Leukocyte-subset counts in idiopathic parkinsonism provide clues to a pathogenic pathway involving small intestinal bacterial overgrowth. A surveillance study

Abstract

Background: Following Helicobacter pylori eradication in idiopathic parkinsonism (IP), hypokinesia improved but flexor-rigidity increased. Small intestinal bacterial-overgrowth (SIBO) is a candidate driver of the rigidity: hydrogen-breath-test-positivity is common in IP and case histories suggest that Helicobacter keeps SIBO at bay.

Methods: In a surveillance study, we explore relationships of IP-facets to peripheral immune/inflammatory-activation, in light of presence/absence of Helicobacter infection (urea-breath- and/or stool-antigen-test: positivity confirmed by gastric-biopsy) and hydrogen-breath-test status for SIBO (positivity: >20 ppm increment, 2 consecutive 15-min readings, within 2h of 25G lactulose). We question whether any relationships found between facets and blood leukocyte subset counts stand in patients free from anti-parkinsonian drugs, and are robust enough to defy fluctuations in performance consequent on short t½ therapy.

Results: Of 51 IP-probands, 36 had current or past Helicobacter infection on entry, 25 having undergone successful eradication (median 3.4 years before). Thirty-four were hydrogen-breath-test-positive initially, 42 at sometime (343 tests) during surveillance (2.8 years). Hydrogen-breath-test-positivity was associated inversely with Helicobacter-positivity (OR 0.20 (95% CI 0.04, 0.99), p<0.05).In 38 patients (untreated (17) or on stable long-t½ IP-medication), the higher the natural-killer count, the shorter stride, slower gait and greater flexor-rigidity (by mean 49 (14, 85) mm, 54 (3, 104) mm.s-1, 89 (2, 177) Nm.10-3, per 100 cells.μl-1 increment, p=0.007, 0.04 & 0.04 respectively, adjusted for patient characteristics). T-helper count was inversely associated with flexor-rigidity before (p=0.01) and after adjustment for natural-killer count (-36(-63, -10) Nm.10-3 per 100 cells.μl-1, p=0.007). Neutrophil count was inversely associated with tremor (visual analogue scale, p=0.01). Effect-sizes were independent of IP-medication, and not masked by including 13 patients receiving levodopa (except natural-killer count on flexor-rigidity). Cellular associations held after allowing for potentially confounding effect of hydrogen-breath-test or Helicobacter status. Moreover, additional reduction in stride and speed (68 (24, 112) mm & 103 (38, 168) mm.s-1, each p=0.002) was seen with Helicobacter-positivity. Hydrogen-breath-test-positivity, itself, was associated with higher natural-killer and T-helper counts, lower neutrophils (p=0.005, 0.02 & 0.008).

Conclusion: We propose a rigidity-associated subordinate pathway, flagged by a higher natural-killer count, tempered by a higher T-helper, against which Helicobacter protects by keeping SIBO at bay.

Figure 1

Stickmen representing postural abnormalities in parkinsonism. Simian (left), with flexion of neck, thoracic and lumbar spine, hips and knees, and hunched shoulders, is the most recognised. In coronal (right), there is lateral flexion of body and related abnormalities.

Figure 2

Relationship between breath-hydrogen concentration and blood leukocyte subsets over time after lactulose administration. Average increase in breath-hydrogen over baseline (343 tests; 15 min sampling intervals over 4h) is standardised for leukocyte count. Test positivity in the first 2h was associated with higher natural killer and T-helper mononuclear counts, lower neutrophils. Subsequently, breath-hydrogen was associated with T-helper count, tended to be with natural-killer (3 (95% CI 0, 4) & 5 (0, 11) ppm per 100 cell.μl^-1 increment, respectively, p=0.02 & 0.06), but was not associated with neutrophil.

Figure 3

Relationship of brady/hypokinesia and flexor-rigidity to natural-killer count in core group, after adjustment for demographic characteristics and, in the case of flexor-rigidity, for T-helper count. (Standardised, as appropriate, to no background medication, age 65 years, height 1.7 m, time since diagnosis 6 years, T-helper count 1000 μl^-1.) Regression line and 95% CI are shown for stride-length, free-walking-speed, the brady/hypokinesia scale and flexor-rigidity on natural-killer count. Although all values for a longitudinal outcome were used to estimate regression lines, the points shown are the average per person. (Brady/hypokinesia scale: 0 = marked impairment on video, 100 = none).

Figure 4

Relationship of rigidity to T-helper count in core group, after adjustment for demographic characteristics, and, in the case of flexor-rigidity, for natural-killer count. (Standardised, as appropriate, to time since diagnosis 6 years, body weight 80 kg, natural-killer count 250 μl^-1.) Regression line and 95% CI are shown for flexor- and extensor-rigidity on T-helper count.

Figure 5

Relationship, in core group, of hypokinesia (stride-length) to bradykinesia (speed) and flexor-rigidity to extensor, and independence of hypokinesia from rigidity. No adjustment is made for demographic covariates. Regression line and 95% CI are shown for stride on speed (upper left graph - point with co-ordinates of stride 378 mm & speed 0.3 m.s^-1 not influential); flexor-rigidity on extensor (upper right); stride on flexor-rigidity (lower left); stride on extensor-rigidity (lower right - after removal of an influential point: co-ordinates stride 378 mm & rigidity 990 Nm.10^-3).

Figure 6

Relationship of supine mean arterial pressure to natural-killer count in core group, after adjustment for demographic covariates (standardised to age 65 years, time since diagnosis 6 years, body weight 80 kg). Regression line and 95% CI are shown. On inclusion of flexor-rigidity in multivariable model, cellular association remained 3.4 (0.4, 6.5) mmHg per 100 cells.μl^-1 increment, p=0.03), and an additional small effect on pressure was seen (increase of 3.4 (0.8, 6.0) mmHg per 500 Nm.10^-3 greater rigidity, p=0.01).

Figure 7

Relationship of mean tremor whilst seated to neutrophil count in core group, after adjustment for time since diagnosis (to 6 years). Regression line and 95% CI are shown. Outlier for neutrophil count (9.48 x10⁹.l^-1) not influential (size of effect after exclusion: decrease in tremor of 7.9 (95% CI 1.3, 14.5) units per 10⁹.l^-1 cell increment, p=0.02). Tremor scale: 0 = most intrusive, 100 = no tremor (N.B. 3 values >100 (i.e. 101, 103, 108) consequent on adjustment for time since diagnosis).

Figure 8

Between-patient relationships of clinical surveillance tools in core group. Outcome measures are represented by discs. Single variable associations, of strength p≤.05, are represented by lines ending at corresponding disc perimeters. The closer the discs, the more variance explained: line length is inversely proportional to variance in one outcome explained by the other. Relationships resting on influential points, or not holding in mixed-effects models, were dismissed. Absence of connecting lines means lack of association. Greatest variance represented by a connecting line between a pair of outcomes (78%) is for free-walking-speed and mean stride-length, least (13%) for reaction time and speed. Variance explained by multiple associates can, of course, be cumulative (e.g. variance in simian posture rating explained individually by flexor- and extensor-rigidity, stride and speed is 30, 53% 40% & 40%, respectively, but together they explain 68%). Principle component analysis of 13 items making up simian posture scale indicated a first component, average score for 9 items, with a greater within-scale consistency than the original (Chronbach’s alpha 0.8 cf 0.7), and retaining association with brady/hypokinesia and rigidity. Other components could not be interpreted simply in terms of remaining items: 3 compensatory strategies (chin projection, hands behind back at stance, shoulder retraction), and dropped jaw. These were not associated with brady/hypokinesia and rigidity, and showed no association inter se.