Glucose, a simple sugar, is an essential energy source for cats, but is not required in the diet as it is produced by the body from protein and fat.

Normal blood glucose levels in cats range from 3.0 – 7.0 mmol/L. Elevated blood glucose is seen in hyperglycaemia and low levels in hypoglycaemia.

Cats are unique in that they also lack taste buds for sugars^[1].

Blood glucose is an important index when assessing a cat for diabetes mellitus, the leading cause of hyperglycaemia. Glucose, in high doses, is a natural diuretic.

The cat is a true carnivore which distinguishes it clearly from the omnivorous dog. The natural diet of wild felids, e.g., mice, contains approximately 70 – 80% water. On a dry matter basis (on DMB), it contains about 55 – 60% of protein, 35% of fat, but less than 10% carbohydrate. This is very different from many commonly used commercial dry cat foods which contain a much higher percentage of carbohydrates, mainly represented by starch from cereals, even if a high digestible dry cat food should not contain more than 40% carbohydrates on DMB. Cats fed a high protein diet (54% on DMB) did not show postprandial hyperglycemia, unless relatively high amounts of simple sugars were added. This may be one of several reasons why diets high in protein, i.e. near-natural diets, have beneficial effects in controlling nutrient metabolism in diabetic cats^[2].

In cats, gluconeogenesis from amino acids is not downregulated even if protein intake is deficient. As a direct effect of a low carbohydrate intake under natural feeding conditions, cats have developed a high capacity for intensive gluconeogenesis from glucogenic amino acids^[3].

The activity of gluconeogenic enzymes is much higher in cats than in dogs. On the other hand, cats seem to be deficient in hepatic glucokinase (GK) function due to low hepatic GK expression or enzymatic activity^[4]. However, regulation of GK activity in cats seems to differ from other species because cats have a very low activity in GK regulating protein which in other species would be associated with high GK activity. The activity of other glycolytic key enzymes, including hexokinase which can perhaps partly compensate for low GK activity, is higher in cats than in dogs^[5].

References

1. ↑ Boudreau JC, et al (1971) Single unit recordings from the geniculate ganglion of the facial nerve of the cat. Exp Brain Res 13:461–488
2. ↑ Bennett N, DS C, Peterson ME. (2001) Comparison of a low carbohydrate versus high fiber diet in cats with diabetes mellitus. J Vet Int Med 15:297
3. ↑ Farrow H, Rand JS. (2002) The effect of high protein, high fat, or high carbohydrate diets on postrprandial glucose and insulin concentrations in normal cats. J Vet Int Med 16:794
4. ↑ Nelson RW, Scott-Moncrieff JC, Feldman EC, et al (2000) Effect of dietary insoluble fiber on control of glycemia in cats with naturally acquired diabetes mellitus. J Am Vet Med Assoc 216:1082-1088
5. ↑ Nguyen P, Leray V, Dumon H, et al (2004) High protein intake affects lean body mass but not energy expenditure in nonobese neutered cats. J Nutr 134:2084S-2086S