Tuesday, February 21, 2017

miRNAs (micro RNAs): Little Engines that Can Regulate a Broad Range of Cellular Functions

So the first question one might ask themselves when reading this post, if not already familiar, is "what exactly is a microRNA (miRNA) and why should I care". First let me point out that the identification and ongoing understanding of miRNAs is not entirely new. The first miRNA activity was discovered in 1993. However, more and more details about the number of miRNA genes and their wide ranging activities are being discovered all the time. MicroRNAs are small non-coding RNAs (also designated sncRNAs) generated from endogenous genes. Non-coding does NOT mean non-functional, it just refers to the fact that these RNAs are not used as templates for the synthesis of proteins. The mechanisms of action of miRNAs are exerted on coding RNAs (the messenger RNAs, mRNAs) in, primarily, a post-transcriptional manner (after an mRNA is produced from a gene). However, miRNAs exert transcriptional control as well. The power of miRNAs is that one is capable of regulating the expression levels of hundreds of transcripts (mRNAs) and each of these mRNA targets may have more than one (i.e. multiple different) miRNA recognition sequences.

For more details of the synthesis of miRNAs go to my website:


The primary functions of miRNAs are to target mRNA stability and inhibition of protein synthesis as a means to change the level of gene expression. However, miRNAs have been shown to interfere with gene expression through alterations in the processes of histone modification and DNA methylation at promoter sites in target genes. These effects represent a form of epigenetic regulation of gene expression. The mechanisms by which miRNAs exert epigenetic regulation is by altering the level of DNA methyltransferases and histone deacetylases. Of profound clinical significance is that dysregulation of miRNA expression and regulation is associated with a contributory effect in the development of numerous human cancers. In addition, the activity of miRNAs appears to be associated with the oncogenic character of several genes as well at to be involved in the down-regulation of tumor suppressor genes in certain cancers. Many of the miRNAs whose activities have been shown to be deregulated in cancers have been shown to have a normal function that would exert tumor suppressive activity and/or to inhibit tumor metastasis. In addition to involvement in cancer, dysregulation or mutation in miRNA genes has been associated with numerous diseases in humans.

Within the past several years there has been an increasing amount of research published on the correlation between dietary constituents and the regulation of miRNA functions. In particular the role of plant derived polyphenolic compounds and regulation of miRNA gene expression and function. For more details on polyphenol sources and functions visit my Supplement Science website:


This post is just a brief introduction to miRNA functions, and a hint of the importance of diet on these processes, but I will be adding more posts about the research in this area over the coming days and weeks, so stay tuned!!!


Sunday, February 19, 2017

Oroxylin A: Potent Anti-Cancer Flavonoid from the Skullcap Plant (Scutellariae)

The flavonoids are chemical compounds of the polyphenol family that are widely distributed within the plant kingdom. The flavonoids represent one of the largest classes of bioactive phytochemicals whose activitites have been shown to exhibit clinical benefit in humans with many showing promise as anti-oxidant, anti-inflammatory, and/or anti-cancer agents. In the realm of Chinese herbal medicine there are several hundred different plant species that have been used for medicinal purposes for thousands of years. Most, if not, all of these plant species have been shown to contain phytochemicals of the flavonoid family. The most common flavonoids are the flavones, flavanones and flavonols. Read more of the details on the antioxidant properties of the flavonoids in my Supplement Science website:

http://supplementscience.org/antioxidants.html

Numerous research papers have been written regarding studies on the potential verifiable health benefits of the consumption of the roots or extracts of the roots of plants of the skullcap family such as Scutellaria baicalensis. The flavonoid, oroxylin A (5′7-dihydroxy-6-methoxy-2phenyl-4H-1-benzopyran-4-one), is the major bioactive compound that can be extracted from the dried roots of Scutellaria baicalensis. The dried roots of skullcap is called Scutellaria radix. Other important compounds in skullcaps include baicalein, wogonin, baicalin, wogonoside and oroxyloside A.

There are numerous peer-reviewed reports that attest to the pharmacological benefits of oroxylin A including its potential as an anti-cancer agent which is primarily exerted through the activation the programmed cell death pathway (apoptosis). Oroxylin A has also been shown to exhibit anti-inflammatory, anti-coagulation, and neuroprotective agent.

A recent review in the journal Phytotherapy Research does an excellent job of highlighting the scientifically verifiable actions of oroxylin A in the anti-cancer arena.


It is clear from the literature that there is great potential for the health benefits of consuming a tea prepared from plants of the skullcap family.

Friday, February 17, 2017

The Ketone Diet for Enhanced Physical Endurance

Ketones are chemical compounds that contain two constituents bonded to a carbon atom that is also double bonded to an oxygen atom. In human metabolism the ketones are the keto acids (also referred to as ketone bodies) identified as beta-hydroxybutyrate and acetoacetate. These ketones are produced in the liver from any nutrient (fat, carbohydrate, and amino acid) that, when oxidized, yields acetyl-CoA (acetyl-coenzyme A). Acetyl-CoA is converted to the ketones in the liver and the ketones are delivered to the blood, taken up by non-hepatic tissues, metabolized back to acetyl-CoA and then oxidized in the TCA cycle yielding the energy needed for ATP synthesis. The process of ketone synthesis is referred to as ketosis. 

The pathway for the hepatic synthesis of ketones and the extra-hepatic tissue utilization of the ketones is outlined in detail in the Fatty Acid Oxidation page of my website:

http://themedicalbiochemistrypage.org/fatty-acid-oxidation.php

Ketosis is the the normal metabolic response to an energy deficit or a metabolic crisis. The typical metabolic process of ketone synthesis occurs continuously under normal metabolism but increases dramatically during periods of fasting and starvation. Indeed, the process of ketosis is critical for long-term survival during periods of starvation. The normal production of ketones during fasting, and in periods of starvation, is essential to provide an oxidizable carbon source for use by the brain while simultaneously conserving precious glucose (produced by the gluconeogenic pathway) reserves for use by red blood cells which can survive only by the oxidaiton of glucose. The consumption of a diet high in fatty acids, such as the Atkins diet (often called the ketogenic diet), can lead to increased ketone production even without an energy deficit. However, in certain disease state, particularly in type 1 diabetes, the aberrant overproduction of ketones results in potentially severe metabolic acidosis referred to as diabetic ketoacidosis, DKA. The pathology of DKA is associated with the potential for life-threatening complications in blood electrolyte balance (particularly potassium) which can easily precipitate cardiac failure and death.

There is significant research demonstrating why and how we make and utilize ketones during periods of fasting, and the metabolic benefits of these pathway to survival. However, little research has looked at the potential benefits, if any, of the dietary consumption of ketones, independent of a caloric or carbohydrate deficit. Essentially all tissues, except the liver, can utilize ketones as an energy source. In addition, ketones regulate the mobilization and utilization of other fuel substance. A recent publication in the journal Cell Metabolism demonstrates a unique and potentially physiological significance associated with dietary ketone intake, that being enhanced endurance performance in athletes. The premise behind this study was the understanding that the metabolic demands of long-term performance exercise closely mimic the metabolic conditions that are precipitated by starvation.

Nutritional Ketosis Alters Fuel Preference and  Thereby Endurance Performance in Athletes

One can achieve ketosis by direct consumption of beta-hydroxybutyrate but due to the necessity of consuming this compound in the acid form or as a salt, it can lead to significant acidification and increasing salt loads. The studies undertaken in this paper utilized an esterified form of ketone, ethyl (R)-3-hydroxybutyrate. The resultant ketone is identified as (R)-3-hydroxybutyl (R)-3-hydroxybutyrate. When this ketone is ingested intestinal esterases cleave the compound into its constituent parts, beta-hydroxybutyrate and (R)-1,3-butanediol. Both of these compounds were shown to be efficiently absorbed and delivered to the portal circulation delivering them to the liver. Within the liver the butanediol is metabolized to beta-hydroxybutyrate. When released from the liver to the blood the beta-hydroxybutyrate can taken up by other tissues and oxidized for energy.

During exercise, especially as the intensity increases, there is an increased demand for, and reliance on, glucose oxidation within skeletal muscle. This condition can result in restricted utilization of glucose by the brain and red blood cells. Therefore, the authors reasoned that the metabolic rearrangements induced by ketosis may represent a means for sustaining physical performance in humans.

Several experiments were carried out in volunteers to examine the fuel selection during exercise when ingesting a drink containing the ketone ester, carbohydrate, or fat. Each individual in the study on each of the "diets" underwent resting and exercise blood ketone analysis.As would be expected those individuals consuming the ketone ester drink showed a rapid rise in blood ketones at rest following an overnight fast. However, the level of blood ketones remained at the elevated level during a 1 hr cycling exercise. Serum lactate levels were similar in all three study groups at rest but were significantly lower in the ketone ester group following exercise. Exercise caused a significant rise in plasma glycerol in the carbohydrate and fat consuming participants but not in the ketone ester participants. Glycerol is normally released from adipose (fat) tissue in response to fasting and exercise induced increases in fatty acid release from triglycerides stored in adipose tissue. Other metabolic parameters, such as blood glucose and insulin levels were as predicted based upon the "diet" consumed. For example glucose ingestion triggers a rapid rise in insulin release and this was seen at greater levels in the participants consuming the carbohydrate "diet".

The ingestion of the ketone ester drink resulted in dramatic alterations in the metabolic profiles of skeletal muscle both at rest and during exercise. Prior to, and following exercise the concentrations of glucose oxidation (glycolysis) products were significantly lower in skeletal muscle in the ketone ester consuming participants compared to those that consumed the fat or carbohydrate drinks. Therefore, consumption of the ketone ester significantly alters muscle glucose utilization during exercise explaining the reduced levels of blood lactate that were observed. In addition, the ingestion of the ketone ester significantly decreased the demand for oxidation of the branched-chain amino acids (BCAA), leucine, isoleucine, and valine. The BCAA are enriched in skeletal muscle proteins due, in part, to their significant energy content that can be utilized during periods of fasting and starvation as well as during strenuous exercise. The sparing of the BCAA during exercise following ketone ester ingestion allows for an increased maintenance of muscle mass.

In the highly trained athletes in this study it was found that the consumption of the ketone ester drink, which alters muscle metabolic profiles, resulted in an approximately 2% increase in exercise performance. Given that skeletal muscle CANNOT obtain energy from acetyl-CoA, ketosis is not advantageous under all physiological conditions such as those conditions that rely almost solely on anaerobic (oxygen free) metabolism. Because anaerobic oxidation of glucose to pyruvate yields ATP it is the only metabolic pathway that can provide muscle the energy it needs during sprinting or short burst high intensity exercise.

The take home from this study is that ingestion of ketones, in conjunction with adequate carbohydrate and fat, alters the normal metabolic processes that take place within skeletal muscle during exercise and that these changes have the potential to increase the level of intensity attainable during endurance physical activity.

Thursday, February 9, 2017

New Genes Predisposing to Type 2 Diabetes: Single Cell Transcriptome Analysis

Numerous studies have been carried out in the past 10-15 years utilizing a technology referred to as "genome-wide association study" (GWAS) to define subtle differences in the DNA sequences of genes in normal individuals and those with type 2 diabetes. These studies were/are aimed at determining if there are any correlations, at the level of the genome, with the likelihood of someone developing type 2 diabetes beyond the most obvious correlations of life style and diet. These GWAS data have indeed found numerous genes harboring nucleotide sequence differences (referred to as polymorphisms), many of which encode proteins critically involved in the overall processes of pancreatic endocrine (hormone) function and whole body metabolic regulation. Many of these genes can be found in the Diabetes page of my website:

http://themedicalbiochemistrypage.org/diabetes.php#type2genetics

It is important to understand that the pancreas is the endocrine organ that secretes insulin in response to increases in blood glucose (sugar) and glucagon in response to low blood glucose. These are not the only hormones secreted by this organ but are the most critical in the context of both type 1 and type 2 diabetes. Cells of the pancreas called alpha cells secrete glucagon and those called beta cells secrete insulin. The pancreas is not the only organ that can contribute to the disturbances in metabolism associated with type 2 diabetes, thus, many of the genes identified in GWAS studies do not participate in pancreatic function directly, but nonetheless the proteins encoded by these other genes are necessary for normal metabolic homeostasis. Several recent studies have focused on analyzing the transcriptional activity (what genes are turned on and at what level of activity and what genes are turned off) of the pancreas in both normal individuals and those with type 2 diabetes. However, the results these studies have provided only average transcriptional activity from all hormone secreting cell population.

A new study published in the prestigious journal, Cell Metabolism, has gone one step further and examined the differences in the patterns of genes that are expressed in single hormone secreting cells of the pancreas and made a comparison between these patterns in normal individuals and those with type 2 diabetes. Because the experiments are designed to analyze the transcription of genes into RNA, the data are examining what is termed the transcriptome of the single cells. 

RNA Sequencing of Single Human Islet Cells Reveals Type 2 Diabetes Genes

The results from this study demonstrate that there are at least 245 genes whose patterns of expression are significantly different when comparing the two groups of individuals: normal versus type 2 diabetic. Several genes were found to be expressed exclusively in the glucagon secreting alpha cells (GCG, DPP4, FAP, PLCE1, LOXL4, IRX2, TMEM236, IGFBP2, COTL1, SPOCK3, and ARRDC4) and several were found to be exclusively expressed in the insulin secreting beta cells (INS, ADCYAP1, IAPP, RGS16, DLK1, MEG3, INS-IGF2, and MAFA). The GCG gene encodes the hormone glucagon and the INS gene encodes the hormone insulin so it is not surprising that these genes are exclusively expressed in the cells known to secrete the encoded proteins. A total of 54 genes expressed in alpha cells and 48 genes expressed in beta cells were found to be differentially expressed in a comparison between normal and type 2 diabetic individuals. The other differentially expressed genes were identified in the two other types of pancreatic cells (delta cells and PP cells) but are not reviewed here. A striking finding from this study was that 28% of the identified differentially expressed genes from all four pancreatic cell populations have no known function.

Beyond the scope of this blog is a listing of all the differentially expressed genes, their functions, and an analysis of what the data mean in relation to the risk one may have for type 2 diabetes or whether there is any correlation to therapeutic intervention in individuals with the observed patterns of altered gene expression. However, I found it exciting that with respect pancreatic function and insulin secretion, there were four genes whose levels of expression were significantly lower in type 2 diabetic beta cells compared with normal pancreatic beta cells. These four genes are G6PC2, FFAR4, and SLC2A2. The protein encoded by the SLC2A2 gene is known as glucose transporter 2 (GLUT2). The function of this glucose transporter is to allow glucose entry into the pancreatic beta cell in order for it to be metabolized for energy (ATP) production. However, it is a relatively inefficient transporter so that glucose entry does not occur until blood glucose levels high in the post-feeding state. Since glucose metabolism is the primary metabolic mechanism stimulating insulin secretion it makes sense that reduced GLUT2 production would lead to reduced insulin secretion as is typical in type 2 diabetes.

To understand the mechanism of glucose-mediated insulin secretion go to the Insulin Functions page of my website:

http://themedicalbiochemistrypage.org/insulin.php

The FFAR4 gene encodes a cell surface receptor for certain types of lipids, particularly the omega-3 fatty acid, DHA (docosahexaenoic acid). The precise function of FFAR4 in the pancreatic beta cell is not yet well defined but it does participate in secretion of the hormone somatostatin from the delta cells. FFAR4 is also important in the regulation of adipose tissue function by enhancing insulin-mediated glucose uptake by adipocytes. Read more about the functions of FFAR4 in the Bioactive Lipids page of my website:

http://themedicalbiochemistrypage.org/bioactivelipids.php#gpr120

The G6PC2 gene encodes a catalytic subunit of the glucose 6-phosphatase enzyme, the enzyme that is responsible for the release of free glucose (from glucose-6-phosphate) from the liver, kidney, and small intestine in the context of the metabolic pathway of gluconeogenesis. Within the pancreas the G6PC2 encoded protein has no phosphate removal activity but it is a major target of cell-mediated autoimmunity in type 1 diabetes suggesting that there may be some component of immune function in the development of type 2 diabetes. Read more about this pathway in the Gluconeogenesis page of my website:

http://themedicalbiochemistrypage.org/gluconeogenesis.php

Friday, February 3, 2017

WE ALL KNOW SUGAR IS BAD FOR US, BUT "FAKE" SUGAR IS EVEN WORSE!!!

It goes without saying that the root of most, if not all, of the obesity and type 2 diabetes in the US and other Westernized industrial countries is due to the consumption of too much carbohydrate (sugar for those of you less scientifically inclined, no disrespect intended at all).

And just to be sure the issue is NOT the consumption of too much high fructose corn syrup (HFCS). For more of the scientific specifics of that statement read up on fructose metabolism in my website:

http://themedicalbiochemistrypage.org/fructose.php

HFCS is only, at most, 55% fructose. That is only 5% more than in, what the food packaging industry calls, "natural sugar" which is the disaccharide sucrose which is 50% glucose and 50% fructose. The play here is that the consumer thinks it's better for them so they are willing to pay more for it. The issue is not fructose, per se, it is TOO MUCH total carbohydrate intake. Too much of what we eat is artificially sweetened, making us FAT!!!

So what are the alternatives?? Well of course self control and a changed life style are the true paths to healthy living but we all know that most people can't, or won't, change. They prefer to get an anti-fat pill, not that one even exists. Food manufacturers then choose to use artificial sweeteners, some of which have toxicities that limit their use, or they are used and the toxicities are only discovered after people start getting sick and dying.

There are several non-nutritive sweeteners which are defined as such because the body senses them as being sweet through taste buds in the mouth but the digestive system cannot digest them so they are just excreted in the feces, and thus, do not contribute to caloric intake. Sucralose (trade name Splenda) is a perfect example of this type of sweetener. Sucralose is sucrose where some of the hydroxyl (-OH) groups in the glucose and fructose molecules are inodinated.

New evidenced published in the esteemed journal Cell Metabolism has demonstrated that consumption of sucralose, while itself not contributing to caloric intake, does indeed disturb the brain signals that regulate feeding behavior:


Sucralose Promotes Food Intake through NPY and a Neuronal Fasting Response


For background information on the mechanisms the brain uses to control ones desire to seek out food and consume food go to the Gut-Brain Interrelationships page of my website:

http://themedicalbiochemistrypage.org/gut-brain.php

The result of this recently published study were obtained in fruit flies and in mice but because the circuitry in the mouse brain that controls feeding behavior is highly similar to those circuits in the human brain these studies indicate profoundly important consequences of sucralose consumption. To be fair, this is not the first study to demonstrate that the consumption of artificial sweeteners enhances ones appetite, but this current study goes a long way to dissecting the molecular mechanisms that are functioning in the context of artificial sweetener consumption. The data from this report defines the mechanism whereby an imbalance of sweetness versus caloric content in ones diet leads to the activation a powerful fasting state which triggers a sensory and behavioral response that drives a desire to increase caloric intake, in other words a desire to eat more. The molecular mechanism of this response include neurotransmitters in the hypothalamus (specifically the potent food intake inducer, NPY), neural insulin receptor-mediated responses, and the master metabolic regulatory enzyme AMPK (AMP-regulated protein kinase). AMPK controls the energy status of the body by responding to changes in the level of ATP, as would occur in the fasted state. AMPK is able to do this through its ability to turn off ATP consuming reactions and turn on ATP producing reactions within the periphery and controlling feeding behavior processes in the brain. Ingestion of a sucralose-containing diet activates AMPK in the hypothalamus resulting in increased NPY synthesis and a consequent increase in the desire to consume food.

The take home from this study is really a "no brainer": choosing to forego changes in the types and amounts of food one eats while simultaneously thinking that consuming that low-cal food or artificially sweetened soda is the key to weight loss is actually doing more harm than good and just contributing to the obesity and type 2 diabetes with which one may already be suffering. Eat RIGHT, exercise and guess what?? You will save THOUSANDS of dollars in health care costs.


Waking from a sleep too long

Well having been much much too busy with University work, consulting work, etc etc I have been "asleep" at the wheel for far too long with my science and health blogging. Time to wake up the beast and get back to it.