This was done due to the lack of research on how factors such as sex, age, obesity and degree of glycemic control effect gluconeogenesis. The experiment was conducted with a control group of individuals that were not considered obese or diabetic. The investigators found that plasma glucagon levels were higher in diabetic participants and these results were positively related to endogenous glucose output. They also found that obese patients had higher levels of plasma insulin that was not related to fluxes in glucose.
Research Design and Method The investigators used experimental design to answer the study question. First, they had the participants drink a predetermined amount of water with a tracer added to it. This methodology was mentioned as a possible area of controversy later in the article. Secondly, the individuals fasted overnight. After the fast, the participants came to the hospital where the experiment was being conducted by 9 am. Here indwelling venous catheters were placed in both arms.
One was placed in the antecubital for the glucose isotope infusion and another in the opposite wrist. The glucose isotope was then infused for 120 minutes for the nondiabetic participants and was extended up to 180 minutes for the diabetic participants. The infusion time for the diabetic patients was extended in proportion to the increase in fasting plasma glucose. Blood samples were taken from each participant before the infusion began to measure the levels of glucose isotope, insulin levels and glucagon concentrations.
Samples of blood were then taken every 10 minutes for the last 20 minutes of the infusion to measure the same levels. The investigators also measured carbon 5 and natural glucose enrichment in blood samples taken the day before the study and measured these levels again at the end of the isotope infusion. One final blood sample was taken to measure the carbon 5 enrichment after 12 hours fasting. There are independent variables that could not be controlled. These items were such things as waist circumference, waist to hip circumference, fasting plasma glucose and others.
The dependent variables were controlled to some degree by means of withholding oral medications from the diabetic patients and treating their plasma glucose by means of diet alone for four weeks prior to the experiment. Insulin dependent diabetics were excluded from the study and nondiabetic subjects were not taking any medications that were known to affect plasma glucose levels. Literature Review The investigators perform a literature review which is discussed in the introduction of the research. In this review, the first 19 items on the reference list are reviewed.
The studies that were reviewed were state of the art at the time and had dates ranging from 1983 to 1998. There was also discussion of the limitations of the previous studies and the need for the study the investigators were undertaking. The author stated, whereas the preponderance of evidence supports enhanced GNC in human diabetes, the role of factors such as sex, age, obesity and degree of glycemic control has not been examined (Gastaldelli, A. , Balsi, S. , Pettiti, M. , Toschi, E. , Camastra, S. , Natali, A. , Landau, B. nd Ferrannini, E. , 2000 pp. 1368).
Research Question and Hypothesis The investigators did not develop a hypothesis, but wanted to answer a specific question. They wanted to know the effect of obesity and diabetes on gluconeogenesis and endogenous glucose output. Sampling The sample population for the study was a purposive sample obtained from a diabetes clinic and an obesity clinic. Because the investigators had a population characteristic in mind for the research, purposive sampling was an effective means by which to obtain participants.
The researchers studied a group of 55 participants that included both men and women. Of the sample population, 40 were considered obese and 15 were considered a healthy weight. Obesity was defined as a BMI greater or equal to 27. Twenty-eight of the obese participants were also diabetic and nine of the healthy weight participants were diabetic. The author of the article stated that the participants gave written informed consent and the protocol was approved by the Institutional Ethics Committee.