Recent studies suggest that the neural retinal response to light is compromised in diabetes. Electroretinogram studies suggest that the dim light retinal rod pathway is especially susceptible to diabetic damage. The purpose of this study was to determine whether diabetes alters rod pathway signaling.
In females, menopause, the cessation of menstrual cycling, is associated with an increase in risk for several diseases such as cardiovascular disease, osteoporosis, diabetes, the metabolic syndrome, and ovarian cancer. The majority of women enter menopause via a gradual reduction of ovarian function over several years (perimenopause) and retain residual ovarian tissue. The VCD mouse model of menopause (ovarian failure in rodents) is a follicle-deplete, ovary-intact animal that more closely approximates the natural human progression through perimenopause and into the postmenopausal stage of life. In this review, we present the physiological parameters of how to use the VCD model and explore the VCD model and its application into the study of postmenopausal disease mechanisms, focusing on recent murine studies of diabetic kidney disease, the metabolic syndrome, and hypertension.
Factors comprising the metabolic syndrome occur with increased incidence in postmenopausal women. To investigate the effects of ovarian failure on the progression of the metabolic syndrome, female B(6)C(3)F(1) mice were treated with 4-vinylcyclohexene diepoxide (VCD) and fed a high-fat (HF) diet for 16 wk. VCD destroys preantral follicles, causing early ovarian failure and is a well-characterized model for the gradual onset of menopause. After 12 wk on a HF diet, VCD-treated mice had developed an impaired glucose tolerance, whereas cycling controls were unaffected [12 wk AUC HF mice 13,455 +/- 643 vs. HF/VCD 17,378 +/- 1140 mg/dl/min, P
Lithium treatment is associated with development of nephrogenic diabetes insipidus, caused in part by downregulation of collecting duct aquaporin-2 (AQP2) and AQP3 expression. In the present study, we carried out cDNA microarray screening of gene expression in the inner medulla (IM) of lithium-treated and control rats, and selected genes were then investigated at the protein level by immunoblotting and/or immunohistochemistry. The following genes exhibited significantly altered transcription and mRNA expression levels, and these were compatible with the changes in protein expression. 11beta-Hydroxysteroid dehydrogenase type 2 protein expression in the IM was markedly increased (198 +/- 25% of controls, n = 6), and immunocytochemistry demonstrated an increased labeling of IM collecting duct (IMCD) principal cells. This indicated altered renal mineralocorticoid/glucocorticoid responses in lithium-treated rats. The inhibitor of cyclin-dependent kinases p27 (KIP) protein expression was significantly decreased or undetectable in the IMCD cells, pointing to increased cellular proliferation and remodeling. Heat shock protein 27 protein expression was decreased in the IM (64 +/- 6% of controls, n = 6), likely to be associated with the decreased medullary osmolality in lithium-treated rats. Consistent with this, lens aldose reductase protein expression was markedly decreased in the IM (16 +/- 2% of controls, n = 6), and immunocytochemistry revealed decreased expression in the thin limb cells in the middle and terminal parts of the IM. Ezrin protein expression was upregulated in the IM (158 +/- 16% of controls, n = 6), where it was predominantly expressed in the apical and cytoplasmic domain of the IMCD cells. Increased ezrin expression indicated remodeling of the actin cytoskeleton and/or altered regulation of IMCD transporters. In conclusion, the present study demonstrates changes in gene expression not only in the collecting duct but also in the thin limb of the loop of Henle in the IM, and several of these genes are linked to altered sodium and water reabsorption, cell cycling, and changes in interstitial osmolality.
The adrenal steroid hormone dehydroepiandrosterone (DHEA) and its sulfated derivative [DHEA(S)] have been extensively studied for their potential anti-aging effects. Associated with aging, DHEA levels decline in humans, whereas other adrenal hormones remain unchanged, suggesting that DHEA may be important in the aging process. However, the effect of DHEA(S) supplementation on cardiac function in the aged has not been investigated. Therefore, we administered to young and old female mice a 60-day treatment with exogenous DHEA(S) at a dose of 0.1 mg/ml in the drinking water and compared the effects on left ventricular diastolic function and the myocardial extracellular matrix composition. The left ventricular stiffness (beta) was 0.30 +/- 0.06 mmHg/mul in the older control mice compared with 0.17 +/- 0.02 mmHg/mul in young control mice. Treatment with DHEA(S) decreased left ventricular stiffness to 0.12 +/- 0.03 mmHg/mul in the older mice and increased left ventricular stiffness to 0.27 +/- 0.04 mmHg/mul in young mice. The mechanism for the DHEA(S)-induced changes in diastolic function appeared to be associated with altered matrix metalloproteinase activity and the percentage of collagen cross-linking. We conclude that exogenous DHEA(S) supplementation is capable of reversing the left ventricular stiffness and fibrosis that accompanies aging, with a paradoxical increased ventricular stiffness in young mice.