Michael D. Sitrin

Comparison of gastric emptying of a nondigestible capsule to a radio-labelled meal in healthy and gastroparetic subjects

Background  Gastric emptying scintigraphy (GES) using a radio‐labelled meal is used to measure gastric emptying. A nondigestible capsule, SmartPill, records luminal pH, temperature, and pressure during gastrointestinal transit providing a measure of gastric emptying time (GET).

Vitamin D deficiency and bone disease in patients with Crohn's disease

The prevalence of vitamin D deficiency in Crohns disease and the relationship of vitamin D status to metabolic bone disease have not been fully characterized. Serum 25-hydroxyvitamin D was measured in 82 patients with Crohns disease; 65% of Crohns disease patients had a low serum 25-hydroxyvitamin D concentration; 25% had deficient levels (less than 10 ng/ml). The lowest 25-hydroxyvitamin D levels were observed in patients with previous ileal resections. Nine patients were studied in detail including transiliac needle bone biopsies; 6 had osteomalacia and 3 osteoporosis. Six patients had repeat bone biopsies 9 to 18 mo after vitamin D treatment. Three patients with osteomalacia and low serum 25-hydroxyvitamin D levels showed histologic improvement after therapy with oral vitamin D restored serum 25-hydroxyvitamin D levels to normal. The adequacy of therapy was assessed accurately by monitoring serum 25-hydroxyvitamin D concentration. Three patients with metabolic bone disease with normal serum 25-hydroxyvitamin D levels at diagnosis did not show histologic improvement after receiving vitamin D.

1,25(OH)2 vitamin D3 stimulates membrane phosphoinositide turnover, activates protein kinase C, and increases cytosolic calcium in rat colonic epithelium.

The hormonal form of vitamin D, 1,25(OH)2 vitamin D3 [1,25(OH)2D3], regulates colonic calcium absorption and colonocyte proliferation and differentiation. In this study, we have examined the effect of 1,25(OH)2D3 on membrane phosphoinositide turnover, protein kinase C activation, and regulation of intracellular calcium concentration [( Ca+2]i) in isolated rat colonic epithelium. In a concentration-dependent manner, 1,25(OH)2D3 stimulated breakdown of membrane phosphoinositides within 15 s, generating diacylglycerol and inositol 1,4,5-triphosphate (IP3). 1,25(OH)2D3 rapidly activated colonic protein kinase C, with maximal translocation of activity from the cytosol to the membrane occurring within 1 min of exposure to the secosteroid. Studies performed in isolated colonocytes with the fluorescent dye fura-2 demonstrated that 10(-8) M 1,25(OH)2D3 caused a rapid rise in [Ca+2]i which then transiently decreased before rising to a new plateau value. When these experiments were performed in a calcium-free buffer, an increase in [Ca+2]i was observed, but both the transient and secondary rise were diminished in magnitude, suggesting that 1,25(OH)2D3 may stimulate both release of intracellular calcium stores and calcium influx. 1,25(OH)2D3 stimulated [3H]thymidine uptake in rat colonocytes, 4 h after an in vivo injection. These studies indicate that 1,25(OH)2D3 exerts a rapid influence on membrane phosphoinositide metabolism which may mediate certain of the secosteroids effects on colonocyte calcium transport and proliferation.

Vitamin D's role in cell proliferation and differentiation

Vitamin D has pleiotropic effects that go beyond its traditional role in calcium homeostasis. Hundreds of genes with vitamin D receptor response elements directly or indirectly influence cell cycling and proliferation, differentiation, and apoptosis. Vitamin D compounds also have effects on cell function that are nongenomic. The noncalcemic actions of vitamin D influence normal and pathological cell growth, carcinogenesis, immune function, and cardiovascular physiology. This review examines many of the various mechanisms by which vitamin D alters cellular growth and differentiation and explores cell-specific factors that influence responsiveness to vitamin D.

Do Stool Form and Frequency Correlate With Whole-Gut and Colonic Transit? Results From a Multicenter Study in Constipated Individuals and Healthy Controls

OBJECTIVES:Despite a lack of supportive data, stool form and stool frequency are often used as clinical surrogates for gut transit in constipated patients. The aim of this study was to assess the correlation between stool characteristics (form and frequency) and gut transit in constipated and healthy adults.METHODS:A post hoc analysis was performed on 110 subjects (46 chronic constipation) from nine US sites recording stool form (Bristol Stool Scale) and frequency during simultaneous assessment of whole-gut and colonic transit by wireless motility capsule (WMC) and radio-opaque marker (ROM) tests. Stool form and frequency were correlated with transit times using Spearmans rank correlation. Accuracy of stool form in predicting delayed transit was assessed by receiver operating characteristic analysis.RESULTS:In the constipated adults (42 females, 4 males), moderate correlations were found between stool form and whole-gut transit measured by WMC (r=−0.61, P<0.0001) or ROM (−0.45, P=0.0016), as well as colonic transit measured by WMC (−0.62, P<0.0001). A Bristol stool form value <3 predicted delayed whole-gut transit with a sensitivity of 85% and specificity of 82% and delayed colonic transit with a sensitivity of 82% and specificity of 83%. No correlation between stool form and measured transit was found in healthy adults, regardless of gender. No correlation was found between stool frequency and measured transit in constipated or healthy adults. The correlation between stool frequency and measured transit remained poor in constipated adults with <3 bowel movements per week.CONCLUSIONS:Stool form predicts delayed vs. normal transit in adults. However, only a moderate correlation exists between stool form and measured whole-gut or colonic transit time in constipated adults. In contrast, stool frequency is a poor surrogate for transit, even in those with reduced stool frequency.

The assessment of regional gut transit times in healthy controls and patients with gastroparesis using wireless motility technology

Background  Wireless pH and pressure motility capsule (wireless motility capsule) technology provides a method to assess regional gastrointestinal transit times.

Motility of the antroduodenum in healthy and gastroparetics characterized by wireless motility capsule.

Background  The wireless motility capsule (WMC) measures intraluminal pH and pressure, and records transit time and contractile activity throughout the gastrointestinal tract. Our hypothesis is that WMC can differentiate antroduodenal pressure profiles between healthy people and patients with upper gut motility dysfunctions.

Vitamin D receptor is not required for the rapid actions of 1,25-dihydroxyvitamin D3 to increase intracellular calcium and activate protein kinase C in mouse osteoblasts

The rapid, non‐genomic actions of 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] have been well described, however, the role of the nuclear vitamin D receptor (VDR) in this pathway remains unclear. To address this question, we used VDR(+/+) and VDR(−/−) osteoblasts isolated from wild‐type and VDR null mice to study the increase in intracellular calcium ([Ca2+]i) and activation of protein kinase C (PKC) induced by 1,25(OH)2D3. Within 1 min of 1,25(OH)2D3 (100 nM) treatment, an increase of 58 and 53 nM in [Ca2+]i (n = 3) was detected in VDR(+/+) and VDR(−/−) cells, respectively. By 5 min, 1,25(OH)2D3 caused a 2.1‐ and 1.9‐fold increase (n = 6) in the phosphorylation of PKC substrate peptide acetylated‐MBP4–14 in VDR(+/+) and VDR(−/−) osteoblasts. The 1,25(OH)2D3‐induced phosphorylation was abolished by GF109203X, a general PKC inhibitor, in both cell types, confirming that the secosteroid induced PKC activity. Moreover, 1,25(OH)2D3 treatment resulted in the same degree of translocation of PKC‐α and PKC‐δ, but not of PKC‐ζ, from cytosol to plasma membrane in both VDR(+/+) and VDR(−/−) cells. These experiments demonstrate that the 1,25(OH)2D3‐induced rapid increases in [Ca2+]i and PKC activity are neither mediated by, nor dependent upon, a functional nuclear VDR in mouse osteoblasts. Thus, VDR is not essential for these rapid actions of 1,25(OH)2D3 in osteoblasts.

Pulmonary Deposition of Calcium Phosphate Crystals as a Complication of Home Total Parenteral Nutrition

A patient on home total parenteral nutrition (TPN) developed a diffuse granulomatous interstitial pneumonitis secondary to calcium phosphate deposition. Calcium and phosphorus concentrations in the TPN formula were not unusually high, indicating that other factors contributed to calcium phosphate crystallization. The effects of duration of storage of the TPN formulation, solution temperature, pH, and magnesium concentration on calcium phosphate precipitation are discussed.

Dietary triacylglycerol modulates sodium-dependent d-glucose transport, fluidity and fatty acid composition of rat small intestinal brush-border membrane

Rats were maintained on nutritionally complete diets enriched in unsaturated (menhaden fish oil) or saturated (butter fat) triacylglycerols. After 4 weeks, the animals were killed, proximal small intestinal brush-border membranes were prepared, and examined and compared with respect to their lipid composition, molecular species of phosphatidylcholine, lipid fluidity and sodium-dependent D-glucose transport. Membranes prepared from the two dietary groups were found to possess similar ratios of cholesterol/phospholipid (mol/mol), sphingomyelin/phosphatidylcholine (mol/mol), and protein/lipid (w/w). In contrast to these findings, however, striking differences were noted in the total fatty acid compositions of these membranes. Plasma membranes prepared from animals fed the fish oil diet possessed higher percentages of saturated fatty acids as well as (n - 3) unsaturated fatty acids and lower percentages of monounsaturated and (n - 6) unsaturated fatty acids than those prepared from animals fed the butter fat diet. Analysis of the molecular species of phosphatidylcholine by HPLC, moreover, revealed that membranes from rats fed fish oil had higher levels of 16:0-20:5, 16:0-22:6 and 18:0-20:5 and lower levels of 18:0-18:2 and 16:0-18:1 than their butter fat counterparts. As assessed by steady-state fluorescence polarization, differential polarized phase fluorometric and excimer/monomer fluorescence intensity techniques using various fluorophores, the lipid fluidity of membranes from rats fed fish oil was also found to be significantly lower compared to membranes from rats fed butter fat. Finally, comparison of the kinetic parameters of Na+-dependent D-glucose transport revealed that fish oil-membrane vesicles had a higher maximum velocity (Vmax) than butter fat membrane vesicles but a similar Km for glucose.