This study contributes to our understanding of the influence of H. pylori on metabolic syndrome status in diabetic patients in Ethiopia. We found H. pylori infection status was positively but not significantly associated with metabolic syndrome. We also found H. pylori positivity was significantly associated with lower HDL-c and higher SB, respectively.
Several other studies have examined the effects of H. pylori infection on various parameters of metabolic syndrome, and have found positive association between H. pylori with lower HDL-c levels (20–22), and higher systolic blood pressure (20). These individual findings are supported by a meta-analysis conducted by Upala et al. (2016), which also found that, overall, H. pylori positivity is significantly associated with higher systolic blood pressure (p = 0.01) and lower HDL-c levels (p < 0.01) (30). However, more recent cross-sectional studies in the United States of America and Iran have found no significant difference in HDL-c levels between H. pylori-positive and negative individuals (31–33).
In this study, our finding of no significant association between H. pylori infection and metabolic syndrome status is supported by few studies. Naja et al. (2012) and Takeoka et al. (2016) which also found that odds of metabolic syndrome did not significantly differ between H. pylori- positive and negative individuals, respectively (27, 28). Similarly, Chen et al. (2019) found that H. pylori was not significantly associated with metabolic syndrome in females only (19). However, this explanation disagrees with previous studies that have found an association between H. pylori infection and metabolic syndrome in apparently healthy populations (16–26). In a meta-analysis conducted by Azami et al. (2021) showed a significant association between H. pylori positivity and metabolic syndrome with a pooled odds ratio of 1.19 (95% CI 1.05–1.35) (6). The magnitude of the odds ratio from this result didn’t not materially different from our observations, although ours failed to reach statistically significant. This inconsistency could be due to variations in age, outcome ascertainment, and differences in the method used to assess H. pylori status.
Several hypotheses have been proposed regarding the mechanism by which H. pylori induces the development of metabolic syndrome. As H. pylori is known to disrupt gastric barrier function through the dysregulation of epithelial tight junctions (34), this predisposes the gut to mucosal damage (35). It has been shown that mucosal damage induces the production of pro-inflammatory cytokines (5), which may affect glucose and lipid metabolism (36, 37), as these cytokines promote systemic inflammatory response (34, 38). Interestingly, Mokhtar et al. found that H. pylori eradication in H. pylori-positive patients with functional dyspepsia resulted in a significant reduction of LDL levels, plasma glucose counts, and waist circumference Field (39), suggesting that H. pylori affects metabolic parameters and increased metabolic syndrome risk through interaction with the gastric epithelium. These findings are further substantiated by others who found that gastroesophageal reflux disease (GERD) and gastric ulcer (GU) Field (19), as well as a duodenal ulcer (DU) (24), were predictive for metabolic syndrome. Our failure to conclude a significant association between H. pylori positivity and metabolic syndrome may be explained by the lack of data on H. pylori-induced gastrointestinal abnormalities such as GU, DU, or GERD in the study population.
Our findings should be interpreted considering the following limitations. First, the cross-sectional design of our study makes it difficult to establish causal findings since we did not have patient data prior to H. pylori infection. Longitudinal studies are needed to improve our understanding of the effects of H. pylori infection. Similarly, H. pylori may be a symptom of other conditions, such as other infections or socioeconomic status. We collected demographic and lifestyle information using self-reported questionnaires, which may be susceptible to misclassification and recall bias. However, the questionnaire had previously been effective in a similar population in Ethiopia, increasing the validity of our findings. Furthermore, enrolling patients with known type I or type II diabetes mellitus introduces the possibility that diabetes status may be associated with H. pylori infection or metabolic syndrome. To account for these possibilities, we adjusted our findings for markers of socioeconomic status that had been significantly associated with the outcome variable (metabolic syndrome). A further potential limitation is our method of H. pylori detection. As we used the IgG Enzyme-linked Immunosorbent Assays (ELISA) method to diagnose H. pylori-positive individuals, Shin et al. (2012) found that serological detection methods were less sensitive than histological methods, and thus less capable of establishing a correlation between H. pylori and metabolic syndrome. However, no other studies have examined the association between H. pylori infection and metabolic syndrome using ELISA methods to detect H. pylori and ELISA methods have been proven to be a useful tool with high diagnostic performance in African settings (40). Finally, the potential of reverse causality may also explain found associations between H. pylori and metabolic syndrome. However, H. pylori infection in developing countries such as Ethiopia frequently occurs early in life (41), which makes it unlikely that patient metabolic parameters abnormality preceded to H. pylori infection.
The definition of metabolic syndrome used for this study was another limitation of this study. We opted to use the modified International Diabetes Federation (IDF) criteria used by Rafaeli et al. (2018), which used a BMI cutoff of ≥ 30 kg/m2 as a proxy for determining central obesity as opposed to waist circumference values (24). However, Body-mass index has been used as substitute for waist circumference because BMI and waist circumference have been found to be associated with BMI (42).
In conclusion, we found that H. pylori infection was significantly associated with lower levels of HDL-c and higher systolic blood pressure. However, we didn’t find a significant association between H. pylori infection status and overall metabolic syndrome. Future studies should seek to examine the relationship between H. pylori and metabolic syndrome in light of gastrointestinal conditions such as GERD, GU, and DU.