Fredrik Nyström

Weight gain restriction for obese pregnant women : A case-control intervention study

Objective  To minimise obese women’s total weight gain during pregnancy to less than 7 kg and to investigate the delivery and neonatal outcome.

Insulin signalling: metabolic pathways and mechanisms for specificity.

Biological actions of insulin are mediated by the insulin receptor, a member of a large family of receptor tyrosine kinases (RTK). Signal transduction by the insulin receptor follows a paradigm for RTK signalling. Many intracellular signalling molecules contain multiple modular domains that mediate protein-protein interactions and participate in the formation of signalling complexes. Phosphorylation cascades are also a prominent feature of RTK signalling. Distal pathways are difficult to dissect because branching paths emerge from downstream effectors and several upstream inputs converge upon single branch points. Thus, insulin action is determined by complicated signalling networks rather than simple linear pathways. Interestingly, many signalling molecules downstream from the insulin receptor are also activated by a plethora of RTKs. Therefore, mechanisms that generate specificity are required. In this review we discuss recent advances in the elucidation of specific metabolic insulin signalling pathways related to glucose transport, one of the most distinctive biological actions of insulin. We also present examples of potential mechanisms underlying specificity in insulin signalling including interactions between multiple branching pathways, subcellular compartmentalization, tissue-specific expression of key effectors and modulation of signal frequency and amplitude.

Regression of left ventricular hypertrophy in human hypertension with irbesartan

Background The Swedish irbesartan left ventricular hypertrophy investigation versus atenolol (SILVHIA). Objective Angiotensin II induces myocardial hypertrophy. We hypothesized that blockade of angiotensin II subtype 1 (AT1) receptors by the AT1-receptor antagonist irbesartan would reduce left ventricular mass (as measured by echocardiography) more than conventional treatment with a beta blocker. Design and methods This double-blind study randomized 115 hypertensive men and women with left ventricular hypertrophy to receive either irbesartan 150 mg q.d. or atenolol 50 mg q.d. for 48 weeks. If diastolic blood pressure remained above 90 mmHg, doses were doubled, and additional medications (hydrochlorothiazide and felodipine) were prescribed as needed. Echocardiography was performed at weeks 0, 12, 24 and 48. Results Baseline mean blood pressure was 162/104 mmHg, and mean left ventricular mass index was 157 g/m2 for men and 133 g/m2 for women. Systolic and diastolic blood pressure reductions were similar in both treatment groups. Both irbesartan (P < 0.001) and atenolol (P < 0.001) progressively reduced left ventricular mass index, e.g. by 26 and 14 g/m2 (16 and 9%), respectively, at week 48, with a greater reduction in the irbesartan group (P = 0.024) . The proportion of patients who attained a normalized left ventricular mass (i.e. ⩽ 131 g/m2 for men and ⩽ 100 g/m2 for women) tended to be greater with irbesartan (47 versus 32%, P = 0.108). Conclusions Left ventricular mass was reduced more in the irbesartan group than in the atenolol group. These results suggest that blocking the action of angiotensin II at AT1-receptors may be an important mechanism, beyond that of lowering blood pressure, in the regulation of left ventricular mass and geometry in patients with hypertension.

Fast food based hyper-alimentation can induce rapid and profound elevation of serum alanine aminotransferase in healthy subjects

Objective: To study the effect of fast-food-based hyper-alimentation on liver enzymes and hepatic triglyceride content (HTGC). Design: Prospective interventional study with parallel control group. Setting: University Hospital of Linköping, Sweden. Participants: 12 healthy men and six healthy women with a mean (SD) age of 26 (6.6) years and a matched control group. Intervention: Subjects in the intervention group aimed for a body weight increase of 5–15% by eating at least two fast-food-based meals a day with the goal to double the regular caloric intake in combination with adoption of a sedentary lifestyle for 4 weeks. Main outcome measures: Weekly changes of serum aminotransferases and HTGC measured by proton nuclear magnetic resonance spectroscopy at baseline and after the intervention. Results: Subjects in the intervention group increased from 67.6 (9.1) kg to 74.0 (11) kg in weight (p<0.001). Serum ALT increased from 22.1 (11.4) U/l at study start to an individual mean maximum level of 97 (103) U/l (range 19.4–447 U/l). Eleven of the 18 subjects persistently showed ALT above reference limits (women >19 U/l, men >30 U/l) during the intervention. Sugar (mono- and disaccharides) intake during week 3 correlated with the maximal ALT/baseline ALT ratio (r = 0.62, p = 0.006). HTGC increased from 1.1 (1.9)% to 2.8 (4.8)%, although this was not related to the increase in ALT levels. ALT levels were unchanged in controls. Conclusion: Hyper-alimentation per se can induce profound ALT elevations in less than 4 weeks. Our study clearly shows that in the evaluation of subjects with elevated ALT the medical history should include not only questions about alcohol intake but also explore whether recent excessive food intake has occurred.

Angiotensin converting enzyme gene polymorphism predicts blood pressure response to angiotensin II receptor type 1 antagonist treatment in hypertensive patients

Objectives To determine whether polymorphisms in the renin–angiotensin system can predict blood pressure-lowering response to antihypertensive treatment; more specifically, in response to treatment with irbesartan or atenolol. Design and methods Eighty-six patients with hypertension were randomized to double-blind treatment with either the angiotensin II type 1 receptor antagonist irbesartan or the β1 adrenergic receptor blocker atenolol and followed for 3 months. We analysed angiotensinogen T174M and M235T, angiotensin converting enzyme (ACE) I/D and angiotensin II type 1 receptor A1166C polymorphisms and related them to blood pressure reduction. Results The mean reductions in blood pressure were similar for both treatments. In the irbesartan group, individuals homozygous for the ACE gene I allele showed a greater reduction in diastolic blood pressure, exceeding those with the D allele (− 18 ± 11 SD versus − 7 ± 10 mmHg, P = 0.0096). This was not the case during treatment with atenolol, and the interaction term between type of treatment and ACE II genotype was significant (P = 0.0176). The angiotensinogen and angiotensin II type 1 receptor polymorhisms were not related to the response to treatment. Conclusions ACE genotyping predicted the blood pressure-lowering response to antihypertensive treatment with irbesartan but not atenolol. Thus, specific genotypes might predict the response to specific antihypertensive treatment.

Retinol-binding protein-4 attenuates insulin-induced phosphorylation of IRS1 and ERK1/2 in primary human adipocytes

Reduced sensitivity to insulin in adipose, muscle, and liver tissues is a hallmark of type 2 diabetes. Animal models and patients with type 2 diabetes exhibit elevated levels of circulating retinol‐binding protein (RBP4), and RBP4 can induce insulin resistance in mice. However, little is known about how RBP4 affects insulin signaling. We examined the mechanisms of action of RBP4 in primary human adipocytes. RBP4‐treated adipocytes exhibited the same molecular defects in insulin signaling, via IRS1 to MAP kinase, as in adipocytes from patients with type 2 diabetes. Without affecting autophosphorylation of the insulin receptor, RBP4 blocked the insulin‐stimulated phosphorylation of IRS1 at serine (307) [corresponding to serine (302) in the murine sequence] and concomitantly increased the EC50 (from 0.5 to 2 nM) for insulin stimulation of IRS1 phosphorylation at tyrosine. The phosphorylation of IRS1 at serine (312) [corresponding to serine (307) in the murine sequence] was not affected in cells from diabetic patients and was also not affected by RBP4. The EC50 for insulin stimulation of downstream phosphorylation of MAP kinase ERK1/2 was increased (from 0.2 to 0.8 nM) by RBP4. We show that ERK1/2 phosphorylation is similarly impaired in adipocytes from patients with type 2 diabetes. However, the sensitivity to insulin for downstream signaling to control of protein kinase B and glucose uptake was not affected by RBP4. When insulin‐resistant adipocytes from patients with type 2 diabetes were incubated with antibodies against RBP4, insulin‐induced phosphorylation of IRS1 at serine (307) was normalized and the EC50 for insulin stimulation of ERK1/2 phosphorylation was reduced. Endogenous levels of RBP4 were markedly reduced in adipocytes from obese or type 2 diabetic subjects, whereas expression levels of RBP4 mRNA were unaffected. These findings indicate that RBP4 may be released from diabetic adipocytes and act locally to inhibit phosphorylation of IRS1 at serine (307), a phosphor‐ylation site that may integrate nutrient sensing with insulin signaling.—Öst, A., Danielsson, A., Liden, M., Eriksson, U., Nystrom, F. N., Strålfors, P. Retinolbinding protein‐4 attenuates insulin‐induced phosphorylation of IRS1 and ERK1/2 in primary human adipocytes. FASEB J. 21, 3696–3704 (2007)

Serum leptin concentrations in a normal population and in GH deficiency: Negative correlation with testosterone in men and effects of GH treatment

To study relationships between leptin and factors regulating body composition as well as metabolic risk factors. Furthermore, to study the effects of GH on leptin.

Angiotensin type 1 receptor antagonists induce human in-vitro adipogenesis through peroxisome proliferator-activated receptor-gamma activation.

Objective In clonal animal cells, certain angiotensin receptor blockers (ARB) activate the peroxisome proliferator-activated receptor-γ (PPARγ). The aim of this work was to validate that observation in human cells and humans. Methods We investigated the induction of in-vitro adipogenesis and the activation of PPARγ-target genes, adiponectin and lipoprotein lipase, by ARB in human preadipocytes. We also studied PPARγ response-element-driven luciferase reporter gene activation in human adipocytes. Finally, we treated 14 obese men for 10 days with placebo crossed over with 150 mg/day irbesartan. Subcutaneous fat was analyzed for mRNA expression of adiponectin and lipoprotein lipase. Results Telmisartan and irbesartan, and to a lesser degree losartan, induced adipogenesis and activated PPARγ-target genes. This stimulation of PPARγ-target genes was prevented by the PPARγ antagonist GW9662. Eprosartan had no effect. Paradoxically, all ARB activated the luciferase reporter gene. PPARγ activity increased approximately two-fold with pioglitazone and 1.5-fold with the ARB in all assays. In the cross-over clinical study, irbesartan lowered blood pressure but had no effect on adiponectin or lipoprotein lipase mRNA expression. Conclusions Our data are the first to show that ARB induce adipogenesis and PPARγ-target gene expression in human adipocytes. Pharmacokinetic differences may contribute to the heterogeneous effects on metabolism and preadipocyte differentiation. In humans, larger doses of ARB, longer treatments, or both may be required to activate PPARγ in adipose cells.

The CYP2C9 genotype predicts the blood pressure response to irbesartan: results from the Swedish Irbesartan Left Ventricular Hypertrophy Investigation vs Atenolol (SILVHIA) trial

Background The cytochrome P450 CYP2C9 enzyme (CYP2C9) metabolizes many clinically important drugs, for example, phenytoin, warfarin and the angiotensin II type 1 (AT1) receptor antagonists, losartan and irbesartan. Single nucleotide polymorphisms in the CYP2C9 gene result in the expression of three important variants, CYP2C9*1 (wild-type), CYP2C9*2 and CYP2C9*3, the last two exhibiting reduced catalytic activity compared with the wild-type. The CYP2C9 genotype is known to determine sensitivity to and dose requirements for both warfarin and phenytoin, and also the rate of metabolism of losartan. However, its influence on clinical response to treatment with the AT1 receptor antagonist, irbesartan, has not been investigated. Objective To determine whether the CYP2C9 genotype influences the blood pressure-decreasing response to antihypertensive treatment with irbesartan. Design and methods One hundred and two patients with essential hypertension and left ventricular hypertrophy were allocated randomly to groups to receive double-blind treatment with either irbesartan (n = 49) or the β1-adrenergic receptor blocker, atenolol (n = 53). Blood pressure was measured before and after 12 weeks of treatment. CYP2C9 genotyping was performed using solid-phase minisequencing. Results The diastolic blood pressure (DBP) response differed in relation to the CYP2C9 genotype in patients given irbesartan: the reduction in patients with genotype CYP2C9*1/ CYP2C9*1 (n = 33) was 7.5% and that with CYP2C9*1/ CYP2C9*2 (n = 12) was 14.4% (P = 0.036). A similar trend was seen for systolic blood pressure. In contrast, no relation was seen between the CYP2C9 genotype and blood pressure response to atenolol, a drug not metabolized via CYP2C9. Conclusions The CYP2C9 genotype seems to predict the DBP response to irbesartan, but not to atenolol, in patients with essential hypertension.

Ethyl glucuronide in human hair after daily consumption of 16 or 32 g of ethanol for 3 months

The overall objectives of the study were to develop a sensitive method for ethyl glucuronide (EtG) determination in hair and then investigate if a low or moderate intake of ethanol could be differentiated from total abstinence. Forty-four subjects were included in the study, 12 males (7 drinkers and 5 abstinent) and 32 females (14 drinkers and 18 abstinent). The study lasted 3 months and the female drinkers consumed one glass (16 g of ethanol) and the males consumed two glasses (32 g of ethanol) of wine (13.5-14%) daily. Hair samples were collected as close as possible above the skin and the proximal 2 cm were analyzed for EtG. Hair was cut into pieces of about 0.5 cm length and washed before incubation overnight in water and then extracted on Clean Screen EtG Carbon columns. The LC/MS/MS system consisted of a Waters ACQUITY UPLC connected to an API 4000 triple quadrupole instrument. Two transitions for EtG and one for the internal standard EtG-D(5) were measured. The method was linear from 60 to 10,000 pg/sample. Imprecision studies were performed at three levels as well as with an authentic sample. Total imprecision was 16% at 200 pg/sample, 8% at 1000 pg/sample, 6% at 8000 pg/sample and 13% at 29 pg/mg in the authentic sample. Of those who drank two glasses of wine every day, four had measurable amounts of EtG in their hair (5-11 pg/mg), and in only one of the females drinking one glass of wine EtG was quantified (3 pg/mg). Among the 23 abstinent subjects two had traces of EtG in the hair. We conclude that persons who ingested 16 or 32 g of ethanol daily for 3 months presented with low concentrations of EtG in hair, well below the proposed threshold for overconsumption set at 30 pg/mg. In addition, none of those who ingested 16 g/day had concentrations over the proposed abstinence threshold of 7 pg/mg.