Extracellular Vimentin Alters Energy Metabolism And Induces Adipocyte Hypertrophy

BACKGRUOUND

Previous studies have reported that oxidative stress contributes to obesity characterized by adipocyte hypertrophy. However, mechanism has not been studied extensively. In the current study, we evaluated role of extracellular vimentin secreted by oxidized low-density lipoprotein (oxLDL) in energy metabolism in adipocytes.

METHODS

We treated 3T3-L1-derived adipocytes with oxLDL and measured vimentin which was secreted in the media. We evaluated changes in uptake of glucose and free fatty acid, expression of molecules functioning in energy metabolism, synthesis of adenosine triphosphate (ATP) and lactate, markers for endoplasmic reticulum (ER) stress and autophagy in adipocytes treated with recombinant vimentin.

RESULTS

Adipocytes secreted vimentin in response to oxLDL. Microscopic evaluation revealed that vimentin treatment induced increase in adipocyte size and increase in sizes of intracellular lipid droplets with increased intracellular triglyceride. Adipocytes treated with vimentin showed increased uptake of glucose and free fatty acid with increased expression of plasma membrane glucose transporter type 1 (GLUT1), GLUT4, and CD36. Vimentin treatment increased transcription of GLUT1 and hypoxia-inducible factor 1α (Hif-1α) but decreased GLUT4 transcription. Adipose triglyceride lipase (ATGL), peroxisome proliferator-activated receptor γ (PPARγ), sterol regulatory element-binding protein 1 (SREBP1), diacylglycerol O-acyltransferase 1 (DGAT1) and 2 were decreased by vimentin treatment. Markers for ER stress were increased and autophagy was impaired in vimentin-treated adipocytes. No change was observed in synthesis of ATP and lactate in the adipocytes treated with vimentin.

CONCLUSION

We concluded that extracellular vimentin regulates expression of molecules in energy metabolism and promotes adipocyte hypertrophy. Our results show that vimentin functions in the interplay between oxidative stress and metabolism, suggesting a mechanism by which adipocyte hypertrophy is induced in oxidative stress.

[Effect and mechanism of cardiac adipose triglyceride lipase overexpression on burn-induced cardiac injury]

Objective: To explore the effect and potential mechanism of cardiac adipose triglyceride lipase (ATGL) overexpression on burn-induced cardiac injury. Methods: Eight-week-old C57BL/6J mice with cardiac ATGL overexpression driven by the myosin heavy chain (MHC) promoter (MHC-ATGL burn group) and wild-type (wild-type burn group) mice were randomly chose to the following experiments with burn injury after 24 h (n=8/group), MHC-ATGL mice and wild-type mice with corresponded age and sex were included as control. Cardiac ATGL protein expression, serum levels of cardiac troponin T and cardiac kinase-MB (CK-MB), cardiac free fatty acid and reactive oxygen species were detected. The wild-type and MHC-ATGL burn groups were not only compared with their corresponded control groups, but also compared between each other. Results: The hair color and development were shown little difference between each group. ATGL protein expression is elevated in wild-type burn group (1.00±0.68 vs 3.09±0.93, P=0.023) and decreased in MHC-ATGL burn group (17.84±2.41 vs 10.36±2.22, P<0.001), while ATGL protein expression is still increased in MHC-ATGL burn group compared with wild-type burn group (P<0.001). Serum levels of cardiac troponin T and CK-MB were both elevated in wild-type burn group and MHC-ATGL burn group [(0.456±0.131) vs (0.076±0.019) μg/L and (0.219±0.089) vs (0.060±0.019) μg/L, (1 421±162) vs (221±67) U/L and (761±142) vs (221±41) U/L] (all P<0.001), while serum levels of cardiac troponin T and CK-MB was still decreased in MHC-ATGL burn group compared with wild-type burn group (P<0.001). In addition, cardiac free fatty acid was increased in wild-type burn group and little difference was found in MHC-ATGL burn group [(2.54±0.51) vs (0.46±0.27) mmol/L, P<0.001, and (0.81±0.38) vs (0.59±0.25) mmol/L, P=0.251], while cardiac free fatty acid was significant reduction in MHC-ATGL burn group compared with wild-type burn group (P<0.001). Levels of cardiac reactive oxygen species was both elevated in wild-type burn group and MHC-ATGL burn group [(1.89±0.23) vs (1.00±0.18) and (1.38±0.17) vs (0.95±0.13)] (both P<0.001), while levels of cardiac reactive oxygen was reduction in MHC-ATGL burn group compared with wild-type burn group (P<0.001). Conclusion: Cardiac ATGL overexpression may protect against burn-induced cardiac injury through reducing free fatty acid and reactive oxygen species production.

Comparison of the Efficacy of Rosuvastatin Monotherapy 20 mg with Rosuvastatin 5 mg and Ezetimibe 10 mg Combination Therapy on Lipid Parameters in Patients with Type 2 Diabetes Mellitus

BACKGROUND

The apolipoprotein B/A1 (apoB/A1) ratio is a stronger predictor of future cardiovascular disease than is the level of conventional lipids. Statin and ezetimibe combination therapy have shown additional cardioprotective effects over statin monotherapy.

METHODS

This was a single-center, randomized, open-label, active-controlled study in Korea. A total of 36 patients with type 2 diabetes mellitus were randomized to either rosuvastatin monotherapy (20 mg/day, n=20) or rosuvastatin/ezetimibe (5 mg/10 mg/day, n=16) combination therapy for 6 weeks.

RESULTS

After the 6-week treatment, low density lipoprotein cholesterol (LDL-C) and apoB reduction were comparable between the two groups (-94.3±15.4 and -62.0±20.9 mg/dL in the rosuvastatin group, -89.9±22.7 and -66.8±21.6 mg/dL in the rosuvastatin/ezetimibe group, P=0.54 and P=0.86, respectively). In addition, change in apoB/A1 ratio (-0.44±0.16 in the rosuvastatin group and -0.47±0.25 in the rosuvastatin/ezetimibe group, P=0.58) did not differ between the two groups. On the other hand, triglyceride and free fatty acid (FFA) reductions were greater in the rosuvastatin/ezetimibe group than in the rosuvastatin group (-10.5 mg/dL [interquartile range (IQR), -37.5 to 29.5] and 0.0 μEq/L [IQR, -136.8 to 146.0] in the rosuvastatin group, -49.5 mg/dL [IQR, -108.5 to -27.5] and -170.5 μEq/L [IQR, -353.0 to 0.8] in the rosuvastatin/ezetimibe group, P=0.010 and P=0.049, respectively). Both treatments were generally well tolerated, and there were no differences in muscle or liver enzyme elevation.

CONCLUSION

A 6-week combination therapy of low-dose rosuvastatin and ezetimibe showed LDL-C, apoB, and apoB/A1 ratio reduction comparable to that of high-dose rosuvastatin monotherapy in patients with type 2 diabetes mellitus. Triglyceride and FFA reductions were greater with the combination therapy than with rosuvastatin monotherapy.

In Vitro Effect of Fatty Acids Identified in the Plasma of Obese Adolescents on the Function of Pancreatic β-Cells

BACKGROUND

The increase in circulating free fatty acid (FFA) levels is a major factor that induces malfunction in pancreatic β-cells. We evaluated the effect of FFAs reconstituted according to the profile of circulating fatty acids found in obese adolescents on the viability and function of the murine insulinoma cell line (mouse insulinoma [MIN6]).

METHODS

From fatty acids obtained commercially, plasma-FFA profiles of three different youth populations were reconstituted: obese with metabolic syndrome; obese without metabolic syndrome; and normal weight without metabolic syndrome. MIN6 cells were treated for 24 or 48 hours with the three FFA profiles, and glucose-stimulated insulin secretion, cell viability, mitochondrial function and antioxidant activity were evaluated.

RESULTS

The high FFA content and high polyunsaturated ω6/ω3 ratio, present in plasma of obese adolescents with metabolic syndrome had a toxic effect on MIN6 cell viability and function, increasing oxidative stress and decreasing glucose-dependent insulin secretion.

CONCLUSION

These results could help to guide nutritional management of obese young individuals, encouraging the increase of ω-3-rich food consumption in order to reduce the likelihood of deterioration of β-cells and the possible development of type 2 diabetes mellitus.