Anti-diabetic activity and mechanism of action of chromium chloride

Is chromium pharmacologically relevant?

Recent research, combined with reanalysis of previous results, has revealed that chromium can no longer be considered an essential trace element. Clinical studies are ambiguous at best as to whether Cr has a pharmacological effect in humans. Observed effects of Cr on rodent models of insulin resistance and diabetes are best interpreted in terms of a pharmacological role for Cr. Studies on the effects of Cr on rat models of diabetes are reviewed herein and suggest Cr increases insulin sensitivity in peripheral tissues of the rodent models. The lack of effects in human studies may stem from humans receiving a comparably smaller dose than the rodent models. However, given the different responses to Cr in the rodent models, humans could potentially have different responses to Cr.

Chromium picolinate attenuates hyperglycemia-induced oxidative stress in streptozotocin-induced diabetic rats

Chromium picolinate is advocated as an anti-diabetic agent for impaired glycemic control. It is a transition metal that exists in various oxidation states and may thereby act as a pro-oxidant. The present study has been designed to examine the effect of chromium picolinate supplementation on hyperglycemia-induced oxidative stress. Diabetes was induced in male Wistar rats by a single intraperitoneal injection of streptozotocin (50mg/kg body weight) and chromium was administered orally as chromium picolinate (1mg/kg body weight) daily for a period of four weeks after the induction of diabetes. As is characteristic of diabetic condition, hyperglycemia was associated with an increase in oxidative stress in liver in terms of increased lipid peroxidation and decreased glutathione levels. The activity of antioxidant enzymes like superoxide dismutase, catalase and glutathione reductase were significantly reduced in liver of diabetic animals. Levels of α-tocopherol and ascorbic acid were found to be considerably lower in plasma of diabetic rats. Chromium picolinate administration on the other hand was found to have beneficial effect in normalizing glucose levels, lipid peroxidation and antioxidant status. The results from the present study demonstrate potential of chromium picolinate to attenuate hyperglycemia-induced oxidative stress in experimental diabetes.

Chromium: is it essential, pharmacologically relevant, or toxic?

Over fifty years ago, the element chromium (as the trivalent ion) was proposed to be an essential element for mammals with a role in maintaining proper carbohydrate and lipid metabolism. Evidence for an essential role came from dietary studies with rodents, studies on the effects of chromium on subjects on total parenteral nutrition, and studies of the absorption and transport of chromium. Over the next several decades, chromium-containing nutritional supplements became so popular for weight loss and muscle development that sales were second only to calcium among mineral supplements. However, the failure to identify the responsible biomolecules(s) that bind chromium(III) and their mode of action, particularly a postulated species named glucose tolerance factor or GTF, resulted in the status of chromium being questioned in recent years, such that the question of its being essential needs to be formally readdressed. At the same time as chromium(III)'s popularity as a nutritional supplement was growing, concerns over its safety appeared. While chromium has been conclusively shown not to have beneficial effects on body mass or composition and should be removed from the list of essential trace elements, chromium(III) compounds are generally nontoxic and have beneficial pharmacological effects in rodents models of insulin insensitivity, although human studies have not conclusively shown any beneficial effects. Mechanisms have been proposed for these pharmacological effects, but all suffer from a lack of consistent supporting evidence.

Favorable effects on metabolic risk factors with daily brewer's yeast in type 2 diabetic patients with hypercholesterolemia: a semi-experimental study

BACKGROUND

The aim of the present study was to investigate the effect of brewer's yeast on plasma glucose and lipid profiles in patients with type 2 diabetes (T2D).

METHODS

The present semi-experimental study was performed on 55 T2D patients with hypercholesterolemia. All patients received 12 tablets of 300 mg yeast per day for 8 weeks. Each tablet contained 1.2 μg chromium. Fasting plasma glucose, total cholesterol, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), and triglyceride levels were measured at baseline and then again at Weeks 4 and 8.

RESULTS

Although there was a tendency for plasma glucose levels to decrease at Week 4, the difference failed to reach statistical significance (P = 0.065). However, after 8 weeks, the decrease in plasma glucose was significant (P = 0.043). Again, although there was a tendency for decreased plasma cholesterol at Week 8 compared with baseline, the difference failed to reach statistical significance (215 ± 29 vs 226 ± 37 mg/dL, respectively; P = 0.056). Brewer's yeast significantly decreased plasma triglyceride and LDL-C levels at Weeks 4 and 8. In contrast, plasma HDL-C levels were significantly increased at both 4 and 8 weeks compared with baseline (41.3 ± 8.8 and 43.3 ± 7.5 vs 36 ± 5 mg/dL, respectively; P < 0.01 and P < 0.01, respectively).

CONCLUSION

In conclusion, the consumption of brewer's yeast over a period of 8 weeks may improve cardiometabolic risk factors in T2D patients. However, these findings need to be confirmed in a large double-blind clinical trial.

Ameliorating effect of chromium administration on hepatic glucose metabolism in streptozotocin-induced experimental diabetes

Chromium has been recognized as an essential trace element that plays an important role in carbohydrate metabolism. However, the molecular mechanisms involved in its action are not clear. This study was undertaken to understand the mechanism of chromium action in experimental diabetes. Streptozotocin-induced diabetic animals were administered chromium as chromium picolinate (CrP) at a daily dose of 1 mg/kg body weight for a period of 4 weeks. It was observed that chromium complexed with picolinate was effective in lowering plasma glucose levels as well as was able to alleviate polyphagia, polydipsia, and weight loss in diabetic animals. Administration of chromium was also found to normalize glycogen content in liver of diabetic animals to near control levels. The reduction in plasma glucose levels by chromium was accompanied by increase in activity of glycolytic enzymes (e.g., glucokinase, phosphofructokinase, and pyruvate kinase) and by suppression in activity of gluconeogenic enzymes (e.g., glucose-6-phosphatase and phosphoenolpyruvate carboxykinase) in liver. Hepatic glucose uptake was found to be increased by chromium supplementation as demonstrated by decrease in Km and increase in Vmax values in diabetic animals. Chromium levels were lower in the liver of diabetic rats when compared with that of control rats. A negative correlation was observed between plasma glucose and chromium concentration in patients with diabetes. The data suggests that chromium supplementation as CrP is beneficial in correcting hyperglycemia, implying that the modulation of the glucose metabolism by chromium may be therapeutically beneficial in the treatment of diabetes.

Effects of chromium histidinate on renal function, oxidative stress, and heat-shock proteins in fat-fed and streptozotocin-treated rats

OBJECTIVE

Chromium is an essential element for carbohydrate, fat, and protein metabolism. The therapeutic potential of chromium histidinate (CrHis) in the treatment of diabetes has been elucidated. The present study investigated the effects of CrHis on serum parameters of renal function, on oxidative stress markers (malondialdehyde [MDA] and 8-isoprostane), and on the expression of heat-shock proteins (HSPs) in rats.

METHODS

Male Wistar rats (n=60, 8 weeks old) were divided into four groups. Group 1 received a standard diet (12% of calories as fat). Group 2 received a standard diet, plus CrHis. Group 3 received a high-fat diet (40% of calories as fat) for 2 weeks, and was then injected with streptozotocin (STZ) on day 14 (STZ, 40 mg/kg intraperitoneally). Group 4 was treated in the same way as group 3 (HFD/STZ), but was supplemented with 110 microg CrHis/kg/body weight/day. Oxidative stress in the kidneys of diabetic rats was evidenced by an elevation in levels of MDA and 8-isoprostane. Protein concentrations of HSP60 and HSP70 in renal tissue were determined by Western blot analyses.

RESULTS

Chromium histidinate supplementation lowered kidney concentrations of MDA, 8-isoprostane levels, serum urea-N, and creatinine, and reduced the severity of renal damage in the STZ-treated group (i.e., the diabetes-induced group). The expression of HSP60 and HSP70 was lower in the STZ group that received CrHis than in the group that did not. No significant effect of CrHis supplementation was detected in regard to the overall measured parameters in the control group.

CONCLUSIONS

Chromium histidinate significantly decreased lipid peroxidation levels and HSP expression in the kidneys of experimentally induced diabetic rats. This study supported the efficacy of CrHis in reducing renal risk factors and impairment because of diabetes.

Effects of chromium picolinate on glucose uptake in insulin-resistant 3T3-L1 adipocytes involve activation of p38 MAPK

Chromium picolinate (CrPic) has been discovered as a supplemental or alternative medication for type 2 diabetes, but its mechanism of action is not well understood. The purpose of this study was to explore the possible anti-diabetic mechanisms of CrPic in insulin-resistant 3T3-L1 adipocytes; the insulin resistance was induced by treatment with high glucose and insulin for 24 h. The effects of CrPic on glucose metabolism and the glucose uptake-inducing activity of CrPic were investigated. Meanwhile, the effects of CrPic on glucose transporter 4 (GLUT4) translocation were visualized by immonofluorescence microscopy. In addition, its effects on insulin signaling pathways and mitogen-activated protein kinase (MAPK) signaling cascades were assessed by immunoblotting analysis and real-time PCR. The results showed that CrPic induced glucose metabolism and uptake, as well as GLUT4 translocation to plasma membrane (PM) in both control and insulin-resistant 3T3-L1 adipocytes without any changes in insulin receptor beta (IR-beta), protein kinase B (AKt), c-Cbl, extracellular signal-regulated kinase (ERK), c-Jun phosphorylation and c-Cbl-associated protein (CAP) mRNA levels. Interestingly, CrPic was able to increase the basal and insulin-stimulated levels of p38 MAPK activation in the control and insulin-resistant cells. Pretreatment with the specific p38 MAPK inhibitor SB203580 partially inhibited the CrPic-induced glucose transport, but CrPic-activated translocation of GLUT4 was not inhibited by SB203580. This study provides an experimental evidence of the effects of CrPic on glucose uptake through the activation of p38 MAPK and it is independent of the effect on GLUT4 translocation. The findings also suggest exciting new insights into the role of p38 MAPK in glucose uptake and GLUT4 translocation.

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.

Antioxidant effects and insulin resistance improvement of chromium combined with vitamin C and e supplementation for type 2 diabetes mellitus

To determine the effects of combined supplementation with chromium (Cr) and vitamins C and E on oxidative stress in type 2 diabetes, adult subjects with HbA1c >8.5%. Subjects (n = 30) in this randomized, double blind, placebo-control study were divided into three groups (placebo, Cr or Cr + C + E) on daily treatment. The Cr group received 1000 microg of Cr (as Cr yeast); the Cr + C + E group received Cr (1000 microg as Cr yeast) together with vitamins C (1000 mg) and E (800 IU); and, a control group received a placebo. Baseline plasma Cr levels were not significant differences comparing the supplementation and placebo groups. Thiobarbituric acid reactive substances (TBARS) and total antioxidative status (TAS) were also not significant different. Following the 6-month study period, the plasma TBARS levels, fasting glucose, HbA1c and insulin resistance were significantly decreased in the Cr and Cr + C + E groups, but not for the placebo group. Plasma TAS and glutathione peroxidase were significantly higher for Cr and Cr + C + E groups relative to the placebo group. These findings suggest that Cr supplementation alone and combined of Cr together with vitamins C and E was effective for minimization of oxidative stress and improvement of glucose metabolism in type 2 DM patients.

Phenotype of subjects with type 2 diabetes mellitus may determine clinical response to chromium supplementation

Considerable controversy exists regarding the use of chromium (Cr) supplementation to modulate carbohydrate metabolism in subjects with diabetes. Recently, we reported that Cr supplementation, provided as 1000 microg/d as Cr picolinate, enhanced insulin sensitivity in subjects with type 2 diabetes mellitus. Our data agreed with some, but not all, studies that evaluated a similar dose and formulation in type 2 diabetes mellitus and suggested that subject selection and characteristics may be important considerations when assessing the clinical response. Thus, the goal of this study was to assess which metabolic or clinical characteristics, when obtained at baseline, best determine a clinical response to Cr when assessing changes in insulin sensitivity. Seventy-three subjects with type 2 diabetes mellitus were assessed in a double-blinded, randomized, placebo-controlled study. Subjects were assessed at baseline for glycemic control with glycated hemoglobin measures, oral glucose tolerance tests, and body weight and body fat measures (dual-energy x-ray absorptiometry). After baseline, insulin sensitivity in vivo was assessed with the use of hyperinsulinemic-euglycemic clamps. After the baseline clamp, subjects were randomized to receive Cr supplementation (1000 microg Cr/d provided as Cr picolinate) or placebo daily for 6 months. All study parameters were repeated after 6 months. The relationship of the baseline characteristics of the study subjects to the change in insulin sensitivity was determined. Sixty-three percent of the subjects with type 2 diabetes mellitus responded to the Cr treatment as compared with 30% with placebo. The only subject variable significantly associated with the clinical response to Cr was the baseline insulin sensitivity, as assessed with the hyperinsulinemic-euglycemic clamp (partial R(2) = .4038) (P = .0004). Subject phenotype appears to be very important when assessing the clinical response to Cr because baseline insulin sensitivity was found to account for nearly 40% of the variance in the clinical response to Cr.

Effect of chromium niacinate and chromium picolinate supplementation on lipid peroxidation, TNF-alpha, IL-6, CRP, glycated hemoglobin, triglycerides, and cholesterol levels in blood of streptozotocin-treated diabetic rats

Chromium (Cr(3+)) supplementation facilitates normal protein, fat, and carbohydrate metabolism, and is widely used by the public in many countries. This study examined the effect of chromium niacinate (Cr-N) or chromium picolinate (Cr-P) supplementation on lipid peroxidation (LP), TNF-alpha, IL-6, C-reactive protein (CRP), glycosylated hemoglobin (HbA(1)), cholesterol, and triglycerides (TG) in diabetic rats. Diabetes (D) was induced in Sprague-Dawley rats by streptozotocin (STZ) (ip, 65 mg/kg BW). Control buffer, Cr-N, or Cr-P (400 microg Cr/kg BW) was administered by gavages daily for 7 weeks. Blood was collected by heart puncture using light anesthesia. Diabetes caused a significant increase in blood levels of TNF-alpha, IL-6, glucose, HbA(1), cholesterol, TG, and LP. Compared with D, Cr-N supplementation lowered the blood levels of TNF-alpha (P=0.04), IL-6 (P=0.02), CRP (P=0.02), LP (P=0.01), HbA(1) (P=0.02), TG (P=0.04), and cholesterol (P=0.04). Compared with D, Cr-P supplementation showed a decrease in TNF-alpha (P=0.02), IL-6 (P=0.02), and LP (P=0.01). Chromium niacinate lowers blood levels of proinflammatory cytokines (TNF-alpha, IL-6, CRP), oxidative stress, and lipids levels in diabetic rats, and appears to be a more effective form of Cr(3+) supplementation. This study suggests that Cr(3+) supplementation can lower the risk of vascular inflammation in diabetes.

Effect of chromium on carbohydrate and lipid metabolism in a rat model of type 2 diabetes mellitus: the fat-fed, streptozotocin-treated rat

Chromium supplements are widely used as an alternative remedy for type 2 diabetes mellitus (T2DM). In vitro study findings show that chromium picolinate (CrPic) may improve insulin sensitivity by enhancing intracellular insulin receptor. In this study, we evaluated the metabolic effects of CrPic in a rat model of T2DM. Male Sprague-Dawley rats (n = 45, 8 weeks old) were divided into 3 groups. The controls (group I) received a standard diet (12% of calories as fat); group II received a high-fat diet (HFD; 40% of calories as fat) for 2 weeks and then were intraperitoneally injected with streptozotocin (STZ, 40 mg/kg; HFD/STZ) on day 14; group III rats were given group II diets with the addition of 80 microg CrPic per kilogram body weight per day. The addition of CrPic in the group III treatment lowered glucose by an average of 63% (P < .001), total cholesterol by 9.7% (P < .001), and triglycerides by 6.6% (P < .001) compared with group II treatment. Compared with group II, CrPic treatment also lowered free fatty acid levels by 24% (P < .001), blood urea by 33% (P < .05), and creatinine level by 25% (P < .01), and reduced the severity of glomerular sclerosis (P < .0001). Histopathologic findings suggest that the CrPic-treated group had normal renal tubular appearance compared with the HFD/STZ-treated group. Normal appearance of hepatocytes was observed in the CrPic-treated group. These results showed that CrPic has marked beneficial effects against microvascular complications. In conclusion, HFD/STZ rats provide a novel animal model for T2DM. Further treatment with CrPic for 10 weeks significantly ameliorated changes in metabolic risk factors including favorable changes in histopathology of the liver, kidney, and pancreas, suggesting its potential role in the management of diabetes.