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

Oral glucose tolerance test after 12 weeks of dietary intervention.

<p>Glucose clearance was significantly improved by whey (P<0.05, HF casein compared to HF whey, Repeated Measurements ANOVA and Tukey's Post Hoc test). Asterisks indicate time points were blood glucose in HF whey is significantly lower than in HF casein (one-way ANOVA). * P<0.05, ** P<0.01, *** P<0.001 in comparison to HF casein. Data is presented as mean ±SEM. HF casein, high-fat diet with casein (n = 15), HF whey, high-fat diet with whey protein isolate (n = 15), LF casein, low-fat diet with casein (n = 10).</p

Fecal microbiota profile after 13 weeks of dietary intervention.

<p>Principal Component Analysis Plot based on Denaturing Gradient Gel Electrophoresis profiles of 16S rRNA gene PCR-derived amplicons of fecal samples. Each ball represents the relative bacterial composition of one fecal sample. No difference in gut microbiota composition was detected between HF casein (red balls) and HF whey (green balls) while the composition significantly differed between high-fat and low-fat groups (LF casein, yellow balls) (P<0.05). HF casein, high-fat diet with casein, HF whey, high-fat diet with whey protein isolate, LF casein, low-fat diet with casein.</p

Body weight during 14 weeks of dietary intervention.

<p>The body weight of HF whey was lower than HF casein at all times after week 0 (P<0.05). The weekly weight gain was lower in HF whey than HF casein at week 1, 2, and 4 (*, P<0.05). Data is presented as mean ±SEM and compared by one-way ANOVA. HF casein, high-fat diet with casein (n = 15), HF whey, high-fat diet with whey protein isolate (n = 15), LF casein, low-fat diet with casein (n = 10).</p

Food intake and feed efficiency.

<p>Results not sharing a common superscript differ significantly (P<0.05).</p

Plasma lipid profile and glycemic parameters.

<p>Results not sharing a common superscript differ significantly (P<0.05).</p><p>HbA1c, glycated haemoglobin. QUICKI, Quantitative Insulin Sensitivity Check Index.</p

Body composition after 14 weeks of dietary intervention.

<p>Results not sharing a common superscript differ significantly (P<0.05).</p