Effects of aging on the recycling via the pentose cycle and on the kinetics of glycogen and protein metabolism in various organs of the rat

Mitochondrial dysfunction in cardiac aging

Cardiovascular diseases are the leading cause of death in most developed nations. While it has received the least public attention, aging is the dominant risk factor for developing cardiovascular diseases, as the prevalence of cardiovascular diseases increases dramatically with increasing age. Cardiac aging is an intrinsic process that results in impaired cardiac function, along with cellular and molecular changes. Mitochondria play a great role in these processes, as cardiac function is an energetically demanding process. In this review, we examine mitochondrial dysfunction in cardiac aging. Recent research has demonstrated that mitochondrial dysfunction can disrupt morphology, signaling pathways, and protein interactions; conversely, mitochondrial homeostasis is maintained by mechanisms that include fission/fusion, autophagy, and unfolded protein responses. Finally, we describe some of the recent findings in mitochondrial targeted treatments to help meet the challenges of mitochondrial dysfunction in aging.

Altered proteome turnover and remodeling by short-term caloric restriction or rapamycin rejuvenate the aging heart

Chronic caloric restriction (CR) and rapamycin inhibit the mechanistic target of rapamycin (mTOR) signaling, thereby regulating metabolism and suppressing protein synthesis. Caloric restriction or rapamycin extends murine lifespan and ameliorates many aging-associated disorders; however, the beneficial effects of shorter treatment on cardiac aging are not as well understood. Using a recently developed deuterated-leucine labeling method, we investigated the effect of short-term (10 weeks) CR or rapamycin on the proteomics turnover and remodeling of the aging mouse heart. Functionally, we observed that short-term CR and rapamycin both reversed the pre-existing age-dependent cardiac hypertrophy and diastolic dysfunction. There was no significant change in the cardiac global proteome (823 proteins) turnover with age, with a median half-life 9.1 days in the 5-month-old hearts and 8.8 days in the 27-month-old hearts. However, proteome half-lives of old hearts significantly increased after short-term CR (30%) or rapamycin (12%). This was accompanied by attenuation of age-dependent protein oxidative damage and ubiquitination. Quantitative proteomics and pathway analysis revealed an age-dependent decreased abundance of proteins involved in mitochondrial function, electron transport chain, citric acid cycle, and fatty acid metabolism as well as increased abundance of proteins involved in glycolysis and oxidative stress response. This age-dependent cardiac proteome remodeling was significantly reversed by short-term CR or rapamycin, demonstrating a concordance with the beneficial effect on cardiac physiology. The metabolic shift induced by rapamycin was confirmed by metabolomic analysis.

Oxygen free radicals, melatonin, and aging

The recognized peripheral and central biochemical, neuroendocrinological, behavioral, pharmacological, and clinical actions of melatonin are involved at different levels of an overall concept of the pathophysiology of aging. This conceptual approach combines the biochemistry of oxygen free radicals, the social behavior of the individual and the resulting cellular alterations. This has allowed us to propose antioxidant properties of melatonin that we have experimentally demonstrated.

Diabetes impairs DRG neuronal attachment to extracellular matrix proteins in vitro

Attachments of dorsal root ganglion (DRG) neurons from streptozotocin (STZ)-induced diabetic and normal C57BL mice to the following substrates were evaluated in vitro: a) poly L-lysine (PL), b) PL + type I collagen (CL-I), c) PL + type IV collagen (CL-IV), d) PL + laminin (LM) and e) PL + fibronectin (FN). After 6 h in culture, there was no significant difference in the average ratio of cells adhesive to PL between the diabetic (74.9%) and normal group of mice (75.6%). In the normal group, the addition of extracellular matrix (ECM) proteins such as CL-I, CL-IV, LM and FN to PL increased the ratios of cell attachment from 75.6% to nearly 90%. In the diabetic group, however, none of these proteins improved the attachment (the ratio changed from 74.9% to nearly 70%). Survival and neurite extension of attached cells after 48 h in culture were not different between the two groups. These results suggest that the cell-surface receptors, which enable DRG neurons to bind to the extracellular matrix proteins, are impaired by diabetes, resulting in being one of the causes of diabetic neuropathy.

Diabetes-induced reduction of neuronal survival in hypotonic environments in culture

Dorsal root ganglion (DRG) neurons from streptozotocin (STZ)-induced diabetic and normal C57BL mice were exposed to three different hypotonic environments (1/2, 1/4, and 1/8 osmolar solutions). After rapid applications of these hypotonic solutions to the neurons, the cell volume autoregulatory mechanism operated in 1/2 osmolar solution but was disrupted in superhypotonic solutions below 1/4 osmolar in both kinds of mice. None of the neurons could survive 12 h after treatment with superhypotonic solutions. On the other hand, a gradual reduction of osmolarity of the culture medium enabled neurons in the normal mice to survive in 1/2 and 1/4 osmolar solutions as well as in an isotonic solution. However, this reduction of osmolarity increased neuronal cell death in the diabetic mice. These results suggest that the ability of DRG neurons to survive in hypotonic environments in culture may be lost in diabetes.