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Metabolic disorders and obesity model

Obesity is a disease that involves excessive body fat and a Body Mass Index (BMI) > 30. It increases the risk of suffering several metabolic-related diseases such as type 2 diabetes, cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD).

Obesity goes along with many alterations that give rise to the so-called metabolic syndrome, such as insulin resistance, liver fat, high blood pressure, heart problems, and atherosclerosis. Abdominal fat accumulation is a key marker in obese patients since it correlates especially well with these metabolic and cardiovascular symptoms.

Zebrafish share remarkable genetic, anatomic, and functional similarities with humans in lipid metabolism, adipogenic pathways, and the presence of all key organs required for lipid metabolism. This high conservation makes zebrafish a valuable model for understanding the mechanisms of obesity and metabolic diseases.

Feeding zebrafish a High Fat Carbohydrates Diet (HFCD) results in the whole body and abdominal fat accumulation, liver steatosis, and increased BMI.

We offer a diet-induced adult and juvenile zebrafish model that recapitulates the key aspects of metabolic diseases and obesity, which represents an alternative, biologically relevant, and cost-effective option to study these conditions.

Applications

  • Study the effect of nutritional interventions on lipid metabolism and fat accumulation and distribution.
  • Perform gene candidate screening for obesity and other metabolic-related diseases.
  • Screening of active compounds with potential regulatory effect on lipid metabolism and fat accumulation, which may be therapeutic candidates for obesity and metabolic diseases.

Advantages

Lipid metabolism and adipogenic pathways in zebrafish and humans are remarkably similar.

Transparent zebrafish larvae facilitate in vivo fat quantification and localization via non-invasive imaging.

High throughput screening of molecules.

Method description

Adult 24 week-old zebrafish are fed a Control Diet (CD) versus High Fat Carbohydrates Diet (HFCD)  for 8 weeks in the presence and absence of the compound of interest. Individuals are posteriorly incubated with a fluorescent dye for evaluation of fat accumulation and distribution, or stained for liver steatosis quantification. This study can be complemented with metabolic evaluations such as glucose, cholesterol, or triglycerides.

Juvenile 20 days post fertilization (dpf) zebrafish are fed a Control Diet (CD) versus High Fat Carbohydrates Diet (HFCD)  for 10 days in the presence and absence of the compound of interest. Individuals are posteriorly incubated with a fluorescent dye for evaluation of fat accumulation and distribution, or stained for liver steatosis quantification. This study can be complemented with metabolic evaluations such as glucose, cholesterol, or triglycerides.

Readouts

  • Body length
  • Bodyweight
  • Body Mass Index (BMI)
  • Lipid accumulation and distribution (visceral fat): total adipose tissue area and abdominal fat accumulation can be assessed with fluorescent lipid dye.
  • Hepatic steatosis: fat accumulation in the liver.
  • Hepatic enzymes
  • Triglycerides quantification
  • Glucose quantification
  • Cholesterol quantification
Figure 1. Juvenile obesity model. A) Protocol summary. Fish are fed from 20 to 30 days post fertilization (dpf) with a Control Diet (CD), or High Fat Carbohydrates Diet (HFCD). B) Length, weight, and Body Mass Index (BMI). Fish fed a HFCD show higher body length, weight and BMI when compared to CD-fed fish. 
Figure 2. Hepatic steatosis in juvenile fish. Fish are fed from 20 to 30 days post fertilization (dpf) with a Control Diet (CD), or High Fat Carbohydrates Diet (HFCD). A) Specific fat staining for evaluation of liver steatosis. Fat accumulation in the liver is observed in fish fed with HFCD. B) Steatotic liver quantification. The amount of dye per fish and diet is measured as red mean intensity. Statistical analyses have shown differences between CD and HFCD.
Figure 3. Lipid accumulation model in juvenile fish. Fish are fed from 20 to 30 days post fertilization (dpf) with a Control Diet (CD), or High Fat Carbohydrates Diet (HFCD). A) Staining of fish adipocytes with a fluorescent dye for evaluation of fat accumulation and distribution. Abdominal fat accumulation is observed in fish fed with HFCD. B) Abdominal fat quantification. Fluorescence intensity measurement was done in the individual under different diets. Statistical analyses have shown significant differences between CD and HFCD.