By DR NANTHIYA PRAVITSITTHIKUL
Once rare in Thailand, childhood obesity is today on the rise, with figures released by Thailand’s Ministry of Public Health in 2013 showing obesity growth rates of 36 per cent in pre-school age kids and 15 per cent in school age children.
Obesity increases the risk of high blood pressure, diabetes and high cholesterol, which in turn heightens the risk of kidney failure.
Some obese children may have a darkening skin around the neck, which does not wash off no matter how hard you scrub. Known as acanthosisnigricans, this skin change indicates the body is resistant to insulin action, which increases the prevalence of diabetes. Insulin is a hormone produced by cells in the pancreas, which controls blood sugar levels by enabling the movement of sugar to the cells that need it. In the case of any insulin disorder, the body has trouble regulating sugar and cannot use glucose for energy supply effectively, thereby resulting in high blood glucose levels that consequently damage the kidneys as well as the body as a whole.
Other hormones that regulate energy use are also affected. The acanthosisnigricans is caused by an abnormality in a related hormone that over-regulates skin pigmentation.
Insulin resistance is one of the key factors leading to kidney failure in obese children even if there are no other complications.
Leptin is a hormone made by fat cells in the body. Leptin levels tend to be higher in people who are obese because it is produced by fat cells. The body does not respond well to leptin in these cases and that spells disaster as leptin is an appetite-suppressing hormone that sends signals to the brain. Leptin makes people feel full when the body has accumulated adequate energy levels and burns body fat for use as energy. Leptin also helps insulin to function properly.
When the brain does not respond well to leptin, the energy expenditure is less than usual and the hormone fails to suppress appetite. As a result, people tend not to feel full after a meal, thereby encouraging abnormal accumulation of body fat, developing a vicious cycle of obesity, and further worsening their insulin resistance.
In cases of obesity, there are some abnormalities of the blood vessels of the kidneys as well as of both renin and aldosterone, which are hormones that regulate renal blood flow, renal blood pressure and body blood pressure.
The hormonal disorders cause high blood pressure and abnormal filtration, thereby damaging the kidneys and altering the kidney tissue. Aldosteronein combined with other hormones may damage small blood vessels in the body. Although the blood pressure may not be very high, the kidneys can be directly damaged by these hormones.
Both adiponectin and resistin are “fat hormones”, like leptin. The roles of resistin and leptin are similar; whereas adiponectin helps control these misbehaving fat hormones. In obesity, the resistin level is usually high while the adiponectin level is frequently low, thereby decreasing the body’s ability to prevent complications.
In conclusion, “fat hormones” from body fat and high insulin level will stimulate reactive oxygen species (ROS) or free radicals that cause many illnesses. The ROS causes inflammation of the kidney cells, abnormal proliferation of tissues, increase in filtration pressure, and renal hypertension.
One initial abnormality is albumin leakage to the urine identified from a specific urine test, urine microalbumin. In the kidney tissues, free radicals cause fibrous bands and abnormal cells, which increase the risk of kidney damage, cause a domino effect of conditions, and ultimately lead to kidney failure. The free radicals also cause high blood pressure, which also affects the kidneys.
A urine test can show up apparent abnormalities in obese child as early as three years of age. This test can indicate the presence of kidney damage at an early stage. While a large number of studies have been conducted to examine the relationship between obesity and kidney disease in adult population, few have been conducted to examine the link between childhood obesity and kidney disease.
However, a recent study in teenage males unveiled potentially correlation between obesity and kidney failure. Additionally, findings from the other studies that have been conducted in this area show that childhood obesity significantly increases the risk of kidney diseases and complications in later adulthood or even during childhood, and the condition may start to develop before high blood pressure or diabetes has been detected.
The long-term complications in the form of heart disease and kidney failure in most adults can be traced back to childhood obesity.
So think hard before you let your kid eat unhealthy fast food, drink sodas and snack on crisps and ice cream. His or her kidneys will be glad you did.
DR NANTHIYA PRAVITSITTHIKUL is a Paediatric Nephrologist at Samitivej Children’s Hospital – |Srinakarin Campus. Call (02) 378 9082-83.