Dose-response Effect of Pine Nut Oil as a Dual FFA1 and FFA4 Agonist on Glucose Tolerance in Healthy Humans.
Condition: Type 2 Diabetes Mellitus
MeSH terms: Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      Several free fatty acids receptors (FFARs) have been discovered. These have been implicated
      in metabolic processes and inflammation. Consequently, these receptors have attracted
      interest as targets for the treatment of metabolic and inflammatory diseases, including
      obesity and type 2 diabetes. Two of these FFARs (FFA1, FFA4), which is activated by specific
      free fatty acids (FFAs), is expressed on enteroendocrine cells, pancreatic beta-cells and
      adipocytes. They have been linked to 1) increased glucagon-like peptide-1 (GLP-1) secretion
      and hence the incretin-mediated increase in glucose-stimulated insulin secretion (GSIS) and
      suppression of glucagon secretion, 2) a direct positive effect on GSIS, 3) reduced
      inflammation and 4) improved insulin sensitivity. These functions and the abundance of fatty
      acids in food suggest that FFARs can be considered as nutrient sensing regulators of
      metabolism. Roux-en-Y gastric bypass (RYGB), frequently results in immediate beneficial
      effects on glucose metabolism and often complete remission of type 2 diabetes. This may in
      part be explained by increased GLP-1 levels after surgery. It appears that the effect depends
      on nutrient delivery directly to the lower parts of the small intestine. It is possible that
      the RYGB effects are partly due to enteroendocrine stimulation of FFA1 and perhaps FFA4 by
      direct nutrient delivery, i.e. FFA release in the lower intestines. Pinolenic acid from pine
      nuts has been shown to be a potent dual FFA1/FFA4 agonist.

      Based on these findings the investigators have planned a number of human intervention studies
      in order to investigate 1) the optimal oral formulation of pine nut oil 2) whether it is
      possible to mimic the beneficial effects observed after RYGB, 2) if it is possible to
      increase GLP-1 secretion by stimulating FFA1/FFA4 on enteroendocrine cells causing improved
      GSIS and increased satiety and 3) enhancement of GSIS by directly stimulating FFA1 on
      beta-cells.
    

Detailed description: 
      Type 2 diabetes (T2D) is one of the greatest health challenges worldwide. The disease is
      strongly associated with obesity, and develops via pre-diabetic conditions, where insulin
      resistance and low-grade inflammation play an important role, to T2D, where failure of the
      pancreatic beta-cell to compensate for insulin resistance causes hyperglycemia. According to
      recent estimates, 350 million people worldwide suffer from diabetes. The disease typically
      leads to many years of reduced quality of life due to complications such as cardiovascular
      disease (CVD), blindness, kidney failure and amputations. T2D is estimated to be the 4th
      leading cause of death in the Western world with 5-10 years reduced life expectancy. It is
      generally agreed that a healthy diet and increased physical activity are effective in
      preventing T2D, and also may help to achieve a better control of T2D and reduce the risk of
      CVD. There is, however, not a general agreement as to what a healthy diet constitutes.

      During the last decade, several cell surface receptors that respond to free fatty acids
      (FFAs) have been discovered. These free fatty acid receptors (FFARs) belong to the
      superfamily of G protein-coupled 7-transmembrane receptors (GPRs), and have all been
      implicated in metabolic processes, energy expenditure and inflammation. Consequently, several
      of the receptors have attracted interest as potential targets for the treatment of metabolic
      and inflammatory diseases, including obesity and T2D.

      FFA1 (GPR40), which is activated by long-chain FFAs, is highly expressed in pancreatic
      β-cells and increases glucose-stimulated insulin secretion (GSIS) [4]. There is evidence that
      FFA1 is also expressed in intestinal enteroendocrine cells, where it promotes secretion of
      incretin hormones such as GLP-1 and glucose-dependent insulinotropic peptide (GIP). GLP-1 is
      highly interesting for treatment of obesity and T2D because of its ability to increase GSIS,
      enhance β-cell growth, increase insulin sensitivity, reduce gastric motility, increase
      satiety and cause a loss of weight. The published phase II clinical trial with the selective
      FFA1 agonist TAK-875 demonstrated high efficacy in reducing plasma glucose without increased
      incidence of hypoglycemia, and has caused considerable interest in the receptor as a new
      target for treatment of T2D.

      FFA4 (GPR120), which is activated by unsaturated long-chain FFA, is expressed in the
      gastrointestinal system, adipose tissue, and β-cells, and is reported to promote GLP-1
      secretion from intestinal cells, to counteract inflammation and to increase insulin
      sensitivity in adipose tissue. Notably, dysfunctional FFA4 was recently connected to the
      development of obesity in both mice and humans. This has considerably increased the interest
      on the receptor as a target for obesity and metabolic diseases. This is supported by
      indications that unsaturated FFAs revert diet-induced hypothalamic inflammation through FFA4,
      and thereby reduce body weight in diet-induced obese mice. These FFARs are thus expressed in
      different tissues in the body where they potentially can affect metabolic and inflammatory
      conditions such as T2D and obesity.

      These functions combined and the abundance of fatty acids in food suggests that FFARs can be
      considered as nutrient sensing regulators of metabolism.

      Roux-en-Y gastric bypass (RYGB) surgery, often used to treat severe obesity, frequently
      results in immediate beneficial effects on glucose metabolism in T2D, often with complete
      remission. These effects are in part independent of weight loss, but may be explained by a
      significant increase in GLP-1 levels immediately after surgery. Thus, it appears that the
      effect depends on delivery of nutrients and pancreatic juices directly to the lower parts of
      the ileum. Normally, FFAs are rapidly absorbed in the upper parts of the gastrointestinal
      tract. It is therefore possible that the RYGB effects are partly due to enteroendocrine
      stimulation of FFA1 and perhaps FFA4 by direct nutrient delivery that is FFA release in the
      lower intestines. A hypothesis to be investigated in this PhD project is that delivery of a
      specific naturally occurring polyunsaturated FFA with proven high efficacy on both FFA1 and
      FFA4 directly to the lower intestines can mimic the beneficial effects observed after RYGB
      with less expense and fewer adverse effects.

      Delivery of a higher load of unabsorbed FFA to the distal small intestine can be achieved by
      taking advantage of enteric coating that dissolves at pH >6.0, which is observed in the lumen
      of the distal jejunum, ileum and colon, and is independent of the colonic flora. This enteric
      coating technology is well established for delivering drugs to the ileum and colon. The
      potential positive effect of this principle was recently reported in a small cohort of
      patients with T2D. Thus, delivery of small amounts of lauric acid (a C12 fatty acid) to the
      distal gut using enteric-coated pellets stimulated GLP-1 secretion and lowered postprandial
      glucose levels in response to meals. No chronic effects where tested in this study. Although
      not suggested by the authors, the increased release of GLP-1 could involve direct stimulation
      of FFAR1 and/or FFAR4 by lauric acid in the distal gut.

      As a part of the FFARMED project supported by the Danish Council for Strategic Research, a
      screening of 36 relevant FFAs and their ability to act as FFA1 and FFA4 agonists in vitro
      have been carried out to identify the most potent naturally occurring dual FFA1/FFA4 agonist
      for clinical studies. Of these, the polyunsaturated fatty acid (PUFA), pinolenic acid showed
      a significantly higher efficacy than the others, and was therefore selected for further
      studies. To further support this choice, the effect of pinolenic acid has been tested using a
      small dose (100 mg/kg) given 30 min prior to an oral glucose tolerance test in mice.
      Convincingly, purified pinolenic acid significantly improved glucose tolerance by reducing
      glucose levels when compared to control (corn oil). The efficacy was similar to that obtained
      with a pharmaceutical selective FFA1 agonist (TUG-905). Pinolenic acid is a fatty acid
      contained in Siberian Pine nuts, Korean Pine nuts and the seeds of other pines. The highest
      percentage of pinolenic acid (~20%) is found in Siberian Pine nuts and the oil produced from
      them. Korean Pine nut oil given as hydrolyzed FFAs, but not as triglycerides has been
      reported to increase secretion of GLP-1 and decrease appetite in overweight females. This is
      in coherence with previous results in mice, and indicates that purified pinolenic acid may be
      superior in improving glucose metabolism.

      Hypotheses: As described, the expression of FFA1 and FFA4 on intestinal enteroendocrine
      cells, pancreatic beta-cells and adipose tissue has been linked to 1) increased secretion of
      GLP-1 and hence the incretin-mediated increase in GSIS and suppression of glucagon secretion,
      2) a direct positive effect on GSIS, 3) reduced inflammation and 4) improved insulin
      sensitivity. Based on the above findings, the investigators are performing a number of
      clinical trials using pinolenic acid derived from Siberian pine nuts as a naturally occurring
      dual FFA1/FFA4 agonist. The investigators hypothesize that ingestion of a small amount of
      pinolenic acid given as enteric-coated pellets dissolved in the lower intestines will 1)
      increase GLP-1 secretion by stimulating FFA1/FFA4 on enteroendocrine cells causing improved
      GSIS and increased satiety, 2) enhance GSIS by directly stimulating FFA1 on beta-cells, and
      3) attenuate the low-grade inflammation seen in insulin resistant conditions such as obesity
      and T2D by stimulating FFA4 on adipocytes.

      The aim of this study is to investigate: The dose-response effect of delayed release
      pinolenic acid (hydrolyzed pine nut oil) on glucose tolerance, insulin and incretin
      secretion, appetite and tolerability in healthy humans.

      This registration covers the third off five planned pilot studies investigating the effect of
      hydrolyzed pine nut oil on glucose metabolism during an oral glucose tolerance test.
    

Intervention name(s): Hydrolyzed pine nut oil
Intervention type(s): Dietary Supplement
Intervention description(s): Randomized cros-over intervention of 3 OGTT with no oil, low dose or high dose.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Subjects complete three oral glucose tolerance tests (OGTT) on different days, with a minimum of one week in between. First visit is a combined screening and baseline OGTT, with no supplementation. At the second and third visit subjects are randomly assigned to either 3 g of hydrolyzed pine nut oil or 6 g of hydrolyzed pine nut oil.
Masking: None (Open Label)
Primary purpose: Basic Science