Dietary LPS traces influences disease expression of the diet-induced obese mouse.

Lipopolysaccharides (LPS) from Gram negative bacteria are generally present in laboratory animal chow diets in unknown amounts, which has been correlated to significant immunological differences between animals receiving diets with either low or high "naturally" occurring LPS content. LPS in the blood stream has been linked to glucose intolerance through Toll-like receptor mediated release of pro-inflammatory cytokines, metabolic endotoxemia, adipose tissue inflammation. LPS uptake increases when co-administered with fat, therefore uncontrolled LPS levels in a high-fat diet may increase variation in development of disease when high-fat diets are used to induce obesity and type 2 diabetes. Three experiments were conducted, in which C57BL/6NTac mice received high-fat (60%) or low fat (10%) diets with or without LPS for 8 or 20 weeks investigating the short and long term effects. Three different doses of LPS were used to investigate dosage effect, and ampicillin to isolate the effect of dietary LPS. Dietary LPS increased LPS levels in the blood stream, and affected the level of glycated haemoglobin (HbA1c), a key parameter in this model, in a dose dependant manner (p < 0.05). There was a strong tendency toward slower glucose uptake in the LPS supplemented groups once obesity was established, but the differences disappeared after 20 weeks. A high-fat diet slightly increased serum LPS and altered ileal expression of il10 and tnfa (p < 0.05). In conclusion, LPS seems to affect the glucose metabolism in a time-dose dependant manner, and uncontrolled variation in LPS levels of a diet may therefore increase inter-study variation.

Transfer of gut microbiota from lean and obese mice to antibiotic-treated mice.

Transferring gut microbiota from one individual to another may enable researchers to "humanize" the gut of animal models and transfer phenotypes between species. To date, most studies of gut microbiota transfer are performed in germ-free mice. In the studies presented, it was tested whether an antibiotic treatment approach could be used instead. C57BL/6 mice were treated with ampicillin prior to inoculation at weaning or eight weeks of age with gut microbiota from lean or obese donors. The gut microbiota and clinical parameters of the recipients was characterized one and six weeks after inoculation. The results demonstrate, that the donor gut microbiota was introduced, established, and changed the gut microbiota of the recipients. Six weeks after inoculation, the differences persisted, however alteration of the gut microbiota occurred with time within the groups. The clinical parameters of the donor phenotype were partly transmissible from obese to lean mice, in particularly ß cell hyperactivity in the obese recipients. Thus, a successful inoculation of gut microbiota was not age dependent in order for the microbes to colonize, and transferring different microbial compositions to conventional antibiotic-treated mice was possible at least for a time period during which the microbiota may permanently modulate important host functions.

Whey protein reduces early life weight gain in mice fed a high-fat diet.

An increasing number of studies indicate that dairy products, including whey protein, alleviate several disorders of the metabolic syndrome. Here, we investigated the effects of whey protein isolate (whey) in mice fed a high-fat diet hypothesising that the metabolic effects of whey would be associated with changes in the gut microbiota composition. Five-week-old male C57BL/6 mice were fed a high-fat diet ad libitum for 14 weeks with the protein source being either whey or casein. Faeces were collected at week 0, 7, and 13 and the fecal microbiota was analysed by denaturing gradient gel electrophoresis analyses of PCR-derived 16S rRNA gene (V3-region) amplicons. At the end of the study, plasma samples were collected and assayed for glucose, insulin and lipids. Whey significantly reduced body weight gain during the first four weeks of the study compared with casein (P<0.001-0.05). Hereafter weight gain was similar resulting in a 15% lower final body weight in the whey group relative to casein (34.0±1.0 g vs. 40.2±1.3 g, P<0.001). Food intake was unaffected by protein source throughout the study period. Fasting insulin was lower in the whey group (P<0.01) and glucose clearance was improved after an oral glucose challenge (P<0.05). Plasma cholesterol was lowered by whey compared to casein (P<0.001). The composition of the fecal microbiota differed between high- and low-fat groups at 13 weeks (P<0.05) whereas no difference was seen between whey and casein. In conclusion, whey initially reduced weight gain in young C57BL/6 mice fed a high-fat diet compared to casein. Although the effect on weight gain ceased, whey alleviated glucose intolerance, improved insulin sensitivity and reduced plasma cholesterol. These findings could not be explained by changes in food intake or gut microbiota composition. Further studies are needed to clarify the mechanisms behind the metabolic effects of whey.

Differential expression of pancreatitis-associated protein and thrombospondins in arterial versus venous tissues.

BACKGROUND/AIMS: Arteries and veins modulate cardiovascular homeostasis and contribute to hypertension pathogenesis. Functional differences between arteries and veins are based upon differences in gene expression. To better characterize these expression patterns, and to identify candidate genes that could be manipulated selectively in the venous system, we performed whole genome expression profiling of arteries and veins. METHODS: We used the CodeLink platform and the major artery (thoracic aorta) and vein (caudal vena cava) of the rat. RESULTS: The most prominent difference was pancreatitis-associated protein (PAP1), expressed 64-fold higher in vena cava versus aorta. Expression of mRNA for thrombospondins (TSP-1, TSP-4) was greater than 5-fold higher in veins versus arteries. Higher mRNA expression of TSP-1, TSP-2, TSP-4 and PAP1 in vena cava versus aorta was confirmed by PCR. Immunohistochemical analysis of tissue sections qualitatively confirmed a higher expression of these proteins in vena cava versus aorta. CONCLUSION: This is the first gene array study of adult rat arterial and venous tissues, and also the first study to report differences in inflammatory genes between arteries and veins. Data from these studies may provide novel insights into the genetic basis for functional differences between arteries and veins in health and disease.