Although placebos have played a critical role in medicine and clinical research for more than 70 years, it has been a mystery why these inactive treatments help to alleviate symptoms in some patients – and not others. Now researchers have for the first time identified genetic differences between placebo responders and non-responders, providing an important new clue to what has come to be known as ‘the placebo effect.’
Led by investigators at Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS), the new findings demonstrate that genetic differences that account for variations in the brain’s dopamine levels help to determine the extent of a person’s placebo response, a discovery that not only has important implications for patient care, but could also prove to be of significant benefit to researchers in designing and conducting clinical trials to help determine a drug’s effectiveness.
‘There has been increasing evidence that the neurotransmitter dopamine is activated when people anticipate and respond to placebos, ‘ explains the study’s first author Kathryn Hall, PhD, a research fellow in the Division of General Medicine and Primary Care and member of the Program in Placebo Studies and Therapeutic Encounter (PiPS) at BIDMC. ‘With this new research, we may now be able to use a person’s genetic makeup to predict whether or not they will respond to a placebo.’
The placebo effect occurs when patients show improvement from treatments that contain no active ingredients. For investigators conducting clinical trials of new drugs — which require that new treatments be tested against a placebo control to determine their efficacy– placebo responses can pose a particularly difficult challenge, requiring investigators to recruit additional patients in order to acquire statistically significant data, and substantially adding to the overall cost of the trial.
Because dopamine is known to be important to both reward and pain, the investigators began their search for a genetic placebo marker in the dopamine pathway. Their focus soon turned to the catechol-O-methyltransferase (COMT) gene.
‘COMT made for an excellent candidate because it’s been implicated in the cause and treatment of many conditions, including pain and Parkinson’s disease,’ says Hall. ‘It’s also been found in behavioural genetic models of reward responsiveness and confirmation bias, the tendency to confirm new information based on your beliefs.’
Polymorphisms are gene variations, and in the case of the COMT val158met polymorphism, the changes in the COMT gene result in people having either two copies of the methionine (met) allele, two copies of the valine (val) allele, or one copy of each.
‘People with two copies of met, the ‘met/mets,’ have three to four times more dopamine available in their prefrontal cortex [the brain area associated with cognition, personality expression, decision making and social behaviour] than the people with two copies of val,’ explains Hall. The scientists hypothesised that if dopamine was indeed involved in the placebo response, they would see a difference between how met/met, val/val and met/val genotypes responded to placebo treatments, with the met/met individuals showing a higher response.
To test this hypothesis, the researchers took advantage of a unique opportunity, revisiting a 2008 clinical trial led by PiPS Director Ted Kaptchuk, designed to study the placebo effect in patients with irritable bowel syndrome (IBS). ‘In our original work, IBS patients were assigned to one of three treatment arms and we explored the placebo response in relation to the patient-provider experience and the clinical environment in which the placebo is administered,’ explains Kaptchuk, Associate Professor of Medicine at HMS and the study’s senior author. The treatment conditions included either being ‘waitlisted’ and receiving no treatment, receiving placebo acupuncture in a business-like clinical manner, or receiving placebo acupuncture treatment from a warm supportive health care provider.
Armed with this original data, the scientists genotyped blood samples from patients from the earlier study, using a statistical method known as regression analysis to analyse the effects of a person’s genotype and the type of treatment received. ‘Our regression analysis found that as the copies of met increased, placebo responses increased in a linear fashion, presumably because more dopamine was available,’ Hall explains. The findings showed that among the IBS patients who had been in the waitlist treatment arm there was no difference in treatment responses between met/met, val/val and met/val genotypes as determined by the IBS-Symptom Severity Scale and Adequate Relief. Among those in the group that received a placebo administered in a businesslike manner, the met/met genotypes showed a small improvement over their val/val and met/val counterparts.
But, says Hall, among the individuals who had received placebo treatment from the warm supportive health care providers, there was a striking difference: the ‘met/mets’ demonstrated a six-fold greater improvement in their IBS symptoms relative to the ‘val/vals.’
‘These findings suggest that it is possible that met/met is a genetic marker for the placebo response and val/val is a marker for non-response,’ says Hall. ‘In addition, our findings underscore differences in placebo response based on the patient’s experience of the clinical environment. In the case of the met/met individuals, you can really see the advantage of a positive doctor-patient relationship. Conversely, our findings suggest that the val/val patients are less influenced by placebo treatment and this sheds light on a clinical challenge faced by many health care providers, whose empathic care helps some people, but makes no difference to others.’ Beth Israel Deaconess Medical Center

As part of their ongoing research on the role of genes in the development of type 1 diabetes, Joslin Diabetes Center scientists, in collaboration with scientists at the University of Würzburg, have demonstrated how a genetic variant associated with type 1 diabetes and other autoimmune diseases influences susceptibility to autoimmunity.
Recent studies of the human genome have identified genetic regions associated with autoimmune diseases such as type 1 diabetes. Joslin scientists in the Section of Immunobiology seek to understand how genes that are most widely associated with various autoimmune diseases contribute to disease risk.
One of these genes is PTPN22, which plays a role in lymphocyte (immune cell) function. A PTPN22 variant (or mutation) has been implicated as a risk factor for type 1 diabetes and several other autoimmune disorders. PTPN22 is involved in the formation of a key protein known as lymphoid tyrosine phosphatase (LYP), which helps control the activity of T and B cells in the immune system. The PTPN22 mutation generates a variation of LYP with a different molecular structure.
Most studies of the PTPN22 disease variant have suggested that this variant is a gain-of-function genetic mutation that enhances LYP activity and lessens the activity of T and B cells, which increases susceptibility to autoimmunity. ‘When immune cells are less reactive during the maturation phase of their development, the cells can evade mechanisms that help protect against autoimmunity,’ says study lead author Stephan Kissler, PhD, of the Section of Immunobiology. However, one study which analysed data from humans and genetically modified mice suggested that the LYP variant associated with type 1 diabetes is a loss-of-function mutation that reduces LYP activity.
To help resolve the conflicting data, Joslin scientists conducted studies with a unique mouse model developed by Dr. Kissler’s graduate student and co-author, Peilin Zheng. Using a technology that combines RNA interference, a method to silence gene expresson, with lentiviral transgenesis, a method to genetically modify animals, the scientists can manipulate gene activity in the most widely used mouse model for type 1 diabetes, the non-obese diabetic mouse (NOD). In this study, the researchers were able to easily turn off and on the PTPN22 gene in the NOD mouse. ‘We are the first to use this approach in the NOD mouse model,’ says Dr. Kissler. ‘It provides a very powerful way to study the contribution of PTPN22 to disease.’
When PTPN22 was turned off in mice, mimicking a loss-of-function mutation, the researchers observed an increase in regulatory T cells and a decreased risk of autoimmune diabetes. ‘This is the first study conducted on the diabetic mouse model that supports the LYP gain-of-function hypothesis,’ says Dr. Kissler. ‘Our work should help to resolve the controversy.’
By providing additional data that suggests the potential therapeutic value of PTPN22 manipulation, the study may further the development of new therapeutic options that inhibit LYP to reduce or prevent autoimmunity. ‘Our goal is to treat autoimmunity. Inhibiting LYP in patients may increase regulatory immune cells and could confer protection against autoimmunity, but it remains to be tested if our promising findings in this mouse model are reflected in humans,’ says Dr. Kissler. Joslin Diabetes Research Center

Investigators at Nationwide Children’s Hospital may have discovered a biological explanation for why low levels of oxygen advance spinal muscular atrophy (SMA) symptoms and why breathing treatments help SMA patients live longer.
SMA is a progressive neurodegenerative disease that causes muscle damage and weakness leading to death. Respiratory support is one of the most common treatment options for severe SMA patients since respiratory deficiencies increase as the disease progresses. Clinicians have found that successful oxygen support can allow patients with severe SMA to live longer. However, the biological relationship between SMA symptoms and low oxygen levels isn’t clear.
To better understand this relationship, investigators at Nationwide Children’s Hospital examined gene expression within a mouse model of severe SMA. ‘We questioned whether low levels of oxygen linked to biological stress is a component of SMA disease progression and whether these low oxygen levels could influence how the SMN2 gene is spliced,’ says Dawn Chandler, PhD, principal investigator in the Center for Childhood Cancer and Blood Diseases at The Research Institute at Nationwide Children’s Hospital.
SMA is caused by mutation or deletion of the SMN1 gene that leads to reduced levels of the survival motor neuron protein. Although a duplicate SMN gene exists in humans, SMN2, it only produces low levels of functional protein. This is caused by a splicing error in SMN2 in which exon 7 is predominantly skipped, lowering the amount of template used for protein construction.
Mouse models of severe SMA have shown changes in how genes are differentially spliced and expressed as the disease progresses, especially near end-stages. ‘One gene that undergoes extreme alteration is Hif3alpha,’ says Dr. Chandler. ‘This is a stress gene that responds to changes in available oxygen in the cellular environment, specifically to decreases in oxygen. This gave us a clue that low levels of oxygen might influence how the SMN2 gene is spliced.’
Upon examining mouse models of severe SMA exposed to low oxygen levels, Dr. Chandler’s team found that SMN2 exon 7 skipping increased within skeletal muscles. When the mice were treated with higher oxygen levels, exon 7 was included more often and the mice showed signs of improved motor function.
‘These data correspond with the improvements seen in SMA patients who undergo oxygen treatment,’ says Dr. Chandler. ‘Our findings suggest that respiratory assistance is beneficial in part because it helps prevent periods of low oxygenation that would otherwise increase SMN2 exon 7 skipping and reduce SMN levels.’
Dr. Chandler says daytime indicators that reveal when an SMA patient is experiencing low oxygen levels during sleep may serve as a measure to include SMA patients in earlier respiratory support and therefore improve quality of life or survival. Nationwide Children’s Hospital

International researchers, including a team at McGill University, have discovered a new cause for thyroid hormone deficiency, or hypothyroidism. This common endocrine disorder is typically caused by problems of the thyroid gland, and more rarely, by defects in the brain or the pituitary gland (hypophysis). However, a new cause of the disease has been discovered from an unsuspected source. The scientists, led by McGill Professor Daniel Bernard, Department of Pharmacology and Therapeutics in the Faculty of Medicine, identified a new hereditary form of hypothyroidism that is more prevalent in males than in females. This sex bias shone a light on where to look for the underlying cause.
‘Our collaborators in the Netherlands had been following a family in which two cousins had an unusual syndrome of hypothyroidisim and enlarged testicles,’ said Prof. Bernard. ‘Using state-of-the-art DNA sequencing technologies, we identified a mutation in a gene called immunoglobulin superfamily, member 1 (IGSF1), in both boys and their maternal grandfather. As one of few labs in the world studying this gene, we initiated a collaboration to determine whether the observed mutation might cause the disorder. At the time, the IGSF1 gene was known to be active in the pituitary gland, but its function was a mystery’.
‘Shortly after, we were contacted independently by a second group of researchers, studying a second family, in which two young brothers suffered from hypothyroidism and also harboured a mutation in the IGSF1 gene, though it was a different mutation than that observed in the Dutch family,’ said Prof. Bernard, ‘The fact that there were two unrelated families with the same male-biased clinical syndrome and mutations in the same gene strongly suggested that the mutations played a causal role in hypothyroidism’.

The groups reached out to researchers in the Netherlands, the UK, Italy and Australia who were following similar families and found that affected males all had mutations in their IGSF1 gene. Overall, the team identified 11 families with 10 different mutations in IGSF1.

‘We went on to show that mutations in IGSF1 block the protein it encodes from moving to the cell surface, where it normally functions’, explained Beata Bak, McGill Ph.D. student and the paper’s co-first author. ‘We also observed that the pituitary glands of mice lacking IGSF1 had reduced levels of the receptor for a brain-derived hormone known as thyrotropin-releasing hormone (TRH). If we think of TRH as a key, then its receptor is the lock into which the key fits to produce its effects. Our results suggest that in the absence of IGSF1, the pituitary gland becomes less sensitive to the brain’s instructions to secrete thyroid-stimulating hormone (TSH). As a result, the thyroid gland receives a reduced impetus to produce thyroid hormones’.

The group’s findings are significant as IGSF1 mutations cause a variable, though principally mild, form of hypothyroidism that would likely escape detection by most perinatal thyroid function screening methodologies. In addition, since the IGSF1 gene is highly polymorphic, there may be many individuals (boys and men, in particular) in the general population with presently undetected, but clinically significant hypothyroidism.

Symptoms of the disease include fatigue, weight gain, cold sensitivity, and muscle weakness. If left untreated, hypothyroidism increases the risk of developing heart disease. In infants, hypothyroidism can cause neurodevelopmental delay and, in extreme circumstances, cretinism.

‘A simple test could identify carriers of IGSF1 gene mutations or variants who might benefit from thyroid hormone replacement therapy. Our results highlight a fundamental role for this protein in how the brain and pituitary gland control thyroid function and therefore the whole body metabolism. We hope our work will inspire new research on IGSF1’s function in the pituitary gland under various physiological and pathophysiological conditions’, said Prof. Bernard. McGill University