Beneficial effects of swimming and pomegranate juice in rats with hypertension: A possible role of serum adropin

Hypertension, characterized by persistent and uncontrolled high blood pressure, is one of the most common significant causes of mortality worldwide. Lifestyle modifications such as exercise and antioxidant intake have showed beneficial effects on hypertensive conditions. Adropin and endothelin-1 (ET-1) have important vasoregulatory functions in the endothelium. However, the underlying mechanisms linking exercise- and/or antioxidant intake-mediated improvement of hypertension are not fully understood. In this study, it was hypothesized that swimming exercise and pomegranate juice (PJ) (as an antioxidant) administration might have protective effects on hypertension development and possible involvements of serum adropin and ET-1. To test the hypothesis, the rats with hypertension, induced by Nω-nitro-L-arginine methyl ester hydrochloride, were subjected to swimming exercise and received PJ for 8 weeks. Weekly systolic and diastolic pressures, serum concentrations of adropin and ET-1, and oxidant/antioxidant parameters in various tissues were measured. The obtained data show that swimming exercise leads to complete protection against hypertension within the 8-week duration, whereas the PJ administration causes an ameliorative effect. In addition, the combination of swimming exercise and PJ administration do not have additive effects in protection against hypertension. Notably, the 8-week swimming exercise restores the diminished serum adropin concentration in rats with hypertension to the control level. Serum adropin significantly correlated with systolic and diastolic pressures, depending on swimming exercise, but not PJ administration. Serum ET-1 concentration inconsistently fluctuates in response to Nω-nitro-L-arginine methyl ester hydrochloride, swimming exercise, and PJ intake. In addition, swimming exercise and/or PJ administration lead to a complete normalization in liver malondialdehyde concentrations of rats with hypertension, whereas these interventions cause slight or no improvements in superoxide dismutase, catalase, and glutathione in the heart, liver, and kidney. In conclusion, 8-week swimming exercise modulates hypertension, possibly by influencing adropin concentration and oxidative stress.

LRP1 in GABAergic neurons is a key link between obesity and memory function

OBJECTIVE

Low-density lipoprotein receptor-related protein-1 (LRP1) regulates energy homeostasis, blood-brain barrier integrity, and metabolic signaling in the brain. Deficiency of LRP1 in inhibitory gamma-aminobutyric acid (GABA)ergic neurons causes severe obesity in mice. However, the impact of LRP1 in inhibitory neurons on memory function and cognition in the context of obesity is poorly understood.

METHODS

Mice lacking LRP1 in GABAergic neurons (Vgat-Cre; LRP1loxP/loxP) underwent behavioral tests for locomotor activity and motor coordination, short/long-term and spatial memory, and fear learning/memory. This study evaluated the relationships between behavior and metabolic risk factors and followed the mice at 16 and 32 weeks of age.

RESULTS

Deletion of LRP1 in GABAergic neurons caused a significant impairment in memory function in 32-week-old mice. In the spatial Y-maze test, Vgat-Cre; LRP1loxP/loxP mice exhibited decreased travel distance and duration in the novel arm compared with controls (LRP1loxP/loxP mice). In addition, GABAergic neuron-specific LRP1-deficient mice showed a diminished capacity for performing learning and memory tasks during the water T-maze test. Moreover, reduced freezing time was observed in these mice during the contextual and cued fear conditioning tests. These effects were accompanied by increased neuronal necrosis and satellitosis in the hippocampus. Importantly, the distance and duration in the novel arm, as well as the performance of the reversal water T-maze test, negatively correlated with metabolic risk parameters, including body weight, serum leptin, insulin, and apolipoprotein J. However, in 16-week-old Vgat-Cre; LRP1loxP/loxP mice, there were no differences in the behavioral tests or correlations between metabolic parameters and cognition.

CONCLUSIONS

Our findings demonstrate that LRP1 from GABAergic neurons is important in regulating normal learning and memory. Metabolically, obesity caused by GABAergic LRP1 deletion negatively regulates memory and cognitive function in an age-dependent manner. Thus, LRP1 in GABAergic neurons may play a crucial role in maintaining normal excitatory/inhibitory balance, impacting memory function, and reinforcing the potential importance of LRP1 in neural system integrity.

LRP1 mediates leptin transport by coupling with the short-form leptin receptor in the choroid plexus

Adipocyte-derived leptin enters the brain to exert its anorexigenic action, yet its transport mechanism is poorly understood. Here we report that LRP1 (low-density lipoprotein receptor-related protein-1) mediates the transport of leptin across the blood-CSF barrier in Foxj1 expressing cells highly enriched at the choroid plexus (ChP), coupled with the short-form leptin receptor, and LRP1 deletion from ependymocytes and ChP cells leads to leptin resistance and hyperphagia, causing obesity. Thus, LRP1 in epithelial cells is a principal regulator of leptin transport in the brain.