Improved glucose metabolism by <i>Eragrostis tef</i> potentially through beige adipocyte formation and attenuating adipose tissue inflammation

<div><p>Background</p><p>Teff is a staple food in Ethiopia that is rich in dietary fiber. Although gaining popularity in Western countries because it is gluten-free, the effects of teff on glucose metabolism remain unknown.</p><p>Aim</p><p>To evaluate the effects of teff on body weight and glucose metabolism compared with an isocaloric diet containing wheat.</p><p>Results</p><p>Mice fed teff weighed approximately 13% less than mice fed wheat (<i>p</i> < 0.05). The teff-based diet improved glucose tolerance compared with the wheat group with normal chow but not with a high-fat diet. Reduced adipose inflammation characterized by lower expression of <i>TNFα</i>, <i>Mcp1</i>, and <i>CD11c</i>, together with higher levels of cecal short chain fatty acids such as acetate, compared with the control diet containing wheat after 14 weeks of dietary treatment. In addition, beige adipocyte formation, characterized by increased expression of <i>Ucp-1</i> (~7-fold) and <i>Cidea</i> (~3-fold), was observed in the teff groups compared with the wheat group. Moreover, a body-weight matched experiment revealed that teff improved glucose tolerance in a manner independent of body weight reduction after 6 weeks of dietary treatment. Enhanced beige adipocyte formation without improved adipose inflammation in a body-weight matched experiment suggests that the improved glucose metabolism was a consequence of beige adipocyte formation, but not solely through adipose inflammation. However, these differences between teff- and wheat-containing diets were not observed in the high-fat diet group.</p><p>Conclusions</p><p>Teff improved glucose tolerance likely by promoting beige adipocyte formation and improved adipose inflammation.</p></div

Comparison of body weight and glucose metabolism between mice fed a chow diet with wheat (CD-wheat: Blue) or teff (CD-teff: Red).

<p>A: Study design. B: Body weight. C: Energy intake. D: Intraperitoneal glucose tolerance test (IPGTT) at week 6 (2.0 g/kg). E: Blood glucose levels after oral mixed meal administration of each assigned diet (2.2g/kg body weight, 33% solution in dH₂O) after 16 h of fasting at week 6. F: Plasma insulin levels during OMTT. G: Oral glucose tolerance test (OGTT) at week 9 (2 g/kg). H: Insulin concentration during OGTT. I: Intraperitoneal insulin tolerance test (IPITT) at week 9 (0.5 U/kg). * <i>p</i> < 0.05, n.s. = not significant. n = 5–9 in each groups.</p

Adipose tissue inflammation in mice fed a chow diet with wheat (CD-wheat) or chow diet with teff (CD-teff) for 14 weeks.

<p>A: Immunostaining of the macrophage marker F4/80 (brown) in adipose tissue (scale bar = 100 μM). B: mRNA levels of the macrophage marker, <i>F4/80</i> and <i>CD11c</i>, tumor necrosis factor α (<i>TNF</i>α), monocyte chemoattractant protein-1 (<i>Mcp-1</i>), Forkhead Boxprotein P3 <i>(Foxp3</i>), and adiponectin in adipose tissue. All mRNA expression data were normalized to <i>36B4</i>. C: Immunofluorescence staining for DAPI (blue), F4/80 (red) and TNFα (green) in adipose tissue (scale bar, 100 μm). * <i>p</i> < 0.05. n.s. = not significant.</p

Composition and energy density of experimental diets.

<p>Composition and energy density of experimental diets.</p

A proposed model of the effects of teff diet on glucose metabolism.

<p>Illustrated is a model of how teff improves glucose tolerance by increasing beige adipocyte formation and inhibiting adipose inflammation through increasing SCFAs concentrations.</p

The possible role of beige adipocyte formation in CD-teff treated mice.

<p>A: mRNA levels of thermogenic and beige adipocyte marker genes in the inguinal adipose tissue from mice fed for 14 weeks with CD-what or CD-teff. All mRNA expression data were normalized to <i>36B4</i>. B: Core body temperatures were measured at 10:00 AM under <i>ad lib</i> feeding conditions. C: Hematoxylin and eosin staining and Ucp-1 immunostaining in iWAT from CD-wheat and CD-teff mice (left and right columns, respectively). D: Immunofluorescence staining of perilipin (green) in iWAT. E: The size and distribution of adipocytes from iWAT pad of CD-wheat and CD-teff mice quantified by ImageJ. F: Number of adipocyte. n = 3. *<i>p</i> < 0.05, ** <i>p</i> < 0.01. n.s. = not significant.</p

Comparison of body weight and glucose metabolism between mice fed a high-fat diet with wheat (HFD-wheat: Blue) or teff (HFD-teff: Red).

<p>A: Study design. B: Body weight. C: Energy intake. D: Intraperitoneal glucose tolerance test (IPGTT) at week 6 (2 g/kg). E: Blood glucose levels after oral mixed meal administration of each assigned diet (2.2g/kg body weight, 33% solution in dH₂O) after 16 h of fasting at week 6. F: Plasma insulin levels during OMTT. G: Oral glucose tolerance test (OGTT) at week 9 (2 g/kg). H: Insulin concentration during OGTT. I: Intraperitoneal insulin tolerance test (IPITT) at week 9 (0.5 U/kg). * <i>p</i> < 0.05, n.s. = not significant. n = 5–9 in each groups.</p

Body weight matching by calorie restriction and glucose tolerance.

<p>A: Experimental design. B: Body weight. C: Intraperitoneal glucose tolerance test (IPGTT) at week 6 (2 g/kg). D: Oral glucose tolerance test (OGTT) at week 6 (2 g/kg). E: Insulin concentration during OGTT. F: mRNA levels of thermogenic and beige adipocyte marker genes in the inguinal adipose tissue from mice fed for 6 weeks with CD-wheat or CD-teff. All mRNA expression data were normalized to <i>36B4</i>. C: Immunofluorescence staining with DAPI (blue), and with antibodies for F4/80 (red), and TNFα (green) in adipose tissue (scale bar, 100 μm). n = 3–4. *<i>p</i> < 0.05, **. n.s. = not significant.</p

RT qPCR primer sequences.

<p>RT qPCR primer sequences.</p

Cecal short chain fatty acids (SCFAs) concentrations.

<p>A: Cecal SCFAs concentrations after 15-h fasting by LC-MS in mice fed with CD-wheat or CD-teff for 14 weeks. B: Cecal SCFAs concentrations were measured by LC-MS after 15-h fasting in mice fed with HFD-wheat or HFD-teff for 14 weeks. C: <i>In vitro</i> teff and wheat fermentation methods. D–F: Acetate, propionate and buyrate concentrations SCFA extracted from <i>in vitro</i> fermented teff and wheat by LC-MS. G& I: Hematoxylin and eosin stained slides of villi. H and J: Ileum villus length determined as indicated in the Materials and Methods for the CD-teff group compared (right panel) with the CD-wheat group (left panel). n = 3–4. *<i>p</i> < 0.05, *** <i>p</i> < 0.0001. n.s. = not significant.</p