Beneficial effects of tamoxifen on leptin sensitivity in young mice fed a high fat diet: Role of estrogen receptor α and cytokines

GPR30 selective agonist G-1 induced insulin resistance in ovariectomized mice on high fat diet and its mechanism

BACKGROUND

Previous in vivo and in vitro studies have demonstrated that estrogen receptor agonist G-1 regulates glucose and lipid metabolism. This study focused on the effects of G-1 on cardiometabolic syndrome and anti-obesity under a high fat diet (HFD).

METHODS

Bilateral ovariectomized female mice were fed an HFD for 6 weeks, and treated them with G-1. A cardiomyocyte insulin resistance model was used to simulate the in vivo environment. The main outcome measures were blood glucose, body weight, and serum insulin levels to assess insulin resistance, while cardiac function and degree of fibrosis were assessed by cardiac ultrasound and pathological observations. We also examined the expression of p-AMPK, p-AKT, and GLUT4 in mice hearts and in vitro models to explore the mechanism by which G-1 regulates insulin signaling.

RESULTS

G-1 reduced body weight in mice on an HFD, but simultaneously increased blood glucose and promoted insulin resistance, resulting in myocardial damage. This damage included disordered cardiomyocytes, massive accumulation of glycogen, extensive fibrosis of the heart, and thickening of the front and rear walls of the left ventricle. At the molecular level, G-1 enhances gluconeogenesis and promotes glucose production by increasing the activity of pyruvate carboxylase (PC) while inhibiting GLUT4 translocation via the AMPK/TBC1D1 pathway, thereby limiting glucose uptake.

CONCLUSION

Despite G-1's the potential efficacy in weight reduction, the concomitant induction of insulin resistance and cardiac impairment in conjunction with an HFD raises significant concerns. Therefore, comprehensive studies of its safety profile and effects under specific conditions are essential prior to clinical use.

The effects of G protein-coupled receptor 30 (GPR30) on cardiac glucose metabolism in diabetic ovariectomized female rats

BACKGROUND

Diabetic cardiometabolic disorders are characterized by significant changes in cardiac metabolism and are increased in postmenopausal women, which emphasize the role of 17β-estradiol (E2). Despite this, there are few safe and effective pharmacological treatments for these disorders. The role of G protein-coupled estrogen receptor (GPR30), which mediates the non-genomic effects of E2, is mostly unexplored.

METHODS

In this study, we used ovariectomy (menopausal model) and type 2 diabetic (T2D) rats' models to evaluate the preclinical action of G-1 (GPR30 agonist) against cardiometabolic disorders. T2D was induced by a high-fat diet and a low dose of streptozotocin. G-1 was administrated for six weeks after the establishment of T2D.

RESULTS

We found that G-1 counteracts the effects of T2D and ovariectomy by increasing the body weight, reducing fasting blood sugar, heart weight, and heart weight to body weight ratio. Also, both ovariectomy and T2D led to decreases in the cardiac protein levels of hexokinase 2 (HK2) and GLUT4, while G-1-treated female rats reversed these changes and only increased HK2 protein level. In addition, T2D and ovariectomy increased glucose and glycogen content in the heart, but G-1 treatment significantly reduced them.

CONCLUSIONS

In conclusion, our work demonstrates that G-1 as a selective GPR30 agonist is a viable therapeutic approach against T2D and cardiometabolic diseases in multiple preclinical female models.

Selective estrogen receptor α and β antagonist aggravate cardiovascular dysfunction in type 2 diabetic ovariectomized female rats

OBJECTIVES

Type 2 diabetes (T2D) is a major risk factor for cardiovascular disorders (CVD), characterized by pathological diastolic as well as systolic dysfunction, ventricular dilation, and cardiomyocyte hypertrophy. CVD is the main cause of death in postmenopausal women. Estradiol (E2) has protective effects on cardiovascular function. The biological effects of E2 are mainly mediated by classical estrogen receptors (ERs). The present study aimed to investigate the cardioprotective effects of classical ERs in ovariectomized (OVX) diabetic female rats.

METHODS

T2D was induced in female rats by high-fat diet feeding along with a low dose of streptozotocin. Then diabetic animals were divided into eight groups: Sham-control, OVX, OVX + Vehicle (Veh), OVX + E2, OVX + E2 + MPP (ERα antagonist), OVX + E2 + PHTPP (ERβ antagonist), OVX + E2 + Veh, OVX + E2 + MPP + PHTPP. Animals received E2, MPP, and PHTPP every four days for 28 days. At the end blood was collected, serum separated, and used for biochemical parameters. Heart tissue was used for cardiac angiotensin II and cytokines measurement.

RESULTS

E2 treatment improved the metabolic disorders caused by T2D, and its receptor antagonists intensified the effects of T2D on the metabolic status. Also, E2 therapy decreased cardiac inflammatory cytokines, and MPP and PHTPP increased cardiac inflammation by increasing TNF-α and IL-6 and decreasing IL-10.

CONCLUSIONS

Classical ERs have protective effects on diabetic hearts by improving the metabolic status and inflammatory balance.

The G-Protein-Coupled Estrogen Receptor Agonist Prevents Cardiac Lipid Accumulation by Stimulating Cardiac Peroxisome Proliferator-Activated Receptor α: A Preclinical Study in Ovariectomized-Diabetic Rat Model

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with cardiometabolic changes, and menopause exacerbates these conditions, leading to a greater risk of cardiovascular diseases (CVDs). The G protein-coupled estrogen receptor (GPER), which mediates the rapid effects of estrogen, has beneficial cardiac effects in both T2DM and menopause, but its mechanism of action is not well understood.

OBJECTIVES

This study aimed to determine whether G1 as a selective GPER-agonist has beneficial effects on cardiac lipid metabolism in ovariectomized rats with T2DM.

METHODS

Female Wistar rats were divided into 5 groups (n = 7 in each group): Sham-control (Sh-Ctl), T2DM, ovariectomized-T2DM (OVX-T2DM), OVX-T2DM-G1 (GPER-agonist), and OVX-T2DM-vehicle (OVX-T2DM-Veh). After stabilization of T2DM, G1 (200 μg/Kg) was administrated for 6 weeks. Then, the levels of free fatty acids (FFAs), CD36, peroxisome proliferator-activated receptor α (PPARα), and lipid accumulation in the cardiac tissue were determined.

RESULTS

Compared with the Sh-Ctl group, cardiac FFAs (P < 0.001), CD36 (P < 0.05), and lipid accumulation (P < 0.001) increased, and cardiac PPARα (P < 0.01) decreased in T2DM animals; ovariectomy intensified these changes. Also, cardiac FFAs, PPARα, and lipid accumulation (P < 0.05) significantly decreased in the OVX-T2DM-G1 group compared to the OVX-T2DM-Veh group. However, cardiac CD36 levels did not change.

CONCLUSIONS

G1 as a selective GPER-agonist affects lipid metabolism in T2DM animals. It also plays a vital role in improving cardiac metabolism during postmenopausal diabetic conditions.

Protective effects of combining SERMs with estrogen on metabolic parameters in postmenopausal diabetic cardiovascular dysfunction: The role of cytokines and angiotensin II

INTRODUCTION

The beneficial effects of the administration of selective estrogen receptor modulators (SERMs) and estrogen (E2), alone or in combination with each other, have been reported in postmenopausal diabetic cardiovascular dysfunction. In the present study, we determined the mechanism of action of SERMs and E2 on inflammatory balance, angiotensin II (Ang II) serum levels, and glycemic profile in a postmenopausal diabetic rat model.

METHODS

Ovariectomized rats with type 2 diabetes received daily SERMs (tamoxifen and raloxifene) and E2 for one month. After treatment, cardiovascular risk indices, glycemic profile, and serum Ang II, TNF-α and IL-10 levels were measured.

RESULTS

Type 2 diabetes caused an abnormal glycemic profile, which was exacerbated by ovariectomy. All treatments inhibited the effects of diabetes and ovariectomy on the glycemic profile, with combined treatments (SERMs + E2) showing stronger effects. Cardiovascular risk indices that became abnormal by diabetes and worsened by ovariectomy were improved in all treatment modalities. Also, combined treatment reduced serum Ang II, TNF-α, and the ratio of TNF-α to IL-10, indicating an improvement in inflammatory balance.

CONCLUSION

Our study showed the administration of SERMs and E2, alone or in combination, could be an effective alternative in the treatment of menopausal diabetes, and generally, the beneficial effects of combined treatments were more effective than the effects of E2 or SERMs alone. It appears that E2 or SERMs benefit the cardiovascular system by improving inflammatory balance and reducing Ang II levels.

The brain neuropeptides and STAT3 mediate the inhibitory effect of 17-β Estradiol on central leptin resistance in young but not aged female high-fat diet mice

Aging and menopause effect on body composition and energy balance. Estrogen (E2) plays an important role in body's metabolism. The aim of the present study was to determine changes in leptin function in young intact and ovariectomized (OVX) animals in comparison to the aged animals treated with E2. Young (Intact and OVX 4 months) and aged (19-21 months) female mice were fed High-fat diet (HFD) for 12 weeks and, then they were divided into eight groups including: Intact + OIL, Intact + E2, Intact + Pair body weight (PBW), OVX + OIL, OVX + E2, OVX + PBW, Aged + OIL, and Aged + E2. E2 was administered subcutaneously every four days for four weeks. Responsiveness to leptin was assessed by measuring energy balance components. Results showed that eating HFD increased weight and calorie consumption in young mice, and chronic treatment with E2 decreased both these variables in young animals. E2 only improved the sensitivity to leptin in young animals. Treatment with E2 resulted in increased α-MSH neuropeptide, reduced NPY and AgRP neuropeptides in the brain, and decreased serum leptin in the young animals. Also, treatment with E2 increased the expression of p-STAT3 molecular level in the hypothalamic arcuate nucleus (ARC) in the young animals. Our results indicated that response to E2 depended on age and E2 protects young HFD fed mice from obesity and improves leptin sensitivity.

Is LRP2 Involved in Leptin Transport over the Blood-Brain Barrier and Development of Obesity?

The mechanisms underlying the transport of leptin into the brain are still largely unclear. While the leptin receptor has been implicated in the transport process, recent evidence has suggested an additional role of LRP2 (megalin). To evaluate the function of LRP2 for leptin transport across the blood-brain barrier (BBB), we developed a novel leptin-luciferase fusion protein (pLG), which stimulated leptin signaling and was transported in an in vitro BBB model based on porcine endothelial cells. The LRP inhibitor RAP did not affect leptin transport, arguing against a role of LRP2. In line with this, the selective deletion of LRP2 in brain endothelial cells and epithelial cells of the choroid plexus did not influence bodyweight, body composition, food intake, or energy expenditure of mice. These findings suggest that LRP2 at the BBB is not involved in the transport of leptin into the brain, nor in the development of obesity as has previously been described.