Glucagon-like Peptide-2 Acutely Enhances Chylomicron Secretion in Humans Without Mobilizing Cytoplasmic Lipid Droplets.

CONTEXT: A portion of ingested fats are retained in the intestine for many hours before they are mobilized and secreted in chylomicron (CM) particles. Factors such as glucagon-like peptide-2 (GLP-2) and glucose can mobilize these stored intestinal lipids and enhance CM secretion. We have recently demonstrated in rodents that GLP-2 acutely enhances CM secretion by mechanisms that do not involve the canonical CM synthetic assembly and secretory pathways. OBJECTIVE: To further investigate the mechanism of GLP-2's potent intestinal lipid mobilizing effect, we examined intracellular cytoplasmic lipid droplets (CLDs) in intestinal biopsies of humans administered GLP-2 or placebo. DESIGN, SETTING, PATIENTS, AND INTERVENTIONS: A single dose of placebo or GLP-2 was administered subcutaneously 5 hours after ingesting a high-fat bolus. In 1 subset of participants, plasma samples were collected to quantify lipid and lipoprotein concentrations for 3 hours after placebo or GLP-2. In another subset, a duodenal biopsy was obtained 1-hour after placebo or GLP-2 administration for transmission electron microscopy and proteomic analysis. RESULTS: GLP-2 significantly increased plasma triglycerides by 46% (P = 0.009), mainly in CM-sized particles by 133% (P = 0.003), without reducing duodenal CLD size or number. Several proteins of interest were identified that require further investigation to elucidate their potential role in GLP-2-mediated CM secretion. CONCLUSIONS: Unlike glucose that mobilizes enterocyte CLDs and enhances CM secretion, GLP-2 acutely increased plasma CMs without significant mobilization of CLDs, supporting our previous findings that GLP-2 does not act directly on enterocytes to enhance CM secretion and most likely mobilizes secreted CMs in the lamina propria and lymphatics.

Oral Glucose Mobilizes Triglyceride Stores From the Human Intestine.

BACKGROUND & AIMS: The small intestine regulates plasma triglyceride (TG) concentration. Within enterocytes, dietary TGs are packaged into chylomicrons (CMs) for secretion or stored temporarily in cytoplasmic lipid droplets (CLDs) until further mobilization. We and others have shown that oral and intravenous glucose enhances CM particle secretion in human beings, however, the mechanisms through which this occurs are incompletely understood. METHODS: Two separate cohorts of participants ingested a high-fat liquid meal and, 5 hours later, were assigned randomly to ingest either a glucose solution or an equivalent volume of water. In 1 group (N = 6), plasma and lipoprotein TG responses were assessed in a randomized cross-over study. In a separate group (N = 24), duodenal biopsy specimens were obtained 1 hour after ingestion of glucose or water. Ultrastructural and proteomic analyses were performed on duodenal biopsy specimens. RESULTS: Compared with water, glucose ingestion increased circulating TGs within 30 minutes, mainly in the CM fraction. It decreased the total number of CLDs and the proportion of large-sized CLDs within enterocytes. We identified 2919 proteins in human duodenal tissue, 270 of which are related to lipid metabolism and 134 of which were differentially present in response to glucose compared with water ingestion. CONCLUSIONS: Oral glucose mobilizes TGs stored within enterocyte CLDs to provide substrate for CM synthesis and secretion. Future studies elucidating the underlying signaling pathways may provide mechanistic insights that lead to the development of novel therapeutics for the treatment of hypertriglyceridemia.

Necrotizing glomerulonephritis caused by Bartonella henselae endocarditis.

Glomerulonephritis secondary to endocarditis is uncommon and usually associated with valvular infection by blood culture-positive bacteria. We report 3 cases of necrotizing glomerulonephritis associated with culture-negative endocarditis caused by Bartonella henselae. Two of the patients presented with renal abnormalities and were investigated for endocarditis after results of renal biopsy. All 3 patients had an immune complex-mediated necrotizing and crescentic glomerulonephritis with mesangial and capillary wall deposition of immunoglobulin M (IgM), IgG, and C3. Electron microscopy showed immune-type electron-dense deposits in the mesangium and segmental subendothelial (2 cases) or subepithelial (1 case) deposits. Patients were treated with antibiotics, including azithromycin or doxycycline and ceftriaxone or tobramycin. In addition, 2 patients were administered steroids and 2 patients underwent valve replacement surgery. The 2 patients who underwent cardiac surgery were discharged from the hospital with stable renal function. The third patient died 4 months after hospital admission of renal failure. In conclusion, glomerulonephritis caused by B henselae endocarditis is an immune complex-mediated disease characterized by segmental necrotizing and crescentic glomerular lesions that can respond to aggressive medical and surgical therapy.

Three atypical cases of Wilson disease: assessment of the Leipzig scoring system in making a diagnosis.

BACKGROUND/AIMS: The diagnosis of this condition in the absence of any neurological findings may pose a dilemma. In 2001, experts from The 8th International Conference on Wilson disease (WD) and Menkes disease in Leipzig, Germany proposed a scoring system that may facilitate diagnosis of WD. METHODS/RESULTS: Three patients were identified as having an atypical presentation of WD as they all presented after the age 40. Two of the three presented with established cirrhosis, and none had any neuropsychiatric manifestations. All three patients fulfilled the Leipzig diagnostic criteria proposed by EASL prior to confirmatory mutation analysis. Patient A died of liver failure despite treatment. Patients B and C have remained with stable liver disease on chelation therapy. CONCLUSIONS: We believe these patients represent a group most likely to be missed in the diagnostic work-up of liver disease due to a combination of atypical features such as older age of onset, presence of other confounders for liver disease, and sometimes absence of Kayser-Fleischer rings. The Leipzig scoring system proposed in 2003 was helpful in support of an initial diagnosis of Wilson disease in these patients, validated later by genetic testing.

Distinguishing nonalcoholic steatohepatitis from fatty liver: serum-free fatty acids, insulin resistance, and serum lipoproteins.

OBJECTIVES: The prognosis of nonalcoholic fatty liver disease is determined by liver biopsy; steatohepatitis can be progressive whereas fatty liver is benign. Insulin resistance and increased hepatic-free fatty acids are central to the pathophysiology of this disorder. Our objective was to assess whether serum-free fatty acids, lipoproteins, and insulin resistance are increased in steatohepatitis compared with fatty liver and healthy controls, and thus may be potential noninvasive markers for liver disease severity. METHODS: Fifteen subjects with biopsy proven nonalcoholic steatohepatitis, 15 with histological fatty liver, and 15 healthy controls were enrolled. Fasting serum glucose and insulin levels, serum-free fatty acids, HDL, LDL, and cholesterol were collected from each subject. Insulin resistance was calculated using the homeostasis assessment model. RESULTS: Insulin resistance, LDL, and cholesterol-to-HDL ratio values were significantly higher in steatohepatitis, whereas HDL was significantly lower compared with both fatty liver and controls. Free fatty acids were similar in all groups. CONCLUSIONS: Along with insulin resistance, serum LDL, and cholesterol-to-HDL ratio values increase with worsening severity of liver histology, and serum HDL values decline. Free fatty acids, however, do not vary between groups.

Successful treatment of cap polyposis with infliximab.

Cap polyposis is a disorder characterized by bloody diarrhea with rectosigmoid polyps covered by a cap of fibropurulent exudate. The pathogenesis is unknown, but histological features suggest that mucosal prolapse may play a role. Drug therapies are usually unsuccessful, and treatment requires sigmoid resection or, if the disease recurs after initial surgical resection, panproctocolectomy. We report the case of a 36-year-old woman with characteristic clinical, endoscopic, and histological features of cap polyposis. Investigations included normal anorectal manometry and defecography, without evidence of prolapse. The patient's disease was unresponsive to treatment with mesalamine, antibiotics, lidocaine enemas, and corticosteroids. One infusion of infliximab 5 mg/kg provided dramatic symptomatic improvement but minimal endoscopic or histological change. After 4 infliximab infusions at 8-week intervals, endoscopy of the rectum and sigmoid colon was normal, and biopsies showed complete histological resolution of the inflammatory process. Well-being with normal endoscopy and histology has been maintained at 38 months, without further treatment. It was concluded that infliximab is effective therapy for cap polyposis and avoids the requirement for surgery. No clinical evidence was obtained to support mucosal prolapse as a causative factor, but the response to infliximab suggests a role for tumor necrosis factor-alpha in the pathogenesis of this disorder.