The Gut Microbiota Mediates Red Raspberry Polyphenol Health Benefits in Diet-Induced Obesity

Mahaa Albusharif Author

04/03/2021 Added

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The gut microbiome plays a role in mediating health benefits found in red raspberry polyphenols in diet induced obesity

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[00:00:01.300]Hello, my name is Mahaa Albusharif.
[00:00:03.460]I'll be presenting on the role of the gut microbiota
[00:00:06.070]in mediating red raspberry polyphenol health benefits
[00:00:09.600]in diet induced obesity.
[00:00:11.750]I worked with Dr. Amanda Ramer-Tait in the Department
[00:00:14.440]of Food Science and Technology.
[00:00:18.260]Obesity is a worldwide health health concern
[00:00:21.110]that is associated
[00:00:22.090]with having excess amount of adipose tissue in our body.
[00:00:25.480]It could be due to environmental factors or genetics.
[00:00:29.130]About 38 million children
[00:00:30.750]under the age of five were overweight or obese in 2019.
[00:00:36.760]Polyphenols are plant derived
[00:00:38.610]organic compounds are made of multiple phenolic units
[00:00:42.900]and they play a vital role
[00:00:44.190]in our health by regulating our metabolism.
[00:00:47.260]One polyphenol that we're interested
[00:00:49.060]in is called ellagic acid
[00:00:51.140]which decreases adiposity, improves insulin sensitivity
[00:00:54.450]and regulates energy homeostasis.
[00:00:57.260]And about 60% of the phenolic compounds
[00:01:00.370]in red raspberries are ellagic acid.
[00:01:03.350]We're also interested in the gut derived metabolites
[00:01:05.950]the urolithins, also known as the Uros,
[00:01:08.990]which our gut metabolites are produced
[00:01:11.300]from ellagic acid containing foods
[00:01:13.189]such as red raspberries, pomegranates, and walnuts.
[00:01:18.310]Some of this ellagic acid can reach the intestine
[00:01:20.910]where it undergoes microbial conversion
[00:01:22.770]to yield these urolithins.
[00:01:26.950]And to this day, there are no causative studies
[00:01:29.540]that determine the microbiota is required
[00:01:32.100]to elicit host metabolic benefits.
[00:01:34.840]And so this brings us
[00:01:35.680]to our central question: is the gut microbiota required
[00:01:39.310]for the metabolic benefit of red raspberry polyphenols
[00:01:42.350]and their gut derived metabolites, the urolithins?
[00:01:46.639]For our study design
[00:01:47.965]we used germ-free mice and split them into two groups.
[00:01:51.090]One remained germ-free with no gut microbiota
[00:01:54.050]and the other was inoculated and given a microbiome,
[00:01:57.260]which we termed conventionalized.
[00:01:59.510]Within these two groups we separated the mice
[00:02:01.580]into three groups depending on their diet.
[00:02:03.880]So we had low fat fed mice, which had 10% calories from fat,
[00:02:08.780]high fat fed mice with 45% calories from fat,
[00:02:12.220]and high-fat with 0.4% of the red raspberry diet
[00:02:16.360]for both germ-free and conventional mice.
[00:02:19.710]And the image in the middle shows the isolator that was used
[00:02:22.900]for the germ-free mice, because they have to be handled
[00:02:25.620]with care since they do not contain any sort of bacteria.
[00:02:29.430]On the right side is a pure polyphenol extract powder
[00:02:32.520]that was given in the high fat red raspberry mouse diet.
[00:02:36.530]This extract does not have any sugars and fibers
[00:02:39.550]and this is important because sugars and fibers
[00:02:41.640]and the whole fruit can play a role
[00:02:43.654]in changing the host metabolism.
[00:02:47.110]And we were interested in how the red raspberry
[00:02:50.330]pure polyphenols influence host metabolic changes.
[00:02:57.370]And so for our methods, we used two techniques.
[00:03:00.550]The first technique was qRT-PCR,
[00:03:03.860]which stands for the Real Time Quantitative Reverse
[00:03:06.614]Transcriptase Polymerase Chain Reaction.
[00:03:10.040]And we used that to determine changes
[00:03:11.970]in the leveraging expression.
[00:03:13.870]We also use a Western Blot
[00:03:15.370]to analyze liver protein expression.
[00:03:20.860]Using preliminary data that was collected
[00:03:22.910]by a PhD student at necropsy
[00:03:25.380]we saw that there was no difference on the body weight
[00:03:28.160]between the high fat and the high fat red raspberry fed mice
[00:03:31.320]for both conventionalized and germ-free mice.
[00:03:34.450]However, we did see
[00:03:35.530]that visceral adipose tissue is decreasing
[00:03:37.846]in conventionalized red raspberry fed mice
[00:03:40.890]but there was no difference in the germ-free mice.
[00:03:47.300]Also again, using preliminary data in figure A
[00:03:50.050]you can see the H and E staining of the livers
[00:03:52.210]from conventionalized and germ-free mice fed with low fat,
[00:03:56.387]high fat, or high fat red raspberry diet for
[00:03:58.430]both conventionalized and germ-free.
[00:04:00.940]And so we see that the low fat diet did not decrease,
[00:04:05.860]or did not increase triglycerides in the liver.
[00:04:08.800]However, we see a large increase of triglycerides
[00:04:11.330]accumulation in the high-fat and mice, which is shown
[00:04:14.093]by the large yellow circles.
[00:04:16.500]Interestingly, we see that the conventionalized mice fed
[00:04:19.390]with high-fat diet and red raspberry, the triglyceride
[00:04:23.809]accumulation is much lower compared to the conventionalized
[00:04:26.654]mice fed with only high-fat diet.
[00:04:30.010]In the germ-free mice,
[00:04:31.070]we do not see a large difference between the high-fat
[00:04:33.540]fed mice and the high fat red raspberry fed mice.
[00:04:36.800]On the gene level,
[00:04:37.680]we see that in the conventionalized mice
[00:04:40.140]the phosphorpenia carboxy kinase was
[00:04:43.240]significantly decreased in the high-fat red raspberry
[00:04:46.310]fed mice compared to the high-fat only fed mice.
[00:04:49.330]And so the Pepck is an enzyme used in the metabolic
[00:04:52.840]pathway of gluconeogenesis and over expression
[00:04:56.300]of this enzyme is implicated in the progression
[00:04:58.630]of type two diabetes in mice.
[00:05:01.300]Interestingly, in the germ-free mice,
[00:05:03.210]we do not see differences in Pepck gene expression
[00:05:06.210]between the groups
[00:05:10.450]Here, we tested two groups and two treatments.
[00:05:13.130]We use germ-free
[00:05:14.100]and conventionalize mice treated with saline or insulin.
[00:05:18.370]We used phospho activated protein kinase antibody
[00:05:22.430]from rabbits, which plays a role,
[00:05:23.900]a key role in regulating energy homeostasis
[00:05:27.680]and use beta actin as a loading control.
[00:05:30.640]In figure A, we looked at the protein expression
[00:05:32.718]of the phosphor AMPK alpha
[00:05:35.840]in conventionalize mice levers.
[00:05:38.510]And so here you can see there was not a major difference
[00:05:42.500]between the high-fat
[00:05:43.333]and the high-fat red raspberry fed mice.
[00:05:46.050]Although polyphenols have been implicated
[00:05:47.980]in up-regulating the AMPK signaling pathway,
[00:05:50.940]it is possible that we're not seeing evident differences
[00:05:53.420]in AMPK phosphorylation, possibly since the mice were fasted
[00:05:57.600]at the time of necropsy.
[00:05:59.690]In the germ-free mice
[00:06:00.770]I'm showing more samples in the Western Blot image
[00:06:03.840]because there were more variability of samples
[00:06:06.570]within the high fat and the high fat red raspberry groups.
[00:06:09.980]We plan to look at more proteins associated
[00:06:12.380]with lipogenic pathways in the liver that might influence
[00:06:15.170]from a chronic consumption of high fat diets,
[00:06:17.420]such as acetyl-CoA carboxylase.
[00:06:20.960]In conclusion, there was no difference in body weight
[00:06:24.150]from conventionalized mice fed a high-fat diet
[00:06:27.740]versus high--fat diet supplemented
[00:06:29.530]with red raspberry polyphenols.
[00:06:31.950]We did see that visceral adipose tissue was lower
[00:06:34.520]in the red raspberry fed mice compared
[00:06:36.280]to the high fat control,
[00:06:37.440]but only in the conventionalized mice group.
[00:06:40.560]Moreover, we do see differences
[00:06:42.320]in the triglyceride accumulation
[00:06:43.920]and levers of the conventionalized mice,
[00:06:45.780]but not in the germ-free mice.
[00:06:47.860]This suggests that mice
[00:06:49.040]with a gut microbiota may have host metabolic benefits
[00:06:52.350]after consuming red raspberry polyphenols
[00:06:55.760]despite being fed high-fat diet.
[00:07:01.190]Moving forward, we plan to look into different lipogenic
[00:07:05.410]inflammatory and insulin signaling pathways
[00:07:08.270]to determine any modulation these pathways
[00:07:12.170]by red raspberry polyphenols in mice
[00:07:14.423]through the gut microbiota.
[00:07:16.160]As we look deeper into our data,
[00:07:17.810]we also plan to study the microbes implicated
[00:07:20.230]in the bio conversion and ellagic acid
[00:07:22.330]into your urolithins, which may help us understand how
[00:07:25.150]the gut microbiome regulates the host metabolic benefits
[00:07:28.140]from red raspberry consumption.
[00:07:31.580]Finally, I would like to acknowledge Dr. Amanda Ramer-Tait
[00:07:34.530]for giving me the opportunity to be part of her lab.
[00:07:37.200]And my amazing mentor, the PhD student, Ashley,
[00:07:39.990]who helped me a lot in the lab, as well as the rest
[00:07:42.479]of my lab mates.
[00:07:44.460]And the Gnotobiotic Mouse Facility for,
[00:07:48.120]and the mouse team for teaching me all about mice research.
[00:07:52.360]Thank you so much.

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The Gut Microbiota Mediates Red Raspberry Polyphenol Health Benefits in Diet-Induced Obesity

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