Buffalo Hump Seen in HIV-Associated Lipodystrophy Is Associated with Hyperinsulinemia But Not Dyslipidemia

Accumulation of dorsocervical fat, or a "buffalo hump" (BH), is commonly reported in adults with HIV-associated lipodystrophy (HIVLD). The pathogenesis underlying this aspect of a syndrome characterized by loss of subcutaneous fat from other body sites is poorly understood.

Supported by an NIH grant, researchers at multiple medical centers aimed to identify risk factors for a BH in HIV-infected adults in cross-sectional analyses of 2 HIV-infected ambulatory populations.

The first group (Australian Lipodystrophy Prevalence Survey [APS]) consisted of 1348 Australian HIV-infected adults (95% male) irrespective of changes in body composition. The second group (Lipodystrophy Case Definition [LDCD] study) comprised 417 subjects (83% male) with at least 1 reported moderate or severe feature of HIVLD.

A BH was reported in 24 (2%) APS subjects and 79 (19%) LDCD study subjects. A BH was not an isolated finding.

Patients with a BH had a high prevalence of other features of HIVLD, similar to lipodystrophic patients without a BH, such as facial lipoatrophy reported in 100% and 61% BH-positive subjects from the APS and LDCD study, respectively.

In both groups, those with a BH had higher fasting insulin (P <= 0.007), a higher body mass index (P <= 0.003), a higher waist/hip ratio (P <= 0.001), higher limb fat (P <= 0.003), and higher systolic blood pressure (P < 0.05).

On multivariate analysis, higher serum insulin, systolic blood pressure, age, and duration of exposure to ritonavir (Norvir) were independently associated with a BH in the APS group.

In the LDCD group, higher insulin, diastolic blood pressure, and duration of exposure to zidovudine (Retrovir) were independently associated with a BH.

There was no association between a BH and hyperlipidemia.

Conclusions

The authors conclude, “These data show that a BH is associated with other physical features of the lipodystrophy phenotype and suggest that hyperinsulinemia, a feature common to HIVLD, obesity, and hypercortisolism, is an important component of this phenotype, thus warranting closer monitoring of BH-positive patients for glucose intolerance and diabetes.”

The National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, 5U01AI042170-10 and 5U01AI046362-03, provided financial support for this study as part of the Flexible Initial Retrovirus Suppressive Therapies (FIRST) study (CPCRA 058) and the Metabolic Substudy of FIRST (CPCRA 061).

01/28/05

Reference
P Mallon and others. Buffalo Hump Seen in HIV-Associated Lipodystrophy is Associated with Hyperinsulinemia But Not Dyslipidemia. Journal of Acquired Immune Deficiency Syndromes 38(2):156-162, February 1, 2005.