Carbohydrate metabolism hormonal

Storage and utilization of tissue glycogen, maintenance of blood glucose concentration, and other aspects of carbohydrate metabolism are meticulously regulated by hormones, including insulin, glucagon, epinephrine, and the glucocorticoids. 

It was known as early as 1927 that the adrenal glands of mammalian species secrete a series of substances essential to the survival of the individual. The hormonal nature of these secretions was suggested by the observation that extracts of the adrenal gland and more specifically of the outer portion of that organ (cortex) would ensure survival of animals whose adrenals had been excised. By 1943 no fewer than 28 steroids had been isolated from adrenal cortical extracts. These compounds were found to be involved in the regulation of such diverse and basic processes as electrolyte balance, carbohydrate metabolism, and resistance to trauma, to name only a few. 

Ghanges in the availability of substrates are responsible for most changes in metabolism either directly or indirectly acting via changes in hormone secretion. Three mechanisms are responsible for regulating the activity of enzymes in carbohydrate metabolism (1) changes in the rate of enzyme synthesis, (2) covalent modification by reversible phosphorylation, and (3) allosteric effects. 

Hormones have a profound effect on carbohydrate metabolism. Great interest has been aroused by reports of hormonal control of hexokinase activity by specific proteins in animal tissues.99- 100 Hexokinase action is the rate-limiting step in the uptake of D-glucose by muscle. Hexokinase is inhibited in diabetic muscle, but the inhibition can be partially reversed by insulin. A protein fraction from the anterior pituitary gland will inhibit the hexokinase of extracts of brain and muscle, and the effect of this... 

Glucagon is a second pancreatic hormone that, like insulin, influences carbohydrate metabolism. However, most of its actions oppose those of insulin. The enkephalins and endorphins are the body s natural painkillers they are thought to be responsible for runner s high. These, among many others, are proteins or are closely related to them. 

In all organisms, carbohydrate metabolism is subject to complex regulatory mechanisms involving hormones, metabolites, and coenzymes. The scheme shown here (still a simplified one) applies to the liver, which has central functions in carbohydrate metabolism (see p. 306). Some of the control mechanisms shown here are not effective in other tissues. 

Diabetes can involve misfolding of proteins that form in the endoplasmic reticulum (ER). The ER secretes certain hormones, enzymes, and antibodies, and so is a key player in our health. In some cases, the misfolded proteins interfere with carbohydrate metabolism leading to diabetes. 

The tenn corticosteroids refers to steroid hormones secreted by the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response, and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte levels, and behavior. 

Allosteric and Hormonal Signals Coordinate Carbohydrate Metabolism... 

As complex as the regulation of carbohydrate metabolism is, it is far from the whole story of fuel metabolism. The metabolism of fats and fatty acids is very closely tied to that of carbohydrates. Hormonal signals such as insulin and changes in diet or exercise are equally important in regulating fat metabolism and integrating it with that of carbohydrates. We shall return to this overall metabolic integration in mammals in Chapter 23,... 

Endocrine Influences. A number of hormones are known to influence carbohydrate metabolism in the mammal. Insulin seems to increase oxidation of glucose, lipogenesis. and glycogenesis. Its primary mode of action may be io facilitate the entry of glucose into the cell. 

Somatotropin (STH) (Growth hormone, GH somatotrophic hormone hypophyseal growth hormone) Structure Known and synthesized coiled, unbranched Promotes general growth of organism Promotes skeletal growth, protein anabolism, fat metabolism, carbohydrate metabolism, water, and salt meiabolism Relates with all vitamins in connection with growth actions... 

Conflicting data concerning the effects of oral contraceptives on carbohydrate metabolism have been presented the effects are probably clinically insignificant. However, estrogen hormone replacement therapy with a sequential-type product containing mestranol and norethisterone caused significantly impaired glucose tolerance (30). 

Sas T, Mulder P, Aanstoot HJ, Houdijk M, Jansen M, Reeser M, Hokken-Koelega A. Carbohydrate metabolism during long-term growth hormone treatment in children with short stature born small for gestational age. Clin Endocrinol (Oxf) 2001 54(2) 243-51. 

Norephedrine and ephedrine mimic and stimulate the release of the adrenal hormones norepinephrine and epinephrine. Norephinephrine raises heart rate and epinephrine stimulates carbohydrate metabolism resulting in an increased metabolic rate, fatty acids release from lipocytes (fat cells), and a protein sparing effect. Caffeine simply prolongs the effect. 

Metabolic Effects. Thyroid hormones affect energy substrate utilization in a number of ways. For instance, these hormones increase intestinal glucose absorption and increase the activity of several enzymes involved in carbohydrate metabolism. Thyroid hormones enhance lipolysis by increasing the response of fat cells to other lipolytic hormones. In general, these and other metabolic effects help to increase the availability of glucose and lipids for increased cellular activity. 

Morphological changes were also observed on callus of Pinus laricio cultured for 4 weeks with HS extracted from forest soil under Abies alba and Fagus sylvatica plantation or the hormones 2,4D, IAA, and 6BAP (Muscolo et al., 2005).The results showed that both high- and low-molecular-weight humic fractions inhibited callus growth compared to the control and affected the enzymes involved in carbohydrate metabolism. 

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