Intestinal Alkaline Phosphatase Deficiency Is Associated with Ischemic Heart Disease

Abstract

Background: We have previously shown that the deficiency of the gut enzyme intestinal alkaline phosphatase (IAP) is associated with type 2 diabetes mellitus (T2DM) in humans, and mice deficient in IAP develop the metabolic syndrome, a precipitant of T2DM and ischemic heart disease (IHD). We hypothesized that IAP deficiency might also be associated with IHD in humans. We aimed to determine the correlation between the IAP level and IHD in humans.

Methods and results: The IHD patients were recruited from the National Institute of Cardiovascular Diseases (NICVD), Dhaka, Bangladesh, and the control healthy participants were recruited from a suburban community of Dhaka. We determined the IAP level in the stools of 292 IHD patients (187 males, 105 females) and 331 healthy control people (84 males, 247 females). We found that compared to controls, IHD patients have approx. 30% less IAP (mean ± SEM: 63.7 ± 3.5 vs. 44.9 ± 2.1 U/g stool, respectively; p < 0.000001), which indicates that IAP deficiency is associated with IHD, and a high level of IAP is probably protective against IHD in humans. The adjusted generalized linear model (GLM) of regression analysis predicted a strong association of IAP with IHD (p = 0.0035). Multiple logistic regression analysis showed an independent inverse relationship between the IAP level and the IHD status (odds ratio, OR = 0.993 with 95% CI 0.987-0.998; p < 0.01).

Conclusions: IAP deficiency is associated with IHD, and a high level of IAP might be protective against IHD.

Figure 1

Patients with ischemic heart disease (IHD) have low level of intestinal alkaline phosphatase (IAP) in their stool. Stool samples of control healthy participants and IHD patients were homogenized in a stool dilution buffer followed by centrifugation and collection of supernatant. The supernatant was assayed for IAP concentration using an automatic biochemistry analyzer. Statistics: values are expressed as mean ± SEM. Statistical significance of the difference between two groups was tested using the unpaired two-tailed Student's t-test. p < 0.05 is considered significant. ^∗p < 0.05, ^∗∗∗p < 0.001. The post hoc statistical power of the study was 99.6%, validating the adequacy of power (conventionally, >80% power at α = 0.05) for sample sizes. Percentage of IAP in IHD patients compared to healthy controls: total, 70.5%; male, 79.9%; female, 72.9%. The average IAP level is 20.7% less in healthy control males compared to healthy females; however, the difference is not significant (p = 0.087223). The average IAP level is 13.0% less in IHD males compared to IHD females; however, the difference is not significant (p = 0.140301).

Figure 2

IAP levels are low in IHD patients at most percentile points. Individual IAP values from each group (healthy controls or IHD patients) were arranged from the lowest to the highest, and then, the average IAP value within each 20th percentile was calculated (n = 29 within each 20th percentile for IHD patients, and n = 66 within each 20th percentile for healthy controls). Average values for corresponding percentiles are plotted. Statistics: values are expressed as mean ± SEM. Statistical significance of the difference between two respective groups was tested using the unpaired two-tailed Student's t-test. p < 0.05 is considered significant. ns: not significant; ^∗∗∗p < 0.001. Note: only the values in first and last 20 percentile divisions will be greatly affected if an “outlier” (a few extremely high or low values, compared to the most other values, affecting the mean value) is present. The values within 20th and 80th percentiles are real, not affected by outliers.

Figure 3

Obese women with high IAP do not develop IHD. Stool samples of healthy participants and IHD patients were assayed for IAP concentration using an automatic biochemistry analyzer (see Figure 1). The healthy controls as well as IHD patients were categorized in two groups, one with high BMI (>25.0 kg/m²) and the other having low BMI (<25.0 kg/m²). Statistics: values are expressed as mean ± SEM. Statistical significance of the difference between two groups was tested using the unpaired two-tailed Student's t-test. p < 0.05 is considered significant. ^∗p < 0.05; ^∗∗p < 0.01; ^∗∗∗p < 0.001. Note: the IAP values are mildly higher in obese male control participants compared to obese male IHD patients; however, the difference is not significant (p = 0.648285). There is no significant difference in IAP levels between high- and low-BMI groups of healthy controls as well as between high- and low-BMI groups of IHD patients. Also, there is no significant difference in IAP levels between males and females of high- and low-BMI groups of the respective study population.