Updated 27 October 2015

Citrus peel: help for diabetes?

A daily supplement of an extract from citrus peel could reduce insulin resistance in hamsters, suggesting the extract could help prevent diabetes, says a North American study.


The citrus peel extracts, polymethoxylated flavones (PMFs), have been reported to have beneficial effects on cholesterol-levels, but this is said to be the first study that looks in more detail at the benefits and reports that the extracts have positive effects on inflammatory cytokine levels.

“This study provides novel evidence that PMFs reverse hypertriglyceridaemia and restores insulin sensitivity,” said researchers from the University of Hawaii, in collaboration with KGK Synergize, a Canadian nutraceutical company.

PMFs are similar to other plant pigments found in citrus fruits that have been increasingly linked to health benefits, including protection against cancer, heart disease and inflammation. The main PMFs in the extracts are tangeretin and nobiletin, as well as small amounts of synephrine.

The research study

The new study, published in the journal Life Sciences (Vol. 79, pp. 365-373), investigated the effects of a daily supplement of PMF on insulin-resistant hamsters.

Twenty-eight hamsters were fed a fructose-rich diet for two weeks to induce hypertriglyceridaemia and insulin resistance. The animals were then divided into four equal groups and fed one of four diets: chow; control fructose diet; fructose plus low-dose PMF (62,5mg/kg body weight per day); fructose plus high-dose PMF (125mg/kg/day).

After four weeks of the test diets, the researchers found that both PMF groups showed a significant decrease in serum triglycerides (TG) and cholesterol levels compared to the fructose-fed hamsters.

The decreases in TG were limited to the heart (33 percent for the 125mg PMF group) and liver (42 percent for the 125mg PMF group), with no changes observed in the epididymal fat and muscle.

“After PMF supplementation for four weeks, significant reductions in TG and cholesterol were observed in a dose-dependent manner related to lipids, cholesterol and inflammation, indicating that the response was specific to PMFs,” wrote lead author Rachel Li.

Decrease in biomarkers

Because insulin resistance, diabetes, and obesity are recognised as inflammatory disorders, say the researchers, they measured concentrations of the mediators for inflammation, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and markers of immune response, the cytokine IFN-gamma.

The researchers found decreased levels of these biomarkers in the PMF supplemented groups and the effect appeared to be dose-dependent.

“The mechanism of PMF in improving insulin sensitivity in this study can be explained, at least in part, by its regulatory effects on cytokines,” said Li.

“These data provide a basis for further investigation of the role of PMF in improving insulin resistance (IR)… in human subjects and for testing dietary reagents for the prevention of IR,” concluded the researchers.

The American Heart Association of Hawaii and the NIH-National Center for Complementary and Alternative Medicine funded the study.

Source: Decision News Media

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