Characterization of a diet-induced obesity rat model for periodontal research

OBJECTIVES

Obesity is associated with periodontitis, but the mechanisms underlying this association have yet to be unraveled. The present investigation was to evaluate a common rat model, in which obesity is induced by high-fat, high-sucrose diet (HFSD), for its applicability in periodontal research.

MATERIALS AND METHODS

Ten male Wistar rats were fed a 3-month HFSD along with a matching control group. Afterwards, the body weight, adipocyte morphology, leptin and adiponectin levels in adipose tissue, gingiva, and serum as well as the serum levels of triglyceride, cholesterol, and glucose were analyzed. For statistical analyses, parametric and non-parametric tests were applied (p < 0.05).

RESULTS

Body weight was significantly higher in the HFSD group after dieting as compared to control. HFSD caused a significant increase in serum triglyceride, low-density lipoprotein cholesterol, and leptin levels and a significant decrease in high-density lipoprotein cholesterol. Furthermore, adipose tissue from HFSD rats exhibited significantly larger adipocytes, displayed a significant upregulation of leptin and, surprisingly, elevated adiponectin levels, which is in contrast to chronic obesity in humans. Although leptin and adiponectin were also observed in gingival biopsies, no obvious differences between the groups were found.

CONCLUSIONS

Although this rat diet-induced obesity model is characterized by changes typical of obesity, it also has limitations, which have to be considered when data, especially with regard to adipokines, are extrapolated to humans.

CLINICAL RELEVANCE

The rodent diet-induced obesity model may be useful for unraveling pathomechanisms underlying the association between obesity and periodontal destruction but conclusions have to be drawn with caution.

Loss of Cyclin E1 attenuates hepatitis and hepatocarcinogenesis in a mouse model of chronic liver injury

Chronic liver injury triggers liver fibrosis and hepatocellular carcinoma (HCC), the third leading cause of cancer-related mortality. Cyclin E1 (CcnE1, formerly designated Cyclin E) is a regulatory subunit of the Cyclin-dependent kinase 2 (CDK2). It is overexpressed in approximately 70% of human HCCs correlating with poor prognosis, while the relevance of its orthologue Cyclin E2 (CcnE2) is unclear. Hepatocyte-specific deletion of NF-kappa-B essential modulator (NEMO^Δhepa) leads to chronic hepatitis, liver fibrosis, and HCC as well as CcnE upregulation. To this end, we generated NEMO^Δhepa/CcnE1^-/- and NEMO^Δhepa/CcnE2^-/- double knockout mice and investigated age-dependent liver disease progression in these animals. Deletion of CcnE1 in NEMO^Δhepa mice decreased basal liver damage and reduced spontaneous liver inflammation in young mice. In contrast, loss of CcnE2 did not affect liver injury in NEMO^Δhepa livers pointing to a unique, non-redundant function of CcnE1 in chronic hepatitis. Accordingly, basal compensatory hepatocyte proliferation in NEMO^Δhepa mice was reduced by concomitant ablation of CcnE1, but not after loss of CcnE2. In aged NEMO^Δhepa mice, loss of CcnE1 resulted in significant reduction of liver tumorigenesis, while deletion of CcnE2 had no effect on HCC formation. CcnE1, but not its orthologue CcnE2, substantially contributes to hepatic inflammatory response, liver disease progression, and hepatocarcinogenesis in NEMO^Δhepa mice.

Intravoxel incoherent motion MRI in the brain: Impact of the fitting model on perfusion fraction and lesion differentiability

PURPOSE

To investigate the effect of the choice of the curve-fitting model on the perfusion fraction (f_IVIM ) with regard to tissue type characterization, correlation with microvascular anatomy, and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters. Several curve-fitting models coexist in intravoxel incoherent motion (IVIM) MRI to derive the (f_IVIM ).

MATERIALS AND METHODS

In all, 29 patients with brain lesions (12 gliomas, 11 meningiomas, three metastases, two gliotic scars, one multiple sclerosis) underwent IVIM-MRI (32 b-values, 0 to 2000 s/mm² ) at 3T. f_IVIM was determined by classic monoexponential, biexponential, and a novel nonnegative least squares (NNLS) fitting in 352 regions of interest (lesion-containing and normal-appearing tissue) and tested their correlation with DCE-MRI kinetic parameters and microvascular anatomy derived from 57 region of interest (ROI)-based biopsies and their capacities to differentiate histologically different lesions.

RESULTS

f_IVIM differed significantly between all three models and all tissue types (monoexponential confidence interval in percent [CI 3.4-3.8]; biexponential [CI 11.21-12.45]; NNLS [CI 2.06-2.60]; all P < 0.001). For all models an increase in f_IVIM was associated with a shift to larger vessels and higher vessel area / tissue area ratio (regression coefficient 0.07-0.52; P = 0.04-0.001). Correlation with kinetic parameters derived from DCE-MRI was usually not significant. Only biexponential fitting allowed differentiation of both gliosis from edema and high- from low-grade glioma (both P < 0.001).

CONCLUSION

The curve-fitting model has an important impact on f_IVIM and its capacity to differentiate tissues. f_IVIM may possibly be used to assess microvascular anatomy and is weakly correlated with DCE-MRI kinetic parameters.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1187-1199.

Modeling hepatic osteodystrophy in Abcb4 deficient mice

Hepatic osteodystrophy (HOD) denotes the alterations in bone morphology and metabolism frequently observed in patients with chronic liver diseases, in particular in case of cholestatic conditions. The molecular mechanisms underlying HOD are only partially understood. In the present study, we characterized the bone phenotypes of the ATP-binding cassette transporter B4 knockout mouse (Abcb4(-/-)), a well-established mouse model of chronic cholestatic liver disease, with the aim of identifying and characterizing a mouse model for HOD. Furthermore, we investigated the influence of vitamin D on bone quality in this model. The bone morphology analyses revealed reduced bone mineral contents as well as changes in trabecular bone architecture and decreased cortical bone densities in Abcb4(-/-) mice with severe liver fibrosis. We observed dysregulation of genes involved in bone remodeling (osteoprotegerin, osteocalcin, osteopontin) and vitamin D metabolism (7-dehydrocholesterol reductase, Gc-globulin, Cyp2r1, Cyp27a1) as well as alterations in calcium and vitamin D homeostasis. In addition, serum RANKL and TGF-β levels were increased in Abcb4(-/-) mice. Vitamin D dietary intervention did not restore the bone phenotypes of Abcb4(-/-) animals. We conclude that the Abcb4(-/-) mouse provides an experimental framework and a preclinical model to gain further insights into the molecular pathobiology of HOD and to study the systemic effects of therapeutic interventions.