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ICV vs. VMH injection of leptin: comparative effects on hypothalamic gene expression
Suresh Ambati1, Jiuhua Duan, Yang-Ho Choi
1Department of Animal and Dairy Science, University of Georgia, Athens, GA 30602, USA.
Leptin injections into the ventromedial hypothalamus (VMH) or cerebral ventricles alter gene expression in the arcuate nucleus-median eminence (ARC-ME). VMH leptin uniquely impacts feeding behavior and ARC-ME gene profiles, suggesting localized effects on body weight regulation.
Area of Science:
- Neuroendocrinology
- Molecular Biology
- Physiology
Background:
- Leptin is a key hormone regulating feeding behavior and body weight.
- Leptin exerts its effects by binding to receptors in specific hypothalamic areas.
- Understanding the molecular mechanisms of leptin action in the hypothalamus is crucial for metabolic research.
Purpose of the Study:
- To investigate the effects of localized leptin administration in the rat hypothalamus on gene expression.
- To compare the impact of leptin injection into the ventromedial hypothalamus (VMH) versus the lateral cerebral ventricle (ICV) on ARC-ME gene profiles.
- To assess changes in feeding behavior, body weight, and related parameters following VMH leptin administration.
Main Methods:
- Rats received leptin injections into the right VMH or right ICV twice daily for 4 days.
- Quantitative measurement of mRNA expression levels of selected genes in the ARC-ME complex using Real-Time Taqman RT-PCR.
- Comparison of gene expression in ipsilateral versus contralateral VMH areas following VMH leptin injection.
- Monitoring of food intake, body weight, fat pad weights, and serum insulin and leptin levels.
Main Results:
- VMH leptin injections significantly increased ARC-ME mRNAs for proopiomelanocortin (POMC), gamma-aminobutyric acid A receptor (GABRD), and thyrotropin-releasing hormone (TRH).
- VMH leptin decreased ARC-ME mRNAs for janus kinase 2 (JAK2), suppressor of cytokine signaling 3 (SOCS3), signal transducer and activator of transcription 3 (STAT3), tyrosine hydroxylase (TH), prostaglandin E synthase (PTGES), tumor necrosis factor-alpha (TNF-alpha), and secretin.
- ICV leptin injections only upregulated GABRD and secretin (SCT) in the ARC-ME.
- VMH leptin injections reduced food intake, body weight, fat pad weights, and serum insulin and leptin levels.
Conclusions:
- Unilateral VMH leptin exposure induces distinct ARC-ME gene expression profiles compared to bilateral ICV exposure.
- Localized VMH leptin administration effectively modulates key genes involved in appetite and metabolism.
- These findings highlight the differential effects of leptin delivery sites on hypothalamic gene regulation and body weight control.
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