1.
Bacteria, Bones, and Stones: Managing Complications of Short Bowel Syndrome.
Johnson, E, Vu, L, Matarese, LE
Nutrition in clinical practice : official publication of the American Society for Parenteral and Enteral Nutrition. 2018;(4):454-466
Abstract
Short bowel syndrome (SBS) occurs in patients who have had extensive resection. The primary physiologic consequence is malabsorption, resulting in fluid and electrolyte abnormalities and malnutrition. Nutrient digestion, absorption, and assimilation may also be diminished by disturbances in the production of bile acids and digestive enzymes. Small bowel dilation, dysmotility, loss of ileocecal valve, and anatomical changes combined with acid suppression and antimotility drugs increase the risk of small intestinal bacterial overgrowth, further contributing to malabsorption. Metabolic changes that occur in SBS due to loss of colonic regulation of gastric and small bowel function can also lead to depletion of calcium, magnesium, and vitamin D, resulting in demineralization of bone and the eventual development of bone disease. Persistent inflammation, steroid use, parenteral nutrition, chronic metabolic acidosis, and renal insufficiency may exacerbate the problem and contribute to the development of osteoporosis. Multiple factors increase the risk of nephrolithiasis in SBS. In the setting of fat malabsorption, increased free fatty acids are available to bind to calcium, resulting in an increased concentration of unbound oxalate, which is readily absorbed across the colonic mucosa where it travels to the kidney. In addition, there is an increase in colonic permeability to oxalate stemming from the effects of unabsorbed bile salts. The risk of nephrolithiasis is compounded by volume depletion, metabolic acidosis, and hypomagnesemia, resulting in a decrease in renal perfusion, urine output, pH, and citrate excretion. This review examines the causes and treatments of small intestinal bacterial overgrowth, bone demineralization, and nephrolithiasis in SBS.
2.
Designing future prebiotic fiber to target metabolic syndrome.
Jakobsdottir, G, Nyman, M, Fåk, F
Nutrition (Burbank, Los Angeles County, Calif.). 2014;(5):497-502
Abstract
The metabolic syndrome (MetS), characterized by obesity, hyperlipidemia, hypertension, and insulin resistance, is a growing epidemic worldwide, requiring new prevention strategies and therapeutics. The concept of prebiotics refers to selective stimulation of growth and/or activity(ies) of one or a limited number of microbial genus(era)/species in the gut microbiota that confer(s) health benefits to the host. Sequencing the gut microbiome and performing metagenomics has provided new knowledge of the significance of the composition and activity of the gut microbiota in metabolic disease. As knowledge of how a healthy gut microbiota is composed and which bacterial metabolites are beneficial increases, tailor-made dietary interventions using prebiotic fibers could be developed for individuals with MetS. In this review, we describe how dietary fibers alter short-chain fatty acid (SCFA) profiles and the intrinsic and extrinsic effects of prebiotics on host metabolism. We focus on several key aspects in prebiotic research in relation to MetS and provide mechanistic data that support the use of prebiotic fibers in order to alter the gut microbiota composition and SCFA profiles. Further studies in the field should provide reliable mechanistic and clinical evidence for how prebiotics can be used to alleviate MetS and its complications. Additionally, it will be important to clarify the effect of individual differences in the gut microbiome on responsiveness to prebiotic interventions.
3.
Evaluation of small bowel bacterial overgrowth.
Schiller, LR
Current gastroenterology reports. 2007;(5):373-7
Abstract
Small bowel bacterial overgrowth historically has been associated with malabsorption syndrome attributed to deconjugation of bile acids in the upper small intestine. Recent reports raise the possibility that bacterial overgrowth may be a cause of watery diarrhea or irritable bowel syndrome. Quantitative culture of jejunal contents has been the gold standard for diagnosis, but a variety of indirect tests have been developed (and mostly discarded) over the years in an attempt to facilitate the diagnosis of small bowel bacterial overgrowth. These include breath tests and biochemical tests based on bacterial metabolism of various substrates. Problems with these indirect tests include rapid transit, which may cause substrate to reach the luxuriant bacterial flora in the colon, producing false positives and vagaries of the tests themselves, which may produce falsely negative results. The perfect test for small bowel bacterial overgrowth is yet to be devised.