Obese state leads to elevated levels of TGF-β and COX isoforms in platelets of Zucker rats

Analysis of platelets from a diet-induced obesity rat model: elucidating platelet dysfunction in obesity

Obesity is one of the main health problems in industrialized countries. The contribution of multiple factors developed in obesity can hardly be modeled in vitro. In this context, the development of animal models mimicking human obesity could be essential. The aim of the present study was to compare platelets from a diet-induced obesity (DIO) rat model with their lean control group in order to elucidate platelet dysfunction mechanisms in obesity and correlate the results with previous data from morbid obese patients. In parallel, we also established a blood collection and platelet isolation methodology to study the DIO rat model at biochemical and functional level. Optimal blood collection was obtained from vena cava and platelet isolation was based on a serial of centrifugations avoiding platelet activation. Our results show that the DIO rat model simulate obesity pathologically since weight gain, fasting glucose and platelet counts are increased in obese rats. Interestingly, platelet levels of the active form of Src (pTyr⁴¹⁹) showed a tendency to increase in DIO rats pointing towards a potential dysfunction in Src family kinases-related signalling pathways in obesity. Moreover, platelets from DIO rats adhere more to collagen compared with the control group, pointing towards Glycoprotein VI (GPVI) as one of the dysregulated receptors in obesity, in agreement with our recent studies in humans. These results confirm that obesity, in line with human studies, present a platelet dysregulation, and highlight the relevance of considering novel antithrombotic drug targets in these patients, such as GPVI.

Food Restriction Prolongs Murine Cardiac Grafts

Overeating and obesity lead to cardiovascular disease, diabetes, and eventually premature death, whereas food or energy restriction reduces risk factors for cardiovascular disease and diabetes and expands the life span. The aim of this study was to investigate the effect of food restriction (FR) in a murine heart transplant model. CBA male recipients (H2(k)) that underwent transplantation of C57BL/6 (H2(b)) hearts were assigned to free access group or FR groups with food intake at 60% (40% FR), 50% (50% FR), or 40% (60% FR) of the average food intake for 1 week after transplantation, and each median survival time was measured. We also performed cell proliferation, cytokine production, and flow cytometry assessments. The 60% FR CBA recipients showed prolongation of allograft survival (median survival time, 24 days). Cell proliferation and interferon-γ were suppressed in the 60% FR CBA recipients. Flow cytometry studies showed a lower CD4(+)CD25(+)Foxp3(+) cell population in splenocytes from the 60% FR CBA recipients. In conclusion, the findings suggest that the prolongation of cardiac allograft resulted from not regulation of alloimmune responses, but partial impairment of alloimmune responses, linking energy restriction to low generation of splenic CD4(+)CD25(+)Foxp3(+) regulatory T cells.

The influence of sleep deprivation and obesity on DNA damage in female Zucker rats

OBJECTIVE

The aim of this study was to evaluate overall genetic damage induced by total sleep deprivation in obese, female Zucker rats of differing ages.

METHOD

Lean and obese Zucker rats at 3, 6, and 15 months old were randomly distributed into two groups for each age group: home-cage control and sleep-deprived (N = 5/group). The sleep-deprived groups were deprived sleep by gentle handling for 6 hours, whereas the home-cage control group was allowed to remain undisturbed in their home-cage. At the end of the sleep deprivation period, or after an equivalent amount of time for the home-cage control groups, the rats were brought to an adjacent room and decapitated. The blood, brain, and liver tissue were collected and stored individually to evaluate DNA damage.

RESULTS

Significant genetic damage was observed only in 15-month-old rats. Genetic damage was present in the liver cells from sleep-deprived obese rats compared with lean rats in the same condition. Sleep deprivation was associated with genetic damage in brain cells regardless of obesity status. DNA damage was observed in the peripheral blood cells regardless of sleep condition or obesity status.

CONCLUSION

Taken together, these results suggest that obesity was associated with genetic damage in liver cells, whereas sleep deprivation was associated with DNA damage in brain cells. These results also indicate that there is no synergistic effect of these noxious conditions on the overall level of genetic damage. In addition, the level of DNA damage was significantly higher in 15-month-old rats compared to younger rats.

Adipokines and thrombosis

1. Obesity is a major risk factor for cardiovascular disease. An increased body mass index (BMI) is associated with venous thromboembolism, myocardial infarction, stroke and stent thrombosis after percutaneous interventions. Studies in mouse models of obesity and induced arterial or venous thrombosis have provided insights into the mechanisms involved. 2. In addition to elevated circulating levels of fibrinogen, factor VII and plasminogen activator inhibitor (PAI)-1, changes in platelet biology and function may underlie the increased (athero) thrombotic risk in obesity. These include elevated platelet counts, an increase in mean platelet volume, an increased platelet aggregatory response to agonists and a reversible resistance to the anti-aggregatory effects of nitric oxide and prostacyclin I(2) . 3. Specific adipokines mediate the prothrombotic state in obesity. Of these, leptin enhances both arterial and venous thrombosis by promoting platelet adhesion, activation and aggregation. Leptin also induces tissue factor expression by human neutrophils and other cells. C-Reactive protein enhances the formation of monocyte-platelet aggregates and also promotes P-selectin expression and platelet adhesion to endothelial cells. Further, the adipose tissue is a significant source of tissue factor and PAI-1. Conversely, the circulating levels of adiponectin, a hormone that exerts vasculoprotective, anti-atherosclerotic and antithrombotic effects, are reduced in obese individuals. 4. A better understanding of the interactions of the adipose tissue with circulating and vascular cells and the dissection of the mechanisms linking adipokines to arterial and venous thrombosis may identify obese individuals at particularly high cardiovascular risk and indicate promising vasculoprotective and therapeutic targets.

Transforming Growth Factor-β1 as a Common Target Molecule for Development of Cardiovascular Diseases, Renal Insufficiency and Metabolic Syndrome

Transforming growth factor-β1 (TGF-β1) is a polypeptide member of the transforming growth factor β superfamily of cytokines. It is a secreted protein that performs many cellular functions including control of cell growth, cell proliferation, cell differentiation and apoptosis. In the cardiovascular system, TGF-β1 plays pivotal roles in the pathogenesis of hypertension, restenosis after percutaneous coronary intervention, atherosclerosis, cardiac hypertrophy and heart failure. In addition, TGF-β1 has been shown to be increased in adipose tissue of obese subjects with insulin resistance. Furthermore, TGF-β1 is a potent initiator of proliferation of renal mesangial cells leading to chronic kidney disease. Some currently available agents can manipulate TGF-β1 expression leading to amelioration of cardiovascular diseases. Thus, an understanding of interactions between chronic kidney disease and metabolic syndrome and the development of cardiovascular diseases is an important issue, and attention should be given to TGF-β1 as a crucial factor for regulation and modulation of those pathological conditions.