Effects of resistant starch on behaviour, satiety-related hormones and metabolites in growing pigs

Abstract

Resistant starch (RS) has been suggested to prolong satiety in adult pigs. The present study investigated RS-induced changes in behaviour, satiety-related hormones and metabolites in catheterized growing pigs to explore possible underlying mechanisms for RS-induced satiety. In a cross-over design with two 14-day periods, 10 pigs (initial BW: 58 kg) were assigned to two treatments comprising diets containing either 35% pregelatinized starch (PS) or 34% retrograded starch (RS). Diets were isoenergetic on gross energy. Pigs were fed at 2.8 × maintenance. Postprandial plasma response of satiety-related hormones and metabolites was measured at the end of each period using frequent blood sampling. Faecal and urinary energy losses were measured at the end of each period. Behaviour was scored 24 h from video recordings using scan sampling. Energy digestibility and metabolizability werẽ 6% lower in RS compared with PS diet ( P < 0.001), and metabolizable energy (ME) intake was~3% lower in RS-fed than in PS-fed pigs ( P < 0.001). RS-fed pigs showed less feeder-directed ( P = 0.001) and drinking ( P = 0.10) behaviours than PS-fed pigs throughout the day. Postprandial peripheral short-chain fatty acid (SCFA) levels were higher in RS-fed than in PS-fed pigs ( P < 0.001). Postprandial glucose and insulin responses were lower in RS-fed than in PS-fed pigs ( P < 0.001). Triglyceride levels were higher in RS-fed than in PS-fed pigs ( P < 0.01), and non-esterified fatty acid levels did not differ between diets ( P = 0.90). Glucagon-like peptide-1 (GLP-1) levels were lower in RS-fed than in PS-fed pigs ( P < 0.001), and peptide tyrosine tyrosine (PYY) levels did not differ between diets ( P = 0.90). Blood serotonin levels were lower ( P < 0.001), whereas monoamine oxidase activity ( P < 0.05) and tryptophan ( P < 0.01) levels were higher in RS-fed than in PS-fed pigs. Despite a lower ME intake, RS seemed to prolong satiety, based on behavioural observations. Possible underlying mechanisms for RS-induced satiety include increased 24 h plasma SCFA levels, and decreased postprandial glucose and insulin responses. GLP-1 and PYY seemed not to play a role in RS-induced satiety. Low blood serotonin levels in RS-fed pigs suggested a difference in intestinal serotonin release between treatments. Increased postprandial plasma triglyceride levels corresponded with increased SCFA levels, but it is unclear whether triglycerides may have signalled satiety in RS-fed pigs.

Effects of alginate and resistant starch on feeding patterns, behaviour and performance in ad libitum-fed growing pigs

“…In humans, it has been demonstrated that blood glucose levels are inversely correlated with appetite and food intake up to 60 min after different carbohydrate meals (Anderson et al, 2002). Thus, reduced blood glucose levels directly after a high-RS meal (Souza da Silva et al, 2014), as has been reported for humans (Raben et al, 1994;Achour et al, 1997), may have delayed the onset of satiation, thereby leading to larger meals in pigs fed RS-containing diets in the present study. Regmi et al (2011) reported that RS increases absorption of short-chain fatty acids (SCFA) in portal vein-catheterized pigs.…”

“…In the present study, microbial production of SCFA was not quantified, but an increase in fermentation activity, and thereby an increase in SCFA production (Haenen et al, 2013;Souza da Silva et al, 2014) could be confirmed by adaptations found in the gastrointestinal tract of pigs fed diets with RS. The empty weight of the colon and total gastrointestinal tract were greater in pigs fed diets with RS than in pigs fed diets without RS, in line with previous studies (Martinez-Puig et al, 2003;Bolhuis et al, 2007).…”

“…Additional blood samples (9 ml) were collected using disposable vacuum containers containing liquid K 3 EDTA in week 12 to measure levels of serotonin (5-hydroxytryptamine (5-HT)) in blood platelets, and monoamine oxidase (MAO) activity in whole blood as previously described (Souza da Silva et al, 2014). Intestinal 5-HT release affects colonic motility and transit time, which may also contribute to satiety regulation.…”

“…Intestinal 5-HT release affects colonic motility and transit time, which may also contribute to satiety regulation. Moreover, intestinal 5-HT release may be related to the activity of the gastrointestinal immune system (Haenen et al, 2013;Souza da Silva et al, 2014). The majority of 5-HT is catabolized by MAO.…”

“…This may have increased the de novo gluconeogenesis in pigs fed diets with RS, in line with increased fasting levels of glucose and insulin found in these animals. Thus, in spite of the reduced glucose supply from enzymatic digestion directly after the meal, RS provides a large amount of SCFA to be oxidized in the postabsorptive phase (Haenen et al, 2013;Souza da Silva et al, 2014). According to Zijlstra et al (2012), absorbed SCFA are metabolized in various cell types, including colonocytes, hepatocytes, and skeletal and cardiac muscle cells.…”