In Obesity Research Unit we study the pathogenesis and treatments for obesity and related metabolic complications, with a particular focus on the role of mitochondria. Our research spans from translational studies on the molecular processes and potential new metabolic therapies for obesity, to novel, digital technologies aiming to effectively treat large patient groups with obesity in the clinic.
Our Research Interests

The prevalence of obesity is increasing rapidly both globally and in Finland. Obesity poses a significant risk for many diseases such as type 2 diabetes, coronary heart disease, stroke, and several cancer types. The of obesity-related complications develop through complex interactions between genetic and enviromental factors, and their manifestations vary remarkably between individuals. The factors responsible for these variations are difficult to disentangle in humans and the predictors of long-term health are poorly understood.

The central theme of Obesity Research Unit is to identify biological pathways that underlie the variability between individuals in obesity. Pietiläinen's group has a special interest in the role of mitochondria in adipose tissue and muscle in obesity. We have previously found that a key process associated with development of metabolic derangements in obesity is mitochondrial downregulation in the adipose tissue and adipocytes, in particular a reduction in the nicotinamide adenine dinucleotide (NAD+) -related pathways. Downregulation of mitochondrial biogenesis paralleled poor adipocyte differentiation, increased fat cell size, inflammation, and high liver fat. These results propose that mitochondrial flexibility to adapt to overnutrition, to dissipate and store excess energy safely, and to drive proliferation of healthy new fat cells in the adipose tissue is key in the prevention of ectopic fat deposition, circulating nutrient overload, and metabolic disturbances.

Our future work, while continuing in the field of adipose tissue, also focuses on muscle mitochondrial biology.

The other main focus of our lab has been on clinical weght loss and nutritoinal interventions, with the aim of improving mitochondrial function in adipose and muscle tissue. As an example of our collaborative efforts with national and international researchers, we compare the effects of dieting vs. bariatric surgery on the metabolism of adipose tissue and muscle. In addition to the molecular and metabolic studies, we have a keen interest in the modern treatment tools for obesity. In the Helsinki University Hospital’s Obesity Center, we have developed a novel web-based coaching program for the management of obesity, the ( in Finnish), where we actively pursue research into the impact and effectiveness of digital obesity management.

Study Designs

Pietiläinen's research group uses highly informative study designs:

  • Observational studies of twin pairs who are discordant for body weight; Comparison of leaner versus heavier co-twin
  • Longitudinal intervention studies involving individuals with obesity who undergo weight loss treatment; Comparison of individuals before and after treatment.
  • Longitudinal intervention studies using novel metabolic therapies: Comparison of individuals before and after treatment with the compounds

All studies include a wide variety of individuals with obesity, overweight and healthy body weight. In the twin studies, the participants are matched for genotype and shared environmental background. In these study designs, an ambitious combination of modern clinical, systems- and molecular methods is utilized to study underlying biological pathways in obesity and to identify potential novel treatment targets.