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Identification of a botanical inhibitor of intestinal diacylglyceride acyltransferase 1 activity via in vitro screening and a parallel, randomized, blinded, placebo-controlled clinical trial.

Velliquette RA, Grann K, Missler SR, Patterson J, Hu C, Gellenbeck KW, Scholten JD, Randolph RK - Nutr Metab (Lond) (2015)

Bottom Line: Phenolic acids (i.e., gallic acid) and polyphenols (i.e., cyanidin) abundantly found in nature appeared to inhibit DGAT1 enzyme activity in vitro.Four polyphenolic rich botanical extracts were identified from in vitro evaluation in both cell-free and cellular model systems: apple peel extract (APE), grape extract (GE), red raspberry leaf extract (RLE) and apricot/nectarine extract (ANE) (IC50 = 1.4, 5.6, and 10.4 and 3.4 μg/mL, respectively).These data suggest that a dietary GE has the potential to attenuate postprandial hypertriglyceridemia in part by the inhibition of intestinal DGAT1 enzyme activity without intolerable side effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Analytical Sciences, Amway R&D, 7575 Fulton St., Building 50-2D, Ada, MI 49355 USA.

ABSTRACT

Background: Diacylglyceride acyltransferase 1 (DGAT1) is the enzyme that adds the final fatty acid on to a diacylglyceride during triglyceride (TG) synthesis. DGAT1 plays a key role in the repackaging of dietary TG into circulating TG rich chylomicrons. A growing amount of research has indicated that an exaggerated postprandial circulating TG level is a risk indicator for cardiovascular and metabolic disorders. The aim of this research was to identify a botanical extract that inhibits intestinal DGAT1 activity and attenuates postprandial hypertriglyceridemia in overweight and obese humans.

Methods: Twenty individual phytochemicals and an internal proprietary botanical extract library were screened with a primary cell-free DGAT1 enzyme assay that contained dioleoyl glycerol and palmitoleoyl Coenzyme A as substrates plus human intestinal microsomes as the DGAT1 enzyme source. Botanical extracts with IC50 values < 100 μg/mL were evaluated in a cellular DGAT1 assay. The cellular DGAT1 assay comprised the analysis of (14)C labeled TG synthesis in cells incubated with (14)C-glycerol and 0.3 mM oleic acid. Lead botanical extracts were then evaluated in a parallel, double-blind, placebo-controlled clinical trial. Ninety healthy, overweight and obese participants were randomized to receive 2 g daily of placebo or individual botanical extracts (the investigational product) for seven days. Serum TG levels were measured before and after consuming a high fat meal (HFM) challenge (0.354 L drink/shake; 77 g fat, 25 g carbohydrate and 9 g protein) as a marker of intestinal DGAT1 enzyme activity.

Results: Phenolic acids (i.e., gallic acid) and polyphenols (i.e., cyanidin) abundantly found in nature appeared to inhibit DGAT1 enzyme activity in vitro. Four polyphenolic rich botanical extracts were identified from in vitro evaluation in both cell-free and cellular model systems: apple peel extract (APE), grape extract (GE), red raspberry leaf extract (RLE) and apricot/nectarine extract (ANE) (IC50 = 1.4, 5.6, and 10.4 and 3.4 μg/mL, respectively). In the seven day clinical trial, compared to placebo, only GE significantly reduced the baseline subtracted change in serum TG AUC following consumption of the HFM (AUC = 281 ± 37 vs. 181 ± 30 mg/dL*h, respectively; P = 0.021). Chromatographic characterization of the GE revealed a large number of closely eluting components containing proanthocyanidins, catechins, anthocyanins and their secondary metabolites that corresponded with the observed DGAT1 enzyme inhibition in the cell-free model.

Conclusion: These data suggest that a dietary GE has the potential to attenuate postprandial hypertriglyceridemia in part by the inhibition of intestinal DGAT1 enzyme activity without intolerable side effects.

Trial registration: This trial was registered with ClinicalTrials.gov NCT02333461.

No MeSH data available.


Related in: MedlinePlus

Role of DGAT1 in the assimilation of dietary TG into circulating TG rich chylomicrons (CM). Dietary TG are first broken down into monoacylglycerides (MG) and fatty acids (FA) by a host of pancreatic lipases. MG and FA are then absorbed into the small intestinal enterocytes and repackaged into diacylglyercides (DG) by monoacylglyceride acyltransferase transferase. DGAT1 then acylates the DG into TG (yellow circles), which are incorporated into CM and secreted into the lymphatic circulation then enter the blood circulation via the thoracic duct
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Fig1: Role of DGAT1 in the assimilation of dietary TG into circulating TG rich chylomicrons (CM). Dietary TG are first broken down into monoacylglycerides (MG) and fatty acids (FA) by a host of pancreatic lipases. MG and FA are then absorbed into the small intestinal enterocytes and repackaged into diacylglyercides (DG) by monoacylglyceride acyltransferase transferase. DGAT1 then acylates the DG into TG (yellow circles), which are incorporated into CM and secreted into the lymphatic circulation then enter the blood circulation via the thoracic duct

Mentions: Diacylglycerol acyltransferase 1 (DGAT1) in enterocytes is a key enzyme involved in the assembly of TG from dietary fatty acids [22]. In the postprandial state, intestinal DGAT1 generated TG are secreted into the lymphatic system, mainly as chylomicron particles, and then enter the blood circulation via the thoracic duct (Fig. 1). DGAT1-deficient (Dgat1−/−) mice are resistant to high fat diet-induced obesity due in part to an increase in systemic energy expenditure induced by body heat loss [23]. It was later reported that intestinal only DGAT1 deficiency could reproduce many of the high fat diet induced phenotypes of the Dgat1−/− mouse [24]. In addition, intestinal only expression of DGAT1 abolished the anti-obesity phenotypes of Dgat1−/− mouse while on a high fat diet [25]. These animal studies lead to the pharmaceutical development of intestinal DGAT1 inhibitors as a mechanistic approach to mitigate metabolic risks associated with elevated postprandial TG levels [12, 26, 27]. These and other reports suggest that delaying and decreasing postprandial circulating TG levels with intestinal DGAT1 inhibition could facilitate the improvement of metabolic and cardiovascular risks and maintenance of health [22, 24, 28–31]. However, a hurdle facing pharmaceutical inhibitors thus far has been the compounds are so selective and potent that the gastrointestinal side effect profiles, like nausea, diarrhea and vomiting are not tolerated [12]. Therefore, nutritional strategies targeting postprandial TG levels via DGAT1 inhibition without intolerable side effects could have meaningful impact on cardiovascular and metabolic risks and health.Fig. 1


Identification of a botanical inhibitor of intestinal diacylglyceride acyltransferase 1 activity via in vitro screening and a parallel, randomized, blinded, placebo-controlled clinical trial.

Velliquette RA, Grann K, Missler SR, Patterson J, Hu C, Gellenbeck KW, Scholten JD, Randolph RK - Nutr Metab (Lond) (2015)

Role of DGAT1 in the assimilation of dietary TG into circulating TG rich chylomicrons (CM). Dietary TG are first broken down into monoacylglycerides (MG) and fatty acids (FA) by a host of pancreatic lipases. MG and FA are then absorbed into the small intestinal enterocytes and repackaged into diacylglyercides (DG) by monoacylglyceride acyltransferase transferase. DGAT1 then acylates the DG into TG (yellow circles), which are incorporated into CM and secreted into the lymphatic circulation then enter the blood circulation via the thoracic duct
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4526202&req=5

Fig1: Role of DGAT1 in the assimilation of dietary TG into circulating TG rich chylomicrons (CM). Dietary TG are first broken down into monoacylglycerides (MG) and fatty acids (FA) by a host of pancreatic lipases. MG and FA are then absorbed into the small intestinal enterocytes and repackaged into diacylglyercides (DG) by monoacylglyceride acyltransferase transferase. DGAT1 then acylates the DG into TG (yellow circles), which are incorporated into CM and secreted into the lymphatic circulation then enter the blood circulation via the thoracic duct
Mentions: Diacylglycerol acyltransferase 1 (DGAT1) in enterocytes is a key enzyme involved in the assembly of TG from dietary fatty acids [22]. In the postprandial state, intestinal DGAT1 generated TG are secreted into the lymphatic system, mainly as chylomicron particles, and then enter the blood circulation via the thoracic duct (Fig. 1). DGAT1-deficient (Dgat1−/−) mice are resistant to high fat diet-induced obesity due in part to an increase in systemic energy expenditure induced by body heat loss [23]. It was later reported that intestinal only DGAT1 deficiency could reproduce many of the high fat diet induced phenotypes of the Dgat1−/− mouse [24]. In addition, intestinal only expression of DGAT1 abolished the anti-obesity phenotypes of Dgat1−/− mouse while on a high fat diet [25]. These animal studies lead to the pharmaceutical development of intestinal DGAT1 inhibitors as a mechanistic approach to mitigate metabolic risks associated with elevated postprandial TG levels [12, 26, 27]. These and other reports suggest that delaying and decreasing postprandial circulating TG levels with intestinal DGAT1 inhibition could facilitate the improvement of metabolic and cardiovascular risks and maintenance of health [22, 24, 28–31]. However, a hurdle facing pharmaceutical inhibitors thus far has been the compounds are so selective and potent that the gastrointestinal side effect profiles, like nausea, diarrhea and vomiting are not tolerated [12]. Therefore, nutritional strategies targeting postprandial TG levels via DGAT1 inhibition without intolerable side effects could have meaningful impact on cardiovascular and metabolic risks and health.Fig. 1

Bottom Line: Phenolic acids (i.e., gallic acid) and polyphenols (i.e., cyanidin) abundantly found in nature appeared to inhibit DGAT1 enzyme activity in vitro.Four polyphenolic rich botanical extracts were identified from in vitro evaluation in both cell-free and cellular model systems: apple peel extract (APE), grape extract (GE), red raspberry leaf extract (RLE) and apricot/nectarine extract (ANE) (IC50 = 1.4, 5.6, and 10.4 and 3.4 μg/mL, respectively).These data suggest that a dietary GE has the potential to attenuate postprandial hypertriglyceridemia in part by the inhibition of intestinal DGAT1 enzyme activity without intolerable side effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Analytical Sciences, Amway R&D, 7575 Fulton St., Building 50-2D, Ada, MI 49355 USA.

ABSTRACT

Background: Diacylglyceride acyltransferase 1 (DGAT1) is the enzyme that adds the final fatty acid on to a diacylglyceride during triglyceride (TG) synthesis. DGAT1 plays a key role in the repackaging of dietary TG into circulating TG rich chylomicrons. A growing amount of research has indicated that an exaggerated postprandial circulating TG level is a risk indicator for cardiovascular and metabolic disorders. The aim of this research was to identify a botanical extract that inhibits intestinal DGAT1 activity and attenuates postprandial hypertriglyceridemia in overweight and obese humans.

Methods: Twenty individual phytochemicals and an internal proprietary botanical extract library were screened with a primary cell-free DGAT1 enzyme assay that contained dioleoyl glycerol and palmitoleoyl Coenzyme A as substrates plus human intestinal microsomes as the DGAT1 enzyme source. Botanical extracts with IC50 values < 100 μg/mL were evaluated in a cellular DGAT1 assay. The cellular DGAT1 assay comprised the analysis of (14)C labeled TG synthesis in cells incubated with (14)C-glycerol and 0.3 mM oleic acid. Lead botanical extracts were then evaluated in a parallel, double-blind, placebo-controlled clinical trial. Ninety healthy, overweight and obese participants were randomized to receive 2 g daily of placebo or individual botanical extracts (the investigational product) for seven days. Serum TG levels were measured before and after consuming a high fat meal (HFM) challenge (0.354 L drink/shake; 77 g fat, 25 g carbohydrate and 9 g protein) as a marker of intestinal DGAT1 enzyme activity.

Results: Phenolic acids (i.e., gallic acid) and polyphenols (i.e., cyanidin) abundantly found in nature appeared to inhibit DGAT1 enzyme activity in vitro. Four polyphenolic rich botanical extracts were identified from in vitro evaluation in both cell-free and cellular model systems: apple peel extract (APE), grape extract (GE), red raspberry leaf extract (RLE) and apricot/nectarine extract (ANE) (IC50 = 1.4, 5.6, and 10.4 and 3.4 μg/mL, respectively). In the seven day clinical trial, compared to placebo, only GE significantly reduced the baseline subtracted change in serum TG AUC following consumption of the HFM (AUC = 281 ± 37 vs. 181 ± 30 mg/dL*h, respectively; P = 0.021). Chromatographic characterization of the GE revealed a large number of closely eluting components containing proanthocyanidins, catechins, anthocyanins and their secondary metabolites that corresponded with the observed DGAT1 enzyme inhibition in the cell-free model.

Conclusion: These data suggest that a dietary GE has the potential to attenuate postprandial hypertriglyceridemia in part by the inhibition of intestinal DGAT1 enzyme activity without intolerable side effects.

Trial registration: This trial was registered with ClinicalTrials.gov NCT02333461.

No MeSH data available.


Related in: MedlinePlus