Effects of over-expressing resistin on glucose and lipid metabolism in mice*

Resistin, a newly discovered peptide hormone mainly secreted by adipose tissues, is present at high levels in serum of obese mice and may be a potential link between obesity and insulin resistance in rodents. However, some studies of rat and mouse models have associated insulin resistance and obesity with decreased resistin expression. In humans, no relationship between resistin level and insulin resistance or adiposity was observed. This suggests that additional studies are necessary to determine the specific role of resistin in the regulation of energy metabolism and adipogenesis. In the present study, we investigated the effect of resistin in vivo on glucose and lipid metabolism by over-expressing resistin in mice by intramuscular injection of a recombinant eukaryotic expression vector pcDNA3.1-Retn encoding porcine resistin gene. After injection, serum resistin and serum glucose (GLU) levels were significantly increased in the pcDNA3.1-Retn-treated mice; there was an obvious difference in total cholesterol (TC) level between the experiment and the control groups on Day 30. In pcDNA3.1-Retn-treated mice, both free fatty acid (FFA) and high density lipoprotein (HDL) cholesterol levels were markedly lower than those of control, whereas HDL cholesterol and triglyceride (TG) levels did not differ between the two groups. Furthermore, lipase activity was expressly lower on Day 20. Our data suggest that resistin over-expressed in mice might be responsible for insulin resistance and parameters related to glucose and lipid metabolism were changed accordingly

Relationship between resistin level in serum and acute coronary syndrome or stable angina pectoris*

Objective: To investigate the relationship between serum resistin level and acute coronary syndrome (ACS) or stable angina pectoris (SAP). Methods: Sixty-five patients, with coronary artery disease, were enrolled and divided into three subgroups: acute myocardial infarction (AMI), unstable angina pectoris (UAP) and SAP, and 26 healthy people were recruited as controls in the cross-sectional study. Serum resistin levels were determined by ELISA (enzyme-linked immunosorbent assay), and WBC (white blood cell count), hsCRP (high sensitive C-reaction protein), CKmax (maximum of creatinkinase), CK-MBmax (maximum of isozyme of creatinkinase) and cTnImax (maximum of troponin) were measured by standard laboratory methods. Results: The serum resistin levels were 4 folds higher in AMI patients, 2.43 folds in UAP patients and 1.12 folds in SAP patients than in the healthy controls (P<0.05). The resistin levels were also significantly different between AMI [(8.16±0.79) ng/ml], UAP [(5.59±0.75) ng/ml] and SAP [(3.45±0.56) ng/ml] groups (P<0.01); WBC, hsCRP, CKmax, CK-MBmax and cTnImax were significantly increased in AMI patients over UAP and SAP patients. Spearman analysis showed that serum resistin levels were positively correlated with WBC (r=0.412, P=0.046), hsCRP (r=0.427, P=0.037), CKmax, CK-MBmax and cTnImax (r=0.731, 0.678, 0.656; P<0.01). Conclusion: Serum resistin levels increased with inflammatory factors and myocardial impairment. The results suggest that human resistin might play an important role in the pathogenesis of atherosclerosis and AMI as an inflammatory factor

Developmental renin expression in mice with defective renin angiotensin system

During nephrogenesis, renin expression shifts from the vessel walls of interlobular arteries to the terminal portions of afferent arterioles in a wave-like pattern. Since the mechanisms responsible for the developmental deactivation of renin expression are as yet unknown, we hypothesized that the developing renin-angiontensin-system (RAS) may downregulate itself via negative feedback to prevent overactivity of renin. To test for a possible role of angiotensin II in the developmental deactivation of renin expression, we studied the development of intrarenal renin expression in mice lacking ANGII-AT1a, -AT1b or -AT2 receptors and in animals with abolished circulating ANGII due to deletion of the gene for angiotensin I-converting enzyme (ACE). The development of intrarenal renin expression was normal in mice lacking ANGII-AT1b or -AT2 receptors. In animals lacking both ANGII-AT1a and -1b receptors, ACE or ANGII-AT1a receptors, renin expression was normal early and renin disappeared from mature vessels until development of cortical interlobular and afferent arterioles began. The development of cortical vessels in these genotypes was accompanied by a markedly increased number of renin-expressing cells, many of which were ectopically located and attached in a grape-like fashion to the outer vessel perimeter. Although the number of renin-expressing cells declined during final maturation of the kidneys, the atypical distribution pattern of renin cells was maintained. These findings suggest that ANGII does not play a central role in the typical developmental shift in renin expression from the arcuate vessels to the afferent arterioles. During postnatal maturation of mouse kidneys, interruption of the RAS causes severe hyperplasia of renin cells via a mechanism that centrally involves AT1a receptors. However, the distribution pattern of renin cells in adult kidneys with an interrupted renin angiotensin system does not mimic any normal developmental stage since renin expression is frequently found in cells outside the arteriolar vessel walls in RAS mutants