The Effects of Orange Juice on Insulin Sensitivity and Plasma Lipids
Condition: Insulin Resistance; Obesity
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      The aim of this study is primarily to investigate the ability of antioxidants found in orange
      juice (OJ) to increase the body's sensitivity to the hormone insulin. Overweight or mildly
      obese women, who are otherwise healthy, will be recruited. The time commitment for subjects
      is ~14wks. Subjects will attend the laboratory on 5 occasions after fasting from midnight.
      The 1st is a medical screening. Laboratory visits 2 & 5 will take ~5hrs and will be separated
      by 3 months, during which time subjects will consume 250ml of an orange drink (either OJ or
      an orange flavoured control drink) once a day. During visits 2 & 5, subjects will have a scan
      to assess their %body fat using a low-dose x-ray machine, and have their insulin sensitivity
      measured using a technique called a 'Glucose Clamp'. During the 3hr glucose clamp, subjects
      receive an infusion of the hormone insulin and a glucose solution directly into their blood
      stream, with insulin sensitivity determined from the amount of glucose required to maintain
      blood glucose at normal levels. In addition, a small sample of fat tissue (about the size of
      a haricot bean) will be taken from underneath the skin of the belly. Subjects will record
      their food intake for 3-days in weeks 3, 7 and 11 of consuming the drink, and come to the lab
      for visits 3&4 during weeks 4&8. Laboratory visits 3&4 repeat measurements taken in the 1st
      (screening) visit.
    

Detailed description: 
      Background:

      Overweight and mild obesity are associated with insulin resistance and mild elevations in
      lipid risk factors which are not usually sufficiently abnormal to merit treatment. Such
      people are encouraged to lose weight to reduce their risk of progressing to type 2 diabetes
      and coronary heart disease, but there is clearly a potential role for dietary modifications
      to maximize any potential benefit of this weight loss. Flavonoids are known to have vascular
      effects which might enhance substrate delivery to metabolically active tissues, and thus
      improve insulin sensitivity. There are many different dietary sources of flavonoids, with
      fruits such as apples, berries and citrus being rich sources. However, some researchers have
      expressed concern that a high dietary intake of 100% juice may contribute to the development
      of insulin resistance, obesity and the Metabolic Syndrome (Bazzano, Li et al. 2008), although
      this is not universally accepted (Fujioka, Greenway et al. 2006; O'Neil and Nicklas 2008). To
      date, there have been no studies investigating the effects of citrus fruits on indices of
      cardio-metabolic health in people who are presently healthy but are at risk of developing
      some features of the Metabolic Syndrome.

      Aims:

      To investigate the effects of orange juice (OJ) intake on insulin sensitivity, appetite
      hormones, blood pressure and plasma lipids. In addition we aim to investigate any gene
      expression changes associated with OJ consumption, in particular in adipose tissue.

      Experimental protocol and methods:

      Overweight or obese women (BMI 27-35), who are otherwise healthy, will be recruited onto the
      study. They will attend the 'David Greenfield Human Physiology' laboratories on 5 convenient
      mornings, following an overnight fast. The 1st visit is a medical screening and will involve
      signing a consent form, completing medical screening, food frequency and activity
      questionnaires, having height, weight, and hip/waist circumference measurements taken and a
      sample of blood taken for CBC, urea, electrolytes, LFT, TFT, glucose and insulin analysis.
      Subjects will then be asked to complete a 3-day diet diary for macronutrient assessment and
      to consume a diet providing 50% of energy as carbohydrate for 3 days prior to the 2nd
      laboratory visit. This 2nd visit will involve having a DEXA body composition scan, an adipose
      tissue biopsy and a 3-hr hyperinsulinemic, euglycemic glucose clamp. Starting on the
      following morning, subjects will then consume an orange drink (either OJ or a carbohydrate
      matched orange flavoured drink) once a day for 12 wks. A 3-day diet diary for macronutrient
      assessment will be recorded during wks 3,7and 11 of taking the drink, and measurements made
      at screening will be repeated on visits 3 and 4 which will take place in weeks 4 and 8. A
      standardized diet will be consumed for 3 days prior to the final laboratory visit, as before.
      This 5th visit will be identical to visit 2.
    

Intervention name(s): orange juice
Intervention type(s): Dietary Supplement
Intervention description(s): 250ml of orange juice or a sugars matched orange drink
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Women; Orange Juice; Insulin Resistance; Obesity