Role of small intestine in caloric compensations to oil premeals in rats

Role of the gut, melanocortin system and malonyl-CoA in control of feed intake in non-ruminant animals

Regulation of feed intake is under complex control, involving physical, chemical, hormonal and neuronal responses. Understanding the regulation of feed intake in farm animals is key to optimisation of intake to meet production and profitability goals. Fundamental mechanisms regulating feed intake include constraints imposed by the gut, systems monitoring current and long-term energy status to increase or decrease intake, and hedonic, reward-related drives. Feed intake is closely related to the rate of passage of digesta and the capacity of the gastrointestinal tract. Indigestible fibre increases the rate of digesta passage and feed intake until excess distension sends signals of satiety to the brain. The presence of partially digested nutrients and products of microbial fermentation in the distal intestines releases peptides (PYY, OXM, GPL-1, Apo A-IV, amylin) from gut and pancreas to activate the intestinal brake, which slows the rate of passage and reduces feed intake. These peptides also act on orexigenic (NPY, AgRP) and anorexigenic (POMC, CART) peptides of the melanocortin system of the hypothalamus to reduce intake over the long term. Immediate energy status of the animal is monitored through the ratio of AMP : ATP via adenosine monophosphate-activated kinase and mammalian target of rapamycin, whereas the overall animal energy status is monitored by insulin, leptin and ghrelin. These energy-monitoring systems control short- and long-term intakes through the melanocortin system of the hypothalamus, primarily via malonyl-CoA, to alter the relative expression of orexigenic and anorexigenic peptides. Gut and hypothalamic control of feed intake can be over-ridden by hedonic, reward-related centres of the brain, predominantly through the release of dopamine. These hedonic responses can lead to over-consumption and obesity under some circumstances or reduced feed intake under stressful or other negative environmental situations. Knowledge of these mechanisms can be used to identify practical strategies for either increasing or decreasing voluntary intake in pigs.

Lipids, CHOs, proteins: can all macronutrients put a 'brake' on eating?

The gastrointestinal (GI) tract and specifically the most distal part of the small intestine, the ileum, has become a renewed focus of interest for mechanisms targeting appetite suppression. The 'ileal brake' is stimulated when energy-containing nutrients are delivered beyond the duodenum and jejunum and into the ileum, and is named for the feedback loop which slows or 'brakes' gastric emptying and duodeno-jejunal motility. More recently it has been hypothesized that the ileal brake also promotes secretion of satiety-enhancing GI peptides and suppresses hunger, placing a 'brake' on food intake. Postprandial delivery of macronutrients to the ileum, other than unavailable carbohydrates (CHO) which bypass absorption in the small intestine en route to fermentation in the large bowel, is an uncommon event and hence this brake mechanism is rarely activated following a meal. However the ability to place a 'brake' on food intake through delivery of protected nutrients to the ileum is both intriguing and challenging. This review summarizes the current clinical and experimental evidence for activation of the ileal brake by the three food macronutrients, with emphasis on eating behavior and satiety as well as GI function. While clinical studies have shown that exposure of the ileum to lipids, CHOs and proteins may activate GI components of the ileal brake, such as decreased gut motility, gastric emptying and secretion of GI peptides, there is less evidence as yet to support a causal relationship between activation of the GI brake by these macronutrients and the suppression of food intake. The predominance of evidence for an ileal brake on eating comes from lipid studies, where direct lipid infusion into the ileum suppresses both hunger and food intake. Outcomes from oral feeding studies are less conclusive with no evidence that 'protected' lipids have been successfully delivered into the ileum in order to trigger the brake. Whether CHO or protein may induce the ileal brake and suppress food intake has to date been little investigated, although both clearly have GI mediated effects. This review provides an overview of the mechanisms and mediators of activation of the ileal brake and assesses whether it may play an important role in appetite suppression.

Oral and gastrointestinal sensing of dietary fat and appetite regulation in humans: modification by diet and obesity

Dietary fat interacts with receptors in both the oral cavity and the gastrointestinal (GI) tract to regulate fat and energy intake. This review discusses recent developments in our understanding of the mechanisms underlying the effects of fat, through its digestive products, fatty acids (FAs), on GI function and energy intake, the role of oral and intestinal FA receptors, and the implications that changes in oral and small intestinal sensitivity in response to ingested fat may have for the development of obesity.

Deficits in gastrointestinal responses controlling food intake and body weight

The gastrointestinal tract serves as a portal sensing incoming nutrients and relays mechanical and chemosensory signals of a meal to higher brain centers. Prolonged consumption of dietary fat causes adaptive changes within the alimentary, metabolic, and humoral systems that promote a more efficient process for energy metabolism from this rich source, leading to storage of energy in the form of adipose tissue. Furthermore, prolonged ingestion of dietary fats exerts profound effects on responses to signals involved in termination of a meal. This article reviews the effects of ingested fat on gastrointestinal motility, hormone release, and neuronal substrates. It focuses on changes in sensitivity to satiation signals resulting from chronic ingestion of high-fat diet, which may lead to disordered appetite and dysregulation of body weight.

The lipid messenger OEA links dietary fat intake to satiety

The association between fat consumption and obesity underscores the need to identify physiological signals that control fat intake. Previous studies have shown that feeding stimulates small-intestinal mucosal cells to produce the lipid messenger oleoylethanolamide (OEA) which, when administered as a drug, decreases meal frequency by engaging peroxisome proliferator-activated receptors-alpha (PPAR-alpha). Here, we report that duodenal infusion of fat stimulates OEA mobilization in the proximal small intestine, whereas infusion of protein or carbohydrate does not. OEA production utilizes dietary oleic acid as a substrate and is disrupted in mutant mice lacking the membrane fatty-acid transporter CD36. Targeted disruption of CD36 or PPAR-alpha abrogates the satiety response induced by fat. The results suggest that activation of small-intestinal OEA mobilization, enabled by CD36-mediated uptake of dietary oleic acid, serves as a molecular sensor linking fat ingestion to satiety.

The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women

Appetite suppressants may be one strategy in the fight against obesity. This study evaluated whether Korean pine nut free fatty acids (FFA) and triglycerides (TG) work as an appetite suppressant. Korean pine nut FFA were evaluated in STC-1 cell culture for their ability to increase cholecystokinin (CCK-8) secretion vs. several other dietary fatty acids from Italian stone pine nut fatty acids, oleic acid, linoleic acid, alpha-linolenic acid, and capric acid used as a control. At 50 μM concentration, Korean pine nut FFA produced the greatest amount of CCK-8 release (493 pg/ml) relative to the other fatty acids and control (46 pg/ml). A randomized, placebo-controlled, double-blind cross-over trial including 18 overweight post-menopausal women was performed. Subjects received capsules with 3 g Korean pine (Pinus koraiensis) nut FFA, 3 g pine nut TG or 3 g placebo (olive oil) in combination with a light breakfast. At 0, 30, 60, 90, 120, 180 and 240 minutes the gut hormones cholecystokinin (CCK-8), glucagon like peptide-1 (GLP-1), peptide YY (PYY) and ghrelin, and appetite sensations were measured. A wash-out period of one week separated each intervention day.

CCK-8 was higher 30 min after pine nut FFA and 60 min after pine nut TG when compared to placebo (p < 0.01). GLP-1 was higher 60 min after pine nut FFA compared to placebo (p < 0.01). Over a period of 4 hours the total amount of plasma CCK-8 was 60% higher after pine nut FFA and 22% higher after pine nut TG than after placebo (p < 0.01). For GLP-1 this difference was 25% after pine nut FFA (P < 0.05). Ghrelin and PYY levels were not different between groups. The appetite sensation "prospective food intake" was 36% lower after pine nut FFA relative to placebo (P < 0.05).

This study suggests that Korean pine nut may work as an appetite suppressant through an increasing effect on satiety hormones and a reduced prospective food intake.

Load-dependent effects of duodenal lipid on antropyloroduodenal motility, plasma CCK and PYY, and energy intake in healthy men

Both load and duration of small intestinal lipid infusion affect antropyloroduodenal motility and CCK and peptide YY (PYY) release at loads comparable to and higher than the normal gastric emptying rate. We determined 1) the effects of intraduodenal lipid loads well below the mean rate of gastric emptying on, and 2) the relationships between antropyloroduodenal motility, CCK, PYY, appetite, and energy intake. Sixteen healthy males were studied on four occasions in double-blind, randomized fashion. Antropyloroduodenal motility, plasma CCK and PYY, and appetite perceptions were measured during 50-min IL (Intralipid) infusions at: 0.25 (IL0.25), 1.5 (IL1.5), and 4 (IL4) kcal/min or saline (control), after which energy intake at a buffet meal was quantified. IL0.25 stimulated isolated pyloric pressure waves (PWs) and CCK release, albeit transiently, and suppressed antral PWs, PW sequences, and hunger (P < 0.05) but had no effect on basal pyloric pressure or PYY when compared with control. Loads >/= 1.5 kcal/min were required for the stimulation of basal pyloric pressures and PYY and suppression of duodenal PWs (P < 0.05). All of these effects were related to the lipid load (R > 0.5 or < -0.5, P < 0.05). Only IL4 reduced energy intake (in kcal: control, 1,289 +/- 62; IL0.25, 1,282 +/- 44; IL1.5, 1,235 +/- 71; and IL4, 1,139 +/- 65 compared with control and IL0.25, P < 0.05). In conclusion, in healthy males the effects of intraduodenal lipid on antropyloroduodenal motility, plasma CCK and PYY, appetite, and energy intake are load dependent, and the threshold loads required to elicit responses vary for these parameters.

Modulation by high-fat diets of gastrointestinal function and hormones associated with the regulation of energy intake: implications for the pathophysiology of obesity

The presence of fat in the small intestine slows gastric emptying, stimulates the release of many gastrointestinal hormones, and suppresses appetite and energy intake as a result of the digestion of fats into free fatty acids; the effects of free fatty acids are, in turn, dependent on their chain length. Given these effects of fat, it is paradoxical that high dietary fat intakes have been linked to increased energy intake and body weight and are considered to play a significant role in the pathogenesis of obesity. However, increasing evidence indicates that a chronic increase in dietary fat is associated with an attenuation of the feedback signals arising from the small intestine induced by fat, with a consequent relative acceleration of gastric emptying, modulation of gastrointestinal hormone secretion, and attenuation of the suppression of energy intake. This review addresses the gastrointestinal factors involved in the regulation of appetite and energy intake, with a particular focus on 1) the gastrointestinal mechanisms triggered by small intestinal fat that modulate energy intake, 2) the potential role of a high dietary fat intake in the development of obesity, and 3) implications for the prevention and management of obesity.

Influence of nutrient preload on encapsulated macronutrient selection in European sea bass

The sea bass is a teleost that is able to regulate its energy intake by selecting from pure macronutrient sources, although the regulatory mechanisms involved in this selection are unknown. Nutrient preloads are known to reduce food intake and modify macronutrient selection patterns in mammals, but no information is available on its effects in fish. The aim of the present work was to determine the effect of orally administered macronutrient preloads of protein (P), fat (F) or carbohydrate (CH) on the subsequent macronutrient selection, using for the purpose feed consisting of CH, P or F packaged separately in gelatin capsules. The macronutrient preloads left the total food intake unaltered, but caused differential changes in the pattern of macronutrient selection. The CH preload increased the selection of CH (39%) and decreased that of P (20%), independently of the fish's previous nutritional preferences. The F preload induced an F increase (32%) and a P decrease (18%) in P-preferring fish, but not in F-preferring fish in which the macronutrient selection pattern remained unaffected. The P preload stimulated F selection by 42% in P-preferring fish, but left the macronutrient selection pattern unchanged in F-preferring fish. In conclusion, oral macronutrient preloads affected the pattern of macronutrient selection in fish, acting by post-ingestive mechanisms. The effect was influenced by the fish's previous nutritional preference and/or status, which could depend on its metabolic capacity.

Effects of load, and duration, of duodenal lipid on antropyloroduodenal motility, plasma CCK and PYY, and energy intake in healthy men

Enterally administered lipid modulates antropyloroduodenal motility, gut hormone release, appetite, and energy intake. We hypothesized that these effects would be dependent on both the load, and duration, of small intestinal exposure to lipid. Eleven healthy men were studied on four occasions in a double-blind, randomized, fashion. Antropyloroduodenal motility, plasma CCK and peptide YY (PYY) concentrations, and appetite perceptions were measured during intraduodenal infusion of lipid (Intralipid) at 1) 1.33 kcal/min for 50 min, 2) 4 kcal/min for 50 min, and 3) 1.33 kcal/min for 150 min, or 4) saline for 150 min. Immediately after the infusions, energy intake was quantified. Pressure wave sequences (PWSs) were suppressed, and basal pyloric pressure, isolated pyloric pressure waves (IPPWs), plasma CCK and PYY stimulated (all P < 0.05), during the first 50 min of lipid infusion, in a load-dependent fashion. The effect of the 4 kcal/min infusion was sustained so that the suppression of antral pressure waves (PWs) and PWSs and increase in PYY remained evident after cessation of the infusion (all P < 0.05). The prolonged lipid infusion (1.33 kcal/min for 150 min) suppressed antral PWs, stimulated CCK and PYY and basal pyloric pressure (all P < 0.05), and tended to stimulate IPPWs when compared with saline throughout the entire infusion period. There was no significant effect of any of the lipid infusions on appetite or energy intake, although nausea was slightly higher (P < 0.05) with the 4 kcal/min infusion. In conclusion, both the load, and duration, of small intestinal lipid influence antropyloroduodenal motility and patterns of CCK and PYY release.

Fat digestion is required for suppression of ghrelin and stimulation of peptide YY and pancreatic polypeptide secretion by intraduodenal lipid

Stimulation of cholecystokinin and glucagon-like peptide-1 secretion by fat is mediated by the products of fat digestion. Ghrelin, peptide YY (PYY), and pancreatic polypeptide (PP) appear to play an important role in appetite regulation, and their release is modulated by food ingestion, including fat. It is unknown whether fat digestion is a prerequisite for their suppression (ghrelin) or release (PYY, PP). Moreover, it is not known whether small intestinal exposure to fat is sufficient to suppress ghrelin secretion. Our study aimed to resolve these issues. Sixteen healthy young males received, on two separate occasions, 120-min intraduodenal infusions of a long-chain triglyceride emulsion (2.8 kcal/min) 1) without (condition FAT) or 2) with (FAT-THL) 120 mg of tetrahydrolipstatin (THL, lipase inhibitor), followed by a standard buffet-style meal. Blood samples for ghrelin, PYY, and PP were taken throughout. FAT infusion was associated with a marked, and progressive, suppression of plasma ghrelin from t = 60 min (P < 0.001) and stimulation of PYY from t = 30 min (P < 0.01). FAT infusion also stimulated plasma PP (P < or = 0.01), and the release was immediate. FAT-THL completely abolished the FAT-induced changes in ghrelin, PYY, and PP. In response to the meal, plasma ghrelin was further suppressed, and PYY and PP stimulated, during both FAT and FAT-THL infusions. In conclusion, in healthy humans, 1) the presence of fat in the small intestine suppresses ghrelin secretion, and 2) fat-induced suppression of ghrelin and stimulation of PYY and PP is dependent on fat digestion.

Effects of drink volume and glucose load on gastric emptying and postprandial blood pressure in healthy older subjects

Postprandial hypotension (PPH) occurs frequently in the elderly; the magnitude of the fall in blood pressure (BP) is related to the rate of glucose entry into the duodenum during intraduodenal glucose infusion and spontaneous gastric emptying (GE). It is unclear if glucose concentration affects the hypotensive response. Gastric distension may attenuate PPH; therefore, meal volume could influence the BP response. We aimed to determine the effects of 1) drink volume, 2) glucose concentration, and 3) glucose content on the BP and heart rate (HR) responses to oral glucose. Ten subjects (73.9 +/- 1.2 yr) had measurements of BP, GE, and blood glucose on 4 days after 1) 25 g glucose in 200 ml (12.5%), 2) 75 g glucose in 200 ml (37.5%), 3) 25 g glucose in 600 ml (4%), and 4) 75 g glucose in 600 ml (12.5%). GE, BP, HR, and blood glucose were measured for 180 min. After all drinks, duodenal glucose loads were similar in the first 60 min. Regardless of concentration, 600-ml (but not 200-ml) drinks initially increased BP, and in the first 30 min, systolic BP correlated (P < 0.01) with volume in both the proximal and total stomach. At the same concentration (12.5%), systolic BP fell more (P = 0.02) at the smaller volume; at the same volumes, there were no effects of concentration on BP. There was no difference in the glycemic response to drinks of identical glucose content. We conclude that 1) ingestion of glucose at a higher volume attenuates and 2) under constant duodenal load, glucose concentration (4-37%) does not affect the fall in BP.

Effects of intraduodenal fatty acids on appetite, antropyloroduodenal motility, and plasma CCK and GLP-1 in humans vary with their chain length

The gastrointestinal effects of intraluminal fats may be critically dependent on the chain length of fatty acids released during lipolysis. We postulated that intraduodenal administration of lauric acid (12 carbon atoms; C12) would suppress appetite, modulate antropyloroduodenal pressure waves (PWs), and stimulate the release of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) more than an identical dose of decanoic acid (10 carbon atoms; C10). Eight healthy males (19-47 yr old) were studied on three occasions in a double-blind, randomized fashion. Appetite perceptions, antropyloroduodenal PWs, and plasma CCK and GLP-1 concentrations were measured during a 90-min intraduodenal infusion of 1) C12, 2) C10, or 3) control (rate: 2 ml/min, 0.375 kcal/min for C12/C10). Energy intake at a buffet meal, immediately after completion of the infusion, was also quantified. C12, but not C10, suppressed appetite perceptions (P < 0.001) and energy intake (control: 4,604 +/- 464 kJ, C10: 4,109 +/- 588 kJ, and C12: 1,747 +/- 632 kJ; P < 0.001, C12 vs. control/C10). C12, but not C10, also induced nausea (P < 0.001). C12 stimulated basal pyloric pressures and isolated pyloric PWs and suppressed antral and duodenal PWs compared with control (P < 0.05 for all). C10 transiently stimulated isolated pyloric PWs (P = 0.001) and had no effect on antral PWs but markedly stimulated duodenal PWs (P = 0.004). C12 and C10 increased plasma CCK (P < 0.001), but the effect of C12 was substantially greater (P = 0.001); C12 stimulated GLP-1 (P < 0.05), whereas C10 did not. In conclusion, there are major differences in the effects of intraduodenal C12 and C10, administered at 0.375 kcal/min, on appetite, energy intake, antropyloroduodenal PWs, and gut hormone release in humans.

Effects of fat digestion on appetite, APD motility, and gut hormones in response to duodenal fat infusion in humans

The presence of nutrients in the small intestine slows gastric emptying and suppresses appetite and food intake; these effects are partly mediated by the release of gut hormones, including CCK. We investigated the hypothesis that the modulation of antropyloroduodenal motility, suppression of appetite, and stimulation of CCK and glucagon-like peptide-1 secretion by intraduodenal fat are dependent on triglyceride hydrolysis by lipase. Sixteen healthy, young, lean men were studied twice in double-blind, randomized, crossover fashion. Ratings for appetite-related sensations, antropyloroduodenal motility, and plasma CCK and glucagon-like peptide-1 concentrations were measured during a 120-min duodenal infusion of a triglyceride emulsion (2.8 kcal/min) on one day with, on the other day without, 120 mg tetrahydrolipstatin, a potent lipase inhibitor. Immediately after the duodenal fat infusion, food intake at a buffet lunch was quantified. Lipase inhibition with tetrahydrolipstatin was associated with reductions in tonic and phasic pyloric pressures, increased numbers of isolated antral and duodenal pressure waves, and stimulation of antropyloroduodenal pressure-wave sequences (all P < 0.05). Scores for prospective consumption and food intake at lunch were greater, and nausea scores were slightly less, and the rises in plasma CCK and glucagon-like peptide-1 were abolished (all P < 0.05). In conclusion, lipase inhibition attenuates the effects of duodenal fat on antropyloroduodenal motility, appetite, and CCK and glucagon-like peptide-1 secretion.

Effects of glucose supplementation on gastric emptying, blood glucose homeostasis, and appetite in the elderly

The aims of this study were to evaluate the effects of dietary glucose supplementation on gastric emptying (GE) of both glucose and fat, postprandial blood glucose homeostasis, and appetite in eight older subjects (4 males, 4 females, aged 65--84 yr). GE of a drink (15 ml olive oil and 33 g glucose dissolved in 185 ml water), blood glucose, insulin, gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), and appetite (diet diaries, visual analog scales, and food intake at a buffet meal consumed after the GE study) were evaluated twice, after 10 days on a standard or a glucose-supplemented diet (70 g glucose 3 times a day). Glucose supplementation accelerated GE of glucose (P < 0.05), but not oil; there was a trend for an increase in GIP (at 15 min, P = 0.06), no change in GLP-1, an earlier insulin peak (P < 0.01), and a subsequent reduction in blood glucose (at 75 min, P < 0.01). Glucose supplementation had no effect on food intake during each diet so that energy intake was greater (P < 0.001) during the glucose-supplemented diet. Appetite ratings and energy intake at the buffet meal were not different. We conclude that, in older subjects, glucose supplementation 1) accelerates GE of glucose, but not fat; 2) modifies postprandial blood glucose homeostasis; and 3) increases energy intake.

Effects of intraduodenal glucose and fructose on antropyloric motility and appetite in healthy humans

Oral fructose empties from the stomach more rapidly and may suppress food intake more than oral glucose. The purpose of the study was to evaluate the effects of intraduodenal infusions of fructose and glucose on antropyloric motility and appetite. Ten healthy volunteers were given intraduodenal infusions of 25% fructose, 25% glucose, or 0.9% saline (2 ml/min for 90 min). Antropyloric pressures, blood glucose, and plasma insulin, gastric inhibitory peptide (GIP), and glucagon-like peptide-1 (GLP-1) were measured concurrently; a buffet meal was offered at the end of the infusion. Intraduodenal fructose and glucose suppressed antral waves (P < 0. 0005 for both), stimulated isolated pyloric pressure waves (P < 0.05 for both), and increased basal pyloric pressure (P = 0.10 and P < 0. 05, respectively) compared with saline, without any significant difference between them. Intraduodenal glucose increased blood glucose (P < 0.0005), as well as plasma insulin (P < 0.0005) and GIP (P < 0.005) more than intraduodenal fructose, whereas there was no difference in the GLP-1 response. Intraduodenal fructose suppressed food intake compared with saline (P < 0.05) and glucose (P = 0.07). We conclude that, when infused intraduodenally at 2 kcal/min for 90 min 1) fructose and glucose have comparable effects on antropyloric pressures, 2) fructose tends to suppress food intake more than glucose, despite similar GLP-1 and less GIP release, and 3) GIP, rather than GLP-1, probably accounts for the greater insulin response to glucose than fructose.

Effects of cholecystokinin on appetite and pyloric motility during physiological hyperglycemia

Recent studies suggest that the interaction between small intestinal nutrient stimulation and the blood glucose concentration is important in the regulation of gastric motility and appetite. The purpose of this study was to determine whether the effects of cholecystokinin octapeptide (CCK-8) on antropyloric motility and appetite are influenced by changes in the blood glucose concentration within the normal postprandial range. Seven healthy volunteers were studied on 4 separate days. A catheter incorporating a sleeve sensor was positioned across the pylorus, and the blood glucose was stabilized at either 4 mmol/l (2 days) or 8 mmol/l (2 days). After the desired blood glucose had been maintained for 90 min, an intravenous infusion of either CCK-8 (2 ng. kg(-1). min(-1)) or saline (control) was given for 60 min. Thirty minutes after the infusion began, the catheter was removed and subjects drank 400 ml of water with guar gum before being offered a buffet meal. The amount of food consumed (kcal) was quantified. The order of the studies was randomized and single-blinded. There were fewer antral waves at a blood glucose of 8 than at 4 mmol/l during the 90-min period before the infusions (P<0.05) and during the first 30 min of CCK-8 or saline infusion (P = 0.07). CCK-8 suppressed antral waves (P<0.05), stimulated isolated pyloric pressure waves (IPPWs) (P<0.01), and increased basal pyloric pressure (P<0.005) compared with control. During administration of CCK-8, basal pyloric pressure (P<0.01), but not the number of IPPWs, was greater at a blood glucose of 8 mmol/l than at 4 mmol/l. CCK-8 suppressed the energy intake at the buffet meal (P<0.01), with no significant difference between the two blood glucose concentrations. We conclude that the acute effect of exogenous CCK-8 on basal pyloric pressure, but not appetite, is modulated by physiological changes in the blood glucose concentration.