Effects of chromium and yeast supplements on carbohydrate and lipid metabolism in diabetic men

The role of chromium supplementation in cardiovascular risk factors: A comprehensive reviews of putative molecular mechanisms

In the recent years, micronutrients play an important role in improving body health with preventing and treating of chronic diseases. Chromium is one of the vital minerals involved in the regulation of insulin action. According to abundant evidences this mineral seems to be an essential factor involved in the reduction of insulin resistance and decreasing the risk of type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVDs). Moreover, it has been proposed that Chromium supplementation affects mechanisms involved in blood pressure, lipid metabolism, inflammation, and oxidative stress. For instance, it may affect blood pressure through alteration of the renin-angiotensin system, as well as reducing the angiotensin-converting enzyme activity. Furthermore, Chromium supplementation might help reduce the coronary heart disease rates. This study aims to provide a comprehensive review regarding to the effects of Chromium supplementation on CVDs risk factors with an emphasis on possible molecular mechanisms.

Effects of chromium supplementation on lipid profile in patients with type 2 diabetes: A systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

The purpose of this study was to determine the influence of chromium supplementation on lipid profile in patients with type 2 diabetes mellitus (T2DM).

METHODS

A systematic search was performed in Scopus, Embase, Web of Science, the Cochrane library and PubMed databases to find randomized controlled trials (RCTs) related to the effect of chromium supplementation on lipid profile in patients with T2DM, up to June 2020. Meta-analyses were performed using the random-effects model, and I² index was used to evaluate heterogeneity.

RESULTS

The primary search yielded 725 publications. 24 RCTs (with 28 effect size) were eligible. Our meta-analysis indicated that chromium supplementation resulted in a significant decrease in serum levels of triglyceride (TG) (MD: -6.54 mg/dl, 95 % CI: -13.08 to -0.00, P = 0.050) and total cholesterol (TC) (WMD: -7.77 mg/dl, 95 % CI: -11.35 to -4.18, P < 0.001). Furthermore, chromium significantly increases high-density lipoprotein (HDL) (WMD: 2.23 mg/dl, 95 % CI: 0.07-4.40, P = 0.043) level. However, chromium supplementation did not have significant effects on low-density lipoprotein (LDL) (WMD: -8.54 mg/dl, 95 % CI: -19.58 to 2.49, P = 0.129) level.

CONCLUSION

Chromium supplementation may significantly improve lipid profile in patients with T2DM by decreasing TG and TC and increasing HDL. However, based on our analysis, chromium failed to affect LDL. It should be noted that the lipid-lowering properties of chromium supplementation were small and may not reach clinical importance.

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.

The effects of chromium supplementation on lipidprofile in humans: A systematic review and meta-analysis ofrandomized controlled trials

BACKGROUND AND AIM

This systematic review and meta-analysis aimed to evaluate the effects of chromium supplementation on lipid profile consisting of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and very low-density lipoprotein (VLDL) in humans.

METHODS

The PubMed/Medline, Scopus, Web of sciences, Google Scholar and Cochrane library were systematically searched for randomised control trails (RCTs) available which published before August 2020. The meta-analysis was conducted using Random or fixed-effects models, and between-study heterogeneity was assessed by I².

RESULTS

Thirty-eight studies comprising 41 treatment arms and 7605 participants included to the present meta-analysis. Our results of overall analysis show only a significant reduction in serum TC level in response to chromium supplementation (WMD: -0.17 mmol/l, 95 % CI: -0.27, -0.07, P = 0.001). In accordance with the results of the subgroup analyses, the lowering-effect of chromium supplementation may be synergist during short-term (less than 12 weeks), low dose (less than 200), diabetics patient, younger adults (less than 54 years) and picolinate and elemental form for TC, older and non-obese subjects (>54 years and ≤ 29 kg/m2, respectively), women, Asian and Australian and picolinate form for TG, short-term, low dose, non-obese subjects, women, and Asian for VLDL, and nicotinate form for HDL-C, but had no effect on LDL-C.

CONCLUSION

Our meta-analysis reveals that there was only an overall significant association between chromium supplementation with decreases in the concentration of TC. Additionally, we found considerable evidence of subgroup analysis that support a significant lowering effect of chromium supplementation on TC, TG and VLDL. Further RCTs with short-term and low dose chromium supplementation in subjects with diabetes are necessitated for a firm conclusion of the lipid-modulating properties.

The effect of chromium supplementation on apolipoproteins: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Apos play a role in lipoprotein metabolism. Several studies have been carried out on the effect of chromium supplement in improving CVD risk factors.

OBJECTIVE

This study is a systematic review and meta-analysis that aimed to investigate the effect of chromium supplementation on Apos levels of human studies.

MATERIALS AND METHODS

We searched PubMed, Scopus up to May 2020 up to September 2019. We retrieved studies from identified articles. The studies' quality was evaluated using Cochrane Risk of Bias Tool. We estimated the effect of chromium supplementation on Apo A, Apo A1, and Apo B by pooling mean and standard deviation (SD) values.

RESULTS

We obtained six trials involving 231 participants. Chromium consumption resulted significantly decreased Apo B while the subjects were ingesting chromium picolinate. Chromium supplementation did not significantly decrease Apo A (WMD: -3.89 mg/dl; 95% CI, -11.96 to 4.18) with no significant heterogeneity (I² = 0.00%, p = 0.37). The serum level of Apo A1 did not statistically change following chromium intervention (WMD: 6.11 mg/dl; 95% CI, -7.01 to 19.23) with no significant heterogeneity (I² = 0.00%, p = 0.68). Chromium supplementation did not significantly decrease Apo B (WMD: 3.81 mg/dl; 95% CI, -5.32 to 12.94). With no significant heterogeneity (I² = 42.3%, p = 0.12).

CONCLUSIONS

The chromium supplement did not have a significant effect on the Apolipoproteins (Apo A, ApoA1 and Apo B).

Chromium Supplementation; Negotiation with Diabetes Mellitus, Hyperlipidemia and Depression

Chromium (Cr) is an essential trace element which found naturally in a daily diet and available in the form of supplementary tablets to boost disorders like diabetes mellitus (DM) and functions like lipid metabolism and beneficial on depression too. Diabetes is one of the most prevalent endocrine diseases or in other words, the most severe metabolic syndrome (MS), which associated with high production of free-radicals which is out of bodies detoxifying machine capacity or high oxidative stress (HOS), vasculitis and elevated lipid profile. many research papers and clinical trials published about the significance of chromium on biological activities, pre and post clinical. For this review research articles, clinical trials, from 1^st Jan'10 to 31^st Dec'18 and refer literature for the biochemical, pharmacological and biological activity of Chromium. Primarily articles gathered from the above search engines. Then precisely according to our aim and goal and regarding designed objectives dismisses similar articles and finally came to 84 articles for the above said period. This review trying to cover the entire picture from what chromium is to the recent updates on their greater role in increasing insulin sensitivity of cells and enhancing lipid metabolism and even recent findings suggest its positive effects including prevention and ameliorating properties on depression. The biological activities, pharmacological features, clinical implications including efficacy and role of chromium compounds on the glycaemic index will be discussed. The outcome of this review is to bring the pros and cons of chromium supplementation along with is safety and toxicity concern beside molecular pathways, biochemistry and clinical trials, all in one comprehensive review.

Comparison of trace element levels after cardiopulmonary bypass between cyanotic and acyanotic patients

Trace elements are essential micronutrients for the human body. In this study, we evaluated the alterations in copper, chromium, manganese, selenium, magnesium, zinc, iron, arsenic, boron, and silicon levels in children with cyanotic and acyanotic CHD who underwent cardiac surgery with cardiopulmonary bypass. Participants were divided into the following three groups: patients acyanotic CHDs (n=34), patients with cyanotic CHDs (n=30), and healthy controls (n=30). Blood samples were collected before the surgery and 1 hour after the sternum was closed. Serum trace elements were determined by Inductively Coupled Plasma Optical Emission Spectrometer-ICAP 6000. The baseline serum arsenic, manganese, and zinc levels of both patient groups were lower compared with controls, but there was no significant difference between baseline serum trace element levels of cyanotic and acyanotic patients. In both the patient groups, there was a significant decrease in postoperative serum arsenic, boron, copper, and zinc levels, and a significant increase in postoperative serum iron and magnesium levels. Silicon levels increased in cyanotic patients. Alterations in trace element levels were in the same direction in cyanotic and acyanotic patients. Copper, zinc, and manganase replacement may be needed after on-pump cardiac surgery.

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.

Probiotic supplementation for management of cardiovascular risk factors in adults with type II diabetes: A systematic review and meta-analysis

BACKGROUND & AIMS

The effectiveness of probiotics in control of hypertension and dyslipidemia in diabetic patients remains unclear. Therefore, we systematically reviewed relevant data to elucidate the effects of probiotics on blood pressure and lipid profile of type 2 diabetic patients.

METHODS

We searched PubMed, ISI Web of Knowledge, Scopus, The Cochrane Library, ClinicalTrials.gov, ProQuest Dissertations and Theses databases until May 2016. The primary outcomes were systolic blood pressure (SBP) and diastolic blood pressure (DBP), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG). Other biochemical response and adverse effects were considered as secondary outcomes. Data was extracted from included studies and pooled in meta-analysis whenever possible (both standardized mean difference (SMD) analysis and weighted mean difference (WMD) analysis were performed).

RESULTS

Eleven eligible randomized controlled trial (n = 641) were identified. Pooling data from these trials demonstrated probiotic consumption significantly decreased SBP (WMD, -3.28 mmHg; 95% confidence interval [CI], -5.38 to -1.18), DBP (WMD, -2.13 mmHg; 95% CI, -4.5 to 0.24), LDL-C (WMD, 8.32 mg/dl; 95% CI, -15.24 to -1.4), TC (WMD, -12.19 mg/dl; 955 CI -17.62 to -6.75) and TG (WMD, -24.48 mg/dl; 95% CI, -33.77 to -11.18) in type 2 diabetic patients compared with placebo. The methodological quality varied across trials included in this study.

CONCLUSION

This systematic review suggests probiotics supplementation may be helpful for control of dyslipidemia and hypertension in type 2 diabetic patients. Conducting more trails with large sample size and long follow-up time still is necessary to develop clinical practice guidelines for management of cardiovascular risk factors in patient with type 2 diabetes.

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.

The effect of a cinnamon-, chromium- and magnesium-formulated honey on glycaemic control, weight loss and lipid parameters in type 2 diabetes: an open-label cross-over randomised controlled trial

PURPOSE

This randomised controlled trial assessed the acute and long-term effects of daily supplementation of kanuka honey, formulated with cinnamon, chromium and magnesium on glucose metabolism, weight and lipid parameters in individuals with type 2 diabetes.

METHODS

Twelve individuals with type 2 diabetes received 53.5 g of a formulated honey and a control (non-formulated) kanuka honey in a random order for 40 days, using cross-over design. Fasting glucose, insulin, HbA1c, lipids and anthropometric measures were measured at baseline and end of treatment. A meal tolerance test was performed at baseline to assess acute metabolic response.

RESULTS

There was no statistically significant difference in acute glucose metabolism between treatment groups, as measured by the Matsuda index and AUC for glucose and insulin. After the 40-day intervention with honey, fasting glucose did not differ significantly between the two treatments (95 % CI -2.6 to 0.07). There was no statistically significant change in HbA1c or fasting insulin. There was a statistically significant reduction in total cholesterol by -0.29 mmol/L (95 % CI -0.57 to -0.23), LDL cholesterol by -0.29 mmol/L (95 % CI -0.57 to -0.23) and weight by -2.2 kg (95 % CI -4.2 to -0.1). There was a trend towards increased HDL and reduced systolic blood pressure in the intervention treatment.

CONCLUSION

The addition of cinnamon, chromium and magnesium supplementation to kanuka honey was not associated with a significant improvement in glucose metabolism or glycaemic control in individuals with type 2 diabetes. Use of the formulated honey was associated with a reduction in weight and improvements in lipid parameters, and should be investigated further.

Chromium does not belong in the diabetes treatment arsenal: Current evidence and future perspectives

Chromium is considered to have positive effects on insulin sensitivity and is marketed as an adjunctive therapy for inducing glucose tolerance in cases of insulin resistance (“the glucose tolerance factor”). Case reports on patients who received prolonged parenteral nutrition indeed showed that the absence of trivalent chromium caused insulin resistance and diabetes. However, whether patients with type 2 diabetes can develop a clinically relevant chromium deficiency is unclear. This review summarizes the available evidence regarding the potential effectiveness of chromium supplementation on glycemic control (Hemoglobin A1c levels) in patients with type 2 diabetes. No studies investigating the long-term safety of chromium in humans were found. All clinical trials that have been performed had a relative short follow-up period. None of the trials investigated whether the patients had risk factors for chromium deficiency. The evidence from randomized trials in patients with type 2 diabetes demonstrated that chromium supplementation does not effectively improve glycemic control. The meta-analyses showed that chromium supplementation did not improve fasting plasma glucose levels. Moreover, there were no clinically relevant chromium effects on body weight in individuals with or without diabetes. Future studies should focus on reliable methods to estimate chromium status to identify patients at risk for pathological alterations in their metabolism associated with chromium deficiency. Given the present data, there is no evidence that supports advising patients with type 2 diabetes to take chromium supplements.

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.

Chromium picolinate supplementation for overweight or obese adults

BACKGROUND

Obesity is a global public health threat. Chromium picolinate (CrP) is advocated in the medical literature for the reduction of bodyweight, and preparations are sold as slimming aids in the USA and Europe, and on the Internet.

OBJECTIVES

To assess the effects of CrP supplementation in overweight or obese people.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, ISI Web of Knowledge, the Chinese Biomedical Literature Database, the China Journal Full text Database and the Chinese Scientific Journals Full text Database (all databases to December 2012), as well as other sources (including databases of ongoing trials, clinical trials registers and reference lists).

SELECTION CRITERIA

We included trials if they were randomised controlled trials (RCT) of CrP supplementation in people who were overweight or obese.We excluded studies including children, pregnant women or individuals with serious medical conditions.

DATA COLLECTION AND ANALYSIS

Two authors independently screened titles and abstracts for relevance. Screening for inclusion, data extraction and 'Risk of bias'assessment were carried out by one author and checked by a second. We assessed the risk of bias by evaluating the domains selection,performance, attrition, detection and reporting bias. We performed a meta-analysis of included trials using Review Manager 5.

MAIN RESULTS

We evaluated nine RCTs involving a total of 622 participants. The RCTs were conducted in the community setting, with interventions mainly delivered by health professionals, and had a short- to medium-term follow up (up to 24 weeks). Three RCTs compared CrPplus resistance or weight training with placebo plus resistance or weight training, the other RCTs compared CrP alone versus placebo.We focused this review on investigating which dose of CrP would prove most effective versus placebo and therefore assessed the results according to CrP dose. However, in order to find out if CrP works in general, we also analysed the effect of all pooled CrP doses versus placebo on body weight only.Across all CrP doses investigated (200 μg, 400 μg, 500 μg, 1000 μg) we noted an effect on body weight in favour of CrP of debatable clinical relevance after 12 to 16 weeks of treatment: mean difference (MD) -1.1 kg (95% CI -1.7 to -0.4); P = 0.001; 392 participants;6 trials; low-quality evidence (GRADE)). No firm evidence and no dose gradient could be established when comparing different doses of CrP with placebo for various weight loss measures (body weight, body mass index, percentage body fat composition, change in waist circumference).Only three studies provided information on adverse events (low-quality evidence (GRADE)). There were two serious adverse events and study dropouts in participants taking 1000 μg CrP, and one serious adverse event in an individual taking 400 μg CrP. Two participants receiving placebo discontinued due to adverse events; one event was reported as serious. No study reported on all-cause mortality,morbidity, health-related quality of life or socioeconomic effects.

AUTHORS' CONCLUSIONS

We found no current, reliable evidence to inform firm decisions about the efficacy and safety of CrP supplements in overweight or obese adults.

Effect of chromium-enriched yeast on fasting plasma glucose, glycated haemoglobin and serum lipid levels in patients with type 2 diabetes mellitus treated with insulin

Chromium is required for a normal insulin function, and low levels have been linked with insulin resistance. The aim of this study was to follow the effect of chromium supplementation on fasting plasma glucose (FPG), glycated haemoglobin (HbA1c) and serum lipids in patients with type 2 diabetes mellitus (DM2) on insulin therapy. Eleven randomly selected patients with DM2 on insulin therapy were supplemented with a daily dose of 100 μg chromium yeast for the first supplementation period of 2 weeks. In the second supplementation period, the chromium dose was doubled and continued for the next 6 weeks. The third phase was a 6-week washout period. After each period, the levels of FPG and HbA1c were compared with the corresponding values at the end of the previous period. Serum triglycerides, total HDL and LDL cholesterol values after supplementation were compared with the baseline values. FPG decreased significantly after the first period of chromium supplementation (p < 0.001), and a tendency to a further reduction was observed after the second supplementation period. Similarly, HbA1c decreased significantly in both periods (p < 0.02 and p < 0.002, respectively). Eight weeks after withdrawal of chromium supplementation, both FPG and HbA1c levels returned to their pre-intervention values. The serum lipid concentrations were not significantly influenced by chromium supplementation. Chromium supplementation could be beneficial in patients with DM2 treated with insulin, most likely due to lowered insulin resistance leading to improved glucose tolerance. This finding needs to be confirmed in a larger study.

Alternative and complementary treatments for metabolic syndrome

Metabolic syndrome is defined by a cluster of cardiovascular disease risk factors that are associated with insulin resistance. In recent years, a number of innovative nutritional strategies have been proposed as safe alternative treatments to reduce the morbidity as well as the cost of treating metabolic syndrome. Of these, dietary supplementation with chromium picolinate or cinnamon extract has been studied most extensively. These interventions may attenuate insulin resistance and reduce the cardiovascular risk factors that together comprise the metabolic syndrome. However, more clinical trials are needed to determine the dose and duration of such treatments to make specific recommendations for populations with metabolic syndrome.

Trace elements in glucometabolic disorders: an update

Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed.

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.

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.

Effects of chromium supplementation on selected metabolic responses in resting and exercising horses

Chromium (Cr) is required for insulin function in the control of cellular glucose uptake. Other functions of Cr relate to its effects on growth, lipid metabolism, immune responses and interactions with nucleic acids. This study was conducted to obtain information on the effect of Cr supplementation on the metabolic responses of five exercising Standardbred horses. During the experiment, horses were fed every day for a 21-day period in a randomized order either a yeast product without Cr (control) or with 4.15 or 8.3 mg Cr day−1. Horses were exercised on a treadmill, alternating a work day of low-speed exercise at 5 m s−1 on a 3% incline for 45 min with a rest day. Each horse was adapted over a 21-day period to his or her respective supplementation before undergoing a standardized exercise test (SET). The SET comprised five incremental steps, each of 4 min duration, on a treadmill with a 3% incline; the first step was at 5 m s−1 and was followed with increments of 1 m s−1. Blood samples were taken for lactate, plasma glucose, serum insulin and cortisol estimation before, during and after each SET (30, 120 min and 24 h post-exercise). Blood Cr was estimated 2 h after feeding the control or Cr-enriched yeast (intake 8.3 mg Cr) in two horses. Heart rate was monitored throughout each SET. Blood lactate and plasma glucose peaks were highest at 8 and 9 m s−1 during the SET when 8.3 mg Cr was supplied. Serum insulin levels declined during the SET and there were no treatment-related changes. Twenty-four hours after exercise, plasma glucose and serum cortisol concentrations returned to basal levels or lower. Serum insulin rebounded 30 min after exercise but 24 h later, serum insulin concentrations were below resting levels. During the recovery period, Cr supplementation did not clearly affect metabolic responses. These results suggest that Cr supplementation had no beneficial effect in healthy, exercising horses.

Clinical studies on chromium picolinate supplementation in diabetes mellitus--a review

Chromium (Cr) picolinate (CrPic) is a widely used nutritional supplement for optimal insulin function. A relationship among Cr status, diabetes, and associated pathologies has been established. Virtually all trials using CrPic supplementation for subjects with diabetes have demonstrated beneficial effects. Thirteen of 15 clinical studies (including 11 randomized, controlled studies) involving a total of 1,690 subjects (1,505 in CrPic group) reported significant improvement in at least one outcome of glycemic control. All 15 studies showed salutary effects in at least one parameter of diabetes management, including dyslipidemia. Positive outcomes from CrPic supplementation included reduced blood glucose, insulin, cholesterol, and triglyceride levels and reduced requirements for hypoglycemic medication. The greater bioavailability of CrPic compared with other forms of Cr (e.g., niacin-bound Cr or CrCl(3)) may explain its comparatively superior efficacy in glycemic and lipidemic control. The pooled data from studies using CrPic supplementation for type 2 diabetes mellitus subjects show substantial reductions in hyperglycemia and hyperinsulinemia, which equate to a reduced risk for disease complications. Collectively, the data support the safety and therapeutic value of CrPic for the management of cholesterolemia and hyperglycemia in subjects with diabetes.

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

The aim of this study is to evaluate the effect and safety of chromium-containing milk powder in patients with type 2 diabetes mellitus. A randomized, double-blind, placebo-controlled trial was conducted in Taiwan. A total of 60 patients with type 2 diabetes mellitus, aged 30 to 75 years, and on a dose of gliclazide sulfonylurea agent (< or =160 mg/d) for at least 3 months were enrolled. Their glycosylated hemoglobin ranged from 7.5% to 12%, fasting plasma glucose (FPG) from 140 to 250 mg/dL, and body mass index from 20 to 35 kg/m(2). The subjects were divided into 2 groups, one group to receive chromium-containing milk powder (chromium 200 microg/20 g milk powder) and the other to receive placebo twice a day for 16 weeks. Frequently sampled intravenous glucose tolerance test (IVGTT) was performed before and after treatment. The chromium group demonstrated a lower FPG and fasting insulin (-38.1 +/- 9.2 vs 63 +/- 8. 5 mg/dL and -1.7 +/- 0.2 vs 1.9 +/- 0.3 microU/mL, respectively; P < .05), especially in male patients (-41 +/- 9.2 vs 85 +/- 11.7 mg/dL and -2.7 +/- 0.2 vs 3.1 +/- 0.3 microU/mL, respectively; P < .01), at the end of the study. Lower glycosylated hemoglobin was observed in chromium-treated male patients (-1.1 +/- 0. 5 vs 0.7 +/- 0. 2; P < .05). However, there were no significant changes in other metabolic parameters (lipid profiles including total cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol), except improvement of insulin resistance (homeostasis model assessment for insulin resistance and insulin sensitivity index from frequently sampled intravenous glucose tolerance test) observed in male patients (-2.1 +/- 1.1 vs -0.41 +/- 1.12 and 0.18 +/- 0.11 vs -0.15 +/- 0. 2, respectively; P < .05). There were no adverse events in both groups, except for mild complaints in the chromium group on constipation (5%) and flatulence (5%). Intake of milk powder containing 400 microg/d of chromium for 16 weeks in subjects with type 2 diabetes mellitus resulted in lowering of FPG, fasting insulin, and improvement of metabolic control in male patients.

Chromium as adjunctive treatment for type 2 diabetes

OBJECTIVE

To review the chemistry, pharmacology, efficacy, and safety of trivalent chromium in the treatment of type 2 diabetes and hyperlipidemia.

DATA SOURCES

The English literature was searched from 1966 through May 2002 using MEDLINE, International Pharmaceutical Abstracts, and EMBASE. The key words included chromium, glucose, lipids, and diabetes. Pertinent references from review articles and studies were used as additional sources.

DATA SYNTHESIS

Trivalent chromium is an essential nutrient and has a key role in lipid and glucose metabolism. Supplementation with chromium does not appear to reduce glucose levels in euglycemia. It may, however, have some efficacy in reducing glucose levels in hyperglycemia. The effects of chromium on lipid levels are variable. Chromium in doses <1000 microg/d appears to be safe for short-term administration. Kidney function and dermatologic changes need to be monitored.

CONCLUSIONS

Chromium appears to be a safe supplement and may have a role as adjunctive therapy for treatment of type 2 diabetes. Additional large-scale, long-term, randomized, double-blind studies examining the effect of various doses and forms of chromium are needed.

Natural products used for diabetes

OBJECTIVE

To review the efficacy and safety of natural products commonly used for diabetes.

DATA SOURCES

English and Spanish-language journals retrieved through a MEDLINE search of articles published between 1960 and December 2001 using these index terms: Opuntia, karela, gymnema, tecoma, alpha lipoic acid, thioctic acid, ginseng, panaxans, and diabetes.

DATA SYNTHESIS

Natural products have long been used in traditional systems of medicine for diabetes. Products in common use include nopal (prickly pear cactus), fenu-greek, karela (bitter melon), gymnema, ginseng, tronadora, chromium, and alpha-lipoic acid. The popularity of these products varies among people of different ethnicities. Nopal is the most commonly used herbal hypoglycemic among persons of Mexican descent. Karela is more commonly used by persons from Asian countries. Some of these agents have gained universal appeal. For a select number of products, studies have revealed single or multiple mechanisms of action. For several of these, high soluble fiber content is a contributing factor.

CONCLUSION

Based on the available evidence, several natural products in common use can lower blood glucose in patients with diabetes. Commonly used natural products often have a long history of traditional use, and pharmacists who have a stronger understanding of these products are better positioned to counsel patients on their appropriate use.

Oral medications for treating diabetes mellitus in dogs and cats

Five classes of oral hypoglycaemic drugs and two trace minerals used to treat diabetes mellitus in humans are reviewed and current knowledge on the use of these drugs in diabetic dogs and cats is presented. Oral sulphonylurea drugs stimulate insulin secretion and have been used successfully to treat diabetes in cats but not dogs. Preliminary studies evaluating the efficacy of the biguanide, metformin, in diabetic cats have not been promising. Pharmacokinetic studies have been performed in healthy cats, but clinical studies evaluating the efficacy of the insulin-sensitising drugs, thiazolidinediones, have not been reported. Treatment with the alpha-glucosidase inhibitor, acarbose, improved control of glycaemia in diabetic dogs; similar studies have not been reported in cats. Although chromium picolinate did not improve control of glycaemia in diabetic dogs, vanadium has improved control of the abnormality in diabetic cats.

Effects of chromium picolinate supplementation on insulin sensitivity, serum lipids, and body composition in healthy, nonobese, older men and women

BACKGROUND

Chromium is an essential nutrient required for carbohydrate and lipid metabolism. Chromium supplementation in humans has been reported to improve glucose metabolism and improve serum lipid parameters and to reduce body fat; parameters that worsen with aging. As a result, chromium picolinate has been widely promoted as a health aid for the general population. The purpose of the study was to examine the effects of chromium supplementation on insulin sensitivity, serum lipids, and body composition in nonobese, healthy men and women of advanced age.

METHODS

A randomized, double-blind, placebo-controlled study with 19 subjects (9 men and 10 women), aged 63-77, were given either chromium picolinate, 1,000 microg/d, or a placebo for 8 weeks. Serum lipids were measured at baseline and 8 weeks. Insulin sensitivity and body composition were measured with the minimal-model intravenous glucose tolerance test and dual-energy x-ray absorptiometry scan, respectively, at baseline and after 8 weeks of chromium or placebo supplementation.

RESULTS

No significant change in serum lipids, insulin sensitivity, or body composition was observed in the chromium group compared with the placebo group.

CONCLUSIONS

Chromium picolinate supplementation alone does not appear to improve insulin sensitivity, serum lipids, or change body composition in nonobese, healthy men and women of advanced age.

Chromium status of tannery workers in relation to metabolic disorders

Chromium (Cr), being an excellent tanning agent, is widely used in the leather industry. In the process of leather production, tannery workers are exposed to either inorganic Cr(III) compounds or Cr bound to proteins (leather dust). The total Cr content in tannery air (1-54 microg m(-3)) is rather high in comparison to ambient air (4-6 ng m(-3)) but the amount of Cr in inhalable particles (<10 microm) is two to three orders of magnitude less (20-60 ng m(-3)). The total daily intake of Cr was estimated by the analysis of diet (24.3 +/- 4.0 microg Cr day(-1)), drinking water (0.3 +/- 0.1 microg Cr dm(-3)) and ambient air. The contribution of the latter was dominant for tannery workers and almost negligible (8%) for the unexposed population. Chromium is an essential nutrient required for sugar and fat metabolism. The normal dietary intake of Cr for the occupationally unexposed population is found to be suboptimal (<30 microg Cr day(-1)) whereas tannery workers receive on average 150-325 microg of supplemental Cr day(-1). Assessment of the Cr status of both populations was made on the basis of the Cr contents of their scalp hair, pre-shift urine and thermally induced sweat. The median Cr contents in these tissues and fluids were significantly higher (P<0.01) in tannery workers (hair: 4 microg Cr g (-1), urine: Cr/creatinine 1.7 microg Cr g(-1), sweat: 25 microg Cr dm(-3)) in comparison with the control group (hair: 0.16 microg Cr g(-1), urine: Cr/creatinine 0.13 microg Cr g (-1), sweat: 0.7 microg Cr dm(-3)). Tannery workers absorbed up to 13 times more Cr in comparison to controls, the amount varying considerably depending on the workplace and duration of exposure. The main route of Cr absorption appears to be through the gastrointestinal tract, where medium to large particles play a dominant role. The absorption of Cr from leather dust may be more efficient in comparison to inorganic Cr(III) compounds. Under normal circumstances sweat Cr losses represent at least 20% of urinary Cr excretion. The incidence of glucose intolerance and disturbed lipid metabolism was compared between the unexposed (control) population (n=150) and a population of tannery workers (n=138) from the same residential area. The percentage of glucose-intolerant subjects was significantly (P<0.01) lower in the older subgroup (age>48 years), who were even more obese, but not in the whole tannery population in comparison to controls. In the group of subjects displaying glucose intolerance, those from the control population showed a significantly higher body mass index (BMI) of 32.3 and a considerably larger proportion of females (86%) in comparison to subjects from the tannery population (28.2 and 60%, respectively). There was no significant difference in total serum cholesterol levels between the groups. Results of other lipid variables, such as high-density lipid (HDL) cholesterol, low-density lipid (LDL) cholesterol and triglycerides, are controversial: namely, the HDL/LDL ratio was higher for the controls, who showed in contrast significantly higher serum triglyceride levels in comparison to the older subgroup of tannery workers. The possible effects of other parameters on serum HDL-cholesterol level are outlined but the influence of Cr on lipid metabolism in tannery workers remains unclear.

Oxidative stress, mitochondrial respiration, and glycemic control: clues from chronic supplementation with Cr3+ or As3+ to male Wistar rats

Multiple experiments in male Wistar rats were designed to clarify the role of mitochondrial dysfunction in the mechanisms of oxidative stress-related diseases and toxicity-induced pathologies. In this particular report, 21 male Wistar rats were supplemented ad libitum with either As3+ or Cr3+ salts in drinking water to assess insulin secretion patterns in vivo and in vitro, mitochondrial dysfunction, oxidative stress, liver damage, basal insulin, and glucose tolerance curves, among other parameters. Results were compared with a control group without any metal supplementation. The CrCl3 supplements were more invasive of metabolism and had a stronger effect on mitochondrial dysfunction than As3+, despite that both seem to use similar mechanisms of toxicity; viz.: binding to thiol or -SS- group in enzymes and proteins, and releasing oxidant species during their redox-cycling and metabolic activation processes, e.g., by cytochrome P450 in liver. Results support our aim to prove the influence of oxidative stress-induced mitochondrial dysfunction on glycemic control.

Effects of chromium supplementation on fasting insulin levels and lipid parameters in healthy, non-obese young subjects

Trivalent chromium is an essential trace element for normal carbohydrate metabolism and insulin sensitivity. Because of this biological activity, chromium supplementation has been studied as a potential therapy of insulin resistant states and dyslipidemias, and has been promoted as a health aid to the general population. To determine if there is a risk of subclinical chromium deficiency in young, otherwise healthy adults, we evaluated the effect of chromium supplementation, versus placebo, on insulin levels and serum lipids in a double-blind, randomized trial in 26 young adults (mean age 36 years). Fasting levels of glucose, immunoreactive insulin (IRI), and lipids (total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides) were measured before and after 90 days of daily supplementation with a chromium (III)-nicotinate preparation, containing 220 micrograms elemental chromium, or placebo. There were no statistically significant differences in the percentage change of fasting glucose, IRI or lipids between the chromium (n = 15) and placebo (n = 11) groups after 90 days of supplementation. However, those individuals within the chromium group with initial fasting IRI levels greater than 35 pmol/l had a significant decrease in IRI level after supplementation (P < 0.03) despite no significant changes in serum lipids. These subjects may benefit from chromium supplementation by improving insulin sensitivity and cardiovascular risk over time.

Chromium supplementation in impaired glucose tolerance of elderly: effects on blood glucose, plasma insulin, C-peptide and lipid levels

Altogether twenty-six elderly subjects (aged 65-74 years) with persistent impaired glucose tolerance (World Health Organization (1985) criteria) identified in a population-based study, were randomly treated either with chromium-rich yeast (160 micrograms Cr/d) or with placebo for 6 months. The 24 h urinary Cr increased from 0.13 (SE 0.03) to 0.40 (SE 0.06) micrograms/d in the Cr group (n 13) but no change was found in the placebo group (n 11) (0.13 (SE 0.02) v. 0.11 (SE 0.02) micrograms/d). No significant change was observed in the oral glucose tolerance test (glucose dose 75 g; 0, 1 and 2 h blood glucose respectively): 5.3 (SE 0.1), 9.3 (SE 0.3), 8.2 (SE 0.3) mmol/l v. 5.0 (SE 0.1), 8.5 (SE 0.4), 7.3(SE 0.5) mmol/l in the Cr group; 4.9 (SE 0.2), 9.2 (SE 0.6), 8.1 (SE 0.3) mmol/l v. 4.8 (SE 0.2), 8.5 (SE 0.5), 7.0 (SE 0.6) mmol/l in the placebo group (baseline v. 6 months). Glycosylated haemoglobin, plasma insulin, C-peptide and apolipoprotein A1 and B levels remained unchanged, and no improvement was seen in serum total cholesterol (6.2 (SE 0.3) v. 6.4 (SE 0.3) mmol/l for the Cr group, 6.2 (SE 0.4) v. 6.5 (SE 0.3) mmol/l for the placebo group), high-density-lipoprotein-cholesterol (1.1 (SE 0.1) v. 1.2 (SE 0.1) mmol/l for the Cr group, 1.0 (SE 0.1) v. 1.1 (SE 0.1) mmol/l for the placebo group) or triacylglycerols (2.5 (SE 0.4) v. 2.0 (SE 0.4) mmol/l for the Cr group, 2.4 (SE 0.2) v. 2.5 (SE 0.2) mmol/l for the placebo group). The present results indicate that Cr supplementation does not improve glucose tolerance or serum lipid levels in elderly subjects with stable impaired glucose tolerance.

Effect of chromium administration on glucose tolerance in stroke-prone spontaneously hypertensive rats with streptozotocin-induced diabetes

The present study was conducted to assess the effect of chromium (Cr) administration on glucose tolerance in insulin-dependent diabetes that accompanies hypertension. Four rat groups were used: stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY) with and without streptozotocin (SZ, 40 mg/kg)-induced diabetes. Each group of rats was subdivided to the Cr-dose group and the control group. The Cr-dose group, which was intraperitoneally administered Cr solution (20 micrograms trivalent chromium/kg body weight/d for 4 weeks), and the control group (saline) were studied for plasma glucose and plasma insulin during intraperitoneal glucose tolerance test (IPGTT) and insulin action by isolated adipocytes. For diabetic SHRSP showing the highest plasma glucose and lowest plasma insulin among the four groups, Cr administration led to the greatest reduction in plasma glucose without a significant effect on plasma insulin during IPGTT. For each diabetic WKY and normal SHRSP and WKY, those given Cr showed lower levels of plasma glucose with lower levels of plasma insulin than the controls. For diabetic SHRSP, glucose uptake by isolated adipocytes in the Cr-dose group was higher than that in the control group. This effect of Cr administration involved enhancement of insulin responsiveness and sensitivity, attributed to enhanced affinity of the insulin receptor. A similar tendency was observed for diabetic WKY. However, for normal SHRSP and WKY, the increase in glucose uptake due to Cr administration coincided only with enhanced insulin responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

A fraction derived from brewer's yeast inhibits cholesterol synthesis by rat liver preparations in vitro

Brewer's yeast was grown on a defined medium containing tracer 51Cr with or without added chromium. The two batches of yeast contained 10 microgram/g (high-Cr) or 80 ng/g (low-Cr). Extracts were prepared and fractionated. A third batch of yeast (third batch) was grown with added Cr, and fractionated. Rats were reared on either rat cubes (normal diet) or on a low-Cr diet (low-Cr), or on rat cubes with added cholestyramine (cholestyramine diet). Preparations of rat liver, both cell-free and intact hepatocytes, incorporated acetate-carbon into fatty acids and cholesterol. These processes were inhibited by a yeast fraction containing small, neutral, water-soluble compounds. The degree of inhibition was the same whether the liver came from normal rats or rats fed on the low-Cr diet. Similarly the inhibitory effect was found with identical amounts of extracts from low- or high-Cr yeasts. Therefore, Cr compounds do not appear to account for the inhibitory effects of brewer's yeast. Use of other substrates indicated that the site of inhibition of sterol synthesis was apparently between acetyl-CoA and mevalonate. One inhibitory substance was isolated from yeast and was found to be nicotinamide riboside. This may have been produced from NAD(P) during the preparation of yeast extracts, and it may be produced from dietary yeast supplements during digestion in vivo. Nicotinamide riboside may be partly responsible for the reported effects of yeast supplements on plasma lipids in humans.

Serum insulin and serum lipid profiles of a selected group of southern Ontario tannery workers with elevated serum and urine chromium concentrations

This study compares the serum insulin and lipid profiles of a group of Southern Ontario tannery workers, with elevated serum and urine Cr levels, with those of men not exposed to industrial chromium (III) oxide. Fasting blood samples were obtained from 72 male tannery workers (TW) (mean age +/- SD = 36 +/- 12 y) and from 52 control subjects (CS) (mean age +/- SD = 41 +/- 13 y), matched by age, sex, race, and socioeconomic group. There were no significant differences between the two groups for median serum insulin (TW = 8 microM/mL vs CS = 9 microM/mL), total cholesterol (TC) (TW = 201 mg/dL vs CS 209 mg/dL), triglycerides (TG) (TW = 131 mg/dL vs 114 mg/dL) and high density lipoprotein cholesterol (HDL-C) (TW = 45 mg/dL vs CS = 43 mg/dL), or, in the calculated median values for low density lipoprotein cholesterol (TW = 117 mg/dL vs CS = 134 mg/dL), percent HDL-C (TW = 23% vs CS = 22%), and the cholesterol atherogenic ratio (TC/HDL-C) (TW = 4.3 vs CS = 4.5). Results of this study, therefore, demonstrate that absorption of trivalent Cr compounds, arising from industrial exposure, has no significant effect on serum insulin and lipid profiles.

Evidence for synergism between chromium and nicotinic acid in the control of glucose tolerance in elderly humans

Impaired glucose tolerance results from Cr restriction in animals, and Cr supplementation improves glucose tolerance in diabetic animals. These effects are presumably due to the role of Cr in glucose tolerance factor (GTF), a complex of Cr and nicotinic acid believed to facilitate insulin binding. Humans, however, do not uniformly respond to Cr supplementation. The present study was designed to evaluate the possibility that the failure results from inadequate levels of dietary nicotinic acid to serve as substrate for GTF synthesis. Sixteen healthy elderly volunteers were divided into three groups and given either 200 micrograms Cr, 100 mg nicotinic acid, or 200 micrograms Cr + 100 mg nicotinic acid daily for 28 days and evaluated on days 0 and 28. Fasting glucose and glucose tolerance were unaffected by either chromium or nicotinic acid alone. In contrast, the combined chromium-nicotinic acid supplement caused a 15% decrease in a glucose area integrated total (p less than .025) and a 7% decrease in fasting glucose. None of the treatments exerted any effect on fasting or one-hour insulin levels. Thus, these data suggest that the inability to respond to chromium supplementation may result from suboptimal levels of dietary nicotinic acid.

Nutritional contributors to cardiovascular disease in the elderly

Cardiovascular disease, so common in the elderly, has become an urgent public health concern. Major contributing factors include hypertension, dyslipidemia, impaired glucose tolerance, physical indolence, and cigarette smoking. Diet plays a major role in atherogenesis by its influence in blood lipids, blood pressure, and glucose tolerance, although its impact in the elderly is speculative owing to a paucity of direct evidence. But a rationale exists. Most cardiovascular risk factors are more prevalent in the elderly than in the young adult. The rise in blood pressure and blood lipids with advancing age is not inevitable. Diet may contribute to hypertension through an excess of calories, saturated fat, cholesterol, or salt and a deficiency of potassium, calcium, and magnesium. Antiatherogenic diets low in saturated fat and cholesterol, rich in fiber, and with substitution of polyunsaturated fat and restricted calories tend to normalize serum lipids and to cause lesions to involute. Emphasis on vegetable protein and fiber-rich food has merit because they provide more fiber, polyunsaturated fatty acids, magnesium, selenium, complex carbohydrate, potassium, and copper, and less cholesterol, saturated fat, and sodium. The recommended fat-modified diets are adequate in protein, vitamins, and minerals and need not be deficient in any nutrient or economically nonfeasible. The accelerating decline in cardiovascular mortality, which has included the elderly, indicates that such disease is controllable and not inevitable, even in the elderly. The decrease has occurred concurrently with reduced consumption of saturated fat and cholesterol, increased use of vegetable oils, and improved levels of cardiovascular risk factors.

Effects of potassium chromate on atherosclerosis prevention and regression in rabbits

The effect of intraperitoneal injections of potassium chromate on prevention and regression of atherosclerosis was observed in New Zealand White rabbits. In rabbits fed a 1% cholesterol diet for 90 days, potassium chromate injection was not associated with a significant difference in weight, serum cholesterol, total cholesterol content per 8.5 cm aorta, cholesterol content per gram of aorta or percent intima covered with plaque compared to controls. Similarly, significant differences were not seen in rabbits fed a 1% cholesterol diet for 90 days followed by 60 days of potassium chromate or distilled water injections and a standard diet. These results are in keeping with recent studies suggesting a more limited role for chromium in a variety of lipid-related disorders.

Glucose metabolism in glucose-intolerant older people during chromium supplementation

The effects of chromic chloride (CrCl3) administered orally for 12 weeks to five elderly subjects with glucose intolerance were assessed. Pretreatment and posttreatment, the hyperglycemic clamp technique was employed to determine glucose utilization, beta-cell sensitivity to glucose, and tissue sensitivity to insulin. In addition, erythrocyte insulin binding was studied. Urinary chromium excretion increased approximately 5 fold indicating good compliance with supplementation. The oral glucose tolerance curves following supplementation were lowered from 60 to 120 minutes but only the 60-minute values were significantly lowered. In agreement with this was significantly increased glucose utilization during the hyperglycemic clamp studies. Tissue sensitivity to insulin, receptor affinity, and total insulin binding were unchanged by supplementation while beta-cell sensitivity to glucose increased following supplementation (P less than 0.04), and explained the increased glucose utilization. HDL and LDL and total cholesterol levels were slightly lower after chromium supplementation, but no change reached statistical significance. The LDL/HDL cholesterol ratio was unchanged. This study shows small but statistically significant effects of CrCl3 on carbohydrate metabolism. The clinical relevance of these effects, that is, their prophylactic or therapeutic significance, remains to be determined.