In the matter of sex...sex matters in medical-scientific research

Sex-related effects of nutritional supplementation of Escherichia coli: relevance to eating disorders

OBJECTIVES

The biological background of sex-related differences in the development of eating disorders (EDs) is unknown. Recent data showed that gut bacteria Escherichia coli induce autoantibodies against anorexigenic α-melanocyte-stimulating hormone (α-MSH) associated with psychopathology in ED. The aim of this study was to compare the effects of E. coli on feeding and autoantibodies against α-MSH and adrenocorticotropic hormone (ACTH), between female and male rats.

METHODS

Commensal E. coli K12 were given in a culture medium daily to adult Wistar rats by intragastric gavage over a 3-wk period; control rats received culture medium only.

RESULTS

Before gavage, E. coli K12 DNA was detected in feces of female but not male rats. E. coli provision was accompanied by an increase in body weight gain in females, but a decrease in body weight gain and food intake in males. Independent of E. coli treatment, plasma levels of anti-α-MSH and ACTH immunoglobulin (Ig)G were higher in female than male rats. Females responded to E. coli by increasing α-MSH IgG levels and affinity, but males by increasing α-MSH IgM levels. Affinity of IgG for ACTH was increased in both E. coli-treated females and males, although with different kinetics. IgG from females stimulated more efficiently α-MSH-induced cyclic adenosine monophosphate production by melanocortin 4 receptor-expressing cells compared with IgG from males.

DISCUSSION

Sex-related response to how E. coli affects feeding and anti-melanocortin hormone antibody production may depend on the presence of these bacteria in the gut before E. coli supplementation. These data suggest that sex-related presence of certain gut bacteria may represent a risk factor for ED development.

Lessons learned from gastric bypass operations in rats

Numerous studies using gastric bypass rat models have been recently conducted to uncover underlying physiological mechanisms of Roux-en-Y gastric bypass. Reflecting on lessons learned from gastric bypass rat models may thus aid the development of gastric bypass models in mice and other species. This review aims to discuss technical and experimental details of published gastric bypass rat models to understand advantages and limitations of this experimental tool. The review is based on PubMed literature using the search terms 'animal model', 'rodent model', 'bariatric surgery', 'gastric bypass', and 'Roux-en-Y gastric bypass'. All studies published up until February 2011 were included. 32 studies describing 15 different rat gastric bypass models were included. Description of surgical technique differs in terms of pouch size, limb lengths, preservation of the vagal nerve, and mortality rate. Surgery was carried out exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly. Technical and experimental variations in published gastric bypass rat models complicate comparison and identification of potential physiological mechanisms involved in gastric bypass. In summary, there is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data.