Plant-Derived Bioactive Lipids Impacts Glucose Homeostasis and Energy Metabolism in Mice

There is a crucial need to identify and test sustainable alternatives to fish oil as a means to supplement dietary omega (n-3) fatty acids which have demonstrated health benefits to humans with metabolic syndrome and its associated diseases. Echium oil has a high content of the n-3 fatty acid stearidonic acid (SDA), a precursor of the bioactive lipids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fatty cold-water fish, with known or possible functions to improve metabolism and delay the onset of or prevent diabetes. To characterize the effects of dietary Echium oil (EO) vs. fish oil (FO), the oils were formulated into either a low-fat (10% kcal; LF) or high fat (60% kcal; HF) diabetogenic diet and fed to male C57BL/6 Tac mice for 12 weeks. Compared to the low-fat or high-fat controls without the supplementation of EO or FO, EO and FO diets had no effect on blood glucose concentrations or plasma insulin levels throughout the study. The EO-enriched HF diet improved glucose tolerance by week 12 compared to the HF-CON (p\u3c0.05) and HF-FO (p\u3c0.1) groups. EO supplementation reduced visceral fat weight without affecting body mass, promoted a metabolically favorable high polyunsaturated fatty acid (PUFA) to saturated fatty acid (SFA) ratio in adipose and muscle tissues compared to the HF-CON and HF-FO diet groups, and led to higher tissue EPA and DHA concentrations compared to both LF and HF CON (p\u3c0.1). Tissue EPA and DHA in EO were not as high as the concentrations found in mice fed the FO diets for both HF and LF. In conclusion, EO-supplemented diets in mice appear to have distinct effects from FO diets that may be exploited in future strategies to curtail metabolic disorders

Hepatocyte Nuclear Factor 3beta is Involved in Pancreatic Beta-Cell-Specific Transcription of the PDX-1 Gene

The mammalian homeobox gene pdx-1 is expressed in pluripotent precursor cells in the dorsal and ventral pancreatic bud and duodenal endoderm, which will produce the pancreas and the rostral duodenum. In the adult, pdx-1 is expressed principally within insulin-secreting pancreatic islet b cells and cells of the duodenal epithelium. Our objective in this study was to localize sequences within the mouse pdx-1 gene mediating selective expression within the islet. Studies of transgenic mice in which a genomic fragment of the mouse pdx-1 gene from kb 24.5 to 18.2 was used to drive a b-galactosidase reporter showed that the control sequences sufficient for appropriate developmental and adult specific expression were contained within this region. Three nuclease-hypersensitive sites, located between bp 22560 and 21880 (site 1), bp 21330 and 2800 (site 2), and bp 2260 and 1180 (site 3), were identified within the 5*-flanking region of the endogenous pdx-1 gene. Pancreatic b-cell-specific expression was shown to be controlled by sequences within site 1 from an analysis of the expression pattern of various pdx-1–herpes simplex virus thymidine kinase promoter expression constructs in transfected b-cell and non-b-cell lines. Furthermore, we also established that this region was important in vivo by demonstrating that expression from a site 1-driven b-galactosidase reporter construct was directed to islet b-cells in transgenic mice. The activity of the site 1-driven constructs was reduced substantially in b-cell lines by mutating a hepatocyte nuclear factor 3 (HNF3)-like site located between nucleotides 22007 and 21996. Gel shift analysis indicated that HNF3b present in islet b cells binds to this element. Immunohistochemical studies revealed that HNF3b was present within the nuclei of almost all islet b cells and subsets of pancreatic acinar cells. Together, these results suggest that HNF3b, a key regulator of endodermal cell lineage development, plays an essential role in the cell-type-specific transcription of the pdx-1 gene in the pancreas

β-Cell Proliferation, but Not Neogenesis, Following 60% Partial Pancreatectomy Is Impaired in the Absence of FoxM1

OBJECTIVE—This study was designed to determine whether the transcription factor FoxM1 was required for regeneration of β-cell mass via proliferation and/or neogenesis in the adult after 60% partial pancreatectomy (PPx)

The Krüppel-like zinc finger protein Glis3 directly and indirectly activates insulin gene transcription

Glis3 is a member of the Krüppel-like family of transcription factors and is highly expressed in islet β cells. Mutations in GLIS3 cause the syndrome of neonatal diabetes and congenital hypothyroidism (NDH). Our aim was to examine the role of Glis3 in β cells, specifically with regard to regulation of insulin gene transcription. We demonstrate that insulin 2 (Ins2) mRNA expression in rat insulinoma 832/13 cells is markedly increased by wild-type Glis3 overexpression, but not by the NDH1 mutant. Furthermore, expression of both Ins1 and Ins2 mRNA is downregulated when Glis3 is knocked down by siRNA. Glis3 binds to the Ins2 promoter in the cell, detected by chromatin immunoprecipitation. Deletion analysis of Ins2 promoter identifies a sequence (5′-GTCCCCTGCTGTGAA-3′) from −255 to −241 as the Glis3 response element and binding occur specifically via the Glis3 zinc finger region as revealed by mobility shift assays. Moreover, Glis3 physically and functionally interacts with Pdx1, MafA and NeuroD1 to modulate Ins2 promoter activity. Glis3 also may indirectly affect insulin promoter activity through upregulation of MafA and downregulation of Nkx6-1. This study uncovers a role of Glis3 for regulation of insulin gene expression and expands our understanding of its role in the β cell