Lessons from rodent gastric bypass model of enteric hyperoxaluria.

PURPOSE OF REVIEW: The aim of the article is to review studies on bone health and oxalate metabolism/therapeutics in the obese rodent model of Roux-en-Y gastric bypass (RYGB) and examine pathways to decrease procedural morbidity. RECENT FINDINGS: Compared with controls, RYGB rodents have up to 40-fold more fat in their stool (steatorrhea) which positively correlates to increased urinary oxalate. These unabsorbed intestinal fatty acids bind calcium and prevent gut calcium oxalate formation, increasing soluble luminal oxalate availability and absorption (enteric hyperoxaluria). When intraluminal fecal fat exceeded about 175 mg/24 h in our model, more paracellular and transcellular oxalate transport across the distal colon occurred. Increasing dietary calcium and colonization with Oxalobacter formigenes reduced hyperoxaluria, whereas vitamin B6 supplementation did not. RYGB animals, when severely calcium deficient, had bone mineral density loss that could not be rescued with vitamin D supplementation. SUMMARY: The findings of hyperoxaluria, steatorrhea, and decreased bone mineral density are seen in both human and rodent RYGB. Our model suggests that a low-fat, low-oxalate diet combined with calcium supplementation can decrease urinary oxalate and improve skeletal bone health. Our model is a useful tool to study renal and bone RYGB effects. Studies of longer duration are required to further evaluate mechanisms of disease and durability of therapeutics.

Chylomicron retention disease: report of two cases from a Greek Island.

Chylomicron retention disease (CRD), or Anderson disease, is a rare, hereditary cause of fat malabsorption. It is one of the familial hypocholesterolaemia syndromes, along with homozygous hypobetalipoproteinaemia (HBL) and abetalipoproteinaemia (ABL). We report clinical, laboratory and histological data as well as molecular DNA analysis in the case of a 4-month-old boy with failure to thrive and steatorrhea who was diagnosed with CRD. His mother's first cousin, who was diagnosed as hypobetalipoproteinaemia 30 years ago, was also reviewed and his diagnosis was revised to CRD. Both patients were treated with a low fat diet and supplementation with fat-soluble vitamins resulting in significant improvement. In conclusion, CRD is a well-defined cause of fat malabsorption and can be distinguished from other forms of familial hypocholesterolaemia because of its specific lipid profile.

Anderson's disease/chylomicron retention disease in a Japanese patient with uniparental disomy 7 and a normal SAR1B gene protein coding sequence.

BACKGROUND: Anderson's Disease (AD)/Chylomicron Retention Disease (CMRD) is a rare hereditary hypocholesterolemic disorder characterized by a malabsorption syndrome with steatorrhea, failure to thrive and the absence of chylomicrons and apolipoprotein B48 post-prandially. All patients studied to date exhibit a mutation in the SAR1B gene, which codes for an essential component of the vesicular coat protein complex II (COPII) necessary for endoplasmic reticulum to Golgi transport. We describe here a patient with AD/CMRD, a normal SAR1B gene protein coding sequence and maternal uniparental disomy of chromosome 7 (matUPD7). METHODS AND RESULTS: The patient, one of two siblings of a Japanese family, had diarrhea and steatorrhea beginning at five months of age. There was a white duodenal mucosa upon endoscopy. Light and electron microscopy showed that the intestinal villi were normal but that they had lipid laden enterocytes containing accumulations of lipid droplets in the cytoplasm and lipoprotein-size particles in membrane bound structures. Although there were decreased amounts in plasma of total- and low-density lipoprotein cholesterol, apolipoproteins AI and B and vitamin E levels, the triglycerides were normal, typical of AD/CMRD. The presence of low density lipoproteins and apolipoprotein B in the plasma, although in decreased amounts, ruled out abetalipoproteinemia. The parents were asymptomatic with normal plasma cholesterol levels suggesting a recessive disorder and ruling out familial hypobetalipoproteinemia. Sequencing of genomic DNA showed that the 8 exons of the SAR1B gene were normal. Whole genome SNP analysis and karyotyping revealed matUPD7 with a normal karyotype. In contrast to other cases of AD/CMRD which have shown catch-up growth following vitamin supplementation and a fat restricted diet, our patient exhibits continued growth delay and other aspects of the matUPD7 and Silver-Russell Syndrome phenotypes. CONCLUSIONS: This patient with AD/CMRD has a normal SAR1B gene protein coding sequence which suggests that factors other than the SAR1B protein may be crucial for chylomicron secretion. Further, this patient exhibits matUPD7 with regions of homozygosity which might be useful for elucidating the molecular basis of the defect(s) in this individual. The results provide novel insights into the relation between phenotype and genotype in these diseases and for the mechanisms of secretion in the intestine.

The effect of zinc supplements in cystic fibrosis patients.

AIM: To study the effect of Zn supplements in cystic fibrosis (CF) on disease evolution. METHODS: A retrospective study of all CF patients treated with Zn supplements (January 2002 to December 2004). Data from patient files for the year before and the first year of supplementation were compared. The controls were CF patients with normal serum Zn and without Zn supplementation. RESULTS: 21 patients (7 females), median age 8.9 (interquartile range 13.1) years, received 5 mg/kg Zn sulfate/day (maximum 150 mg). The number of infections decreased from 3 (1.25) to 2 (2.0) (tied p < 0.02) and the forced expiratory volume in 1 s (FEV(1)) increased from 72.0 (38.4) to 76.5 (52)% (p < 0.02). Energy intake improved (92.3 (14.5) to 117.0 (28.5)%; tied p < 0.02), as did weight for height (W/H; 90 (9.4) to 94 (8.5)%; tied p = 0.043). In the CF control patients the number of infections (2.0 (2.0)), energy intake (116 (43.3)%) and nutritional status remained stable (W/H 99 (17.2)%), but pulmonary function decreased significantly (DeltaFEV(1) loss of 2.0 (8.0)%). There was a significantly different evolution for the change in forced vital capacity (p < 0.004) and DeltaFEV(1) (p < 0.001) between supplemented and control patients. CONCLUSIONS: Analysis of the clinical data on Zn supplementation in CF showed beneficial effects in Zn-deficient CF patients. These results must be confirmed in a prospective double-blind randomized control trial.

Unresponsive or non-compliant steatorrhea in cystic fibrosis?

In 105 pancreatic insufficient CF patients (steatorrhea and low fecal elastase-1 concentrations), the effectiveness of pancreatic enzyme therapy (PET) has been assessed (fecal fat losses and coefficient of fat reabsorption). Eight unresponsive subjects were checked for PET compliance with fecal chymotrypsin assay. Three patients were documented to be non-compliant. Unresponsive patients should undergo evaluation for PET compliance.