Gastric Emptying and Gastrointestinal Transit Compared among Native and Hydrolyzed Whey and Casein Milk Proteins in an Aged Rat Model

Abstract

Little is known about how milk proteins affect gastrointestinal (GI) transit, particularly for the elderly, in whom digestion has been observed to be slowed. We tested the hypothesis that GI transit is faster for whey than for casein and that this effect is accentuated with hydrolysates, similar to soy. Adult male rats (18 months old) were fed native whey or casein, hydrolyzed whey (WPH) or casein (CPH), hydrolyzed blend (HB; 60% whey:40% casein), or hydrolyzed soy for 14 days then treated with loperamide, prucalopride, or vehicle-control for 7 days. X-ray imaging tracked bead-transit for: gastric emptying (GE; 4 h), small intestine (SI) transit (9 h), and large intestine (LI) transit (12 h). GE for whey was 33 ± 12% faster than that for either casein or CPH. SI transit was decreased by 37 ± 9% for casein and 24 ± 6% for whey compared with hydrolyzed soy, and persisted for casein at 12 h. Although CPH and WPH did not alter transit compared with their respective intact counterparts, fecal output was increased by WPH. Slowed transit by casein was reversed by prucalopride (9-h), but not loperamide. However, rapid GE and slower SI transit for the HB compared with intact forms were inhibited by loperamide. The expected slower GI transit for casein relative to soy provided a comparative benchmark, and opioid receptor involvement was corroborated. Our findings provide new evidence that whey slowed SI transit compared with soy, independent of GE. Increased GI transit from stomach to colon for the HB compared with casein suggests that including hydrolyzed milk proteins in foods may benefit those with slowed intestinal transit.

Alteration in propagating colonic contractions by dairy proteins in isolated rat large intestine

“…Application of MPH to the colonic tissue increased motility by increasing the frequency of propagating synchronous contractions compared with the pretreatment control (Figure 2), and this effect persisted after washout. This finding was consistent with the enhanced fecal output associated with MPH compared with CPH in vivo (Dalziel et al, 2017b). However, MPH did not alter the frequency of nonsynchronous contractions in the proximal colon.…”

“…The following 4 milk protein products were studied: WPC (lactic whey protein concentrate WPC7009; 80% protein wt/ wt), CPH (partially hydrolyzed casein MPH948; degree of hydrolysis 7.6%; 94% protein wt/wt); WPH (partially hydrolyzed whey WPH917; degree of hydrolysis 7.0%; 90% protein wt/wt); and MPH (partially hydrolyzed blend of 60:40 whey: casein MPH942; degree of hydrolysis 12-17%; 85% protein wt/wt). Note that MPH has previously been referred to as a "hydrolyzed blend" (Dalziel et al, 2017b). The protein powders were dissolved in Krebs buffer at 1 mg/mL (concentration estimated to reach the infant lower GI tract) and perfused into the tissue bath at a rate of 20 mL/min.…”

“…Because this process is controlled by the enteric nervous system, it operates independently of the central nervous system. Recently, fecal output was shown to increase for rats fed a diet containing whey protein hydrolysate (WPH) or milk protein hydroylsate (MPH; a mixed whey: casein blend) compared with those fed casein protein hydrolysate (CPH; Dalziel et al, 2017b). We therefore predicted that whey protein concentrate (WPC) and MPH would increase colonic motility compared with CPH in ex vivo large intestine.…”

Effect of N‐palmitoylethanolamine‐oxazoline on comorbid neuropsychiatric disturbance associated with inflammatory bowel disease

“…The methods used for measuring GI transit have been described in detail previously by Dalziel et colleagues. [22][23][24]…”

Bioavailability of Vitamin B12 from Dairy Products Using a Pig Model

“…In dairy cows, Artegoitia et al [ 25 ] reported a better absorption of B 12 after a post-ruminal infusion of a solution of cyanocobalamin + casein hydrolysate than after infusions of cyanocobalamin + whey protein or free cyanocobalamin solutions. Proteins are known to slow gastric emptying [ 26 ] and, although both casein and whey are proteins with high B 12 -binding capacity [ 27 ], casein (hydrolyzed or not) has a gastric emptying time 33% slower than whey [ 28 ]. This may be caused by formation of curd-like structures by caseins once in the stomach whereas whey remains liquid.…”