Exercise changes the size of cardiac neurons and protects them from age-related neurodegeneration

Age-related changes of neurochemically different subpopulations of cardiac spinal afferent neurons in rats

This study investigated the effect of aging on cardiac spinal afferent neurons in the rat. A patch loaded with retrograde tracer Fast Blue (FB) was applied to all chambers of the rat heart. Morphological and neurochemical characteristics of labeled cardiac spinal afferent neurons were assessed in young (2 months) and old (2 years) rats using markers for likely unmyelinated (isolectin B4; IB4) and myelinated (neurofilament 200; N52) neurons. The number of cardiac spinal afferent neurons decreased in senescence to 15% of that found in young rats (1604 vs. 248). The size of neuronal soma as well as proportion of IB4+ neurons increased significantly, whereas the proportion of N52+ neurons decreased significantly in senescence. Unlike somatic spinal afferents, neurochemically different populations of cardiac spinal afferent neurons experience morphological and neurochemical changes related to aging. A major decrease in total number of cardiac spinal afferent neurons occurs in senescence. The proportion of N52+ neurons decreased in senescence, but it seems that nociceptive innervation is preserved due to increased proportion and size of IB4+ unmyelinated neurons.

Obesity and the ageing brain: could leptin play a role in neurodegeneration?

Obesity and ageing are both characteristics of the human population that are on the increase across the globe. It has long been established that ageing is the major risk factor for neurodegenerative conditions such as Alzheimer's disease, and it is becoming increasingly evident that obesity is another such factor. Leptin resistance or insensitivity has been uncovered as a cause of obesity, and in addition the leptin signalling system is less potent in the elderly. Taken together, these findings reveal that this molecule may be a link between neurodegeneration and obesity or ageing. It is now known that leptin has beneficial effects on both the survival and neurophysiology of the neurons that are lost in Alzheimer's disease suggesting that it may be an important research target in the quest for strategies to prevent, halt, or cure this condition.

Energy metabolism and ageing regulation: metabolically driven deamidation of triosephosphate isomerase may contribute to proteostatic dysfunction

Research carried out up to 3 decades ago by Gracy and co-workers revealed that the activity of the glycolytic enzyme triosephosphate isomerase (TPI), which converts dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (G3P), gradually declines whilst carrying out its catalytic function, primarily due to deamidation of certain asparagine residues. It is suggested here that excessive or continuous glycolysis increases TPI deamidation and thereby lowers TPI activity and causes accumulation of its substrate, DHAP, which in turn decomposes into methylglyoxal (MG), a well-recognised reactive bicarbonyl whose actions in cells and tissues, as well as at the whole organism level, mimic much age-relate dysfunction. The proposal helps to explain why suppression of glycolysis by caloric restriction, fasting and increased aerobic activity also suppresses generation of altered proteins which characterise the aged phenotype. It is proposed that these effects on TPI activity, though seemingly neglected in biogerontological contexts, reveal a mechanistic link between energy metabolism and age-related proteostatic dysfunction.