An Atypical Presentation of a Patient With Postprandial Hypoglycemic Induced Seizures

Background: Insulinomas are exceptionally uncommon pancreatic islet cell neuroendocrine tumors. Typically, insulinoma induced hypoglycemia occurs exclusively in the fasting state in 73 percent, reported in a retrospective analysis of 237 patients, whereas 6 percent reported only postprandial symptoms.

Clinical Case: A 53-year-old female with a history of rheumatoid arthritis, obesity, and prediabetes initially admitted for new onset seizures and recurrent spontaneous hypoglycemic episodes. She experienced recurrent, symptomatic, post-prandial, hypoglycemia daily for the past 8 years. Each episode was closely associated with a high carbohydrate meal, inducing a post-prandial hypoglycemia more consistently and more profoundly than intermittent fasting. Symptoms of lightheadedness, shakiness, and seizure were exacerbated by each carbohydrate meal. Initial labs revealed serum glucose of 35 mg/dl. After recovery with dextrose infusion, a brief fasting trial less than 24 hours was performed with no recurrence of hypoglycemia. However, a mixed meal study utilizing watermelon resulted in a postprandial serum hypoglycemia of 28 mg/dl, provoking a seizure within 30 minutes. During her hospitalization, recurrent hypoglycemia was found during the postprandial period rather than intermittent fasting periods requiring dextrose infusion and octreotide. A Hypoglycemia panel sent during the initial episode was consistent with endogenous hyperinsulinism (Serum glucose=35, Insulin level=24, Proinsulin=166, C-peptide=0.9, BHB=undetectable, Sulfonurea=negative). A subsequent CT of the abdomen/pelvis revealed a mass associated with the pancreatic tail, measuring 4.1 x 4.4 x 5.2 cm concerning for pancreatic malignancy. A fine needle aspiration followed by a distal pancreatectomy and splenectomy with histopathological and immuno-histochemical evaluation confirming a well differentiated (grade 1), 5.0 x 4.5 x 3.0 cm, neuroendocrine tumor (insulinoma). Her recovery, post-operatively, was complicated by an intraabdominal abscess, left pleural effusion, necessitating insulin therapy for hyperglycemia believed to be secondary to morbid obesity, weight gain, and insulin resistance. Hypoglycemic symptoms resolved, blood glucose normalized, and insulin therapy was weaned over the following 3 months and she remains on metformin to date with no evidence of recurrence.

Conclusion: Although rare, an insulinoma should be considered in the differential diagnosis of any individual with recurrent episodes of frequent symptomatic hypoglycemia. The classical clinical manifestation of an insulinoma is a fasting hypoglycemia, with distinct episodes of autonomic symptoms. However, postprandial symptoms have been reported with increasing frequency. Here we present a case of surgically confirmed insulinoma with predominantly post-prandial hypoglycemia.

BINDING SITE ANALYSIS OF THE CAENORHABDITIS ELEGANS NR4A NUCLEAR RECEPTOR NHR-6 DURING DEVELOPMENT

Members of the NR4A subfamily of nuclear receptors make up a highly conserved, functionally diverse group of transcription factors implicated in a multitude of cellular processes such as proliferation, differentiation, apoptosis, metabolism and DNA repair. The gene nhr-6, which encodes the sole C. elegans NR4A nuclear receptor homolog, has a critical role in organogenesis and regulates the development of the spermatheca organ system. Our previous work revealed that nhr-6 is required for spermatheca cell divisions in late L3 and early L4 and spermatheca cell differentiation during the mid L4 stage. Here, we utilized chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) to identify NHR-6 binding sites during both the late L3/early L4 and mid L4 developmental stages. Our results revealed 30,745 enriched binding sites for NHR-6, ~70% of which were within 3 kb upstream of a gene transcription start site. Binding sites for a cohort of candidate target genes with probable functions in spermatheca organogenesis were validated through qPCR. Reproductive and spermatheca phenotypes were also evaluated for these genes following a loss-of-function RNAi screen which revealed several genes with critical functions during spermatheca organogenesis. Our results uncovered a complex nuclear receptor regulatory network whereby NHR-6 regulates multiple cellular processes during spermatheca organogenesis.

A web-based restriction endonuclease tool for mycobacteriophage cluster prediction

A recent explosion in the amount of genomic data has revealed a large genetic diversity in the bacteriophages that infect Mycobacterium smegmatis. In an effort to assess the novelty of newly described mycobacteriophage isolates and provide a preliminary determination of their probable cluster assignment prior to full genome sequencing, we have developed a systematic approach that relies on restriction endonuclease analysis. We demonstrate that a web-based tool, the Phage Enzyme Tool (or PET), is capable of rapidly facilitating this analysis and exhibits reliability in the putative placement of mycobacteriophages into specific clusters of previously sequenced phages. We propose that this tool represents a useful analytical step in the initial study of phage genomes and that this tool will increase the efficiency of phage genome characterization and enhance the educational activities involving mycobacteriophage discovery.

C. elegans nuclear receptor NHR-6 functionally interacts with the jun-1 transcription factor during spermatheca development

The NR4A nuclear receptor NHR-6 is an essential regulator of spermatheca organogenesis in C. elegans. In this study, we perform a focused, RNAi-based screen to identify modifiers of partial nhr-6 loss of function. Ninety-eight genes that encode signaling proteins expressed in the spermatheca were screened for enhancement of the nhr-6 RNAi phenotype. We identify the C. elegans gene jun-1, which encodes the homolog of the Jun transcription factor, as a strong enhancer of nhr-6 partial loss of function. We show that nhr-6 and jun-1 function together to regulate development of the spermatheca and are necessary for generating an organ with the normal number of cells. jun-1 is expressed in all cells of the developing spermatheca. We also provide evidence that NHR-6 and JUN-1 can physically interact in a yeast two-hybrid assay. Our results provide in vivo evidence that NR4A nuclear receptor and Jun transcription factor interactions are essential in regulating developmental processes in metazoans.

Expanding the diversity of mycobacteriophages: insights into genome architecture and evolution

Mycobacteriophages are viruses that infect mycobacterial hosts such as Mycobacterium smegmatis and Mycobacterium tuberculosis. All mycobacteriophages characterized to date are dsDNA tailed phages, and have either siphoviral or myoviral morphotypes. However, their genetic diversity is considerable, and although sixty-two genomes have been sequenced and comparatively analyzed, these likely represent only a small portion of the diversity of the mycobacteriophage population at large. Here we report the isolation, sequencing and comparative genomic analysis of 18 new mycobacteriophages isolated from geographically distinct locations within the United States. Although no clear correlation between location and genome type can be discerned, these genomes expand our knowledge of mycobacteriophage diversity and enhance our understanding of the roles of mobile elements in viral evolution. Expansion of the number of mycobacteriophages grouped within Cluster A provides insights into the basis of immune specificity in these temperate phages, and we also describe a novel example of apparent immunity theft. The isolation and genomic analysis of bacteriophages by freshman college students provides an example of an authentic research experience for novice scientists.