Chromium chloride increases insulin-stimulated glucose uptake in the perfused rat hindlimb

Effects of Whey Protein Combined with Amylopectin/Chromium on the Muscle Protein Synthesis and mTOR Phosphorylation in Exercised Rats

This study aimed to examine the impact of varying doses of whey protein (WP) and amylopectin/chromium complex (ACr) supplementation on muscle protein synthesis (MPS), amino acid and insulin levels, and the rapamycin (mTOR) signaling pathways in exercised rats. A total of 72 rats were randomly divided into nine groups: (1) Exercise (Ex), (2) Ex + WPI to (5) Ex + WPIV with various oral doses of whey protein (0.465, 1.55, 2.33, and 3.1 g/kg) and (6) Ex + WPI + ACr to (9) Ex + WPIV + ACr with various doses of whey protein combined with 0.155 g/kg ACr. On the day of single-dose administration, the products were given by oral gavage after exercise. To measure the protein fractional synthesis rate (FSR), a bolus dose of deuterium-labeled phenylalanine was given, and its effects were evaluated 1 h after supplementation. Rats that received 3.1 g/kg of whey protein (WP) combined with ACr exhibited the most significant increase in muscle protein synthesis (MPS) compared to the Ex group (115.7%, p < 0.0001). In comparison to rats that received the same dose of WP alone, those given the combination of WP and ACr at the same dosage showed a 14.3% increase in MPS (p < 0.0001). Furthermore, the WP (3.1 g/kg) + ACr group exhibited the highest elevation in serum insulin levels when compared to the Ex group (111.9%, p < 0.0001). Among the different groups, the WP (2.33 g/kg) + ACr group demonstrated the greatest increase in mTOR levels (224.2%, p < 0.0001). Additionally, the combination of WP (2.33 g/kg) and ACr resulted in a 169.8% increase in 4E-BP1 levels (p < 0.0001), while S6K1 levels rose by 141.2% in the WP (2.33 g/kg) + ACr group (p < 0.0001). Overall, supplementation with various doses of WP combined with ACr increased MPS and enhanced the mTOR signaling pathway compared to WP alone and the Ex group.

Efficacy and Safety of Nutrient Supplements for Glycaemic Control and Insulin Resistance in Type 2 Diabetes: An Umbrella Review and Hierarchical Evidence Synthesis

Background: Nutrient supplements are widely used for type 2 diabetes (T2D), yet evidence-based guidance for clinicians is lacking. Methods: We searched the four electronic databases from November 2015−December 2021. The most recent, most comprehensive, high-ranked systematic reviews, meta-analyses, and/or umbrella reviews of randomised controlled trials in adults with T2D were included. Data were extracted on study characteristics, aggregate outcome measures per group (glycaemic control, measures of insulin sensitivity and secretion), adverse events, and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessments. Quality was assessed using A Measurement Tool to Assess Systematic Reviews Version 2.0 (AMSTAR 2). Results: Twelve meta-analyses and one umbrella review were included. There was very low certainty evidence that chromium, Vitamin C, and omega-3 polyunsaturated fatty acids (Ω-3 PUFAs) were superior to placebo for the primary outcome of glycated hemoglobin (HbA1c) (Mean Difference/MD −0.54, −0.54 and ES −0.27, respectively). Probiotics were superior to placebo for HbA1c (Weighted Mean Difference/WMD −0.43%). There was very low certainty evidence that Vitamin D was superior to placebo for lowering HbA1c in trials of <6 months (MD −0.17%). Magnesium, zinc, Vitamin C, probiotics, and polyphenols were superior to placebo for FBG. Vitamin D was superior to placebo for insulin resistance. Data on safety was limited. Conclusions: Future research should identify who may benefit from nutrient supplementation, safety, and optimal regimens and formulations.

Effects of chromium supplementation on body composition, human and animal health, and insulin and glucose metabolism

PURPOSE OF REVIEW

Chromium(III) has been proposed to have a nutritional or pharmacological role in changing body composition and improving symptoms of insulin resistance, type 2 diabetes, and related conditions although the mode of action of Cr(III) at a molecular level has failed to be elucidated. This review details the current status of studies into Cr(III) supplementation.

RECENT FINDINGS

Clinical trials, meta-analyses and systematic reviews have failed to demonstrate clinically significant effects from Cr(III) supplementation on body composition or symptoms of insulin resistance and related conditions in humans and farm animals. Although new Cr(III) supplements continue to appear in the scientific literature, studies have failed to elucidate the mechanism of chromium action at a molecular level. Conflicting results on a role of transferrin in Cr(III) transport and detoxification have appeared.

SUMMARY

Cr(III) supplementation cannot currently be recommended in humans or farm animals. Further studies are required to probe the mechanism of Cr(III) action in increasing insulin sensitivity and glucose uptake in rodent models of insulin resistance and diabetes, with particular attention being turned to a potential role of transferrin in Cr(III) transport and detoxification.

Mechanism of insulin-like effect of chromium(III) ions on glucose uptake in C2C12 mouse myotubes involves ROS formation

Chromium is considered a trace element which improves glucose tolerance, but mechanism accounting for this insulin-like action is not recognized. The main purpose of this study was to examine the role of reactive oxygen species (ROS) in chromium and insulin stimulated glucose transport using antioxidants. Effect of chromium ions on phosphatases, enzymes involved in inhibition of insulin signaling was also investigated. Experiments were performed in vitro on C2C12 mouse myotubes. ROS level was measured with the use of confocal microscope and 2',7' dichlorodihydrofluorescein diacetate (DCFH-DA). Glucose metabolism was assayed by the measurement of 2-[³H]-deoxyglucose uptake. Cr³⁺ ions and insulin treatment caused significant increase of ROS formation and also stimulated glucose uptake in C2C12 cells in concentration dependent manner. Antioxidants (L-ascorbic acid and N-acetyl cysteine 100μM) and DPI (diphenyleneiodonium-NADPH oxidase inhibitor, 10μM) abolished insulin- and Cr-inducted glucose transport. Our results confirm the hypothesis that the ROS are integral part of insulin signaling pathway and that the insulin mimetic effect of Cr³⁺ ions depends on the antioxidant status of the cells. Surprisingly, chromium treatment resulted in increased activity of membrane phosphatases.