The influence of chromium chloride-containing milk to glycemic control of patients with type 2 diabetes mellitus: a randomized, double-blind, placebo-controlled trial

Effect of Chromium Supplementation on Blood Glucose and Lipid Levels in Patients with Type 2 Diabetes Mellitus: a Systematic Review and Meta-analysis

In recent years, the prevalence and incidence of diabetes mellitus (DM) have increased sharply worldwide. In order to evaluate the effect of chromium supplementation on patients with type 2 diabetes, a meta-analysis was conducted by searching the relevant literature. Randomized controlled trials on the effects of chromium supplements on glucose metabolism or lipid profile in patients with type 2 diabetes were retrieved from multiple databases. Literature screening, quality evaluation, and data extraction were conducted according to the inclusion and exclusion criteria, and Review Manager 5.4.0 was used for data analysis. A total of 10 randomized controlled trials involving 509 patients were included, including 269 cases in the experimental group and 240 cases in the placebo control group. Statistical analysis was conducted on the glycosylated hemoglobin (HbA1c), fasting plasma glucose (FPG), triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) to evaluate the blood glucose and lipid levels. Meta-analysis results showed that the differences between the experimental group and the control group in only one indicator of HbA1c were statistically significant, while there were no statistically significant differences in other indicators. The use of chromium supplements can reduce the glycosylated hemoglobin of type 2 diabetic patients to a certain extent, but it cannot effectively improve the fasting blood glucose and blood lipid levels of type 2 diabetic patients.

Effects of chromium supplementation on glycemic control in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

We aimed to investigate the effect of chromium supplementation on glycemic control indices in patients with type 2 diabetes (T2DM).

METHODS

Randomized controlled trials examining the effect of chromium supplementation on glycemic control indices and published before February 2020 were detected by searching online databases, including PubMed, Scopus, Embase, Web of sciences and The Cochrane Library, using a combination of suitable keywords. Mean change and standard deviation (SD) of the outcome measures were used to estimate the mean difference between the supplementation group and the control group at follow-up.

RESULTS

Twenty-eight studies reported fasting plasma glucose (FPG), insulin, hemoglobin A1C (HbA1C) and homeostatic model assessment for insulin resistance (HOMA-IR) as an outcome measure. Results revealed significant reduction in FPG (weighted mean difference (WMD): -19.00 mg/dl, 95% CI: -36.15, -1.85, P = 0.030; I²: 99.8%, p < 0.001), insulin level (WMD: -12.35 pmol/l, 95% CI: -17.86, -6.83, P < 0.001), HbA1C (WMD: -0.71 %, 95% CI: -1.19, -0.23, P = 0.004) and HOMA-IR (WMD: -1.53, 95% CI: -2.35, -0.72, P < 0.001; I²: 89.9%, p < 0.001) after chromium supplementation.

CONCLUSION

The results of the current meta-analysis study might support the use of chromium supplementation for the improvement of glycemic control indices in T2DM patients.

Chromium supplementation for adjuvant treatment of type 2 diabetes mellitus: Results from a pooled analysis

SCOPE

We conducted a pooled analysis of randomized controlled trials to evaluate the effects of chromium supplementation on clinically relevant metabolic biomarkers in type 2 diabetes mellitus (T2DM) patients.

METHODS AND RESULTS

Electronic searches were conducted and the bibliographies of located articles were searched, and 28 studies were suitable for statistical pooling. Endpoints were calculated as weighted mean differences (WMDs) with 95% confidence intervals (CIs) by using fixed-effects or random-effects models. Statistical heterogeneity, publication bias, subgroup analyses, sensitivity analysis and meta-regression assessments were also assessed. Chromium reduced levels of fasting plasma glucose (WMD, -0.99 mmol/L; 95% CI, -1.72 to -0.25; p = 0.008), hemoglobin A1c (WMD, -0.54 %; 95% CI, -0.82 to -0.25; p = 0.0002), triglycerides (WMD, -11.71 mg/dL; 95% CI, -18.38 to -5.04; p = 0.0006). Chromium also increased levels of high-density lipoprotein cholesterol (WMD, 1.73 mg/dL; 95% CI, 0.50 to 2.96; p = 0.006). These results were robust in sensitivity analysis and were not dependent on the chromium dose and duration of supplementation. Subgroup analyses indicated that these notably favorable effects were presented in T2DM subjects ingesting chromium chloride and chromium picolinate formulations.

CONCLUSION

Our pooled analysis suggested that chromium supplementation might be a candidate as an adjunct to pharmacological management in patients with T2DM.

Controlling type-2 diabetes by inclusion of Cr-enriched yeast bread in the daily dietary pattern: a randomized clinical trial

PURPOSE

Chromium (Cr)-enriched yeast supplementation to whole wheat bread (WWCrB) has been shown to ameliorate postprandial glycemic response in healthy subjects. The present study investigates the long-term benefit of WWCrB consumption for patients with type-2 diabetes mellitus (T2DM).

METHODS

Thirty patients with T2DM were randomly assigned to a group receiving WWCrB or the plain whole wheat bread (WWB) group. Plasma glucose, insulin, glycosylated hemoglobin (HbA_1c) and insulin resistance were determined, and oral glucose tolerance test (OGTT) was performed at the beginning and the end of the dietary intervention, which lasted for 12 weeks. Biochemical parameters related to the disease, markers of inflammation as well as body weight and energy balance were examined.

RESULTS

At the end of the study, subjects of WWCrB group exerted lower levels of glucose, insulin and HbA_1c and improved insulin resistance (P < 0.05 against before treatment). Area under the glucose curve attained during OGTT decreased after the intervention (28,117.5 ± 1266.4 vs. 31,588.5 ± 1187.5 mg min/dL before treatment, P < 0.05) with significantly lower values of glucose concentration at 0 and 60 min. A significant reduction in body weight and systolic blood pressure (SBP) was observed (P < 0.05 against before treatment). Markers of inflammation and lipid profiles were not affected by WWCrB consumption.

CONCLUSIONS

Inclusion of WWCrB in the daily dietary pattern of diabetic patients resulted in improvement of glucose tolerance and insulin resistance, significant reduction in HbA_1c, weight loss and lower SBP. Patients with inadequate glycemic control may benefit from the consumption of WWCrB.

Chromium supplements for glycemic control in type 2 diabetes: limited evidence of effectiveness

Some adults with type 2 diabetes mellitus (T2DM) believe that chromium-containing supplements will help control their disease, but the evidence is mixed. This narrative review examines the efficacy of chromium supplements for improving glycemic control as measured by decreases in fasting plasma glucose (FPG) or hemoglobin A1c (HbA1c). Using systematic search criteria, 20 randomized controlled trials of chromium supplementation in T2DM patients were identified. Clinically meaningful treatment goals were defined as an FPG of ≤7.2 mmol/dL, a decline in HbA1c to ≤7%, or a decrease of ≥0.5% in HbA1c. In only a few randomized controlled trials did FPG (5 of 20), HbA1c (3 of 14), or both (1 of 14) reach the treatment goals with chromium supplementation. HbA1c declined by ≥0.5% in 5 of 14 studies. On the basis of the low strength of existing evidence, chromium supplements have limited effectiveness, and there is little rationale to recommend their use for glycemic control in patients with existing T2DM. Future meta-analyses should include only high-quality studies with similar forms of chromium and comparable inclusion/exclusion criteria to provide scientifically sound recommendations for clinicians.

Chromium supplementation improved post-stroke brain infarction and hyperglycemia

Hyperglycemia is common after acute stroke and is associated with a worse outcome of stroke. Thus, a better understanding of stress hyperglycemia is helpful to the prevention and therapeutic treatment of stroke. Chromium is an essential nutrient required for optimal insulin activity and normal carbohydrate and lipid metabolism. Beyond its nutritional effects, dietary supplement of chromium causes beneficial outcomes against several diseases, in particular diabetes-associated complications. In this study, we investigated whether post-stroke hyperglycemia involved chromium dynamic mobilization in a rat model of permanent focal cerebral ischemia and whether dietary supplement of chromium improved post-stroke injury and alterations. Stroke rats developed brain infarction, hyperglycemia, hyperinsulinemia, glucose intolerance, and insulin resistance. Post-stroke hyperglycemia was accompanied by elevated secretion of counter-regulatory hormones including glucagon, corticosterone, and norepinephrine, decreased insulin signaling in skeletal muscles, and increased hepatic gluconeogenesis. Correlation studies revealed that counter-regulatory hormone secretion showed a positive correlation with chromium loss and blood glucose increased together with chromium loss. Daily chromium supplementation increased tissue chromium levels, attenuated brain infarction, improved hyperglycemia, and decreased plasma levels of glucagon and corticosterone in stroke rats. Our findings suggest that stroke rats show disturbance of tissue chromium homeostasis with a net loss through urinary excretion and chromium mobilization and loss might be an alternative mechanism responsible for post-stroke hyperglycemia.

Effect of Chromium Supplementation on Element Distribution in a Mouse Model of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder and one of the most common causes of anovulatory infertility. In addition, insulin resistance is commonly associated with PCOS and contributed to pathophysiology connected to dietary minerals including chromium (Cr), copper (Cu), iron (Fe), and zinc (Zn). The aims of this study were to explore whether PCOS in mice alters levels of these elements and determine if Cr supplementation resolves changes. Twenty-four female BALB/c mice were divided into three groups of eight mice [normal control (NC), PCOS+placebo milk (PP), and PCOS+Cr-containing milk (PCr)]. Each group received a high-fat diet for 4 weeks. Our results show significantly higher levels of dehydroepiandrosterone (DHEA) (p<0.001), fasting glucose (p<0.05), and fasting insulin (p<0.05) in the PP group compared with both NC and PCr group. However, Cr levels were significantly lower in muscle, bone, and serum in the PP group (p<0.05) compared with NC and PCr groups. In liver, bone, and serum, Fe levels were significantly higher in the PP group compared with the NC group (p<0.05). In addition, we found significant correlations between Cu/Zn ratio and fasting insulin in all mice (r=0.61; p=0.002). Given that significant research shows that Cr supplementation improves fasting glucose, fasting insulin, and metal metabolism disorders for PCOS mice, our data suggest that trace element levels can serve as biomarkers to prescribe therapeutic supplementation to maintain a healthy metabolic balance and treat disease conditions.

Natural products for the management of type 2 diabetes mellitus and comorbid conditions

OBJECTIVE

To provide pharmacists with practical information to guide consumers in their choices of herbal products and dietary supplements for the management of type 2 diabetes mellitus (T2DM) and its comorbid disease states.

SUMMARY

The herbal and dietary supplement market has grown exponentially over the past decade as Americans increasingly use such agents for generalized health and the prevention and treatment of chronic disease states.1 Pharmacist advice is often requested on the use of these agents for the management of T2DM; however, this is an area that has insufficient evidence to support confident recommendations. Many published studies involving herbal agents and dietary supplements are small and poorly designed, with heterogeneous results. Pharmacists should be aware of the safety and efficacy data available for these agents, recognize potential drug interactions, and identify acceptable manufactured products.

CONCLUSION

The strongest scientific evidence for blood glucose lowering effect is associated with alpha-lipoic acid and fenugreek. There is also good evidence supporting the use of ivy gourd, gymnema, and vitamin E for management of hyperglycemia; however, caution should be used when recommending vitamin E. Pharmacists should advise consumers to disclose use of any of these products to all of their health care providers.

Melatonin administration in diabetes: regulation of plasma Cr, V, and Mg in young male Zucker diabetic fatty rats

The use of melatonin, a neurohormone present in plants, represents an exciting approach for the maintenance of optimum health conditions. Melatonin administration ameliorates glucose homeostasis in Zucker diabetic fatty (ZDF) rats. The objective of this study was to investigate the effects of melatonin in diabetes in relation to the levels and regulation of plasma chromium (Cr), vanadium (V), and magnesium (Mg) in Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats. At the age of 6 weeks, ZDF (n = 30) and ZL (n = 30) groups were each subdivided into three groups: control (C) (n = 10), vehicle-treated (V') (n = 10) and melatonin-treated (M) (10 mg kg(-1) per day; n = 10) groups for a 6 week period. After treatment, plasma mineral concentrations were measured by flame (Mg) and electrothermal (Cr and V) atomic absorption spectrometry. No significant differences were found between the C and V' groups (p > 0.05). Plasma Mg levels were significantly lower in C-ZDF vs. C-ZL rats, demonstrating the presence of hypomagnesemia in this diabetes mellitus model. Plasma V and Cr levels were significantly higher in M-ZDF vs. C-ZDF rats. Plasma Mg levels in ZDF rats were not affected by melatonin treatment (p > 0.05). Melatonin administration ameliorates the diabetic status of ZDF rats by enhancing plasma Cr and V concentrations. This appears to be the first report of a beneficial effect of melatonin treatment on plasma Cr and V regulation in ZDF rats.

Systematic review and meta-analysis of the efficacy and safety of chromium supplementation in diabetes

WHAT IS KNOWN AND OBJECTIVE

Chromium is an essential mineral for carbohydrate and lipid metabolism. Results of previous systematic reviews and meta-analyses of chromium supplementation and metabolic profiles in diabetes have been inconsistent. Recently, several published trials have emerged. We conducted a systematic review and meta-analysis to assess the effects on metabolic profiles and safety of chromium supplementation in diabetes mellitus.

METHODS

Clinical trials were identified through MEDLINE, the Cochrane library, CINAHL, Web of Science, Scopus and www.clinicaltrial.gov up to May 2013. Historical search of reference lists of related articles was also conducted. Studies were included if they (i) were randomized controlled trials comparing chromium mono- or combined supplementation against placebo, (ii) reported HbA1c or fasting plasma glucose and (iii) were of at least 3 weeks when reporting fasting plasma glucose, or of at least 8 weeks if HbA1c was reported. No language restriction was imposed. Treatment effect and adverse events were estimated with mean difference and odds ratio, respectively.

RESULTS AND DISCUSSION

Twenty-five randomized controlled trials met the inclusion criteria. Of these, 22 studies evaluated chromium monosupplementation. One study evaluated chromium yeast combined with vitamins C and E, and two others evaluated chromium picolinate plus biotin (CPB). Overall, chromium mono- and combined supplementation significantly improved glycaemic control (mean difference for HbA1c -0·55%; 95% CI -0·88 to -0·22%; P = 0·001, mean difference for FPG -1·15 mm; 95% CI -1·84 to -0·47 mm; P = 0·001). In particular, chromium monotherapy significantly reduced triglycerides and increased HDL-C levels. The effects on glucose and triglycerides levels were shown especially with chromium picolinate. Glycaemic control may improve with chromium monosupplementation of more than 200 μg daily. HbA1c and FPG also improved in patients with inadequate glycaemic control at baseline. The risk of adverse events did not differ between chromium and placebo.

WHAT IS NEW AND CONCLUSIONS

The available evidence suggests favourable effects of chromium supplementation on glycaemic control in patients with diabetes. Chromium monosupplement may additionally improve triglycerides and HDL-C levels. Chromium supplementation at usual doses does not increase the risk of adverse events compared with placebo. Data on chromium combined supplementation are limited and inconclusive. Long-term benefit and safety of chromium supplementation remain to be further investigated.

Improved meta-analytic methods show no effect of chromium supplements on fasting glucose

The trace mineral chromium has been extensively researched over the years in its role in glucose metabolism. Dietary supplement companies have attempted to make claims that chromium may be able to treat or prevent diabetes. Previous meta-analyses/systematic reviews have indicated that chromium supplementation results in a significant lowering of fasting glucose in diabetics but not in nondiabetics. A meta-analysis was conducted using an alternative measure of effect size, d(ppc2) in order to account for changes in the control group as well as the chromium group. The literature search included MEDLINE, the Cochrane Controlled Trials Register, and previously published article reviews, systematic reviews, and meta-analyses. Included studies were randomized, placebo-controlled trials in the English language with subjects that were nonpregnant adults, both with and without diabetes. Sixteen studies with 809 participants (440 diabetics and 369 nondiabetics) were included in the analysis. Screening for publication bias indicated symmetry of the data. Tests of heterogeneity indicated the use of a fixed-effect model (I² = 0 %). The analysis indicated that there was no significant effect of chromium supplementation in diabetics or nondiabetics, with a weighted average effect size of 0.02 (SE = 0.07), p = 0.787, CI 95 % = -0.12 to 0.16. Chromium supplementation appears to provide no benefits to populations where chromium deficiency is unlikely.

Anti-atherogenic effect of chromium picolinate in streptozotocin-induced experimental diabetes

BACKGROUND

Several studies have implicated changes in the levels of trace elements in diabetes. Chromium is one such element that seems to potentiate insulin action, thereby regulating carbohydrate and lipid metabolism. The aim of the present study was to evaluate the effect of chromium supplementation as chromium picolinate on the lipid profile of streptozotocin (STZ)-induced diabetic rats.

METHODS

Rats were rendered diabetic by a single injection of STZ (50 mg/kg, i.p.). Chromium picolinate (1 mg/kg per day, p.o.) was administered to rats for a period of 4 weeks. At the end of the treatment period, plasma total lipids, triglycerides, total cholesterol and lipoprotein levels were determined, as was hepatic glucose-6-phosphate dehydrogenase activity.

RESULTS

Total plasma lipids increased significantly in diabetic rats and this increase was ameliorated by chromium treatment for 4 weeks. Elevated total lipids in diabetic rats were due to increased plasma triglyceride and cholesterol levels. Chromium supplementation lowered plasma triglyceride and cholesterol levels to near normal. Chromium treatment also normalized low-density lipoprotein-cholesterol (LDL-C) and very low-density lipoprotein-cholesterol levels and improved the total cholesterol:high-density lipoprotein-cholesterol (HDL-C) and HDL-C:LDL-C ratios, suggesting an anti-atherogenic effect. In addition to improving the plasma lipid profile, chromium supplementation normalized liver glucose-6-phosphate dehydrogenase activity in diabetic rats.

CONCLUSIONS

These results provide evidence that chromium picolinate effectively attenuates the dyslipidemia associated with diabetes and thus can be used as an adjuvant therapy in the treatment of diabetes and its associated complications.

Effects of combined dietary chromium(III) propionate complex and thiamine supplementation on insulin sensitivity, blood biochemical indices, and mineral levels in high-fructose-fed rats

Insulin resistance is the first step in glucose intolerance and the development of type 2 diabetes mellitus, thus effective prevention strategies should also include dietary interventions to enhance insulin sensitivity. Nutrients, such as microelement chromium(III) and thiamine, play regulatory roles in carbohydrate metabolism. The objective of this study was to evaluate the insulin-sensitizing potential of the combined supplementary chromium(III) propionate complex (CrProp) and thiamine in insulin resistance animal model (rats fed a high-fructose diet). The experiment was carried out on 40 nine-week-old male Wistar rats divided into five groups (eight animals each). Animals were fed ad libitum: the control diet (AIN-93 M) and high-fructose diets with and without a combination of two levels of CrProp (0.1 and 1 mg Cr/kg body mass/day) and two levels of thiamine (0.5 and 10 mg/kg body mass/day) for 8 weeks. At the end of the experiment rats were sacrificed to collect blood and internal organs for analyses of blood biochemical and hematologic indices as well as tissular microelement levels that were measured using appropriate methods. It was found that both supplementary CrProp and thiamine (given alone) have significant insulin-sensitizing and moderate blood-lipid-lowering properties, while the combined supplementation with these agents does not give synergistic effects in insulin-resistant rats. CrProp given separately increased kidney Cu and Cr levels, while thiamine alone increased hepatic Cu contents and decreased renal Zn and Cu contents.

Effects of chromium brewer's yeast supplementation on body mass, blood carbohydrates, and lipids and minerals in type 2 diabetic patients

Chromium(III) is considered as an essential element for carbohydrate and lipid metabolism. The aim of this clinical study was to evaluate the efficacy of Cr brewer's yeast supplementation on body mass, carbohydrate, lipids and mineral indices in type 2 diabetic patients. Twenty adult type 2 diabetic subjects (11 males and 9 females aged 37-63) were supplemented with Cr brewer's yeast in dosages of 500 μg Cr/person/day or placebo for 8 weeks in a double-blind, placebo-controlled crossover design. It was found that supplemental Cr did not affect body mass, blood lipid profile, resistin levels, and the serum and hair Zn, Fe, and Cu levels, but increased serum Cr (by 116%) and hair Cr (by 20.6%) concentrations and improved some blood carbohydrate indices (significant increase in the β cell function index by 18.8%) in type 2 diabetic patients. In conclusion, Cr brewer's yeast has a weak hypoglycemic potential, but does not affect body mass, blood biochemical profile, and microelement levels in type 2 diabetic subjects.

Evaluation of anti-diabetic potential of chromium(III) propionate complex in high-fat diet fed and STZ injected rats

The aim of this study was to examine the anti-diabetic potential of the chromium(III) propionate complex (CrProp) in a diabetic rat model. Male Wistar rats (n=28, 8-week old) were divided into 4 groups (with 7 rats each) and fed at libitum: the control diet (AIN-93M), and high-fat diets with or without supplementary CrProp (10 and 50mg Crkg(-1) diet; 1 and 5 mg kg(-1) body mass per day) for 5 weeks, and subsequently injected with STZ to induce diabetes. Rats were further fed the same diets for another week until the end of the experiment. Blood indices and the contents of minerals (Fe, Zn, Cu and Cr) in rat tissues were determined by atomic absorption spectrometry. Supplementary CrProp did not affect blood glucose level, but significantly improved insulin sensitivity (HOMA-IR index) and reduced serum levels of triacylglycerols, total and LDL cholesterols. Both supplementary dosages of CrProp (10 and 50mg Cr kg(-1) diet) normalized the increased liver Fe content, reduced hepatic and renal Cu levels and elevated renal Cr contents in diabetic rats. In conclusion, CrProp has a significant anti-diabetic (insulin-sensitizing and hypolipidemic) potential; thus it might be a candidate for a therapeutic agent in 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.

Beneficial effect of chromium supplementation on glucose, HbA1C and lipid variables in individuals with newly onset type-2 diabetes

PROJECT

Chromium is an essential nutrient involved in normal carbohydrate and lipid metabolism. It influences glucose metabolism by potentiating the action as taking part in insulin signal amplification mechanism. A placebo-controlled single blind, prospective study was carried out to investigate the effect of chromium supplementation on blood glucose, HbA(1)C and lipid profile in newly onset patients with type-2 diabetes.

PROCEDURE

Total 40 newly onset type-2 diabetics were selected and after 1 month stabilization further randomly divided into two groups viz. study group and placebo group. The study group received 9 g brewer's yeast (42 μg Cr) daily and the other placebo group received yeast devoid of chromium for 3 months. Subjects were instructed not to change their normal eating and living habits. Fasting blood glucose, HbA(1)C and lipid profile were analyzed at beginning and completion of the study.

RESULTS

Results revealed that fasting blood glucose level significantly reduced in the subjects consuming yeast supplemented with chromium (197.65±6.68 to 103.68±6.64 mg/dL; p<0.001). HbA(1)C values improved significantly from 9.51±0.26% to 6.86±0.28%; p<0.001 indicating better glycaemic control. In experimental group total cholesterol, TG and LDL levels were also significantly reduced from 199.66±3.11 to 189.26±3.01 mg/dL; p<0.02, 144.94±8.31 to 126.01±8.26; p<0.05 and 119.19±1.71 to 99.58±1.10; p<0.001 respectively.

CONCLUSIONS

These data demonstrate beneficial effect of chromium supplementation on glycaemic control and lipid variables in subjects with newly onset type-2 diabetes.

Effect of cellulose, pectin and chromium(III) on lipid and carbohydrate metabolism in rats

The effects of cellulose, pectin and chromium(III) on lipid and carbohydrate metabolism were investigated in rats. Eighty male Buffalo rats (n=10/group, 4 weeks old) were fed experimental diets for 6 weeks. The two control groups received a fiber free diet (FF) or a fiber free diet plus chromium (FF+Cr) (2.53 mg Cr/kg diet). The other groups were fed diets containing 5% of cellulose (CEL), 5% of pectin (PEC) or 2.5% of cellulose plus 2.5% of pectin (CEL+PEC) with or without chromium. The daily food intake and body weight of the rats were not affected by the experimental diets. Total cholesterol level in plasma was significantly lower (p≤0.05) in the PEC group than the rats fed the FF diet. Feeding of rats with the PEC+Cr diet resulted in a significantly higher concentration of plasma HDL cholesterol (p≤0.05) when compared with the CEL+Cr group. No statistically significant differences in the concentrations of plasma triglycerides (TG) and non-esterified fatty acids (NEFA) between the groups were observed. Rats fed the CEL+Cr diet had a significantly lower content of cholesterol and rats fed the CEL+Cr diet lower contents of cholesterol and TG in the liver (p≤0.05) when compared with other groups. The concentration of HbA1c was significantly lower (p≤0.05) in rats fed the CEL and CEL+Cr diets than in other groups. A significantly lower concentration of plasma glucose (p≤0.05) was observed in rats receiving the CEL+PEC diet in comparison with the FF group. A significant effect of fiber and chromium combination was shown only in the case of triglyceride content in the liver of rats (p≤0.05). In conclusion, our results suggest that a diet containing fiber (PEC) and chromium or their supplements may be beneficial for correcting some disturbances of lipid metabolism, and a diet containing cellulose or its supplements may be used to improve glycemic control.

Chromium(III) propionate complex supplementation improves carbohydrate metabolism in insulin-resistance rat model

The purpose of this study was to evaluate the antidiabetic potential and safety of the chromium(III) propionate complex (CrProp) in insulin resistance induced by a high-fructose diet in rats. The experiment was carried out on 32 nine-week old male Wistar rats divided into 4 groups of 8 rats each. Animals were fed at libitum: the control diet (AIN-93M), and high-fructose diets (HF) containing various levels of Cr(III) given as CrProp (1 mg Cr kg(-1) diet (HF) and supplemented with 10 mg Cr kg(-1) diet (HFCr10), or 50 mg Cr kg(-1) diet (HFCr50), equal to approx. 0.1, 1 and 5 mg kg(-1) body mass per day) for 8 weeks. It was found that supplemental CrProp improved carbohydrate metabolism indices (decreasing serum insulin levels and insulin resistance indices HOMA-IR and HOMA-B, while increasing insulin sensitivity index QUICKI). Supplemental CrProp did not affect overall nutritional indices, blood morphology, most of the toxicity indices, blood glucose and lipids levels, while it increased kidney Cr level (HFCr50), normalized decreased liver Cu concentrations, and decreased kidney Fe and Cu levels (HFCr50). Supplemental CrProp administered at 10- and 50-fold doses of the basal dietary Cr level has a significant antidiabetic effect in insulin resistant rats. However, a prolonged treatment with this compound can affect Fe status.

Chromium supplementation enhances insulin signalling in skeletal muscle of obese KK/HlJ diabetic mice

AIM

Chromium is an essential nutrient required for glucose and lipid metabolism. Laboratory and clinical evidences indicate that chromium supplementation may improve insulin sensitivity by enhancing intracellular signalling. Considerable evidence suggests that serine phosphorylation of insulin receptor substrate 1 (IRS1) at 307 residue (IRS1-Ser307) inhibits insulin signalling and results in peripheral insulin resistance. Therefore, we investigated whether chromium-associated insulin action was mediated by modulation of IRS1-Ser307 phosphorylation.

METHODS

Male KK/HlJ mice (genetically obese and insulin resistant) were supplemented daily with chromium-containing milk powder or placebo for 7 weeks. In analysing functionally characterized insulin resistance, the changes of blood biochemicals, inflammatory factors and insulin signalling molecules in skeletal muscle were analysed.

RESULTS

Using KK mice model, we demonstrated that daily supplementation of trivalent chromium-containing milk powder reduced serum levels of glucose, insulin and triglycerides, and improved glucose and insulin tolerance. Mechanistic study showed that chromium supplementation activated postreceptor insulin signalling such as increasing IRS1, IRS1 tyrosine phosphorylation, p85alpha regulatory subunit of phosphatidylinositol 3-kinase and glucose transporter 4 expression, stimulating Akt activity, downregulating c-Jun N-terminal kinase (JNK) activity and decreasing IRS1 ubiquitinization and insulin resistance-associated IRS1 phosphorylation (IRS1-Ser307) in skeletal muscle. In addition, chromium supplementation attenuated pro-inflammatory cytokine expression in both blood circulation and skeletal muscle.

CONCLUSION

Our data suggest that chromium-containing milk powder supplementation can provide a beneficial effect in diabetic subjects by enhancing insulin signalling in skeletal muscle. The improvement in insulin signalling by chromium was associated with the decreased IRS1-Ser307 phosphorylation, JNK activity and pro-inflammatory cytokine production.

Niacin bound chromium treatment induces myocardial Glut-4 translocation and caveolar interaction via Akt, AMPK and eNOS phosphorylation in streptozotocin induced diabetic rats after ischemia-reperfusion injury

Diabetes, one of the major risk factors of metabolic syndrome culminates in the development of Ischemic Heart Disease (IHD). Refined diets that lack micronutrients, mainly trivalent chromium (Cr(3+)) have been identified as the contributor in the rising incidence of diabetes. We investigated the effect of niacin-bound chromium (NBC) during ischemia/reperfusion (IR) injury in streptozotocin induced diabetic rats. Rats were randomized into: Control (Con); Diabetic (Dia) and Diabetic rats fed with NBC (Dia+NBC). After 30 days of treatment, the isolated hearts were subjected to 30 min of global ischemia followed by 2 h of reperfusion. NBC treatment demonstrated significant increase in left ventricular functions and significant reduction in infarct size and cardiomyocyte apoptosis in Dia+NBC compared with Dia. Increased Glut-4 translocation to the lipid raft fractions was also observed in Dia+NBC compared to Dia. Reduced Cav-1 and increased Cav-3 expression along with phosphorylation of Akt, eNOS and AMPK might have resulted in increased Glut-4 translocation in Dia+NBC. Our results indicate that the cardioprotective effect of NBC is mediated by increased activation of AMPK, Akt and eNOS resulting in increased translocation of Glut-4 to the caveolar raft fractions thereby alleviating the effects of IR injury in the diabetic myocardium.

Effect of chromium supplementation on glucose metabolism and lipids: a systematic review of randomized controlled trials

OBJECTIVE

A systematic review of the effect of chromium supplementation on glucose metabolism and lipid levels.

RESEARCH DESIGN AND METHODS

A literature search was conducted in MEDLINE and the Commonwealth Agricultural Bureau. Eligible studies were English language randomized controlled trials of chromium supplement intake > or = 3 weeks, with > or = 10 participants receiving chromium. All trials with glucose metabolism outcomes and trials of individuals with diabetes or glucose intolerance for lipid outcomes were included. Meta-analyses were performed as appropriate.

RESULTS

Forty-one studies met criteria, almost half of which were of poor quality. Among participants with type 2 diabetes, chromium supplementation improved glycosylated hemoglobin levels by -0.6% (95% CI -0.9 to -0.2) and fasting glucose by -1.0 mmol/l (-1.4 to -0.5) but not lipids. There was no benefit in individuals without diabetes. There were some indications of dose effect and differences among chromium formulations. Larger effects were more commonly observed in poor-quality studies. The evidence was limited by poor study quality, heterogeneity in methodology and results, and a lack of consensus on assessment of chromium status.

CONCLUSIONS

No significant effect of chromium on lipid or glucose metabolism was found in people without diabetes. Chromium supplementation significantly improved glycemia among patients with diabetes. However, future studies that address the limitations in the current evidence are needed before definitive claims can be made about the effect of chromium supplementation.