Body composition, bone metabolism and insulin resistance interrelationship in spontaneous obese rats feeding different calcium content

Abstract

Nutrition and Health National Survey (Argentina, 2004–2006) sowed a high calcium intake (CaI) deficiency. A later analysis showed an inverse relationship between CaI and obesity/overweight (Ob/OW) incidence, data similar to NHANES III (USA). These findings are in agreement with MB Zemel theory postulates (2004): “A high CaI would be a preventive factor for Ob/OW development”. Objective: to evaluate the effect of feeding different Ca content diet on body composition, bone metabolism and insulin-resistance in rats that spontaneously develop Ob in adolescent state. Female IIMbb rats fed from pregnancy one of 3 isocaloric diets only varied in Ca content: 0.9 g% (HG), 0.5 g% (NG) and 0.2 g% (LG). At weaning male offspring continued feeding the same mother diet till 50 days of age (Tf). Food consumption, body weight (BW) and % Ca absorption (%CaAbs) were evaluated. At the end of the experience (Tf) body composition (water, lipids, protein and ashes) (AOAC), BMD and BMC (DXA), body Ca and P content and serum bone markers: bALP, BGP and CTX (ELISA), insulin and glucose were determined. Results (mean ± SD): groups HG, NG & LG , respectively: BW (g); 195 ± 9a; 227 ± 13b; 262 ± 7c; % CaAbs; 64 ± 6a; 87 ± 1b; 91 ± 9c; ASHES (g/100 g BW); 2.4 ± 0.1a; 2.2 ± 0.1a; 1.5 ± 0.1b; Ca (mg/100 g BW); 620 ± 34a; 640 ± 22a; 394 ± 40b; P (mg/100 g BW); 532 ± 22 a; 520 ± 31 a; 882 ± 15b; %Fat; 14.2 ± 0.9a; 13.7 ± 0.9a; 15.9 ± 0.6bc; BMC (g/g BW); 1.09 ± 0.02a; 1.29 ± 0.08b; 0.83 ± 0.03c; BGP (ng/dl); 279 ± 73a; 375 ± 46b; 478 ± 45c; bALP (IU/L); 115 ± 57a; 143 ± 46a; 98 ± 39b; sCTX(ng/dl); 64.9 ± 22.5a; 71.9 ± 12.4a,b; 80.6 ± 14.1b; Glucose (mg/dl); 111.8 ± 25.5a; 151.9 ± 21.9b; 207.0 ± 11.0c; Insulin (ng/ml); 1.92 ± 0.75a; 4.07 ± 0.93b; 6.87 ± 2.24c. Different letters: p < 0.05. No differences in food consumption, water and protein body content, total skeleton BMD and serum Ca and P levels were found. The low Ca diet increased BW by an increment in body fat; despite the increment in %CaAbs increased P and decreased Ca body content and bone remodeling increased (BGP), showing a tendency to a low bone formation (bALP) and a high bone resorption (sCTX). Conversely, the HG decrease BW by the diminution in fat content, also %CaAbs, bone remodeling and insulin resistance were decreased. There was an inverse relationship between the Ca intake and the increment in insulin resistance. Conclusions: the results suggest a negative effect of low CaI not only in bone metabolism but also in body composition and insulin resistance in spontaneous obese rats.