Pharmaceutical Forced Degradation (Stress Testing) Endpoints: A Scientific Rationale and Industry Perspective

Forced degradation (i.e., stress testing) of small molecule drug substances and products is a critical part of the drug development process, providing insight into the intrinsic stability of a drug that is foundational to the development and validation of stability-indicating analytical methods. There is a lack of clarity in the scientific literature and regulatory guidance as to what constitutes an "appropriate" endpoint to a set of stress experiments. That is, there is no clear agreement regarding how to determine if a sample has been sufficiently stressed. Notably, it is unclear what represents a suitable justification for declaring a drug substance (DS) or drug product (DP) "stable" to a specific forced degradation condition. To address these concerns and to ensure all pharmaceutically-relevant, potential degradation pathways have been suitably evaluated, we introduce a two-endpoint classification designation supported by experimental data. These two endpoints are 1) a % total degradation target outcome (e.g., for "reactive" drugs) or, 2) a specified amount of stress, even in the absence of any degradation (e.g., for "stable" drugs). These recommended endpoints are based on a review of the scientific literature, regulatory guidance, and a forced degradation data set from ten global pharmaceutical companies. The experimental data set, derived from the Campbell et al. (2022) benchmarking study,1 provides justification for the recommendations. Herein we provide a single source reference for small molecule DS and DP forced degradation stress conditions and endpoint best practices to support regulatory submissions (e.g., marketing applications). Application of these forced degradation conditions and endpoints, as part of a well-designed, comprehensive and a sufficiently rigorous study plan that includes both the DS and DP, provides comprehensive coverage of pharmaceutically-relevant degradation and avoids unreasonably extreme stress conditions and drastic endpoint recommendations sometimes found in the literature.

Impact of oral administration of four Lactobacillus strains on Nugent score - systematic review and meta-analysis

We aimed at assessing the evidence for an effect on vaginal dysbiosis by oral administration of a mixture of Lactobacillus strains isolated from vaginal microbiota. For this purpose, we systematically reviewed the literature for randomised clinical trials (RCTs) in which the effect of oral administration of a mixture of four Lactobacillus strains (Lactobacillus crispatus LbV 88 (DSM 22566), Lactobacillus gasseri LbV 150N (DSM 22583), Lactobacillus jensenii LbV 116 (DSM 22567) and Lactobacillus rhamnosus LbV96 (DSM 22560)) on vaginal dysbiosis was examined based on Nugent score. Four RCTs were identified: a double-blind (DB)-RCT in 60 male-to-female transsexual women with neovagina; an open label RCT in 60 pregnant women with herpes virus infection; a DB-RCT in 36 women with bacterial vaginosis; a DB-RCT in 22 postmenopausal breast cancer patients receiving chemotherapy. Only in the three DB-RCTs Nugent score was assessed. The meta-analysis of these trials showed a significant reduction of Nugent score by probiotics compared to placebo in the fixed (standardised mean differences (SMD) -0.561; confidence interval (CI) -0.935 to -0.186; P=0.004 and random effect models (SMD -0.561; CI -0.935 to -0.186; P=0.004). The odds ratio (OR) of the cases presenting with improved Nugent score after probiotics compared to placebo treatment showed a significant effect in the fixed (OR=3.936; CI 1.702 to 9.100; P=0.001) and random effect model (OR=3.902; CI 1.681 to 9.059; P=0.001) Cochran's Q and I2 statistics showed no heterogeneity. This meta-analysis indicates that the oral intake of the pertinent Lactobacillus strains improves the microbial pattern in vaginal dysbiosis.

Glycemic response to low sugar apple juice treated with invertase, glucose oxidase and catalase

BACKGROUND/OBJECTIVES

Investigating the effect on post-prandial glycemic and venous serum insulin response of an apple drink following the conversion of its glucose to gluconate.

SUBJECTS/METHODS

In a double-blind randomized placebo-controlled clinical trial with cross-over design, 30 male adults with impaired fasting glucose (IFG) received a drink of 500 ml: 1. Verum: Apple juice treated with invertase, glucose oxidase/catalase (glucose 0.05 g; gluconate 18.2 g); 2.

CONTROL

Untreated apple juice (free glucose 8.5 g; bound glucose 6.7 g; gluconate below detection limit). Postprandial fingerprick capillary blood glucose and venous serum insulin were measured twice at baseline and at times 0 (start of drink), 15, 30, 45, 60, 90 and 120 min. Gastrointestinal symptoms, stool consistency and satiety were also assessed.

RESULTS

The incremental area under the curve (iAUC₁₂₀) of glucose levels (primary parameter) was significantly lower after verum (mean ± SD: 63.6 ± 46.7 min × mmol/l) compared to control (mean ± SD: 198 ± 80.9 min × mmol/l) (ANOVA F = 137.4, p < 0.001; α = 0.05). Also, iAUC₁₂₀ of venous serum insulin levels (secondary parameter) was significantly lower after verum (mean ± SD: 2045 ± 991 min × mmol/l) compared to control (3864.3 ± 1941 min × mmol/l), (ANOVA F = 52.94, p < 0.001; α = 0.025). Further parameters of glucose metabolism and ISI = 2/[AUC venous serum insulin × AUC glucose +1] were also improved after verum compared to control. Verum increased stool frequency and decreased stool consistency, as assessed by Bristol stool form scale.

CONCLUSIONS

By enzymatic treatment of apple juice its sugar content could be reduced by 21% and postprandial glycemic and venous serum insulin response by 68 and 47%, respectively resulting in a reduction of glycemic load by 74.6% without any adverse gastrointestinal side-effects.

Calcium isotope ratios in blood and urine: A new biomarker for the diagnosis of osteoporosis

We assessed the potential of Calcium (Ca) isotope fractionation measurements in blood (δ^44/42Ca_Blood) and urine (δ^44/42Ca_Urine) as a new biomarker for the diagnosis of osteoporosis. One hundred post-menopausal women aged 50 to 75 years underwent dual-energy X-ray absorptiometry (DXA), the gold standard for determination of bone mineral density. After exclusion of women with kidney failure and vitamin D deficiency (<25 nmol/l) 80 women remained in the study. Of these women 14 fulfilled the standard diagnostic criteria for osteoporosis based on DXA. Both the δ^44/42Ca_Blood (p < 0.001) and δ^44/42Ca_Urine (p = 0.004) values were significantly different in women with osteoporosis (δ^44/42Ca_Blood: −0.99 ± 0.10‰, δ ^44/42Ca_Urine: +0.10 ± 0.21‰, (Mean ± one standard deviation (SD), n = 14)) from those without osteoporosis (δ^44/42Ca_Blood: −0.84 ± 0.14‰, δ^44/42Ca_Urine: +0.35 ± 0.33‰, (SD), n = 66). This corresponded to the average Ca concentrations in morning spot urine samples ([Ca]_Urine) which were higher (p = 0.041) in those women suffering from osteoporosis ([Ca]_{Urine-Osteoporosis}: 2.58 ± 1.26 mmol/l, (SD), n = 14) than in the control group ([Ca]_Urine-_Control: 1.96 ± 1.39 mmol/l, (SD), n = 66). However, blood Ca concentrations ([Ca]_Blood) were statistically indistinguishable between groups ([Ca]_Blood, control: 2.39 ± 0.10 mmol/l (SD), n = 66); osteoporosis group: 2.43 ± 0.10 mmol/l (SD, n = 14) and were also not correlated to their corresponding Ca isotope compositions. The δ^44/42Ca_Blood and δ^44/42Ca_Urine values correlated significantly (p = 0.004 to p = 0.031) with their corresponding DXA data indicating that both Ca isotope ratios are biomarkers for osteoporosis. Furthermore, Ca isotope ratios were significantly correlated to other clinical parameters ([Ca]_Urine, ([Ca]_Urine/Creatinine)) and biomarkers (CRP, CTX/P1NP) associated with bone mineralization and demineralization. From regression analysis it can be shown that the δ^44/42Ca_Blood values are the best biomarker for osteoporosis and that no other clinical parameters need to be taken into account in order to improve diagnosis. Cut-off values for discrimination of subjects suffering from osteoporosis were − 0.85‰ and 0.16‰ for δ^44/42Ca_Blood and δ^44/42Ca_Urine, respectively. Corresponding sensitivities were 100% for δ^44/42Ca_Blood and ~79% for δ^44/42Ca_Urine. Apparent specificities were ~55% for δ^44/42Ca_Blood and ~71%. The apparent discrepancy in the number of diagnosed cases is reconciled by the different methodological approaches to diagnose osteoporosis. DXA reflects the bone mass density (BMD) of selected bones only (femur and spine) whereas the Ca isotope biomarker reflects bone Ca loss of the whole skeleton. In addition, the close correlation between Ca isotopes and biomarkers of bone demineralization suggest that early changes in bone demineralization are detected by Ca isotope values, long before radiological changes in BMD can manifest on DXA. Further studies are required to independently confirm that Ca isotope measurement provide a sensitive, non-invasive and radiation-free method for the diagnosis of osteoporosis.

Effect of a yoghurt drink containing Lactobacillus strains on bacterial vaginosis in women - a double-blind, randomised, controlled clinical pilot trial

Bacterial vaginosis (BV) is characterised by a depletion of lactobacilli in favour of an overgrowth of anaerobic bacteria. It is associated with increased risk for urogenital infections and abortion. In this study we assessed the effect of a yoghurt drink containing Lactobacillus strains on BV. The strains had been isolated from healthy pregnant women and selected for acidification capacity, production of H₂O₂, glycogen utilisation, bile salt tolerance and inhibition of pathogens. Using Amsel criteria BV was diagnosed in 36 women aged ≥18 years with stable menstrual cycle or menopause. They were treated with oral metronidazole for 7 days (2×500 mg/d). Starting with the treatment, women consumed twice daily either verum or placebo during 4 weeks. Verum was 125 g yoghurt containing (besides Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) living strains Lactobacillus crispatus LbV 88 (DSM 22566), Lactobacillus gasseri LbV 150N (DSM 22583), Lactobacillus jensenii LbV 116 (DSM 22567) and Lactobacillus rhamnosus LbV96 (DSM 22560), each 1×107 cfu/ml; placebo was 125 g chemically acidified milk. After 4 weeks of intervention 0 of 17 had BV in the verum group versus 6 of 17 in the s.a. control (0.018 in Fisher Exact test). Amsel score decreased during the intervention period by 4.0 (median) (4.0; 3.0) (25^th; 75^th percentile) in the verum group compared to 2.0 (4.0; 0.0) in the control group (P=0.038 in Mann-Whitney test). Discharge and odour (Amsel criteria 2+3) also decreased by 2.0 (2.0; 1.0) in the verum compared to 1.0 (2.0; 0.0) in the control group (P=0.01) and differed after 4 weeks intervention between the groups 0.0 (0.0; 0.0) versus 1.0 (0.0; 2.0) (P=0.001). Nugent score decreased during the intervention period by 5.5 (7.0;2.3) in the verum compared to 3.0 (6.0;0.5) in the control group (P=0.158). Additional intake of yoghurt containing these probiotic strains improved the recovery rate and symptoms of BV and tended to improve the vaginal microbial pattern.

Effect of quercetin on traits of the metabolic syndrome, endothelial function and inflammation in men with different APOE isoforms

BACKGROUND AND AIMS

The polyphenol quercetin may prevent cardiovascular diseases due to its vasorelaxant and anti-oxidative properties. We investigated the effects of quercetin on risk factors of atherosclerosis, biomarkers of inflammation and oxidative stress, depending on the apolipoprotein E (APOE) genotype.

METHODS AND RESULTS

In a double-blind crossover study 49 healthy male subjects with APOE genotype 3/3 (n = 19), 3/4 (n = 22) and 4/4 (n = 8) consumed 150 mg/d quercetin or placebo for 8 weeks each, intermitted by a three-week washout phase. After each intervention, endothelial function, anthropometry, metabolic and inflammatory parameters were measured in the fasting and postprandial state following a standardized lipid-rich meal. Endothelial function was not changed. In all subjects combined, quercetin significantly decreased waist circumference (P = 0.004) and postprandial systolic blood pressure (P = 0.044). Postprandial triacylglycerol concentrations were significantly decreased and HDL-cholesterol concentrations increased after quercetin as compared to placebo consumption (P = 0.025). Quercetin also moderately increased levels of TNFα (P = 0.024). There was a significant gene-diet interaction for waist circumference and for body mass index (BMI).

CONCLUSIONS

Quercetin supplementation improved some risk factors of cardiovascular disease, yet exerted slightly pro-inflammatory effects. Genotype-dependent effects were seen only on waist circumference and BMI.

On-line gas chromatographic studies of Rf, Zr, and Hf bromides

The Heavy Element Volatility Instrument (HEVI), an on-line isothermal gas chromatography system, has been used to separate the volatile bromide compounds of the group 4 elements Zr and Hf and the transactinide Rf according to their volatilities, and to provide data on the gas phase chemical properties of very short-lived isotopes in amounts as low as a few atoms. For these studies261Rf was produced via the248Cm(18O, 5n) reaction.165-167Hf was produced via the reactionnatEu(19F, xn), and85Zr was produced via thenatCu(28Si, 3p3n) reaction. The half-life for261Rf was measured to be 75±7 seconds.

A Monte Carlo code was used to deduce the enthalpy of adsorption (ΔHa) from the observed volatility and parameters of the chromatography system. The resulting adsorption enthalpies for the Zr, Hf, and Rf tetrabromides are: -108±5 kJ · mol-1, -113±5 kJ · mol-1 and -87±7 kJ · mol-1, respectively.

Volatilities of the group 4 bromides support the conclusion from previous results for the group 4 chlorides that Rf deviates from the trend expected by simple extrapolation of the properties of its lighter homologs in the periodic table. The group 4 bromides are also observed to be less volatile than their respective chlorides, as predicted by relativistic calculations.

An EC-branch in the decay of 27-s 263Db: Evidence for the isotope 263Rf

27-s 263Db was produced in the 249Bk ( 18O, 4n) reaction at 93 MeV. The activity was transported by a He/KCl-jet to the laboratory where it was collected for 15 min and then subjected to a chemical separation specific for group-4 elements. The activity was dissolved in 0.5 M unbuffered α-HiB and eluted from a cation-exchange column. The effluent was made 9 M in HCl and group-4 tetrachlorides were extracted into TBP/Cyclohexane which was evaporated to dryness on a Ta disc. The Ta discs were assayed for α and SF activity. A SF activity with a half life on the order of 20 min was observed and assigned to the nuclide 263Rf. It is formed by electron-capture decay of 263Db with a decay branch of 3+4 -1%.

Isomer-specific effects of CLA on gene expression in human adipose tissue depending on PPARgamma2 P12A polymorphism: a double blind, randomized, controlled cross-over study

BACKGROUND

Peroxisome proliferator-activated receptor (PPAR)gamma is a key regulator in adipose tissue. The rare variant Pro12Ala of PPARgamma2 is associated with a decreased risk of insulin resistance. Being dietary PPARgamma ligands, conjugated linoleic acids (CLAs) received considerable attention because of their effects on body composition, cancer, atherosclerosis, diabetes, obesity and inflammation, although some effects were only demonstrated in animal trials and the results in human studies were not always consistent. In the present study effects of CLA supplementation on genome wide gene expression in adipose tissue biopsies from 11 Ala12Ala and 23 Pro12Pro men were investigated. Subjects underwent four intervention periods (4 wk) in a randomized double blind cross-over design receiving 4.25 g/d of either cis-9, trans-11 CLA, trans-10,cis-12 CLA, 1:1 mixture of both isomers or a reference linoleic acid oil preparation. After each intervention biopsies were taken, whole genome expression microarrays were applied, and genes of interest were verified by realtime PCR.

RESULTS

The following genes of lipid metabolism were regulated by CLA: LDLR, FASN, SCD, FADS1 and UCP2 were induced, while ABCA1, CD36 and CA3 were repressed. Transcription factors PPARgamma, NFAT5, CREB5 and EBF1, the adipokine NAMPT, members of the insulin signaling cascade SORBS1 and IGF1 and IL6ST were repressed, while the adipokine THBS1 and GLUT4 involved in insulin signaling were induced. Compared to trans-10,cis-12 CLA and the CLA mixture the cis-9, trans-11 CLA isomer exerted weaker effects. Only CD36 (-1.2 fold) and THBS1 (1.5 fold) were regulated. The CLA effect on expression of PPARgamma and leptin genes depends on the PPARgamma2 genotype.

CONCLUSION

The data suggest that the isomer specific influence of CLA on glucose and lipid metabolism is genotype dependent and at least in part mediated by PPARgamma.

TRIAL REGISTRATION

http://www.controlled-trials.com: ISRCTN91188075.

Effect of extracellular pH on insulin secretion and glucose metabolism in neonatal and adult rat pancreatic islets

Changes in extracellular pH are known to affect glucose-stimulated insulin secretion. In the present study, glucose metabolism in pancreatic islets cultured at different pHs was investigated. Also, for islet transplantation purposes, insulin secretion and glucose metabolism were compared in neonatal and adult islets at different pHs to determine which islet preparation is more tolerant to acidity and alkalinity. The results revealed a dependency of insulin secretion on the external pH in both neonatal and adult islets. Reduction of insulin secretion was observed at both the acidic and alkaline sides of pH 7.3. Glucose stimulated increases of insulin secretion in all cases. Similar results were obtained for ATP and pyruvate contents. Intracellular insulin increased with the increase of pH value. In contrast, calcium content decreased with the increase of pH. The results demonstrate that neonatal islets are more acid tolerant than adult islets. Both basal and glucose-stimulated insulin secretions, as well as other parameters of neonatal islets were significantly higher than those of adult islets in response to low pH. The differences under alkaline conditions were not significant but give an indication that neonatal islets are more tolerant to alkalinity than are adult islets.

Probiotics--compensation for lactase insufficiency

Yogurt and other conventional starter cultures and probiotic bacteria in fermented and unfermented milk products improve lactose digestion and eliminate symptoms of intolerance in lactose maldigesters. These beneficial effects are due to microbial beta-galactosidase in the (fermented) milk product, delayed gastrointestinal transit, positive effects on intestinal functions and colonic microflora, and reduced sensitivity to symptoms. Intact bacterial cell walls, which act as a mechanical protection of lactase during gastric transit, and the release of the enzyme into the small intestine are determinants of efficiency. There is a poor correlation between lactose maldigestion and intolerance; in some studies, low hydrogen exhalation without significant improvement of clinical symptoms was observed. Probiotic bacteria, which by definition target the colon, normally promote lactose digestion in the small intestine less efficiently than do yogurt cultures. They may, however, alleviate clinical symptoms brought about by undigested lactose or other reasons.

Improved yield and functionality of parathyroid cells separated by using collagenase-digestion with cold pre-incubation

Preparation of cells from solid organs often induces a functional impairment due to the proteolytic cell damage by the applied digestive enzyme like collagenase, trypsin or dispase. To preserve the tissue and to enhance the yield of cells, Laue et al. reported an islet cell isolation with pre-incubation at 4 C permitting the enzyme to diffuse into the tissue and explicite activity equally throughout the whole particle. The aim of this study was to investigate whether this procedure can be applied to parathyroid glands. Therefore porcine parathyroid glands were dissected into 1 mm3 pieces. Subsequently one group of these pieces was incubated 22 h at 4 C in 2 mg/ml collagenase before activating the enzyme by elevating the temperature to 37 C for 30 min. The other group was incubated directly at 37 C for 30 min. The yield of cells and their viability was assessed by light-microscopy and staining with trypan-blue. After the cells were immobilized in barium-alginate and cultivated for 7 days, the function was tested by incubation in different calcium concentrations and PTH-measurement. Finally, the viability was assessed by histology. Using a cold pre-incubation with collagenase, a significantly higher number of isolated cells was retrieved compared with collagenase-digestion without pre-incubation. The viability was about 100% and did not differ between both groups. After immobilization and cultivation the viability decreased to less than 30%, with and without pre-incubation. In contrast to viability the PTH-secretion of the cells differed significantly between both procedures. By pre-incubation with collagenase at 4 C a gentle method is presented resulting in an enhancement of yield and function of single cells of parathyroid glands.

Xenotransplantation of parathyroids in rats using barium-alginate and polyacrylic acid multilayer microcapsules

The integrity and function of encapsulated parathyroid tissue following xenotransplantation is limited by oxygen and nutrition supply and capsule fibrosis. Since some of these factors depend on stability and biocompatibility of the coating material, multilayer microcapsules have been developed. Parathyroid tissue pieces and digested single cells from pigs were encapsulated in barium-alginate and in polyacrylic acid (PAA) multilayer capsules. After 7 days of culture the function of the encapsulated cells were assessed. Subsequently, in a part of the cultured microcapsules the viability was directly assessed whereas the other part was transplanted in dark animal [DA] rats for 30 days. After explantation viability and fibrotic reaction were examined. Single cells showed a significant increase in parathyroid hormone [PTH] secretion when exposed to medium low in calcium, whereas minced tissue pieces revealed necrosis without stimulatory responsiveness. Morphometry showed significantly better viability of single cells compared with minced tissue in vitro and in vivo. The fibrotic reaction against capsules with minced tissue was more pronounced than for capsules containing single cells. There was no difference between barium alginate and PAA capsules when containing minced tissue. In single cells, however, the fibrous tissue reaction differed significantly between barium alginate and PAA capsules. Encapsulated single cells of parathyroid tissue maintain detectable function and viability. In contrast minced tissue underwent necrosis and induced significantly more connective tissue reaction than single cells indicating an interrelationship between necrosis and fibrosis.

Effect of media composition on long-term in vitro stability of barium alginate and polyacrylic acid multilayer microcapsules

For a number of applications stability of microcapsules is a critical factor. Since the maintenance of polyelectrolyte complexes depends considerably on the ion composition we tested the physical properties of barium alginate capsules and searched for conditions to improve stability by a multilayer coating with polyethylenimine (PEI) and polyacrylic acid (PAA). Mechanical stability and diameters were determined in barium alginate capsules and compared with multilayer capsules. Multilayer coating resulted in smaller capsules than barium complexing alone. The difference was more pronounced when CaCl2 was used instead of NaCl during coating. Barium alginate capsules and application of CaCl2 during coating led to continuous pressure profiles, whereas NaCl resulted in bursting at a defined pressure, indicating the additional contribution to mechanical stability by the outer layers. After 7 d culture, mechanical stability of coated capsules decreased in RPMI and NaCl but was most pronounced in sodium citrate. The capsule diameter increased in sodium citrate, less pronounced in NaCl and was significantly different to RPMI and double distilled water. During long-term culture in RPMI, the diameter increased and mechanical stability decreased significantly. Multilayer coating improved mechanical stability which was impeded most in sodium citrate, to a lesser extent by NaCl and RPMI even after long-term exposure.

The effect of alginate and hyaluronate on the viability and function of immunoisolated neonatal rat islets

Recent observations suggest that the extracellular matrix plays a role as regards the viability and morphological integrity in long-term culture of Langerhans islets. For the present study we encapsulated neonatal rat islets without extracellular matrix (WEM), with alginate solution (AL) and with hyaluronate solution (HY) into cuprophane hollow fibers. Function was tested after week 1 and 5. The insulin release of WEM encapsulated islets decreased significantly during the culture period. In contrast to this, AL and HY embedded islets had stable secretion values throughout the whole cultivation. Histological examination confirmed that viability of HY and of AL embedded islets differed significantly from that of WEM encapsulated islets. Furthermore, HY seems to be a more advantageous environment to immunoisolated islets than AL. Both the insulin secretion values and the viability of HY embedded islets were higher than of AL embedded islets. We conclude that an extracellular matrix is important for immunoisolated islets, to maintain their function and morphological integrity and that HY is especially suitable for this application.

The phenomenon of a high triglyceride response to an oral lipid load in healthy subjects and its link to the metabolic syndrome

Excessive postprandial triglyceride (TG) responses despite normal fasting TG levels have been described in single cases within small groups of healthy subjects and in patients with obesity or precocious atherosclerosis, known to be associated with high insulin fasting levels. To clarify this association, fasting and postprandial TG and insulin levels were studied in 113 healthy young (25.7 +/- 2.6 years), normal weight (body mass index 20.8 +/- 2.3 kg/m2) male subjects who were selected from among 117 subjects on the basis of TG fasting levels < 200 mg/dl. After a 12-hour fast a standardized liquid lipid load was administered containing 58 g mainly saturated fat and 1,017 kcal energy. Both fasting TG values and postprandial TG peak values showed bimodal frequency distributions. Statistical analysis of fasting TG discriminated two groups: a low fasting TG group with normally distributed values < 150 mg/dl (mean +/- SEM: 79.5 +/- 2.7 mg/dl; n = 104) and a high fasting TG group > 150 mg/dl (194.5 +/- 7.2 mg/dl; n = 13). Likewise, two groups could be differentiated according to their maximal postprandial TG response (TG max) to the lipid load: (1) normal responders with TG max < 260 mg/dl (mean +/- SEM: 123 +/- 4.8 mg/dl; n = 96) and (2) high responders with TG max > 260 mg/dl (272.5 +/- 20.5 mg/dl; n = 17). Fasting TG and TG max were highly correlated (r = 0.745; p < 0.0001). However, 9 of 17 (53%) high responders had fasting TG < 150 mg/dl, which means that the prediction of high response is only 47.0% based on fasting TG values. Fasting insulin levels were significantly higher in high responders than in normal responders, whereas they did not differ between the low and high fasting TG group. In conclusion, the bimodal frequency distribution of TG max after a lipid load permitted the differentiation of two groups, normal responders and high responders, with higher fasting insulin levels, which might indicate a link to the metabolic syndrome.

Long-term function of porcine islets and single cells embedded in barium-alginate matrix

The influence of alginate-embedding on the maintenance of functioning and morphological integrity in long-term culture of isolated porcine islets and islet cells was studied. Free-floating islets and islet cells served for control. Function was tested after the 1st, 2nd and 4th week. Basal and glucose-stimulated insulin secretion of embedded islets decreased slightly, but significantly after the first week (from 4.39 +/- 0.64 to 2.87 +/- 0.47 at normal and from 11.96 +/- 1.44 to 4.76 +/- 0.78 microU pro 24 h pro islet at elevated glucose concentration, p < 0.05 and < 0.01, resp.) and remained unchanged thereafter. Glucose-stimulation resulted in significant increases in insulin secretion at all three testings (p < 0.001, < 0.01 and < 0.01). Single cells in alginate matrix had even more stable insulin secretion throughout the whole cultivation with significant increases to glucose challenge (p < 0.01, < 0.01 and < 0.05). In contrast, insulin secretion of free-floating islet cells decreased from 5.70 +/- 1.19 to 2.04 +/- 0.64 and to 1.05 +/- 0.33 at basal conditions (p < 0.01 and < 0.05) and from 11.39 +/- 1.87 to 2.76 +/- 0.76 and to 2.15 +/- 0.71 microU pro 24 h pro islet under stimulation (p < 0.01 and not sign). In addition, the secretory response to glucose challenge was significant only at the first testing (p < 0.05). Non-embedded islets could be tested only at the first week since after this time they dissociated to single cells. Embedded islets and single cells showed intact morphology after four weeks with trypan blue (TPB) positivity of less than 5%.(ABSTRACT TRUNCATED AT 250 WORDS)