Homeostatic Control of Energy Metabolism
Katsuya Nagai, Hachiro Nakagawa in Central Regulation of Energy Metabolism with Special Reference to Circadian Rhythm, 2022
Control of fat metabolism is very important for maintenance of energy metabolism in the brain as well as in the rest of the body. Much additional attention has been directed to the contributions of the central and autonomic nervous systems to homeostatic controls of blood glucose. Blood glucose is the immediate source of brain energy. Thus, maintenance of its homeostasis is essential in coping with the urgent need of energy supply to the brain. Our body is endowed with three means of maintaining homeostasis of the level of blood glucose: glycogen storage, food intake, and gluconeogenesis. In the 1940s several lines of evidence were presented that in rats, cats, and rabbits the hypothalamus was responsible for the control of food intake. It has been established that brown adipose tissues are involved in thermogenesis, in a cold environment, and after food intake.
Synergy
Nigel Starey in Health and Social Care in the Digital World, 2020
This chapter describes the elements which make the NHS primary healthcare sector a “complex adaptive system” and are analogous to the archetypes and paradigms discussed in the following chapters. These elements determine how the system works – its physiology rather than its structure or anatomy. The chapter outlines examples of how the system adapts to remain “fit for purpose” and the extent to which form and function live in perfect harmony. Key concepts and examples which promote understanding include symmetry synergy, entropy and homeostasis (positive and negative feedback loops) as well as issues from evolution and genetic healthcare. Whether form is following function and the fitness of organisational form for the future are raised.
Homeostasis of Dopamine
Nira Ben-Jonathan in Dopamine, 2020
This chapter provides an overview of the fundamental processes that govern dopamine (DA) homeostasis: synthesis, metabolism, release, reuptake, and storage. At any given time, DA homeostasis is determined by multiple complementary processes that are tightly regulated and well-coordinated. Catecholamine biosynthesis involves several sequential enzymatic reactions, with tyrosine hydroxylase (TH) serving as the rate-limiting step. Metabolic degradation is carried out primarily by monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT), with additional glucuronidation and sulfation reactions. Within the producing cells, DA is stored in secretory vesicles whose main function is to protect it from degradation and enable its regulated release by a calcium-dependent exocytosis. Several types of transporters-the dopamine transporter (DAT), the vesicular monoamine transporters (VMATs), and organic cation transporters (OCTs)-are involved with the termination of the action of released DA through reuptake mechanisms and repackaging into the secretory granules. The different cytoarchitecture of DA within the "closed system" of the brain and the "open system" of the periphery necessitates several modifications of the fundamental processes of synthesis, metabolism, storage, transport and release of peripheral DA.
Allergies and Asthma: Do Atopic Disorders Result from Inadequate Immune Homeostasis arising from Infant Gut Dysbiosis?
Published in Expert Review of Clinical Immunology, 2016
Christine C. Johnson, Dennis R. Ownby
Our global hypothesis is that atopic conditions and asthma develop because an individual’s immune system is not able to appropriately resolve inflammation resulting from allergen exposures. We propose that the failure to appropriately down-regulate inflammation and produce a toleragenic state results primarily from less robust immune homeostatic processes rather than from a tendency to over-respond to allergenic stimuli. An individual with lower immune homeostatic capacity is unable to rapidly and completely terminate, on average over time, immune responses to innocuous allergens, increasing risk of allergic disease. A lack of robust homeostasis also increases the risk of other inflammatory conditions, such as prolonged respiratory viral infections and obesity, leading to the common co-occurrence of these conditions. Further, we posit that the development of vigorous immune homeostatic mechanisms is an evolutionary adaptation strongly influenced by both 1) exposure to a diverse maternal microbiota through the prenatal period, labor and delivery, and, 2) an orderly assemblage process of the infant’s gut microbiota ecosystem shaped by breastfeeding and early exposure to a wide variety of ingested foods and environmental microbes. This early succession of microbial communities together with early allergen exposures orchestrate the development of an immune system with a robust ability to optimally control inflammatory responses and a lowered risk for atopic disorders.
The homeostatic feeding response to fasting is under chronostatic control
Published in Chronobiology International, 2018
David Rivera-Estrada, Raúl Aguilar-Roblero, Claudia Alva-Sánchez, Iván Villanueva
Eating behavior is controlled by the energy needs of the organism. The need to provide a constant supply of energy to tissues is a homeostatic drive that adjusts feeding behavior to the energetic condition of the organism. On the other hand, food intake also shows a circadian variation synchronized to the light-dark cycle and food availability. Thus, feeding is subjected to both homeostatic and circadian regulation mechanisms that determine the amount and timing of spontaneous food intake in normal conditions. In the present study we contrasted the influence of the homeostatic versus the chronostatic mechanisms on food intake in normal conditions and in response to fasting. A group of rats was subjected to food deprivation under two different temporal schemes. A constant-length 24-h food deprivation started at different times of day resulted in an increased compensatory intake. This compensatory response showed a circadian variation that resembled the rhythm of intake in non-deprived animals. When subjected to fasting periods of increasing length (24–66 h), the amount of compensatory feeding varied according to the time of day in which food was made available, being significantly less when the fast ended in the middle of the light phase or beginning of the dark phase. These oscillatory changes did not have a correlation with variations in the level of glucose or β-hydroxybutyrate in the blood. The results suggest that the mechanism of homeostatic compensation is modulated chronostatically, presumably as part of the alternation of catabolic and anabolic states matching the daily cycles of activity.
Circadian and homeostatic modulation of the attentional blink
Published in Chronobiology International, 2019
Carlos Gallegos, Aída García, Candelaria Ramírez, Jorge Borrani, Carolina V. M. Azevedo, Pablo Valdez
An important property of attention is the limitation to process new information after responding to a stimulus. This property of attention can be evaluated by the Attentional Blink (AB), a phenomenon that consists of a failure to detect the second of two targets when the interval between them is 200–500 ms. The aim of the present work is to determine the possible existence of time awake (homeostatic changes) and time of day (circadian rhythm) variations in the AB. Eighteen undergraduate students, 11 men and 7 women, age = 18.06 ± 1.16 years, participated voluntarily in this research. They were recorded in a constant routine protocol during 29 h, in which rectal temperature was recorded every minute, while subjective sleepiness and responses to a Rapid Serial Visual Presentation (RSVP) task, to measure the AB, were recorded every hour. Homeostatic and circadian variations in all parameters of the RSVP task were observed, including changes in the capacity to process a new stimulus (Target 1 accuracy), a second stimulus occurring in a short interval after the first (Target 2 accuracy at lag 2, 200 ms) and to process another successive independent stimulus (Target 2 accuracy at lag 8, 800 ms). The acrophase of these parameters occurred with a phase delay of 2 h compared to the circadian rhythm of rectal temperature. The AB magnitude, an index of the AB, showed a decline with time awake, but no variations with time of day. In conclusion, there are homeostatic and circadian variations in the capacity to process any incoming information, especially in tasks with brief duration stimuli presented at a high frequency.
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