Effect of norepinephrine on expression of leptin and leptin receptor in hepatic stellate cells

AIM: To investigate the effect of sympathetic neurotransmitter norepinephrine (NE) on the expression of leptin and leptin receptor in hepatic stellate cells (HSCs) in vitro.

METHODS: Different concentrations of NE were applied on HSCs for 24, 48 or 72 h. Immunohistochemical staining was used to detect the expression of α-smooth muscle actin (α-SMA) in activated HSCs. Western blot was used to detect the expression of leptin and soluble leptin receptor (sOB-R) proteins. Real-time PCR was used to examine the effect of NE on mRNA expression of leptin and sOB-R in HSCs.

RESULTS: Immunohistochemistry results showed that after 1, 10, or 100 μmol/L NE was used on HSCs, the expression of α-SMA increased significantly at 24 h (14.1 ± 4.4, 17.5 ± 5.2, 19.8 ± 4.1 vs 11.3 ± 4.5; P < 0.05), suggesting that NE could activate HSCs and promote their proliferation. When 10 μmol/L NE was applied for 24, 48 or 72 h, α-SMA expression gradually increased (17.5 ± 5.2; 18.5 ± 5.4; 19.2 ± 6.2, P < 0.05), indicating that NE induced HSC proliferation in a time-dependent manner. Western blot analysis showed that leptin protein expression was significantly higher in HSCs after treatment with 1, 10 and 100 μmol/L NE for 24 h compared with the control group (1.54 ± 0.08, 2.72 ± 0.09, 2.84 ± 0.18 vs 0.85 ± 0.12, P < 0.05); the expression of leptin receptor protein was also significantly higher than that in the control group (1.57 ± 0.18, 2.51 ± 0.17, 2.89 ± 0.19 vs 0.98 ± 0.15, P < 0.05). Real-time PCR was used to detect mRNA expression of leptin and leptin receptor, and the results showed that leptin mRNA expression was significantly higher than that in the control group (1.51 ± 0.08, 2.58 ± 0.09, 3.63 ± 0.12 vs 1.00 ± 0.07, P < 0.05); the expression of leptin receptor mRNA was also significantly higher than that in the control group (1.71 ± 0.08, 2.87 ± 0.10, 4.01 ± 0.14 vs 1.00 ± 0.08, P < 0.05).

CONCLUSION: The sympathetic neurotransmitter NE plays a role in the process of liver fibrosis possibly by promoting leptin and sOB-R expression in activated HSCs.

Higher fetuin-A, lower adiponectin and free leptin levels mediate effects of excess body weight on insulin resistance and risk for myelodysplastic syndrome

OBJECTIVE

Excess body weight has been implicated in the pathogenesis of myelodysplastic syndrome (MDS). We thus explored the role of serum fetuin-A reflecting ectopic hepatic fat deposition when storage capacity of adipocytes has been exceeded, free leptin reflecting overall fat mass and adiponectin reflecting visceral fat mass, all potential mediators of the effects of obesity on insulin resistance and, consequently, to MDS risk.

MATERIALS & METHODS

In a hospital-based case-control study, we studied 101 cases with incident, histologically confirmed primary MDS and 101 controls matched on gender, age and date of diagnosis, between 2004 and 2007. Serum fetuin-A, adiponectin, leptin, leptin receptor, free leptin and insulin were determined.

RESULTS

Higher serum fetuin-A, lower adiponectin and lower free leptin were all individually and independently associated with higher risk of MDS before and after controlling for matching and risk factors, such as age, gender, date of diagnosis, body mass index (BMI), family history of lymphohematopoietic cancer, smoking history and serum insulin. Interestingly, we have shown that these associations were prominent among overweight/obese individuals and persisted after controlling for BMI and serum insulin indicating that their effects are above and beyond insulinemia only.

CONCLUSION

Elevated serum fetuin-A but lower adiponectin and free leptin are associated with higher risk of MDS particularly among overweight/obese individuals. These findings suggest that the association between excessive weight gain and the risk of MDS could be mediated by fetuin-A, adiponectin and free leptin, which may have potential clinical and preventive implications.