Dietary chromium and effect of chromium supplementation on glucose tolerance of elderly Canadian women

Exploration of Hypoglycemic Activity of Saccharomyces pastorianus Extract and Evaluation of the Molecular Mechanisms

Although the hypoglycemic potential of brewer’s yeast extract has been reported, there is limited information pertaining to the hypoglycemic ingredients of Saccharomyces pastorianus extract and their mechanisms of action available. This study aimed to investigate the in vivo and in vitro hypoglycemic effect of S. pastorianus extract and to elucidate its molecular mechanisms. S. pastorianus extract was mainly composed of proteins followed by carbohydrates. In diabetic rats, oral administration of S. pastorianus extract significantly reduced the levels of plasma glucose and enhanced the activity of hepatic glucose-6-phosphatase dehydrogenase. Treatment with S. pastorianus extract increased the localization of type 4 glucose transporter (GLUT4), PTP, and insulin receptor at 3T3-L1 cell membranes and raised the levels of P38 MAPK, PI3K, and AKT in the cytosol. In agreement with these results, pretreatment of 3T3-L1 cells with inhibitors of PTP, PI3K, Akt/PKB, and p38 MAPK inhibited glucose uptake induced by application of S. pastorianus extract. Most importantly, a 54 kDa protein with hypoglycemic activity was identified and suggested as the major ingredient contributing to the hypoglycemic activity of S. pastorianus extract. In summary, these results clearly confirm the hypoglycemic activity of S. pastorianus extract and provide critical insights into the underlying molecular mechanisms.

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.

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.

Chromium picolinate for insulin resistance in subjects with HIV disease: a pilot study

AIM

Multidrug regimens in HIV disease are associated with an increased incidence of insulin resistance, by as much as 50%. Not only does insulin resistance predisposes subjects to diabetes but also it is associated with the metabolic syndrome and increased risk of cardiovascular disease. Previous studies suggest that chromium picolinate can improve insulin resistance in patients with type 2 diabetes. The objective was to study the efficacy and safety of chromium picolinate as a treatment of insulin resistance in subjects infected with HIV.

METHODS

The ability of chromium picolinate (1000 mug/day) to improve insulin sensitivity, determined with a hyperinsulinaemic-euglycaemic insulin clamp, was determined in eight HIV-positive subjects on highly active antiretroviral therapy.

RESULTS

The mean rate of glucose disposal during the clamp was 4.41 mg glucose/kg lean body mass (LBM)/min (range 2.67-5.50), which increased to 6.51 mg/kg LBM/min (range 3.19-12.78, p = .03), an increase of 25% after 8 weeks of treatment with chromium picolinate. There were no significant changes in blood parameters, HIV viral burden or CD4+ lymphocytes with chromium picolinate treatment. Two subjects experienced abnormalities of liver function during the study. Another subject experienced an elevation in blood urea nitrogen.

CONCLUSIONS

The study shows that chromium picolinate therapy improves insulin resistance in some HIV-positive subjects, but with some concerns about safety in this population.

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.

Chromium picolinate intake and risk of type 2 diabetes: an evidence-based review by the United States Food and Drug Administration

The labeling of both health claims that meet significant scientific agreement (SSA) and qualified health claims on conventional foods and dietary supplements requires pre-market approval by the US Food and Drug Administration (FDA). Approval by the FDA involves, in part, a thorough review of the scientific evidence to support an SSA or a qualified health claim. This article discusses FDA's evidence-based review of the scientific evidence on the role of chromium picolinate supplements in reducing the risk of type 2 diabetes. Based on this evidence-based review, FDA issued a letter of enforcement discretion for one qualified health claim on chromium picolinate and risk of insulin resistance, a surrogate endpoint for type 2 diabetes. The agency concluded that the relationship between chromium picolinate intake and insulin resistance is highly uncertain.

Glucose and insulin responses to dietary chromium supplements: a meta-analysis

BACKGROUND

Several authors, mostly on the basis of nonrandomized studies, have suggested dietary trivalent chromium supplementation as an attractive option for the management of type 2 diabetes and for glycemic control in persons at high risk of type 2 diabetes.

OBJECTIVE

The study aimed to determine the effect of chromium on glucose and insulin responses in healthy subjects and in individuals with glucose intolerance or type 2 diabetes.

DESIGN

The study design was a systematic review and meta-analysis of randomized clinical trials (RCTs).

RESULTS

The authors identified 20 reports of RCTs assessing the effect of chromium on glucose, insulin, or glycated hemoglobin (Hb A(1c)). This review summarizes data on 618 participants from the 15 trials that reported adequate data: 193 participants had type 2 diabetes and 425 were in good health or had impaired glucose tolerance. The meta-analysis showed no association between chromium and glucose or insulin concentrations among nondiabetic subjects. A study of 155 diabetic subjects in China showed that chromium reduced glucose and insulin concentrations; the combined data from the 38 diabetic subjects in the other studies did not. Three trials reported data on Hb A(1c): one study each of persons with type 2 diabetes, persons with impaired glucose tolerance, and healthy subjects. The study of diabetic subjects in China was the only one to report that chromium significantly reduced Hb A(1c).

CONCLUSIONS

Data from RCTs show no effect of chromium on glucose or insulin concentrations in nondiabetic subjects. The data for persons with diabetes are inconclusive. RCTs in well-characterized, at-risk populations are necessary to determine the effects of chromium on glucose, insulin, and Hb A(1c).

Serum chromium does not predict glucose tolerance in late pregnancy

BACKGROUND

Chromium is an essential element in human nutrition. Serum concentrations of chromium are not well characterized during pregnancy or in gestational diabetes mellitus.

OBJECTIVE

The objective of this study was to determine whether low plasma chromium concentrations (< or =3 nmol/L) are associated with altered glucose, insulin, or lipid concentrations during pregnancy.

DESIGN

The study was conducted prospectively and took place at the medical obstetric clinic of a tertiary referral hospital. Seventy-nine women with abnormal results of a 50-g glucose challenge test in the third trimester of pregnancy were studied. All women had a formal 75-g oral-glucose-tolerance test, and fasting insulin, lipid, and chromium concentrations were determined. Chromium was measured by graphite furnace atomic absorption spectrometry.

RESULTS

The median chromium concentration was 2 nmol/L (95% CI: 0, 12). There were no significant differences in age, plasma glucose, insulin, lipids, calculated insulin resistance, or calculated ss cell function between women with normal and those with abnormal (< or =3 nmol/L) chromium concentrations.

CONCLUSIONS

Plasma chromium during pregnancy does not correlate with glucose intolerance, insulin resistance, or serum lipids. Plasma chromium concentrations may not accurately reflect tissue stores of chromium. Several trials showed a beneficial effect of chromium supplementation on glucose tolerance, insulin, and lipids. A method for assessing body chromium stores is required to allow further study.

Chromium as a supplement

Chromium (Cr) is an essential mineral element that has received considerable public attention. The suggestion that Cr intake is generally low has generated interest regarding the purported beneficial effects of Cr supplementation on biological function and health of animals and humans. This review briefly describes key aspects of Cr nutritional status and evaluates the effects of Cr supplementation on various components of biological function, body composition, and health. A novel biological role of Cr in regulation of insulin function is described. Although promising results of Cr supplementation are presented, the considerable challenge of developing methods for routine assessment of Cr nutriture in humans remains.

Mechanisms of chromium action: low-molecular-weight chromium-binding substance

Chromium has long been known to be essential for proper lipid and carbohydrate metabolism in mammals, with chromium deficiency leading to symptoms associated with adult-onset diabetes and cardiovascular disease. Elucidating the structure, function, and mode of action of the biologically active form of chromium has proved enigmatic. However, a naturally-occurring oligopeptide, low-molecular-weight chromium-binding substance (LMWCr), has been found in our laboratory to activate insulin receptor kinase activity up to 7-fold with a dissociation constant of 250 picomolar in the presence of 100 nanomolar insulin, and it has been partially characterized in terms of structural and spectroscopic properties. LMWCr may function in a manner similar to that of the calcium-binding signal protein calmodulin. In other words, LMWCr is maintained in its active apo-oligopeptide form; in response to a chromium flux, LMWCr binds 4 chromic ions. The holoprotein is then capable of binding to insulin receptor (and perhaps other enzymes) activating the enzyme. Establishing a link between the nutrient chromium, LMWCr's activation of insulin receptor kinase activity, and adult-onset diabetes and related conditions could result in a new treatment for these conditions.

Chromium, glucose intolerance and diabetes

Within the last 5 years chromium (Cr) has been shown to play a role in glucose intolerance, Type 2 diabetes mellitus (Type 2 DM), and gestational diabetes. In addition, diabetes and the neuropathy of a patient on home parenteral nutrition were alleviated when supplemental Cr was added to total parenteral nutrition (TPN) solutions. In a study conducted in China that has been supported by studies in the United States, supplemental Cr as Cr picolinate improved the blood glucose, insulin, cholesterol, and hemoglobin A1C in people with Type 2 DM in a dose dependent manner. Follow-up studies of > 1 year have confirmed these studies. The requirement for Cr is related to the degree of glucose intolerance: 200 microg/day of supplemental Cr is adequate to improve glucose variables of those who are mildly glucose intolerant. However, people with more overt impairments in glucose tolerance and diabetes usually require more than 200 microg/day. Daily intake of 8 microg of Cr per kg body weight was also more effective than 4 microg/kg in women with gestational diabetes. The mechanism of action of Cr involves increased insulin binding, increased insulin receptor number, and increased insulin receptor phosphorylation. In summary, supplemental Cr has been shown to have beneficial effects without any documented side effects on people with varying degrees of glucose intolerance ranging from mild glucose intolerance to overt Type 2 DM.

Chromium picolinate effects on body composition and muscular performance in wrestlers

PURPOSE

The purpose of this study was to assess the effects of 14 wk of chromium picolinate supplementation during the final 16 wk of a preseason resistance and conditioning program on body composition and neuromuscular performance in NCAA Division I wrestlers. During this phase of training, wrestlers are primarily interested in trying to improve physical performance and wrestling technique and are not engaged in severe, acute weight loss practices commonly employed before competition.

METHODS

This double-blinded, randomized placebo-controlled study involved 20 wrestlers from the University of Oklahoma assigned to either a treatment group (Cr+3; N = 7; 20.4 yr +/- 0.1) receiving 200 micrograms chromium picolinate daily, a placebo group (P; N = 7; 19.9 yr +/- 0.2), or a control group (C; N = 6; 20.2 yr +/- 0.1) using a stratified random sampling technique based on weight classification. Body composition, neuromuscular performance, metabolic performance, and serum insulin and glucose were measured before and immediately following the supplementation and training period.

RESULTS

Repeated measures ANOVA indicated no significant changes in body composition for any of the groups. Aerobic power increased significantly (P < 0.002) in all groups, independent of supplementation. There were significant trial and group x trial interactions for upper body endurance (P = 0.038) and relative bench press power (P = 0.050). Post-hoc analyses revealed that the C group increased upper body endurance (P = 0.006), but none of the pre- to post-test changes in bench press power were significant.

CONCLUSIONS

These results suggest that chromium picolinate supplementation coupled with a typical preseason training program does not enhance body composition or performance variables beyond improvements seen with training alone.

Chromium, glucose tolerance, and diabetes

Chromium functions in maintaining normal glucose tolerance primarily by regulating insulin action. In the presence of optimal amounts of biologically active chromium, much lower amounts of insulin are required. Glucose intolerance, related to insufficient dietary chromium, appears to be widespread. Improved chromium nutrition leads to improved sugar metabolism in hypoglycemics, hyperglycemics, and diabetics.

Chromium in the elderly

Several studies indicate that glucose tolerance improves and lipid levels decline in the elderly after supplementation with Cr-rich brewer's yeast or inorganic Cr. Other studies report equivocal results or no changes. Interpretation of these investigations is hampered by 1. Lack of a marker to identify Cr-deficient people 2. Artifactually high levels of dietary and body Cr, owing to inadequate analytic techniques and 3. The interplay of chronic health problems, medications, institutionalization, and dietary practices. Investigators have studied the effects of aging on Cr in the body. In the rat, tissue retention of 51Cr decreases, and organ distribution changes with age. In humans, plasma Cr levels of healthy elderly subjects are not different from those of young adults. There is no evidence of malabsorption in aged humans or animals. Nevertheless, higher urinary Cr losses are reported in elderly people. These data suggest that Cr retention may decrease with aging and that aging may alter Cr metabolism. Diets of many healthy elderly people contain less than 30 micrograms Cr. Two elderly men living under controlled conditions maintained Cr balance with 37 micrograms/d. However, these levels may be insufficient during the stresses and illnesses associated with aging.