Long-term Intermittent Fasting (IF) Initiated at Night Prevents Development of Diabetic Retinopathy by Restoration of Bile Acid Metabolism in db/db Mice

Abstract

Purpose : Diabetes is associated with an altered composition of the bile acid pool and with gut dysbiosis. We investigated whether influencing the commensal microbes by use of intermittent fasting (IF) would alter key microbes that influence bile acid metabolism and impact development of diabetic retinopathy (DR).

Methods : db/db and db/m mice (8 weeks old) were maintained either on ad libitum (ad lib) or every other 24-h interval IF regimen (food removed at night time) for 7 months. Fecal samples were collected every 4 h for 48 h and genomic DNA sequencing was used to discover and distinguish various bacterial taxa. The presence/severity of DR was assessed by enumeration of acellular capillaries in the IF and ad lib cohorts and in mice treated with the dual FXR/TGR5 agonist INT-767 (30 mg/kg bw/day).

Results : IF showed a beneficial effect on survival, lipid metabolism, liver function and the microbiota of db/db mice. Fecal genomic DNA showed that IF corrected dysbiosis and restored toward nondiabetic levels key microbial species that are known to influence bile acid metabolism. Specifically, the family of Clostridiaceae are increased in db/db and restored to nondiabetic levels with IF. In addition, Bacillus firmus, Lactobacillus reuteri, Clostridium perfringens, Methanobrevibacter sp., Lactobacillaceae, Ruminonococcaceae and Bifidobacterium, were beneficially altered by IF in db/db mice. A long-term IF regimen resulted in reduced development of DR. db/db mice of eleven months of age showed the expected increased numbers of acellular capillaries (20±4mm² p<0.05) compared to age-matched control mice (5±1mm²). db/db mice under the IF regimen did not show this increase in acellular capillaries (9± 2/mm²). We next examined whether INT-767 would similarly prevent development of DR as did IF. Treatment of diabetic mice with INT-767, resulted in reduced numbers of acellular capillaries compared to vehicle treated mice (p<0.05).

Conclusions : The protective effects of IF on DR occur by restoring key species of the gut microbiota that influence bile acid metabolism and can be duplicated by use of a bile acid agonist.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.