Maternal separation enhances anticontractile perivascular adipose tissue function in male rats on a high-fat diet

Perivascular Adipose Tissue and Vascular Smooth Muscle Tone: Friends or Foes?

Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H₂S, H₂O₂, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies.

Programming of Vascular Dysfunction by Maternal Stress: Immune System Implications

A growing body of evidence highlights that several insults during pregnancy impact the vascular function and immune response of the male and female offspring. Overactivation of the immune system negatively influences cardiovascular function and contributes to cardiovascular disease. In this review, we propose that modulation of the immune system is a potential link between prenatal stress and offspring vascular dysfunction. Glucocorticoids are key mediators of stress and modulate the inflammatory response. The potential mechanisms whereby prenatal stress negatively impacts vascular function in the offspring, including poor hypothalamic–pituitary–adrenal axis regulation of inflammatory response, activation of Th17 cells, renin–angiotensin–aldosterone system hyperactivation, reactive oxygen species imbalance, generation of neoantigens and TLR4 activation, are discussed. Alterations in the immune system by maternal stress during pregnancy have broad relevance for vascular dysfunction and immune-mediated diseases, such as cardiovascular disease.

Maternal Obesity Programming of Perivascular Adipose Tissue and Associated Immune Cells: An Understudied Area With Few Answers and Many Questions

At present, the worldwide prevalence of obesity has become alarmingly high with estimates foreshadowing a continued escalation in the future. Furthermore, there is growing evidence attributing an individual’s predisposition for developing obesity to maternal health during gestation. Currently, 60% of pregnancies in the US are to either overweight or obese mothers which in turn contributes to the persistent rise in obesity rates. While obesity itself is problematic, it conveys an increased risk for several diseases such as diabetes, inflammatory disorders, cancer and cardiovascular disease (CVD). Additionally, as we are learning more about the mechanisms underlying CVD, much attention has been brought to the role of perivascular adipose tissue (PVAT) in maintaining cardiovascular health. PVAT regulates vascular tone and for a significant number of individuals, obesity elicits PVAT disruption and dysregulation of vascular function. Obesity elicits changes in adipocyte and leukocyte populations within PVAT leading to an inflammatory state which promotes vasoconstriction thereby aiding the onset/progression of CVD. Our current understanding of obesity, PVAT and CVD has only been examined at the individual level without consideration for a maternal programming effect. It is unknown if maternal obesity affects the propensity for PVAT remodeling in the offspring, thereby enhancing the obesity/CVD link, and what role PVAT leukocytes play in this process. This perspective will focus on the maternal contribution of the interplay between obesity, PVAT disruption and CVD and will highlight the leukocyte/PVAT interaction as a novel target to stem the tide of the current obesity epidemic and its secondary health consequences.

Epididymal Fat-Derived Sympathoexcitatory Signals Exacerbate Neurogenic Hypertension in Obese Male Mice Exposed to Early Life Stress

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Long-term cerebrovascular dysfunction in the offspring from maternal electronic cigarette use during pregnancy

Electronic cigarettes (E-cigs) have been promoted as harm-free or less risky than smoking, even for women during pregnancy. These claims are made largely on E-cig aerosol having fewer number of toxic chemicals compared with cigarette smoke. Given that even low levels of smoking are found to produce adverse birth outcomes, we sought to test the hypothesis that vaping during pregnancy (with or without nicotine) would not be harm-free and would result in vascular dysfunction that would be evident in offspring during adolescent and/or adult life. Pregnant female Sprague Dawley rats were exposed to E-cig aerosol (1 h/day, 5 days/wk, starting on gestational day 2 until pups were weaned) using e-liquid with 0 mg/mL (E-cig0) or 18 mg/mL nicotine (E-cig18) and compared with ambient air-exposed controls. Body mass at birth and at weaning were not different between groups. Assessment of middle cerebral artery (MCA) reactivity revealed a 51%-56% reduction in endothelial-dependent dilation response to acetylcholine (ACh) for both E-cig0 and E-cig18 in 1-mo, 3-mo (adolescent), and 7-mo-old (adult) offspring (P < 0.05 compared with air, all time points). MCA responses to sodium nitroprusside (SNP) and myogenic tone were not different across groups, suggesting that endothelial-independent responses were not altered. The MCA vasoconstrictor response (5-hydroxytryptamine, 5-HT) was also not different across treatment and age groups. These data demonstrate that maternal vaping during pregnancy is not harm-free and confers significant cerebrovascular health risk/dysfunction to offspring that persists into adult life. NEW & NOTEWORTHY These data established that vaping electronic cigarettes during pregnancy, with or without nicotine, is not safe and confers significant risk potential to the cerebrovascular health of offspring in early and adult life. A key finding is that vaping without nicotine does not protect offspring from cerebrovascular dysfunction and results in the same level of cerebrovascular dysfunction (compared with maternal vaping with nicotine), indicating that the physical and/or chemical properties from the base solution (other than nicotine) are responsible for the cerebrovascular dysfunction that we observed. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/maternal-vaping-impairs-vascular-function-in-theoffspring/.

Role of Perivascular Adipose Tissue-Derived Adiponectin in Vascular Homeostasis

Studies of adipose tissue biology have demonstrated that adipose tissue should be considered as both passive, energy-storing tissue and an endocrine organ because of the secretion of adipose-specific factors, called adipokines. Adiponectin is a well-described homeostatic adipokine with metabolic properties. It regulates whole-body energy status through the induction of fatty acid oxidation and glucose uptake. Adiponectin also has anti-inflammatory and antidiabetic properties, making it an interesting subject of biomedical studies. Perivascular adipose tissue (PVAT) is a fat depot that is conterminous to the vascular wall and acts on it in a paracrine manner through adipokine secretion. PVAT-derived adiponectin can act on the vascular wall through endothelial cells and vascular smooth muscle cells. The present review describes adiponectin's structure, receptors, and main signaling pathways. We further discuss recent studies of the extent and nature of crosstalk between PVAT-derived adiponectin and endothelial cells, vascular smooth muscle cells, and atherosclerotic plaques. Furthermore, we argue whether adiponectin and its receptors may be considered putative therapeutic targets.

Liver circadian clock disruption alters perivascular adipose tissue gene expression and aortic function in mice

The liver plays a central role that influences cardiovascular disease outcomes through regulation of glucose and lipid metabolism. It is recognized that the local liver molecular clock regulates some liver-derived metabolites. However, it is unknown whether the liver clock may impact cardiovascular function. Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue surrounding blood vessels. Importantly, cross talk between the endothelium and PVAT via vasoactive factors is critical for vascular function. Therefore, we designed studies to test the hypothesis that cardiovascular function, including PVAT function, is impaired in mice with liver-specific circadian clock disruption. Bmal1 is a core circadian clock gene, thus studies were undertaken in male hepatocyte-specific Bmal1 knockout (HBK) mice and littermate controls (i.e., flox mice). HBK mice showed significantly elevated plasma levels of β-hydroxybutyrate, nonesterified fatty acids/free fatty acids, triglycerides, and insulin-like growth factor 1 compared with flox mice. Thoracic aorta PVAT in HBK mice had increased mRNA expression of several key regulatory and metabolic genes, Ppargc1a, Pparg, Adipoq, Lpl, and Ucp1, suggesting altered PVAT energy metabolism and thermogenesis. Sensitivity to acetylcholine-induced vasorelaxation was significantly decreased in the aortae of HBK mice with PVAT attached compared with aortae of HBK mice with PVAT removed, however, aortic vasorelaxation in flox mice showed no differences with or without attached PVAT. HBK mice had a significantly lower systolic blood pressure during the inactive period of the day. These new findings establish a novel role of the liver circadian clock in regulating PVAT metabolic gene expression and PVAT-mediated aortic vascular function.

Maternal high-fat diet regulates glucose metabolism and pancreatic β cell phenotype in mouse offspring at weaning

Background

Maternal malnutrition is a critical factor in determining the risk of obesity and glucose intolerance in offspring. However, little is known about the effects of a maternal high-fat diet (HFD) on the β cell phenotype in offspring, which is a major factor in glucose homeostasis, especially during the early life of offspring.

Methods

Dams were randomly fed a HFD (60% kcal from fat) or a chow diet before pregnancy and during gestation and lactation. Glucose metabolism and the β cell phenotype were assessed in male offspring at weaning.

Results

Dams fed a HFD showed impaired glucose tolerance. A HFD predisposed the offspring to increased impairment of metabolic health, including obesity, glucose intolerance and insulin resistance, compared with offspring from chow diet-fed dams. Furthermore, increased islet sizes and islet densities were observed in male offspring from HFD-fed dams at weaning. There were increases in the insulin-positive area, β cell mass and β cell proliferation in male offspring from HFD-fed dams at weaning age. Next, we further determined whether a maternal HFD could affect β cell apoptosis in mouse offspring and found that there was no significant change in β cell apoptosis between the HFD and control groups.

Conclusion

Our study is novel in showing that a maternal HFD predisposes offspring to impaired glucose metabolism and has a profound effect on β cell mass and proliferation in offspring mice, which is observed in mice as early as at weaning age. However, further study to clarify the underlying mechanisms is warranted.

Maternal separation-induced increases in vascular stiffness are independent of circulating angiotensinogen levels

The renin-angiotensin system (RAS) precursor angiotensinogen (AGT) has been implicated in the functional and mechanical alterations of the vascular wall in response to high-fat diet (HFD). Previously, we showed that HFD exacerbates angiotensin II-induced constriction in isolated aortic rings from male rats exposed to maternal separation (MatSep), a model of early-life stress. Thus, the aim of this study was to investigate whether MatSep increases AGT secretion promoting vascular stiffness in rats fed a HFD. Male Wistar-Kyoto MatSep offspring were separated (3 h/day, postnatal days 2-14), and undisturbed littermates were used as controls. At weaning, rats were fed for 17 wk a normal diet (ND) or a HFD, 18% or 60% kcal from fat, respectively. In plasma, there was a main effect of MatSep reducing AGT concentration (P < 0.05) but no effect due to diet. In urine, ND-fed MatSep rats displayed higher AGT concentrations that were further increased by HFD (P < 0.05 vs. control). AGT mRNA abundance and protein expression were increased in adipose tissue from HFD-fed MatSep rats compared with control rats (P < 0.05). No significant differences in liver and kidney AGT levels were found between groups. In addition, MatSep augmented vascular stiffness assessed on freshly isolated aortic rings from ND-fed rats (P < 0.05), yet HFD did not worsen vascular stiffness in either MatSep or control rats. There was no correlation between plasma AGT and vascular stiffness in ND-fed rats; however, this relationship was negative in HFD-fed MatSep rats only (P < 0.05). Therefore, this study shows that MatSep-induced increases in vascular stiffness are independent of diet or plasma AGT.NEW & NOTEWORTHY This study demonstrates that there was no correlation between circulating levels of angiotensinogen (AGT) and the development of vascular stiffness in rats exposed to early-life stress and fed a normal diet. This study also shows that early-life stress-induced hypersensitive vascular contractility to angiotensin II in rats fed a high-fat diet is independent of circulating levels of AGT and occurs without further progression of vascular stiffness. Our data show that early-life stress primes the adipose tissue to secrete AGT in a sex- and species-independent fashion.

Female Mice Exposed to Postnatal Neglect Display Angiotensin II-Dependent Obesity-Induced Hypertension

Background We have previously reported that female mice exposed to maternal separation and early weaning (MSEW), a model of early life stress, show exacerbated diet-induced obesity associated with hypertension. The goal of this study was to test whether MSEW promotes angiotensin II-dependent hypertension via activation of the renin-angiotensin system in adipose tissue. Methods and Results MSEW was achieved by daily separations from the dam and weaning at postnatal day 17, while normally reared controls were weaned at postnatal day 21. Female controls and MSEW weanlings were placed on a low-fat diet (LF, 10% kcal from fat) or high-fat diet (HF, 60% kcal from fat) for 20 weeks. MSEW did not change mean arterial pressure in LF-fed mice but increased it in HF-fed mice compared with controls (P<0.05). In MSEW mice fed a HF, angiotensin II concentration in plasma and adipose tissue was elevated compared with controls (P<0.05). In addition, angiotensinogen concentration was increased solely in adipose tissue from MSEW mice (P<0.05), while angiotensin-converting enzyme protein expression and activity were similar between groups. Chronic enalapril treatment (2.5 mg/kg per day, drinking water, 7 days) reduced mean arterial pressure in both groups of mice fed a HF (P<0.05) and abolished the differences due to MSEW. Acute angiotensin II-induced increases in mean arterial pressure (10 μg/kg SC) were attenuated in untreated MSEW HF-fed mice compared to controls (P<0.05); however, this response was similar between groups in enalapril-treated mice. Conclusions The upregulation of angiotensinogen and angiotensin II in adipose tissue could be an important mechanism by which female MSEW mice fed a HF develop hypertension.