Journal of Yeungnam Medical Science

Review

Improvement of Leptin Resistance.: Yong Woon Kim; Yeungnam Univ J Med. 2013;30(1):4-9. Published online June 30, 2013; DOI: https://doi.org/10.12701/yujm.2013.30.1.4

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Abstract PDF: Leptin, a 16-kDa cytokine, is secreted by adipose tissue in response to the surplus of fat store. Thereby, the brain is informed about the body's energy status. In the hypothalamus, leptin triggers specific neuronal subpopulations (e.g., POMC and NPY neurons) and activates several intracellular signaling events, including the JAK/STAT, MAPK, PI3K, and mTOR pathway, which eventually translates into decreased food intake and increased energy expenditure. Leptin signal is inhibited by a feedback inhibitory pathway mediated by SOCS3. PTP1B involves another inhibitory pathway of leptin. Leptin potently promotes fat mass loss and body weight reduction in lean subjects. However, it is not widely used in the clinical field because of leptin resistance, which is a common feature of obesity characterized by hyperleptinemia and the failure of exogenous leptin administration to provide therapeutic benefit in rodents and humans. The potential mechanisms of leptin resistance include the following: 1) increases in circulating leptin-binding proteins, 2) reduced transport of leptin across the blood-brain barrier, 3) decreased leptin receptor-B (LRB), and/or 4) the provocation of processes that diminish cellular leptin signaling (inflammation, endoplasmic reticulum stress, feedback inhibition, etc.). Thus, interference of the cellular mechanisms that attenuate leptin signaling improves leptin action in cells and animal models, suggesting the potential utility of these processes as points of therapeutic intervention. Various experimental trials and compounds that improve leptin resistance are introduced in this paper.

Original Article

Effect of Leptin on the Expression of Chemokine Genes in THP-1 Cells.: Jin Hee Choi, Ho Sun Park, Tae Yoon Lee, Sung Kwang Kim, Hee Sun Kim; Yeungnam Univ J Med. 2003;20(2):129-141. Published online December 31, 2003; DOI: https://doi.org/10.12701/yujm.2003.20.2.129

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Abstract PDF: BACKGROUND
Leptin is a 16-KDa non-glycosylated peptide hormone synthesized almost exclusively by adipocytes. The well-known function of leptin is regulation of food intake and energy expenditure. Leptin also plays a regulatory role in immune and inflammatory process including cytokine production. The purpose of this study was to investigate the effect of leptin on the expression of several chemokine genes(RANTES, IL-8, MCP-1, IP-10, Mig, MIP-1alpha, MIP-1beta, and GRO-alpha) in THP-1 cells. MATERIALS AND METHODS: Total RNA of THP-1 cells were prepared by Trizol method, and then stimulated with the leptin(250 ng/microliter) or LPS(100 ng/microliter). We examined the expression patterns of various chemokine mRNAs in THP-1 cell lines by RT-PCR and Northern blot. RESULTS: Leptin did not induce the expression of chemokine mRNAs in THP-1 cells. The expression patterns of RANTES, IL-8, MCP-1, IP-10, and Mig mRNAs in THP-1 cells stimulated with leptin and LPS simultaneously was almost same to the patterns of LPS alone-induced chemokine mRNAs. RANTES mRNA expression was independent on the concentrations of leptin. Although leptin did not have strong effect on the expression of RANTES, IL-8, MCP-1, IP-10, Mig, MIP-1alpha, MIP-1beta, and GRO-alpha mRNAs in THP-1 cells, leptin could induce the expression of long isoform of leptin receptor(OB-RL) mRNA, and its expression was elevated in simultaneous stimulation of leptin and LPS. CONCLUSION: These data suggest that leptin is able to induce OB-RL in THP-1 cells, however, leptin has little effect on the expression of pro-inflammatory chemokine genes.

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