Asian aquatic herb combined with lutein suppresses cataracts in diabetes model

By Hank Schultz

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An extract of a common Asian aquatic herb combined with lutein suppressed the development of cataracts in a rat model of diabetes, a new study has found.

In a study published in the January edition of the Journal of Clinical Biochemistry and Nutrition​, researchers associated with research institutions in Japan and a Japanese eye health company looked at the effect of an extract of the botanical Trapa bispinosa​ Roxb. along with lutein to affect the development of advanced glycation end products (AGEs), which are postulated to be a mechanism for the changes observed in the proteins that make up the lens of the eye.

Trapa bispinosa​ Roxb., which is known by a variety of names including Singhara nut, is a species consumed as a food in India and used in medicinal applications in the Ayurvedic and TCM traditions.  The researchers used an extract of the herb, though they did not specify which parts, or the whole plant, were used to make the extract.

The researchers noted that the development of cataracts, especially when connected to the rising tide of diabetes, is a significant global public health concern.  While highly effective surgical solutions for cataracts exist, these are not currently available to cataract sufferers in many countries. According to a 2010 report by the World Health Organization, the prevalence of cataracts has been increasing each year, accounting for approximately 51% of blind cases worldwide. Approximately 20 million patients are believed to suffer from this disorder.

High polyphenol content in extract

The researchers used a hot water extract of the plant, which they dubbed TBE.  When analyzed, it was found to contain 25% polyphenols by weight.  Among the polyphenols present were gallic acid, ellagic acid, and eugeniin.

The researchers noted that previous research has shown that the formation of AGEs has been has an important role in the development of diabetic complications​. The authors examined the levels of two specific AGEs: Ne-(carboxy- methyl)lysine (CML) and Ne-(carboxyethyl)lysine (CEL). In addition to those biochemical assays, the researchers also did a physical examination of the lenses of the euthanized Wistar rats.

The study included both short term administration over four weeks with a high dose of TBE and lutein (100 mg/kg and 10 mg/kg respectively) and a 69-day longer term arm using a lower dose (10 mg/kg and 0.4 mg/kg).  In each case the rats were divided into groups of eight animals each that consisted of an untreated diabetic group, a TBE only group, one that received lutein only and a TBE plus lutein group.  The lower dose was studied because the researchers wanted to mimic a dose that was practical for long term use in humans.

The researchers found that the high doses of TBE and lutein significantly suppressed the development of CML and CEL, and the effect was most pronounced in the TBE plus lutein group.  But this effect was not observed in the longer-term portion of the study.

Mechanism of action unclear

But TBE and lutein were observed to suppress the development of cataracts in both arms of the study and did so most effectively when the two study materials were administered together.  This led the researchers to conclude that while their instincts were correct in the choice of study materials, they still don’t have the cataract-suppression mechanism nailed down.

“However, we did not observe a suppression of AGE accumulation in the lenses by administering TBE and lutein (data not shown), suggesting that CML and CEL were not directly related to the pathogenesis of cataracts or other AGEs are involved.  . . . [T]o our knowledge, this study provides the first evidence that TBE and lutein inhibit cataractogenesis even at a practical concentration and are more effective when ingested together,”​ they concluded.

The research was supported by grants from Japanese institutions and by the Santen Pharmaceutical Co.

Source:Journal of Clinical Biochemistry and Nutrition
DOI: 10.3164/jcbn.19-34
Trapa bispinosa Roxb. And Lutein Ameliorate Cataract in Type 1 Diabetic Rats
Authors: Kinoshita S, et al.

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