β cell acetate production and release are negligible

BACKGROUND

Studies suggest that short chain fatty acids (SCFAs), which are primarily produced from fermentation of fiber, regulate insulin secretion through free fatty acid receptors 2 and 3 (FFA2 and FFA3). As these are G-protein coupled receptors (GPCRs), they have potential therapeutic value as targets for treating type 2 diabetes (T2D). The exact mechanism by which these receptors regulate insulin secretion and other aspects of pancreatic β cell function is unclear. It has been reported that glucose-dependent release of acetate from pancreatic β cells negatively regulates glucose stimulated insulin secretion. While these data raise the possibility of acetate's potential autocrine action on these receptors, these findings have not been independently confirmed, and multiple concerns exist with this observation, particularly the lack of specificity and precision of the acetate detection methodology used.

METHODS

Using Min6 cells and mouse islets, we assessed acetate and pyruvate production and secretion in response to different glucose concentrations, via liquid chromatography mass spectrometry.

RESULTS

Using Min6 cells and mouse islets, we showed that both intracellular pyruvate and acetate increased with high glucose conditions; however, intracellular acetate level increased only slightly and exclusively in Min6 cells but not in the islets. Further, extracellular acetate levels were not affected by the concentration of glucose in the incubation medium of either Min6 cells or islets.

CONCLUSIONS

Our findings do not substantiate the glucose-dependent release of acetate from pancreatic β cells, and therefore, invalidate the possibility of an autocrine inhibitory effect on glucose stimulated insulin secretion.

Intestinal FFA2 promotes obesity by altering food intake in Western diet-fed mice

Short-chain fatty acids (SCFAs) are key nutrients that play a diverse set of roles in physiological function, including regulating metabolic homeostasis. Generated through the fermentation of dietary fibers in the distal colon by the gut microbiome, SCFAs and their effects are partially mediated by their cognate receptors, including free fatty acid receptor 2 (FFA2). FFA2 is highly expressed in the intestinal epithelial cells, where its putative functions are controversial, with numerous in vivo studies relying on global knockout mouse models to characterize intestine-specific roles of the receptor. Here, we used the Villin-Cre mouse line to generate a novel, intestine-specific knockout mouse model for FFA2 (Vil-FFA2) to investigate receptor function within the intestine. Because dietary changes are known to affect the composition of the gut microbiome, and can thereby alter SCFA production, we performed an obesogenic challenge on male Vil-FFA2 mice and their littermate controls (FFA2-floxed, FFA2fl/fl) to identify physiological changes on a high-fat, high-sugar 'Western diet' (WD) compared to a low-fat control diet (CD). We found that the WD-fed Vil-FFA2 mice were transiently protected from the obesogenic effects of the WD and had lower fat mass and improved glucose homeostasis compared to the WD-fed FFA2fl/fl control group during the first half of the study. Additionally, major differences in respiratory exchange ratio and energy expenditure were observed in the WD-fed Vil-FFA2 mice, and food intake was found to be significantly reduced at multiple points in the study. Taken together, this study uncovers a novel role of intestinal FFA2 in mediating the development of obesity.

The future treatment for type 1 diabetes: Pig islet- or stem cell-derived β cells?

Replacement of β cells is only a curative approach for type 1 diabetes (T1D) patients to avoid the threat of iatrogenic hypoglycemia. In this pursuit, islet allotransplantation under Edmonton's protocol emerged as a medical miracle to attain hypoglycemia-free insulin independence in T1D. Shortage of allo-islet donors and post-transplantation (post-tx) islet loss are still unmet hurdles for the widespread application of this therapeutic regimen. The long-term survival and effective insulin independence in preclinical studies have strongly suggested pig islets to cure overt hyperglycemia. Importantly, CRISPR-Cas9 technology is pursuing to develop "humanized" pig islets that could overcome the lifelong immunosuppression drug regimen. Lately, induced pluripotent stem cell (iPSC)-derived β cell approaches are also gaining momentum and may hold promise to yield a significant supply of insulin-producing cells. Theoretically, personalized β cells derived from a patient's iPSCs is one exciting approach, but β cell-specific immunity in T1D recipients would still be a challenge. In this context, encapsulation studies on both pig islet as well as iPSC-β cells were found promising and rendered long-term survival in mice. Oxygen tension and blood vessel growth within the capsules are a few of the hurdles that need to be addressed. In conclusion, challenges associated with both procedures, xenotransplantation (of pig-derived islets) and stem cell transplantation, are required to be cautiously resolved before their clinical application.

OR23-4 Intestinal FFA2 and FFA3 Mediate Obesogenic Effects in Mice on a Western Diet

Free fatty acid receptor 2 and free fatty acid receptor 3 (FFA2/3) are two highly similar G protein-coupled receptors belonging to the free fatty acid receptor family. Their ligands are short-chain fatty acids (SCFAs), which are key nutrients that play a diverse role in physiological function, including the regulation of metabolic homeostasis and glycemic control. FFA2/3 are broadly expressed in a multitude of tissues including the intestine, pancreas, adipose and central nervous system, where they contribute to metabolic homeostasis via a summation of tissue-specific effects. Consequently, FFA2/3 have been identified as a potential drug target for metabolic diseases including obesity and type-2 diabetes.

Both FFA2 and FFA3 are highly expressed within the intestinal epithelium – the major site of SCFA generation – and have been identified in hormone-secreting enteroendocrine cells as well as intestinal epithelial cells. However, due conflicting data, the respective roles of FFA2/3 within the intestine and their effects on physiology and metabolism are still largely unclear. Previous in vivo studies involving this receptor have largely relied on global knockout mouse models, making it difficult to isolate their effects in the intestine. To overcome this challenge, we generated a novel intestine-specific knockout mouse model for FFA2 and FFA3 individually, utilizing Cre-mediated recombination under the expression of the villin promoter. Here, we report the first in vivo characterization of FFA2/3 in the intestine and reveal novel insights into receptor function.

Following model validation, we conducted a general metabolic assessment of male Villin-Cre-FFA2 (Vil-FFA2) and Villin-Cre-FFA3 (Vil-FFA3) mice on standard chow and observed no major congenital or time-dependent defects. Because dietary changes are known to alter gut microbial composition, and thereby SCFA production, a pilot study was performed on male Vil-FFA2 and Vil-FFA3 mice and their littermate controls to probe for a phenotype on a high-fat, high-sugar "western diet." Mice were placed on either a low-fat control diet (CD) or western diet (WD) at 10 weeks of age and metabolically profiled for 25 weeks. We found that both Vil-FFA2 and Vil-FFA3 mouse strains were largely protected from diet-induced obesity and had significantly lower fat mass as well as adipose hypertrophy. Additionally, both mouse strains had reduced intestinal inflammation and improved glucose homeostasis. These differences were driven by lower food intake in the Vil-FFA2 strain only. Our findings suggest a novel role of FFA2/3 in mediating the metabolic consequences of a western diet – a state of high inflammation, dysbiosis and metabolic stress. Moreover, these data support an intestine-specific role of FFA2/3 in whole-body metabolic homeostasis and in the development of adiposity and hyperglycemia.

Presentation: Monday, June 13, 2022 12:00 p.m. - 12:15 p.m.

Intestinal FFA3 mediates obesogenic effects in mice on a Western diet

Free fatty acid receptor 3 (FFA3) is a recently-deorphanized G-protein-coupled receptor. Its ligands are short-chain fatty acids (SCFAs), which are key nutrients derived from the gut microbiome fermentation process that play diverse roles in the regulation of metabolic homeostasis and glycemic control. FFA3 is highly expressed within the intestine, where its role and its effects on physiology and metabolism are unclear. Previous in vivo studies involving this receptor have relied on global knockout mouse models, making it difficult to isolate intestine-specific roles of FFA3. To overcome this challenge, we generated an intestine-specific knockout mouse model for FFA3, Villin-Cre-FFA3 (Vil-FFA3). Model validation and general metabolic assessment of male mice fed a standard chow diet revealed no major congenital defects. Because dietary changes are known to alter gut microbial composition, and thereby SCFA production, an obesogenic challenge was performed on male Vil-FFA3 mice and their littermate controls to probe for a phenotype on a high-fat, high-sugar "Western diet" (WD) compared with a low-fat control diet (CD). Vil-FFA3 mice versus FFA3fl/fl controls on WD, but not CD, were protected from the development of diet-induced obesity and exhibited significantly less fat mass as well as smaller adipose depositions and adipocytes. Although overall glycemic control was unchanged in the WD-fed Vil-FFA3 group, fasted glucose levels trended lower. Intestinal inflammation was significantly reduced in the WD-fed Vil-FFA3 mice, supporting protection from obesogenic effects. Furthermore, we observed lower levels of gastric inhibitory protein (GIP) in the WD-fed Vil-FFA3 mice, which may contribute to phenotypic changes. Our findings suggest a novel role of intestinal FFA3 in promoting the metabolic consequences of a WD, including the development of obesity and inflammation. Moreover, these data support an intestine-specific role of FFA3 in whole body metabolic homeostasis and in the development of adiposity.NEW & NOTEWORTHY Here, we generated a novel intestine-specific knockout mouse model for FFA3 (Vil-FFA3) and performed a comprehensive metabolic characterization of mice in response to an obesogenic challenge. We found that Vil-FFA3 mice fed with a Western diet were largely protected from obesity, exhibiting significantly lower levels of fat mass, lower intestinal inflammation, and altered expression of intestinal incretin hormones. Results support an important role of intestinal FFA3 in contributing to metabolism and in the development of diet-induced obesity.

The hexokinase "HKDC1" interaction with the mitochondria is essential for liver cancer progression

Liver cancer (LC) is the fourth leading cause of death from cancer malignancies. Recently, a putative fifth hexokinase, hexokinase domain containing 1 (HKDC1), was shown to have significant overexpression in LC compared to healthy liver tissue. Using a combination of in vitro and in vivo tools, we examined the role of HKDC1 in LC development and progression. Importantly, HKDC1 ablation stops LC development and progression via its action at the mitochondria by promoting metabolic reprogramming and a shift of glucose flux away from the TCA cycle. HKDC1 ablation leads to mitochondrial dysfunction resulting in less cellular energy, which cannot be compensated by enhanced glucose uptake. Moreover, we show that the interaction of HKDC1 with the mitochondria is essential for its role in LC progression, and without this interaction, mitochondrial dysfunction occurs. As HKDC1 is highly expressed in LC cells, but only to a minimal degree in hepatocytes under normal conditions, targeting HKDC1, specifically its interaction with the mitochondria, may represent a highly selective approach to target cancer cells in LC.

Effects of Sleep-Extend on glucose metabolism in women with a history of gestational diabetes: a pilot randomized trial

Objectives

Women with a history of gestational diabetes (GDM) are at 7-fold increase in the risk of developing diabetes. Insufficient sleep has also been shown to increase diabetes risk. This study aimed to explore the feasibility of a sleep extension in women with a history of GDM and short sleep, and effects on glucose metabolism.

Methods

Women age 18–45 years with a history of GDM and actigraphy confirmed short sleep duration (<7 h/night) on weekdays were randomized at a ratio of 1 control (heathy living information) to 2 cases (6 weeks of “Sleep-Extend” intervention: use of a Fitbit, weekly digital content, and weekly coaching to increase sleep duration). An oral glucose tolerance test (OGTT), 7-day actigraphy recording, and questionnaires were obtained at baseline and 6 weeks. Mean differences between baseline and end-of-intervention parameters were compared using independent samples t-tests.

Results

Mean (SD) sleep duration increased within the Sleep-Extend group (n=9, +26.9 (42.5) min) but decreased within the controls (n=5, − 9.1 (20.4) min), a mean difference (MD) of 35.9 min (95% confidence interval (CI) − 8.6, 80.5). Fasting glucose increased, but less in Sleep-Extend vs. control groups (1.6 (9.4) vs 10.4 (8.2) mg/dL, MD − 8.8 mg/dL (95% CI − 19.8, 2.1), while 2-h glucose levels after an OGTT did not differ. Compared to controls, Sleep-Extend had decreased fatigue score (MD − 10.6, 95%CI − 20.7, − 0.6), and increased self-report physical activity (MD 5036 MET- minutes/week, 95%CI 343, 9729. Fitbit compliance and satisfaction in Sleep-Extend group was high.

Conclusion

Sleep extension is feasible in women with a history of GDM, with benefits in fatigue and physical activity, and possibly glucose metabolism. These data support a larger study exploring benefits of sleep extension on glucose metabolism in these high-risk women.

Trial registration

ClinicalTrials.gov, NCT03638102 (8/20/2018)

Gestational Insulin Resistance Is Mediated by the Gut Microbiome-Indoleamine 2,3-Dioxygenase Axis

BACKGROUND & AIMS

Normal gestation involves a reprogramming of the maternal gut microbiome (GM) that contributes to maternal metabolic changes by unclear mechanisms. This study aimed to understand the mechanistic underpinnings of the GM-maternal metabolism interaction.

METHODS

The GM and plasma metabolome of CD1, NIH-Swiss, and C57 mice were analyzed with the use of 16S rRNA sequencing and untargeted liquid chromatography-mass spectrometry throughout gestation. Pharmacologic and genetic knockout mouse models were used to identify the role of indoleamine 2,3-dioxygenase (IDO1) in pregnancy-associated insulin resistance (IR). Involvement of gestational GM was studied with the use of fecal microbial transplants (FMTs).

RESULTS

Significant variation in GM alpha diversity occurred throughout pregnancy. Enrichment in gut bacterial taxa was mouse strain and pregnancy time point specific, with the species enriched at gestation day 15/19 (G15/19), a point of heightened IR, being distinct from those enriched before or after pregnancy. Metabolomics revealed elevated plasma kynurenine at G15/19 in all 3 mouse strains. IDO1, the rate-limiting enzyme for kynurenine production, had increased intestinal expression at G15, which was associated with mild systemic and gut inflammation. Pharmacologic and genetic inhibition of IDO1 inhibited kynurenine levels and reversed pregnancy-associated IR. FMT revealed that IDO1 induction and local kynurenine level effects on IR derive from the GM in both mouse and human pregnancy.

CONCLUSIONS

GM changes accompanying pregnancy shift IDO1-dependent tryptophan metabolism toward kynurenine production, intestinal inflammation, and gestational IR, a phenotype reversed by genetic deletion or inhibition of IDO1. (Gestational Gut Microbiome-IDO1 Axis Mediates Pregnancy Insulin Resistance; EMBL-ENA ID: PRJEB45047. MetaboLights ID: MTBLS3598).

Fiber Diet-Mediated Increases in Short Chain Fatty Acids Alleviate Western Diet Induced Metabolic Dysfunction

Objectives

Short chain fatty acids (SCFAs), which are gut microbial fermentation byproducts with suggested positive health effects, have emerged as a therapeutic modality against metabolic diseases like obesity and type 2 diabetes. Alluringly, in vivo SCFA levels are easily modifiable by consumption of fermentable fibers (FF). Most rodent studies on dietary FF supplementation report terminal increased cecal/fecal SCFA levels but the time course of this increase remains elusive. Also, there is limited information on the effect of this sustained SCFA increase on physiology. Thus, we investigated dietary FF-dependent temporal increases in plasma SCFA levels and its metabolic effects on a western diet (WD) mouse model.

Methods

C57BL/6J male mice (age 10 weeks) were fed test diets for 8 weeks. In Phase I, to establish time-course of plasma SCFA increase, mice were fed the following isocaloric diets: control (low fat + 0% FF); WD; control + 20% FF, where FF was fructooligosaccharides (FOS), inulin (In), guar gum (GG) or pectin (Pec). In Phase II mice were fed a control diet, or a WD with or without 20% FOS, Pec or GG. End points were weekly plasma SCFAs (by MS/MS), body weight, random glucose and insulin, and at the end of experimental period body fat composition and metabolic tests.

Results

Phase I. Compared to control, WD lowered while FF induced significant increases in total plasma SCFAs (FOS, Pec, GG &gt; In) in a time dependent manner that plateaued beyond 2 weeks. All FF increased propionate and acetate but not butyrate. Phase II. WD caused metabolic dysfunctions (increased body weight and fat mass; glucose intolerance; insulin resistance; P &lt; 0.0001 by two-way ANOVA) that were alleviated in mice fed FF enriched WD (Pec = GG &gt; FOS). Compared to WD, food intake was similar except high in the WD-Pec group, while WD-Pec and GG showed higher energy expenditure. All 3 plasma SCFAs were significantly higher in all WD-FF groups. FF supplementation of the control diet showed no significant difference compared to control.

Conclusions

We conclude that: 1) FF feeding induced SCFA production reaches saturation within 2 weeks, suggesting selection of specific gut bacterial features; and 2) all FFs were protective from weight gain and its metabolic consequences.

Funding Sources

2R01 DK104927 (NIH/NIDDK) Layden.

Loss of Intestine-Specific FFA3 Has Protective Effects Against Diet-Induced Obesity and Hyperglycemia in Mice on a Western Diet

Free fatty acid receptor 3 (FFA3) is a recently-deorphaned G protein-coupled receptor belonging to the free fatty acid receptor family. Its ligands are short-chain fatty acids (SCFAs), which are key nutrients that play a diverse role in physiological function, including the regulation of metabolic homeostasis and glycemic control. FFA3 is broadly expressed in a multitude of tissues including the intestine, pancreas, and central nervous system, and is thought to contribute to metabolic homeostasis via a summation of its tissue-specific effects. Consequently, FFA3 has been identified as a potential drug target for metabolic diseases including obesity and type-2 diabetes. FFA3 is highly expressed in enteroendocrine cells (EECs) within the intestinal epithelium - the major site of SCFA generation - and is hypothesized to play a role in the secretion of postprandial incretin hormones, which are a group of specialized gut peptides that regulate a variety of metabolic and digestive functions following a meal. However, due to a paucity of data, the role of FFA3 within the intestine and its effects on physiology and metabolism is largely unclear. Previous in vivo studies involving this receptor have largely relied on global knockout mouse models, making it difficult to isolate its effects in EECs. To overcome this challenge, we have generated a novel intestine-specific knockout mouse model for FFA3, utilizing Cre-mediated recombination under the expression of the villin promoter. Here, we report the first in vivo characterization of FFA3 in the intestine and reveal novel insights into receptor function. Following model validation, we conducted a general metabolic assessment of male Villin-Cre-FFA3 mice on normal chow and observed no major congenital or time-dependent defects. Because dietary changes are known to alter gut microbial composition, and thereby SCFA production, a pilot study was performed on male Villin-Cre-FFA3 mice and their littermate controls to probe for a phenotype on a high-fat, high-sugar “western diet.” Mice were placed on either normal chow (NC) or western diet (WD) at 10 weeks of age and metabolically profiled for 25 weeks. Our data reveals that Villin-Cre-FFA3 mice on WD, but not NC, were protected from diet-induced metabolic dysfunction, and displayed significantly lower levels of fat mass as well as modestly improved glycemic control. Our findings suggest a novel role of FFA3 in mediating the metabolic consequences of a western diet - a state of high inflammation, dysbiosis and metabolic stress. Moreover, these data support an intestine-specific role of FFA3 in both glucose and lipid metabolism, and further suggest the receptor’s role in whole-body metabolic homeostasis and in the development of adiposity and hyperglycemia.

Microbe-Derived Butyrate and Its Receptor, Free Fatty Acid Receptor 3, But Not Free Fatty Acid Receptor 2, Mitigate Neointimal Hyperplasia Susceptibility After Arterial Injury

Background

Arterial restenosis after vascular surgery is a common cause of midterm restenosis and treatment failure. Herein, we aim to investigate the role of microbe‐derived butyrate, FFAR2 (free fatty acid receptor 2), and FFAR3 (free fatty acid receptor 3) in mitigating neointimal hyperplasia development in remodeling murine arteries after injury.

Methods and Results

C57BL/6 mice treated with oral vancomycin before unilateral femoral wire injury to deplete gut microbiota had significantly diminished serum and stool butyrate and more neointimal hyperplasia development after arterial injury, which was reversed by concomitant butyrate supplementation. Deficiency of FFAR3 but not FFAR2, both receptors for butyrate, exacerbated neointimal hyperplasia development after injury. FFAR3 deficiency was also associated with delayed recovery of the endothelial layer in vivo. FFAR3 gene expression was observed in multiple peripheral arteries, and expression was increased after arterial injury. Treatment of endothelial but not vascular smooth muscle cells with the pharmacologic FFAR3 agonist 1‐methylcyclopropane carboxylate stimulated cellular migration and proliferation in scratch assays.

Conclusions

Our results support a protective role for butyrate and FFAR3 in the development of neointimal hyperplasia after arterial injury and delineate activation of the butyrate‐FFAR3 pathway as a valuable strategy for the prevention and treatment of neointimal hyperplasia.

Free fatty acid receptor 3 differentially contributes to β-cell compensation under high-fat diet and streptozotocin stress

The free fatty acid receptor 3 (FFA3) is a nutrient sensor of gut microbiota-generated nutrients, the short-chain fatty acids. Previously, we have shown that FFA3 is expressed in β-cells and inhibits islet insulin secretion ex vivo. Here, we determined the physiological relevance of the above observation by challenging wild-type (WT) and FFA3 knockout (KO) male mice with 1) hyperglycemia and monitoring insulin response via highly sensitive hyperglycemic clamps, 2) dietary high fat (HF), and 3) chemical-induced diabetes. As expected, FFA3 KO mice exhibited significantly higher insulin secretion and glucose infusion rate in hyperglycemic clamps. Predictably, under metabolic stress induced by HF-diet feeding, FFA3 KO mice exhibited less glucose intolerance compared with the WT mice. Moreover, similar islet architecture and β-cell area in HF diet-fed FFA3 KO and WT mice was observed. Upon challenge with streptozotocin (STZ), FFA3 KO mice initially exhibited a tendency for an accelerated incidence of diabetes compared with the WT mice. However, this difference was not maintained. Similar glycemia and β-cell mass loss was observed in both genotypes 10 days post-STZ challenge. Higher resistance to STZ-induced diabetes in WT mice could be due to higher basal islet autophagy. However, this difference was not protective because in response to STZ, similar autophagy induction was observed in both WT and FFA3 KO islets. These data demonstrate that FFA3 plays a role in modulating insulin secretion and β-cell response to stressors. The β-cell FFA3 and autophagy link warrant further research.

Relationship between Intrinsically Photosensitive Ganglion Cell Function and Circadian Regulation in Diabetic Retinopathy

BACKGROUND

Intrinsically photosensitive retinal ganglion cells (ipRGCs) control non-visual light responses (e.g. pupillary light reflex and circadian entrainment). Patients with diabetic retinopathy (DR) show reduced ipRGC function, as inferred by abnormalities in the post illumination pupil response (PIPR). We explored whether ipRGC function in DR is associated with circadian outputs and sleep/wake behavior.

METHODS

Forty-five participants (15 without diabetes, 15 with type 2 diabetes (T2D) and no DR, 15 with T2D and DR) participated. ipRGC function was inferred from the PIPR (pupil size following stimulus offset). Circadian outputs were melatonin amplitude (overnight urinary 6-sulfatoxymelatonin (aMT6s)) and timing (dim light melatonin onset (DLMO)), and evening salivary cortisol levels. Sleep/wake patterns were measured with wrist actigraphy and insomnia symptoms were assessed subjectively.

RESULTS

Patients with T2D and DR had smaller PIPR and lower urinary aMT6s than other groups (p < 0.001). In adjusted regression models, smaller PIPR was associated with lower urinary aMT6s (β = 4.552, p = 0.005). Patients with DR were more likely to have no detectable DLMO (p = 0.049), higher evening salivary cortisol, greater insomnia symptoms and greater sleep variability compared to other groups. Sleep duration, efficiency and rest-activity rhythms were similar.

CONCLUSION

Reduced ipRGC function in DR is associated with circadian dysregulation and sleep disturbances, although a causal relationship cannot be established in this cross-sectional study. Prospective mechanistic and intervention studies examining circadian and sleep health in these patients are warranted.

Predictors of Obesity among Gut Microbiota Biomarkers in African American Men with and without Diabetes

Gut microbiota and their biomarkers may be associated with obesity. This study evaluated associations of body mass index (BMI) with circulating microbiota biomarkers in African American men (AAM) (n = 75). The main outcomes included fecal microbial community structure (16S rRNA), gut permeability biomarkers (ELISA), and short-chain fatty acids (SCFAs, metabolome analysis). These outcomes were compared between obese and non-obese men, after adjusting for age. The results showed that lipopolysaccharide-binding protein (LBP), the ratio of LBP to CD14 (LBP/CD14), and SCFAs (propionic, butyric, isovaleric) were higher in obese (n = 41, age 58 years, BMI 36 kg/m²) versus non-obese (n = 34, age 55 years, BMI 26 kg/m²) men. BMI correlated positively with LBP, LBP/CD14 (p < 0.05 for both) and SCFAs (propionic, butyric, isovaleric, p < 0.01 for all). In the regression analysis, LBP, LBP/CD14, propionic and butyric acids were independent determinants of BMI. The study showed for the first time that selected microbiota biomarkers (LBP, LBP/CD14, propionic and butyric acids) together with several other relevant risks explained 39%–47% of BMI variability, emphasizing that factors other than microbiota-related biomarkers could be important. Further research is needed to provide clinical and mechanistic insight into microbiota biomarkers and their utility for diagnostic and therapeutic purposes.

Probing the structural interactions between methotrexate and dexamethasone with muscle cystatin: a biophysical study

Drug protein interactions have gained considerable attention over the past many years. In the current communication the association of muscle cystatin (MC) with anti-rheumatic drugs methotrexate and dexamethasone was studied by thiol proteinase inhibitor assay, ultra violet (UV) absorption, fluorescence spectroscopy, and fluorescence transform infra-red spectroscopy (FTIR). A static pattern of quenching was noticed between muscle cystatin and methotrexate (MTX). Binding constant (K_a) of methotrexate to muscle cystatin was found to be 1 × 10^-7 M^-1 and the stoichiometry of binding was calculated to be one. Fluorescence measurement of the emission quenching reveals that the quenching process of cystatin by dexamethasone (DXN) was also static. The stoichiometry of binding and binding constant was also obtained. Additional evidence regarding MTX-MC and DXN-MC was obtained from UV spectroscopy and FTIR spectroscopic results. Such spectroscopic studies would help in modelling new candidate drugs for rheumatoid arthritis based on their cystatin binding profile.Communicated by Ramaswamy H. Sarma.

OR31-3 Role of a Novel Short Chain Fatty Acid Receptor OLFR78 in Mediating Gluco-metabolic Hormone Secretion

Olfactory receptor OLFR78 is a G protein-coupled receptor (GPCR) which is activated by short chain fatty acids (SCFAs), especially propionate. OLFR78 is expressed in islets as well as intestinal epithelial cells. Based on these properties, we hypothesized its role in the regulation of metabolic hormone secretion. Our emerging data shows that OLFR78 signaling regulates GLP-1 secretion from murine enteroendocrine cells in vitro and ex vivo. We demonstrate that knockdown of Olfr78 through siRNA in the murine enteroendocrine cell line STC-1 results in a significant reduction in propionate-induced GLP-1 secretion. Utilizing constitutive and cyclic AMP inducible transcriptional luciferase promoters in addition to G protein pathway modulators, we further demonstrate that the signaling pathway downstream of active OLFR78 involves the activation of a Gα_s subunit. As GLP-1 is an insulinotropic factor, we sought to determine the role of OLFR78 in insulin secretion and β cell mass maintenance. Using islets isolated from both wildtype and global OLFR78 knockout mice, we show that OLFR78 signaling in islets does not have a significant effect on insulin secretion. Additionally, we observed no differences in beta cell mass in wildtype versus OLFR78 knockout mice. Furthermore, no differences are observed in incretin secretion in response to oral glucose challenge between wildtype and knockout mice fed normal chow. However, ileal explants prepared from wildtype mice reveal higher secretion of GLP-1 in response to propionate challenge. These data suggest that specific activation of the receptor, rather than its presence alone, affects GLP-1 secretion. We have previously shown that the activity of other SCFA-sensing GPCRs, such as FFA2 and FFA3, are dependent on gut microbiota-derived metabolites which fluctuate with physiological stress. Similarly, we believe that the function of OLFR78 will be more evident under conditions of dietary stress, which is a crucial determinant of gut microbial activity.

Hepatic hexokinase domain containing 1 (HKDC1) improves whole body glucose tolerance and insulin sensitivity in pregnant mice

Hexokinase domain containing 1, a recently discovered putative fifth hexokinase, is hypothesized to play key roles in glucose metabolism. Specifically, during pregnancy in a recent genome wide association study (GWAS), a strong correlation between HKDC1 and 2-h plasma glucose in pregnant women from different ethnic backgrounds was shown. Our earlier work also reported diminished glucose tolerance during pregnancy in our whole body HKDC1 heterozygous mice. Therefore, we hypothesized that HKDC1 plays important roles in gestational metabolism, and designed this study to assess the role of hepatic HKDC1 in whole body glucose utilization and insulin action during pregnancy. We overexpressed human HKDC1 in mouse liver by injecting a human HKDC1 adenoviral construct; whereas, for the liver-specific HKDC1 knockout model, we used AAV-Cre constructs in our HKDC1fl/fl mice. Both groups of mice were subjected to metabolic testing before and during pregnancy on gestation day 17-18. Our results indicate that hepatic HKDC1 overexpression during pregnancy leads to improved whole-body glucose tolerance and enhanced hepatic and peripheral insulin sensitivity while hepatic HKDC1 knockout results in diminished glucose tolerance. Further, we observed reduced gluconeogenesis with hepatic HKDC1 overexpression while HKDC1 knockout led to increased gluconeogenesis. These changes were associated with significantly enhanced ketone body production in HKDC1 overexpressing mice, indicating that these mice shift their metabolic needs from glucose reliance to greater fat oxidation and ketone utilization during fasting. Taken together, our results indicate that hepatic HKDC1 contributes to whole body glucose disposal, insulin sensitivity, and aspects of nutrient balance during pregnancy.

Decreased microbial co-occurrence network stability and SCFA receptor level correlates with obesity in African-origin women

We compared the gut microbial populations in 100 women, from rural Ghana and urban US [50% lean (BMI < 25 kg/m²) and 50% obese (BMI ≥ 30 kg/m²)] to examine the ecological co-occurrence network topology of the gut microbiota as well as the relationship of short chain fatty acids (SCFAs) with obesity. Ghanaians consumed significantly more dietary fiber, had greater microbial alpha-diversity, different beta-diversity, and had a greater concentration of total fecal SCFAs (p-value < 0.002). Lean Ghanaians had significantly greater network density, connectivity and stability than either obese Ghanaians, or lean and obese US participants (false discovery rate (FDR) corrected p-value ≤ 0.01). Bacteroides uniformis was significantly more abundant in lean women, irrespective of country (FDR corrected p < 0.001), while lean Ghanaians had a significantly greater proportion of Ruminococcus callidus, Prevotella copri, and Escherichia coli, and smaller proportions of Lachnospiraceae, Bacteroides and Parabacteroides. Lean Ghanaians had a significantly greater abundance of predicted microbial genes that catalyzed the production of butyric acid via the fermentation of pyruvate or branched amino-acids, while obese Ghanaians and US women (irrespective of BMI) had a significantly greater abundance of predicted microbial genes that encoded for enzymes associated with the fermentation of amino-acids such as alanine, aspartate, lysine and glutamate. Similar to lean Ghanaian women, mice humanized with stool from the lean Ghanaian participant had a significantly lower abundance of family Lachnospiraceae and genus Bacteroides and Parabacteroides, and were resistant to obesity following 6-weeks of high fat feeding (p-value < 0.01). Obesity-resistant mice also showed increased intestinal transcriptional expression of the free fatty acid (Ffa) receptor Ffa2, in spite of similar fecal SCFAs concentrations. We demonstrate that the association between obesity resistance and increased predicted ecological connectivity and stability of the lean Ghanaian microbiota, as well as increased local SCFA receptor level, provides evidence of the importance of robust gut ecologic network in obesity.

Role of Short Chain Fatty Acid Receptors in Intestinal Physiology and Pathophysiology

Nutrient sensing is a mechanism for organisms to sense their environment. In larger animals, including humans, the intestinal tract is a major site of nutrient sensing for the body, not surprisingly, as this is the central location where nutrients are absorbed. In the gut, bacterial fermentation results in generation of short chain fatty acids (SCFAs), a class of nutrients, which are sensed by specific membrane bound receptors, FFA2, FFA3, GPR109a, and Olfr78. These receptors are expressed uniquely throughout the gut and signal through distinct mechanisms. To date, the emerging data suggests a role of these receptors in normal and pathological conditions. The overall function of these receptors is to regulate aspects of intestinal motility, hormone secretion, maintenance of the epithelial barrier, and immune cell function. Besides in intestinal health, a prominent role of these receptors has emerged in modulation of inflammatory and immune responses during pathological conditions. Moreover, these receptors are being revealed to interact with the gut microbiota. This review article updates the current body of knowledge on SCFA sensing receptors in the gut and their roles in intestinal health and disease as well as in whole body energy homeostasis. © 2017 American Physiological Society. Compr Physiol 8:1091-1115, 2018.

Gut Microbiota: FFAR Reaching Effects on Islets

The G protein-coupled receptors, free fatty acid (FFA) receptors 2 and 3 (FFA2 and FFA3), belonging to the free fatty acid receptor (FFAR) class, sense a distinct class of nutrients, short chain fatty acids (SCFAs). These receptors participate in both immune and metabolic regulation. The latter includes a role in regulating secretion of metabolic hormones. It was only recently that their role in pancreatic β cells was recognized; these receptors are known now to affect not only insulin secretion but also β-cell survival and proliferation. These observations make them excellent potential therapeutic targets in type 2 diabetes. Moreover, expression on both immune and β cells makes these receptors possible targets in type 1 diabetes. Furthermore, SCFAs are generated by gut microbial fermentative activity; therefore, signaling by FFA2 and FFA3 represents an exciting novel link between the gut microbiota and the β cells. This review enumerates the role of these receptors in β cells revealed so far and discusses possible roles in clinical translation.

Gut Microbiota in Vascular Disease: Therapeutic Target?

BACKGROUND

Gut microbiota is increasingly recognized as a powerful regulator of host physiology. Most of its effects are mediated through metabolites acting as energy sources, signaling receptor ligands and substrates for host enzymes. Owing to the meta-stability and high amenability of the gut microbiota to modification by diet and environment predicting specific gut microbes or its metabolites responsible for different host metabolic states is often confounded.

METHODS

The Pubmed was searched for research articles on gut microbiota and cardiovascular disease.

RESULTS

The searched articles reported a direct role of gut microbes in cardiovascular disorders (CVD). The interaction among gut microbial metabolism (through breakdown of certain dietary nutrients like choline), host immune system and lipid metabolism generate conditions that promote atherosclerosis development. Importantly, components of this interactive system can be explored to identify points of intervention in the path of disease development. Based on this strategies targeting gut microbial composition and activity are being explored as therapies against CVD. Use of archaebiotics and 3,3-dimethyl- 1-butanol aiming to reduce TMA (trimethylamine) conversion to TMAO (trimethylamine-N-oxide) and high fibre diets to reduce TMA precursors while simultaneously selecting for beneficial gut bacteria are attractive anti-atherogenic approaches.

CONCLUSION

Success of these approaches in humans however, requires extensive research.

Homology modeling of FFA2 identifies novel agonists that potentiate insulin secretion

Critical aspects of maintaining glucose homeostasis in the face of chronic insulin resistance and type 2 diabetes (T2D) are increased insulin secretion and adaptive expansion of beta cell mass. Nutrient and hormone sensing G protein-coupled receptors are important mediators of these properties. A growing body of evidence now suggests that the G protein-coupled receptor, free fatty acid receptor 2 (FFA2), is capable of contributing to the maintenance of glucose homeostasis by acting at the pancreatic beta cell as well as at other metabolically active tissues. We have previously demonstrated that Gα_q/11-biased agonism of FFA2 can potentiate glucose stimulated insulin secretion (GSIS) as well as promote beta cell proliferation. However, the currently available Gα_q/11-biased agonists for FFA2 exhibit low potency, making them difficult to examine in vivo. This study sought to identify Gα_q/11-biased FFA2-selective agonists with potent GSIS-stimulating effects. To do this, we generated an FFA2 homology model that was used to screen a library of 10 million drug-like compounds. Although FFA2 and the related short chain fatty acid receptor FFA3 share 52% sequence similarity, our virtual screen identified over 50 compounds with predicted selectivity and increased potency for FFA2 over FFA3. Subsequent in vitro calcium mobilization assays and GSIS assays resulted in the identification of a compound that can potentiate GSIS via activation of Gα_q/11 with 100-fold increased potency compared with previously described Gα_q/11-biased FFA2 agonists. These methods and findings provide a foundation for future discovery efforts to identify biased FFA2 agonists as potential T2D therapeutics.

SCFA Receptors in Pancreatic β Cells: Novel Diabetes Targets?

Nutrient sensing receptors are key metabolic mediators of responses to dietary and endogenously derived nutrients. These receptors are largely G-protein-coupled receptors (GPCRs) and many are gaining significant interest as drug targets with a potential therapeutic role in metabolic diseases. A distinct subclass of nutrient sensing GPCRs, two short chain fatty acid (SCFA) receptors (FFA2 and FFA3) are uniquely responsive to gut microbiota derived nutrients (such as acetate, propionate, and butyrate). Pharmacological, molecular, and genetic studies have investigated their role in organismal glucose metabolism and recently in pancreatic β cell biology. Here, we summarize the present knowledge on the role of these receptors as metabolic sensors in β cell function and physiology, revealing new therapeutic opportunities for type 2 diabetes.

HKDC1 Is a Novel Hexokinase Involved in Whole-Body Glucose Use

In a recent genome-wide association study, hexokinase domain-containing protein 1, or HKDC1, was found to be associated with gestational glucose levels during 2-hour glucose tolerance tests at 28 weeks of pregnancy. Because our understanding of the mediators of gestational glucose homeostasis is incomplete, we have generated the first transgenic mouse model to begin to understand the role of HKDC1 in whole-body glucose homeostasis. Interestingly, deletion of both HKDC1 alleles results in in utero embryonic lethality. Thus, in this study, we report the in vivo role of HKDC1 in whole-body glucose homeostasis using a heterozygous-deleted HKDC1 mouse model (HKDC1(+/-)) as compared with matched wild-type mice. First, we observed no weight, fasting or random glucose, or fasting insulin abnormalities with aging in male and female HKDC1(+/-) mice. However, during glucose tolerance tests, glucose levels were impaired in both female and male HKDC1(+/-) mice at 15, 30, and 120 minutes at a later age (28 wk of age). These glucose tolerance differences also existed in the female HKDC1(+/-) mice at earlier ages but only during pregnancy. And finally, the impaired glucose tolerance in HKDC1(+/-) mice was likely due to diminished whole-body glucose use, as indicated by the decreased hepatic energy storage and reduced peripheral tissue uptake of glucose in HKDC1(+/-) mice. Collectively, these data highlight that HKDC1 is needed to maintain whole-body glucose homeostasis during pregnancy but also with aging, possibly through its role in glucose use.

Loss of Free Fatty Acid Receptor 2 leads to impaired islet mass and beta cell survival

The regulation of pancreatic β cell mass is a critical factor to help maintain normoglycemia during insulin resistance. Nutrient-sensing G protein-coupled receptors (GPCR) contribute to aspects of β cell function, including regulation of β cell mass. Nutrients such as free fatty acids (FFAs) contribute to precise regulation of β cell mass by signaling through cognate GPCRs, and considerable evidence suggests that circulating FFAs promote β cell expansion by direct and indirect mechanisms. Free Fatty Acid Receptor 2 (FFA2) is a β cell-expressed GPCR that is activated by short chain fatty acids, particularly acetate. Recent studies of FFA2 suggest that it may act as a regulator of β cell function. Here, we set out to explore what role FFA2 may play in regulation of β cell mass. Interestingly, Ffar2(-/-) mice exhibit diminished β cell mass at birth and throughout adulthood, and increased β cell death at adolescent time points, suggesting a role for FFA2 in establishment and maintenance of β cell mass. Additionally, activation of FFA2 with Gαq/11-biased agonists substantially increased β cell proliferation in in vitro and ex vivo proliferation assays. Collectively, these data suggest that FFA2 may be a novel therapeutic target to stimulate β cell growth and proliferation.

The short-chain fatty acid receptor, FFA2, contributes to gestational glucose homeostasis

The structure of the human gastrointestinal microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wild-type (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short-chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein-coupled receptors (GPCRs) such as free fatty acid receptor-2 (FFA2), and we have previously demonstrated that the fatty acid receptor-2 gene (Ffar2) expression is higher in pancreatic islets during pregnancy. Using female Ffar2-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion compared with WT mice during, but not before, pregnancy. Insulin tolerance tests were similar in Ffar2-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β-cell mass, observing that Ffar2-/- mice had diminished gestational expansion of β-cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Together, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis.

An Acetate-Specific GPCR, FFAR2, Regulates Insulin Secretion

G protein-coupled receptors have been well described to contribute to the regulation of glucose-stimulated insulin secretion (GSIS). The short-chain fatty acid-sensing G protein-coupled receptor, free fatty acid receptor 2 (FFAR2), is expressed in pancreatic β-cells, and in rodents, its expression is altered during insulin resistance. Thus, we explored the role of FFAR2 in regulating GSIS. First, assessing the phenotype of wild-type and Ffar2(-/-) mice in vivo, we observed no differences with regard to glucose homeostasis on normal or high-fat diet, with a marginally significant defect in insulin secretion in Ffar2(-/-) mice during hyperglycemic clamps. In ex vivo insulin secretion studies, we observed diminished GSIS from Ffar2(-/-) islets relative to wild-type islets under high-glucose conditions. Further, in the presence of acetate, the primary endogenous ligand for FFAR2, we observed FFAR2-dependent potentiation of GSIS, whereas FFAR2-specific agonists resulted in either potentiation or inhibition of GSIS, which we found to result from selective signaling through either Gαq/11 or Gαi/o, respectively. Lastly, in ex vivo insulin secretion studies of human islets, we observed that acetate and FFAR2 agonists elicited different signaling properties at human FFAR2 than at mouse FFAR2. Taken together, our studies reveal that FFAR2 signaling occurs by divergent G protein pathways that can selectively potentiate or inhibit GSIS in mouse islets. Further, we have identified important differences in the response of mouse and human FFAR2 to selective agonists, and we suggest that these differences warrant consideration in the continued investigation of FFAR2 as a novel type 2 diabetes target.

Oxidative stress mediated mitochondrial and vascular lesions as markers in the pathogenesis of Alzheimer disease

Mitochondrial dysfunction plausibly underlies the aging-associated brain degeneration. Mitochondria play a pivotal role in cellular bioenergetics and cell-survival. Oxidative stress consequent to chronic hypoperfusion induces mitochondrial damage, which is implicated as the primary cause of cerebrovascular accidents (CVA) mediated Alzheimer's disease (AD). The mitochondrial function deteriorates with aging, and the mitochondrial damage correlates with increased intracellular production of oxidants and pro-oxidants. The prolonged oxidative stress and the resultant hypoperfusion in the brain tissues stimulate the expression of nitric oxide synthase (NOS) enzymes, which further drives the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ROS and RNS collectively contributes to the dysfunction of the blood-brain barrier (BBB) and damage to the brain parenchymal cells. Delineating the molecular mechanisms of these processes may provide clues for the novel therapeutic targets for CVA and AD patients.

Differential effects of anti-cancer and anti-hepatitis drugs on liver cystatin

The drug-protein interaction has been the subject of increasing interest over the decades. In the present communication, the interaction of liver cystatin with anti-cancer (adriamycin) and anti-hepatitis (adevofir dipivoxil) drugs was studied by thiol-protease inhibitory assay, UV absorption, fluorescence spectroscopy and circular dichroism (CD). A static type of quenching was observed between the protein and the drug molecules. Binding constant (Ka) of adriamycin to liver cystatin (LC) was found to be 1.08 × 10(6) M(-1). Moreover, binding site number was found to be 2. Importantly, cystatin loses its activity in the presence of adriamycin. However, intrinsic fluorescence studies in the presence of adevofir dipivoxil showed enhancement in the fluorescence intensity suggesting that binding of adevofir to LC caused unfolding of the protein. The unfolding of the test protein was also accompanied by significant loss of inhibitory activity. CD spectroscopy result showed, both adriamycin and adevofir dipivoxil caused perturbation in the secondary structure of liver cystatin. The possible implications of these results will help in combating drug induced off target effects.

FFAR3 modulates insulin secretion and global gene expression in mouse islets

The short chain fatty acid (SCFA) receptor (free fatty acid receptor-3; FFAR3) is expressed in pancreatic β cells; however, its role in insulin secretion is not clearly defined. Here, we examined the role of FFAR3 in insulin secretion. Using islets from global knockout FFAR3 (Ffar3(-/-)) mice, we explored the role of FFAR3 and ligand-induced FFAR3 signaling on glucose stimulated insulin secretion. RNA sequencing was also performed to gain greater insight into the impact of FFAR3 deletion on the islet transcriptome. First exploring insulin secretion, it was determined that Ffar3(-/-) islets secrete more insulin in a glucose-dependent manner as compared to wildtype (WT) islets. Next, exploring its primary endogenous ligand, propionate, and a specific agonist for FFAR3, signaling by FFAR3 inhibited glucose-dependent insulin secretion, which occurred through a Gαi/o pathway. To help understand these results, transcriptome analyses by RNA-sequencing of Ffar3(-/-) and WT islets observed multiple genes with well-known roles in islet biology to be altered by genetic knockout of FFAR3. Our data shows that FFAR3 signaling mediates glucose stimulated insulin secretion through Gαi/o sensitive pathway. Future studies are needed to more rigorously define the role of FFAR3 by in vivo approaches.

Maternal short-chain fatty acids are associated with metabolic parameters in mothers and newborns

During the course of pregnancy, dynamic remodeling of the gut microbiota occurs and contributes to maternal metabolic changes through an undefined mechanism. Because short chain fatty acids (SCFAs) are a major product of gut microbiome fermentation, we investigated whether serum SCFA levels during pregnancy are related to key metabolic parameters in mothers and newborns. In this prospective study, 20 pregnant women without gestational diabetes were evaluated at 36-38 weeks of gestation, and their newborns were assessed after parturition. In this cohort, which included normal (n = 10) and obese (n = 10) subjects based on prepregnancy body mass index, serum levels of SCFAs (acetate, propionate, and butyrate), maternal adipokines, maternal glucose, and C-peptide were measured at 36-38 weeks of gestation. Maternal weight gain and newborn anthropometrics were also determined. Data were analyzed using linear regression to test for associations, adjusting for prepregnancy obesity. In this cohort, serum acetate levels were associated with maternal weight gain and maternal adiponectin levels. In addition, serum propionate correlated negatively with maternal leptin levels, newborn length, and body weight. Taken together, this study observed that novel relationships exist among maternal SCFA levels and multiple interrelated maternal/newborn metabolic parameters.

Ribosylation of bovine serum albumin induces ROS accumulation and cell death in cancer line (MCF-7)

Formation of advanced glycation end products (AGE) is crucially involved in the several pathophysiologies associated with ageing and diabetes, for example arthritis, atherosclerosis, chronic renal insufficiency, Alzheimer's disease, nephropathy, neuropathy, and cataracts. Because of devastating effects of AGE and the significance of bovine serum albumin (BSA) as a transport protein, this study was designed to investigate glycation-induced structural modifications in BSA and their functional consequences in breast cancer cell line (MCF-7). We incubated D-ribose with BSA and monitored formation of D-ribose-glycated BSA by observing changes in the intensity of fluorescence at 410 nm. NBT (nitro blue tetrazolium) assay was performed to confirm formation of keto-amine during glycation. Absorbance at 540 nm (fructosamine) increased markedly with time. Furthermore, intrinsic protein and 8-anilino-1-naphthalenesulfonate (ANS) fluorescence revealed marked conformational changes in BSA upon ribosylation. In addition, a fluorescence assay with thioflavin T (ThT) revealed a remarkable increase in fluorescence at 485 nm in the presence of glycated BSA. This suggests that glycation with D-ribose induced aggregation of BSA into amyloid-like deposits. Circular dichroism (CD) study of native and ribosylated BSA revealed molten globule formation in the glycation pathway of BSA. Functional consequences of ribosylated BSA on cancer cell line, MCF-7 was studied by MTT assay and ROS estimation. The results revealed cytotoxicity of ribosylated BSA on MCF-7 cells.

MicroRNA: novel modulators of the cholinergic anti-inflammatory pathway

MicroRNAs (miRNAs) have emerged as key gene regulators controlling the expression of many target mRNAs. The nervous system harbors highest number of miRNAs expressed in a spatially and temporally controlled manner. Neural miRNAs have been accredited with diverse roles like regulation of neural differentiation, synaptogenesis, inflammation, memory and cognition. Their aberrant expression and/or function has been linked to various neurodegenerative, neuroinflammatory and stress related disorders. Recent evidence indicates that miRNAs are essential to the fine tuning of the immune responses. Besides controlling the maturation, proliferation and differentiation of myeloid and lymphoid lineages they participate directly by modulating the signaling pathways through the Toll-like receptors and thus the cytokine response. The miRNAs commuting between the nervous and immune systems and affecting the neuro-immune dialogue are emerging.

Benzo(a)pyrene induced structural and functional modifications in lung cystatin

Cystatins are thiol proteinase inhibitors ubiquitously present in the mammalian body. They serve a protective function to regulate the activities of endogenous proteinases, which may cause uncontrolled proteolysis and damage. In the present study, the effect of benzo(a)pyrene [BaP] on lung cystatin was studied to explore the hazardous effects of environmental pollutant on structural and functional integrity of the protein. The basic binding interaction was studied by UV-absorption, FT-IR, and fluorescence spectroscopy. The enhancement of total protein fluorescence with a red shift of 5 nm suggests structural scratch of lung cystatin by benzo(a)pyrene. Further, ANS binding studies reaffirm the unfolding of the thiol protease inhibitor (GLC-I) after treating with benzo(a)pyrene. The results of FT-IR spectroscopy reflect perturbation of the secondary conformation (alpha-helix to β-sheet) in goat lung cystatin on interaction with BaP. Finally, functional inactivation of cystatin on association with BaP was checked by its papain inhibitory activity. Benzo(a)pyrene (10 μM) caused complete inactivation of goat lung cystatin. Benzo(a)pyrene-induced loss of structure and function in the thiol protease inhibitor could provide a caution for lung injury caused by the pollutants and smokers.

A zebrafish model of PINK1 deficiency reveals key pathway dysfunction including HIF signaling

The PTEN induced putative kinase 1 (PINK1) gene is mutated in patients with hereditary early onset Parkinson's disease (PD). The targets of PINK1 and the mechanisms in PD are still not fully understood. Here, we carried out a high-throughput and unbiased microarray study to identify novel functions and pathways for PINK1. In larval zebrafish, the function of pink1 was inhibited using splice-site morpholino oligonucleotides and the samples were hybridized on a two-color gene expression array. We found 177 significantly altered genes in pink1 morphants compared with the uninjected wildtype controls (log fold change values from -1.6 to +0.9). The five most prominent pathways based on critical biological processes and key toxicological responses were hypoxia-inducible factor (HIF) signaling, TGF-β signaling, mitochondrial dysfunction, RAR activation, and biogenesis of mitochondria. Furthermore, we verified that potentially important genes such as hif1α, catalase, SOD3, and atp1a2a were downregulated in pink1 morphants, whereas genes such as fech, pax2a, and notch1a were upregulated. Some of these genes have been found to play important roles in HIF signaling pathways. The pink1 morphants were found to have heart dysfunction, increased erythropoiesis, increased expression of vascular endothelial growth factors, and increased ROS. Our findings suggest that a lack of pink1 in zebrafish alters many vital and critical pathways in addition to the HIF signaling pathway.

Cancer chemoprevention by polyphenols and their potential application as nanomedicine

Today cancer is a leading cause of death among the developed countries. Its highly complex nature makes it difficult to understand as it entails multiple cellular physiological systems such as cell signaling and apoptosis. The biggest challenges faced by cancer chemoprevention/chemotherapy is maintaining drug circulation and avoiding multidrug resistance. Overall there is modest evidence regarding the protective effects of nutrients from supplements against a number of cancers. Numerous scientific literatures available advocate the use of polyphenols for chemoprevention. Some groups have also suggested use of combination of nutrients in cancer prevention. However, we have yet to obtain the desired results in the line of cancer chemotherapy research. Nanotechnology can play a pivotal role in cancer treatment and prevention. Moreover, nanoparticles can be modified in various ways to prolong circulation, enhance drug localization, increase drug efficacy, and potentially decrease the chances of multidrug resistance. In this communication, we will cover the use of various polyphenols and nutrients in cancer chemoprevention. The application of nanotechnology in this regard will also be included. In view of available reports on the potential of nanoparticles, we suggest their usage along with different combination of nutrients as cancer chemotherapeutic agents.

MANF regulates dopaminergic neuron development in larval zebrafish

Mesencephalic astrocyte derived neurotrophic factor (MANF) is recognized as a dopaminergic neurotrophic factor, which can protect dopaminergic neurons from neurotoxic damage. However, little is known about the function of MANF during the vertebrate development. Here, we report that MANF expression is widespread during embryonic development and in adult organs analyzed by qPCR and in situ hybridization in zebrafish. Knockdown of MANF expression with antisense splice-blocking morpholino oligonucleotides resulted in no apparent abnormal phenotype. Nevertheless, the dopamine level of MANF morphants was lower than that of the wild type larvae, the expression levels of the two tyrosine hydroxylase gene transcripts were decreased and a decrease in neuron number in certain groups of th1 and th2 cells in the diencephalon region in MANF morphants was observed. These defects were rescued by injection of exogenous manf mRNA. Strikingly, manf mRNA could partly restore the decrease of th1 positive cells in Nr4a2-deficient larvae. These results suggest that MANF is involved in the regulation of the development of dopaminergic system in zebrafish.

Alzheimer's disease and type 2 diabetes: exploring the association to obesity and tyrosine hydroxylase

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are two debilitating health disorders afflicting millions worldwide. Recent research has revealed similarities between AD and T2DM. Both these protein conformational disorders are associated with obesity, insulin resistance, inflammation and endoplasmic reticulum stress, en-route initiation and/or stage aggravation. In this mini review we have tried to summarize studies describing obesity, insulin resistance and glucocorticoid imbalance as common patho-mechanisms in T2DM and AD. A reduction in tyrosine hydroxylase (TH) in the brain has been found to occur in Parkinson's disease (PD). AD, T2DM and PD share common risk factors like depression. Thus, whether TH is involved in the 'state of cognitive depression' that is the hallmark of AD and often accompanies PD and T2DM is also explored.

Methotrexate binding causes structural and functional changes in lung cystatin

Regulation of cysteine proteinases and their inhibitors is of utmost importance in diseases like lung cancer, chronic inflammatory conditions such as asthma, emphysema, and idiopathic pulmonary fibrosis. Protease-antiprotease imbalance accelerates disease progression. In the present study, the effect of antineoplastic and antirheumatic drug methotrexate (MTX) on lung cystatin (a cysteine protease inhibitor) was studied to explore drug induced changes in functional and structural integrity of the protein. The basic binding interaction was studied by UV-absorption, FT-IR and fluorescence spectroscopy. The quenching of protein fluorescence confirmed the binding of MTX with goat lung cystatin (GLC-I). Stern-Volmer analysis of MTX-GLC-I system at different temperatures indicates the presence of static component in the quenching mechanism. The thermodynamic parameters ΔH⁰ and ΔS⁰ were -3.8 kJ/mol and 94.97 J•mol⁻¹•K⁻¹, respectively, indicating that both hydrogen bonds and hydrophobic interactions played a major role in the binding of MTX to GLC-I. Methotrexate (7 µM) caused complete inactivation of lung cystatin after 6 hours. The results of FT-IR spectroscopy reflect perturbation of the goat lung cystatin on interaction with MTX. Methotrexate induced loss of function change in the inhibitor could provide a rationale for the off target tissue injury caused by the drug and for the design of agents against such an injury.

Methotrexate binding causes structural and functional changes in lung cystatin

Regulation of cysteine proteinases and their inhibitors is of utmost importance in diseases like lung cancer, chronic inflammatory conditions such as asthma, emphysema, and idiopathic pulmonary fibrosis. Protease-antiprotease imbalance accelerates disease progression. In the present study, the effect of antineoplastic and antirheumatic drug methotrexate (MTX) on lung cystatin (a cysteine protease inhibitor) was studied to explore drug induced changes in functional and structural integrity of the protein. The basic binding interaction was studied by UV-absorption, FT-IR and fluorescence spectroscopy. The quenching of protein fluorescence confirmed the binding of MTX with goat lung cystatin (GLC-I). Stern-Volmer analysis of MTX-GLC-I system at different temperatures indicates the presence of static component in the quenching mechanism. The thermodynamic parameters ΔH⁰ and ΔS⁰ were -3.8 kJ/mol and 94.97 J•mol⁻¹•K⁻¹, respectively, indicating that both hydrogen bonds and hydrophobic interactions played a major role in the binding of MTX to GLC-I. Methotrexate (7 µM) caused complete inactivation of lung cystatin after 6 hours. The results of FT-IR spectroscopy reflect perturbation of the goat lung cystatin on interaction with MTX. Methotrexate induced loss of function change in the inhibitor could provide a rationale for the off target tissue injury caused by the drug and for the design of agents against such an injury.

Physicochemical properties of thiol proteinase inhibitor isolated from goat pancreas

Thiol proteinase inhibitors are crucial to proper functioning of all living tissues consequent to their cathepsin regulatory and myriad important biologic properties. Equilibrium denaturation of dimeric goat pancreas thiol proteinase inhibitor (PTPI), a cystatin superfamily variant has been studied by monitoring changes in the protein's spectroscopic and functional characteristics. Denaturation of PTPI in guanidine hydrochloride and urea resulted in altered intrinsic fluorescence emission spectrum, diminished negative circular dichroism, and loss of its papain inhibitory potential. Native like spectroscopic properties and inhibitory activity are only partially restored when denaturant is diluted from guanidine hydrochloride unfolded samples demonstrating that process is partially reversible. Coincidence of transition curves and dependence of transition midpoint (3.2M) on protein concentration in guanidine hydrochloride-induced denaturation are consistent with a two-state model involving a native like dimer and denatured monomer. On the contrary, urea-induced unfolding of PTPI is a multiphasic process with indiscernible intermediates. The studies demonstrate that functional conformation and stability are governed by both ionic and hydrophobic interactions.

The comparative neuroanatomy and neurochemistry of zebrafish CNS systems of relevance to human neuropsychiatric diseases

Modulatory neurotransmitters which signal through G protein-coupled receptors control brain functions which deteriorate in degenerative brain diseases. During the past decade many of these systems have been mapped in the zebrafish brain. The main architecture of the systems in zebrafish brain resembles that of the mammals, despite differences in the development of the telencephalon and mesodiencephalon. Modulatory neurotransmitters systems which degenerate in human diseases include dopamine, noradrenaline, serotonin, histamine, acetylcholine and orexin/hypocretin. Although the number of G protein-coupled receptors in zebrafish is clearly larger than in mammals, many receptors have similar expression patterns, binding and signaling properties as in mammals. Distinct differences between mammals and zebrafish include duplication of the tyrosine hydroxylase gene in zebrafish, and presence of one instead of two monoamine oxidase genes. Zebrafish are sensitive to neurotoxins including MPTP, and exposure to this neurotoxin induces a decline in dopamine content and number of detectable tyrosine hydroxylase immunoreactive neurons in distinct nuclei. Sensitivity to important neurotoxins, many available genetic methods, rapid development and large-scale quantitative behavioral methods in addition to advanced quantitative anatomical methods render zebrafish an optimal organism for studies on disease mechanisms.