Abstract
Prospective epidemiological studies concur in an association between habitual coffee consumption and a lower risk of type 2 diabetes. Several aspects of these studies support a cause–effect relationship. There is a dependency on daily coffee dose. Study outcomes are similar in different regions of the world, show no differences between sexes, between obese versus lean, young versus old, smokers versus nonsmokers, regardless of the number of confounders adjusted for. Randomized controlled intervention trials did not find a consistent impact of drinking coffee on acute metabolic control, except for effects of caffeine. Therefore, lowering of diabetes risk by coffee consumption does not involve an acute effect on the post-meal course of blood glucose, insulin or insulin resistance. Several studies in animals and humans find that the ingestion of coffee phytochemicals induces an adaptive cellular response characterized by upregulation and de novo synthesis of enzymes involved in cell defense and repair. A key regulator is the nuclear factor erythroid 2-related factor 2 (Nrf2) in association with the aryl hydrocarbon receptor, AMP-activated kinase and sirtuins. One major site of coffee actions appears to be the liver, causing improved fat oxidation and lower risk of steatosis. Another major effect of coffee intake is preservation of functional beta cell mass via enhanced mitochondrial function, lower endoplasmic reticulum stress and prevention or clearance of aggregates of misfolded proinsulin or amylin. Long-term preservation of proper liver and beta cell function may account for the association of habitual coffee drinking with a lower risk of type 2 diabetes, rather than acute improvement of metabolic control.
Highlights
The perception of coffee has experienced a remarkable transition from a stimulant drink which may stress your cardiovascular system to a beverage that is good for your health
Cellular targets for physical binding of phytochemicals include the complex of nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECHassociating protein-1 (Keap1) [68,69,70,71], the aryl hydrocarbon receptor (AHR) [72,73,74,75], protein disulfide isomerase3 [76], 3-hydroxy-3-methylglutaryl-coenzyme A reductase [77], protein kinase B (AKT) [78], glutathione S-transferase pi isoform-1 [79], vascular endothelial growth factor receptor [80], PPARγ [81], amyloid forming peptides [55,82,83,84,85,86,87], basic proline-rich protein in saliva [88], human serum albumin [89,90] or low density lipoprotein [91]
Randomized controlled trials do not show a consistent effect of coffee intake on acute metabolic control, except for some effects of caffeine
Summary
The perception of coffee has experienced a remarkable transition from a stimulant drink which may stress your cardiovascular system to a beverage that is good for your health The latter view is derived from a large number of prospective cohort studies which observed an association of socioeconomic or lifestyle factors including habitual coffee consumption and clinical outcomes including type 2 diabetes mellitus, non-alcoholic fatty liver disease, liver cancer, gout, kidney stones and Parkinson’s disease [1]. We consider that coffee constituents appear to exert similar molecular effects at the cellular level as reported for phytochemicals of other dietary plants From these data, a picture emerges how coffee consumption promotes resistance to the development of type 2 diabetes. For the discussion of a possible molecular mechanism, we conducted an additional search in PubMed with the items coffee/caffeine/chlorogenic acid in combination with the items Nrf2/anti-oxidative/anti-inflammatory, respectively
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