Small bowel bacterial overgrowth and type 1 diabetes

Cardiovascular autonomic testsDiabetic autonomic neuropathyGastrointestinal dysmotilityGlycemic ControlGut Microbiota

Small bowel bacterial overgrowth and type 1 diabetes

Why this matters for your health

Diabetic autonomic neuropathy (DAN) affects about 20% of people with diabetes and is often undiagnosed. It can slow stomach emptying and gut movement, which may allow bacteria to overgrow in the small intestine (SIBO). SIBO can cause diarrhea, weight loss and poor absorption of nutrients and vitamins. This study suggests SIBO is far more common in type 1 diabetics with autonomic neuropathy. It also links SIBO to higher insulin requirements, which might matter for blood-sugar control.

Summary

This small study at Catholic University of the Sacred Heart in Rome enrolled 50 type 1 diabetic patients. Group A (25 patients) had normal cardiovascular autonomic tests, and Group B (25 patients) had abnormal ones. Autonomic neuropathy was diagnosed with four standard cardiovascular tests scored by the Ewing and Clarke method. All patients had a lactulose hydrogen breath test, and a rise in hydrogen above 20 ppm by 90 or 180 minutes counted as positive. Patients on laxatives, acid-suppressing drugs, probiotics, antibiotics or steroids in the previous month were excluded, as were those with previous stomach or pancreatic surgery and other known causes of SIBO. SIBO was far more common in the neuropathy group, and within that group, SIBO-positive patients needed more daily insulin. The authors suggest that poor gut motility maintains SIBO, and that SIBO-related sugar malabsorption and fermentation may raise insulin needs. They stress that larger studies are required.

Key findings

SIBO was found in 2 of 25 (8%) patients with normal autonomic tests (Group A) versus 11 of 25 (44%) with abnormal tests (Group B) (p < 0.01).
Daily insulin requirement did not differ between Group A and Group B overall (0.60 ± 0.2 vs 0.62 ± 0.1 U/kg, not significant).
Within Group B, SIBO-positive patients needed more insulin than SIBO-negative patients (p < 0.05). The abstract gives 0.66 ± 0.3 vs 0.59 ± 0.1 U/kg, while the results text gives 0.67 ± 0.2 vs 0.59 ± 0.3 U/kg.
Group B was older (52.4 ± 6 vs 44.2 ± 7 years) and had longer diabetes duration (29.8 ± 3.6 vs 22.3 ± 2 years). The paper gives no statistical comparison of these differences, so they could partly explain the SIBO difference.
The authors propose that in SIBO, glucose may be fermented or malabsorbed in the small bowel, which could raise insulin needs. This is a hypothesis, not something the study tested.
The paper cites earlier work showing abnormal small-bowel motility in about 80% of long-standing diabetics with delayed gastric emptying.
The lactulose breath test is described as non-invasive and cheaper than jejunal aspiration. Compared with aspiration, its sensitivity is cited as higher (68% vs 16.7%) and its specificity lower (44% vs 70%), so false positives are possible.
Limitations: the cohort was small and single-centre, and the design cannot show cause and effect. The authors themselves call for larger studies.
Although the aim mentions glycaemic control, and HbA1c was measured, no HbA1c results are reported in the text.
The authors acknowledge funding for the Catholic University Research Group on Gut Microflora from Fondazione Ricerca in Medicina.

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Citation

Ojetti V, Pitocco D, Scarpellini E, Zaccardi F, Scaldaferri F, Gigante G, Gasbarrini G, Ghirlanda G, Gasbarrini A. Small bowel bacterial overgrowth and type 1 diabetes. European Review for Medical and Pharmacological Sciences. 2009;13(6):419–423.