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1.
A new perspective on mechanisms involved in the regulation of a constant fat body mass and its relation to body energy balance is presented on the basis of a series of experiments. A study of the neuroendocrine conditions underlying the daily weight gain-weight loss cycle in rat and man and experimentally induced over and underweight, leads to the notion that lipogenesis and lipolysis above and below a range of physiological fluctuations of body fat develop a counter-regulatory tendency to correcting lipolysis and lipogenesis respectively. This development is attributed to a chronic central action of plasma insulin concentration on hypothalamic insulin receptors. This liporegulatory system which controls and regulates the filling and emptying of fat stores modulates the feeding system which controls and regulates the filling of a gastrointestinal store by eating and its emptying by metabolic food utilization.  相似文献   

2.
Bilateral electrolytic lesions were produced in eight different hypothalamic areas in weanling female rats to localize the area associated with hypothalamic obesity. Animals were maintained for five weeks and food intake measured. After sacrifice, changes in carcass fat content, plasma insulin and plasma glucose were compared to value obtained from sham-operated controls. Only rats with lesions primarily in the ventromedial hypothalamic nuclei had significantly elevated plasma insulin levels and carcass fat content despite normoglycemia, normophagia and normal to reduced body weight gain. The results indicate the existence in the rat hypothalamus of a locus limited to the region of the ventromedial nuclei which affects insulin secretion and lipogenesis. The possible mechanisms responsible for this phenomenon are discussed.  相似文献   

3.
Body weight regulation is the result of food intake and energy expenditure. The central nervous system (CNS), and in particular, the hypothalamus, controls food intake as well as metabolism, the latter mainly by autonomic effects on the islet of Langerhans, hepatocytes and adipocytes. Body weight, more precisely body fat content, is probably controlled by a feedback mechanism in which insulin, released from the B cell of the islet of Langerhans, plays a key role. The islet of Langerhans is an intricate neuroendocrine unit in which the release of glucagon, insulin, and somatostatin from A, B, and D cells, respectively, is controlled by the CNS via a rich autonomic innervation. In addition, the endocrine cells of the pancreas influence each other by paracrine actions. The CNS control of the islets shapes the plasma insulin and blood glucose profiles during the circadian cycle and thereby regulates the nutrient flow to the different tissues in the body. Thus, the CNS structures involved in regulation of body weight and food intake control also metabolism. The mechanisms contributing to match food intake and the needs of metabolism are discussed.  相似文献   

4.
We hypothesize that age-related metabolic alterations originate in the brain (studies in rodents), and that the functional decline of the brain may be protected by a favorable metabolic profile (studies in human centenarians). The metabolic decline with aging is associated with a progressive increase in fat mass in mammals and caloric restriction enhances life span in rodents. Here we show that a diminished biological response to leptin is a feature of aging. Leptin is a fat derived peptide that decreases body weight, fat mass, improves insulin sensitivity and energy expenditure through its receptors in the hypothalamus. We examined the effects of exogenous leptin on several metabolic parameters as a function of aging in rats. A prolonged elevation in plasma leptin levels in aging rats failed to decrease food intake, total fat mass, and intra-abdominal fat. Furthermore, the effects of leptin on liver triglyceride content, on insulin action and insulin secretion were markedly decreased in these animals compared to young controls. Leptin's failure in this aging model suggests its role in age-associated body fat accumulation, fat distribution and insulin resistance. We propose that a central nervous system resistance to leptin is probably a primary event that leads to the metabolic syndrome of aging, especially when availability of calories is unrestricted. Families of centenarians often have extremely high levels of high-density lipoprotein (HDL), which may have neurological as well as cardiovascular protective effects during aging. Because HDL level declines with aging, we tested if centenarians with higher HDL levels have greater cognitive protection. HDL levels correlated significantly with mini-mental state score (MMSE) of the centenarian, and each decrease in HDL tertile was associated with significant decrease in MMSE. These data suggests that the appearance of cognitive dysfunction in centenarians is associated with a decline in HDL cholesterol. This underscores the protective effects of increased HDL cholesterol, and its role in longevity. Taken together, these data suggest a determinant role for brain in the metabolic decline of aging, and highlight the advantage of favorable metabolic profile on the protection of brain from age-related cognitive decline.  相似文献   

5.
The antidepressant phenelzine is a monoamine oxidase inhibitor known to inhibit various other enzymes, among them semicarbazide-sensitive amine oxidase (currently named primary amine oxidase: SSAO/PrAO), absent from neurones but abundant in adipocytes. It has been reported that phenelzine inhibits adipocyte differentiation of cultured preadipocytes. To further explore the involved mechanisms, our aim was to study in vitro the acute effects of phenelzine on de novo lipogenesis in mature fat cells. Therefore, glucose uptake and incorporation into lipid were measured in mouse adipocytes in response to phenelzine, other hydrazine-based SSAO/PrAO-inhibitors, and reference agents. None of the inhibitors was able to impair the sevenfold activation of 2-deoxyglucose uptake induced by insulin. Phenelzine did not hamper the effect of lower doses of insulin. However, insulin-stimulated glucose incorporation into lipids was dose-dependently inhibited by phenelzine and pentamidine, but not by semicarbazide or BTT2052. In contrast, all these SSAO/PrAO inhibitors abolished the transport and lipogenesis stimulation induced by benzylamine. These data indicate that phenelzine does not inhibit glucose transport, the first step of lipogenesis, but inhibits at 100 μM the intracellular triacylglycerol assembly, consistently with its long-term anti-adipogenic effect and such rapid action was not found with all the hydrazine derivatives tested. Therefore, the alterations of body weight control consecutive to the use of this antidepressant drug might be not only related to central effects on food intake/energy expenditure, but could also depend on its direct action in adipocytes. Nonetheless, phenelzine antilipogenic action is not merely dependent on SSAO/PrAO inhibition.  相似文献   

6.
Some atypical antipsychotics have been linked to an increased propensity for weight gain and metabolic disturbances, including type II diabetes. The objective of this study was to investigate an animal model to help understand the mechanisms underlying this phenomenon. Female, Sprague-Dawley rats were treated with olanzapine (2.0 or 7.5 mg/kg, via osmotic mini-pump) for 4 weeks, followed by the hyperinsulinemic/euglycemic and hyperglycemic clamp procedures to assess insulin sensitivity and secretion in vivo. Changes in body weight, visceral fat, food intake and locomotor activity were also assessed. Hepatic glucose production (R(A)) was increased in the hyperinsulinemic/euglycemic clamp for both treatment groups compared to control rats, while the high-dose olanzapine group had decreased peripheral glucose utilization (R(D)). No changes in insulin secretion were detected in the hyperglycemic clamp. Olanzapine did not change body weight or food intake, but did result in significant accumulation of visceral fat and decreases in locomotor activity. Like others, we found that a rodent model for antipsychotic-related weight gain per se is not tenable. However, chronic treatment with olanzapine was found to confer both hepatic and peripheral insulin resistance independent of weight gain, indicating a direct effect on glucose dysregulation.  相似文献   

7.
The hypothalamic melanocortin system regulates feeding in part through interaction of the appetite stimulating peptide, agouti-related protein (AGRP), and the anorectic peptide, alpha-melanocyte stimulating hormone, a peptide derived from the pro-opiomelanocortin (POMC) polyprotein. Central administration of AGRP induces hyperphagia and increased gain in body weight in rodents, but may also exert metabolic effects even when hyperphagia is prevented. In the present studies, the effects of AGRP on hypothalamic neuropeptide gene expression and metabolism were examined in the rat. Central administration of AGRP for 3- and 7-day periods resulted in hyperphagia, increased body weight and increased plasma leptin and insulin concentrations compared to saline-injected controls. Hypothalamic concentrations of Pomc mRNA were also increased by 27% and 44% (in 3- and 7-day experiments, respectively). The hypothalamic concentration of Agrp mRNA was unchanged after 3 days, but was significantly decreased by 33% after 7 days of AGRP infusion. To determine if these changes were dependent upon AGRP-induced hyperphagia, pair-fed rats with restricted food intake receiving central administration of AGRP were also studied. In the absence of hyperphagia, intracerebralventricular administration of AGRP caused significant increases in plasma leptin and insulin concentrations (two-fold and 1.5-fold, respectively) and fat pad mass. A significant increase in hypothalamic Pomc mRNA concentrations was not detected in pair-fed rats. In contrast, Agrp mRNA concentrations remained suppressed by 45% in the pair-fed group after 7 days of AGRP infusion despite equal body weight compared to saline controls. The ratio of hypothalamic Pomc to Agrp mRNA was elevated two-fold in ad libitum and pair-fed AGRP-injected rats, which is consistent with increased stimulation of central melanocortin signalling pathways. Thus, central administration of AGRP exerts changes in hypothalamic neuropeptide gene expression and metabolic effects that are independent of the effects on food intake and body weight.  相似文献   

8.
PURPOSE: The aim of the study was to determine the influence of valproic acid (VPA) treatment on leptin, the soluble leptin receptor (sOB-R), the sOB-R/leptin ratio, body composition and insulin resistance in epileptic children. METHODS: A cross-sectional cohort study was conducted at the Medical University Innsbruck, Austria. Children >6 years with idiopathic epilepsy and antiepileptic drug therapy since at least six months were eligible. Leptin concentration, the sOB-R, the sOB-R/leptin ratio, body composition and glucose homeostasis were determined. RESULTS: 87 children (median [range] age 12.8 years [6.0-18.6]) were on treatment with VPA, 55 (12.3 years [6.4-18.3]) on other AEDs, comprising the non-VPA group. VPA-treated children had higher leptin concentrations, body-mass-index standard-deviation score (SDS), body fat (each p<0.001), serum insulin concentrations (p=0.014) and homeostasis model assessment (HOMA) index (p=0.009), as well as a lower sOB-R/leptin ratio (p<0.001) when compared to the non-VPA group. Overweight VPA-treated children showed lower sOB-R concentrations and a lower sOB-R/leptin ratio (each p<0.001) as well as higher body fat and leptin levels (each p<0.001) compared to lean VPA-treated children. CONCLUSION: VPA monotherapy was associated with higher body weight, body fat and serum leptin concentrations as well as impaired glucose homeostasis. Low sOB-R concentrations and a low sOB-R/leptin ratio in overweight VPA-treated patients might contribute to disturbances in glucose homeostasis and to the development of the metabolic syndrome in these children later in life.  相似文献   

9.
Background Numerous hormones secreted by the gut, during both the fasted state and in response to a meal, influence gastrointestinal motor and/or sensory function, and appear to contribute to the pathogenesis of delayed gastric emptying associated with gastroparesis, functional dyspepsia (FD) and feed intolerance in critical illness. Gut hormones are, accordingly, potential targets for the management of these patients. Purpose This article will discuss the hypersensitivity to enteral fat and endogenous (nutrient‐stimulated) and exogenous cholecystokinin (CCK) in patients with FD, and the elevation in both fasting and postprandial CCK levels evident in this group. It will review the use of pharmacological agonists of motilin and ghrelin, which accelerate gastric emptying, in the management of gastroparesis and FD. The frequent finding of markedly delayed gastric emptying in the critically ill will be examined; this is associated with elevated plasma CCK and peptide YY in both the fasted and postprandial states, which may account for the increase in small intestinal nutrient inhibitory feedback on gastric motility in this group. The concepts that the rate of gastric emptying is a major determinant of postprandial glycemic excursions in diabetes, and that modulation of gastric emptying may improve glycemic control, will be addressed; in type 1 and insulin‐treated type 2 diabetic patients, co‐ordination of insulin administration with nutrient delivery and absorption should be optimized, while type 2 patients who are not on insulin are likely to respond to dietary and/or pharmacological interventions which slow gastric emptying.  相似文献   

10.
IntroductionThere is some evidence that Parkinson's Disease (PD) patients have lower body weight and lower fat mass when compared to healthy subjects and that lower body weight and fat mass influence disease risk and progression. It remains unclear, however, if weight loss of fat mass loss occurs only in a subgroup of patients and whether fat distribution is altered during PD. The aim of this study was to prospectively investigate adipose tissue content and distribution in PD patients.MethodsThe body fat composition of PD patients (N = 54) was compared with age matched healthy controls (N = 55) using a magnetic resonance imaging (MRI)-based method. A longitudinal MRI scan was acquired in 25 PD patients after a mean follow up period of 12 months.ResultsThe volume of total body fat as well as of visceral fat showed no difference between PD patients and healthy controls at baseline or at follow up. However, PD patients displayed decreased subcutaneous fat tissue (p = 0.01) and a higher visceral to subcutaneous fat ratio as compared to controls (p = 0.004). After follow up, 16 PD patients did not lose weight, while 9 PD patients lost between 0.5 and 10 kg.ConclusionFat distribution is altered in PD patients, with an increased ratio of visceral to subcutaneous fat.  相似文献   

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