Search

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 FFA3

A primary role of the liver is to regulate whole body glucose homeostasis. Glucokinase (GCK) is the main hexokinase (HK) expressed in hepatocytes and functions to phosphorylate the glucose that enters via GLUT transporters to become glucose-6-phosphate (G6P), which subsequently commits glucose to enter downstream anabolic and catabolic pathways. In the recent years, hexokinase domain-containing-1 (HKDC1), a novel 5th HK, has been characterized by our group and others. Its expression profile varies but has been identified to have low basal expression in normal liver but increases during states of stress including pregnancy, nonalcoholic fatty liver disease (NAFLD), and liver cancer. Here, we have developed a stable overexpression model of hepatic HKDC1 in mice to examine its effect on metabolic regulation. We found that HKDC1 overexpression, over time, causes impaired glucose homeostasis in male mice and shifts glucose metabolism towards anabolic pathways with an increase in nucleotide synthesis. Furthermore, we observed these mice to have larger liver sizes due to greater hepatocyte proliferative potential and cell size, which in part, is mediated via yes-associated protein (YAP) signaling.

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.

The gut microbiome is intricately coupled with immune regulation and metabolism, but its role in Coronavirus Disease 2019 (COVID-19) is not fully understood. Severe and fatal COVID-19 is characterized by poor anti-viral immunity and hypercoagulation, particularly in males. Here, we define multiple pathways by which the gut microbiome protects mammalian hosts from SARS-CoV-2 intranasal infection, both locally and systemically, via production of short-chain fatty acids (SCFAs). SCFAs reduced viral burdens in the airways and intestines by downregulating the SARS-CoV-2 entry receptor, angiotensin-converting enzyme 2 (ACE2), and enhancing adaptive immunity via GPR41 and 43 in male animals. We further identify a novel role for the gut microbiome in regulating systemic coagulation response by limiting megakaryocyte proliferation and platelet turnover via the Sh2b3-Mpl axis. Taken together, our findings have unraveled novel functions of SCFAs and fiber-fermenting gut bacteria to dampen viral entry and hypercoagulation and promote adaptive antiviral immunity.

Despite decades of research on strategies to address disparities in diabetes screening, prevention and treatment, disparities particularly by race/ethnicity and socioeconomic status persist. An innovative approach to diabetes screening was therefore piloted in the Emergency Department (ED) at the University of Illinois Hospital in Chicago from February to April 2021. A best practices advisory (BPA) was built into the electronic medical records system that flagged ED patients at risk for diabetes for a provider to add a A1c test to an already planned blood specimen. The criteria were: all patients age >= 45 years, or patients age 18-44 years with a BMI >= 25; and, with no history of diabetes in the chart and no A1c performed in the last 3 years. Of the 8441 ED visits during the pilot timeframe, the BPA was triggered in 2691, and 2118 visits had a A1c resulted. Approximately half of the results (52%, n=1098) were abnormal. Of the abnormal results, 70% were in the prediabetes range (A1c 5.7-6.4%) and 30% in the diabetes range (A1c >= 6.5%; with 62 of the A1c results >=10%) . As A1c results were not immediately available in the ED, study staff successfully contacted 352 patients with an abnormal result by phone; the remaining were sent a letter informing them of their abnormal result. Of the 352, the average age was 52.2 years, 55% were female, 65% Non-Hispanic Black, 20% Hispanic, 15% Non-Hispanic White/Other. Half were on either Medicare or Medicaid, and 4% uninsured. The median income of the patients’ zipcodes fell at the 44th percentile of the U.S. income. During this initial phase, our novel screening in the ED identified a significant number of patients with undiagnosed diabetes, particularly minority and poor patients, indicating this approach could be leveraged to further stymie health disparities. Future research will now test the linkage of these new patients to diabetes education and care within the health care system. Disclosure K.K.Danielson: None. B.Rydzon: None. Y.Eisenberg: None. B.T.Layden: None. J.Lin: Research Support; Gilead Sciences, Inc., Novo Nordisk. Funding Novo Nordisk (G2111)

The influence of gut bacteria on host energy homeostasis is increasingly recognized, but mechanistic links are lacking. The gut microbiota digests and ferments nutrients, which result in short-chain fatty acids (SCFAs) . The body senses these nutrients in large part through free fatty acid receptors 2 (FFA2) and 3 (FFA3) . Accumulating evidence indicates that the gut microbiota/SCFAs interact with the central nervous system (CNS) to regulate brain metabolic function. Consistently, we found that a single acute intracerebroventricular (ICV) injection of acetate (ACE) , propionate (PRO) , or butyrate (BUT) dose-dependently inhibited food intake in an FFA2/3-dependent manner. The reduced food intake induced by ACE, PRO, or BUT was attributed to decreased meal size or increased intermeal interval. These regulatory effects on meal patterns were blunted in FFA2 and FFA3 double-receptor knockout mice, suggesting a mediating role of brain FFA2/3. Interestingly, RNAscope analysis showed that FFA3 but not FFA2 highly expressed in the cerebellar granule neurons. Using brain slice patch-clamp, we consistently showed that PRO or FFA3-selective agonists inhibited these granule neurons. Notably, the hyperpolarization effects of PRO on cerebellar granule neurons were blocked by pertussis toxin (PTX) , a G-protein coupled receptor subunit Gi/o blocker, further supporting an FFA3-Gi/o-mediated inhibition on granule neurons. These results suggest a model that SCFAs inhibit food intake through FFA3 expressed by the cerebellar granule neurons. Key words: SCFA; Brain; FFA3 Disclosure P. Luo: None. P. Xu: None. H. Ye: None. B.T. Layden: None. Y. He: None. V.C. Torres Irizarry: None.

Background & Aims Nonalcoholic steatohepatitis (NASH) is commonly observed in patients with type 2 diabetes, and thiazolidinediones (TZD) are considered a potential therapy for NASH. Although TZD increase insulin sensitivity and partially reduce steatosis and alanine aminotransferase, the efficacy of TZD on resolving liver pathology is limited. In fact, TZD may activate peroxisome proliferator-activated receptor gamma (PPARγ) in hepatocytes and promote steatosis. Therefore, we assessed the role that hepatocyte-specific PPARγ plays in the development of NASH, and how it alters the therapeutic effects of TZD on the liver of mice with diet-induced NASH. Methods Hepatocyte-specific PPARγ expression was knocked out in adult mice before and after the development of NASH induced with a high fat, cholesterol, and fructose (HFCF) diet. Results HFCF diet increased PPARγ expression in hepatocytes, and rosiglitazone further activated PPARγ in hepatocytes of HFCF-fed mice in vivo and in vitro. Hepatocyte-specific loss of PPARγ reduced the progression of HFCF-induced NASH in male mice and increased the benefits derived from the effects of TZD on extrahepatic tissues and non-parenchymal cells. RNAseq and metabolomics indicated that HFCF diet promoted inflammation and fibrogenesis in a hepatocyte PPARγ–dependent manner and was associated with dysregulation of hepatic metabolism. Specifically, hepatocyte-specific loss of PPARγ plays a positive role in the regulation of methionine metabolism, and that could reduce the progression of NASH. Conclusions Because of the negative effect of hepatocyte PPARγ in NASH, inhibition of mechanisms promoted by endogenous PPARγ in hepatocytes may represent a novel strategy that increases the efficiency of therapies for NAFLD., Graphical abstract

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.

Hexokinase domain containing protein-1, or HKDC1, is a widely expressed hexokinase that is genetically associated with elevated 2-hour gestational blood glucose levels during an oral glucose tolerance test, suggesting a role for HKDC1 in postprandial glucose regulation during pregnancy. Our earlier studies utilizing mice containing global HKDC1 knockdown, as well as hepatic HKDC1 overexpression and knockout, indicated that HKDC1 is important for whole-body glucose homeostasis in aging and pregnancy, through modulation of glucose tolerance, peripheral tissue glucose utilization, and hepatic energy storage. However, our knowledge of the precise role(s) of HKDC1 in regulating postprandial glucose homeostasis under normal and diabetic conditions is lacking. Since the intestine is the main entry portal for dietary glucose, here we have developed an intestine-specific HKDC1 knockout mouse model, HKDC1Int–/–, to determine the in vivo role of intestinal HKDC1 in regulating glucose homeostasis. While no overt glycemic phenotype was observed, aged HKDC1Int–/– mice fed a high-fat diet exhibited an increased glucose excursion following an oral glucose load compared with mice expressing intestinal HKDC1. This finding resulted from glucose entry via the intestinal epithelium and is not due to differences in insulin levels, enterocyte glucose utilization, or reduction in peripheral skeletal muscle glucose uptake. Assessment of intestinal glucose transporters in high-fat diet–fed HKDC1Int–/– mice suggested increased apical GLUT2 expression in the fasting state. Taken together, our results indicate that intestinal HKDC1 contributes to the modulation of postprandial dietary glucose transport across the intestinal epithelium under conditions of enhanced metabolic stress, such as high-fat diet.

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

This cross-sectional study describes a screening program that was developed to screen for type 2 diabetes in an urban emergency department setting in the US.

Hepatocellular carcinoma (HCC) is a leading cause of death from cancer malignancies. Recently, hexokinase domain containing 1 (HKDC1), was shown to have significant overexpression in HCC compared to healthy tissue. Using in vitro and in vivo tools, we examined the role of HKDC1 in HCC progression. Importantly, HKDC1 ablation stops HCC progression by promoting metabolic reprogramming by shifting glucose flux away from the TCA cycle. Next, HKDC1 ablation leads to mitochondrial dysfunction resulting in less cellular energy which cannot be compensated by enhanced glucose uptake. And finally, we show that the interaction of HKDC1 with the mitochondria is essential for its role in HCC progression, and without this mitochondrial interaction mitochondrial dysfunction occurs. In sum, HKDC1 is highly expressed in HCC cells compared to normal hepatocytes, therefore targeting HKDC1, specifically its interaction with the mitochondria, reveals a highly selective approach to target cancer cells in HCC.

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-hr 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 HKDC1(fl/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.

Background and aimsNormal gestation involves reprogramming of maternal gut microbiome (GM) that may contribute to maternal metabolic changes by unclear mechanisms. This study aimed to understand the mechanistic underpinnings of GM – maternal metabolism interaction.MethodsThe GM and plasma metabolome of CD1, NIH-Swiss and C57BL/6J mice were analyzed using 16S rRNA sequencing and untargeted LC-MS throughout gestation and postpartum. 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 in the process was studied using fecal microbial transplants (FMT).ResultsSignificant variation in gut microbial alpha diversity occurred throughout pregnancy. Enrichment in gut bacterial taxa was mouse strain and pregnancy time-point specific, with species enriched at gestation day 15/19 (G15/19), a point of heightened IR, distinct from those enriched pre- or post- pregnancy. Untargeted and targeted metabolomics revealed elevated plasma kynurenine at G15/19 in all three 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 levels effects on IR derive from the GM in both mouse and human pregnancy.ConclusionsGM 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.

PURPOSE OF REVIEW: Gestational diabetes mellitus (GDM) is a common pregnancy complication conferring an increased risk to the individual of developing type 2 diabetes. As such, a thorough understanding of the pathophysiology of GDM is warranted. Hexokinase domain containing protein-1 (HKDC1) is a recently discovered protein containing hexokinase activity which has been shown to be associated with glucose metabolism during pregnancy. Here, we discuss recent evidence suggesting roles for the novel HKDC1 in gestational glucose homeostasis and the development of GDM and overt diabetes. RECENT FINDINGS: Genome wide association studies identified variants of the HKDC1 gene associated with maternal glucose metabolism. Studies modulating HKDC1 protein expression in pregnant mice demonstrate that HKDC1 has roles in whole-body glucose utilization and nutrient balance, with liver-specific HKDC1 influencing insulin sensitivity, glucose tolerance, gluconeogenesis, and ketone production. SUMMARY: HKDC1 has important roles in maintaining maternal glucose homeostasis extending beyond traditional hexokinase functions, and may serve as a potential therapeutic target.

Glucose phosphorylation by hexokinases (HKs) traps glucose in cells and facilitates its usage in metabolic processes dependent on cellular needs. HK domain-containing protein-1 (HKDC1) is a recently discovered protein with wide expression containing HK activity, first noted through a genome-wide association study (GWAS) to be linked with gestational glucose homeostasis during pregnancy. Since then, HKDC1 has been observed to be expressed in many human tissues. Moreover, studies have shown that HKDC1 plays a role in glucose homeostasis by which it may affect the progression of many pathophysiological conditions such as gestational diabetes mellitus (GDM), nonalcoholic steatohepatitis (NASH), and cancer. Here, we review the key studies contributing to our current understanding of the roles of HKDC1 in human pathophysiological conditions and potential therapeutic interventions.

Introduction: Changes to the overall diversity and relative abundance of the microbiota have been shown to alter not only the functionality of the gut system, in particular with regards to the metabolic rates and levels of pro-inflammatory cytokines, but also the development of disease states such as metabolic syndrome (METS). The purpose of this study was to explore the composition of the gut microbiota diversity, and metabolic outcomes, across three populations: the United States, Ghana and South Africa. Hypothesis: We assessed the hypothesis that differences between the three populations, including variations in diet, would affect the diversity and composition of the microbiome of the participants; these changes would in turn be reflected in the gut-related metabolic outcomes. Methods: Participants(N=560) provided a fecal sample which was analyzed using the analysis of Composition of Microbiome to identify differentially abundant bacterial exact sequence variants (ESVs), and general linearized models (GLM) to test associations between selected ESVs and gut-related metabolic outcomes. Results: Not surprisingly, macronutrient intake was significantly different across the 3 sites (p Conclusion: In conclusion, we found that country of origin was significantly associated with bacterial diversity. These differences were associated with alterations in the bacterial functional metabolic and proinflammatory pathways, suggesting a role in cardiovascular health and the development of the METS.

Background Studies on the inhibition of inflammation by infection with helminth parasites have, until recently, overlooked a key determinant of health: the gut microbiota. Infection with helminths evokes changes in the composition of their host’s microbiota: one outcome of which is an altered metabolome (e.g., levels of short-chain fatty acids (SCFAs)) in the gut lumen. The functional implications of helminth-evoked changes in the enteric microbiome (composition and metabolites) are poorly understood and are explored with respect to controlling enteric inflammation. Methods Antibiotic-treated wild-type, germ-free (GF) and free fatty-acid receptor-2 (ffar2) deficient mice were infected with the tapeworm Hymenolepis diminuta, then challenged with DNBS-colitis and disease severity and gut expression of the il-10 receptor-α and SCFA receptors/transporters assessed 3 days later. Gut bacteria composition was assessed by 16 s rRNA sequencing and SCFAs were measured. Other studies assessed the ability of feces or a bacteria-free fecal filtrate from H. diminuta-infected mice to inhibit colitis. Results Protection against disease by infection with H. diminuta was abrogated by antibiotic treatment and was not observed in GF-mice. Bacterial community profiling revealed an increase in variants belonging to the families Lachnospiraceae and Clostridium cluster XIVa in mice 8 days post-infection with H. diminuta, and the transfer of feces from these mice suppressed DNBS-colitis in GF-mice. Mice treated with a bacteria-free filtrate of feces from H. diminuta-infected mice were protected from DNBS-colitis. Metabolomic analysis revealed increased acetate and butyrate (both or which can reduce colitis) in feces from H. diminuta-infected mice, but not from antibiotic-treated H. diminuta-infected mice. H. diminuta-induced protection against DNBS-colitis was not observed in ffar2−/− mice. Immunologically, anti-il-10 antibodies inhibited the anti-colitic effect of H. diminuta-infection. Analyses of epithelial cell lines, colonoids, and colon segments uncovered reciprocity between butyrate and il-10 in the induction of the il-10-receptor and butyrate transporters. Conclusion Having defined a feed-forward signaling loop between il-10 and butyrate following infection with H. diminuta, this study identifies the gut microbiome as a critical component of the anti-colitic effect of this helminth therapy. We suggest that any intention-to-treat with helminth therapy should be based on the characterization of the patient’s immunological and microbiological response to the helminth.

The advance in microbiome and metabolome studies has generated rich omics data revealing the involvement of the microbial community in host disease pathogenesis through interactions with their host at a metabolic level. However, the computational tools to uncover these relationships are just emerging. Here, we present MiMeNet, a neural network framework for modeling microbe-metabolite relationships. Using ten iterations of 10-fold cross-validation on three paired microbiome-metabolome datasets, we show that MiMeNet more accurately predicts metabolite abundances (mean Spearman correlation coefficients increase from 0.108 to 0.309, 0.276 to 0.457, and -0.272 to 0.264) and identifies more well-predicted metabolites (increase in the number of well-predicted metabolites from 198 to 366, 104 to 143, and 4 to 29) compared to state-of-art linear models for individual metabolite predictions. Additionally, we demonstrate that MiMeNet can group microbes and metabolites with similar interaction patterns and functions to illuminate the underlying structure of the microbe-metabolite interaction network, which could potentially shed light on uncharacterized metabolites through “Guilt by Association”. Our results demonstrated that MiMeNet is a powerful tool to provide insights into the causes of metabolic dysregulation in disease, facilitating future hypothesis generation at the interface of the microbiome and metabolomics.

Introduction: Reduced expression of cholesterol transporter ABCA1 is critical in pathogenesis of type 2 diabetes (T2D) and related conditions, such as cardiovascular disease (CVD) and Alzheimer’s disease (AD). Thus, increasing ABCA1 represents a novel therapeutic strategy for these conditions. However, prior drug development efforts have achieved limited success at increasing ABCA1 (controlled by liver X receptor [LXR] β) while avoiding unwanted liver triglyceride production (through LXRα via transcription factor SREBP1c). Hypothesis: We hypothesized that phenotypic screening for selective ABCA1 inducers followed by medicinal chemistry optimization would bypass the isoform selectivity issues encountered in traditional target-based drug discovery and enable development of lead therapeutic candidates with preclinical efficacy and safety. Methods/Results: We screened 20k compounds for ABCA1 and SREBP1c-linked luciferase activity, followed by qPCR to validate and prioritize selective ABCA1-inducing hits. We synthesized ~70 structural analogs of the best hit, achieving substantial EC 50 (4.5 μM to 270 nM) and E max (3.5-fold to 6.0-fold vs. vehicle) improvements in ABCA1 luciferase assay while maintaining selectivity against SREBP1c. Direct binding assays confirmed selectivity for LXRβ vs. LXRα, corroborating cell-based data. Lead compounds enhanced cellular cholesterol efflux, reduced inflammation in vitro , and attenuated high-fat diet (HFD) induced weight gain, insulin resistance, and inflammation in mice. Metabolomics analysis revealed that our lead compound corrected HFD-induced perturbations in liver glucose and fatty acid synthesis. Finally, side effects associated with published LXR agonists - liver steatosis and neutropenia - were not observed with our compound. Conclusions: We established a platform to develop selective ABCA1 inducers as drug candidates. Via this platform, we identified a safe and efficacious lead compound for T2D. Our study also represents the first report of an LXR agonist characterized by metabolomics - a powerful tool to complement biochemical readouts. Continued optimization to improve pharmacokinetic parameters, plus evaluation in CVD and AD models, is ongoing.

[Image: see text] Selective liver X receptor (LXR) agonists have been extensively pursued as therapeutics for Alzheimer’s disease and related dementia (ADRD) and, for comorbidities such as type 2 diabetes (T2D) and cerebrovascular disease (CVD), disorders with underlying impaired insulin signaling, glucose metabolism, and cholesterol mobilization. The failure of the LXR-focused approach led us to pursue a novel strategy to discover nonlipogenic ATP-binding cassette transporter A1 (ABCA1) inducers (NLAIs): screening for ABCA1-luciferase activation in astrocytoma cells and counterscreening against lipogenic gene upregulation in hepatocarcinoma cells. Beneficial effects of LXRβ agonists mediated by ABCA1 include the following: control of cholesterol and phospholipid efflux to lipid-poor apolipoproteins forming beneficial peripheral HDL and HDL-like particles in the brain and attenuation of inflammation. While rare, ABCA1 variants reduce plasma HDL and correlate with an increased risk of ADRD and CVD. In secondary assays, NLAI hits enhanced cholesterol mobilization and positively impacted in vitro biomarkers associated with insulin signaling, inflammatory response, and biogenic properties. In vivo target engagement was demonstrated after oral administration of NLAIs in (i) mice fed a high-fat diet, a model for obesity-linked T2D, (ii) mice administered LPS, and (iii) mice with accelerated oxidative stress. The lack of adverse effects on lipogenesis and positive effects on multiple biomarkers associated with T2D and ADRD supports this novel phenotypic approach to NLAIs as a platform for T2D and ADRD drug discovery.

Background Therapeutic agents with novel mechanisms of action are needed to combat the growing epidemic of type 2 diabetes (T2D) and related metabolic syndromes. Liver X receptor (LXR) agonists possess preclinical efficacy yet produce side effects due to excessive lipogenesis. Anticipating that many beneficial and detrimental effects of LXR agonists are mediated by ABCA1 and SREPB1c expression, respectively, we hypothesized that a phenotypic optimization strategy prioritizing selective ABCA1 induction would identify an efficacious lead compound with an improved side effect profile over existing LXRβ agonists. Methods We synthesized and characterized a novel small molecule for selective induction of ABCA1 vs. SREBP1c in vitro. This compound was evaluated in both wild-type mice and a high-fat diet (HFD) mouse model of obesity-driven diabetes through functional, biochemical, and metabolomic analysis. Findings Six weeks of oral administration of our lead compound attenuated weight gain, glucose intolerance, insulin signaling deficits, and adiposity. Global metabolomics revealed suppression of gluconeogenesis, free fatty acids, and pro-inflammatory metabolites. Target identification linked these beneficial effects to selective LXRβ agonism and PPAR/RXR antagonism. Interpretation Our observations in the HFD model, combined with the absence of lipogenesis and neutropenia in WT mice, support this novel approach to therapeutic development for T2D and related conditions.

The advance in microbiome and metabolome studies has generated rich omics data revealing the involvement of the microbial community in host disease pathogenesis through interactions with their host at a metabolic level. However, the computational tools to uncover these relationships are just emerging. Here, we present MiMeNet, a neural network framework for modeling microbe-metabolite relationships. Using ten iterations of 10-fold cross-validation on three paired microbiome-metabolome datasets, we show that MiMeNet more accurately predicts metabolite abundances (mean Spearman correlation coefficients increase from 0.108 to 0.309, 0.276 to 0.457, and -0.272 to 0.264) and identifies more well-predicted metabolites (increase in the number of well-predicted metabolites from 198 to 366, 104 to 143, and 4 to 29) compared to state-of-art linear models for individual metabolite predictions. Additionally, we demonstrate that MiMeNet can group microbes and metabolites with similar interaction patterns and functions to illuminate the underlying structure of the microbe-metabolite interaction network, which could potentially shed light on uncharacterized metabolites through “Guilt by Association”. Our results demonstrated that MiMeNet is a powerful tool to provide insights into the causes of metabolic dysregulation in disease, facilitating future hypothesis generation at the interface of the microbiome and metabolomics., Author summary The microbiome has shown to functionally interact with its host or environment at a metabolic level, however the exact nature of these interactions is not well understood. In addition, metabolic dysregulation caused by the microbiome is believed to contribute to the development of diseases such as inflammatory bowel disease, diabetes mellitus, and obesity. In this manuscript, we introduce a computational framework to integrate microbiome and metabolome data to uncover microbe-metabolite interactions in a data-driven manner. Our model uses neural networks to predict metabolite abundances from microbe abundances. The trained models are then used to derive microbe-metabolite feature scores, which are used for clustering microbes and metabolites into functional modules. These module-based interactions are useful in generating biological insights and facilitating hypothesis generation for the investigation of their roles in various metabolic diseases. The software of our model is made freely available to interested researchers.

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 C57 BL /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 FFAR 3 but not FFAR2, both receptors for butyrate, exacerbated neointimal hyperplasia development after injury. FFAR 3 deficiency was also associated with delayed recovery of the endothelial layer in vivo. FFAR 3 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 FFAR 3 agonist 1‐methylcyclopropane carboxylate stimulated cellular migration and proliferation in scratch assays. Conclusions Our results support a protective role for butyrate and FFAR 3 in the development of neointimal hyperplasia after arterial injury and delineate activation of the butyrate‐ FFAR 3 pathway as a valuable strategy for the prevention and treatment of neointimal hyperplasia.

Sleep disorders are increasingly being characterized in modern society as contributing to a host of serious medical problems, including obesity and metabolic syndrome. Changes to the microbial community in the human gut have been reportedly associated with many of these cardiometabolic outcomes. In this study, we investigated the impact of sleep length on the gut microbiota in a large cohort of 655 participants of African descent, aged 25–45, from Ghana, South Africa (SA), Jamaica, and the United States (US). The sleep duration was self-reported via a questionnaire. Participants were classified into 3 sleep groups: short (

Hexokinase domain-containing protein 1 (HKDC1) is a recently discovered putative fifth hexokinase that is widely expressed in a variety of human and mouse tissues. Previous work indicate that HKDC1 is important for whole-body glucose homeostasis and utilization in pregnancy and aging, and suggest roles for HKDC1 in nonalcoholic fatty liver disease development and progression of hepatocellular carcinoma. Prior work in the lab further showed that global heterozygous-deleted HKDC1 mice exhibit blunted uptake of triglycerides following an olive oil bolus compared to wild-type mice, suggesting a role for intestinal HKDC1 expression in intestinal lipid metabolism (unpublished results). To specifically study the significance of intestinal HKDC1 on whole-body glucose and lipid homeostasis, we utilized Cre-mediated recombination of HKDC1 in which Cre was expressed under the control of the villin gene promoter, creating a mouse model in which HKDC1 expression is specifically deleted in the intestinal epithelium. Quantitative RT-PCR data confirmed the knockout of HKDC1 within the mouse intestine in young and aged mice, while HKDC1 expression in other tissues was comparable to wild-type mice. Next, intestinal HKDC1 knockout mice and their wild-type littermate controls were either maintained on a normal diet or were switched to a high fat diet at 6 weeks of age to simulate the state of impaired glucose tolerance, and the effects of intestinal HKDC1 on glucose and lipid homeostasis were analyzed between 28-34 weeks of age. Mice fed a normal diet did not exhibit any differences in serum glucose or triglyceride during oral/intraperitoneal glucose tolerance tests or oral olive oil bolus, respectively, regardless of intestinal HKDC1 status. Interestingly, mice lacking intestinal HKDC1 that were on a high fat diet demonstrated improved overall glycemic control compared to wild-type mice after the administration of an oral glucose load, all while there were no changes in insulin levels, gluconeogenesis or insulin tolerance related to HKDC1 status. Additionally, introduction of an intraperitoneal glucose load to mice fed a high fat diet did not alter glucose control in the presence or absence of intestinal HKDC1. However, high fat diet-fed mice lacking intestinal HKDC1 did not have a significant increase in serum triglyceride following an oral olive oil bolus, while their stool fat and triglyceride content were comparable to wild-type. Collectively, these data indicate that intestinal HKDC1 has important roles in glucose and triglyceride metabolism within the intestinal epithelium, and further suggest a role in whole-body glucose homeostasis and in the development of insulin resistance and diabetes.

Background: The Pulvers’ silhouette showcards provide a non-invasive, easy-to-use, and possibly cross-culturally acceptable way of assessing an individual’s perception of their body size. This study examined, in three different populations: 1) the relationship between silhouettes and body mass index (BMI), 2) the predictive performance of silhouettes to predict dichotomous adiposity categories, and 3) whether silhouette ranking performed similarly in predicting BMI, waist circumference (WC), and waist-to-height ratio (WHR). Methods: This study included 751 participants of African-origin from the United States of America (USA), the Republic of Seychelles, and Ghana, from the ongoing cohort Modeling the Epidemiological Transition Study. We assessed the mean BMI for each silhouette rank by country and sex and performed a least-squares linear regression for the silhouette’s performance by country and sex. The performance of the silhouettes to predict overweight and obesity (BMI ≥ 25 kg/m2), and obesity alone (BMI ≥ 30 kg/m2) was examined through a receiver operator curve (ROC) analysis with corresponding sensitivities and specificities. Finally, a ROC analysis area under the curve (AUC) was also performed for the detection of elevated waist circumference (men ≥ 94 cm; women ≥ 80 cm) and waist-to-height ratio (> 0.5) by country and sex.Results: Mean measured BMI (kg/m2) in men/women differed largely across countries: 28.9/35.8 in the USA, 28.3/30.5 in Seychelles, and 23.9/28.5 in Ghana. The slope of the relation between silhouette ranking and BMI (i.e., linear regression coefficient and 95% confidence intervals) was similar between sexes of the same country but differed between countries: 3.65 [95% CI: 3.34-3.97 BMI units/silhouette unit] in the USA, 3.23 [2.93-3.74] in Seychelles, and 1.99 [1.72-2.26] in Ghana. Different silhouette cut-offs predicted dichotomous adiposity categories differently in the three countries. For example, a silhouette ≥ 5 had sensitivity/specificity of 77.3%/90.6% to predict BMI ≥ 25 kg/m2 in the USA, but 77.8%/85.9% in Seychelles and 84.9%/71.4% in Ghana. Finally, silhouettes predicted BMI, WC, and WHR similarly, within each country and sex, based on Spearman correlations coefficients (continuous scale) and c-statistic (dichotomous classification).Conclusion: Our data suggest that Pulvers’ silhouette showcards can be a useful tool to objectively predict different adiposity measures in different populations when direct measurement cannot be performed. However, population-specific differences in the slopes of the associations, which possibly partly reflect differences in perceptions of one’s body size according to country adiposity prevalence, stress the need to calibrate silhouette showcards when using them as a survey tool.

The product of hexokinase (HK) enzymes, glucose-6-phosphate, can be metabolized through glycolysis or directed to alternative pathways, such as the pentose phosphate pathway (PPP) to generate anabolic intermediates. However, it is not known what determines the fate of G6P. HK1 contains an N-terminal mitochondrial–binding domain, but its physiologic significance remains unclear. We overexpressed full-length and truncated HK1 in tissue culture and generated mice lacking the HK1 mitochondrial-binding domain (ΔE1HK1). Although ΔE1HK1 mice displayed no overt phenotype, HK1 dislocation from the mitochondria increased glucose flux through the PPP, decreased flux below the level of GAPDH, and induced a hyper-inflammatory response to lipopolysaccharide. The mechanism for the increased PPP flux is through glycolytic block at GAPDH, which is mediated by binding of cytosolic HK1 with S100A8/A9 and increased GAPDH nitrosylation through iNOS. Additionally, human and mouse macrophages from conditions of low-grade inflammation, such as aging and diabetes, displayed an increase in cytosolic HK1 and cytokine production, along with reduced GAPDH activity. Our data indicate that HK1 mitochondrial-binding alters glucose metabolism through regulation of GAPDH.

Summary: Autophagy, a stress-induced lysosomal degradative pathway, has been assumed to exert similar metabolic effects in different organs. Here, we establish a model where autophagy plays different roles in insulin-producing β cells versus insulin-responsive cells, utilizing knockin (Becn1F121A) mice manifesting constitutively active autophagy. With a high-fat-diet challenge, the autophagy-hyperactive mice unexpectedly show impaired glucose tolerance, but improved insulin sensitivity, compared to mice with normal autophagy. Autophagy hyperactivation enhances insulin signaling, via suppressing ER stress in insulin-responsive cells, but decreases insulin secretion by selectively sequestrating and degrading insulin granule vesicles in β cells, a process we term “vesicophagy.” The reduction in insulin storage, insulin secretion, and glucose tolerance is reversed by transient treatment of autophagy inhibitors. Thus, β cells and insulin-responsive tissues require different autophagy levels for optimal function. To improve insulin sensitivity without hampering secretion, acute or intermittent, rather than chronic, activation of autophagy should be considered in diabetic therapy development. : Yamamoto et al. report that, in response to a high-fat-diet challenge, Becn1-mediated autophagy hyperactivation increases insulin sensitivity by reducing ER stress but decreases insulin secretion and storage via autophagic degradation of insulin granules. The results reveal differing roles of autophagy on metabolic regulation in insulin-responsive cells versus insulin-secreting β cells. Keywords: autophagosome, autophagy, β cell, Becn1, glucose tolerance, insulin granule, insulin-responsive tissue, insulin sensitivity, type 2 diabetes, vesicophagy

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.

Introduction: Obesity and metabolic syndrome are increasingly prevalent in the United States, particularly among African Americans and Latinos. Bariatric surgery has become one of the primary treatment modalities for obesity and type 2 diabetes. However, fewer Latinos and African Americans are undergoing bariatric surgery than whites. The aim of this article is to describe the disparities in seeking and accessing bariatric surgery, describe the outcomes following bariatric procedures in Latinos and African Americans, and offer recommendations and future research directions that may assist in addressing these disparities. Methods: Original research and review articles published in English were reviewed. Results: Potential reasons why Latinos and African Americans have low rates of seeking bariatric surgery are described. Disparities in access to care and financial coverage, low rates of referral by primary care providers, and cultural attitudes toward obesity in conjunction with mistrust of the healthcare system are discussed as potential contributors to the low rate of bariatric surgery in Latinos and African Americans. Finally, disparities in bariatric surgery outcomes, comorbidities, and complications are reviewed. Conclusions: Additional research studies in bariatric surgical disparities are needed. Recommendations and future directions that may help to reduce disparities in bariatric surgery are discussed.

Hexokinase domain component 1 (HKDC1) is a recently discovered novel protein, which is being promoted as a putative fifth hexokinase. Although the exact role HKDC1 plays in physiology is still unclear, it has been shown to be important during pregnancy in the regulation of glucose homeostasis. In this study, we have comprehensively studied the expression pattern of HKDC1 in the human body. Using human tissue sample, immunohistochemistry imaging was performed. Our studies indicate that the tissues with highest HKDC1 expression were the brush border epithelium of the intestines, parts of the pancreas, and lung alveolar macrophages. Future directions will be to understand the role of this fifth hexokinase in these tissues, with a focus on its relative function as compared with other endogenously expressed hexokinases.

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 Gαq/11-biased agonism of FFA2 can potentiate glucose stimulated insulin secretion (GSIS) as well as promote beta cell proliferation. However, the currently available Gαq/11-biased agonists for FFA2 exhibit low potency, making them difficult to examine in vivo. This study sought to identify Gαq/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 Gαq/11 with 100-fold increased potency compared with previously described Gαq/11-biased FFA2 agonists. These methods and findings provide a foundation for future discovery efforts to identify biased FFA2 agonists as potential T2D therapeutics.

Continuous glucose monitoring (CGM) systems have been explored in a few studies for non–intensive care unit (ICU) patients (1–3). During the coronavirus disease 2019 (COVID-19) pandemic, shortage of personal protective equipment (PPE) became a concern. On 1 April 2020, the U.S. Food and Drug Administration announced it would not object to the use of CGM systems to assist with COVID-19 patient monitoring (4). This study was conducted to explore the feasibility of using CGM in noncritically ill patients hospitalized with COVID-19. Non-ICU adult COVID-19–positive patients receiving subcutaneous insulin injection and point of care (POC) glucose testing (Accu-Chek Inform II) were eligible to participate. Exclusion criteria included unstable glucose levels (POC glucose 350 mg/dL) at entry, hypotension, significant edema, being on dialysis, being postsurgical or with planned surgery/computed tomography/MRI, and taking hydroxyurea, ascorbic acid, or acetaminophen >1 g every 6 h. Participants gave informed consent. The protocol was approved by the Institutional Review Board at the University of Illinois at Chicago. Dexcom G6 sensor was placed in the lower abdomen by the team physician. iPhone 5S was used as a receiver, placed at the patient’s door. The data were transmitted to the Dexcom Follow app in the smartphone at the nurses’ station and the investigator’s smart devices. Participants continued to …

Pregnancy radically changes all aspects of intermediary metabolism of the mother. In particular, dramatic changes occur in how glucose is utilized and how insulin sensitivity is altered throughout the course of a pregnancy. These adaptations are specific to the stages of pregnancy, which are related to the metabolic demands of the fetus and mother. Gestational insulin resistance (IR), which is driving these metabolic changes, is important to understand, as this will help us better manage pregnancies, including those complicated by diabetes and obesity. This chapter focuses on explaining in depth the available knowledge about the regulation of glucose metabolism and insulin sensitivity during pregnancy, as well as how hormones and cytokines regulate these processes.

Microbiota-derived acetate coordinates innate immune responses during intestinal Clostridium difficile infection through its cognate receptor FFAR2. Acetate accelerates early neutrophil recruitment and increases ILC3 expression of the IL-1 receptor, boosting ILC3 production of IL-22 in response to neutrophil-derived IL-1β., Antibiotic-induced dysbiosis is a key predisposing factor for Clostridium difficile infections (CDIs), which cause intestinal disease ranging from mild diarrhea to pseudomembranous colitis. Here, we examined the impact of a microbiota-derived metabolite, short-chain fatty acid acetate, on an acute mouse model of CDI. We found that administration of acetate is remarkably beneficial in ameliorating disease. Mechanistically, we show that acetate enhances innate immune responses by acting on both neutrophils and ILC3s through its cognate receptor free fatty acid receptor 2 (FFAR2). In neutrophils, acetate-FFAR2 signaling accelerates their recruitment to the inflammatory sites, facilitates inflammasome activation, and promotes the release of IL-1β; in ILC3s, acetate-FFAR2 augments expression of the IL-1 receptor, which boosts IL-22 secretion in response to IL-1β. We conclude that microbiota-derived acetate promotes host innate responses to C. difficile through coordinate action on neutrophils and ILC3s., Graphical Abstract

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 > 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 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.

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.

The transition from urinary glucose measurement to more sophisticated self-monitoring of blood glucose (SMBG) systems in the 1970s and 1980s dramatically changed the approach to and understanding of diabetes management (1). Innovations in the design and technology of portable blood glucose meters have become integral to the success of intensive treatment of both type 1 and type 2 diabetes, and the outcome of this treatment has led to a tremendous decrease in the development of long-term micro- and macrovascular complications (2–4). However, intensive insulin therapy has its limitations, including increased frequency of hypoglycemia and the need for frequent SMBG testing. In the past decade, continuous glucose monitoring (CGM) technology has evolved into a novel tool to support diabetes management. Unlike conventional glucose meters, which provide a snapshot of the blood glucose value at the time of testing, CGM provides semi-continuous information about glucose levels. It does this indirectly, by extrapolating blood glucose levels from interstitial fluid glucose via an algorithm. Importantly, CGM allows users to make decisions regarding their day-to-day diabetes management using real-time glucose trends. Along with this information, CGM systems provide customizable hypo- and hyperglycemia alarms and display trends of the rate of change of glucose levels. Most recently, CGM systems have been integrated with insulin pumps and are being used in artificial pancreas clinical trials. In this article, we discuss the clinical benefits of CGM; its challenges, including accuracy and user experience; and its present and future role in the management of diabetes. Numerous studies have explored whether sustained use of CGM offers clinical benefits in individuals with diabetes. Randomized, multicenter clinical trials have shown improved glycemic control in adults with type 1 diabetes using CGM compared to those using SMBG and a reduction in the time spent in hypoglycemia with concomitant improvement in A1C …

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). Pharmacologic, molecular and genetic studies have investigated their role in organismal glucose metabolism and recently in pancreatic beta-cell biology. Here we summarize the present knowledge on the role of these receptors as metabolic sensors in beta cell function and physiology, revealing new therapeutic opportunities for type 2 diabetes.

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.

Adipose tissue PKA has roles in adipogenesis, lipolysis, and mitochondrial function. PKA transduces the cAMP signal downstream of G protein-coupled receptors, which are being explored for therapeutic manipulation to reduce obesity and improve metabolic health. This study aimed to determine the overall physiological consequences of PKA activation in adipose tissue. Mice expressing an activated PKA catalytic subunit in adipose tissue (Adipoq-caPKA mice) showed increased PKA activity in subcutaneous, epididymal, and mesenteric white adipose tissue (WAT) depots and brown adipose tissue (BAT) compared with controls. Adipoq-caPKA mice weaned onto a high-fat diet (HFD) or switched to the HFD at 26 wk of age were protected from diet-induced weight gain. Metabolic health was improved, with enhanced insulin sensitivity, glucose tolerance, and β-cell function. Adipose tissue health was improved, with smaller adipocyte size and reduced macrophage engulfment of adipocytes. Using metabolic cages, we found that Adipoq-caPKA mice were shown to have increased energy expenditure, but no difference to littermate controls in physical activity or food consumption. Immunoblotting of adipose tissue showed increased expression of uncoupling protein-1 (UCP1) in BAT and dramatic UCP1 induction in subcutaneous WAT, but no induction in the visceral depots. Feeding a HFD increased PKA activity in epididymal WAT of wild-type mice compared with chow, but did not change PKA activity in subcutaneous WAT or BAT. This was associated with changes in PKA regulatory subunit expression. This study shows that adipose tissue PKA activity is sufficient to increase energy expenditure and indicates that PKA is a beneficial target in metabolic health.

Type 2 diabetes is associated with obesity, insulin resistance and β-cell failure. Therapeutic aims are to reduce adiposity, improve insulin sensitivity and enhance β-cell function. However, it has been proposed that chronically increasing insulin release leads to β-cell exhaustion and failure. We previously developed mice to have increased activity of the cAMP-dependent protein kinase (PKA), specifically in β-cells (β-caPKA mice). β-caPKA mice have enhanced acute phase insulin release, which is the primary determinant of the efficacy of glucose clearance. Here these mice were used to determine the sustainability of enhanced insulin secretion, and to characterize peripheral effects of enhanced β-cell function. Increased PKA activity was induced by tamoxifen administration at 10 weeks of age. Male mice were aged to 12 months of age and female mice to 16 months. Glucose control in both male and female β-caPKA mice was significantly improved relative to littermate controls with ad libitum feeding, upon refeeding after fasting, and in glucose tolerance tests. In female mice insulin release was both greater and more rapid than in controls. Female mice were more insulin sensitive than controls. Male and female β-caPKA mice had lower body weights than controls. DEXA analysis of male mice revealed that this was due to reduced adiposity and not due to changes in lean body mass. This study indicates that targeting β-cells to enhance insulin release is sustainable, maintains insulin sensitivity and reduces body weight. These data identify β-cell PKA activity as a novel target for obesity therapies.

This study explored adipocytokine associations with acute and chronic hyperglycemia in African-American men (AAM). Fourteen adipocytokines were measured from men with normal glucose tolerance (NGT) or type 2 diabetes (T2D, drug-na&iuml, ve MF(&minus, ) or using metformin MF(+)). Acute and chronic hyperglycemia were evaluated by 120 min oral glucose tolerance test (OGTT) and glycohemoglobin A1c (HbA1c). AAM with T2D (n = 21) compared to NGT (n = 20) were older, had higher BMI and slightly higher glucose and insulin. In the fasted state, TNF-&alpha, IL-6, PAI-1, IL-13, adiponectin, adipsin, and lipocalin were lower in T2D vs. NGT. At 120 min post-glucose load, TNF-&alpha, IL-6, IL-13, IL-8, PAI-1, adiponectin, adipsin, lipocalin, and resistin were lower in T2D vs. NGT. There were no statistical differences for GM-CSF, IL-7, IL-10, IP-10, and MCP-1. Regression analysis showed that fasting IL-8, TNF-&alpha, adiponectin, lipocalin, resistin, adipsin, and PAI-1 were associated with HbA1c. After adjusting for age, BMI, glucose tolerance, and metformin use, only adipsin remained significantly associated with HbA1c (p = 0.021). The model including adipsin, TNF-&alpha, age, BMI, and group designation (i.e., NGT, MF(&minus, ), MF(+)) explained 86% of HbA1c variability. The data suggested that adipsin could be associated with HbA1c in AAM with varied glucose tolerance.