Role of calorie restriction on pathophysiological changes in tongue fat and its relation to increased risk factors of obstructive sleep apnea in WNIN/Ob obese rats



Obstructive sleep apnea is an outcome of obesity, resulting from abnormal upper airway structures. Our main objective was to assess the fat infiltration into the tongue of calorie-restricted rats and its consequences on upper airway obstruction in comparison with lean and obese rats.


A total of 24 adults lean, obese and CR obese rats were included in the study. Body fat and lean body mass were determined by TOBEC, DXA measured fat depositions around the neck region, and radiographs of upper airway structure were analysed by digital X-ray. Ex vivo biochemistry was carried out for leptin, and lipids in blood/tissues, and fat infiltration by ORO staining. The tongue, masseter muscle fat, fibre and taste bud morphology was assessed by SEM.


Body composition analysis showed higher body fat and low lean body mass in obese animals; DXA results showed excess fat around the neck region of obese rats. Higher triglyceride and reduced leptin levels were observed in CR obese rats compared to lean and obese rats. ORO and SEM analysis showed varying degree of fat accumulation among the groups. Tongue muscle fibres of obese rats showed rugged abnormal folding with an increase in width in comparison with calorie-restricted obese rats. The distance and width between the taste buds of calorie-restricted obese rats were reduced to the levels of lean rats.


The calorie restriction in obese rats reduced the fat deposition around the neck and improves the upper airway structures, the morphology of tongue fibre and increased the stiffness of the tongue, thereby reducing the risk of obstructive sleep apnea.

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Fig. 1
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Obstructive Sleep Apnea


Calorie restricted


Total body electrical conductivity


Lean body mass


Longitudinal Sections


Phospate buffer saline


Scanning electron microscopy


Oil Red-O


Haematoxylin and Eosin




dual X-ray absorptiometry


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Authors acknowledge the Indian Council of Medical Research (ICMR), Governmentof India, New Delhi, for the financial support, and Shriyut K. Satyanarayana, and N. Yadagiri Animal Caretakers, for their co-operation in the maintenance of the obese rat colony. Mr. P. Madhusudhanachari for technical assistance. Authors also thank Dr. R. Hemalatha, Director, National Institute of Nutrition for her support.


The present experiment is an intramural research project of the National Centre for Laboratory Animal Sciences, National Institute of Nutrition, funded by Indian Council of Medical Research. The findings expressed in the manuscript represent the view of the authors and do not pose the views of the National Institute of Nutrition.

Author information




K. Prathap Reddy carried out the animal experiment and analysis. N. Shivaram helped in the surgical removal of masseter muscle and tongue from lean and obese rats. P. UdayKumar helped in analysing the results of scanning electron microscopy. M.V. Surekha carried out the haemogram analysis and histopathology of masseter and tongue muscle tissues. P. Suresh contributed equally to this paper in various aspects of this study. N. Harishankar drafted and evaluated the manuscript along with the other authors. All authors read and approved the final manuscript.

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Correspondence to Nemani Harishankar.

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Reddy, K.P., Shivaram, N., Kumar, P.U. et al. Role of calorie restriction on pathophysiological changes in tongue fat and its relation to increased risk factors of obstructive sleep apnea in WNIN/Ob obese rats. Nutrire 45, 10 (2020).

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  • Calorie restriction
  • Lipids
  • Masseter muscle
  • Obesity
  • Upper airway structures