Jejunal administration of linoleic acid increases activity of neurons in the paraventricular nucleus of the hypothalamus

Abstract

administration of linoleic acid increases activity of neurons in the paraventricular nucleus of the hypothalamus. Am J Physiol Regul Integr Comp Physiol 286: R166-R173, 2004; 10.1152/ajpregu.00431.2003.-The present experiment examined whether neurons located in the paraventricular nucleus of the hypothalamus (PVN) respond to intestinal infusions of long-chain fatty acids. Single-unit recordings were made of neurons located in and adjacent to the PVN during jejunal administration of linoleic acid. Jejunal administration of linoleic acid increased single-unit activity of neurons located in the PVN but did not affect activity of neurons located in adjacent tissue outside the PVN. The largest increases in neuronal activity were observed in the anterior PVN (0.9-1.3 mm posterior to bregma) compared with the posterior PVN (1.8-2.1 mm posterior to bregma). Jejunal administration of saline failed to affect activity of neurons located either inside or outside the PVN. When the same neurons were subsequently tested for their response to intravenous administration of 2 g/kg of CCK-8, excitatory responses were more frequently observed than inhibitory responses, but both types of responses were observed regardless of whether neurons were located inside or outside the PVN. In addition, there was no strong correlation between the magnitude of the neuronal response evoked by jejunal administration of linoleic acid compared with intravenous CCK-8. These data suggest that neurons located in the anterior PVN may play a role in the mediation of suppression of food intake produced by intestinal administration of lipids.INFUSIONS OF LIPIDS INTO the small intestine can suppress food intake. Under some conditions, the suppression is large enough to result in negative energy balance (4,8,9,35), suggesting a potential clinical role for weight management in humans. For example, we found that jejunal infusions of the long-chain fatty acids (linoleic acid or oleic acid) reduced total caloric intake by ϳ15%. When infusions were administered on 21 consecutive days, body weight was reduced by 10% and carcass fat by 48% compared with controls (8). This effect depends, in part, on activation of vagal afferents, especially those in the celiac branches. Infusions of lipids into the small intestine increase celiac vagal afferent activity (23,25). In addition, we observed that selective celiac vagotomy attenuated linoleic acid-induced suppression of food intake by ϳ50% (Ref. 9; but see Ref. 33). However, because total subdiaphragmatic vagotomy was no more effective in this regard than was celiac vagotomy (6), there must be a nonvagal component that also contributes to suppression of food intake.Our laboratories were especially interested in the potential role of the paraventricular nucleus of the hypothalamus (PVN) in mediating suppression of intake produced by intraintestinal lipids because of its central role in energy balance (cf. Refs. 3, 15, 27, and 34). For example, bilateral lesions of the PVN can produce hyperphagia (7, 28, 31) and local in...

Early changes in insulin secretion and action induced by high-fat diet are related to a decreased sympathetic tone

“…In addition, glucose sensors have been detected in the portal vein (9,18), lipid sensors could exist and mediate to the brain the modifications induced by the HF diet. Consistent with this idea, it has been shown that a jejunum administration of linoleic acid increased the activity of neurons in the PVN of the hypothalamus (38) through the increase of hepatic vagal afferent activity (39). Among the hormonal signals from periphery to brain that could also trigger CNS modifications, ghrelin, a gut hormone acting on the hypothalamus to regulate food intake (20,35,52) and reported to inhibit insulin secretion (41,51), could be a candidate.…”

Nutrient-Sensing Mechanisms in the Gut as Therapeutic Targets for Diabetes

“…In fact, direct jejunal lipid (46–50) or glucose (47) but not protein (47) administration lowers food intake. The underlying mechanisms of jejunal nutrient sensing remain unclear, but the roles of peptide YY (46,47), GLP-1 (46–48), CCK (46), and/or a gut-brain neuronal axis (46,51,52) have been implicated. Nonetheless, given that jejunal nutrient sensing regulates feeding (46–50) and that, as discussed above, duodenal lipid sensing regulates glucose production (12), a potential glucoregulatory role of jejunal nutrient sensing has been examined as well (6) (Fig.…”

Dietary fat stimulates endogenous enkephalin and dynorphin in the paraventricular nucleus: role of circulating triglycerides

“…Either directly or indirectly, these lipid metabolites can alter central neural processes by affecting neuronal activity, enzyme activity, and gene expression (3,13,18,49,53,73). Recent studies (13,56) show that injection of Intralipid or linoleic acid produces an increase in neuronal activity and peptide mRNA, specifically in the PVN and PFH. This effect can be detected in hypothalamic neurons that express the orexin peptides that, like the opioids, stimulate feeding and, in turn, are stimulated by the consumption of a high-fat diet and elevated TG (13).…”