The study of Japanese T2DM patients demonstrated for the first time that 1) the prevalence of T2DM with FSSG score ≥ 8 was 23% (n = 15/66), 2) the coexistence of Mets and low levels of serum adiponectin was associated with GERD symptoms. We have demonstrated that adiponectin suppresses inflammation in various organs, such as the heart, lung, aorta, kidney, liver, colon and pancreas . Adiponectin may also play a protective role of erosive esophagitis. To clarify the protective effect of adiponectin on GERD, further experimental studies are required. On the other hand, increased systemic IL-6 concentrations are associated with the pathophysiology of T2DM, with adipose tissue being the major source of this cytokine . Exposure to components of the gastric refluxate is sufficient to stimulate esophageal cells to release a pro-inflammatory cytokine, IL-6, with the potential to mediate the esophageal motor abnormalities associated with GERD-induced esophagitis . However, the present study show serum IL-6 levels are not associated with GERD symptoms in T2DM. Taken together, the results suggest that decreased anti-inflammatory cytokines rather than increased pro-inflammatory cytokines may be associated with the development of GERD-induced erosive esophagitis. We described here the prevalence and characteristics of Japanese diabetics with GERD symptoms, and it may be therefore necessary to diagnose a treatable GERD from the standpoint of prevention of lifestyle-related diseases as well as improvement of QOL in T2DM patients. Large-scale interventional trials, such as weight reduction, intensive anti-GERD and anti-diabetes (especially thiazolidinedione which is known to increase serum adiponectin) drugs or combinations of these therapies, should be provided to assess the effects of appropriate treatment on the outcome of T2DM patients with GERD symptoms.
Several limitations of this study must be considered. First, this is a cross-sectional study, making it difficult to establish a cause-effect relationship. Further prospective studies should be conducted in the future to analyze this relationship. Second, the results may not be applicable to females or non-Japanese populations. Third, the current study did not include the effects of alcohol intake, smoking habits, mental status, dietary habit and use of pharmacotherapy (such as nonsteroidal anti-inflammatory drugs; NSAIDs). The current study found that the prevalence of FSSG score ≥ 8 and average FSSG score were not influenced by smoking habits and use of NSAIDs. Finally, further replication studies of larger sample need to be designed including these confounding variables, such as potential factors to be influenced serum adiponectin levels, such as smoking status, use of pharmacotherapy (ACE-I/ARB, statin), in the future.
In conclusion, the coexistence of MetS and low levels of serum adiponectin was associated with the higher prevalence of GERD symptom in subjects with T2DM.