Expression of the fatty acid receptor GPR120 in the gut of diet-induced-obese rats and its role in GLP-1 secretion.

Stimulation of the G protein coupled receptor GPR120 has been shown to have anti-inflammatory and insulin-sensitizing effects, to promote glucagon like peptide-1 (GLP-1) secretion, and to play a key role in sensing dietary fat and control energy balance. In a search for differentially expressed genes potentially involved in food intake and body-weight regulation we identified GPR120 to be differentially regulated in the intestine of selectively bred diet induced obese (DIO) and diet resistant (DR) rats. Subsequently we investigated the effect of GPR120 receptor stimulation with the long chain fatty acid alpha linolenic acid (ALA) on GLP-1 secretion in rats. Independent of diet (high or low fat), GPR120 expression showed a two-fold increase in the intestine of DIO compared to DR rats. In situ hybridization revealed a broad expression of GPR120 in the gut mucosa in both intestinal epithelial and endocrine cells. Using double in situ hybridization GPR120 mRNA did not appear to be enriched in preproglucagon expressing L-cells. In line with the anatomical data, ALA administration did not increase circulating GLP-1 levels. Our data shows a widespread expression of GPR120 in the gut epithelium and can not confirm a major role for GPR120 in the regulation of GLP-1 secretion. The broad expression of GPR120 in the gut epithelium supports reports indicating a putative role of GPR120 as a sensor of dietary fat

Plasma levels of insulin (a) and active GLP-1 (b) upon gavage with ALA or OA in Sprague-Dawley rats.

<p>Sprague-Dawley rats were gavaged with vehicle or 28 mg/kg ALA/OA, and the levels of active GLP-1 and insulin were determined. N = 6. Two-way ANOVA with Bonferroni’s multiple comparisons correction (repeated measures) revealed no differences between GLP-1 or insulin plasma levels after administration of ALA when compared both to OA and vehicle treated animals. ALA: acid alpha-linolenic acid; OA: octanoic acid.</p

Expression of GPR120 in the intestine of DR and DIO rats aged 6 (a) and 12 (b) months.

<p>An L-cell rich part of the intestine (distal ileum) was used for RNA isolation and subsequent quantification by PCR. Two way ANOVA revealed a main effect of both genotype at 6 and 12 months of age (F = 96.15, P<0.001 and F = 14.42, p = <0.001 respectively). There was a main effect of diet at 6 but not 12 months of age (F = 4.69, p = 0.04 and F = 0.16, p = 0.69 respectively). There was no interaction between genotype and diet at 6 or 12 months. One way ANOVA showed statistical differences between both chow and HE fed DR and DIO rats at 6 months of age (p<0.001), and chow and HE fed DIO rats at 12 months of age (p<0,05). * = p<0.05; *** = <0.001.</p

Plasma levels of total GLP-1 upon oral gavage with glucose, ALA or OA.

<p>Wistar rats were gavaged with vehicle, 2 g/kg glucose or 28 mg/kg ALA/OA. N = 10. No GLP-1 secretagogue effect was seen upon ALA/OA gavage, whereas glucose gavage stimulated GLP-1 release and hence raised the levels of total GLP-1 (Two way ANOVA, Bonferroni posttest). ALA: acid alpha-linolenic acid; OA: octanoic acid. *** = p<0.001.</p

GPR120 and preproglucagon expression in the ileum and colon of the rat.

<p>Panel a and b: Low power photomicrographs of emulsion-dipped slides exposed to ileal (a) and colonic (b) sections hybridized with a ³³P labelled cRNA antisense probe to rat GPR120. GPR120 expression is in virtually all epithelial cells lining the villi (villi in ileal section outlined with dashed line in (a)). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088227#pone-0088227-g002" target="_blank">Fig 2</a> f is a higher power microphotograph illustrating the expression of GPR120 (silver grains) in the epithelial cells in the ileum (f). No signal is seen in a section hybridized with a sense GPR120 cRNA (c). In contrast, to the widespread distribution of GPR120 mRNA preproglucagon is only expressed in the endocrine L-cell in the gut. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088227#pone-0088227-g002" target="_blank">Figure 2</a> g shows preproglucagon expression (two cells indicated by arrows) in the ileum of a rat (longitudinal section) (g). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088227#pone-0088227-g002" target="_blank">Figure 2</a> h and 2 i are high power fluorescence photomicrographs of ileal sections subjected to a double in situ hybridization procedure. Preproglucagon expressing neurons appear green (arrows) and GPR120 expressing cells have overlaying silver grains (h & i). Both preproglucagon and non-preproglucagon cells contain silvergrains showing that GPR120 expression is not restricted to the L-cell. Scale bars: a, b, d, e = 500 µm, c-f = 100 µm, g = 100 µm, h-i = 10 µm.</p

Plasma levels of insulin and active GLP-1 upon gavage with ALA or OA in DIO and DR rats.

<p>DIO and DR rats fed either chow or a HE diet received an acute gavage of 28/kg ALA or OA. N = 8. Both ALA and OA gavage caused a modest but non-significant increase in plasma insulin levels in all four groups. Two-way ANOVA with Bonferroni’s multiple comparisons correction (repeated measures) revealed no differences between the effect of ALA and OA in any of the four different rat groups. The statistical analysis revealed that GLP-1 plasma levels were not affected by either ALA or OA and did not differ between the four different rat groups (p<0.05 considered statistically significant). ALA: acid alpha-linolenic acid; OA: octanoic acid.</p

Molecular epidemiology of the SARS-CoV-2 variant Omicron BA.2 sub-lineage in Denmark, 29 November 2021 to 2 January 2022

Following emergence of the SARS-CoV-2 variant Omicron in November 2021, the dominant BA.1 sub-lineage was replaced by the BA.2 sub-lineage in Denmark. We analysed the first 2,623 BA.2 cases from 29 November 2021 to 2 January 2022. No epidemiological or clinical differences were found between individuals infected with BA.1 versus BA.2. Phylogenetic analyses showed a geographic east-to-west transmission of BA.2 from the Capital Region with clusters expanding after the Christmas holidays. Mutational analysis shows distinct differences between BA.1 and BA.2