Glucose and glycogen stores are depleted during long distance running.
which pathway is responsible for providing energy for glucose-dependent cells,such as brain cells,during extended periods of exercise?
Answers
Answer:
The mammalian brain depends upon glucose as its main source of energy, and tight regulation of glucose metabolism is critical for brain physiology. Consistent with its critical role for physiological brain function, disruption of normal glucose metabolism as well as its interdependence with cell death pathways forms the pathophysiological basis for many brain disorders. Here, we review recent advances in understanding how glucose metabolism sustains basic brain physiology. We aim at synthesizing these findings to form a comprehensive picture of the cooperation required between different systems and cell types, and the specific breakdowns in this cooperation which lead to disease.
Explanation:
The mammalian brain depends on glucose as its main source of energy. In the adult brain, neurons have the highest energy demand [1], requiring continuous delivery of glucose from blood. In humans, the brain accounts for ~2% of the body weight, but it consumes ~20% of glucose-derived energy making it the main consumer of glucose (~5.6 mg glucose per 100 g human brain tissue per minute [2]). Glucose metabolism provides the fuel for physiological brain function through the generation of ATP, the foundation for neuronal and non-neuronal cellular maintenance, as well as the generation of neurotransmitters. Therefore, tight regulation of glucose metabolism is critical for brain physiology and disturbed glucose metabolism in the brain underlies several diseases affecting both the brain itself as well as the entire organism.
Here, we provide a comprehensive overview of the functional implications and recent advances in understanding the fundamental role of glucose metabolism in physiological and pathological brain function. Although brain energy metabolism has been investigated for decades, certain aspects remain controversial, in particular in the field of energy substrate consumption and utilization. It is beyond the scope of this review to resolve these controversies; rather it is our aim to highlight conflicting concepts and results to stimulate discussion in key areas. To this end, we review the bioenergetics of neurotransmission, the cellular composition of a metabolic network, the regulation of cerebral blood flow (CBF), how peripheral glucose metabolism and energy homeostasis are sensed and controlled by the CNS, and the tight regulation of cellular survival through glucose-metabolizing enzymes.
Glucose is required to provide the precursors for neurotransmitter synthesis and the ATP to fuel their actions as well as the brain’s energy demands not related to signaling. Cellular compartmentation of glucose transport and metabolism is intimately related to local regulation of blood flow, and glucose-sensing neurons govern the brain-body nutrient axis. Glucose metabolism is connected to cell death pathways by glucose-metabolizing enzymes. Thus, disruption of pathways of glucose delivery and metabolism leads to debilitating brain diseases. We highlight the multifaceted role and complex regulation of glucose metabolism in the CNS as well as the physiological and pathophysiological consequences of balanced and disturbed glucose metabolism (Figure 1).