Increased plasma D-lactic acid associated with impaired memory in rats

Aim D Lactic acidosis is associated with memory impairment in humans Recent research indicates that D-lactic acid may inhibit the supply of energy from astrocytes to neurons involved with memory formation However little is known about the effects of increased hind-gut fermentation due to changes in diet on circulating lactic acid concentrations and memory Method Thirty-six male Wistar rats were fed three dietary treatments a commercial rat and mouse chow a soluble carbohydrate based diet or a fermentable carbohydrate based diet The parameters estimating memory were examined by employing the object recognition test Physical parameters of fermentation including hind-gut and plasma lactic acid concentrations were examined after sacrifice either 3 or 21 h after feeding Results Increased fermentation in the hind-gut of rats indicated by lower caecum pH was associated with increased plasma L-lactic acid (r=-041 p= 0 020) and D lactic acid (r=-033 p= 0 087) Memory being able to discriminate between a familiar and a novel object during the object recognition test was reduced with increasing plasma D-lactic acid (r=-0 51 p= 0 021) Conclusions Memory impairment was associated with alterations in plasma El-lactic acid following the fermentation of carbohydrate in the hind-gut Further work is still required to determine whether these effects are mediated centrally or via direct connections through the enteric nervous system (C) 2010 Elsevier Inc All rights reserved