High fructose diet suppresses exercise-induced increase in AQP7 expression in the in vivo rat heart

Voluntary physical activity suppresses adipocyte hypertrophy through the activation of cGMP mediated pathway in a fructose-induced metabolic syndrome model in rat

PURPOSE

A high-fructose diet is supposed to induce the so-called metabolic syndrome, associated with increased fat deposition in adipose tissue. Physical exercise may counteract the induction of the metabolic syndrome. The present study aims to investigate the effect of voluntary physical activity (VPA) on cGMP-mediated lipolysis in retroperitoneal adipose tissue in a metabolic syndrome model induced in rats by a high-fructose diet.

METHODS

Male Sprague-Dawley rats in control and fructose (F) groups had free access to either plain drinking water or a solution of 20% D-fructose, combined with a standard diet for 8 wk. Rats in the fructose + activity (F + A) group performed voluntary physical activity with a running wheel. Blood pressure, serum glucose, lipids and natriuretic peptide levels were measured on the last day of the feeding period. In retroperitoneal adipose tissue, cGMP, hormone-sensitive lipase (HSL), perilipin-1, aquaglyceroporin levels, and adipocyte diameter were analyzed.

RESULTS

Systolic blood pressure, glucose, and triacylglycerol were higher in the F groups compared to the control. The C-type natriuretic peptide was higher in the F group compared to the control. The cGMP level in retroperitoneal adipose tissue was higher in the F + A group than F group. Higher HSL and perilipin-1 levels were observed in the F + A group compared to the F and control groups. Adipocyte diameter was lower in the F + A group compared to the F group.

CONCLUSION

Regular physical exercise triggers lipolytic effects in adipose tissue through cGMP, HSL, and perilipin-1-mediated pathway in fructose-induced metabolic syndrome model in rats, preventing the increase in adipocyte diameter.

Walnut Supplementation Restores the SIRT1-FoxO3a-MnSOD/Catalase Axis in the Heart, Promotes an Anti-Inflammatory Fatty Acid Profile in Plasma, and Lowers Blood Pressure on Fructose-Rich Diet

The benefits of walnut (Juglans regia) consumption for metabolic health are known, but the molecular background underlying their putative antioxidant and anti-inflammatory/immunomodulatory effects is underexplored. We assessed that walnut supplementation (6 weeks) reverted unfavorable changes of the SIRT1/FoxO3a/MnSOD/catalase axis in the heart induced by fructose-rich diet (FRD). Intriguingly, Nox4 was increased by both FRD and walnut supplementation. FRD increased the cytosolic fraction and decreased the nuclear fraction of the uniquely elucidated ChREBP in the heart. The ChREBP nuclear fraction was decreased in control rats subjected to walnuts. In addition, walnut consumption was associated with a reduction in systolic BP in FRD and a decrease in fatty acid AA/EPA and AA/DHA ratios in plasma. In summary, the protective effect of walnut supplementation was detected in male rats following the fructose-induced decrease in antioxidative/anti-inflammatory capacity of cardiac tissue and increase in plasma predictors of low-grade inflammation. The current results provide a novel insight into the relationship between nutrients, cellular energy homeostasis, and the modulators of inflammatory/immune response in metabolic syndrome, emphasizing the heart and highlighting a track for translation into nutrition and dietary therapeutic approaches against metabolic disease.

Implications of Aquaglyceroporin 7 in Energy Metabolism

The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with increased lipolysis, such as fasting and diabetes, glycerol is released from adipose tissue and metabolized in other tissues. AQP7 is expressed in adipose tissue where it facilitates the efflux of glycerol, and AQP7 deficiency has been linked to increased glycerol kinase activity and triglyceride accumulation in adipose tissue, leading to obesity and secondary development of insulin resistance. However, AQP7 is also expressed in a wide range of other tissues, including kidney, muscle, pancreatic β-cells and liver, where AQP7 also holds the potential to influence whole body energy metabolism. The aim of the review is to summarize the current knowledge on AQP7 in adipose tissue, as well as AQP7 expressed in other tissues where AQP7 might play a significant role in modulating whole body energy metabolism.

Fructose Consumption in the Development of Obesity and the Effects of Different Protocols of Physical Exercise on the Hepatic Metabolism

Fructose consumption has been growing exponentially and, concomitant with this, the increase in the incidence of obesity and associated complications has followed the same behavior. Studies indicate that fructose may be a carbohydrate with greater obesogenic potential than other sugars. In this context, the liver seems to be a key organ for understanding the deleterious health effects promoted by fructose consumption. Fructose promotes complications in glucose metabolism, accumulation of triacylglycerol in the hepatocytes, and alterations in the lipid profile, which, associated with an inflammatory response and alterations in the redox state, will imply a systemic picture of insulin resistance. However, physical exercise has been indicated for the treatment of several chronic diseases. In this review, we show how each exercise protocol (aerobic, strength, or a combination of both) promote improvements in the obesogenic state created by fructose consumption as an improvement in the serum and liver lipid profile (high-density lipoprotein (HDL) increase and decrease triglyceride (TG) and low-density lipoprotein (LDL) levels) and a reduction of markers of inflammation caused by an excess of fructose. Therefore, it is concluded that the practice of aerobic physical exercise, strength training, or a combination of both is essential for attenuating the complications developed by the consumption of fructose.