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This study will evaluate the effects of encapsulated botanical extracts, previously shown to inhibit the enzyme diacylglycerol-acyltransferase-1 (DGAT-1) in vitro, on fasting and postprandial lipid metabolism during an oral fat tolerance test (OFTT) in apparently healthy, overweight and obese adult men and women.
Full description
Medications currently approved for the treatment of obesity act primarily to promote a state of energy balance - by either suppressing appetite or interfering with lipid absorption in the small intestine. Similarly, it may be possible to reduce or inhibit the synthesis of triglycerides (TG) from dietary fat by targeting the activity of diacylglycerol-acyltransferase-1 (DGAT-1) in the enterocytes of the small intestine.
DGAT-1 catalyzes the final step in the biosynthesis of TG and is most abundantly expressed in the small intestine and adipose tissue. DGAT-1 in enterocytes is critical for assembly of TG from fatty acids derived from food intake. Ingested dietary fat is cleaved to monoacylglycerol and free fatty acids by lipases in the gut lumen and these are next taken up by the enterocytes, where they are re-esterified to TG in the postprandial period. TG is eventually released into circulation, primarily transported by chylomicrons. Thus, DGAT-1 plays a critical role in the absorption of dietary fat and inhibition of DGAT-1 has been shown to delay and decrease re-esterification of dietary fats into circulating TG. It is hypothesized that this effect may lead to decreased deposition of excess dietary fat as adipose tissue, perhaps due to increased fatty acid oxidation in the enterocytes.
The potential physiological benefits of DGAT-1 inhibition lead to the development of the potent, selective DGAT-1 inhibitor, AZD7687. Human clinical trials of AZD7687 demonstrated attenuation of postprandial TG excursions, consistent with inhibition of gut DGAT-1. However, this compound has limited, if any, therapeutic potential due to profound gastrointestinal (GI) side effects, particularly diarrhea, nausea, and abdominal cramping which were deemed intolerable. Moreover, no consistent dose-related treatment effects on body weight, glucose or lipid metabolism were found in the small trials which were deemed to be non-representative of the target therapeutic population.
Both cell-free and cellular in vitro models have been used to identify botanical extracts that have potential to inhibit DGAT-1. In a follow-up 7-d parallel arm proof-of-mechanism human clinical trial, each of four lead ingredients (2 g/d) were evaluated for the ability to inhibit the intestinal release of dietary fat into circulation following a high-fat meal challenge using post-prandial TG response as a surrogate marker. Of the four lead botanical ingredients, whole grape extract (WGE) reduced fasting and postprandial TG levels (total area under the curve from 0 to 6 h) by ~ 7% to 8% following a high-fat meal challenge. This demonstration of efficacy, albeit modest, was sufficient to warrant continued exploration. Importantly, only a few subjects reported very mild GI side effects, primarily bloating, in this trial.
Combinations of WGE with other botanical extracts possessing biological activity against supportive secondary mechanisms that might strengthen the overall inhibition of dietary fat release into circulation and fat deposition were then explored. To examine potential synergistic interactions, WGE was combined with other ingredients known to act on complementary biological pathways that converge into a single efficacy outcome; in this case, cellular TG levels. Ingredients that had effects on both glucose and fatty acid metabolism that could ultimately synergize with the DGAT-1 pathway were chosen. The complementary pathway targets chosen for these experiments were Peroxisome-Proliferator-Activated Receptor-gamma Coactivator 1-alpha (PGC1-α) and Sterol Regulatory Element Binding Protein 1c (SREBP1c).
In the cellular DGAT-1 model, grape seed extract (GSE) resulted in a significant inhibition of DGAT-1 activity when combined with WGE. The combination index (CI), a quantitative measure of synergy, indicated a strong synergistic effect (CI = 0.61). Synergy occurred at a 1:1 ratio of WGE to GSE, and at ratios that induced no effect on DGAT-1 activity when either was used alone. The synergy data, together with the proof of mechanism clinical data, forms the basis for conducting the presently proposed clinical trial at a WGE level below that used in the previous study.
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Exclusion criteria
Subject has abnormal laboratory test results of clinical significance at visit 1b (week -1), at the discretion of the Investigator. One re-test will be allowed on a separate day prior to visit 2 (week 0), for subjects with abnormal laboratory test results.
Subject has a history or presence of clinically important endocrine (including type 1 or 2 diabetes mellitus), cardiovascular (including, but not limited to history of myocardial infarction, peripheral arterial disease, stroke), pulmonary (including uncontrolled asthma), hepatic, renal, hematologic, immunologic, dermatologic, neurologic, psychiatric or biliary disorders.
Subject has a history or current GI disorder that, in the judgment of the Investigator, may have the potential to disrupt normal digestion and absorption of dietary fats, including, but not limited to, Crohn's disease, inflammatory bowel disease, irritable bowel syndrome, significant lactose intolerance and/or egg allergy.
Subject has a known genetic predisposition to hyperlipidemia - as diagnosed by a health care professional.
Subject is a heavy smoker, defined as a history of smoking >1 pack-per-day in the 3 months prior to visit 1b (week -1).
Subject has a history of difficulty swallowing tablets/capsules that could affect ability to consume the study product.Subject has a history or presence of cancer in the prior two years, except for non-melanoma skin cancer.
Subject has extreme dietary habits (e.g., Atkins diet, very high protein, vegetarian), in the opinion of the Investigator.
Subject has had a weight loss or gain >4.5 kg in the 3 months prior to visit 1b (week -1).
Subject has uncontrolled hypertension (systolic blood pressure ≥160 mm Hg or diastolic blood pressure ≥100 mm Hg) as defined by the blood pressure measured at visit 1b (week -1). One re-test will be allowed on a separate day prior to visit 2 (week 0), for subjects whose blood pressure exceeds either of these cut points, in the judgment of the Investigator.
Subject has not been on a stable dose of antihypertensive medication (at least 4 weeks prior to visit 1b, week -1 and for the duration of the study period.
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93 participants in 3 patient groups, including a placebo group
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Data sourced from clinicaltrials.gov
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