Biomedical subjects

Yanyun Chen

Publications and source records attributed to Yanyun Chen.

4 recordsLinked to original sources

PubMed2006

Central CART gene delivery by recombinant AAV vector attenuates body weight gain in diet-induced-obese rats.

Cocaine- and amphetamine-regulated transcript (CART) peptide is a neuro-peptide implicated in the regulation of energy homeostasis. CART mRNA and its encoded peptide have been found in many brain regions that regulate energy balance. To investigate the effects of chronic central expression of CART in the diet-induced-obese (DIO) rats, we constructed and packaged recombinant adeno-associated virus (AAV) 2 vector containing rat CART cDNA and a reporter gene encoding green fluorescence protein (AAV-rCART-hrGFP) driven by the CMV promoter. Approximately 1x10(11) particles of AAV-rCART-hrGFP or control vector AAV-IRES-hrGFP (AAV-hrGFP in short) were injected through intracerebroventricular (ICV) cannulas into adult male DIO Long-Evans rats. Throughout the 7-month study period, AAV-rCART-hrGFP-injected rats had a significantly decreased food intake and body weight gain when compared with those of AAV-hrGFP-injected rats. AAV-rCART-hrGFP injection also modulated hyperphagia following a 24-hour fasting in these rats. Body composition analysis indicated that decreased body weight gain was due to reduction in lean body mass while fat mass was not affected. Expression of green fluorescence protein (GFP) suggested that recombinant AAV virions are located at cells surrounding the third ventricle and medial eminence. Our results demonstrate that chronic expression of CART in brain can modulate energy intake in diet-induced-obese rats. The CART pathway plays an important role in body mass regulation in DIO rats.

Animals↗

PubMed2005

Leptin: structure, function and biology.

Leptin is an adipocyte-derived hormone that acts as a major regulator for food intake and energy homeostasis. Leptin deficiency or resistance can result in profound obesity, diabetes, and infertility in humans. Since its discovery, our understanding of leptin's biological functions has expanded from anti-obesity to broad effects on reproduction, hematopoiesis, angiogenesis, blood pressure, bone mass, lymphoid organ homeostasis, and T lymphocyte systems. Leptin orchestrates complex biological effects through its receptors, expressed both centrally and peripherally. Leptin receptor belongs to the class I cytokine receptor superfamily. At least five isoforms of leptin receptor exist, primarily because of alternate splicing. The longest form is capable of full signal transduction. The short forms may serve as leptin binding proteins and play a role in leptin transporting across the blood-brain barrier. In this review, we present the crystal structure of leptin and the structural comparison with other four-helical cytokines, discuss the leptin-receptor binding models based on other cytokine-receptor complex structures, and summarize the most recent progress on leptin signal transduction pathways--especially its link to peripheral lipid metabolism through AMP-activated protein kinase and hepatic stearoyl-CoA desaturase-1 pathways. Furthermore, we propose the structure based design of leptin analogs with increased stability, improved potency, enhanced blood-brain barrier transport, and extended time action for future therapeutic application.

AMP-Activated Protein Kinase Kinases↗

PubMed2004

Diet-induced changes in stearoyl-CoA desaturase 1 expression in obesity-prone and -resistant mice.

OBJECTIVE: To investigate stearoyl-coenzyme A desaturase (SCD) 1 expression in obesity-prone C57BL/6 mice and in obesity-resistant FVB mice to explore the relationship of SCD1 expression and susceptibility to diet-induced obesity. RESEARCH METHODS AND PROCEDURES: Nine-week-old C57BL/6 and FVB mice were fed either a high- or low-fat diet for 8 weeks. Body weight and body composition were measured before and at weeks 4 and 8 of the study. Energy expenditure was measured at weeks 1 and 5 of the study. Hepatic SCD1 mRNA was measured at 72 hours and at the end of study. Plasma leptin and insulin concentrations were measured at the end of study. RESULTS: When C57BL/6 mice were switched to a calorie-dense high-fat diet, animals gained significantly more body weight than those maintained on a low-calorie density diet primarily due to increased fat mass accretion. Fat mass continued to accrue throughout 8 weeks of study. Increased calorie intake did not account for all weight gain. On the high-fat diet, C57BL/6 mice decreased their energy expenditure when compared with mice fed a low-fat diet. In response to 8 weeks of a high-fat diet, SCD1 gene expression in liver increased >2-fold. In contrast, feeding a high-fat diet did not change body weight, energy expenditure, or SCD1 expression in FVB mice. DISCUSSION: Our study showed that a high-fat hypercaloric diet increased body adiposity first by producing hyperphagia and then by decreasing energy expenditure of mice susceptible to diet-induced obesity. Consumption of a high-fat diet in species predisposed to obesity selectively increased SCD1 gene expression in liver.

Animals↗

PubMed2002

Targeted disruption of the melanin-concentrating hormone receptor-1 results in hyperphagia and resistance to diet-induced obesity.

The hypothalamic neuropeptide melanin-concentrating hormone (MCH) has been implicated in a variety of physiological functions including the regulation of feeding and energy homeostasis. Two MCH receptors (MCHR1 and MCHR2) have been identified so far. To decipher the functional role of the MCH receptors, we have generated and phenotypically characterized mice rendered deficient in MCHR1 expression by homologous recombination. Inactivation of MCHR1 results in mice (MCHR1-/-) that are resistant to diet-induced obesity. With a high-fat diet, body fat mass is significantly lower in both male (4.7 +/- 0.6 g vs. 9.6 +/- 1.2 g) and female (3.9 +/- 0.2 vs. 5.8 +/- 0.5 g) MCHR1-/- mice than that of the wild-type control (P < 0.01), but the lean mass remains constant. When normalized to body weight, female mice are hyperphagic, and male mice are hyperphagic and hypermetabolic, compared with wild-type mice. Consistent with the lower fat mass, both leptin and insulin levels are significantly lower in male MCHR1-/- mice than in the wild-type controls. Our data firmly establish MCHR1 as a mediator of MCH effects on energy homeostasis and suggest that inactivation of MCHR1 alone is capable to counterbalance obesity induced by a high-fat diet.

Adipose Tissue↗