival compared with offspring nursed by littermate control dams. Protein products of predicted miR-150 targets Fasn, Olah, Acaca, and Stat5B were significantly suppressed in MECs of bitransgenic mice with constitutive miR-150 expression as compared with control mice at L2. Lipid profiling revealed a significant reduction in fatty acids synthesized by the de novo pathway in L2 MECs of bitransgenic versus control mice. Collectively, these data support the hypothesis that a synchronized decrease in miRNAs, such as miR-150, at late pregnancy serves to allow translation of targets crucial for lactation.

Thyroid hormone responsive (THRSP) promotes the synthesis of medium-chain fatty acids in goat mammary epithelial cells

In nonruminants, thyroid hormone responsive (THRSP) is a crucial protein for cellular de novo lipogenesis. However, the role of THRSP in regulating the synthesis of milk fatty acid composition in goat mammary gland remains unknown. In the present study, we compared gene expression of THRSP among different goat tissues. Results revealed that THRSP had the highest expression in subcutaneous fat, and expression was higher during lactation compared with the dry period. Overexpression of THRSP upregulated the expression of fatty acid synthase (FASN), stearoyl-coenzyme A desaturase 1 (SCD1), diacylglycerol acyltransferase 2 (DGAT2), and glycerol-3-phosphate acyltransferase (GPAM) in goat mammary epithelial cells. In contrast, overexpression of THRSP led to downregulation of thrombospondin receptor (CD36) and had no effect on the expression of acetyl-coenzyme A carboxylase α (ACACA) and sterol regulatory element binding transcription factor1 (SREBF1). In addition, overexpressing THRSP in vitro resulted in a significant increase in triacylglycerol (TAG) concentration and the concentrations of C12:0 and C14:0. Taken together, these results highlight an important role of THRSP in regulating lipogenesis in goat mammary epithelial cells.

XBP1 Regulates the Biosynthetic Capacity of the Mammary Gland During Lactation by Controlling Epithelial Expansion and Endoplasmic Reticulum Formation

Cells composing the mammary secretory compartment have evolved a high capacity to secrete not only proteins but also triglycerides and carbohydrates. This feature is illustrated by the mouse, which can secrete nearly twice its own weight in milk proteins, triglycerides and lactose over a short 20-day lactation. The coordination of synthesis and export of products in other secretory cells is orchestrated in part by the transcription factor X-box binding protein 1 (XBP1). To assess the role of XBP1 in mammary epithelial cells (MEC), we studied floxed XBP1 female mice lacking (wild type; WT) or expressing the Cre recombinase under the control of the ovine β-lactoglobulin promoter (ΔXBP1(MEC)). Pregnant ΔXBP1(MEC) females had morphologically normal mammary development and gave birth to the same number of pups as WT mice. Their litters, however, suffered a weight gain deficit by lactation day 3 (L3)3 that grew to 80% by L14. ΔXBP1(MEC) dams had only modest changes in milk composition (-21% protein, +24% triglyceride) and in the expression of associated genes in isolated MEC. By L5, WT glands were fully occupied by dilated alveoli, whereas ΔXBP1(MEC) glands contained fewer, mostly unfilled alveoli and retained a prominent adipocyte population. The smaller epithelial compartment in ΔXBP1(MEC) glands was explained by lower MEC proliferation and increased apoptosis. Finally, endoplasmic reticulum ribbons were less abundant in ΔXBP1(MEC) at pregnancy day 18 and failed to increase in abundance by L5. Collectively, these results show that XBP1 is required for MEC population expansion during lactation and its ability to develop an elaborate endoplasmic reticulum compartment.

Modulation of tumor fatty acids, through overexpression or loss of thyroid hormone responsive protein spot 14 is associated with altered growth and metastasis

Introduction

Spot14 (S14), encoded by the THRSP gene, regulates de novo fatty acid synthesis in the liver, adipose, and lactating mammary gland. We recently showed that S14 stimulated fatty acid synthase (FASN) activity in vitro, and increased the synthesis of fatty acids in mammary epithelial cells in vivo. Elevated de novo fatty acid synthesis is a distinguishing feature of many solid tumors compared with adjacent normal tissue. This characteristic is thought to be acquired during tumor progression, as rapidly proliferating cells have a heightened requirement for membrane phospholipids. Further, overexpression of FASN is sufficient to stimulate cell proliferation. While many studies have focused on the FASN enzyme in cancer biology, few studies have addressed the roles of proteins that modify FASN activity, such as S14.

Methods

Tumor fatty acids were modulated using two mouse models, mouse mammary tumor virus (MMTV)-neu mice overexpressing S14 and MMTV-polyomavirus middle T antigen (PyMT) mice lacking S14, and associations between elevated or impaired fatty acid synthesis on tumor latency, growth, metastasis, and signaling pathways were investigated. We evaluated S14-dependent gene expression profiles in mouse tumors by microarray and used publicly available microarray datasets of human breast tumors.

Results

S14 overexpression in the MMTV-Neu transgenic model is associated with elevated medium-chain fatty acids, increased proliferation and a shorter tumor latency, but reduced tumor metastasis compared to controls. Loss of S14 in the MMTV-PyMT model decreased FASN activity and the synthesis of medium-chain fatty acids but did not alter tumor latency. Impaired fatty acid synthesis was associated with reduced solid tumor cell proliferation, the formation of cystic lesions in some animals, and decreased phosphorylation of Src and protein kinase B (Akt). Analysis of gene expression in these mouse and human tumors revealed a relationship between S14 status and the expression of genes associated with luminal epithelial differentiation.

Conclusions

This study demonstrates a potential role for S14 in regulating mammary tumor growth and fatty acid synthesis in vivo. Furthermore, these results suggest that modulating the amount of medium chain fatty acids, by changing the levels of S14, has the potential to impact malignant mammary tumor phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0481-z) contains supplementary material, which is available to authorized users.