One more cup of coffee for the (non-diabetic) road?

Discussing previous research, Cheng et al. said previous studies showed that coffee drinkers were at a lower risk of developing Type 2 diabetes mellitus (T2DM), which accounts for 90-95% of diabetes cases worldwide.

The academics cited epidemiological studies concluding that people who drank four or more cups of coffee daily had a 50% lower risk of developing the illness (Tuomilehto et al. 2004), incidences of which are on the increase globally – with every additional cup bringing about a decrease in risk of almost 7% (Huxley et al. 2009).

Cheng et al. wrote: “In cross-sectional studies conducted in Japan and northern and southern Europe, similar inverse associations between coffee consumption and T2DM or impaired glucose tolerance (an early signal of T2DM) have been observed.”​

The team noted that previous work had identified two compounds in coffee that they said significantly inhibited the ‘misfolding’ of the substance ‘human islet amyloids polypeptide’ (hIAPP) or amylin, as one causative factor causing Type 2 diabetes (T2DM).

Key diabetes indicator​

The authors noted that the presence of amyloid fibrils (insoluble fibrous protein aggreagates) in the pancreas as a result of amylin was a key indicator of T2DM, where increasing evidence suggested that hIAPP amyloid formation can result in β-cell apoptosis (pancreatic cell death).

“Thus, preventing the formation of toxic hIAPP amyloid fibrils, especially the most toxic oligomers, has been considered to be a novel therapeutic approach for T2DM," ​they wrote.

As one chlorogenic acid (CGA) in coffee, 3-CQA was the component focused on in the current study, where the authors cited estimates that a ‘regular’ coffee drinker (3 cups per day) approximate daily CGA intake was 1000mg, along with 500mg of caffeine and 500mg of caffeic acid.

Cheng et al. tested a hypothesis that CA and CGA (and their metabolite DHCA), due to their ‘typical’ polyphenolic structures, may inhibit the formation of hIAPP amyloid.

Significant inhibitory effects​

They found that CA, CGA and DHCA all had “significant inhibitory effects” ​on hIAPP fibril formation and alleviated the toxicity of hIAPP to pancreatic INS-1 cells; caffeine showed only a weak inhibitory effect on amyloid formation and protection of INS-1 cells.

Turning to the effects of caffeine on diabetes, Cheng et al. wrote: “Compared with decaffeinated coffee, our results demonstrate for the first time that caffeine shows mild beneficial effects, including an inhibitory effect on fibril formation and a protection effect on pancreatic INS-1 cell viability.”​

They added: “The present in vitro study suggests that coffee components may reduce the risk of T2DM through preventing toxic hIAPP assembly, and an in-depth in vivo study will be of future interest.​

As such, the scientists said that coffee-derived compounds might also be useful candidates for anti-diabetes drug development, while other recent work suggested that coffee might be used as a therapeutic agent against Alzheimer’s disease (Arendash & Cao 2010).

Title: ​‘Coffee components inhibit amyloid formation of human islet amyloid polypeptide in vitro: possible link between coffee consumption and diabetes mellitus’

Authors: ​B. Cheng, X.Liu, H.Gong, L.Huang, H.Chen, X.Zhang, C.Li, M.Yang, B.Ma, L.Jiao, L.Zheng, K.Huang

Source: ​Journal of Agricultural and Food Chemistry ​(2011, 59, 13147–13155) dx.doi.org/10.1021/jf201702h |J. Agric. Food Chem. 2011, 59, 13147–13155​