DIET, BACTERIA AND INFLAMMATION: THE INTESTINAL MUCOSA AND METABOLIC SYNDROME

Long term consumption of a high fat diet (HFD) increases the risk of developing Metabolic Syndrome and type 2 diabetes. This led us to hypothesize that long term HFD consumption impairs immune tolerance to the intestinal bacteria. Our studies had two goals. First, we characterized the effect of long term HFD consumption on the systemic immune response by comparing C57BL6 mice fed a HFD and low fat diet (LFD). Plasma immunoglobulin G (IgG) against Escherichia coli (LF-82), E. coli (Nissle 1917), Bacteroides thetaiotaomicron and Lactobacillus acidophilus were measured by a lab-developed ELISA. Fasting blood glucose and inflammation were measured in LFD mice and HFD mice. To test whether our findings were clinically relevant, anti-bacterial IgG and TNF-α were measured in plasma samples from lean healthy individuals, obese non-diabetics and obese diabetics. Our second aim was to investigate the relationship between HFD consumption and intestinal immunity. The effect of HFD consumption on immune responses in the GI tract was assessed by measuring fecal IgA levels in HFD mice and LFD mice. HFD mice had higher plasma IgG against the LF82 strain of Escherichia coli as well as higher plasma TNF-α, neutrophil percentage and fasting blood glucose levels. Obese diabetics had higher plasma IgG against the LF82 strain of E. coli than lean healthy controls. Studies on the effect of HFD on intestinal immunity revealed that HFD mice had lower fecal IgA than LFD mice. Our findings are novel in that they show an association between long term HFD consumption, systemic inflammatory immune responses to pathogenic intestinal bacteria and insulin resistance. These studies also showed that HFD consumption may impair intestinal immunity