Diet and exercise intervention can delay or prevent development of type-2-diabetes (T2D), and high habitual coffee consumption is associated with reduced risk of developing T2D. This study aimed to test whether selected bioactive substances in coffee acutely and/or chronically increase insulin secretion from β-cells and improve insulin sensitivity in skeletal muscle cells. Insulin secretion from INS-1E rat insulinoma cells was measured after acute (1-h) and long-term (72-h) incubation with bioactive substances from coffee. Additionally, we measured uptake of radioactive glucose in human skeletal muscle cells (SkMC) after incubation with cafestol. Cafestol at 10(-8) and 10(-6) M acutely increased insulin secretion by 12% (p < 0.05) and 16% (p < 0.001), respectively. Long-term exposure to 10(-10) and 10(-8) M cafestol increased insulin secretion by 34% (p < 0.001) and 68% (p < 0.001), respectively. Caffeic acid also increased insulin secretion acutely and chronically. Chlorogenic acid, trigonelline, oxokahweol, and secoisolariciresinol did not significantly alter insulin secretion acutely. Glucose uptake in SkMC was significantly enhanced by 8% (p < 0.001) in the presence of 10(-8) M cafestol. This newly demonstrated dual action of cafestol suggests that cafestol may contribute to the preventive effects on T2D in coffee drinkers and be of therapeutic interest.

Daily coffee consumption is inversely associated with risk of type-2 diabetes (T2D). Cafestol, a bioactive substance in coffee, increases glucose-stimulated insulin secretion in vitro and increases glucose uptake in human skeletal muscle cells. We hypothesized that cafestol can postpone development of T2D in KKAy mice. Forty-seven male KKAy mice were randomized to consume chow supplemented daily with either 1.1 (high), 0.4 (low), or 0 (control) mg of cafestol for 10 weeks. We collected blood samples for fasting glucose, glucagon, and insulin as well as liver, muscle, and fat tissues for gene expression analysis. We isolated islets of Langerhans and measured insulin secretory capacity. After 10 weeks of intervention, fasting plasma glucose was 28-30% lower in cafestol groups compared with the control group (p < 0.01). Fasting glucagon was 20% lower and insulin sensitivity improved by 42% in the high-cafestol group (p < 0.05). Cafestol increased insulin secretion from isolated islets by 75-87% compared to the control group (p < 0.001). Our results show that cafestol possesses antidiabetic properties in KKAy mice. Consequently, cafestol may contribute to the reduced risk of developing T2D in coffee consumers and has a potential role as an antidiabetic drug.

The effects of chronic coffee exposure in models of type 2 diabetes mellitus (T2D) is scarcely studied, and the efficacy of the main coffee species has never been compared. We tested the hypothesis that long-term consumption of arabica and robusta coffee may differentially delay and affect T2D development in Zucker diabetic fatty rats. Three study groups received either chow mixed with arabica or robusta instant coffee (1.8% w/w) or unsupplemented chow food for 10 weeks. Both coffee species reduced liver triglyceride content and area under the curve of fasting and postprandial insulin. At study end, plasma adiponectin, total cholesterol and high density lipoprotein levels were higher in the robust group compared with both arabica and control groups. The liver gene expression of Glucose-6-phosphatase, catalytic subunit (G6pc) and Mechanistic target of rapamycin (mTOR) in robusta and Cpt1a in both coffee groups was downregulated. In conclusion, long-term consumption of both coffee species reduced weight gain and liver steatosis and improved insulin sensitivity in a rat model of T2D. Robusta coffee was seemingly superior to arabica coffee with respect to effects on lipid profile, adiponectin level and hepatic gene expression.

OBJECTIVES: Aronia melanocarpa (Aronia) is a shrub with small berries, chokeberries. Chokeberries are claimed to possess health benefits due to a high content of polyphenols. Aronia is known to be extremely antioxidant; however, evidence for its health benefits is not established. This review gives an overview of the impact of Aronia on cardiometabolic risk factors and diseases. METHODS: Seventeen studies on cardiometabolic risk factors and diseases were identified through a systematic search on PubMed, Embase, and Cochrane. Inclusion criteria were studies with Aronia as intervention, performed in individuals with cardiometabolic disease or risk factors, e. g., type 2 diabetes (T2D), cardiovascular disease, hypertension, dyslipidaemia, impaired glucose tolerance, overweight, central obesity and smoking. Four of these studies were applicable for a quantitative analysis. RESULTS: Aronia did not influence body weight, circulating triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, or blood pressure. The quantitative analysis revealed a mean reduction in blood glucose of 0.44 mmol/l (P=0.0001) in the treatment group compared with the control group suggesting that Aronia treatment may have a beneficial impact on blood glucose. In addition, treatment durations of 6 weeks to 3 months tended to decrease low-density lipoprotein (LDL) cholesterol, while shorter treatment durations had no effect on LDL cholesterol. The quantitative analysis did not provide data on long-term effects of Aronia on lipids. CONCLUSIONS: More long-term high-quality randomized controlled studies are needed to clarify if dietary supplementation with Aronia has beneficial effects on cardiometabolic diseases.