The stability of the bile acid analogue [75Se]-selenohomotaurocholic acid (75SeH-CAT) was studied in man. When 75SeHCAT was administered to patients for diagnostic purposes the majority of labeled material present in the feces was found deconjugated. In vitro incubation of 75SeHCAT, by addition of fecal homogenate or with addition of purified enzyme, showed identical deconjugation. The relative differences in polarities of 75SeHCAT, [75Se]-selenohomocholic acid (75SeHCA), [14C]-taurocholic acid (14C-TCA) and [14C]-cholic acid (14C-CA) were estimated by isoelectric focusing and selective chloroform extractions at various pH values. The pI values representing the pH where these molecules become uncharged were for 75SeHCA and 75SeHCAT 3.1, for 14C-TCA 3.0 and for 14C-CA 3.9. These results suggest that from these bile acids only 14C-CA is a candidate for passive absorption in the colon, while 75SeHCA would be far too polar for passive diffusion. Indeed, we could demonstrate the inability of 75SeHCA for passive absorption in healthy persons. In conclusion, 75SeHCAT, specifically selected to monitor active ileal bile acid transport, functions as a good indicator of this process in its conjugated form. In contrast to published data it is susceptible to bacterial degradation, and therefore gives rise to a diminished whole-body retention.
Photodynamic therapy may selectively destroy Barrett's epithelium in the esophagus. To optimize photosensitizer administration, the kinetics of 5-aminolevulinic acid (ALA)-induced porphyrin accumulation in the normal and Barrett's-like esophagus were studied in the rat.Animals received 200 mg/kg ALA intravenously (n = 21) or orally (n = 21). Six rats served as controls. At t = 1, 2, 3, 4, 6, 12, and 24 hr, porphyrin concentration in the esophagus was measured by using chemical extraction, and porphyrin localization was determined by laser scanning microscopy (LSM). In addition, in 20 animals, porphobilinogen deaminase, ferrochelatase, and iron concentration were determined. In a second group (n = 24), an esophagojejunostomy was performed to induce a Barrett's-like esophagus. After 18 weeks, animals received ALA, and LSM was performed at t = 1, 2, 3, 4, 6, 8, and 12 hr.Porphyrin accumulation in normal mucosa was 3.5-fold higher than in muscularis, with a maximum at 3 hr after ALA administration. With LSM, strong homogeneous fluorescence of the squamous epithelium was shown, with minor fluorescence of submucosa and muscularis. In Barrett's-like epithelium, fluorescence was heterogeneous but was also restricted to epithelial cells. There was no difference in fluorescence intensity between Barrett's-like and adjacent squamous epithelium. Porphobilinogen deaminase activity was higher and iron concentration was lower in the mucosa than in the muscularis (P < 0.001).ALA-induced porphyrin accumulation selectively occurs in esophageal mucosa, whether normal or Barrett's-like, compared with the muscularis, with a maximum at 3 hr after ALA administration. Selectivity may be caused by a different activity of heme-synthetic enzymes or relative iron deficiency in the mucosa.
We performed an extended oral glucose tolerance test (OGTT) to investigate the relationship between early and late beta-cell response and type 2 diabetes (T2D) in families of South Asian origin and indigenous Dutch, burdened by T2D. Based on the OGTT, 22 individuals were normoglycemic, 12 glucose intolerant and 23 had T2D in the South Asian families; these numbers were 34, 12 and 18 in the Caucasian families, respectively. The OGTT had 11 blood samplings in 3.5 h for glucose, insulin and C-peptide measurements. Through early and late insulin secretion rate (ISR), the above basal glucose area-under-the-curve after glucose load (glucose disposal) and insulin sensitivity index (ISI), we obtained early and late disposition indices (DI). South Asians on average had lower ISI than Caucasians (3.8 ± 2.9 vs. 6.5 ± 4.7, respectively, P < 0.001), with rapid decline of their early and late DI between normal glucose tolerance versus impaired fasting glucose/impaired glucose tolerance (late DI; P < 0.0001). Adjusted for ISI, age, gender and waist-to-hip ratio, early ISR was significantly associated with glucose disposal in South Asians (β = 0.55[0.186; 0.920]), but not in Caucasians (β = 0.09[-0.257; 0.441]). Similarly, early ISR was strongly associated with late ISR (β = 0.71[0.291; 1.123]; R (2) = 45.5 %) in South Asians, but not in Caucasians (β = 0.27[-0.035; 0.576]; R (2) = 17.4 %), with significant interaction between ethnicity and early ISR (β = 0.341[0.018; 0.664]). Ordinal regression analyses confirmed that all South Asian OGTT subgroups were homogenously resistant to insulin and solely predicted by early ISR (β = -0.782[-1.922; 0.359], β = -0.020[-0.037; -0.002], respectively), while in Caucasian families both ISI and early ISR were related to glucose tolerance state (β = -0.603[-1.105; -0.101], β = -0.066[-0.105; -0.027], respectively). In South Asian individuals, rapid beta-cell deterioration might occur under insulin resistant conditions. As their early insulin response correlates strongly with both glucose disposal and late insulin response, alterations in beta-cell dynamics may give an explanation to their extreme early onset of T2D, although larger prospective studies are required.
The Peutz-Jeghers syndrome (PJS) is a rare hereditary disorder in which gastrointestinal hamartomatous polyposis, mucocutaneous pigmentation, and a predisposition for developing cancer are transmitted in an autosomal dominant fashion. The recently identified LKB1/STK11 gene located at chromosome 19p13.3 is mutated in a number of PJS pedigrees. We performed mutation analysis in 19, predominantly Dutch, PJS families. In 12 of these families, we identified LKB1/STK11 mutations, none of which has been described before. These 12 novel LKB1/STK11 mutations consist of one nonsense mutation, three frameshift deletions, three frameshift insertions, two acceptor splice site mutations, and three missense mutations. In addition, we detected four polymorphisms in LKB1/STK11. In the remaining seven PJS families, we found no apparent abnormalities of the LKB1/STK1I gene, which could reflect the existence of locus heterogeneity in PJS. None of the mutations occurred in more than one family, and a number were demonstrated to have arisen de novo. The diverse array of mutations found, the apparent high mutation rate, as well as the existence of a possible second PJS locus, renders diagnostic or predictive genetic testing in individual patients difficult, although future identification of additional mutations or even gene(s) will help in increasing the yield of direct mutation analysis.
Dyslipidemia precedes type 2 diabetes (T2D) and worsens with increasing glucose intolerance. First degree relatives of T2D patients have an increased risk to develop dyslipidemia and glucose intolerance. The aim of the present study was to assess the relation between the development of dyslipidemia and glucose intolerance in first-degree relatives of T2D patients.Fasting lipoprotein profiles were determined by density gradient ultracentrifugation in T2D patients and their first-degree relatives (42 Caucasians and 33 South Asians), and in 29 normoglycemic controls from non-T2D families. Glucose tolerance, insulin sensitivity index (ISI) and insulin disposition index (DI) were assessed by an extended, frequently sampled oral glucose tolerance test (OGTT), and fractional insulin synthesis rate (FSR) was measured by 13C-leucine enrichment in urinary C-peptide during the OGTT.Of the first-degree relatives, 40, 16 and 19 had NGT, prediabetes and T2D, respectively. NGT family members had lower plasma HDL-cholesterol (HDLC) (1.34 ± 0.07 vs 1.58 ± 0.06 mmol/L; p = 0.015), HDL2-C (0.41 ± 0.05 vs 0.57 ± 0.05 mmol/L; p = 0.021) and HDL3-C (0.62 ± 0.03 vs 0.72 ± 0.02 mmol/L; p = 0.043) than controls. HDL2-C levels tended to decrease with increasing glucose intolerance state. In South Asians, buoyant LDL-C levels decreased with increasing glucose intolerance state (p = 0.006). In South Asian families, HDL-C correlated with both ISI and DI (β 0.42; p = 0.04 and β 0.53; p = 0.01, respectively), whereas HDL2-C and HDL3-C levels correlated with DI (β 0.64; p = 0.002 and β 0.57; p = 0.005, respectively). HDL2-C and plasma triglyceride correlated with FSR (β 0.48; p = 0.033 and β -0.50; p = 0.029, respectively).Low HDL2-C and HDL3-C levels are present in NGT first-degree relatives of T2D patients, and HDL2-C tend to decrease further with increasing glucose intolerance. In South Asian families HDL2-C and HDL3-C levels linked predominantly to deteriorating beta cell function.
ABSTRACT. Increased fecal bile acid loss in cystic fibrosis (CF) may result from ileal dysfunction. A method to quantitate in vitro Na + ‐dependent taurocholate uptake into brush border membrane vesicles prepared from frozen ileum and ileal biopsy specimen is described. This transport across the ileal brush border membrane can be measured selectively, in contrast to in vivo measurements which represent a complex overall process. Preliminary results obtained with ileal specimen of 2 CF patients, suggest that in vitro bile acid uptake is low but not abnormal.
