Glucose, Tolerance Factor

Brewers and bakers dried yeasts are used as dietary supplements. They contribute some protein and trace minerals, and some B vitamins, but no vitamin C, vitamin B 2 or fat-soluble vitamins. The glucose tolerance factor (GTE) of yeast, chromium nicotinate, mediates the effect of insulin. It seems to be important for older persons who caimot synthesize GTE from inorganic dietary chromium. The ceU wall fraction of bakers yeast reduces cholesterol levels in rats fed a hypercholesteremic diet. 

Rice bran is the richest natural source of B-complex vitamins. Considerable amounts of thiamin (Bl), riboflavin (B2), niacin (B3), pantothenic acid (B5) and pyridoxin (B6) are available in rice bran (Table 17.1). Thiamin (Bl) is central to carbohydrate metabolism and kreb s cycle function. Niacin (B3) also plays a key role in carbohydrate metabolism for the synthesis of GTF (Glucose Tolerance Factor). As a pre-cursor to NAD (nicotinamide adenine dinucleotide-oxidized form), it is an important metabolite concerned with intracellular energy production. It prevents the depletion of NAD in the pancreatic beta cells. It also promotes healthy cholesterol levels not only by decreasing LDL-C but also by improving HDL-C. It is the safest nutritional approach to normalizing cholesterol levels. Pyridoxine (B6) helps to regulate blood glucose levels, prevents peripheral neuropathy in diabetics and improves the immune function. 

Chromium deficiency may be related to the glucose tolerance factor (Herold and Fitzgerald 1994). The determination of this deficiency, however, is questioned, because the lack of accuracy of the Cr determination in the earlier publications. 

Chromium was recognized as an essential trace element in 1955.1190 Rats fed a chromium-deficient diet developed an impaired tolerance for intravenous glucose, which could be reversed by an insulin-potentiating factor present in brewer s yeast, meat and various other foods. The insulin-potentiating factor was found to be a complex of chromium(IH)1191 and such substances have been termed Glucose Tolerance Factor(s) (GTFs). Chromium was demonstrated to be essential for humans in 1975.1192 There are several reviews of the chemistry of chromium(III) and its relationship to glucose tolerance.1193-1196... 

Essential to ascidians ("sea squirts"), which concentrate in a miilionfold from sea water. Essential to chicks and rats. Deficiencies cause reduced growth, impaired reproduction and sirvival of young, impaired tooth and bone metabolism and feather development.4 May be a factor in manic-depressive illness/ Essential involved in gkicose metabolism and diabetes potentiates effect of insulin. Presence in glucose tolerance factor from brewer s yeast questioned/... 

Glucose tolerance factor chromium in 888 Glucose transporters 415, 416 GLUT1, topology diagram 416 GLUT4, response to insulin 416 Glucosidase... 

Finally, it should be noted that this chemistry may have biological relevance. Several metalloenzymes are believed to contain more than one metal ion bound at the active site. One relevant example is the glucose tolerance factor (GTF) which is important for the metabolic degradation of glucose (398-401). GTF is a low-molecular-weight protein which contains chromium(III). Its structure is not known, but it has been suggested that the active site contains a dinuclear chromium(III) complex (401). The fact that hydroxo-bridged dinuclear chromium(III) complexes exhibit reactions which are often very fast compared with those observed for the parent mononuclear species seems to support such a proposal. 

An oligopeptide of relative molar mass 1600 that binds Fem and functions to enhance the cellular uptake of Fe has been isolated from mouse cells.51 The peptide also binds Co11 but does not enhance the uptake of this metal. The peptide has been referred to as the siderophore-like growth factor (SGF). There is also a proposed Cr-chelating peptide this glucose tolerant factor is essential for the utilization of Cr in the proper functioning of insulin in cells.72 Whilst Zn11 is normally associated... 

Chromium was proposed as an essential element after the observation that rats fed with Torula yeast developed impaired glucose tolerance.1085 The active ingredient in other yeasts was suggested to be a chromium complex, named the glucose-tolerance factor . Brewers yeast contains chromium in the range 0.35-5.4 xgg-1.1086... 

In humans and animals, chromium(ni) is an essential nutrient that plays a role in glucose, fat, and protein metabolism by potentiating the action of insulin (Anderson 1981). The biologically active form of chromium, called glucose tolerance factor (GTF), is a complex of chromium, nicotinic acid, and possibly amino acids (glycine, cysteine, and glutamic acid). Both humans and animals are capable of converting... 

Redox reactions Pellagra as glucose tolerance factor (GTF) in conjunction with Cr... 

Cr Cr3+ 50-200 /zg Glucose tolerance factor (GTF) Deficiency causes a diabetes-like syndrome, esp. in the elderly... 

Chromium This metal is essential for normal insulin and glucose function. Chromium is involved in the glucose tolerance factor affecting insulin and the clearance of glucose from the body [14, 15],... 

Nicotinic acid has been tentatively identified as the organic component of the (as yet uncharacterized) chromium-containing glucose tolerance factor that enhances the interaction of insulin with cell surface receptors. 

In patients with a normal nutritional status, alcohol often results in hyperglycaemia. Apart from an alcohol-induced increase in catecholamines and cortisol (or ACTH), the reason for this also seems to be a reduced sensitivity of insulin receptors (e.g. due to zinc deficiency) (s. p. 50) and/or a lower glucose tolerance factor, (s. p. 51) (s. tab. 28.2)... 

Essential involved in glucose metabolism and diabetes potentiates effect of insulin." Presence in glucose tolerance factor from brewer s yeast questioned. ... 

The molecular composition of a biologically active form of Cr " found in brewer s yeast, known as glucose tolerance factor (GTF), is not established. The structure of the Cr " bioactive molecule is thought to be the octahedral... 

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