Rosiglitazone in the management of older patients with type 2 diabetes mellitus

The prevalence of type 2 diabetes increases dramatically with age in all populations. This report describes a post-hoc analysis of eight rosiglitazone monotherapy studies to characterise the efficacy and safety of rosiglitazone in older patients with type 2 diabetes, using a designation of > or = 70 years for elderly. A total of 3,127 patients were randomised to rosiglitazone (<70 years: n=2099; > or = 70 years: n = 427) or placebo (<70 years: n = 497; > or = 70 years: n=104). In both age groups, rosiglitazone 4 mg/day and 8 mg/day reduced HbA1c and fasting plasma glucose compared with baseline and placebo at week 26 with no difference between age groups. There was no difference between the nature, severity or type of adverse events experienced by older or younger patients. Rosiglitazone improves glycaemic control and is well tolerated in older as well as younger patients with type 2 diabetes.

Effects of glucagon on renal and hepatic glutamine gluconeogenesis in normal postabsorptive humans

Glutamine is an important gluconeogenic amino acid in postabsorptive humans. To assess the effect of glucagon on renal and hepatic glutamine gluconeogenesis, we infused six normal healthy postabsorptive subjects with glucagon at a rate chosen to produce circulating glucagon concentrations found during hypoglycemia and, using a combination of isotopic and net balance techniques, determined the systemic, renal, and hepatic glucose release and renal and hepatic production of glucose from glutamine. Infusion of glucagon increased systemic and hepatic glucose release (both P < .02), but had no effect on renal glucose release (P = .26). Systemic and hepatic glutamine gluconeogenesis increased from 0.45 +/- 0.3 and 0.11 +/- 0.02 micromol x kg(-1) x min(-1), respectively, to 0.61 +/- 0.04 (P = .002) and 0.31 +/- 0.03 micromol x kg(-1) x min(-1) (P = .001), respectively, whereas renal glutamine gluconeogenesis was unchanged (from 0.33 +/- 0.03 to 0.30 +/- 0.04 micromol x kg(-1) x min(-1), P = .20). The hepatic contribution to systemic glutamine gluconeogenesis increased from 25.2% +/- 6.2% to 51.6% +/- 5.5% (P = .002), while that of the kidney decreased from 74.8% +/- 6.2% to 48.4% +/- 5.5% (P = .003). Glucagon had no effect on the renal net balance, fractional extraction, or uptake and release of either glucose or glutamine. We thus conclude that glucagon stimulates glutamine gluconeogenesis in normal postabsorptive humans, predominantly due to an increase in hepatic glutamine conversion to glucose. Thus, under certain conditions such as counterregulation of hypoglycemia, the liver may be an important site of glutamine gluconeogenesis.

Human kidney and liver gluconeogenesis: evidence for organ substrate selectivity

To assess the contribution of the human kidney to gluconeogenesis (GN) and its role in conversion of glutamine and alanine to glucose, we used a combination of isotopic and organ balance techniques in nine normal postabsorptive volunteers and measured both overall and renal incorporation of these precursors into glucose before and after infusion of epinephrine. In the postabsorptive basal state, renal incorporation of glutamine (27 +/- 2 mumol/min) and alanine (2.1 +/- 0.5 mumol/min) into glucose accounted for 72.8 +/- 3.3 and 3.9 +/- 0.5% of their overall incorporation into glucose (37 +/- 2 and 51 +/- 6 mumol/min, respectively) and 19.0 +/- 3.5 and 1.4 +/- 0.2%, respectively, of overall renal glucose release. Infusion of epinephrine, which increased systemic and renal glucose release more than twofold (P < 0.001), increased overall glutamine and alanine incorporation into glucose (both P < 0.001) and increased renal GN from glutamine (P < 0.001) but not from alanine (P = 0.15). Renal glutamine GN now accounted for 90.3 +/- 4.0% of overall glutamine GN (P = 0.01 vs. basal), whereas renal alanine GN still accounted for only 4.8 +/- 1.7% of overall alanine GN (P = 0.36 vs. basal). With the assumption that kidney and liver are the only gluconeogenic organs in humans, these results indicate that glutamine GN occurs primarily in kidney, whereas alanine GN occurs almost exclusively in liver. Isotopic studies of glutamine and alanine incorporation into plasma glucose may provide a selective, noninvasive method to assess hepatic and renal GN.

Effects of hypothyroidism on rat circadian activity and temperature rhythms and their response to light

Male rats made hypothyroid by administration of propylthiouracil plus sodium ipodate in drinking water were compared to controls in terms of period of circadian activity and temperature rhythms, amount of gross motor activity, and mean temperature. Animals were studied under entrainment, constant darkness (DD), and constant dim light (LL). There was no difference in the period of the circadian activity rhythm between groups in DD. However, hypothyroid rats showed significant blunting of the period-lengthening response to increasing ambient illumination. As expected, the period of the circadian temperature rhythm increased in controls with increasing ambient illumination. In contrast, the period of the circadian temperature rhythm in hypothyroid animals actually shortened under LL compared to DD. This blunting of the period-lengthening response to increasing ambient illumination of both activity and temperature rhythms in hypothyroid animals could not be explained by differences in activity level or mean temperature between the groups.

Effects of intrabulbar injections of 6-hydroxydopamine on ethyl acetate odor detection in castrate and non-castrate male rats

The function of norepinephrine-containing neurons which project to the olfactory bulb is poorly understood. Although there has been suggestion that norepinephrine (NE) may modulate general olfactory sensitivity by attenuating the inhibitory feedback of granule cells upon mitral and tufted cells, behavioral indices of olfactory sensitivity have not been measured in animals with depletions of bulbar NE. The present experiment used computerized olfactometry and signal detection methodology to assess the odor detection performance of castrate and non-castrate male rats to a range of perithreshold concentrations of ethyl acetate following 6-hydroxydopamine (6-OHDA) depletion of bulbar NE. Such depletion had no significant influence on odor detection performance at any of the odorant concentrations examined in either castrate or non-castrate animals, as indexed by the non-parametric sensitivity measure SI. This observation implies that general olfactory sensitivity is unaltered by major depletion of intrabulbar NE, but does not preclude the possibility that NE modulates sensitivity to select odorants or odorant mixtures, or alters detection ability under atypical states of arousal.

Brain serotonin depletion and nipple attachment in rat pups

5,7-DHT (104 micrograms) was injected into the third brain ventricle of three-day-old rat pups 1 hr after desmethylimipramine pretreatment (20 mg/kg IP). Whole-brain serotonin was depleted by 50%, and there was some retardation of weight gain. Nipple attachment was observed in sucklings and in weaned pups. When 9 days old, attachment in 5-HT depleted pups was delayed and they were less active when undeprived, but not when 8 hr deprived. In comparison with pups raised in litters of 6 or 14, which served to control for reduced body weight, depleted pups' behavior was more similar to the heavier pups, suggesting that the behavioral differences were not due to retarded growth. After weaning at 21 days, depleted pups attached more up to 37 days of age, after which attachment was not reinstated by treatment with methysergide, suggesting that the waning of depletion induced attachment was not due to recovery of serotonergic function. Again, body weight controls showed that the effects were not due to retarded weight gain in the depleted pups. The results confirm the biphasic action of 5-HT antagonism on attachment, i.e., inhibition in the neonate and disinhibition in the weanling. The findings also show that central 5-HT systems are involved in the inhibition of attachment during weaning, but that this involvement is transient, and apparently not crucial.