Earlier intensified insulin treatment of Type 1 diabetes and its association with long-term macrovascular and renal complications.

AIMS: To investigate the incidence of all-cause mortality, composite mortality and morbidity in people with Type 1 diabetes formerly randomized in the Stockholm Diabetes Intervention Study. METHODS: A total of 102 people with Type 1 diabetes were randomized in the period 1982-1984 to intensified conventional treatment or standard treatment with insulin for a mean of 7.5 years. We prospectively re-evaluated this cohort for the period until 2011 with regard to all-cause mortality and composite mortality, which consisted of myocardial infarction, stroke and end-stage renal disease as primary endpoints. Secondary endpoints were first-time hospitalization for myocardial infarction and stroke or end-stage renal disease. Data on HbA1c levels (mean of 22 values/person) were retrospectively collected between 1996 and 2011. RESULTS: During the median follow-up of 28 years, 22 people died: seven in the intensified conventional insulin group compared with 15 in the standard treatment group (P = 0.30). With regard to composite mortality, six people in the intensified conventional insulin group died compared with 11 in the standard treatment group (P = 0.56). For the secondary endpoints, 11 people in the intensified conventional insulin group developed myocardial infarction or stroke compared with 17 in the standard treatment group (P = 0.72), and one person in the intensified conventional insulin compared with seven people in the standard treatment group developed end-stage renal disease (P = 0.09). Mean HbA1c levels did not differ between groups during the follow-up years. CONCLUSIONS: All-cause mortality, cardiovascular morbidity and progression to end-stage renal disease did not differ in people with Type 1 diabetes earlier randomized to intensified insulin treatment.

Orally given melatonin may serve as a probe drug for cytochrome P450 1A2 activity in vivo: a pilot study.

BACKGROUND: Melatonin is a hormone that is metabolized by cytochrome P450 (CYP) 1A2 to its main primary metabolite 6-hydroxymelatonin. We therefore evaluated the utility of oral melatonin as a marker of hepatic CYP1A2 activity. METHODS: Twenty-five milligrams of melatonin was given at 9:30 am to 12 healthy Swedish volunteers, who had previously been phenotyped for CYP1A2 with caffeine. Melatonin and conjugated 6-hydroxymelatonin were analyzed by liquid chromatography-mass spectrometry in blood samples taken between 0.5 and 6.5 hours after drug intake. Serum concentrations of melatonin and conjugated 6-hydroxymelatonin, or their ratio at different time points, and the apparent melatonin clearance were tested for correlation with caffeine clearance. RESULTS: We found a significant correlation between apparent clearance of melatonin and caffeine clearance with a Spearman rank correlation coefficient (Rs) of 0.75 (P =.005). The melatonin concentration 1.5 hours after administration also closely correlated with the caffeine clearance (Rs = -0.62; P =.03). Inclusion of conjugated 6-hydroxymelatonin gave no closer correlations. CONCLUSION: Melatonin might be developed as an alternative to caffeine as a probe drug for CYP1A2 phenotyping.

Caffeine raises the serum melatonin level in healthy subjects: an indication of melatonin metabolism by cytochrome P450(CYP)1A2.

Caffeine is metabolized in the liver by cytochrome P450(CYP)1A2. Recent findings imply that this enzyme may also be of importance for the metabolism of human melatonin (MT). If caffeine and MT are metabolized by the same enzyme, one may expect to find different serum MT levels after ingestion of coffee compared with placebo. Although coffee is consumed by people all over the world, few studies have focused on whether caffeine actually affects serum MT levels in normal subjects. We decided to study that particular topic. For that purpose 12 healthy individuals were tested on two occasions, one week apart. On one of these occasions they were given a capsule containing 200 mg caffeine in the evening. On the other, they received placebo. The experimental order was randomized. Serum MT levels were determined every second hour between 22:00 h and 08:00 h, and the melatonin areas under the curve (MT-AUCs) were calculated. After caffeine the serum MT level rose from 0.09 +/- 0.03 nmol/l at 22:00 h to 0.48 +/- 0.07 nmol/l at 04:00 h. The corresponding rise after placebo was less prominent (from 0.06 +/- 0.01 to 0.35 +/- 0.06 nmol/l). This was reflected by the MT-AUC which was 32% larger after ingestion of caffeine compared with placebo (MT-AUC(caffeine) 3.16 +/- 0.44 nmol/l x h vs MT-AUC(placebo) 2.39 +/- 0.40 nmol/l x h; p < 0.02). These findings imply that caffeine, ingested in the evening at a dose corresponding to two ordinary cups of coffee, augments the nocturnal serum MT level, which in turn supports the notion that cytochrome P450(CYP)1A2 is involved in the hepatic metabolism of human MT.

Fluvoxamine but not citalopram increases serum melatonin in healthy subjects-- an indication that cytochrome P450 CYP1A2 and CYP2C19 hydroxylate melatonin.

OBJECTIVE: The nocturnal serum melatonin (MT) level increases after ingestion of fluvoxamine (FLU)-- a selective serotonin re-uptake inhibitor (SSRI) with antidepressive properties. The mechanism behind the MT increase is unknown. Citalopram (CIT) is another SSRI. It is not known whether CIT affects the serum MT level. It may well be that these two compounds affect serum MT levels differently, inasmuch as the ways they inhibit cytochrome P450 (CYP) enzymes in the liver differ markedly. FLU inhibits CYP1A2 potently, and to some extent also CYP2C19, whereas CIT is without such an effect. CYP enzymes are probably involved in the hepatic metabolism of MT. If FLU, but not CIT, inhibits liver enzymes involved in the metabolism of MT, different serum MT concentrations should probably ensue. The objective of this investigation was to test this hypothesis. METHODS: Seven healthy subjects participated in three different experiments, which were performed in random order 6-8 days apart. In experiment A, placebo was given, in experiment B 40 mg CIT and in experiment C 50 mg FLU. All doses were given orally at 1600 hours. Serum MT concentrations were determined at regular intervals between 1600 hours and noon next day (20 h). Plasma concentrations of CIT were measured repeatedly in experiment B, and plasma FLU concentrations in experiment C. MT areas under the curve representing the 20-h period (MT-AUC(0-20)) were compared in the three experiments, and differences were statistically evaluated. RESULTS: FLU augmented the MT-AUC(0-20) by a factor of 2.8 compared with the effect of placebo (P < 0.01), whereas CIT was without significant effect. More MT was excreted in the urine after ingestion of FLU than after placebo. In contrast, CIT did not influence the MT excretion. A clear relationship was found between serum levels of MT and plasma concentrations of FLU. CONCLUSION: The serum MT level increased markedly after ingestion of FLU but not after CIT. The exact mechanism behind this finding is unknown, but decreased hepatic metabolism of MT by either CYP1A2 or CYP2C19, or both, is probable. Although exogenous MT, causing high MT concentration in plasma, has sleep-promoting properties in man, it is at this stage unknown whether serum MT concentrations in the range found in this study have similar effects. This has to be given further attention in additional studies.

Determination of exogenous melatonin and its 6-hydroxy metabolite in human plasma by liquid chromatography-mass spectrometry.

SUMMARY: Melatonin has recently garnered interest as a possible treatment for sleep disorders, and this has created a desire for appropriate pharmacokinetic studies. No method has yet been published that can measure the concentrations of both melatonin and its main metabolite, 6-hydroxymelatonin, in plasma or serum. Therefore, a liquid chromatography-mass spectrometry (LC/MS) method including enzymatic hydrolysis and one-step liquid-liquid extraction was developed for this purpose. The mean extraction recovery was 59% for melatonin and 42% for 6-hydroxymelatonin. The mean precision of the method as calculated from the interassay coefficient of variation of quality control samples at high and low concentrations was 18% for 6-hydroxymelatonin and 15% for melatonin. The inaccuracy was always less than 2%. The limit of detection was approximately 2 ng/mL for 6-hydroxymelatonin (signal/noise ratio = 4) and less than 2 ng/mL for melatonin (signal/noise ratio at 2 ng/mL = 10). The method was applied to the analysis of plasma from a healthy volunteer who had received a single oral dose of 25 mg melatonin.

Does hepatic metabolism of melatonin affect the endogenous serum melatonin level in man?

Melatonin (MT) is metabolized in the liver by cytochrome P450 (CYP) 1A2 but its importance for the metabolic process has not been fully elucidated. Therefore, the objective of this investigation was to study whether patients with different CYP1A2 activity would have different nocturnal serum MT levels. For that purpose serum MT concentrations were determined every second hour during the night in 12 healthy subjects and their MT areas under the curve (MT-AUCs) were calculated. Caffeine (CA) clearance was determined in advance. It is generally accepted that CA clearance reflects CYP1A2 activity. This made it possible to evaluate whether a relationship prevails between endogenous MT-AUCs and CYP1A2 activity. If CYP1A2 is of importance for the metabolism of MT one would expect to find an inverse correlation between the MT-AUCs and the CA clearance. However, such correlation did not exist in the current study (Rs=-0.021, NS). Since endogenous MT-AUC is dependent not only on MT elimination by CYP1A2 but also on MT secretion, it is possible that an increased MT secretion counter-balances an increased hepatic MT metabolism. If so, this could explain why the MT-AUCs and the CA clearance values were not inversely correlated in this study.