In this paper, we aimed to probe the association between carbohydrate and fat contents of diet with inflammatory markers in women in reproductive age with overweight and obesity. Our findings illustrated that serum MCP-1 levels were positively correlated to total carbohydrate.
Our results suggest that high carbohydrate diets can probably lead to an increase in the levels of MCP-1, a chemokine whose role has been demonstrated in the etiology of obesity-related diseases [16].
The results of this article are in accordance with Forsythe et al.’s study [17] in which a very low carbohydrate diet led to a decrease in inflammatory markers such as TNF-a, MCP-1, IL-6, IL-8, and PAI-1 in comparison with a low fat diet. They expressed that the anti-inflammatory influences of carbohydrate restriction may be mediated through down-regulation of nuclear factor kappa B (NF-κB) pathway [17, 18]. It has also been established that HCD induces the production of the major lipogenic products and increases lipogenesis that it is related to higher levels of adiposity [17] which is associated with elevated levels of MCP-1 [16]. In the current study also, an inverse correlation was observed between MCP-1 and fat content in the diet, however this finding was insignificant, possibly due to small sample size.
However, Hall et al [19] demonstrated that the serum levels of MCP-1 remained constant after reduction of both fat and carbohydrate intakes in 6 weeks in obese subjects. The inconsistency between results of current study and tHall et al’s study might be due to various designs of study and different numbers of participants.
The TGF-β levels had positive significant relationship with dietary carbohydrate amount in and borderline significant negative association with dietary fat amount.
TGF-β is a recently recognized cytokine that regulates insulin resistance in obesity. In addition, it has been illustrated to induce macrophages proliferation and deposition in adipose tissue of obese mice [3]. TGF-β over-expression along with high carbohydrate consumption was reported to be related to high blood glucose level that leads to stimulated IKK phosphorylation and secretion of NF-κB-mediated pro-inflammatory such as TGF-β [20, 21]. In line with the current results an experimental study indicated that in fishes with HCDs, TGF-β, TNF-α and IL 1β, NF-κB, and IL-6 increased [21]. A human study also reported that low-carbohydrate diets with high amounts of fat contributed to reduction in serum level of TGF-β [22]. Near to significant negative association between total dietary fat and TGF- β was also observed in our study which might have reached to significant level with a larger study population. Although there is no clear explanation for this negative relationship, it is possible that the insignificant reducing trend of body weight during dietary fat tertiles, mediated the reduction of TGF by higher fat intake [23]. Despite the pro-fibrogenic dark side of TGF-β’s function, its healing effects on tissue injuries as well as on the modification of the immune responses have been observed, indicating its paradoxical effects on inflammatory state [24]. In fact, the multi-faceted properties of this cytokine are environmental and cellular context dependent. Contrary to our results, Ohtomo et al. in 2010 investigated the effects of high-carbohydrate/low-fat diet and middle-carbohydrate/middle-fat diet (as normal group) on hypertensive, obese, type 2 diabetic rats for 12 weeks and observed that the TGF-β in the kidney tissue meaningfully reduced in the high- carbohydrate/low-fat diet compared to the control group. Inconsistency between human and animal findings might be a result of bias or unsuitability of animal models in mimicking biochemical functions adequately [25].
We also explored that the galectin-3 level had significant negative relationship with dietary carbohydrate amount in adjusted model. Several investigations have shown that galectins are involved in various diseases including atherosclerosis and diabetes [26, 27]. Galectin-3, a member of this group, plays various and sometimes contradictory roles in pathological and physiological pathways depending on type of involved organs [28]. In case of kidney and vessels, lack of galectin-3 and its scavenging function in kidney raise the production of advanced lipoxidation and glycation end products (ALEs and AGEs) and contribute to damages to these tissues [29]. Moreover, further studies revealed that galectin-3 correlates with the prevention of the chronic inflammation and associated metabolic illnesses [28].
We did not explore any article investigating the impact of macronutrients proportion on galectins levels. Although, a clinical trial study in mice with progressive hepatopathy indicated that low-carbohydrate and high-fat ketogenic diets (KDs) led to significant expression of galectin-3 gene in comparison to control diet which was probably due to improved mitochondria-related functions [30].