Trans Fat Diet Induces Abdominal Obesity and Changes in Insulin Sensitivity in Monkeys

Abstract

Trans fat diet induces abdominal obesity and changes in insulin sensitivity in monkeys. Obesity. 2007;15: 1675-1684. Objective: There is conflicting evidence about the propensity of trans fatty acids (TFAs) to cause obesity and insulin resistance. The effect of moderately high intake of dietary monounsaturated TFAs on body composition and indices of glucose metabolism was evaluated to determine any prodiabetic effect in the absence of weight gain. Research Methods and Procedures: Male African green monkeys (Chlorocebus aethiops; n ϭ 42) were assigned to diets containing either cis-monounsaturated fatty acids or an equivalent diet containing the trans-isomers (ϳ8% of energy) for 6 years. Total calories were supplied to provide maintenance energy requirements and were intended to not promote weight gain. Longitudinal body weight and abdominal fat distribution by computed tomography scan analysis at 6 years of study are reported. Fasting plasma insulin, glucose, and fructosamine concentrations were measured. Postprandial insulin and glucose concentrations, and insulin-stimulated serine/threonine protein kinase (Akt), insulin receptor activation, and tumor necrosis factor-␣ concentrations in subcutaneous fat and muscle were measured in subsets of animals. Results: TFA-fed monkeys gained significant weight with increased intra-abdominal fat deposition. Impaired glucose disposal was implied by significant postprandial hyperinsulinemia, elevated fructosamine, and trends toward higher glucose concentrations. Significant reduction in muscle Akt phosphorylation from the TFA-fed monkeys suggested a mechanism for these changes in carbohydrate metabolism. Discussion: Under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction.

Trans fats—sources, health risks and alternative approach - A review

“…A Swedish study indicates that certain conjugated linoleic acid isomers that are present only in very low levels in ruminant fat increase the insulin resistance of men with abdominal obesity (Ricerus et al 2002). A six year study revealed that monkeys fed on a trans fat diet gained 7.2% of their body weight, as compared to 1.8% for monkeys on a monounsaturated fat diet (Kavanagh et al 2007). …”

Microbial translocation and skeletal muscle in young and old vervet monkeys

“…All analyses were measured by ELISA in plasma and endpoints included the following: LBP-1 (Hycult Biotech, Netherlands), C-reactive protein (CRP; ALPCO Inc., Salem, NH), interleukin 6 (IL-6), and sCD14 (R&D Systems, Minneapolis, MN). Fasting insulin, glucose, lipids, and lipoprotein concentrations were measured as previously described (Kavanagh et al, 2007b).…”

“…On the midpoint slice, muscle attenuation values were obtained from three regions of interest placed over the quadriceps musculature of each leg, and all six Hounsfield unit (HU) values were averaged for a final estimate. The images were further analyzed for composition by applying HU thresholds to isolate lean tissue (−5 to 135 HU) and fat tissue (−140 to −40 HU) as previously described (Kavanagh et al, 2007b). Lean tissue area at the midpoint slice was recorded as crosssectional area.…”

“…Insulin sensitivity Basal-and insulin-stimulated skeletal muscle biopsies were collected from 20 monkeys (Table S1 and Figure S1) in a procedure previously described (Kavanagh et al, 2007b). Muscle biopsies were taken from the vastus lateralis muscle, and then regular insulin was infused into a peripheral vein at 40 U/ m 2 /min for 15 min.…”

“…Akt activation is the last committed step in the insulin signaling pathway before the glucose transporter gets translocated to the cell membrane. In our laboratory, Akt activation has been a reliable indicator of insulin resistance in muscle (Kavanagh et al, 2007b). Data are reported as the induction of total protein activated with insulin.…”