Dr. Ron’s Research Review – August 11, 2010

This week’s research review contains several articles on food allergies, beginning with a recent review published in JAMA:

Food Allergies

Diagnosing and managing common food allergies: a systematic review (Chafen, Newberry et al. 2010)

Food allergy: separating the science from the mythology (Brandtzaeg 2010)

David Artis: Fear no worm. Interview by Amy Maxmen (Artis 2009)

Of Interest

Alpha-tocopherol: looking beyond an antioxidant (Engin 2009)

Alpha-lipoic Acid Improves Endothelial Dysfunction in Patients with Subclinical Hypothyroidism  (Gd, Jh et al. 2010)

In the News

On nutrition: Diabetes and celiac disease

By Barbara Quinn, Seattle Times, Link

Dr. Ron


Articles

Alpha-tocopherol: looking beyond an antioxidant

(Engin 2009) Download

Vitamin E is an important natural antioxidant, and its most common and biologically active form is alpha-tocopherol. In addition to this, specific regulatory effects of vitamin E have been revealing. The body exerts a certain effort to regulate its tissue levels with specific tocopherol transport proteins and membrane receptors. Antiproliferative and protein kinase C-suppressing effects of alpha-tocopherol have been previously demonstrated, which have not been mimicked by beta-tocopherol or probucol. Protein kinase C promises to be an important area of interest in the means of glaucoma and cataractogenesis. It has been shown in different models that retinal vascular dysfunction due to hyperglycemia could be prevented by alpha-tocopherol via the diachylglycerol-protein kinase C pathway. Glutamate transporter activity has been shown to be modulated by protein kinase C. This pathway is also important in intraocular pressure-lowering effects of prostaglandin and its analogs in glaucoma therapy. Filtran surgery became another possible area of usage of alpha-tocopherol since its antiproliferative effect has been demonstrated in human Tenon's capsule fibroblasts. Prevention of posterior capsule opacification is another area for future studies. It is evident that when correct and safe modulation is the objective, alpha-tocopherol merits a concern beyond its mere antioxidant properties.

Alpha-lipoic Acid Improves Endothelial Dysfunction in Patients with Subclinical Hypothyroidism

            (Gd, Jh et al. 2010) Download

OBJECTIVE: Many studies showed that impairment of flow-mediated endothelium-dependent arterial dilation (FMD) exists in patients with subclinical hypothyroidism (sHT). The crucial mechanism of this endothelial dysfunction remain unclear. We hypothesized that oxidative stress may be partially responsible for the impairment in FMD in patients with sHT. Thus, the present study was designed to assess whether the antioxidant alpha-lipoic acid can improve endothelial dysfunction in patients with sHT. PATIENTS AND METHODS: Forty women with newly diagnosed sHT and 18 healthy women with euthyroid status were enrolled. Patients were randomized into 2 groups to receive no treatment (n=20), alpha-lipoic acid (n=20) for 3 weeks. We measured the FMD at baseline and after 3 weeks. RESULTS: FMD in alpha-lipoic acid and no-treatment group were 3.92% and 4.02%, respectively, which were significantly lower than that in controls (5.64%) (p<0.001). After 3 weeks treatment, compared with before treatment in sHT patients, plasma thiobarbituric acid reactive substances (TBARS) levels decreased significantly in alpha-lipoic acid group (p<0.001), and remain unchanged in no-treatment group (p>0.05). FMD improved markedly (4.82%) in alpha-lipoic acid group (p<0.01), and remain unchanged in no-treatment group (p>0.05). The absolute changes in FMD showed significant negative correlation with the changes in TBARS (r=-0.773, p<0.001). CONCLUSION: Our data showed that sHT patients exists impaired endothelial function, and antioxidant alpha-lipoic acid can improve endothelial function, through decrease of oxygen- derived free radicals.

David Artis: Fear no worm. Interview by Amy Maxmen

            (Artis 2009) Download

As the incidence of inflammatory disease and food allergies increases in the industrialized world, David Artis wonders if something is wrong with the little friends in our guts.

Food allergy: separating the science from the mythology

            (Brandtzaeg 2010) Download

Numerous genes are involved in innate and adaptive immunity and these have been modified over millions of years. During this evolution, the mucosal immune system has developed two anti-inflammatory strategies: immune exclusion by the use of secretory antibodies to control epithelial colonization of microorganisms and to inhibit the penetration of potentially harmful agents; and immunosuppression to counteract local and peripheral hypersensitivity against innocuous antigens, such as food proteins. The latter strategy is called oral tolerance when induced via the gut. Homeostatic mechanisms also dampen immune responses to commensal bacteria. The mucosal epithelial barrier and immunoregulatory network are poorly developed in newborns. The perinatal period is, therefore, critical with regard to the induction of food allergy. The development of immune homeostasis depends on windows of opportunity during which innate and adaptive immunity are coordinated by antigen-presenting cells. The function of these cells is not only orchestrated by microbial products but also by dietary constituents, including vitamin A and lipids, such as polyunsaturated omega-3 fatty acids. These factors may in various ways exert beneficial effects on the immunophenotype of the infant. The same is true for breast milk, which provides immune-inducing factors and secretory immunoglobulin A, which reinforces the gut epithelial barrier. It is not easy to dissect the immunoregulatory network and identify variables that lead to food allergy. This Review discusses efforts to this end and outlines the scientific basis for future food allergy prevention.

Diagnosing and managing common food allergies: a systematic review

(Chafen, Newberry et al. 2010) Download

CONTEXT: There is heightened interest in food allergies but no clear consensus exists regarding the prevalence or most effective diagnostic and management approaches to food allergies. OBJECTIVE: To perform a systematic review of the available evidence on the prevalence, diagnosis, management, and prevention of food allergies. DATA SOURCES: Electronic searches of PubMed, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effects, and Cochrane Central Register of Controlled Trials. Searches were limited to English-language articles indexed between January 1988 and September 2009. STUDY SELECTION: Diagnostic tests were included if they had a prospective, defined study population, used food challenge as a criterion standard, and reported sufficient data to calculate sensitivity and specificity. Systematic reviews and randomized controlled trials (RCTs) for management and prevention outcomes were also used. For foods where anaphylaxis is common, cohort studies with a sample size of more than 100 participants were included. DATA EXTRACTION: Two investigators independently reviewed all titles and abstracts to identify potentially relevant articles and resolved discrepancies by repeated review and discussion. Quality of systematic reviews and meta-analyses was assessed using the AMSTAR criteria, the quality of diagnostic studies using the QUADAS criteria most relevant to food allergy, and the quality of RCTs using the Jadad criteria. DATA SYNTHESIS: A total of 12,378 citations were identified and 72 citations were included. Food allergy affects more than 1% to 2% but less than 10% of the population. It is unclear if the prevalence of food allergies is increasing. Summary receiver operating characteristic curves comparing skin prick tests (area under the curve [AUC], 0.87; 95% confidence interval [CI], 0.81-0.93) and serum food-specific IgE (AUC, 0.84; 95% CI, 0.78-0.91) to food challenge showed no statistical superiority for either test. Elimination diets are the mainstay of therapy but have been rarely studied. Immunotherapy is promising but data are insufficient to recommend use. In high-risk infants, hydrolyzed formulas may prevent cow's milk allergy but standardized definitions of high risk and hydrolyzed formula do not exist. CONCLUSION: The evidence for the prevalence and management of food allergy is greatly limited by a lack of uniformity for criteria for making a diagnosis.


References

Artis, D. (2009). "David Artis: Fear no worm. Interview by Amy Maxmen." J Exp Med 206(2): 262-3.

Brandtzaeg, P. (2010). "Food allergy: separating the science from the mythology." Nat Rev Gastroenterol Hepatol 7(7): 380-400.

Chafen, J. J., S. J. Newberry, et al. (2010). "Diagnosing and managing common food allergies: a systematic review." JAMA 303(18): 1848-56.

Engin, K. N. (2009). "Alpha-tocopherol: looking beyond an antioxidant." Mol Vis 15: 855-60.

Gd, X., P. Jh, et al. (2010). "Alpha-lipoic Acid Improves Endothelial Dysfunction in Patients with Subclinical Hypothyroidism." Exp Clin Endocrinol Diabetes.