Small molecule kaempferol modulates PDX-1 protein expression and subsequently promotes pancreatic β-cell survival and function via CREB.
ABSTRACT Chronic hyperlipidemia causes β-cell apoptosis and dysfunction, thereby contributing to the pathogenesis of type 2 diabetes (T2D). Thus, searching for agents to promote pancreatic β-cell survival and improve its function could be a promising strategy to prevent and treat T2D. We investigated the effects of kaempferol, a small molecule isolated from ginkgo biloba, on apoptosis and function of β-cells and further determined the mechanism underlying its actions. Kaempferol treatment promoted viability, inhibited apoptosis and reduced caspase-3 activity in INS-1E cells and human islets chronically exposed to palmitate. In addition, kaempferol prevented the lipotoxicity-induced down-regulation of antiapoptotic proteins Akt and Bcl-2. The cytoprotective effects of kaempferol were associated with improved insulin secretion, synthesis, and pancreatic and duodenal homeobox-1 (PDX-1) expression. Chronic hyperlipidemia significantly diminished cyclic adenosine monophosphate (cAMP) production, protein kinase A (PKA) activation, cAMP-responsive element binding protein (CREB) phosphorylation and its regulated transcriptional activity in β-cells, all of which were restored by kaempferol treatment. Disruption of CREB expression by transfection of CREB siRNA in INS-1E cells or adenoviral transfer of dominant-negative forms of CREB in human islets ablated kaempferol protection of β-cell apoptosis and dysfunction caused by palmitate. Incubation of INS-1E cells or human islets with kaempferol for 48h induced PDX-1 expression. This effect of kaempferol on PDX-1 expression was not shared by a host of structurally related flavonoid compounds. PDX-1 gene knockdown reduced kaempferol-stimulated cAMP generation and CREB activation in INS-1E cells. These findings demonstrate that kaempferol is a novel survivor factor for pancreatic β-cells via up-regulating the PDX-1/cAMP/PKA/CREB signaling cascade.
SourceAvailable from: Andrija R CiricKaempferol: Chemistry, Natural Occurrences and Health Benefits, Edited by Garion Villers, Yves Fougere, 01/2013: chapter Metal Complexes of Kaempferol and Their Speciation in Human Plasma: pages 187 - 202; Nova Science Publishers., ISBN: 978-1-62618-515-9
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ABSTRACT: With the worldwide increase in diabetes prevalence there is a pressing unmet need for novel antidiabetic therapies. Insufficient insulin production due to impaired β‐cell function and apoptotic reduction of β‐cell mass is a common denominator in the pathogenesis of diabetes. Current treatments are directed at improving insulin sensitivity, and stimulating insulin secretion or replacing the hormone, but do not target progressive apoptotic β‐cell loss. Here we review the current development of small‐molecule inhibitors designed to rescue β‐cells from apoptosis. Several distinct classes of small molecules have been identified that protect β‐cells from inflammatory, oxidative and/or metabolically induced apoptosis. Although none of these have yet reached the clinic, β‐cell protective small molecules alone or in combination with current therapies provide exciting opportunities for the development of novel treatments for diabetes.Diabetes Obesity and Metabolism 09/2013; 15. DOI:10.1111/dom.12158 · 5.46 Impact Factor
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ABSTRACT: Flavonoids are polyphenolic compounds that are abundant in fruits and vegetables, and increasing evidence demonstrates a positive relationship between consumption of flavonoid-rich foods and disease prevention. Epidemiological, in vitro and animal studies support the beneficial effects of dietary flavonoids on glucose and lipid homeostasis. It is encouraging that the beneficial effects of some flavonoids are at physiological concentrations and comparable to clinically-used anti-diabetic drugs; however, clinical research in this field and studies on the anti-diabetic effects of flavonoid metabolites are limited. Flavonoids act on various molecular targets and regulate different signaling pathways in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibers. Flavonoids may exert beneficial effects in diabetes by (i) enhancing insulin secretion and reducing apoptosis and promoting proliferation of pancreatic β-cells; (ii) improving hyperglycemia through regulation of glucose metabolism in hepatocytes; (iii) reducing insulin resistance, inflammation and oxidative stress in muscle and fat and (iv) increasing glucose uptake in skeletal muscle and white adipose tissue. This review highlights recent findings on the anti-diabetic effects of dietary flavonoids, including flavan-3-ols, flavanones, flavonols, anthocyanidins, flavones and isoflavones, with particular emphasis on the studies that investigated the cellular and molecular mechanisms involved in the beneficial effects of the compounds.The Journal of nutritional biochemistry 09/2013; DOI:10.1016/j.jnutbio.2013.06.003 · 4.59 Impact Factor