Prevalence of insulin resistance and its association with metabolic syndrome criteria among Bolivian children and adolescents with obesity

Obesity is one of the most common nutritional problems in developed countries. Actually the incidence of obesity is increasing considerably in Latin America countries too.[1] In Bolivian children, malnourishment secondary to poor intake is still the most prevalent nutritional problem, but obesity is emerging in alarming rates between the last 10 years in the most economical productive sectors inside the country. [2, 3]

Health care professionals should be concerned about overweight and obesity because of the well established relations between excess body weight and such medical conditions as type 2 diabetes, hypertension, atherosclerotic cardiovascular disease and osteoarthritis.

The metabolic syndrome also called (insulin resistance syndrome and X syndrome) is a common pathophysiologic condition with implications for the development of many chronic diseases. Obesity beginning in childhood often precedes the hyperinsulinemic state. The metabolic syndrome is rapidly increasing in prevalence with rising childhood obesity and sedentary lifestyles worldwide. Although chronic diseases are now well recognized as a growing problem for low- and middle-income countries, limited data are available for these countries, and the developing world has been largely ignored in health strategies. [4]

The insulin resistance is defined as an impaired ability of plasma insulin to promote peripheral glucose disposal, suppress hepatic glucose, and inhibit very low density lipoprotein (VLDL) output. The clinical phenotype of insulin resistance syndrome mainly includes, centrally obesity, acanthosis nigricans (AN), skin tags, striae, acne, hirsutism, hypertension and atherogenic dyslipidemia manifested by increased VLDL, triglycerides and reduced levels of high density lipoprotein (HDL) cholesterol. [5, 6]

It is well established that insulin resistance is also present in patients without obesity, whereas obese children can be insulin sensitive. There are no clear genetic studies to support a racial predilection, but actually obesity and insulin resistance syndrome is more frequent in white people and African-Americans people. Africans, Asiatic, Arabic and Latin American race are less commonly affected. Apparently, cultural differences, economical disadvantages and lifestyle behaviors may account for some of the race disparity in obesity-related diseases and disease outcomes, but the rates of obesity are clearly increasing in all groups in the last 20 years. [7–9]

In adults, the definition of insulin resistance syndrome varies in terms of the indicators and cutpoints used. The US National Cholesterol Education Program includes abnormalities in any three of the following factors: glucose level, triglyceride level, high density lipoprotein cholesterol level, systolic blood pressure, and waist circumference. [10]

In the current study we examined the presence of insulin resistance and most of the metabolic and clinical characteristics associated with this syndrome. The absence of studies in our country as in other poor Latin American countries, make interesting to design the current study about this emerging problem in comparison with another countries.

The objective of our study was to determine the association between insulin-resistance and components of the metabolic syndrome in a group of Bolivian obese children and adolescents. The second objective was determining the relation of acanthosis nigricans and insulin-resistance.

A total of 13668 pediatric visits were performed between august 2006 to August 2007 finding 155 patients with the diagnosis of obesity. Only 61 patients of the 155 concluded with all the biochemical analysis required for the final analysis. No significant differences were found between children that concluded the study and those who did not.

Racial variables were not considered because all of the patients correspond to Hispanic race.

Acanthosis nigricans was found in (70%) of patients resistant to insulin, but it was also present in 54% of patients sensitive to insulin (p = 0.14).

The lack of previous studies about metabolic syndrome in Bolivia makes it interesting to know the actual situation in one of the poorest country in South America. The number of patients was not the ideal to try to show the prevalence in the entire country, but it would be an initial point for future studies.

The economical situation was an important determinant factor in our study since many obese children were not included because of lack of enough money for medical visits and some of the diagnostic test that were not financed by research committee of the hospital.

Insulin resistance was found in 39.4% of obese children and adolescents. This rate is similar as other found in studies conducted in developing countries like France, Italy, Spain and United States of America. [15–19]

There are no clear definition for metabolic syndrome in children and adolescents, existing different criteria used according to the place or population of the study. [20–24] NCEP-ATP III definition with modified cut-off values for youths was considered for the diagnosis of metabolic syndrome in the current study.

Waist-hip ratio was also determined; however, it is important to know that neither insulin concentration nor centrally obesity is considered like criteria in children groups in contrast with adolescents groups where some definitions include WHR as criteria. [22, 25, 26] This association was demonstrated specially in studies conducted in adult patients with metabolic syndrome. [13, 14] In the current study WHR was the only one characteristic that demonstrated statistical significance according to sex (p = 0.046).

The metabolic syndrome was found in 36% of studied patients, with a slightly predilection in males but without statistical significance (p = 0.59). Lipidic abnormalities account for most of the criteria of definition metabolic syndrome. High blood pressure and impairment of glucose tolerance frequencies are still low in the current investigation as expected in comparison with another studies.

In pigmented races, acanthosis nigricans (AN) is an important early manifestation of the obesity syndrome. AN helps identify persons at particular risk of developing the obesity syndrome, dyslipidaemia, hypertension and insulin resistance. Recognition of AN, therefore, offers important opportunities for health screening and preventative medicine. [27–31]

Acanthosis nigricans was found in 70% of the insulin resistant group of patients, but it was also present in the 54% of sensitive insulin group. This factor was important in the lack of statistical significance of this association. The existent relation between obesity and AN is more prevalent in this study as in other published investigations. [32–34] A stronger correlation was found between high blood pressure and high triglyceride levels in patients with insulin resistance. This association was also determined in some studies. [35, 36]

It is clear that the incidence and prevalence of metabolic syndrome and obesity tend to increase with the passage of time, becoming an alarming problem of public health. Therefore, all health politics and efforts should be conducted for nutritional education, sports practice, change dietary habits (increase the amount of fiber, reduce the intake of junk food and saturated fat) that may have important role in the reduction of obesity and metabolic syndrome prevalence.

Our sample has a prevalence of 36% among children and adolescent with obesity in Bolivia. Insulin resistance is very common among children and adolescents with obesity, significantly associated with high blood pressure and high triglycerides levels. Obesity as malnourishment is an alarming problem of public health even in developing countries.