The distribution and adipogenic potential of perivascular adipose tissue adipocyte progenitors is dependent on sexual dimorphism and vessel location

Therapeutic application of adipose-derived stromal vascular fraction in myocardial infarction

The insufficiency of natural regeneration processes in higher organisms, including humans, underlies myocardial infarction (MI), which is one of the main causes of disability and mortality in the population of developed countries. The solution to this problem lies in the field of revealing the mechanisms of regeneration and creating on this basis new technologies for stimulating endogenous regenerative processes or replacing lost parts of tissues and organs with transplanted cells. Of great interest is the use of the so-called stromal vascular fraction (SVF), derived from autologous adipose tissue. It is known that the main functions of SVF are angiogenetic, antiapoptotic, antifibrotic, immune regulation, anti-inflammatory, and trophic. This study presents data on the possibility of using SVF, targeted regulation of its properties and reparative potential, as well as the results of research studies on its use for the restoration of damaged ischemic tissue after MI.

Perivascular Adipose Tissue Remodels Only after Elevation of Blood Pressure in the Dahl SS Rat Fed a High-Fat Diet

INTRODUCTION

Tunica media extracellular matrix (ECM) remodeling is well understood to occur in response to elevated blood pressure, unlike the remodeling of other tunicas. We hypothesize that perivascular adipose tissue (PVAT) is responsive to hypertension and remodels as a protective measure.

METHODS

The adventitia and PVAT of the thoracic aorta were used in measuring ECM genes from 5 pairs of Dahl SS male rats on 8 or 24 weeks of feeding from weaning on a control (10% Kcal fat) or high-fat (HF; 60%) diet. A PCR array of ECM genes was performed with cDNA from adventitia and PVAT after 8 and 24 weeks. A gene regulatory network of the differentially expressed genes (DEGs) (HF 2-fold > con) was created using Cytoscape.

RESULTS

After 8 weeks, 29 adventitia but 0 PVAT DEGs were found. By contrast, at 24 weeks, PVAT possessed 47 DEGs while adventitia had 3. Top DEGs at 8 weeks in adventitia were thrombospondin 1 and collagen 8a1. At 24 weeks, thrombospondin 1 was also a top DEG in PVAT. The transcription factor Adarb1 was identified as a regulator of DEGs in 8-week adventitia and 24-week PVAT.

CONCLUSION

These data support that PVAT responds biologically once blood pressure is elevated.

The pathobiology of perivascular adipose tissue (PVAT), the fourth layer of the blood vessel wall

The perivascular adipose tissue (PVAT) is an adipose tissue depot which surrounds most human blood vessels. It is metabolically active and has both a protective and a pathogenic role in vascular biology and pathobiology. It regulates vascular homeostasis and promotes vascular dysfunction. The purpose of this review is to consider the origin, structure, function, and dysfunction of this unique adipose depot consisting of white (WAT), brown (BAT) and beige adipose tissue, to support the concept that PVAT may be considered the fourth layer of the normal arterial wall (tunica adiposa), in which dysfunction creates a microenvironment that regulates, in part, the initiation and growth of the fibro-inflammatory lipid atherosclerotic plaque. Experimental in-vivo and in-vitro studies and human investigations show that the adipocytes, extracellular matrix, nerve fibers and vasa vasorum found in PVAT form a functional adipose tissue unit adjacent to, but not anatomically separated from, the adventitia. PVAT maintains and regulates the structure and function of the normal arterial wall through autocrine and paracrine mechanisms, that include modulation of medial smooth muscle cell contractility and secretion of anti-inflammatory molecules. PVAT shows regional phenotypic heterogeneity which may be important in its effect on the wall of specific sections of the aorta and its muscular branches during perturbations and various injuries including obesity and diabetes. In atherosclerosis, a pan-vascular microenvironment is created that functionally links the intima-medial atherosclerotic plaque to the adventitia and PVAT beneath the plaque, highlighting the local impact of PVAT on atherogenesis. PVAT adipocytes have inflammatory effects which in response to injury show activation and phenotypic changes, some of which are considered to have direct and indirect effects on the intima and media during the initiation, growth, and development of complicated atherosclerotic plaques. Thus, it is important to maintain the integrity of the full vascular microenvironment so that design of experimental and human studies include investigation of PVAT. The era of discarding PVAT tissue in both experimental and human research and clinical vascular studies should end.

Endothelial Nitric Oxide Synthase in the Perivascular Adipose Tissue

Perivascular adipose tissue (PVAT) is a special type of ectopic fat depot that adheres to most vasculatures. PVAT has been shown to exert anticontractile effects on the blood vessels and confers protective effects against metabolic and cardiovascular diseases. PVAT plays a critical role in vascular homeostasis via secreting adipokine, hormones, and growth factors. Endothelial nitric oxide synthase (eNOS; also known as NOS3 or NOSIII) is well-known for its role in the generation of vasoprotective nitric oxide (NO). eNOS is primarily expressed, but not exclusively, in endothelial cells, while recent studies have identified its expression in both adipocytes and endothelial cells of PVAT. PVAT eNOS is an important player in the protective role of PVAT. Different studies have demonstrated that, under obesity-linked metabolic diseases, PVAT eNOS may be even more important than endothelium eNOS in obesity-induced vascular dysfunction, which may be attributed to certain PVAT eNOS-specific functions. In this review, we summarized the current understanding of eNOS expression in PVAT, its function under both physiological and pathological conditions and listed out a few pharmacological interventions of interest that target eNOS in PVAT.

PIEZO1 mechanoreceptor activation reduces adipogenesis in perivascular adipose tissue preadipocytes

During hypertension, vascular remodeling allows the blood vessel to withstand mechanical forces induced by high blood pressure (BP). This process is well characterized in the media and intima layers of the vessel but not in the perivascular adipose tissue (PVAT). In PVAT, there is evidence for fibrosis development during hypertension; however, PVAT remodeling is poorly understood. In non-PVAT depots, mechanical forces can affect adipogenesis and lipogenic stages in preadipocytes. In tissues exposed to high magnitudes of pressure like bone, the activation of the mechanosensor PIEZO1 induces differentiation of progenitor cells towards osteogenic lineages. PVAT's anatomical location continuously exposes it to forces generated by blood flow that could affect adipogenesis in normotensive and hypertensive states. In this study, we hypothesize that activation of PIEZO1 reduces adipogenesis in PVAT preadipocytes. The hypothesis was tested using pharmacological and mechanical activation of PIEZO1. Thoracic aorta PVAT (APVAT) was collected from 10-wk old male SD rats (n=15) to harvest preadipocytes that were differentiated to adipocytes in the presence of the PIEZO1 agonist Yoda1 (10 µM). Mechanical stretch was applied with the FlexCell System at 12% elongation, half-sine at 1 Hz simultaneously during the 4 d of adipogenesis (MS+, mechanical force applied; MS-, no mechanical force used). Yoda1 reduced adipogenesis by 33% compared with CON and, as expected, increased cytoplasmic Ca2+ flux. MS+ reduced adipogenesis efficiency compared with MS-. When Piezo1 expression was blocked with siRNA [siPiezo1; NC=non-coding siRNA], the anti-adipogenic effect of Yoda1 was reversed in siPiezo1 cells but not in NC; in contrast, siPiezo1 did not alter the inhibitory effect of MS+ on adipogenesis. These data demonstrate that PIEZO1 activation in PVAT reduces adipogenesis and lipogenesis and provides initial evidence for an adaptive response to excessive mechanical forces in PVAT during hypertension.

Regional Heterogeneity of Perivascular Adipose Tissue: Morphology, Origin, and Secretome

Perivascular adipose tissue (PVAT) is a unique fat depot with local and systemic impacts. PVATs are anatomically, developmentally, and functionally different from classical adipose tissues and they are also different from each other. PVAT adipocytes originate from different progenitors and precursors. They can produce and secrete a wide range of autocrine and paracrine factors, many of which are vasoactive modulators. In the context of obesity-associated low-grade inflammation, these phenotypic and functional differences become more evident. In this review, we focus on the recent findings of PVAT’s heterogeneity by comparing commonly studied adipose tissues around the thoracic aorta (tPVAT), abdominal aorta (aPVAT), and mesenteric artery (mPVAT). Distinct origins and developmental trajectory of PVAT adipocyte potentially contribute to regional heterogeneity. Regional differences also exist in ways how PVAT communicates with its neighboring vasculature by producing specific adipokines, vascular tone regulators, and extracellular vesicles in a given microenvironment. These insights may inspire new therapeutic strategies targeting the PVAT.

Male and female high-fat diet-fed Dahl SS rats are largely protected from vascular dysfunctions: PVAT contributions reveal sex differences

Vascular dysfunctions are observed in the arteries from hypertensive subjects. The establishment of the Dahl salt-sensitive (SS) male and female rat models to develop a reproducible hypertension with high-fat (HF) diet feeding from weaning allows addressing the question of whether HF diet-associated hypertension results in vascular dysfunction similar to that of essential hypertension in both sexes. We hypothesized that dysfunction of three distinct vascular layers, i.e., endothelial, smooth muscle, and perivascular adipose tissue (PVAT), would be present in the aorta from HF diet-fed versus control diet-fed male and female rats. Dahl SS rats were fed a control (10% kcal of fat) or HF (60%) diet from weaning for 24 wk. Male and female Dahl SS rats became equally hypertensive when placed on a HF diet. For male and female rats, the thoracic aorta exhibited medial hypertrophy in HF diet-induced hypertension versus control, but neither displayed a hyperresponsive contraction to the α-adrenergic agonist phenylephrine nor an endothelial cell dysfunction as measured by acetylcholine-induced relaxation. A beneficial PVAT function, support of stress relaxation, was reduced in the male versus female rats fed a HF diet. PVAT in the aorta of males but not in females retained the anticontractile activity. We conclude that this HF model does not display the same vascular dysfunctions observed in essential hypertension. Moreover, both male and female show significantly different vascular dysfunctions in this HF feeding model.NEW & NOTEWORTHY Although the aorta exhibits medial hypertrophy in response to HF diet-induced hypertension, it did not exhibit hyperresponsive contraction to an α-adrenergic agonist nor endothelial cell dysfunction; this was true for both sexes. Unlike other hypertension models, PVAT around aorta from (male) rats on the HF diet retained significant anticontractile activity. PVAT around aorta of the male on a HF diet was modestly more fibrotic and lost the ability to assist in arterial stress relaxation.

Adipose-Derived Mesenchymal Stromal Cells in Regenerative Medicine: State of Play, Current Clinical Trials, and Future Prospects

Significance: Wound healing is a complex process involving pain and inflammation, where innervation plays a central role. Managing wound healing and pain remains an important issue, especially in pathologies such as excessive scarring (often leading to fibrosis) or deficient healing, leading to chronic wounds. Recent Advances: Advances in therapies using mesenchymal stromal cells offer new insights for treating indications that previously lacked options. Adipose-derived mesenchymal stromal cells (AD-MSCs) are now being used to a much greater extent in clinical trials for regenerative medicine. However, to be really valid, these randomized trials must imperatively follow strict guidelines such as consolidated standards of reporting trials (CONSORT) statement. Indeed, AD-MSCs, because of their paracrine activities and multipotency, have potential to cure degenerative and/or inflammatory diseases. Combined with their relatively easy access (from adipose tissue) and proliferation capacity, AD-MSCs represent an excellent candidate for allogeneic treatments. Critical Issues: The success of AD-MSC therapy may depend on the robustness of the biological functions of AD-MSCs, which requires controlling source heterogeneity and production processes, and development of biomarkers that predict desired responses. Several studies have investigated the effect of AD-MSCs on innervation, wound repair, or pain management separately, but systematic evaluation of how those effects could be combined is lacking. Future Directions: Future studies that explore how AD-MSC therapy can be used to treat difficult-to-heal wounds, underlining the need to thoroughly characterize the cells used, and standardization of preparation processes are needed. Finally, how this a priori easy-to-use cell therapy treatment fits into clinical management of pain, improvement of tissue healing, and patient quality of life, all need to be explored.

Blood pressure changes PVAT function and transcriptome: use of the mid-thoracic aorta coarcted rat

Perivascular adipose tissue (PVAT) modifies the contractile function of the vessel it surrounds (outside-in signaling). Little work points to the vessel actively affecting its surrounding PVAT. We hypothesized that inside-out arterial signaling to PVAT would be evidenced by the response of PVAT to changes in tangential vascular wall stress. Rats coarcted in the mid-thoracic aorta created PVAT tissues that would exemplify pressure-dependent changes (above vs. below coarctation); a sham rat was used as a control. Radiotelemetry revealed a ∼20 mmHg systolic pressure gradient across the coarctation 4 wk after surgery. Four measures (histochemical, adipocyte progenitor proliferation and differentiation, isometric tone, and bulk mRNA sequencing) were used to compare PVAT above versus below the ligature in sham and coarcted rats. Neither aortic collagen deposition in PVAT nor arterial media/radius ratio above coarctation was increased versus below segments. However, differentiated adipocytes derived from PVAT above the coarctation accumulated substantially less triglycerides versus those below; their relative proliferation rate as adipogenic precursors was not different. Functionally, the ability of PVAT to assist stress relaxation of isolated aorta was reduced in rings above versus below the coarctation. Transcriptomic analyses revealed that the coarctation resulted in more differentially expressed genes (DEGs) between PVAT above versus below when compared with sham samples from the same locations. A majority of DEGs were in PVAT below the coarctation and were enriched in neuronal/synaptic terms. These findings provide initial evidence that signaling from the vascular wall, as stimulated by a pressure change, influences the function and transcriptional profile of its PVAT.NEW & NOTEWORTHY A mid-thoracic aorta coarcted rat was created to generate a stable pressure difference above versus below the coarctation ligature. This study determined that the PVAT around the thoracic aorta exposed to a higher pressure has a significantly reduced ability to assist stress relaxation versus that below the ligature and appears to retain the ability to be anticontractile. At the same time, the PVAT around the thoracic aorta exposed to higher pressure had a reduced adipogenic potential versus that below the ligature. Transcriptomics analyses indicated that PVAT below the coarctation showed the greatest number of DEGs with an increased profile of the synaptic neurotransmitter gene network.

Perivascular Adipocytes Store Norepinephrine by Vesicular Transport

Objective- Perivascular adipose tissue (PVAT) contains an independent adrenergic system that can take up, metabolize, release, and potentially synthesize the vasoactive catecholamine norepinephrine. Norepinephrine has been detected in PVAT, but the mechanism of its protection within this tissue is unknown. Here, we investigate whether PVAT adipocytes can store norepinephrine using VMAT (vesicular monoamine transporter). Approach and Results- High-performance liquid chromatography identified norepinephrine in normal male Sprague Dawley rat aortic, superior mesenteric artery, and mesenteric resistance vessel PVATs, and retroperitoneal fat. Real-time polymerase chain reaction revealed VMAT1 and VMAT2 mRNA expression in the adipocytes and stromal vascular fraction of mesenteric resistance vessel PVAT. Immunofluorescence demonstrated the presence of VMAT1 and VMAT2, and the colocalization of VMAT2 with norepinephrine, in the cytoplasm of adipocytes in mesenteric resistance vessel PVAT. A protocol was developed to capture real-time uptake of Mini 202-a functional and fluorescent VMAT probe-in live rat PVAT adipocytes. Mini 202 was taken up by freshly isolated and differentiated adipocytes from mesenteric resistance vessel PVAT and adipocytes from thoracic aortic and superior mesenteric artery PVATs. In adipocytes freshly isolated from mesenteric resistance vessel PVAT, addition of rose bengal (VMAT inhibitor), nisoxetine (norepinephrine transporter inhibitor), or corticosterone (organic cation 3 transporter inhibitor) significantly reduced Mini 202 signal. Immunofluorescence supports that neither VMAT1 nor VMAT2 is present in retroperitoneal adipocytes, suggesting that PVAT adipocytes may be unique in storing norepinephrine. Conclusions- This study supports a novel function of PVAT adipocytes in storing amines in a VMAT-dependent manner. It provides a foundation for future studies exploring the purpose and mechanisms of norepinephrine storage by PVAT in normal physiology and obesity-related hypertension.

Tipping the scales: Are females more at risk for obesity- and high-fat diet-induced hypertension and vascular dysfunction?

Obesity is a common metabolic disorder that has become a widespread epidemic in several countries. Sex and gender disparities in the prevalence of cardiovascular disease (CVD) have been well documented with premenopausal women having a lower incidence of CVD than age-matched men. However, women are more likely than men to suffer from obesity, which can predispose them to a greater risk of CVD. The mechanisms underlying high-fat diet (HFD)- or obesity-induced hypertension are not well defined, although immune system activation and inflammation have been implicated in several studies. Further, the sex of the subject can have a profound influence on the immune response to hypertensive stimuli. Therefore, the purpose of this review is to examine the effects of sex and gender on the role of the immune system in HFD-induced hypertension and vascular dysfunction. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Uterine perivascular adipose tissue is a novel mediator of uterine artery blood flow and reactivity in rat pregnancy

KEY POINTS

In vivo, uterine perivascular adipose tissue (PVAT) potentiates uterine artery blood flow in pregnant rats, although not in non-pregnant rats. In isolated preparations, uterine PVAT has pro-contractile and anti-dilatory effects on uterine arteries. Pregnancy induces changes in uterine arteries that makes them responsive to uterine PVAT signalling.

ABSTRACT

An increase in uterine artery blood flow (UtBF) is a common and necessary feature of a healthy pregnancy. In the present study, we tested the hypothesis that adipose tissue surrounding uterine arteries (uterine perivascular adipose tissue; PVAT) is a novel local mediator of UtBF and uterine artery tone during pregnancy. In vivo experiments in anaesthetized Sprague-Dawley rats showed that pregnant animals (gestational day 16, term = 22--23 days) had a three-fold higher UtBF compared to non-pregnant animals. Surgical removal of uterine PVAT reduced UtBF only in pregnant rats. In a series of ex vivo bioassays, we demonstrated that uterine PVAT had pro-contractile and anti-dilatory effects on rat uterine arteries. In the presence of PVAT-conditioned media, isolated uterine arteries from both pregnant and non-pregnant rats had reduced vasodilatory responses. In non-pregnant rats, these responses were mediated at the level of uterine vascular smooth muscle, whereas, in pregnant rats, PVAT-media reduced endothelium-dependent relaxation. Pregnancy increased adipocyte size in ovarian adipose tissue but had no effect on uterine PVAT adipocyte morphology. In addition, pregnancy down-regulated the gene expression of metabolic adipokines in uterine but not in aortic PVAT. In conclusion, this is the first study to demonstrate that uterine PVAT plays a regulatory role in UtBF, at least in part, as a result of its actions on uterine artery tone. We propose that the interaction between the uterine vascular wall and its adjacent adipose tissue may provide new insights for interventions in pregnancies with adipose tissue dysfunction and abnormal UtBF.

Adipogenic potential of perivascular adipose tissue preadipocytes is improved by coculture with primary adipocytes

Perivascular adipose tissue (PVAT) has the capacity to secrete vasoactive mediators with the potential to regulate vascular function. Given its location adjacent to the vasculature, PVAT dysfunction may be part of the pathophysiology of cardiovascular diseases. To study the mechanisms of PVAT dysfunction, several adipogenic models have been proposed. However, these approaches do not adequately reflect PVAT adipocyte phenotypes variability that depends on their anatomical location. Despite PVAT importance in modulating vascular function, to date, there is not a depot-specific adipogenic model for PVAT adipocytes. We present a model that uses coculturing of PVAT stromal vascular fraction derived preadipocytes with primary adipocytes isolated from the same PVAT. Preadipocytes were isolated from thoracic aorta PVAT and mesenteric resistance artery PVAT (mPVAT). Upon confluency, cells were induced to differentiate for 7 and 14 days using a standard protocol (SP) or standard protocol cocultured with primary adipocytes isolated from the same adipose depots (SPA) for 96, 120, and 144 h. SPA reduced the time for differentiation of stromal vascular fraction derived preadipocytes and increased their capacity to store lipids compared with SP as indicated by lipid accumulation, lipolytic responses, gene marker profile expression, and adiponectin secretion. The coculture system improved adipogenesis efficiency by enhancing lipid accumulation and reducing the time of induction, therefore, is a more efficient method compared to SP alone.

Gender and age-related cell compositional differences in C57BL/6 murine adipose tissue stromal vascular fraction

Adipose tissue is now recognized as a functional organ that contains cellular heterogeneity and diversity within anatomical depots. The stromal vascular fraction (SVF) of adipose contains endothelial progenitors, fibroblasts, lymphocytes, monocyte/macrophages, pericytes, pre-adipocytes, and stromal/stem cells, among others. In recent years, there has been a growing appreciation of the influence of age and gender in the field of stem cell biology. Yet few studies have evaluated the influence of biological age or sex on either SVF cell heterogeneity or immunophenotype. To address this issue, the current study has compared the flow cytometric characteristics between murine SVF of inguinal (iWAT), epidydimal (eWAT), and brown (BAT) adipose tissue of male and female, as well as young (6-8 week) and middle-aged (8-12 month) male C57BL/6 mice. Murine gender comparisons revealed male iWAT expressed higher percentages of leukocyte and CD34⁺ ASC-like sub-populations than female iWAT. Murine age comparisons revealed younger male iWAT, eWAT, and BAT SVF all contained a significantly higher percentage of pre-adipocytes, HSC-like cells, CD25^-, and FoxP3⁺ T-regulatory cells compared to SVF from middle-aged male mice. These findings highlight the potential contribution of biological variables on adipose-derived cell applications and experimental outcomes.

Fetuin-A: A negative acute-phase protein linked to adipose tissue function in periparturient dairy cows

Fetuin-A (FetA) is a free fatty acid transporter and an acute-phase protein that enhances cellular lipid uptake and lipogenesis. In nonruminants, FetA is involved in lipid-induced inflammation. Despite FetA importance in lipid metabolism and inflammation, its expression and dynamics in adipose tissue (AT) of dairy cows are unknown. The objectives of this study were to (1) determine serum and AT FetA dynamics over the periparturient period and in mid-lactation cows in negative energy balance (NEB) after a feed restriction protocol and (2) characterize how an inflammatory challenge affects adipocyte FetA expression. Blood and subcutaneous AT were collected from 16 cows with high (≥3.75, n = 8) or moderate (≤3.5, n = 8) body condition score (BCS) at -26 ± 7 d (far off) and -8 ± 5 d (close up) before calving and at 10 ± 2 d after parturition (early lactation) and from 14 nonpregnant mid-lactation cows (>220 d in milk) after a feed restriction protocol. Serum FetA concentrations were 0.89 ± 0.13 mg/mL at far off, 0.96 ± 0.13 mg/mL at close up, and 0.77 ± 0.13 mg/mL at early lactation and were 1.09 ± 0.09 and 1.17 ± 0.09 mg/mL in feed-restricted and control cows, respectively. Serum and AT FetA contents decreased at the onset of lactation when lipolysis was higher. No changes in AT and serum FetA were observed after feed restriction induced NEB in mid-lactation cows. Prepartum BCS had no effect on serum FetA, but AT expression of AHSG, the gene encoding FetA, was reduced in periparturient cows with high BCS at dry-off throughout all time points. Circulating FetA was positively associated with serum albumin and calcium and with BCS variation over the periparturient period. The dynamics of AHSG expression were analogous to the patterns of lipogenic markers ABDH5, ELOVL6, FABP4, FASN, PPARγ, and SCD1. Expression of AHSG and FetA protein in AT was inversely correlated with AT proinflammatory markers CD68, CD44, SPP1, and CCL2. In vitro, bovine adipocytes challenged with lipopolysaccharide downregulated FetA protein expression. Adipocytes treated with FetA had lower CCL2 expression compared with those exposed to lipopolysaccharide. Overall, FetA is a systemic and local AT negative acute-phase protein linked to AT function in periparturient cows. Furthermore, FetA may support physiological adaptations to NEB in periparturient cows.

Periparturient lipolysis and oxylipid biosynthesis in bovine adipose tissues

The periparturient period of dairy cows is characterized by intense lipolysis in adipose tissues (AT), which induces the release of free fatty acids (FFA) into circulation. Among FFA, polyunsaturated fatty acids are susceptible to oxidation and can modulate inflammatory responses during lipolysis within AT. Linoleic and arachidonic acid oxidized products (oxylipids) such as hydroxy-octadecadienoic acids (HODE) and hydroxy-eicosatetraenoic acids (HETE), were recently identified as products of lipolysis that could modulate AT inflammation during lipolysis. However, the effect of lipolysis intensity during the transition from gestation to lactation on fatty acid substrate availability and subsequent AT oxylipid biosynthesis is currently unknown. We hypothesized that in periparturient dairy cows, alterations in AT and plasma fatty acids and oxylipid profiles coincide with changes in lipolysis intensity and stage of lactation. Blood and subcutaneous AT samples were collected from periparturient cows at -27±7 (G1) and -10±5 (G2) d prepartum and at 8±3 d postpartum (PP). Targeted lipidomic analysis was performed on plasma and AT using HPLC-MS/MS. We report that FFA concentrations increased as parturition approached and were highest at PP. Cows exhibiting high lipolysis rate at PP (FFA>1.0 mEq/L) had higher body condition scores at G1 compared to cows with low lipolysis rate (FFA<1.0 mEq/L). Concentrations of plasma linoleic and arachidonic acids were increased at PP. In AT, 13-HODE, and 5-, 11- and 15-HETE were increased at PP compared to G1 and G2. Concentrations of beta hydroxybutyrate were positively correlated with those of 13-HODE and 15-HETE in AT. Plasma concentrations of 5- and 20-HETE were increased at PP. These data demonstrate that prepartum adiposity predisposes cows to intense lipolysis post-partum and may exacerbate AT inflammation because of increased production of pro-inflammatory oxylipids including 5- and 15-HETE and 13-HODE. These results support a role for certain linoleic and arachidonic acid-derived oxylipids as positive and negative modulators of AT inflammation during periparturient lipolysis.

Deletion of UCP1 enhances ex vivo aortic vasomotor function in female but not male mice despite similar susceptibility to metabolic dysfunction

Females are typically more insulin sensitive than males, which may be partly attributed to greater brown adipose tissue (BAT) activity and uncoupling protein 1 (UCP1) content. Accordingly, we tested the hypothesis that UCP1 deletion would abolish sex differences in insulin sensitivity and that whitening of thoracic periaortic BAT caused by UCP1 loss would be accompanied with impaired thoracic aortic function. Furthermore, because UCP1 exerts antioxidant effects, we examined whether UCP1 deficiency-induced metabolic dysfunction was mediated by oxidative stress. Compared with males, female mice had lower HOMA- and AT-insulin resistance (IR) despite no significant differences in BAT UCP1 content. UCP1 ablation increased HOMA-IR, AT-IR, and whitening of BAT in both sexes. Expression of UCP1 in thoracic aorta was greater in wild-type females compared with males. Importantly, deletion of UCP1 enhanced aortic vasomotor function in females only. UCP1 ablation did not promote oxidative stress in interscapular BAT. Furthermore, daily administration of the free radical scavenger tempol for 8 wk did not abrogate UCP1 deficiency-induced increases in adiposity, hyperinsulinemia, or liver steatosis. Collectively, we report that 1) in normal chow-fed mice housed at 25°C, aortic UCP1 content was greater in females than males and its deletion improved ex vivo aortic vasomotor function in females only; 2) constitutive UCP1 content in BAT was similar between females and males and loss of UCP1 did not abolish sex differences in insulin sensitivity; and 3) the metabolic disruptions caused by UCP1 ablation did not appear to be contingent upon increased oxidative stress in mice under normal dietary conditions.

Expansion and Adipogenesis Induction of Adipocyte Progenitors from Perivascular Adipose Tissue Isolated by Magnetic Activated Cell Sorting

Expansion of Perivascular Adipose Tissue (PVAT), a major regulator of vascular function through paracrine signaling, is directly related to the development of hypertension during obesity. The extent of hypertrophy and hyperplasia depends on depot location, sex, and the type of Adipocyte Progenitor Cell (APC) phenotypes present. Techniques used for APC and preadipocytes isolation in the last 10 years have drastically improved the accuracy at which individual cells can be identified based on specific cell surface markers. However, isolation of APC and adipocytes can be a challenge due to the fragility of the cell, especially if the intact cell must be retained for cell culture applications. Magnetic-activated Cell Sorting (MCS) provides a method of isolating greater number of viable APC per weight unit of adipose tissue. APC harvested by MCS can be used for in vitro protocols to expand preadipocytes and differentiate them into adipocytes through use of growth factor cocktails allowing for analysis of the prolific and adipogenic potential retained by the cells. This experiment focused on the aortic and mesenteric PVAT depots, which play key roles in the development of cardiovascular disease during expansion. These protocols describe methods to isolate, expand, and differentiate a defined population of APC. This MCS protocol allows isolation to be used in any experiment where cell sorting is needed with minimal equipment or training. These techniques can aid further experiments to determine the functionality of specific cell populations based on the presence of cell surface markers.

Time-Dependent Differences in the Influence of Perivascular Adipose Tissue on Vasomotor Functions in Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) facilitates the development of cardiovascular disease due to atherosclerosis, which is accelerated by defects of the vascular endothelium. Vascular dysfunction in response to nitric oxide (NO) occurs in the mesenteric arteries of an animal model of MetS, SHRSP.Z-Lepr^fa/IzmDmcr (SHRSP.ZF) rats. Vascular responses to vasodilators are affected by perivascular adipose tissue (PVAT) that surrounds the outsides of arteries. In this study, we assessed the role of PVAT in vascular dysfunction observed in SHRSP.ZF.

METHODS

To determine the effects of PVAT on vasodilators in SHRSP.ZF and control Wistar-Kyoto (WKY) rats, we used organ bath bioassay techniques to assay acetylcholine and nitroprusside-induced relaxations of isolated mesenteric arterial ring preparations with PVAT intact or removed.

RESULTS

A PVAT-mediated enhancement of relaxations induced by acetylcholine and nitroprusside occurred in SHRSP.ZF at 20 weeks of age, but not at 10 and 30 weeks, and did not occur in WKY. Furthermore, the enhancing effects of PVAT from SHRSP.ZF at 20 weeks could not be substituted by replacement with PVAT from either WKY or 30-week-old SHRSP.ZF, was inhibited by NO synthase inhibitor, and abolished by removal of the arteries' endothelium. Cyclic guanosine monophosphate (cGMP) accumulation elicited by nitroprusside was higher in SHRSP.ZF arteries with PVAT than arteries without PVAT at 20 weeks, but the enhancement of cGMP accumulation did not occur at 30 weeks.

CONCLUSIONS

PVAT may regulate arterial tone by releasing diffusible vasorelaxing factor(s), which, through endothelium-derived NO production, compensates for impaired vasodilations at early stages of MetS.

Cellular Mechanisms Driving Sex Differences in Adipose Tissue Biology and Body Shape in Humans and Mouse Models

Sex differences in adipose tissue distribution and the metabolic, endocrine, and immune functions of different anatomical fat depots have been described, but they are incompletely documented in the literature. It is becoming increasingly clear that adipose depots serve distinct functions in males and females and have specific physiological roles. However, the mechanisms that regulate the size and function of specific adipose tissues in men and women remain poorly understood. New insights from mouse models have advanced our understanding of depot differences in adipose growth and remodeling via the proliferation and differentiation of adipose progenitors that can expand adipocyte number in the tissue or simply replace dysfunctional older and larger adipocytes. A limited ability of a depot to expand or remodel can lead to excessive adipocyte hypertrophy, which is often correlated with metabolic dysfunction. However, the relationship of adipocyte size and function varies by depot and sex. For example, femoral adipose tissues of premenopausal women appear to have a greater capacity for adipose expansion via hyperplasia and hypertrophy; although larger, these gluteal-femoral adipocytes remain insulin sensitive. The microenvironment of specific depots, including the composition of the extracellular matrix and cellular composition, as well as cell-autonomous genetic differences, influences sex- and depot-dependent metabolic and growth properties. Although there are some species differences, studies of the molecular and physiological determinants of sex differences in adipocyte growth and function in humans and rodents are both needed for understanding sex differences in health and disease.

The distribution and adipogenic potential of perivascular adipose tissue adipocyte progenitors is dependent on sexual dimorphism and vessel location

There are sex associated differences in the risk for cardiovascular comorbidities in obesity and metabolic syndrome. A common clinical finding in these diseases is the expansion of perivascular adipose tissues (PVAT) which is associated with alterations in their role as regulators of vessel function. PVAT hyperplasia and hypertrophy are dependent on the biology of populations of adipocyte progenitor cells (APC). It is currently unclear if PVAT enlargement diverges between males and females and the mechanisms linking APC biology with sexual dimorphism remain poorly understood. This study tested the hypothesis that vessel location and sexual dimorphism affect the distribution and adipogenic capacity of APC in cardiovascular disease risk relevant PVAT sites. PVAT from thoracic aorta (aPVAT) and mesenteric resistance arteries (mPVAT) was collected from 10-week-old female and male Sprague-Dawley rats. Differences in APC distribution in stromal vascular fraction cells from PVAT were determined. APC were defined as cells expressing CD34, CD44, and platelet derived growth factor α In both sexes aPVAT had fewer APC compared to mPVAT and perigonadal adipose tissue (GON). Sex-related differences were observed in the expression of CD34, where females had fewer CD34+ cells in PVATs. APC proliferation and adipogenic capacity in vitro were not affected by sex. However, APC from aPVAT had a lower proliferation capacity compared to mPVAT These data demonstrate that the distribution of APC within PVAT exhibits sexual dimorphism and is affected by anatomical location.