A novel polyphenol-rich combination of 5 plant extracts prevents high-fat diet-induced body weight gain by regulating intestinal macronutrient absorption in mice.

Global prevalence of obesity and type 2 diabetes are rapidly increasing to pandemic proportions. A novel supplement composed of 5 plant extracts from olive leaf, bilberry, artichoke, chrysanthellum, and black pepper was designed to prevent type 2 diabetes development in people at risk. It was previously shown to improve body weight and glucose control in preclinical rodent models, with these effects being accompanied by increased fecal energy excretion and in vitro inhibition of several digestive enzymes. Thus, we hypothesized that, in mice fed a high-fat diet (HFD), a single dose of this botanical supplementation would decrease the responses to oral fat and carbohydrate tolerance tests, and that chronic supplementation would result in increased fecal triglyceride content. We showed that acute administration in HFD-fed mice (1.452 g/kg body weight) markedly reduced circulating triglycerides following an oral lipid gavage, whereas glycemic responses to various carbohydrate tests were only mildly affected. When incorporated into the food (2.5%) of HFD-fed mice, chronic supplementation prevented body weight gain and improved glucose homeostasis and lipid tolerance. Fecal free fatty acid content, but not triglyceride, was significantly increased in supplemented animals, suggesting reduced lipid absorption in the digestive tract. Congruently, this botanical supplementation downregulated several genes associated with fatty acid transport whose expression was increased by HFD, principally in the jejunum. This study provides novel insights as for the mode of action behind the antiobesity effect of this plant-based supplementation, in HFD-fed mice.

Effects of Totum-63 on glucose homeostasis and postprandial glycemia: a translational study.

Global prevalence of type 2 diabetes (T2D) is rising and may affect 700 million people by 2045. Totum-63 is a polyphenol-rich natural composition developed to reduce the risk of T2D. We first investigated the effects of Totum-63 supplementation in high-fat diet (HFD)-fed mice for up to 16 wk and thereafter assessed its safety and efficacy (2.5 g or 5 g per day) in 14 overweight men [mean age 51.5 yr, body mass index (BMI) 27.6 kg·m-2] for 4 wk. In HFD-fed mice, Totum-63 reduced body weight and fat mass gain, whereas lean mass was unchanged. Moreover, fecal energy excretion was higher in Totum-63-supplemented mice, suggesting a reduction of calorie absorption in the digestive tract. In the gut, metagenomic analyses of fecal microbiota revealed a partial restoration of HFD-induced microbial imbalance, as shown by principal coordinate analysis of microbiota composition. HFD-induced increase in HOMA-IR score was delayed in supplemented mice, and insulin response to an oral glucose tolerance test was significantly reduced, suggesting that Totum-63 may prevent HFD-related impairments in glucose homeostasis. Interestingly, these improvements could be linked to restored insulin signaling in subcutaneous adipose tissue and soleus muscle. In the liver, HFD-induced steatosis was reduced by 40% (as shown by triglyceride content). In the subsequent study in men, Totum-63 (5 g·day-1) improved glucose and insulin responses to a high-carbohydrate breakfast test (84% kcal carbohydrates). It was well tolerated, with no clinically significant adverse events reported. Collectively, these data suggest that Totum-63 could improve glucose homeostasis in both HFD-fed mice and overweight individuals, presumably through a multitargeted action on different metabolic organs.NEW & NOTEWORTHY Totum-63 is a novel polyphenol-rich natural composition developed to reduce the risk of T2D. Totum-63 showed beneficial effects on glucose homeostasis in HFD-fed mice, presumably through a multitargeted action on different metabolic organs. Totum-63 was well tolerated in humans and improved postprandial glucose and insulin responses to a high-carbohydrate breakfast test.

Menin regulates Inhbb expression through an Akt/Ezh2-mediated H3K27 histone modification.

Although Men1 is a well-known tumour suppressor gene, little is known about the functions of Menin, the protein it encodes for. Since few years, numerous publications support a major role of Menin in the control of epigenetics gene regulation. While Menin interaction with MLL complex favours transcriptional activation of target genes through H3K4me3 marks, Menin also represses gene expression via mechanisms involving the Polycomb repressing complex (PRC). Interestingly, Ezh2, the PRC-methyltransferase that catalyses H3K27me3 repressive marks and Menin have been shown to co-occupy a large number of promoters. However, lack of binding between Menin and Ezh2 suggests that another member of the PRC complex is mediating this indirect interaction. Having found that ActivinB - a TGFß superfamily member encoded by the Inhbb gene - is upregulated in insulinoma tumours caused by Men1 invalidation, we hypothesize that Menin could directly participate in the epigenetic-repression of Inhbb gene expression. Using Animal model and cell lines, we report that loss of Menin is directly associated with ActivinB-induced expression both in vivo and in vitro. Our work further reveals that ActivinB expression is mediated through a direct modulation of H3K27me3 marks on the Inhbb locus in Menin-KO cell lines. More importantly, we show that Menin binds on the promoter of Inhbb gene where it favours the recruitment of Ezh2 via an indirect mechanism involving Akt-phosphorylation. Our data suggests therefore that Menin could take an important part to the Ezh2-epigenetic repressive landscape in many cells and tissues through its capacity to modulate Akt phosphorylation.

ActivinB Is Induced in Insulinoma To Promote Tumor Plasticity through a ß-Cell-Induced Dedifferentiation.

Loss of pancreatic ß-cell maturity occurs in diabetes and insulinomas. Although both physiological and pathological stresses are known to promote ß-cell dedifferentiation, little is known about the molecules involved in this process. Here we demonstrate that activinB, a transforming growth factor ß (TGF-ß)-related ligand, is upregulated during tumorigenesis and drives the loss of insulin expression and ß-cell maturity in a mouse insulinoma model. Our data further identify Pax4 as a previously unknown activinB target and potent contributor to the observed ß-cell dedifferentiation. More importantly, using compound mutant mice, we found that deleting activinB expression abolishes tumor ß-cell dedifferentiation and, surprisingly, increases survival without significantly affecting tumor growth. Hence, this work reveals an unexpected role for activinB in the loss of ß-cell maturity, islet plasticity, and progression of insulinoma through its participation in ß-cell dedifferentiation.

ßig-h3 Represses T-Cell Activation in Type 1 Diabetes.

ßig-h3/TGF-ßi is a secreted protein capable of binding to both extracellular matrix and cells. Human genetic studies recently revealed that in the tgfbi gene encoding for ßig-h3, three single nucleotide polymorphisms were significantly associated with type 1 diabetes (T1D) risk. Pancreatic islets express ßig-h3 in physiological conditions, but this expression is reduced in ß-cell insult in T1D. Since the integrity of islets is destroyed by autoimmune T lymphocytes, we thought to investigate the impact of ßig-h3 on T-cell activation. We show here that ßig-h3 inhibits T-cell activation markers as well as cytotoxic molecule production as granzyme B and IFN-γ. Furthermore, ßig-h3 inhibits early T-cell receptor signaling by repressing the activation of the early kinase protein Lck. Moreover, ßig-h3-treated T cells are unable to induce T1D upon transfer in Rag2 knockout mice. Our study demonstrates for the first time that T-cell activation is modulated by ßig-h3, an islet extracellular protein, in order to efficiently avoid autoimmune response.

Islet Cells Serve as Cells of Origin of Pancreatic Gastrin-Positive Endocrine Tumors.

The cells of origin of pancreatic gastrinomas remain an enigma, since no gastrin-expressing cells are found in the normal adult pancreas. It was proposed that the cellular origin of pancreatic gastrinomas may come from either the pancreatic cells themselves or gastrin-expressing cells which have migrated from the duodenum. In the current study, we further characterized previously described transient pancreatic gastrin-expressing cells using cell lineage tracing in a pan-pancreatic progenitor and a pancreatic endocrine progenitor model. We provide evidence showing that pancreatic gastrin-expressing cells, found from embryonic day 12.5 until postnatal day 7, are derived from pancreatic Ptf1a(+) and neurogenin 3-expressing (Ngn3(+)) progenitors. Importantly, the majority of them coexpress glucagon, with 4% coexpressing insulin, indicating that they are a temporary subpopulation of both alpha and beta cells. Interestingly, Men1 disruption in both Ngn3 progenitors and beta and alpha cells resulted in the development of pancreatic gastrin-expressing tumors, suggesting that the latter developed from islet cells. Finally, we detected gastrin expression using three human cohorts with pancreatic endocrine tumors (pNETs) that have not been diagnosed as gastrinomas (in 9/34 pNETs from 6/14 patients with multiple endocrine neoplasia type 1, in 5/35 sporadic nonfunctioning pNETs, and in 2/20 sporadic insulinomas), consistent with observations made in mouse models. Our work provides insight into the histogenesis of pancreatic gastrin-expressing tumors.

The conditional expression of KRAS G12D in mouse pancreas induces disorganization of endocrine islets prior the onset of ductal pre-cancerous lesions.

BACKGROUND/OBJECTIVES: Pdx1-Cre; LSL-KRAS(G12D) mice develop premalignant pancreatic ductal lesions that can possibly progress spontaneously to pancreatic ductal adenocarcinoma (PDAC). Although Pdx1-Cre is expressed in the embryonic endoderm, which gives rise to all pancreatic lineages, the possible consequences of KRAS(G12D) expression in the endocrine compartment have never been finely explored. METHODS: We examined by histology whether Pdx1-driven expression of KRAS(G12D) could induce islets of Langerhans defects. RESULTS: We observed in Pdx1-Cre; LSL-KRAS(G12D) early disorganization of the endocrine compartment including i) hyperplasia affecting all the endocrine lineages, ii) ectopic onset of Ck19-positive (ductal-like) structures within the endocrine islets, and iii) the presence of islet cells co-expressing glucagon and insulin, all occurring before the onset of ducts lesions. CONCLUSIONS: This work indicates that expression of KRAS(G12D) in Pdx1-expressing cells during embryogenesis affects the endocrine pancreas, and highlights the need to deepen possible consequences on both glucose metabolism and PDAC initiation.

Generation of a conditional mouse model to target Acvr1b disruption in adult tissues.

Alk4 is a type I receptor that belongs to the transforming growth factor-beta (TGF-ß) family. It takes part in the signaling of TGF-ß ligands such as Activins, Gdfs, and Nodal that had been demonstrated to participate in numerous mechanisms ranging from early embryonic development to adult-tissue homeostasis. Evidences indicate that Alk4 is a key regulator of many embryonic processes, but little is known about its signaling in adult tissues and in pathological conditions where Alk4 mutations had been reported. Conventional deletion of Alk4 gene (Acvr1b) results in early embryonic lethality prior gastrulation, which has precluded study of Alk4 functions in postnatal and adult mice. To circumvent this problem, we have generated a conditional Acvr1b floxed-allele by flanking the fifth and sixth exons of the Acvr1b gene with loxP sites. Cre-mediated deletion of the floxed allele generates a deleted allele, which behaves as an Acvr1b null allele leading to embryonic lethality in homozygous mutant animals. A tamoxifen-inducible approach to target disruption of Acvr1b specifically in adult tissues was used and proved to be efficient for studying Alk4 functions in various organs. We report, therefore, a novel conditional model allowing investigation of biological role played by Alk4 in a variety of tissue-specific contexts.

Tif1γ suppresses murine pancreatic tumoral transformation by a Smad4-independent pathway.

Transcriptional intermediary factor 1γ (TIF1γ; alias, TRIM33/RFG7/PTC7/ectodermin) belongs to an evolutionarily conserved family of nuclear factors that have been implicated in stem cell pluripotency, embryonic development, and tumor suppression. TIF1γ expression is markedly down-regulated in human pancreatic tumors, and Pdx1-driven Tif1γ inactivation cooperates with the Kras(G12D) oncogene in the mouse pancreas to induce intraductal papillary mucinous neoplasms. In this study, we report that aged Pdx1-Cre; LSL-Kras(G12D); Tif1γ(lox/lox) mice develop pancreatic ductal adenocarcinomas (PDACs), an aggressive and always fatal neoplasm, demonstrating a Tif1γ tumor-suppressive function in the development of pancreatic carcinogenesis. Deletion of SMAD4/DPC4 (deleted in pancreatic carcinoma locus 4) occurs in approximately 50% of human cases of PDAC. We, therefore, assessed the genetic relationship between Tif1γ and Smad4 signaling in pancreatic tumors and found that Pdx1-Cre; LSL-Kras(G12D); Smad4(lox/lox); Tif1γ(lox/lox) (alias, KSSTT) mutant mice exhibit accelerated tumor progression. Consequently, Tif1γ tumor-suppressor effects during progression from a premalignant to a malignant state in our mouse model of pancreatic cancer are independent of Smad4. These findings establish, for the first time to our knowledge, that Tif1γ and Smad4 both regulate an intraductal papillary mucinous neoplasm-to-PDAC sequence through distinct tumor-suppressor programs.