Here is every single study I could find on the matter.
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1: J Am Coll Nutr 2001 Aug;20(4):327-36
A hydroxychalcone derived from cinnamon functions as a mimetic for insulin in
3T3-L1 adipocytes.
Jarvill-Taylor KJ, Anderson RA, Graves DJ.
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State
University, Ames 50011, USA.
OBJECTIVES: These studies investigated the ability of a hydroxychalcone from
cinnamon to function as an insulin mimetic in 3T3-LI adipocytes. METHODS:
Comparative experiments were performed with the cinnamon methylhydroxychalcone
polymer and insulin with regard to glucose uptake, glycogen synthesis.
phosphatidylinositol-3-kinase dependency, glycogen synthase activation and
glycogen synthase kinase-3beta activity. The phosphorylation state of the
insulin receptor was also investigated. RESULTS: MHCP treatment stimulated
glucose uptake and glycogen synthesis to a similar level as insulin. Glycogen
synthesis was inhibited by both wortmannin and LY294002, inhibitors directed
against the PI-3-kinase. In addition, MHCP treatment activated glycogen synthase
and inhibited glycogen synthase kinase-3beta activities, known effects of
insulin treatment. Analysis of the insulin receptor demonstrated that the
receptor was phosphorylated upon exposure to the MHCP. This supports that the
insulin cascade was triggered by MHCP. Along with comparing MHCP to insulin,
experiments were done with MHCP and insulin combined. The responses observed
using the dual treatment were greater than additive, indicating synergism
between the two compounds. CONCLUSION: Together, these results demonstrate that
the MHCP is an effective mimetic of insulin. MHCP may be useful in the treatment
of insulin resistance and in the study of the pathways leading to glucose
utilization in cells.
PMID: 11506060 [PubMed - indexed for MEDLINE]
2: J Agric Food Chem 2000 Mar;48(3):849-52
Insulin-like biological activity of culinary and medicinal plant aqueous
extracts in vitro.
Broadhurst CL, Polansky MM, Anderson RA.
Nutrient Requirements and Functions Laboratory, Beltsville Human Nutrition
Research Center, Agricultural Research Service, U.S. Department of Agriculture,
Beltsville, Maryland 20705-2350, USA.
To evaluate the possible effects on insulin function, 49 herb, spice, and
medicinal plant extracts were tested in the insulin-dependent utilization of
glucose using a rat epididymal adipocyte assay. Cinnamon was the most bioactive
product followed by witch hazel, green and black teas, allspice, bay leaves,
nutmeg, cloves, mushrooms, and brewer's yeast. The glucose oxidation enhancing
bioactivity was lost from cinnamon, tea, witch hazel, cloves, bay leaf and
allspice by poly(vinylpyrrolidone) (PVP) treatment, indicating that the active
phytochemicals are likely to be phenolic in nature. The activity of sage,
mushrooms, and brewers's yeast was not removed by PVP. Some products such as
Korean ginseng, flaxseed meal, and basil have been reported to be effective
antidiabetic agents; however, they were only marginally active in our assay. Our
technique measures direct stimulation of cellular glucose metabolism, so it may
be that the active phytochemicals in these plants improve glucose metabolism via
other mechanisms or that this in vitro screening is not a reliable predictor of
hypoglycemic effects in vivo for some products. In summary, the positive effects
of specific plant extracts on insulin activity suggest a possible role of these
plants in improving glucose and insulin metabolism.
PMID: 10725162 [PubMed - indexed for MEDLINE]
3: Horm Res 1998 Sep;50(3):177-82
Regulation of PTP-1 and insulin receptor kinase by fractions from cinnamon:
implications for cinnamon regulation of insulin signalling.
Imparl-Radosevich J, Deas S, Polansky MM, Baedke DA, Ingebritsen TS, Anderson
RA, Graves DJ.
Department of Biochemistry and Biophysics, Iowa State University, Ames, Iowa,
USA.
Bioactive compound(s) extracted from cinnamon potentiate insulin activity, as
measured by glucose oxidation in the rat epididymal fat cell assay. Wortmannin,
a potent PI 3'-kinase inhibitor, decreases the biological response to insulin
and bioactive compound(s) from cinnamon similarly, indicating that cinnamon is
affecting an element(s) upstream of PI 3'-kinase. Enzyme studies done in vitro
show that the bioactive compound(s) can stimulate autophosphorylation of a
truncated form of the insulin receptor and can inhibit PTP-1, a rat homolog of a
tyrosine phosphatase (PTP-1B) that inactivates the insulin receptor. No
inhibition was found with alkaline phosphate or calcineurin suggesting that the
active material is not a general phosphatase inhibitor. It is suggested, then,
that a cinnamon compound(s), like insulin, affects protein
phosphorylation-dephosphorylation reactions in the intact adipocyte. Bioactive
cinnamon compounds may find further use in studies of insulin resistance in
adult-onset diabetes.
PMID: 9762007 [PubMed - indexed for MEDLINE]
4: Horm Res 1992;37(6):225-9
Insulin activity: stimulatory effects of cinnamon and brewer's yeast as
influenced by albumin.
Berrio LF, Polansky MM, Anderson RA.
Vitamin and Mineral Nutrition Laboratory, Beltsville Human Nutrition Research
Center, US Department of Agriculture, ARS, MD 20705-2350.
Cinnamon and Brewer's yeast extracts have been shown to potentiate the action of
insulin in isolated adipocytes. In this study, isolated rat epididymal
adipocytes were used to evaluate the influence of bovine serum albumin on
insulin activity as affected by cinnamon and Brewer's yeast extracts. Albumin at
0.01-0.1% decreased the insulin stimulatory effects of cinnamon from 11.8- to
5.3-fold and 2% albumin decreased this effect to near control levels.
Conversely, the insulin-enhancing properties of Brewer's yeast remained low in
the presence of less than 0.25% albumin but subsequently increased 2.8-, 4.8-
and 5.6-fold in the presence of 0.25, 0.50 and 1.0% albumin, respectively. In
the absence of added insulin, increased activity of the insulin-stimulated
utilization of glucose by both extracts was observed but only Brewer's yeast
extract displayed additive effects when tested at higher insulin levels. Due to
the inhibitory and enhancing effects of albumin on the insulin activity of
cinnamon and Brewer's yeast, respectively, it is suggested that the effects of
albumin be assessed when evaluating the insulin-enhancing effects of other
substances using isolated adipocytes.
PMID: 1292975 [PubMed - indexed for MEDLINE]
5: Biol Trace Elem Res 1990 Mar;24(3):183-8
Insulin potentiating factor and chromium content of selected foods and spices.
Khan A, Bryden NA, Polansky MM, Anderson RA.
US Department of Agriculture, Beltsville Human Nutrition Research Center, MD
20705.
An unidentified factor that potentiates the action of insulin in glucose
metabolism was investigated in selected foods and spices. Chromium content of
these foods and spices was also determined. Foods and spices were extracted with
0.1N NH4OH (1:20, w/v) and the supernatants assayed for insulin potentiation
activity in the rat epididymal fat cell assay. Among the selected foods, tuna
fish, peanut butter, and vanilla ice cream had some insulin potentiating
activity. Among the spices, apple pie spice, cinnamon, cloves, bay leaves, and
turmeric potentiated insulin activity more than three-fold. Chromium
concentration of foods ranged from 1 to 145 ng/g, and spices ranged from 4 to
1818 ng/g. Insulin potentiating activity of foods and spices did not correlate
with total chromium. Spices are generally used for flavor and taste in food
preparations, but cinnamon, cloves, bay leaves, and turmeric may have an
additional role in glucose metabolism.
PMID: 1702671 [PubMed - indexed for MEDLINE]
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