Endothelial leptin receptor is dispensable for leptin-induced sympatho-activation and hypertension in male mice

Emerging Role of Leptin in Vascular and Placental Dysfunction in Preeclampsia

Leptin is a well-known metabolic hormone that plays diverse roles in various body functions, including growth, reproduction, and blood pressure regulation. In pregnancy, leptin produced from the placenta is crucial for ensuring proper fetal development and angiogenesis; however, pathological increases in leptin in maternal circulation are strongly associated with vascular endothelial dysfunction and preeclampsia. Leptin has a strong role in fertility and healthy pregnancy; however, numerous clinical reports over the last 2 decades show that leptin levels pathologically increase in patients with preeclampsia independent of metabolic status (ie, obesity). Despite this strong correlation, the role of leptin in preeclampsia is largely unexplored compared with other biomarkers likely due to differences in placental leptin production among mammals. Emerging literature has recently begun to shed light on this hormone in preeclampsia pathogenesis and uncovered some key mechanisms whereby pathologically elevated leptin production leads to cardiovascular complications for pregnant women.

The Impact of Gastric Leptin and Leptin Receptor Expression on Metabolic Outcomes Post Laparoscopic Sleeve Gastrectomy

PURPOSE

Obesity is a growing global crisis, with predictions that nearly half of the world's population will be overweight or with severe obesity by 2030. Metabolic bariatric surgery, effective for those unable to lose weight through conventional methods, results in significant weight loss and alleviates associated medical problems. This study investigates changes in gastric leptin (LE) and leptin receptor (LER) expression following laparoscopic sleeve gastrectomy (LSG) and explores their metabolic contributions to surgical outcomes.

MATERIALS AND METHODS

Immunohistochemical staining for LE and LER was performed on gastric tissue biopsies from 54 patients pre- and post-LSG. Expression levels were scored for each epithelium and connective tissue component. Changes in these scores post-LSG were analyzed and correlated with body mass index (BMI), total weight loss (TWL), blood hemoglobin A1c, blood cholesterol, and triglyceride levels. Statistical analysis included paired t-tests, Pearson correlation coefficients, and one-way ANOVA.

RESULTS

Significant decreases in LE and LER receptor expression were observed post-LSG, correlating with reductions in BMI, blood hemoglobin A1c, total cholesterol, and triglyceride levels. The mean BMI decreased from 46.82 kg/m2 pre-surgery to 32.45 kg/m2 at 1 year post-surgery (p < 0.001). Hemoglobin A1c levels reduced from 7.8% to 5.9% (p < 0.001). Total cholesterol and triglyceride levels showed significant reductions, with cholesterol decreasing from 220 mg/dL to 180 mg/dL (p < 0.001) and triglycerides from 180 mg/dL to 120 mg/dL (p < 0.001). Pearson correlation coefficients demonstrated strong negative correlations between LE expression and BMI (r = -0.65, p < 0.001) and between LER expression and hemoglobin A1c (r = -0.60, p < 0.001).

CONCLUSIONS

Beyond weight reduction, the decreased expression of gastric LE and LER post-LSG contributes metabolically to weight loss and improved associated metabolic parameters following the metabolic bariatric surgery.

Both endothelial mineralocorticoid receptor expression and hyperleptinemia are required for clinical characteristics of placental ischemia in mice

One of the initiating events in preeclampsia (PE) is placental ischemia. Rodent models of placental ischemia do not present with vascular endothelial dysfunction, a hallmark of PE. We previously demonstrated a role for leptin in endothelial dysfunction in pregnancy in the absence of placental ischemia. We hypothesized that placental ischemia requires hyperleptinemia and endothelial mineralocorticoid receptor (ECMR) expression to induce PE-associated endothelial dysfunction in pregnant mice. We induced placental ischemia via the reduced uterine perfusion pressure (RUPP) procedure in pregnant ECMR-intact (ECMR+/+) and ECMR deletion (ECMR-/-) mice at gestational day (GD) 13. ECMR+/+ RUPP pregnant mice also received concurrent leptin infusion via miniosmotic pump (0.9 mg/kg/day). RUPP increased blood pressure via radiotelemetry and decreased fetal growth in ECMR+/+ pregnant mice. Both increases in blood pressure and reduced fetal growth were abolished in RUPP ECMR-/- mice. Placental ischemia did not decrease endothelial-dependent relaxation to acetylcholine (ACh) but increased phenylephrine (Phe) contraction in mesenteric arteries of pregnant mice, which was ablated by ECMR deletion. Addition of leptin to RUPP mice significantly reduced ACh relaxation in ECMR+/+ pregnant mice, accompanied by an increase in soluble FMS-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PLGF) ratio. In conclusion, our data indicate that high leptin levels drive endothelial dysfunction in PE and that ECMR is required for clinical characteristics of hypertension and fetal growth restriction in placental ischemia PE. Collectively, we show that both ECMR and leptin play a role to mediate PE.NEW & NOTEWORTHY Leptin is a key feature of preeclampsia that initiates vascular endothelial dysfunction in preeclampsia characterized by placental ischemia. Endothelial mineralocorticoid receptor (ECMR) deletion in placental ischemia protects pregnant mice from elevations in blood pressure and fetal growth restriction in pregnancy. Increases in leptin production mediate the key pathological feature of endothelial dysfunction in preeclampsia in rodents. ECMR activation contributes to the increase in blood pressure and fetal growth restriction in preeclampsia.

12-week Dolutegravir treatment marginally reduces energy expenditure but does not increase body weight or alter vascular function in a murine model of Human Immunodeficiency Virus infection

Combination antiretroviral therapy (cART) has markedly increased life expectancy in people with HIV (PWH) but has also resulted in an increased prevalence of cardiometabolic disorders, whose etiopathology remains ill-defined. Notably, the respective contribution of cART and HIV-derived proteins to obesity and vascular alterations remain poorly understood. Therefore, we investigated the individual and combined effects of HIV-proteins and of the integrase strand transfer inhibitor Dolutegravir (DTG) on body composition and vascular reactivity. Male wildtype (WT) and HIV transgenic (Tg26) mice, received DTG or vehicle for 12 weeks. Viral proteins expression in Tg26 mice lowered fat mass, increased heat production, and induced a 2-fold increase in brown adipose tissue (BAT) uncoupling protein 1 (UCP1) expression. DTG increased the expression of markers of adipogenesis in adipocytes in culture, but also reduced heat production and BAT UCP1 and UCP3 expression in Tg26 mice. DTG increased food intake, fat percentage and protected from lean mass reduction in Tg26 mice only. However, DTG did not increase body weight in either WT or Tg26 mice. Viral protein expression reduced acetylcholine (endothelium)-mediated relaxation by 14% in mesenteric arteries preconstricted with phenylephrine. However, DTG did not impair nor improve endothelium-dependent relaxation. Together, these data indicate that DTG's effects on food intake, adipogenesis and energy expenditure are insufficient to increase body weight, even in the presence of HIV-proteins, suggesting that body weight gain in PWH involves additional factors likely including other cART components and pre-existing comorbidities. Moreover, these data rule out DTG as a source of vascular disorders in PWH.

Leptin antagonism attenuates hypertension and renal injury in an experimental model of autoimmune disease

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that is characterized by B- and T-lymphocyte dysfunction and altered cytokine production, including elevated levels of the adipocytokine leptin. Leptin has various immunomodulatory properties, including promoting the expansion of proinflammatory T lymphocytes and the proliferation and survival of B cells. In the present study, we hypothesized that leptin antagonism would improve B- and T-cell dysfunction and attenuate hypertension in an experimental model of SLE, the NZBWF1 mouse. To test this hypothesis, 28-week-old female control and SLE mice were administered 5 mg/kg of murine leptin superantagonist (LA) or vehicle via ip injection every other day for four weeks. Analysis of peripheral blood immune cell populations showed no changes in total CD45R+ B and CD3+ T cell percentages after treatment with LA. However, SLE mice treated with LA had an improved CD4/CD8 ratio and decreased CD3+CD4-CD8- double negative (DN) T cells. Blood pressure was higher in SLE than in control, and treatment with LA decreased blood pressure in SLE mice. Treatment with LA also delayed the onset of albuminuria and decreased glomerulosclerosis in SLE mice. Renal immune cell infiltration was significantly higher in SLE mice as compared with control, but LA treatment was associated with decreased levels of renal CD4+ T cells. In conclusion, these data suggest that leptin plays a pathogenic role in the development of hypertension in SLE, in part, by promoting the expansion of inflammatory DN T cells and the infiltration of T cells into the kidneys.

Mechanisms of leptin-induced endothelial dysfunction

PURPOSE OF REVIEW

Endothelial dysfunction is a major risk factor for many cardiovascular diseases, notably hypertension. Obesity increases the risk of endothelial dysfunction in association with increasing production of the adipokine leptin. Preclinical studies have begun to unravel the mechanisms whereby leptin leads to the development of endothelial dysfunction, which are sex-specific. This review will summarize recent findings of mechanisms of leptin-induced endothelial impairment in both male and females and in pregnancy.

RECENT FINDINGS

Leptin receptors are found in high concentrations in the central nervous system (CNS), via which leptin promotes appetite suppression and upregulates sympathetic nervous system activation. However, leptin receptors are expressed in many other tissues, including the vascular endothelial cells and smooth muscle cells. Recent studies in mice with vascular endothelial or smooth muscle-specific knockdown demonstrate that endothelial leptin receptor activation plays a protective role against endothelial dysfunction in male animals, but not necessarily in females. Clinical studies indicate that women may be more sensitive to obesity-associated vascular endothelial dysfunction. Emerging preclinical data indicates that leptin and progesterone increase aldosterone production and endothelial mineralocorticoid receptor activation, respectively. Furthermore, decades of clinical studies indicate that leptin levels increase in the hypertensive pregnancy disorder preeclampsia, which is characterized by systemic endothelial dysfunction. Leptin infusion in mice induces the clinical characteristics of preeclampsia, including endothelial dysfunction.

SUMMARY

Novel preclinical data indicate that the mechanisms whereby leptin promotes endothelial dysfunction are sex-specific. Leptin-induced endothelial dysfunction may also play a role in hypertensive pregnancy as well.