Thyrotropin-releasing hormone (TRH) is released from the median eminence upon neural stimulation such as cold or suckling exposure. Concomitant with the cold- or suckling-induced release of TRH is a rapid and transient increase in the expression of proTRH mRNA in the paraventricular nucleus (PVN) of the hypothalamus. We employed two strategies to determine whether TRH neurons responding to cold exposure are different from those responding to suckling. First, we attempted to identify a marker of cellular activation in TRH neurons of the PVN. Cold induced c-fos expression in about 25% of TRH neurons of the PVN, but no induction was observed by suckling. Moreover, we explored the expression of a variety of immediate early genes including NGFI-A, fra-1 and c-jun, or CREB phosphorylation but found none to be induced by suckling. The number of cells expressing high levels of proTRH mRNA was counted and compared to total expressing cells. An increased number of cells expressing high levels of proTRH mRNA was observed when both stimuli were applied to the same animal, suggesting that different cells respond separately to each stimulus. We therefore analyzed the distribution of responsive TRH neurons as defined by the cellular level of proTRH mRNA. The proTRH mRNA signal was analyzed within three rostrocaudal zones of the PVN and within six mediolateral columns. Results showed that in response to cold, all areas of the PVN of the lactating rat present increased proTRH mRNA levels, including the anterior zone where few hypophysiotropic TRHergic cells are believed to reside. The distribution of the proTRH mRNA expressing cells in response to cold was quite comparable in female and in male rats. In contrast, the response after suckling was confined to the middle and caudal zones. Our results provide evidence of a functional specialization of TRH cells in the PVN.

Energy expenditure and thermogenesis are regultated by thyroid and sex hormones. Several parameters of hypothalamic-pituitary-thyroid (HPT) axis function are modulated by 17β-oestradiol (E(2)) but its effects on thyrotrophin-releasing hormone (TRH) mRNA levels remain unknown. We evaluated, by in situ hybridisation and Northern bloting, TRH expression in the paraventricular nucleus of the hypothalamus (PVN) of cycling rats, 2 weeks-ovariectomised (OVX) and OVX animals injected s.c. during 1-4 days with E(2) (5, 50, 100 or 200 μg ⁄ kg) (OVX-E). Serum levels of E(2), thyroid-stimulating hormone (TSH), prolactin, corticosterone and triiodothyronine (T(3)) were quantified by radioimmunoassay. Increased serum E(2) levels were observed after 4 days injection of 50 μg ⁄ kg E(2) (to 68.5 ± 4.8 pg ⁄ ml) in OVX rats. PVN-TRH mRNA levels were slightly higher in OVX than in virgin females at dioestrous 1 or pro-oestrous, decreasing proportionally to increased serum E(2) levels. E(2) injections augmented serum T(3), prolactin, and corticosterone levels. Serum TSH levels augmented with 4 days 50 μg ⁄ kg E(2), but not with the higher doses that enhanced serum T(3) levels. Exposure to cold for 1 h resulted in marked HPT axis activation in OVX rats, increasing the levels of TRH mRNA along the rostro-caudal PVN areas, as well as serum TSH, T(3), corticosterone and prolactin levels. By contrast, no significant changes in any of these parameters were observed in cold-exposed OVX-E (50 μg ⁄ kg E(2)) rats. Very few PVN-TRHergic neurones expressed the oestrogen receptor type-α, suggesting that the effects of E(2) on PVN-TRH expression are indirect, most probably as a result of its multiple modulatory effects on circulating hormones and their receptor sensitivity. The blunted response of OVX-E rats to cold coincides with the effects of E(2) on the autonomic nervous system and increased cold tolerance.

BackgroundDyslipidemia is associated with cardiovascular morbidities and mortality. Currently, fasting lipid profile determination is used to monitor treatment response. Recently, postprandial lipemia is of increasing interest because of its atherogenic and thrombogenic potential and also was found to be more predictive for cardiovascular diseases.ObjectivesTo demonstrate postprandial lipemia among patients with cardiovascular diseases despite low fat diet, normal fasting lipid profile and even statin regimen.Patients and MethodsPatients aged 40-80 years old with cardiovascular diseases (i.e. coronary artery disease and cerebrovascular disease) more than 6 months, on statin treatment for more than 6 months and normal fasting lipid profile (according to NCEP ATP III guidelines) were included.Study exclusion criteria were pregnancy, acute cardiovascular events < 6 months, hepatic or renal failure. Finally, twelve patients were included.ResultsThe triglyceride level showed a significant rise from fasting to 2 hours after breakfast with a mean difference of 23.86 mg/dL (P =0.012). The level peaked at 4 hours after breakfast with a mean difference (MD) of 72.02 mg/dL (P =0.002). Subsequent triglyceride levels plateaued and were significantly higher than the baseline (P <0.05) until the 12th hour of observation. VLDL levels showed a similar pattern. Levels increased significantly from fasting to 2h after breakfast (mean difference: 4.49 mg/dL, P = 0.007), then plateaued and further increased 4 hours after breakfast (MD: 14.01 mg/dL, P = 0.002). VLDL levels were significantly higher than fasting (P < 0.05) and did not return to baseline until the 12th hour of observation. In contrast, the levels of total cholesterol, HDL and LDL decreased postprandially.ConclusionsTriglyceride and VLDL peaking and plateauing were observed in patients with cardiovascular diseases despite low fat diet, normal fasting lipid profile and statin regimen. These findings may raise more attentions in monitoring and management of dyslipidemia in patients with cardiovascular and cerebrovascular events.

BackgroundPostprandial lipemia has been found to be strongly associated with atherosclerosis due to its atherogenic and thrombogenic lipoprotein changes. This phenomenon occurs even in normal subjects especially after high fat meals. Orlistat, an anti- obesity drug, has been shown to address postprandial lipemia after a single high fat meal.ObjectivesTo compare the effects of orlistat and placebo on the postprandial lipid levels after sequential high-fat meals in healthy individuals with normal fasting lipid levels.Patients and MethodsThirty-one healthy adult volunteers with normal fasting lipid levels were fed 50% fat meals (3 meals and 2 snacks of pre-weighted butter and bread). The subjects were blindly randomized to receive either placebo or orlistat 120 mg before each main meal. The outcome parameters were total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and very-low–density lipoprotein (VLDL) cholesterol levels measured at fasting (0 h) and every 2 h thereafter, until the sixteenth hour. Additionally, we estimated the lipid levels at the fifth and ninth hour.ResultsThe non-orlistat group showed a significant postprandial rise in the levels of TG and VLDL, which began 4 h after breakfast (P < 0.05); this rise in levels was sustained until 9 h after breakfast for TG and up to 10 h after breakfast for VLDL. In contrast, only one significant rise in both TG and VLDL levels (at 4 h after breakfast) was noted in the orlistat group. The maximum mean difference from the baseline TG level for the orlistat group was lower than that for the non-orlistat group (0.22 mmol/L vs. 0.756 mmol/L, respectively). Similarly, the maximum mean difference from the baseline VLDL level from baseline in the orlistat group was only 0.099 mmol/L, which was lower than that in the non-orlistat group (0.588 mmol/L). LDL levels rose to a lesser extent in the orlistat group than in the non-orlistat group (0.268 vs. 0.362 mmol/L). The TC levels did not show a postprandial rise; instead, the levels reduced in both groups, with the orlistat group showing a higher reduction than the non-orlistat group (-0.288 vs. -0.188 mmol/L). The orlistat group did not show any significant differences in the HDL measurements.ConclusionsAdministration of orlistat abolished the significantly sustained postprandial rise of TG and VLDL levels in healthy individuals who were fed sequential 50% fat meals.

BAVS with glucagon stimulation will lead to early diagnosis of microscopic pheochromocytoma, thus preventing chronic complications like atherosclerosis, and untoward events like myocardial infarction and stroke.