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

Steviol Glycoside, L-Arginine, and Chromium(III) Supplementation Attenuates Abnormalities in Glucose Metabolism in Streptozotocin-Induced Mildly Diabetic Rats Fed a High-Fat Diet

Stevia rebaudiana Bertoni and its glycosides are believed to exhibit several health-promoting properties. Recently, the mechanisms of the anti-diabetic effects of steviol glycosides (SG) have been the subject of intense research. The following study aims to evaluate the results of SG (stevioside (ST) and rebaudioside A (RA)) combined with L-arginine (L-Arg) and chromium(III) (CrIII) supplementation in streptozotocin- (STZ) induced mild type 2 diabetic rats fed a high-fat diet (HFD), with particular emphasis on carbohydrate and lipid metabolisms. The experiment was carried out on 110 male Wistar rats, 100 of which were fed an HFD to induce insulin resistance, followed by an intraperitoneal injection of streptozotocin to induce mild type 2 diabetes. After confirmation of hyperglycemia, the rats were divided into groups. Three groups served as controls: diabetic untreated, diabetic treated with metformin (300 mg/kg BW), and healthy group. Eight groups were fed an HFD enriched with stevioside or rebaudioside A (2500 mg/kg BW) combined with L-arginine (2000 or 4000 mg/kg BW) and Cr(III) (1 or 5 mg/kg BW) for six weeks. The results showed that supplementation with SG (ST and RA) combined with L-arg and Cr(III) could improve blood glucose levels in rats with mild type 2 diabetes. Furthermore, ST was more effective in improving blood glucose levels, insulin resistance indices, and very low-density lipoprotein cholesterol (VLDL-C) concentrations than RA. Although L-arg and Cr(III) supplementation did not independently affect most blood carbohydrate and lipid indices, it further improved some biomarkers when combined, particularly with ST. Notably, the beneficial impact of ST on the homeostatic model assessment–insulin resistance (HOMA-IR) and on the quantitative insulin-sensitivity check index (QUICKI) was strengthened when mixed with a high dose of L-arg, while its impact on antioxidant status was improved when combined with a high dose of Cr(III) in rats with mild type 2 diabetes. In conclusion, these results suggest that supplementary stevioside combined with L-arginine and Cr(III) has therapeutic potential for mild type 2 diabetes. However, further studies are warranted to confirm these effects in other experimental models and humans.

Insulin-like and mimetic molecules from non-mammalian organisms: potential relevance for drug discovery

Insulin was first discovered in extracts of vertebrate pancreas during a focused search for a therapy for diabetes. Subsequent efforts to discover and isolate a similar active principle from yeast and plants driven by the hope to identify insulin-like/mimetic molecules with critical advantages in the pharmacokinetic profile and expenditure of production compared to authentic human insulin were not successful. As a consequence, it has generally been assumed that hormones evolved exclusively during course of the evolution of vertebrate endocrine organs, implying a rather recent origin. Concomitantly, the existence and physiological role of vertebrate hormones in lower multi- and unicellular eukaryotes have remained a rather controversial subject over decades, albeit there is some evidence that hormones and hormone-binding proteins resembling those of vertebrates are expressed in fungi and yeast. Past and recent findings on the existence of insulin-like and mimetic materials, such as the glucose tolerance factor, in lower eukaryotes, in particular Neurospora crassa and yeast, will be presented. These data provide further evidence for the provocative view that the evolutionary roots of the vertebrate endocrine system may be far more ancient than is generally believed and that the identification and characterisation of insulin-like/mimetic molecules from lower eukaryotes may be useful for future drug discovery efforts.

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.

Evaluation of 90-day Repeated Dose Oral Toxicity, Glycometabolism, Learning and Memory Ability, and Related Enzyme of Chromium Malate Supplementation in Sprague-Dawley Rats

Our previous study showed that chromium malate improved the regulation of blood glucose in mice with alloxan-induced diabetes. The present study was designed to evaluate the 90-day oral toxicity of chromium malate in Sprague-Dawley rats. The present study inspected the effect of chromium malate on glycometabolism, glycometabolism-related enzymes, lipid metabolism, and learning and memory ability in metabolically healthy Sprague-Dawley rats. The results showed that all rats survived and pathological, toxic, feces, and urine changes were not observed. Chromium malate did not cause measurable damage on liver, brain, and kidney. The fasting blood glucose, serum insulin, insulin resistance index, C-peptide, hepatic glycogen, glucose-6-phosphate dehydrogenase, glucokinase, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglyceride levels of normal rats in chromium malate groups had no significant change when compared with control group and chromium picolinate group under physiologically relevant conditions. The serum and organ content of Cr in chromium malate groups had no significant change compared with control group. No significant changes were found in morris water maze test and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and true choline esterase (TChE) activity. The results indicated that supplementation with chromium malate did not cause measurable toxicity and has no obvious effect on glycometabolism and related enzymes, learning and memory ability, and related enzymes and lipid metabolism of female and male rats. The results of this study suggest that chromium malate is safe for human consumption.

Effect of glucose tolerance factor (GTF) from high chromium yeast on glucose metabolism in insulin-resistant 3T3-L1 adipocytes

Relative expression of IR, IRS-1, IRS-2 and GLUT4 mRNA was determined in insulin-resistant 3T3-L1 adipocytes with different treatments.

Purification and characterization of chromium-binding substances from high-chromium yeast

As a highly efficient and easily absorbable source of chromium, the identities of the chromium-binding substances in yeast remain unclear. In this study, a mild extraction procedure involving extraction with ammonia, three-gel filtration, and high-performance liquid chromatography was adopted to obtain two chromium-binding substances from high-chromium yeast. A low-molecular-weight chromium-binding substance was identified, with mass-to-charge ratios (m/z) of 769 and 712, which included glutamic acid, glycine, and cysteine in an approximate ratio of 1:1:1, as well as nicotinic acid and chromium(III). Furthermore, it significantly potentiated (by 51%) the action of insulin to stimulate the conversion of (14)C-glucose into lipid in adipocytes. A novel high-molecular-weight chromium-binding substance was also isolated: electrospray ionization tandem mass spectrometry tentatively identified it as HUB1 target protein-1, glyceraldehyde-3-phosphate dehydrogenase, or ribosomal protein L2A(L5A)(rp8)(YL6). This is the first report of a high-molecular-weight chromium-binding substance in yeast and merits further studies.

Chromium levels in healthy and newly diagnosed type 1 diabetic children

BACKGROUND

The aim of this study was to compare the chromium levels of plasma (PCL), erythrocyte (ECL) and urine (UCL) in type 1 diabetics and healthy subjects and to review the relation between metabolic parameters.

METHODS

We evaluated 165 subjects who were: newly diagnosed type 1 diabetics (group 1 [n= 29]); previously diagnosed type 1 diabetics (group 2 [n= 18]); non-diabetic control subjects who were admitted and treated for any reason in hospital (group 3 [n= 21]); and two other groups of control subjects from two schools that have different socioeconomic levels (group 4 [n= 48] and group 5 [n= 49]).

RESULTS

PCL in group 1 and group 2 subjects (7.21 ± 4.78 and 10.94 ± 3.04 mcg/L, respectively) was significantly lower than in all control groups (21.84 ± 7.87, 16.11 ± 7.44, 17.25 ± 8.58 mcg/L, respectively) (P < 0.05). A significant difference in PCL between the group 1 and group 2 subjects was present (7.21 ± 4.78 and 10.94 ± 3.04, respectively) (P= 0.021). ECL (as tissue chromium) in group 1 and group 2 subjects (13.99 ± 11.37 and 19.64 ± 12.58, respectively) was significantly lower than in all control groups (28.20 ± 7.34.25, 49 ± 12.47, 26.37 ± 9.77 mcg/L, respectively) (P= 0.05). UCL in group 1 and group 2 subjects (11.44 ± 6.88 and 15.68 ± 6.75 mcg/L, respectively) was significantly lower than in group 3 subjects (28.83 ± 9.37 mcg/L) (P < 0.05). There were significant correlations between length, bodyweight and PCL in the group 1 subjects (r = 0.42, P= 0.22 and r = 0.53, P= 0.03, respectively). There was a negative correlation between plasma glucose and UCL, which was not statistically significant in group 2 subjects (r =-0.4, P= 0.061).

CONCLUSION

There was a negative chromium balance in type 1 diabetics. This negative balance may affect the insulin function badly. If this negative balance should be confirmed by recent studies we suggest that chromium supplementation with insulin is necessary for type 1 diabetes.

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.