Effects of sugar solutions on hypothalamic appetite regulation

Abstract

There are multiple hypotheses for the causes of the obesity epidemic. One such hypothesis is that dietary intake patterns have significantly shifted to include unprecedented amounts of refined sugar. We set out to determine some the unique metabolic changes that occur with initial exposure to dilute glucose, sucrose, high fructose corn syrup, or fructose solutions. Rats were given access to food, water and a sugar solution for 24 h, after which blood and tissues were collected. Fructose access (as opposed to other sugars investigated) resulted in a doubling of circulating triglycerides. Glucose consumption resulted in upregulation of 7 satiety related hypothalamic peptides whereas changes in gene expression were mixed for remaining sugars. Also, following multiple verification assays, 6 satiety related peptides were verified as being affected by sugar intake. These data provide evidence that not all sugars are equally effective in affecting the control of intake.

Overnight Access to Sugar Solutions Affects mRNA Expression of Several Neuropeptides in Different Hypothalamic Regions in Rats

“…This initial responses to sugar solutions are not the result from excess energy intake, as total caloric intake did not significantly differ among all five groups (Table 2). We also examined NPY and AgRP and failed to detect any significant differences (data not shown), which was consistent with our recent report [12].…”

“…These observations support the view that hypothalamic CCK plays an important role in energy control. We recently reported that 24 hour access to glucose solutions upregulated CCK expression whereas access to fructose resulted in significant downregulation of CCK [12]. In the current study, we replicated our finding that fructose access down-regulated CCK and can now report that this suppression takes place mainly in the PVN, not in the VMH or the LH.…”

“…The slight increase of TNF-α caused by glucose or sucrose was probably insufficient to have an effect on energy balance in the short term. Although fructose was reported to increase TNF-α in the whole hypothalamus [12], that observation was probably a reflection of the fact that the entire hypothalamus was sampled.…”

“…The formula below was used to plot the final result from qPCR data: The Ct mean value from ribosomal protein, large, P1 (RPLP1) was used as the reference gene as before [12] and the water treated group mean Ct was used as the calibrator. All values were expressed as means ± SEM.…”

“…We recently measured 84 obesity-related genes (using PCR arrays) in the hypothalamus of Sprague Dawley rats fed different sugar solutions. We found that several hypothalamic neuropeptides are affected differently by different sugar intakes from solution [12]. These neuropeptides include CCK, TNF-α, GH, receptor activity modifying peptide (RAMP3), corticotropin releasing hormone (CRH) and thyrotropin releasing hormone (TRH).…”