Page 574 - Small Animal Clinical Nutrition 5th Edition

Cancer 595

important to consider that glucose-containing fluids delivered
VetBooks.ir to septic, critically ill patients can exacerbate the septic state.
Because alterations in insulin and glucose metabolism occur
in cancer patients, concerns about dietary carbohydrate (glu-
cose) are further warranted from the perspective of oxidative
metabolism of tumor cell growth and metabolic mechanisms of
stress hyperglycemia (Mechanick, 2006). In acute and chronic
cancer patients, as with all critically ill patients, the stress
response leads to a plurality of organ-system derangements
including glucose allostasis, immune-neuroendocrine axis acti-
vation and insulin receptor signal transduction (Mechanick and
Brett, 2005). The concurrent inflammation, tissue catabolism
and hyperglycemia should be evaluated when designing a feed-
ing protocol. Manipulating the dietary fat, protein (amino
acids) and digestible carbohydrate concentrations can poten-
tially minimize physiologic sequelae resulting from the stress
response and slow tumor progression. Digestible carbohydrates
may be poorly used because of peripheral insulin resistance. Figure 30-5. Blood lactate concentrations from dogs with and with-
Feeding high levels of digestible carbohydrate may lead to out lymphoma before and during intravenous infusion of lactated
hyperglycemia, glucosuria, hyperosmolarity, hepatic dysfunc- Ringer’s solution (LRS). Asterisks indicate values from dogs with
lymphoma that differ significantly (p <0.05) from control dog values
tion, respiratory insufficiency and hyperlactatemia. More
obtained at the same time. Plus signs indicate values that differ sig-
specifically, until further information is known about the effects nificantly (p <0.05) from pre-infusion baseline values within the same
of hyperlactatemia on critically ill animals with cancer, glucose- test group. (Adapted from Vail DM, Ogilvie GK, Fettman MJ, et al.
and lactate-containing fluids should generally be avoided. Exacerbation of hyperlactatemia by infusion of lactated Ringer’s
Carbohydrate levels in foods for canine cancer patients should solution in dogs with lymphoma. Journal of Veterinary Internal
Medicine 1990; 4: 228-232.)
contain no more than 25% DM digestible carbohydrate.
The specific role of dietary carbohydrates has not been
reported in feline cancer patients. Although carbohydrate met- ditions (Ristow, 2006; Swinnen et al, 2006; Menendez and
abolism in healthy cats differs from that of healthy dogs, it is Lupu, 2006). Although tumor type may influence fat usage, a
suspected that tumors in cats use carbohydrates as an energy high proportion of weight loss in cachectic cancer patients is
source. Redistribution of hexokinase and its influence on the attributed to loss of body fat. Not surprisingly, people and ani-
rate of glycolysis in tumor cells may be of particular interest for mals with cancer have marked abnormalities in lipid metabo-
managing the nutritional aspect of feline cancer patients. Based lism (Chlebowski and Heber, 1986; Dewys, 1982; McAndrew,
on guidelines discussed below for dietary fat of 25 to 40% DM 1986; Ogilvie et al, 1994; Shein et al, 1986; Tisdale et al, 1987;
and protein of 40 to 50% DM, the caloric contribution from Daly et al, 1991).
digestible carbohydrate is limited to 25% DM or less. The decreased lipogenesis and increased lipolysis observed in
people and rodents with cancer cachexia alter the lipid profile
Fat and Fatty Acids dramatically. Changes include increased blood concentrations
In contrast to the ready use of carbohydrates and proteins by of free fatty acids, very low-density lipoproteins (VLDL),
tumor cells, some tumor cells have difficulty using lipids as a triglycerides (TG), plasma lipoproteins and hormone-depend-
fuel source.Theoretically, this preferential use of digestible car- ent lipoprotein lipase activity and decreased concentrations of
bohydrates and proteins leaves lipids available as an energy endothelial-derived lipoprotein lipase (McAndrew, 1986).
source for the host (Shein et al, 1986). This finding led to the Lipid profiles have been evaluated in dogs with lymphoma to
hypothesis that foods relatively high in fat may benefit patients determine if alterations similar to those reported in other
with cancer compared to foods relatively high in carbohydrates. species are present (Ogilvie et al, 1994). In contrast to healthy
Recent studies have identified alterations of lipid metabolism in controls, dogs with lymphoma had significantly altered concen-
canine cancer patients; this knowledge is paramount for devel- trations of cholesterol-associated VLDL, TG, VLDL-TG,
oping feeding protocols. An overview of the current literature low-density lipoprotein (LDL-TG) and high-density lipopro-
may help determine if the focus should be on total amount of tein (HDL-TG). In dogs with lymphoma, HDL-TG and
fat, specific sources of fat or both for cancer patients. VLDL-TG concentrations were significantly increased above
Highly malignant tumors, in rodent models and in vitro cell pretreatment values after remission was lost. Additionally, dogs
cultures, can exhibit up to an 85% decrease in the rate of fatty developed overt signs of cancer cachexia. These abnormalities
acid usage. This decrease is linked to decreased activity of the did not normalize when clinical remission was obtained. The
key activating enzyme of β-oxidation, acyl thiokinase (Ristow, clinical significance of the previously mentioned lipid parame-
2006). Conversely, well-differentiated tumors can retain the ters in dogs with lymphoma is unknown.
ability to metabolize fatty acids, especially under hypoxic con- Epidemiologic studies and meta-analyses examining the