FFAR Agonist on Incretins, Insulin, Lipids and Inflammation
Condition: Type2 Diabetes Mellitus; Obesity
MeSH terms: Obesity; Diabetes Mellitus, Type 2; Inflammation
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 T2D. Two of these FFARs (FFAR1, FFAR4), 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 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 suggests 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 T2D. 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 FFAR1 and perhaps FFAR4 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 FFAR1/FFAR4 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 meal-related GLP-1 secretion by stimulating FFAR1/FFAR4 on enteroendocrine cells
      causing improved GSIS and increased satiety and 3) enhancement of GSIS by directly
      stimulating FFAR1 (and perhaps FFAR4) 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 side 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
      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 (FFA)
      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.

      FFAR1 (GPR40), which is activated by long-chain FFA, is highly expressed in pancreatic
      β-cells and increases glucose-stimulated insulin secretion (GSIS) [4]. There is evidence that
      FFAR1 is also expressed in intestinal enteroendocrine cells, where it promotes secretion of
      incretin hormones such as GLP-1 and 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 FFAR1 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.

      FFAR4 (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 FFAR4 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 FFA revert diet-induced hypothalamic inflammation through FFAR4,
      and thereby reduce body weight in diet-induced obese (DIO) 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 the weight loss, but may be explained by
      a significant increase in GLP-1 levels immediately after surgery. Thus, it appears that the
      effect depends purely on delivery of nutrients and pancreatic juices directly to the lower
      parts of the ileum. Normally, FFA 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 FFAR1 and perhaps FFAR4 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 FFAR1 and FFAR4 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 FFA and their ability to act as FFAR1 and FFAR4 agonists in vitro
      have been carried out to identify the most potent naturally occurring dual FFAR1/FFAR4
      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 (OGTT) in
      mice. Convincingly, purified pinolenic acid significantly improved glucose tolerance by
      reducing AUC-glucose, and peak-glucose levels when compared to control (corn oil). The
      efficacy was similar to that obtained with a pharmaceutical selective FFAR1 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
      FFA, but not as TG, has been reported to increase secretion of GLP-1 and decrease appetite in
      overweight females. This supports previous results, and indicates that only purified
      pinolenic acid improved glucose metabolism in mice.

      Hypotheses

      As described above, the expression of FFAR1 and FFAR4 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, 4) improved insulin sensitivity and
      5) increased energy expenditure. 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 FFAR1/FFAR4 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 meal-related GLP-1
      secretion by stimulating FFAR1/FFAR4 on enteroendocrine cells causing improved GSIS and
      increased satiety, 2) enhance GSIS by directly stimulating FFAR1 (and perhaps FFAR4) on
      beta-cells, and 3) attenuate the low-grade inflammation seen in insulin resistant conditions
      such as obesity and T2D by stimulating FFAR4 on adipocytes.

      Aims

      To test the hypotheses, the aims of this project are to investigate:

        1. The effect of enteric coated pellets of pinolenic acid (hydrolyzed pine nut oil) and
           placebo (corn oil) on tolerability, safety and levels of glycemia in five pilot studies
           of healthy individuals.

        2. The acute effects of pinolenic acid on meal-induced changes in I) circulating levels of
           glucose, insulin, GLP-1, GIP and glucagon, II) plasma lipids and inflammatory markers,
           III) appetite ratings, and IV) substrate metabolism in patients with T2D and lean
           healthy and non-diabetic obese individuals.

        3. The chronic effects of pinolenic acid given 3 times daily for 8 weeks on I) the incretin
           effect, II) GSIS, III) body composition, IV) lipids and inflammatory markers V)
           substrate metabolism and VI) markers of insulin resistance and inflammation in tissue
           biopsies (muscle and adipose tissue) in patients with T2D and non-diabetic obese
           individuals.

      This registration covers the second of five planned pilot studies and investigates the
      difference in effect between pine nut oil and hydrolyzed pine nut oil on insulin, glucose and
      incretin hormones when administered acutely in combination with an oral glucose tolerance
      test.
    

Intervention name(s): Pine nut oil
Intervention type(s): Dietary Supplement
Intervention description(s): Subjects are supplemented with either no oil, hydrolyzed oil or non-hydrolyzed oil in combination with an OGTT
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Subjects complete three oral glucose tolerance test (OGTT) on different days, with a minimum of one week in between. First visit is a combined screening and baseline OGTT, with no supplementation. The second and third visit subjects are randomly assigned to either 1 g of non-hydrolyzed pine nut oil or 1 g of hydrolyzed pine nut oil.
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: incretin; insulin; glucose; appetite; ghrelin