Free fatty acid receptors: emerging targets for treatment of diabetes and its complications

Metabolomics of repetitive myocardial stunning in chronic multivessel coronary artery stenosis: Effect of non-selective and selective β1-receptor blockers

Chronic coronary artery stenosis can lead to regional myocardial dysfunction in the absence of myocardial infarction by repetitive stunning, hibernation or both. The molecular mechanisms underlying repetitive stunning-associated myocardial dysfunction are not clear. We used non-targeted metabolomics to elucidate responses to chronically stunned myocardium in a canine model with and without β-adrenergic blockade treatment. After development of left ventricular systolic dysfunction induced by ameroid constrictors on the coronary arteries, animals were randomized to 3 months of placebo, metoprolol or carvedilol. We compared these two β-blockers with their different β-adrenergic selectivities on myocardial function, perfusion and metabolic pathways involved in tissue undergoing chronic stunning. Control animals underwent sham surgery. Dysfunction in stunned myocardium was associated with reduced fatty acid oxidation and enhanced ketogenic amino acid metabolism, together with alterations in mitochondrial membrane phospholipid composition. These changes were consistent with impaired mitochondrial function and were linked to reduced nitric oxide and peroxisome proliferator-activated receptor signalling, resulting in a decline in adenosine monophosphate-activated protein kinase. Mitochondrial changes were ameliorated by carvedilol more than metoprolol, and improvement was linked to nitric oxide and possibly hydrogen sulphide signalling. In summary, repetitive myocardial stunning commonly seen in chronic multivessel coronary artery disease is associated with adverse metabolic remodelling linked to mitochondrial dysfunction and specific signalling pathways. These changes are reversed by β-blockers, with the non-selective inhibitor having a more favourable impact. This is the first investigation to demonstrate that β-blockade-associated improvement of ventricular function in chronic myocardial stunning is associated with restoration of mitochondrial function. KEY POINTS: The mechanisms responsible for the metabolic changes associated with repetitive myocardial stunning seen in chronic multivessel coronary artery disease have not been fully investigated. In a canine model of repetitive myocardial stunning, we showed that carvedilol, a non-selective β-receptor blocker, ameliorated adverse metabolic remodelling compared to metoprolol, a selective β1-receptor blocker, by improving nitric oxide synthase and adenosine monophosphate protein kinase function, enhancing calcium/calmodulin-dependent protein kinase, probably increasing hydrogen sulphide, and suppressing cyclic-adenosine monophosphate signalling. Mitochondrial fatty acid oxidation alterations were ameliorated by carvedilol to a larger extent than metoprolol; this improvement was linked to nitric oxide and possibly hydrogen sulphide signalling. Both β-blockers improved the cardiac energy imbalance by reducing metabolites in ketogenic amino acid and nucleotide metabolism. These results elucidated why metabolic remodelling with carvedilol is preferable to metoprolol when treating chronic ischaemic left ventricular systolic dysfunction caused by repetitive myocardial stunning.

Management of Cardiovascular Diseases by Short-Chain Fatty Acid Postbiotics

PURPOSE OF REVIEW

Global health concerns persist in the realm of cardiovascular diseases (CVDs), necessitating innovative strategies for both prevention and treatment. This narrative review aims to explore the potential of short-chain fatty acids (SCFAs)-namely, acetate, propionate, and butyrate-as agents in the realm of postbiotics for the management of CVDs.

RECENT FINDINGS

We commence our discussion by elucidating the concept of postbiotics and their pivotal significance in mitigating various aspects of cardiovascular diseases. This review centers on a comprehensive examination of diverse SCFAs and their associated receptors, notably GPR41, GPR43, and GPR109a. In addition, we delve into the intricate cellular and pharmacological mechanisms through which these receptors operate, providing insights into their specific roles in managing cardiovascular conditions such as hypertension, atherosclerosis, heart failure, and stroke. The integration of current information in our analysis highlights the potential of both SCFAs and their receptors as a promising path for innovative therapeutic approaches in the field of cardiovascular health. The idea of postbiotics arises as an optimistic and inventive method, presenting new opportunities for preventing and treating cardiovascular diseases.

Malic Enzyme 1 (ME1) Promotes Adiposity and Hepatic Steatosis and Induces Circulating Insulin and Leptin in Obese Female Mice

Malic Enzyme 1 (ME1) supports lipogenesis, cholesterol synthesis, and cellular redox potential by catalyzing the decarboxylation of L-malate to pyruvate, and the concomitant reduction of NADP to NADPH. We examined the contribution of ME1 to the development of obesity by provision of an obesogenic diet to C57BL/6 wild type (WT) and MOD-1 (lack ME1 protein) female mice. Adiposity, serum hormone levels, and adipose, mammary gland, liver, and small intestine gene expression patterns were compared between experimental groups after 10 weeks on a diet. Relative to WT female mice, MOD-1 female mice exhibited lower body weights and less adiposity; decreased concentrations of insulin, leptin, and estrogen; higher concentrations of adiponectin and progesterone; smaller-sized mammary gland adipocytes; and reduced hepatosteatosis. MOD-1 mice had diminished expression of Lep gene in abdominal fat; Lep, Pparg, Klf9, and Acaca genes in mammary glands; Pparg and Cdkn1a genes in liver; and Tlr9 and Ffar3 genes in the small intestine. By contrast, liver expression of Cdkn2a and Lepr genes was augmented in MOD-1, relative to WT mice. Results document an integrative role for ME1 in development of female obesity, suggest novel linkages with specific pathways/genes, and further support the therapeutic targeting of ME1 for obesity, diabetes, and fatty liver disease.

Current Research on the Effects of Non-Digestible Carbohydrates on Metabolic Disease

Metabolic diseases (MDs), including cardiovascular diseases (CVDs) and diabetes, occur when the body’s normal metabolic processes are disrupted. Behavioral risk factors such as obesity, physical inactivity, and dietary habits are strongly associated with a higher risk of MD. However, scientific evidence strongly suggests that balanced, healthy diets containing non-digestible carbohydrates (NDCs), such as dietary fiber and resistant starch, can reduce the risk of developing MD. In particular, major properties of NDCs, such as water retention, fecal bulking, viscosity, and fermentation in the gut, have been found to be important for reducing the risk of MD by decreasing blood glucose and lipid levels, increasing satiety and insulin sensitivity, and modifying the gut microbiome. Short chain fatty acids produced during the fermentation of NDCs in the gut are mainly responsible for improvement in MD. However, the effects of NDCs are dependent on the type, source, dose, and duration of NDC intake, and some of the mechanisms underlying the efficacy of NDCs on MD remain unclear. In this review, we briefly summarize current studies on the effects of NDCs on MD and discuss potential mechanisms that might contribute to further understanding these effects.

Free Fatty Acid Receptors (FFARs) in Adipose: Physiological Role and Therapeutic Outlook

Fatty acids (FFAs) are important biological molecules that serve as a major energy source and are key components of biological membranes. In addition, FFAs play important roles in metabolic regulation and contribute to the development and progression of metabolic disorders like diabetes. Recent studies have shown that FFAs can act as important ligands of G-protein-coupled receptors (GPCRs) on the surface of cells and impact key physiological processes. Free fatty acid-activated receptors include FFAR1 (GPR40), FFAR2 (GPR43), FFAR3 (GPR41), and FFAR4 (GPR120). FFAR2 and FFAR3 are activated by short-chain fatty acids like acetate, propionate, and butyrate, whereas FFAR1 and FFAR4 are activated by medium- and long-chain fatty acids like palmitate, oleate, linoleate, and others. FFARs have attracted considerable attention over the last few years and have become attractive pharmacological targets in the treatment of type 2 diabetes and metabolic syndrome. Several lines of evidence point to their importance in the regulation of whole-body metabolic homeostasis including adipose metabolism. Here, we summarize our current understanding of the physiological functions of FFAR isoforms in adipose biology and explore the prospect of FFAR-based therapies to treat patients with obesity and Type 2 diabetes.

Free fatty acid receptor 1: a ray of hope in the therapy of type 2 diabetes mellitus

Free fatty acid receptor 1 (FFAR1) is a G-protein coupled receptor with prominent expression on pancreatic beta cells, bones, intestinal cells as well as the nerve cells. This receptor mediates a multitude of functions in the body including release of incretins, secretion of insulin as well as sensation of pain. Since FFAR1 causes secretion of insulin and regulates glucose metabolism, efforts were made to unfold its structure followed by discovering agonists for the receptor and the utilization of these agonists in the therapy of type 2 diabetes mellitus. Development of such functional FFAR1 agonists is a necessity because the currently available therapy for type 2 diabetes mellitus has numerous drawbacks, of which, the major one is hypoglycemia. Since the most prominent effect of the FFAR1 agonists is on glucose concentration in the body, so the major research is focused on treating type 2 diabetes mellitus, though the agonists could benefit other metabolic disorders and neurological disorders as well. The agonists developed so far had one major limitation, i.e., hepatotoxicity. Although, the only agonist that could reach phase 3 clinical trials was TAK-875 developed by Takeda Pharmaceuticals but it was also withdrawn due to toxic effects on the liver. Thus, there are numerous agonists for the varied binding sites of the receptor but no drug available yet. There does seem to be a ray of hope in the drugs that target FFAR1 but a lot more efforts towards drug discovery would result in the successful management of type 2 diabetes mellitus.

Recent Updates on Free Fatty Acid Receptor 1 (GPR-40) Agonists for the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

The global incidence of type 2 diabetes mellitus (T2DM) has enthused the development of new antidiabetic targets with low toxicity and long-term stability. In this respect, free fatty acid receptor 1 (FFAR1), which is also recognized as a G protein-coupled receptor 40 (GPR40), is a novel target for the treatment of T2DM. FFAR1/GPR40 has a high level of expression in β-cells of the pancreas, and the requirement of glucose for stimulating insulin release results in immense stimulation to utilise this target in the medication of T2DM.

METHODS

The data used for this review is based on the search of several scienctific databases as well as various patent databases. The main search terms used were free fatty acid receptor 1, FFAR1, FFAR1 agonists, diabetes mellitus, G protein-coupled receptor 40 (GPR40), GPR40 agonists, GPR40 ligands, type 2 diabetes mellitus and T2DM.

RESULTS

The present review article gives a brief overview of FFAR1, its role in T2DM, recent developments in small molecule FFAR1 (GPR40) agonists reported till now, compounds of natural/plant origin, recent patents published in the last few years, mechanism of FFAR1 activation by the agonists, and clinical status of the FFAR1/GPR40 agonists.

CONCLUSION

The agonists of FFAR1/GRP40 showed considerable potential for the therapeutic control of T2DM. Most of the small molecule FFAR1/GPR40 agonists developed were aryl alkanoic acid derivatives (such as phenylpropionic acids, phenylacetic acids, phenoxyacetic acids, and benzofuran acetic acid derivatives) and thiazolidinediones. Some natural/plant-derived compounds, including fatty acids, sesquiterpenes, phenolic compounds, anthocyanins, isoquinoline, and indole alkaloids, were also reported as potent FFAR1 agonists. The clinical investigations of the FFAR1 agonists demonstrated their probable role in the improvement of glucose control. Though, there are some problems still to be resolved in this field as some FFAR1 agonists terminated in the late phase of clinical studies due to "hepatotoxicity." Currently, PBI-4050 is under clinical investigation by Prometic. Further investigation of pharmacophore scaffolds for FFAR1 full agonists as well as multitargeted modulators and corresponding clinical investigations will be anticipated, which can open up new directions in this area.

A Review on Cellular and Molecular Mechanisms Linked to the Development of Diabetes Complications

Modern lifestyle, changing eating habits and reduced physical work have been known to culminate into making diabetes a global pandemic. Hyperglycemia during the course of diabetes is an important causative factor for the development of both microvascular (retinopathy, nephropathy and neuropathy) and macrovascular (coronary artery disease, stroke and peripheral artery disease) complications. In this article, we summarize several mechanisms accountable for the development of both microvascular and macrovascular complications of diabetes. Several metabolic and cellular events are linked to the augmentation of oxidative stress like the activation of advanced glycation end products (AGE) pathway, polyol pathway, Protein Kinase C (PKC) pathway, Poly-ADP Ribose Polymerase (PARP) and hexosamine pathway. Oxidative stress also leads to the production of reactive oxygen species (ROS) like hydroxyl radical, superoxide anion and peroxides. Enhanced levels of ROS rescind the anti-oxidant defence mechanisms associated with superoxide dismutase, glutathione and ascorbic acid. Moreover, ROS triggers oxidative damages at the level of DNA, protein and lipids, which eventually cause cell necrosis or apoptosis. These physiological insults may be related to the microvascular complications of diabetes by negatively impacting the eyes, kidneys and the brain. While underlying pathomechanism of the macrovascular complications is quite complex, hyperglycemia associated atherosclerotic abnormalities like changes in the coagulation system, thrombin formation, fibrinolysis, platelet and endothelial function and vascular smooth muscle are well proven. Since hyperglycemia also modulates the vascular inflammation, cytokines, macrophage activation and gene expression of growth factors, elevated blood glucose level may play a central role in the development of macrovascular complications of diabetes. Taken collectively, chronic hyperglycemia and increased production of ROS are the miscreants for the development of microvascular and macrovascular complications of diabetes.

G protein-coupled receptors: Key molecules in metabolic associated fatty liver disease development

Metabolic associated fatty liver disease (MAFLD) is a range of hepatic disorders with progression to steatohepatitis with risk of development of fibrosis, cirrhosis, and hepatocellular carcinoma. MAFLD is strongly related to metabolic disorders of active fatty acids, which seem to be selective according to their specific ligand of G protein-coupled receptors (GPRs) located in immune response cells. An approach to study the pathophysiological mechanisms of MAFLD could be through the expression of active fatty acids ligands. The expression of GPRs is associated with obesity, microbiota environment, and dietary characteristics in patients with MAFLD. More specifically, GPR41, GPR43, GPR20, and GPR120 have been associated with alteration of lipid metabolism in hepatic and intestinal cells, and consequently they have a key role in metabolic diseases. We observed that GPR120 is not expressed in nonoverweight/obese patients, regardless of the presence of MAFLD; meanwhile the expression of GPR41 is increased in patients with lean MAFLD. GPRs role in liver disease is intriguing and a field of research opportunity. More studies are necessary to define the role of active fatty acids in the development of metabolic diseases.

Obesity-Related Fatty Acid and Cholesterol Metabolism in Cancer-Associated Host Cells

Obesity-derived disturbances in fatty acid and cholesterol metabolism are linked to numerous diseases, including various types of malignancy. In tumor cells, metabolic alterations have been long recognized and intensively studied. However, metabolic changes in host cells in the tumor microenvironment and their contribution to tumor development have been largely overlooked. During the last decade, research advances show that fatty acid oxidation, cholesterol metabolism, and lipid accumulation play critical roles in cancer-associated host cells such as endothelial cells, lymph endothelial cells, cancer-associated fibroblasts, tumor-associated myeloid cells, and tumor-associated lymphocytes. In addition to anti-angiogenic therapies and immunotherapy that have been practiced in the clinic, metabolic regulation is considered another promising cancer therapy targeting non-tumor host cells. Understanding the obesity-associated metabolism changes in cancer-associated host cells may ultimately be translated into therapeutic options that benefit cancer patients. In this mini-review, we briefly summarize the lipid metabolism associated with obesity and its role in host cells in the tumor microenvironment. We also discuss the current understanding of the molecular pathways involved and future perspectives to benefit from this metabolic complexity.

Advances in fatty acids nutrition in dairy cows: from gut to cells and effects on performance

High producing dairy cows generally receive in the diet up to 5-6% of fat. This is a relatively low amount of fat in the diet compared to diets in monogastrics; however, dietary fat is important for dairy cows as demonstrated by the benefits of supplementing cows with various fatty acids (FA). Several FA are highly bioactive, especially by affecting the transcriptome; thus, they have nutrigenomic effects. In the present review, we provide an up-to-date understanding of the utilization of FA by dairy cows including the main processes affecting FA in the rumen, molecular aspects of the absorption of FA by the gut, synthesis, secretion, and utilization of chylomicrons; uptake and metabolism of FA by peripheral tissues, with a main emphasis on the liver, and main transcription factors regulated by FA. Most of the advances in FA utilization by rumen microorganisms and intestinal absorption of FA in dairy cows were made before the end of the last century with little information generated afterwards. However, large advances on the molecular aspects of intestinal absorption and cellular uptake of FA were made on monogastric species in the last 20 years. We provide a model of FA utilization in dairy cows by using information generated in monogastrics and enriching it with data produced in dairy cows. We also reviewed the latest studies on the effects of dietary FA on milk yield, milk fatty acid composition, reproduction, and health in dairy cows. The reviewed data revealed a complex picture with the FA being active in each step of the way, starting from influencing rumen microbiota, regulating intestinal absorption, and affecting cellular uptake and utilization by peripheral tissues, making prediction on in vivo nutrigenomic effects of FA challenging.

GPR120 agonists for the treatment of diabetes: a patent review (2014 present)

INTRODUCTION

G protein-coupled receptor 120 (GPR120) is a G_αq coupled GPCR specifically activated by long-chain fatty acids (LCFAs). Functionally, it has been identified as a member of a family of lipid-binding free fatty acid receptors including GPR40, GPR41, and GPR43. Upon stimulation by LCFAs, GPR120 can directly or indirectly modulate hormone secretion from the gastrointestinal tract and pancreas, and regulate lipid and/or glucose metabolism in adipose, liver, and muscle tissues. Additionally, GPR120 is postulated to mediate anti-inflammatory and insulin-sensitizing effects in adipose and macrophages. These benefits suggest that GPR120 agonists have the potential to be an effective treatment for obesity, type 2 diabetes mellitus (T2DM), and other metabolic syndromes.

AREA COVERED

This article highlights and reviews research advances in this field that have been published in patent literature and peer-reviewed journals since 2014.

EXPERT OPINION

Current development has been hindered by species differences in GPR120 distribution, differences in GPR120-mediated signaling in distinct tissue types, and lack of available ligands with suitable selectivity for GPR120 over GPR40 in both human and rodents. The discovery of β-arrestin biased GPR120 agonists will help elucidate the potential of selective therapeutics that may discriminate between desirable and undesirable pharmacological effects.

ABBREVIATIONS

ALA: α-linolenic acid; AUC: area under the curve; BRET: bioluminescence resonance energy transfer; CCK: cholecystokinin; CHO-K1 cell: Chinese hamster ovary-K1 cell; db/db mouse: diabetic mouse; DHA: docosahexaenoic acid; DIO: diet-induced obesity; DMSO: dimethyl sulfoxide; DPP-4: dipeptidyl peptidase 4; EPA: eicosapentaenoic acid; FA(s): fatty acid(s); FFA(s): free fatty acid(s); FFAR: free fatty acid receptor; FLIPR: fluorescent imaging plate reader; GIR: glucose infusion rate; GLP-1: glucagon-like peptide 1; GP(C)R: G protein-coupled receptor; GSIS: glucose-stimulated insulin secretion; HEK293 cell: human embryonic kidney 293 cell; HOMA-IR: homeostatic measurement assessment of insulin resistance; IP1: inositol phosphate turnover; IPGTT: intraperitoneal glucose tolerance test; LCFA(s): long-chain fatty acid(s); MED_max: maximal efficacy; MIN6 cell: mouse insulin-secreting cell; NPY: neuropeptide Y; OGTT: oral glucose tolerance test; pERK: phosphorylated ERK; PPAR: peroxisome proliferator-activated receptor; QD: once daily; SAR: structure-activity relationship; siRNA: small interfering ribonucleic acid; STC-1: intestinal secretin tumor cell; T2DM: type 2 diabetes mellitus; U2OS cell: human bone osteosarcoma epithelial cell; uHTS: ultrahigh-throughput screening; ZDF: zucker diabetic fatty.

Short chain fatty acids produced by colonizing intestinal commensal bacterial interaction with expressed breast milk are anti-inflammatory in human immature enterocytes

Necrotizing enterocolitis (NEC) is a devastating intestinal emergency that affects ten percent of very low birth weight premature babies and costs society in both expense and heartache. It is probably caused by an inappropriate interaction of colonizing bacteria with an immature intestine. A possible preventative measure is to feed prematures their mother's expressed breast milk in conjunction with a probiotic. This synbiotic prevention reduces the severity and incidence of this condition. This study was designed to determine the mechanism of the synbiotic effect in human and mouse fetal intestine. Breast milk interacting with a NEC preventative probiotic such as Bifidobacterium infantis can produce increased levels of short chain fatty acids (acetate, propionate and butyrate) (SCFAs). SCFAs are known to be anti-inflammatory in mature enterocytes and immunocytes. Very little is known about their role in immature intestine. When exposed to a human fetal cell line, fetal intestinal organoids and fetal mouse intestine, these SCFAs were anti-inflammatory. Their mechanism of anti-inflammation differed from those reported for mature cells by involving the G-protein coupled receptor (GPR 109A) and inhibiting histone deacetylase 4 and 5. These bacterial metabolites may help explain the synbiotic anti-inflammatory effect of breast milk and probiotics given to premature infants at risk for NEC.

Low Expression of FFAR2 in Peripheral White Blood Cells May Be a Genetic Marker for Early Diagnosis of Acute Myocardial Infarction

Objective

To find molecular markers for the diagnosis of acute myocardial infarction (AMI), this research further verified the relationship between the expression level of FFAR2 gene and AMI by expanding the sample size based on the previous gene chip results.

Methods

Peripheral venous leukocytes were collected from 113 patients with AMI and 94 patients with noncoronary artery disease as the experimental group and the control group, respectively. Real-time fluorescence quantitative polymerase chain reaction was used to detect the expression of the FFAR2 gene. Western blot analysis was applied to detect the relative expression of the FFAR2 gene at the level of protein. Furthermore, the relationship between gene expression and clinical data was also analyzed and compared.

Results

The level of expression of FFAR2 gene in peripheral blood of patients with AMI was significantly lower than that of the control group (0.33 [0.04–1.08], 0.62 [0.07–1.86], respectively; p < 0.05), which was 0.53 times that of the control group. Western blot results presented that the FFAR2 protein level in the peripheral blood of the AMI group was lower than that of the control group (0.114; p=0.004). Analyzing clinical data of the subjects indicated that the average age of the AMI group was significantly higher than the age of control group (p < 0.01). Also, the fasting blood glucose level was higher (p < 0.01), and the high-density lipoprotein cholesterol (HDL-C) level was lower (p=0.03). The FFAR2 mRNA level correlated positively with the HDL-C level (p < 0.01). Logistic regression analysis suggested that the low expression of the FFAR2 gene in peripheral blood may be a risk factor for AMI independent of age, family history of diabetes, fasting blood glucose level, and HDL-C level (p=0.025). Compared with the high FFAR2 expression group, the risk of AMI in the low FFAR2 expression group was 6.308 times higher.

Conclusion

The expression level of the FFAR2 gene in peripheral blood of patients with AMI was significantly lower than that in the control group. Low expression of the FFAR2 gene in peripheral blood is an independent risk factor for AMI. Hence, it may also be a potential biomarker to predict AMI.

A Recent Achievement In the Discovery and Development of Novel Targets for the Treatment of Type-2 Diabetes Mellitus

Type 2 diabetes (T2DM) is a chronic metabolic disorder. Impaired insulin secretion, enhanced hepatic glucose production, and suppressed peripheral glucose use are the main defects responsible for developing the disease. Besides, the pathophysiology of T2DM also includes enhanced glucagon secretion, decreased incretin secretion, increased renal glucose reabsorption, and adipocyte, and brain insulin resistance. The increasing prevalence of T2DM in the world beseeches an urgent need for better treatment options. The antidiabetic drugs focus on control of blood glucose concentration, but the future treatment goal is to delay disease progression and treatment failure, which causes poorer glycemic regulation. Recent treatment approaches target on several novel pathophysiological defects present in T2DM. Some of the promising novel targets being under clinical development include those that increase insulin sensitization (antagonists of glucocorticoids receptor), decreasing hepatic glucose production (glucagon receptor antagonist, inhibitors of glycogen phosphorylase and fructose-1,6-biphosphatase). This review summarizes studies that are available on novel targets being studied to treat T2DM with an emphasis on the small molecule drug design. The experience gathered from earlier studies and knowledge of T2DM pathways can guide the anti-diabetic drug development toward the discovery of drugs essential to treat T2DM.

The Gut Microbiota Affects Host Pathophysiology as an Endocrine Organ: A Focus on Cardiovascular Disease

It is widely recognized that the microorganisms inhabiting our gastrointestinal tract-the gut microbiota-deeply affect the pathophysiology of the host. Gut microbiota composition is mostly modulated by diet, and gut microorganisms communicate with the different organs and tissues of the human host by synthesizing hormones and regulating their release. Herein, we will provide an updated review on the most important classes of gut microbiota-derived hormones and their sensing by host receptors, critically discussing their impact on host physiology. Additionally, the debated interplay between microbial hormones and the development of cardiovascular disease will be thoroughly analysed and discussed.

Insights on modulators in perception of taste modalities: a review

A major challenge in taste research is to overcome the flavour imperfections in food products and to build nutritious strategies to combat against obesity as well as other related metabolic syndromes. The field of molecular taste research and chemical senses has contributed to an enormous development in understanding the taste receptors and mechanisms of taste perception. Accordingly, the development of taste-modifying compounds or taste modulators that alter the perception of basic taste modalities has gained significant prominence in the recent past. The beneficial aspects of these substances are overwhelming while considering their potential taste-modifying properties. The objective of the present review is to provide an impression about the taste-modulating compounds and their distinctive taste-modifying properties with reference to their targets and proposed mechanisms of action. The present review also makes an effort to discuss the basic mechanism involved in oro-gustatory taste perception as well as on the effector molecules involved in signal transduction downstream to the activation of taste receptors.

A high-fat diet promotes depression-like behavior in mice by suppressing hypothalamic PKA signaling

Obesity is associated with an increased risk of depression. The aim of the present study was to investigate whether obesity is a causative factor for the development of depression and what is the molecular pathway(s) that link these two disorders. Using lipidomic and transcriptomic methods, we identified a mechanism that links exposure to a high-fat diet (HFD) in mice with alterations in hypothalamic function that lead to depression. Consumption of an HFD selectively induced accumulation of palmitic acid in the hypothalamus, suppressed the 3', 5'-cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway, and increased the concentration of free fatty acid receptor 1 (FFAR1). Deficiency of phosphodiesterase 4A (PDE4A), an enzyme that degrades cAMP and modulates stimulatory regulative G protein (Gs)-coupled G protein-coupled receptor signaling, protected animals either from genetic- or dietary-induced depression phenotype. These findings suggest that dietary intake of saturated fats disrupts hypothalamic functions by suppressing cAMP/PKA signaling through activation of PDE4A. FFAR1 inhibition and/or an increase of cAMP signaling in the hypothalamus could offer potential therapeutic targets to counteract the effects of dietary or genetically induced obesity on depression.

Fatty acid receptor GPR120 promotes breast cancer chemoresistance by upregulating ABC transporters expression and fatty acid synthesis

BACKGROUND

Chemoresistance is the major cause of neoadjuvant treatment failure in breast cancer patients. Despite recent progress, the mechanism underlying chemoresistance remains to be further defined.

METHODS

Expression of G protein-coupled receptor 120 (GPR120) was analyzed by immunohistochemistry in the biopsies of primary breast cancer who subsequently underwent preoperative neoadjuvant chemotherapy. In vitro and in vivo loss- and gain-of -function studies were performed to reveal the effects and related mechanism of GPR120 signaling pathway in the chemoresistance of breast cancer cells.

FINDINGS

We identified that GPR120, a receptor for long-chain fatty acids, was important for the acquisition of chemoresistance in breast cancer cells. We showed that GPR120 expression was positively associated with clinical response to neoadjuvant chemotherapy in patients. In breast cancer cells, GPR120 enhanced the de novo synthesis of fatty acids that served as GPR120 ligands to activate GPR120 signaling via a feedback mechanism. Upregulated GPR120 signaling rendered cells resistant to epirubicin-induced cell death by upregulating ABC transporters expression and thus decreasing the intracellular accumulation of epirubicin. Akt/NF-κB pathway was responsible for the GPR120-mediated expression of ABC transporters leading to modulation of the concentration of chemotherapeutic drugs in cells. The functional importance of GPR120 in chemoresistance was further validated using epirubicin-treated tumor xenografts, in which we showed that blockade of GPR120 signaling with AH7614 or GPR120-siRNA significantly compromised chemoresistance.

INTERPRETATION

Our results highlight that GPR120 might be a promising therapeutic target for breast cancer chemoresistance. FUND: National Natural Science Foundation of China, Ministry of Science and Technology of China, Program of Science and Technology Commission of Shanghai Municipality.

Transferred maternal fatty acids stimulate fetal adipogenesis and lead to neonatal and adult obesity

The prevalence of adult and childhood obesity are increasing. Most of the human newborn's body fat accumulates in the last half of intrauterine life. Fat in the fetus was thought to be mostly synthesized from glucose, but now it is commonly accepted that the bulk of it is the product of placental transfer of maternal fatty acids. Transported fatty acids originate in maternal plasma "free" fatty acids, fatty acids hydrolyzed from maternal plasma triglycerides, and the poly-unsaturated fatty acid component of maternal phospholipids. Glucose remains an important precursor of alpha-glycerol phosphate, to which most transported fatty acids are eventually esterified. Maternal plasma lipids are elevated in late pregnancy and even more in obese and diabetic pregnant women. This accelerates the placental transport of fatty acids. The hypothesis presented in this paper rests on the observations that the exponential increase in fat tissue in the human embryo's body occurs in time to parallel the increase of lipids in the mother's blood and depends on the chemical affinity of the transcription factor PPAR gamma to fatty acids and on fatty acid stimulation of adipocyte generation from precursor cells. The hypothesis asserts that transported maternal fatty acids activate the transcription factors in the fetus and initiate conversion of the mesenchymal stem cells into adipocytes. In obese and diabetic mothers, the higher plasma lipids facilitate increased placental fatty acid transfer. This will increase adipocyte generation and, through this, the prevalence of babies with increased fat cell size and number. Babies born with increased adipose tissue cellularity will have greater probability of growing up to become obese adolescents and adults. These newborns, whose obesity is hyperplastic as well as hypertrophic, as adults will have difficulty losing weight through diet and exercise or will regain the lost weight more quickly than others without these characteristics. Accordingly, increased placental fatty acid transfer and accelerated adipocyte generation may explain not only neonatal obesity, but some aspects of the adult obesity epidemic also. It is therefore recommended that prevention of fetal fat cell hyperplasia, by lowering maternal plasma lipids in mid and late pregnancy, should be attempted in pregnancies at risk for macrosomia.

Reduced expression of stearoyl-CoA desaturase-1, but not free fatty acid receptor 2 or 4 in subcutaneous adipose tissue of patients with newly diagnosed type 2 diabetes mellitus

Background

In subcutaneous adipose tissue (SAT), higher stearoyl-CoA desaturase-1 (SCD1) expression has been related to improved insulin sensitivity in thiazolidinedione-treated type 2 diabetes mellitus patients. In animal models, deficiency of the free fatty acid receptor (FFAR) 2 associated with higher and FFAR4-deficiency with lower insulin sensitivity. We hypothesized that increased FFAR2 expression and reductions in FFAR4 and SCD1 expression in SAT of type 2 diabetes mellitus patients associate positively with insulin resistance and impaired beta cell function.

Methods

Twenty-five type 2 diabetes mellitus patients and 25 glucose-tolerant humans (CON) matched for sex, age, and BMI underwent mixed-meal tests to assess insulin sensitivity (OGIS) and beta cell function (ΔAUC(C-peptide)_{0–180 min}/ΔAUC(glucose)_{0–180 min}) in a cross-sectional study. Gene and protein expression of SCD1 and FFAR2/4 were quantified in SAT biopsies.

Results

Insulin sensitivity was 14% and beta cell function 71% (both p < 0.001) lower in type 2 diabetes mellitus patients. In type 2 diabetes mellitus, SCD1 mRNA was fivefold (p < 0.001) and protein expression twofold (p < 0.01) lower. While FFAR2/4 mRNA and protein expression did not differ between groups, FFAR2 protein levels correlated negatively with beta cell function only in CON (r = −0.74, p < 0.01). However, neither SCD1 nor FFAR2/4 protein expression correlated with insulin sensitivity in both groups.

Conclusions

Type 2 diabetes patients have lower SCD1, which does not associate with insulin resistance. Only in non-diabetic humans, FFAR2 associated with impaired beta cell function.

The Role of Metabolite-Sensing G Protein-Coupled Receptors in Inflammation and Metabolic Disease

SIGNIFICANCE

Great attention has been placed on the link between metabolism and immune function giving rise to the term "immunometabolism." It is widely accepted that inflammation and oxidative stress are key processes that underlie metabolic complications during obesity, diabetes, and atherosclerosis. Therefore, identifying the mechanisms and mediators that are involved in the regulation of both inflammation and metabolic homeostasis is of high scientific and therapeutic interest. Recent Advances: G protein-coupled receptors (GPCRs) that signal in response to metabolites have emerged as attractive therapeutic targets in inflammatory disease. Critical Issues and Future Directions: In this review, we discuss recent findings about the physiological role of the main metabolite-sensing GPCRs, their implication in immunometabolic disorders, their principal endogenous and synthetic ligands, and their potential as drug targets in inflammation and metabolic disease. Antioxid. Redox Signal. 29, 237-256.

GPR40 is a low-affinity epoxyeicosatrienoic acid receptor in vascular cells

Endothelium-derived epoxyeicosatrienoic acids (EETs) have numerous vascular activities mediated by G protein-coupled receptors. Long-chain free fatty acids and EETs activate GPR40, prompting us to investigate the role of GPR40 in some vascular EET activities. 14,15-EET, 11,12-EET, arachidonic acid, and the GPR40 agonist GW9508 increase intracellular calcium concentrations in human GPR40-overexpressing HEK293 cells (EC₅₀ = 0.58 ± 0.08 μm, 0.91 ± 0.08 μm, 3.9 ± 0.06 μm, and 19 ± 0.37 nm, respectively). EETs with cis- and trans-epoxides had similar activities, whereas substitution of a thiirane sulfur for the epoxide oxygen decreased the activities. 8,9-EET, 5,6-EET, and the epoxide hydrolysis products 11,12- and 14,15-dihydroxyeicosatrienoic acids were less active than 11,12-EET. The GPR40 antagonist GW1100 and siRNA-mediated GPR40 silencing blocked the EET- and GW9508-induced calcium increases. EETs are weak GPR120 agonists. GPR40 expression was detected in human and bovine endothelial cells (ECs), smooth muscle cells, and arteries. 11,12-EET concentration-dependently relaxed preconstricted coronary arteries; however, these relaxations were not altered by GW1100. In human ECs, 11,12-EET increased MAP kinase (MAPK)-mediated ERK phosphorylation, phosphorylation and levels of connexin-43 (Cx43), and expression of cyclooxygenase-2 (COX-2), all of which were inhibited by GW1100 and the MAPK inhibitor U0126. Moreover, siRNA-mediated GPR40 silencing decreased 11,12-EET-induced ERK phosphorylation. These results indicated that GPR40 is a low-affinity EET receptor in vascular cells and arteries. We conclude that epoxidation of arachidonic acid to EETs enhances GPR40 agonist activity and that 11,12-EET stimulation of GPR40 increases Cx43 and COX-2 expression in ECs via ERK phosphorylation.

9- and 13-HODE regulate fatty acid binding protein-4 in human macrophages, but does not involve HODE/GPR132 axis in PPAR-γ regulation of FABP4

BACKGROUND

Both activation of monocytes and increased serum fatty acid binding protein-4 (FABP4) occur in diabetes and are associated with increased atherosclerosis. The oxidized lipid, 9-hydroxyoctadecadienoic acid (9-HODE) increases FABP4 in macrophages, and is a ligand for G protein-coupled receptor 132 (GPR132). We investigated the involvement of GPR132 in mediating the 9-, 13-HODE stimulation of FABP4 secretion, and whether GPR132 expression is increased in monocytes from patients with type 2 diabetes.

METHODS

The effects of siRNA silencing of GPR132 gene and of the PPAR-γ antagonist T0070907 were studied in THP-1 cells. Serum levels of FABP4 and other adipokines were measured in patients with diabetes, and monocyte subpopulations were analyzed using flow cytometry. GPR132 mRNA was quantified in isolated CD14⁺ cells.

RESULTS

9-HODE and 13-HODE increased FABP4 expression in THP-1 monocytes and macrophages, and also increased GPR132 expression. Silencing of GPR132 did not influence the increase in FABP4 with 9-HODE, 13-HODE, or rosiglitazone (ROSI). By contrast, T0070907 inhibited the effect of all three ligands on FABP4 expression. Diabetic subjects had increased serum FABP4, and activated monocytes. They also expressed higher levels of GPR132 mRNA in CD14⁺ cells.

CONCLUSIONS

We conclude that GPR132 is an independent monocyte activation marker in diabetes, but does not contribute to PPAR-γ-mediated induction of FABP4 by HODEs.

Exercise training alters the genomic response to acute exercise in human adipose tissue

Aim:

To determine the genomic mechanisms by which adipose tissue responds to acute and chronic exercise.

Methods:

We profiled the transcriptomic and epigenetic response to acute exercise in human adipose tissue collected before and after endurance training.

Results:

Although acute exercises were performed at same relative intensities, the magnitude of transcriptomic changes after acute exercise was reduced by endurance training. DNA methylation remodeling induced by acute exercise was more prominent in trained versus untrained state. We found an overlap between gene expression and DNA methylation changes after acute exercise for 32 genes pre-training and six post-training, notably at adipocyte-specific genes.

Conclusion:

Training status differentially affects the epigenetic and transcriptomic response to acute exercise in human adipose tissue.

β-glucans and cholesterol (Review)

Hypercholesterolemia is one of primary risk factors of cardiovascular disease, together with metabolic syndrome, hypertension and diabetes. Although progress has been made, the search for novel methods of preventing and treating dyslipidemia is ongoing and current therapies for cardiovascular disease induce various side effects. β-glucans are linear unbranched polysaccharides found in various natural sources, such as mushrooms. Due to their structure they are able to interact with innate immunity receptors, however they also act as dietary fibers in the digestive tract. As there are two forms of β-glucans, insoluble and soluble forms, they are able to interact with lipids and biliary salts in the bowel and consequently reduce cholesterol levels. Therefore, they may be developed as a suitable therapeutic option to treat patients with dyslipidemia, as they are natural molecules that do not induce any significant side effects. The current review discusses the evidence supporting the effects of β-glucans on cholesterol levels.

Fatty Acid-Induced Lipotoxicity in Pancreatic Beta-Cells During Development of Type 2 Diabetes

Type 2 diabetes is caused by chronic insulin resistance and progressive decline in beta-cell function. Optimal beta-cell function and mass is essential for glucose homeostasis and beta-cell impairment leads to the development of diabetes. Elevated levels of circulating fatty acids (FAs) and disturbances in lipid metabolism regulation are associated with obesity, and they are major factors influencing the increase in the incidence of type 2 diabetes. Chronic free FA (FFA) treatment induces insulin resistance and beta-cell dysfunction; therefore, reduction of elevated plasma FFA levels might be an important therapeutic target in obesity and type 2 diabetes. Lipid signals via receptors, and intracellular mechanisms are involved in FFA-induced apoptosis. In this paper, we discuss lipid actions in beta cells, including effects on metabolic pathways and stress responses, to help further understand the molecular mechanisms of lipotoxicity-induced type 2 diabetes.

Epistatic effects between pairs of the growth hormone secretagogue receptor 1a, growth hormone, growth hormone receptor, non-SMC condensin I complex, subunit G and stearoyl-CoA desaturase genes on carcass, price-related and fatty acid composition traits in Japanese Black cattle

Growth hormone secretagogue receptor 1a (GHSR1a), growth hormone (GH), growth hormone receptor (GHR), non-SMC condensin I complex, subunit G (NCAPG) and stearoyl-CoA desaturase (SCD), are known to play important roles in growth and lipid metabolisms. Single and epistatic effects of the five genes on carcass, price-related and fatty acid (FA) composition traits were analyzed in a commercial Japanese Black cattle population of Ibaraki Prefecture. A total of 650 steers and 116 heifers for carcass and price-related traits, and 158 steers for FA composition traits were used in this study. Epistatic effects between pairs of the five genes were found in several traits. Alleles showing strain-specific differences in the five genes had significant single and epistatic effects in some traits. The data suggest that a TG-repeat polymorphism of the GHSR1a.5'UTR-(TG)_n locus plays a central role in gene-gene epistatic interaction of FA composition traits in the adipose tissue of Japanese Black cattle.

Discovery of an Isothiazole-Based Phenylpropanoic Acid GPR120 Agonist as a Development Candidate for Type 2 Diabetes

We have discovered a novel series of isothiazole-based phenylpropanoic acids as GPR120 agonists. Extensive structure-activity relationship studies led to the discovery of a potent GPR120 agonist 4x, which displayed good EC₅₀ values in both calcium and β-arrestin assays. It also presented good pharmaceutical properties and a favorable PK profile. Moreover, it demonstrated in vivo antidiabetic activity in C57BL/6 DIO mice. Studies in WT and knockout DIO mice showed that it improved glucose handling during an OGTT via GPR120. Overall, 4x possessed promising antidiabetic effect and good safety profile to be a development candidate.

Coffee consumption is associated with DNA methylation levels of human blood

Beneficial health effects have been attributed to coffee consumption, but it is not yet known whether epigenetics may have a role in this process. Here we associate epigenome-wide DNA methylation levels to habitual coffee consumption from two studies with blood (2100 and 215 participants), and one with saliva samples (256 participants). Adjusting for age, gender, and blood cell composition, one CpG (cg21566642 near ALPPL2) surpassed genome-wide significance (P=3.7 × 10^-10) and from among 10 additional CpGs significant at P≤5.0 × 10^-6, six were located within 1500 bps of a transcriptional start site. Results for these 11 top-ranked CpGs remained significant after further adjusting for smoking. Also, methylation levels of another 135 CpGs were influenced by both coffee drinking and smoking (P≤1.0 × 10^-7). Functional enrichment analysis suggested that coffee-associated CpGs were located near transcription factor binding (P=1.2 × 10^-6) and protein kinase activity genes (P=2.9 × 10^-5). Interestingly, when we stratified by menopausal hormone therapy (MHT), methylation differences with coffee consumption were observed only in women who never used MHT. We did not replicate any of the associations found in blood in our saliva samples, suggesting that coffee may affect DNA methylation levels in immune cells of the blood but not in saliva.

Exploration of phenylpropanoic acids as agonists of the free fatty acid receptor 4 (FFA4): Identification of an orally efficacious FFA4 agonist

The long chain free fatty acid receptor 4 (FFA4/GPR120) has recently been recognized as lipid sensor playing important roles in nutrient sensing and inflammation and thus holds potential as a therapeutic target for type 2 diabetes and metabolic syndrome. To explore the effects of stimulating this receptor in animal models of metabolic disease, we initiated work to identify agonists with appropriate pharmacokinetic properties to support progression into in vivo studies. Extensive SAR studies of a series of phenylpropanoic acids led to the identification of compound 29, a FFA4 agonist which lowers plasma glucose in two preclinical models of type 2 diabetes.

Metabolic effects of orally administered small-molecule agonists of GPR55 and GPR119 in multiple low-dose streptozotocin-induced diabetic and incretin-receptor-knockout mice

AIMS/HYPOTHESIS

Abnormal cannabidiol (Abn-CBD) and AS-1269574 are potent selective agonists for GPR55 and GPR119, respectively. The present study evaluated the actions and ability of these small-molecule agonists to counteract experimental diabetes in mice.

METHODS

Diabetes was induced in NIH Swiss mice by five consecutive daily intraperitoneal injections of 40 mg/(kg body weight) streptozotocin. Diabetic mice received daily oral administration of Abn-CBD or AS-1269574 (0.1 μmol/kg) or saline vehicle (0.9% wt/vol. NaCl) over 28 days. Body weight, food intake, fluid intake, plasma glucose, insulin, glucose tolerance, insulin release, lipid profile and pancreatic morphology were examined. Mechanism of action of agonists was assessed in acute studies using incretin-receptor-knockout mice.

RESULTS

Abn-CBD and AS-1269574 decreased plasma glucose (20-26%, p < 0.05) and increased circulating insulin (47-48%, p < 0.05) by 10-28 days, compared with saline-treated diabetic controls. Food intake and polydipsia were reduced by both agonists (21-23%, p < 0.05 and 33-35%, p < 0.01, respectively). After 28 days of treatment, plasma glucagon concentrations were reduced (p < 0.01) and glucose tolerance was enhanced by 19-44% by Abn-CBD (p < 0.05 or p < 0.001) and AS-1269574 (p < 0.05 to p < 0.001). Plasma insulin responses were improved (p < 0.01) and insulin resistance was decreased (p < 0.05 or p < 0.01) in both Abn-CBD- and AS-1269574-treated groups. Triacylglycerols were decreased by 19% with Abn-CBD (p < 0.05) and 32% with AS-1269574 (p < 0.01) while total cholesterol was reduced by 17% (p < 0.01) and 15% (p < 0.05), respectively. Both agonists enhanced beta cell proliferation (p < 0.001) although islet area was unchanged. Acute studies in Gipr- and Glp1r-knockout mice revealed an important role for the glucagon-like peptide 1 (GLP-1) receptor in the actions of both agonists, with the glucose-lowering effects of Abn-CBD also partly mediated through the glucose-dependent insulinotropic peptide (GIP) receptor.

CONCLUSIONS/INTERPRETATION

These data highlight the potential for fatty acid G-protein-coupled receptor-based therapies as novel insulinotropic and glucose-lowering agents acting partly through the activation of incretin receptors.

The role of gut microbiota in metabolic regulation

Obesity and metabolic syndrome are among the major problems of modern society. The increase in obesity is associated with a corresponding increase in type 2 diabetes, cardiovascular disease and cancer. A huge amount of scientific research has been devoted to the development of methods to reduce obesity and its complications. In recent years, attention has shifted towards studying the intestinal microbiota not only as a possible component of the pathological process but also as a target of therapeutic intervention. Recent evidence, primarily from investigations in animal models, suggests that the intestinal microbiota affects nutrient acquisition and energy regulation. This review will discuss the role of the intestinal microbiota in metabolic processes as well as the latest developments on the improvement of disturbances specific to obesity and metabolic syndrome.

The shift work and health research agenda: Considering changes in gut microbiota as a pathway linking shift work, sleep loss and circadian misalignment, and metabolic disease

Prevalence and impact of metabolic disease is rising. In particular, overweight and obesity are at epidemic levels and are a leading health concern in the Western world. Shift work increases the risk of overweight and obesity, along with a number of additional metabolic diseases, including metabolic syndrome and type 2 diabetes (T2D). How shift work contributes to metabolic disease has not been fully elucidated. Short sleep duration is associated with metabolic disease and shift workers typically have shorter sleep durations. Short sleep durations have been shown to elicit a physiological stress response, and both physiological and psychological stress disrupt the healthy functioning of the intestinal gut microbiota. Recent findings have shown altered intestinal microbial communities and dysbiosis of the gut microbiota in circadian disrupted mice and jet lagged humans. We hypothesize that sleep and circadian disruption in humans alters the gut microbiota, contributing to an inflammatory state and metabolic disease associated with shift work. A research agenda for exploring the relationship between insufficient sleep, circadian misalignment and the gut microbiota is provided.

Bacteria within the Gastrointestinal Tract Microbiota Correlated with Improved Growth and Feed Conversion: Challenges Presented for the Identification of Performance Enhancing Probiotic Bacteria

Identification of bacteria associated with desirable productivity outcomes in animals may offer a direct approach to the identification of probiotic bacteria for use in animal production. We performed three controlled chicken trials (n = 96) to investigate caecal microbiota differences between the best and poorest performing birds using four performance measures; feed conversion ratio (FCR), utilization of energy from the feed measured as apparent metabolisable energy, gain rate (GR), and amount of feed eaten (FE). The shifts in microbiota composition associated with the performance measures were very different between the three trials. Analysis of the caecal microbiota revealed that the high and low FCR birds had significant differences in the abundance of some bacteria as demonstrated by shifts in microbiota alpha and beta diversity. Trials 1 and 2 showed significant overall community shifts, however, the microbial changes driving the difference between good and poor performers were very different. Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae families and genera Ruminococcus, Faecalibacterium and multiple lineages of genus Clostridium (from families Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae) were highly abundant in good FCR birds in Trial 1. Different microbiota was associated with FCR in Trial 2; Catabacteriaceae and unknown Clostridiales family members were increased in good FCR and genera Clostridium (from family Clostridiaceae) and Lactobacillus were associated with poor FCR. Trial 3 had only mild microbiota differences associated with all four performance measures. Overall, the genus Lactobacillus was correlated with feed intake which resulted in poor FCR performance. The genus Faecalibacterium correlated with improved FCR, increased GR and reduced FE. There was overlap in phylotypes correlated with improved FCR and GR, while different microbial cohorts appeared to be correlated with FE. Even under controlled conditions different cohorts of birds developed distinctly different microbiotas. Within the different trial groups the abundance of certain bacterial groups correlated with productivity outcomes. However, with different underlying microbiotas there were different bacteria correlated with performance. The challenge will be to identify probiotic bacteria that can reliably deliver favorable outcomes from diverse microbiotas.

Type 2 diabetes and gut microbiome: at the intersection of known and unknown

The prevalence of metabolic syndrome is increasing rapidly across the globe. Though the prevalence of the disease is similar in population of upper middle income and high income countries, the age of affected population is lower in upper middle income countries. This is attributed to genetic as well as changing life style factors. The contributing factors for type 2 diabetes range from genetic/epigenetic disposal, intra uterine nutrition, dietary pattern to sedentary lifestyle. The role of the gut microbiota in metabolic disorders is increasingly gaining importance. Several studies have reported significant difference in the profile of the gut microbiota in Caucasian population considering obese and type 2 diabetic populations while limited number of studies are available on populations from the developing world. The metabolites from the gut microbes contribute to the gut barrier integrity and a compromised barrier leads to leakage of inflammatory mediators into systemic circulation and hence increases insulin resistance. Attempts have been made at correcting metabolic syndrome through dietary changes by altering the gut microbiota with some success. This report is an attempt to explain the hypothesis of compromised nutrition altering the gut microbiota, gut metabolites, gut barrier function, systemic inflammation and hence insulin response.

Brain delivery of proteins via their fatty acid and block copolymer modifications

It is well known that hydrophobic small molecules penetrate cell membranes better than hydrophilic molecules. Amphiphilic molecules that dissolve both in lipid and aqueous phases are best suited for membrane transport. Transport of biomacromolecules across physiological barriers, e.g. the blood-brain barrier, is greatly complicated by the unique structure and function of such barriers. Two decades ago we adopted a simple philosophy that to increase protein delivery to the brain one needs to modify this protein with hydrophobic moieties. With this general idea we began modifying proteins (antibodies, enzymes, hormones, etc.) with either hydrophobic fatty acid residues or amphiphilic block copolymer moieties, such as poy(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (pluronics or poloxamers) and more recently, poly(2-oxasolines). This simple approach has resulted in impressive successes in CNS drug delivery. We present a retrospective overview of these works initiated in the Soviet Union in 1980s, and then continued in the United States and other countries. Notably some of the early findings were later corroborated by brain pharmacokinetic data. Industrial development of several drug candidates employing these strategies has followed. Overall modification by hydrophobic fatty acids residues or amphiphilic block copolymers represents a promising and relatively safe strategy to deliver proteins to the brain.

The role of short-chain fatty acids in health and disease

There is now an abundance of evidence to show that short-chain fatty acids (SCFAs) play an important role in the maintenance of health and the development of disease. SCFAs are a subset of fatty acids that are produced by the gut microbiota during the fermentation of partially and nondigestible polysaccharides. The highest levels of SCFAs are found in the proximal colon, where they are used locally by enterocytes or transported across the gut epithelium into the bloodstream. Two major SCFA signaling mechanisms have been identified, inhibition of histone deacetylases (HDACs) and activation of G-protein-coupled receptors (GPCRs). Since HDACs regulate gene expression, inhibition of HDACs has a vast array of downstream consequences. Our understanding of SCFA-mediated inhibition of HDACs is still in its infancy. GPCRs, particularly GPR43, GPR41, and GPR109A, have been identified as receptors for SCFAs. Studies have implicated a major role for these GPCRs in the regulation of metabolism, inflammation, and disease. SCFAs have been shown to alter chemotaxis and phagocytosis; induce reactive oxygen species (ROS); change cell proliferation and function; have anti-inflammatory, antitumorigenic, and antimicrobial effects; and alter gut integrity. These findings highlight the role of SCFAs as a major player in maintenance of gut and immune homeostasis. Given the vast effects of SCFAs, and that their levels are regulated by diet, they provide a new basis to explain the increased prevalence of inflammatory disease in Westernized countries, as highlighted in this chapter.

The health benefits of dietary fiber: beyond the usual suspects of type 2 diabetes mellitus, cardiovascular disease and colon cancer

Dietary fiber (DF) is deemed to be a key component in healthy eating. DF is not a static collection of undigestible plant materials that pass untouched or unencumbered through the gastrointestinal (GI) tract; instead, DFs are a vast array of complex saccharide-based molecules that can bind potential nutrients and nutrient precursors to prevent their absorption. Some DFs are fermentable, and the GI tract catabolism leads to the generation of various bioactive materials, such as short-chain fatty acids (SCFAs), that can markedly augment the GI tract biomass and change the composition of the GI tract flora. The health benefits of DFs include the prevention and mitigation of type 2 diabetes mellitus, cardiovascular disease and colon cancer. By modulating food ingestion, digestion, absorption and metabolism, DFs reduce the risk of hyperlipidemia, hypercholesterolemia and hyperglycemia. Emerging research has begun to investigate the role of DFs in immunomodulation. If substantiated, DFs could facilitate many biologic processes, including infection prevention and the improvement of mood and memory. This review describes the accepted physiologic functions of DFs and explores their new potential immune-based actions.

Management of type 2 diabetes: new and future developments in treatment

The increasing prevalence, variable pathogenesis, progressive natural history, and complications of type 2 diabetes emphasise the urgent need for new treatment strategies. Longacting (eg, once weekly) agonists of the glucagon-like-peptide-1 receptor are advanced in development, and they improve prandial insulin secretion, reduce excess glucagon production, and promote satiety. Trials of inhibitors of dipeptidyl peptidase 4, which enhance the effect of endogenous incretin hormones, are also nearing completion. Novel approaches to glycaemic regulation include use of inhibitors of the sodium-glucose cotransporter 2, which increase renal glucose elimination, and inhibitors of 11β-hydroxysteroid dehydrogenase 1, which reduce the glucocorticoid effects in liver and fat. Insulin-releasing glucokinase activators and pancreatic-G-protein-coupled fatty-acid-receptor agonists, glucagon-receptor antagonists, and metabolic inhibitors of hepatic glucose output are being assessed. Early proof of principle has been shown for compounds that enhance and partly mimic insulin action and replicate some effects of bariatric surgery.