Decreased insulin secretion and increased risk of type 2 diabetes associated with allelic variations of the WFS1 gene: the Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) prospective study

AIMS/HYPOTHESIS

We investigated associations of allelic variations in the WFS1 gene with insulin secretion and risk of type 2 diabetes in a general population prospective study.

METHODS

We studied 5,110 unrelated French men and women who participated in the prospective Data from Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study. Additional cross-sectional analyses were performed on 4,472 French individuals with type 2 diabetes and 3,065 controls. Three single nucleotide polymorphisms (SNPs) were genotyped: rs10010131, rs1801213/rs7672995 and rs734312.

RESULTS

We observed statistically significant associations between the major alleles of the three variants and prevalent type 2 diabetes in the DESIR cohort at baseline. Cox analyses showed an association between the G-allele of rs10010131 and incident type 2 diabetes (HR 1.34, 95% CI 1.08-1.70, p = 0.007). Similar results were observed for the G-allele of rs1801213 and the A-allele of rs734312. The GGA haplotype was associated with an increased risk of diabetes as compared with the ACG haplotype (HR 1.26, 95% CI 1.04-1.42, p = 0.02). We also observed statistically significant associations of the three SNPs with plasma glucose, HbA(1c) levels and insulin secretion at baseline and throughout the study in individuals with type 2 diabetes or at risk of developing diabetes. However, no association was observed in those who remained normoglycaemic at the end of the follow-up. Associations between the three variants and type 2 diabetes were replicated in cross-sectional studies of type 2 diabetic patients in comparison with a non-diabetic control group.

CONCLUSIONS/INTERPRETATION

The most frequent haplotype at the haplotype block containing the WFS1 gene modulated insulin secretion and was associated with an increased risk of type 2 diabetes.

Spinal administration of adrenergic agents produces analgesia in amphibians

Direct intraspinal injection of the catecholamines epinephrine and norepinephrine, and the alpha-adrenergic agents dexmedetomidine and clonidine, produced a dose-dependent elevation of pain thresholds in the Northern grass frog, Rana pipiens. Significant analgesic effects were noted for at least 4 h. The analgesic effect of intraspinal dexmedetomidine or epinephrine was blocked by systemic pretreatment with the alpha 2-adrenoceptor antagonists, yohimbine and atipamezole, but not with the alpha 1-adrenoceptor antagonist, prazosin. Dose-response analyses showed that dexmedetomidine, epinephrine, norepinephrine had similar analgesic potencies, but clonidine was significantly less potent. Analgesia was observed without accompanying motor or sedative effects. These results suggest that alpha 2-adrenoceptor mechanisms which mediate analgesia may have evolved early in vertebrate evolution and that descending epinephrine-containing fibers in the amphibian nervous system may be the source of endogenous catecholamines regulating nociceptive sensitivity in the amphibian spinal cord.

Analgesic potency of alpha adrenergic agents after systemic administration in amphibians

The analgesic and behavioral effects produced by systemic adrenergic agonists dexmedetomidine (0.1-3 nmol/g), clonidine (100-1000 nmol/g), epinephrine (1-30 nmol/g) and norepinephrine (10-300 nmol/g) were determined in Rana pipiens using the acetic acid test. Each agonist produced a dose-dependent analgesic effect that was sustained for at least 4 hr with all agonists. The analgesic effect of epinephrine and dexmedetomidine was observed 15 min after agonist administration and continued for more than 8 hr. Dexmedetomidine was the most potent agonist followed by epinephrine, norepinephrine and clonidine, and the relative potencies compared to epinephrine = 1.0 were 0.01 (clonidine), 0.02 (norepinephrine) and 4.83 (dexmedetomidine). Pretreatment with selective alpha-2 receptor antagonists, yohimbine and atipamezole, significantly decreased the analgesic effect of dexmedetomidine (80 and 87%) and clonidine (66 and 60%), whereas the selective alpha-1 receptor antagonist, prazosin, had no effect on dexmedetomidine but augmented clonidine analgesia. All animals treated with alpha adrenergic agonists retained corneal, righting and hind limb withdrawal reflexes and exhibited normal behavior. These studies demonstrate that systemic adrenergic agonists produce analgesia in amphibians, with a similar order of potency as reported in mammalian studies, and suggest that this analgesia is mediated by adrenergic alpha-2 receptors.

Effects of sex steroids on myocardial anoxic resistance

Eight treatment groups of CD strain castrate male or female rats were injected daily with cottonseed oil (sham), testosterone propionate (50 micrograms/100 g body wt), estradiol benzoate (7 micrograms/100 g body wt), or a combination of both steroids dissolved in cottonseed oil. These physiologic replacement dosages of sex steroids, determined by bioassay procedures, were injected in a 0.1-ml bolus of cottonseed oil daily (intraperitoneally) for 16 weeks. Myocardial anoxic resistance was quantified by means of an in vitro right ventricular strip preparation that evaluated the ability of the isolated right ventricle to maintain contractions in response to electrical pacing at 1 Hz after 10 min of anoxia. While this parameter was elevated 2- to 3-fold in the estrogen-treated groups of male and female castrates compared with the sham (oil)-injected groups, neither testosterone treatment alone nor combination steroid treatment produced anoxic resistance values that differed significantly from those of the sham-injected animals. Thus, although estrogen alone may afford anoxic protection to the myocardium, testosterone is able to abolish this hormone-induced protection.

Effect of dietary lipids on inotropic responses of isolated rat left atrium: attenuation of maximal responses by an unsaturated fat diet

The effect of varying the dietary fatty acid composition on inotropic responses to various pharmacological agents was investigated in isolated rat left atrium. Pregnant rats were fed either semisynthetic diets supplemented with coconut oil (saturated fatty acids), sunflower oil (unsaturated) or Purina Rodent Chow. Newborns were exposed through the maternal milk and later fed the same diets throughout adulthood. Sunflower oil caused a significant decrease in the maximal response of adult atria to norepinephrine, epinephrine and isoproterenol compared with the other diets. However, no differences in contractile response to norepinephrine were detected at ages 11 and 30 days, indicating a delayed onset of the response changes. We had previously demonstrated defects in the beta adrenoceptor-adenylate cyclase system in homogenates of atria from adult rats fed sunflower oil that may partly explain the attenuated adrenergic response. Additional inotropic studies were performed to further examine the role of this system. There was no change in the maximal contractile response to agents acting through cyclic AMP [cAMP (adenosine 3',5'-cyclic monophosphate)]-independent mechanisms, calcium and phenylephrine. In contrast, maximal responses to forskolin, 3-isobutyl-1-methylxanthine, and N6,2'-O-dibutyryl cAMP, which act via cAMP-dependent mechanisms, were significantly depressed by dietary sunflower oil. No differences were detected in cAMP hydrolysis by phosphodiesterase. These data are consistent with the hypothesis that alterations in adrenergic responsiveness of rat atria after dietary lipid treatment involve functional changes in the adenylate cyclase pathway distal to the enzyme.

Adrenergic beta receptors mediating submandibular salivary gland hypertrophy in the rat

Multiple injections of dobutamine, a selective adrenergic beta-1 receptor agonist, or isoproterenol, a nonselective beta receptor agonist, produced significant dose-dependent enlargement of the submandibular glands of male rats. The glandular enlargement induced by dobutamine or isoproterenol was characterized by significant increases in glandular protein and nucleic acid content and a marked increase in the RNA/DNA ratio. Metoprolol, a selective beta-1 receptor antagonist, significantly inhibited the glandular enlargement induced by dobutamine or isoproterenol and produced a parallel shift in the isoproterenol dose-response curve. Metoprolol also inhibited the increased protein and nucleic acid content induced by dobutamine or isoproterenol. Multiple injections of selective adrenergic beta-2 receptor agonists, terbutaline, fenoterol or salmefamole, failed to produce submandibular gland enlargement. These results indicate that adrenergic beta-1 receptors mediate submandibular gland hypertrophy in the rat.

Latent effects on in vitro development following cytochalasin B treatment of 8-cell mouse embryos

Eight-cell mouse embryos when treated with 4.0 microgram/ml cytochalasin B (CB) in vitro undergo a reversible developmental arrest. Upon rinsing of embryos and subsequent culture in control medium, normal morphogenetic processes such as compaction of 8-cell embryos, cavitation, and post-blastocyst attachment and outgrowth are restored. However, the effects of CB on mouse embryos are not completely reversible; latent post-blastocyst defects become increasingly more prevalent as CB treatment duration increases. The present study was conducted to quantitatively determine latent effects of CB on post-blastocyst embryos by comparing their ability to attach and to sustain the growth and differentiation of ICM and trophoblast tissues. Groups of 8-cell embryos were cultured in Brinster's BMOC-3 medium containing 4.0 microgram/ml cytochalasin B for 6, 12, 18, and 24 h. Following treatment, embryos were rinsed and cultured until 190 h post coitum (h.p.c.) in Eagle's MEM/10% fetal calf serum modified to contain optimal levels of essential amino acids. Blastocysts generally attached to the surface of the plastic substratum by 120 h.p.c. At selected time periods after attachment (130, 160, and 190 h.p.c.), embryos were scored for outgrowth size, ICM size, extent of peripheral hyaloplasmic fan, and number of trophoblast nuclei per outgrowth. Analyses of variance (ANOVAs) were conducted for each of the four parameters listed above. Rates of attachment were analyzed by chi2 test. Results show that the treatments affect (P less than 0.01) embryo attachment, number of trophoblast nuclei per outgrowth, hyaloplasmic fan production, and ICM growth in a duration-dependent manner. Interestingly, since treatment effects on outgrowth areas are nonsignificant apparently CB does not significantly change total outgrowth area. But CB treatment does cause abnormal fan production and decreased trophoblast nuclei numbers. However, trophoblast cells are apparently more resistant than ICM to CB as is evident by the high incidence of trophoblast outgrowths devoid of ICM. CB (4.0 microgram/ml) treatments at 8-cell stages for relatively short durations (6 and 12 h) induce latent effects on post-blastocyst embryos. Finally, there exists a definite 4.0 microgram/ml CB duration response over the 68-190 h.p.c. observation interval.

Latent effects on in vitro development following cytochalasin B treatment of 8-cell mouse embryos

Eight-cell mouse embryos when treated with 4·0 μg/ml cytochalasin B (CB) in vitro undergo a reversible developmental arrest. Upon rinsing of embryos and subsequent culture in control medium, normal morphogenetic processes such as compaction of 8-cell embryos, cavitation, and post-blastocyst attachment and outgrowth are restored. However, the effects of CB on mouse embryos are not completely reversible; latent post-blastocyst defects become increasingly more prevalent as CB treatment duration increases.

The present study was conducted to quantitatively determine latent effects of CB on post-blastocyst embryos by comparing their ability to attach and to sustain the growth and differentiation of ICM and trophoblast tissues. Groups of 8-cell embryos were cultured in Brinster's BMOC-3 medium containing 40 μg/ml cytochalasin B for 6, 12, 18, and 24h. Following treatment, embryos were rinsed and cultured until 190 h post coitun (h.p.c.) in Eagle's MEM/10% fetal calf serum modified to contain optimal levels of essential amino acids. Blastocysts generally attached to the surface of the plastic substratum by 120 h.p.c. At selected time periods after attachment (130, 160, and 190 h.p.c), embryos were scored for outgrowth size, ICM size, extent of peripheral hyaloplasmic fan, and number of trophoblast nuclei per outgrowth. Analyses of variance (ANOVAs) were conducted for each of the four parameters listed above. Rates of attachment were analyzed by χ2 test.

Results show that the treatments affect (P < 0·01) embryo attachment, number of trophoblast nuclei per outgrowth, hyaloplasmic fan production, and ICM growth in a durationdependent manner. Interestingly, since treatment effects on outgrowth areas are nonsignificant apparently CB does not significantly change total outgrowth area. But CB tieatment does cause abnormal fan production and decreased trophoblast nuclei numbers. However, trophoblast cells are apparently more resistant than ICM to CB as is evident by the high incidence of tiophoblast outgrowths devoid of ICM.

CB (4·0 μg/ml) treatments at 8-cell stages for relatively short durations (6 and 12 h) induce latent effects on post-blastocyst embryos. Finally, there exists a definite 4·0 μg/ml CB duration response over the 68–190 h.p.c. observation interval.