Naturally occurring chromium compounds in brewer's yeast and the saltbush plant

Antidiabetic Effect of High-Chromium Yeast Against Type 2 Diabetic KK-Ay Mice

High chromium yeast has attracted many researchers for its high efficiency and high safety among chromium supplements. The preventive effect of oral high-chromium yeast on diabetes was assessed using KK-A^Y mice. Sixteen-wk-old type 2 diabetic KK-A^Y mice were divided into five groups and orally administered with two types of drying processed high-chromium yeast, chromium picolinate at 1000 μg Cr/kg/d, metformin (positive control), and normal yeast (negative control) for 13 weeks. The spray-dried high-chromium yeast significantly delayed the onset of hyperglycemia in type 2 diabetic KK-A^Y mice (P < 0.05) and significantly improved fasting blood glucose, TG(triglyceride), and TCHO(total cholesterol) . Histopathological analysis showed that the spray-dried high-chromium yeast led to high affinities for the stains to the β-cells in the islets of Langerhans and alleviated hepatic steatosis. High-chromium yeast could be a potential candidate for nutritional supplement to ameliorate diabetes.

PRACTICAL APPLICATION

Chromium plays an important role in fat and carbohydrate metabolism. The result show that spray-dried high chromium yeast significantly delayed the onset of hyperglycemia in type 2 diabetic KK-A^Y mice. As one of chromium supplements, the purpose of this study is to examine the efficacy of high chromium yeast on the type 2 diabetes and drying method on its bioactivity, which will be useful for research and development of high-chromium yeast and improvement of pharmacological activity-based quality control.

Featured Article: Inhibition of diabetic cataract by glucose tolerance factor extracted from yeast

Diabetes leads to many complications; among them is the development of cataract. Hyperglycemia brings to increased polyol concentration in the lens, to glycation of lens proteins, and to elevated level of ROS (Reactive Oxygen Species) causing oxidative stress. The glucose tolerance factor (GTF) was found by several groups to decrease hyperglycemia and oxidative stress both in diabetic animals and humans. The aim of our study was to explore the damages induced by high glucose to the eye lens and to assess the protective effects of GTF both in vivo and in vitro The in vivo study included control healthy rats, streptozotocin (STZ) diabetic untreated rats, and STZ diabetic rats orally treated with 15 doses of GTF. The diabetic untreated rats developed cataracts, whereas the development of cataract was totally or partially prevented in GTF treated animals. In vitro studies were done on bovine lenses incubated for 14 days. Half of the lenses were incubated in normal glucose conditions, and half in high glucose conditions (450 mg%). To one group of the normal or high glucose condition GTF was added. The optical quality of all the lenses was measured daily by an automated scanning laser system. The control lenses, whether with or without GTF addition, did not show any reduction in their quality. High glucose conditions induced optical damage to the lenses. Addition of GTF to high glucose conditions prevented this damage. High glucose conditions affected the activity of aldose reductase and sodium potassium ATPase in lens epithelial cell. Addition of GTF decreased the destructive changes induced by high glucose conditions. The amount of soluble cortical lens proteins was decreased and structural changes were detected in lenses incubated in high glucose medium. These changes could be prevented when GTF was added to high glucose medium. Our findings demonstrate the anticataractogenic potential of GTF.

Metal-based anti-diabetic drugs: advances and challenges

The current status and likely future directions of complexes of V(V/IV), Cr(III), Mo(VI), W(VI), Zn(II), Cu(II), and Mn(III) as potential oral drugs against type 2 diabetes are reviewed. We propose a unified model of extra- and intracellular mechanisms of anti-diabetic efficacies of V(V/IV), Mo(VI), W(VI), and Cr(III), centred on high-oxidation-state oxido/peroxido species that inhibit protein tyrosine phosphatases (PTPs) involved in insulin signalling. The postulated oxidative mechanism of anti-diabetic activity of Cr(III) via carcinogenic Cr(VI/V) (which adds to safety concerns) is consistent with recent clinical trials on Cr(III) picolinate, where activity was apparent only in patients with poorly controlled diabetes (high oxidative stress), and the correlation between the anti-diabetic activities and ease of oxidation of Cr(III) supplements and their metabolites in vivo. Zn(II) and Cu(II) anti-diabetics act via different mechanisms and are unlikely to be used as specific anti-diabetics due to their diverse and unpredictable biological activities. Hence, future research directions are likely to centre on enhancing the bioavailability and selectivity of V(V/IV), Mo(VI), or W(VI) drugs. The strategy of potentiating circulating insulin with metal ions has distinct therapeutic advantages over interventions that stimulate the release of more insulin, or use insulin mimetics, because of many adverse side-effects of increased levels of insulin, including increased risks of cancer and cardiovascular diseases.

Oral administration of the high-chromium yeast improve blood plasma variables and pancreatic islet tissue in diabetic mice

The in vivo effects of oral administration of the high-chromium yeast to healthy and diabetic mice are described. Given that these complexes are proposed to function by potentiating the actions of insulin and activating the insulin receptor kinase, changes in lipid and carbohydrate metabolism would be expected. After 15 weeks administration (500 μg Cr/kg body mass) to healthy mice, abnormal metabolism and pathological change were not observed. After 15 weeks of treatment (0-1,000 μg Cr/kg body mass) of diabetic mice, the effect of high-chromium yeast on blood lipids and blood glycosylated hemoglobin (GHb) of diabetes are not consistent. High-chromium yeast results in a lowering (P < 0.05) of GHb and triglyceride, lowering (P < 0.01) of total cholesterol, and restoration (P < 0.01) of insulin; these results are in stark contrast to those of diabetic mice of administration of normal yeast, which have no effect on these parameters and serve as control group. The histopathological analysis of pancreas islet shows that high-chromium yeast could profoundly protect the impaired pancreatic islet and β-cells from inflammatory infiltration and fibrosis.

Inhibition of diabetic nephropathy in rats by an oral antidiabetic material extracted from yeast

Diabetic nephropathy is one of the major complications of diabetes. The glucose tolerance factor (GTF) is a dietary agent extracted from several natural sources; the richest among them is brewer's yeast. Extraction and purification of an active and stable GTF preparation from brewer's yeast previously was successful, and a remarkable decrease in plasma glucose and lipids from administration of GTF to animals with type 1 diabetes was demonstrated. The purpose of the present study was to examine whether GTF affects nephropathy in diabetic rats. The average urinary volume and protein excretion throughout the collection period in diabetic rats was 56.95 +/- 2.2 ml/d and 5.42 +/- 0.95 mg/d, respectively. These values were significantly (P < 0.001 versus baseline values) higher compared with healthy controls (average urine volume 15.12 +/- 0.5 ml/d; average protein excretion 0.15 +/- 0.08 mg/d). Treatment with GTF reduced average urine volume and protein excretion to 29.1 +/- 1.94 ml/d (P < 0.01) and 1.55 +/- 1.17 mg/d (P < 0.05), respectively. Kidney weight, which was elevated in diabetic rats, slightly decreased in diabetic animals that were treated with GTF, in association with reduction of lipid peroxidation levels in the renal cortex and the heart. Endothelial nitric oxide immunoreactivity in the renal cortex of both healthy and diabetic rats that were treated with GTF was remarkably lower than that found in renal cortex of untreated diabetic animals. This study demonstrates that yeast-derived material, GTF, can inhibit the development of nephropathy that is induced by diabetes.